Four dipoles can form a chicane, a device commonly used to compress electron bunches longitudinally. In the chicane the faster particles in the beam travel along shorter trajectories:
.
Linear compression coefficient R56 is defined by the chicane geometry
;
whereas, 2nd order compression coefficient T566 is generally insignificant, yet can be artificially enhanced - by offsetting a beam central energy E - to compensate for the electron beam longitudinal phase space curvature due to the space charge.