Abstract
In this study, obtaining muon beams with high-density in 6D phase-space is essential for realization of muon colliders, neutrino factories based on accelerated muons beams and other experiments involving muons. While several schemes to compress the beam phase-space by means of muon cooling having been proposed, very little is known about the impact of particle-particle interactions in the whole design. In this paper, we examine the influence of space-change fields on the cooling process of muon beams. We show that the cooling efficiency decreases with the degree of intensity, leading to emittance growth and particle loss for beams with large intensities. We further show that the emittance growth is only longitudinal and present a space-charge compensation solution by means of increasing the rf gradient. With the aid of numerical simulations, we obtain a quantitative relationship between the required compensation gradient and bunch charge and compare our results to earlier theoretical findings.
Highlights
Muons are “heavy electrons” that have negligible synchrotron radiation and beamsstrahlung emission, and can be accelerated and stored in multiturn recirculating devices or rings [1,2]
A salient feature of our study is that the transverse emittance is not affected by the bunch charge, suggesting that the deterioration of the cooling performance is primarily caused by the longitudinal space-charge force
We showed that the cooling efficiency decreases with the degree of intensity, yielding to emittance growth and particle loss for beams with large intensities
Summary
Muons are “heavy electrons” that have negligible synchrotron radiation and beamsstrahlung emission, and can be accelerated and stored in multiturn recirculating devices or rings [1,2]. Ionization cooling is achieved by reducing the beam momentum through ionization energy loss in absorbers and replenishing the momentum loss only in the longitudinal direction through rf cavities This mechanism can effectively reduce the transverse phase space of a beam in the same way as radiation damping does to an electron beam. It does not effectively cool the longitudinal momentum spread because the energy-loss rate is not sensitive to beam momentum except for very low-energy muons. Average momentum of 200 MeV=c and rms length of 2 cm With this beam current, and relativity low momentum, it is likely that the cooling performance of the channel will be limited by space charge, and it is uncertain whether we can achieve the micron-scale emittances required for a muon collider. We note that this paper focuses on the 6D cooling channel after the merge only
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