Terminal Ion Source System for the Brookhaven Three-Stage Tandem Facility

A negative ion source has been installed and operated reliably in the high-voltage terminal of the injector accelerator at the Brookhaven Three-stage MP Tandem Van de Graaff Facility. Negative ions extracted directly from an off-axis-type duoplasmatron are focused, mass analyzed, and pre-accelerated to match the beam optics of the acceleration tubes. The ions are then deflected through 90° onto the acceleration axis using an improved electrostatic mirror and steered for optimum beam transmission. Other design features include multiple control rods, TV telemetry, surge-protected power supplies, terminal vacuum pumping, closed-loop liquid cooling and high-speed insulating-gas transfer which permits quick access to the terminal. Beams in excess of 30 μA, 1H- and 5 μA, 16O- have been accelerated by the injector to over 9 MeV. Less intense beams have been further accelerated through all three stages to provide 30 MeV, 1H+ and 100 MeV, 16O8+ for experimental use.