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

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.