MITO: a new directional muon telescope

Abstract

Muon telescopes are instruments devoted to the observation of muons. They are produced in the atmosphere by means of the interaction of cosmic ray and solar energetic particles with atmospheric nuclei. Muons, as cosmic rays that produce them, present non uniform arrival directions and temporal variations at ground level and, along certain observation directions, could forecast the arrival of interplanetary coronal mass ejections (ICMEs) at the Earth, even earlier than neutron monitors. However, multidirectional muon telescopes are not easily affordable because of their complexity, size and cost. In this work, we present the muon impact tracer and observer (MITO) design concept. It is composed of only two stacked scintillators (1 m2) with an optional lead layer that allows the filtering of unwanted particles depending on the type of application. In the case presented here, a 10 cm lead layer corresponding to the lead of a 3NM64 neutron monitor around which MITO has been built. Eight photomultipliers (PMTs) gather the light emerging from the four lateral sides of the scintillators. MITO has been conceived not only to achieve muon flux registering, but also to register muon arrival directions through the capture and analysis of multiple PMT pulse height data. The number of scintillators and electronic components is reduced, simplifying its design and construction and reducing complexity, volume, weight, power consumption and cost, and thus, achieving a reasonable performance-cost ratio in comparison to other directional telescopes based on two-layer matrices. The first prototype was shipped from Spain to Antarctica where it is now recording data. Some preliminary results are also presented.

Keywords

• cosmic ray
• instrumentation
• muon telesope