A particle accelerator basically contains a beam of particles for study. Doing this by moving at high speeds. Typically you can't contain such particles as energy typically turns into something else eventually.
Barry’s explanation: “Imagine that that • dot is everything the human race has ever learned until this moment. That *draws big circle around the dot* ⭕️ Is everything we could learn from the particle accelerator. It’s a whole new way of looking at physics, it will literally change the way that we think, about everything.”