TUOCN6
ANL, Argonne, USA
LBNL, Berkeley, California, USA
Transverse to longitudinal emittance exchange was proposed in* as a tool for matching of the electron beam phase space to requirements of a possible application. Here we propose a new purpose, namely, use of two consequential emittance exchanges and the focusing telescope for a bunch compression that can be done without the energy chirp in the electron bunch. It allows to move bunch compressor to the end of the linac and thus to reduce the electron peak current in the linac and relax collective effects. It is also possible to have a split action compression when the first part is done inside the low energy part of the linac and the second and final part is done after the linac. We also demonstrate how proposed bunch compressor can be used for frequency up conversion of the energy modulation provided by laser interacting with the electron beam and thus can prepare a significantly higher frequency seed for seeded free-electron lasers. Same approach can be used for a frequency down conversion that can be useful for a generation of a THz radiation. Finally we note that the proposed bunch compression is practically free from destructive effects of coherent synchrotron radiation.
* M. Cornacchia, P. Emma, Phys. Rev. Spec. Topics – Acc. and Beams, 5, 084001(2002).
ANL, Argonne, USA
A rectangular cavity BPM / tilt monitor for the APS storage ring has been designed to detect residual vertical-longitudinal tilt caused by the proposed short-pulse x-ray (SPX) project crab cavities. Electromagnetic simulations have been performed to verify the conceptual design and evaluate design alternatives. MAFIA and Microwave Studio have been applied to simulate the device in both time and frequency domains. The device geometry has been optimized to efficiently damp strongly driven lower- and higher-order modes while preserving the tilt-sensitive mode of interest. This mode is coupled out to the processing electronics using a waveguide geometry chosen to maximize isolation from the beam-driven modes.
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.
Northern Illinois University, DeKalb, Illinois, USA
ANL, Argonne, USA