Model of a fusion cryopumping system for condition monitoring

Cryopumping systems provide an essential function in most magnetic confinement nuclear fusion experiments. The maintenance of an ultra-high vacuum in a magnetic confinement vessel is required for experiments to be conducted, without exception, and cryopumping systems are widely used to achieve this. As such, the availability of this type of nuclear fusion experiment depends in part upon the availability of its vacuum system. In order to reduce experimental time lost to unplanned maintenance, investigation and avoidable failures, a condition monitoring scheme targeted on a cryopumping vacuum system is proposed. A model of the cryopumping system deployed on the Joint European Torus is presented. The model is supported by a first principles derivation and is validated using historical data. Its application to a condition monitoring scheme is discussed. This paper contributes to the wider nuclear fusion development programme by addressing a key maintenance and reliability issue, which is an important step on the road to commercial fusion energy.