Muon Collider/Neutrino Factory: Status and Prospects
  During the 1990s an international collaboration has been studying the possibility of constructing and operating a high-energy high-luminosity $\mu^+\mu^-$ collider. Such a machine could be the approach of choice to extend our discovery reach beyond that of the LHC. More recently, a growing collaboration is exploring the potential of a stored-muon-beam "neutrino factory" to elucidate neutrino oscillations. A neutrino factory could be an attractive stepping-stone to a muon collider. Its construction, possibly feasible within the coming decade, could have substantial impact on neutrino physics. 
Daniel M. Kaplan