The later method has been employed at SwissFEL. For this method to work, we demonstrated that the Swiss FEL injector test facility beam jitter was minimal and so was the vibration of the wire scanner.

While the wire is being moved through the beam, some particles interact with the wire and undergo a change in trajectory and energy. Since the beam has a well-known energy, the beam is bent with a dipole. But most of those particles that interacted with the beam do not bend with the beam and are lost. By observing the beam that is lost, one can measure transverse beam profile. Also by introducing a transverse deflection cavity (TDC), longitudinal bunch length information can be converted to a transverse beam profile. Using the TDC and wire scanner in the setup described, the longitudinal bunch length could also be measured.