Use of proportional tubes in a muon polarimeter

A prototype muon polarimeter was built to study the feasibility of measuring the positive muon polarization in the decay K_L→μ⁺μ^-. The system consisted of alternating layers of extruded-aluminum gas proportional tubes and polarization-retaining absorber plates of either aluminum or marble. Longitudinally polarized positive muons from the stopped muon channel at LAMPF were stopped in the absorber plates where they precessed in a field of 60 G. Decay times were recorded in 100-ns first-in-first-out memories for all wires hit during a 12.8-μs period centered about the muon stop trigger. The performance of the system was studied for different beam rates and absorber thicknesses. The value of imposing time and spatial cuts on track data to enhance the precession signal was also investigated. The study suggests that the goal of measuring the polarization with a sensitivity of 15% is obtainable