Journal of Medical Physics
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Year : 1986  |  Volume : 11  |  Issue : 3  |  Page : 587

Parameter Specification Required For A Semiconductor Detector


Correspondence Address:
Goran Rikner


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Semiconductor detectors are frequently used in radiation dosimetry. During the last years several papers have been presented showing that there are many parameters to take into consideration in order to describe the characteristics of a semiconductor detector. In this presentation these parameters are described and discussed. 1) Type of doping. n-or p-doped detectors can be used. For an n-type detector a nonlinear response with dose rate will be developed as an effect of radiation damage. p-type detectors will not see this drawback. p-type doping also shows a less sensitivity loss when radiation damaged. 2) Doping level. An increased doping level will normally give shorter life times and thus also a lower sensitivity of the detector. The maximum dose per pulse for linear response is also depending on the doping level. The higher doping level the higher the linearity will stay between dose rate and signal. 3) Preirradiation level. Except a sensitivity drop and a dose rate non-linearity (for n-type detectors) the sensitivity variation with temperature (SVWT) will increase as a function of preirradiation. Unirradiated the SVWT will be less stays fairly constant. 4) Mechanical description. As for other detectors the knowledge of the mechanical of the detector is very important. Incapsulation, connector design, energy compensation etc. must be described in detail as the effective measuring point and directional dependence will change with these parameters. 5) The effective measuring point should be given with an accuracy of 0.5 mm for at least one radiation quality for a detector to be used in a water phantom and within 1 mm if used in patient dosimetry. 6) Directional dependence. The directional dependence for must be known, as if correction factors are applied to the reading they have to be weighted in accordance to the directional dependence. 7) Detector volume. Both the detector area and the effective measuring volume must be known as the statistical noice in the reading is correlated to the detector size. The spatial resolution is also depending on the detector size. 8) Leakage current and connection to electrometer. In order to avoid incorrect readings it is important to use a detector with as small leakage current as possible in a short curcuit mode to an electrometer. The electrometer itself must have a low input offset drift but not necessarily a high electronic gain.


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