H. "Sasao

S. Inagaki

Y." Nagayama

National Institute for Fusion Science (NIFS-Repository)

§S7. ECE Measurement with the Inner Mirror on LHD Sasao, H. (The Grad. Univ. Advanced Studies), Inagaki, S., Nagayama, Y. The LI fl) has two electron cyclotron resonance regions in tile clJuatorial plane because the magnetic field strengtil docs not ci1cUlgC monotonically. The electron cyclotron wave. which is emitted from tile electron cyclotron resoncUlce region in tile inboard side. is absorOcd at tile resonance region in tile outboard side. Therefore. it is difficult to measure tile electron temperature in tile inboard region witil an EeE diagnostic system installed in the outer port. Therefore. we installed a mirror in tile inner port of tile LI-ID in order to measure tile emission of the electron cyclotron wave propagating inwards. This mirror is designed, based on tile gaussian beam optics. and hence. tile concept of tile constant phase. proposed by S. Kubo et al.l) This means that tile surface of tile mirror is determined by the following optical condition: tile minowave phase is kept constant. independently of the optical path through the mirror. Figure 1 shows the EeE diagnostic system in tile inner port in tile tilird experimental campaign. The electron temperature in the inboard side was measured witil tile ECE inner mirror and two hetercxiyne radiometers. The fundamental ordinal mode of the EeE in tile 52-84 GHz fLmge is used for electron temperature measurement in the high magnetic field operation. The second harmonic extraordinary mexie is used for tile 116-148GI-lz range measurements . By using tilese frelJuency f(Ulges. both modes become optically thick in tile high field operation. The ECE mode is chosen witil a universal polarization rotator. The EeE is polarized strongly because of tile LI ID magnetic shear. The degree of the polarization is determined hy the angle of tile magnctic field line to tile clJuatorial pi;me at tile edgc of thc plasma.2) Thus. tile polarization rotator :mgle is set by using tile magnetic field line calculated in tile vacuum. to be matched 'vVitil the polarization of the mexico An example of the EeE measurement wi til tile inner mirror is shown in Fig. 2. The closed circles show the data in tile inboard side. obtained witil tile low frelJuency radiometer. The closed triangles are tile data in tile outboard side. taken Witil tile GPC . The dotted line shows a fitting curve of the tilOmson scattering data. The EeE data are calihrated with the thomson scattering data. By Ulis study. tile diagnostic range of tile EeE measurement on LIm could be expanded to tile inboard side of plasmas. Low freyuency heterodyne radiometer High frequency 1-----::01~ ... 1 heterodyne 1..-....;,"----1.'--1 radiometer Fig. 1 Schematic diagram of the inner ECE diagnostic system #13082 • inl'k"f ECE (raii(lflt"lc"r) • Oukr ECE (GPC\ - - --- ·· 1l1o lffion fdting •••. • .&. ' -"'-~ '- J' .... " .. f/ .~ .... J . S R (m) .• A ...... Fig. 2 A example of the ECE measurement with the inner mirror References 1) S. Kubo et al.: Fusion Eng. Des . 26 (1995) 319. 2) P. C. dc Vries el al: lo be published in Fus. Eng . Design (2000) . 61 

ECE Measurement with the Inner Mirror on LHD

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