Improved pyroelectric x-ray generator for planetary active x-ray spectroscopy

The elemental composition on planetary surface provides us an essential information to improve geological and geochemical understanding of planets. An active X-ray spectrometer (AXS) was developed and proposed as one of the mission payloads to perform in-situ X-ray fluorescence analysis. The AXS consists of multiple pyroelectric X-ray generators (PXGs) and a silicon drift detector (SDD). Although the PXG is light in weight and low in electric consumption, the limited X-ray intensity and reproducibility hamper obtaining the elemental composition by short time observation. This is attributed mainly to the less known mechanism of X-ray and electron emission by the pyroelectric crystal. In this study, we observed the crystal surface during X-ray emission as a function of the distance between the crystal top and a Cu target. Two types of light emission derived from the electric discharge were observed. The dependence of light emission on the distance was found to be related with the physical mechanism of pyroelectric X-ray emission. The study provides clues to obtain high intensity and reproducible X-rays emission. The experimental results and discussion are presented in this paper.