DIY Muon Detector

Muons are fundamental particles created when cosmic rays collide with particles in Earth’s atmosphere. They are way more powerful than x-rays—but can be used in similar ways to CT Scan devices; but with larger/thicker objects. Instead of CT Scanning someone’s body, you can use the stronger muons to image entire Egyptian/Mexican pyramids and find hidden, undiscovered rooms. Likewise, instead of just x-raying a suitcase at an airport—you can scan an entire plane’s cargo hold. Its first real-world use was in 1970 when scanning the Pyramid of Khafre, looking for hidden rooms.

 

So, of course I want to try detecting a muon. Not a whole bunch—just one. Reliably.

 

How do scientists detect muons?  They can follow the tracks in a spark chamber (which I have, but it’s too small). They can use photographic film—I have a darkroom. They can use scintillation crystal sensors—which I have, but I don’t have dozens of them.

 

How will I  detect muons? By using the humble Geiger counter with a Geiger-Muller tube. A Geiger counter is basically a lightbulb with a tiny gap in it filled with gas. When a particle passes through the lightbulb (tube) it completes an electrical circuit and you get a click noise.

 

Basically Geiger-Muller tubes are just like those bug zapper lights people have in their backyards.

I'm using the humble Soviet era, 400 volt SBM-20 tube for this. Two of them.

 

But Geiger counters will click when hit by X-rays, gamma rays, alpha particles, beta particles, etc. Plus all the background radiation makes them click around 20 times a minute in a normal room.

 

So, we cover the Geiger-Muller tube in a lead sheet, which will block most of those particles.

Then we get a second Geiger-Muller tube and cover that with lead.

 

Then, and here is the genius part, we stack the tubes on top of each other so that the only particles/rays that would trigger both tubes would have to be: traveling at 90 degrees to the Earth’s surface; be powerful enough to pass through not one, but two sheets of lead and two tubes; and be moving so fast as to trigger both tubes virtually at the same time via relativistic motion.

 

How do we know if the tubes are triggered at the same time (not just close)? With a humble AND-gate microchip. This microchip has two inputs and one output. Only if it receives two input signals at the same time will it output its own triggered signal (and light an LED or make a click on a speaker or a spike on my oscilloscope).

 

 

If you look at the pinout of the chip (a 74HC08 AND gate  logic chip) you will see that if PIN1 and PIN2 get a signal at the same exact time = it will output a signal to PIN3.

Pin1 and Pin2 also each get a 100k resistor to ground (this lets the chip reset to off).

The yellow wires are input Pins 1 and 2. They have 100k resistors going to negative rail. 

The other end of the yellow wires go to the 3rd pin of the NE555 chips on the geiger boards. One yellow goes to one pin3 of geiger board, the other yellow wire goes to pin3 of the other NE555 chip on the other board. 

Here are the yellow wires going to Pins 1 and 2 on the 74HC08 chip. Notice the 100k resistors going from each one to the (blue) negative rail on the breadboard.

Here is the other end going to Pin3 of the NE555 chip. According to the schematics it should be possible to tie into this via a jumper or LED or speaker connection of the geigers, but that doesn't to work. 

Thus, this is what's known as a coincidence detector.

So, stack two cheap Geiger counters sandwiched in lead plates.

Output from both go to a $2 logic AND-gate chip.

AND-gate chip outputs to: LED or Oscilloscope or Speaker.

Literal back of an envelope layout:

Any output basically must equal a muon. They occur about once per minute on Earth.

To make things easier I connected one geiger board to a 5v USB wall plug that had a higher (2 amp) current rating than usual. Not sure this is necessary.

Then I connected the always on screw tightening power block things together from both units. That poweeed the other board. 

Then I ran a second pair of power wires to the breadboard.

So, USB wall plug to first geiger board. Then red and black wires between the boards:

Then another pair of red and black split off to power the breadboard:

Those go to the red and blue power rails on the breadboard. I also ran a short black wire from the right blue negative to the left vlue negative rail on the breadboard. That way I could easily run 100k resistors from the 74HC08 1 &2 Pins to the negative easily.

I'll probably reroute that more cleanly in the future. It was a quick test. My breadboard LED came on with mo input! That's why the resistors are needed to zero everything out and start with an OFF LED. Weird, but thats how logic chips like the AND gate work. You have to tell them what 0 or off looks like or else they go nuts.

So, it works.

If I test by turning both on I get an occasional light up by the LED on the breadboard. Especially if I put a radioactive substance near them. Even then, it doesn't light up often relative to the individual Geiger counters clicking and blinking. Good!

In the future I might pull each Geihlger board's J1 jumper to disable their speakers--and then put a speaker on thr breadboard.