Author: Edstrom, D.R.
Paper Title Page
WEP034 Diagnostics Upgrades for Investigations of HOM Effects in TESLA-type SCRF Cavities 492
  • A.H. Lumpkin, N. Eddy, D.R. Edstrom, P.S. Prieto, J. Ruan, Y.-M. Shin, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
  Funding: Work at FNAL supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DoE. Work at LANL supported by U.S. DoE through the LANL/LDRD Program.
We describe the upgrades to diagnostic capabilities on the Fermilab Accelerator Science and Technology (FAST) electron linear accelerator that will allow investigations of the effects of high-order modes (HOMs) in SCRF cavities on macropulse-average beam quality. We focus here on the dipole modes in the first pass-band generally observed in the 1.6-1.9 GHz regime in TESLA-type SCRF cavities due to uniform transverse beam offsets of the electron beam. Such cavities are the basis of the accelerator for the European XFEL and the proposed MaRIE XFEL facility. Initial HOM data indicate that the mode intensities oscillate for about 10 microseconds after the micropulse enters the cavity, resulting in centroid shifts throughout the train. This results in a blurring of the averaged beam image size. The upgrades will include optimizing the HOM detectors' bandpass filters and adding a 1.3-GHz notch filter, converting the BPM electronics to bunch-by-bunch processing, and using the C5680 streak camera in a framing mode for bunch-by-bunch spatial information at the <20-micron level. The preliminary HOM detector data, prototype BPM test data, and first framing camera OTR data will be presented.
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