Evaluation of focusing characteristics of spherical plasma focus diode

Abstract

Experiments and the associated simulations for the evaluation of the focusibility of spherical Plasma focus diode (SPFD) were carried out. To evaluate the ion beam focusibility, two types of time-integrated Rutherford scattering pinhole camera were used: angle-integrated and angle-resolved type. From the former method, the ion beam has been found to focus in a cylindrical area with 4.5mmφ × 6.0 mm. The ion density profile shows a peak at 2.5 mm downstream from the geometric focusing point. From the latter method, it is found that a large fraction of the ion beam is produced from the downstream region of the diode. In simulations, the influence of an initial ion thermal energy was evaluated on the ion beam focusibility. When the initial energy is 20 eV, the ion beam focused in a cylindrical area of 0.4 mmφ × 2.4 mm. The experimental focusing parameters seem to be much worse than those evaluated numerically presumably due to the aiming error of ion beam.