Speaker
Dr
Alex Lumpkin
(Fermilab)
Description
We report the direct observations of sub-macropulse beam centroid oscillations correlated with higher order modes (HOMs) which were generated by off-axis electron beam steering in TESLA-type SCRF cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a photocathode rf gun injecting beam into two separated 9-cell cavities in series with corrector magnets and beam position monitors (BPMs) located before, between, and after them. Oscillations of ~100 kHz in the vertical plane and ~380 kHz in the horizontal plane with up to 600-µm amplitudes were observed in a 3-MHz micropulse repetition rate beam with charges of 100, 300, 500, and 1000 pC/b. However, the effects were much reduced at 100 pC/b. The measurements are based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch array data, imaging cameras, and a framing camera. Calculations reproduced the oscillation frequencies of the phenomena in the vertical case. In principle, these fundamental results may be scaled to cryomodule configurations of major accelerator facilities.
Primary authors
Dr
Alex Lumpkin
(Fermilab)
Dr
Bruce Carlsten
(LANL)
Mr
Dean Edstrom
(Fermilab)
Dr
Jinhao Ruan
(Fernilab)
Dr
Nathan Eddy
(Fermilab)
Dr
Olivier Napoly
(CEA-Saclay)
Mr
Peter Prieto
(Fermilab)
Dr
Randy Thurman-Keup
(Fermilab)
