CLASSE, Ithaca, New York, USA
KEK, Ibaraki, Japan
CLASSE, Ithaca, New York, USA
Cornell University, Ithaca, New York, USA
Energy Recovery Linacs (ERLs) are proposed as drivers for hard X-ray sources because of their ability to produce electron bunches with small, flexible cross sections and short lengths at high repetition rates. The advantages of ERL lightsources will be explained, and the status of plans for such facilities will be described. In particular, Cornell University plans to build an ERL light source, and the preparatory research for its construction will be discussed. This will include the prototype injector for high current CW ultra-low emittance beams, superconducting CW technology, the transport of low emittance beams, halo formation from intrabeam scattering, the mitigation of ion effects, the suppression of instabilities, and front to end simulations. Several of these topics could become important for other modern light source projects, such as SASE FELs, HGHG FELs, and XFELOs.
CLASSE, Ithaca, New York, USA
We report on the status of emittance tuning techniques at the CESR Test Accelerator CesrTA. The CesrTA experimental program requires the capability to operate in a variety of machine lattices with the smallest possible emittance. We have attempted to minimize the turn-around time of our low emittance tuning procedure. We utilize high bandwidth BPM electronics for fast, precision measurements of orbit, betatron phase, transverse coupling, and dispersion. Turn by turn data is used to measure BPM button electrode gains to a under a percent. Gain-corrected coupling data is utilized to determine BPM tilts to 10mrad, allowing for measurement of vertical dispersion at the level of 10mm. Measurement and analysis of the data for characterizing BPM response takes 5 minutes. Beam based measurement of machine functions, data analysis, and implementing corrections in the machine takes another 5 minutes. An x-ray beam size monitor provides a real time check on the effectiveness of the procedure. A typical correction results in an emittance less than 20pm at 2.1GeV in 1-2 iterations. Sub 15pm has been achieved with adjustment of closed coupling/vertical dispersion bumps and betatron tunes.
CLASSE, Ithaca, New York, USA
CalPoly, San Luis Obispo, California, USA
Cornell University, Ithaca, New York, USA
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.
CLASSE, Ithaca, New York, USA
LBNL, Berkeley, California, USA
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.