Fluke Biomedical 30-471 - Manual (Page 14)

Nuclear Associates 30-471
Operators Manual
2-6
2.3 Electron Detectors
These detectors are used in the measurement of radiation in the range of 5 MeV to 25 MeV. They are
available with a negative or positive output. They are color coded for ease of identification. Following is a
list of the detectors, polarity, color codes, and range.
Model Number Range Polarity Color
30-475 5-25 MeV Electron Positive Gray
30-475-8000 5-25 MeV Electron Negative Gray
The semiconducting material in these diodes is planar and the diode as a whole is hemispherical in
shape, thus they have a preferred direction. Following are typical graphs of the angular dependence of
these electron detectors.
The output of a typical detector is 1.00 nano coulombs/RAD (1.00 nC/cGy).
Angular Dependence
The electron diodes in a 20 MeV electron beam, shown in the following two figures have a I % change
after a 30 degrees deflection, in both planes from 180.
Gantry angle (degree with 180 being vertical)
Diode (type 475 [electron diode]) output vs. incident angle;
asymmetric setup in 20 MeV electrons
Diode out
p
ut (n
ormalized
to
180°)