Can Geiger Counter Ticks be converted into particle/wave counts?

[kvidtr]

TL;DR Summary: Currently working on a project for lab where we're sending Geiger counters 100k feet into the air. Goal is to determine radiation as a function of altitude. Need some guidance.

Hi everyone,

I'm currently working on a project for lab where we're sending Geiger counters 100k feet up into the stratosphere via weather balloons. The professor has asked us to determine radiation as a function of altitude. We're sending up two counters with the intent on measuring radiation due to gamma rays and beta particles.

The gamma ray Geiger counter will be fully covered to prevent alpha and beta particles from setting it off, with the beta particle counter being lightly covered as to just block alpha particles. Then, we'll subtract the gamma counts from the beta counts to get our beta number.

I initially thought this was going to be as simple as, "Send up the Geiger counters, measure the tick rate as a function of altitude, mission accomplished." But my professor is not interested in ticks related to Sieverts; they want actual counts of how many gamma rays and beta particles are coming through.

My thought was that if I can somehow convert Sieverts into some sort of unit of energy, I can then use Sieverts to eventually get to a gamma ray number, and then I can use the same process as above for figuring out my beta particle number.

The problem is, I don't think I know enough about what I'm looking for in order to produce meaningful google results. If anyone could give me some breadcrumbs to follow, I'd be greatly appreciative.

Also, I apologize if this is the wrong section for this sort of question. The papers I was trying to read through were labeled as "Nuclear particle physics," and while this is 'homework' in some sense, I didn't see an option that really fit this description. Also I'm in first year physics, currently doing E&M.

 

[Tom.G]

Each 'Tick' is an instance of the radiation hitting some atom(s) in the sensor, making that atom an ion. This ionization spreads to nearby atoms and creates a small amount of plasma. The electric field applied to the sensor then has a conductive path for current flow. The current flow is then amplified and heard as a 'TIck.'

The 'Ticks' are then integrated and displayed on a meter.

Of course not all radiation will succesfully ionize a conductive path, so there will be some calibration needed for the meter reading.

Hopefully that is enough theory to get the project started.

Have Fun!
Tom

And please keep us updated on your progress and results, we like to learn too!

 

[kvidtr]

Each 'Tick' is an instance of the radiation hitting some atom(s) in the sensor, making that atom an ion. This ionization spreads to nearby atoms and creates a small amount of plasma. The electric field applied to the sensor then has a conductive path for current flow. The current flow is then amplified and heard as a 'TIck.'

The 'Ticks' are then integrated and displayed on a meter.

Of course not all radiation will succesfully ionize a conductive path, so there will be some calibration needed for the meter reading.

Hopefully that is enough theory to get the project started.

Have Fun!
Tom

And please keep us updated on your progress and results, we like to learn too!

Thank you for your response! I understand (I think) the basic process of ionization leading to ticks, but is there a way to know the minimum amount of energy required to cause that ionization?

I'm pretty sure the glass chamber in our Geiger counter is filled with air, which means it can sustain an E-field of a magnitude ## 3 \cdot 10^6 \frac V M##. Is that something that will help me figure out the energy contained in the ionization and allow me to reverse engineer my way back to finding the minimum energy required? Or is that even going to be useful information?

Also I'll gladly post the progress/results after if you and anyone else are interested! Can't post the whole report online probably, but some graphs and potential videos from 100k feet in the air, provided I keep our GoPro well insulated, is definitely on the table :)

 

[Tom.G]

As I recall, the fill gas is an inert gas such as Argon and at low pressure.

Try these links for more info:
https://www.google.com/search?hl=en&q=operation+of+geiger+muller+tube
https://en.wikipedia.org/wiki/Geiger–Müller_tube

Cheers,
Tom

 

[kvidtr]

As I recall, the fill gas is an inert gas such as Argon and at low pressure.

Try these links for more info:
https://www.google.com/search?hl=en&q=operation+of+geiger+muller+tube
https://en.wikipedia.org/wiki/Geiger–Müller_tube

Cheers,
Tom

Just sent out our balloon this last Wednesday. Will be working on a post with the fun stuff this week. Thanks again!

 

[kvidtr]

[Mentor Note: The results post below has been merged back into the original thread about the project]

TL;DR Summary: Bad news: Our SD Shield likely failed and it appears that we got no data.
Good news: We learned a handful of practical takeaways.

I asked for some help some weeks back concerning measuring background radiation as a function of altitude using Geiger counters and said I would post the results after the experiment was done. Unfortunately, due to technical failures, there's no data, so this is more-so a failure analysis with a cool video attached.

What were we doing?

