Studies of emittance growth and halo particle production in intense charged particle beams using the Paul Trap Simulator Experiment

Abstract

The Paul Trap Simulator Experiment (PTSX) is a compact laboratory experiment that places the physicist in the frame-of-reference of a long, charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system. The transverse dynamics of particles in both systems are described by the same set of equations, including nonlinear space-charge effects. The time-dependent voltages applied to the PTSX quadrupole electrodes in the laboratory frame are equivalent to the spatially periodic magnetic fields applied in the AG system. The transverse emittance of the charge bunch, which is a measure of the area in the transverse phase space that the beam distribution occupies, is an important metric of beam quality. Maintaining low emittance is an important goal when defining AG system tolerances and when designing AG systems to perform beam manipulations such as transverse beam compression. Results are reviewed from experiments in which white noise and colored noise of various amplitudes and durations have been applied to the PTSX electrodes. This noise is observed to drive continuous emittance growth and increase in root-mean-square beam radius over hundreds of lattice periods. Additional results are reviewed from experiments that determine the conditions necessary to adiabatically reduce the charge bunch’s transverse size and simultaneously maintain high beam quality. During adiabatic transitions, there is no change in the transverse emittance. The transverse compression can be achieved either by a gradual change in the PTSX voltage waveform amplitude or frequency. Results are presented from experiments in which low emittance is achieved by using focusing-off-defocusing-off waveforms.

Coherent resonance stop bands in alternating gradient beam transport

“…There is another dedicated ion trap at Princeton Plasma Physics Laboratory in the US. Gilson and his co-workers have done interesting beamphysics experiments, using a different type of LPT [46][47][48]. Their work includes a detailed study of beam-quality degradation induced by white and colored noises on the linear focusing function K rf ðτÞ [49,50].…”

“…In previous S-POD experiments as well as WARP simulations [14][15][16][17][18][19], we have often assumed the sinusoidal focusing potential commonly used for regular LPTs while the FODO waveform was employed in some earlier iontrap experiments [47,54]. Theoretically, the sinusoidal focusing channel has a resonance feature very similar to that of the FODO channel.…”

Double stop-band structure near half-integer tunes in high-intensity rings

“…Another LPT system, substantially the same as S-POD, is under construction at Rutherford Appleton Laboratory [20]. Gilson and his co-workers of Princeton Plasma Physics Laboratory also developed a relatively large LPT dedicated to beam physics [21][22][23].…”