2 photon detectors – Fluke Biomedical 30-471 User Manual
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Nuclear Associates 30-471
Operators Manual
2-2
2.2 Photon Detectors
These detectors are used in the measurement of radiation in the range of 1 MV to 25 MV. They are
available with a negative or positive output. They have been color coded for ease of identification.
Following is a list of the detectors, polarity, color codes, and range.
Model Number
Range
Polarity
Color
30-471
1-4 MV Photon
Positive
Blue
30-471-8000
1-4 MV Photon
Negative
Blue
30-472 5-11
MV
Photon
Positive
Yellow
30-472-8000 5-11
MV
Photon
Negative Yellow
30-473
12-17 MV Photon
Positive
Red
30-473-8000
12-17 MV Photon
Negative
Red
30-474
18-25 MV Photon
Positive
Green
30-474-8000
18-25 MV Photon
Negative
Green
30-475
5-25 MeV Electron
Positive
Gray
30-475-8000
5-25 MeV Electron
Negative
Gray
Build-up shields are utilized in their design to provide equilibrium and filtering of low energy radiation.
These build-up shields also increase the detector's stability along with increasing the sensitivity in their
respective ranges. The output of a typical detector is 1.2 nano coulombs/RAD (1.2 nC/cGy).
The semiconducting material in these diodes is planar and the diodes as a whole is hemispherical in
shape, thus they have a preferred direction. Following are typical angular dependence of these photon
detectors.
Angular Dependence
1-4 MV Diodes
The following figures show the results for incident angles rotation along the diode cable axis and along
the axis perpendicular to diode cable axis. For angle deflections less than 50 degrees from the diodes
preferred direction, 180 degrees, the diode output changed by less than 1%.
Gantry angle (degree with 180 being vertical)
Diode (type 471 [1–4 MV rated]) output vs. incident angle;
symmetric setup in 6 MV photons
Diode out
p
ut (n
ormalized
to
180°)