EPS Souvenir / MGB / 090727
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A Souvenir of the
36th European Conference on Plasma Physics,
Sofia, Bulgaria, 29 June - 3 July 2009
Michael Bell
EPS Souvenir / MGB / 090727
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Conference was a bit smaller than usual
• 530 participants
• 85 invited talks– 15 plenary, 70 in 4 parallel sessions
• 72 contributed talks in 4 parallel sessions
• 699 contributed posters in 4 afternoon sessions1.6 presentations per participant!
Held in the National Palace of Culture in Sofia
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1 invited talk and 7 contributed posters from NSTX– "Plasma Response to Lithium-Coated Plasma-Facing Components in
NSTX", M. Bell et al. (invited) – "High speed IR camera diagnostic in NSTX", J-W. Ahn et al. – "Multi-energy SXR characterization of stabilized resistive wall modes in
NSTX", L. Delgado-Aparicio et al.– "Modeling Fast Ion Transport in TAE Avalanches in NSTX", E.
Fredrickson et al.– "Modification of edge plasma profiles in ELM-suppressed discharges
with lithium coatings in NSTX", R. Maingi et al.– "Coaxial Helicity Injection Non-inductive Startup on NSTX", B. Nelson
et al.– "Fast ion transport by toroidicity induced Alfvén eigenmodes on NSTX",
M. Podestà et al.
– "High flux expansion divertor studies in NSTX", by V. Soukhanovskii et al.
• All had a pretty good reception - good traffic at the posters
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JET• Four invited:
– Saibene: “Qualification of the ITER baseline operating scenarios in JET”
– Beurskens: “Pedestal identity studies in JET, DIII-D and AUG”
– Hobirk: “Improved Confinement in JET Hybrid Discharges”
– De Vries: “Identity experiments on Internal Transport Barriers in JT-60U & JET”
plus many contributed talks and posters
• JET confirms ITER design with proviso that H-mode pedestal behaves as expected (Saibene): pedestal height = pmax wped
pmax set by MHD but how does wped behave?
• JET/DIII-D consistent, so far, with wped *0 and excludes wped *1/2 favorable for ITER (Beurskens)
– but DIII-D at top and JET at bottom of range: adequate representation?
• JET gets ELM size scaling *0 whereas DIII-D gets *>0
• Rotation shear does not affect onset of ITG-related turbulence but does reduce rate of rise of thermal flux with gradient above threshold
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JET (2)• Toroidal field ripple (varied 0.08 - 1.0 %) affects thermal particle
transport below level where it is expected to affect fast-ions– ITER may need to add more ferritic shims to get ripple <0.2%
• Success in pacing ELMs with pellets, vertical kicks and n = 1, 2 perturbations– reduces ELM size by 30 - 40% but – also degrades thermal confinement by ~10% – concern for ITER
• Have not yet suppressed ELMs with magnetic perturbations
• Validate specific operational scenarios for ITER– inductive breakdown with Etor 0.2 V/m
– low-internal-inductance x-point discharge by early heating– maintained stable H-mode through current rampdown
• Campaign now to develop ELM control further and study occurrence and characteristics of H-mode in helium plasmas
• Then install and operate ITER-like wall: beryllium and tungsten
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Hobirk: “Hybrid Modes” in JET• Raised many questions and, for me, hackles
• JET definition: q0 > 1 or slightly below 1 and a broad region of low magnetic shear with no sawteeth and “mild” NTMs
• HH ≈ 1 in JET whereas HH up to 1.5 in DIII-D
• Conjectures HH scales with * not good for ITER
• JET uses LH and/or current ramps to set up “hybrid” q-profile
• Current ramp-up modified q0 but HH and N limit unchanged
• However, current ramp-down increased HH to 1.35 and N limit to 3 %.m.T/MA– Was speaker aware of TFTR results on this? - No!– When plotted against current before rampdown was there a
benefit? - Didn’t know
• Benefit died out after ~2s ~ current diffusion time
• Stability of “AT” regimes in JET also discussed by Buratti O2.007– Highest N ≈ 4 %.m./MA for qmin ≈ 1; no RWMs in JET
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Huysmans “3D non-linear MHD simulations of ELMs
• JOREK code encompasses core and open field lines out to conducting boundary
• Applied to JET-like equilibrium– Large Jedge due to bootstrap current in edge pressure gradient
– Sees growth of pure ballooning mode with dominant n = 9• For equilibrium from plasma with smaller ELMs, gets n = 18
– Plasma expelled onto open field lines – cools and detaches• Sees fine structure of heat flux to outer divertor target
– ELM is not one event but involves discrete bursts over ~200µs
• Applied to pellet triggering of ELMs– Model as big local ne perturbation
– Pellet triggers low-n, typically n = 2, ballooning-like instability through effect on J(r), p(r), irrespective of pre-existing profiles
– Ergodizes edge
