Visible-Light Tomography Using an Optical Imaging-System

A system for tomography in the wavelength range 200-1 100 nm has been designed for the Rijnhuizen Tokamak Project (RTP). The plasma is viewed from five directions in one poloidal plane with a total of 80 detectors. An optical imaging system consisting of two spherical mirrors for each viewing direction is used to combine a good spatial resolution (1 cm, the minor radius of RTP being 17 cm) with a sufficiently high signal level for the fast electronics (200 kHz). Because of the complexity of the imaging, implementation of the system into common tomography codes is not straightforward. Ray tracing is used to calculate the contribution of the local emissivities in the plasma to the measured signals of the various detectors