Electron beam profile measurement using enhanced dual-techniques in high heat flux test facility at Institute for Plasma Research

Abstract

During operation of an ITER-like plasma fusion device, Plasma Facing Components (PFCs) of a divertor are subjected to steady-state and transient heat loads of up to 20 MW/m2. At High Heat Flux Test Facility (HHFTF) at Institute for Plasma Research, PFCs are subjected to such heat flux scenarios using 200 kW electron beam (EB). A heat flux distribution on PFCs is significantly influenced by the EB profile and scanning technique. A novel dual-technique approach is used to measure EB cross-sectional profiles in HHFTF. A single setup is designed, fabricated, and installed in HHFTF consisting of (1) the knife-edge technique involving graphite and tungsten rectangular tiles bonded on a copper block adjacent to each other to form a sharp edge and (2) the wire scanner technique wherein tungsten wires are placed at equal distances. Current collected by the setup is measured as EB is rastered across the wire and tile boundaries. Current measured as a function of EB position is used to calculate the EB profile using a customized LabVIEW software application. Experiments are conducted by varying EB power from 28 to 200 kW and correspondingly the full width at half maximum of the EB profile grows from 5.30 to 16.04 mm, as observed by both these techniques. The COMSOL Multiphysics simulation of the wire scanner technique is performed to verify the experimental results. X-ray and infra-red imaging diagnostics of HHFTF are also used to measure the EB profile in a unique and first-of-its-kind way, and they are found to agree well with the dual-technique measurements.