ABSOLUTE CALIBRATION OF AN X-RAY SPECTROMETER ON THE NIST ELECTRON-BEAM ION-TRAP - CONTROL, DESIGN AND SYSTEMATICS

The course of Electron-Beam Ion Trap (EBIT) experiments depends more a nd more on precision measurement. To design and test a system of absol ute spectroscopy to 10-20 parts per million for such a source is a cha llenging task. Other design criteria include good efficiency in the 3- 10keV energy range, ability to focus a line source and high vacuum com patibility. Some difficulties are discussed. The use of a non-scanning Johann focusing spectrometer and its consequent calibration is discus sed The spectrometer has been used in a series of experiments on the N IST EBIT. The detector location is shown (both experimentally and by m odelling) to provide a major systematic contribution, which can howeve r be controlled to a suitable tolerance. Future directions are indicat ed.