The initial uniform section AB may

The initial uniform section AB may be interrupted by one or more severs. At B, the beam is losing velocity due to the extraction of RF power, and a progressive shortening of the cavities is begun, to maintain synchronism. Many different patterns are used by different designers; some omit the fat sections CD and EF, while others make the transitions abrupt. Ideally, cold test data should be taken for as many different sections as possible to minimize the amount of interpolation. If data for AB only are available, then, in the taper region, the phase velocity should be taken to vary directly as the cavity period Ln the interaction impedance as Ln2.5, and the losses as Ln-2