Spectral characterization of flash and high flux x-ray radiographic sources with a magnetic Compton spectrometer

M Espy; M Klasky; M James; D Moir; J Mendez; R Morneau; R Shurter; R Sedillo; P Volegov; A Gehring

doi:10.1063/5.0053184

Spectral characterization of flash and high flux x-ray radiographic sources with a magnetic Compton spectrometer

Rev Sci Instrum. 2021 Aug 1;92(8):083102. doi: 10.1063/5.0053184.

Authors

M Espy¹, M Klasky², M James³, D Moir⁴, J Mendez⁵, R Morneau⁶, R Shurter⁴, R Sedillo⁴, P Volegov², A Gehring²

Affiliations

¹ Non-destructive Testing and Evaluation, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
² Neutron Science and Technology, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
³ Nuclear and Radiochemistry, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
⁴ DARHT Physics and Pulsed Power, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
⁵ DARHT Experiments and Diagnostics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
⁶ Detonation Science and Technology, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

PMID: 34470406
DOI: 10.1063/5.0053184

Abstract

In this work, we present a new analysis method applied to revitalize permanent magnet Compton spectrometers used to measure photon energy spectra in the MeV range. The inversion of the measured electron distribution to determine the original photon distribution is achieved via a method of consistent coupled radiation transport and magnetic field mapping of the input photon spectra to the measured electron distribution. The method of linear least squares was used to perform the unfolding of the electron distribution to the initial photon spectra, without any assumptions made regarding the electron distribution. We present an application of this method to data from a nominal 19.4 MeV flash radiographic source (the first axis of the Dual Axis Radiographic Hydro-Test Facility) capable of generating 500 R @ 1 m in ∼60 ns and a medical therapy source (a Scanditronix M22, Microtron) capable of variable energies with nominal endpoints of 6, 10, 15, and 20 MeV and an output of ∼1000-2000 R/min @ 1 m. The results provide agreement between the modeled and unfolded experimentally measured photon spectra as quantified by statistical tests, from 1.5 to 20 MeV. Experimental results are presented as well as a discussion of the novel MCNP6-based simulations and methods for reconstruction of the spectra.