Production of a 95% proton yield beam in a semicylindrical plasma generator

A high proton yield beam was produced in a semicylindrical multicusp plasma generator. The dimension of the cylinder is 34 cm in diameter and 129 cm in length, and the beam extraction area is 8 cm in width and 120 cm in length. A strongly linked magnetic field configuration was utilized to confine the primary electrons in the cylinder and prevent them from flowing into the beam extraction region. As a temporary test hydrogen ion beams were extracted from the central region of the plasma generator. Ion species in the beam were measured by a Doppler‐shifted spectroscopy of Balmer‐alpha light and found to be 95% at a beam current density of 175 mA/cm2 at the filling pressure of 0.4 Pa.