The prototype of the MICE Electron–Muon Ranger: Design, construction and test

Muon Ionization Cooling Experiment (MICE) and its goal to demonstrate the feasibility of ionization cooling represent the first step toward a neutrino factory. Muons in MICE are produced by pions which derive from the interaction of protons with a target. Muons being short lived particles, a special cooling procedure has to be developed, to be able to reduce the emittance quickly. MICE intends to measure the emittance value with a 0.1% accuracy before and after the cooling element; thus a detector able to reconstruct and identify individual particles is required. The presence of electrons due to muon decay introduces a systematic error on the emittance and cooling measurements. For this reason a particle identification system is being developed based on a totally active scintillator tracker/calorimeter (Electron–Muon Ranger (EMR)). The detector consists of 40 planes of extruded scintillator bars 1 m long; the bars are read out with 0.8 mm WLS fibers coupled to multianode photomultipliers. The readout segmentation will be chosen accordingly to the rate (600 good muons per 1 ms spill every 1 s).
This paper describes the design, construction and test at the CERN PS T9-line of the first small size prototype of the EMR with full analog readout, consisting of eight layers (4 x and 4 y) with 10 bars 19 cm long each.