Calibration of the X-Ray Probe

TM 11-6665-245-34

f. After the calibrator is set up and the main

probe attached must be calibrated. The x-ray

probe is in position, set the radiacmeter selector

probe is then attached to the radiacmeter a

switch to 100K position.

outlined in para. 2-2. b of TM 11-6665-245-12

Calibration of the x-ray probe is then accom-

g. Set R26 (cal. control) so that the meter

p l i s h e d without readjusting the radiacmeter

reading for the 100K scale is the same value as

calibration controls or the high voltage setting of

listed on the calibration report for the AN/UDM-

the radiacmeter. The calibration of the x-ray prob

7C.

involves the adjustment of the probe amplifier

h. Set up the calibrator using source A only.

gain to set the 14-21 keV x-ray photo peak within

Then set the radiacmeter selector switch to the

the discriminator window of the single channel

1M position and place the main probe in position

analyzer (SCA). The lower and upper threshold of

on the calibrator.

the SCA are fixed at -2.3 volts and -6.0 volts

i. The meter reading should be within the

respectively and should not need adjustment.

limits specified on the calibration report.

Once the amplifier gain is properly set, the x-ray

j. Set up the calibrator using source C only.

probe sensitivity factor (cpm/mg/cm2 of Pu-239) is

Set the radiacmeter selector switch to the 10K

determined using the UDM-7B source A.

position and place the main probe in position on

the calibrator.

Prior to a source calibration, ensure that the

k. The meter reading should be within the

probe is functioning. Proceed as follows:

limits specified on the calibration report.

(1) Unscrew the end cap from the probe,

l. Set up the calibrator using attenuator #1

exposing the two calibration potentiometers and

and source- C. Then set the radiacmeter selector

related test points.

switch to the 1K position and place the main

(2) Position the phosphor end of probe

probe in position on the calibrator.

approximately one inch from a UDM-7 "A" source.

m. The meter reading should be within the

(3) Turn selector switch to 100K scale.

limits specified on the calibration report.

(4) Connect Digital Voltmeter or

n. Remove the main probe from the calibrator.

Multimeter to Test Point 2 (Figure 3-8) and check

The meter reading should go to zero.

for -2.3 Vdc 0.1 Vdc.

o. Set the selector switch to OFF, reassemble

(5) Connect Digital Voltmeter o

the radiacmeter and put the calibrator away.

Multimeter to Test Point 3 (Figure 3-8) and adjust

p. Connect the headset to the radiacmeter

R54 for -6.0 Vdc 0.1 Vdc.

and set the selector switch to the 1 K position.

(6) Connect oscilloscope probe to Test

q. Listen in the headset for clicks caused by

Point 1 of Figure 3-8 and adjust R49 so that the

background radiation. Count the clicks for one

center band of negative pulses is between -3.5

minute. The count should not exceed 15 for 1

and -4 V (refer to wave shape on Figure 3-8).

minute (15 cpm).

( 7 ) The meter reading of a properly

calibrated probe should be in the range of 32 to 40

3-16. Calibration of the X-Ray Probe

K cpm.

The x-ray probe is also calibrated using the

(8) Secure the calibration pots with glyp-

AN/UDM-7 Pu-239 alpha calibration sources.

tol (or equivalent).

B e f o r e calibrating the x-ray probe, the lM-

(9) Reinstall end cap on the probe.

160F/PDR-56 radiacmeter with the main alpha

3-12

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