Opening

• Calin Alexandru Ur, Victor Malka

Investigation of pulse duration reduction and intensity increase of Petawatt-class laser systems

• Gabriel Petrisor Bleotu (LSD)

The motivation for this work arises from the need to advance the future development of peak power energy laser systems to pave the road for a better understanding of fundamental physics, Universe genesis, quantum vacuum properties, materials science etc.. In pursuing these multifaceted applications, a major goal is the increase of the maximum attainable peak power achievable by laser systems developed around the world in the last decades. The emphasis of our investigation will reside in a comprehensive exploration of the interaction between high-intensity laser pulses with thin transparent media to generate ultra-short pulses, close to 3 femtoseconds. In this work, I will present the need for ultra-short laser pulses, how we succeded in implementing the post-compression technique, and its impact in several applications.

Nuclear structure and nuclear reaction studies using microscopic theoretical models

• Emanuela Boicu (GDED)

Large Scale Shell Model was used to study magnetic dipole strength below and around the nuclear emission threshold. Spectral distributions in Cr nuclei were obtained, where the contributions of spin-flip and orbital counterparts are calculated with LSSM. Nuclear structure input based on Quasiparticle-Phonon Model calculations of ground and transition densities and spectroscopic amplitudes was prepared to be used for the calculation of alpha-scattering cross sections.

Exploring the mass-limits for statistical reaction model calculations with the TALYS code into the region of light nuclei

• Maria Brezeanu (GDED)

Calculations of nuclear reactions for astrophysical reaction networks can be a large scale computational effort. While dedicated fine tuned models can reproduce cross-sections in specific regions with high precision, network calculations usually use a global approach that can reproduce a large fraction of the nuclear chart although with less precision. For this purpose, the reaction code TALYS is commonly used and it is known to work well for intermediate and heavy nuclei – for example nuclei involved in the s-process. One recent undertaking that has begun is the PANDORA project coordinated as a collaboration between ELI-NP in Romania, RCNP in Japan, and iThemba LABS in South Africa. In this collaboration, the goal is to measure the nuclear properties, with special focus on photo-disintegration, for the understanding of the propagation of ultra-high energy cosmic rays (UHECSs). The nuclei involved in this process are, however, in the light region of the nuclear chart, below 56Fe, where global TALYS calculations in the same manner as for the s-process is significantly more difficult. In this contribution we will show recent work comparing experimental data on photo-nuclear reactions with theoretical calculations in TALYS for light nuclei to understand what the limits of global calculations are, and how to reach beyond this limit. By using different nuclear structure inputs, in particular regarding level densities and gamma strength functions, we want to find the most important quantities and improve the predictability of the TALYS code in the region relevant to UHECRs.

Tunable reflectivity beamsplitter

• Radu Laurentiu Caragea (LSD)

Laser beamsplitters are widespread in present day experiments. Yet, they offer fixed, discrete values of the splitting ratio. A tunable, continuously variable ratio of the transmitted to reflected power would be a helpful addition. One way to achieve this is by adding a polarizing component after a waveplate that controls the polarization components of the beam. In this study, however, we investigate an alternative approach based on Frustrated Total Internal Reflection using two prisms. We model the beam splitting ratio using a matrix propagation formalism, implemented in a programming code, to calculate the reflection and transmission coefficients for the proposed system. The addition of a thin layer TiO2 coating on one of the prisms improves the dynamic range from 7.2 (13.1 – 97 % tunable range for reflectivity) to 14 (6.5 – 95.2 % tunable range).

High energy photon generation from PW laser pulse interaction with a T-shaped target

• Bogdan Corobean (LDED)

We report an enhanced X-ray generation scheme based on the interaction of the PW-class pulses with a T-shaped overdense target, developing the previously suggested peeler scheme for acceleration of monoenergetic ion bunches. Including the reflective mirror segment of the target, the advantage of the scheme relies on a large number of electrons being accelerated to highly relativistic energies by a diffracted laser pulse and by the surface plasma wave colliding with the reflected laser pulse. This nonlinear Compton scattering mechanism greatly increases both energy and the number of emitted photons, compared to contemporary techniques. Our research has been conducted by means of large-scale numerical simulations with a 3D particle-in-cell code SMILEI with its radiation module.

