Jefferson Lab
Information Resources
Jefferson Lab Home Search Contact JLab

    Online Measurement and Tuning of Multipass Recirculation Time in the CEBAF Linac

    CEBAF is a recirculating electron accelerator with negligible synchrotron motion of the particles within each bunch. On-crest RF acceleration is used to minimize the time-averaged energy spread of the beam. Previously installed diagnostics** allow us to m aintain the relative timing of the beam and the RF, noninvasively compensating for residual drifts of the RF timing system on the first acceleration pass. However, residual setup errors for the path length (recirculation time) and variable path length dri ft between passes result in relative drifts of beam energy at the 10-4 scale for some passes, even when the energy of any one of the recirculation passes is held fixed by adjusting the RF gradient. We have extended the diagnostic system to the higher acceleration passes and can correct the recirculation timing at the scale of hundreds of femtoseconds (tenths of a degree of 1497 MHz RF phase). Variation in the higher-pass beam to RF timing indicates drift in the beam recirculation time. The prev ious procedure for measuring and tuning the path length required suspension of beam delivery to the users. These actions can now be done without interruption of beam to the experimenters.

    This work was supported by U.S. DOE under contract DE-AC05-84ER40150.

    ** High-Precision Beam-Based RF Phase Stabilization at Jefferson Lab, V.A. Lebedev, J. Musson, and M.G. Tiefenback, Proceedings of the 1999 Part. Acc. Conf., New York, NY, USA

    Author: M.G. Tiefenback

    Abstract submitted to PAC 2001, Chicago, IL, June 18-24, 2001

    Updated March 28, 2001



    maintained by the Publications Manager