Notices
Results 1 to 10 of 10

Thread: reusing junkyard CRT monitor lectron guns as harassment weapons?

  1. #1 reusing junkyard CRT monitor lectron guns as harassment weapons? 
    Junior Member
    Join Date
    Feb 2014
    Posts
    2
    I've been hearing strange rumors that a certain group of unethical engineers have been going around and secretly installing the electron guns from out of CRT monitors behind the walls of other people's offices to harass them while working. Is this possible? I realize that CRT's normally have lead glass, etc... but what if they removed it and just used the gun? The office I work in seem to have a strange electronics sound and the feeling of pelted on your skin by something at random times during the day... how would you detect free electrons pinging you from inside a wall? A Geiger counter don't seem to measure electrons below a certain electron Volts level?? What about secondary radiation from electrons striking something outside of a vaccum, etc?

    take a look at this experiment:
    Ion Ray Gun - YouTube


    What is making the crookes radiometer wheel turn? its behind a piece of glass there's no way atoms could be bouncing off of the pads to turn the wheel; and is not getting hit by visual light photons from the gun? it doesn't look like electrostatic charge to me from the youtube video... I looks more like little particles pinging off of something and can somehow go through a piece of glass?

    I was thinking maybe some of the electrons can get through the air without ionizing them and hit the radiometer glass cause it to fluoresce the glass creating x-ray photons that cause the heating to turn the radiometer???
    Reply With Quote  
     

  2. #2  
    Senior Member
    Join Date
    Jan 2014
    Location
    out there
    Posts
    306
    Free electrons in air?

    Here`s a better one How to recharge a battery
    Reply With Quote  
     

  3. #3  
    Junior Member
    Join Date
    Feb 2014
    Posts
    2
    Free electrons... sure why not....its my understanding that beta particles can travel a few meters in the air?
    so what if it ionizes a few air molecules along the way... the point is that its a harassment weapon that nobody can detect...
    except for the annoying ionizing hum sound it makes... I'm guessing the old electron gun would need to be put inside another tube by blowing a glass jar doped with Beryllium and vacuum sealed....maybe add in some Xenon gas so it emits VUV ultraviolet that is impossible for anybody to detect since they don't sell cheap meters to detect it for under 5,000 dollars...

    I'm wondering how might you retrofit the electron gun into emiting soft-xrays in the 10Kev range instead of low end VUV?
    Reply With Quote  
     

  4. #4  
    Senior Member
    Join Date
    Jan 2013
    Posts
    354
    Quote Originally Posted by squirrelmonger View Post
    Free electrons... sure why not....its my understanding that beta particles can travel a few meters in the air?
    so what if it ionizes a few air molecules along the way... the point is that its a harassment weapon that nobody can detect...
    except for the annoying ionizing hum sound it makes... I'm guessing the old electron gun would need to be put inside another tube by blowing a glass jar doped with Beryllium and vacuum sealed....maybe add in some Xenon gas so it emits VUV ultraviolet that is impossible for anybody to detect since they don't sell cheap meters to detect it for under 5,000 dollars...

    I'm wondering how might you retrofit the electron gun into emiting soft-xrays in the 10Kev range instead of low end VUV?
    There are several problems with the above discussion. Let's start with minor stuff, with the characteristics of the types of cathodes actually used in CRTs. These are oxide-coated "Wehnelt" type cathodes. The oxides lower the surface work function to improve emissivity. They work great, but are easily poisoned. By air. And humidity. Emission would drop very quickly when operated in a non-vacuum. You could compensate to a degree by increasing the heater temperature, but at the expense of a precipitous drop in lifetime.

    More seriously, the figure of a several-meter range for betas is not some sort of physical constant; surely you must understand that it is a function of energy. A 1MeV beta has a range of about 3-4 meters. In this energy range, we can pretend that the range is linear with energy. Thus, a 100keV beta will travel less than a meter, and a 10keV beta will travel centimeters. And that's in air. A wall will block it.

