
New Particle Accelerator Fits on a Silicon Chip - pseudolus
https://www.scientificamerican.com/article/new-particle-accelerator-fits-on-a-silicon-chip1/
======
sigmaprimus
This article keeps conflating this new "electron" accelerator with traditional
"particle" accelerators.

I think it is important to understand that theres a big difference between
accelerating an electron and accelerating a protron or neutron.

It is my understanding that the value of traditional particle accelerators is
in the sub atomic pieces produced after creating a collision between two
particles traveling in opposite directions.

Is it even possible to cause two electrons to collide? Don't electrons occupy
multiple points in space at the same time?

That being said the work is still impressive and I am imagining super
efficient solar panels being produced from this new tech.

~~~
gus_massa
This is a very small particle accelerator. It's small because it only can give
the particles an energy of a few MeV and it's small because the usual
equipment has the size of a a refrigerator or a building.

You can accelerate electrons, protons, or other particles. It's easier to
accelerate electrons/positrons and protons/antiprotons because they have a
looooong life and they are charged.

Usually in modern big accelerators they use a particle and an antiparticle,
because you can reuse the big tunnel for both. The largest one that used
electrons-positrons was the LEP
[https://en.wikipedia.org/wiki/Large_Electron–Positron_Collid...](https://en.wikipedia.org/wiki/Large_Electron–Positron_Collider)
, but they "dismantle" it and are using the big tunnel for the LHC that use
protons-antiprotons.

But if you want to construct two gigantic tunnels instead of one you can make
an electron-electron collider. It's probably easier to convince an electron to
colide with a positron, but I'd like to ask an expert to get the exact number.

If a very fast electron goes nearby another electron they can get very close
before the electrostatic repulsion wins. When there are nearby, they can
interchange some very high energy photons, and perhaps some W or Z particles.
If you are lucky enough, some of the particles they interchange may escape and
steal some energy from the fas electron.

The electrons never really collide, they never touch the other electron. But
if you see this from far away (like a few millimeters away) it looks like they
have collided and released a particle.

For an exact calculation you must replace the handwaving an small balls story
with some Feynman diagrams and quantum mechanics, but the story is close
enough.

When you have an electron and a positron, they also don't really collide. They
release some photons and other particles. Sometimes all the intermediate
particles get reabsorbed and the electron/positron just change direction.
Sometimes both disappear and you just see the other particles that gamma
rays(that are photons). Sometimes something in between.

With protons-antiprotons it's more complicated because each has three quarks
and a lot of gluons that make the calculation more complicated, but at the end
it's the same story. The quarks never really colide.

Edit: There are electron-positron nodes in Feynman diagrams, so it's better to
say that they can colide, but at high energy the collision is much more
complicated than expected because they can interchange particles before the
collision.

