THOCI1
DESY, Hamburg, Germany
DESY, Hamburg, Germany
Paul Scherrer Institut, Villigen, Switzerland
DESY, Hamburg, Germany
Uni HH, Hamburg, Germany
DESY, Hamburg, Germany
| Paper | Title | Page |
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THOCI1 |
Measurement and Control of the Longitudinal Phase Space at High-Gain Free-electron Lasers | |
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| Free-electron lasers provide a high degree of flexibility in terms of pulse intensity and wavelength range. In the case of high-gain FELs with a two-frequency accelerator in front of the bunch compressors, the flexibility is extended with electron bunch shape and length tunability. The final goal is to get control of the FEL photon pulses which might be achieved by controlling the longitudinal phase space (LPS) of the driving electron bunch. This can be achieved by using transverse deflecting structures/cavities (TDS/C) in combination with energy spectrometers which provide a direct measurement method with high resolutions in both energy and time. In this talk, the basic concepts of longitudinal phase space diagnostics, using transverse deflecting structures/cavities in combination with energy spectrometers, will be discussed with examples from FLASH at DESY and LCLS at SLAC. The obtainable resolutions and limitations due to the accelerator optics, induced energy spread by the TDS/C itself, and coherent synchrotron radiation will be shown by simulations and measurements. Finally, an overview of planned LPS diagnostics at other facilities, like the European XFEL, will be presented. | ||
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Slides THOCI1 [3.849 MB] | |
| THPA12 | Beam Energy Measurements in the FLASH Injector using Synchrotron Radiation and Bunch Arrival Monitors | 489 |
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| The high beam energy stability required for stable operation of linac-driven free-electron lasers demands for precise cavity RF field regulation. This is in particular true for the accelerator modules at low beam energies which are used to induce an energy correlation on the electron beam for longitudinal bunch compression in magnetic chicanes. At FLASH, a major upgrade of the injector has taken place in the shutdown 2009/2010 including the installation of a 3rd harmonic accelerating module, exchange of modulators and re-cabling and temperature stabilization of the low-level RF electronics. Several beam-based techniques have been developed recently which can be used to monitor the beam energy with high precision or as fast feedbacks for the RF regulation. In this paper, we report on bunch-resolved energy measurements recorded independently with a synchrotron radiation monitor and two bunch arrival monitors. Good agreement between the monitors was found and the measurement data are compared with the results from RF detection. | ||
| THPB06 | Coherent Terahertz Radiation Monitors for Multiple Spectral Bands | 572 |
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| The SwissFEL Injector Test Facility is destined for demonstrating electron beam parameters that are suitable for FEL operation. Of particular interest is the on-line measurement of longitudinal phase space properties, as this provides insight into the bunch compression process. The spectral distribution of diffraction radiation offers a robust way to assess bunch length and longitudinal profile. The bunch length at the SwissFEL Injector Test Facility can be varied by changing the photocathode laser. Diffraction radiation is emitted as the electron bunches pass through a hole in a titanium foil. The emitted Terahertz radiation has been simulated by the code THz Transport, and the propagation to the detectors has been modeled. | ||
| THPB16 | Beam Profile Measurements Using a Fast Gated CCD Camera and a Scintillation Screen to Suppress COTR | 590 |
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| For standard beam profile measurements of high-brightness electron beams using optical transition radiation (OTR) screens, coherence effects induced by microbunching instabilities render direct imaging of the beam impossible. A technique of using a scintillation screen with a fast gated CCD camera has been demonstrated to successfully suppress coherent OTR (COTR) in transverse beam diagnostics at FLASH. The fast gated CCD camera has been installed next to a standard CCD camera setup and images the same viewing screens. The results of transverse beam profile measurements under operating conditions without COTR are compared for both setups. The fast gated camera has also been employed for longitudinal bunch profile measurements with a transverse deflecting structure (TDS). Results obtained under operating conditions with COTR are compared to those from longitudinal phase space measurements in a dispersive arm, where no coherence effects have been observed so far. In this paper, we examine the performance of the fast gated CCD camera for beam profile measurements and present further studies on the use of scintillation screens for high-energy electron beam diagnostics. | ||