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Design and Test of Passively Operated Heat Switches for 0.2 to 15 KHeat switches have many uses in cryogenics, from regulating heat flow between refrigeration stages to thermally isolating components once they have cooled to low temperature. Among the techniques one can use for thermal switching, the gas-gap technique has the advantages of wide operating temperature range, high switching ratio, and no moving parts. The traditional gas-gap switch uses copper conductors separated by a small gap and an external getter. The switch is activated by heating and cooling the getter by moving gas into and out of the gap, turning the switch on and off. We have designed, built and tested heat switches that use an internal getter to passively turn off at temperatures between 0.2 and 15 K. The getter is thermally anchored to one side of the switch, and when that side of the switch cools through a transition region, gas adsorbs onto the getter and the switch turns off. The challenges are to make the transition region very narrow and tailorable to a wide range of applications, and to achieve high gas conductance when the switch is on. We have made switches using He-3, He-4, hydrogen, and neon gas, and have used charcoal and various metal substrates as getters. Switching ratios range from 1000 to over 10,000. Design and performance of these switches will be discussed in detail.
Document ID
20040015141
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
DiPirro, M. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Shirron, P. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Canavan, E. R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Francis, J. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Tuttle, J. G.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Mechanical Engineering
Meeting Information
Meeting: Cryogenic Engineering Conference
Location: Anchorage, AK
Country: United States
Start Date: September 22, 2003
End Date: September 26, 2003
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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