Thermal and chaotic distributions of plasma in laser driven Coulomb explosions of deuterium clusters

TL;DR

This study investigates whether plasma ions from laser-driven Coulomb explosions of deuterium clusters exhibit chaotic motion that mimics thermalization, analyzing energy distributions and fusion yields to understand their behavior.

Contribution

The paper demonstrates that ion energy distributions in Coulomb explosions are highly chaotic and resemble thermal distributions, providing insights into plasma behavior in laser-cluster interactions.

Findings

Maxwell-Boltzmann and shifted MB distributions fit experimental data well

Log-normal distribution overestimates fusion yields and high-energy ions

Ion kinetic energy distribution appears highly chaotic and thermal-like

Abstract

In this work we explore the possibility that the motion of the deuterium ions emitted from Coulomb cluster explosions is chaotic enough to resemble thermalization. We analyze the process of nuclear fusion reactions driven by laser-cluster interactions in experiments conducted at the Texas Petawatt laser facility using a mixture of D2+3He and CD4+3He cluster targets. When clusters explode by Coulomb repulsion, the emission of the energetic ions is nearly isotropic. In the framework of cluster Coulomb explosions, we analyze the energy distributions of the ions using a Maxwell- Boltzmann (MB) distribution, a shifted MB distribution (sMB) and the energy distribution derived from a log-normal (LN) size distribution of clusters. We show that the first two distributions reproduce well the experimentally measured ion energy distributions and the number of fusions from d-d and d-3He reactions. The LN distribution is a good representation of the ion kinetic energy distribution well up to high momenta where the noise becomes dominant, but overestimates both the neutron and the proton yields. If the parameters of the LN distributions are chosen to reproduce the fusion yields correctly, the experimentally measured high energy ion spectrum is not well represented. We conclude that the ion kinetic energy distribution is highly chaotic and practically not distinguishable from a thermalized one.