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Minimizing the Heat Leak Associated with DC Leads

IP.com Disclosure Number: IPCOM000096453D
Original Publication Date: 1963-Jun-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Jones, RE: AUTHOR

Abstract

Electrical leads carrying currents into cryogenic apparatus introduce heat into such apparatus. The mechanical power needed to remove such heat can be as much as one hundred or more times the heat flow itself. If the currents and input leads are very heavy, a very large refrigerator is needed. Some compromise must be reached relating the length and cross-sectional area of a conductor with the current it carries, when such conductor lies in a temperature bath whose range is T(2)-T(1).

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Minimizing the Heat Leak Associated with DC Leads

Electrical leads carrying currents into cryogenic apparatus introduce heat into such apparatus. The mechanical power needed to remove such heat can be as much as one hundred or more times the heat flow itself. If the currents and input leads are very heavy, a very large refrigerator is needed. Some compromise must be reached relating the length and cross-sectional area of a conductor with the current it carries, when such conductor lies in a temperature bath whose range is T(2)-T(1).

The temperature range for the refrigerator lies between 300 degrees K and 1 degrees K. A number of uniformly parallel strips 2 of conductive material, such as copper, are deposited on a suitable carrier. Such strips 2 become the input leads for a cryogenic circuit 4 maintained at a temperature of about 1 to 3 1/2 degrees K. Since each strip 2 can have different current-carrying requirements, the refrigerator would have to extract more heat from some leads than from others. By placing individual resistors in the path of each strip 2, either in series with or in parallel with each individual conductor 2, heat flow to the lower temperatures of the refrigerator can be minimized. An additional resistor 6, 8, 10, etc., must be placed either in series with or parallel to a given conductor strip 2 if the following relationships exist: (1) if where W(1) is the resistance of the fixed lead, then W(2) is to be placed in series with such fixed re...