Our goal was to send two Geiger counters to an altitude of 95000 feet in order to measure background radiation due to gamma rays and beta particles. We wrapped one Geiger counter in paper and foil (the paper was to avoid any shorting), and left one Geiger counter open to experience all that background radiation had to offer. The plan was to get the total radiation from our exposed Geiger, then subtract our covered counter from that. This would have given us our total radiation due to beta particles and gamma rays individually.

Originally my professor had the idea of getting an exact number of rays/particles, but the math for that was nearing impossible due to the unit conversions being extremely complicated with so many changing variables. So instead, we were going to figure out what the total radiation was from both gamma rays and beta particles in Sieverts.

What did you build and how?

We constructed a payload skeleton out of insolated Styrofoam (pink board stuff). It was roughly the size of a larger piece of paper (12x9 inches roughly). We used one solid layer with one additional layer as a perimeter, with the perimeter being about 3cm wide all around. We held these pieces together by piercing small holes through the boards while they were clamped down and pushing zip ties through. Then, we cut up some dollar store pool noodles to act as bumpers. Once again, pierce and zip tie them onto the payload. We made a small "house" for our battery, which would be wrapped in mega handwarmers.

To secure everything, we used toothpicks and small toothpick-like dowels. The smaller toothpicks were used to secure things laterally, and the larger ones were used to secure things vertically.

The GoPro was secured by asinine amounts of space tape.

The payload consisted of:
- One 5v portable charger
- SD Shield + SD Card
- Bread board for circuits
- Arduino Uno
- 2 Geiger Counters
- Last minute additions: GoPro + GPS Unit (literally had these handed to me day of launch).

Total Payload weight: Roughly 1.1lb (think it was 570g)

Coding for the adruino was handled by another teammate who had little experience but did an excellent job learning and creating the code on the fly. Saying he was essential to the project is an understatement.

What happened?

We had issues with our SD card corrupting and not saving properly as we approached launch day. Unfortunately, at a community college there isn't much to work with in terms of extra parts. We could get our SD card to save properly about 85% of the time, and initiate properly about 2-3% of the time. It would take many, many restarts of the arduino to get the SD card to initiate (which we tracked by coding lights to blink rapidly or blink once for 5 seconds to tell us if it initiated).

We decided to send it up on launch day, and when it returned, we had no data.

We concluded that it's likely the SD shield not working properly, as the card seemed to carry data just fine in other electronics. The arduino also seemed to always execute the code properly as well.

Some Takeaways

Our biggest pitfall was not having backups. I think in retrospect, I should have just shelled out more money for backup parts. I probably could have doubled our equipment for less than $100... but I'm also a college student, so it's hard to part ways with $100. If I could go back and do it again, I would have done that though.

I would go back and wrap the "house" in foil before securing it. Although our batteries never froze, I still think the added layer of insolation would have been helpful.

Conclusion

While the experiment ultimately failed, I can say I enjoyed every second of it and wasn't remotely discouraged. The only sad part is that I won't have a second chance to do it due to the quarter almost being over. The failure only made me want to run it back and try it again with the new insights gained from the failure.

For those interested, here's the GoPro footage we managed to get. If anyone wants pictures of the payload itself, let me know. I'll be going in to lab today to dismantle it, and I'll grab some pictures during the process.

 

[Flyboy]

Outstanding post-mortem review! I'm sorry about the hardware failure, but I'm glad you enjoyed the project.

 

[Klystron]

For future experiments consider using scintillation counters as measuring devices to replace, augment or calibrate the Geiger counters.

NASA and DOD used to have education enrichment programs that supplied used/obsolete electronic equipment to schools but I confess to no recent knowledge of these programs.

 

[Vanadium 50]

I am glad you had a good time!

If you do it again, I am going to disagree with @Klystron. He is correct that scintillation counters would work better, but they are also minimum a few hundred dollars apiece, I think you would be much better served by, as you say, buying more spare parts. After all, a better detector that can't be read out is not helpful.

I think you want Bq, not Sv or Gy, but I would not try and calculate the conversion. As you learned, it's a mess. Instead, I'd try and calibrate it. If you have a source putting out 100 Bq, and you measure 40, you know you have to multiply by 2.5.

As far as shielding, remember that your tube is a..well, a tube. If you have additional shielding that is thin compared to the tube, it might not do very much. OTOIH, you can't lift a ton of lead. So you need to carefully consider what to use and where to use it. Testing on the ground, for example, might be a useful thing to do.

Finally, I hope this experience has taught you the value of dry runs. Taking ten on the ground for every one in the sky does not strike me as crazy.