KJ workshop 2016 W @Pohang, Korea B. Na, J. H. Jeong, S. W. Jung, S. J. Wang, J. G. Kwak, Y. S. Kim, and NBI Team National Fusion Research Institute, Daejeon, Korea T. S. Kim and S. H. Jeong Korea Atomic Energy Research Institute, Daejeon, Korea 1
NBI-1 has been major heating source for KSTAR operation 1 beam box with three ion sources 100 kev, D+ based arc discharge/ion sources placed in horizontal mid-plane On-axis CD profile No. 2 (2012) No. 1 (2010) No. 3 (2014) 3 1 2 Long pulse capable positive ion based ion source & multi-aperture plasma grid with CuCrZr SECOND Beam Line 2
KSTAR for high Beta & steady-state operation Main mission of KSTAR is to achieve Advanced Tokamak (AT) operation mode in long pulse capable superconducting tokamak device High β & Steady-state operation (fully non-inductive CD) Basically target to high betan, steady-state Increased power and off-axis current drive Approach to high betat & low q95 For broad q profile with larger I P operation Approach to high betap & q95 Stable operation with high B T operation (2016) 3
Off-axis CD for advanced tokamak mode One approach to AT mode is utilizing bootstrap current. Additional off-axis CD provides more flexible, localized control of current profile. Current profile is controlled by the angle between NBI and magnetic field pitch angle. M. Murakami et al., NF 49, 065031 (2009). 4
New tangential NBI having off-axis CD capability tangential radius Advantages maximizing driving current maximizing/optimizing off-axis CD capability compromise with installation constraints minimizing additional R&D requirements Specification of NBI2 vertical slant angle Beam energy <100 kev Beam power <6 MW Duration <300 sec Tangential radius 1.6m Vertical slant angle 0, +/- 5.5 5
Vertical slant angle determines off-axis capability vertical slant angle scan for up-looking beam At lower angle, optimum R t moves to higher radius At higher angle, off-axis characteristics are enhanced, however efficiency decreases Angle 7.5 degrees seems to be better for CD, however absorption decreases At lower angle (5.5 deg), absorption increases Engineering limit ~ 5.5 deg. I drv rho peak P abs /P b rho w 6
Accident on ion dump in 2016 campaign Surface metal of full energy ion dump melted. Even though TC array is installed, the failure was not alarmed. Sudden change of surface metal may not be detected.
Heat load calculation using BTR code <NBI-2 specifications> Specifications Remarks Beam energy 100 kev Injected neutral beam power >6 MW = 2.0 MW 3 ea Number of Ion sources 3 EA Beam target position, (R t ) 1.6 m The goal of the BTR calculation - Neutral beam transport, loss and ionization calculation - Heat load calculation of beam line components by collision of neutron or ion particles BTR code calculation results without beamline components Vertical slant angle 5.5 Beam size Beam input port 450 mm 130 mm H port < Size of ion source for the NBI-2 > 130mm 450 mm ( No. of beamlets: 28 10 ) Beam energy 100 kev Beam current 60 A No. of Beamlets 28 10 No. of Focal beamlets 8 3 Focal position(m) 10 Beam power@12m(in Tokamak)(MW) 5.5 Transmission rate(%) 90.9 8
BTR calculation with beam line components-ii single beam three beams <Full energy> Full energy <Full energy> <Half energy> <1/3 energy> Total loaded beam power(mw) Peak power density(mw/m 2 ) Full energy Half energy 1/3 energy 2.134 0.134 0.081 6.716 0.674 1.619 Total loaded beam power(mw) 6.402 Peak power density(mw/m 2 ) 6.716 The cooling capacity of hypervapotron is satisfied ( <10MW/m 2 ). The margin is not enough Heat load on a calorimeter: 9 6.49 MW/m2
Improvement of ion dump-i IR camera will be installed to monitor front surface temperature in real-time Camera with alarm system partially replaces TC arrays at the back of target Two cameras will see both full and half energy dump for feasibility study (harsh environment unstable temperature, electric noise, neutron, magnetic field)
Improvement of ion dump-ii 0kV 0kV H + Ion dump 0kV H + H + Neutralizer H Plasma Ion beam trajectory not inducing depression electric potential Acceleration grid Bending magnet 50kV 0kV Energy recovery ion dump is being studied Reducing thermal load Increasing power efficiency 50kV Ion beam trajectory inducing depression electric potential
Improvement of full energy beam fraction E=0 IS-B 90kV n n H H + 2 + 1 = C 21 I α, E / 2 I F α, E A * l l, E l C 21 = * l Fl, E / 2 Al λ third 0 = λ 0 half v c cosθ full Preparing a full energy fraction measurement system. Doppler shift of D-alpha * S. J. Yoo et al., RSI 71, 1421 (2000). 24
Summary Main mission of KSTAR is steady state high beta AT mode operation. Off-axis CD provides AT operation and more controllability of current profile. The effect of slant angle on heating and CD is calculated, but 5.5 degree is determined by engineering limit. Heat loads on beam components satisfy the heat capability of hypervapotron. Ion dump temperature measurement system is under consideration. Ion energy recovery system and full energy beam fraction are being studied. 13
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