While there are ion chambers in smoke detectors that use a radioisotope, I was referring to an ion chamber designed to measure radiation.

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While I probably have more then a dozen "professional" articles in ion chambers, Charles Wenzel gets down to the practical "This is how you can build them." [And his work!]

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https://techlib.com/science/ion.html

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Alpha, Beta, and Gamma all produce ions as they pass through "air" [Neutrons not so much] and Ionized air is conductive. [slightly]

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It is easy peasy to build an ion chamber, really REALLY difficult to accurately calibrate them. The old Civil Defense units were off by up to 200%.

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Your dipping a Geiger Muller tube into wax is interesting, not as effective as lining the tube with boron.

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This video shows the effect I was referring to.

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Back in 1975ish, we called it 'dead time,' today it is called "foldback."

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https://www.youtube.com/watch?v=afBrwo96jV8&t=417s

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Note how the count increases then drops off. Not quite what one would expect from the inverse square law.

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Note 1: DO NOT PLAY WITH DRY LOOSE RADIUM PAINT UNLESS YOU WISH TO DIE A HORRIBLE DEATH OF LUNG CANCER! Don't scrape it off clock faces or hands or the needles in some military meters either!

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My best, as in most intense, radiation sample is a 0-1mA analog meter from some obscure, long forgotten, piece of military test equipment.

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It is stored outside with my uranium and thorium oar samples, and a pack of 36 Coleman lantern mantles from 1970ish, also stored outside.

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Pre 1980ish Coleman lantern mantles had thorium oxide and are reasonably "hot." Not sure I like the idea of lighting silk impregnated with thorium, some thorium has to escape and you get to breath some....

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They now use a rare earth. [After I tossed my Coleman lanterns in the trash. Bummer, but LED lanterns are fun to design and build!]

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Some welding rods have [?had?] thorium....quite a bit, fairly hot, and trust me, you get some really odd looks when you go into a welding supply company with a Geiger Counter as a 9th grader to get a radioactive sample for a science project.

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I used a fume hood at the university to crumble the 'stuff' off the thorium welding rods into a plastic 35mm film cartridge case.

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I glued on the top to keep things safe.

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[Hey I was 15 and my concept of safe might have left a bit to be desired.]

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The science teacher freaked out when she checked the radiation level from my sample as in..."My God Terry! Where did you get this?"

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"Made it from thorium welding rods."

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"I think I'll take this for safe keeping."

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I'd intended to demonstrate the inverse square law. I received an "A" but wasn't allowed to do the demonstration.

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She called my mother who nixed further thorium welding rod radioactive samples. Bummer.

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Note 2: Proof one can get a bit too much into their hobby. This guy has way too much radiation in his life. Surprised he hasn't moved to Chernobyl.

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And

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https://www.youtube.com/shorts/51DsRaUtuns?app=desktop

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Different Geiger Muller tubes and circuitry have?different responses to radiation overload. Enough gamma will overload any GM tube. Some fancier systems have secondary sensors to indicate "extremely high radiation levels." Some special silicon diodes are perfect, their leakage goes up extremely rapidly when the gamma or neutron flux is above some level. [I've never studied this in detail because I'll never be in such intense radiation fields.]

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Another option is to include a small ion chamber. During normal operation the small ion chamber's conductivity due to radiation ionization is minimal, at high levels the ionization increases dramatically, increasing the conductivity, giving a warning "your GM tube is overloaded." [Simple in concept, I suspect it'd turn into a design nightmare in practice.]

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Oh, and as a child my dinner plate was a bright red Fiestaware. The red was caused by uranium oar. [That might explain a lot about me.]

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Mom's uncle was an engineer who never spoke of his work. He gave me a Geiger counter, yea at the age of 5 I owned a Geiger counter, it lit up with the Fiestaware.

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"Lit up?"

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Pegged the first 3 scales.

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https://www.orau.org/health-physics-museum/collection/consumer/ceramics/fiestaware.html

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"My" Fiestaware was pre-WWII.

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And Mom threw it away to keep me safe!

[If she only knew how futile that plan was!]

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I strongly suggest any Fiestaware, or similar glazed ceramics, be retired from use.

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To keep radiation safety in perspective, a person in a sea level city will receive ~300 millirems per year, a person in Denver will receive ~400 millirems per year.

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Aircraft crews typically receive?between 3 and 6 millisieverts (mSv)? 3000 and 6000 millirems

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1 mSv = 100 mrem.

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And I won't mention the 'gazillion' or so 'cosmic rays' that punch through us every moment of the day.

Yawn.

[Gazillion is hyperbole, a literary device, not hard science.]

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Oh, useless trivia, Tobacco concentrates ?polonium-210 and lead-210.

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There is a boatload of Uranium dissolved in the world's oceans. Limestone is the result of the remains of ancient sea critters. Their remains have uranium, true, trace amounts, but uranium. Radon in Kentucky comes from the decay products of the uranium deposited way back when.

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Polonuum-219 and led-210 are decay products, as is radium, as is radon. Some spots of limestone in Kentucky produce enough radon to be a real nightmare.

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Of course granite also has uranium, it decays and eventually produces radon. You can't win because the universe conspires against you

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For the truly demented, grab an ion chamber smoke detector. There is a small bit of American-241 in the non photoelectric detectors.

