IPAC2013 - List of Authors (Veitzer, S.A.)

Paper	Title	Page
MOPWO068	Simulating Electron Cloud Evolution using Modulated Dielectric Models	1043
	S.A. Veitzer, P. Stoltz Tech-X, Boulder, Colorado, USA
	Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920) Electron clouds can pose a serious threat to accelerator performance, and understanding cloud buildup and the effectiveness of different mitigation techniques can provide cost-saving improvements in accelerator design and fabrication. Microwave diagnostics of electron clouds are a non-destructive way to measure cloud buildup, but it is very difficult to measure the cloud density from spectral signals alone. Modeling travelling-wave rf diagnostics is very hard because of the large range of spatial and temporal scales that must be resolved to simulate spectra. New numerical models have been used to generate synthetic spectra for electron clouds when the cloud density is not changing, and results have been compared to theoretical results. Here we use dielectric models to generate spectra for clouds that evolve over many bunch crossings. We first perform detailed simulations of cloud buildup using kinetic particle models, and then use an equivalent plasma dielectric model corresponding to this density, at a finer time resolution, to compute spectra. The stability and accuracy of dielectric models that spectra can be accurately determined in these very long timescale simulations.

TUPWO059	Reducing Emittance of a H⁻ Beam in a Solenoid-based Low-energy Beam Transport through Numerical Modeling	2000
	J. von Stecher, D.L. Bruhwiler, B.T. Schwartz, S.A. Veitzer Tech-X, Boulder, Colorado, USA B. Han, M.P. Stockli ORNL, Oak Ridge, Tennessee, USA
	Funding: This work is supported by the US DOE Office of Science, Office of Basic Energy Sciences, including grant No. DE-SC0000844 A solenoid-based low-energy beam transport (LEBT) subsystem is under development for the H⁻ linac front end of the Spallation Neutron Source. The LEBT design includes MHz frequency chopping of the partially neutralized H⁻ beam that can potentially lead to beam instabilities. We report results of numerical modeling using the parallel Vorpal framework for 3D electrostatic particle-in-cell (PIC) to simulate H⁻ beam dynamics in the LEBT, over multiple chopping events. We detail how the addition of a positively biased potential barrier near the entrance of the chopper can improve LEBT performance by eliminating chopper-induced emittance increases over many chopping events. DLB is now at University of Colorado, Boulder

Paper

Title

Page

Simulating Electron Cloud Evolution using Modulated Dielectric Models

1043

S.A. Veitzer, P. Stoltz
Tech-X, Boulder, Colorado, USA

Funding: This work was performed under the auspices of the Department of Energy as part of the ComPASS SCiDAC-2 project (DE-FC02-07ER41499), and the SCiDAC-3 project (DE-SC0008920)
Electron clouds can pose a serious threat to accelerator performance, and understanding cloud buildup and the effectiveness of different mitigation techniques can provide cost-saving improvements in accelerator design and fabrication. Microwave diagnostics of electron clouds are a non-destructive way to measure cloud buildup, but it is very difficult to measure the cloud density from spectral signals alone. Modeling travelling-wave rf diagnostics is very hard because of the large range of spatial and temporal scales that must be resolved to simulate spectra. New numerical models have been used to generate synthetic spectra for electron clouds when the cloud density is not changing, and results have been compared to theoretical results. Here we use dielectric models to generate spectra for clouds that evolve over many bunch crossings. We first perform detailed simulations of cloud buildup using kinetic particle models, and then use an equivalent plasma dielectric model corresponding to this density, at a finer time resolution, to compute spectra. The stability and accuracy of dielectric models that spectra can be accurately determined in these very long timescale simulations.

TUPWO059

Reducing Emittance of a H⁻ Beam in a Solenoid-based Low-energy Beam Transport through Numerical Modeling

2000

J. von Stecher, D.L. Bruhwiler, B.T. Schwartz, S.A. Veitzer
Tech-X, Boulder, Colorado, USA
B. Han, M.P. Stockli
ORNL, Oak Ridge, Tennessee, USA

Funding: This work is supported by the US DOE Office of Science, Office of Basic Energy Sciences, including grant No. DE-SC0000844
A solenoid-based low-energy beam transport (LEBT) subsystem is under development for the H⁻ linac front end of the Spallation Neutron Source. The LEBT design includes MHz frequency chopping of the partially neutralized H⁻ beam that can potentially lead to beam instabilities. We report results of numerical modeling using the parallel Vorpal framework for 3D electrostatic particle-in-cell (PIC) to simulate H⁻ beam dynamics in the LEBT, over multiple chopping events. We detail how the addition of a positively biased potential barrier near the entrance of the chopper can improve LEBT performance by eliminating chopper-induced emittance increases over many chopping events.
DLB is now at University of Colorado, Boulder