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.

In order to measure negative-ion temperature, the experimental result of the negative-ion recovery ratio from the two-laser photodetachment is usually fitted with the theoretical curve derived from the ballistic kinetic theory of negative ions. The particle-in-cell (PIC) code with a one-dimensional slab model has been developed to analyze the effect of the ambipolar electric field, which is neglected in the ballistic theory, on the negative-ion recovery. The preliminary results of the PIC simulation indicate that our PIC code is a useful tool for the analyses of the negative-ion recovery in the photodetachment.

Experimental studies were performed on the interactions of a CO2 laser beam of long pulse duration (∼50 ns FWHM) and peak power up to 4×1012 W/cm2 with plasma blobs produced by this laser from a massive planar target of aluminum or polyethylene. Special attention was paid to the laser reflectivity (R) due to the stimulated Brillouin backscattering (SBS), in particular to the correlation between the SBS reflectivity and the e-folding scale-length for spatial plasma density variation (L n ). It is shown that (1) the experimental L n -values are consistent with the theoretical ones predicted from an ellipsoidally-expanding self-regulating plasma model, and (2) taking those predicted L n -values into account, the experimental R-values agree well with those estimated from an existing simulation model, which is restricted to a relatively low percentage (15–20%) even for longer pulse duration.

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