Non-canonical method of producing graphene using Graphite Intercalated Compound exfoliated by Microwave Radiation

• Cosmin Jalba (LSD)

One highly used route to high throughput solution-based synthesis of graphene is the oxidation/intercalation of the bulk graphite followed by layer separations, with a resulting highly oxidized graphene, and then a reduction to graphene. The required oxidation state generally induces a large number of structural defects in the final graphene. Here we report a scalable H2SO4 intercalation driven synthesis method for graphite intercalated compound (GIC), followed by energetic exfoliation via microwave exposure at ambient conditions that produces with high efficiency and throughput a material consisting of a few layers graphene sheets. The 2D morphological surface characterization has been done by SEM analysis, the film chemical composition has been identified by EDS and XPS techniques and the graphene layer plus its lateral dimension have been determined using AFM analysis based on its topographic height images.

Radiation Biomarkers and Free Radicals Detection Using Magnetic Resonance Methods

• Diana-Cristina Serafin (Biophysics Lab)

Nuclear Magnetic Resonance methods play a crucial role in the novel, toxicity reduced, high dose-rates radiotherapy technique for cancer treatment, by providing useful information about early radiation effects on biochemical processes occurring in tissues. Metabolic profiling, by identification of biomarkers associated with radiation response, serves as indication of treatment efficiency, which is done using NMR spectroscopy studies. On the other hand, real-time imaging of free-radical formation, by direct experimental methods, is also very important in radiobiology. This presentation will provide insight into the NMR methods that are used in the context of ELI-NP, containing both metabolic profiling studies of radiation dose-rate effects on cancer and healthy cells, by NMR spectroscopy, and detection studies of free-radical formation during the time course of a chemical reaction, which can be imaged through NMR relaxation measurements of water protons in Earth’s magnetic field, in an open-coil spectrometer.

Towards radiobiological experiments at ELI-NP facility: the first trials at 100 TW and 1 PW

• Ioana Fidel (Biophysics Lab)

Radiotherapy is used in combination with other techniques to treat different types of cancer. High dose-rate delivery of radiation, as afforded by high-power laser systems, may improve radiotherapy methods. The aim of high dose-rate 'FLASH' radiation delivery is to spare the healthy tissue, while maintaining at the same time the desired therapeutic effect on tumors. We have established an irradiation setup using secondary radiation (electrons) stemming from the interaction chambers of 100 TW and 1 PW laser beams operating in pulses of 1.5-2 J, 29.5-30 J and 28 fs duration delivered onto a gas target. Variations in metabolite concentrations between control and irradiated samples for U251 Glioblastoma cells (tumoral cell line) and BV-2 Microglia cells (non-tumoral cell line) were measured using high-field Nuclear Magnetic Resonance spectroscopy. The metabolic profiles from the two types of cell lines allow us to assess the effects of FLASH radiation immediately after delivery to cells.

Analysis of High-Energy (p,p') data on 12C for the PANDORA Project

• Andreea Gavrilescu (LGED)

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 test experiment at RCNP on 12,13C. These measurements can further be used to constrain the propagation and the origin of UHECRs.

Proton Protein Paintings

• Octavian Ianc (Biophysics Lab)

Proteins are the cornerstone of virtually all biological processes in the known forms of life. Gaining a better understanding of protein structure and function is, therefore, a goal of utmost importance in comprehending vital processes. In the context of ELI-NP, the analysis of the effects of radiation on proteins is a key element in evaluating their therapeutic effect. NMR is a significant tool for protein analysis, with the main advantages of non-destructive measurements and the ability to assess temporal dynamics. However, this method does, of course, have its limitations, primarily stemming from the limited lifetimes of the used quantum states, which, in turn, constrain measurement duration and accuracy. In this presentation, we will explore the key concepts and methods used for NMR protein structure determination and introduce a potential novel method developed by our research group to enhance this process using long-lived quantum coherences.

