FEL2013 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOPSO06	Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method	vacuum, simulation, radiation, synchrotron	32
	D. A. Bizzozero, J.A. Ellison, K.A. Heinemann, S.R. Lau UNM, Albuquerque, New Mexico, USA
	Funding: This work was primarily supported by DOE under DE-FG-99ER41104. The work of DB and SL was partially supported by NSF grant PHY 0855678 to the University of New Mexico. We continue our study* of CSR from a bunch moving on an arbitrary curved trajectory. In that study we developed an accurate 2D CSR Vlasov-Maxwell code (VM3@A) and applied it to a four dipole chicane bunch compressor. Our starting point now is the well-established paraxial approximation** with boundary conditions for a perfectly conducting vacuum chamber with uniform cross-section. This is considerably different from our previous approach* where we calculated the fields from an integral over history, using parallel plate boundary conditions. In this study, we present a Discontinuous Galerkin (DG) method for the paraxial approximation equations. Our basic tool is a MATLAB DG code on a GPU using MATLAB's gpuArray; the code was developed by one of us (DB). We discuss our results in the context of previous work and outline future applications for DG, including a Vlasov-Maxwell study. * See PRST-AB 12 080704 (2009) and Proceedings from ICAP2012 TUSDC2. ** See PRST-AB 7 054403 (2004), PRST-AB 12 104401 (2009) and Jpn. J. Appl. Phys. 51 016401 (2012).

MOPSO65	Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping	wakefield, undulator, electron, FEL	108
	J. Qiang, C.E. Mitchell LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Wakefields from resistive wall and surface roughness inside an undulatory can cause significant growth of beam energy spread and limit the performance of x-ray FEL radiation. In this paper, we propose a method to mitigate such energy modulation by appropriately conditioning the electron beam current profile. Numerical example and potential applications will also be discussed.

MOPSO73	Suface Roughness Wakefield in FEL Undulator	wakefield, undulator, electron, FEL	127
	G.V. Stupakov SLAC, Menlo Park, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL. [1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.

Paper

Title

Other Keywords

Page

MOPSO06

Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method

vacuum, simulation, radiation, synchrotron

32

D. A. Bizzozero, J.A. Ellison, K.A. Heinemann, S.R. Lau
UNM, Albuquerque, New Mexico, USA

Funding: This work was primarily supported by DOE under DE-FG-99ER41104. The work of DB and SL was partially supported by NSF grant PHY 0855678 to the University of New Mexico.
We continue our study* of CSR from a bunch moving on an arbitrary curved trajectory. In that study we developed an accurate 2D CSR Vlasov-Maxwell code (VM3@A) and applied it to a four dipole chicane bunch compressor. Our starting point now is the well-established paraxial approximation** with boundary conditions for a perfectly conducting vacuum chamber with uniform cross-section. This is considerably different from our previous approach* where we calculated the fields from an integral over history, using parallel plate boundary conditions. In this study, we present a Discontinuous Galerkin (DG) method for the paraxial approximation equations. Our basic tool is a MATLAB DG code on a GPU using MATLAB's gpuArray; the code was developed by one of us (DB). We discuss our results in the context of previous work and outline future applications for DG, including a Vlasov-Maxwell study.
* See PRST-AB 12 080704 (2009) and Proceedings from ICAP2012 TUSDC2.
** See PRST-AB 7 054403 (2004), PRST-AB 12 104401 (2009) and Jpn. J. Appl. Phys. 51 016401 (2012).

MOPSO65

Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping

wakefield, undulator, electron, FEL

108

J. Qiang, C.E. Mitchell
LBNL, Berkeley, California, USA

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Wakefields from resistive wall and surface roughness inside an undulatory can cause significant growth of beam energy spread and limit the performance of x-ray FEL radiation. In this paper, we propose a method to mitigate such energy modulation by appropriately conditioning the electron beam current profile. Numerical example and potential applications will also be discussed.

MOPSO73

Suface Roughness Wakefield in FEL Undulator

wakefield, undulator, electron, FEL

127

G.V. Stupakov
SLAC, Menlo Park, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL.
[1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.