The 5th Nuclear Photonics Conference

Oct 6, 2025, 8:55 AM → Oct 10, 2025, 6:00 PM Europe/Berlin

TU Darmstadt

The Fifth International Conference on Nuclear Photonics will be held October 6 – 10, 2025 in Darmstadt, Germany. Nuclear Photonics 2025 is part of a series of biennial conferences devoted to the science and applications of photon-induced phenomena on a nuclear (MeV) energy scale. Previous editions had been held at    -  Monterey, CA, USA (2016)   -  Brasov, Romania (2018)   -  Osaka, Japan (2021)   -  Durham, NC, USA (2023)   The Nuclear Photonics 2025 is organized by the International Research Training Group on "Nuclear Photonics" at Technische Universität Darmstadt in collaboration with the Romanian National University for Science and Technology POLITEHNICA Bucharest, Romania.   The scientific program will comprise oral presentations, presentations of posters, and an excursion. Conference proceedings will not be collected.

Scientific_Program_NP2025_Summary.pdf

upload_slides_manual.pdf

Mon, October 6

9:00 AM → 9:15 AM Welcome

9:15 AM → 10:30 AM Session I

Convener: Daniel Ursescu

9:15 AM Recent laser advances and their applications for nuclear physics research

Laser technology continues to advance and contribute to nuclear physics research and applications, and it has the promise of playing an ever larger role. Ultrashort-pulse lasers can produce secondary radiation, including energetic particles and photons that can initiate nuclear reactions and probe nuclear states. Laser-driven implosion facilities also create conditions relevant for nuclear physics studies and applications.

This talk will address the current laser technology state of the art and its uses in various nuclear science and applications ranging from spectroscopy and nucleosynthesis to isotope production and probing materials.

Speaker: Prof. Jonathan Zuegel (LLE - University of Rochester)

10:00 AM Developments on the Laser-Driven Neutron Source and Single-shot Resonance Spectroscopy at ILE Osaka

The Laser-Driven Neutron Source (LDNS), a novel approach to neutron generation, has attracted significant attention due to its capability to produce neutron pulses with ultra-short duration and high flux [1].
In this presentation, we introduce our recent progress on high-flux neutron generation [1] and single-shot neutron resonance spectroscopy using LDNS [2]. In our experiments, the petawatt LFEX laser was focused onto a CD foil target to accelerate protons and deuterons. These accelerated ions subsequently interacted with a cylindrical beryllium target used as a neutron converter. Through nuclear reactions such as 9Be(p, n)9B and 9Be(d, n)10B, neutrons were generated with yields up to ~10¹¹ per pulse and durations shorter than 1 ns [1].
The generated high-energy neutrons were moderated to epithermal and lower energy ranges (meV–eV) using a high-density polyethylene (HDPE) block. A neutron beamline of 1.8 m was developed to measure neutron resonance absorption peaks near 4.28 eV from a tantalum sample heated to various temperatures. The measured neutron resonance widths exhibited clear temperature dependence due to Doppler broadening. We have successfully demonstrated isotope-selective nuclear thermometry with LDNS in a single-shot mode. The correlation between resonance width and sample temperature was determined in the range from approximately 300 K to 650 K [2]. Such single-shot, resonance-based temperature measurements would be practically impossible with conventional accelerator-driven neutron sources due to insufficient neutron flux. Detailed experimental results and their implications will be discussed.

[1] Akifumi Yogo et al, PRX 13, 011011 (2023)
[2] Zechen Lan et al, Nat. Commun. 15, 5365 (2024)

Speaker: Zechen Lan (ILE, Osaka Univ.)

NP2025_Lan.pptx

10:30 AM → 11:00 AM Coffee break

11:00 AM → 12:10 PM Session II

Convener: Stephan Kuschel

11:00 AM Temporal bunching of laser-driven ions by ultrafast phase-space rotation

Laser-driven ion sources of picosecond duration enable new frontiers in the exploration of proton radiolysis, ultrafast atomic dynamics, and nanostructured dose distribution, providing unprecedented insights into how energy deposition influences chemical and structural change, with broad implications in medicine, chemistry, and materials science. However, ions produced by intense laser interactions, the most common and robust mechanism being the Target Normal Sheath Acceleration (TNSA), exhibit a broad energy spectrum and wide angular divergence. These factors result in significant dispersion and broadening of the ion pulses in both space and time as they propagate away from the source. A true game-changer would be a narrow-band, collimated proton beam that preserves its picosecond-scale duration well beyond the laser interaction point - yet no existing method has fully achieved this goal.
One method of generating a narrowband and collimated proton beam from a laser-plasma setup is through the use of a helical coil (HC) target design. In addition to focusing, energy selection and post-acceleration, the HC target induces simultaneous phase rotation of the proton bunch as it traverses through the HC. The phase rotation of proton beams on a picosecond timescale is demonstrated by measuring the bunch duration at a significant distance from the source using Chirped Optical streaking diagnostics. Our findings also show that this method is scalable, with simulations indicating efficient phase space rotation of protons of clinically relevant energies.

Speaker: Prof. Satyabrata Kar (Queen's University Belfast)

11:30 AM Enhancing Quasi-Monoenergetic Deuteron Acceleration via Boosted Coulomb Explosion by Reflected Picosecond Laser Pulse

Laser-driven ion acceleration has attracted significant research interest due to its ability to generate high-flux pulsed ions. Applications such as compact neutron sources [1] have already been demonstrated. However, for further applications such as cancer therapy and nuclear physics studies, quasi-monoenergetic ions with controllable energy are highly desirable.

In this presentation, we report our recent works on producing quasi-monoenergetic deuterons using the petawatt LFEX laser. We developed a method to fabricate D₂O-deposited targets [2] inside the laser focal chamber using heavy water capsules. This method enables the deposition of a D₂O layer with a thickness of several tens of nanometers on a metal target. Using these targets, we achieved quasi-monoenergetic deuteron pulse (ΔE/E = 4.6%) via the Target Normal Sheath Acceleration (TNSA) mechanism, though the peak energy was limited to ~11 MeV. This limitation arises because protons play a significant role in shaping the quasi-monoenergetic component of the deuterons. To overcome this limitation, we have proposed an acceleration mechanism, boosted Coulomb explosion, initiated by a standing wave [3]. This standing wave is formed in a pre-expanded plasma by the interference of the incident main laser pulse and the pulse reflected from a solid target. The pre-expanded plasma is generated from a thin surface layer by a relatively strong pre-pulse. This mechanism creates a persistent Coulomb field on the front surface of the target with field strengths on the order of TV/m lasting several picoseconds. Using the D₂O-deposited targets [2], we successfully generated quasi-monoenergetic deuteron pulse with an energy of up to 50 MeV at the target front side. Furthermore, our results indicate that the deuteron peak energy can be tuned by adjusting the laser pulse duration.

A relatively long pulse duration and a relatively strong pre-pulse have important roles for generation of the standing wave in the present scheme. The boosted Coulomb explosion mechanism thus provides a tunable and efficient approach for generating quasi-monoenergetic ion beams using high-power laser systems. Additionally, ion species selection is feasible by depositing specific surface layers, e.g., T₂O layers for quasi-monoenergetic triton generation.

Ref.
[1] Zechen Lan, et al, Nat. Commun. 15, 5365 (2024)
[2] Tianyun Wei, et al, Phys. Plasmas 31, 073903 (2024)
[3] Tianyun Wei, et al, arXiv preprint arXiv:2504.19789 (2025).

Speaker: Tianyun Wei (National Institutes for Quantum Science and Technology)

SLIDES_NP2025.pdf

11:50 AM Increasing the electron charge in laser-driven electron acceleration using orbital angular momentum beams

Neutron beams have various applications, ranging from nuclear physics to medical and security. Laser-driven neutron sources are a compact technique for generating neutron beams from laser-accelerated particles. A high-power laser is directed at a target (pitcher), where it produces an ion beam with target normal sheath acceleration (TNSA). Subsequently, the ion beam propagates towards a second target (catcher), in which nuclear reactions convert the beam partially into a beam of neutrons [Alvarez 2014]. While this pitcher-catcher scheme is usually introduced with laser-accelerated ions, it has recently been shown, that an electron beam can also exhibit a high conversion efficiency. The conversion rate of electrons into neutrons exhibits a linear relashinship with the electron energy, leading to conversion rates of up to 25% at 350 MeV [Scheuren 2024]. However, the total number of neutrons is constrained by the accelerated charge. Our simulations demonstrate the potential enhancement of the charge in laser-wakefield acceleration by using orbital angular momentum beams (OAM). Utilizing such beams, the wakefield changes from a point-like equillibirum to a ring-shaped wakefield, thereby enhancing the accelerated charge up to nC.

[Alvarez 2014]: J. Alvarez et al: Laser Driven Neutron Sources: Characteristics, Applications and Prospects. Physics Procedia (2014)
[Scheuren 2024]: Stefan Scheuren et al: Scaling of laboratory neutron sources based on laser wakefield-accelerated electrons using Monte Carlo simulations. Eur. Phys. J. Plus (2024)

Speaker: Carl Georg Boos (TU Darmstadt)

12:10 PM → 1:30 PM Lunch break

1:30 PM → 3:00 PM Session III

Convener: Andreas Zilges

1:30 PM On the horizon: the $^{229m}$Th nuclear clock

The quest for an optical nuclear frequency standard, the ‘nuclear clock’ based on the elusive and uniquely low-energetic ‘thorium isomer’ $^{229m}$Th, has increasingly triggered experimental and theoretical research activities in numerous groups worldwide in the last decade. Today’s most precise timekeeping is based on optical atomic clocks.However, those could potentially be outperformed by a nuclear clock, based on a nuclear transition instead of an atomic shell transition. Only one nuclear state is known so far that could drive a nuclear clock: the ‘Thorium Isomer $^{229m}$Th’, i.e. the isomeric first excited state of $^{229}$Th, representing the lowest nuclear excitation so far reported. Such a nuclear clock promises intriguing applications in applied as well as fundamental physics, ranging from geodesy and seismology to the investigation of possible time variations of fundamental constants and the search for Dark Matter [1].
After years of nuclear-spectroscopy driven identification and characterization activities of $^{229m}$Th, the year 2024 witnessed seminal breakthroughs with first laser-driven excitations of the isomeric nuclear resonance in $^{229}$Th, both using intense broad-band [2,3] and VUV frequency-comb based narrow-band lasers [4], respectively. Hardly any physical observable experienced an improvement by 11 orders of magnitude within only 5 years, as it was reached for the excitation energy of the thorium isomer. Hence, the question is no longer ‘Will there be a nuclear clock?’, but rather ‘Which types of nuclear clocks with which properties will be realized in the coming years?’, driven by the requirements of a variety of fundamental and applied physics applications. While recent progress with optical excitation of $^{229m}$Th was achieved via fluorescence detection in a solid-state approach using doped large-bandgap crystals and thin films [5], recently also laser-driven conversion-electron Mössbauer spectroscopy of the thorium isomer was demonstrated [6], while the complementary approach using individual laser-cooled trapped ions in vacuum is still under study.
The talk will review the status and perspectives of ongoing activities towards realizing a nuclear frequency standard based on the thorium isomer both in the solid-state and trapped $^{229m}$Th$^{3+}$ ion approach.

[1] E. Peik et al., Quantum Sci. Technol. 6, 034002 (2021)
[2] J. Tiedau et al., Phys. Rev. Lett. 132, 182501 (2024)
[3] R. Elwell et al., Phys. Rev. Lett. 133, 013201 (2024)
[4] Ch. Zhang et al., Nature 633, 63-70 (2024)
[5] Ch. Zhang et al., Nature 636, 603 (2024)
[6] R. Elwell et al., arXiv:2506.03018 (submitted to Nature)

Speaker: Prof. Peter Thirolf (Ludwig-Maximilians-University Munich)

2:00 PM Photoelectron spectroscopy of nuclear transitions

Electron dynamics play a fundamental role in the behavior of matter and underpin many essential natural phenomena. Notably, these processes are also crucial to fundamental mechanisms in nuclear physics. Nuclear states can exchange energy with surrounding electrons, and nucleus–electron couplings drive a wide range of nuclear decay processes that are of significant scientific and technological interest.

In this context, we present a Helmholtz-funded project aimed at investigating electron dynamics involved in low-energy nuclear transitions triggered by photoexcitation using various advanced light sources. Specifically, we report recent results on the photoelectron spectroscopy of nuclear excitation in the Mössbauer resonance of 57Fe, induced by resonant synchrotron radiation at PETRA III (DESY).

We also explore the potential to extend this approach to photoelectron spectroscopy of internal conversion in 229Th, using non-resonant visible-to-ultraviolet table-top laser sources. The ability to study and control electron processes in nuclear transitions through light not only deepens our understanding of fundamental physics but also opens up innovative applications across multiple disciplines. As the field advances, its convergence with broader studies of electron dynamics promises to establish a novel platform at the intersection of nuclear science, atomic physics, and photonics—poised to drive groundbreaking scientific and technological developments.

Speaker: Andrea Trabattoni (DESY and LUH)

Trabattoni_NP2025.key

Trabattoni_NP2025.pdf

2:30 PM Nuclear photo-excitation for quantum control and metrology

Nuclear physics studies atomic nuclei and their constituents and interactions. While not particularly spectacular from nuclear physics point of view, the photo-excitation of low-lying nuclear states opens the new field of nuclear quantum optics and may bring substantial progress in the field of metrology. These developments aim to exploit the fact that nuclei are very clean quantum systems, well isolated from the environment and benefiting from long coherence times. The talk will follow these perspectives at the borderline between nuclear and atomic physics on the one hand side and metrology and quantum optics on the other hand side. First, the present status of the efforts to use the unique low-lying $^{229}$Th isomer at approx. 8.34 eV for a nuclear frequency standard will be briefly discussed, including the recent experimental success in laser excitation of the so far lowest known nuclear transition energy [1].

