Theoretical study of power relativistic amplifiers for electron beam bunching

Two schemes of electron-positron linear colliders with energy in the TeV range based on the two beam accelerator (TBA) concept are being studied. In a TBA the first accelerator-driver produces a high current electron beam. The beam must be bunched along all collider length. There are some schemes for generating of such high-intensity drive beam bunches. One of the schemes for generating of high-intensity drive beam bunches involves Choppertron transverse velocity modulation of a beam. Another idea for generating drive beam is to use the bunching in the free electron laser (FEL) It has been shown that a high degree of bunching can be rather easily achieved in a short FEL amplifier. The first direct observation of the bunching of a relativistic electron beam, produced by a high power FEL interaction, was previously presented. This work is devoted to the computer simulation and comparison of the bunching of a relativistic electron beam produced by a FEL and by a travelling wave tube (TWT). The calculation results of the electron beam bunching in the FEL are also compared with the experimental results. With the help of rather simple model it is shown that one can obtain electron beam bunching in the TWT at a shorter length than in the FEL because the space gain in the TWT is higher than in the FEL