Apposition Muon Camera

Using cosmic rays to peer into the heart of pyramids, mountains or dangerous nuclear reactors & volcanos.

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The aim of this project is to build a simple low-cost camera that uses muons from cosmic rays to peer into the heart of pyramids, mountains or dangerous nuclear reactors and volcanos. Surprisingly, using muons to see through these things is not a new idea, but such systems are rare and very expensive. The idea for this project is the culmination of many other successful cosmic ray detector projects I have built in recent years ( This work has lead to the development of a low-cost solid-state muon detector using off-the-shelf components. Originally, designed to reduce the cost of my Cosmic Array project it has allowed an interesting detour from visualising cosmic rays to using them to possibly see into the heart of a mountain.

Fast moving high energy muons created in the upper atmosphere by cosmic rays rain down across the entire surface of the surface of the earth. They do this continuously at approximately 200 muons per second, per square metre. When counting muons over time the average flux is nearly uniformly and isotopic varying little over time, other than small gradual variations during the solar magnetic cycle every 11 years.

Muons lose their energy gradually, as they have little mass and travel at nearly the speed of light meaning they can travel through large amounts of matter before being stopped.  When averaging muon flux over time from a specific direction, it is unlikely it will be any different to any other angle. Except where it is passing through different densities of matter like a mountain.  

The muon detector used in this project use low-cost off-the-shelf Si Pin Photodiodes commonly used small low cost geiger counters used with mobile phones.  However the Si Pin Photodiodes in this detector are stacked in an array to create a collimator effect that amplifies muons detections coming from one specific direction. 

It does this using an array of 8 detectors that are enclosed in copper shielding to reduce background radiation, rfi and light proofing.  This creates a virtual collimator as each detector is stacked one above the other, where the signal from each is added together using a voltage summing operational amplifier.  

Consequently, when a muon travels directly through the entire length of 8 detectors they will be triggered simultaneously, and so will have the highest signal amplification.  Whereas, muons or local background radiation passing through at other angles will have a lower signal and so can be filtered.

Similarly an apposition element in the compound eye of  a butterfly or other arthropods focus light from one direction on the ommatidium where as light from other angles is absorbed by its dark sided walls.

An array of 16 virtual collimators each grouped together to form a simple compound eye camera will be first tested and maybe increased in number depending on the results of field testing.

The image will be created based on the summed count rates of each virtual collimator detector tube spanning a number of week/days for a specific elevation angle and location coordinates.  Possible caverns or thick dense material concealed within a mountain may result in lower count rates than the surround detectors or in different locations and/or elevation angles. 

This design is not solely limited to use as the AMC: 

  • As it could also be used individually as a single cosmic ray telescope.  
  • In a small coincidence bundle like I have used in my Cosmic Array art project  ( the impetus that created this new design).
  • In other linear array configurations using raster scanning methods or,
  • Meridian drift scanning for an "all of sky" muon mapping. 

The design also lends itself to be arranged into a flat matrix of Si Pin Photodiodes and used as a beta, gamma and X-ray monitoring.  Also enhanced with the use of larger aperture Si Pin Photodiodes and/or scintillators. Consequently suitable for gamma ray spectroscopy.


Low-cost Si PIN photodiode with 7.7 mm2 sensitive area.

Adobe Portable Document Format - 151.03 kB - 04/17/2018 at 06:08



Dual Ultra Low Noise Wideband Operational Amplifier

Adobe Portable Document Format - 2.04 MB - 03/18/2018 at 09:01


  • 8 × TEMD5080 Low-cost Si Pin Photodiodes with 7.7 mm2 sensitive area.
  • 1 × LMH6624 Ultra Low Noise Wideband Operational Amplifier
  • 1 × TinyFPGA A1 TinyFPGA boards are a new series of low-cost, open-source FPGA board
  • 8 × 200mm x 20mm Dia Copper Tubing Light-proof shielding for array stack

  • Preparing for prototype build array element

    Robert Hart3 days ago 0 comments

    After building many, breadboard, ratnest and prototype designs to test out a number of different approaches. It's become very clear that I need to knuckle-down and start developing a number of PCB prototypes on a multilayer pcb using all SMD components. 

    As both the input impedance and gain required on each Si Pin Photodiodes is extremely high and so not only is noise an issue including feedback, crosstalk and vulnerable to RFI, it is also affected by static electric fields. This will becoming an even greater problem when arranged in a multi element array.  

    From my last project experience I found that although the PCB CAD package I was using was fast, very easy to use and free, I couldn't import component footprints CAD files nor export Gerber pcb files.  Meaning I had to a number of custom footprints and could get competitive pricing when needing to have multiple PCBs manufactured.  As will be the case again for this project I'm making a move over to KiCad EDA.  The disadvantages are learning a new CAD package but so far so good. 

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Robert Mateja wrote 7 days ago point

Mr.Alvarez would be proud.Keep cool project going!

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Robert Hart wrote 03/17/2018 at 10:02 point

Thank you David it should be interesting to try :)

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David H Haffner Sr wrote 03/16/2018 at 16:32 point

Wow! I really hope U get this project up and running, this is completely facinating :)

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