Second, combining the advantages of x-rays and nuclei, a prominent incentive is to use nuclei to exploit x-rays as the future quantum information carriers or for novel probing technologies based on quantum effects. A tool for this are resonant nuclear transitions, for instance the 14.4 keV Mössbauer transition in $^{57}$Fe. The control of x-rays in resonant interactions can be achieved in the combination of a cavity or equivalent structured media to support the coupling to certain modes of
radiation only and an ensemble of identical scatterers that allow to gain control over the radiation via collective effects. Promising x-ray quantum optics effects have been so far observed in thin-film layered structures in both cavity [2] and recently in waveguide geometries [3]. The talk will focus on quantum control opportunities in these structures, using nuclear resonances to control single x-ray photons.

[1] C. Zhang et al., Nature 633, 63 (2024)
[2] J. Haber et al., Nature Photonics 11, 720 (2017)
[3] L. M. Lohse et al., arXiv:2403.06508 (2024)

Speaker: Prof. Adriana Pálffy (University of Würzburg, Germany)

3:00 PM → 3:30 PM Coffee break

3:30 PM → 5:20 PM Session IV

Convener: Michael Jentschel

3:30 PM Measurements of Prompt Neutron Emission from Photofission of 235U, 238U, and 239Pu

Photon-induced fission provides a mechanism for studying fission stimulated via the theoretically well understood electromagnetic interaction. The lack of hadronic processes in the entrance channel limit the angular momentum transferred to the excited nucleus prior to fission to typically 1 unit, i.e. either an electric or magnetic dipole excitation. We have performed extensive double differential (in neutron kinetic energy and angle) measurements of prompt neutrons emitted from photofission of 235U, 238U, and 239Pu.

The nearly monoenergetic incident photon beam was produced by the High Intensity Gamma-ray Source (HIGS) from 5.0 to 13.5 MeV at the Triangle Universities Nuclear Laboratory (TUNL). Measurements from 5-10 MeV used thick targets to obtain sufficient luminosity, and fission neutrons were distinguished from photoneutrons by fits to the neutron energy spectra as measured by time-of-flight. Measurements above 10 MeV used multiple active targets to tag fission fragments and form timing coincidences to isolate neutrons produced by fission. In this presentation a brief review of past photofission measurements will be given, the experiment will be described, and our results will be discussed.

*This research is supported in part by the US Department of Homeland Security under Grant No. 20CWDARI00035-01-00, the National Nuclear Security Administration under Grant Nos. DE-NA0003887 and DE-NA0004069, and by the US Department of Energy under Grant No. DE-FG02-97ER41033.

Speaker: Forrest Friesen (Duke University)

friesen_nuclear_photonics_2025_d6.pdf

4:00 PM Improved 235U, 238U, 239Pu, and 240Pu Photofission Cross Sections Across the GDR

Measurements of photofission cross sections utilizing quasimonoenergetic $\gamma$-ray beams historically rely on neutron detection, producing photoneutron data that must be sorted into the relevant reaction channels: ($\gamma$,n), ($\gamma$,2n), ($\gamma$,3n), and ($\gamma$,f). This deconvolution is a model-dependent process that has led to longstanding systematic discrepancies in photonuclear measurements from LLNL (USA) and Saclay (France), the two main laboratories performing these measurements. In order to resolve these discrepancies for a new photonuclear data evaluation, we have performed new photofission measurements
utilizing fission ionization chambers – an approach that does not depend on neutron detection. An experimental campaign was carried out at the High Intensity Gamma-ray Source (HIGS) facility at Triangle Universities Nuclear Laboratory in spring 2025. Fission ionization chambers loaded with highly enriched spectroscopic samples of $^{235}$U, $^{238}$U, $^{239}$Pu, and $^{240}$Pu were simultaneously irradiated with the quasimonoenergetic HIGS $\gamma$-ray beam for 45 incident energies from 7 to 19 MeV. The absolute $\gamma$-ray beam flux was measured with a novel mirror-paddle system, in addition to $^{197}$Au($\gamma$,n) activation measurements at select energies. The $^{238}$U($\gamma$,n) reaction cross section was also measured at select energies via activation and post-irradiation $\gamma$-ray spectroscopy. Preliminary photofission cross sections will be presented and compared with literature data.

Speaker: Forrest Friesen (on behalf of Jack Silano)

Photofission_Nuclear_Photonics.pdf

4:30 PM Electromagnetic excitations of heavy deformed nuclei with Ex=2-4 MeV studied by Monte Carlo Shell Model

Electromagnetic excitations (primarily M1 and E2) of heavy deformed nuclei, such as $^{154}$Sm, $^{166}$Er, etc., with excitation energies $E_x=2-4$ MeV will be discussed in terms of the most advanced Monte Carlo Shell Model (MCSM) calculations. For M1 excitations, the recent MCSM result indicates M1 spectrum very close to experimental ones, but we also see strong spin contributions. Such calculations can be extended to other nuclei. For E2 excitations, the triaxiality in the ground state has been clarified in a recent theoretical work, and this triaxiality induces an associated "gamma" band at high excitation energy. For instance, this results in a $2^+$ state of $E_x=2.5-3$ MeV with $B(E2; 0^+_1 \to 2^+)\sim 400~e^2 fm^4$.
We can survey this type of E2 excitation, which is stronger than usual E2 excitations to states in this energy range. Thus, the recent advancement of the MCSM calculations brings about new features to be explored by photon and/or electron scattering experiments.

Speaker: Prof. Takaharu Otsuka

5:00 PM First Data on Dipole Excitations of Pu-242 from Nuclear Resonance Fluorescence

The availability of nuclear structure information on transuranium actinides has a direct impact on the modeling of stellar nucleosynthesis and supports isotope-selective material inspection via photonuclear reactions. However, experimental data in this region are still scarce.
The first nuclear resonance fluorescence (NRF) experiment on $^{242}$Pu was conducted at the S-DALINAC at TU Darmstadt to probe its low-energy dipole response under stringent safety precautions. A $^{242}$PuO$_2$ sample with a mass of $1\,\mathrm{g}$ was irradiated with bremsstrahlung up to an endpoint energy of $3.7\,\mathrm{MeV}$. By comparing NRF spectra with measurements of the sample's activity and the natural background, photo-excited states with spin quantum number $J=1$ of $^{242}$Pu were identified. Based on the assignment of the intrinsic projection quantum number $K$ from measured decay branching ratios, evidence was found for five fragments of the $M1$ scissors mode, as well as for low-lying $E1$ excitations. Experimental details, $\gamma$-ray spectra, and first results on the most prominent transitions observed in $^{242}$Pu will be presented.

This work is supported by the DFG through the research grant GRK 2891 Nuclear Photonics under Project-ID No. 499256822.

Speaker: Maike Beuschlein (Institute for Nuclear Physics, TU Darmstadt, Germany)

NP2025_Beuschlein_main.pdf

5:30 PM → 8:00 PM Reception

Tue, October 7

9:00 AM → 10:35 AM Session I

Convener: Norbert Pietralla

9:00 AM Distributed Charge Compton Sources and the Path to Narrowband, High Brilliance Gamma Beams

Narrow-bandwidth, high-brilliance, tunable, MeV-class, x-ray sources fundamentally enable nuclear spectroscopy and applications in ways that are not possible with existing bremsstrahlung based emitters.

This presentation will review the motivation for creation of such sources based on laser-Compton scattering, outline how a distributed charge Compton scattering (DCCS) architecture can optimize performance for nuclear photonics, and review recent record results from the compact, DCCS source which has been constructed in Irvine, California.

Speaker: Prof. Christopher P.J. Barty (University of California - Irvine)

9:45 AM Exploring new possibilities in Compton sources based on free-electron lasers

Compton sources based on free-electron lasers (FELs) have a long history and have been successfully implemented for practical use, notably as gamma-ray sources utilizing storage rings. A prominent example is the High Intensity Gamma-ray Source (HIGS) facility at Duke University, which delivers tunable gamma-ray beams in the energy range of 1–100 MeV for nuclear physics experiments.
In this presentation, we explore new possibilities for Compton sources employing FELs.
One promising direction is the generation of narrow-band GeV photons using an X-ray FEL oscillator (XFELO). With recent advancements in superconducting accelerator technology, XFELOs are being actively pursued at major facilities such as the European XFEL and SLAC’s LCLS-II. Unlike conventional self-amplified spontaneous emission (SASE) XFELs, XFELOs offer highly monochromatic spectra and excellent temporal coherence. In our previous work [1], we proposed a scheme to generate narrow-band GeV photons via Compton scattering of hard X-ray photons from an XFELO. The resulting photon beam exhibits a sharp spectral peak with a bandwidth of approximately 0.1% (FWHM), attributed to the significant momentum transfer from electrons to photons. For typical parameters based on a 7-GeV electron beam operating at a 3-MHz repetition rate, the expected spectral photon density is on the order of 10² ph/(MeV·s).
Another potential application is a compact X-ray source utilizing a superradiant infrared FEL oscillator. Infrared FEL oscillators can be operated in the superradiant regime, generating few-cycle optical pulses with high conversion efficiency from the electron beam to the laser pulse. In our experimental work at KU-FEL [2], we successfully demonstrated the generation of superradiant FEL pulses. In this experiment, 19-mJ FEL pulses (peak power of 0.13 TW) were circulated in an optical cavity at a repetition rate of 30 MHz. A compact X-ray source can be realized by leveraging intra-cavity Compton scattering between these FEL pulses and the electron beam to drive the FEL. We will discuss the expected performance of the X-ray source.
[1] R. Hajima, M. Fujiwara, Phys. Rev. Acc. Beams, 19, 020702 (2016).
[2] H. Zen, R. Hajima, H. Ohgaki, Sci. Rep. 13, 6350 (2023).

Speaker: Ryoichi Hajima (National Institutes for Quantum Science and Technology)

hajima-NP2025-talk.pptx

10:15 AM High-Repetition Laser-Driven Heavy Ion Bunches for the Quantum Scalpel Injector

Laser-driven ion acceleration has gained significant attention as a next-generation acceleration technology, offering key advantages such as compactness, high accelerating electric fields, and short pulse durations. In this study, we aim to realize a novel accelerator system called the Quantum Scalpel, which combines a laser-driven heavy ion injector with a superconducting synchrotron accelerator. The Quantum Scalpel is expected to contribute to the broader deployment of heavy ion cancer therapy by enabling compact treatment systems that can be installed within existing hospital infrastructures.

This presentation reports on the development of a laser-driven ion injector capable of 10 Hz high-repetition operation using carbon ions, a representative heavy ion species. Ion acceleration was achieved by irradiating thin foil targets with a high-intensity femtosecond laser, utilizing the Target Normal Sheath Acceleration (TNSA) mechanism. To support continuous high-repetition operation, we implemented automated target delivery, debris shielding, and optimization of laser temporal contrast. These improvements collectively enabled stable and sustained generation of heavy ion bunches suitable for injection into downstream accelerator stages.

Speaker: Dr Sadaoki Kojima (KPSI, QST)

10:35 AM → 11:00 AM Coffee break

11:00 AM → 1:00 PM Session II

Convener: Andrea Trabattoni

11:00 AM Explorations in nuclear photonics with X-ray lasers

Accelerator-driven X-ray sources had a profound impact on the applications of the Mössbauer effect in all natural sciences. The enormous brilliance of X-rays delivered by these sources enabled access to smallest amounts of materials under extreme conditions and allowed for studies with time resolution and polarization sensitivity that were virtually impossible in the lab. In this way it was possible, for example, to transfer concepts of quantum optics into the regime of hard X-rays [1]. With the advent of ever brighter sources, especially X-ray lasers, this research field continues to expand and flourish. In this presentation I will describe new regimes of nuclear photonics in the low-energy (Mössbauer) regime around a few 10 keV, ranging from anomalies in coherent nuclear forward scattering to the excitation of nuclear clock isomers like Scandium-45 [2].

[1] Ralf Röhlsberger et al., Nature 482, 199 (2012)
[2] Yuri Shvyd’ko, Ralf Röhlsberger, Olga Kocharovskaya, Jörg Evers et al., Nature 622, 472 (2023)

Speaker: Ralf Röhlsberger (Helmholtz Institut Jena)

NuclearPhotonics2025_Röhlsberger_v3.pdf

NuclearPhotonics2025_Röhlsberger_v3.pptx

11:30 AM Nuclear resonance spectroscopy at X-ray free electron lasers

Probing resonances in Mössbauer nuclei with x-rays or γ-rays is widely used to study structure and dynamics of matter with a remarkably high energy resolution. So far, most experiments use radioactive or synchrotron radiation sources. In the past few years, self-seeded X-ray free electron lasers have become available, which provide qualitatively new conditions for studying interactions of the nuclei with the intense x-ray radiation.

In this talk, I will review our recent theoretical and experimental progress in exploring the new capabilities for nuclear resonance scattering offered by the XFELs. These can broadly be classified into methods relying on the exceptionally high number of nuclear-resonant photons per second (average flux), or per x-ray pulse (peak flux).
As an example for the high average flux per second, I will briefly discuss the recent direct resonant X-ray excitation of the Mössbauer clock transition in $^{45}$Sc [1].

The high peak flux leads to a disruptive change in experimental conditions, from less than one resonant photon per pulse at synchrotrons to several hundreds at XFELs. To explore these capabilities, the $^{57}$Fe EuXFEL collaboration (led by R. Röhlsberger and J. Evers) has established nuclear resonance scattering on $^{57}$Fe in a series of experiments at the European X-ray free electron laser. As a first result, I will discuss an experiment which demonstrates the possibility to record entire Mössbauer datasets with single XFEL pulses. This new “single-shot” capability opens perspectives for the exploration of nonequilibrium phenomena using the Mössbauer effect, by disentangling different possible system evolution pathways from out-of-equilibrium back to equilibrium on the level of individual x-ray pulses [2].

