Reverse Emittance Exchange for Muon Colliders

79264 In the proposed muon collider, luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. However, an adequate luminosity requires large muon intensities because, as presently envisioned, the method to cool the beam, ionization cooling, does not cool the beam sufficiently to provide adequate luminosity without large muon intensities. This leads to several problems: (1) the proton drivers to produce the required muon intensity are expensive, (2) neutrino induced radiation is an environmental problem, and (3) the decays of the large number of muons in the storage ring make experiments difficult. To address these problems, six-dimensional cooling schemes are being developed that would allow smaller, high-frequency radio frequency (RF) cavities to be used for later cooling stages and for acceleration. However, the bunch length at collision energy becomes shorter than needed to match the interaction region beta function. This project will develop a new concept for shrinking transverse beam dimensions by lengthening each bunch (reverse emittance exchange) to achieve high luminosity in a muon collider with fewer muons. In Phase I, computer simulations will be used to confirm the general analytical predictions. Critical technical issues will be identified for computational and experimental investigation in Phase II. Commercial Applications and Other Benefits as described by the awardee: The technology should allow the requirements for muon production rates to be relaxed enough so that existing or near future facilities could be modified for use as a muon collider. If the case for a muon collider as the next energy frontier machine can be made compelling, it becomes a candidate to be added to the other options for the High Energy Physics community.