required for a pellet to reach the focal point of the laser beam is determined by using two photosensors to measure the pellet's position and velocity while falling. This is done to ensure that the magnetic nozzle and laser pulse are generated synchronously with the passage of the pellet through the focal point of the laser beam. The magnetic nozzle is an axisymmetric magnetic mirror produced by two solenoid coils as shown in Fig. 3. The magnetic field strength produced by the forward coil is higher than that produced by the rear coil. This results in a thrust production since laser-induced plasma flows downstream through the rear coil. By controlling the entire experimental system by microcomputer, comparatively high precision and flexibility in changing experimental conditions were realized. The characteristics of plasmas and expansion processes in the magnetic nozzle were investigated using Langmuir probes (this method is applicable for streaming plasma produced by laser pulses [9]). Results and Discussion Fig. 4 shows typical wave forms of the pulsed laser beam detected by a fast photodiode and ion saturation current measured by a Langmuir probe located 50 mm downstream from the focal point. The wave forms were obtained without applied field and the halfwidth of the laser pulse is about 2 //sec. As seen in this figure, the ion saturation
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