Opening Session

• Calin Alexandru Ur

Liquid Targets for High-Repetition-Rate Laser Applications

• Stefan Popa (LSD)

Laser driven particle acceleration from high repetition rate targets

• Vlad Andrei Popescu (LSD)

Quasi-monochromatic carbon ion beams with the “peeler” acceleration scheme

• Bogdan Corobean (LDED)

The “peeler” scheme, originally proposed for proton acceleration, involves irradiating the narrow (sub-micron) side of a solid tape target. The large number of extracted electrons travel to the target rear and create a strong space charge field, which accelerates and collimates hydrogen ions found in the contaminant layer. However, the energy spectrum of higher Z (such as carbon) ion bunches is still thermal-like. Using full 3D particle-in-cell simulations with the particle-in-cell code SMILEI, we optimize this process in order to obtain high peak energy, quasi-monochromatic and low divergence carbon ion beams. Thus, with a PW-class laser, we can obtain 1e8 carbon ions with peak energy ~110 MeV/u, with a divergence of 20 degrees in the vertical plane and ~1 degree in the horizontal plane. With these parameters, the scheme is attractive for practical applications such as heavy ion radiotherapy, higher resolution diagnostics of extreme plasma states, ion fusion studies, and nuclear physics.

Optimisation of secondary particle production from laser wakefield accelerated electrons

• Maxim Andronic (LDED)

Efficient gamma and neutron production from laser-accelerated electrons is crucial for advancing applications in science and technology. It relies on generating γ−photons via Bremsstrahlung and subsequent photo-nuclear reaction within the high-Z converter. This work considers the evolution of the electron bunch studied by Particle-in-Cell (PIC) simulations of Laser Wakefield Acceleration and subsequently optimises converter configurations for maximizing gamma and neutron yields using Monte Carlo simulations. A high-resolution PIC simulation, inspired by the work of V. Horný et al. (Phys. Rev. E 110, 035202), was performed using Smilei to model a 6-fs interaction of a 1.5-J laser pulse. The simulation captured the acceleration of several nanocoulombs of electron bunches, achieving energies of up to 300 MeV in the primary Laser Wakefield Acceleration (LWFA) regime and up to 600 MeV in the secondary Plasma Wakefield Acceleration (PWFA) regime. Electron energy spectra from different phases of the PIC simulation were extracted and used as inputs for FLUKA simulations, where lead converter thickness was varied to optimize gamma and neutron production separately. Complementing this, idealized electron beam simulations in FLUKA explored neutron and photon responses for fixed beam energies and varying target lengths, providing additional insights. This study highlights the interplay between electron beam properties, target geometry and particle yields, offering practical strategies for optimizing secondary particle sources in laser-plasma experiments.

Enhancing light-matter interaction by tailoring nanostructured targets

• Stefania Ionescu (Target Laboratory)

The two main components in the extreme light-matter interaction are the laser pulse and the targets. By adjusting one of them, different results can be obtained and the interaction can be improved. In this work, nanostructured targets obtained by aluminum anodization and electrodeposition of nickel were put to the test for enhancing the accelerated particle energy, compared with flat targets. The particle cut-off energies and electron and photon signal will be presented for both types of targets.

Analysis of High-Energy (p,p’) data on 10,11B for the PANDORA Project

• Andreea Gavrilescu (GDED)

The propagation of Ultra-High-energy cosmic rays (UHECR) in extragalactic space has gathered significant attention in the field of high-energy astrophysics. The motivation behind the PANDORA(Photo-Absorbtion of Nuclei and Decay Observation for Reactions in Astrophysics) project lies in investigating the photo-disintegration and energy loss processes experienced by UHECR particles lighter than iron during their interaction with the strongly Doppler-shifted Cosmic Microwave Background (CMB) photons, seen by UHECRs as high-energy gamma rays. Understanding these complex interactions is essential in comprehending the origins of UHECRs and the mechanism responsible for their acceleration to such high energy ranges. The issue with this particular study is that the data is often sparse and with several inconsistencies between individual measurements.. For heavy nuclei, mainly the (γ, xn) reaction has been investigated and been assumed to be the equal to the total photo-absorbtion cross-section. However, this assumption is not necessarily valid for light nuclei. One of the methods used follows inelastic proton scattering at 0° with proton energies of hundreds of MeV, which favors excitation of dipole modes by relativistic Coulomb excitation. Another method is to use real gamma rays from a dedicated photon facility. For achieving this goal a joined collaboration between ELI-NP, RCNP and iThemba LABS has been created. In both iThemba and RCNP labs an array of double-sided Si strip detectors and a magnetic spectrometer are used for particle decay and excitation strength. The gamma decay branches will be measured with large-volume LaBr3:Ce detectors. Here we will present the PANDORA project and report preliminary analysis from the first experiment at RCNP on 10,11B. These measurements can further be used to constrain the propagation and the origin of UHECRs.