Qualification of spiral phase plates for high power laser systems

• Vicentiu Iancu (LSD)

Qualification of spiral phase plates for high power laser systems The application of light beams exhibiting Orbital Angular Momentum (OAM), commonly known as optical vortices (OV), has led to notable progress in various fields, such as optical metrology and the exploration of new interactions between light and matter. Despite the emergence of several techniques for generating and detecting structured light beams, including those with OAM, accurately characterizing these beams—especially in terms of their amplitude, wavefront, and mode content—remains a challenging and unresolved issue. The high-power laser system (HPLS) at ELI-NP [1] will be able to produce focused intensities of up to few I0 ∼ 1×1023Wcm−2. Therefore, increase availability and access to such spatially and temporally ultra-intense laser solutions provides an opportunity to produce and inevitable to implement in any experiment optical vortices. In this research, we introduce a method for precisely measuring full aperture phase discontinuities using a Shack-Hartmann wavefront sensor. OV beams were generated by employing spiral phase plates (SPPs), already used in the first user experiments campaign at ELI-NP [2]. The wavefront was characterized by measuring the transmitted or reflected wavefront with the detector positioned in the relay imaging plane across a 70mm aperture, utilizing a flat mirror with a central hole. The experimental setup demonstrated the capability to distinguish between the 16 steps of the helical phase plate, and reconstruct the low order aberrations introduced by the wavefront. The obtained results were combined with measurements from a non-contact optical profilometer, thus offering an alternative to conventional measurement methods. The approach based on the characterized large aperture helical phase plate make possible continuous operation of HPLS to deliver hollow ultra-short laser pulses [2], for ion acceleration experiments [3].

Nanotubes and nanowires targets fabrication for high power laser experiments

• Stefania Ionescu (Target Lab)

In high power laser-solid target interaction experiments, usually a flat target is used to accelerate ions, create X-ray emission, neutrons, or other particles. If on top of the flat target surface nanostructures are added, the surface area is larger, resulting in a better coupling of the laser pulse with the target. Therefore, the laser absorption and conversion efficiency of the laser energy to accelerated particle energy is increased, leading to better proton acceleration (in terms of energy and particle numbers), x-ray emission, and high energy density matter creation. Highly ordered metallic nanotubes and nanowires were fabricated at ELI-NP Target Laboratory by electrochemical methods. The raw material is an aluminum plate which is pre-processed by polishing, rolling, and thermal treatment, and then anodized to obtain a porous alumina template in which the metallic structures are grown by electrodeposition from Watts bath containing the metals salts (e.g. nickel chloride and nickel sulfate for nickel nanostructures). The template is then dissolved, and the structures liberated. The diameter of the wires/tubes varies from 100 to 400 nm, with distances between them of 100-300nm and length of few microns on a very thin substrate (from 300nm to microns thick). The nanostructured thin films of a few cm2 areas are then cut into pieces and mounted on frames to be used in high power laser experiments. Nickel nanowires and nanotubes were shoot in 3 different laser configurations: at ILIL PW laser in Pisa, at ELI-NP 1 PW user experiment, and in Gemini laser from Rutherford Appleton Laboratory, where proton acceleration and x-ray emission were measured in comparison with flat targets. Preliminary data analysis showed that there is an increased efficiency of the laser energy absorption on these types of nanostructured targets, as compared to flat surface targets.

Betatron radiation and Lienard-Wiechert potentials

• Rares Iovanescu (LDED)

Electrons injected in the bubble of laser wakefield acceleration produce due to their oscillations, synchrotron-like radiation called betatron radiation. In studying this process the trajectory of electrons determines the regime of oscillation, wiggler or undulator. The radation produced by an accelerated charge in electromagnetic field was described by the Larmor formula for nonrelativistic cases and using the Lienard-Wiechert potentials for the relativistic case. The link between the particle dynamics and the emitted radiation is the Poynting vector, which integrated on surface gives the radiated power. We examine these and the effect of the Abraham-Lorentz force (radiation reaction force). Besides, we present results obtained from PIC simulations with the photons emitted energy and parameters of the betatron oscillation such as wiggler strength parameter K, critical harmonics and critical energy.

The study of Li-7 photodisintegration with mono-energetic gamma-ray beams

• Ioana Kuncser (LDED)

