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Why is my plasma globe causing a geiger counter to go crazy?

  1. Jul 12, 2015 #1
    The reason I did not place this in the nuclear engineering forum is because I feel that it is closer to an electrical engineering problem than a nuclear engineering problem.


    Now to the question.

    I recently got another geiger counter and a plasma globe for my birthday. Being the person I am I used the geiger counter on anything I could and compared it to my other geiger counter. I also used it on my plasma globe and found something a tad out of the ordinary. The plasma globe seemingly emits not insignificant amounts of radiation. By not insignificant I mean in excess of 20 000 counts per minute.

    I also put paper in front of my geiger counter and noted that it did stop the "radiation" (I use scare quotes because I do not know what it is at this point) until I moved it closer, then the device began to detect "radiation".

    I then decided to put a magnet to my geiger counter. This had more interesting results. When I placed my magnet directly on the tube it caused it to detect "radiation" as normal, but when I put it just slightly to the side of the tube, not very far away from it, but only slightly to the side of it, it caused it to stop detecting so much "radiation" but still detect normal amounts of background.

    Because it is likely that plasma globes would be banned for sale to unlicensed individuals if they emitted harmful amounts of ionizing radiation during operation I have decided that it is probably not a threat to me, but it is still mystifying for me to have my geiger counter go off when it is placed within a few centimeters of it.

    My bet is on somehow the electricity jumping from the globe and causing ionization in the geiger tube, making my geiger counter act like it being exposed to a lot of radiation. Probably it picking up radio or other waves form the device and converting them to electricity. I would like confirmation on this because I really do not know that much about electrical engineering.


    So what do you think it is?
     
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  3. Jul 12, 2015 #2

    jedishrfu

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  4. Jul 12, 2015 #3

    meBigGuy

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  5. Jul 12, 2015 #4
    I see, exactly as I guessed, radio waves interfering with my geiger counter. Thanks for the help.
     
  6. Jul 12, 2015 #5

    CWatters

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    If that's the cause how do you explain...

     
  7. Jul 12, 2015 #6
    The plasma from a plasma globe is a cold plasma. That means the heat in the atoms does not follow a thermal curve (like a candle flame does). Instead it is caused by an electron avalanche. An electron in the globe is knocked out of its atom by background radiation. The electric field accelerates the electron to high speed. It then strikes another atom, knocking out another electron and emitting a photon. Both electrons now accelerate. (The resulting positive ions move slower in the opposite direction.) Rinse and repeat.

    The photons meanwhile zip off to eyeballs or wherever. Some of them add to the discharge. Some of them leave the globe and strike atoms in the air, ionizing them. This leaves free electrons (and ions) for the Geiger counter to detect. It's possible your Geiger counter can detect the photons directly depending on its construction (The reading window can be made of different substances to block UV, different particles, etc.).

    Paper will block the violet/UV photons as well as the free electrons. A magnet can draw an electron off course.

    I could be wrong about this. You could test it by checking to see what your other radiation detectors detect. Different detectors will be sensitive to different wavelengths/radiation. Or you could trust me.:devil:
     
  8. Jul 12, 2015 #7

    jim hardy

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    GM tubes will count whatever beta makes it through their thin skin.
    Beta radiation being simply electrons in motion, one wonders whether plasma globes might make a little of it.

    I don't know the answer.

    The test for "Is it RFI or Beta?" would be to turn off the high voltage to the GM tube. Easier said than done, though.
     
  9. Jul 12, 2015 #8

    mfb

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    Some UV light might be a plausible explanation. It is produced inside. The glass should absorb most of it, but maybe that is not perfect. On the other hand, paper is not such a great UV absorber.
     
  10. Jul 12, 2015 #9
    The reason I recently got another GM counter is because the first was a homebuilt one. So how would turn off the high voltage? Do I rewire my GM counter a bit so that it bypasses the HV power supply?

    Oh, and another thing beta radiation would explain the magnet seemingly blocking the radiation when it was placed slightly to the side of the GM tube. Still the gieger counter being overloaded at about four centimeters would mean that that is one hell of a beta emitter.

    If I were to put photographic film in a cardboard box, put it next to the plasma globe for a few hours in operation, and then develop it later, and the film were black, would that tell me that the globe was emitting beta particles or some other form of ionizing radiation?
    The paper was not a good shield at all, only giving my geiger counter an extra few centimeters before it would become overloaded by it. An entire book (War and Peace to be precise) would not provide enough shielding for it to be touching the book as the book touched the plasma lamp and not go off. However that would not explain the seeming shielding effect of the magnet.
     
  11. Jul 12, 2015 #10

    jim hardy

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    Homebuilt - BRAVO for YOU !

    got schematic ?
    Lift the wire carrying DC to the hv oscillator ? Or the hi meg dropping resistor in series with tube ?
     
  12. Jul 12, 2015 #11

    meBigGuy

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    I I know I said HF EMI, but I take that back. I vote for electrons (which was my first instinct, until I "researched" it. I got myself "bam-googled")
     
  13. Jul 13, 2015 #12
    The second is the current setup I have, unfortunately I cannot so easily take it apart so I will have to leave it alone.

    ____________________________________

    I left my geiger counter on top of my cell phone and turned on my plasma globe. While touching the plasma globe with the geiger counter out of the range of the "radiation" I noted that my geiger counter would detect "radiation". This detection of "radiation" would stop when I removed the phone or when I stopped touching the plasma globe. The detection of "radiation" also only occurred when my phone and geiger counter had direct line of site to the plasma globe.

    This does not look like any beta particles that I know of.


    Also:

    If I were to put photographic film in a cardboard box, put it next to the plasma globe for a few hours in operation, and then develop it later, and the film were black, would that tell me that the globe was emitting beta particles or some other form of ionizing radiation?
     
  14. Jul 13, 2015 #13

    Baluncore

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    Maybe the plasma to anode collision is generating very soft X-rays that pass through the GM tube window but not damp paper ?
    Plasma balls do not have a lead glass screen as used on colour CRTs.
     
  15. Jul 13, 2015 #14
    Than how do you explain my iphone somehow being set off by it as explained here? I am not arguing with you, I just want your take on the situation.

     
  16. Jul 13, 2015 #15

    Baluncore

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    There are too many poorly designed unknowns here to be conclusive. Was your hand touching the globe or was the GM detector touching the globe?
     
  17. Jul 13, 2015 #16
    I was touching the globe, the GM counter was around three feet from the globe. The GM detector was also touching my iphone during this. And yes, I really should of worded that better.
     
  18. Jul 13, 2015 #17

    Baluncore

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    Your hand might conduct electrostatic RFI, or block higher energy radiation.

    Cheap electronics is unreliable unless it is stand alone. It seems you have RFI incompatibilities between plasma ball, the electronics in the Geiger and mobile phone. A spark transmitter generates very broadband RF clicks.

    Experiment: Use an AM radio, (tuned between stations), to listen to the hiss and clicks. Turn up the volume and listen to the character of nearby switching power supplies & etc, Then turn on the plasma ball. You should hear the wide band spark impulses that are upsetting the electronic detector and amplifier of the GM tube and the phone.
     
  19. Jul 13, 2015 #18
    My wild guess is that the cell phone acts as a nearfield antenna for RF radiation.

    I've seen something similar happen with Tesla coils. The theory is that two resonant LC tanks will transfer power between them. My guess is the high voltage source in the globe is resonating with the cell phone. Once again, this sets up an electron avalanche.

    This can be checked with the line of sight thing. Is it actually line of sight? Or is it distance? If you intervene with wood (paper) does that change things? What about dielectrics such as plastic or glass?
     
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