Long Term Simulations of Space Charge and Beam Loss Observed in the CERN Proton Synchrotron

Abstract

Long term storage of high intensity beams with small loss is required in the FAIR [1] project at GSI as well as for JPARC [2]. In this paper we discuss that an important contribution to the loss in bunched beams can be explained it terms of particles trapped into lattice and space charge driven islands. Dedicated experiments at the CERN-Proton Synchrotron to confirm the theoretical model have shown the existence of an emittance growth dominated regime for working points sufficiently far from the lattice resonance, and of a beam loss dominated regime for tunes very close to the resonance. While the emittance growth dominated regime has been investigated in previous studies [3], we focus here on the beam loss dominated regime and compare simulation results with measurements made in the CERN-Proton Synchrotron ring. Abstract. Long term storage of high intensity beams with small loss is required in the FAIR [1] project at GSI as well as for JPARC [2]. In this paper we discuss that an important contribution to the loss in bunched beams can be explained it terms of particles trapped into lattice and space charge driven islands. Dedicated experiments at the CERN-Proton Synchrotron to confirm the theoretical model have shown the existence of an emittance growth dominated regime for working points sufficiently far from the lattice resonance, and of a beam loss dominated regime for tunes very close to the resonance. While the emittance growth dominated regime has been investigated in previous studies [3], we focus here on the beam loss dominated regime and compare simulation results with measurements made in the CERN-Proton Synchrotron ring.

Observation of octupole driven resonance phenomena with space charge at the CERN Proton Synchrotron

“…Hence, the loss difference between octupole ON/OFF, about 10%, should mainly be due to trapping/detrapping by the additional octupole. This loss difference is in much better agreement with the simulation result of maximum 8% loss with the octupole ON [3,4]. The loss observed in the experiment must be related to the shrinking of the dynamic aperture, since the beam was too small to hit a physical aperture.…”

“…Particles with large longitudinal amplitude, instead, can periodically cross the resonance and therefore may get trapped and eventually get lost. Note that the curves chosen to fit the measured data are similar to the ones used to fit the simulation results [3,4].…”

“…The first case leads to a loss-free (if the mechanical aperture is sufficiently large) core-emittance blow-up, where the distribution is almost conserved [1]. The second leads to a diffusion of the tail particles and a subsequent beam loss [2][3][4]. The explanation of the beam loss regime is in terms of the synchrotron oscillation, which causes a periodic tune modulation due to space charge, and leads to trapping and detrapping on the resonance islands [2].…”

Space charges can significantly affect the dynamics of accelerator maps

“…The role of collective effects and resonances has attracted considerable attention, since they can cause significant beam quality deterioration and losses [15]. Another relevant issue is the coupling with the longitudinal motion which modulates the transverse tune and induces losses by resonance crossing as shown by recent experiments [10].…”

“…The interplay between nonlinear effects, typical of single-particle dynamics, and space charge, typical of multi-particle dynamics induced by the Coulomb interaction, represents a difficult challenge. To understand better these phenomena, an intense experimental campaign was launched at the CERN Proton Synchrotron [10]. It is very important, therefore, to develop analytical techniques which could be utilized in order to study and localize the associated web of resonances (see e.g.…”