Finally, I will revisit the old question if it is possible to fully invert an ensemble of nuclei using electromagnetic fields, in light of the new XFEL conditions and recent developments in nuclear quantum optics. In particular, I will discuss the interaction of strongly focused x-ray pulses with ensembles of nuclei embedded in an x-ray waveguide [3].

[1] Y. Shvyd’ko et al., “Resonant x-ray excitation of the nuclear clock isomer $^{45}$Sc”, Nature 622 (2023) 471.
[2] M. Gerharz et al., “Single-shot sorting of Mössbauer time-domain data at X-ray free electron lasers”, submitted
[3] D. Lentrodt, C. H. Keitel, and J. Evers, “Towards nonlinear optics with Mössbauer nuclei using x-ray cavities”, Phys. Rev. Lett. in print (2025)

Speaker: Prof. Jörg Evers (MPI Heidelberg, Germany)

evers.pdf

12:00 PM Transition Edge Sensors for Antiprotonic Atom X-ray Spectroscopy in the few hundred keV regime

The advent of quantum sensing x-ray microcalorimeters such as Transition Edge Sensors (TESs) [1] has created exciting new opportunities to push the limits of precision physics in the hard x-ray domain. Thanks to the factor of 50 improvement in energy resolution offered by TESs over high-purity germanium [2, 3], and their high efficiency compared to crystal spectrometers [4], anti-protonic atom x-ray spectroscopy has entered a new era compared to the previous generation of experiments. The PAX project (anti-Protonic Atom X-ray spectroscopy) will employ a next-generation TES detector for spectroscopy of transitions between circular Rydberg states in antiprotonic atoms to establish new benchmarks for bound-state QED at field strengths well beyond the Schwinger limit with a precision of $10^{-5}$ in the few hundred keV regime [5]. Details of the PAX experiment at the CERN’s ELENA facility [6,7] and preliminary results from the test beam conducted in 2025 including unique challenges for detector development related to annihilation and electromagnetic background will be discussed.

[1] Review of superconducting transition-edge sensors for x-ray and gamma-ray spectroscopy, J.N. Ullom and D.A. Bennett. Supercond. Sci. Tech. 28, 084003 (2015).
[2] Recent Results on Antiprotonic Atoms using a Cyclotron Trap at LEAR, L.M. Simons. Physica Scripta 1988, 90 (1988).
[3] X-ray transitions from antiprotonic noble gases, D. Gotta, K. Rashid, B. Fricke, P. Indelicato and L.M. Simons. Eur. Phys. J D 47, 11-26 (2008).
[4] Balmer a transitions in antiprotonic hydrogen and deuterium, D. Gotta, D.F. Anagnostopoulos, M. Augsburger, G. Borchert, C. Castelli, D. Chatellard, J.P. Egger, P. El-Khoury, H. Gorke, P. Hauser, P. Indelicato, K. Kirch, S. Lenz, T. Siems and L.M. Simons. Nucl. Phys. A 660, 283-321 (1999).
[5] Testing Quantum Electrodynamics with Exotic Atoms, N. Paul, G. Bian, T. Azuma, S. Okada and P. Indelicato. Phys. Rev. Lett. 126, 173001 (2021).
[6] The ELENA facility, W. Bartmann, P. Belochitskii, H. Breuker, F. Butin, C. Carli, T. Eriksson, W. Oelert, R. Ostojic, S. Pasinelli and G. Tranquille. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, 20170266 (2018).
[7] Towards Precision Spectroscopy of Antiprotonic Atoms for Probing Strong-field QED, Gonçalo Baptista, Shikha Rathi, Michael Roosa, Quentin Senetaire, Jonas Sommerfeldt, Toshiyuki Azuma, Daniel Becker, Francois Butin, Ofir Eizenberg, Joseph Fowler, Hiroyuki Fujioka, Davide Gamba, Nabil Garroum, Mauro Guerra, Tadashi Hashimoto, Takashi Higuchi, Paul Indelicato, Jorge Machado, Kelsey Morgan, Francois Nez, Jason Nobles, Ben Ohayon, Shinji Okada, Daniel Schmidt, Daniel Swetz, Joel Ullom, Pauline Yzombard, Marco Zito, Nancy Paul. Proceedings of Science: In submission; arXiv:2501.08893

Speaker: Dr Michael Roosa (Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University)

Roosa _NP2025.pdf

12:30 PM Manipulating nuclear transition on demand

One of the uncharted territories in nuclear physics concerns a thrilling frontier in the study of systems where particles interact with relatively low-energy (< 20 MeV) yet extraordinarily high-intensity fields. In such environments, multi-particle processes rival and surpass traditional one-to-one interactions, opening the door to groundbreaking discoveries.
Here, we focus on a new scheme that enables the control of nuclear transitions on demand. The high-power laser systems are exploited as a driver to generate energetic (gamma-ray) photons. Together with additional low-energy photons provided by a second, less intense laser, a multi-photon absorption scheme enables a very attainable manipulation of nuclear transitions including isomer pumping and depletion. Furthermore, the technique can potentially be utilized to uncover hidden states and rare transitions in the nuclei as well as to realize stimulated amplification of $\gamma$-rays (graser). Realistic calculations suggest that the aforementioned sensational events could be realized already on those sites equipped with PW-class high-power laser systems.

Speaker: chieh-jen yang (eli-np)

nuclear_photonics2025.pdf

1:00 PM → 2:00 PM Lunch break

2:00 PM → 3:50 PM Session III

Convener: Gianluca Colo

2:00 PM Nuclear response to electromagnetic probes: toward spectroscopically accurate many-body theory

I will present selected results on nuclear giant and pygmy resonances at zero and finite temperatures, based on recent advancements in nuclear many-body theory [1-6]. The theory will be compactly introduced in the most general quantum field theory formalism with only the bare fermionic interaction input. A special focus will be placed on the emergent scale of the quasiparticle-vibration coupling (qPVC) with the order parameter associated with the qPVC vertex. An efficient treatment of the nuclear many-body problem is thus organized around the qPVC hierarchy, which takes over the power counting, dominating the bare nucleon-nucleon interaction and few-body systems [1-3].

Self-consistent solutions of the relativistic Bethe-Salpeter-Dyson equation (BSDE) for the nuclear response function in medium-heavy nuclei will be presented and discussed. In this formulation, the dynamical interaction kernel of the BSDE is the source of the richness of the nuclear wave functions in terms of their con guration complexity and the major ingredient for an accurate description with quanti ed uncertainties. Low-multipolarity resonances in calcium, nickel, and tin mass regions will be analyzed in the context of the role of high-complexity configurations in reproducing spectral data [2,3,7]. Finite-temperature theory and implementations will be discussed in light of their astrophysical relevance [4-6]. Finally, I will outline the prospect of the quantum equation of motion to generate complex configurations, based on the example of the solvable Lipkin Hamiltonian [3].

[1] E. Litvinova and Y. Zhang, Microscopic response theory for strongly-coupled superfluid fermionic systems, Phys. Rev. C 106, 064316 (2022).
[2] E. Litvinova, On the dynamical kernels of fermionic equations of motion in strongly-correlated media, Eur. Phys. J. A59, 291 (2023).
[3] J. Novak, M. Q. Hlatshwayo, and E. Litvinova, Response of strongly coupled fermions on classical and quantum computers, arXiv:240502255.
[4] E. Litvinova and H. Wibowo, Finite-temperature relativistic nuclear field theory: an application to the dipole response, Phys. Rev. Lett. 121, 082501 (2018).
[5] E. Litvinova, C. Robin, and H. Wibowo, Temperature dependence of nuclear spin-isospin response and beta decay in hot astrophysical environments, Phys. Lett. B800, 135134 (2020).
[6] S. Bhattacharjee and E. Litvinova, Finite-temperature microscopic response theory for strongly-coupled superfluid fermionic systems, arXiv:2412.20751.
[7] M. Markova, P. von Neumann-Cosel, and E. Litvinova, Systematics of the low-energy electric dipole strength in the Sn isotopic chain, Phys. Lett. B860, 139216 (2025).

Speaker: Prof. Elena Litvinova (Western Michigan University)

Photonics-2025-a.pdf

2:30 PM Deviations from the Porter-Thomas distribution due to non-statistical $\gamma$ decay

Random Matrix Theory provides a comprehensive framework for the description of complex, chaotic quantum systems [1,2]. It is exploited across various domains of physics as for instance in the statistical treatment of nuclear reactions within the Hauser-Feshbach formalism [3]. One important aspect in the practical application of Hauser-Feshbach codes is the fluctuation property of partial transition widths. Experimentally, the applicability of so-called Porter-Thomas (PT) fluctuations [4] has been extensively studied in thermal neutron capture experiments [5]. Former analyses of the nuclear data ensemble (NDE) of neutron resonances [5] validate the PT distribution. Recent studies and thorough reanalyses of the NDE revealed significant deviations from PT predictions [6] partially explained by non-statistical $\gamma$ decays. Neutron resonances provided a vast amount of precision data on fluctuation properties of nuclear resonances. However, no experimental data exist, to date, for width fluctuations \textit{below} neutron separation thresholds. This region is particularly interesting because it contains the onset of the quasicontinuum region. There, the nuclear spectra transition from a few individual states at low excitation energies to an ensemble of states at high excitation energies. The latter are assumed to be well described by the ansatz of the Hauser-Feshbach statistical model.
In this contribution, we introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly-polarized photon beams below particle separation thresholds [7]. Assuming (\chi^2)-distributed partial transition widths, average branching ratios of internal $\gamma$ decay transitions are related to the degree of freedom $\nu$ of the (\chi^2) distribution. Recent studies with $^{150}$Nd result in a degree of freedom of (\nu = \num{1.93(12)}) in clear disagreement with the PT distribution [8,9]. The recent findings will be discussed in the context of non-statistical effects in the (\gamma)-decay behavior that are potentially connected to the survival of good $K$ quantum numbers in the covered excitation-energy region.

This work is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 279384907 - SFB~1245, Project-ID 460150577 - ZI 510/10-1, and Project-ID 499256822 - GRK~2891 “Nuclear Photonics”, by the State of Hesse under the grant “Nuclear Photonics” within the LOEWE program (LOEWE/2/11/519/03/04.001(0008)/62), by the BMBF under grant number 05P21RDEN9. Furthermore, this work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under grants DE-SC0023010, DE-FG02-97ER41041 (UNC), and DE-FG02-97ER41033 (Duke, TUNL), and by the UK-STFC (Grant No. ST/P005101/1).

[1] H. A. Weidenmüller and G. E. Mitchell, Rev. Mod. Phys. 81, 539 (2009).
[2] T. Guhr, A. Müller-Groeling, and H. A. Weidenmüller, Phys. Rep. 299, 189 (1998).
[3] W. Hauser and H. Feshbach, Phys. Rev. 87, 366 (1952).
[4] C. E. Porter and R. G. Thomas, Phys. Rev. 104, 483 (1956).
[5] R. U. Haq, A. Pandey, and O. Bohigas, Phys. Rev. Lett. 48, 1086 (1982).
[6] P. E. Koehler, Phys. Rev. C 84, 034312 (2011).
[7] A. Zilges, D. Balabanski, J. Isaak, and N. Pietralla, Prog. Part. Nucl. Phys. 122, 103903 (2022).
[8] O. Papst, J. Isaak, V. Werner, D. Savran, N. Pietralla, G. Battaglia, T. Beck, M. Beuschlein, S. W. Finch, U. Friman-Gayer, K. E. Ide, R. V. F. Janssens, M. D. Jones, J. Kleemann, B. Löher, M. Scheck, M. Spieker, W. Tornow, R. Zidarova, and A. Zilges, accepted for publication in Phys. Rev. Lett. (2025).
[9] O. Papst, J. Isaak, V. Werner, D. Savran, N. Pietralla, G. Battaglia, T. Beck, M. Beuschlein, S. W. Finch, U. Friman-Gayer, K. E. Ide, R. V. F. Janssens, M. D. Jones, J. Kleemann, B. Löher, M. Scheck, M. Spieker, W. Tornow, R. Zidarova, and A. Zilges, (2025), arXiv:2501.19185 [nucl-ex].

Speaker: Johann Isaak (Technische Universität Darmstadt, Institut für Kernphysik)

3:00 PM Photon strength functions and nuclear level densities at the ELI-NP/IFIN-HH facilities

The $\gamma$-ray beam under construction at the ELI-NP facility is projected to provide users with high-energy, high-intensity and narrow bandwidth photon beams for nuclear structure studies. Two major topics that can be studied at such a facility, with the almost complete selectivity of electromagnetic probes, are high-precision measurements of nuclear $J^{P}=1^{-}$ level densities and the electric dipole photon strength functions. In parallel to the ongoing construction of the ELI-NP photon beams, an experimental program of complementary measurements of photon strength functions and nuclear level densities with charged particle probes has started at the 9~MV Tandem facilities at IFIN-HH using large-volume scintillator detectors from ELI-NP [1]. This is an important preparatory step for the ELI-NP photon beams, in addition to being a complementary technique where photon probes and hadronic probes can be used together to extract as model-independent data as possible on these quantities.

In a first experiment in 2023, we measured photon-ray strength functions and nuclear level densities of ${}^{112,114}$Sn for the first time at the 9~MV Tandem accelerator facilities at IFIN-HH using the Oslo method [2]. Comparisons with the quasiparticle-phonon model results show the importance of complex configurations to the low-energy dipole response in the pygmy dipole resonance energy region. The experimental data are further included in the cross-section and reaction rate calculations for the $(\mathrm{n},\gamma)$ reaction, showing a significant increase in reaction rates at high temperatures. In a second $(\mathrm{p},\mathrm{p} '\gamma)$ scattering experiment in 2024, we have extracted the nuclear level density of ${}^{128}$Te [3]. Here, the decay data were normalised using photonuclear data, resulting in nuclear level densities without intrinsic model dependencies from the constant temperature or Fermi gas models, showing the potential of complementary experiments with photon beams and charged particle beams for the future ELI-NP facility. In a third experiment, scheduled for June 2025, we intend to measure the nuclear level densities and photon strength functions of $^{140}$Ce using the same methods. This measurement will continue comparing the nuclear level densities obtained in photonuclear reactions with those determined from proton-beam data.

