Dynamic beam cleaning by a nonlinear resonance

Chao, Alexander W.; Month, M.

doi:10.1016/0029-554x(76)90422-5

Cited by 7 publications

(6 citation statements)

References 2 publications

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“…On a long run it thus frequently jumps between halo and core, which implies also a large jump in the periodic tune modulation due to the strong dependence of the betatron tune on transverse distance. This process of trapping and detrapping by an island is, in principle, closely related to previous studies of the effect of machine tune modulation in the absence of space charge [7,8,10,11,14]. The main difference lies in the fact that the space charge tune modulation is exposed to these large jumps following trapping or detrapping events, hence the relative position of islands changes in time and from particle to particle.…”

Section: E Interpretationsupporting

confidence: 80%

Space charge and octupole driven resonance trapping observed at the CERN Proton Synchrotron

Franchetti

Hofmann

Giovannozzi

et al. 2003

Phys. Rev. ST Accel. Beams

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The combined effect of space charge and nonlinear resonance on beam loss and emittance was measured in a benchmarking experiment over a 1.2 s long flat bottom at 1.4 GeV kinetic energy in the presence of a single controllable octupole. By lowering the working point towards the resonance, a gradual transition from a loss-free core emittance blowup to a regime dominated by continuous loss was found. We compare the observation with 3D simulations based on a new analytical space charge model and obtain good agreement in the emittance blowup regime. Our explanation 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. For working points very close to the resonance this induces a beam halo with large radius. The underlying dynamics is studied in detail, and it is claimed that the predicted halo in conjunction with a reduced dynamic aperture for the real machine lattice is the source of the loss observed in the experiment.

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Section: E Interpretationsupporting

confidence: 80%

Space charge and octupole driven resonance trapping observed at the CERN Proton Synchrotron

Franchetti

Hofmann

Giovannozzi

et al. 2003

Phys. Rev. ST Accel. Beams

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“…The efficiency of the process has been investigated in [4,5] and mechanisms for detrapping have been studied as well [6]. Applications of the trapping of particles have been proposed as a method to clean the beam from halo particles [7] and recently for multi-turn extraction [8,9]. Contrary to a "useful" controlled trapping/detrapping of particles, in the beam loss issue for high intensity we are dealing with uncontrolled trapping/detrapping phenomena.…”

Section: Introductionmentioning

confidence: 99%

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

Franchetti¹,

Hofmann²,

Giovannozzi³

et al. 2005

AIP Conference Proceedings

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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.

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“…[8], and proposed as beam cleaning method in Ref. [11]. A relatively large number of particles is thus able to cross periodically the resonance at various betatron amplitudes, until trapping occurs.…”

Section: Discussionmentioning

confidence: 99%

Observations and simulation of a fourth order resonance with space charge

Franchetti¹,

Hofmann²,

Giovannozzi³

et al. 2003

AIP Conference Proceedings

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A benchmarking experiment with a high intensity bunched beam stored for 1.2 s in a nonlinear lattice has been performed at the CERN Proton Synchrotron (PS). Beam emittance and beam intensity have been measured for several working points at different distances from a lattice-induced resonance. We found a regime of emittance growth for machine tunes far from the resonance and a regime of emittance shrink/beam loss for working point close the resonance. We compare the observations with 3D simulations and in the blow-up regime we find good agreement. We interpret these results in terms of space charge induced trapping and de-trapping on the lattice resonance. We show that this mechanism is responsible of halo formation which depends on the distance from the resonance and discuss the interplay of dynamic aperture and halo size as main mechanism to explain beam loss in the experiment. Abstract. A benchmarking experiment with a high intensity bunched beam stored for 1.2 s in a nonlinear lattice has been performed at the CERN Proton Synchrotron (PS). Beam emittance and beam intensity have been measured for several working points at different distances from a lattice-induced resonance. We found a regime of emittance growth for machine tunes far from the resonance and a regime of emittance shrink/beam loss for working point close the resonance. We compare the observations with 3D simulations and in the blow-up regime we find good agreement. We interpret these results in terms of space charge induced trapping and de-trapping on the lattice resonance. We show that this mechanism is responsible of halo formation which depends on the distance from the resonance and discuss the interplay of dynamic aperture and halo size as main mechanism to explain beam loss in the experiment. Contributed paper at the 29th ICFA Advanced Beam Dynamics

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Dynamic beam cleaning by a nonlinear resonance

Cited by 7 publications

References 2 publications

Space charge and octupole driven resonance trapping observed at the CERN Proton Synchrotron

Space charge and octupole driven resonance trapping observed at the CERN Proton Synchrotron

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

Observations and simulation of a fourth order resonance with space charge

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