Halo measurements of the extracted beam at the Los Alamos Proton Storage Ring

The spatial beam density distribution beyond 2.5 to 3 standard deviations of the beam center is an important property for understanding the relatively small fractional losses of high intensity beams at the Los Alamos Proton Storage Ring (PSR) and transport lines to the neutron production target. This part of the distribution (sometimes referred to as beam halo) is not well determined by the LANSCE-standard wire scanner system nor is it yet reliably predicted by the simulation codes. To significantly improve the experimental determination of the beam halo, an improved wire scanner has been developed, tested and installed in the extraction line. To enhance the signal-to-noise ratio, an amplifier consisting of a wide dynamic-range, integrating amplifier, sample-and-hold circuit, log amplifier and line driver is located near the beam line. Offset errors at the input of the amplifiers are actively cancelled and timing gates are derived from a single input pulse. We will describe the prototype instrument, discuss our encouraging test results and report our experience with the instrument in the PSR extraction line.