Question: What is a particle accelerator?

Hywel Owen answered on 19 Jun 2012:

As the name suggests, it’s a thing that accelerates particles!

Think of a battery with a piece of wire connecting the positive and negative terminals together. The voltage from the battery pushes electrons down the wire from the negative to the positive terminal. In its simplest form a particle accelerator is just like this, except there’s no wire and the electrons travel down an empty tube – this means they can go fast without hitting anything. Of course, you have to suck all the air out of the tube, which is why the tube is called a vacuum vessel.

But, where do the electrons come from? It turns out that it’s easy to make electrons leave a piece of metal – you just heat it, and then apply a big voltage between the piece of metal (which we call a cathode) and something else. The electrons get drawn off.

The Large Hadron Collider starts by using a bottle of hydrogen gas, and you pass a spark voltage across a bit of the gas at a time. The spark destroys the hydrogen molecules making free protons and electrons, and a voltage pulls the protons away and down the vaccum tube. More voltages make the protons go faster and faster, just like with electrons. We also use magnets to help to confine the protons or electrons – they work a bit like lenses work on light.