TFTR confinement results

Bell, M.G.; Arunsalam, V.; Bitter, M.; Blanchard, W.; Boody, F.P.; Bretz, N.; Budny, R.; Bush, C. E.; Callen, J. D.; Cecchi, J. L.; Cohen, Samuel A.; Colchin, R.J.; Combs, S. K.; Coonrod, J.; Davis, S.; Dimock, D.; Dylla, H. F.; Efthimion, P. C.; England, A.C.; Eubank, H. P.; Fonck, R.J.; Fredrickson, E. D.; Grisham, L.; Goldston, Robert James; Grek, B.; Hawryluk, R. J.; Heidbrink, W. W.; Hendel, H. W.; Hill, K. W.; Hinnov, E.; Hiroe, S.; Hülse, R.; Hsuan, H.; Johnson, D.; Johnson, L. C.; Kaita, R.; Kamperschroer, R.; Kaye, S. M.; Kilpatrick, S. J.; Kugel, H.; LaMarche, P. H.; Little, R.; Manos, D. M.; Mansfield, D. K.; McCarthy, Michael; McCann, R.; McCune, D.; McGuire, K.; Meade, D. M.; Medley, S. S.; Milora, S.L.; Mikkelsen, D. R.; Morris, W.; Mueller, D.; Nieschmidt, E. B.; Owens, D. K.; Paré, V.K.; Park, H.; Prichard, B.; Ramsey, A. T.; Redi, M. H.; Roquemore, A. L.; Sauthoff, N.; Schivell, J.; Schmidt, G. L.; Scott, S.D.; Šesnić, S.; Shimada, M.; Simpkins, J. E.; Sinnis, J.; Stauffer, F. J.; Stratton, B.; Tait, G. D.; Taylor, G.; Towner, H. H.; Ulrickson, M.; Goeler, S. von; Wieland, R.; Wilgen, J. B.; Williams, M. D.; Wong, K. L.; Yoshikawa, S.; Young, K. M.; Zarnstorff, M. C.; Zweben, S. J.

doi:10.1088/0741-3335/28/9a/011

Cited by 16 publications

(3 citation statements)

References 7 publications

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“…• Tj from carbon [10] n_(o) from interferometry [11] F. = ",_de)_ from interferometry [11] <n_> Z¢]] from visible bremsstrahlung [12] Zm_t of high Z metals from X-ray PHA [13] -r E from magnetics [14] Limiter condition -CII light emission [15] -D_ light emission [15] ....... Ratio of SEMP_ plotted against SEMp_.…”

