Happy new year!
A technical update (facelift) is coming out from the Muon Hunter ST Nucleo K8 version at the end of January.
Happy new year!
Have rev1, but want to have some of the new features? Read on to find out how to modify your kit.
You'd expect more muons to come from the direction of the top of the atmosphere than from close to parallel to the surface of the Earth.
This initial data was taken with the highest aperture, so it merely shows the magnitude of the counts.
When the tubes were set parallel to the surface of the earth, I measured the following with one of the prototypes - look at the muons / hour data:
Testing the boards and getting ready: double checks and a bit of abuse...
In most of the typical accidental abuse cases it shuts down gently and recovers... It's got a resettable fuse for overheating / overcurrent / overvoltage protection. Unplug, wait then restart and it works again.
Of course, always read the label...
Nothing comes out of vacuum except for a few elusive particles, so this kit has its story, too.
Mine started when I was looking for a tool for demonstrations when teaching particle physics on a budget. Something that actually could do physics in this domain. The first thing I looked at was these cheap GM counters and started to think about turning them into a coincidence detector.
First I built a lead coincidence detector that detects electromagnetic cascades caused by muons at the end of 2014. You can check out this prototype here.
I was fortunate enough to have the chance to go on a 3 week course in CERN called HST 2015. I wanted to try out my detector with a cloud chamber so I thought I would bring it along if the programme allows to test it out. The organizers had been very helpful, so we were given the chance to set it up.
We had two opportunities to test the circuit - so the time was tight. However, we managed to capture a muon decay on camera, although we had trouble with the lighting in the cloud chamber. We fixed it somewhat, but still can be improved. Still, a faint, but clear trace of the decay can be seen on the picture below.
I've been working on this project for a while, check out this post about the user interface, this about the coincidence testing and this about the Geiger logger program. Finally, here's the previous anode type lead array detector I built.
The demo interface is not going to be accurate in the sense that you won't be able to see every hit when they are more frequent than 16 ms. If you need to count the individual us pulses, you'll need a different counter application to connect it to the detection circuit. I might actually have a go at it with some dedicated hardware at some point. That would be a natural way to improve on this project. Just for your demo / educational purposes I wrote a logger program for these applications in python which you can use on the Raspberry Pi to log these events. It's accurate enough to do the basic Rossi experiments with.
Not so long ago I tuned the pulse lengths and coincidence times for the anode detection coincidence detector circuit. You can find it here.
At that time it didn't even include an LED to give any visible information to the outside world. Today was the time to create a small LED-buzzer interface (if you can call that) for the muon detector for demo purposes. In the first coincidence detection prototype I built, I used a monostable 555 circuit to lengthen the (previously shortened) pulse form the GM tubes, since I had these 555s lying around. The GM pulse is shortened, because you can achieve more accurate coincidence detection that way, but for us those pulses are too short to see, they need lengthening. Since there will be a little beeper and 3 different LED signals (on 2 bi-coloured LEDs) plus a button in this project, I decided to use an ATtiny microcontroller instead of the 555s. The package is going to be smaller and it can source/sink the sort of current these LEDs or the buzzer need. Also, it's quicker to write some C code than going through the whole circuit design process just for some LED - buzzer - button business. I had an ATtiny44A lying around. It's a tremendous overkill for this project with its 4kb flash and 256B RAM. The code even with a little self test is less than 1 kb. Considering the size of the prototype case, this dip14 was the sort of size I wanted to solve this problem with.
The prototype is in the making, here's the a short video about the progress so far. This is the LED interface. The high voltage connectors are in the case, too.
The previous muon detector I built used GM tubes in an anode detection circuit. Now it's time to build the brother circuit, the cathode detection circuit. This would be useful in a couple of applications where the GM tubes can be separated.
The aim is the same 2 us coincidence time as with the previous design. That reduces the number of accidental coincidences considerably even with a 2 tube design. The GM pulse will be shortened this time, too. Since the detection circuit will be different this time, this part of the circuit has to be redesigned. I've just done some initial tests on a breadboard. It all looks good so far, the 2 us time has been achieved as planned, in fact it's a little bit less, which is good news. Stay tuned for the next prototype...
CODE examples are on GitHub
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