Gas gap heat switch for a cryogen-free magnet system. Issue 1 (November 2015)

• Record Type: Journal Article
• Authors: Barreto, J; de Sousa, P Borges; Martins, D; Kar, S; Bonfait, G; Catarino, I
• Is Part Of: IOP conference series. Volume 101:Issue 1(2015)
• Publication Date: 2015-11
• Subjects: Materials science -- Periodicals; 620.1105
• DOI: 10.1088/1757-899X/101/1/012144
• Languages: English
• ISSNs: 1757-8981

Abstract

Abstract: Cryogen-free superconducting magnet systems (CFMS) have become popular over the last two decades for the simple reason that the use of liquid helium is rather cumbersome and that helium is a scarce resource. Some available CFMS use a mechanical cryocooler as the magnet's cold source. However, the variable temperature insert (VTI) for some existing CFMS are not strictly cryogen-free as they are still based on helium gas circulation through the sample space. We designed a prototype of a gas gap heat switch (GGHS) that allows a thermal management of a completely cryogen-free magnet system, with no helium losses. The idea relies on a parallel cooling path to a variable temperature insert (VTI) of a magnetic properties measurement system under development at Inter-University Accelerator Centre. A Gifford-McMahon cryocooler (1.5 W @ 4.2 K) would serve primarily as the cold source of the superconducting magnet, dedicating 1 W to this cooling, under quite conservative safety factors. The remaining cooling power (0.5 W) is to be diverted towards a VTI through a controlled GGHS that was designed and built with a 80 μm gap width. The built GGHS thermal performance was measured at 4 K, using helium as the exchange gas, and its conductance is compared both with a previously developed analytical model and a finite element method. Lessons learned lead to a new and more functional prototype yet to be reported.