2011 Particle Accelerator Conference - List of Authors (De Santis, S.)

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.

WEP195	Time Resolved Measurement of Electron Clouds at CesrTA using Shielded Pickups	1855
	J.P. Sikora, M.G. Billing, J.A. Crittenden, Y. Li, M.A. Palmer CLASSE, Ithaca, New York, USA S. De Santis LBNL, Berkeley, California, USA
	Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538. The Cornell Electron Storage Ring has been reconfigured as a Test Accelerator (CesrTA). Shielded pickups have been installed at three locations in CesrTA for the purpose of studying time resolved electron cloud build-up and decay. The pickup design provides electromagnetic shielding from the beam wakefield while allowing cloud electrons in the vacuum space to enter the detector. This paper describes the hardware configuration and capabilities of these detectors at CesrTA, presents examples of measurements, and outlines the interpretation of detector signals with regard to electron clouds. Useful features include time-of-flight measurement of cloud electrons and the use of a solenoidal field for energy measurement of photoelectrons. Measurement techniques include the use of two bunches spaced in multiples of 4ns, where the second bunch samples the decay of the cloud produced by the first bunch.

WEP222	Low Energy Beam Diagnostic for APEX, the LBNL VHF Photo-injector	1903
	D. Filippetto, J.M. Byrd, M.J. Chin, C.W. Cork, S. De Santis, L.R. Doolittle, J. Feng, W.E. Norum, C. F. Papadopoulos, G.J. Portmann, D.G. Quintas, F. Sannibale, M.E. Stuart, R.P. Wells, M.S. Zolotorev LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231 A high-repetition rate (MHz-class), high-brightness electron beam photo-gun is under construction at Lawrence Berkeley National Laboratory in the framework of the Advanced Photo-injector EXperiment (APEX). The injector gun is based on a normal conducting 187 MHz RF cavity operating in CW mode. In its first operational phase it will deliver short bunches (~ 1 to tens of picoseconds) with energy of 750keV, and bunch charges ranging from 1pC to 1nC. Different high efficiency cathode materials will be tested, and the beam quality will be studied as a function of parameters as charge, initial bunch length and transverse size, focusing strength. Both the laser and electron beam diagnostics have been designed to assure the needed flexibility. In particular a high-resolution electron diagnostic section after the photo-gun provides the necessary dynamical range for scanned beam parameters: energy and energy spread, charge and current, transverse and longitudinal phase spaces, slice properties. The photo-gun electron beam diagnostic layout is presented, and the hardware choices, resolution and achievable dynamical ranges are also discussed.

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.

WEP195

Time Resolved Measurement of Electron Clouds at CesrTA using Shielded Pickups

1855

J.P. Sikora, M.G. Billing, J.A. Crittenden, Y. Li, M.A. Palmer
CLASSE, Ithaca, New York, USA
S. De Santis
LBNL, Berkeley, California, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538.
The Cornell Electron Storage Ring has been reconfigured as a Test Accelerator (CesrTA). Shielded pickups have been installed at three locations in CesrTA for the purpose of studying time resolved electron cloud build-up and decay. The pickup design provides electromagnetic shielding from the beam wakefield while allowing cloud electrons in the vacuum space to enter the detector. This paper describes the hardware configuration and capabilities of these detectors at CesrTA, presents examples of measurements, and outlines the interpretation of detector signals with regard to electron clouds. Useful features include time-of-flight measurement of cloud electrons and the use of a solenoidal field for energy measurement of photoelectrons. Measurement techniques include the use of two bunches spaced in multiples of 4ns, where the second bunch samples the decay of the cloud produced by the first bunch.

WEP222

Low Energy Beam Diagnostic for APEX, the LBNL VHF Photo-injector

1903

D. Filippetto, J.M. Byrd, M.J. Chin, C.W. Cork, S. De Santis, L.R. Doolittle, J. Feng, W.E. Norum, C. F. Papadopoulos, G.J. Portmann, D.G. Quintas, F. Sannibale, M.E. Stuart, R.P. Wells, M.S. Zolotorev
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
A high-repetition rate (MHz-class), high-brightness electron beam photo-gun is under construction at Lawrence Berkeley National Laboratory in the framework of the Advanced Photo-injector EXperiment (APEX). The injector gun is based on a normal conducting 187 MHz RF cavity operating in CW mode. In its first operational phase it will deliver short bunches (~ 1 to tens of picoseconds) with energy of 750keV, and bunch charges ranging from 1pC to 1nC. Different high efficiency cathode materials will be tested, and the beam quality will be studied as a function of parameters as charge, initial bunch length and transverse size, focusing strength. Both the laser and electron beam diagnostics have been designed to assure the needed flexibility. In particular a high-resolution electron diagnostic section after the photo-gun provides the necessary dynamical range for scanned beam parameters: energy and energy spread, charge and current, transverse and longitudinal phase spaces, slice properties. The photo-gun electron beam diagnostic layout is presented, and the hardware choices, resolution and achievable dynamical ranges are also discussed.