Operation and performance of the FAST detector at the AD machine

The FAST (Fiber Antiproton Scintillating Tracker) detector has been installed at the Antiproton Decelerator at the CERN PS. Its goal is the measurement of the annihilation cross section of slow antiprotons (around 5 MeV) in gaseous targets in the ASACUSA experiment. FAST has to reconstruct the charged pions tracks to identify the annihilation vertices.The detector consists of 2 axial and 4 stereo layers of scintillating fibers. Each layer is built with 1 mm 50 cm long BCF-10 fibers readout by 64 channel multianode PMTs for a total of 2688 readout channels. The anode outputs, amplified and discriminated, are sampled with a 320 MHz clock inside a Cyclone II FPGA by Altera, in order to retrieve the time information of each hit. The readout system is designed to cope with a spilled beam which lasts 250 ns every minute. The expected number of events per spill was around 10.This paper will describe the operation and the performance of the FAST detector during the tests with cosmic rays (August 2006) and during the data taking on the beam (September 2006).