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Long-Term Performance of 4 K Gifford-McMahon Refrigerators on the Bima Array

  • R. L. Plambeck
Part of the Advances in Cryogenic Engineering book series (ACRE, volume 43)

Abstract

Eight radio telescopes in the Berkeley-Illinois-Maryland Array (BIMA) are outfitted with 4 K Gifford-McMahon refrigerators. The refrigerators cool superconducting detectors (SIS mixers) on the radio receivers; the heat load at 4 K is 10 to 20 mW. The refrigerators were constructed by welding third stages onto standard CTI model 1020 cryocoolers; Er3Ni or ErNi spheres are used as the low temperature regenerators. The refrigerators are operated almost continuously; one has been in service for 4 years. Maintenance consists of disassembling the cold heads every 1 to 2 years to clean out water and dust.

On the telescopes the refrigerators’ third stage temperatures range from 2.7 to ~5 K. Often these temperatures are stable within ± 0.1 K for weeks, even while the refrigerators are tipped from 0 to 90 degrees as the telescopes track radio sources. Sometimes, however, the temperature creeps up by > 1 K over a period of days or weeks, then jumps back to its original value following a power interruption or “defrost” cycle. Contaminants within the cold head may possibly cause this behavior. With active temperature regulation, the SIS mixer temperatures can be stabilized to ±0.01 K despite the refrigerator fluctuations.

Keywords

Radio Telescope Heater Power Stage Temperature Optimum Bias Mixer Block 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • R. L. Plambeck
    • 1
  1. 1.Radio Astronomy LabUniversity of CaliforniaBerkeleyUSA

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