Production of high brightness H- beam by charge exchange of hydrogen atom beam in sodium jet

Production of H- beam for accelerators applications by charge exchange of high brightness hydrogen neutral beam in a sodium jet cell is experimentally studied in joint BNL-BINP experiment. In the experiment, a hydrogen-neutral beam with 3-6 keV energy, equivalent current up to 5 A and 200 microsecond pulse duration is used. The atomic beam is produced by charge exchange of a proton beam in a pulsed hydrogen target. Formation of the proton beam is performed in an ion source by four-electrode multiaperture ion-optical system. To achieve small beam emittance, the apertures in the ion-optical system have small enough size, and the extraction of ions is carried out from the surface of plasma emitter with a low transverse ion temperature of ∼0.2 eV formed as a result of plasma jet expansion from the arc plasma generator. Developed for the BNL optically pumped polarized ion source, the sodium jet target with recirculation and aperture diameter of 2 cm is used in the experiment. At the first stage of the experiment H- beam with 36 mA current, 5 keV energy and ∼0.15 cm · mrad normalized emittance was obtained. To increase H- beam current ballistically focused hydrogen neutral beam will be applied. The effects of H- beam space-charge and sodium-jet stability will be studied to determine the basic limitations of this approach.