    As a weapon of mass destruction or mass irritation, a CRT electron gun fails miserably. No one is using such a thing for that purpose. You have fallen for another internet urban legend.
    Last edited by tk421; 02-19-2014 at 04:52 AM.
    Reply With Quote  
     

  5. #5  
    Senior Member
    Join Date
    Jan 2013
    Posts
    354
    Quote Originally Posted by squirrelmonger View Post
    What is making the crookes radiometer wheel turn? its behind a piece of glass there's no way atoms could be bouncing off of the pads to turn the wheel; and is not getting hit by visual light photons from the gun? it doesn't look like electrostatic charge to me from the youtube video... I looks more like little particles pinging off of something and can somehow go through a piece of glass?

    I was thinking maybe some of the electrons can get through the air without ionizing them and hit the radiometer glass cause it to fluoresce the glass creating x-ray photons that cause the heating to turn the radiometer???
    I agree that no matter is penetrating the glass. Inducing fluorescence is possible, but any heating produced by that would likely be much smaller than that produced by his camera light. In the video, you can see that orientation matters; if heating caused by fluorescence were the mechanism, it shouldn't. Rather, he is able to induce enough of a field to ionise some of the gas inside the radiometer. Depending on the field configuration, that can set up a "recombination wind" oriented the right way to push the vanes around.
    Reply With Quote  
     

  6. #6  
    Senior Member
    Join Date
    Jan 2014
    Location
    out there
    Posts
    306
    The crookes radiometer is well described here. It operates as a heat engine. The partial vacuum inside is adjusted to a sweet spot. Above and below that spot the radiometer does not function.
    Reply With Quote  
     

  7. #7  
    Senior Member
    Join Date
    Jan 2013
    Posts
    354
    Quote Originally Posted by pikpobedy View Post
    The crookes radiometer is well described here. It operates as a heat engine. The partial vacuum inside is adjusted to a sweet spot. Above and below that spot the radiometer does not function.
    Yup. And the interesting thing is that exactly why a Crookes radiometer's vanes spin is not understood.
    Reply With Quote  
     

  8. #8  
    Senior Member
    Join Date
    Jan 2014
    Posts
    185
    "What is making the crookes radiometer wheel turn?"

    The light in the room.
    Reply With Quote  
     

  9. #9  
    Senior Member
    Join Date
    Jan 2013
    Posts
    354
    Quote Originally Posted by Useful Idiot View Post
    "What is making the crookes radiometer wheel turn?"

    The light in the room.
    Amusing and trivially true, but not quite an explanation. It isn't radiation pressure, as originally postulated by Crookes himself (as made evident by the lack of spinning if the bulb is evacuated to a hard vacuum). It's apparently thermal, but -- to my knowledge as of 2005 or so, when I last made a somewhat serious effort to track down the literature on the subject -- there is no theory that quantitatively agrees with experiment. Einstein and Reynolds both offered explanations of their own, but neither fully agrees with data.

    The radiometer is a fun toy. Getting it to spin the other way around is a great geek-party activity.
    Reply With Quote  
     

  10. #10  
    Senior Member
    Join Date
    Jan 2014
    Posts
    185
    Quote Originally Posted by tk421 View Post
    Amusing and trivially true, but not quite an explanation. It isn't radiation pressure, as originally postulated by Crookes himself (as made evident by the lack of spinning if the bulb is evacuated to a hard vacuum). It's apparently thermal, but -- to my knowledge as of 2005 or so, when I last made a somewhat serious effort to track down the literature on the subject -- there is no theory that quantitatively agrees with experiment. Einstein and Reynolds both offered explanations of their own, but neither fully agrees with data.

    The radiometer is a fun toy. Getting it to spin the other way around is a great geek-party activity.
    Yeah, the electrostatic source is freeing the friction. The light in the room makes it turn in a preferable direction. The electrostatic influence of the gun-thing can make it go back and forth. The net effect is to make it move over-all in one direction. There is ever a short section of the video where it is turning without the gun-thing influencing it. No big deal.
    Reply With Quote  
     

Tags for this Thread

View Tag Cloud

Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •