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Spark Detector - Alpha Radiation Detector

DARK$$ 21343 21
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  • Spark Detector - Alpha Radiation Detector
    Hello!

    1. What is this?
    The detector I want to introduce to you is a simple device that allows the detection of alpha particles in the air at atmospheric pressure. It consists of two parallel electrodes: one in the form of a metal plate and the other made of thin wires. As I mentioned earlier, this type of detector is only sensitive to ? radiation, which is why it can be used as a measure of the activity of radioactive elements in this range.
    2. How it works
    During detector operation, high voltage (slightly below breakdown voltage) is applied to the electrodes. The active area of the detector is in close proximity to the wire electrodes. Alpha particles passing through such an area cause the formation of a sufficiently large amount of free charges for an avalanche (electric) breakdown to occur. As a result, the alpha particle in the detector leaves a trace in the form of audible and visible sparks to the naked eye.


    Construction
    1) HV power supply - electronic part
    Necessarily regulated, giving about 4-5kV output. The current efficiency of the power supply should be large enough to be able to maintain the current resulting from a corona discharge. In the design of my power supply I used a CCFL converter (on the ~ 1kV output) on the input, which I placed an adjustable voltage stabilizer (LM317). The voltage output from the inverter is further increased by a four-stage voltage multiplier. The whole is powered by 12V. The design with a linear stabilizer is simple but terribly coarse. A fairly large 0.6A current flows through the stabilizer, so you must give a radiator. A much better idea is to use a lowering impulse stabilizer. The diodes working in the voltage multiplier cooperating with the CCFL converter should be fairly fast and withstand high back-up voltages (at least 1.5kV). I used the "GP02-20" diode.
    2) Detector
    When it comes to the design of the detector, the key is the thickness of the wires. They should be very thin otherwise the device will not work at all. In my construction I used tungsten wires with a diameter of ~ 0.1mm. An important factor is also the smoothness of the structure, no wire bends or scratches on the sheet. This greatly facilitates voltage regulation.
    3) Pictures
    Spark Detector - Alpha Radiation Detector Spark Detector - Alpha Radiation Detector Spark Detector - Alpha Radiation Detector
    Spark Detector - Alpha Radiation Detector Spark Detector - Alpha Radiation Detector
    4) Movies


    Link


    Link


    Link

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    About Author
    DARK$$
    Level 12  
    Offline 
    DARK$$ wrote 95 posts with rating 54, helped 1 times. Live in city Ełk. Been with us since 2005 year.
  • #2
    Maticool
    Level 20  
    When you apply the source to the side (in the plane of the wires), does alpha particles have enough energy to leave a row of sparks as a trace of the passage of the particle?
  • #3
    c4r0
    Level 36  
    Maticool wrote:
    When you apply the source to the side (in the plane of the wires), does alpha particles have enough energy to leave a row of sparks as a trace of the passage of the particle?
    In general, that's how it should work. However, I do not know if it will succeed in the presented project. I once saw such a model in the observatory, only instead of wires there was a pile of sheets. There were maybe 10 sheets, about 50x50cm in size, and there was a space of about 1cm between the sheets. High voltage and alternating polarization were connected to them (sheets plus, minus, plus, minus, etc.). Discharges happened a few times a minute, and when viewed from the side, there were several discharges between various sheets in the stack and these discharges formed a fairly straight line - the flight path of the ionizing particle :D

    edit:
    For those interested, similar projects can be found under the slogan "spark particle detector".
  • #4
    DARK$$
    Level 12  
    Maticool wrote:
    When you apply the source to the side (in the plane of the wires), does alpha particles have enough energy to leave a row of sparks as a trace of the passage of the particle?

