Single and multiple beam klystron modeling with TESLA

Summary form only given. TESLA (telegraphist's equations solution for linear-beam amplifiers) is a large-signal 2.5 D code successfully applied to the modeling of single beam and multiple beam klystron amplifiers. The current implementation of TESLA is based on the Fortran-95 language with a wide use of dynamically allocated memory. Advanced performance of the code together with highly efficient use of computer memory, user- friendly Python-based GUI and set of post-processing tools makes the TESLA package very useful as a primary design tool. Recent improvement in the TESLA model allows to accurately model the effects of slow and reflected particles, whose contribution becomes especially important for the simulation of high-efficiency devices. In addition, the extension of the code to a parallel version enables us to model beams in separate parallel processes. This allows more accurate simulation of multiple beam klystrons, having a large spread in the values of R/Q for the different beam- tunnels of the resonant cavities. The results of TESLA modeling of several devices and comparison with available experimental data are discussed.