| Paper |
Title |
Page |
| TUPB12 |
BPMs for the XFEL Cryo module
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84 |
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- D. Nölle, N. Baboi, K. Knaack, D. Lipka, J. Lund-Nielsen, N. Mildner, R. Neumann, F. Schmidt-Föhre, M. Siemens, T. Traber, S. Vilcins
DESY, Hamburg
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The European XFEL is based on superconducting accelerator technology developed in the context of the TESLA collaboration. The accelerator itself consist of cryo modules each equipped with 8 cavities, followed by a quadrupole/steerer package, a BPM and a HOM absorber. This contribution will present the layout of the BPM system for the cryo modules, describing the monitor itself, its integration into the cryo module. Additionally, the electronics concept will be discussed. Finally the results of beam measurements at FLASH using prototypes of the monitor and the electronics will be presented.
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| TUPC26 |
Button Beam Position Monitors for FLASH
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201 |
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- J. Lund-Nielsen, N. Baboi
DESY, Hamburg
- W. Riesch
DESY Zeuthen, Zeuthen
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Abstract: FLASH (Free Electron Laser in Hamburg) accelerates electron bunches to up to 750 MeV for producing intense, coherent, very short pulses of radiation. Various types of BPMs (beam position monitors) are installed in the facility: cavity and re-entrant-cavity BPMs in the accelerating cryo-modules and button and stripline BPMs in most of the room-temperature sections. The undulator section, where the FEL radiation is produced, is one of the most critical areas of the linac in terms of requirements on the position monitoring. Due to the tight space, button BPMs were chosen for this area. The electronics is based on the AM/PM principle. In the past couple of years these BPMs were commissioned and intensively studied. A few modifications have been made in the electronics, in order to deal with the small signals and the very high frequencies of the ultra-short bunches. In this paper the button-BPMs at FLASH will be presented. The studies made in the RF laboratory and the measurements made on the performance of the BPMs will be discussed.
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| WEPB02 |
Design of an Intra-Bunch-Train Feedback System for the European X-Ray FEL
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232 |
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- B. Keil, G. J. Behrmann, M. Dehler, R. Kramert, G. Marinkovic, P. Pollet, M. Roggli, M. Rohrer, T. Schilcher, V. Schlott, D. M. Treyer
PSI, Villigen
- J. Lund-Nielsen, D. Nölle, M. Siemens, S. Vilcins
DESY, Hamburg
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After joining the preparatory phase of the European X-ray FEL project, the Paul Scherrer Institute agreed in taking over responsibility for electron beam stabilization by developing a fast intra-bunch-train feedback (IBFB) system, which will be tested in its prototype version at the FLASH linac of the collaboration partner DESY. The proposed IBFB topology consists of two beam position monitors ("upstream BPMs") followed by two kicker magnets for each transverse plane and two more BPMs ("downstream BPMs"). By measuring the position of each bunch at the upstream BPMs and applying suitable transverse kicks individually to the following bunches, the architecture of the FPGA-based digital IBFB electronics (with a latency preferably below the bunch spacing of 200 ns and 1000 ns for the XFEL and FLASH) allows to damp beam motions up to hundreds of kHz. In addition to the FPGA-based feedback, DSPs enable adaptive feed-forward correction of repetitive beam motions as well as feedback parameter optimisation using the downstream BPMs. This paper gives an overview of the architecture and status of the IBFB subsystems being developed, like stripline BPMs, digital electronics and kicker magnets.
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