storage ring and collider
Accelerating a beam to high energy is hard work, so it would be wasteful to use it just once and throw it away. A storage ring is a circular machine designed to keep a high-energy beam circulating steadily for hours, like a racing car kept doing perfect laps long after it has reached full speed. The beam is no longer being sped up much; it is being maintained, lap after lap, ready to be used over and over.
A collider is a storage ring (or a pair of rings) built so that two beams cross and smash into each other at chosen points. Usually the two beams travel in opposite directions — protons one way and protons the other, or electrons one way and positrons the other — and they are steered to meet at specific spots wrapped in detectors. Each beam circulates for hours, and on every single lap the two beams pass through each other at the crossing points, giving millions of chances for collisions without having to make fresh beams each time. The detectors sit exactly where the beams cross, recording the spray of particles from each collision.
This combination is why modern discovery machines look the way they do. By keeping intense beams stored and colliding them head-on, a collider squeezes the maximum number of useful collisions out of beams that were expensive to make. The Large Hadron Collider, LEP, and the Tevatron were all collider storage rings; their experiments depended on the same beams crossing each other tens of millions of times per second for months on end.
In the LHC, two proton beams are stored circulating in opposite directions for many hours; where the rings cross inside the big detectors, the bunches pass through each other about 40 million times a second.
Store the beam, then cross it with another beam millions of times a second.
Most beam crossings produce nothing interesting — the particles simply miss each other — so a collider depends on storing intense, tightly squeezed beams that cross enormous numbers of times to make rare collisions happen often enough to study.