Influence of space-charge fields on the cooling process of muon beams

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 have 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-charge 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.