AbstractA high speed gas pumping system is required to minimize the reionization loss of neutral beams in a neutral beam injector; until now the beam line design has made use of a condensation cryopump system. The system becomes more expensive as size increases and needs high maintenance and has a high operation cost. Instead of the cryocondensation pump a cryosorption pump is considered for the beam line. This paper describes the development of a high speed cryosorption pump for a neutral beam injector. A module test has been carried out to have a fundamental data base. A cryosorption pump with a pumping speed of about 300 m3 s−1 has been designed on the basis of the result of the module test and has been applied on the neutral beam injector of JIPP T-IIU Tokamak. In this paper, the design and the experimental results are discussed.