Relative Calibration of Photodiodes in the Soft-X-Ray Spectral Range
A method of obtaining a relative calibration of Si photodiodes for the spectral range of soft x rays (1-30 KeV) is presented. A simple mathematical model of the p-n diode is adopted which allows the response to be described in terms of a small set of parameters. The diffusion length as well as the thickness of a dead layer below the front surface of the diodes are obtained from measurements of angular dependences of the photoinduced current. It is shown that a precise characterization of the diode response and an accurate relative calibration can be obtained using this method. However, it was found that the presence of a dead layer a few tenths of a micrometer thick can pose severe restrictions on the use of planar diode arrays in x-ray tomography systems where uniformity of response is crucial. The method has been applied to the diode arrays equipping the x-ray tomography system built for the TCV tokamak, a magnetic fusion research device. (C) 1995 American Institute of Physics.
Record created on 2008-04-16, modified on 2016-08-08