Performance of a hybrid vacuum pump at low temperature

In this paper a novel concept of a mechanical pump able to run at low tempe ratures (80-25 K) is presented. Since gas density varies inversely with tem perature, a pump delivers much higher mass flow rate at low temperature tha n at room temperature for a given size. Advantages of this concept are redu ction in size and weight, when compared with a conventional pump scaled for the same mass flow rate at room temperature. The inlet gas temperature is set in order to avoid condensation on the rotor blades and surroundings. A temperature gradient between the different pumping stages allows optimizati on of the exhaust pressure. This pump should be a solution for continuous t ritium extraction and minimization of the mass inventory for fusion tokamak s fuel cycle control. (C) 2000 Elsevier Science B.V. All rights reserved.