Optimized online filter stack spectrometer for ultrashort X-ray pulses

Currently, with the advent of high-repetition-rate laser-plasma experiments, the demand for online diagnosis for the X-ray spectrum is increasing because the laser-plasma-generated X-ray spectrum is very important for characterizing electron dynamics and applications. In this study, scintillators and silicon PIN (P-type-intrinsic-N-type semiconductor) diodes were used to construct a wideband online filter stack spectrometer. The X-ray sensor and filter arrangement was optimized using a genetic algorithm to minimize the condition number of the response matrix. Consequently, the unfolding error was significantly reduced based on numerical experiments. The detector responses were quantitatively calibrated by irradiating the scintillator and PIN diode with various nuclides and comparing the measured gamma\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}-ray peaks. A prototype 15-channel spectrometer was developed by integrating an X-ray detector with front- and back-end electronics. The prototype spectrometer could record X-ray pulse signals at a repetition rate of 1 kHz. Furthermore, an optimized spectrometer was employed to record the real-time spectra of laser-driven bremsstrahlung sources. This optimized spectrometer offers a compact solution for spectrum diagnostics of ultrashort X-ray pulses, exhibiting improved accuracy in terms of spectrum measurements and repetition rates, and could be widely used in next-generation high-repetition-rate high-power laser facilities.