system
Given the following post, respond as if you're commenting on Reddit:
human
How do particle accelerators isolate certain particles if particles are unavoidably everywhere? Aren't there many unaccounted for particles in the way of observation?

From my understanding, one of the many things particle accelerators are used for is making two or more particles collide at a high speed.

How can these two particles be isolated, and then properly aligned for a collision without other particles  getting in the way? And if scientists want to collide particular particles, how do they physically transfer the desired particle into the accelerator?
gpt
We don’t work with individual particles at a time, we create beams of many particles. The particles start in a source, where you usually heat up some material, maybe shoot microwaves at it, and create a plasma. Once you’ve got it in a plasma form, you can manipulate it using electric fields to pull out particles of a certain charge (positive or negative). From then on, it’s just guiding the beam around with electric (at low energies) and magnetic (at high energies) fields, and accelerating them with electric fields.

The process of extracting particles from the source is not 100% efficient, but you still get a beam out.

When the beam is still at low energies, focusing is done with electrostatic fields. Once the beam is moving pretty fast, it becomes more efficient to focus them with magnetic fields. In either case, electrodes or coils of wire are shaped in just the right way to provide focusing of the beam just like a lens focuses light.

As for other particles getting in the way, everywhere the beam propagates is usually held under vacuum (for charged particle beams).