Conceptual design of Fiber Bragg Grating temperature sensors for heat load measurements in COMPASS-U plasma-facing components

Abstract

Information about the temperature of plasma-facing components is important for a reliable tokamak operation. A temperature monitoring system using Fiber Bragg Grating (FBG) sensors is foreseen for the new tokamak COMPASS Upgrade, which is currently starting its construction. This diagnostic can be a valuable complement to IR thermography, thermocouples, and Langmuir probe divertor diagnostics. The system will be optimized to estimate the steady-state and transient heat loads, such as runaway electrons, on the divertor and limiters. In this contribution, current progress in the design of the FBG sensors for the COMPASS-U initial open divertor and guard limiters is presented. The heat flux on the plasma-facing components is modeled for diverted and first phase circular plasma scenarios by the PFCFlux code. The subsequent heating and the mechanical strain in the components dedicated for the placement of the sensors is simulated by the finite element analysis software ANSYS. Using these results, the optimal placement and configuration of the sensors are determined with respect to the anticipated maximum temperature and gradients.