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An active thermal compensator for closed-cycle helium refrigeratorsA technique was developed for reducing the amplitude of the temperature oscillation in He closed-cyle refrigerators. The device uses a semiconductor diode as a heating element to actively supply a small oscillating input of heat at a point between the laser and the cold-tip to cancel the heat oscillations due to the refrigerator. It was found that the heater diode could drive the temperature of the heat sink more effectively, i.e., with lower current and therefore less heat, if the heat sink was insulated slightly from the rest of the mount. A sine-wave generator was used to drive the programmable supply which provided the offset current to the heater diode. By matching the frequency and phase of the oscillator to that of the refrigerator cycle, and by adjusting the amplitude of the oscillator signal, the temperature fluctuations at the laser could be minimized. Residual fluctuations were about 0.003K peak-to-peak, at an operating temperature of 9.5K.
Document ID
19770023328
Acquisition Source
Legacy CDMS
Document Type
Preprint (Draft being sent to journal)
Authors
Jennings, D. E. (NASA Goddard Inst. for Space Studies New York, NY, United States)
Hillman, J. J. (NASA Goddard Inst. for Space Studies New York, NY, United States)
Date Acquired
September 3, 2013
Publication Date
July 1, 1977
Subject Category
Engineering (General)
Report/Patent Number
NASA-TM-X-71367
X-693-77-164
Accession Number
77N30272
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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