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

Abstract

Several benchmarking space charge experiments have been performed during the last few years in the CERN Proton Synchrotron. These controlled experiments are of paramount importance to validate the present very powerful simulation codes. The observations of the combined effect of space charge and nonlinear resonance on beam loss and emittance, using a single controllable octupole during ~ 1 s at 1.4 GeV kinetic energy, are discussed in some detail in the present paper. By lowering the working point towards the octupolar resonance, a gradual transition from a regime of loss-free core emittance blow-up to a regime of continuous loss was found. Several benchmarking space charge experiments have been performed during the last few years in the CERN Proton Synchrotron. These controlled experiments are of paramount importance to validate the present very powerful simulation codes. The observations of the combined effect of space charge and nonlinear resonance on beam loss and emittance, using a single controllable octupole during ~ 1 s at 1.4 GeV kinetic energy, are discussed in some detail in the present paper. By lowering the working point towards the octupolar resonance, a gradual transition from a regime of loss-free core emittance blow-up to a regime of continuous loss was found.

Identification and characterization of high order incoherent space charge driven structure resonances in the CERN Proton Synchrotron

“…As expected, particles with smaller amplitude have lower tunes due to the incoherent space charge tune shift. More interestingly, it turns out that the "space charge induced periodic resonance crossing", which was extensively studied in the context of magnet driven resonances in presence of space charge [1][2][3][4], is also the mechanism resulting in losses here: for the chosen vertical machine tune, the test particles with high amplitude periodically cross the 8Q y = 50 resonance. In some cases the crossing of the resonance leads to a rapid diffusion also referred to as "scattering" of the particle trajectory on the resonance [3], as can be observed by a change of the particle's action.…”

Investigations of Field Dynamics in Laser Plasmas with Proton Imaging

“…In comparison to conventional proton accelerators with an usual emittance in the order of 1 π mm mrad [100] laser generated proton beams have tenfold up to hundredfold lower emittance. Therefore the proton beams are well suited for imaging experiments as presented in Part III.…”

Identification and characterization of high order incoherent space charge driven structure resonances in the CERN Proton Synchrotron

“…As expected, particles with smaller amplitude have lower tunes due to the incoherent space charge tune shift. More interestingly, it turns out that the "space charge induced periodic resonance crossing," which was extensively studied in the context of magnet driven resonances in the presence of space charge [1][2][3][4], is also the mechanism resulting in losses here: for the chosen vertical machine tune, the test particles with high amplitude periodically cross the 8Q y ¼ 50 resonance. In some cases the crossing of the resonance leads to a rapid diffusion also referred to as "scattering" of the particle trajectory on the resonance [3], as can be observed by a change of the particle's action.…”

“…Different tune shifts of individual particles lead to a tune spread in the transverse tune space. The interplay between the space charge tune spread and excited resonances was previously studied on a controlled normal octupole resonance [1][2][3]. The experimentally observed transverse emittance growth and beam loss was identified to be caused by the periodic resonance crossing and trapping of individual particles due to the modulation of the transverse space charge force through the synchrotron oscillations.…”