MGR: An innovative, low-cost and compact cosmic-ray detector

We will illustrate the design, assembly and test of an innovative, compact and low-cost cosmic-ray tracking detector developed at the INFN laboratories of Trieste and Perugia (Italy), which makes use of the most recent technologies for scintillating fibres and multianode photomultiplier tubes. The detector has been designed in particular for underground investigation: it lies inside a cylinder made of aluminium and can be lowered down a 20 cm diameter hole drilled into the ground, reaching a depth of 10–30 m. It measures the cosmic ground penetrating muon flux as a function of the direction to obtain information about the density of the material through which the cosmic rays travel before reaching the detector itself. The whole instrumentation (that is, the detector, a computer for data acquisition and a power supply), is simple to install and easy to handle. Examples of fields in which the instrument can be useful are geology, archaeology, spelaeology. In the last few months we tested the performance of the detector in two different Italian archaeological sites (Aquileia, UD and Fiumicino, RM). The acquired data are presented in this work.