BJ. "Peterson

R." Sakamotor

S. Masuzaki

National Institute for Fusion Science (NIFS-Repository)

§48. The Effects of Divertor Material on Radiation Profi les in LH 0 Peterson, BJ., Masuzaki, S., Sakamotor, R. 1 Helium j R =3.6m ax 8 :: 2.5-2.75 T t • .,. carbon • SS In the Large Helical Device (LHD) (1) a..:g measurements of radiation profiles are made 'C .. I • • • ... .,. ...: .... Y Y • ~ Y.,. using arrays of resistive metal foil bolometers a.. e ~ Y .., ; "t' (2). During the second experimental calnpaign, stainless steel was used as the prilnary plaslna facing material in the divertor. Prior to the third experimental campaign graphite tiles were installed in the di vertor resulting in a general decrease in the radiation. i' .::;: 0.1 o Y "t' ..,.." ..,"t' "t' , 2 .., "t' Y· .".,. , 1 4 6 8 10 n (10 19mv 3) e Fig. I Radiated power fraction versus line averaged density for helium gas, Rax = 3.6 m and Bax = 2.5 - 2.75 T. Shot # 6607 t 1.00s 300 ~ (a) 5S divertor He glow In particular for the magnetic configuration of Rax = 3.6 m and at line averaged densities below 3 x 1019In-3, a reduction of the radiated power fraction from 350/0 in the second campaign to down to 12 % in third campaign was observed as seen in Fig. 1. Comparing similar shots (in terms of discharge parameters) froin the second and third caInpaigns, the core (0 < ria < 0.79) radiation fraction was reduced from 440/0 to 300/0 of the ':' 200 I- Pin = 3.0 MW -PraiPin = 34% Q) ~ .0 0.. total radiation and the radiated power fraction ~ .~ reduced from 34 0/0 to 200/0 as is shown in Fi g. -g 2. This change can be attributed to a 0:: i' .::;: 100 r o 0.0 300 4 PcorelPrad = 440/r ~ ~ ~ 10 Z2- T~ -II 0.2 0.4 0.6 0.8 1.0 p Shot # 11562 t 1.57s (b) Graphite divertor ,lL-H glow, Ti getter reduction in the radiation frOln iron as was seen from spectroscopic measuren1ents. However at a magnetic axis position of Rax = 3.75 m no significant change was seen in the radiated power fraction and only a slight decrease was seen In the core radiation comparing the graphite divertor data to the stainless steel divertor data. In addition comparing data from the middle and the end of the third calnpaign an increase in the core ':' 200 Pin = 3.5 MW -Q) ~ o 0.. u radiation from 33% to 48% of the total Q) .~ radiation was observed, even though Rax = 3.6 -g 0:: m. References (1) A. Iiyoshi, et aI., Nuclear Fusion 39, (1999) 1245. (2) B.J. Peterson, In Proc. 26th EPS, Europhysics Conf. Abstr. 23J, (1999)1337. 52 100 - 0 .7 a 0.0 PradIPin = 20% PcorelPrad = 30% rr 7.0 2 .2 .1 1 0 .2 0.4 0.6 p ~ ~ -~ 0 .8 1.0 Fig. 2. Radiated power profiles for hydrogen gas, Rax = 3.6 m, Bax = 2.5 - 2.75 T and ne = 3.3 xl0 19 n1-3 with (a) SS divertor plates and (b) graphite tiles. 

The Effects of Divertor Material on Radiation Profi les in LHD

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