A Nuclear-Based Diagnostic Scheme for Nonthermal Ion Spectrum in High Energy Density Plasmas Experiments

TL;DR

This paper introduces a nuclear diagnostic method to measure nonthermal ion spectra in high-energy-density plasmas, utilizing product energy spectra to determine ion energy characteristics, demonstrated through PIC simulations of laser-driven magnetic reconnection.

Contribution

A novel nuclear diagnostic scheme that accurately characterizes nonthermal ion energy spectra using product energy spectra in high-energy-density plasmas.

Findings

pB reaction rate increased by 4 orders of magnitude in simulations

Product spectral peak and width shift to higher energy in reconnection

New analysis approach effective for laser-driven magnetic reconnection parameters

Abstract

The nuclear reactions in a plasma system with energy distribution deviated from Maxwellian are proved to have some unique characteristics including those in their product energy spectrum. Based on this, a new nuclear diagnostic scheme for measuring the nonthermal ion energy spectrum in high-energy-density plasmas is proposed, where the effective temperature and spectral peak of the nonthermal ion energy spectrum are uniquely determined by the spectral width and spectral peak of the product energy spectrum. Then, taking the laser-driven magnetic reconnection experiment as an example, according to the particle-in-cell (PIC) simulation results coupled with the proton-boron (pB) fusion reaction, the pB reaction rate is increased by 4 orders of magnitude; meanwhile, the product spectral peak and spectral width are shifted towards higher energy, deviating from the predictions of the thermal equilibrium assumption, both of which are on account of the accelerated and heated suprathermal protons in magnetic reconnection. Furthermore, analyzing a series of simulation results, the new product spectrum analysis approach suitable for the parameter range of laser-driven magnetic reconnection is found.