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Cosmic Watch Muon Detectors

Contact: Spencer N. Axani (

Office: 5323 WiPAC Building
222 W. Washington Ave. #500
Madison WI 53703

The CosmicWatch Desktop Muon Detectors are an MIT based undergraduate-level physics project that incorporates various aspects of electronics-shop and machine-shop technical development. The itself is a self-contained apparatus that employs plastic scintillator as a detection medium and a silicon photomultiplier for light collection. These detectors can be battery powered and used in conjunction with the provided software to make interesting physics measurements.

Information regarding the detectors or program can be found on our website:

The CosmicWatch Desktop Muon Detector consists of a 5 cm×5 cm×1 cm slab of solid plastic scintillator instrumented with a silicon photomultiplier (SiPM) to detect scintillation light emitted from charged particles as they pass through the scintillator. The signal from the SiPM is sent through a custom designed printed circuit board (PCB) which shapes the signal such that a micro-controller can measure the time and amplitude of the SiPM signal. We use an Arduino Nano to measure the pulse amplitude and record the count number, time of the event, pulse amplitude, and detector dead time. The threshold for a signal from the SiPM to trigger the data acquisition can be tuned in the provided Arduino software. The detector can be powered by a mini-USB to USB connector.


The detectors are capable of making various measurements, including measuring:
1. the angular distribution of cosmic ray muons
2. the altitude of an airplane (Figure below)
3. the amount of overburden above the detector, such as underground or in the basement of a building
4. radioactivity in materials, particularly gamma rays
The participants working on the project will become proficient in soldering and populating printed circuit boards, trouble shooting electronics using oscilloscopes and waveform generators, and understanding the basic principles behind particle detection. Beyond this, participants will also gain experience using the programing language Python and reading/writing code for Arduinos.

The first day will be used to give a breif introduction into the project, then move to the lab and build a complete detector. This will involve learning about surface mount technology, learning to solder, and testing the electronics. The second day will be dedicated to building a second detector in the morning, then using both detectors to begin making measurements. During the final day, we will begin working with the data, which will include writing a python based plotting program.

The only recommended equipment for the project would be a laptop (preferentially MAC or Linux based, but we will be able to set things up on Windows as well, if needed). There are no serious safety concerns, however, students will work with radioactive sources and soldering irons.

The material cost of each detector is approximately $100. If the participants would like to keep the detector that they build, or put together a kit to bring back with them, they will be required to pay for the material cost. We will be working in a lab at the Wisconsin IceCube Particle Astrophysics Center (WiPAC) in Madison Wisconsin. 

Further information on the detectors or the project can be found here:

In particular, the instructions.pdf document goes through in detail how to build and test the detectors.