A. Matsubara

A. Tonegawa

K. Kawamura

K. Sato

T. Shibuya

National Institute for Fusion Science (NIFS-Repository)

§ 9. Impurity Transport in High DensityPlasma Produced by TPD-II (II)The intensity of helium spectral line (281.28nm)increases with the increase of discharge current forhollow cathode electrode made of SUS304.Shibuya, T. (Dep. Appl. Sci., Tokai Univ.),Kawamura, K. (Res. lnst. Sci. Tech., Tokai Univ.),Tonegawa, A. (Dep. Phys., Tokai Univ.),Matsubara, A., Sato, K.i) IntroductionA reduction of reversed gas flow toward main plasma in agas divertor is required to achieve both a low thermal loadon a divertor plate and high magnetic confmement in themain plasma. In the divertor system proposed by us, a highvacuum region is set between the divertor region and themonitoring region. 1,2) In this paper, impurity transport ofthe divertor materials in the plasma is investigated usingTPD-II (fest Plasma generated by Direct Current)........................................... 1.8......................... 1.6 '=I··· .. ·_··14 $.............................................................................. 1.2_._ _ 1.00.40.20.0200 220 240 260 280 300Wavelength [nm]Fig. 2. Emission spectra as a function of the dischargecurrent using a hollow cathode electrode made ofSUS304.2.5 r-:o::J2.0 $1.5Cl.50.500200260240220200For the electrode fit up of carbon sheets, the intensity ofC emission spectral lines (283.67, 283.76nm) increase withthe increase the discharge current. In both electrodes, highdischarge current of 60mA fails to heat up the electrode forlongtime.Electrode surface on which carbon particles deposited iscleaned up under the flow of hydrogen as working gas.The experimental fact that the intensity of carbon spectradecreases with the elapsed time supports the cleaning ofdeposited carbon mentioned above.Wavelength [nm]Fig. 3. Emission spectra as a function of the dischargecurrent using a hollow cathode electrode with carbonsheets.ffiOVs'IMPii) Experimental apparatusExperimental setup was shown in Fig. 1. The heliumplasma produced in a plasma source traveled through amonitoring chamber, contact with a metal divertor or gasdivertor, and finally relaxed to neutral gasses.The hollow type electrodes made of SUS304 was placedin front of the metal divertor for the impurity measurementexperiment. The electrode equipped with a slit was size ofI50mm in diameter, 50mm in width, Imm in thickness.Carbon sheets or carbon particles fit up to inner surfaceof the electrodes. Only one electrode was set up in thevacuum chamber in the operation. The used dischargegases were helium and hydrogen. Chemical species in thehollow discharge was measured by using emissionspectroscopy for the plasma.L..-__----J'L.....J' IfllV9tor IN 'IPDduumer duumer dlaniu H8SIID. SWIreFig. 1. Experimental apparatus ofTPD-II (NIFS).iii) Experimental resultsEmission spectroscopy in hollow cathode discharge areshown in Figs. 2,3 respectively. Discharge voltage arefrom 600V to IkV corresponding to discharge current offrom 20mA to 60mA.References1) Matsubara, A., et. aI, J. Nucl. Sci. Technol., 37 (2000)555.2) Matsubara, A., et. aI, J. Plasma Fusion Res., 78, (2002)196.3) Dno, M., et. al. J. Society of Advanced Science ,13,(2001) 533.295

Impurity Transport in High Density Plasma Produced by TPD-II (II)

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