current has two peaks in its shape. This wave form appears frequently when a high- intensity laser pulse irradiates the pellet surface [10]. The propagation speeds of the first and second peaks, which were derived using the time-of-flight method, were estimated to be approximately 104 km/sec and 20 km/sec, respectively. This indicates the existence of two different plasma groups with different plasma generation and acceleration processes [11], However, the contribution of the first peak to thrust production is considered to be small since the amount of plasma generated in the first peak is much less than that in the second peak. For this reason, hereafter we examine the effect of the magnetic nozzle on only the second peak plasma. The effect of the magnetic nozzle configuration on the expansion process of laser- induced plasma was examined using two types of magnetic nozzles as characterized by Figs. 5 and 6. The phenomena of the plasma expansion in these magnetic nozzles are shown in Figs. 7 and 8. In both magnetic nozzles A and B, the probe output (ion saturation current) in the direction 0=90° decreases monotonically with the applied field, indicating that radial expansion is more intensely restrained towards the centre axis of the magnetic nozzle. In magnetic nozzle B, the probe output in the direction 0= 10° increases with increasing field strength. This also means that the laser-induced plasma is concentrated
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