B 4 C protective coating under irradiation by QSPA-T intensive plasma fluxes
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Protective Coating under Irradiation by QSPA-T Intensive Plasma Fluxes O. I. Buzhinskija, V. A. Barsuka, L. B. Begrambekovb*, N. S. Klimova,b, V. G. Otroshchenkoa, and A. B. Putrica aTroitsk Institute for Innovation and Fusion Research (TRINITI), ul. Pushkovykh, vladenie 12, Troitsk, Moscow oblast, 142190 Russia b National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe sh. 31, Moscow, 115409 Russia *e-mail: [email protected]
Received March 26, 2015
Abstract—The effect of the QSPA-T pulsed plasma irradiation on the crystalline boron carbide B4C coating was examined. The duration of the rectangular plasma pulses was 0.5 ms with an interval of 5–10 min between pulses. The maximum power density in the central part of plasma stream was 1 GW/m2. The coating thickness varied from 20 to 40 μm on different surface areas. Modification of the surface layers and transformation of the coating at elevated temperature under plasma pulse irradiation during four successive series of impulses are described. It is shown that the boron carbide coating withstood the full cycle of tests under irradiation with 100 plasma pulses with peak power density of 1GW/m2. Constitutive surface deterioration was not detected and the boron carbide coating kept crystal structure B4C throughout the irradiation zone at the surface depth no less 2 μm. Keywords: boron carbide, coating, plasma, irradiation. DOI: 10.1134/S1063778816070061
INTRODUCTION Numerous experiments performed in various plasma chambers and tokamaks showed that a boron carbide coating satisfies the basic requirements for the properties of the materials used for the plasma-facing components of the chambers used in controlled thermonuclear fusion (in particular, ITER). The main specifications of crystalline boron carbide В4С deposited on MPG-8 and RGT graphites, particularly low erosion coefficients under irradiation, low retention capacity of hydrogen isotopes, and stability at high temperatures and irradiation, were shown by electron and ion beam irradiation experiments (at heat loads of 1.1–1.3 GW/m2) at the Sandia National Laboratories [1], at the PLADIS plasma gun facility at the University of New Mexico [2], in the DIII-D tokamak divertor plasma [3, 4], and in the T-10 and T-11M tokamaks [5, 6]. The coating maintained its integrity, chemical composition, and structure, and no surface deterioration was detected. It should be mentioned that no subsequent studies on the influence of plasma fluxes of high power density on crystalline boron carbide В4С coatings and no corresponding life tests leading to the complete degradation of the coating under plasma irradiation in extreme conditions were performed until now. Such data on behavior of the coating under intense plasma fluxes are necessary for choosing the
material of the renewable protective coating for ITER tungsten divertor tiles and protective materials for other chambers. EXPERIMENTAL Irradiation of the В4С coating by plasma flux was performed in the QSPA-T one-step coaxial high-current p
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