The 7Li photodisintegration below 6 MeV at HIGS

• Ioana Kuncser (GDED)

The abundances of the light elements can be spectroscopically determined by observing the low-metallicity stars. Usually, those measurements are in agreement with the Big Bang Nucleosynthesis predictions. Particularly, the Li-7 measured abundance is 3-4 times lower than expected, discrepancy known as the “cosmological Li problem”. The reaction 3H(α,γ)7Li contributes to the production of Li-7 in Universe and can be studied through its inverse reaction, according to the reciprocity theorem. In consequence, the Li-7 photodisintegration has been measured by our team in 2017 at the High Intensity γ-ray Source (HIγS) Laboratory of Duke University (USA) using a silicon detector array (SIDAR) to observe the coincidences between the alpha particles and the tritons. The considered energies of the gamma beam have been between 4.4 and 10 MeV, but below 6 MeV the coincidences have been observed only in the thinner detectors. In 2023, a new similar experimental campaign, with an improved set-up, took place at HIγS for gamma-beam energies between 3.7 and 6 MeV. The coincidences have been clearly separated and the preliminary astrophysical S-factor of the direct 3H(α,γ)7Li reaction has been successfully extracted. A R-matrix fit has been performed to the data from 2023 together with the data from 2017. The set-up and the preliminary results of the experimental campaign performed at HIγS in 2023 will be presented.

The Cosmological Lithium problem: direct measurement and study of the 6Li(p,a)3He reaction

• Ana Lupoae (GDED)

When it comes to the well-known ”Cosmological Lithium Problem”, one might be inevitably fooled by this general yet comprehensive name. In reality, there are multiple Lithium problems, each with its own perks, making it harder for us than we might like. The 6Li(p,α)3He reaction measurement can provide further understanding of the Big Bang nucleosynthesis (BBN) model and the so-called ”Lithium depletion” in stars. The reaction has been previously measured directly and indirectly (in the framework of the Trojan Horse Method) in the context of the ”Cosmological 6Li Problem”, nonetheless, there are still discrepancies in cross-section measurements below Ep = 3 MeV.

Advancing high-energy gamma imaging with pixelated scintillator technologies

• Raluca Miron (GDED)

High-energy gamma-ray imaging is essential in non-destructive testing and gamma beam diagnostics applications. To enhance spatial resolution and detection efficiency, structured scintillators have been developed, offering superior image quality compared to traditional monolithic scintillators. While structured scintillators have been extensively studied for X-ray detection, their response to high-energy photons remains unexplored. In this work, we investigate the performance of pixelated scintillator detector panels for high-energy gamma imaging through GEANT4 Monte Carlo simulations. Various scintillator materials were analyzed, including CsI(Tl), LYSO, and BGO, of thicknesses ranging from 0.5 to 2 mm. The optimization process focused on evaluating the deposited energy, the absorption efficiency, and the spatial energy distribution for incident gamma-ray energies between 0.1 and 10 MeV. Pixel size optimization for maximizing the spatial resolution was performed using the modulation transfer function (MTF). In addition, we present a comparative testing of a plain scintillator and a columnar (nanostructured) scintillator, assessing their imaging performance. The results highlight the potential of pixelated scintillators for high-resolution gamma imaging and provide insights into optimizing detector design for advanced gamma-ray applications.

Nuclear Resonance Fluorescence on 106Pd

• Teodora-Maria Sebe (GDED)

This study aims at understanding the dependence of the E1 strength in the transition region from vibrational to rotational nuclei. The chosen method of study is the Nuclear Resonance Fluorescence method, a two-step photonuclear process which consists of the absorption of a photon and the subsequent resonant re-emission of gamma rays [1]. The experimental data has been acquired using the DHIPS (Darmstadt High-Intensity Photon Source) setup at the S-DALINAC facility, in Darmstadt, Germany. A monoenergetic electron beam impinging on two Ag bremsstargets (1mm and 5 mm thickness) and creating bremsstrahlung radiation with an end-point energy of 8.7 MeV and a current of 40 μA was employed. An array of three high-purity Germanium (HPGe) detectors [2], positioned at 130◦ and two at 90◦ with respect to the incoming beam, was employed. They were equipped with bismuth germanate (BGO) shields for active Compton suppression and additionally mounted in lead collimators. The primary target consists of 0.991 g of 106Pd and was placed in between the three detectors. This first measurement in 106Pd uncovered new transitions in the 3.5-8 MeV energy range. The data will be analyzed and will provide an overview of the γ-ray transition energies, photon strength functions, integrated cross-sections, spin-parity assignments and branching ratios

Anti-Compton shield characterization for clover and CeBr3 detectors of ELIADE

• Ioan Paul Parlea (GDED)

The present report covers the characterization and fine-tuning of Compton suppression shields for Clover and CeBr3 detectors of the ELIADE gamma-ray spectrometer at ELI- NP.

