Fabrication of the MEBT chopper system for the Spallation Neutron Source

Los Alamos completed design, fabrication, procurement, and initial testing (without beam) of the SNS medium-energy beam-transport (MEBT) chopper, including the meander-line traveling-wave structure and the electrical-pulser system. This report reviews the design parameters and discusses the fabrication process for the chopper structures, including measurements of the impedance and rise time. (The MEBT vacuum system and chopper-target beam stop were developed at and reported by LBNL.) We discuss the specifications for the pulse generator and its fabrication and testing at Directed Energy, Inc. of Ft. Collins, CO. Experimental tests of the chopper system are currently being performed at the SNS site at ORNL and will be reported separately.