An improved capacitive divider probe for plasma potential measurements in the Phaedrus tokamak

Abstract

High bandwidth capacitive probes are useful tools for potentials measurements in the tokamak scrape off layer. An improved capacitive divider probe design with very high frequency bandwidth is shown. The gain of this system is between 0 and -8 dB for frequencies from 0.1 Hz to more than 100 MHz, with the -3 dB point at approximately 40 MHz. The probe structure, circuits, performance, and experimental results from the Phaedrus-T tokamak are given.