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Charged particles passing through a magnetic wave?

  1. Aug 10, 2015 #1
    Random thought...
    Is it possible for a charged particle to travel fast enough, or simply enter a magnetic field at just the right time in the magnetic wave's cycle, to pass through the magnetic field unaffected?
    If so, what is that calculation.
    If not, why not.

    Roy
     
  2. jcsd
  3. Aug 10, 2015 #2

    sophiecentaur

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    The deflecting force is given by
    F = qv B, where v and B are the velocity and magnetic field vectors. If you're not into vectors the simplest way to look at it is to say that, when the particle is travelling at rignt angles to the field lines, it will experience a force that's at right angles to the motion and the field (like Flemmings Left hand rule). The path of the particle will be circular. The faster the velocity, the stronger this force is BUT the radius of the path will increase, despite this. So, however fast the particle travels it will always be affected by the field it travels through. You can't dodge it by going fast enough :wink: but the deflection will be less and less. Same idea as when you calculate how far a bullet will drop on its journey. The faster it goes, the less it will lose height because the transit time is less. It may be fast enough to ake no odds over a short distance.

    I notice you also mention a magnetic wave as the fields are varying in time. This is more complicated, of course and, if the particle crosses a directed (coherent) beam of EM waves, you could imagine dodging through when the E and B fields happen to be near zero in the cycle. If the waves are random them there will be no time when the fields are zero. (Plus there will be the effect of the E fields too.)
     
  4. Aug 10, 2015 #3
    Thanks.
    Your first answer was what I expected, but the second answer is interesting.
    If the waves are random, then there should be a theoretical probability when E and B are both near zero in the cycle.
    If so, then the probabilities would say, for example, that 1 in a billion (pure guess) particles would get through at this moment.
    That moment could start as E & B are nearing their low point, passing through that low point, and then rising back to a point that would have significant reaction with the charged particles.
    So during that "moment", is there a way to manipulated the waves, or their timing, to coincide with a generated particle speed, that is a speed achieved by accelerating particles, to take advantage of this "moment" where the laws of probabilities suggest 1 particle per billion would get through. If so, then the solution would be to create the sufficient magnetic field and then accelerate billions of particles such that at least 1 billion of them are arriving at the magnetic field during each "moment" cycle.
    The probabilities would then suggest that at a particular moment the E and B fields would be near zero as the required number of charged particles are entering the field and at least 1 particle should pass through.
    If this theory holds, then we should be able to work with the magnetic fields and a sufficient number of charged particles, to enable significantly more than 1 particle per "moment" to pass through.
    If so, I have some other wonderings on how to put that to work.

    This is just another thought experiment. Something that crossed my mind while watching the science channel...
    Thanks
     
  5. Aug 10, 2015 #4

    sophiecentaur

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    I have a feeling that you are thinking along the same lines as the operation of charged particle accelerators, perhaps of a type called "travelling wave' - or maybe the cyclotron. But, rather than choosing the point in time and space where the field is minimum, they choose the time and place where the fields are at their peak (to maximise energy transfer). Or would you be talking about 'beam modulation' - or even a form of mass spectrometer??
    There are bits of lot of existing things in your post and I'm not sure exactly where you are going with your ideas.
     
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