Effect of Ion Decoherence on Fast Beam-Ion Instability∗
نویسندگان
چکیده
The ionization of residual gas by an electron beam in an accelerator generates ions that can resonantly couple to the beam through a wave propagating in the beam-ion system. A beam-ion instability is studied for a multi-bunch train taking into account the decoherence of ion oscillations due to the ion frequency spread. It is shown that while the decoherence does not completely suppress the instability, it makes the growth rate appreciably smaller. A comparison of analytical and numerical results indicates a good agreement with direct macro-particle simulation of the instability.
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The ionization of residual gas by an electron beam in an accelerator generates ions that can resonantly couple to the beam through a wave propagating in the beam-ion system. The original theory of the Fast Ion Instability [1, 2] was developed assuming both a constant external focusing and the beam size. The theory predicts an instability in which an initial perturbation grows as ∼ exp(α√t). In ...
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