  The SeaQuest spectrometer at Fermilab was designed to detect
oppositely-charged pairs of muons (dimuons) produced by interactions between a
120 GeV proton beam and liquid hydrogen, liquid deuterium and solid nuclear
targets. The primary physics program uses the Drell-Yan process to probe
antiquark distributions in the target nucleon. The spectrometer consists of a
target system, two dipole magnets and four detector stations. The upstream
magnet is a closed-aperture solid iron magnet which also serves as the beam
dump, while the second magnet is an open aperture magnet. Each of the detector
stations consists of scintillator hodoscopes and a high-resolution tracking
device. The FPGA-based trigger compares the hodoscope signals to a set of
pre-programmed roads to determine if the event contains oppositely-signed,
high-mass muon pairs.
