| Paper | Title | Page |
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| TUPA22 | FLASH II: A Project Update | 247 |
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| FLASH II is an extension of the existing FLASH facility by an undulator line and an experimental Hall of which the construction will start before the end of the year. Aims are to increase beamtime for users and implement HHG seeding for the longer wavelength range from 10 to 40 nm at a reduced repetition rate of 100 kHz. Additional seeding schemes are under discussion as a future option. We will present a progress report of FLASH II. | ||
| WEPA19 | Report on the Redesign of the Fibre Link Stabilisation Units at FLASH | 370 |
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Funding: This work is partly supported by IRUVX-PP an EU co-funded project under FP7 (Grant Agreement 211285) Recently, the fibre link stabilisation unit of the optical synchronisation system at FLASH has been subject to several design changes involving some major issues. Enhancements of the optical design have led to improvements in the efficiency of the free space optics and a new optical delay line allows for a more than two times longer adjustment range. The amplitude noise, encountered previously at the remote station of the links, was drastically decreased by a new beam splitting configuration. In future, this new link design will not only be used for the planned additional fibre links at FLASH, but it will also replace the already installed ones. In this paper we report on the changes of opto-mechanical design and we present first results from the recently commissioned links. |
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| THPA07 | A Multichannel Wavelength Resolved Coherent Radiation Detector for Bunch Profile Monitoring at FLASH | 477 |
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| Measuring the wavelength integrated intensity of coherent radiation in the micrometer to millimeter regime (THz radiation) is a widespread method to monitor the compression process in FEL linacs. While these devices give valuable information about the overall bunch length, they don't provide any information on the longitudinal structure and shape of the bunches. In this paper, we present a real time bunch profile monitor based on wavelength resolved THz detection. An in-vacuum spectrometer with four dispersive gratings and parallel read out of 120 individual wavelength bins provides detailed information shot-to-shot information on the bunch shape. The device can be operated in short (4-40 μm) and long range (40-400 μm) mode to cover the entire longitudinal phase space for compressed bunches of the FLASH linac. It is used as online monitoring device just as for bunch profile measurements during machine development. It's sensitivity down to the few micrometer scale allows to study very short features of the bunch profile as well as microbunching phenomena in this regime. | ||
| THPA14 | Upgrade of the Optical Synchronization System for FLASH II | 496 |
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| The optical synchronization system at FLASH has been in operation since 2008. Due to continuous improvement and several upgrades it has become an integral part of the machine operation and of pump-probe experiments as both rely on its performance. In summer 2013, a second FEL section, called FLASH II, which is using the same accelerator as FLASH will start its operation to increase the number of user experiments and to test new seeding schemes. This also requires a major extension of the synchronization system since new clients have to be supplied with a 10 fs-stable timing signal. Six additional stabilized fiber links and the according end stations like bunch arrival time monitors and laser synchronization setups will be installed. | ||
| THPA32 | Femtosecond Stable Laser-to-RF Phase Detection Using Optical Modulators | 551 |
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| Free-Electron Lasers like FLASH and the European XFEL require the synchronization of RF stations to the optical timing reference of the accelerator. For this purpose, a new technique to phase-lock RF sources to an optical pulse train has been invented. The new technique uses an opto-microwave coupling device together with an ultra-low phase-noise RF source operating at a frequency of 1.3 GHz. In our arrangement, the laser-to-RF phase detector is insensitive to amplitude fluctuations of the optical reference pulse train, which allows the detector to achieve femtosecond precision over long time periods. In this paper, we present the balanced laser-to-RF phase detection principle along with a tolerance study of the arrangement and first results from our prototype setup. | ||
| 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. | ||