Ion Acceleration by Ion-Cyclotron Resonance in Non-Uniform Magnetic Field Using the TPD-Sheet IV Linear Divertor Simulator

Characteristics of extracted ion beam from a cesium-free negative ion source using sheet plasma

We report the characteristics of extracted beam current in the test plasma produced by direct current for sheet plasma upgrade producing negative ions by volume production without cesium (Cs) seeding. The negative hydrogen ion beam is extracted by a two-grid extraction system, which is located at the periphery of the sheet plasma. Experimental observations show that (i) negative hydrogen ions are successfully extracted from the sheet plasma by single/multi-aperture grids and (ii) the ratio of the extracted electron current I_EG(e) and the hydrogen negative ion current I_EG(H^-), I_EG(e)/I_c(H^-), decreases from 8.0 to 2.0 with an increase in the height of the electron fence (H_EF), which is a filter that prevents electron diffusion from the extraction region.

Applicability of micro-channel plate followed by phosphor screen to charged particles

This paper experimentally investigates the applicability of a micro-channel plate (MCP) followed by a phosphor screen to charged particles along with a calibration method for estimating the acceptable limit of input particle flux and appropriate operation parameters of a particular MCP. For the first time, plasmas consisting of only lithium ions are injected into the MCP. Despite large ion numbers (Ni) on the order of ≃10(7), no deterioration in the effective gain (αG) of the MCP owing to an excess amount of the extracted charge occurs in a certain range of the amplifier voltage (ΔUM) applied to the MCP. The measured αG nearly agrees with the expected value. However, once ΔUM exceeds a limit value, αG eventually begins to saturate. This is also verified in experiments using pure electron plasmas. An appropriate range of ΔUM is presented to avoid saturation and, finally, derive Ni directly from the secondary electron current outputted from the MCP only after the indispensable calibration.