Tag Archives: CERN

Building a distributed cosmic ray detector in a weekend at CERN Webfest

This weekend I made a Android/Arduino based web enabled Muon (Cosmic ray) detector. I have to give a tonne of thanks to the team who did it with me (Ramviyas, Olof, Brad, Justin and Hugo) who deserve full credit for making it happen. I should also thank the ERGO Telescope team for thinking up the whole scheme of a distributed cosmic ray observatory in the first place and sending us the missing elements for our project.

Our Muon Source


One ERGO pixel unit (which I hacked)

One Geiger-Muller tube and amp/PSU board (which we didn’t use in the end)

One Arduino MEGA ADK

Arduino Mega ADK

One Android Phone (with GPS, running 2.3.4 or better) – we used a Samsung Galaxy Mini GT-S5570

CNY17 optocoupler

Some Arduino Code, some Java and some web scripting

Muon Detector (ERGO Pixel)


1) We hooked up the GM tube (in the end I had to hack the LED on the front of the ERGO box) to the Arduino MEGA ADK via a CNY-17 Opto-isolator. The signals out of the Geiger-Muller tube PCB were a bit too noisy to use straight up, and I didn’t manage to build myself a suitable high impedance device/amp to read them directly. We did the whole project in a weekend, so there wasn’t much time for anything!

Writing code…

2)We wrote some Arduino code that will hook up to an android phone and log events with an accuracy of 0.000212s. This is effectively a polling loop which checks a single input pin repeatedly and sends a signal to the Android when it sees a logical high on the input. The code will take any input on pin2 and output a packet with the relative timestamp to the Android. With this method we can resolve to approx 4700 loop cycles within the Arduino, using a counter (declared as a simple int that we add to). The counter is also re-set each 1s by a signal from the Android GPS clock. Counter values at reset are logged to use for a rolling timing calibration, but we didn’t get chance to implement this in the weekend.
3)We wrote an android app that reads NMEA sentences to get the raw time out of the GPS chipset (tested on Samsung phones running Android 2.3.4 and cyanogenmod) and sends a reset to the Arduino every second based on this value. The app also receives signals from the Arduino with the local timestamp (the loop counter in the Arduino) and adds this to the Navstar time (being the correct name for GPS time) We also correct the Arduino timestamp by multiplication with the constant of 0.000212 (our measured resolvable time interval) which bring the Arduino timestamp into seconds. We couldn’t get the date out of the GPS, so the leapsecond (Navstar time is 13 seconds behind UTC at the moment) correction will be necessary to datestamp it correctly – unless we figure out how to get the date from GPS directly.
4) For the moment we’re pushing it via HTTP post to  http://posttestserver.com/data/2012/08/05/populous/  Eventually we will send it to the ERGO database, once we have done some more precise measurements of the timing accuracy.

The Android App in action

We have a few things that would also be nice to add:
The Arduino code could do with some optimisation – we can probably increase the timing accuracy significantly (but this will obviously take more time than we had over the weekend) to go beyond the 212 microsecond resolution. It’s also running as a polling loop without any de-bounce, so duplicate readings are a distinct possibility. Using interrupts caused problems with the Arduino crashing, I’ll put it on my list to figure out when I have time.

Our system timing and architecture drawing

Timing calibration has been worked out on the back of an envelope, with some work the Android could do a rolling calibration on the Arduino (so that the 4700 loop cycles are adjusted based on observed performance).

As for the GM tube interface (which I struggled with), SEEED studio make a geiger shield that at first glance it looks like it would plug straight in fine – the design is open source as well. It can be found here: http://www.seeedstudio.com/depot/grove-geiger-counter-p-867.html?cPath=190

A great team!

That’s everything for the moment –  here are some links for the resources/websites we used/made:
Source code (arduino and android): https://github.com/jussy/cern-webfest
Pirate pads (where we did the working out..) http://piratepad.net/ep/pad/view/ro.-NYTlmpQZIl/latest
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My Day Job – from Anticipations Magazine

A while ago (Nov 2010) I wrote a short article about my new job at CERN for Anticipations, the magazine of the Young Fabians. Mostly it’s full of left/centre left politics/social issues related articles, but they also have a ‘My Day Job’ column for people to write in with ‘genuinely’ interesting jobs. Hopefully mine fits the bill!

