Model 15
Technical Manual
Section 6
Ludlum Measurements, Inc.
Page 6-3
June 2020
Plot the data from the previous two steps. Pick an operating point just
above the knee of the count plateau, but at a voltage less than the Gamma
cutoff found in the previous step. Record this voltage and adjust the
HVN
calibration potentiometer for operation at this voltage.
Efficiency Calibration
With the instrument fully calibrated, set the
B
-
G
/
N
switch to
N
. Connect
the neutron detector within the moderator. Expose the detector to a
known neutron field and determine counts/minute per mrem/hr for that
energy source. Note that the Model 15 is energy dependent.
Repeat the above procedure with the
B
-
G
/
N
switch in the
B
-
G
position and
the gamma detector connected and exposed to a known gamma field.
Determine counts/minute per mR/hr.
Maintenance
Instrument maintenance consists of keeping the instrument clean and
periodically checking the batteries and the calibration. The Model 15
instrument may be cleaned with a damp cloth (using only water as the wetting
agent). Do not immerse instrument in any liquid. Observe the following
precautions when cleaning:
1.
Turn the instrument
OFF
and remove the batteries.
2.
Allow the instrument to sit for one minute before accessing
internal components.
Recalibration
Recalibration should be accomplished after maintenance or adjustments have
been performed on the instrument. Recalibration is not normally required
following instrument cleaning, battery replacement, or detector cable
replacement of equal length.
Note:
Ludlum Measurements, Inc. recommends recalibration at
intervals no greater than one year. Check the appropriate
regulations to determine required recalibration intervals.
