The TJNAF Hall B is equipped with a
Large Acceptance Spectrometer (CLAS) based on a toroidal magnetic filed. This field is
generated by six superconducting coils arranged around the beam line to produce a magnetic
field primarily in the PHI direction. Each region between two coils is equipped with a)
three layers of drift chambers to track charged particles, b) a Cherenkov counter to
discriminate electrons from negative pions, c) scintillation counters for the time of
flight measurements and, finally, d) an electromagnetic shower calorimeter to detect
electrons and photons
The AIACE collaboration designed,built and calibrated two
modules of the Large Angle Calorimeter (LAC) of the CLAS spectrometer to detect particles
at angles up to 70deg in the laboratory system. The LAC is also used for the
electron/pion discrimination, the detection of photons from the decay of neutral mesons as
PIzero and/or ETA and the measurement of neutron momentum using time-of-flight technique.