Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Cancellation of klystron-induced energy and arrival-time variations in linear accelerators with arc-type bunch compressors

Mansten, Erik LU ; Svärd, Robin LU orcid ; Thorin, Sara LU ; Eriksson, Mikael LU and Tavares, Pedro Fernandes LU (2024) In Physical Review Accelerators and Beams 27(4).
Abstract

We explain how the accelerating field amplitude and phase vary with modulator voltage in pulsed radio frequency high-power amplifiers based on klystron tubes. Changes in modulator voltage give rise to correlated changes of amplitude and phase, affecting the properties of the accelerated beam, in particular energy, arrival time, and bunch duration. We show, both theoretically and experimentally, that there exists a postcrest acceleration phase (the magic angle) where the changes of beam energy due to phase and amplitude shifts caused by modulator-voltage variations cancel out. When accelerating at the magic angle, the klystron modulator voltage jitter no longer contributes to energy and arrival-time jitter in the accelerator. Off-crest... (More)

We explain how the accelerating field amplitude and phase vary with modulator voltage in pulsed radio frequency high-power amplifiers based on klystron tubes. Changes in modulator voltage give rise to correlated changes of amplitude and phase, affecting the properties of the accelerated beam, in particular energy, arrival time, and bunch duration. We show, both theoretically and experimentally, that there exists a postcrest acceleration phase (the magic angle) where the changes of beam energy due to phase and amplitude shifts caused by modulator-voltage variations cancel out. When accelerating at the magic angle, the klystron modulator voltage jitter no longer contributes to energy and arrival-time jitter in the accelerator. Off-crest operation at the magic angle can be implemented for bunch compression schemes in accelerators with arc-type bunch compressors, which have positive momentum compaction. The experimental results, obtained at the MAX IV laboratory, show the benefit of operating close to the magic angle in arc-type bunch compressors. In a direct measurement of normalized electron-energy jitter, the energy jitter was reduced by a factor of 1.8 down to 8.2×10-5 when operating at the magic angle.

(Less)
Please use this url to cite or link to this publication:
author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review Accelerators and Beams
volume
27
issue
4
article number
040401
publisher
American Physical Society
external identifiers
  • scopus:85191335353
ISSN
2469-9888
DOI
10.1103/PhysRevAccelBeams.27.040401
language
English
LU publication?
yes
id
fb1d5009-a4ad-406e-80f9-972dfde5c992
date added to LUP
2024-05-07 12:16:07
date last changed
2024-05-07 12:17:33
@article{fb1d5009-a4ad-406e-80f9-972dfde5c992,
  abstract     = {{<p>We explain how the accelerating field amplitude and phase vary with modulator voltage in pulsed radio frequency high-power amplifiers based on klystron tubes. Changes in modulator voltage give rise to correlated changes of amplitude and phase, affecting the properties of the accelerated beam, in particular energy, arrival time, and bunch duration. We show, both theoretically and experimentally, that there exists a postcrest acceleration phase (the magic angle) where the changes of beam energy due to phase and amplitude shifts caused by modulator-voltage variations cancel out. When accelerating at the magic angle, the klystron modulator voltage jitter no longer contributes to energy and arrival-time jitter in the accelerator. Off-crest operation at the magic angle can be implemented for bunch compression schemes in accelerators with arc-type bunch compressors, which have positive momentum compaction. The experimental results, obtained at the MAX IV laboratory, show the benefit of operating close to the magic angle in arc-type bunch compressors. In a direct measurement of normalized electron-energy jitter, the energy jitter was reduced by a factor of 1.8 down to 8.2×10-5 when operating at the magic angle.</p>}},
  author       = {{Mansten, Erik and Svärd, Robin and Thorin, Sara and Eriksson, Mikael and Tavares, Pedro Fernandes}},
  issn         = {{2469-9888}},
  language     = {{eng}},
  number       = {{4}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Accelerators and Beams}},
  title        = {{Cancellation of klystron-induced energy and arrival-time variations in linear accelerators with arc-type bunch compressors}},
  url          = {{http://dx.doi.org/10.1103/PhysRevAccelBeams.27.040401}},
  doi          = {{10.1103/PhysRevAccelBeams.27.040401}},
  volume       = {{27}},
  year         = {{2024}},
}