The abundances of the light elements produced in the early stages of the Universe are accurately predicted by Big Bang Nucleosynthesis (BBN). However, following the observations on low-metallicity stars, the measured 𝐿𝑖7 abundance is 3-4 times lower than expected. Due to this discrepancy, known as “cosmological Li problem”, it can be assumed that either the measurements are leading to anomalous results, or an error is present in the theoretical models. Since two main reactions are responsible for the production of mass 7 elements, 𝐻(𝛼, 𝛾) 𝐿𝑖73 and especially 𝐻𝑒(𝛼, 𝛾) 𝐵𝑒73 , the error can be related to the WMAP baryonic density. A lower value for this quantity corresponds to a higher effect of the 𝐻(𝛼, 𝛾) 𝐿𝑖73 reaction. While 𝐻𝑒(𝛼, 𝛾) 𝐵𝑒73 reaction have been well studied, only a few experiments were performed over the 𝐻(𝛼, 𝛾) 𝐿𝑖73 reaction. Although an experiment implying a tritium target cannot be performed anymore, the 𝐻(𝛼, 𝛾) 𝐿𝑖73 reaction can still be studied by its inverse reaction: 𝐿𝑖(𝛾, 𝑡) 𝐻𝑒47 . A measurement of the photodisintegration of 𝐿𝑖7 was performed in 2017 by our team at High Intensity γ-ray Source (HIγS) Laboratory at Duke University (USA). The detection of the alpha-triton coincidences was performed using an array of segmented silicon detectors. The considered energies of the gamma beam were between 4.4 and 10 MeV, but the coincidences have been clearly separated only for energies higher than 6 MeV and especially in the thinner detectors. As a continuation, a similar experimental campaign took place at HIγS in the first part of April 2023, to measure the cross section and the angular distributions of 𝐻(𝛼, 𝛾) 𝐿𝑖73 reaction at energies lower than 6 MeV. The study used a 𝐿𝑖𝐹 target and an improved array of segmented silicon detectors with a similar arrangement but thinner than in the previous set-up such as the coincidences were properly separated for those lower energies. The preliminary results of the experimental campaign performed at HIγS in the beginning of April 2023 problem will be presented.

Neutron detection in an high intensity laser environment

• Vincent Lelasseux (GDED)

With the advent of multi-PW lasers, it is foreseen that laser-driven proton beams could reach hundreds of MeV energy cutoff. In this regard, an application for such high energy protons could be the creation of ultra intense laser-driven neutron sources. Indeed through the spalliation process, it is possible to efficiently convert those high energy protons into neutrons with a widespread spectrum, up to the energy cutoff of the incoming proton beam. In order to characterize such neutron sources, one must first develop detection devices adapted to the peculiar environment of the ultra high intensity lasers. In this regard, we present here some neutron detectors that has been tested during the commissioning of the E1 10 PW area and the first results obtained.

The Cosmological Lithium Problem: direct measurement and study of the 6Li(p,α)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 nucleosyn-thesis (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.

Development of ultra-low density C double layer targets for enhanced laser-driven proton acceleration

• Alexandru Magureanu (LDED)

Target Normal Sheath Acceleration (TNSA) has been widely recognized as a robust mechanism for proton acceleration, and extensive efforts have been dedicated to enhancing the number of protons, their energy, and the stability of the acceleration scheme, over the past two decades. We propose an approach based on developing specifically designed targets which can facilitate an improved laser absorption. This design aims to enhance the cut-off energy and flux of accelerated protons. The utilization of structured targets comprising a low density carbon foam deposited on a simple Al foil is presented. A much improved proton cut-off energy is demonstrated in experiments carried out with the Gemini Laser System using a Double Plasma Mirror set-up delivering a contrast better than 1010 at a few picoseconds before the peak pulse and with some pre-pulses identified at the ns level.

Drift free 11 fs jitter measurements at HPLS

• Andrei Naziru (LSD)

Investigation of nuclear levels to improve the predictions of astrophysical reaction rate

• Cosmina Nedelcu (GDED)

One particularly challenging piece of the stellar nucleosynthesis puzzle is the origin of the heavy elements. Elements heavier than iron are mainly produced by neutron-capture reactions within the slow and rapid neutron-capture processes (s- and r-process, respectively). The r-process is believed to take place in environments characterized by high neutron densities, such that successive neutron captures can proceed into neutron-rich regions well off the β-stability valley. It involves a large number (typically five thousand) of unstable nuclei for which many different properties have to be determined and cannot be obtained experimentally. One of such fundamental properties concerns the radiative neutron capture reaction. The radiative neutron capture is traditionally estimated within the framework of the statistical Hauser–Feshbach formalism. This approach enables the calculation of nuclear level density and energy-averaged cross section, so it provides information about the reaction rate. The present study aims to investigate the astrophysical neutron-capture reaction rates of nuclei far from the β-stability valley. First, a systematic comparison of theoretical predictions and β-Oslo data is performed for unstable nuclei. It is followed by an analysis of purely theoretical and experimental NLD levels for the neutron-rich nuclei, as well as an examination of how astrophysical temperatures affect the reaction rates. The sensitivity of the radiative neutron-capture cross section is then evaluated in various NLD energy ranges to determine the most effective NLD energy interval.

