A. Iwamae

H. Zushi

I. Murakami

K. Kawakami

K. Takiyama

M. Goto

M. Yoshikawa

S. Ohtani

S. Tanaka

T. Fujimoto

T. Kato

National Institute for Fusion Science (NIFS-Repository)

§ 1 5. Development of Plasma Polarization Spectroscopy (PPS) and Its Research Coordination Fujimoto, T., Iwamae, A., Kawakami, K., Tanaka, S. (Dept. Eng. Phys. and Mech., Grad School of Eng., Kyoto Univ.), Zushi, H. (Res. Inst. Appl. Mech., Kyushu Univ.), Yoshikawa, M. (Plasma Res. Center, Tsukuba Univ.), Takiyama, K. (Hiroshima Univ.), Ohtani, S. (Electr. Com Univ.), Kato, T., Murakami, I., Goto, M. The objective of this Cooperation Research Program 1S to develop PPS as a plasma diagnostic teclmique by making polarization the keyword. In this fiscal year we examined the following subjects. 1. Anomaly of Balmer alpha line profile from tokamaks At Kyushu University, a Zeeman (or Paschen-Back) split line was observed on the TRIAM-IM. In the majority of discharges, the profile showed the usual Zeeman pattern with the stronger central n component and the weaker (J components on the both sides. 1 or 2 shots out of ten showed a profile with the central n component significantly weak or almost absent. If we assume tlle equal populations among tlle magnetic sublevels of the n = 3 level. the anomalous profile is interpreted that tlle magnetic field makes an angle about 45 degrees with respect to tlle toroidal direction. Since tlus assumption is quite unlikely, \ve have to explore another possible interpretation. One possibility is tllat tlle strong microwave creates resonant population transfer among the magnetic sublevels resulting in strong aligmnent. 2. Studies of the electric field from tlle polarization of emission lines At Hiroshima University, a unique electric-field diagnostic metllOd has been developed in which the degree of Stark mixing of tlle optically allowed transition component to tlle forbidden transition is determined from the polarization degree of the line. At Kanazawa University, tlle Langmuir turbulent state is being investigated wluch is produced by the injection of a strong relativistic electron beam into a plasma. So far, tlle electric field strength inside the caviton has been estimated from tlle Stark shift and the intensity of a neutral helium emission I ine. An oscillating electric field of tlle order of 100 kV/cm Witll tlle frequancy of 10 GHz was concluded. A possibility was discussed to determine tlle direction of the field on the basis of the polarization observation of the optically forbidden transition. 368 3. PPS on the WT-3 tokamak By the image reduction optics of 118 the image of tlle WT -3 plasma was focussed on tlle entrance slit of the monochromator. The two polarized components were resolved by the calcite plate located just behind tlle entrance slit. Thus, tlle space (poloidal direction) resolved and polarization resolved spectra were obtained on a CCD detector. The quality of the image was improved by compensating tlle change in tlle focal plane position owing to tlle introduction of the calcite plate. The transitions from tlle J = 1 and 2 levels of berylliumlike oxygen of 2s3p3PJ showed polarization. The two weak components of heliumlike carbon 23S1 - 23PO,I.2 lines were barely resolved. 4. Directional electron collisions on rydberg atoms Yoneda et al. I) showed that heliumlike fluorine lines from tlle laser produced plasma are polarized. The line intensity distribution in tlle spectrum clearly indicates tllat tlle plasma is recombining. This conclusion is consistent with tlle presence of tlle recombination continuum, which is also polarized, indicating that the continuum electrons have an anisotropic velocity distribution. Highly excited ions are produced by three-body recombination of ions with the directionally indident elecf!ons. Ditmire2) presents a formula of three-body recombination rate, but tlus formula is based on tlle two assumptions which are not justified. A classical Monte Carlo calculation of directional electron collisions on 17 = 10 hydrogen atoms is performed. For elastic collisions the populations tend to drift to J7l j = 0 sublevels, suggesting positive polarization for the resonance-series lines, which is consistent with Yoneda' s experiment. In ionization events .tlle two electrons leave tlle proton Witll relative angles larger tllan 60 degrees. This suggests reduced rdte for three-body recombination in comparison witll tlle isotropic velocity distribution. 5. X-ray spectroscopy of highly-ionized ions by Tokyo-EBIT From the direction perpendicular to the electron beam tlle Lyman alpha line of hydrogenlike titmuum was observed with the quartz crystal spectrograph. From the apparent intensity ratio of the Lyman alpha 1 and alpha 2 lines, polarization degree of the latter line was estimated. The polarization degree against the excitation energy was significantly smaller than calculation. A thorough examination of experimental uncertainties will be made. References 1) Yoneda, H. et aj. , Phys . Rev. E 56, 988 (1997). 2) Ditnure, T, Phys. Rev. E 54, 6735 (1996). 

Development of Plasma Polarization Spectroscopy (PPS) and Its Research Coordination

Development of Plasma Polarization Spectroscopy (PPS) and Its Research Coordination

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