The single stage mini cryocooler manufactured by Semiconductor devices and likely decommissioned from defence system was obtained from Part2Go Ltd, Israeli. Upon visual inspection, it is very similar to the Ricor K526 and consists of a compressor (A), a split pipe (B), and a cold finger (C). It requires a 24V (D) power supply (E) (see right). For the initial test the cryocooler was connected to an AC-DC switching power supply (Type: S-50-24 24V/2A). After 2 minutes cold finger was covered with frost (move above). The only noticeable problem was poor heat dissipation from the hot end of the cold finger.
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The mini cryocooler was attached to the custom made power supply (+12V/5A and +24V/2A). The hot end of the cold finger was attached to the Peltier thermoelectric module (12V/3A) for active cooling (see left). The type K thermocouple connected to the multimeter (Precision Gold N56FU) was attached to the cold finger (see below). The cold finger was isolated by a simple Styrofoam block. After switching on the cryocooler compressor the temperature started to slowly and gradually decrease. After approximately 10 minutes the multimeter readings stabilize at around -133℃. |
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The multimeter measurement is based on the assumption that the type K thermocouple is linear (coefficient equal 41microVolts/degree). This assumption is not true for temperatures below 0℃ In this range a type K thermocouple can be used but it’s characteristic is strongly non linear with the coefficient decreasing from 39 microvolts/degree at 0℃ to 16microVolts at -200℃. |
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| A cryothermometer for measuring themperatures in the range of 300K to 77K was built (for details please see separate article at [www.jabolatorium.com]. After switching on the cryocooler compressor the temperature starts to slowly and gradually decrease. After approximately 10 minutes the readings stabilize at around 90K (see left) |
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