28 June 2015 to 2 July 2015
JW Marriott Starr Pass Resort
Etc/GMT-7 timezone

Cool-down acceleration for G-M cryocoolers with thermal oscillations passively damped by helium

1 Jul 2015, 11:45
15m
Tucson Ballroom IJ ()

Tucson Ballroom IJ

Contributed Oral Presentation CEC-03 - Cryocoolers (Non-Aerospace) C3OrD - 4K Cryocoolers

Speaker

Robert Webber (Hypres, Inc.)

Description

4 K Gifford-McMahon cryocoolers suffer from inherent temperature oscillations which can be a problem for certain attached electronic instrumentation; Sumitomo Heavy Industries has exploited the high volumetric specific heat of super-critical He to quell these oscillations (approx. 10 dB) by strongly thermally linking a separate vessel of He to the second stage; no significant thermal resistance is added between the payload and the working gas of the cryocooler. A noticeable effect of the helium damper is to increase the cool-down time of the second stage, particularly below 10 K when the heat capacity of the He is dominant. For the operation of niobium-based superconducting electronics (NbSCE), a common practice is to warm the circuits above the critical temperature (~9 K) and then cool to the operating point in order to redistribute trapped magnetic fluxons, so for NbSCE users, the time to cool from 10 K is important. The gas in the helium damper is shared between a room-temperature canister and the 2nd stage vessel, which are connected by a capillary tube. We show that the total cool-down time below 10 K can be substantially reduced by introducing a combination of thermal linkages between the cryocooler and the capillary tube and in-line relief valves, which control the He mass distribution between the warm canister and cold vessel. The time to reach operating temperature from the superconducting transition has been reduced to <25% of the time needed without these low-cost modifications.

Primary author

Robert Webber (Hypres, Inc.)

Co-author

Mr Jean Delmas (Applied Materials, Inc.)

Presentation Materials

Your browser is out of date!

If you are using Internet Explorer, please use Firefox, Chrome or Edge instead.

Otherwise, please update your browser to the latest version to use Indico without problems.

×