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A Novel Electrostatic Ion-Current Absolute-Value Detector Under Circumstances with Simultaneous Electron Incidence by The Use of a Proposed “Self-Collection” Method for Secondary Electron Emission

M. Hirata, S. Nagashima, T. Cho, J. Kohagura, M. Yoshida, H. Ito, S. Tokioka, T. Numakura, R. Minami, Y. Nakashima, T. Kondoh, K. Yatsu, S. Miyoshi

Fusion Science and Technology / Volume 43 / Number 1T / January 2003 / Pages 262-264

Diagnostics /

Published:February 8, 2018

For the purpose of observations of the absolute values of ion-end-loss currents in open-field plasma devices including the GAMMA 10 tandem mirror, a newly developed electrostatic ion-current detector is proposed on the basis of a “self-collection” principle for secondary-electron emission from a metal collector. The newly developed ion-current detector is constructed with a set of parallelly placed metal plates with respect to lines of ambient magnetic forces in an open-ended device. One of the most essential characteristic properties of the proposed detector is based on the physics principle of a “self-collection” mechanism due to E×B drifts for secondary electrons impinged by ion-current collections from the metal-plate collector; that is, the secondary electrons are returned back into the collector through E×B drifts by the use of no further additional magnetic systems except the ambient open-ended fields B. The proposed idea is tested in an ion-beam line along with an additional set of the Helmholtz coil for producing and mocking up open-ended fields for simulating the GAMMA10 magnetic fields. The characterization experimental data in the ion-beam line give good agreement with computer-simulated trajectory-calculation results. The novel ion-current detector is preliminarily and usefully applied to the GAMMA10 plasma experiments.

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