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 m 2 ) 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.

Izaña Cosmic Ray Observatory

“…ICaRO ICRM, form ICaRO. ICRO is a standard 3NM64 neutron monitor, ICRB is a set of three boron trifluoride (3BNM) bare counter tubes and ICRM is a muon telescope based on the MITO design [5], which consists of two 1𝑚 2 scintillators, one at the top of ICaRO and the second at the bottom (see Figure 3). The technical characteristics are shown in Table 1.…”

“…The muon telescope in ICaRO is based on the Muon Impact-Tracer Observer (MITO) [5]. This is a telescope composed by a stack of two BC-400 organic scintillators (100 cm x 100 cm x 5 cm, polyvinil-toluene with a light output 65% of that of antrhacene), placed at the top and bottom of a metallic structure (and thus, named Top and Bottom), 136.5 cm apart FROM each other, with ICRB and ICRO, and therefore, a 10 cm layer of lead in between (dark grey rings around ICRO tubes in Figure 3).…”

“…These four coincidence configurations can be changed to any possible combination of the eight PMTs. As it was stated above, it is possible to establish a relationship between the particle impact point on the scintillator plane and the light gathered through the opposite lateral sides [5]. A different approach to the estimation of the impact point based on a neural network approach can be found in [6].…”

ICaRO: a new cosmic ray detector at Izaña Atmospheric Observatory

“…The Izaña Cosmic Ray Observatory (ICaRO) is a ORCA's twin instrument. ICaRO will measure neutron and moun counting rates, and muon incident direction thanks to two instruments, NEMO and MITO [9,10]. Both instruments share a common structure which keeps the relative position of the dierent elements of NEMO and MITO.…”

“…The Muon Impact-Tracer Observer (MITO) [10] is a telescope made by a stack of two (MITO-Top and MITO-Bottom) BC-400 organic scintillators (100 cm x 100 cm x 5 cm, poly-vinyl-toluene with 65% anthracene). Four photomultipliers tubes (PMTs) are coupled to each scintillator by means of a pyramidal light guide.…”