MIL-PRF-49175C(CR)
b.
The 1440 joule coldstation shall consist of the
following elements as defined on drawing 54490 5004372:
copper block, temperature sensor, resistor, thermally
conductive epoxy and a clamp screw.
c.
The coldstation assembly will have the following
characteristics:
1.
The temperature sensor and resistor will be bonded to the
copper block with the thermally conductive epoxy.
2.
The thermal energy which must be removed when cooling the
coldstation from 300 K to 80 K shall be 1440, (+25, -0)
joules. The mass of the coldstation shall be adjusted until
it meets this requirement.
3.
The resistor in the coldstation shall have a voltage applied
to obtain a 1000, (+20, -0) mw thermal load. The applied
voltage shall be such that the product of the voltage and the
current of the resistor shall equal 1000,(+20,-0) mw.
4.
The resistor and temperature sensor shall be connected to a
vacuum feedthru by four teflon coated constantan wires. The
wires shall be less than six inches in length and the
resistance shall be less than one percent of the value of the
resistor in the coldstation.
5.
The coldstation is clamped to the coldfinger, sufficiently
tight to effect good heat transfer without damaging the
coldfinger.
6.
Good thermal conductivity is assured by applying a metal oxide
impregnated silicone thermal joint compound to the end of the
coldfinger that is in contact with the coldstation.
7.
A radiation shield shall not be used.
4.5.2 Cooldown time. Cooldown time shall be measured using the test
Dewar and the copper mass described in 4.5.1. Failure to meet requirements of
3.5.2 shall constitute failure of this test.
4.5.3 Input power. Input power shall be measured when the cold tip
temperature has stabilized below 80 K with heat load applied. Temperature
stabilization has occurred when the output of the temperature sensor diode does
not change more than .015 Vdc over a 5 minute period. Failure to meet
requirements of 3.5.3 shall constitute failure of this test.
4.5.4 Acoustic noise. The cooler shall be set up for operation in an
area where the background noise level is at least 5 dB below the sound level to
be measured. The cooler shall be operated and sound pressure measurements made
with the cooler oriented in 4 positions in the same plane with each position
approximately 90 degrees apart. Measurements shall be made with an octave-band
analyzer. Failure to meet requirements of 3.5.4 shall constitute failure of
this test.
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