Studies in JET divertors of varied geometry. I: Non-seeded plasma operation

Horton, L. D.; Vlases, G.; Andrew, P.; Bhatnagar, V.P.; Chankin, A.; Clement, S.; Conway, G. D.; Davies, S.; Haas, J.C.M. de; Ehrenberg, J.; Fishpool, G.; Gauthier, E.; Guo, Heng; Harbour, P.J.; Ingesson, L. C.; Jäckel, H.; Lingertat, J.; Loarte, A.; Lowry, C.; Maggi, C. F.; Matthews, G. F.; McCracken, G.M.; Mohanti, R.; Monk, R.D.; Reichle, R.; Righi, E.; Saibene, G.; Sartori, R.; Simonini, R.; Stamp, M.; Taroni, A.; Thomsen, K.

doi:10.1088/0029-5515/39/1/301

Cited by 79 publications

(45 citation statements)

References 24 publications

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“…A further improvement in the divertor exhaust rate was achieved in Mark IIGB with the corner configuration, (C) in the figure, where the strike points were placed next to the entrance of the pumping ducts. The difference in subdivertor pressure is less evident in the steady state ELMy H mode discharges due to the presence of ELMs [20].…”

Section: Particle Throughputmentioning

confidence: 91%

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Effects of divertor geometry and chemical sputtering on impurity behaviour and plasma performance in JET

et al. 2000

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Abstract. The effects of increased geometrical closure on the behaviour of the recycling and intrinsic impurities are investigated in JET Mark I, Mark IIA and Mark IIGB pumped divertors. Increasing the divertor closure leads to a significant improvement in exhaust for both deuterium and recycling impurities. However, the impurity enrichment in the exhaust gases remains unchanged due to a simultaneous increase in deuterium and impurity compression in the divertor. A comparison is made for helium, neon and argon under different plasma conditions. In addition, the operation of the Mark II and Mark IIGB divertors has shown that Z eff is reduced with the improved divertor closure in the L mode discharges, although no obvious changes in the Z eff values have been observed in the ELMy H modes. The divertor target surface temperature has a strong influence on intrinsic carbon production. The carbon source in the Mark II and Mark IIGB divertors is significantly higher than that in the Mark I divertor, which is attributed to enhanced chemical sputtering at the increased divertor tile temperature of the Mark II and Mark IIGB divertors (related to the divertor cooling system), as opposed to the increased closure. The consequences of this elevated yield for plasmas under different operation conditions are discussed, and further evidence, obtained from a specific wall/divertor temperature reduction experiment, is presented. The effect of the divertor screening on the chemically produced impurities is investigated using the EDGE2D/NIMBUS/DIVIMP codes for the different recycling regimes and comparisons are made with experimental observations from the Mark I, Mark IIA and Mark IIAP divertors taking into account the change in chemical sputtering yield due to the different tile temperatures of these divertors.

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Section: Particle Throughputmentioning

confidence: 91%

“…Further results on the effect of divertor geometry from JET are given in Refs [19][20][21]. In outline the present article is as follows.…”

Section: Introductionmentioning

confidence: 99%

Effects of divertor geometry and chemical sputtering on impurity behaviour and plasma performance in JET

et al. 2000

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“…However, as has been found in many tokamaks, a puffing of too much intensity can lead to a progressive deterioration of the energy and particle confinement. In particular, a back transition from the high (H) confinement mode to the low (L) confinement mode has been observed in the divertor tokamaks, JET, JT-60, DIII-D and ASDEX-U (Horton et al 1999, Petrie et al 1993, Suttrop et al 1999 during a strong gas puff. Normally, this development is accompanied by a decrease of the averaged density time derivative, ∂n/∂t, and finally can lead to the fuelling density limit (Greenwald et al 1988).…”

Section: Introductionmentioning

confidence: 99%

Modelling of confinement degradation in the radiative improved mode caused by a strong gas puff

Kalupin

Tokar

Dumortier

et al. 2001

Plasma Phys. Control. Fusion

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Confinement deterioration and rollover from the radiative improved (RI) mode to the low (L) confinement mode in plasmas with a strong gas puff in the tokamak TEXTOR-94 are modelled by the one-dimensional transport code RITM (radiation from impurities in the transport model). The anomalous transport coefficients in the plasma core include contributions from the ion temperature gradient and dissipative trapped electron instabilities. This model allows us to reproduce the L-RI bifurcation with impurity seeding in good agreement with experimental observations. Whereas the transport at the plasma edge under the RI-mode conditions might be described by the electrostatic turbulence caused by electric currents in the scrape-off layer of the limiter, the present computations show that the level of the edge transport must be increased by at least a factor of three in order to reproduce the evolution of the plasma density profile and the effective ion charge during RI-to-L back transitions. An increase of this order is in agreement with reflectometer measurements and could tentatively be explained by the effect of neutrals on resistive drift modes.

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“…The experimental results on this subject are varied, to say the least. Results from JET [9], JFT-2M [10], and DIII-D [11] indicate that increased divertor closure (geometry as well as closing leaks through the divertor structure) leads to a reduction in the midplane pressure. Results from the closing of leaks on C-Mod and ASDEX Upgrade [12][13][14], as well as the most recent changes in the JET divertor [15,8],lead to an increase in divertor pressure with no change in midplane pressure .…”

Section: Introductionmentioning

confidence: 99%