NEW METHOD TO IMPROVE HE-REMOVAL PERFORMANCE OF PUMP LIMITER BY RF PONDEROMOTIVE FORCE

摘要

A new method to improve He-removal performance of a pump limiter by using rf ponderomotive force is proposed. A part of the helium neutralized at the plate in the pump limiter is re-ionized by the plasma in the channel under the limiter blade (''scoop'') and flows back out of the scoop. The method proposed here is to suppress this back stream and improve the He exhaust rate by an application of rf ponderomotive force. When the frequency is slightly above the cyclotron frequency of low energy re-ionized He+ ions,the ponderomotive force is applied only on the He+ ions to reduce the back stream and the He pumping efficiency is improved. It is also shown that this method can be extended to improve tritium inventory together with He ash removal by choosing the frequency slightly above the tritium cyclotron frequency. [References: 9]