Cosmic Pi

Cosmic Pi - a low cost distributed cosmic ray detector, based on Raspberry Pi.

Cosmic rays are everywhere, flying through the atmosphere, our bodies, our computers, everything. Previously the detection and analysis of Cosmic Rays was the exclusive domain of high energy physicists. We aim to make the detection and analysis of cosmic rays accessible to students, educators and ordinary people with an interest. The Cosmic Pi started as an after work project at CERN and is available here under the CERN OHL for all to build. It uses a specially designed detector combined with the low cost hardware of the Raspberry Pi computer for data storage and online analysis.

At the moment we're using the free version of EagleCAD to develop our electronics and all files available for download are in this format.

As featured in THE Port 2014 (Pier X1 team).

Latest news 26/3/17:
We've now completed assembly and distribution of our first 40 units (Version 1). However we have some issues with the signal/noise ratio. We're working on some changes to our Arudino firmware to attempt to fix this. We're also going to start development of a Version 2 to address the issues we've found on our Version 1. This will be starting in April.
Issue tracking is now turned on, if you have issues with the design you can track them here under the issues tab.

Known bugs with Version 1
The current mainline firmware has issues adjusting the voltage and thresholds applied to the SiPM detectors, leading to very high noise at the output. A significant part of this issue is due to a single HV supply for the biassing of both SiPM's, which will be addressed in Version 2. We are also working on delivery of a client to run on the PC (Linux) - for connection to our servers.

Technical Specification Prototype 1
*Low cost plastic scintillator detection medium
*SiPMT readout from scintillator
*On-board multi-stage analog front end
*Coincidence triggering with variable threshold
*2 channel, 12 bit ADC
*Integrated -72V DC power supply (Version 1)
*GPS for detector localisation and 300uS timing accuracy
*33 MHz event clock (Version 1)
*MEMS barometer for altitude and atmospheric pressure
*I2C Temperature & Relative Humidity sensor for calibration and Scintillator monitoring
*Raspberry Pi Hat form factor compatible for easy integration with Raspberry Pi
*Data acquisition, representation and storage software stack written in Python
*Fully open source design, released under CERN Open Hardware License to encourage widespread use and adoption

Known bugs with Prototype 1
Lots: Hard limit of 1 Hz for event rate due to timer implementation, Murata PSU isn't suitable for SiPMT as it's too noisy. The ADC's are not pipelined and we have issues getting the Raspberry Pi to respond fast enough via the interrupt using standard Raspian. Version 2 is going to have a different hardware architecture to avoid these flaws!

Block diagram

Project information


Commercial producers

  • Work in progress


  • James Devine - General question about project
  • Cosimo Cantini
  • Etam Noah
  • Hugo Day
  • Justin Salmon
  • Le├»la Haegel
  • Ruslan Asfandiyarov
  • Julian Lewis

Project Status

Date Event
02-08-2012 Prototype Cosmic Ray Detector using Android Phone at CERN Webfest
02-11-2014 Development of Prototype Version 1 for The Port Hackathon @ CERN
09-03-2016 Working on custom analog amplifier board
07-04-2016 Analog amplifier board ready for assembly and test

25 June 2015

CosmicPiVersion1Arch.jpg (64.4 kB) James Devine, 2015-06-25 10:18

Proto1.JPG (76.2 kB) James Devine, 2016-03-09 17:26

Proto2.JPG (86.6 kB) James Devine, 2016-03-09 17:26