Darmstadt 2008 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 18: Instrumentation und Anwendungen I

HK 18.2: Talk

Tuesday, March 11, 2008, 09:00–09:15, 2C

Measurement and stabilization of the longitudinal and transversal tune on the fast energy ramp at ELSA — •Maren Eberhardt — Electron Stretcher Accelerator ELSA, Physikalisches Institut, Universität Bonn, Germany

At the electron stretcher accelerator ELSA, an external beam of unpolarized or polarized electrons is supplied to experimental set-ups. In order to correct for dynamic effects caused by eddy currents induced on the fast energy ramp, the accelerator tunes have to measured in situ with high precision. The measurements of betatron tunes during the fast energy ramp are based on the excitation of coherent betatron oscillations generated by a pulsed kicker magnet. The betatron frequency is determined by a Fourier analysis of the measured oscillations of the beam position. This technique was successfully applied to measure the horizontal tune on the fast energy ramp. During the fast energy ramp shifts of the betatron tune caused by eddy currents are induced. These tune shifts are measured and corrected when operating the accelerator with polarized beam.

Measurements of coherent synchrotron oscillations will also be presented. These are excited by a phase modulation of the acceleration voltage using an electrical phase shifter in the reference RF signal path.