Model 2363
Technical Manual
Section 6
Ludlum Measurements, Inc.
Page 6-2
January 2015
Replace 2363 cover and proceed with use.
Establishing an Operating Point
The Model 2363 contains an internal energy-compensated GM (Geiger-
Mueller) detector for gamma measurements. The operating point for this
detector is fixed, with a high-voltage requirement of 550 Vdc, and a threshold
of -50mV.
The Model 2363 is normally sold with an external PRESCILA neutron
detector (Model 42-41). The PRESCILA detector operating parameters are
established by adjusting the detector operating voltage (
HV
) and neutron
threshold to find an optimum efficiency for the neutron scintillator with a
known level of gamma cross-talk. The following is an outline of this
procedure.
1. Using the Ludlum Model 500 pulser or equivalent, adjust the
neutron threshold (NTHR) of the Model 2363 to -10 mV and set
the HV (NHV) to 635 Vdc.
2. Connect the Model 42-41 PRESCILA to the Model 2363 with a
0.99 m (39 in.) cable. Using the front face of the detector as the
detector reference point (not the center of the detector), point the
detector at the source. Ensure that all internal dipswitches are set
to the ON position.
3. Connect the Model 2363 to a computer using a straight-thru 9
pin cable. Use the Ludlum Model 2363 Software interface to
ensure that the following parameters are set:
SE10350
Neutron calibration constant of
350 cpm/mrem/hr
SE21050
Gamma calibration constant of
1000 cpm/mR/hr
RP100
Gamma dead time correction of
100 µsec
SI00
Automatic time constant
ST
Set the current time
SD
Set the current date
SC
Set the calibration due date
(one year, unless specified)
