Two-dimensional visualization of excitation temperature and chemical species in divertor plasmas: Trace CD molecules by chemical sputtering of fusion plasma reactor wall

The divertor region is among the most important section of nuclear fusion reactors. In order to investigate the behavior of deuterium in divertor plasmas, emission profiles of the Balmer series lines of deuterium atoms, molecular bands of D2 and CD intensities have been two-dimensionally visualized with a CCD camera fitted with a bandpass filter, using a test system, the Nagoya Divertor Simulator II (NAGDIS-II). It has been clarified that profiles of emission from deuterium atoms and excitation temperature varied significantly with changes of the discharge current. From profiles of the ratio of the atomic emission intensity to the deuterium molecular emission, the increase in the dissociation fraction of deuterium molecule with the increase of the discharge current has been confirmed. Two dimensional visualization of the divertor plasma is a promising method for studies in nuclear fusion science.