Internal measurement of magnetic turbulence in ELMy H-mode tokamak plasmas

Abstract

Magnetic turbulence is directly observed internally in the pedestal of ELMy H-mode tokamak plasmas using a newly developed Faraday-effect polarimetry measurement. Fluctuation amplitude is $\delta b_r\ge 15\hspace{0.17em}G$ (150–500 kHz), with a ratio of magnetic to density fluctuation $|\delta b_r/B|/|\delta n/n|\ge 0.15$ . Magnetic turbulence is identified as resulting from micro-tearing-instability and mode growth accompanied by degraded plasma confinement is observed.