[1] S. Aogaki, et al. Nucl. Instrum. Methods Phys. Res. A 1056 (2023) 168628
[2] P.-A. Söderström, et al. Phys. Rev. C, in print
[3] P.-A. Söderström, et al. Phys. Scripta, in print

On behalf of the 2023, 2024, 2025 joint ELI-NP/Nuclear Physics Department IFIN-HH experimental collaborations

This work was supported by the ELI-RO program funded by the Institute of Atomic Physics, Măgurele, Romania, contract number ELI-RO/RDI/2024-002 (CIPHERS) and the Romanian Ministry of Research and Innovation under
research contract PN 23 21 01 06.

Speaker: Pär-Anders Söderström (ELI-NP/IFIN-HH)

np2025.pdf

3:20 PM Excited 0+ Levels, Spin-4 States, and Everything In-Between in 68Zn with Nuclear Resonance Fluorescence

Driven by recent advances in the understanding of coexisting shapes in the even-even Ni isotopes, the structure of neighboring $^{68}$Zn was investigated using nuclear resonance fluorescence. Low-spin levels were excited using linearly polarized photon beams at energies ranging from 3 MeV to the particle threshold using the High Intensity $\gamma$-Ray Source (HI$\gamma$S). In addition, $\gamma-\gamma$ coincidence data enabled the study of the low-energy level scheme, populated from a high-energy and low-spin entrance point just below the particle emission threshold. The new data resulting from this work are interpreted in the shell-model picture in two different model spaces using several effective interactions. The distribution of $E1$ levels and $M1$ strength, paired with properties of the low-energy level scheme, reveal the involvement of a large number of orbitals active across a wide range of excitation energies in $^{68}$Zn. The coincidence capabilities of the Clover Array at HI$\gamma$S are explored, with highlights including the population of low-energy states with spins $J=0-4$ and the potential of lifetime measurements with the CeBr$_3$ scintillators.

This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Grants No. DE-FG02-97ER41041 (UNC), and No. DE-FG02-97ER41033 (TUNL), and by the U.S. National Science Foundation under Grant No. PHY-2110365 (FRIB, MSU).

Speaker: Samantha Johnson (University of North Carolina at Chapel Hill and Triangle Universities Nuclear Laboratory)

NuclearPhotonics2025_SJohnson.pdf

NuclearPhotonics2025_SJohnson.pptx

3:50 PM → 4:20 PM Coffee break

4:20 PM → 5:50 PM Session IV

Convener: Vincent Bagnoud

4:20 PM Advances in Direct Laser Acceleration: High-Brightness X-ray and Neutron Sources via Plasma Guiding, High-Z Targets, and Flying Focus Pulses

Intense lasers enable a range of schemes for generating high-energy particle beams in university-scale laboratories. In direct laser acceleration (DLA), the leading edge of the laser pulse ionizes the target material, forming a positively charged plasma channel that traps and accelerates electrons. DLA offers exceptional conversion efficiency — often exceeding 20% — making it highly suitable for driving secondary radiation sources. This talk reviews recent advances aimed at pushing the efficiency and applicability of DLA for X-ray and neutron generation.

I will present experimental and numerical studies showing how DLA performance can be enhanced by tailoring the target’s atomic number to sustain electron injection, and by employing flying-focus pulses to stabilize the plasma channel and extend the acceleration length.

Building on these developments, I will demonstrate how high accumulated neutron yields were achieved via bremsstrahlung from MeV electron beams in high-repetition-rate laser shots, and how a bright Compton X-ray source can be realized using counter-propagating pulses in a near-critical plasma plume.

The talk will conclude with projections for scaling these approaches to the multi-petawatt regime, where improved overlap between electron energies and neutron production cross-sections is expected to enable non-destructive material analysis and support industrial applications.

Cohen, I., et. al, Undepleted direct laser acceleration, Sci. Adv.10,eadk1947(2024).
Cohen, I., et. al, Multi-scale analytical description of an expanding plasma slab, Physics of Plasmas 31.1 (2024).
Meir, T., et. al, Plasma-guided Compton source, Physical Review Applied, 22(4), p.044004 (2024).
Cohen, I., et. al, Accumulated laser-photoneutron generation, The European Physical Journal Plus, 139(7), pp.1-7(2024).

Speaker: Prof. Ishay Pomerantz (Tel Aviv University)

4:50 PM Enhanced Isomer Population in Solid-Density Targets using Laser-Plasma Accelerators

Excitation of long-lived states in bromine nuclei using a table-top laser-plasma accelerator providing pulsed (<100 fs) electron beams provided a sensitive probe of gamma strength and level densities in the nuclear quasicontinuum, and may indicate angular momentum coupling through electron-nuclear interactions. Solid-density LaBr$_{3}$ active targets absorb real and virtual photons up to 35 ± 2.5 MeV and de-excite through gamma cascade into different states. A factor of 4.354 ± 0.932 enhancement of the $^{80m}$Br/$^{80g}$Br isomeric ratio was observed following electron irradiation, as compared to bremsstrahlung. Additional angular momentum transfer could possibly occur through nuclear-plasma or electron-nuclear interactions enabled by the ultra-short electron beam. Extension of this enhanced angular momentum coupling into heavy nuclei is being explored as a potential method for production of $^{225}$Ac, an isotope of strong interest to the radiopharmaceutical and research communities, through the enhanced alpha-decay of $^{229}$Th.

Speaker: Robert Jacob (Lawrence Berkeley National Laboratory)

RJacob_NP2025.pdf

5:20 PM Broadband MeV to multi-GeV 10 PW laser-driven gamma-rays generation, characterization and possible applications

Broadband MeV to multi-GeV 10 PW laser-driven gamma-rays generation, characterization and possible applications
V. Lelasseux1, P. Ghenuche$^1$, V.L.J. Phung$^1$, H. Ahmed$^2$, D.L. Balabanski$^1$, M.O. Cernaianu$^1$, D. Choudhury$^{1,3}$, S. Corde$^{4,5}$, F. D’Souza$^{1,6}$, M. Gugiu$^1$, V. Iancu$^1$, S. Krishnamurty$^7$, I. Kargapolov$^7$, L. Lancia$^8$, G. Lorusso$^9$, A. Leblanc$^4$, V. Malka$^{1,7}$, J.R. Marques$^8$, Y. Nakamiya$^1$, F. Rotaru$^1$, K. Ta Phuoc$^{10}$, A.M. Talposi$^7$
1. Extreme Light Infrastructure – Nuclear Physics (ELI-NP), Horia Hulubei National Institute for R&D in Physics and Engineering (IFIN-HH), 30 Reactorului Str., 077125 Bucharest-Magurele, Romania
2. Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
3. Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001, India
4. Laboratoire d’Optique Appliquée, ENSTA Paris, CNRS, École Polytechnique, Institut Polytechnique de Paris, 91762 Palaiseau, France
5. SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
6. Department of Physics, Lund University, P.O. Box 118, SE-22100, Lund, Sweden
7. Weizmann Institute of Science, 7610001 Rehovot, Israel
8. LULI, CNRS, École Polytechnique, CEA, Sorbonne Université, Institut Polytechnique de Paris, 91128 Palaiseau, France
9. National Physical Laboratory, Teddington TW11 0LW, United Kingdom
10. CELIA, Université de Bordeaux-CNRS-CEA, 33405 Talence, France

Recent advancements in high intensity laser technology, with the advent of multi-PW facilities around the world [1], is allowing the investigation of multiple regimes to produce various compact high intensity particle sources [2,3,4,5]. Among the most promising techniques, the use of a multi-GeV electron beam accelerated through Laser WakeField Acceleration (LWFA) [6] to produce a secondary photon beam through a variety of processes (Bremsstrahlung [7], reverse Compton scattering [8], betatron radiation [9]) has been investigated during several experimental campaigns in the 10 PW long focal experimental area of ELI-NP. Due to the bunched nature of those photon beams, classical germanium or scintillator-based photon by photon detectors cannot be used, rendering the beam characterization in itself challenging. To circumvent this difficulty, diagnostics using scintillator stacks have been developed [10]. We will report here on the effort done at ELI-NP to develop a reliable gamma spectrometer adapted to this high intensity laser environment as well as the results it obtained during the commissioning campaigns of the 10 PW long focal experimental area.

References:
[1] C. N. Danson et al, Petawatt and exawatt class lasers worldwide, High Power Laser Science and Engineering 7, e54 (2019)
[2] E. Rockafellow et al, High charge laser accelerations of electrons to 10 GeV, Nucl. Instr. and Meth. A, 170586 (2025)
[3] M. Mirzaie et al, All-optical nonlinear Compton scattering performed with a multi-petawatt laser, Nat. Phot. 18(11), 1212-1217 (2024)
[4] T. Ziegler et al, Laser-Driven high-energy proton beams from cascading acceleration regimes, Nat. Phys. 20(7), 1211-1216 (2024)
[5] F. Zhang et al, Proof-of-principle demonstration of muon production with an ultrashort high-intensity laser, Nat. Phys. 1-7 (2025)
[6] T. Tajima and J.M. Dawson, Laser Electron Accelerator, Phys. Rev. Lett. 43, 267 (1979)
[7] A. Compant La Fontaine, C. Courtois and E. Lefebvre, Phys. Plas. 19(2) (2012)
[8] K. Ta Phuoc et al, All-optical Compton gamma-ray source, Nat. Phot. 6(5), 308-311 (2012)
[9] J. Ferri et al, High-Brilliance betatron gamma-ray source powered by laser-accelerated electrons, Phys. Rev. Lett. 120(25), 254802 (2018)
[10] G. Fauvel et al, Compact in-vacuum gamma-ray spectrometer for high-repetition rate PW-class laser-matter interaction, Rev. Sci. Instr. 96(2) (2025)

Speaker: Vincent Lelasseux (ELI-NP, IFIN-HH)

Presentation_Nuclear_Photonics.pdf

6:00 PM → 8:00 PM Poster Session

Wed, October 8

8:45 AM → 10:15 AM In memoriam of Prof. Sydney Gales

Convener: Calin Ur

8:45 AM Introductory remarks

8:55 AM Operational Performance and Experimental Advancements at the ELI-NP 10 PW Laser Facility for Nuclear Photonics Applications

The Extreme Light Infrastructure – Nuclear Physics (ELI-NP) has established itself as a world-leading facility by operating the first dual-arm 10 petawatt (PW) laser system, HPLS, which serves as a cornerstone for experimental nuclear photonics research. In 2024 alone, ELI-NP achieved 67 operational weeks of beam delivery for users, including 30 weeks at full 10 PW output at a 1 shot/minute repetition rate. The E6 experimental area supported experiments targeting electron acceleration, Compton backscattering, and muon production using a gaseous target, reaching up to 274 shots per day. This operational throughput represents a milestone for high-repetition-rate ultraintense laser facilities and demonstrates ELI-NP’s capacity for robust experimental deployment.
Beyond high energy output, HPLS provides optically synchronized 2×1 PW beams at 1 Hz with <11 fs pulse duration in the E5 experimental area. This capability enables novel dual-beam configurations for simultaneous generation of proton and electron bunches, facilitating secondary radiation production (x-rays, neutrons). A regenerating liquid target delivery system in vacuum is under implementation, set to support high-repetition-rate irradiation for radiation hardness testing of inertial fusion materials.
Ongoing developments include beam shaping and control via spatio-temporal coupling diagnostics, structured light fields (e.g., helical beams), and coherent combination techniques. These efforts aim to enhance experimental precision, optimize intensity delivery, and advance the field of strong-field QED and laser-plasma interaction physics. The ELI-NP infrastructure thus serves as a unique platform for both fundamental and application-driven advances in nuclear photonics.

Speaker: Dr Daniel Ursescu (UNSTPB)

9:25 AM Progress on laser-driven dual neutron-X-ray radiography

We will present results aimed at enabling a novel dual (neutron and x-ray) interrogation method, based on ultra-intense lasers irradiating solid targets. The objective is to
perform dense material probing, while also supporting imaging of high speed events. The concept is to produce both a bright X-ray source
appropriate for high-resolution radiography from thin primary (pitcher) targets optimized for proton acceleration, and high-yield neutron sources with a secondary (catcher) target. We will present results obtained both at Apollon (France) and ELI-NP (Romania), characterizing the neutrons generated at the PW level at and demonstrating that their yield is adequate for material probing, as well as characterizing the produced X-rays in the same regime. The latter are the first quantitative measurements of X-ray spectra and angular distribution in the novel ultra-relativistic regime of very short pulse durations (20 fs) and ultra-high intensity (10^22 W/cm^2).

Speaker: Ishay Pomerantz (on behalf of Julien Fuchs)

9:55 AM Energy-Resolved Photoresponse of the Nuclear Giant Dipole Resonance: Circumstantial Evidence for its Sub-Zeptosecond Lifetime

The giant dipole resonance (GDR) of atomic nuclei dominates their response to an oscillating electromagnetic radiation field. It represents the archetype of a collective nuclear mode. It is particle unbound and decays predominantly by particle emission. Its (small) probability for internal decay by gamma-ray emission is proportional to the maximum of its photon absorption cross section.
Our group has recently conducted photon-scattering spectroscopy on the GDR of heavy spherical nuclei (Ce-140 and Pb-208) and deformed nuclei (Sm-154, Dy-164, and Th-232). For the first time, the data utilize quasimonochromatic gamma-ray beams and cover the entire energy range of the GDR. Our data show that exclusively its photon decay is sensitive to the very character of this collective mode and provide circumstantial evidence that the GDR decays on a sub-zeptosecond timescale into compound states as it was conjectured by Niels Bohr [2] more than 80 years ago.

