Electron response in windowless Si(Li), SDD and PIN diode photodetectors

The photon response of small volume, low capacitance semiconductor X-ray detectors is widely reported and is characterized by the ability to resolve closely spaced X-ray lines. But the response to electrons is less well known. We present spectra from commercially available high-resolution X-ray detectors irradiated with mono-energetic internal conversion electrons with energies from 45 keV to 300 keV. Many radioisotopes emit conversion electrons in this range, and electron spectroscopy offers an additional tool for detection and identification. One application reported in this work is the detection of trace amounts of radioactive Xenon gas, where the simultaneous measurement of high-resolution X-rays and conversion electrons in Silicon X-ray detectors offers an improvement in the Xenon detection limit compared to scintillator-based systems. Future plans for improvements by the use of multiple detector arrays and coincidence gating are briefly discussed.