First tomographic reconstructions and a study of interference filters for visible-light tomography on RTP

An 80‐channel visible‐light tomography diagnostic is operational on the Rijnhuizen Tokamak Project. This diagnostic uses optical imaging systems from five directions in one poloidal plane to view emission by the plasma. For the application of tomography algorithms, measurements need to be preprocessed to take into account the properties of the imaging system. These properties have been measured and a consistent treatment is demonstrated. An example of a tomographic inversion of a glow‐discharge plasma is given. Optical filters can be used to select various wavelength ranges. Because the imaging system gives large angles of incidence on the filter (<16°), a study has been made to determine the minimum useful bandwidth of interference filters to select spectral lines, which was found to be 5 nm.