Since the successful first plasma generation in the middle of 2008, three experimental campaigns were successfully made for the KSTAR device, accompanied with a necessary upgrade in the power supply, heating, wall-conditioning and diagnostic systems. KSTAR was operated with the toroidal magnetic field up to 3.6 T and the circular and shaped plasmas with current up to 700 kA and pulse length of 7 s, have been achieved with limited capacity of PF magnet power supplies. The mission of the KSTAR experimental program is to achieve steady-state operations with high performance plasmas relevant to ITER and future reactors. The first phase (2008–2012) of operation of KSTAR is dedicated to the development of operational capabilities for a super-conducting device with relatively short pulse. Development of start-up scenario for a super-conducting tokamak and the understanding of magnetic field errors on start-up are one of the important issues to be resolved. Some specific operation techniques for a super-conducting device are also developed and tested. The second harmonic pre-ionization with 84 and 110 GHz gyrotrons is an example. Various parameters have been scanned to optimize the pre-ionization. Another example is the ICRF wall conditioning (ICWC), which was routinely applied during the shot to shot interval. The plasma operation window has been extended in terms of plasma beta and stability boundary. The achievement of high confinement mode was made in the last campaign with the first neutral beam injector and good wall conditioning. Plasma control has been applied in shape and position control and now a preliminary kinetic control scheme is being applied including plasma current and density. Advanced control schemes will be developed and tested in future operations including active profiles, heating and current drives and control coil-driven magnetic perturbation.

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A multi-megawatt long pulse ion source (LPIS) was developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) neutral beam (NB) injector. Arc discharge characteristics of the ion source were investigated on the NB test stand. The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerators with circular apertures. The inner volume of the ion source, including the accelerator column, is approximately 150 litres. Design requirements for the ion source were a 120 kV/65 A deuterium beam and a 300 s pulse length and initially an 80 kV/48 A hydrogen beam for a 20 s pulse length. Arc discharges of the plasma generator with hydrogen gases have been controlled by the emission-limited mode, operated by the applied heating voltage of the cathode filaments. Stable and efficient arc plasmas, with a maximum arc power of 110 kW, have been produced by a constant voltage (CV) mode operation of an arc power supply. The CV mode operation of the arc powers was more efficient than the constant power (CP) mode operation in the LPIS. A maximum ion density of 9.1 × 10 11 cm −3 was measured by using electrostatic probes. The plasma non-uniformity of the ion source was less than 8% and was under the design limit. An optimum arc efficiency, defined by the ratio of extractible ion beam current to arc input power, of 0.46 A kW −1 was estimated for the CV mode operation and 0.44 A kW −1 for the CP mode operation. This arc efficiency is enough to extract the expected hydrogen beam of 48 A.

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