Reduction of the net wall particle inventory has been achieved in the DIII-D tokamak by the use of a divertor cryopump for the particle exhaust. A sequence of 12 discharges was conducted without helium glow discharge cleaning (HeGDC) and without active cryopump exhaust, resulting in a net wall loading of 1250 torr.L (8.8*1022 atoms) by the end of the sequence. The cryopump was activated for the subsequent set of 10 discharges. At the end of this set of discharges, the net wall loading was reduced to its initial value or less, i.e. the wall loading state for the reference discharges with HeGDC. Plasma performance did not suffer without the HeGDC in that the stored energy during the ELMy phase was restored to the reference discharge level during the discharges with the active cryopump. Hence, with continuous particle exhaust (provided, for example, by a pumped divertor), next generation, long pulse devices, such as ITER, will not require interdischarge HeGDC for particle control, which would require turning off superconducting coils between discharges

Cryopump

Particle (ecology)

DIII-D

Neutral particle

10.1088/0029-5515/36/2/i11

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Citations (46)

Validation of on- and off-axis neutral beam current drive against experiment in DIII-D

Physics of Plasmas (2009)

J.M. Park M. Murakami C. C. Petty W. W. Heidbrink T.H. Osborne

Neutral beam current drive (NBCD) experiments in DIII-D using vertically shifted plasmas to move the current drive away from the axis have clearly demonstrated robust off-axis NBCD. Time-dependent measurements of magnetic field pitch angles by the motional Stark effect diagnostic are used to obtain the evolution of the poloidal magnetic flux, which indicates a broad off-axis NBCD profile with a peak at about half the plasma minor radius. In most cases, the measured off-axis NBCD profile is consistent with calculations using an orbit-following Monte Carlo code for the beam ion slowing down including finite-orbit effects provided there is no large-scale magnetohydrodynamic activity such as Alfvén eigenmodes modes or sawteeth. An alternative analysis method shows good agreement between the measured pitch angles and those from simulations using transport-equilibrium codes. Two-dimensional image of Doppler-shifted fast ion Dα light emitted by neutralized energetic ions shows clear evidence for a hollow profile of beam ion density, consistent with classical beam ion slowing down. The magnitude of off-axis NBCD is sensitive to the alignment of the beam injection relative to the helical pitch of the magnetic field lines. If the signs of toroidal magnetic field and plasma current yield the proper helicity, both measurement and calculation indicate that the efficiency is as good as on-axis NBCD because the increased fraction of trapped electrons reduces the electron shielding of the injected ion current, in contrast with electron current drive schemes where the trapping of electrons degrades the efficiency. The measured off-axis NBCD increases approximately linearly with the injection power, although a modest amount of fast ion diffusion is needed to explain an observed difference in the NBCD profile between the measurement and the calculation at high injection power.

Neutral Beam Injection

Pitch angle

DIII-D

Large Helical Device

10.1063/1.3213614

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Citations (27)

Divertor Plasma Conditions and Pumping Efficiency in DIII-D

APS Division of Plasma Physics Meeting Abstracts (2001)

J.G. Watkins M. A. Mahdavi T. C. Luce T.W. Petrie M. R. Wade

DIII-D

Source

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Citations (1)

Particle transport in DIII-D discharges with internal regions of enhanced confinement and counter injected neutral beams

Physics of Plasmas (2001)

D. R. Baker C. M. Greenfield J. C. DeBoo M. R. Wade B. W. Stallard

An analysis of experimentally measured particle transport in tokamak plasmas with negative central magnetic shear is presented. The analysis is presented in terms of a simple model for turbulent transport which allows the separation of diagonal and off diagonal terms and allows the direct comparison of particle and energy transport. Comparing the measured fluxes to the fluxes predicted by a simple quasi analytical model which specifies a relation between the diagonal and off diagonal terms allows an understanding of the reason for the difference between energy and particle fluxes. In the center of discharges with a region of enhanced confinement (or internal transport barrier), the ion thermal diffusivity becomes small and comparable to neoclassical values and the particle diffusivity also becomes small and approaches the neoclassical values.

DIII-D

Particle (ecology)

Alpha particle

Convection–diffusion equation

10.1063/1.1358311

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Citations (4)

Results of ITER Test Blanket Module Mock-Up Experiments on DIII-D

J. Snipes M. J. Schaffer P. Gohil Antti Salmi Diii-D Team

Author(s): Snipes, JA; Schaffer, MJ; Gohil, P; De Vries, P; Fenstermacher, ME; Evans, TE; Gao, X; Garofalo, AM; Gates, DA; Greenfield, CM; Heidbrink, WW; Kramer, GJ; Liu, S; Loarte, A; Nave, MFF; Oyama, N; Park, JK; Ramasubramanian, N; Reimerdes, H; Saibene, G; Salmi, A; Shinohara, K; Spong, DA; Solomon, WM; Tala, T; Boedo, JA; Budny, R; Chuyanov, V; Doyle, EJ; Jakubowski, M; Jhang, H; Nazikian, RM; Pustovitov, VD; Schmitz, O; Osborne, TH; Srinivasan, R; Taylor, TS; Wade, MR; You, KI; Zeng, L

Source

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Citations (4)

Enhanced confinement discharges in DIII-D with neon and argon induced radiation

Journal of Nuclear Materials (1999)

G.L. Jackson M. Murakami G. M. Staebler M. R. Wade A. Messiaen

DIII-D

10.1016/s0022-3115(98)00653-9

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Citations (41)

Core Turbulence Structures and $\rho_*$ Scaling Properties in H-Mode Plasmas

Bulletin of the American Physical Society (2005)