Deconvolution of multi-Boltzmann x-ray distribution from linear absorption spectrometer via analytical parameter reduction.

C D Armstrong,P Mckenna,R J Gray,D Kumar,D Neely,A S Pirozhkov

doi:10.1063/5.0057486

Abstract

Accurate characterization of incident radiation is a fundamental challenge for diagnostic design. Herein, we present an efficient spectral analysis routine that is able to characterize multiple components within the spectral emission by analytically reducing the number of parameters. The technique is presented alongside the designof a hard x-ray linear absorption spectrometer using the example of multiple Boltzmann-like spectral distributions; however, it is generally applicable to all absorption based spectrometer designs and can be adapted to any incident spectral shape. This routine is demonstrated to be tolerable to experimental noise and suitable for real-time data processing at multi-Hz repetition rates.

Highlights

Hard x-ray emission from high intensity laser interactions with solid targets is a broad spectral distribution extending up to the peak energies of the accelerated electrons
The design used here is an adaption to this technique, presented initially by Armstrong,6 that utilizes tungsten filters and Lu1.8Y0.2SiO5 (LYSO) scintillators to make a more compact rail that can operate both inside and outside a vacuum chamber—filtering from the external flange must be considered in the latter case
We present a novel approach that reduces the number of explicit variables that need to be scanned by directly calculating the optimum flux for each spectral component, i.e., the number of photons, ni, that minimizes the difference between the measured data and the trial spectra for a given set of control variables

Summary

INTRODUCTION

Hard x-ray emission from high intensity laser interactions with solid targets is a broad spectral distribution extending up to the peak energies of the accelerated electrons. We present a novel approach that reduces the number of explicit variables that need to be scanned by directly calculating the optimum flux for each spectral component, i.e., the number of photons, ni, that minimizes the difference between the measured data and the trial spectra for a given set of control variables Applying this technique to the measurement of the multiple components of an x-ray distribution can provide insight into the underlying physical processes, such as isolating a low-energy thermal emission that can otherwise dominate the interaction or probing an energetic but low flux component of the emission.. We note that depending on the interaction details, such as the presence of preplasma and electron distribution function, the QED regimes can produce Boltzmann-like distributions as well, as in the following simulations exhibiting no signs of decreased spectral density at low photon energies. the ability to deal with multi-component Boltzmann-like distributions and to distinguish them from non-Boltzmann distributions is of major interest for the present and future experiments

LINEAR ABSORPTION SPECTROMETER DESIGN

Example case

Comparison to other methods

DISCUSSION

SUMMARY