GERHARD Fuch Forschungszentrum Juelich(独)IPP, Research A
KLAUS Hothke Forschungszentrum Juelich(独)IPP, Research A
矢野 勝喜 理化学研究所, プラズマ物理研究室, 研究員
FUCHS Gerhard Forschungszentrum/Juelich Germany, Institute fuer Plasmaphysik
YANO Katsuki Institute of Physical and Chemical Research Plasma Physics Laboratry
HOETHKER Klaus Forschungszentrum/Juelich Germany, Institute fuer Plasmaphysik
|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 1990 : ¥3,400,000 (Direct Cost : ¥3,400,000)
The purpose of the present study is to clarify a method for reducing the load of the wall of a tokamak through the investigation of the transport process of electrons and ions behind the limiter. Particularly, in order to examine the recent problem of the excess of the positive ion temperature above the electron temperature, we intended to develop a reliable method of measuring the ion and electron temperatures and the space potential. Results are as follows.
1. Dr. K. Hoethker, Institute fuer Plasmaphysik Forschungszentrum/Germany, was invited to Riken. The reliability of his measuring method for ion temperature using a rotating double probe was tested in our mirror type ECR (electron cyclotron resonance) plasma and a reasonable result was obtianed. The method will be applied in JT60 in Japan Atomic Energy Research Institute (JAERI) in a near future. The calibration of the probe will be made by using a magnetic device in the Institute of Space and Astronautical Science.
Another double p
robe method for the measurement of ion temperature which was developed by Riken was applied in Textor in Forschungszentrum. A Montecarlo simulation was made by Dr. Belitz there and supported the analytical formula and extended the applicability region of the probe. Furthermore, a method of measuring the electron temperature developed by Riken was also examined in Textor.
2. Dr. G. Fuchs, Institute fuer Plasmaphysik Forschungszentrum/Germany, was invited to Riken. The effect of emission of secondary electrons from the porbe was studied by using a cusp type ECR plasma in Riken. Six kinds of double probe were installed in the machine and the distortion of the characteristics was examined. A possibility of simulating the surface effect was proven but a more detailed study will be made in the near future by hitting a beam on a emissive material in the machine. A method for estimating the space potential was also tested by using the probes. Further, the space potential and the positive ion temperature were estimated from the spectrum of positive ion beams extracted from the machine.
3. The ash gas, He, produced by fusion should be introduced into the boundary plasma region and exhausted efficiently by a pump limiter, etc. An experimental study of the efficiency of exhaustion was made in the pump limiter ALT-II in Textor by using a new method based upon the principle of ion scattering spectroscopy. In order to separate He from the fuel gas D_2, both He and D_2 were ionized, accelerated and impinged upon a target. Thus, He could be separately measured, since only D_2 was decomposed by the target. A good result was obtained by detecting He in the douwstream of the limiter under the condition of the switching of NBI and the variation of the plasma density through He gas puffing.
4. An experiment of investigating the relation between the hydrogen ions and the elecotron energy distribution was made in the above cusp type ECR machine. The existence of H_4^+ to H_5^+ besides H^+, H_2^+, and H_3^+ were identified. The condition of the optimum density of the latter ions was clarified. Although the density of H^- was less than one order of that of positive ions, negative ions can influence the behavior of the sheath near the wall. Therefore, the optogalvanic method was examined as a method to detect negative ions and was found to be successful.