Considering the above, it seems that magnetic nozzle B is more appropriate for laser propulsion. As seen in Fig. 8, the ion saturation current becomes saturated at a field strength of 0.4 Tesla. If laser-produced ions are assumed to be singly charged and at the same temperature as the electrons, the ion Larmor radius at a field strength of 0.4 Tesla is 3 mm - comparable with, or less than, the characteristic length of the magnetic nozzle. Consequently, the application of a stronger field has little influence on the laser-induced plasma in our experiment. Characteristics of the expanding plasma in magnetic nozzle B were investigated using Langmuir probes which were set at positions 50 mm and 100 mm apart from the focal point with several different angles. Figs. 9 and 10 show the angular distribution of the velocity and the peak density of the expanding plasma, respectively. The expansion velocity is in the range of 20 to 30 km/sec and is largely insensitive both to angle and to the presence of an applied field. On the other hand, a large angular
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