Magnetic measurement based methods in determination of plasma equilibrium parameters in Damavand tokamak

Abstract

Determination of plasma equilibrium parameters such as poloidal beta (βp) with half of plasma internal inductance (li) known as Shafranov parameter (asymmetry factor) (βp+\U0001d521li2) and edge safety factor plays very important role in primary equilibrium and stability analysis and control of tokamak plasma. In this study, the well known Shafranov semi-empirical model, based on external magnetic measurements is used to extract Shafranov parameter and effective edge safety factor in low-β operating regime of Damavand tokamak. The well known integral representation of βp+\U0001d521li2 was modified for non-circular tokamaks with ellipse-like cross section. After calibration of magnetic pick-up coils, Shafranov parameter was estimated with respect to the first and second Fourier harmonic of radial and poloidal components of magnetic field. The results were compared with approximate, semi-analytical determination of Shafranov parameter which is based on analytical solution of Grad-Shafranov equation (GSE). Founding evolution of Shafranov parameter, effective edge safety factor was obtained in terms of Shafranov parameter and compared with semi-empirical description. It was found that between the ramp-up and ramp-down domain of the plasma current, the result from Shafranov model is approximately in good agreement with the semi-analytical and semi-empirical benchmarks and the integral model provides more reliable trace of the Shafranov parameter in out of ramp domains of the discharge.