| Paper |
Title |
Other Keywords |
Page |
| MOP017 |
4GLS Beam-Break-Up Investigations
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focusing, linac, simulation, quadrupole |
67 |
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- E. Wooldridge, P. A. McIntosh
CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
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Beam Break Up (BBU) thresholds have been studied as part of the Linac focusing scheme for the proposed 4GLS accelerator. A graded gradient focusing scheme, with a triplet of quadrupoles between each of the modules within the Linac has been chosen. These quadrupoles are set-up in a defocusing – focusing – defocusing format with strengths of -1/2k, k, -1/2k. This value of k was altered and the BBU thresholds for the machine calculated using various BBU codes. Alternate cavity designs have also been investigated using CST’s Microwave Studio to see how the effects of higher order modes (HOMs) can be minimised whilst maintaining fundamental field flatness across theaccelerating cells. The number of cells/unit length and cell-to-cell geometries have also been parameterised and the corresponding BBU thresholds presented as a function of cavity geometry, with the intention of providing an optimum solution for 4GLS.
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| MOP019 |
Methods to Reduce the Electron Beam Energy Spread at the S-DALINAC
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electron, linac, controls, feedback |
73 |
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- R. Eichhorn, A. Araz, U. Bonnes, M. Brunken, M. Gopych, H.-D. Gräf, S. Paret, M. Platz, A. Richter, S. Watzlawik
TU Darmstadt, Darmstadt
- W. F.O. Müller, B. Steiner, T. Weiland
TEMF, Darmstadt
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The S-DALINAC is a recirculating superconducting electron linac operating at 3 GHz. The accelerator delivers a cw beam with energies up to 130 MeV to serve electron scattering experiments where highest momentum resolutions, typ. below 1·10-4 are required. Current activities aim to reduce the energy spread of the accelerator by two methods: Long term drifts, mainly a result of temperature drifts, will be corrected by a feedback system which measures the energy variation of the extracted beam continuously using rf-monitors. By means of time-of-flight analysis in a modified beamline a correction signal can be generated as a feedback for the rf control of the accelerating cavities. This system was set-up recently and first results will be reported. Furthermore, the influence of short term fluctuations, e.g. triggered by micro-phonics, on the electron energy can significantly be reduced utilizing the inherent stability of a microtron, if the synchronous phase and longitudinal dispersion are chosen properly. The concept, particle simulations and the experimental verification will be shown as well as necessary modifications to the recirculation scheme to use it in an all-day operation.
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