How are electromagnetic fields generated in the cavity resonator for particle acceleration?

In the acceleration tube of a linear accelerator, the electric field direction runs in and against the direction of electron flight. The magnetic and electric fields of an electromagnetic wave are perpendicular to the direction of propagation, which is why I think that the fields in the cavity resonator of the linear accelerator are generated…

How many particles collide simultaneously in the particle accelerator?

In the particle accelerator, do 1 proton collide with 1 proton, or a proton beam collide with a proton beam (several protons at the same time)? Is care taken to ensure that there is a certain distance between the accelerated particles and that only individual protons collide with each other, or are clusters of protons…