Gas gap heat switch for a cryogen-free magnet system

Cryogenic Engineering Conference 2015

材料科学;物理学

Barreto, J.^1 ; De Sousa, P. Borges^1 ; Martins, D.^1 ; Kar, S.^2 ; Bonfait, G.^1 ; Catarino, I.^1

LIBPhys-UNL, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal^1

Inter-University Accelerator Centre, New Delhi, India^2

关键词: Cooling power;    Cryogen free magnets;    Functional Prototypes;    Heat switches;    Magnetic properties measurement systems;    Scarce resources;    Thermal Performance;    Variable temperature inserts;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/101/1/012144/pdf
DOI  :  10.1088/1757-899X/101/1/012144

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

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.