The U. S. magnetic fusion energy program has developed a single design, long-pulse neutral beam source for TFTR, MFTF-B, and DIII-D. The arc is a very compact axial magnetic line cusp. The accelerator is an actively cooled tetrode with water-cooled grid tubes of shaped molybdenum forming ‘‘slot’’ beamlets. DIII-D and MFTF-B configurations have an 80-kV accelerator gap, with a 12×18 cm aperture, and a 10-m ‘‘module’’ focus. TFTR modules are unfocused, with a 120-kV gap and 12×43-cm mask. The first CLPS was tested in the TFTR configuration, at 120 kV, 2s. Optimum current was 73 A, or 1.76 μpervs (deuterium), with 80%–85% atomic fraction. Optimum divergence of ions plus neutrals was 0.4° parallel to the slots, and 0.7° perpendicular to the slots (1/e half-angle). The combination of an axial cusp magnetic bucket and slot accelerator apertures gives the common long pulse source about twice the beam power per unit cross section of other long pulse sources, plus lower divergence in the direction parallel to the slots.

The 10 x 40 cm Long Pulse neutral beam source developed at Lawrence Berkeley Laboratory has been selected as the prototype for the design of the U.s. Common Long Pulse Source to be used on TFTR, Doublet-III, and MFTF-B. The Long Pulse Source consists of a magnetic line cusp bucket with an actively cooled backplate electron dump, and a four-grid accelerator using slot apertures and water-cooled molydenum rails. Deuterium testing of the long pulse source at 120 kV, 53 A, and two-second pulse length has been completed on the Neutral Beam Engineering Test Facility, including an 8 hour, 100 shot test to demonstrate the durability and reliability of the source. Maximum 2 second beam parameters obtained (not simultaneously) are 125 kV, 58 A (deuterium), and 7.1 MW. Beam pulse length has been extended to 5 seconds at * This work was supported by the U.S. Department of Energy under Contract No. DE-AC03-16SF00098.

No abstract

No abstract

No abstract