ICRF studies on JET

Jacquinot, J.; Anderson, R.J.; Arbez, J; Bartlett, D.V.; Beaumont, B.; Behringer, K.; Bertolini, E.; Bhatnagar, V.P.; Bonicelli, T.; Bosia, G.; Brinkschulte, H.; Browne, M.L.; Brusati, M.; Bureš, Michal; Campbell, D.J.; Christiansen, J.; Christodoulopoulos, C; Chuilon, P.; Claesen, R.; Coad, J.P.; Cordey, J.G.; Corti, S.; Costley, A. E.; Cottrell, Geoff; Denne, B.; Dietz, K.J.; Ejima, S.; Erents, S.K.; Eriksson, B.; Evrard, M.; Fullard, K.; Gambier, D.J.; Gill, R.D.; Gottardi, N.; Green, B; Grosso, G.; Hawkes, N.; Hellsten, T.; Hemmerich, J.L.; Huguet, M.; Jarvis, O.N.; Jones, Edward C.; Kaye, A.; Kimura, Hiroyuki; Kock, J de; Kock, L. de; Krause, H.; Lallia, P.; Lazzaro, E.; Lomas, P.; Magyar, G.; Mansfield, M. W. D.; Marchese, Valentina; Mast, F.; McCracken, G.M.; Mondino, P.L.; Morgan, P. D.; Niestadt, R.M.; O’Rourke, J.; Piekaar, H.W.; Plancoulaine, J.; Rebut, P.H.; Rhoden, G; Sadler, G.; Sand, F.; Santaquistina, A; Schmid, Martin; Schueller, F.C.; Segrè, S. E.; Sibley, A.; Stamp, M.; Steed, Chad A.; Stott, P.E.; Summers, D.; Tanga, A.; Tagle, J.A.; Thomas, Paul R.; Thomsen, K.; Tubbing, B.J.D.; Valisa, M.; Beken, H. van der; Watkins, M.L.; Wade, T.; Walker, Chris

doi:10.1088/0741-3335/28/1a/002

Cited by 37 publications

(12 citation statements)

References 1 publication

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“…Corroborating evidence of FW coupling to the beam ions is seen in both the lengthening of the sawtooth period and the peaking of a radially localized group of beam ions, manifested as an off-axis peak in the fast-ion density profile measured by FIDA. Early experiments on JET showed that, in discharges with high-power ICRF heating, the sawtooth period can be extended up to several seconds [42]. Years later, similar observations were made on DIII-D with lower ICRF power [43,44].…”

Section: Sawteeth On Diii-dmentioning

confidence: 82%

Measurements of fast-ion transport by mode-particle resonances on DIII-D

et al. 2012

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Magnetohydrodynamic (MHD) instabilities in tokamak plasmas manifest in a variety of ways, characterized by different scale lengths and mode frequencies. MHD activity can cause significant degradation of plasma performance due to transport of particles, energy and current. Among the many different types of MHD, arguably fishbones, sawteeth and Alfvén eigenmodes (AEs) are observed to cause the largest fluxes of superthermal ions. DIII-D's expansive suite of diagnostics makes it possible to rigorously characterize these instabilities and study their interaction with fast ions. This review paper first presents an overview of the recent additions to DIII-D's collection of fast-ion diagnostics. The extended diagnostic capabilities are employed in a series of experiments to investigate fast-ion dynamics in the presence of fishbones, sawteeth and AEs. Results from these seemingly unrelated studies are highlighted, and they reveal that mode-particle resonances play the central role in the observed deterioration of fast-ion confinement.

