Frontend and readout electronics of the MICE Electron Muon Ranger detector

The MICE experiment is being commissioned at RAL to study the feasibility of a Neutrino Factory: muons are cooled by a dedicated system based on radiofrequency while the particle ID is performed by a KLOE-light detector followed by EMR (Electron Muon Ranger), a fully active tracker-calorimeter positioned at the end of the beamline. EMR consists of 48 planes of 59 1.1 m long scintillator bars with a triangular section. The light in each bar is collected by one 1.2 mm WLS fiber and is readout by a single PMT (Philips XP2972) on one side to provide the information on the charge deposit in the plane and a 64 channel multianode PMT (Hamamatsu) on the other one to digitize the trigger output of each single bar. The single PMT is readout by a CAEN V1731 Waveform Digitizer, while the frontend electronics to treat the multianode signals is organized in two near-detector boards: a FEB (FrontEnd Board) and a buffer board. The FEB hosts a dedicated socket for the MAPMT, the frontend ASIC and two control FPGAs (Altera CYCLONE II) while the buffer board stores the data during the spill. The PMT is connected to the FEB through a flexible multilayer kapton cable. The 64 MAPMT signals are pre-amplified, shaped and discriminated by the MAROC-2 (Omega, LAL), a low noise single power rail ASIC with multiplexed analog and parallel digital outputs. The experiment foresees one event every 5 µs during a spill of 1 ms every 1 s. The 64 discriminated signals are sampled with a 400 MHz clock and in presence of the experiment trigger, the above threshold bars numbers are stored together with a timestamp in the buffer board to be sent to the VME DAQ system during the interspill. The communication is based on the TLK1501 Gigabit link: 6 buffer boards are daisy chained for a total of 8 VME control boards. A configuration board completes the DAQ and is responsible of the configuration of the frontend and of the distribution of the trigger and synchronization clock signals. This paper presents the tests of the electronics and its performance both with a small EMR prototype with square bars and in the test system for the mass production of the final modules.