Ludlum Measurements 16, Technical Manual

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Model 16 Analyzer Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-2 July 2011
GM D
ETECTORS
Note:
The GM detector pulse is NOT proportional to Gamma
Energy.
WINDOW
operation has no function.
1. Check GM detector specifications for proper operating high
voltage. Select this voltage with the
HV
calibration control.
Press
HV
test and confirm the proper high-voltage reading.
2. Set
THR
control for 40 ±10 mV.
3. Set
WIN IN
/
OUT
to
OUT
.
4. Set
F
/
S
and
AUD ON
/
OFF
as per local requirements.
5. Connect GM detector and confirm proper operation with a
radiation source.
P
ROPORTIONAL
D
ETECTORS
1. Set
THR
for 2 mV.
2. Set
WIN IN
/
OUT
to
OUT
.
3. Expose detector to a radiation source and observe count
rate with and without the source as voltage is increased in 50
volt increments. Plot this Data vs High Voltage.
4. Select an operating High Voltage point with minimum
change in Count Rate vs High Voltage (i.e. on the plateau).
5. Record this High Voltage for future operational check.
Note:
Gas proportional detectors and some pure argon detectors
will develop a very rapid increase of background count.
This is called “voltage breakdown.” Operate at least 100 V
below this point.