H. Arimoto

H. Kawazome

K. Ida

K. Kondo

K. Sato

K. Takiyama

N. Noda

N. Ohyabu

S. Sudo

T. Oda

T. Ohgo

National Institute for Fusion Science (NIFS-Repository)

§ 17. Measurements of Fine Spectral Profile of Ha in LHD Steady State Plasmas Kondo, K., Kawazome, H., Arimoto, H. (Kyoto Univ.) Oda, T. (Hiroshima Kokusai Gakuin Univ.) Takiyama, K. (Hiroshima Univ.) Ohgo, T. (Fukuoka Univ. Educ.) Sudo, S., Ohyabu, N., Noda, N., Ida, K., Salo, K. , It is an important task to study the behav-ior of neutral hydrogen atoms in the edge plasma region for achieving a good confinement. Essential parameters of the neutral hydrogen atoms are their velocity distri-bution function and flow velocity_ In this study, Ha line spectral profiles are measured with a high-resolution spectroscopic measurement system. The system consists of object optics, optical fiber bundle, an echelle grating spectrometer and a CCD detector. The achieved recip-rocal linear dispersion of 0.0024 nm/pixel is confirmed by precise calibration experiments. Figure 1 shows schematic drawings of the view-ing chords and the measurement area. As shown in Fig. l(a) and l(b), three chords in the toroidal direction and ten in the poloidal direction are arranged at regu-lar intervals. Any sets of seven chords are available for simultaneous measurements. The rectangle in Fig. l(c) indicates the measurement area. Several viewing chords in the upper region can view inner divertor plates. Since Ha emissions are mainly from the inboard side of the tOfns, a linear polari:6cr is inserted to measure only the Zeeman 7T component of the inboard emissions. Figure 2 shows the Ha line spectral profiles obtained at (.) ," ~ r (b) (e) Fig. 1: Schematic drawings of the viewing chords and the measurement area. (a)Thc viewing chords projected on the poloidal cross section, (b) the 2-D imaging optical fiber array and (c) the view from the measurement port. 166 the viewing chord #2-9, which spots on an inner di-vertar plate, at the different magnetic field configura-tion. Figure 2(a) and 2(b) show the profiles measured at the magnetic axis position Rax=3.60 m and 3.75 TIl) respectively. These profiles can be decomposed into two Gaussian components, a narrow and a broad component. The former represents the contributions of atoms pro-duced by dissociations of molecules and molecular ions, and the latter represents the contributions of reHected atoms and atoms produced by charge exchange reac-tions. At· Rax=3.60 m, the central wavelength of each component shifts significantly toward the blue side and the profile of the total emission exhibits an asymmetric feature, while little shifts are observed at Rax=3.75 m. At Rax=3.60 m, 4.6x 103 m/s and 1.8x 104 m/s of the flow velocity are estimated corresponding to the shift of the central wavelength of the narrow and the broad com-ponent, respectively. There exist the hydrogen atoms which have the large velocity component along the view-ing chords in consequence of the remarkably large shifts of the broad component. The divertor flux concentrates at the inboard side of the torus at Rax=3.60 III 1). There-fore , the asymmetric feature of Ha line spectral profiles at R ax =3.60·m is ascribed to the contribution of the atoms reflected by the inner uivertor plates. 600 '" #39978 2.00 - 3.00 (sec) Sight Line #4 (2-9) slit width: 1S (jIm) ,'It: I,OO{sec) Narrow : ' Measured Tow] .~ 300 .E Brood, . 200 "._~".I:!~/ L . i ~,_ ~-L_,~,_j 655.9 656.1 656.3 656.5 Wavelength (nm) (a) Rax= 3.60 m #44921 l75-4.50(sec) ~::::I ... =§ ........~ ...... ··1 =::""c::" .. Sight Line #6 (2-9) Measured slit width:?S (,urn) 6t: 750 (ms<:c) Towl ii 350 .. , Nimllw .e '" '" 250 ] 150 i' .. 655.9 656.1 656.3 656.5 Wavelength (nm) (b) Rax= 3.75 m Fig. 2: Ha line spectral profiles obtained at magnetic axis position (a)Rax=3.60 m and (b)Rax=3.75 m. An asymmetric feature is observed at Rax=3.60 m. Reference 1) T. Morisaki et al., Contirb. Plasma Phys. 42 (2002) 2-4321 

Measurements of Fine Spectral Profile of Hα in LHD Steady State Plasmas

Measurements of Fine Spectral Profile of Hα in LHD Steady State Plasmas

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