The CCVV high-current megavolt-range DC accelerator

Abstract

We describe a constant-current variable-voltage (CCVV) accelerator, intended to operate in the MeV energy range but tunable down to a few percent of an MeV without loss of beam current. We present experimental results from OUT 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. We discuss a proposed 1 MeV accelerator and a conceptual design for a multiaperture system accelerating 10 A of Dions 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 allows us 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.

Injector for RFQ using electrostatically focused transport and matching

“…Our LEBT uses ESQ technology [5] which was developed and tested for the DOE magnetic fusion energy program [6] and adapted for the present application.…”

“…1. The hardware is the same as used for the 200 kV Constant Current Variable Voltage (CCVV) prototype accelerator tested and described previously [5,8,9]. Two ESQ modules containing a total of five sets of quadrupoles are shown in the figure.…”

“…because the pre accelerator voltage. which determines the beam current, is always kept at the same value [5].…”

Envelope code for electrostatically accelerated beam with ESQ focusing

“…The code described here has been used to design a number of accelerators and transport systems, including: a 200 kV CCVV prototype accelerator [1] built and tested by the MFE group at LBL; a 1 MV accelerator for a proposed test facility [2]; a 1.3 MV, 1A D-accelerator . channel for ITER [3]; a high-current electron accelerator for an FEL [4]; and an injector proposed for SSC and CERN [5].…”

“…1 for the CCVV prototype accelerator [1], [2) in which the ESQ electrodes are supported by end plates. In the trapezoidal case, the potential along the axis (dotted line in Fig.…”