Ion acceleration in the divergent gas-puff Z-pinch plasma

Summary form only given. The divergent gas-puff z pinch is a non-uniform system in the axial direction. The degree of non-uniformity can be controlled by the angle of gas-puffing. High-energy ions around 1 MeV have been observed in the divergent gas-puff z-pinch experiment. As the ion acceleration has also been observed in the current reversal experiment, the acceleration has been attributed to some mechanism independent of the current direction. The result indicates that the acceleration mechanism is not the electromagnetic induction, and the further understanding of the mechanism is desired. Here the experiment was carried out to examine the relationship between the non-uniformity and the ion acceleration in the axial direction. The experiment was carried out on the SHOTGUN-III z-pinch device in which divergent gas nozzle was installed. Three divergent gas nozzles (10, 20 and 30 degrees) were prepared. The high-speed gas valve was filled with 5 atm argon gas. The device is equipped with a capacitor bank of 12 μF, which can be charged either positively or negatively. Typical discharge current is 150 kA at the charged voltage of 25 kV. A Thomson parabola energy analyzer was used for the ion analysis in the axial direction. Track detector (BaryotrakP) was used for observing the ions. Singly to triply ionized argon ions were observed in the series of experiment, and the maximum energy was about 1MeV. The preliminary result showed that ions with higher energy were observed at the smaller gas angle. The tendency supports the ion acceleration model of multiple reflections by the magnetic wall.