Transient decay of beam-produced fields in thin-walled tubes

An electromagnetics problem that arises in long-pulse beam experiments is t he decay of image currents (and their fields) resulting from a beam that is offset from the geometric axis of the beam tube. A related problem, which arises in calibration of beam diagnostics, is that of simulating the beam u sing a current-carrying conductor. These problems are solved analytically i n the limit that the tube walls are thin compared with the magnetic-field p enetration depth. It is shown that the transient decay time of the fields f or these two cases is different. (C) 2001 American Institute of Physics.