A new 2.5 MeV injector and beam test facility for the spallation neutron source

Abstract

The U.S. Spallation Neutron Source (SNS) now operates with 1.2 MW of beam power on target with the near-term goal of delivering 1.4 MW and a longer-term goal of delivering >2 MW to support a planned second target station. Presently, H− beam pulses (50-60 mA, 1 ms, 60 Hz) from an RF-driven, Cs-enhanced, multi-cusp ion source are first accelerated to 2.5 MeV by a Radio Frequency Quadrupole (RFQ) accelerator, injected into a ∼1 GeV linac, compressed to <1μs in an accumulator ring and ultimately delivered to a liquid mercury target for pulsed neutron production. In recent years concerns about the RFQ performance has motivated the procurement of a new RFQ and the creation of a Beam Test Facility (BTF) to allow off-line testing. The purpose of the BTF is to first validate performance of the new RFQ before installing it in place of the existing RFQ and later to serve as a stand-alone 2.5 MeV research accelerator employing the original SNS RFQ. After validating the new RFQ with respect to energy, emittance and transmission, the initial applications of the BTF will be to conduct 6D beam dynamic studies, develop & demonstrate ion sources capable of meeting the current and future requirements of the SNS, and contribute to neutron moderator development. This report provides a facility update, description of the BTF ion source systems as well as a discussion of the first LEBT and RFQ beam current measurements performed at the BTF.