Cosmic Rays

A minor departure from things entirely radio today, into the fascinating world of fundamental particles and cosmic rays.  It could be your next practical activity, too!

 

Some years ago, I began running an American cosmic ray detector on my mobile phone.  It never seemed to work for long without trouble, and the academics supporting it were extremely poor and almost disinterested.

Then came along the fabulous CRAYFIS cosmic ray detector app for smartphones.  Well, being a Polish programme, I would say that!  This ran fairly well on my then ageing Android phone.  But eventually, it didn't run at all.  

The latest version of CRAYFIS seems to be faultless, and runs daily on my newer, but still quite basic Samsung phone.  

My muon detector starts to run yesterday afternoon.  It now lives under a wardrobe!

 

Then, earlier this year, I came across MuonPi.  This is based around a slab of plastic, which catches muons as they decelerate in the material, giving off tiny amounts of light in the process.  This is fed into a HAT circuit attached to any Raspberry Pi computer from model 2 onward.  A 3B+ is probably a good minimum-performance model to choose if you don't already have one.

The HAT takes time signals for extremely accurate synchronisation of data with other detectors from an attached GPS antenna.  I'm happy to say my system often has the best time of all detectors, currently at 22ns accuracy.  It also generally has the highest muon count rates, and best GPS position accuracy (as good as +/- 0.3m).

Hardware and software installation is relatively straightforward.  The detector, once assembled, can simply be shoved under your bed, or placed in a cupboard, etc; muons aren't stopped by everyday materials.  But in a bedroom, the many, very bright lights on the HAT will need some attenuation with a sock or other cover!

Active muon detectors yesterday evening, including mine!

The hardware is not free, but the small price only really covers the costs of Giessen University in making and sending out the kit to you.  In my case, it was about £87, including the postage.  The support provided is outstanding, and even includes online conferencing if you really get stuck.  Data for all stations is freely available via the Grafana page for the project.

Victor Hess, ca. 1912, about to take to the skies in a balloon.  He thus determined that strange radiation on the ground was reaching us from space, earning him a share of the 1936 Nobel Prize in Physics.  In 1938, with his Jewish wife, Hess fled his native Austria to America, in order to escape Nazi persecution.

 

If you need any motivation to take part, just remember that muons only get to the surface of Earth because their relativistic speeds (~0.9993c) result in their time, relative to ours, running much slower - about 27 times slower in fact.  Without accounting for special relativity, muons would only make it 660 metres down through the atmosphere before decay, and we would have taken a lot longer to know they existed.  With special relativity factored in, the muons travel over 17km before decay, far enough to reach the surface, and a little beyond.  A good text on this is found by scrolling down to 'Hall of Fame' on this site.

So you can see Einstein's special relativity in action, in your own home.  That's pretty amazing, as is the fact that most of the primary cosmic rays generating the muons possess energies way beyond what machines like the LHC can generate.