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ELM control by RMP is foreseen in ITER to suppress or reduce size of ELM energy loss

Effects of ELM control with RMP on Edge Power/Particle Fluxes between ELMs and at ELMs (I). A. Kavin. I p = 15 MA. I p = 10 MA. ELM control by RMP is foreseen in ITER to suppress or reduce size of ELM energy loss

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ELM control by RMP is foreseen in ITER to suppress or reduce size of ELM energy loss

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  1. Effects of ELM control with RMP on Edge Power/Particle Fluxes between ELMs and at ELMs (I) A. Kavin Ip = 15 MA Ip = 10 MA • ELM control by RMP is foreseen in ITER to suppress or reduce size of ELM energy loss • Application of RMP affects edge magnetic field structure and power/particle fluxes between ELMs and at ELMs • ELM control in ITER required for large range of plasma conditions not only flat top of 15 MA scenario dependences on plasma parameters of effects on power/particle fluxes required to determine compatibility with other scenario requirements : acceptable stationary power fluxes, erosion, etc. • Understanding of effects influences application of scheme in ITER (perturbation rotation…) ITER ELM control requirements

  2. Effects of ELM control with RMP on Edge Power/Particle Fluxes between ELMs and at ELMs (II) • Application of RMP coils affects both magnitude and spatial distribution of power/particle fluxes at the plasma edge between ELMs and at ELMs • Spreading of steady power and particle fluxes & lower of separatrix fluxes  but • Possible loss of high recycling regime and high divertor radiation  (qdiv/qmp ~ ¼) • Large power fluxes away from separatrix • High stationary fluxes in “unexpected” areas  • possible large erosion on toroidally asymmetric deposition regions (lower redeposition) • “Sharing” of ELM power flux on various flux bundles • Reduced requirements for DWELM in controlled ELMs by increased of AdivELM  • Larger ELM fluxes on divertor wall and baffles  T. Evans and O. Schmidt 5 Mwm-2 10 Mwm-2

  3. Effects of ELM control with RMP on Edge Power/Particle Fluxes between ELMs and at ELMs (III) Experimental plan Plasma conditions for with high Padd for good H-mode and large pedestal plasma with Ip as high as possible (compatible with q95 ~ 5-6) • Establish q95 = 3 low <ne> H-mode plasma and apply best aligned RMP coil current distribution to achieve DIII-D criterion. Scan RMP coil magnitude around this value  Total : 4-6 shots • Misalign RMP coil spectrum by Dq95 = 0.5 and increase RMP coil current to match Chirikov criterion. Scan RMP coil magnitude around this value  Total 4-6 shots • Perform density scan in 3-4 discharges for q95 = 3 H-mode plasmawith optimum RMP coil distribution and repeat at higher or lower power level  Total 8-10 shots • Establish q95 = 5-6 low <ne> H-mode plasma with same current as in 1. and repeat study in 1  Total : 4-6 shots (If not possible to keep same Ip then use Ip to vary q95)

  4. Physics processes leading to ELM triggering by Vertical Jogs and extrapolation to ITER (I) • ITER will be equipped with in-vessel coils for vertical stability control which provide fast feedback on vertical plasma position • If compatible with requirements for VS, the plasma in ITER could be jogged to reduce ELM size to acceptable levels (estimated frequency 20-40 Hz) • Vertical plasma jogging demonstrated successfully in various tokamaks (TCV, AUG, JET, NSTX, … but physics of ELM triggering unclear (shape deformation, edge current, ?)  requirements for ITER difficult to specify (magnitude and speed of jog) • Experiment in NSTX proposed to address this issue and to get some empirical guidance for assessing viability of method in ITER VS coils

  5. Effects of ELM control with RMP on Edge Power/Particle Fluxes between ELMs and at ELMs (II) Experimental plan Plasma conditions for successful ELM control “demonstrated” at 45 Hz (~1.0 MA) • Perform density scan (3-4 shots) at fixed power with fixed jog amplitude (assessment of jedge effect) • Perform a jog amplitude scan at two densities (3-4 discharges) • If 2 shows effect repeat 1,2 at high input powers to see Tped dependence (3-4) shots • Establish Ip = 0.6 MA plasma to change ratio of jedge/Ip and allow larger jog. Repeat experiments in 1 and 2. (4-8 shots)

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