Equilibrium reconstruction of the safety factor profile in tokamaks from motional Stark effect data

Abstract

Articles you may be interested inOverview of equilibrium reconstruction on DIII-D using new measurements from an expanded motional Stark effect diagnostica) Rev. Sci. Instrum. 79, 10F518 (2008); Equilibrium reconstructions of reversed-shear discharges based on motional Stark effect measurements Rev. Sci. Instrum. 68, 392 (1997); 10.1063/1.1147837Equilibrium qprofile determination and stability analysis from magnetic field pitch angle measurements using motional Stark effect polarimetry Rev.The motional Stark effect (MSE) diagnostic has been used to obtain accurate measurements of the internal magnetic pitch angle tan-1(Bz/B r ) in finite-pressure tokamaks. The MSE data, together with external magnetic probe data, are used to reconstruct self-consistently the equilibrium safety factor (q) profile and, hence, the plasma current density, in the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. 1, 51 (1986)] and the Princeton Beta Experiment-Modified (PBX-M) tokamak [Phys. Fluids B 2, 1271]. An efficient computational scheme, based on an inverse coordinate representation of the magnetic field, has been developed to solve the coupled nonlinear equations describing both the magneto hydrodynamic (MHD) equilibrium and the q profile, which best match all the experimental data.

Radial Electric Field Measurements in Reversed Shear Plasmas

“…Then the difference between the fitted and measured pitch angles is the E r contribution. The MSE pitch angle computed by the VMEC equilibrium code [23] without using the affected sight line is also shown in Fig. 2(a) for this discharge.…”

“…Assuming that there are no other electric fields present, then the direction of the polarized emission is a measure of the local direction of the magnetic field. This is directly related to the safety factor by numerical solution of the Grad-Shafranov equation [23].…”

A global collisionless PIC code in magnetic coordinates

“…Nonlinear benchmark is usually performed by plotting the ion diffusivity defined by χ i ≡ −Q/(n i ∇T i ) versus R 0 /L T,i . Note that no assumption is done on Q, n i and ∇T i : these profiles are reconstructed with appropriate moments of Vlasov equation and then smoothed using splines with tension interpolation [44]. In [43], Dimits proposed a fit to express the ion diffusivity as a function of R 0 /L T,i when the system has reached (quasi-)steady state:…”

Edge equilibrium code for tokamaks

“…The needs in adaptive solvers were understood long time ago [14][15][16][17][18][19][20][21] and led to creation of POLAR (2-dimensional) and VMEC (2-and 3-dimensional). The first one uses a finite difference scheme in both radial and poloidal directions and is uniquely capable of reproducing extreme plasma configurations, e.g., with a high beta.…”