Abstract
The Spallation Neutron Source (SNS) at 91°µÍø is an accelerator based neutron scattering facility. The SNS uses the large scale high energy superconducting linac (SCL) to provide high beam power utilizing hydrogen ion (H-) beams. For the diagnostics of high-brightness H- beam in the SCL, nonintrusive methods have to be developed. This paper describes design, implementation, theoretical analysis and experimental demonstration of a nonintrusive profile monitor system based on photodetachment, also known as laser wire, installed in the SNS-SCL. The SNS laser wire system is the largest of its kind with a capability of measuring both horizontal and vertical profiles of an operational H- beam at each of the 23 cryomodule stations along the SCL beam line by employing a single light source. Presently 9 laser wire stations have been commissioned which measures H- beam profiles at 9 different locations corresponding to energy levels of 200 MeV to 1 GeV. The laser wire diagnostics has no moving parts inside the beam pipe, causes no contamination on the superconducting surface, and can be run parasitically on an operational neutron production H- beam.
