Browse Prior Art Database

Magnet Temperature Control

IP.com Disclosure Number: IPCOM000085688D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 49K

Publishing Venue

IBM

Related People

Double, GP: AUTHOR [+2]

Abstract

Field drift in a permanent magnet, due to temperature variations, is stabilized to one part in 10/9/ for short periods (~ 30 minutes) by controlling the magnet temperature to within four microdegrees.

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Magnet Temperature Control

Field drift in a permanent magnet, due to temperature variations, is stabilized to one part in 10/9/ for short periods (~ 30 minutes) by controlling the magnet temperature to within four microdegrees.

As shown in the drawing, magnet 1 is surrounded by, but spaced from, copper walls 2. Thermistors 3 on each wall detect temperature variations in the copper walls of 0.1 degrees C. The interior of the box is set at some predetermined temperature above the outside ambient temperature, e.g., at 35 degrees C. A controlled thickness of insulation 4 surrounds the outside of copper walls 2 so that heat escapes to the outside at a controlled rate.

As soon as the copper walls drop in temperature by 0.1 degree C, heating pads 5 between insulation 4 and walls 2 are turned on until the thermistors detect that the copper walls 2 have increased in temperature by +0.2 degrees C. The result is that the copper walls continually oscillate between +/- .0.1 degree C about the nominal temperature of 35 degrees C.

If the temperature oscillation of the coppcr walls 2 is fast enough the large thermal mass of the magnet 1 (~ 300 lbs) with its correspondingly long thermal relaxation time cannot keep up. Therefore the temperature variations in the magnet become negligible.

The thickness of the insulation 4 is chosen to provide a heat loss rate, such that a temperature oscillation occurs in walls 2 at a rate of about once per minute. The variations in temperature of magnet 1 become approximately four microdegrees. Temperature control of the walls 2 may be improved by independently controlling the heating, of each of the six walls.

In the illustrated system, the controlling environment is spaced from the thermal mass so that they cannot easily interact. This feature gives much greater temperature stability than in the case where the controlling environment is coup...