The Run 2 DØ Muon System at the Fermilab Tevatron

The Run 2 DØ muon detector at the Fermilab Tevatron has three subsystems: Proportional Drift Tubes (PDTs), Mini-Drift Tubes (MDTs) and trigger scintillation counters. The PDTs were used in the 1992-1996 data taking run and provide tracking coverage for pseudorapidity | η | ≤ 1.0. The forward muon tracking system, new for Run II, uses planes of mini-drift tubes and extends muon detection to | η | = 2.0. Scintillation counters are used for triggering and for cosmic muon and accelerator backgrounds rejection. Toroidal magnets and special shielding complete the muon system. All subsystems interact with 3 levels of triggers. Level 1 generates trigger information synchronously with the beam crossing. Level 2 operates asynchronously with a maximum decision time of 0.1msec. All three muon detector subsystems use a common readout system based on a 16-bit fixed point digital signal processor, which buffers the data from the front-end, re-formats the data if accepted by Level 2 and sends it to the Level 3 trigger system, which is a farm of Linux workstations running software trigger filters. Muon triggers accepted by Level 3 are written to tape for offline reconstruction.