Development and experimental studies of cryopanels for the torus cryopump used in tokamak

Abstract

The pumping performance of divertor torus cryopumps plays a crucial role in tokamak particle removal, and their performance largely depends on the performance of the cryopanels. This paper conducts simulation and experiments on the particle exhaust performance of three types of cryopanels under tokamak application conditions. The simulation results indicate that the cryopanels composed solely of metal plates exhibit superior surface cooling performance compared to the cryopanels coated with granular activated carbon (GAC), and the latter's surface cooling performance is affected by the adhesive types and contact condition between the GAC and the adhesive. Subsequently, the manufacturing processes of different cryopanels were developed and their prototypes were produced, and a testing platform was established to test their performance. The experimental results indicate that the cryopanel without GAC coating exhibit high pumping speeds for deuterium and hydrogen at low temperature, but they are highly sensitive to temperature fluctuations. Above 8 K for deuterium and 5.5 K for hydrogen, this cryopanel becomes ineffective in pumping these gases. Conversely, cryopanels coated with GAC exhibit less temperature sensitivity in pumping deuterium and hydrogen, with minimal changes in pumping speeds observed between 4.5 K and 20 K. Within the experimental temperature range, cryopanel without GAC coating exhibits no pumping ability on helium, whereas those with GAC coating possess helium pumping capability. Based on the above systematic study, this paper proposes selection schemes for the cryopanels used in torus cryopumps in various application scenarios, providing references for the future design of torus cryopumps for future tokamaks.