ICAP 2002 Abstracts and Posters

Linear Quadrupole Cooling Channels for Ultra-large emittance Muon Beams

Abstract

In a scenario for either a Neutrino Factory or Muon Collider, the anticipated transverse beam emittance subsequent to capture and phase rotation is so large that it permits a relaxation of the requirements on beam spot size in the early stages relative to the final stages of ionization cooling. Staging the cooling process according to initial emittances, coupled with modest cooling factors, permits more optimal and efficient cooling channel designs and avoids much of the difficulty encountered with channels which attempt to maintain strong focusing (large divergences) across ultra-large momentum ranges (±20% dp/p). This relaxation of spot size at the absorber, especially in the "precooling" stage, allowed development of an efficient cooling channel based simply on a quadrupole FODO cell.

This work describes a quadrupole cooling channel designed to cool initial emittances of 15-20 cm (normalized) by a factor of two in each transverse plane. Its application is clearly as the most upstream stage of cooling and, being a linear channel with no bends, serves to reduce the large transverse beam size before introduction into emittance exchange channels or ring coolers. As will be shown, this channel cools efficiently and beyond the momentum reach of a solenoidal precooler. It uses large bore, normal-conducting quadrupoles with fringe-field and other higher-order effects fully included in the simulations. Some of the attractions of such a channel are that superconducting magnetic elements are not required and rf cavities and absorbers can be placed entirely in the region between quadrupoles, thus removing the difficulty of inserting them within magnetic elements. There is a marked reduction, at least, in the component cost and technical difficulty of such a channel.

C. J. Johnstone: Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510, USA. Email: cjj@fnal.gov.
M. Berz: Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA. Email: berz@msu.edu.,
D. Errede, K. Makino: Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL 61801-3080, USA. Email: derrede@uiuc.edu, makino@uiuc.edu.

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