Design of the Muon Collider Lattice: Present Status

The last component of a muon collider facility, as presently envisioned[1], is a colliding-beam storage ring. Design studies on various problems for this ring have been in progress over the past year[2]. In this paper we discuss the current status of the design. The projected muon currents require very low beta values at the IP, β∗ = 3mm, in order to achieve the design luminosity of L = 10 cm−2 s−1. The beta values in the final-focus quadrupoles are roughly 400 km. To cancel the corresponding chromaticities, sextupole schemes for local correction have been included in the optics of the experimental insertion[3]. The hourglass effect constraints the bunch length to be comparable to β∗. To obtain such short bunches with reasonable rf voltage requires a very small value of the momentum compaction α, which can be obtained by using flexible momentum compaction (FMC) modules in the arcs[4]. A preliminary design of a complete collider ring has now been made; it uses an experimental insertion and arc modules as described in refs.[2]-[4] as well as a utility insertion. The layout of this ring is shown schematically in Fig.1, and its parameters are summarized in Tb.1. Though some engineering features are unrealistic, and the beam performance needs some imFigure 1. The complete collider ring layout.