[1] J.Kleemann, NP, et al. Phys. Rev. Lett. 134, 022503 (2025); J. Kleemann, Probing the Giant Dipole Resonance Using Nuclear Resonance Fluorescence (Dissertation, Technische Universität Darmstadt 2024),10.26083/tuprints-00027008.
[2] Niels Bohr, Nature 141, 326 (1938).

This work has been supported by DFG Project No. 279384907–SFB 1245, 499256822-GRK 2891 "Nuclear Photonics", and U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Grants No. DE-FG02-97ER41041 (UNC), and No. DE-FG02-97ER41033 (Duke, TUNL).

Speaker: Norbert Pietralla (TU Darmstadt)

Pietralla-talk_GDR.pdf

Pietralla-talk_GDR.pptx

10:15 AM → 10:35 AM Coffee break

10:35 AM → 11:55 AM Session II

10:35 AM A Theoretically Grand Tour of Compton Scattering and Nucleon Polarisabilities

I review the theory side of the synergetic international effort of experimentalists and theorists in Compton scattering on one- and few-nucleon systems. It probes the symmetries and strengths of nucleonic and nuclear interactions and relates them to lattice-QCD computations of fundamental hadronic properties. The polarisabilities parametrise the stiffness of charge distributions against deformations. Their spin components encode the stiffness of the spin in external electro-magnetic fields (nucleonic Faraday effect) and probe the spin-dependent component of the pion-nucleon interaction. As the scalar components are crucial for the proton-neutron mass difference, we focus on the prediction and extraction of their neutron values from few-nucleon experiments which also test the chiral symmetry of the charged pion-exchange contribution to nuclear binding. Precision theory is available for the proton and deuteron. For the first-ever descriptions of Compton scattering on $^3$He, $^4$He and $^6$Li, the transition-density formalism is highly efficient for computing reactions with perturbative probes. One- and two-body transition densities that encode the nuclear structure of the target are evaluated once and stored. They are then convoluted with an interaction kernel to produce observables, exploiting factorisation between nuclear structure and interaction kernel in Chiral EFT. The same densities can be used with different kernels, like pion-photoproduction and pion scattering. We summarise the prospects and identify kinematics and observables for the likely biggest improvement of the polarisability values.

Speaker: Prof. Harald W. Griesshammer (Institute for Nuclear Studies, Department of Physics, George Washington University, Washington DC)

griesshammer.polarisabilities.pdf

11:05 AM Proton & Neutron Polarizabilities with Compton Scattering from Low-Mass Nuclear Targets at the High Intensity Gamma-ray Source (HIGS)

The Compton@HIGS collaboration is embarking on a program of absolute differential cross-section measurements of elastic Compton scattering from 1H [1], 2H, 3He, and 4He [2,3] nuclei over a wide range of scattering angles at energies below the pion production threshold. Using a Chiral Effective Field Theory (𝜒EFT) framework [4], we can extract the electric and magnetic polarizabilities of protons and neutrons. These quantities characterize the response of a nucleon’s internal degrees of freedom to external electromagnetic fields and offer insight into its internal dynamics. They provide stringent tests of Quantum Chromodynamics (QCD) at low energies in the non-perturbative regime, serving as a bridge between EFTs and lattice QCD calculations, which can now be performed at the physical pion mass [5]. Proton polarizabilities are also an important input in determining the proton charge radius. Despite their significance, these quantities remain relatively poorly constrained; for example, the neutron’s electric and magnetic polarizabilities (𝛼n and 𝛽n) are known to approximately ±10% and ±30%, respectively. While the proton’s electric and magnetic polarizabilities (𝛼p and 𝛽p) are better known, there is an approximate 2𝜎 tension between our recent proton electric polarizability result and that from MAMI [6].

To measure these nanobarn-scale cross-sections at the few-percent level, our collaboration uses ~ 60–110 MeV monoenergetic, linearly or circularly polarized photon beams from the free-electron-laser-based High Intensity Gamma-ray Source (HIGS) at the Triangle Universities Nuclear Laboratory (TUNL). This is combined with an array of large NaI detectors—featuring single-crystal cores up to ~ 90 L in size—and a cryogenic liquid target system capable of reaching temperatures down to ~ 1.5 K. The target includes optical access and thin-walled, low-background windows to a 0.3-liter-sized liquid cell. In the summer of 2024, we completed our first runs with liquid 3He at nominal energies of 60 MeV and 100 MeV, safely handling 350 STP-bar-L of 3He inventory, and achieved our operational temperature and stability goals. These results should improve our uncertainties in 𝛼n and 𝛽n by approximately a factor of two. In parallel, we have initiated R&D efforts for a scintillating polarized proton target, which is essential for our future intent to measure proton spin polarizabilities.

[1] Li et al. (Compton@HIGS), Phys. Rev. Lett. 128, 132502 (2022)
[2] Sikora et al. (Compton@HIGS), Phys. Rev. C 96, 055209 (2017)
[3] Li et al. (Compton@HIGS), Phys. Rev. C 101, 034618 (2020)
[4] Griesshammer et al., Prog. Part. Nucl. Phys. 67, 841 (2012)
[5] Wang et al., Phys. Rev. Lett. 133, 141901 (2024).
[6] Mornacchi et al., Phys. Rev. Lett. 128, 132503 (2022)

Speaker: Prof. Kent Leung (Montclair State University, Department of Physics & Astronomy, Montclair, USA)

Kent Leung - Nuclear Photonics Compton HIGS.pdf

11:35 AM First observation of $\gamma$-ray beam production via Compton scattering of undulator X-rays in an electron storage ring

For the first time, we succeeded in observing the $\gamma$-ray beam production via Compton scattering of X-rays at an electron storage ring. Compared with laser Compton scattering, the X-ray Compton scattering is attractive because $\gamma$-ray energies can be drastically increased approaching to the ring energy. We developed a new innovative $\gamma$-ray beam source at NewSUBARU, which is a 1 GeV storage ring. Soft X-rays of 92 eV was obtained from an undulator, and was reflected back to the original ring by a Mo/Si multilayer mirror, whose reflectance reached 65.8% with a concave refractive surface to make a focus at the scattering point. Our method is unique and cost-effective by completing all the processes at one beamline.

Recently, we conducted a demonstration experiment of the X-ray Compton scattering. The reflected X-ray direction was optimized by precision rotary stages attached to the multilayer mirror. The $\gamma$-ray energy spectrum was measured by a PWO calorimeter with and without X-ray reflection to subtract a residual-gas bremsstrahlung radiation background. As a result, a clear Compton spectrum was observed with a significance of 12.5$\sigma$, showing the Compton edge of 0.543 GeV as predicted. The $\gamma$-ray production rate of X-ray Compton scattering was 1.36 kcps for the energies above 0.160 GeV and quantitatively understood from the luminosity with the known cross section. This achievement is applicable, for instance, to SPring-8-II, where the maximum $\gamma$-ray energy can be raised up to 5.4 GeV with 92 eV X-rays for the next-generation hadron photoproduction experiments.

Speaker: Norihito Muramatsu (Institute of Modern Physics, Chinese Academy of Sciences)

np2025mura_v2.pptx

11:55 AM → 12:25 PM Lunch break

12:25 PM → 4:00 PM Excursion

Thu, October 9

9:00 AM → 10:45 AM Session I

Convener: Gabriel Martinez-Pinedo

9:00 AM Contemporary aspects of the theory for the nuclear giant dipole resonance

The isovector giant dipole resonance (IVGDR) is one of the dominant excitations of the atomic nucleus. In addition to providing insights on nuclear structure, it is involved in many applications, such as in nuclear astrophysics. Characterizing the IVGDR over the nuclear chart is of fundamental importance, and experimental data in both stable and exotic nuclei provide cornerstones in the validation of the theoretical description of the IVGDR. Calculations can be undertaken in specific nuclei to compare to the data and learn about their structure. Large-scale predictions in many stable and exotic nuclei, where the IVGDR has not yet been measured, are also of interest. In recent years, an increased variety of complementary theoretical methods could predict the IVGDR, such as improved energy density functional approaches, shell-model based calculations, or ab initio related ones. They allow for the microscopic investigation of the IVGDR in various cases, including deformed nuclei.

Speaker: Prof. Elias Khan (IJCLab)

Photonics25_EK.pdf

9:45 AM "First results from the PANDORA project"

The PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project explores photo-nuclear reactions in light nuclei (A $<$ 60) through both experimental and theoretical studies. This research is particularly relevant to ultra-high-energy cosmic rays (UHECRs), where energy and mass loss primarily occur via electromagnetic interactions between nuclei and the cosmic microwave background, driven by the isovector giant dipole resonance (IVGDR) and it also has profound significance for nuclear physics for reaction calculations, theoretical models and nuclear data benchmarks. A key limitation in current UHECR propagation models is the scarcity of reliable experimental data for critical nuclei. To address this, PANDORA will utilize virtual photon experiments at iThemba LABS and RCNP, as well as real photon experiments at ELI-NP, to extract essential nuclear parameters, including IVGDR cross-sections, E1 strength distributions, and branching ratios for particle decay. The project's first experiment was conducted at RCNP in late 2023, focusing on photo-absorption and charged particle decay in $^{12}$C and $^{13}$C. This study utilized the Grand Raiden spectrometer, SAKRA (a backward-angle silicon detector array), and SCYLLA (a LaBr$_3$ detector array). This presentation will discuss the analysis of these measurements and their implications for UHECR propagation, particularly in refining loss length calculations.

Speaker: Jacob Bekker (University of the Witwatersrand, iThemba LABS, South Africa)

PANDORA_JB_Nuclear_Photonics.pptx

10:15 AM Electromagnetic response functions and electric dipole polarizability from coupled-cluster theory

Electromagnetic excitations are a unique probe to the internal structure of a nucleus. In this talk, nuclear electromagnetic responses are investigated using the ab initio coupled-cluster theory. We determine dipole response functions and electric dipole polarizabilities in both closed-shell nuclei and open-shell isotopes close to magicity, and discuss their evolution along isotopic chains.

References:
1. S. Bacca et al., Phys. Rev. Lett. 111, 122502 (2013).
2. F. Bonaiti et al., Phys. Rev. C 110, 044306 (2024).
3. F. Marino et al., arXiv:2504.11012.
4. F. Marino et al., EPJ Web Conf. 324, 00021 (2025).

Speaker: Dr Francesco Marino (JGU Mainz)

Talk_NuclearPhotonics_Francesco_Marino.pdf

Talk_NuclearPhotonics_Francesco_Marino.pptx

10:45 AM → 11:05 AM Coffee break

11:05 AM → 12:45 PM Session II

Convener: Elena Litvinova

11:05 AM Understanding the nuclear collective states with photons

Our understanding of the nuclear collective behaviour is not yet complete. There are elusive collective modes, and new types of probes, such as vortex photons, have been proposed as a means to access them. Vortex photons could enable the identification of isovector modes other than the Giant Dipole Resonance (GDR) and thus provide new information on the nuclear Equation of State (EoS). In this respect, there is a clear connection between nuclear collective excitations and the status and perspectives in nuclear photonics.
In this spirit, I will start my contribution with a general introduction on what we have achieved so far by extracting information on the EoS from collective modes; I will discuss in particular the usual GDR, the dipole polarizability and other observables related to the symmetry energy. Then, I will focus on the gamma decay of giant resonances.
This decay is a severe test for theory, and I will argue that the attempt to reproduce experimental numbers for the gamma decay does indeed challenge our understanding of the excitation and dynamics of giant resonances as a whole. I will present results for the decay of various multipole excitations, either to the ground state or excited state. I will discuss how this sheds light on the isospin character of these states and, to a large extent, on their microscopic structure.

Speaker: Prof. Gianluca Colo (University of Milano and INFN)

11:35 AM First high-accuracy, model-independent NRF measurements on $^{78,80}$Kr$ to constrain photon strength functions for p-process nucleosynthesis calculations

This presentation brings into focus $^{78,80}$Kr$(\gamma,\gamma’)$ cross section measurements carried out using real photons at the HIGS/TUNL facility. The overarching physics motivation for these experimental investigations is to advance knowledge on a forefront topic in nuclear astrophysics – the nucleosynthesis beyond Fe of the rarest stable isotopes naturally occurring on Earth (the origin of p-nuclei) by constraining the statistical models that are used to calculate the unknown stellar reaction rates. In particular, these stellar reaction rates are highly sensitive to the low-energy tail of the nuclear photon strength function (PSF).
Due to its high selectivity for dipole excitations, real photon scattering via nuclear resonance fluorescence (NRF) is the method of choice to extract experimentally, with high accuracy and model independently, the dipole PSFs in stable nuclei. The quasi-monochromatic and linearly
polarized photon beam of very high flux available at HIGS makes this facility ideal for investigation of photoabsorption reaction cross section with p-nuclei as targets.
The NRF measurements on $^{78,80}$Kr will provide for the first time information for the low-energy part of the E1-PSF in $^{78,80}$Kr, as direct input into the p-process nucleosynthesis modeling.
In this presentation we will report on the status of data analysis of these recent measurements.

Speaker: Prof. Adriana Banu (James Madison University, Department of Physics and Astronomy)

NuclearPhotonics2025-ABanu-for-web.pdf

12:05 PM What can we learn from studying PDR and GDR with microscopic theory including phonon coupling?

