TY - JOUR

T1 - Identifying the impact of rotation, anisotropy, and energetic particle physics in tokamaks

AU - Hole, M. J.

AU - Von Nessi, G.

AU - Fitzgerald, M.

AU - McClements, K. G.

AU - Svensson, J.

PY - 2011/7

Y1 - 2011/7

N2 - In this paper we study the effects of poloidal and toroidal rotation, and anisotropy in tokamaks. To resolve these effects from uncertainties in the data, we introduce a Bayesian inference framework which calculates the magnetic configuration probabilistically using motional Stark effect and magnetic data. Drawing on these calculations, we compute the poloidal and toroidal Mach numbers in MAST for a discharge with good rotation data. Our calculations confirm that the poloidal Mach number Ms, = v/vi × B/B is near zero (with v and vi the poloidal and thermal velocity, respectively), even on the outboard side where the scaling of poloidal field strength B to total field B is large. In contrast, the toroidal rotation of this plasma reaches a Mach number of 0.5 on axis. The impact of the toroidal rotation on the equilibrium reconstructions of the plasma is however small: it acts to increase the radius of the magnetic axis by ≈1%, and lower the central safety factor by ≈5%. In comparison, corrections to make the pressure profile consistent with internal measurements such as charge exchange recombination spectroscopy and Thomson scattering have a much larger impact. In other work we compute the level of anisotropy from a TRANSP simulation of a neutral beam-heated MAST discharge. This shows a large level of anisotropy, with p⊥/p∥ ≈ 1.7, sufficient to boost the central safety factor by 15%. For this discharge, which is representative of many MAST discharges, the effect of anisotropy and consistent pressure profiles is more pronounced than the toroidal rotation of the plasma.

AB - In this paper we study the effects of poloidal and toroidal rotation, and anisotropy in tokamaks. To resolve these effects from uncertainties in the data, we introduce a Bayesian inference framework which calculates the magnetic configuration probabilistically using motional Stark effect and magnetic data. Drawing on these calculations, we compute the poloidal and toroidal Mach numbers in MAST for a discharge with good rotation data. Our calculations confirm that the poloidal Mach number Ms, = v/vi × B/B is near zero (with v and vi the poloidal and thermal velocity, respectively), even on the outboard side where the scaling of poloidal field strength B to total field B is large. In contrast, the toroidal rotation of this plasma reaches a Mach number of 0.5 on axis. The impact of the toroidal rotation on the equilibrium reconstructions of the plasma is however small: it acts to increase the radius of the magnetic axis by ≈1%, and lower the central safety factor by ≈5%. In comparison, corrections to make the pressure profile consistent with internal measurements such as charge exchange recombination spectroscopy and Thomson scattering have a much larger impact. In other work we compute the level of anisotropy from a TRANSP simulation of a neutral beam-heated MAST discharge. This shows a large level of anisotropy, with p⊥/p∥ ≈ 1.7, sufficient to boost the central safety factor by 15%. For this discharge, which is representative of many MAST discharges, the effect of anisotropy and consistent pressure profiles is more pronounced than the toroidal rotation of the plasma.

UR - http://www.scopus.com/inward/record.url?scp=79958161057&partnerID=8YFLogxK

U2 - 10.1088/0741-3335/53/7/074021

DO - 10.1088/0741-3335/53/7/074021

M3 - Article

SN - 0741-3335

VL - 53

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

IS - 7

M1 - 074021

ER -