The CCVV high-current megavolt-range DC accelerator

The authors describe a constant-current variable-voltage (CCVV) accelerator, intended to operate in the megaelectronvolt energy range but tunable down to a few percent of magnetoelectronvolt without loss of beam current. They present experimental results from a 200-keV single-beam prototype system designed to accelerate up to 0.2 A of H⁺ or H^- or the equivalent current of heavier ions. The beam is accelerated by a series of stackable 100-keV modules, the number depending on the maximum beam energy required. The authors discuss a proposed 1-MeV accelerator and a conceptual design for a multiaperture system accelerating 10 A or D^- ions to 1-2 MeV for current drive in a fusion reactor. The use of electrostatic quadrupole focusing allows a conservative design with reduced risk of voltage breakdown and makes it possible to maintain high currents while varying the beam energy. These features are useful for fusion reactor startup and for industrial applications, such as semiconductor processing and surface hardening