Delay Line Proportional Chambers for the Fermilab External Muon Identifier

Thirty nine, one meter square proportional chambers with delay line readout have been constructed for the external muon identifier of the Fermilab 15 foot bubble chamber. 1 They provide X, Y, U(45°) and T (avalanche time) information using a single wire plane, etched strip cathodes and nine amplifiers. They have a time resolution of ±27ns, single particle spatial resolution of ±2 to ±3mm and double particle resolution of ~2 1/2 to 4cm. The energy accessable to each wire is limited so none of the wires in the first 25 chambers has broken since their installation in 1973-4.