Study of silicon PIN diode responses to low energy gamma-rays

Low energy gamma-ray detectors play an important role in diagnosis in nuclear medicine, in detection of gamma-ray bursts for gravitational wave research and in detection of underground nuclear tests. The silicon positive-intrinsic-negative (PIN) diode detector is useful for detection of low energy gamma radiation without using a scintillator because it generates a high signal in a small active volume, has a fast response time and has good intrinsic energy resolution. We measured the detector responses, energy resolutions and signal-to-noise ratios for various gamma energies by using manufactured silicon PIN diode and photodiodes. Radioactive gamma sources, Am-241, Ba-133, and Co-57, providing gamma-rays with energies between 14.4 keV and 136.5 keV are used for the measurements. The energy resolution and the signal-to-noise ratio for 14.4 keV gamma-ray are measured to be 17.1 % and 12.8 for a 500 mu m thick silicon diode. The energy resolutions measured at the FWHM for 59.5 keV and 122.1 keV gamma-rays by using the silicon diode are better by up to two times compared to those obtained using the NaI:Tl or the BGO scintillator with a photomultiplier tube. The dependence of detection speeds of the signals on the diode's thickness is also measured.