Abstract
The new SNS Allison emittance scanner measures emittances of 65 kV ion beams over a range of +/- 116 mrad. Its versatile control system allows for time-dependent emittance measurements using an external trigger to synchronize with pulsed ion beam systems. After an adjustable initial delay, the system acquires an array of equally-delayed beam current measurements, each averaged over a certain time span, where all three time parameters are user selectable. The zero offset of the beam current measurements is determined by averaging a fraction of 1 ms shortly before the start of the ion beam pulse.
This paper discusses the optimization of the angular range. In addition it presents the first results and reports an unresolved artefact. Data are presented on the time evolution of emittance ellipses during 0.8 ms long H- beam pulses emerging from the SNS test LEBT, which is important for loss considerations in the SNS accelerator. Additional data explore the emittance growth observed with increasing beam current and/or increasing RF-power.
