Browse Prior Art Database

Helium Fill Pipe for Superconducting Magnets

IP.com Disclosure Number: IPCOM000061885D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Harrison, CG: AUTHOR

Abstract

A superconducting magnet has a helium fill pipe selectively connectable to an electrical power source to melt frozen blockages within the pipe.

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Helium Fill Pipe for Superconducting Magnets

A superconducting magnet has a helium fill pipe selectively connectable to an electrical power source to melt frozen blockages within the pipe.

Superconducting magnets such as those used in Nuclear Magnetic Imaging are maintained at very low absolute temperatures by immersion in a bath of liquid helium. A liquid helium reservoir is suspended inside a vacuum vessel and shielded room temperatures by one or more intermediate temperature shields. Liquid helium is transferred into the reservoir through a pipe which descends from a service stack at the top of the vacuum vessel to the very bottom of the helium reservoir. It extends to the bottom of the reservoir so that during cool- down the evaporating helium passes over the entire magnet before leaving through the stack.

During cool-down it is not uncommon for the fill pipe to become blocked by a plug of frozen gas, usually nitrogen. The gas gets into the pipe during change- over from one liquid helium storage vessel to another. Another rarer occurrence is for the bottom of the pipe to be blocked by a frozen pool of nitrogen left over from the cool-down from room temperature to 77 degrees Kelvin. Sometimes these blockages can be removed by pressuring the fill pipe or by probing with a thin wire. Often, however, the only solution is to warm-up the entire magnet and then re-cool it after the blockage has cleared.

Shown schematically in the figure is a cross section of a super...