Last month I started a new job. By almost all measures, it’s rather unusual – It involves a massive high voltage electrical network, but this isn’t the National Grid, over 27km of underground tunnel system, but it’s not the London Underground, international co-operation on a huge scale, though this isn’t (quite!) the United Nations. I’m lucky enough to work on a small part of what is arguably the most complicated and technically advanced machine ever created by the human race, so far… I work at CERN, home of the Large Hadron Collider.

 CERN is an international collaboration in the field of particle physics which was founded by a number of European nations in 1954. The UK was one of the twelve founder members and continues to benefit from access to the unique research facilities which CERN offers. On a typical day here there may be up to ten thousand people on site (which spans the French-Swiss border near Geneva), the majority of whom are research physicists. They are the ‘users’ of the huge underground machines. The remainder of those on site are permanent staff responsible for running CERN (everything from catering contracts to particle accelerator design and engineering) number only about two thousand, which makes for a demanding working environment. The collaboration exists to provide facilities which are far beyond the scale and scope of what individual member could achieve on their own. At CERN active research takes place in fundamental physics across the board, rather than the specific quest for the next ‘new’ particle such as the Higgs Boson. Although of course everyone here is hoping that the discovery of the Higgs will be made possible by the LHC.

  As an electrical engineer, my particular work involves the provision of power supplies for the particle accelerators and physics experiments. At the moment I’m working on some new supplies for the safety system which protects the particle beams circulating within the LHC and the new experimental ground control room for the Alpha Magnetic Spectrometer, which is scheduled to be attached to the International Space Station next year and will be searching for dark matter and anti-matter in space.

 The languages that I’ve heard spoken so far since my arrival include English, French, German, Portuguese and Japanese as well as many others that I can’t yet recognise! The electrical team I work in is predominantly French speaking, although as part of the procurement procedure all major items of work must be tendered in a process, open exclusively to companies from member states (which now include 20 European nations) with all documentation provided in English. Most of my colleagues have a good degree of fluency in two languages, with a few being fully tri- or even quad-lingual! The majority of my meetings take place in French and when projects come to the implementation stage most of the workers actually doing the construction and installation work are also French speakers. I studied French at A-level and throughout university, though at the moment working in a foreign language every day is proving to be a real (and enjoyable) challenge!

 Of course, it isn’t just about the job. I’ve had to move countries to come here, which like all major changes in life brings both advantages and inconveniences. The best thing about being here so far is definitely the food. The range of wines and cheeses available in local shops is superb, with competitive prices. The countryside here is breath-taking, I can see snow covered mountains from my office window, and on clear day even Mt Blanc! The biggest downside is that I’ve left my friends and family behind in the UK. Fortunately flights from Geneva to London are frequent and not too expensive, so I can at least visit regularly. The ski season is also rapidly approaching so I’m expecting an influx of welcome visitors to take advantage of cheap (free!) accommodation on the floor of my flat and the proximity of many nearby ski slopes.

 It’s probably a fair question to ask how I ended up in my current position, so here’s a little explanation: I first visited CERN back in 1999, as part of an international school trip I persuaded my parents to send me on (thanks Mum & Dad!). During that first visit I was inspired by the possibilities of the groundbreaking physics research and the incredible machines being constructed here. After graduating with a degree in Electrical Engineering, I was able to obtain a CERN ‘Summer Student’ internship in 2005. During my internship I worked directly on a tiny (just 10 square centimetres across) part of the particle detection system for one of the gigantic physics experiment called LHCb, which is part of the LHC complex. I highly recommend applying for the CERN programme to anyone currently studying a Physics, Engineering or Computing related course at the moment!

 After finishing my internship, I spent 5 years working in the UK construction sector, designing buildings. At the same time I was making progress towards obtaining my registration as a Chartered Engineer, which can only be gained through a period of working as an engineer. Demonstrating good progress towards registration was an integral part of the application for my current position at CERN. I was able to achieve Chartered Engineer status just before taking up my new role here.

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