Computer tomography of M=1 mode during sawtooth oscillation with three soft X-ray detector arrays on the WT-3 tokamak

Soft X-rays (SXRs) emitted from plasma in the WT-3 tokamak were measured by three SXR detector arrays, viewing the plasma from three different angles. From these experimental data, the authors reconstructed the two dimensional (2-D) contour of constant SXR emissivity as a function of time, using the technique of computer tomography (CT). Computer simulation results show that data from three or more sets of detector arrays are required to reconstruct the 2-D emissivity structure with sufficient accuracy to distinguish Kadomtsev's model from the quasi-interchange (Wesson's) model of sawtooth crash. Further, it is shown that if the noise amplitude is more than 1.5%, reconstruction of the real 2-D SXR emissivity structure is difficult.