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A theoretical question about mater/antimatter and capacitors

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calzap:
The voltage source, resistors and wires are irrelevant.  With metal plates of matter and antimatter that close, there would quickly be a nuclear explosion. Even without heating, at any temperature above 0 K, there would be occasional electrons or positrons making the journey through the vacuum to the other side or meeting in the middle.  The time lag at usual room temperatures would be very short.  In addition, to thermal excitation, bombarding cosmic rays or radioactive impurities in the plates could excite electrons and positrons into leaving.  The annihilation gamma radiation from electrons and positrons meeting would bombard the plates, interact there, and release more electrons/positrons.  As the lepton interactions become more frequent, the increasing energy release will knock atoms or their nuclei across the gap.  Then the really big energy release starts.  A runaway chain reaction ensues.

Mike in Calfornia

Mechatrommer:

--- Quote from: RoGeorge on January 09, 2020, 02:49:35 am ---How can matter and antimatter annihilate through vacuum?

--- End quote ---
if its that easy? CERN scientists will already have vaccum pendant filled with anti-hydrogen going around.

atmfjstc:

--- Quote from: calzap on January 09, 2020, 08:04:34 am ---The voltage source, resistors and wires are irrelevant.  With metal plates of matter and antimatter that close, there would quickly be a nuclear explosion. Even without heating, at any temperature above 0 K, there would be occasional electrons or positrons making the journey through the vacuum to the other side or meeting in the middle.  The time lag at usual room temperatures would be very short.  In addition, to thermal excitation, bombarding cosmic rays or radioactive impurities in the plates could excite electrons and positrons into leaving.  The annihilation gamma radiation from electrons and positrons meeting would bombard the plates, interact there, and release more electrons/positrons.  As the lepton interactions become more frequent, the increasing energy release will knock atoms or their nuclei across the gap.  Then the really big energy release starts.  A runaway chain reaction ensues.

Mike in Calfornia

--- End quote ---

Not necessarily. Yes, there will always be a non-zero amount of electrons/positrons that escape and meet due to random processes. But the system will only run away exponentially if every single annihilation is guaranteed to cause at least one other annihilation some time later. I find this unlikely, given how easy it is for the resulting photon to just miss the plates entirely, knock electrons off in the wrong direction etc.

Let's say there are 1000 annihilations caused by temperature, cosmic radiation etc. every instant. If each annihilation has a 1/10 chance of causing another, at the next instant we'll have the base 1000 annihilations, plus another 100 caused by the ones at the previous instant, for a total of 1100. The next instant we'll have the base 1000, plus 110 caused by the ones at the previous instant, totalling 1110. The number converges towards 1111.1111... and thus we reach an equilibrium. The system will converge for any cascade probability less than 100%.

It really looks a lot like fission. There is always a non-zero amount of spontaneous fission. But it will only become self-sustaining under specific conditions.

Domagoj T:
Unless you have just a tiny bit of ablation which knock a bit of material to the opposite side, causing much bigger event that quickly goes out of hand.

calzap:
Let's not forget that electrons and positrons are attracted to each other unlike neutrons and nuclei in fission reactions.  So, any electron or positron that gets freed from its home plate has a  high probability of being annihilated.   Electron/positron annihilation produces two gamma rays of 512 KeV each traveling in opposite directions.  If the plates have lateral dimensions significantly larger than 1 micron, they are virtually certain to be struck by the gamma rays.  Whether the gamma rays interact depends on the elemental composition of the plates and their thickness.

Mike in California



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