Non-invasive beam profile measurements using an electron-beam scanner

Two electron scanners, one for each plane, have been installed in the SNS (Spallation Neutron Source) Ring to measure the profile of the high intensity proton beam. The SNS Ring accumulates 0.6 μs long proton bunches up to 1.6e14 protons, with a typical peak current of over 50 Amp during a 1 ms cycle. The measurement is non-destructive and can be done during production. Electron guns with dipoles, deflectors, and quadrupoles scan pulsed electrons through the proton beam. The EM field of the protons changes the electrons' trajectory and projection on a fluorescent screen. Cameras acquire the projected curve and analysis software determines the actual profile of the bunch. Each scan lasts only 20 nsecs, which is much shorter than the proton bunch. Therefore the longitudinal profile of the proton bunch can be reconstructed from a series of scans made with varying delays. This talk will describe the theory, hardware and software of the electron scanner, as well as the results and progress made in improving the measurements.