A. Komori

A.C. England

C.C. Klepper

H. Suzuki

J.F. Lyon

S. Masuzaki

T. Morisaki

National Institute for Fusion Science (NIFS-Repository)

§4. Neutral Pressure Measurements in the CHS LID Klepper, C. C. , Lyon, J. F. , England, A. C. (ORNL), Komori, A., Masuzaki, S., Morisaki, T., Suzuki, H. An ASDEX-style fast (1-ms response time) ion gauge (FIG) mounted in the LID chamber on CHS has been used to study the LID pumping effective-ness for a variety of conditions. In these experiments, the current CILID) in 8 pairs of coils above and below CHS was set to create either an 0-point or an X-point of an min= 111 island at the location of the LID head. Figure 1 shows the time history of the gas puff, the averaged density (ne), the neutral beam pulse (NB) and the FIG signal with Raxis = 99.5 em and Bo = 0.92 T. 0.6 1.5 2 -0.4 '? ·c: E :J () ..0 "' ~ ~0 ,.... (!J 0.2 0.5 "' u:: c:: ~~~~~~~~~~~~ 0 0.05 0.1 0.15 0.2 t (sec) Fig. 1. Time history for a typical LID shot Figure 2 (top) shows the variation of the FIG signal at 80 ms as ILID is varied from 0 (no island) to 1.1 kA for a fixed gas puff. The symbols "0" and "X" indicate 0-point and X-point operation, respectively. The largest difference between 0-point and X -point operation occurs for Iun ::::: 0.6 kA. The plasma density also changes as the island size is varied (Fig. 2, middle), but the 0-point and X-point nl values are the same for Iuo :::; 0.4 kA and 2:: 1 kA although the FIG values are quite different. The FIG pressure normalized to nl is shown in Fig. 2 (bottom). The 0-point ratio has a broad peak as I LID is varied, but the X -point ratio isindependentofiLID· Similiar behavior is seen at other radial loca-tions for the LID head. The FIG signal increases as the LID head is moved closer to the plasma and generally varies in the same way as the ion satura-tion current measured with a Langmuir probe in the LID chamber [ 1]. -0 -0 .§. 0.8 0 oo 0 G) 0 ... 0.6 0 :::::J X (/) X (/) X X G) 0.4 X ... X X a. X (!) 0.2 u:: 0 0 0.2 0.4 0.6 0.8 1.2 I (kA} LID 0.7 0.6 ~ ~ox c 0 ~ 0.5 X > X .-:: 0.4 (/) 0 X X 0 c 0 G) 0.3 0 0 0 "C 0 Q) 0.2 c :J 0.1 0 0 0.2 0.4 0.6 0.8 1 1. 2 I (kA} LID 3.5 0 0 3 c 0 -0 0 G) 2.5 ... :::::J (/) 2 0 (/) 0 0 Q) 0 Q. 1. 5 oo 0 " X X X X X X X X u:: 0.5 0 0 0.2 0.4 0.6 0.8 1.2 I (kA} LID Fig. 2. Variation of FIG pressure (top), nl (mid-dle) and the ratio (bottom) as I LID is varied. Reference 1) Komori, A., et al., in 12th Int. Conf on PSI 1996, St. Raphael, p.161. 213 

Neutral Pressure Measurements in the CHS LID

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