Large Aperture LIDT: preliminary data analysis, current work

• Andrew-Hiroaki Okukura (LSD)

Laser-induced damage threshold (LIDT) experiments are fundamental in high-powered laser research for controlling damage on optical components and pushing the boundaries of using higher-powered laser pulses. Therefore, optimal characterization of materials and components used in the experiment is necessary. LIDT research is challenging due to the large quantity of statistics needed, which can be obtained using large-aperture pulses. My work consists of the data analysis performed on the first large-aperture LIDT experiment using femtosecond pulses, employing image processing techniques. Preliminary LIDT curves have already been obtained for Ag (SiO2) and chirped mirrors, with ongoing work to improve the algorithm and data to obtain LIDT curves. The experiment could demonstrate the viability of using large-aperture LIDT in quality control for optical mirror production, such as in the upcoming COMP facility.

Theoretical Predictions For Radiative Capture Cross-sections Of Interest For Astrophysics In The Fast Neutron Region

• Paul Parlea (GDED)

The radiative capture reaction plays a key role in the nucleosynthesis process. The applications of nuclear astrophysics involve thousands of unstable nuclei for which no experimental data are available, therefore theoretical predictions of the reaction data are needed. The present study intents to establish if and at what extent the reaction models with empirical parameters - as opposed to microscopical inputs - implemented in the evaluation codes could be used for the estimation of the reaction cross sections of the nuclei away from the stability valley, at energies above the resonance region. For this purpose, the EMPIRE code was used to provide an overall description for the cross sections of the neutron induced reactions on Molybdenum and Stanium, with incident energies up to 20 MeV. The results of the calculations for the stable isotopes are compared with evaluations from major libraries and with the existing experimental data.

Position sensitive scintillation detector for gamma-spectroscopy

• Bogdan 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.

TPC data analysis (analysis of frames) in ROOT: how to approach

• Stefan Niculae (GDED)

The mini-eTPC, found at ELI-NP, is a detector used in nuclear physics experiments. A successful experiment may yield a large volume of data that needs to be analyzed. Doing this analysis manually is time consuming, thus an automated method is necessary. By using data science methodology and image analysis algorithms, the efficiency of the analysis can be greatly increased. The algorithms can find the equations of the traces left by particles and compute the location of the interaction points. This information can be further used to compute different statistics that can be used to understand the physical phenomenons.

Vacuum effect on bulk etch rate of polymer track detectors

• Mara Popovici (Dosimetry Lab)

Polymer track detectors are considered to be reliable means used in particle detection, their analysis implying a chemical etching process. The process of placing track detectors in vacuum, irradiating them for specific periods and then restoring them to normal pressure can induce damages or changes in the polymer structure. The purpose of this study is to evaluate the effect of vacuum exposure on the polymer track detectors and on the way they respond to the upcoming chemical processing. The analysis of these polymer track detectors implies a chemical etching process which is dependent on the etching time, temperature and etchant concentration. The investigation of vacuum-induced modifications was studied in terms of bulk etch rate by irradiating the PADC (Poly(allyl diglycol carbonate)) detectors with a 252Cf source for different periods of time.

Advancements in Nuclear Reaction Analysis: A Data Science Approach with the mini-eTPC Detector at ELI-NP

• Oana-Adriana Sirbu (GDED)

Situated at ELI-NP, the mini-eTPC detector is a gas-based time-projection chamber that investigates photonuclear reactions in astrophysical energy ranges. With its highly segmented anode and sophisticated Gas Electron Multiplier (GEM)-based read-out system, it explores mechanisms leading to 12C and 16O isotope formation. This detector is developed by ELI-NP/IFIN-HH in collaboration with University of Warsaw and facilitates inverse reactions like neutron-12C interactions, enabling the measurement of triple alpha to 12C cross-sections. Comparing with our previous work that relied on time-consuming data analysis methods, this study marks a revolutionary change. By introducing data science algorithms, we enhance analysis efficiency, estimated to reduce the timeline from a year to a few weeks. The study is based on data from the IFIN-HH's 3MV Tandetron Accelerator commissioning experiment, specifically designed for the TPC detector, featuring a neutron beam directed at a CO2 target. Effectively comparing old and new analysis methods using this dataset, we underscore the strength of our innovative approach. We incorporate new strategies, such as color-based feature extraction from images, to accelerate data sorting. This not only validates previous findings but also highlights the profound impact of our improved analysis on advancing complex nuclear reaction investigations.

