| Paper |
Title |
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| FRPMN017 |
Beam Position Monitor Calibration at the FLASH Linac at DESY
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3937 |
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- N. Baboi
- P. Castro, O. Hensler, J. Lund-Nielsen, D. Noelle, L. M. Petrosyan, E. Prat, T. Traber
DESY, Hamburg
- M. Krasilnikov, W. Riesch
DESY Zeuthen, Zeuthen
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In the FLASH (Free electron LASer in Hamburg) facility at DESY more than 60 beam position monitors (BPM) with single bunch resolution are currently installed, and more are planned for future installation. Their calibration has been initially made by measuring each electronics board in the RF laboratory. However the ultimate calibration of each monitor is made by measuring its response to beam movement. This is a time-consuming procedure depending on the availability and accuracy of other components of the machine such as corrector magnets. On the other hand it has the advantage of getting in one measurement the answer of the monitor with all its components and of being independent of the monitor type. The calibration procedure and particularities for various types of BPMs in various parts of the linac will be discussed. A procedure based on the response matrices is also now under study. This would significantly speed up the calibration procedure, which is particularly important in larger accelerators such as the European XFEL (X-ray Free Electron Laser), to be built at DESY.
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| THOAC03 |
Measurement of the Beam's Trajectory Using the Higher Order Modes it Generates in a Superconducting Accelerating Cavity
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2642 |
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- S. Molloy
- N. Baboi, O. Hensler, R. Paparella, L. M. Petrosyan
DESY, Hamburg
- N. E. Eddy, L. Piccoli, R. Rechenmacher, M. Wendt
Fermilab, Batavia, Illinois
- J. C. Frisch, J. May, D. J. McCormick, M. C. Ross, T. J. Smith
SLAC, Menlo Park, California
- O. Napoly, C. Simon
CEA, Gif-sur-Yvette
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Funding: US DOE Contract #DE-AC02-76SF00515
It is well known that an electron beam excites Higher Order Modes (HOMs) as it passes through an accelerating cavity~[panofsky68]. The properties of the excited signal depend not only on the cavity geometry, but on the charge and trajectory of the beam. It is, therefore, possible to use these signals as a monitor of the beam's position. Electronics were installed on all forty cavities present in the FLASH~[flashref] linac in DESY. These electronics filter out a mode known to have a strong dependence on the beam's position, and mix this down to a frequency suitable for digitisation. An analysis technique based on Singular Value Decomposition (SVD) was developed to calculate the beam's trajectory from the output of the electronics. The entire system has been integrated into the FLASH control system.
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Slides
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| THPMS049 |
Investigations of the Wideband Spectrum of Higher Order Modes Measured on TESLA-style Cavities at the FLASH Linac
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3100 |
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- S. Molloy
- C. Adolphsen, K. L.F. Bane, J. C. Frisch, Z. Li, J. May, D. J. McCormick, T. J. Smith
SLAC, Menlo Park, California
- N. Baboi
DESY, Hamburg
- N. E. Eddy, L. Piccoli, R. Rechenmacher
Fermilab, Batavia, Illinois
- R. M. Jones
UMAN, Manchester
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Funding: US DOE Contract #DE-AC02-76SF00515
Higher Order Modes (HOMs) excited by the passage of the beam through an accelerating cavity depend on the properties of both the cavity and the beam. It is possible, therefore, to draw conclusions on the inner geometry of the cavities based on observations of the properties of the HOM spectrum. A data acquisition system based on two 20 GS/s, 6 GHz scopes has been set up at the FLASH facility, DESY, in order to measure a significant fraction of the HOM spectrum predicted to be generated by the TESLA cavities used for the acceleration of its beam. The HOMs from a particular cavity at FLASH were measured under a range of known beam conditions. The dipole modes have been identified in the data. 3D simulations of different manufacturing errors have been made, and it has been shown that these simulations can predict the measured modes.
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