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@inproceedings{thurman-keup:ipac2021-mopab232,
author = {R.M. Thurman-Keup and J.A. Diaz Cruz and D.R. Edstrom and B.T. Jacobson and A.H. Lumpkin and P.S. Prieto and J. Ruan and J.P. Sikora and F. Zhou},
% author = {R.M. Thurman-Keup and J.A. Diaz Cruz and D.R. Edstrom and B.T. Jacobson and A.H. Lumpkin and P.S. Prieto and others},
% author = {R.M. Thurman-Keup and others},
title = {{Observation of Polarization-Dependent Changes in Higher-Order Mode Responses as a Function of Transverse Beam Position in Tesla-Type Cavities at FAST}},
booktitle = {Proc. IPAC'21},
pages = {756--759},
eid = {MOPAB232},
language = {english},
keywords = {cavity, HOM, electron, dipole, cryomodule},
venue = {Campinas, SP, Brazil},
series = {International Particle Accelerator Conference},
number = {12},
publisher = {JACoW Publishing, Geneva, Switzerland},
month = {08},
year = {2021},
issn = {2673-5490},
isbn = {978-3-95450-214-1},
doi = {10.18429/JACoW-IPAC2021-MOPAB232},
url = {https://jacow.org/ipac2021/papers/mopab232.pdf},
note = {https://doi.org/10.18429/JACoW-IPAC2021-MOPAB232},
abstract = {{Higher-order modes (HOMs) in superconducting rf cavities present problems for an electron bunch traversing the cavity in the form of long-range wakefields from previous bunches. These may dilute the emittance of the macropulse average, especially with low emittance beams at facilities such as the European X-ray Free-electron Laser (XFEL) and the upgraded Linac Coherent Light Source (LCLS-II). Here we present observations of HOMs driven by the beam at the Fermilab Accelerator Science and Technology (FAST) facility. The FAST facility features two independent TESLA-type cavities (CC1 and CC2) after a photocathode rf gun followed by an 8-cavity cryomodule. The HOM signals were acquired from cavities using bandpass filters of 1.75 ± 0.15 GHz, 2.5 ± 0.2 GHz, and 3.25 ± 0.2 GHz and recorded using an 8-GHz, 20 GSa/s oscilloscope. The frequency resolution obtained is sufficient to separate polarization components of many of the HOMs. These HOM signals were captured from CC1 and cavities 1 and 8 of the cryomodule for various initial trajectories through the cavities, and we observe correlations between trajectory, HOM signals, and which polarization component of a mode is affected.}},
}