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How do colliding-beam storage rings differ from fixed-target accelerators?

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Diagram of a linear proton resonance accelerator, or linac, showing protons entering from a source, passing through a series of labeled drift tubes powered by a radio-frequency source, and exiting as a beam through a cavity. — particle accelerator The accelerator is a large-diameter tube within which an electric field oscillates at a high radio frequency. Within the accelerator tube are smaller diameter metallic drift tubes, which are carefully sized and spaced to shield the protons from decelerating oscillations of the electric field. In the spaces between the drift tubes, the electric field is oriented properly to accelerate the protons in their direction of travel.

Colliding-beam storage rings and fixed-target accelerators differ primarily in how they utilize energy for particle interactions.

In a fixed-target accelerator, a beam of accelerated particles strikes a stationary target. Because the target is at rest, a significant portion of the beam's energy is consumed by the motion of the resulting particles to satisfy the law of conservation of momentum, leaving only a fraction of the energy available for the interaction itself.12

In contrast, colliding-beam storage rings accelerate two beams in opposite directions and bring them into head-on collision. Because the net momentum of the two beams is zero, virtually all of the combined kinetic energy is available for the interaction, such as the creation of new, massive subatomic particles.12

However, these systems have distinct trade-offs:
* Interaction Rate: Fixed-target accelerators provide a high density of target particles, leading to frequent interactions. In colliders, the number of particles is much smaller, making actual interactions relatively rare.12
* Secondary Particles: Storage rings do not produce the intense beams of secondary particles that fixed-target experiments can generate.1

Ultimately, colliders are essential for reaching the highest possible interaction energies, placing them at the forefront of particle physics research.12