The (changing) MFTF vacuum environment Available to Purchase

The mirror fusion test facility (MFTF) vacuum vessel will be about 60 m long and 10 m in diameter at the widest point. The allowable operating densities range from 2×10⁹ to 5×10¹⁰ particles per cm³. The maximum leak rate of 10⁻⁶ Torrπl/s is dominated during operation by the deliberately injected cold gas of 250 Torrπl/s. This gas is pumped by over 1000 m² of cryopanels, external sorbtion pumps, and getters. The design and requirements have changed radically over the past several years, and they are still not in final form. The vacuum system design has also changed, but more slowly and less radically. This paper discusses the engineering effort necessary to meet these stringent and changing requirements. Much of the analysis of the internal systems has been carried out using a three‐dimensional Monte Carlo computer code, which can estimate time‐dependent operational pressures. This code and its use will also be described.