The electric dipole response of the nucleus reveals important spectroscopic features of its structure and the mechanism of its interaction with external electromagnetic and hadronic fields. Here, we present new results on dipole strength distributions of direct and cascade transitions to GDR energies in neutron-excess nuclei from various mass ranges, obtained within a theoretical approach based on energy-density functional theory and the quasiparticle-phonon model [1]. The method and its recent developments, including a reaction theory [2, 3], have been successfully applied in spectroscopic studies of various types of nuclear excitations, including two-phonon states, pygmy, and giant resonances, demonstrating its effectiveness and reliability. In addition to the single-particle nature of the excited nuclear states from the PDR region, the analysis of inelastic photon and proton scattering data and branching ratios reveals various properties of the low-energy dipole strength, which can be used to investigate the role of quasi-continuum’s coupling with the low-energy dipole strength [3, 4]. Due to this effect, we observe a shift in the dipole strength from the neutron threshold region and the low-energy GDR tail to low excitation energies in Fe-56, Mo-96, and Sn isotopes, as well as other nuclei of medium and heavy atomic mass. This clearly shows a strong increase in the overall low-energy dipole strength.
An interesting recent extension of our theoretical studies on PDR is the systematic investigation of electric dipole transitions between nuclear excited states with different spin and parity. We observe an enhanced electric dipole strength below the neutron threshold of Fe-56, which, based on its spectroscopic properties, strongly resembles a PDR mode built on the excited states of this nucleus. Furthermore, the γ-decay of the GDR has not been systematically studied to date. Recently, a novel NRF experiment on the γ-decay of the GDR of the deformed Sm-154 nucleus was conducted at HIγS to investigate its properties [5]. The obtained result from the GDR γ-decay branching ratio to the first 2+ and the ground state can serve as a new observable for interpreting the GDR structure. In this context, new theoretical results that could be of fundamental importance for these studies are discussed.
This research is supported in part by the ELI-RO program funded by the Institute of Atomic Physics, Măgurele, Romania, contract number ELI-RO/RDI/2024-002 (CIPHERS) and the Romanian Ministry of Research and Innovation under research contract PN 23 21 01 06.

[1] N. Tsoneva, H. Lenske, Energy-density functional plus quasiparticle-phonon model theory as a powerful tool for nuclear structure and astrophysics, Physics of Atomic Nuclei 79, 885–903 (2016) and refs. therein.
[2] M. Spieker, A. Heusler, B.A. Brown, T. Faestermann, R. Hertenberger, G. Potel, M. Scheck, N.Tsoneva, M. Weinert, H.-F. Wirth, and A. Zilges, Accessing the Single-Particle Structure of the Pygmy Dipole Resonance in 208Pb, Phys. Rev. Lett. 125, 102503 (2020).
[3] M. Weinert, M. Spieker, G. Potel, N. Tsoneva, M. Müscher, J. Wilhelmy, and A. Zilges, Microscopic Structure of the Low-Energy Electric Dipole Response of 120Sn, Phys. Rev. Lett. 127, 242501 (2021).
[4] T. Shizuma, S. Endo, A. Kimura, R. Massarczyk, R. Schwengner, R. Beyer, T. Hensel,H. Hoffmann, A. Junghans, K. Römer, S. Turkat, A. Wagner, and N. Tsoneva, Low-lying dipole strength distribution in 204Pb, Phys. Rev. C 106, 044326 (2022).
[5] J. Kleemann, N. Pietralla, U. Friman-Gayer et al., Gamma Decay of the 154Sm Isovector Giant Dipole Resonance: Smekal-Raman Scattering as a Novel Probe of Nuclear Ground-State Deformation, Phys. Rev. Lett. 134, 022503 (2025).

Speaker: Nadia Tsoneva (Extreme Light Infrastructure-Nuclear Physics (ELI-NP)/Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH))

ELI-NP-NuclPh_2025NTsoneva_2.pdf

12:25 PM Study of the K quantum number of pygmy states in 154Sm

This work focuses on exploring the Pygmy Dipole Resonance (PDR) in the deformed $^{154}$Sm nucleus. The study employs the ($\vec{\gamma}$,$\vec{\gamma}^{\prime}$) reaction to probe dipole states in the energy range of 3.5$~$MeV to 7.05$~$MeV, approaching the neutron separation energy at 8$~$MeV. Measurements were conducted at the HI$\gamma$S facility of the Triangle Universities Nuclear Laboratory using the Clover Array. The facility provides a polarised photon beam, which enables measurements via the asymmetry method, allowing for the differentiation between $1^{-}$ and $1^{+}$ states. Additionally, the high-resolution beam mode (with an energy spread below 2%) allows for the determination of decay branching ratios to the first $2^{+}$ state, thereby enabling the identification of the $K$ quantum number for the excited states. Since the Alaga rules have so far been investigated in the PDR region only for $^{150}$Nd, the present study aims to extend this investigation to the case of $^{154}$Sm. We present preliminary results and outline prospects for future analysis.

This work is based on the research supported in part by the National Research Foundation of South Africa (Grants No. MND210503598725, No. REP_SARC180529336567) and the US Department of Energy (Grants No. DE-FG02-97ER41041 (UNC), No. DE-FG02-97ER41033 (TUNL)).

Speaker: Refilwe Molaeng (University of the Witwatersrand and iThemba LABS)

Study_of_the_K_quantum_number_Refilwe.pdf

12:45 PM → 1:45 PM Lunch break

1:45 PM → 3:15 PM Session III

Convener: Harald W. Griesshammer

1:45 PM Probing Nuclear Structure and Reactions with Vortex Photons

Over the past decade the use of twisted photons to probe the properties of atomic and nuclear systems was considered both theoretically and experimentally [1-3]. Since the angular momentum is conserved in the transitions involving the electromagnetic radiation, it is convenient to consider the states of photons with well-defined total angular momentum. Therefore in the first part we discuss the structure of twisted photons in terms of the spherical ones and show how this distribution is controlled by the opening (pitch) angle. We determine the transition amplitude for the absorption of a twisted photon as well as the cross sections for the population of various final states having the same energy but different angular momenta, including the nuclear rotational bands and isomeric states. Our previous studies include calculation of reaction rates in astrophysical plasmas accounting for twisted gamma photons [4] and multipole selection rules in the absorption of superimposed Bessel beams [5]. By means of angular momentum algebra, we extend the calculations to vortex particles and factorize the scattering cross sections into reduced, spherically averaged nuclear quantities, multiplied by geometrical factors that depend on the initial beam parameters—total angular momentum, pitch angle, spin helicity—and on the distance from the nucleus to the beam singularity. The impact parameter is shown to play a major role together with the transition energy in the enhancement of multipolarities.

Emphasis is also placed on the initial spin-polarization of the vortex beams and its effects on the scattering process. Our results will include analytical expressions for both the vortex-beam absorption cross section and the angular distribution and polarization of the emitted particles, accounting for different nuclear multipolarities and their interference via partial-wave analysis. The present work is useful for proposing experiments aiming to probe more elusive nuclear states. An example is provided for the electromagnetic multipolarity ratios in the absorption cross section of superimposed Bessel beams by Th-229 isotope. Based on these formalisms we will also speculate about the possibility to detect experimentally such twisted photons and on the angular momentum transfer mechanism at various beam intensities.

[1] A. Afanasev, C.E Carlson, M. Solyanik, Phys. Rev. A 97 023422 (2018)
[2] B.A. Knyazev, V.G. Serbo, Physics-Uspekhi 61 449-479 (2018)
[3] Y.Taira, T. Hayakawa, M. Katoh, Scientific Reports, 7:5018 (2017)
[4] Y. Xu et al., Phys.Lett. B, 852, 138622 (2024)
[5] C. Iorga et al., Phy. Scr. 100, 065306 (2025)

Speaker: Prof. Virgil Baran (University of Bucharest)

2:15 PM Nuclear Excitation in Photonuclear Reactions by Photon Vortex with Large Angular Momentum in Astrophysical System

Photon vortices are light carrying large orbital angular momentum (OAM) at the quantum level [1]. They can be described by Laguerre-Gaussian or Bessel wave functions, which are waves that are eigenstates of the total angular momentum along their propagation direction. Unlike plane-wave photons, photon vortices interact differently with materials because their OAM affects the way they transfer angular momentum.
In gamma-ray bursts (GRBs), keV photons may become highly polarized due to strong magnetic fields. This raises the question of whether similar polarization or angular momentum structures may occur in strongly magnetized environments. We have studied the process by which photon vortices form when electrons undergo spiral motion in magnetic fields as strong as 1012-1013 G, using Landau quantization. Our calculations show that such vortices are likely to be generated in environments with extremely strong fields, such as magnetars or magnetized accretion disks around black holes [2]. These results support the possibility that photon vortices are not rare, but rather abundant in high-field astrophysical systems.
Liu et al [3] found that the amplitudes of low-multipole giant resonances are suppressed when a photon vortex interacts with a nucleus at relatively small impact parameters.　This suggests that photon vortices may change the isotopic abundances in nucleosynthesis processes in the Universe.
In this paper we calculate the ratios of photon absorption transition probabilities for Bessel-type photon vortices compared to plane-wave photons [4]. Our results show that excitations of nuclear states with large total angular momentum are enhanced by optimizing the divergence angle of the incident vortex in momentum space. This implies that photon vortices could selectively excite high angular momentum states. However, the average absorption cross section remains the same.

[1] L. Allen, et al. Phys. Rev. A 45, 8185 (1992).
[2] T. Maruyama, et al. Phys. Lett. B826. 136779 (2022).
[3] Z.-W, Lu, et al., Phys. Rev. Lett. 131, 202502 (2023).
[4] T. Maruyama, et al. Astrophys. J. 975, 51 (2024).

Speaker: Tomoyuki Maruyama (BRS, Nihon university)

VPhNuc-NPh.pdf

VPhNuc-NPh.pptx

2:35 PM Measurement of spatial polarization distributions of inverse Compton scattered gamma rays

In the UVSOR synchrotron facility, gamma rays with a maximum energy of 6.6 MeV are generated by 90-degree inverse Compton scattering (ICS) between a 750 MeV electron beam and a Ti:Sa laser with a wavelength of 800 nm. The gamma rays are used for atomic-scale defect analysis using gamma-ray-induced positron annihilation spectroscopy [1] and for evaluation of polarized gamma-ray detectors. The generation of polarized gamma rays is one of the key features for ICS. It is well known that polarized gamma rays are generated by using linearly and circularly polarized lasers, but their polarization state varies with the position of the gamma-ray beam cross section. For example, the polarization axis of linearly polarized gamma rays changes with the position of the cross section. Moreover, the degree of circular polarization of circularly polarized gamma rays varies with the scattering angle and changes to linear polarization in the region outside the cross section [2]. On the other hand, ICS using lasers with polarization states different from linear or circular could generate gamma rays with novel polarization states [3]. We have developed a Compton polarimeter capable of measuring the two-dimensional polarization distribution of ICS gamma rays.
In this conference, we will present the measurement results of the spatial polarization distribution of gamma rays generated using linearly, circularly, and axially symmetric polarized lasers. It was clearly observed that the polarization axis of linearly polarized gamma rays changed with the position of the cross section. We also demonstrated that the gamma rays generated by a circularly polarized laser transitioned to linear polarization in the outer region with the polarization axis aligning along the azimuthal direction. Furthermore, the gamma rays generated by an axially symmetric polarized laser were randomly polarized around the central axis and azimuthally polarized in the outer region.
[1] Y. Taira et al., Rev. Sci. Instr., 93 (2022) 113304.
[2] Y. Taira et al., Phys. Rev. A, 107 (2023) 063503.
[3] Y. Taira, Phys. Rev. A, 110 (2024) 043525.

Speaker: Yoshitaka Taira (Institute for Molecular Science)

NuclearPhotonics_taira_oral.pdf

2:55 PM 20 MeV electrons and bremsstrahlung at Turkish Accelerator and Radiation Laboratory

The Turkish Accelerator and Radiation Laboratory (TARLA) is a user facility based on a superconducting linear accelerator designed to reach 40 MeV and 1.6 mA. TARLA will be equipped with two beamlines: one for bremsstrahlung and the other for a free-electron laser. Currently, the first accelerating section, providing 20 MeV acceleration, is completed, while the second, for 40 MeV, is under construction. Out of the two beamlines the bremsstrahlung beamline is expected to be available first and start to serve Nuclear resonance fluorescence experiments as soon as available. The current status of the accelerator, project plans, and beam application schedule will be presented. This presentation will detail the accelerator's current status, project plans, and beam application schedule. Furthermore, we will discuss the planned utilization of the operational 20 MeV section for activation and other radiation physics experiments during a pause in the 40 MeV section's construction. By employing a fast sample transfer system measurements of bremsstrahlung and decay properties of nuclei can be made by activation. Thus a set of of activation measurements using 20 MeV bremsstrahlung is planed. These measurements aim at accelerator characterization by establishing the relationship to the generated bremsstrahlung, as well as for measurements of half-lifes of a few short lived nuclei as demonstrator of the sample transfer system capabilities. For accelerator characterization via bremsstrahlung properties activation of Copper (Cu), gold (Au), and tantalum (Ta) will be used, and for studying short lived nuclei Mg-23, S-31, Si-27 and others will be used. After transfer the irradiated samples will be counted using two pairs of CLOVER and single-crystal HPGe detectors with BGO active Compton suppression. The aim of this research was to measure the energy transitions and half-lives of these isotopes as a test of the detector and transfer system capabilities. We will present the status the system and well as of the measurements.

