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Response of large area avalanche photodiodes to low energy X-rays



Thomas R. Gentile, Uwe Arp, M J. Bales, R Farrell


For an experiment to study neutron radiative beta-decay, we operated large area avalanche photodiodes (APDs) at liquid nitrogen temperature to detect X-rays with energies between 0.2 keV and 15 keV. Whereas there are numerous reports of X-ray spectrometry using APDs at energies above 1 keV, operation at liquid nitrogen temperature allowed us to reach a nominal threshold of 0.1 keV. However, due to the short penetration depth of X-rays below 1 keV, the pulse height spectrum of the APD become complex. We studied the response using monochromatic X-ray beams and employed phenomenological fits of the pulse height spectrum to model the measurement of a continuum spectrum from a synchrotron. In addition the measured pulse height spectrum was modelled using a profile for the variation in efficiency of collection of photoelectrons with depth into the APD. The best results are obtained with the collection efficiency model.
Review of Scientific Instruments


avalanche photodiodes, beta-decay, X-ray


, T. , Arp, U. , Bales, M. and Farrell, R. (2012), Response of large area avalanche photodiodes to low energy X-rays, Review of Scientific Instruments, [online], (Accessed June 13, 2024)


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Created April 30, 2012, Updated February 19, 2017