Sensitive detection system for soft x-ray appearance potential spectroscopy

A sensitive x-ray detection system has been used in the recording of soft x-ray appearance potential spectra with an electron excitation current of a few microamperes covering a sample area of 1 cm2. The system included a 6μ thick aluminum foil, a cesium iodide photocathode, a continuous-channel electron multiplier, and conventional pulse-counting electronics. The aluminum foil was placed over the entrance window of the detector in order to filter out the ultraviolet and extreme-soft x-ray emissions from the sample prior to detection of the soft x rays that passed through the foil. The transmitted soft x rays were incident on a cesium iodide photocathode and the resulting photoelectron events were individually detected with a high-gain electron multiplier whose output pulses were processed with pulse-counting electronics.