MultiCam measurements on the TCV tokamak

In expectation of the 10 camera MANTIS diagnostic (see main page), we have studied the divertor plasma of the TCV tokamak in Lausanne (Switserland) using the 4 camera MultiCam diagnostic, measuring the emission from the divertor in four different frequency bands. The figure below illustrated the strength of such a diagnostic, as each frequency band (corresponding to a different emission lines of the various ions or atoms in the plasma) shows strikingly different behaviour.   

Camera images for three different densities, showing the line radiation from both Carbon 2+ (top) and Hydrogen (bottom). Carbon 2+ radiates at temperatures around 5eV, whereas Hydrogen radiates at lower temperatures around 1eV. With rising density, the high temperature (Carbon 2+) region is receding from the wall, while at the same time a low temperature region (hydrogen) forms near the wall. In this type of 'detached' divertor state the peak heat load to the wall is strongly reduced.