Characterization of X-ray gas attenuator plasmas by   optical emission and tunable laser absorption spectroscopies

The objective of this work is to demonstrate experimentally the generation of plasma by the X-ray beam and to investigate its spatial distribution by measuring some of its parameters, simultaneously with the X-ray power absorption. The gases used in this study were argon and krypton between 13 and 530   mbar. The distribution of the 2p excited states of both gases was measured using optical emission spectroscopy, and the density of argon metastable atoms in the 1s5 state was deduced using tunable laser absorption spectroscopy. The amount of power absorbed was measured using calorimetry and X-ray transmission. The results showed a plasma confined around the X-ray beam path, its size determined mainly by the spatial dimensions of the X-ray beam and not by the absorbed power or the gas pressure. In addition, the X-ray absorption showed a hot central region at a temperature varying between 400 and 1100   K, depending on the incident beam power and on the gas used. The results show that the plasma generated by the X-ray beam plays an essential role in the X-ray absorption. Therefore, plasma processes must be taken into account in the design and modeling of gas attenuators.

Source: Journal of Synchrotron Radiation - October 6, 2017 Category: Physics Authors: Mart í n Ortega, Á . Lacoste, A. B é chu, S. B è s, A. Sadeghi, N. Tags: gas attenuator power absorption optical emission spectroscopy tunable laser absorption spectroscopy plasma research papers Source Type: research