How a linear accelerator works:
1. A powerful radio frequency system, similar to a radar transmitter,
produces high electric fields in the gaps between electrodes.
2. The electric fields in each gap oscillate together at the frequency
of the rf power.
3. The charged particles arrive in bunches, timed to enter the first gap
when the field is accelerating.
4. When the field is reversed, i.e. decelerating, the particles are
hidden in the bore of the drift tube, shielded from the electric field.
5. The drift tube length and spacing increases to keep pace with the
increasing particle velocity as they gain energy.
6. The bunches are timed to arrive in the center of the gap, as the field
is increasing, so that those arriving early gain less energy, and those
arriving late gain more energy.
7. The beam is focused in the transverse direction by strong permanent
magnet quadrupoles inside each drift tube.
Click here to view
line drawings of a LINAC.