| Paper |
Title |
Page |
| WEPLT063 |
Investigation of Cavity Induced Longitudinal Coupled Bunch Mode Instability Behaviour and Mechanisms
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1987 |
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- R.G. Heine, P. Hartmann, H. Huck, G. Schmidt, T. Weis
DELTA, Dortmund
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The narrowband impedances of RF-resonators in a circular accelerator can drive coupled bunch mode - CBI - instabilities which might spoil the overall beam quality. Often, as in synchrotron radiation light sources e.g. the instability does not lead to beam loss but to a severe degradation of the source brilliance. Investigations of longitudinal CBIs have been performed at the DELTA storage ring with a single DORIS-type cavity for future comparision with the behaviour of a HOM-damped cavity to be tested at DELTA. This resonator is presently developed and built within an EU-collaboration. The beam was deliberately driven into instability using the beam current as well as the cavity temperature as individual parameters. The instability characterisations at low (542 MeV) and high (1,5 GeV) energy exhibit a complex behaviour. The strength of the instability measured by the bunch excursions in the case of longitudinal CBIs, but also the spreading of the instability across neighbouring modes depends on parameters such as beam energy, resonant impedance but also on counteracting mechanisms like synchrotron radiation and Landau damping. The paper will cover the experimental results together with estimations of the influence and mechanism of Landau damping.
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| THPKF017 |
Status of the Synchrotron Light Source DELTA
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2293 |
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- D. Schirmer, U. Berges, J. Friedl, A. Gasper, M. Grewe, P. Hartmann, R.G. Heine, H. Huck, G. Schmidt, C. Sternemann, M. Tolan, T. Weis, C. Westphal, K. Wille
DELTA, Dortmund
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Since 1999, the Dortmunder 1.5 GeV electron storage ring DELTA was continuously extended. The facility serves universities and industries as a source of synchrotron radiation on a regional level. The consolidation of the machine was finally completed in 2002. By now, DELTA, operated for 3000 hours per year, has reached a reliability comparable to other facilities in the world. Large improvements have been made in the installation of the beamlines. At present, two undulator beamlines and several dipole beamlines in the range of soft X-rays are in operation. The 5.3 T superconducting asymmetric wiggler (SAW) serves three beamlines in the hard X-ray regime with circular polarized light. Also the accelerator physics research program has been promoted. The vacuum system was revised during the last year to provide extra space for test sections and additional diagnostics. Substantial progress was achieved by SVD based orbit correction and LOCO based optics modelling as well as detailed CBM studies and a new method for fast tune measurements has been implemented. Future developments for machine improvements, such as DSP-based fast local orbit feedback and a frequent injection mode are in preparation.
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| THPKF018 |
Study for a Frequent Injection Mode at Delta with Beam Shutters Open
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2296 |
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- G. Schmidt, M. Benna, U. Berges, J. Friedl, A. Gasper, M. Grewe, P. Hartmann, R.G. Heine, H. Huck, D. Schirmer, S. Strecker, T. Weis, K. Wille, N. Zebralla
DELTA, Dortmund
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The Dortmunder Electron Accelerator (DELTA) is a 1.5 GeV synchrotron light source. DELTA is now operated for 3000 h per year including 2000 h beam time for synchrotron radiation use. The maximum beam current is limited by rf power. To increase the average beam current a frequent injection scheme with beam shutters open is discussed for Delta. The peak current is not enlarged but the number of injections is increased to establish a quasi constant beam current. The quasi constant beam current has in addition the advantage of a constant synchrotron radiation heat-load on vacuum chambers and experiments. First tests at Delta have shown the gain in stability of the closed orbit during frequent injection. This article shows the possibility to install a frequent injection mode with beam shutters open during injection at DELTA. The results of measurements and simulations are presented.
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