Ultrashort Laser Pulses with Space-Time Coupling at ELI-NP

• Maria Talposi (LSD)

Petawatt peak-power laser systems, like HPLS at ELI-NP, could be obtained in the past few years using the Chirped Pulse Amplification (CPA) technique - which was awarded with the Nobel Prize for Physics in 2018. CPA implies stretching and compressing the pulse duration by introducing controlled space-time coupling (STC) in the laser field. Non-perfect compensation along with dispersive optical elements cause residual STC at the output of the laser chain. We present STC signatures in the near-field and at focus of the laser field, as simulated with a home-made propagation code. Furthermore, we compare the simulations with experimental measurements of laser pulses with controlled STC. Finally, we show the STC optimization method at HPLS and the consequent improvement of the focus quality.

Computational and experimental studies of metallic hydrides

• Maria-Iulia Zai (Target Lab)

Metallic hydrides (MeHx) have proven in the last decade highly attractive to the scientific community as room-temperature superconductors and, due to their composition (a controllable mixture of heavy and light elements), also as potential materials for solid targets for high power laser experiments. Computational methods were used to study the structure and physical properties of several hydrides from Me-H systems (with Me=Cr and Pd) via density functional theory (DFT) in order to observe the superconducting phase originating from the strong electron-phonon coupling and high-frequency modes provided by hydrogen embedded in metallic interstitial sites. In order to determine the stable structures, the formation enthalpy as a function of stoichiometry and pressure was investigated using an efficient structure prediction software (CALYPSO), while physical properties were determined using an all electron linearized augmented plane wave code (ELK). The computational data showed that most of the studied hydrides feature a closely-packed metal lattices, with hydrogen filling interstitial sites, while electron-phonon coupling calculations showed that, when superconducting, these phases are phonon-mediated superconductors. Experimental results of hydride films fabricated by RF sputtering, including epitaxial PdH thin films obtained for the first time by a physical deposition method, will also be presented, with focus on hydride phase stability.

Laser prepulse induced implosion of nanowires based targets

• Alexei Zubarev (LGED)

Nanostructured targets allow better performance of laser-driven experiments due to deep penetration of laser radiation and uniform heating of the target. For correct implementation of experimental, tasks it is important to preserve the target form during all exposition time. However, laser prepulse influence is inevitable and the energy amount transferred during the prepulse can be considerable. In this work, we studied the influence of laser contrast on the generation of the overcritical layer in front of the nanostructured target and nanowires implosion. We considered aluminum nanowire arrays with different fulfillment factors supposed to be a prepulse with form reproduced from the real experiments implemented at ELI-NP. We implemented numerical simulations using radiation-hydrodynamic FLASH code. We observed the implosion for 250ps laser prepulse for 1PW laser. As well, overcritical density regions are generated in front of the nanowires. A continuous overcritical density layer appears only for 10 PW laser after 250 ps prepulse. Moreover, we estimated the implosion speed, as the speed of the overcritical density region. The implosion speed is higher than the speed of sound in the nanowires, but lower than the sound speed in plasma.

Digital Pulse processing in gamma spectroscopy

• Sara-Rebeca Ban (GDED)

Digital pulse processing (DPP) represents the core of extracting information about useful data from the radiation detector pulses. It is a well-known method used in the field of nuclear physics. One such DPP is the Pulse Shape Discriminator (PSD). It is used at ELI-NP for differentiating between different particles such as neutrons and gammas based on the shape of their voltage pulses. The used digitizers in the experimental set-ups contain built-in PSD and Constant Fraction Discriminator (CFD) algorithms. One drawback with commercial digitizers is the fact that the processing code is enclosed without any easy access. In this work, I will present the equivalent code, done in-house, which will ensure custom solutions for future nuclear physics experiments.

