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The MuonPi Cosmic Detector Project

The MuonPi Project is a RaspberryPi-based system using an inexpensive plastic scintillator + SiPM photo sensor to detect muons from cosmic air showers with a time-stamping accuracy of several tens of nanoseconds utilizing the u-blox NEO-M8N GNSS module's "timemark" feature.

Learn about cosmic radiation

Learn about the detectors

Related and similar projects

  • CosmicPi: A CERN-based project that aims to build the world's largest open-source distributed cosmic ray telescope.
  • HiSPARC: A distributed muon detection network aimed for high-schools and an experience of over 15 years.
  • Thundercloud Project: Exploring high-energy phenomena in thundercloud and lightning. -> Nature Article
  • Cosmic Watch: Cosmic Watch is simple, physics-motivated machine- and electronics-shop project for university students and schools.
  • A truly inspiring community-based network for the detection and triangulation of lightning and thunderstorms.

The Hardware


The SiPM photo sensor which detects the dim light generated inside the scintillation detector is mounted on a small SiPM board. Different numbers of SiPMs and read-out configurations can be realized through it's flexible design.


The preamplifier is located in close vicinity to the SiPM photodetector board and amplifies the weak signals for transmission to the MuonPi board, where they are further processed and evaluated.

The MuonPi-Board

The main signal processing, voltage generation and parameter monitoring and adjustment is done on the Raspberry Pi plug-on MuonPi Board. The board's design is open source hardware and exhibits only commercially available off-the-shelf components which can be obtained from several distributors. With some soldering experience, the MuonPi HAT can be assembled utilizing a standard soldering equipment. A how-to guide and useful hints are available in the Assembly Guide.

The Software

The MuonPi software collection is entirely open source and available on github It consists of several components:

  • muondetector-daemon The main control program running as a background system service on the RPi. The daemon configures, controls and supervises the components on the MuonPi HAT board, handles the comunication to the u-Blox chip and to the outside world via MQTT link and direct access socket, monitors system parameters, such as temperature, voltages, curent, rates etc., performs statistics collections, calculations and logging and much more. The daemon can be installed through the standard system software management tools (such as apt) from our package repository or compiled from the github source and is everything which is needed to operate a MuonPi detector.
  • muondetector-gui A graphical user interface (GUI) program which can be launched on any computer in the same network as the MuonPi detector in order to monitor and adjust all operation parameters of the detector, if required. The GUI is available for download as binary package for several platforms (Raspbian, Ubuntu, Windows) or can be compiled from the current github master branch.
  • muondetector-login A small command line helper tool to initially set up the MQTT telemetry link. The program will ask for the supplied MQTT credentials and stores them locally in encrypted form for continuous use.
  • muondetector-cluster Allows the operation of a multi-detector cluster as an entity. The program is the cluster head or interface towards the server, searches for coincidences within the cluster and sends the combined coincidence events instead of the single event telegrams to the server. One cluster instance is also running on the main server collecting the data streams from the entire network, finding the online coincidences and writing the coincidence events as well as detailed logs and statistics summaries into the MuonPi InfluxDB database. The source code is available in the cluster github repository.

Setup and Operation of the Detector

Here you find a collection of HOW-TOs useful to procure, set up, and operate a detector:

The completed setup is fairly insensitive to the location where it will operate. Basic requirement is a good GPS signal, low humidity and obviously power and network connectivity. A stable temperature for the scintillator and preamp is desirable, as it affects the noise level of the setup. Muons will penetrate several meters of granite rock, so placing the detector in the basement leaves the muon measurements unaffected. However due to radon collection in basement rooms and potassium decay a slightly higher natural radioactive background can be observed.

In case there are problems with the set-up or operation of the detector, have a look in the Troubleshooting section.

Related Articles

News and articles about cosmic rays and similar projects.

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