Using surface impedance for calculating wakefields in flat geometry

Bane, K.; Stupakov, Gennady

doi:10.1103/physrevstab.18.034401

Cited by 24 publications

(35 citation statements)

References 9 publications

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“…The general form of the impedances for a flat structure, one that can be described using the surface impedance concept, is developed in Refs. [5,6]. A conclusion of this work was that the final results-the impedances-were approximate and valid, provided that the frequency k = ω/c 1/a-which is satisfied-and that |ζ| 1 (or h/a 1), which is not.…”

Section: Flat Geometrymentioning

confidence: 89%

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Estimate of Joule Heating in a Flat Dechirper

Bane

Stupakov

Gjonaj

2017

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We have performed Joule power loss calculations for a flat dechirper. We have considered the configurations of the beam on-axis between the two plates-for chirp control-and for the beam especially close to one plate-for use as a fast kicker. Our calculations use a surface impedance approach, one that is valid when corrugation parameters are small compared to aperture (the perturbative parameter regime). In our model we ignore effects of field reflections at the sides of the dechirper plates, and thus expect the results to underestimate the Joule losses. The analytical results were also tested by numerical, time-domain simulations. We find that most of the wake power lost by the beam is radiated out to the sides of the plates. For the case of the beam passing by a single plate, we derive an analytical expression for the broad-band impedance, and-in Appendix B-numerically confirm recently developed, analytical formulas for the short-range wakes. While our theory can be applied to the LCLS-II dechirper with large gaps, for the nominal apertures we are not in the perturbative regime and the reflection contribution to Joule losses is not negligible.With input from computer simulations, we estimate the Joule power loss (assuming bunch charge of 300 pC, repetition rate of 100 kHz) is 21 W/m for the case of two plates, and 24 W/m for the case of a single plate.

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Section: Flat Geometrymentioning

confidence: 89%

“…In previous work, the surface impedance approach to obtaining the impedances and wakes of a short, high energy bunch in a flat dechirper was derived [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Estimate of Joule Heating in a Flat Dechirper

Bane

Stupakov

Gjonaj

2017

Self Cite

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“…[5,6]. A conclusion of this work was that the final results-the impedances-were approximate and valid, provided that the frequency k ¼ ω=c ≫ 1=a-which is satisfied-and that jζj ≪ 1 (or h=a ≪ 1), which is not for our nominal corrugation parameters (see Table I).…”

Section: Flat Geometrymentioning

confidence: 97%

“…[5], which explicitly gives the fields and wakefields in structures with flat geometry for which the effect at the boundaries can be approximated by a surface impedance. First the frequency representation of the fields are Fourier transformed in x asĤ…”

Section: Flat Geometrymentioning

confidence: 99%

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Joule heating in a flat dechirper

Bane

Stupakov

Gjonaj

2017

Phys. Rev. Accel. Beams

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We perform Joule power loss calculations for a flat dechirper. We consider the configurations of the beam on-axis between the two plates-for chirp control-and for the beam especially close to one platefor use as a fast kicker. Our calculations use a surface impedance approach, one that is valid when corrugation parameters are small compared to aperture (the perturbative parameter regime). We find that most of the wake power lost by the beam is radiated out to the sides of the plates. For the case of the beam passing by a single plate, we derive an analytical expression for the broadband impedance. Our analytical results are also tested by numerical, time-domain simulations. While our theory can be applied to the LCLS-II dechirper with large gaps, for the nominal apertures we are not in the perturbative regime. With input from computer simulations, we estimate the Joule power loss for nominal apertures (assuming bunch charge of 300 pC, repetition rate of 100 kHz) is 21 W=m for the case of two plates, and 24 W=m for the case of a single plate.

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Wakefields studies for the SXFEL user facility

et al. 2017

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Besides the original seeded undulator line, in the Soft X-ray free-electron laser (SXFEL) user facility at Shanghai, a second undulator line based on self-amplified spontaneous emission is proposed to achieve 2 nm laser pulse with extremely high brightness. In this paper, the beam energy deviation induced by the undulator wakefields is numerically obtained, and it is verified to have a good agreement between 3D and 2D simulation results. The beam energy loss along the undulator degrades the expected FEL output performance. Impact of wakefields on pulse energy, radiation power and spectrum is discussed, as well as the benefits of compensation obtained with a taper in the undulator field. And using the planned SXFEL diagnostic, a longitudinal wakefields measurement experiment is proposed and simulated.

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Using surface impedance for calculating wakefields in flat geometry

Cited by 24 publications

References 9 publications

Estimate of Joule Heating in a Flat Dechirper

Estimate of Joule Heating in a Flat Dechirper

Joule heating in a flat dechirper

Wakefields studies for the SXFEL user facility

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