Fast Fourier Transform Algorithm for Extraction of Attenuation, Phase, and Scattering Images in Phase-Contrast Imaging

• Ionut-Cristian Ciobanu (X-ray Imaging Lab)

Phase contrast imaging is based on the refraction of the X-ray beam as it passes through the material and shows excellent results for biological tissues. In this presentation, we present a new approach for a Python algorithm that can filtrate phase contrast images (attenuation, phase, and scattering) and improve the identification of the interest object. The images used in this work were obtained with a 5.66 m long Talbot-Lau interferometer with a record angular sensitivity of 0.82 µradians, a phase stepping procedure of 16 steps, and a mean energy of 30 keV. The sample used was 0.89 mm diameter fiber from an accredited mammographic phantom. The proposed algorithm extracts the attenuation, phase, and scattering images from the dataset using Fast Fourier Transform. For filtration, we implemented a non-linear filter (median) to eliminate the noise generated by the acquisition system and the projection processing and to improve the contrast. The results were analyzed by calculation of the contrast-to-noise ratio (CNR).

Controlling the electromagnetic field in the optical and THz bands with metasurfaces

• Alexandra-Elena Grigore (LSD)

Presenting theoretical analyses of a nanoantenna based on a metal-dielectric metasurface designed to operate within the frequency range of 7-10 THz. This metasurface demonstrates strong responsiveness to external electromagnetic fields and offers a wide dynamic range for both reflection and absorption. Its characteristics are adjustable based on input polarization, making it suitable for various terahertz applications, including dichroic filters, tunable switches, and absorbers, with the possibility of being scaled to operate in the IR and visible optical spectra.

Beam Pointing Drift and Stability Analysis in HPLS

• Alexandru Lazar (LSD)

While our colleagues focus on improvements in the experiments with high-power laser system, on the LSD side we focus on improving the quality of the laser beam. Ago 2 months we started to investigate the spatial stability of the beam pointing in our HPLS. First of all, beam-pointing instability means that, after the propagation of the laser pulse, at the endpoint of the system, every beam position of the beam is changing in space. I will show you the eforts in data analysis of the experimental team from E1 area with the laser beam fluctuation and from E4 area with the beam pointing drift. So the purpose of this research is to improve the stability of the laser beam.

Plasma mirror

• Ana-Maria Lupu (LSD)

he plasma mirror, operating as a distinctive ultrafast switch on a sub-picosecond scale, poses a remarkable yet not fully elucidated switching behavior. The formation of a plasma is initiated by the interaction of an intense femtosecond laser pulse with a transparent material, swiftly increasing the reflectivity of the surface. This plasma mirror formation takes place on a time scale of sub-picosecond. It is investigated here the interplay between intense laser pulses and plasma mirrors by implementing of a pump-probe method based on the retrieval of spectrally encoded temporal information. The exceptional ultrafast switching capabilities exhibited by plasma mirrors unlock a spectrum of applications, ranging from high-speed data transmission to laser pulses characterization and temporal contrast enhancement.

Back reflection monitoring developments for 10 PW experiments

• Dmitrii Nistor (LSD)

The purpose of this presentation is to outline the plan to install a back-reflection (BR) monitoring system in Vacuum Transport System for the 10 PW experiments held in experimental chamber E6. Here we will propose two possible solutions to capture the BR light. The first solution is to capture a small aperture of the BR from the leakage of the large steering mirror located in the first turning box by extracting it with a couple of mirrors through a DN200 viewport. The second proposal is installation of a setup that will allow us to capture the leakage of the Long Focal Distance Mirror (LFD) located in the second turning box.

Preparation and Delivery of the Laser Beam at 1 PW configuration

• Saidbek Norbaev (LSD)

This work presents the stages of preparing a laser system for an experiment using the 1 PW configuration, and also describes the process of delivering the beam to the experimental chamber with different attenuation levels

Implementation of the control system for VEGA

• Robert-Daniel Patrascoiu (GSD)

The Variable Energy Gamma (VEGA) System, currently under construction at Extreme Light Infrastructure - Nuclear Physics (ELI-NP), is a storage ring-based gamma source that aims to provide users with gamma-ray beams spanning a variable energy range from 1 MeV to 19.5 MeV. The control system of VEGA is designed to be an EPICS-based distributed system, which contains subsystems for the control of vacuum, cooling, magnets, interlocks, etc. This will include an alarm system for important events. This presentation will introduce the integration of Mydax 3MP34W chillers for cooling, QPC Ion pump controllers for vacuum, and radiation detectors for personal protection subsystems. Devices for the subsystems have been integrated into the EPICS Input / Output Controllers (IOCs), while the Operator Interfaces (OPIs) have been designed using Python and Qt Designer.

