Three-dimensional, tight focusing of intense pulsed light-ion beam by spherical plasma focus diode

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Abstract
A new type of ion-beam diode, self-magnetically insulated, spherical plasma focus diode (SPFD), was developed. With the SPFD, three-dimensional focusing of an intense pulsed light-ion beam was obtained. Experiments and simulations were carried out to study the behavior of the SPFD. In the experiments, diagnostic results of the Rutherford scattering pinhole camera and the shadow-box showed that the ion beam was focused into a small cylindrical area with ∽0.5 mm in diameter and ∽2.5 mm in length. The average ion-beam current density at the anode surface was found to be ∽2 kA/cm2. In the simulations, it was observed that most of the diode gap is well insulated by the self-magnetic field induced by the diode current. The electron sheath in the diode gap significantly enhances the ion flow from the anode. As a result, the ion current density is several times higher than the single-species space-charge limited value.