Speaker: Haris Dapo (Turkish Accelerator and Radiation Laboratory (TARLA))

HD_Nuclear_photonics_2025.pdf

3:15 PM → 3:40 PM Coffee break

3:40 PM → 5:00 PM Session IV

Convener: Myung-Ki Cheoun (Department of Physics, Soongsil University,)

3:40 PM Nuclear Reaction Rates in Laser-Driven Non-Equilibrium Plasmas

Recent advancements in laser-based particle acceleration technologies have opened new possibilities for conducting nuclear reaction studies at tabletop scales. Among various laser-based nuclear reaction experiments, this research focuses on the pitcher-catcher configuration utilizing laser-driven ion beams.
Typically, nuclear reaction rates in equilibrium plasmas, such as astrophysical environments, are calculated using Maxwell-Boltzmann distributions. However, laser-driven ion beams generated through the Target Normal Sheath Acceleration (TNSA) mechanism [1,2] inherently produce non-equilibrium ion distributions. As a result, equilibrium-based models are insufficient, requiring a framework that accounts for non-equilibrium ion distributions.
In this study, we first conduct detailed numerical calculations focusing on the p + $^{11}$B fusion reaction, widely investigated in pitcher-catcher experiments. By numerically modeling the proton beam's non-equilibrium distribution, we determine the reaction rates as functions of the relevant laser parameters, identifying optimal conditions under which the fusion reactivity reaches a theoretical maximum of $\left\langle \sigma v \right\rangle = 8.12 \times 10^{-16}\,{\rm cm^3/s}$ [3]. These findings establish a fundamental upper limit for achievable fusion reactivity in laser-driven p + $^{11}$B experiments, even under optimized experimental conditions.
Second, we present an analytical formulation of nuclear reaction rates derived from the self-similar solution of the TNSA mechanism [1], offering explicit results for non-resonant nuclear reactions. This analytical approach redefines the traditional Gamow energy window, extending its applicability to non-equilibrium, laser-driven plasmas. The outcomes of this framework not only provide valuable guidance for designing future laser-driven nuclear fusion experiments but also enhance our understanding of astrophysical nuclear processes.

[1] Mora, P. 2003, PhRvL, 90, 185002
[2] Fuchs, J., Antici, P., d’Humières, E., et al. 2006, NatPh, 2, 48
[3] Hwang, E., Cheoun, M.-K., & Jang, D. 2025, arXiv:2504.07124

Speaker: Eunseok Hwang (Department of Physics, Soongsil University)

Nuclear_Photonics_HWANG.pptx

4:00 PM Ultra-intense neutron source generation from (p,xn) and (γ,xn) reactions driven by the PETAL laser

This work focuses on the experimental characterization of a neutron source driven by the high-energy (between 300 and 700 J), short pulse (700 fs) LMJ-PETAL facility. For this purpose, we have developed two experimental platforms, both operating in a pitcher-catcher configuration [1], but using either a solid target or a gas plasma to generate the primary high-energy particle beam.
Our first approach was to produce neutrons by (p,xn) reactions triggered by a target normal sheath accelerated (TNSA) proton beam. The TNSA target was a 50 μm thick CH foil producing protons up to 50 MeV [2]. The converters were two-layer targets of lithium fluoride (LiF) and lead (Pb), the thicknesses of which were varied to optimize the neutron yield [3].
Our second approach used a supersonic helium gas jet as a target to generate a relativistic electron beam through self-modulated laser wakefield acceleration (SMLWFA) [4]. The accelerated electron reached energies up to 350 MeV and a total charge exceeding 1 μC, a performance comparable with the state of the art [5]. This electron beam was converted into intense Bremsstrahlung radiation in a thick lead (Pb) converter [6], which in turn produced neutrons through (𝛾,xn) reactions.
The properties of the primary protons or electrons, as well as emitted gamma and neutron populations were inferred by a suite of diagnostics, including radiochromic films, imaging plates, magnetic particle spectrometers, nuclear activation, bubble dosimeters and neutron time-of-flight (nToF) detectors [7].
The total number of fast neutrons (above 1 MeV and emitted quasi-isotropically) is estimated to be in the 1010−5×1010 range per shot. Such sources could find applications in nuclear physics and astrophysics [8,9,10], as well as in radiography of high-energy-density environments and fast neutron material characterization techniques [11].
References
[1] W. Cayzac et al., “Experimental capabilities of the LMJ-PETAL facility”, High Energy Density Physics 52, 101125 (2024).
[2] D. Raffestin et al., “Enhanced ion acceleration using the high-energy petawatt PETAL laser”, Matter and Radiation at Extremes 6, 056901 (2021).
[3] B. Martinez et al., “Numerical investigation of spallation neutrons generated from petawatt-scale laser-driven proton beams”, Matter and Radiation at Extremes 7, 024401 (2021).
[4] F. Albert et al., “Laser wakefield accelerator based light sources: potential applications and requirements”, Plasma Physics and Controlled Fusion 56, 084015 (2014).
[5] J. Shaw et al., “Microcoulomb (0.7 ± 0.4/0.2 μC) laser plasma accelerator on OMEGA EP”, Scientific Reports 11, 7498 (2021).
[6] J. Ferri et al., “Electron acceleration and generation of high-brilliance x-ray radiation in kilojoule, subpicosecond laser-plasma interactions”, Physical Review Accelerators and Beams 19, 101301 (2016).
[7] D. P. Higginson et al., “Global characterization of a laser-generated neutron source”, Journal of Plasma Physics 90, 90590308 (2024).
[8] A. Yogo et al., “Laser-Driven Neutron Generation Realizing Single-Shot Resonance Spectroscopy”, Physical Review X 13, 011011 (2023).
[9] S. N. Chen et al., “Extreme brightness laser-based neutron pulses as a pathway for investigating nucleosynthesis in the laboratory”, Matter and Radiation at Extremes 4, 054402 (2019).
[10] V. Horny et. al., “Quantitative feasibility study of sequential neutron captures using intense lasers”, Physical Review C 109, 025802 (2024).
[11] F. Mirani et. al., “Laser-Driven Neutron Generation with Near-Critical Targets and Application to Materials Characterization”, Physical Review Applied 19, 044020 (2023).

Speaker: Guillaume Boutoux (CEA DAM DIF)

NP2025_Neutrons_PETAL_Boutoux.pptx

4:20 PM Progress on laser-driven spin polarized neutron beam generation

Low energy neutron (thermal neutron) sources are widely used in various fields such as neutron radiography, neutron diffraction, and Boron Neutron Capture Therapy (BNCT). Spin-polarized neutrons are also considered as one of the next generation quantum sources, enabling analysis of magnetic structures of materials. Laser-driven neutron sources are considered promising due to their point source and short pulse. The generation of thermal neutrons by lasers has been studied by using specially designed moderators [1-3]. In this study, we have proposed a novel method based on the Stern–Gerlach principle, where neutrons are spatially separated into fully spin-polarized states by a magnetic field gradient. By combining a laser-driven neutron source with a laser-driven magnetic field, this method enables generation of spin-polarized neutrons having both short pulse duration and point-source characteristics.
The experiment is conducted at GEKKO XII–LFEX laser facility at Institute of Laser Engineering, The University of Osaka. Photonuclear reactions induced by deuterons were utilized to produce thermal neutrons without any moderators. The LFEX laser generates x-rays, which then induce neutron production at a deuterated plastic target. The resulting neutron spectrum spans a broad energy range from meV to MeV. A magnetic field is subsequently generated using GEKKO XII laser triggered after the LFEX pulse. A delay time is applied to ensure the arrival of the thermal neutrons at the magnetic field region, and then short pulse, monoenergetic, spin polarized neutrons are extracted.
The detector package is also developed for the experiment. The thermal neutron beam pattern is measured using a stack of radiochromic film (RCF), CR-39, and a ⁶LiF sheet, placed 15 mm from the neutron source target. The CR-39/⁶LiF combination provides high selectivity and sensitivity for thermal neutrons. Preliminary experimental data confirm that thermal neutrons are successfully detected by the detector package, although spin-polarized neutrons have not yet been identified due to an insufficient signal-to-background ratio. We also discuss further experiments to improve this ratio and enable the clear detection of spin-polarized neutrons.
References
[1] S.R. Mirfayzi, et, al, Sci. Rep, 10, 20157 (2020). [2] S. R. Mirfayzi et al., Appl. Phys. Lett. 116, 174102 (2020). [3] A. Yogo et al., Appl. Phys. Express 14 106001 (2021).

Speaker: Ryuya Yamada (Institute of Laser Engineering, The University of Osaka)

2510_NP2025_RyuyaYamada_v1.pdf

2510_NP2025_RyuyaYamada_v1.pptx

4:40 PM Towards a vacuum birefringence experiment at the Helmholtz International Beamline for Extreme Fields

Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent. This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory. A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence manifesting itself in a polarization-flipped signal component. This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics (QED) in an uncharted parameter regime.
In this talk I will provide an update on the status of the dark-field approach devised to measure the leading (both polarization-flipped and unflipped) quantum vacuum signals in a dedicated experiment at the European X-ray Free Electron Laser (EuXFEL) within the Helmholtz International Beamline for Extreme Fields (HIBEF) User Consortium.

Speaker: Felix Karbstein

2025_NuclearPhotonics_Felix_Karbstein.pdf

7:00 PM → 10:00 PM Conference Dinner

Fri, October 10

9:00 AM → 10:25 AM Session I

Convener: Ryoichi Hajima

9:00 AM Perspectives for Nuclear Photonics Experiments at the new Research Campus Biblis

Biblis is the site of a former 2.6 GW fission power plant facility, currently under decommission. In 2025, by the invitation of the Hessian government, a round table meeting took place on site, involving partners from industry, academia, and research laboratories to sign a memorandum of understanding to repurpose the site for a future research campus on laser fusion energy.

As a first project, a laser-driven neutron source will be installed for non-destructive testing applications. The goal is to form a new center for research on fusion and nuclear photonics with involvement of national and international partners.

I will present the current state of work, including experimental results on laser-driven neutron and x-ray sources, and the future roadmap for the research campus.

Speaker: Prof. Markus Roth (TU Darmstadt & Focused Energy)

9:45 AM DICE: A Proposal for Energy-Efficient Electron Acceleration for Nuclear Photonics Applications*

Institut für Kernphysik, Fachbereich Physik, Technische Universität Darmstadt

Technische Universität Darmstadt is operating the first performant superconducting multi-turn energy recovery linac (ERL) [1]: S-DALINAC. With this technology, the kinetic energy of accelerated electron bunches can be recycled after their usage in a dedicated interaction. The recycled energy is used to accelerate subsequent electron bunches with nearly no externally provided radio-frequency power. Experiments having only little impact on the electron bunches can be served by an ERL, e.g. laser Compton backscattering (LCB), where a laser beam is scattered at an electron beam, which leads to energy-boosted photons. Based on the expertise and experiences of the operation, the team at the Institut für Kernphysik has developed a machine concept of a future ERL called DICE: Darmstadt Individual-Recirculating Compact ERL. This ERL is planned to deliver an electron beam of up to 520 MeV and 20 mA. An LCB setup is intended as an interaction during ERL operation, leading to a quasi-monochromatic brilliant photon beam in the order of a few megaelectronvolts. This photon beam is ideally suited for nuclear photonics applications. In this contribution, we introduce the facility concept DICE and show its conceptual design.

[1] F. Schliessmann, M. Arnold, L. Juergensen, N. Pietralla, M. Dutine, M. Fischer, R. Grewe, M. Steinhorst, L. Stobbe, S. Weih, “Realization of a multi-turn energy recovery accelerator”, Nat. Phys. 19, 597–602 (2023).

*This work is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 499256822 – GRK 2891 'Nuclear Photonics'.

Speaker: Michaela Arnold (Institut für Kernphysik, TU Darmstadt)

Nuclear_Photonics_25_Arnold_DICE_V2.pdf

10:05 AM Tritium-Induced Reactions with Neutron-Rich Light Nuclei

Experimental data on tritium-induced nuclear reactions involving neutron-rich light nuclei such as 6He, 8Li, and 11Be remain scarce, despite their critical importance in nuclear astrophysics. These nuclei play a pivotal role in the rapid neutron capture process (r-process), acting as seed nuclei that influence nucleosynthesis pathways beyond the A=5 and A=8 mass gaps. Their relevance covers multiple astrophysical environments, including core-collapse supernovae, Big Bang nucleosynthesis, and neutron star mergers [Ter01]. Laser-ion acceleration presents a novel opportunity to generate radioactive tritium beams—capabilities currently unavailable at conventional accelerator facilities. The high-power laser systems at the University of Rochester’s Laboratory for Laser Energetics (OMEGA and OMEGA-EP) enable the production of multi-MeV radioactive ion beams using compact, laser-driven targets. However, key challenges persist, including the suppression of parasitic proton acceleration from surface contaminants and the generation of monoenergetic, high-yield tritium sources. Ongoing and planned experimental campaigns are focused on optimizing laser-driven tritium beam production from target-normal sheath acceleration (TNSA) mechanism. These efforts aim to establish a controllable and reproducible beam platform, with insights directly informing the design and operation of future petawatt-class facilities, including the proposed NSF-OPAL laser facility [Sch22]. This material is based upon work supported by the Department of Energy [National Nuclear Security Administration] University of Rochester “National Inertial Confinement Fusion Program” under Award Number(s) DE-NA0004144.

References:
[Ter01] M. Terasawa et al: “New nuclear reaction flow during r-process nucleosynthesis in supernovae: Critical role of light, neutron-rich nuclei’, The Astrophysical Journal, 562 (2001)
[Sch22] A. Schwemmlein et al: “First Demonstration of a Triton Beam Using Target Normal Sheath Acceleration”, Nuclear Inst. and Methods in Physics Research B 522 (2022)

Speaker: Dr Chad Forrest (LLE, University of Rochester)

10:25 AM → 10:50 AM Coffee break

10:50 AM → 12:20 PM Session II

Convener: Dimiter Balabanski

10:50 AM The study of the $^3$H(α,γ)$^7$Li reaction through the inverse $^7$Li(γ,α)$^3$H reaction

In contrast with the other light elements, the Li-7 measured abundance is 3-4 times lower than expected from the Big Bang Nucleosynthesis predictions. This fact is known as the “cosmological Li problem” and a better understanding of the disagreement may be achieved by studying the reactions which are leading to the Li-7 production and destruction. The $^3$H(α,γ)$^7$Li reaction contributes to the production of Li-7 in Universe and has been previously studied in a direct measurement in 1994 for center-of-mass energies below 1.2 MeV. According to the reciprocity theorem, the $^3$H(α,γ)$^7$Li ground state cross-section can be determined by measuring the Li-7 photodisintegration cross section. Therefore, the $^7$Li(γ,α)$^3$H reaction has been studied by our team in a series of experiments at the High Intensity γ-ray Source (HIγS) Laboratory of Duke University (USA) in 2017 and 2023. Alpha particles and the triton coincidences were detected using a silicon detector array (SIDAR) from Oak Ridge National Laboratory. In 2017 the energies of the gamma beam have been between 4.4 and 10 MeV, but below 6 MeV the coincidences have been observed only in a thinner set of detectors. In 2023, the set-up has been improved and the reaction has been studied for energies of the gamma-ray beam between 3.7 and 6 MeV. The preliminary astrophysical S-factor has been extracted and an R-matrix fit has been performed over the data from 2023, together with the data from 2017.
The experimental details and the comparison of the results from the 2017 and 2023 campaigna at HIγS with the direct measurement obtained in 1994 will be presented.

