| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2002: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
One of important problems in divertor plasma is to reduce the heating load from internal plasma to divertor plate where the sputtering of the plate is frequently, occurred in nuclear fusion reactor. When the sputtering of the plate is discussed, it is important to clarify two dimensional behavior of energy and temperature of ions incident to the plate. In this work, measurement of two dimensional velocity distributions of ions has been performed in DC discharge plasma. Ion temperature measurement has been done in simulated divertor plasma using inductively coupled plasma. Energy distribution functions of ions incident to substrate biased negatively has also measured in electron cyclotron resonance microwave plasma. In these measurements, grid and directional analyzers were used. The interesting results on ion behaviors were obtained as follows.
1.Measurement of ion two-dimensional velocity space structure by means of directional analyzer
For fundamental experiment on ion velocity distrib
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ution, two dimensional velocity distribution functions were measured in do discharge double plasma using directional analyzer which was consisted from capillary plate, retarding grid and ion collector. The analyzer has a high angular resolution of 1.4 degree. The two dimensional ion velocity space maps were estimated from velocity distribution functions obtained at all directions. It was confirmed that the directional analyzer could evaluate the spread on two dimensional ion velocity spaces.
2.Development of stimulated divertor plasma
Inductively coupled plasma (ICP) source where 3 turns helical antenna was wounded around glass tube with 3 cm, is used as one of the stimulated divertor plasma. ICP with electron 'density of 10^<12> cm^<-3> was obtained for optimum stimulated divertor plasma.
3.Ion measurement in ICP
Ion measurement Ti was done comparing with electron temperature Fe in ICP under a divergent magnetic configuration. The dependency of the magnetic field and gas pressure on both of T_e and T_i was also studied. In the former case, T_i was found to decrease for ion hole-parameter hi【greater than or equal】3, while Te decreased drastically for electron hole-parameter h_e【greater than or equal】200 and saturated for h_e【greater than or equal】10^3. In the latter case, T_e in, a non-magnetized plasma (B=0) provides the same gas pressure tendency as the T_i at magnetic flux density B=575G, while Te at B=575 G decreased, gradually with the pressure.
4.Measurement of energy distribution of ions incident to RF biased substrate
Time averaged energy distribution functions of ions impacted in the rf-biased substrate have been investigated in ECR microwave plasma from the viewpoint of the ion plasma frequency. It was observed that TIIEDF has a bimodal profile for a wide range of f_<pi>/f_<b-> Here fpi and fb are ion plasma frequency and RF biased frequency, respectively. It was found that even for f_<pi>/f_b<<1, the bimodal profile was observed at high rf-biased voltages. It was revealed that the energy difference in TIIEDFs increased with increasing the rf-biased voltage for f_<pi>/f_b<1, while for f_<pi>/f_b>1, the energy difference decreased with increasing f f_<pi>/f_<b->. Less
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