| Paper |
Title |
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| WEPLS045 |
Study on Low-energy Positron Polarimetry
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2475 |
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- A. Schaelicke, K. Laihem, S. Riemann, A. Ushakov
DESY Zeuthen, Zeuthen
- R. Dollan, Th. Lohse
Humboldt University Berlin, Institut für Physik, Berlin
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For the design of the International Linear Collider (ILC) a polarised positron source based on a helical undulator system has been proposed. In order to optimise the positron beam, i.e., to ensure high intensity as well as high degree of polarisation, a measurement of the polarisation close to the positron creation point is envisaged. In this contribution methods to determine the positron polarisation at low energies are investigated. These studies are based on simulations with an extended version of Geant4, which allows the tracking of polarised particles taking into account the spin effects.
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| THPCH083 |
A Tune Feedback System for the HERA Proton Storge Ring
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2979 |
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- S.G. Brinker, S.W. Herb, F.J. Willeke
DESY, Hamburg
- Th. Lohse
Humboldt University Berlin, Institut für Physik, Berlin
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The transverse tunes of an accelerator or storage ring are important parameters which have to be controlled and adjusted continuously during beam operation in order to assure good experimental background conditions. For the HERA proton storage ring, persistent current effects of the superconducting magnets are the main source for the inadequate repeatability of the tunes without a feedback while the proton beam is accelerated. A tune feedback has been developed, implemented and tested during beam acceleration and luminosity operation. Considering the different conditions during energy ramps and luminosity runs two versions of this feedback system have been established based on different correction and peak-finding algorithms (e.g. wavelet analysis). No additional excitation is needed on top of the standard tune indication system in HERA. The tunes could be kept constant during beam accceleration with a standard deviation of delta Q = 0.003. In luminosity runs where the tune control is more critical, first tests resulted in a standard deviation which was a factor of ten smaller. The feedback system is implemented as a standard tool for beam acceleration.
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