X-ray analysis methods for sources from self-modulated laser wakefield acceleration driven by picosecond lasers

P M King; N Lemos; J L Shaw; A L Milder; K A Marsh; A Pak; B M Hegelich; P Michel; J Moody; C Joshi; F Albert

doi:10.1063/1.5082965

X-ray analysis methods for sources from self-modulated laser wakefield acceleration driven by picosecond lasers

Rev Sci Instrum. 2019 Mar;90(3):033503. doi: 10.1063/1.5082965.

Authors

P M King¹, N Lemos¹, J L Shaw², A L Milder², K A Marsh³, A Pak¹, B M Hegelich⁴, P Michel¹, J Moody¹, C Joshi³, F Albert¹

Affiliations

¹ NIF and Photon Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
² Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA.
³ Department of Electrical Engineering, University of California Los Angeles, Los Angeles, California 90095, USA.
⁴ Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA.

PMID: 30927775
DOI: 10.1063/1.5082965

Abstract

A versatile set of methods for analyzing x-ray energy spectra and photon flux has been developed for laser plasma accelerator experiments driven by picosecond lasers. Forward fit provides extrapolated broad energy spectrum measurements, while Ross pair and differential average transmission analysis provide directly measured data points using a particular diagnostic. Combining these methods allows the measurement of x-ray energy spectra with improved confidence. We apply the methods to three diagnostics (filter wheel, stacked image plate spectrometer, and step wedge), each sensitive to a different region of x-ray energies (<40 keV, 35-100 keV, and 60-1000 keV, respectively), to characterize the analysis methods using laser-driven bremsstrahlung x-rays. We then apply the methods to measure three x-ray mechanisms, betatron, inverse Compton scattering, and bremsstrahlung, driven by a laser plasma accelerator. The analysis results in the measurement of x-ray energy spectra ranging from 10 keV to 1 MeV with peak flux greater than 10¹⁰ photons/keV/Sr. The combined analysis methods provide a robust tool to accurately measure broadband x-ray sources (keV to MeV) driven by laser plasma acceleration with picosecond, kilojoule-class lasers.