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Title: Three-dimensional envelope instability in periodic focusing channels

The space-charge driven envelope instability can be of great danger in high intensity accelerators and was studied using a two-dimensional (2D) envelope model and three-dimensional (3D) macroparticle simulations before. In this paper, we study the instability for a bunched beam using a three-dimensional envelope model in a periodic solenoid and radio-frequency (rf) focusing channel and a periodic quadrupole and rf focusing channel. This study shows that when the transverse zero current phase advance is below 90°, the beam envelope can still become unstable if the longitudinal zero current phase advance is beyond 90°. For the transverse zero current phase advance beyond 90°, the instability stopband width becomes larger with the increase of the longitudinal focusing strength and even shows different structure from the 2D case when the longitudinal zero current phase advance is beyond 90°. Breaking the symmetry of two longitudinal focusing rf cavities and the symmetry between the horizontal focusing and the vertical focusing in the transverse plane in the periodic quadrupole and rf channel makes the instability stopband broader. This suggests that a more symmetric accelerator lattice design might help reduce the range of the envelope instability in parameter space.
Authors:
 [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 21; Journal Issue: 3; Related Information: © 2018 authors. Published by the American Physical Society.; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS
OSTI Identifier:
1427329
Alternate Identifier(s):
OSTI ID: 1465449

Qiang, Ji. Three-dimensional envelope instability in periodic focusing channels. United States: N. p., Web. doi:10.1103/PhysRevAccelBeams.21.034201.
Qiang, Ji. Three-dimensional envelope instability in periodic focusing channels. United States. doi:10.1103/PhysRevAccelBeams.21.034201.
Qiang, Ji. 2018. "Three-dimensional envelope instability in periodic focusing channels". United States. doi:10.1103/PhysRevAccelBeams.21.034201.
@article{osti_1427329,
title = {Three-dimensional envelope instability in periodic focusing channels},
author = {Qiang, Ji},
abstractNote = {The space-charge driven envelope instability can be of great danger in high intensity accelerators and was studied using a two-dimensional (2D) envelope model and three-dimensional (3D) macroparticle simulations before. In this paper, we study the instability for a bunched beam using a three-dimensional envelope model in a periodic solenoid and radio-frequency (rf) focusing channel and a periodic quadrupole and rf focusing channel. This study shows that when the transverse zero current phase advance is below 90°, the beam envelope can still become unstable if the longitudinal zero current phase advance is beyond 90°. For the transverse zero current phase advance beyond 90°, the instability stopband width becomes larger with the increase of the longitudinal focusing strength and even shows different structure from the 2D case when the longitudinal zero current phase advance is beyond 90°. Breaking the symmetry of two longitudinal focusing rf cavities and the symmetry between the horizontal focusing and the vertical focusing in the transverse plane in the periodic quadrupole and rf channel makes the instability stopband broader. This suggests that a more symmetric accelerator lattice design might help reduce the range of the envelope instability in parameter space.},
doi = {10.1103/PhysRevAccelBeams.21.034201},
journal = {Physical Review Accelerators and Beams},
number = 3,
volume = 21,
place = {United States},
year = {2018},
month = {3}
}