Section: Discussionmentioning

confidence: 99%

Neutron emission from TFTR supershots

Strachan¹,

Bell²,

Bitter³

et al. 1992

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Empirical scaling relations are deduced describing the neutron emission from TFTR• supershots using a data base that includes all of the supershot plasmas (525) from the 1990 campaign. A physics-based scaling for the neutron emission is derived from the dependence of the central plasma parameters on machine settings and the energy confinement time. Thi:.scaling has been used to project the fusion rate for equivalent DT plasmas in TFTR, aad to explore machine operation space which optimizes the fusion rate. Increases in neutron emission are possible by either increasing the toroidal magnetic field or further improving the limiter conditioning.. 1MIT Plasma Fusion Center, Cambridge, MA 02139 I. INTRODUCTION '4,One goal of the TFTR experimental research program is to achieve scientific breakeven wherein the fusion power produced equals the power required to heat the plasma. Presently, the highest performance TFTR deuterium plasmas are the supershot plasmas [1] which have produced equivalent QDT values _ 1/3 [2] (where "equivalent" is a projection that is defined in Sec. 8). Clearly, there is a need to operate the supershot plasma in a manner that will further optimize its fusion performance.This paper evaluates the statistical dependence of the d(d,n)ZHe fusion neutron emission from TFTR deuterium supershots upon the TFTR machine settings (e.g., plasma current, toroidal magnetic field, neutral beam power, etc.). Empirical and physics-based scaling relations are derived and compared to the neutron emission as well as to that predicted by Q one-dimensional transport codes. The supershot neutron emission is described in terms of a zero-dimensional model which identifies the variables related to the underlying physics of the fusion reactions. This model was used to evaluate equivalent fusion rates for DT plasmas and to suggest machine conditions for optimal performance.The analysis indicates that the primary limitation of the TFTR supershots is the apparent f3-1imit of the supershots when the plasma energy content is about 0.S of the Troyon value [3].Above this limit, TFTR supershots experience some disruptions. Even sporadic disruptions make experiments in the supershot regime difficult due to the sensitivity of supershots to the wall conditions. Another conclusion from the statistical analysis is that the deuterium neutron emission was independent of the neutral beam voltage (from 85 kV to 105 kV).However, considerable improyement was achieved by conditioning the walls with lithium pellet injection. A further improvement is projected by increasing the toroidal magnetic 2 field.The organization of this paper is first to describe the database. Scaling relations are then derived for the neutron emission based upon entirely empirical regression analysis.The measured neutron rates are then compared with those predicted by one-dimensional transport calculations.A zero-dimensional model for the neutron emission is then derived.TFTR supershot scaling for the relevant plasma parameters that describe the classical physics o...

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Section: Discussionmentioning

confidence: 99%

Neutron emission from TFTR supershots

Strachan¹,

Bell²,

Bitter³

et al. 1992

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“…Presumably the strong pumping effect of carbon accounts for the difference seen with gas fueling [14]. A similar effect probably accounts for the higher densities reported on TFTR with helium gas when compared to hydrogen or deuterium [15,16]. Limiters, walls, and divertors can all compete effectively with the plasma for hydrogen fuel at the plasma edge.…”

Section: Fueling Related Limitsmentioning

confidence: 97%

A new look at density limits in tokamaks

et al. 1988

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While early work on the density limit in tokamaks from the ORMAK [1] and DITE (2,3] groups has held up well over the years, results from recent experiments and the requirements for extrapolation to future experiments have prompted a new look at this subject. There are many physical processes which limit attainable densities in tokamak plasmas. These processes include 1) radiation from low Z impurities, convection, charge exchange and other losses at the plasma edge, 2) radiation from low or high Z impurities in the plasma core, 3) deterioration of particle confinement in the plasma core, and 4) inadequate fueling, often exacerbated by strong pumping by walls, limiters, or divertors.Depending upon the circumstances, any of these processes may dominate and determine a density limit. In general, these mechanisms do not show the same dependence on plasma parameters. The multiplicity of processes which lead to density limits with a variety of scaling, has led to some confusion when comparing density limits from different machines. In this paper we attempt to sort out these various limits and extend the scaling * Present address: Shin-Etsu Chemical Co., Ltd., 2-13-1, Isobe Annaka, Gunma, Japan 1 law for one of them to include the important effects of plasma shaping, namely that iK, = x 7 where n, is the line average electron density (1020 / M 3 ), x is the plasma elongation and 7 ( MA / M 2 ) is the average plasma current density, defined as the total current divided by the plasma cross sectional area. In a sense this is the most important density limit since, together with the q limit, it yields the maximum operating density for a tokamak plasma. We show that this limit may be caused by a dramatic deterioration in core particle confinement occurring as the density limit boundary is approached. This mechanism can help explain the disruptions and marfes that are associated with the density limit.

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“…The l i model takes as boundary conditions the values obtained from the equation l i = 2•(BEI LI 2 − β p,MHD ) which is valid when the plasma pressure is isotropic before and after the NBI. In the H-mode current ramp-down shots, l i was interpolated with the variation of the edge q between the initial and final conditions [71]. This heuristic model was checked against calculations of l i in the TRANSP code based on solving the resistive diffusion equation for the toroidal current density based on neoclassical resistivity and the measured profiles.…”

Section: Tftrmentioning

confidence: 99%