A longitudinal multibunch feedback system for PEP

A bunch-by-bunch feedback system to suppress longitudinal multibunch instabilities is discussed. The feedback system is designed to operate on up to 18 equally spaced electron bunches for synchrotron radiation applications or up to nine electron by nine positron bunches for colliding beam operation. As an initial step in developing a very capable multibunch stabilizer, the system, which is based on a de-Qed 850-MHz 3-cell cavity, should enable stable storage of a total current of about 36 mA in about 18 bunches at 7 GeV in low-emittance mode for synchrotron radiation research. This is based on observed single bunch limits of about 2 mA in the low-emittance mode at 7 GeV. At higher electron energy, and/or with modifications to the low-emittance lattice, it is likely that even higher currents could be achieved, ultimately limited by transverse instabilities.<
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