Scaling of H-mode energy confinement withIpandBTin the MAST spherical tokamak

Valovič, M.; Akers, R.; Cunningham, G.; Garzotti, L.; Lloyd, B.; Muir, D.G.; Patel, A.; Taylor, D.; Turnyanskiy, M.; Walsh, M. J.

doi:10.1088/0029-5515/49/7/075016

Cited by 88 publications

(103 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Above this threshold the transport roughly doubles over the range β e ≈7-13% (0.8-1.5×β e,exp ). While this is qualitatively consistent with NSTX and MAST experimental results [36,40], the degradation is much stronger than the experimentally determined scaling exponent, (B T τ E ) ~β e -0.1 . In all the above scans the transport predictions qualitatively follow the linear stability analysis [11].…”

Section: Electron Temperature Gradientsupporting

confidence: 89%

“…7 implies a confinement time that, for fixed ρ * and β, should scale similar to those deduced from dedicated dimensionless scaling experiments in both NSTX [36][37][38] and MAST [39,40], (Ω i τ E )…”

Section: Transport Parametric Dependenciesmentioning

confidence: 60%

“…Dedicated dimensionless scaling studies in both NSTX [36][37][38] and MAST [39,40] find that the normalized energy confinement time exhibits a strong inverse scaling with collisionality, (Ωτ E ) ~ν *e -(0. 8-0.95) .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Simulation Of Microtearing Turbulence In NSTX

Guttenfelder¹,

Kaye²,

Nevins³

et al. 2012

View full text Add to dashboard Cite

Thermal energy confinement times in NSTX dimensionless parameter scans increase with decreasing collisionality. While ion thermal transport is neoclassical, the source of anomalous electron thermal transport in these discharges remains unclear, leading to considerable uncertainty when extrapolating to future ST devices at much lower collisionality.Linear gyrokinetic simulations find microtearing modes to be unstable in high collisionality discharges. First non-linear gyrokinetic simulations of microtearing turbulence in NSTX show they can yield experimental levels of transport. Magnetic flutter is responsible for almost all the transport (~98%), perturbed field line trajectories are globally stochastic, and a test particle stochastic transport model agrees to within 25% of the simulated transport. Most significantly, microtearing transport is predicted to increase with electron collisionality, consistent with the observed NSTX confinement scaling. While this suggests microtearing modes may be the source of electron thermal transport, the predictions are also very sensitive to electron temperature gradient, indicating the scaling of the instability threshold is important. In addition, microtearing turbulence is susceptible to suppression via sheared E×B flows as experimental values of E×B shear (comparable to the linear growth rates) dramatically reduce the transport below experimental values. Refinements in numerical resolution and physics model assumptions are expected to minimize the apparent discrepancy. In cases where the predicted transport is strong, calculations suggest that a proposed polarimetry diagnostic may be sensitive to the magnetic perturbations associated with the unique structure of microtearing turbulence.

show abstract

Section: Electron Temperature Gradientsupporting

confidence: 89%

Section: Transport Parametric Dependenciesmentioning

confidence: 60%

See 1 more Smart Citation

Simulation Of Microtearing Turbulence In NSTX

Guttenfelder¹,

Kaye²,

Nevins³

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Detailed parameter scans, however, indicate that confinement scales differently in STs [2,9], and the MAST scaling in terms of engineering parameters, τ E = 0.186I…”

Section: Confinement Transport and Gyrokinetic Studies Of Stsmentioning

confidence: 99%

Gyrokinetic simulations of spherical tokamaks

Roach

Abel

Akers

et al. 2009

Plasma Phys. Control. Fusion

167

View full text Add to dashboard Cite

Abstract. This paper reviews transport and confinement in spherical tokamaks (STs) and our current physics understanding that is partly based on gyrokinetic simulations. We show that equilibrium flow shear can sometimes entirely suppress ion scale turbulence in today's STs. Advanced nonlinear simulations of electron temperature gradient (ETG) driven turbulence, including kinetic ion physics, collisions and equilibrium flow shear, support the model that ETG turbulence can explain electron heat transport in many ST discharges.

show abstract

“…sustainment in the spherical torus/tokamak (ST). In particular, NSTX [3] and MAST [4] observe a strong (nearly inverse) scaling of normalized confinement with ν * . An example of this scaling is show in Figure 1 for NSTX experiments in which the plasma q, β, and ρ * were approximately fixed as the electron collisionality ν * e was varied by a factor of 3.…”

Section: Introductionmentioning

confidence: 96%

Overview of the physics and engineering design of NSTX upgrade

et al. 2012

View full text Add to dashboard Cite

Abstract-The spherical tokamak (ST) is a leading candidate for a fusion nuclear science facility (FNSF) due to its compact size and modular configuration. The National Spherical Torus eXperiment (NSTX) is a MA-class ST facility in the U.S. actively developing the physics basis for an ST-based FNSF. In plasma transport research, ST experiments exhibit a strong (nearly inverse) scaling of normalized confinement with collisionality, and if this trend holds at low collisionality, high fusion neutron fluences could be achievable in very compact ST devices. A major motivation for the NSTX Upgrade (NSTX-U) is to span the next factor of 3-6 reduction in collisionality. To achieve this collisionality reduction with equilibrated profiles, NSTX-U will double the toroidal field, plasma current, and NBI heating power and increase the pulse length from 1-1.5s to 5s. In the area of stability and advanced scenarios, plasmas with higher aspect ratio and elongation, high βN , and broad current profiles approaching those of an ST-based FNSF have been produced in NSTX using active control of the plasma β and advanced resistive wall mode control. High non-inductive current fractions of 70% have been sustained for many current diffusion times, and the more tangential injection of the 2nd NBI of the Upgrade is projected to increase the NBI current drive by up to a factor of 2 and support 100% non-inductive operation. More tangential NBI injection is also projected to provide non-solenoidal current ramp-up (from IP = 0.4MA up to 0.8-1MA) as needed for an ST-based FNSF. In boundary physics, NSTX and higher-A tokamaks measure an inverse relationship between the scrape-off layer heat-flux width and plasma current that could unfavorably impact nextstep devices. Recently, NSTX has successfully demonstrated very high flux expansion and substantial heat-flux reduction using a snowflake divertor configuration, and this type of divertor is incorporated in the NSTX-U design. The physics and engineering design supporting NSTX Upgrade are described.

show abstract

Scaling of H-mode energy confinement withI_pandB_Tin the MAST spherical tokamak

Cited by 88 publications

References 15 publications

Simulation Of Microtearing Turbulence In NSTX

Simulation Of Microtearing Turbulence In NSTX

Gyrokinetic simulations of spherical tokamaks

Overview of the physics and engineering design of NSTX upgrade

Contact Info

Product

Resources

About