Absolute calibration of an x-ray spectrometer on the NIST electron-beam ion trap: Control, design and systematics

Abstract

The course of Electron-Beam Ion Trap (EBIT) experiments depends more and more on precision measurement. To design and test a system of absolute spectroscopy to 10-20 parts per million for such a source is a challenging task. Other design criteria include good efficiency in the 3-10 keV energy range, ability to focus a line source and high vacuum compatibility. Some difficulties are discussed. The use of a non-scanning Johann focussing spectrometer and its consequent calibration is discussed. The spectrometer has been used in a series of experiments on the NIST EBIT. The detector location is shown (both experimentally and by modelling) to provide a major systematic contribution, which can how..