Experimental Database and Design Concept for a 1-MW, 200-Kev Neutral Beam Line Based on a Sitex Negative Ion Source

Abstract

Scaling studies for a SITEX negative ion source to produce 200-keV, 10-A, long pulse D/sup -/ beams are under way at Oak Ridge National Laboratory (ORNL). Designs have been restricted to the use of established techniques and reasonably welldemonstrated scaling. The results show that the 1-A SITEX source can be directly scaled to produce 200-keV, 10-A long pulse ion beams with a source power efficiency of less than or equal to5 kW of total plasma generator power per ampere of D/sup -/ beam generated. Extracted electron-to-D/sup -/ ratios should be less than or equal to0.06, with all extracted electrons recovered at less than or equal to10% of the first gap potential energy difference. The close-coupled accelerating structure will be 5 cm long and have five electrodes with 21 slits each, with a 50-kV/cm field in each gap. No decel electrode was included because of the transverse magnetic field. Electrons formed in each gap by the about16% charge-exchange loss of D/sup -/ in the total accelerator column will be collected by electron recovery structures associated with the gaps at an average energy of 50% of a gap's potential energy difference. Atomic gas efficiency will be greater than or equal to67%. Beammore » divergence calculations using the ORNL optics code give theta /SUB rms/ = + or -0.4/sup 0/. The ion source magnetic field provides momentum dispersion of the extracted beam, separating out both the electrons and all heavy ion impurities and low energy D/sup 0/ particles formed by charge exchange in the accelerating column. A D/sub 2/ gas neutralization cell and a charge separation magnet provide 1 MW of D/sup 0/ beam at 200 keV for injection. The overall beam line dimensions are 2.2 X 1.0 X 5.0 m (H X W X L).« less