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Section: Sawteeth On Diii-dmentioning

confidence: 82%

Measurements of fast-ion transport by mode-particle resonances on DIII-D

et al. 2012

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“…In combined OH-LHCD plasmas, Trg t exceeding the ohmic value could be obtained even at higher densities and higher currents (jI = 4 x 1013 cm- 3 and I, = 200 kA). The global energy confinement time, rgt was maximized when the applied rf power was comparable to the residual ohmic power, which was approximately half of the original ohmic input power.…”

Section: Discussionmentioning

confidence: 94%

“…Although energy confinement in neutral beam heated plasmas has been studied extensively and is well documented [1], the study of energy confinement in intensely rf (radio frequency) wave heated plasmas has only recently begun and relatively little information is available at present [2,3].…”

Section: Introductionmentioning

confidence: 99%

Energy confinement studies of lower hybrid current driven plasmas in the Alcator C tokamak

et al. 1987

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ABSTRACT. Energy confinement is studied in lower hybrid current driven (LHCD) plasmas in Alcator C in the density range ii = (1-8) x 1013 cm-3 . In LHCD plasmas, the stored energy in the electron tail Wail can be a significant fraction of the total stored energy W"*, especially at lower densities. At sufficiently low densities, the energy confinement time of the high energy electrons is expected to become shorter than their collisional energy slowing down time, and direct energy losses from the electron tail can become important in the overall power balance. The global energy confinement time, defined as rE** = W**t/Ptot, is found to be comparable to or exceed that in ohmically heated (OH) plasmas at low densities n, < 3 x 1013 cm-3 , where a steady state current can be maintained with * present address : University of Texas, Austin, Texas, U.S.A. 1 relatively low rf power. However, at higher densities where substantially more rf power is needed (relative to the ohmic power required to maintain a similar plasma), a deterioration of rtot relative to ohmic confinement, similar to that predicted by the neutral beam heated L-mode scaling, is observed.Theoretical modeling with the aid of a ray tracing-Fokker Planck-transport code suggests that the deteriorated confinement in this high density, high power regime may be attributed to an enhanced bulk electron thermal diffusivity. In a combined OH-LHCD plasma, a value of r' greater than the ohmic value is obtained as long as the applied rf power does not significantly exceed the ohmic power.2

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“…For plasma parameters Ip = 265 kA, BT = 6.2 T, ft, = 1.1 -1.2 x 1014 cm-3 , the sawteeth are stabilized at an input rf power of P,. 1 > 600kW.…”

Section: Suppression Of Sawteeth At High Powersmentioning

confidence: 99%

“…The possibility of suppressing the sawtooth instability, particularly in high density, reactor-grade plasmas has recently attracted interest because of substantial electron energy losses associated with giant sawteeth in ICRF-heated plasmas [1]. It is expected that by eliminating large sawteeth, the average critical electron temperature will increase and concurrently the central electron energy confinement will be significantly improved.…”

Section: Introductionmentioning

confidence: 99%

Stabilization of sawteeth by lower hybrid waves in the Alcator C tokamak

1988

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Sawteeth have been suppressed by lower hybrid current drive in high density Alcator C plasmas. At a density of 1.1 x 10 1 4 cm-3 and q(a) = 4.7 the sawteeth were eliminated by application of P,.f = 600 kW at 4.6 GHz, which represents an estimated 30% of the rf power required to fully sustain the discharge in the absence of ohmic power. Strong electron heating is observed with both current drive and anti-current drive phasings of the waveguide arrays but sawtooth stabilization occurs only in the former case. For the current drive phasing, the sawtooth period increases with rf power until the sawteeth are stabilized, while the period remains unchanged for rf injection with anti-current drive phasing. The internal inductance of the plasma increases during current drive relative to the anti-current drive case. The disappearance of sawteeth and the increase in internal inductance suggests that the rf current is driven near the q = 1 surface. At high power (Pf, > 850 kW), the sawteeth return 40 -60 ms into the rf pulse, indicating that an optimal power range, or rf deposition profile, exists for successful sawtooth suppression.

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ICRF studies on JET

Cited by 37 publications

References 1 publication

Measurements of fast-ion transport by mode-particle resonances on DIII-D

Measurements of fast-ion transport by mode-particle resonances on DIII-D

Energy confinement studies of lower hybrid current driven plasmas in the Alcator C tokamak

Stabilization of sawteeth by lower hybrid waves in the Alcator C tokamak

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