Speaker: I. Kuncser (Extrem Light Infrastructure - Nuclear Physics / IFIN-HH)

11:20 AM Nuclear photo-excitation data relevant for weak-interaction physics

With the low angular-momentum transfer in the inelastic scattering of real photons, the photo-excited states often have relevance also for other nuclear processes, in particular weak processes. For example, scattering of neutrinos off atomic nuclei, governed by the weak force, can predominantly excite magnetic-dipole excitations, which subsequently decay via gamma or particle emission, depending on their energy relative to particle thresholds. As such, large-scale neutrino experiments can be sensitive to the detection of, e.g., super-nova neutrinos through the nuclear excitation of the detection material via incoherent neutrino scattering. Furthermore, the spin-M1 operator, which is dominant in the electro-magnetic M1 operator, has a structure analog to the Gamov-Teller operator, which mediates spin-isospin changing electron-capture decays. This analogy between weak and electro-magnetic operators can be exploited to constrain weak processes through the measurement of electro-magnetic properties, in turn interesting for violent astrophysical processes and nucleo-genesis. Another aspect is the sensitivity of nuclear model predictions of weak processes to the structure of the involved nuclear eigenstates, which, in turn, is governed mostly by the strong interaction. The sensitivity of, in particular, isovector nuclear excitations like the scissors mode to the structure of states relevant for double-beta and neutrino-less double-beta decays has previously been tested on key isotopes. These aspects connecting photo-nuclear science and weak-interaction physics will be discussed in view of recent advancements and related present and future experiments using gamma beams.

Speaker: Dr Volker Werner (IKP TU Darmstadt)

vw_photonics25.pdf

11:40 AM Direct Observation of the competing M1 and isospin-forbidden M3 transitions from the decay of the IAS in $^{10}$B

Structural effects in the lightest stable nuclei were the first to be studied experimentally. Early research focused on isospin mixing, properties of isospin multiplets, and α clustering. Recently, the existing experimental data for the γ decay of the stable N = Z doubly odd nuclei and the β decay of the corresponding isospin multiplets were reviewed [1]. Nowadays, with the advances in ab initio many-body theories, there is renewed interest in the structure of these nuclei. The reason is that most of the data were obtained in the second half of the last century and, in some cases, lacked the needed precision to meet these advances. Thus, many subtle structural effects remained unexplored.
A unique worldwide experimental setup created with a hybrid array of large-volume ELI-NP LaBr$_3$∶Ce and CeBr$_3$ and ROSPHERE HPGe detectors placed in BGO anti-Compton shields, which provides unprecedented γ-ray efficiency for high-energy γ-rays at IFIN 9 MV Tandem [2]. Excited states in $^{10}$B were populated with the $^{10}$B(p, pʹγ)$^{10}$B reaction at 8.5 MeV, and their γ decay was investigated via the method of coincidence γ-ray spectroscopy. The state-of-art spectrometer allowed the observation of weak γ-ray transitions, such as the M3 transition between the $J_\pi, T = 0_1^+, 1$ isobaric analog state (IAS) and the $J_\pi, T = 3_1^+, 0$ ground state which competes with an M1 transition to the first excited $J_\pi, T = 1_1^+, 0$ state and the E2 transition between the $J_\pi, T = 2_1^+, 0$ state and the IAS, i.e., performing measurements of branching ratios at the level of $10^{-5}$ [3-6]. For the first time in $^{10}$B, the competing M1 and isospin-forbidden M3 transitions from the decay of the IAS have been observed in an γ spectroscopy experiment. As a result, clustering effects in both the $3_1^+, 0$ gs, and the $0_1^+, 1$ IAS are suggested to enhance the M3 transition.

References:

[1] A. Kuşoğlu, D.L. Balabanski, Quantum Beam Sci., 7(3), 28 (2023)
[2] S. Aogaki, et al., Nucl. Instrum. Methods Phys. Res. A, 1056, 168628 (2023)
[3] A. Kuşoğlu, et al., Phys. Rev. Lett. 133, 072502 (2024)
[4] A. Kuşoğlu, Sci. Bull. 69 (21), 3303 (2024)
[5] A. Kuşoğlu, et al., Nuovo Cim. C, 47, 47 (2024)
[6] A. Kuşoğlu, et al., EPJ Web of Conferences 00020, 4 (2024)

Acknowledgment: This work was supported by the Romanian Ministry of Research and Innovation under research contract PN 23 21 01 06, the ELI-RO program funded by the Institute of Atomic Physics, Măgurele, Romania, contract number ELI-RO/RDI/2024-002 CHIPHERS and ELI-RO/RDI/2024-007 ELITE. FRX acknowledges support from the National Natural Science Foundation of China under Grants No. 12335007, 12035001, and 11921006, and the High-Performance Computing Platform of Peking University.

Speaker: Aslı Kuşoğlu (Extreme Light Infrastructure-Nuclear Physics (ELI-NP), Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), 30 Reactorului Str., 077125 Bucharest-Măgurele, Romania)

12:00 PM Low-lying dipole response of the $N=84$ isotones $^{142}$Ce and $^{144}$Nd

The Pygmy Dipole Resonance (PDR) is a low-energy excitation mode contributing to the electric dipole response in atomic nuclei. Despite significant theoretical and experimental progress over the past decades [1-3], its precise nature and origin are still under investigation. To clarify these open questions, systematic studies along isotopic and isotonic chains are essential. Such research has been performed near the $N=82$ shell closure, focusing on the $N=84$ isotones $^{144}$Nd and $^{142}$Ce. These nuclei were examined using Nuclear Resonance Fluorescence (NRF), a method based on real-photon scattering. Due to their low angular momentum transfer, photons are particularly well suited for studying the PDR [4]. This contribution presents and compares NRF data obtained for $^{144}$Nd and $^{142}$Ce. Supported by the DFG (ZI510/10-2).

References
[1] D. Savran et al., Prog. Part. Nucl. Phys. 70 (2013) 210.
[2] A. Bracco et al., Prog. Part. Nucl. Phys. 106 (2019) 360.
[3] E.G. Lanza et al., Prog. Part. Nucl. Phys. 129 (2023) 104006.
[4] A. Zilges et al., Prog. Part. Nucl. Phys. 122 (2022) 103903.

Speaker: Florian Kluwig (Institute for Nuclear Physics, University of Cologne)

Nuclear_Photonics_2025_FKluwig.pdf

12:20 PM → 1:20 PM Lunch break

1:20 PM → 2:20 PM Session III

Convener: Michael Seimetz (CSIC - Instituto de Instrumentación para Imagen Molecular (i3M))

1:20 PM CONICAL COIL FOCUSING OF LASER-PLASMA ACCELERATED PROTON BEAMS FOR BIOMEDICAL APPLICATIONS

The major advances in laser-plasma acceleration techniques for charged particle beams have generated significant interest in the development of laser-based solutions for proton beam therapy [1, 2]. The particularities of laser-plasma accelerated ion beams that could benefit the biomedical field feature ultra-short pulse durations, down to tens of picoseconds, and high fluxes, with peak values ranging from $10^{11}$ to $10^{13}$ particles per shot. These properties enable the potential delivery of ultra-high dose rates far exceeding 40 Gy/s, the threshold for FLASH therapy. To benefit from these features, the scientific community needs to overcome the more challenging aspects of employing ultra-short accelerated hadrons in clinical applications, which stem from their broadband energy spectrum and large divergence.
In this work we present a simulation-based study that investigates the feasibility of employing high-current solenoid-generated magnetic fields for focusing a proton beam characterised by a broad angular divergence of 21.25 degrees and an energy spectrum ranging from 4 to 20 MeV. The proposed focusing solution consists of a conical solenoid, oriented with its narrow opening facing the proton beam, followed by a coaxial cylindrical one. High currents of 20 and 16 kA were applied to the solenoids, generating peak axial magnetic fields of 9 T and 6 T, respectively. Two versions of the dual-solenoid configuration are compared in terms of focused beam size and position, as well as capturing efficiency, to identify the optimised focusing solution. Protons of over 16 MeV were captured with a 94% efficiency, in a focus spot of 9 mm diameter, located at 1 m from the source.
Additionally, using the optimised dual-solenoid configuration, a 16 to 20 MeV focused proton beam was employed in a dose deposition study targeting a millimeter-scale cylindrical water phantom, resembling a superficial tumour, to explore its potential for therapeutic applications within the flash therapy regime. The study monitored the spatial distribution of the absorbed dose across transverse planes at various depths within the sample. Due to the beam exposure, the total absorbed dose received by the water phantom was 25 mGy with a rate of $1.2 \cdot 10^7$ Gy/s, reaching the FLASH therapy regime.
This work provides valuable insight into beam modulation techniques that support the development of laser-based solutions for proton beam therapy.

Keywords: laser-plasma acceleration, proton beam, dose deposition, FLASH effect.

Acknowledgments: This work is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 499256822 – GRK 2891’Nuclear Photonics’ and by Project ELIRO/DFG/2023_001 ARNPhot funded by the Institute of Atomic Physics, Romania.

References
[1] F. Romano, et al., The ELIMED transport and dosimetry beamline for laser-driven ion beams. Nuclear Instruments and Methods in Physics Research, A 829, (2016), 153-158
[2] F. Kroll, et al., Tumor irradiation in mice with a laser-accelerated proton beam. Nature Physics 18, (2022), 316-322

Speaker: Laura-Anamaria Nălbaru (National University of Science and Technology Politehnica Bucharest, SDSA, Splaiul Independenţei no. 313, RO-060042, Bucharest, Romania)

Laura_NALBARU_NPC2025.pdf

1:40 PM Production of pre-clinical activities of C-11 for PET imaging using a HRR laser-driven proton source

In recent years, there has been a growing interest in laser-driven ion accelerators as a potential alternative to conventional accelerators [1]. A particularly promising application is the production of radionuclides relevant for medical diagnosis, such as $^{11}$C for PET imaging. Typically, the production of these nuclides is centralised at cyclotrons, reducing the number of facilities required, but limiting the range of usable radionuclides to those with longer lifetimes [2]. In this context, compact laser-driven accelerators appear as an appealing option for the in-situ generation of short-lived isotopes. Albeit the activities required for PET imaging (>MBq) are well above those achievable from a single laser irradiation (~kBq), the advent of high-power, high-repetition-rate laser systems opens the path to demonstrating relevant activities through the continuous irradiation, provided a suitable target system is developed. A target assembly based on a rotating wheel and automatic alignment procedure for laser-driven proton acceleration at multi-Hertz rates has been developed and commissioned [3]. The assembly, capable of hosting >5000 targets and ensuring continuous replenishment of the target with micron-level precision, has been demonstrated to achieve stable and continuous MeV proton acceleration at rates of up to 10 Hz using our in-house 45 TW laser system [3].

The continuous production of 11C via the proton-boron reaction [$^{11}$B(p,n)$^{11}$C] has been recently demonstrated from our target assembly using the 1 Hz, 1 PW VEGA-3 system (CLPU, Spain) [4]. Following an initial demonstration, where an activity of ~12 kBq/shot was measured using coincidence detectors [4], we have achieved the production of activation levels in excess of 4 MBq, which to the best of our knowledge is the highest activity measured from a laser-driven setup. We demonstrate that the degradation of the laser-driven ion beam due to heating of optics is currently the only bottleneck preventing from the production of pre-clinical (~10 MBq) PET activities with current laser systems. The scalability to next-generation laser systems will be explored to study the potential for production of clinical (~200 MBq) activities.

References
[1] A. Macchi et al., Rev. Mod. Phys. 85, 751 (2013)
[2] S. Fritzler et al., Appl. Phys. Lett. 83, 3039 (2003)
[3] J. Peñas et al., HPLSE 12 (2024)
[4] J. Peñas et al., Scientific Reports 14.1 (2024)

Speaker: Aaron Alejo (IGFAE, USC)

2:00 PM Towards high sensitivity and low dose medical imaging with laser X-ray sources

Interferometric X-ray imaging based on refraction (differential phase contrast) can be much more sensitive to small soft tissue lesions than conventional X-ray imaging based on absorption, being a potential game changer for medical diagnostics. In addition, because interferometry uses the transmitted radiation, the radiation dose can be reduced by imaging at higher X-ray energy, where the tissues become transparent. The imaging technique best suited for clinical implementation is grating interferometry. Current grating setups utilize around 1 m long interferometers and relatively high radiation dose. We show that by using several meters long, few µm period interferometers, one can strongly increase the sensitivity and lower the dose in soft tissue imaging applications, such as mammography. Conventional X-ray tubes do not provide however sufficient X-ray flux for clinical imaging with such long interferometers. Instead, 100-TW class lasers may provide the highly directional and intense X-ray sources needed for high sensitivity medical interferometry. We present the X-ray source characteristics required for clinical interferometry, the advantages and disadvantages of betatron versus inverse Compton scattering mechanisms for clinical X-ray sources, and the Dr. LASER project at ELI-NP for the development of laser-based, high sensitivity and low dose interferometric mammography.

Speaker: Dr Calin Alexandru Ur (on behalf of Dan Stutman)

ELI-NP X-ray imaging - Nuclear Photonics 2025 - presented.pdf

2:20 PM → 2:40 PM Farewell