What to detect

A project log for Low-Cost Solid-State Cosmic Ray Observatory

Multiple nodes detect photons to within nanoseconds to analyze cosmic ray air showers and help solve the Greisen-Zatsepin-Kuzmin paradox.

aelias36aelias36 08/31/2014 at 02:331 Comment

I've been doing a bit of reading on other solid state detectors and have decided that it's a great idea to detect muons rather than gamma rays. Secondary showers consist mainly of electrons, photons, and muons. Unlike photons, muons are easily able to pass through thick metal shielding. This means I can detect only muons by adding thick metal around the pin diode. (I was going to add some shielding anyway to prevent electromagnetic interference. I realize now that this simultaneously decreases gamma ray sensitivity in a somewhat unpredictable way.) The benefit of detecting muons rather than gamma rays is that the node will detect less terrestrial background radiation, which is important if I intend for the node to be used in somewhat populated areas.

At this point I'm not sure what kind of material or thickness is needed for the shield, nor am I totally positive that detecting only muons is the right way to go. Thankfully, my detector design is flexible enough that I can continue working on the electronics and software while simultaneously working on the particle physics aspect.

Coincidence detection might also be something to look into. This is where two PIN diodes (or hopefully array of diode) have shielding in between them, and a circuit is used to record only events where the top detector get a pulse a certain amount of time before the bottom detector. This should reduce terrestrial radiation interference even more.


PsiStarPsi wrote 09/13/2014 at 00:59 point
I think you have a very solid project concept. As government budgets for fundamental science continue to contract, I think capturing the general public's attention and, more importantly, getting their participation is a great way to keep the path of discovery moving forward.

I highly recommend reading up on the details of how some other similar experiments (Volcano Ranch, Havera Park, Pierre Auger, etc.) were designed, as they may have a lot of useful information for you. Some of what you might need is paywalled, but a lot of pre-prints of the more recent papers (e.g., Auger) can be found on

If you're interested in the highest energy cosmic rays, you'll want to reconstruct extended air showers. In that case you'll want to be sensitive to the main components of the shower: gammas, electrons, and muons.

Auger uses large water tanks and detects Cherenkov radiation from the charged particles in the shower, as well as charged particles produced by gamma interactions in the water. If you're trying to stay compact, you might consider a design with scintillator to generate light that you can detect with your PIN diodes. You could do something like a sampling calorimeter with alternating layers of metal and scintillator. There are, of course, lots of options!

A nice (and freely available) tool that physicists use to design such detectors is called Geant4:

I recommend checking it out if you can make the time. Simulating your energy resolutions and designing a good detector node are going to be key.

Looking forward to watching your progress!

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