Recent Performance of the SNS H-Source for 1-MW Neutron Production

Abstract

This paper describes the performance of the SNS ion source and LEBT as they continue to deliver ~50 mA H- beams at a 5.3% duty factor required for neutron production with a ~1MW proton beam since the fall of 2009. The source continues to deliver persistent H- beams for up to 6 weeks without adding Cs after an initial dose of ~4 mg, except when there are excessive plasma impurities. In one case the H- beam decayed due to an air leak, which is shown to be consistent with sputtering of the Cs layer, and which allows to bracket the plasma potential. In another case, the performance of two sources degraded progressively, which appears to be consistent with a progressive deterioration of the Cs covered Mo converter. These two and other recently discovered issues are discussed in detail.