Cryopump design for the ITER heating neutral beam injector

Abstract

Forschungszentrum Karlsruhe (FZK) is developing the cryopumps for the ITER heating neutral beam injectors. The system is characterized by high gas flows coming from different sources against which the cryopumps must maintain a pressure between 10-2 and 10-3 Pa in the beam line vessel. In the close arrangement of the beam line the size of the cryopump is limited to a flat rectangular geometry of 8 m length, 2.75 m height and a depth of 0.5 m. Two cryopumps of this size will be included in each beam line. Within gas profile calculations of the detailed beam line geometry it showed up that the gas capture probability of the pumping surface must achieve 30 % to guaranty the beam pulse operation. This paper describes the vacuum requirements given by the ITER heating neutral beam injector and presents gas profile calculations of different beam line configurations to outline the effect on the operation of the cryopump. The design of the novel cryopump is presented and the heat load calculations to the cryogenic circuits will be discussed and summarized for the different operation scenarios. It is shown that the cryopump for the ITER heating neutral beam injectors covers all vacuum requirements and it is adapted to the ITER cryogenic supply.

The European contribution to the development of the ITER NB injector

“…The design of the cryopump [19,20] for the HNB will take advantage of the R&D activities performed in a dedicated facility to measure pressure drop of the hydroformed components, such as the 80 K radiation shielding. It is foreseen to adapt the design to MITICA in particular to comply with the enhanced diagnostics needs of the test bed.…”

An Indian test facility to characterise diagnostic neutral beam for ITER

“…The DNB configuration has two panels of cryosorption pumps [13]. The panels, each having a capture coefficient of 0.3, are lined along the walls of the vacuum vessel on either side of the beam line components.…”

Axisymmetric Magnetic Mirror Fusion-Fission Hybrid

“…Cryopump designs for the ITER torus [Hauer 2007], or its neutral beam lines [Dremel 2009], provide a reasonable starting point for engineering design. Studies of ITER cryopump regeneration have found three regeneration temperature regimes: 90 K releases all hydrogen isotopes and helium, 300 K releases all other gases except water, and 475 K releases water [Hauer 2007].…”

“…Pump the gas in the end tank. All are readily pumped by cryosurfaces, with one exception: Helium is harder to cryopump, but can be pumped with surfaces below 4.6 K, or by spraying Argon gas onto a cryosurface to weakly bond to helium, or by coating the cryosurface with activated carbon [Sedgley 1988, Dremel 2009]. …”