    Unfortunately not. This is probably because the detector has a strong electric field and the particle is quickly "pulled" to the negative electrode.

    c4r0 wrote:
    Maticool wrote:
    When you apply the source to the side (in the plane of the wires), does alpha particles have enough energy to leave a row of sparks as a trace of the passage of the particle?
    In general, that's how it should work. However, I do not know if it will succeed in the presented project. I once saw such a model in the observatory, only instead of wires there was a pile of sheets. There were maybe 10 sheets, about 50x50cm in size, and there was a space of about 1cm between the sheets. High voltage and alternating polarization were connected to them (sheets plus, minus, plus, minus, etc.). Discharges happened a few times a minute, and when viewed from the side, there were several discharges between various sheets in the stack and these discharges formed a fairly straight line - the flight path of the ionizing particle :D

    edit:
    For those interested, similar projects can be found under the slogan "spark particle detector".

    Not completely. The detector you talk about in English literature (just like in Polish) is called the "spark chamber". The operation of such a detector requires a so-called "trigger" in the form of an electronic system in which the passage of the particle is detected by scintillation detectors.
    In the attachment I put the article of the authors of the invention ("spark detector") from Physic Review from 1945.
  • #5
    Kuniarz
    Moderator Design
    Interesting design, radiation is fascinating mainly because it is not visible ;-)
    Searching the web for the given password I found such a video:

    Link
    , isn't it a little dangerous to take such radioactive sources in hand?
  • #6
    pcx
    Level 12  
    I have a question: what material did you use as the source of alpha radiation?
  • #7
    kip
    Level 12  
    c4r0 wrote:
    Discharges happened a few times a minute, and when viewed from the side, there were several discharges between various sheets in the stack and these discharges formed a fairly straight line - the flight path of the ionizing particle

    Are you sure they were alpha and not gamma particles? Alpha (and most bets) should stop on the first tray ...

    Kuniarz wrote:
    isn't it a little dangerous to take such radioactive sources in hand?

    It is dangerous. Such a source taken in hand is not a special threat yet, but inside the body is already very large. Disposable gloves bow.
  • #8
    DARK$$
    Level 12  
    pcx wrote:
    I have a question: what material did you use as the source of alpha radiation?


    On the first and second video of Americas 241, on the third TIG electrode with 2% content of Toru 232.
  • #9
    komster
    Level 10  
    Hello

    A very interesting idea. I have a question about where tungsten wire. Can you use 0.17mm acupuncture needles instead? And another question about the WN power supply, will the author provide the diagram.

    As a side note, I recommend the book "Nuclear Radiation Detection Methods" by Z.Strugalski.

    Regards
  • #10
    daroslav15
    Level 15  
    And I have a question from another barrel. The whole detector looks nice and is neatly prepared, but do such discharges cause erosion of the electrodes? Will you not see the burned miniature points?
  • #11
    DARK$$
    Level 12  
    komster wrote:
    Hello

    A very interesting idea. I have a question about where tungsten wire. Can you use 0.17mm acupuncture needles instead? And another question about the WN power supply, will the author provide the diagram.

    As a side note, I recommend the book "Nuclear Radiation Detection Methods" by Z.Strugalski.

    Regards


    The diameter of my tungsten wire is in the range [0.05mm, 0.10mm]. As you can see, this wire works correctly. I also checked wires with 0.25mm diameter (E1 string of an acoustic guitar) and 0.20mm (steel), but both did not work. I do not know if a wire of such thickness as yours will be suitable. It is quite possible that it will work. This has to be checked experimentally :) Some time ago I found this thread on the triode: link . There is a link to the Polish manufacturer's website and the prices of such wires are described. Wires do not necessarily have to be tungsten. You can even use copper wires drawn from thin cables just like the author of this project: link
    I will try to insert the scheme in the near future.

    Quote:
    And I have a question from another barrel. The whole detector looks nice and is neatly prepared, but do such discharges cause erosion of the electrodes? Will you not see the burned miniature points?

