| Paper |
Title |
Page |
| TUPB26 |
Characterisation of the Systematic Effects of the Insertion Devices with Photon Beam Position Monitors
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126 |
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- E. D. van Garderen, M. Böge, J. T.M. Chrin, J. Krempasky, V. Schlott, T. Schmidt, A. Streun
PSI, Villigen
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The X-ray photon monitors at Swiss Light Source are used for beam-position stabilisation down to sub-micron level. The beam position changes are mainly induced by changing the insertion device (ID) settings. An ID correction scheme involves both digital beam-position monitors (DBPM) located inside the storage ring and analog photon monitors (XBPM) located inside beamline front-ends. However, a beam-position correction scheme optimised for the electron beam is not automatically optimal for the photon beam. A sub-micron stability of the photon beam by changing the ID-settings is possible only if the XBPM readouts are well characterised for each considered ID-setting. We account for some limitations of the XBPM readouts as well as for examples where a sub-micron stability for all considered ID-settings is achieved.
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| TUPB27 |
Recent Results from the Electron Beam Profile Monitor at the Swiss Light Source
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129 |
| |
- Å. Andersson
MAX-lab, Lund
- O. V. Chubar
SOLEIL, Gif-sur-Yvette
- A. Lüdeke, M. Rohrer, V. Schlott, A. Streun
PSI, Villigen
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Two different methods of beam profile measurements using a) visible-to-UV range synchrotron radiation and b) X-ray synchrotron radiation have been realized in a single diagnostics beam line at the Swiss Light Source (SLS). In the visible-to-UV case the vertically polarized synchrotron radiation renders an image heavily influenced by inherent emission and diffraction effects of synchrotron radiation. This nevertheless turns out to be an advantageous influence when determining rms beam profiles below 10 μm. However, high-precision wave-optics based calculations of the synchrotron light characteristics need to be performed (SRW-code) to ensure correct interpretation of the measured profiles. The visible-to-UV branch has a few built-in features allowing numerous cross-checks of the SRW-model. Surprisingly, wave-optics based calculations are also applicable, and required, for the X-ray pinhole camera setup. We briefly discuss the advantage of applying two different measuring techniques at the same source point. In total, for standard user operation at the SLS, the beam line has helped to establish a vertical emittance below 10 pmrad.
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| TUPC25 |
Design and Calibration of an Emittance Monitor for the PSI XFEL Project
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198 |
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- V. Schlott, Å. Andersson, M. Dach, S. C. Leemann, M. Rohrer, A. Streun
PSI, Villigen
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Paul Scherrer Institute (PSI) intends to realize a compact X-ray Free Electron Laser (XFEL) by developing a high brightness, high current electron source. Field emitter arrays (FEA) in combination with high gradient acceleration promise a substantial reduction of transverse emittances by up to one order of magnitude compared to existing electron sources for XFELs. A flexible, high resolution emittance monitor based on the "pepperpot measurement techique" has been designed for this "low emittance gun" project at PSI. The realization and the calibration procedure of the monitor will be described in this presentation.
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| WEPB02 |
Design of an Intra-Bunch-Train Feedback System for the European X-Ray FEL
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232 |
| |
- 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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| WEPC21 |
Diagnostics of the Waveform of Picosecond Electron Bunches Using the Angular Distribution of Coherent Sub-mmTransition and Diffraction Radiation
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355 |
| |
- A. G. Shkvarunets, R. B. Fiorito
UMD, College Park, Maryland
- F. Mueller, V. Schlott
PSI, Villigen
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The spectra of sub-mm wavelength coherent transition radiation (TR) and diffraction radiation (DR) have previously been used to measure the bunch length of picosecond electron beam pulses. However, both the spectral and angular distributions of the radiation from a finite target or aperture with size r, are strong functions of the wavelength, when λ ≈ 2πr/γ where γ is the relativistic factor of the beam. This dependence must be taken into account in the determination of the bunch form factor and bunch shape. Also the spectral density of the bunch is a strong function of wavelength when λ ≈ d, the characteristic length of the bunch. When both the above conditions are fulfilled, i.e. λ ≈ 2πr/γ ≈ d, the spectral and angular distribution (AD) of the radiation are very sensitive to the longitudinal distribution of the bunch. We are investigating the use of the AD of TR or DR, to diagnose the bunch length and shape. Here we present a comparison of measured and calculated angular distributions from two targets: a solid disk and a rectangular slit, which we have used to determine the waveform of the beam bunch produced at PSI’s SLS pre-injector LINAC.
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