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Electrons in a dielectric

  1. Oct 8, 2014 #1
    So I have seen some people doing making lichtenberg figures using a particle accelerator to blast electrons into a dielectric where they get stuck until the dielectric breaks down.
    Here is an example http://www.capturedlightning.com/
    Are there other ways to get electrons into a dielectric other than using a particle accelerator?
     
  2. jcsd
  3. Oct 8, 2014 #2
    Damn, I would bet a solid dielectric like glass should fail explosively under such stress...oo)
     
  4. Oct 11, 2014 #3
    Yes. A pointed electrode can be melted into a transparent polymer, such as acrylic (polymethylmethacrylate), epoxy, or polycarbonate and a flat electrode applied to the opposite side of the polymer. When the pointed electrode is energized from a HV AC source or from a pulsed HV source, charges will be injected into the nearby dielectric region around the point (where the electrical field is strongest) forming an area of space charge within the nearby dielectric. The space charge regions may suddenly discharge back to the electrode during removal or reversal of the applied voltage, a process called "charge detrapping". These detrapping events, or "partial discharges" within the polymer permanently damage the dielectric. Successive partial discharges create growing microscopic hollow tubules within the dielectric that have partially-conductive walls. The newl-formed tubules extend and concentrate the electrical fields at tubule tipe, injecting charge into more distant regions of dielectric material. Under repetitive charge injection and detrapping events, the tree channels grow and branch, eventually forming a 3D complex electrical tree within the polymer that originates from the pointed electrode, extending a significant distance into the polymer. Over time, the tree grows roughly in the direction of the opposite electrode. It may eventually completely propagate to the opposite side, culminating in complete dielectric failure. If tree growth is stopped before complete breakdown, the result is a 3D electrical tree that may have longer branches (called a "branch tree"). Branch trees typically develop under under positive DC, positive pulses, or lower voltage AC. Shorter and denser "bushy trees" tend to develop under HV negative pulses, under higher frequency AC, or under higher AC voltage excitation. Although these electrical trees are smaller than trees created using a particle accelerator, they are every bit as detailed and the branched trees have similar fractal dimensions.
     
  5. Oct 12, 2014 #4
    @BertHickman, very interesting. Do you know if other solid dielectric materials plates behave like that under the HV pulses?
     
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