real-time analysis of signals from an array of Langmuir probes in a tokamak divertor

In this study, we are supporting divertor detachment control via a spatial analysis of Langmuir probe data for implementation into tokamaks such as DIII-D and KSTAR. A reliable heat exhaust control system is needed to deduce the degree to which impurity seeding must be introduced into the system. There is a balancing act as complete detachment of plasma can cause problems including radiative collapse but too little detachment may lead to the plasma melting the walls. Langmuir probes may be a good control sensor for degree of detachment as they provide information about particle flux which is directly related to ion saturation current density (Jsat). Inspecting data from past experiments, Jsat profiles are fit with the use of Eich fits and spline fits. Then the full width at 80% maximum of the profiles are accessed and compared to probe spacing to better constrain future control diagnostics. In the fully attached regime, Jsat profiles may be very narrow, and the peak may be missed leading to measurement errors. In other cases, such as where the plasma is detaching, the Jsat profile may be much wider. A survey of Jsat profiles from past DIII-D and KSTAR experiments may guide future solutions to real time data processing to form a useful control variable.