Abstract:

Primary cosmic rays are high-energy particles, mostly protons, that come from space and constantly hit the higher part of the Earth’s atmosphere. They arrive mostly from the sun and, to a lesser extent, from deep space. When primary cosmic rays collide with molecules in the Earth's atmosphere, they produce large showers of secondary particles like pions, kaons and muons. In particular, muons can reach the Earth's surface, contributing to about 10% of the total natural radioactivity. Detection of these secondary particles is relatively simple and can be a used as a valuable didactic experience to introduce high-school students to modern physics.

In recent years, we have developed a relatively simple “muon telescope”, which has been installed at the Legnaro National Laboratories (LNL), one of the four national laboratories of the Italian National institute for Nuclear Physics (INFN). It is made by two plastic-scintillator plates one above the other at a distance of 72 cm and mounted on a structure that can be rotated at angles between 0 and 90 degrees with respect to the vertical direction. A muon particle is counted by two coincident signals in both plates. The particle counting is done by an electronic board with an integration time window of 1 minute. The same board is also recording environmental variables (temperature and atmospheric pressure) that can influence the counting rate. A simple data acquisition system based on a Raspberry Pi 3 board produces daily files containing records of counting data, atmospheric pressure and temperature. Files are available for download in a public repository.

The instrument's characteristics allow it to be used for different types of activities both in person and remotely. LNL regularly hosts groups of students from different schools, mainly from the Veneto region, for afternoons that are dedicated to measuring cosmic rays. Thanks to the rotating structure of the telescope, a typical experiment is the measurement of the muon flux at various angles with respect to the vertical direction. The aim of this activity is to discuss and model the atmospheric penetration of cosmic rays and, more generally, handling the inherent errors of each experimental measurement. Thanks to the availability online of historical data since 2022, students can also work remotely (at home or at school) to analyze the correlations of environmental variables with the muon flux on a monthly or even annual basis. The data analysis is a good exercise to apply concepts like statistical average, statistical and systematic errors as well as an opportunity to develop computer skills through the use of programming languages like Python or C++.

Furthermore, during the years, some groups of students, inspired by our work, developed their own cosmic ray detector under the teacher’s guidance and with our advice and monitoring.

Keywords:

STEM Education, hands-on workshop.