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DECO is a citizen science project that enables users around the world to detect cosmic rays and other energetic particles with their cell phones and tablets. The recorded events are automatically uploaded to a central database. In addition to detecting particle events, users can analyze the data produced by their own or other users’ phones.

Source: CERN

Cosmic rays are energetic subatomic particles produced by powerful cosmic accelerators such as black holes and exploding stars. When they hit the top of the atmosphere, they produce showers of secondary particles, including electrons, photons, neutrinos, and muons. Many of these muons, which are particles similar to electrons but heavier, reach the ground at sea level and are a great tool to study cosmic rays because they are easy to detect.

Digital camera sensors detect muons in much the same way that they detect photons when we take a picture of friends or a landscape. When a cosmic-ray muon hits the camera sensor, it liberates some electrons. The accumulated charge tells us about the energy of the incoming particle, while the distribution of this charge in our sensor, the shape, tells us about the kind of particle that has produced it.

The DECO app currently runs on Android OS devices. Information about how it works and how to install it can be found below.

Data

Data can be downloaded in this data repository.

Teacher and student summer internships – apply by April 7

WIPAC is looking for one high school teacher and a few students to develop data analysis tools for DECO. These are paid internships with a commitment of up to 6 weeks for students and up to 8 weeks for the teacher.
Further details can be found here: teacher leaflet and poster, student leaflet and poster.

How does the DECO app work?

Screen shot of the DECO app

DECO works by recording a camera image, called a sample, once every 1-2 seconds. The app analyzes the image to determine bright pixels.
If enough bright pixels are found, the sample is considered a candidate for a high-energy particle interaction. A second analysis performs more thorough follow-up processing to determine if the candidate should be considered an event. Many events are due to cosmic-ray muons, but DECO can also detect electrons, gamma rays, and alpha particles (helium nuclei) produced by the decay of trace amounts of radioactive elements that occur naturally in the environment and in the materials of the phone.
Only a small fraction of the samples turn out to be candidates, and a fraction of these are classified as events. For a typical device, you need to run the app for around 24 hours to get a few events.
Every time you start data taking with DECO, the app performs a short calibration procedure to measure the background noise in the sensor.

Example images from various particles (obtained by zooming in on the signal region of the full recorded image):

A straight "track" shape indicates a muon produced by a cosmic ray

A "worm" shape indicates an electron produced by a radioactive decay that either produced an electron directly or produced a gamma ray that then knocked loose an electon

A "spot" shape indicates an electron or gamma ray

"Multi-hit" patterns such as this are intriguing, with several possible origins

How do I run DECO on my device?

DECO currently runs on Android OS devices. We are working on an iOS version that will be launched in 2015.
You need two apps to run DECO: the data logger (download) and the DECO app (download). The apps are in beta development. Please send any problems or suggestions for improvement to Justin Vandenbroucke or Silvia Bravo.
The data logger automatically synchronizes event data to a central database. Please note that this includes geolocation data. These data are essential for comparing cosmic ray rates at different locations and altitudes and also for detecting the same high-energy cosmic-ray shower with multiple devices. The data logger automatically synchronizes data to a central database.
The apps use a data connection to upload to the database. We recommend using WiFi to avoid charges due to wireless data usage.
A few suggestions:

Cover the lens of the camera (electrical tape works well) in order to minimize background light.
The phone can be placed in any orientation, but it’s easiest to keep it dark if it is face up, with the main camera facing down, on a flat surface.
Muons can penetrate through roofs and walls, so it does not matter if you place the phone inside or outside, near a window or not, or on the top or bottom floor of a building.
Run the app with the phone plugged in because it will only last a few hours on battery power.

Google group

We recommend joining the “deco-users” Google group to be informed of future releases and participate in discussions of DECO and its data. You can join the group here.

User's guide

You can download a guide to getting started with DECO here.

DECO for education

WIPAC is working with students and teachers to develop resources for using the app in formal and informal educational environments.
DECO is a unique app for learning about cosmic rays, physics, and astronomy, but it also serves as a means to:

develop research experiences through hands-on and inquiry-based learning
develop a collaborative mindset and a goal-oriented approach to learning
incorporate critical thinking, problem solving and communication skills
learn how to use technology to address a problem

If you are a teacher interested in collaborating with us or using the app in the classroom, please write to Silvia Bravo or Justin Vandenbroucke.
DECO is made possible by support from the American Physical Society, the Knight Foundation, and the Simon-Strauss Foundation. Teacher participation is supported by QuarkNet.