Soiciro Aogaki

The investigation of the effects of atomic ionization on nuclear reactions is of prime importance for nuclear astrophysics. However, no direct experimental measurement of this effect using a plasma target could be done as of yet. In this regard, we measured for the first time the neutron yield of a (p,n) reaction taking place in a target having different states of ionization. The studied nuclear reaction in this work was 51V(p,n)51Cr, induced in a natural vanadium target exposed to an external, laser-driven proton beam. In the solid target case, we measured 91(26)% of the expected neutrons, but this rate dropped to 30(18)% when the target was ionized. This significant reduction remains unexplained, even after taking into account electron screening effects, the stopping power in the target, and target expansion. Our findings open new avenues for investigating how plasma ionization influences nuclear reactions in hot matter relevant for astrophysical environments.

A direct measurement of the Li 7 ( p , α ) He 4 reaction at astrophysical energies was performed at the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) using a scaled-down version of the ELISSA detector array and the 3 MV Tandem accelerator. This reaction plays a crucial role in both primordial and stellar nucleosynthesis. In Big-Bang Nucleosynthesis (BBN), it is directly linked to the long-standing “Cosmological Lithium Problem,” the discrepancy between observed and predicted primordial Li 7 abundances. In stellar environments, it constitutes the final step in the hydrogen-to-helium burning chain. The experiment utilized a Li 7 beam incident on a CH 2 target at ten laboratory energies ( E lab ) corresponding to center-of-mass energies ( E c.m. ) ranging from 59.5 to 990 keV. The astrophysical S factors were extracted using both the Distorted Wave Born Approximation (DWBA) and polynomial fitting techniques. Updated reaction rates were calculated from the present DWBA results, supplemented by existing experimental data. The impact of the theoretical DWBA calculation on the reaction rate is investigated.

Modern nuclear physics experiments require flexible data acquisition (DAQ) systems for high data rates from diverse detector arrays. This paper presents DELILA (Digital ELI-NP List-mode Acquisition), an open-source DAQ system for high-throughput experiments at the Extreme Light Infrastructure – Nuclear Physics (ELI-NP) facility. DELILA employs a distributed, modular architecture with five components: Data Sources, Merger, Data Sinks, User Interface (UI), and Application Programming Interface (API). The system supports triggerless list-mode acquisition from silicon strips, scintillators, and germanium detectors using CAEN digitizers with various firmware (FW) (Digital Pulse Processing - Pulse Shape Discrimination (DPP-PSD), Pulse Height Discrimination (DPP-PHA), Charge Integration (DPP-QDC), waveform recording). Key features include robust clock synchronization, network transparency for distributed control, and optimized low-latency data transfer. Performance evaluation demonstrates sustained acquisition at 100 kHz per channel with FELib libraries and 2 MHz for single-channel 2730 digitizers. The system achieves 60 MB/s data rates with compact 30-byte events, enabling efficient storage. DELILA scales from 3 to 320 channels with real-time monitoring and event rate displays updated every 1-10 seconds. The Angular-based web interface with RESTful API facilitates remote operation and automated monitoring integration. Comprehensive testing using PuppEx signal generation validated stable operation across multiple digitizer configurations, with performance limited by disk I/O rather than acquisition electronics. DELILA’s open-source design promotes collaborative development and customization for diverse nuclear physics experimental requirements [1].

Here we report on the measurements of the γ -ray strength functions and nuclear level densities of Sn 112 , 114 performed for the first time at the 9-MV Tandem accelerator facilities at Horia Hulubei Institute for Physics and Nuclear Engineering using the Oslo method. We extract thermodynamic properties and gross and fine properties of the pygmy dipole resonance for systematic comparison in the chain of Sn isotopes. The results are compared with microscopic models implemented in the TALYS reaction code and the fully microscopic quasiparticle-phonon model for the underlying nuclear structure of the dipole strength in Sn 112 , 114 . 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 ( n , γ ) reaction of the p -process nuclei Sn 112 , 114 showing a significant increase in reaction rates at high temperatures compared to existing nuclear databases.

In order to enhance the performance of the ELI-NP Array of DEtectors (ELIADE), add-back procedure has been implemented and investigated. At the crystal level, an add-back factor of 1.41(2) at 1.173 MeV and 1.43(2) at 1.332 MeV have been obtained, increasing the P/T value from 0.13(1) to 0.21(1) for a ⁶⁰Co γ-ray source. To further improve those characteristics, algorithms to decide on event-by-event mode whether to perform or not this summation, have been investigated, as well as crosstalk correction techniques. Realistic Geant4 simulations have been implemented and tested to extrapolate to conditions with higher γ-ray energies and multiplicities.

Velocity vector measurement of laser-driven ions is essential to reconstructing electromagnetic fields in plasmas with ion radiography. A stack of solid-state nuclear track detectors can be used to diagnose the energy and incident angle of protons, which corresponds to the velocity vector measurement. However, the measured incident angle deviates from the normal when the ions are irradiated from a normal direction to the detector. In order to calibrate this, we irradiate an accelerator-generated proton beam on the CR-39 stack by changing incident angles. We analyze ion etch pits on scanned microscope images of the CR-39 with a convolutional neural network. While the measured angle agrees well with the incident angle when the incident angle ≲75 degrees, it tends to deviate from the incident angle as the incident angle approaches the normal direction. By numerically evaluating the proton incident angles using Monte Carlo simulations, we show qualitatively consistent results with our experimental results. We discuss the theoretical limitation of the standard formulation of etch pit analyses. We also show that the angle measurements are significantly affected by the resolution of etch pit images.