A Proof-of-Principal Experiment for a High-Power Target System

The MERIT experiment, to be run at CERN in 2007, is a proof-of-principle test for a target system that converts a 4-MW proton beam into a high-intensity muon beam for either a neutrino factory complex or a muon collider. The target system is based on a free mercury jet that intercepts an intense proton beam inside a 15-T solenoidal magnetic field. A muon collider or neutrino factory requires intense beams of muons, which are obtained from the decay of pions. Pion production by a proton beam is maximized by use of a high-Z target such as mercury. A liquid jet target has the advantages over a solid target that a flowing jet can readily remove heat and that it is immune to radiation damage. However the proton beam energy disrupts the jet and the system could be operationally unstable. Efficient capture of low-energy secondary pions (for transfer into the subsequent muon accelerator complex) requires that the target system be immersed in a strong magnetic field of solenoidal geometry. This magnetic field should stabilize the mercury flow in regions of nearly uniform field, but it perturbs the liquid metal jet as it enters the field. Hence, the behavior of the mercury jet plus an intense proton beam inside a strong magnetic field needs to be understood better before resources are committed to a larger facility. The MERIT experiment is to be conducted at CERN in 2007 for this purpose.