Influence of different level-density models on the extrapolation in the Oslo method

• Maria Brezeanu (GDED)

In the Oslo method, we need to extrapolate experimental data up to the neutron threshold. To do this, we rely on theoretical models—most commonly, the Back-Shifted Fermi Gas (BSFG) model and the Constant Temperature (CT) model. These two models offer well-established, two-parameter approaches to nuclear level densities. In this presentation, we’ll compare them in the context of recent 2023 measurements of γ strength functions (γSF) and nuclear level densities (NLDs) conducted at IFIN-HH, highlighting their impact on data interpretation and model selection.

Nuclear Structure Studies Using Large Scale Shell Model

• Emanuela Boicu (GDED)

The low-lying 1⁺ and 2⁺ states hold significant interest in nuclear structure studies as they offer insights into the isovector nature of low-lying nuclear excitations. In even-even Cr isotopes, low-lying M1 modes, arising from the interference between orbital and spin magnetic moments, have been explored using the advanced microscopic theoretical model of the large-scale shell model (LSSM). Theoretical results from LSSM are compared with existing experimental data. For Cr isotopes yet to be experimentally studied, these findings serve as valuable predictions.

Sensitivity of nucleon capture reactions to nuclear level density across different energy ranges

• Cosmina Nedelcu (GDED)

Radiative processes are fundamental to nucleosynthesis, governing the emission and absorption of photons during nuclear reactions, and significantly influencing the energy balance, reaction rates, and the production of elemental abundances in astrophysical environments. This study systematically investigates the sensitivity of nucleon capture cross-sections and astrophysical reaction rates to variations in nuclear level density (NLD) energies for several Sn and Mo isotopes. In particular, the NLDs derived from the microscopic Hartree-Fock-Bogoliubov plus combinatorial method are considered, providing a robust basis for identifying the most effective energy range for nucleon capture reactions. These results show that the 4 - 5 MeV energy interval has the greatest impact on both cross-sections and reaction rates. Moreover, significant uncertainties are observed in experimental NLDs obtained using the Oslo method, particularly within this critical energy range for 121Sn. This highlights the necessity of further experimental and theoretical investigations focused on the 4 - 5 MeV interval, which could offer valuable insights for improving level-scheme calculations. All cross-section and reaction rate calculations are performed using the Hauser-Feshbach statistical model.

Openning session

• Calin Alexandru Ur

Digital Signal Processing for Nuclear Physics Experiments

• Sara Rebeca Ban (GDED)

We describe a hardware simulation of a particle identification (PID) technique, offering a novel alternative to traditional E-Δ E detector telescope and time-of-flight methods. Our approach involves accurately replicating the original software algorithms, analyzing the raw digitized waveforms. This work serves as a preceding step toward the future development of a fully hardware-based solution for PID.

Hardware trigger system for nuclear physics experiments using digital data acquisition

• Radu-Vasile Corbu (GDED)

A reconfigurable hardware trigger system is a tool that can add a significant layer of flexibility to nuclear physics research by allowing specific experimental requirements to be integrated into the data acquisition process. The development and testing solutions of a custom trigger system are presented.

Fine tuning of the positron beam line

• Andrei Covali (GDED)

The presentation will focus on adjusting beam accuracy using a setup consisting of two HPGe detectors and one Scintillator, for material science using positron beams.

Position Sensitive Scintillation Detector for Gamma Spectroscopy

• Bogdan Octavian Temelie (GDED)

Scintillation detectors are often used for gamma spectroscopy given their performance in measuring the energy and timing of gamma radiation. Typical detectors, that make use of photomultiplier tubes cannot provide accurate data regarding the particle interaction position. Such setups exist but their scale and position resolution make them unsuitable for practical applications. The introduction of silicon photomultipliers has transformed these setups into viable alternatives, overcoming the limitations of conventional detectors. In my work I utilize a matrix of silicon photomultipliers and a thin scintillator to construct a detector capable of pinpointing the particles’ interaction locations with high resolution. For this to be accomplished, the elaboration of a reliable testing platform and data processing procedure was necessary in order to test the precision and accuracy of such setups. Precise measurements of particle interaction positions were obtained by raster scanning the detector using a collimated 241Am gamma radiation source. For the data processing, special algorithms to extract the interaction position from data provided by the detector were used.

