H. Funaba

J.E. Rice

K. Sato

National Institute for Fusion Science (NIFS-Repository)

§56. Spatial Profiles and Transport of Metal Impurities in LHD Funaba, H., Sato, K., Rice, J.E. (MIT) In the long pulse discharges of LHD, spatial pro-files of VUV spectra could be obtained by changing the line of sight of the spectrometer. The VUV spectrom-eter looks at the plasma horizontally from an outer port. Figure 1 shows the schematic view of the line of sight of the spectrometer for spatial scanning. The line of sight was moved from the upper region to the lower region through the plasma center during one dis-charge. The VUV spectra of a 120-second ICRF discharge are shown in Fig. 2. As the plasma parameters in this discharge were almost steady, the time axis of this figure corresponds to the spatial positions. The ob-served vertical position, Z, was changed from +45 em to about 0 em, where is the midplane. The data was acquired every 4 seconds. This time resolution corre-sponds to about 1.88 em in scanning, but the actual spatial resolution is abou·t 9 em. The signals in the beginning phase represent the emission from the edge region and the signals near the end of the discharge are almost from the central chords. In this data, a peaked profile of the line emission of FeXXIII (132.87 A) can be seen, while some other lines show flat profiles. In order to evaluate the impurity diffusion coef-ficient, D, and the velocity, v, the experimental data are compared with the calculation results of MIST, which is an impurity transport code. The experimen-velocity of impurity ions is necessary in the peripheral region . These D and v values are also compared with sim-ulation results of the time evolution of the emission of the Ka-line of titanium after the Ti pellet injec-tion. The laser blow-off impurity injection experiment is also planned for the next experimental campaign. 1,00 z Rax" 3.6 m, beta "' 0.11% case 2.~0 J.OO J.~ 4.00 4 . ~0 5.00 R [m] Fig. 1. The schematic view of the line of sight of the VUV spectrometer for spatial scanning. #26191 200 400 FeXXIII (132.87-f..) .... ... ......... .. .... .... ; .... .... ...... ,., .. " 'j ···· ; Intensity (au] :I "ooo ········ ··· ····r ~ ·-· ........ .. .... ...... . . ~ 4000 .. . ; ... .. . . 3000 2000 1000 0 600 800 1 ooo channel tal line intensity is evaluated by subtracting a certain Fig. 2. The VUV spectra of an ICRF long dischrge. offset value from the acquired data. The density of ~) (~ each charge state of the impurity is calculated and in-tegrated along the lines of spectrometer sight. The ~ ~ normalized intensity of FeXXIII and FeXVI lines are _i i._ compared with the results of MIST calculation in Fig. 3.(a) and (b) respectively. D, and v, are given as some functions of the minor radius, r . The same D and v values are used for different charge states of impurity ions. The dotted line indicates the case of v = 0 in the whole plasma region. In this case, the calculated profile of the FeXVI line is broader than the profile of observed data. The solid line shows the calcula-tion results with a inward velocity, v < 0, profile in the peripheral region. These D and v are shown in Fig. 3. (c) and (d). In the v < 0 case, the calculated FeXXIII line has a narrower profile. One of the reasons of the broadening of the experimental data may be the overlap of FeXXIII and FeXX lines at this wave length. From these comparison, it is seemed that the inward 0.0 LJ.i..u..L.U...-'.U..U.....U..U..u.lJ.J..J.J..U.I~~.I.l..u .......... u.uJ 0.0 UJ...I.I..IJ,I.J.J.J.J..L.U.J.J.J.J..L.J..U..l.J..J.LU..u..u..J..I...I.J.JJ~.L.U.LL.LU o.oo 0 ,10 0.20 0.50 0.~0 0.50 0.00 o. 10 0 .20 0.50 Z lm] Z lm] 0 .50 ~o.~_ . . ; .;-10 - : v~O(ulput) 0o.:?l=-----------~: -20 . v<O(input) ~:::~ _ f;(,np,t). I ~: ;>,:~=:.::.:..:.;:,· 0.0 I : -30 ....__.~---..,.L_~~--1...---~~~ 0.0 0.2 r [m] 0.4 0.6 0.0 0.2 r (m] 0.~ Fig. 3. Comparison of the line intensity with the normalized emissivity calculated by MIST. (a) FeXXIII, (b) FeXVI, (c) assumed D and (d) v. 61 0.6 

Spatial Profiles and Transport of Metal Impurities in LHD

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)