Beam breakup instability in induction accelerators

In particle accelerators, there are numerous beam instabilities. There are essentially space charge effects, chromatic effects and Beam Breakup instability. This instability results from progressively larger electromagnetic fields excited by the beam in subsequent sections of the accelerator, which affect the beam motion. This effect becomes more pronounced as the beam goes further down the accelerator. This instability put a limit on the beam intensity and drastically reduce the beam quality. We have studied theoretically the different processes of this phenomenon for an induction linac, and we have found the amplification laws for different beam conditions. From these results, we have developed a code of beam transport, and made some numerical studies on the Beam Breakup instability in the case of PlVAIR accelerator (8 cells, 8 MeV, 3,5 kA, 60 ns). We have evaluated the influence of the different parameters of the beam and of the accelerator, in particular the transverse impedance of the cells. Some experiments achieved on PlVAIR accelerator have allowed to observe this phenomenon and to reconcile with code predictions. We have determined the transverse impedance of the cells and extrapolated these results to AlRIX accelerator accelerator (64 cells, 8 MeV, 3,5 kA, 60 ns). (author)