A new method using a thick dielectric plate is discussed to measure the intensity distribution of a gyrotron's RF output in one step, unlike the conventional method in two steps. 1D simulation of the thermal diffusion in the plate removes the effect of convection cooling from the measured temperature distribution on the backside of the plate. As a result, the output radiation of UT-94 gyrotron is successfully measured. The peak intensity and the integrated power are 0.048 GW/m2 and 64.5 kW , respectively, within the uncertainty of 2.6%. The error of the measurement is expected to be less than 8.0 %.

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Outer Coil Effects of Anode-Layer-Type Hall Thruster SBS SystemIn Japan, collaborative research and development of cluster systems consisting of multi anode-layer type Hall thruster heads “RAIJIN” has started. At Gifu University, to investigate influences of the plume interference on the discharge characteristics and the thrust performance in the cluster systems, side by side (SBS) systems consisting of two anode-layer heads and a hollow cathode have been developed. In this study, dependencies of the effects of the plume interference on the outer coil current were evaluated. With the increase in the outer coil current, the discharge current was suppressed by 14~20% at 1A and decreased by up to 8% at 1A~3A. Thrust also tended to increase clearly up to 1A. As a result, the maximum thruster efficiency was about 40%.

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The alumina reduction method using laser ablation has been developed for recent several years. In this study, translational temperature and column density measurements of laser ablation plasma generated by nanosecond pulsed laser were conducted. Laser absorption spectroscopy using Al I 394.401 nm was performed at the pressure of 10 Pa and the translational temperature and column density were determined by spectral fittings to the Gaussian function. These peak values at the height of 5 mm were 10,200 K and 1.5×1017 m-2, respectively. The column density decreased at a height farther than 8 mm because of recombination and this affects the alumina reduction efficiency directly, which suggests that the height of the collected plate should be adjusted according to the pressure to increase the collected mass of the ejected Al atoms.

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