Time-dependent hydrogen and helium pressure profiles in a long, cryogenically cooled tube, pumped at periodic intervals.

摘要

Many particle accelerators and colliders throughout the world make use of superconducting magnets to focus highly relativistic beams. These magnets are cooled to (approximately)4.2(degree)K For practical reasons, the beam pipes, encircled by the magnets, also operate at these cryogenic temperatures. This paper presents a theoretical model for determining pressure profiles, in space and time, stemming from either hydrogen or helium gas leak into the cold-bore tube with appendage pumps located at periodic intervals. It is shown that a wave-like pressure gradient propagates from the leak source at a rate which is dependent on the leak magnitude, gas species, speed and location of appendage pumps, and the geometry and effective roughness of the cold-bore tube. Steady-state, linear pressure gradients eventually equilibrate between the appendage pumps in a magnitude commensurate with both the adsorption isotherm of the species and mass flow in the beam pipe. Results are given for a variety of conditions relevant to the Relativistic Heavy Ion Collider being constructed at Brookhaven, and a general procedure, with expressions, is provided for the making of similar calculations in other installations.