2011 Particle Accelerator Conference - List of Authors (Dugan, G.)

Paper	Title	Page
MOP214	Methods for Quantitative Interpretation of Retarding Field Analyzer Data	501
	J.R. Calvey, J.A. Crittenden, G. Dugan, M.A. Palmer CLASSE, Ithaca, New York, USA M.A. Furman LBNL, Berkeley, California, USA K.C. Harkay ANL, Argonne, USA
	Funding: US Department of Energy grant DE-FC02-08ER41538 US National Science Foundation grant PHY-0734867 Over the course of the CesrTA program at Cornell, over 30 Retarding Field Analyzers (RFAs) have been installed in the CESR storage ring, and a great deal of data has been taken with them. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. Obtaining a quantitative understanding of RFA data requires use of cloud simulation programs, as well as a detailed model of the detector itself. In a drift region, the RFA can be modeled by postprocessing the output of a simulation code, and one can obtain best fit values for important simulation parameters with a chi-square minimization method.

WEP108	Application of Coherent Tune Shift Measurements to the Characterization of Electron Cloud Growth	1680
	D.L. Kreinick, J.A. Crittenden, G. Dugan, M.A. Palmer, G. Ramirez CLASSE, Ithaca, New York, USA M.A. Furman, M. Venturini LBNL, Berkeley, California, USA R. Holtzapple, M. Randazzo CalPoly, San Luis Obispo, California, USA
	Funding: DOE = DE-FC02-08ER41538 NSF = PHY-0734867 Measurements of coherent tune shifts at the Cornell Electron Storage Ring Test Accelerator (CesrTA) have been made for electron and positron beams under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of several electron cloud simulation programs allows the evaluation of important parameters in these models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders. We outline recent improvements to the analysis techniques that should improve the fidelity of the modeling.

WEP109	Simulations of Electron Cloud Induced Instabilities and Emittance Growth for CesrTA	1683
	K.G. Sonnad, K.R. Butler Cornell University, Ithaca, New York, USA G. Dugan, M.A. Palmer CLASSE, Ithaca, New York, USA M.T.F. Pivi SLAC, Menlo Park, California, USA
	Funding: US Department of Energy DE-FC02-08ER41538, National Science Foundation PHY-0734867 We present results of a series of studies obtained using the simulation code CMAD to study how electron clouds affect the dynamics of positron beams in CesrTA. The study complements ongoing experiments dedicated for studying the same phenomena. The simulation involves tracking positrons through the CesrTA lattice and simultaneously computing the force exerted due to space charge of the electrons on each of the tracked positrons. The electrons themselves are allowed to evolve under the influence of the positrons. Several results bear a close resemblance to what has been observed experimentally.

WEP194	Measurement Techniques to Characterize Instabilities Caused by Electron Clouds	1852
	M.G. Billing, G. Dugan, M.J. Forster, R.E. Meller, M.A. Palmer, G. Ramirez, J.P. Sikora, H.A. Williams CLASSE, Ithaca, New York, USA R. Holtzapple CalPoly, San Luis Obispo, California, USA K.G. Sonnad Cornell University, Ithaca, New York, USA
	Funding: Work is supported by NSF (PHY-0734867) and DOE (DE-FC02-08ER41538) grants. The study of electron cloud-related instabilities for the CESR-TA project has required the development of new measurement techniques. The dynamics of the interaction of electron clouds with trains of bunches has been undertaken employing three basic observations. Measurements of tune shifts of bunches along a train has been used extensively with the most recent observations permitting the excitation of single bunches within the train to avoid collective train motion from driving the ensemble of bunches. Another technique has been developed to detect the coherent self-excited spectrum for each of the bunches within a train. This method is particularly useful when beam conditions are near the onset of an instability. The third method was designed to study bunches within the train in conditions below the onset of unstable motion. This is accomplished by separately driving each bunch within the train for several hundred turns and then observing the damping of its coherent motion. These last two techniques have been applied to study both transverse dipole (centroid) and head-tail motion. We will report on the observation methods and give examples of typical results.

