This paper describes the content of an L-mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR, and Tore-Supra. The database consists of a total of 2938 entries, 1881 of which are in the L-phase while 922 are ohmically heated only (OH). Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning, and configuration. The paper presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER. The L-mode thermal confinement time scaling, determined from a subset of 1312 entries for which the T E ,~F , are provided, is
The paper describes the content of an H-mode confinement database that has been assembled for the ITER project. Data were collected from six machines of different sizes and shapes: ASDEX, DIII-D, JET, JFT-2M, PBX-M and PDX. A detailed description of the criteria used in the selection of the data and the definition of each of the variables is given. The paper also presents an analysis of the conditions of the database, the scalings (power law and offset linear) of the data with both dimensional and dimensionless variables, and predictions of the expected confinement time for ITER.
This paper describes an update of the H mode confinement database that has been assembled for the ITER project. Data were collected from six machines of different sizes and shapes: ASDEX, DIII-D, JET, JFT-2M, PBX-M and PDX. The updated database contains better estimates of fast ion energy content and thermal energy confinement times, discharges with RF heating, data using boronization, beryllium and pellets, more systematic parameter scans, and other features. The list of variables in the database has been expanded, and the selection criteria for the standard dataset have been modified. We also present simple scalings of the total and thermal energy confinement time to the new dataset.
Simultaneous achievement of high energy confinement, 'ZE, and high plasma beta, P. leads to an economically attractive compact tokamak fusion reactor. High confinement enhancement, H = 'CF/'ZE.ITER~~P = 4, and high normalized beta PN = P/(UaB) = 6%-m-T/MA. have been obtained in DIU-D experimental discharges.These improved confinement and/or improved stability limis are observed in several Dll-D high performance operational regimes: VH-mode, high 4 H-mode, second stable core, and high beta poloidal. We have identified several important features of the improved performance in these discharges: details of the plasma shape, toroidal rotation or ErB flow profile, q profile and current density profile, and pressure profile. From our improved physics understanding of these enhanced performance regimes, we have developed operational scenarios which maintain the essential features of the improved confinement and which increase the stability limits using localized current profile control. The stability limit is increased by modifying the interior safety factor profile to be nonmonotonic with high central q. while maintaining the edge current density consistent with the improved transport regimes and the high edge bootstrap current. We have calculated high beta equilibria with BN = 6.5, stable to ideal n=l kinks and stable to ideal ballooning modes.The safety factor at the 95% flux surface is 6. the central q value is 3.9 and the minimum in q is 2.6. The current density profile is maintained by the natural profile of the bootstrap current, and a modest amount of electron cyclotmn current drive. ' T E R ~R -S ~~)are observed in several operational regimes; VH-mode (Jackson 1991), high internal inductance (&) H-mode (Lao 1993a). and high poloidal @ (Politzer 1994). The performance in the high confinenent regimes observed in the JET, JT4OU, TFTR, and DIU-D tokamaks is no longer limited by transport or heating power, but instead are limited by stability limits at~high @T ( E T Team 1993. Mauel 1993, Zamstorff 1993. Taylor 1993. Strait 1993. Perfomance in present day tokamaks can be improved if the @-limit can be increased while maintaining the observed high confinement. Our ssategy for identifying 3 self-consistent high confinement high beta steady-state discharge scenario is to identify and maintain those features that are favorable for the high confinement and then modify the profiles to increase the stability limit, without adversely affecting the confinement. The features that we have identified that are favorable for high confinement are: (1) strong plasma shaping, high triangularity (6) and high elongation (K):(2) high plasma rotation. large shear in the ExB flow;(3) finite current density near the edge; (4) negative central shear; and (5) high q(0). We intend to show are compatible with steady-state high p.In the next section, we review a number of high performance regimes that have been identified in DlI-D experimental discharges, and discuss the features that we believe are important for achieving the high
Following boronization, tokamak discharges in DIII-D have been obtained with confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling and 1.8 times greater than the DIII-D/JET Hmode scaling relation. Very high confinement phases are characterized by relatively high central density with n e (0) ~ 1 xlO 20 m~3, and central ion temperatures up to 13.6 keV at moderate plasma currents (1.6 MA) and heating powers (12.5-15.3 MW). These discharges exhibit a low fraction of radiated power, F< 25%, Z e nr(0) close to unity, and lower impurity influxes than comparable DIII-D discharges before boronization.PACS numbers: 52.55.Fa, 52.25.Fi, 52.25.Vy In order to achieve ignition in proposed future fusion devices such as the Burning Plasma Experiment (BPX) and the International Thermonuclear Experimental Reactor (ITER), global energy confinement significantly better than the low-mode (L-mode) scaling relation is required in discharges with a low influx of impurities and low dilution of hydrogenic species [1]. Following boronization we have recently obtained discharges in the DIII-D tokamak with a very high confinement quiescent phase. These discharges have been repeated over many experimental days. We refer to this very high confinement phase as the VH mode. A number of tokamaks have obtained a high confinement mode (// mode) [2] with energy confinement times approximately a factor of 2 greater than for the L mode. In F/Z-mode discharges global energy confinement times are as much as a factor of 3.5 above ITER89-P [1] L-mode scaling and 1.8 times greater than the DIII-D/JET //-mode thermal confinement scaling relation [3]. This dramatic improvement in confinement quality is of great importance since the triple product noT,TE (related to the ratio of fusion power to heating power) in a tokamak fusion system increases as the square of the confinement enhancement factor over the L-mode scaling. Moreover, the VH phase of these discharges has shown less radiated power loss than is usually observed in comparable quiescent, i.e., ELM-free, //-mode discharges. [Edge-localized modes (ELMs) are transient phenomena which can occur in the outer plasma region and produce enhanced particle and energy transport, //-mode behavior is often described by the presence or absence (quiescent phase) of ELMs.] Temperature and density profiles show steep edge gradients extending further into the plasma than in the normal H mode, indicating a thicker edge transport barrier region.Boronization is a plasma-assisted chemical vapor deposition (CVD) process which deposits a thin, amorphous boron or boron-carbon film on all plasma facing components [4,5]. The boronization process was first implemented and later optimized in the TEXTOR tokamak at Forschungszentrum Julich GmbH [4]. Boronization in DIII-D (in collaboration with Julich) was accomplished using a glow discharge [6] in a helium-diborane gas mixture, 90% He and 10% B 2 D 6 , at a pressure of 5x10 ~3 mbar. A film of 100 nm average thickness was deposited. Depth profiles of a sample...
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