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Title: Submacropulse electron-beam dynamics correlated with higher-order modes in Tesla-type superconducting rf cavities

Here, we report the direct observations of submacropulse beam centroid oscillations correlated with higher order modes (HOMs) which were generated by off-axis electron beam steering in TESLA-type superconducting rf 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 nine-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 were 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.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. CEA-Saclay, Gif-sur-Yvette (France)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
FERMILAB-PUB-18-044-AD-APC
Journal ID: ISSN 2469-9888; PRABCJ; 1677441
Grant/Contract Number:
AC02-07CH11359
Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 21; Journal Issue: 6; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; electron beam; SCRF accelerator; HOMs; beam centroid oscillation; framing camera
OSTI Identifier:
1440282
Alternate Identifier(s):
OSTI ID: 1457153