Characteristics of nonequilibrium plasma in disk MHD generator

Performances of closed cycle disk MHD generator have been studied at Tokyo Institute of Technology. As well known, fluctuation of nonequilibrium plasma due to the ionization instability reduces the disk MHD generator performances. Therefore, the nonequilibrium plasma should be kept stable and uniform to obtain high performance of the disk MHD generator. In the past, characteristics of nonequilibrium plasma such as electron temperature, electron number density and their fluctuation were studied. However, previous studies were not focused on fluctuation in a nozzle but that in an MHD channel. Experimental studies at T.I.Tech. have suggested that an enthalpy extraction from the MHD channel is influenced by an external load condition (short circuit or open circuit) at the nozzle. This indicates that electron number density, electron temperature and their fluctuation in the nozzle affect the nonequilibrium plasma in the MHD channel. Therefore, in the present experiment, fluctuations of electron number density both in the nozzle and in the MHD channel were measured and a relation between them was investigated. Furthermore, effects of these fluctuations on enthalpy extractions were clarified. Experiments were carried out using a shock-tube driven disk MHD generator with cesium seeded argon. Fluctuation of cesium continuum recombination radiation was measuredmore » both in the nozzle and in the MHD channel with photomultiplier, and electron temperature was measured in the MHD channel with spectrometric multi-channel analyzer. In this paper, fluctuation is defined as a deviation to time mean of its intensity.« less