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ASDEX-Upgrade (AUG) with Tungsten Wall • E. Wolfrum “Investigation of H-mode Pedestal Physics in AUG”
– Program R(t) synch’ed to ELM cycle to get high-resolution profiles
– Use T(Rsep) defined by 2-point power balance model to locate Rsep
– Showed pmax evolving to common limit but well before ELM
So, maybe the pedestal gradient is actually set by transport and
Something else is evolving to trigger ELM: J(r)
• Pegourié “Fuelling and plasma control by pellet injection with application to ITER”
– ASDEX experience: with HFS pellets, need only get to ~1/2 pedestal height to fuel core
– For ITER fueling 5mm pellets on HFS at 10 – 15 Hz probably OK
– For ELM triggering, 2.2mm pellets on LFS at 10 – 25 Hz needed
– Just within capability of ITER cryo-pumps and tritium plant
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ASDEX-Upgrade (AUG) with Tungsten Wall • G. Pautasso “Disruption studies” - massive He,Ne,Ar injection
– achieved about 1/4 of density needed in ITER to suppress runaways
• V. Rohde “Wall Retention of Deuterium and Gaseous Impurities”
– Operated without boronization for many months after W wall installed
–Bake only to 150°C
– Also eliminated HeGDC
–He became buried in W and released later
– W-wall recycles deuterium 1 - RD ~ 1.5%
– Up to 1/3 of input D held briefly on wall – released over ~10 min
– Now puff N2 to maintain edge radiation
–Used to be provided by intrinsic C but C lower with all W-wall
–Better overall performance than with carbon wall
– Related results also in posters (Kallenbach, Herrmann and others)
• AUG will return to operation with 2 generators this month
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MAST
• E. Nardon “ELM control by resonant magnetic perturbations on MAST”– Upper, lower outboard rows of 6 coils each; 6kA-turns
– In L-mode get pump-out ne/ne ~ -50% and splitting of outer strike point
• Perturbation threshold consistent with ergodization of edge
– In DN H-modes, Type III ELMs become dithering with RMP
– With Type I ELMs, little effect even with (vacuum) ergodization N > 0.94
– In LSN H-modes, perturbation returns discharge to L-mode
• M. Turnyanskiy “Off-axis NBCD experiments on MAST” (contributed)– Displace plasma down - plasma volume does decrease ~10%
• Need to move back to midplane to make measurements
• TRANSP calculates hollow deposition profile and JNBCD
– TRANSP over-predicts Wtot, SDD by 25 - 30 % at 4 MW (better at lower P)
– Correlate with fishbone activity
– Model with HAGIS code add anomalous Dfi ~ 0.5 m2s-1 in TRANSP
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Tuesday Evening Session on New Facilities
• ITER status (A. Loarte, IO)– Mainly discussed Scenario 1 for construction and operation
• First plasma with limited capability and diagnostics in late 2018
• Followed by 2+ years of installation, commissioning
• Start serious research in H, He plasmas with H&CD in 2021
• Accelerate research and licensing to reach full DT operation in 2027
• JT-60SA (S. Ishida, JAEA) – JA-EU joint project at Naka– “Re-baselined” in 2008 to reduce cost, regain schedule - dumped
– TF built in EU, PF in JA, all ferritic steel VV
– Reduce B to 2.2T but keep 5.5MA by lower A = 2.5, higher = 1.9
– NNBI 10MW, PNBI 24MW, ECH 7MW, all for 100s pulse
– Full remote handling because of high DD neutron yield 1.5E21 /year
– First plasma in 2016, planned to operate for 15 years
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Tuesday Evening Session on New Facilities (cont.)
• FAST (F. Zonca, ENEA) – “ITER satellite” at Frascati site– Aimed to study fast-ion physics created by ICH instead of fusion– Want to be similar in dimensionless parameters to ITER but have to
compromise• * has to go!
– Based on cryogenically cooled (20K start) copper TF
– R = 1.82m, = 1.7, BT = 8 (8.5) T, Ip = 6.8 (8.0) MA for 170s (shorter)
– Mainly rely on ICH but planning for NNBI and ECH too!– Full tungsten wall
• Admits challenge of this with ICH– Question: why is this being built and who will pay for it with ITER
demanding more resources?
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Other Presentations and Points of Interest (to me)
• Angioni (I4.060): Particle transport in tokamaks– Mused on and extolled virtues of density profile peaking for ITER
• Paley (I3.045): Plasma control in TCV with ECH– ECH with control of launch angle to broaden J(r) for high- (≈ 2.8)– Implemented real-time analysis of data from 64 channel SXR fan– Allowed control of sawteeth by depositing ECH in-/out- side q = 1– Control code is adaptive to plasma response
• Some hysteresis in response due to cumulative heating
• Imbeaux (O2.018): Long-term plasma control in Tore-Supra with LH– Control of LH power by MHD signatures only: OK but not great– Plan to use polarimetry
• Van de Sanden (I2.022): Solar cell technology and developments
• Ebert (I4.059): Sprite discharges and terrestrial gamma-ray bursts– 50/day, energy > 35MeV: big noisy spectacular stuff!