CLASSE, Ithaca, New York, USA
CalPoly, San Luis Obispo, California, USA
A horizontal beam profile monitor utilizing visible synchrotron radiation from a bending magnet has been designed and installed in CESR. The monitor employs a double-slit interferometer which has been successfully implemented to measure horizontal beam sizes over a wide range of beam currents. By varying the separation of the slits, beam sizes ranging from 50 to 500 microns can be measured with a resolution of approximately 5 microns. The method for extracting the horizontal beam size from the interference pattern is presented and its application to intrabeam scattering studies is described. A configuration for measuring the small vertical beam size is also discussed.
CLASSE, Ithaca, New York, USA
CalPoly, San Luis Obispo, California, USA
CMU, Pittsburgh, Pennsylvania, USA
KEK, Ibaraki, Japan
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
Electron clouds can adversely affect the performance of accelerators, and are of particular concern for the design of future low emittance damping rings. Studies of the impact of electron clouds on the dynamics of bunch trains in CESR have been a major focus of the CESR Test Accelerator program. In this paper, we report measurements of coherent tune shifts, emittance growth, and coherent instabilities carried out using a variety of bunch currents, train configurations, beam energies, and transverse emittances, similar to the design values for the ILC damping rings. We also compare the measurements with simulations which model the effects of electron clouds on beam dynamics, to extract simulation model parameters and to quantify the validity of the simulation codes.
Cornell University, Ithaca, New York, USA
CERN, Geneva, Switzerland
CLASSE, Ithaca, New York, USA
CalPoly, San Luis Obispo, California, USA
Intrabeam scattering dilutes the emittance of low energy, low emittance rings. Because CesrTA can be operated at low energies with low transverse emittances and high bunch intensity, it is an ideal laboratory for the study of IBS effects. Furthermore, CesrTA is instrumented for accurate beam size measurements in all three dimensions, providing the possibility of a complete determination of the intensity dependence of emittances. Models based on classical IBS theories and multi-particle simulations are used to estimate the effect of IBS at CesrTA at different beam emittances, intensities and energies. The first measurements from machine studies at CesrTA are presented.
CLASSE, Ithaca, New York, USA
CMU, Pittsburgh, Pennsylvania, USA
KEK, Ibaraki, Japan
CalPoly, San Luis Obispo, California, USA
Electron cloud-induced beam dynamics is being studied at CESRTA under various conditions. These measurements detect the the coherent self-excited spectrum for each bunch within a train and bunch-by-bunch beam size. In the position spectrum coherent betatron dipole and head-tail motion is detectable for each individual bunch within the train with a sensitivity for the motion of 1.1 (2) microns-rms in the vertical (horizontal) direction for a 1 mA bunch current. These techniques are utilized to study the electron cloud-related interactions, which cause the growth of coherent motion and beam size along the train. We report on the observations and results from studies of the instability growth vs. changes in chromaticity, the current per bunch and the length of the train.