Advanced, high energy neutral beam injector

The BNL design of a high energy neutral beam injector is based on the neutralization of negative ions, a process that remains very efficient even at energies up to and above 1 MeV. The principal elements of such an injector are: source of negative ions, beam extraction and transport system, accelerator, neutralizing cell, and system for the removal and dumping (or energy recovery) of the remaining charged components of the beam. Among several possible source geometries, the most advanced is the BNL version of the magnetron. Best results have been obtained by using geometrical focusing of surface produced H/sup -/ ions and an asymmetric discharge chamber. A large water cooled model is being fabricated, to deliver 1-2 A of H/sup -//D/sup -/ beam currents in pulses longer than 5 s, with a source power efficiency of about 6 kW/A and a gas efficiency of 6-10%. First tests are scheduled for July 1980. Two options of the beam transport are being studied theoretically and experimentally: a weak focusing bending magnet and a strong focusing chain of electrostatic quadrupoles