The direct jumping of molecules through the compression of gas centrifuge

A 3D numerical simulation of pressure distribution in the helicoid multi-groove Holweck pump as the compression of a gas centrifuge is carried out. It was shown that the combination of the free molecular regime and clearance between the compression rotor and stator leads to an appreciable effect of collisionless jumping, which essentially influences the pressure in a high vacuum chamber. When neglecting the jumping effect, the limit compression ratio is very large. The jumping considerably reduces the compression ratio to approximately the same moderate value for different gases. As a result of the simulation, the limit compression ratio can be obtained as an optimizable function of variable parameters such as the groove depth, width and angle of inclination. The numerical results can be interpreted within the framework of a simple phenomenological model.