Steady state power balance studies of double null plasmas in ST40*

Power balance studies in tokamak devices is important in characterizing and understanding the performance of plasma facing components (PFCs). Recent campaigns in ST40 have successfully achieved diverted plasmas. Traditionally, power balance studies in toroidal confinement devices are difficult to perform even with a full suite of diagnostics [1]. In this research, the Heat Flux Engineering Analysis Toolkit (HEAT) [2] is used to aid in the calculation of power sharing among the four divertor legs in double null (DN) magnetic configurations in ST40. The effect of the disconnection of the two separatrices, dR_sep, on the power sharing is investigated. The simulation results are compared with available experimental measurements such as IR thermography, bolometry and Langmuir probes on the divertor to constrain the fraction of power that goes to the divertor. The results of these simulations are essential in establishing trends on the relationship between poloidal magnetic flux balance as defined by dR_sep and power sharing in ST40.