2011 Particle Accelerator Conference - List of Keywords (RF-structure)

Paper	Title	Other Keywords	Page
TUP049	Vacuum Arcs and Gradient Limits	plasma, vacuum, cavity, ion	895
	J. Norem, Z. Insepov ANL, Argonne, USA A. Moretti Fermilab, Batavia, USA
	Funding: DOE/OHEP We have been extending and refining our model of vacuum breakdown and gradient limits and will describe recent developments. The model considers a large number of mechanisms but finds that vacuum arcs can be described fairly simply and self consistently, however simulations of individual mechanisms can be, in some cases, involved. Although based on accelerator rf data, we believe our model of vacuum arcs should have general applicability.

WEP159	Improved Algorithms for Multipacting Simulation in the Analyst Code	cavity, simulation, resonance, multipactoring	1785
	J.F. DeFord, B.L. Held, K.J. Willis STAAR/AWR Corporation, Mequon, USA
	Funding: Work funded by the U.S. Dept. of Energy, Office of Science, SBIR Contract No. DE-FG02-05ER84373. Electron multipacting is often deleterious in RF structures and must be controlled via modifications to the geometry, materials, or external fields. Recent improvements to the capabilities for modeling multipacting in the Analyst software package are presented in this paper. A backward difference scheme, coupled with Newton-Raphson iteration, is used to integrate particle position/momentum, with integrations interrupted at element faces to minimize errors and lost particles. Support for the Furman-Pivi secondary emission model* has been implemented, with separate representations for low energy, re-diffused, and backscattered secondary particles, and multiple emissions per impact based upon a probability distribution. We have also developed a method to prune the tree of secondary particles resulting from an impact that minimizes particle count growth while maintaining important statistical information about the resonance. Finally, we have added support for volumetric sourcing of primaries, wherein the model volume is seeded with a population of particles with random positions and initial velocities. These improvements, along with benchmark calculations, will be presented. * D. Darmofal, et al., Jour. Comp. Phys., 123, 1996, pp. 182-195. ** M. Furman, et al., LBNL-52807, June, 2003.

THP184	Tuning of the LCLS Linac for User Operation	linac, diagnostics, electron, feedback	2462
	H. Loos, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, P. Emma, A.S. Fisher, J.C. Frisch, A. Gilevich, P. Hering, Z. Huang, R.H. Iverson, N. Lipkowitz, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, T.J. Smith, J.L. Turner, J.J. Welch, W.E. White, J. Wu, G. Yocky SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. With the Linac Coherent Light Source (LCLS) now in its third user run, reliable electron beam delivery at various beam energies and charge levels has become of high operational importance. In order to reduce the beam tuning time required for such changes, several diagnostics and feed-forward procedures have been implemented. We report on improved lattice diagnostics to detect magnet, model, and diagnostics errors as well as on measurements of transverse RF kicks and static field contributions and corresponding correction procedures to facilitate beam energy changes.

Paper

Title

Other Keywords

Page

TUP049

Vacuum Arcs and Gradient Limits

plasma, vacuum, cavity, ion

895

J. Norem, Z. Insepov
ANL, Argonne, USA
A. Moretti
Fermilab, Batavia, USA

Funding: DOE/OHEP
We have been extending and refining our model of vacuum breakdown and gradient limits and will describe recent developments. The model considers a large number of mechanisms but finds that vacuum arcs can be described fairly simply and self consistently, however simulations of individual mechanisms can be, in some cases, involved. Although based on accelerator rf data, we believe our model of vacuum arcs should have general applicability.

WEP159

Improved Algorithms for Multipacting Simulation in the Analyst Code

cavity, simulation, resonance, multipactoring

1785

J.F. DeFord, B.L. Held, K.J. Willis
STAAR/AWR Corporation, Mequon, USA

Funding: Work funded by the U.S. Dept. of Energy, Office of Science, SBIR Contract No. DE-FG02-05ER84373.
Electron multipacting is often deleterious in RF structures and must be controlled via modifications to the geometry, materials, or external fields. Recent improvements to the capabilities for modeling multipacting in the Analyst software package are presented in this paper. A backward difference scheme*, coupled with Newton-Raphson iteration, is used to integrate particle position/momentum, with integrations interrupted at element faces to minimize errors and lost particles. Support for the Furman-Pivi secondary emission model** has been implemented, with separate representations for low energy, re-diffused, and backscattered secondary particles, and multiple emissions per impact based upon a probability distribution. We have also developed a method to prune the tree of secondary particles resulting from an impact that minimizes particle count growth while maintaining important statistical information about the resonance. Finally, we have added support for volumetric sourcing of primaries, wherein the model volume is seeded with a population of particles with random positions and initial velocities. These improvements, along with benchmark calculations, will be presented.
* D. Darmofal, et al., Jour. Comp. Phys., 123, 1996, pp. 182-195.
** M. Furman, et al., LBNL-52807, June, 2003.

THP184

Tuning of the LCLS Linac for User Operation

linac, diagnostics, electron, feedback

2462

H. Loos, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, P. Emma, A.S. Fisher, J.C. Frisch, A. Gilevich, P. Hering, Z. Huang, R.H. Iverson, N. Lipkowitz, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, T.J. Smith, J.L. Turner, J.J. Welch, W.E. White, J. Wu, G. Yocky
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
With the Linac Coherent Light Source (LCLS) now in its third user run, reliable electron beam delivery at various beam energies and charge levels has become of high operational importance. In order to reduce the beam tuning time required for such changes, several diagnostics and feed-forward procedures have been implemented. We report on improved lattice diagnostics to detect magnet, model, and diagnostics errors as well as on measurements of transverse RF kicks and static field contributions and corresponding correction procedures to facilitate beam energy changes.