Rectilinear six-dimensional ionization cooling channel for a muon collider: A theoretical and numerical study

Abstract

A muon collider requires a reduction of the six-dimensional emittance of the captured muon beam by several orders of magnitude. In this study, we describe a novel rectilinear cooling scheme that should meet this requirement. First, we present the conceptual design of our proposed scheme wherein we detail its basic features. Then, we establish the theoretical framework to predict and evaluate the performance of ionization cooling channels and discuss its application to our specific case. Finally, we present the first end-to-end simulation of 6D cooling for a muon collider and show a notable reduction of the 6D emittance by 5 orders of magnitude. We find good agreement between simulation and theory.

Unconventional ideas for ionization cooling of muons

“…The rectilinear channel [42] is tapered (also true of the helical channel) and grows smaller transversely as the muon beam cools [45]. Short solenoids provide strong focusing in short regions.…”

“…In simulation, the channel works both with vacuum and with hydrogen to prevent breakdown in the RF cavities [46]. [42] is shown on the left. B1 follows stages A1, A2, A3, and A4.…”

Emittance Measurement in the Muon Ionization Cooling Experiment

“…RF acceleration then restores longitudinal momentum, resulting in transverse emittance reduction. Several orders of magnitude in 6D cooling has been achieved in simulation [2].…”

Results from Mice Step IV

“…Ionization cooling [4] is the only technique that operates quickly enough to achieve the necessary phase space contraction with manageable losses. A factor of close to a million in 6D muon cooling has been reached in a simulation [5]. The rate of change in normalised emittance when passing through an absorber can be approximated by the following "cooling equation" [4] dε N ds…”