KSTAR Construction, Commissioning and its Implication to the ITER Proj…

"KSTAR, the first Nb3Sn technology-based fully superconducting tokamak device, has come a long way with all critical aspects resolved, and now successfully tested, commissioned and achieved “first plasma” operation exceeding initial target parameters. The commissioning process of KSTAR has been progressed from April to July 2008, through following four steps: vacuum, cryogenic cool-down, superconducting magnet test, and plasma start-up. The first two major steps, namely vacuum and cryogenic cool-down commissioning, have been successfully passed with vacuum pressure less than 3.0x10-8 mbar, and reached all superconducting magnet temperature under 4.5 Kelvin without “helium cold leak” at the first trial of all processes. Then, plasma start-up experiments were conducted using integrated “plasma control system(PCS)” for fast current and position control. The “first plasma” discharge was initiated under time synchronized operation of the power supplies, ECH pre-ionization system, gas-puffing system and initial set of diagnostics systems. After successive test discharge sequences, successively controlled plasma with flat-top current of 133 kA, duration up to 800 msec has been obtained. These results confirms that one of the important technical risks associated with superconducting PF systems have been resolved, and convincingly proved selection criteria of ECH frequency of pre-ionization as well as main electron heating systems. Subsequently, the machine performance test including “ac-loss” of Nb3Sn PF Systems has been conducted and then full superconducting magnet system “warm-up” process has been completed without anomaly. The complementary power supplies, diagnostics, heating systems as well as in-vessel components need to be installed in series during a couple of years, so that the full performance experiments for “advanced tokamak physics” with 300 sec long-pulse could be exploited within year 2012. Especially, specially designed in-vessel coil systems would allow physics study of high-beta plasma with resistive wall mode control, and edge localized mode control, so that the extension of operation envelop of strongly shaped tokamak plasma would be achieved. This talk will cover KSTAR construction and commissioning experience that is relevant to ITER Project construction phase. Also, the KSTAR experimental plan with ITER relevant physics as well as engineering issues will be presented.








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