OBSERVATION OF TOKAMAK PLASMAS WITH AN ARRAY OF PIN DIODE DETECTORS*

Soft x-ray emission from the Oak Ridge Tokamak (ORMAK) has been studied with an array of diode detectors. The thermal character of the plasma emission allows observation of phe-nomena associated with fluctuations in electron temperature. Measurements of internal disruption growth rates and repetition times corroborate a theoretical tearing-mode insta-bility model. Heat pulses from the disruption evolve diffusively, but with a heat conduc-tion coefficient larger than that inferred from the plasma equilibrium. The Diagnostic System The hot plasma of a tokamak discharge emits soft x rays as a result of electron-ion free-free and free-bound collisions. One method of extracting information from this flux of x rays is to use a crude pinhole camera arrangement such as shown in Figure 1. On ORMAK, the plasma is viewed by nine diffused-junction PIN diode detectors through a slit aperture along the chords shown in the figure. Because (1) the x-ra