Plasma radiometry with 30 chord resolution for fast transients in the DIII-D tokamak

Abstract

A diagnostic capable of providing time resolved measurements of plasma radiated power during disruptions and other fast transients, e.g., edge localized modes has been employed in the DIII-D tokamak. The radiation is detected with absolute extreme ultraviolet (AXUV) photodiode arrays. Thirty chords from a single port provide measurements from a full slice of the plasma at one toroidal location. The analog bandwidth is up to 1 MHz for the brightest events, i.e., disruptions. Active cooling of the diode arrays prevents damage during high temperature vessel baking. Effective responsivity values of 0.12–0.18 A/W are taken from previous work on the application of AXUV diodes in DIII-D. The total radiated energy in disruptions typically agrees with bolometer measurements within about 12%.