Investigation of the Spectral Composition of X-Ray Radiation from Femtosecond Laser Plasma by Thermoluminescent Detectors

A technique based on thermoluminescent LiF(Mg,Ti) lithium fluoride detectors has been developed to study the spectral composition of  X-ray radiation of femtosecond laser plasma in a wide range of photon energies from 1 keV to almost 1 MeV. This technique has been experimentally tested together with matrix-type semiconductor detectors. The plasma parameters have been measured under the action of a femtosecond pulse with a peak intensity of ~10¹⁸ W/cm² on a metal (copper) target, and good agreement is demonstrated between data from different detector types in terms of determining both the spectrum shape and the coefficient of the laser-pulse energy conversion into an X-ray flux. The temperature of hot electrons has been estimated, and its value exceeds 100 keV. The X-ray flux of copper K-lines, which exceeds 10⁹ per shot, has been determined. The advantages and drawbacks of techniques for measuring spectra in problems of laser-plasma interaction are considered.