Suppression of secondary electrons from an endplate of a tandem mirror by use of a biased mesh

Negative bias is applied to a mesh placed in front of an endplate of the GAMMA 10 tandem mirror [Phys. Rev. Lett. 55, 939 (1985)]. A bias voltage of around 10 V results in an increase of the potential difference by an order of kV in the end region. The increment is about two times the temperature of end‐loss electrons and most of that stems from the sheath potential drop in front of the endplate. Provided that almost all the secondary electrons emitted from endplate are reflected, these results agree with the prediction of a potential model for the open magnetic field configuration [J. Phys Soc. Jpn. 61, 3153 (1992)].

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