Dynamics of a magnetized relativistic electron beam in composite drift tubes with virtual cathodes

A computer simulation of the dynamics of a magnetized electron beam in comp osite drift tubes with multiple virtual cathodes is presented. For a single -cavity tube, the value of the limiting current is found to equal that give n by an exact formula. For two- and three-cavity tubes, it is revealed that the values of the limiting currents are smaller than those reported previo usly and that the current diagram may have a different structure. These phe nomena are attributed to Pierce instability. The efficiency of microwave ge neration as a function of injection current is examined. It is established that the efficiency is minimum if the current equals any of the limiting va lues refined. (C) 2001 MAIK "Nauka/Interperiodica".