MIL-PRF-1/986J
TABLE I. Testing and inspection - Continued.
1/
The tube response (count rate) due to the combined effects of background, contamination, and photo-
sensitivity determined as specified herein, shall be not more than the limit specified herein. The tube may be
shielded from extraneous radiation fields by lead and aluminum interposed between it and the tube. The
lead shall have a maximum thickness of 2.00 inches (50.8 mm), the aluminum shall have a maximum
thickness of .125 inch (3.18 mm). In determining tube response (count rate), Ebb = 750 volts and Rp = 1
Meg. The count rates shall be determined using a scaler having a resolving time of 5 microseconds and a
discrimination level of 0.25 volt.
2/
Apply approximately 800 volts anode voltage. Decrease this voltage until the largest visible pulses are 2
volts ± 20 percent. This voltage shall be considered the starting voltage.
3/
All tubes shall pass this test. Testing shall be performed 30 or more days after previous production tests on
the same tubes. A tube that fails this test may be retested after an additional 30 or more days with the
provision that the value of Ebb for anode voltage for pulse amplitude test does not change by more than ± 5
volts from the value at the beginning of the last 30-day period, and that the tubes conform to the initial limits
for starting voltage and background, contamination, and photosensitivity.
4/
Test shall be made using Government approved standard test unit. The source of radiation shall be Cesium
137. (Preliminary calibration of unit shall be as directed on operating instructions.) The external connections
shall be as follows:
a.
Counting circuit shall have a discrimination of +3 volts.
b.
DC high voltage input shall be 680 ± 0.5 volts.
c.
Trigger input shall be 1,000 ± 10 prr.
5/
Test shall be made with calibrated beta source. Ebb shall be anode voltage ± 5 volts for 50-volt pulse as
determined in the pulse amplitude test. The count rate shall be determined by using a scaler having a
resolving time of 5 microseconds, and a discrimination level of 0.25 volt.
6/ The counting rate shall not vary by more than ± 0.3 N/t from the value of N/t of the calibrated beta source
furnished.
7/ Criterion for passing this test shall be compliance after test of at least 80 percent of the tubes with the
requirements for the following:
a.
Starting voltage.
b.
Pulse amplitude.
c.
Response count rate (beta).
8/
Test shall be conducted in the circuit as shown on figure 2 (in lieu of figure 6211-1). The procedure shall be
as follows:
Apply 950 volts anode voltage. Observe the pulse pattern to determine if the tube goes into glow discharge.
If the tube goes into a glow discharge, it shall be considered as a defective tube. If no glow discharge
occurs, decrease this voltage until the largest visible pulses are 50 ± 2 volts. This voltage shall be
considered anode voltage for a 50 volt pulse.
3
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