A volume H- ion source with a toroidal discharge chamber

A new volume H^- ion source has been designed with the objective of reaching a current of 50 mA in 1-ms pulses, to be eventually used on the new RF quadrupole (RFQ) preinjector at Brookhaven National Laboratory´s Alternating Gradient Synchrotron. Its main feature is a full rotation symmetry, with a toroidal discharge chamber separated from the central extraction region by a conically shaped dipole field. Preliminary studies consisted of measurements of the H^- yield and the accompanying electron component as a function of the discharge current, discharge voltage, pressure, and extraction voltage for several geometries of the conical field; effects of the filament heating current were also studied, both for DC and AC cases. It was possible to extract an H^- current of 30 mA through an aperture of 1 cm², with an electron component of about 750 mA