H. Idei

K." Ohkubo

M. Sato

M. Shirasaka

S. "Morimoto

S. Ito

T. Shimozuma

Y. Takita

National Institute for Fusion Science (NIFS-Repository)

§9. Cooling Performance of a Forced Gas-cooled Brewster Window Morimoto, S., Shirasaka, M. (Kanazawa Institute of Tech-nology), Shimozuma, T., Idei, H., Ito, S., Takita, Y, Sato, M., Ohkubo, K. Cooling performance of the gas-cooled Brewster window was studied [1] The disk (Kyocera SN-287, 120x320mm2, 2.53mm-thick) was heated by dielectric loss due to microwave transmission and also by a dummy heat source. In the latter case, a film resistor (0. 12mm-thick, 90mmx300mm) was pressed to the disk surface (vacuum side) and DC currents of ~120A were induced. Temperature distribution on the disk surface (atmospheric side) was measured with an IR camera. Figure 1 shows two cooling-gas (dried air) ejecting methods . The gas is ejected onto the disk surface from 9 1 mm-diam. holes which are distributed along (a) the straight manifold mounted on the disk-supporting flange and (b) the edge of the circular waveguide (atmospheric-side) . The circumference of the disk is water-cooled. Ca)Manifold type Manifold Brewster window (120x32Omm2 :SN-287) (b) Tube type Reservoir Fig.1 Cooling-gas ejection systems. Figure 2 shows temperature distributions along the major axis at the dummy heating power of 300W (type a gas ejection) . The disk (particularly central part) is effectively cooled down by gas cooling. This is because the gas-nozzles are concentrated around the central part. The water-cooling is also effective, indicating high thermal conductivity of the present silicon nitride disk. 130 I--,.---- -----r-~· --1-......,...~~~~--- -- ~--~ ~- T - ·-.---...,---~~~r~~-.-! 140 l Dummy heat source ~ I (a) Man i fo I d type j 120 ~ I No cool jng/ ~ ~ 100 ~ ~ ~ 80 r '\""l ~ 60 I : .. ~:~:_:~.I~n~ _._~ __ .. \J ~ II 1 40 f' .-"'----- -- -.-- -~ ~ f - 7- .-----.- . j 20 r---- I Gas coo ling/ -.:~ [ / Gas and wat er coo ling 1 o ~~~I ~ _____ ... _ . ___ • ...L~~~-'--'--'-....L.... __ ~_~.! -150 -100 - 50 0 50 100 Distance (Major ax i s) [mm] Fig.2 Temperature distributions along the major axis (dummy heat source power=300W) . 150 Figure 3 shows temperature distributions after the 30sec transmission of 58kW microwave (type a gas ejection). The distribution before cooling indicates that the incident microwave power has a fairly peaked profile. This is supposed from the fact that the water-cooling is not so effective as in the dummy heat source experiment (heating power distribution is flat). The profile also shows non-symmetry in the major axis direction. The temperatures at Z=+ 150mm and Z=-150mm should be equal to each other and close to that of cooling water ( the cooling pipe is located at Z=± 160mm). The reason is not understood yet. 30 ~ f I No coo I j ng . '. ------.... I Ga s coo I j nt Microwave 1 (a)Manifold type J I Gas and water coo I j ~g 20 t~~~-- 150 - 100 - 50 50 100 150 Distance(Major ax i s) [mm] Fig.3. Temperature distributions along the major axis (microwave power=58kW, t=30sec). Flow rates of gas and water are 180/lmin and 2/lmin, respectivel y. Reference 1) Shimozuma, T, Ito, S" Takita, Y, Sato, M" Kubo, S., Idei , H. , Ohkubo, K , Shirasaka, M., Morimoto, S., this annual report . 

Cooling Performance of a Forced Gascooled Brewster Window

Cooling Performance of a Forced Gascooled Brewster Window

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