Tumor segmentation from scattering images obtained with a Talbot-Lau interferometer using Convolutional Neural Networks

• Ionut Cristian Ciobanu (XIL)

Detecting breast tumors using imaging techniques remains a critical challenge in medical diagnostics, with limitations in contrast and resolution affecting early detection. Traditional mammography methods struggle to differentiate between healthy and tumorous tissue, particularly in cases with low-density differences. This study investigates the potential of combining ultrahigh-sensitivity Talbot-Lau interferometry with Convolutional Neural Networks (CNNs) to enhance breast tumor segmentation from scattering images. The research aims to improve tumor detection accuracy and efficiency by leveraging phase contrast imaging. The experimental setup utilized an ultrahigh-sensitivity Talbot-Lau interferometer operated with a conventional X-ray tube to generate scattering images, which were processed using a Fourier Transform-based algorithm. Five CNN architectures - U-Net, ResNet50, DeepLabV3, PSPNet, and SegNet -were trained and tested. Performance was evaluated based on accuracy, precision, specificity, recall, and F1-score. U-Net demonstrated the most stable performance with an accuracy of 86.34% and an F1-score of 90.2%, making it the most reliable model for tumor segmentation in scattering images. The combination of Talbot-Lau interferometry with CNNs presents a promising approach for breast tumor detection. U-Net emerged as the most stable model, suggesting its potential application in medical diagnostics. Future work should focus on optimizing CNN architectures and expanding the dataset to improve the segmentation of small tumor-like masses.

Simulating the behavior of HPLS

• Dmitrii Nistor (LSD)

Understanding and predicting spectral changes in high-power laser amplification is critical for optimizing performance and stability in ultra-intense laser systems. We present a numerical model that simulates spectral evolution by slicing the pulse in the frequency domain, capturing key effects such as red-shifting and gain-narrowing. By incorporating wavelength-dependent saturation fluence and amplification dynamics based on the Frantz-Nodvik equations, our approach provides insight into spectral distortions introduced by nonlinear gain competition and energy redistribution. These simulations enable precise predictions of spectral behavior in high-power laser chains, supporting the development of next-generation ultra-intense laser sources for high-field physics applications.

Design of a Shack cube for focus alignement in high intensity laser experiments

• Bianca Stan (LSD)

In this presentation we propose a design of a Shack cube for assisting in the alignment of the focus in dual beam experiments at ELI-NP. The Shack cube is a classic alignment aiding device, consisting of a beamsplitter bonded to a plano-convex lens. Shack cube is used in the alignment of focusing optical systems. The preliminary design that we are presenting here is based on off the shelf components. Optic Studio (from Ansis Zemax) simulations will be presented to demonstrate the design parameters and showcase the proposed alignment method.

Contamination measurements for HPLS mirrors in use

• Fattima Al-Abedj (LSD)

This study investigates the impact of contamination on several types of mirrors from the high-power laser system, focusing on parameters like phase, group dispersion (GD), and group delay dispersion (GDD). In this study are compared silver and two dielectric coatings in terms of contamination level, surface porosity, stability of the method via statistics and cleaning methods. The findings offer insights into optimizing mirror coatings for improved efficiency and durability in advanced laser systems.

Coputational evaluation of phonons and critical temperatures in superconductors

• Iulia Maria Zai (Target Laboratory)

Metallic hydrides have become popular in recent years among theoretical as well as experimental physics due to their exhibition of superconductivity at or near room temperature [1,2]. The superconducting transition temperature (Tc) of such materials can be determined by electron-phonon calculations, that requires extensive computational resources. Computational simulations can allow to determine which particular hydride system and structure might show high temperature superconducting properties. Moreover, a vast majority of hydride structures are meta-stable under pressure, which makes exhaustive and accurate theoretical investigation of this kind of materials even more challenging. This work presents an alternative way to study new high- and low-Tc superconductors using the ELK code with a set of input parameters tested on experimentally known superconductors and then proceeding to search and screen CrxHy and PdH systems for experimentally relevant and reliable superconductive properties. 1. Shipley, Alice M., et al. "High-throughput discovery of high-temperature conventional superconductors." Physical Review B 104.5 (2021): 054501. 2. Duan, Defang, et al. "Structure and superconductivity of hydrides at high pressures." National Science Review 4.1 (2017): 121-135.

Closing Ceremony