Optimizing the statistical and systematic reach of the PanEDM experiment

• Vlad Popescu (LSD)

The detection of a neutron electric dipole moment with a magnitude larger than the Standard Model prediction would imply the existence of new physics. Currently, the limit is set at 1.8×10−26 e cm (90% C.L.) by a technique employing the storage of ultra cold neutrons. The PanEDM experiment installed at Institut Laue-Langevin is the first to use the new ultra cold neutron source, SuperSUN, and aims to improve the limit by an order of magnitude. Such an improvement implies extending the statistical reach and strongly suppressing and characterising the systematic effects. To take full advantage of the ultra cold neutron source output, the neutron transport from the source to the experiment needs to be optimized. One way of doing this is by using nickel-phosphorus (89.5/10.5) (NiP) as a neutron guide coating, as it has a high optical potential, it is non-magnetic and exhibits low roughness if deposited through electroless deposition. The characterization of the NiP was done using profilometry, atomic force microscopy and neutron reflectometry. The control of the systematics will be done using an array of optically pumped Hg magnetometers, and is being commissioned

Fusion-Based Algorithm for X-Ray Phase Contrast Imaging Techniques

• Cezara Diana Rasinar (X-ray Imaging Lab)

Phase Contrast X-ray Imaging represents a technique that has shown remarkable potential in the research field, by providing better visualization of soft tissue, high-contrast images, and high spatial resolution. In the phase contrast imaging technique, the extraction of the three images represented by attenuation, differential phase contrast, and dark-field contrast is essential, providing, in a specific way, information about the nature of the analyzed tissue. This study introduces a new method based on the three acquired images merging while adjusting the weighting factors, aiming to identify the interest object and to extract the information provided by each contrast channel. In this regard, a fusion-based algorithm was applied to images acquired, using a 5.66 m long Interferometer Talbot-Lau with ultrahigh sensitivity of 0.84 µradians and mean energy of 30 keV.

Rapid prototyping technologies at LSD

• Sergiu-Vlad Rusnac (LSD)

Rapid prototyping, including 3D printing and additive manufacturing techniques, has emerged as a transformative tool in various industries, revolutionizing traditional manufacturing processes. This presentation delves into the specific applications and advancements of these technologies at ELI-NP, emphasizing their pivotal role in expediting the prototyping and development of intricate components for experimental setups.

Numerical study of lens focusing methods

• Georgiana Bianca Stan (LSD)

The aim of this numerical study is to compare the focusing of four beams of different intensity distributions at the entrance to a lens. The comparison is quantitative because I compared the values of the standard deviation and the full width at half maximum in focus for each distribution. This was followed by the identification of which distributions focus better in terms of the mentioned parameters, as well as the identification of the reasons why some distributions do not focus as well as others.

The degradation level of the optical components inside the pumping lasers of HPLS

• Lidia Vasescu (LSD)

The High Power Laser System is a complex machine that needs scheduled preventive maintenance. One of the key components of this system are the pumping lasers for which I made a presentation of how the operation team is performing the preventive maintenance. Even if this maintenance is very rigorous done, some unexpected issues might occur during beamtime.

Designing Smart Eyewear for Photophobia Management in Medical and Clinical Cases

• Fattima Al-Abedj (LSD)

Photophobia can significantly impact the quality of life for affected individuals, hindering daily activities and exacerbating underlying health conditions. This study introduces the design and development of smart eyewear as an innovative solution for managing photophobia in medical and clinical cases.

Contamination reduction in vacuum systems using Silica gel

• Antonia Toma (LSD)

This work intends to bring in the atention of laser comunity the importance of reducing contamination in vacuum systems. We also present an inovative and easy to apply method which we already tested in our lab and which we will continue to improve until we reduce the contamination to the minimum level

Parameters stability in dual arm femtosecond laser systems

• Alice Dumitru (LSD)

Experiments using two multi-petawatt laser pulses promise access to experiments with extraordinary field strengths. To perform such challenging experiments, very high stability of the laser parameters must be achieved. In this study, the main laser pulse parameters are considered (spectral distribution, spatial shape, energy stability and temporal duration) for the purpose of overlapping multiple beams. Data from the HPLS laser diagnostics are collected and analyzed from both a normal day of operations and a day of dual-beam jitter experimental campaign. HPLS stability is measured for each parameter. Complementary, AVESTA system is being upgraded with a second arm, a multi-pass amplifier and a compressor, for future dual beam parameters stability, pulse overlapping and synchronization investigations.