The Nagoya cosmic-ray muon spectrometer. 1. Apparatus

A new cosmic-ray muon spectrometer using a solid iron magnet has been constructed at Nagoya. The spectrometer detects muon tracks optically by wide gap spark chambers, mean detection efficiency of which is 95+-2%. The spark chambers are triggered by a time-of-flight counter system and the time resolution of this system is 11+-0.5 nsec F. W.H.M. Through an optical system of 10 mirrors and 2 cameras, the muon trajectories in spark chambers are photographed stereoscopically. To measure the coordinates of the spark images on the photographic films, an automatic scanning equipment using a solid-state image sensor has been developed. Aperture angle of this spectrometer is 57.1 cm2 sterad for the muon with infinite momentum. The maximum detectable momentum is estimated over 10 TeV/c by the Monte Carlo calculation including the effect due to the detection efficiency of spark chambers