A real-time longitudinal phase-space measurement technique for H- beams

The authors describe a system that should be capable of producing longitudinal phase-space measurements of an H/sup -/ beam at a 2-Hz rate. The phase is selected by photoneutralization with a mode-locked laser. A deflector magnet downstream of the neutralization point deflects the charged beam, and the neutral particles enter a spectrometer through a slit covered with a stripping foil. During the 20- to 40- mu s laser burst, a ramp signal shifts the laser base with respect to the beam phase. The same ramp signal controls electric deflection plates in the exit beamline of the spectrometer, which bend the beam perpendicular to the dispersion plane. If the spectrometer magnet bends the beam horizontally, then the beam-current distribution at the focal plane is analyzed horizontally in energy and vertically in phase.<>