Wake-field characteristics of a high-intensity, multi-bunched beam

A systematic experimental study on the wake-field characteristics of a high-intensity, multi-bunched electron beam was carried out in detail at the primary electron section of the KEK positron generator linac. The observed energy spectrum, which indicated the energy variation of one bunch from another, was explained fairly well by the multibunch effect of a longitudinal wake field; the importance of introducing a self-wake loss and a bunch-length effect into calculations of the energy loss due to a longitudinal wake field is noted. On the other hand, a transverse motion of each bunch, showing a peculiar behavior when the transverse instability occurred, was in good agreement with the results of a numerical calculation based on a multibunch version of P.B. Wilson's two-particle model. In both cases, the wake field for our cavity was estimated using a computer code called TBCI. (author)