MIL-PRF-1/1388G
TABLE I. Testing and inspection - Continued.
After the holding period, starting voltage shall not vary by more than ± 7 volts.
5/
6/
The tube shall be mounted vertically in the lead shield (see figure 3) of the excitation unit.
7/
The tube shall have been inoperative for a 24-hour period prior to test.
8/
Beta reference source shall be in position as specified in 3/.
9/
Test shall be performed with the assembly shown on figure 3 in a 1.4 mr/hr Cobalt-60 radiation field (calculated).
10/
The tube shall be tested only with its longitudinal axis vertical and parallel to the direction of motion. The tube shall be
mounted by means of a rigid clamp at the base of the tube.
11/
The tube shall be tested only with its longitudinal axis horizontal and parallel to the direction of motion of the hammer. The
tube shall be mounted by means of a rigid clamp at the base of the tube.
12/
This test shall be performed at the conclusion of the holding period.
13/
All tube windows shall be tested to assure that they can withstand an internal pressure of half of an atmosphere less than
ambient pressure.
14/
The shelf life requirements shall be as follows:
(a)
Tubes tested and acquired in accordance with this document shall be capable of a shelf life for a period of 18 months
after the date of shipment from the manufacturer's plant. At any time during this shelf life period the tubes shall be
capable of meeting all requirements of conformance inspection, part 1, as specified herein. Tubes found to be
defective within the shelf life period shall be replaced by the manufacturer at no cost to the Government.
(b)
A shelf life of 90 days with the conformance inspection, part 1, starting voltage test shall be instituted during continuous
production, but shipments of that month's production shall not be held pending completion of the test. Tubes shall be
considered to conform to this document when three of the four tubes for each of the first 3 month's production and 75
percent of the cumulative quantity pass the test. If either of the above conditions are not satisfied, shipments shall be
halted until three or four tubes of current production conform to the starting voltage test.
The relative plateau slope requirements shall be with the discrimination level of the scaler set at 0.25 V ± 10 percent for
15/
standard Geiger-Mueller counter tube operation, and accomplished in accordance with the following steps:
(a)
With the equipment in operation and prepared for counting, set the high voltage adjust control to obtain 1,400 V dc.
(b)
Mount standard reference source SBRS on the sample positioning shelf, place the shelf in position 1 of the tube, mount
assembly and count for 5 minutes at 1,400 V dc. A new Geiger-Mueller counter tube (one that has not been used for a
month or more) should be counted for 15 minutes rather than 5 minutes. It is not necessary to record the count rate
obtained in this step.
(c)
If the background is unknown, remove SBRS and obtain and record a 20 minute background count rate (cpm).
(d)
Place SBRS on the sample positioning shelf; place shelf in position 1 of the tube mount assembly.
CAUTION
If at any time while performing steps 16e through 16g it becomes apparent that the tube under test is in continuous
discharge (rapidly increasing count rate for a constant value of applied voltage), immediately set high voltage adjust
control to 1,200 V dc. Determine if tube damage has occurred by raising the voltage in 50 V dc increments every 5
minutes. Do not exceed a high voltage setting of 1,500 V dc at any time. Otherwise continuous discharge will damage
the tube. If continuous discharge occurs, again, replace tube.
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