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That bit can be safely removed and used as a check source for Geiger Counters.

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There are youtube videos showing how to do this.

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My standard is a bit of American-241 that I check every year or so against NIST traceable instruments.

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I here someone wail, "But radioactive stuff is dangerous!"

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[Ion detectors have reduced the loss of life in house fires in the US by over 50%.]

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So why does my Civil Defense Geiger counter have a radiation check sources....that has long since decayed to barely detectable....

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"You're trying to tell me a device designed to detect dangerous radiation had a built in radioactive source?"

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"Yep. Deal with it."

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https://www.orau.org/health-physics-museum/collection/civil-defense/cdv-instruments/cdv-700-check-sources.html

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FWIW, The Cuban Missile Crisis happened when I was 12, in the 6th grade and left a deep impression on me. I took the civil defense shelter manager classes and was a certified shelter manager at the age of 16. I'm sure people would have listened to a 16 year old in a nuclear war. When they rolled CD into FEMA and shut down all the shelters, I ended up with Geiger Counters, dosimeters and ion chambers, all legally, I still have the paperwork.

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So I know a bit too much about radiation et al then probably is healthy.

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Oh a boring paper on Radon by the feds.

https://pubs.usgs.gov/gip/7000018/report.pdf

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I have oodles of papers, some require a Ph.D. in physics that I can't begin to comprehend.

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FWIW, Geiger Counters are fun to play with. Optimizing the high voltage inverter is a challenge, you want an extremely stable HV with the lowest practical current drain. This is generally the biggest current hog in a Geiger Counter.

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I have a pair of GM tubes mounted about 20 feet above the ground in water proof cases. They are designed to measure and record "cosmic rays." Designing a HV power supply that is stable, draws as little current as practical that will work over a 150 degree F temperature range was an interesting challenge.

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The weather in Kentucky can ranged from -130F to +120F. Yea the extremes are sooooo much fun.

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My active antennas do not like it when the temps drop below -5F. Cross modulation goes through the roof. Still working on that one.

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If they really want people to conform to the NEC then they should make it more easily available. Like downloadable or similar. But no, they see that as a money making source, so they don't.

but I've often wondered who the hell did that...

A safety hint.

If you decide you've just got to look at the AC Mains with a battery powered oscilloscope, reconsider, if you still decide 'I just have to do this...' then consider using a AC mains to 12 to 30V step down transformer. The transformer will isolate you and pass the 50/60Hz. It will show you the turn on of a SCR/Triac light dimmer.

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If you believe you need higher accuracy, reconsider why? What are you looking for? High frequency noise on the AC mains?

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OK you've decided to play Russian Roulette.

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Obtain a 9K 10W resistor, obtain a 1K 10W resistor, wire in series. I like the Dale aluminum body units because you can mount them on a heatsink that you can connect to the safety/protective ground.

Wire one end of the 9k to the AC Mains hot, wire the other end to the 1K, wire the other end of the 1K to neutral.

Monitor the voltage across the 1K, it will be 1/10 the incoming voltage.

Touching it and ground probably won't hurt or kill you. Just tested mine while sitting on a chair in a 1/4" sheet of Lexan. Used my right finger and thumb. As expected I felt nothing. This is still stupid silly but the safest way to actually directly monitor the AC mains.

However, I doubt your scope will see any HF trash on the AC mains.

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I live to fight EMI/RFI, interference on the AC Mains created by all the switch mode power supplies.

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I have an intrinsically safe AC Mains to communication receiver, spectrum analyzer interface that has been hi-pot tested over night with 10kV on the AC mains side.

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In addition to extreme isolation from the AC Mains voltage, either 120V US, 240V the rest of the world, the output is clamped at +/- 2.1V.

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It was an extremely non trivial project, the actual schematic is bog simple, obtaining components that could withstand 10kV for ~10 hours was the royal PITA.

Capacitors large enough to pass 50kHz with "no loss" and withstand 10kV are rare. And pricey.

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There are commercial units

https://www.reliantemc.com/laplace-voltage-probe-plip/

https://www.onfilter.com/test-and-measurements

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These are serious scientific instruments not "magic hocus pocus dirty power will harm your health or kill you."

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If you can't afford either, and if you don't have the skill set and access to a certified hi-pot tester, to roll your own, don't.

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Again, before monitoring the AC Mains for anything but voltage with a meter and current with a clamp on, really think "Do I need to do this?"

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With "Why do I need to look at the AC Mains."

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Death is for keeps.

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[The afterlife doesn't count because we won't be bothering with such trivial things in heaven or hell of Valhalla or 贵ó濒办惫补苍驳谤. <sorry for the font change there, had to look it up> I'd cover more religions but can't think of their afterlife policies off the top of my head right now, but I'm pretty sure none of them suggest we'll much care about earthly problems.]?

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I lost a friend in college who was trying to look at the AC Mains with a scope and isolation transformer. He was alone so I don't know how he screwed up. Smart guy, not prone to foolishness, yet he died.

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So yea I'm a bit too focused on the safety issues with scopes and AC Mains.

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Going to the funeral for a good friend sucked bilge water.

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