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IOS-2.2 Ramp-down from q 95 =3 Topic Group: Integrated Operation Scenarios

IOS-2.2 Ramp-down from q 95 =3 Topic Group: Integrated Operation Scenarios Spokes person: G. Sips (JET) Key persons: G. Sips (JET), S. Wolfe (C-Mod), G. Jackson (DIII-D), W. Suttrop (AUG) Devices: JET, C-Mod, DIII-D, AUG Outline and aims:

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IOS-2.2 Ramp-down from q 95 =3 Topic Group: Integrated Operation Scenarios

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  1. IOS-2.2Ramp-down from q95=3 • Topic Group: Integrated Operation Scenarios • Spokes person: G. Sips (JET) • Key persons: G. Sips (JET), S. Wolfe (C-Mod), G. Jackson (DIII-D), W. Suttrop (AUG) • Devices: JET, C-Mod, DIII-D, AUG • Outline and aims: • Demonstrate ramp-down from an ITER base-line plasma (at q95=3, with similar shape). • Starting ramp down from both H- and L-mode (to simulate fault condition). Demonstration how to stay within (k, li,q95) stability envelope of ITER. Develop shape control for vertical stability, fixed divertor strike points with increasing top gap (MHD-TG). • Document merits/demerits of staying (as long as) in H mode or L mode during the ramp-down. • Also document heating requirements during ramp down.

  2. IOS-2.2: Results so far…. • JET: Investigated “controlled” and “emergency” ramp-down (22 pulses in 2008) • Effect of Ip ramp rate from 0.07MA/s (slow) to 0.5MA/s (emergency). • Ohmic ramp down (H-mode in f/t or not) gives plasma profile peaking up to li~1.8 • Heating: See viewgraphs…. • DIII-D: Detailed experiments, matching proposed scenario for ITER. • C-Mod: Dedicated experiments in 2008, varying the Ip ramp down rate (5 pulses) • AUG: Many parasitic data are available, although NOT many discharges at q95~3 • To be done: More detailed modelling of these discharges

  3. JET: H-mode ramp-down li(3) 15MW Padd Vloop Ip 5x1019m-3 <ne> Da

  4. JET: H-mode ramp-down li(3) 15MW Padd Vloop Ip 5x1019m-3 <ne> Da

  5. DIII-D results, 2009 See T. Luce talk tomorrow, April 1st

  6. C-Mod: Current ramp down experiments Ramp down in divertor shape with kappa reduction (1.8  1.4) 1.32MA 0.98MA 0.61MA 0.26MA 2MA/s 1.14 s 1.34 s 1.54 s 1.72 s time (s)

  7. 1.4 Ip [MA] 1.0 k~1.8 k 0.6 k k1.4 k1.4 0.2 2.0 1.6 li(3) 1.2 0.8 IOH [kA] 24 10% 20 16 12 1.0 1.2 1.4 1.6 1.8 2.0 Time (s)‏ C-Mod: Current ramp down experiments • Elongation reduced from 1.8 to 1.4 to keep plasma vertically stable. Current ramp down keeping ~1.8 has VDE. • For ohmic or L-mode discharges, fast decay (dIp/dt ~ 4MA/s) or standard decay (dIp/dt ~ 2MA/s) li(3) > 1.5. • 1MA/s ramp down keeps li(3) < 1.2 However, this ramp down requires ~10% increase in central OH current.

  8. ASDEX Upgrade: Ramp down phase • Shopping list for ASDEX-Upgrade: • Design a scenario for ITER: Avoidance of high li for termination phase. • Control of plasma shape and vertical stability with PF coils saturated. (central solenoid). • Conditioning effects of the current decay. • Simulate the (sudden) termination of the burn and H to L transition. ASDEX Upgrade (2008/2009, no dedicated pulses): Collect the data already available.

  9. IOS-2.2: Ramp down experiments in 2009 • Aims: Dedicated experiments !!! • Experiments • JET: Further dedicated experiments in deuterium, hydrogen and helium. • DIII-D: Matching ITER proposals for ramp-down • C-Mod: Some more (parasitic) experiments planned at high Ip. • AUG: Experiments are proposed…. • Modelling:

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