2nd INFN School and Workshop on “High Power Lasers for Fundamental Science and Applications” (HPLA2025)

Laser-driven p($^{11}$B,α)2α reaction in pitcher-catcher configuration: CR39 and activation measurement supported by Monte Carlo simulation

Not scheduled

20m

Aula "Migneco" (Laboratori Nazionali del Sud - Istituto Nazionale di Fisica Nucleare )

Poster Poster Session

Speaker

Nicolò Macaluso (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, Catania (IT))

Description

The proton boron-11 fusion reaction is gaining interest as aneutronic alternative to conventional fusion approaches, due to its characteristic to produce three alpha particles without neutron emission. This feature makes it attractive for clean energy production with reduced radiological impact.
In this context, an experimental campaign was conduced at the PALS facility in 2024 to investigate alpha particle production from boron-enriched targets irradiated with a high-intensity laser. The study employed a mixed setup combining both “in-target” and “pitcher-catcher” configurations. The main laser pulse interacts with a primary target, initiating both in-target fusion reaction and the emission of energetic particles (mainly protons). These particles then strike a secondary thick target composed of natural boron, where further p($^{11}$B,α)2α ructions occur in the pitcher-catcher configuration.
Various diagnostics were employed during the experiment, including Time of Flight (TOF) systems for real-time monitoring, Thomson Parabola (TP) spectrometers for ion characterization, and CR39 nuclear track detectors for particle identification. This work focuses on the fusion reactions occurring in the secondary target. Alpha particles emitted from the boron target were detected using CR39 detectors positioned in front of the target shielded with aluminum filters of varying thickness to suppress low-energy background contributions. Preliminary analysis of the CR39 detectors indicates an estimated alpha fluence of about 10$^5$ α/cm$^2$, meaning a yield of 10$^6$ α/str.
A key aspect of the experiment was the successful activation of the natural boron target (secondary) by the ion beam produced via the ablation and the backward acceleration of the protons from the primary target. Activation was quantified using an HPGe detector, leading to an estimate of approximately 10$^7$ proton boron-11 fusion reactions occurring inside the secondary target per laser shot.
To support and interpret the experimental results, Monte Carlo simulations were carried out. A first simulations, incorporating the experimentally measured proton and carbon spectra from the TP diagnostic, evaluated the impact of backscattered ions (protons and carbons) on CR39 signals. Another simulation then was carried out to study the alpha emission from the thick secondary natural boron target and compare it with CR39 measurements.
In summary, this study combines various experimental diagnostics and numerical modeling to validate the alpha yield measurements, with particular attention to CR39 detectors, which are especially challenging to interpret.