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

Paper	Title	Page
MOP228	TE Wave Measurements of the Electron Cloud in a Dipole Magnetic Field	531
	S. De Santis, J.M. Byrd LBNL, Berkeley, California, USA J.R. Calvey, J. Joseph, J.A. Livezey, J.P. Sikora, K.G. Sonnad CLASSE, Ithaca, New York, USA K.C. Hammond Harvard University, Cambridge, Massachusetts, USA
	Funding: Work supported by the U.S. Department of Energy under Contract Nos. DE-AC02-05CH1123 and DE-FC02-08ER41538 and by the National Science Foundation Grant PHY-0734867. The TE wave propagation method has become a widely used technique for measuring electron cloud density in an accelerator beampipe. In most instances the wave very low power is not capable of affecting the low-energy electrons distribution. During experiments in the CESR Damping Ring Test Accelerator (Cesr-TA), we have observed a particular situation where a resonance between the wave and a dipole magnetic field produces a large modification in the electron cloud distribution that can be measured by other detectors. We believe this resonance is strongly dependent on the geometry of standing waves pattern that discontinuities in the beampipe generate. We present measurements in Cesr-TA, which describe the effect and are in support of our hypothesis.

WEP005	Modeling the Low-Alpha-Mode at ANKA with the Accelerator Toolbox	1510
	M. Klein, N. Hiller, A. Hofmann, E. Huttel, V. Judin, B. Kehrer, S. Marsching, A.-S. Müller KIT, Karlsruhe, Germany K.G. Sonnad CLASSE, Ithaca, New York, USA
	The ANKA storage ring is operated frequently with low momentum compaction lattices to produce short bunches for the generation of coherent synchrotron radiation in the THz range. The bunch length can be varied in steps from one centimeter down to the sub millimeter level. These low alpha optics are modeled by using the Matlab based tools, Accelerator Toolbox (AT) and LOCO. The results are compared with measurements such as orbit response matrices, dispersion and chromaticity. This paper provides results of a study on the feasibilities as well as limitations of the measurements and calculations.

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.

WEP110	Electron Cloud Modeling for the ILC Damping Rings	1686
	J.A. Crittenden, D. Sagan CLASSE, Ithaca, New York, USA K.G. Sonnad Cornell University, Ithaca, New York, USA
	Funding: Support by DOE contract DE-FC02-08ER41538 and NSF contract PHY-0734867 Electron cloud buildup is a primary concern for the performance of the damping rings under development for the International Linear Collider. We have performed synchrotron radiation profile calculations for the 6.4-km DC04 and 3.2-km DSB3 lattice designs using the SYNRAD utility in the Bmad accelerator software library. These results are then used to supply input parameters to the electron cloud modeling package ECLOUD. Contributions to coherent tune shifts from the field-free sections and from the dipole and quadrupole magnets have been calculated, as well as the effect of installing solenoid windings in the field-free regions. For each element type, SYNRAD provides ring occupancy, average beam sizes, beta function values, and beta-weighted photon rates for the coherent tune shift calculation. An approximation to the antechamber design has been implemented in ECLOUD as well, moving the photoelectron source point to the edges of the antechamber entrance and removing cloud particles which enter the antechamber.

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

TE Wave Measurements of the Electron Cloud in a Dipole Magnetic Field

531

S. De Santis, J.M. Byrd
LBNL, Berkeley, California, USA
J.R. Calvey, J. Joseph, J.A. Livezey, J.P. Sikora, K.G. Sonnad
CLASSE, Ithaca, New York, USA
K.C. Hammond
Harvard University, Cambridge, Massachusetts, USA

Funding: Work supported by the U.S. Department of Energy under Contract Nos. DE-AC02-05CH1123 and DE-FC02-08ER41538 and by the National Science Foundation Grant PHY-0734867.
The TE wave propagation method has become a widely used technique for measuring electron cloud density in an accelerator beampipe. In most instances the wave very low power is not capable of affecting the low-energy electrons distribution. During experiments in the CESR Damping Ring Test Accelerator (Cesr-TA), we have observed a particular situation where a resonance between the wave and a dipole magnetic field produces a large modification in the electron cloud distribution that can be measured by other detectors. We believe this resonance is strongly dependent on the geometry of standing waves pattern that discontinuities in the beampipe generate. We present measurements in Cesr-TA, which describe the effect and are in support of our hypothesis.

WEP005

Modeling the Low-Alpha-Mode at ANKA with the Accelerator Toolbox

1510

M. Klein, N. Hiller, A. Hofmann, E. Huttel, V. Judin, B. Kehrer, S. Marsching, A.-S. Müller
KIT, Karlsruhe, Germany
K.G. Sonnad
CLASSE, Ithaca, New York, USA

The ANKA storage ring is operated frequently with low momentum compaction lattices to produce short bunches for the generation of coherent synchrotron radiation in the THz range. The bunch length can be varied in steps from one centimeter down to the sub millimeter level. These low alpha optics are modeled by using the Matlab based tools, Accelerator Toolbox (AT) and LOCO. The results are compared with measurements such as orbit response matrices, dispersion and chromaticity. This paper provides results of a study on the feasibilities as well as limitations of the measurements and calculations.

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.

WEP110

Electron Cloud Modeling for the ILC Damping Rings

1686

J.A. Crittenden, D. Sagan
CLASSE, Ithaca, New York, USA
K.G. Sonnad
Cornell University, Ithaca, New York, USA

Funding: Support by DOE contract DE-FC02-08ER41538 and NSF contract PHY-0734867
Electron cloud buildup is a primary concern for the performance of the damping rings under development for the International Linear Collider. We have performed synchrotron radiation profile calculations for the 6.4-km DC04 and 3.2-km DSB3 lattice designs using the SYNRAD utility in the Bmad accelerator software library. These results are then used to supply input parameters to the electron cloud modeling package ECLOUD. Contributions to coherent tune shifts from the field-free sections and from the dipole and quadrupole magnets have been calculated, as well as the effect of installing solenoid windings in the field-free regions. For each element type, SYNRAD provides ring occupancy, average beam sizes, beta function values, and beta-weighted photon rates for the coherent tune shift calculation. An approximation to the antechamber design has been implemented in ECLOUD as well, moving the photoelectron source point to the edges of the antechamber entrance and removing cloud particles which enter the antechamber.

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.