Superthermal electron generation and transport in the reversed-field pinch

A new technique for the analysis and interpretation of reversed-field pinch discharges is presented, using the fast electron population in the plasma core as an indicator of the level of magnetic turbulence. The method combines X-ray measurements of the superthermal electron distribution in the plasma core with a self-consistent three-dimensional Fokker-Planck code. This technique is illustrated by an application to low-density discharges of the MST device, using measured soft X-ray spectra to constrain the simultaneous computation of the electron distribution function and of the magnetic fields. The consistency of the experimental results, analysed in this way with both kinetic and MHD dynamo theories is discussed. The best agreement between the code and the measured X-ray spectrum occurs when an MHD dynamo field of the appropriate level and shape is included with radial diffusion due to fluctuating fields B/B ≅ (0.3 ± 0.05)%. (Author)