Low energy x-ray sources utilized at NBS for detector calibration

Low energy x-ray sources (1 to 10 keV) have been produced utilizing dc and pulsed electron beams to excite the characteristic K-line radiation of elemental targets. The steady state x-ray sources are continuously variable in intensity from 1012 K x rays per sr . s. A parallel plate ionization chamber was calibrated in the steady state sources and used with Ross filter pairs to measure the 10 ns pulsed source K x-ray fluence. Typical measured peak x-ray flux intensities are 10-18 to 1019 K x rays per sr . s. The pulsed source contains four identical ports for simultaneous measurements of the K x-ray fluence by the ionization chamber and detectors being calibrated. The steady state and pulsed K x-ray sources, which differ in flux density by 10 orders of magnitude, have been utilized to determine the responses of a photoelectric diode, a scintillator-vacuum photodiode combination, a silicon PIN vacuum photodiode combination, and a silicon PIN diode