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Comment by splittingTimes | Hacker News Reader

Since 2014 I can find 34 citations, none of which are an actual experimental realization of their scheme [1]. Anyhow,

TL;DR: They theoretically propose the following experiment:

First, accelerate electrons to just below the speed of light and fire them into a slab of gold. This creates the beam of nessesary high-energy photons.

Second, fire a high-energy laser at the inner surface of a tiny hohlraum (German for ‘empty room’) gold can, to create a thermal radiation field which generates light similar to that emitted by stars.

Finally, direct the photon beam from (1) through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can.

===

[1] https://www.researchgate.net/publication/270858006_A_photon-...

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I know it's from the article, but the expression "Accelerate Electrons just below the speed of light" tells you pretty much nothing. An electron travelling at .9 the speed of light has 1.1 MeV of energy.

Nature seems to be down, so I can't access the abstract, but the google tagline has the following.

'Photons emitted above 100 MeV as a function of target width, for 1 × 109 incident electrons of energy 500 MeV (blue), 1 GeV (black) and 2 GeV (red).'

A table for comparison

        .9    1.1 MeV 
       .99    3.6 MeV
      .999   11 MeV
     .9999   36 MeV
    .99999  114 MeV
   .999999  361 MeV
  .9999999  1.14 GeV

So it's somewhere in the .999999c-.999999999c. Assuming that snippet was accurate. The LHC gets particles up to the TeV range, but, as the name suggests, they are much larger particles. An actual particle physicist can probably tell you more about whether it is significantly harder to get the much lighter Electron (and associated radiation losses) up to those energies.

SLAC (https://en.wikipedia.org/wiki/SLAC_National_Accelerator_Labo...) apparently can get electrons up to 50 GeV, so if those energies from the snippet are the target ones, that part should be achievable.

I'm not a particle physicist but a particle accelerator engineer.

GeV energies for electrons are achievable with a reasonably sized synchrotron like Diamond Light Source[0]. The magnets required to keep electrons in line are quite a bit smaller than those required for protons due to the mass difference. Small refrigerator sized verses small car sized.

[0] https://en.wikipedia.org/wiki/Diamond_Light_Source

That struck me as odd as well. 57 citations none of them where they actually ran the experiment and created electron / positron pairs. This was fun though (from 2013) "A table-top laser-based source of femtosecond, collimated, ultra-relativistic positron beams" -- https://arxiv.org/pdf/1304.5379.pdf

Comments such as this one make me always check comments before reading the submission. Thanks!

To be fair very few labs in the world have the ability to do that. Possibly only the NIF has powerful enough lasers

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