[2E01-08] Vaccuum Science and Technology (VST)

9:00 AM - 9:30 AM JST(12:00 AM - 12:30 AM UTC)

[2E01【学会賞】] XHV by cryopumping?

*ichiro arakawa¹ (1. Gakushuin University (Japan))

The ability and the difficulty to get XHV, as low as 10^-11 Pa or lower, by cryopumping are discussed. On the assumption of static condition, the pressure in a vacuum system may be determined by the equilibrium pressure of hydrogen adsorbed or condensed on the cryosurface at the lowest temperature. In a realistic vacuum system, the pressure is determined by the dynamic balance between desorption(evaporation) and adsorption(condensation) at the surfaces of a wide variety of temperatures. Adsorbed(condensed) hydrogen that has the equilibrium pressure of 10^-9 ~ 10^-10 Pa must be removed to get the lower pressure. However these species have long sojourn time of 10⁴ ~ 10⁵ s and such a long time is a basic difficulty in a practical use of a cryopump at XHV.

Password required to view