    I forgot to write that at the output of the entire HV power supply, to protect the electrodes, a 1-10M? resistor should be inserted with a capacity of at least 1W. You can give more, it is worth choosing experimentally. I inserted just 1M? because I couldn't get higher resistances. Despite this current limitation, discoloration occurs on the plate electrode. They do not resemble points, only stains. Most likely, they are caused by chemical reactions of ionized oxygen with a zinc coating on the sheet.
  • #12
    Jarek1321
    Level 10  
    Hello, it looks very impressive but I would be afraid that I would move these wires and kick me :)
    I have a question - does this phenomenon occur in the X-ray D-08?
    It has an ionization chamber, but it is a bit large:
    link
  • #13
    kip
    Level 12  
    Jarek1321 wrote:
    I have a question - does this phenomenon occur in the X-ray D-08?
    It has an ionization chamber, but it is a bit large:

    No - the ionization chamber is another type of detector. It is polarized with voltages of the order of several dozen - several hundred volts and measures a very small current (nano order, and even picoamps), proportional to the dose rate.
  • #14
    Jatsekku2
    Level 12  
    I understand that the amount of spark jumps indicates how much radiation the source gives. In the movies, the American 241 is clearly better, which sparks while TIG spent one for about 1 minute. Hence the question, where did you get the sample from America?
  • #16
    DARK$$
    Level 12  
    Quote:
    I understand that the amount of spark jumps indicates how much radiation the source gives. In the movies, the American 241 is clearly better, which sparks while TIG spent one for about 1 minute. Hence the question, where did you get the sample from America?

    It's just like you wrote. As for the sample, it's like komatssu wrote.
    There were once such smoke detectors on the Allegro for PLN 10 ;) The radioactivity of such a sample is 1uCi. The whole is sealed in a metal casing so if you do not swallow it and do not open it should not be life threatening.
  • #17
    Kaatan
    Level 10  
    Interesting design, I'd like to see a diagram of this converter. Recently, I have become interested in radiation and maybe I will think about doing something like that.
    I advise you to check the ? radiation of the grid to the gas lamp, its ? radiation is much stronger than TIG electrodes with an admixture of track, so ? probably also. I do not know if all the nets for gas lamps have so because I found an old house from 10 years old, maybe it has a slightly different composition than the current ones.
  • #18
    Jatsekku2
    Level 12  
    DARK$$ wrote:
    The radioactivity of such a sample is 1uCi. The whole is sealed in a metal housing


    Well, I don't understand something, alpha radiation is supposedly stopped already by a piece of paper, let's say that in practice it is different and this sheet will be overcome, but how would it handle the metal? Is there maybe a window or something where this radiation escapes?
  • #20
    Jatsekku2
    Level 12  
    Well, that's all clear, now it remains to get a smoke detector :D It is also interesting that in the description of the video to which Jarek1321 gave the link, there is information that Am241 also emits gamma radiation (only in small quantities) - "The Americium 241 source emits 5.5 MeV alpha particles and low energy gamma radiation ( 59.5 keV -35.9% -, 26.3 keV -2.4% - and 13.9 keV -42%). " I wonder if it is easier / better to use an ionization chamber, a Darligton and an indicator instead of such a detector, although it must be admitted that this one is more effective - ideal for shows :)
  • #21
    DARK$$
    Level 12  
    :arrow: Kaatan : I added the diagram in the first post. As you can see, this is not a complicated device.
    Quote:
    Well, I don't understand something, alpha radiation is supposedly stopped already by a piece of paper, let's say that in practice it is different and this sheet will be overcome, but how would it handle the metal? Is there maybe a window or something where this radiation escapes?


    There is a window, as in the video given by Jarek1321. It is a thin plate made of some metal. The Americas (American oxide) is inside anyway.
    Out of curiosity, I checked how many alpha particles pass through the aluminum foil. It turns out quite a lot. It is true that after passing through they lose a significant part of their energy. The range of such particles (coming straight out of America) in the air is ~ 5cm, after passing through aluminum foil ~ 1cm. In contrast, plain printer paper does not let them go at all.
  • #22
    cefaloid
    Level 32  
    DARK$$ wrote:
    The radioactivity of such a sample is 1uCi.

    That is 37kBq link .
    The permissible activity of the 241 isotope in the human body is 18 kBq (a cube from America with a side equal to a diameter of 2-3 hair), i.e. the detector is a double dose acceptable for humans. In addition, it is American oxide - especially, because it is very poorly absorbed into the body, e.g. if swallowed. Theoretically, then, dinner with such a source should not hurt us too much ...
    But never too much caution. Why risk your health?