Paper

Title

Page

Methods for Quantitative Interpretation of Retarding Field Analyzer Data

501

J.R. Calvey, J.A. Crittenden, G. Dugan, M.A. Palmer
CLASSE, Ithaca, New York, USA
M.A. Furman
LBNL, Berkeley, California, USA
K.C. Harkay
ANL, Argonne, USA

Funding: US Department of Energy grant DE-FC02-08ER41538 US National Science Foundation grant PHY-0734867
Over the course of the CesrTA program at Cornell, over 30 Retarding Field Analyzers (RFAs) have been installed in the CESR storage ring, and a great deal of data has been taken with them. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. Obtaining a quantitative understanding of RFA data requires use of cloud simulation programs, as well as a detailed model of the detector itself. In a drift region, the RFA can be modeled by postprocessing the output of a simulation code, and one can obtain best fit values for important simulation parameters with a chi-square minimization method.

WEP108

Application of Coherent Tune Shift Measurements to the Characterization of Electron Cloud Growth

1680

D.L. Kreinick, J.A. Crittenden, G. Dugan, M.A. Palmer, G. Ramirez
CLASSE, Ithaca, New York, USA
M.A. Furman, M. Venturini
LBNL, Berkeley, California, USA
R. Holtzapple, M. Randazzo
CalPoly, San Luis Obispo, California, USA

Funding: DOE = DE-FC02-08ER41538 NSF = PHY-0734867
Measurements of coherent tune shifts at the Cornell Electron Storage Ring Test Accelerator (CesrTA) have been made for electron and positron beams under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of several electron cloud simulation programs allows the evaluation of important parameters in these models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders. We outline recent improvements to the analysis techniques that should improve the fidelity of the modeling.

WEP109

Simulations of Electron Cloud Induced Instabilities and Emittance Growth for CesrTA

1683

K.G. Sonnad, K.R. Butler
Cornell University, Ithaca, New York, USA
G. Dugan, M.A. Palmer
CLASSE, Ithaca, New York, USA
M.T.F. Pivi
SLAC, Menlo Park, California, USA

Funding: US Department of Energy DE-FC02-08ER41538, National Science Foundation PHY-0734867
We present results of a series of studies obtained using the simulation code CMAD to study how electron clouds affect the dynamics of positron beams in CesrTA. The study complements ongoing experiments dedicated for studying the same phenomena. The simulation involves tracking positrons through the CesrTA lattice and simultaneously computing the force exerted due to space charge of the electrons on each of the tracked positrons. The electrons themselves are allowed to evolve under the influence of the positrons. Several results bear a close resemblance to what has been observed experimentally.

WEP194

Measurement Techniques to Characterize Instabilities Caused by Electron Clouds

1852

M.G. Billing, G. Dugan, M.J. Forster, R.E. Meller, M.A. Palmer, G. Ramirez, J.P. Sikora, H.A. Williams
CLASSE, Ithaca, New York, USA
R. Holtzapple
CalPoly, San Luis Obispo, California, USA
K.G. Sonnad
Cornell University, Ithaca, New York, USA

Funding: Work is supported by NSF (PHY-0734867) and DOE (DE-FC02-08ER41538) grants.
The study of electron cloud-related instabilities for the CESR-TA project has required the development of new measurement techniques. The dynamics of the interaction of electron clouds with trains of bunches has been undertaken employing three basic observations. Measurements of tune shifts of bunches along a train has been used extensively with the most recent observations permitting the excitation of single bunches within the train to avoid collective train motion from driving the ensemble of bunches. Another technique has been developed to detect the coherent self-excited spectrum for each of the bunches within a train. This method is particularly useful when beam conditions are near the onset of an instability. The third method was designed to study bunches within the train in conditions below the onset of unstable motion. This is accomplished by separately driving each bunch within the train for several hundred turns and then observing the damping of its coherent motion. These last two techniques have been applied to study both transverse dipole (centroid) and head-tail motion. We will report on the observation methods and give examples of typical results.