The high-β{sub N} hybrid scenario for ITER and FNSF steady-state missions

Journal Article · Fri May 15 00:00:00 EDT 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4921161· OSTI ID:22410393

Turco, F. ^[1]; Petty, C. C.; Luce, T. C.; Carlstrom, T. N.; Van Zeeland, M. A.; Ferron, J. R. ^[2]; Heidbrink, W. ^[3]; Carpanese, F. ^[4]; Solomon, W. ^[5]; Holcomb, C. T. ^[6]

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1. Columbia University, New York, New York 10027 (United States)
2. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
3. University of California, Irvine, Irvine, California 92697 (United States)
4. Dipartimento di Energia, Politecnico di Milano, via Ponzio 34/3, I-20133 Milano (Italy)
5. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
6. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

New experiments on DIII-D have demonstrated the steady-state potential of the hybrid scenario, with 1 MA of plasma current driven fully non-inductively and β{sub N} up to 3.7 sustained for ∼3 s (∼1.5 current diffusion time, τ{sub R}, in DIII-D), providing the basis for an attractive option for steady-state operation in ITER and FNSF. Excellent confinement is achieved (H{sub 98y2} ∼ 1.6) without performance limiting tearing modes. The hybrid regime overcomes the need for off-axis current drive efficiency, taking advantage of poloidal magnetic flux pumping that is believed to be the result of a saturated 3/2 tearing mode. This allows for efficient current drive close to the axis, without deleterious sawtooth instabilities. In these experiments, the edge surface loop voltage is driven down to zero for >1 τ{sub R} when the poloidal β is increased above 1.9 at a plasma current of 1.0 MA and the ECH power is increased to 3.2 MW. Stationary operation of hybrid plasmas with all on-axis current drive is sustained at pressures slightly above the ideal no-wall limit, while the calculated ideal with-wall MHD limit is β{sub N} ∼ 4–4.5. Off-axis Neutral Beam Injection (NBI) power has been used to broaden the pressure and current profiles in this scenario, seeking to take advantage of higher predicted kink stability limits and lower values of the tearing stability index Δ′, as calculated by the DCON and PEST3 codes. Results based on measured profiles predict ideal limits at β{sub N} > 4.5, 10% higher than the cases with on-axis NBI. A 0-D model, based on the present confinement, β{sub N} and shape values of the DIII-D hybrid scenario, shows that these plasmas are consistent with the ITER 9 MA, Q = 5 mission and the FNSF 6.7 MA scenario with Q = 3.5. With collisionality and edge safety factor values comparable to those envisioned for ITER and FNSF, the high-β{sub N} hybrid represents an attractive high performance option for the steady-state missions of these devices.

• OSTI ID: 22410393
• Journal Information: Physics of Plasmas, Vol. 22, Issue 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAM INJECTION
BETA RATIO
COMPUTER CODES
DIFFUSION
DOUBLET-3 DEVICE
ECR HEATING
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
FIRST WALL
ITER TOKAMAK
KINK INSTABILITY
MAGNETIC FLUX
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA CONFINEMENT
SAWTOOTH OSCILLATIONS
STEADY-STATE CONDITIONS
TEARING INSTABILITY