| Paper | Title | Page |
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THP068 |
Recent Developments for the Improved Bunch Arrival Time Monitors at FLASH and for the European XFEL | |
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| At today's free-electron lasers, pump-probe experiments and seeding schemes put high demands on the timing stability of electron bunches. At FLASH and the upcoming European XFEL a reliable and precise arrival time detection down to the femtosecond level has to cover a broad range of bunch charges, which may even change from 1 nC down to 20 pC within a bunch train. At FLASH, the new bunch arrival time monitor has to cope with the special operation mode where the MHz repetition rate bunch train is separated into two segments for FLASH1 and FLASH2 beam lines. Each of the two segments will exhibit individual timing jitter characteristics since they are generated from two different injector lasers and can be accelerated with individual energy gain settings. This operation mode places high demands on both, the hardware and the required servers for the bunch arrival time monitor, with regard to automated control and exception handling. In this paper, we describe the adapted electro-optical subsystem and show latest results from the newly implemented read-out electronics based on the MTCA.4 platform. | ||
| THP069 | Performance Study of High Bandwidth Pickups Installed at FLASH and ELBE for Femtosecond-Precision Arrival Time Monitors | 893 |
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| At today's free-electron lasers, high-resolution electron bunch arrival time measurements have become increasingly more important in fast feedback systems for a timing jitter reduction down to the femtosecond level as well as for time-resolved pump-probe experiments. This is fulfilled by arrival time monitors which employ an electro-optical detection scheme by means of synchronised ultrashort laser pulses. Even more, at FLASH and the European XFEL the measurement has to cover a wide range of bunch charges from 1 nC down to 20 pC with equally sub-10 fs resolution. To meet these requirements, recently a high bandwidth pickup electrode with a cut-off frequency above 40 GHz has been developed. These pickups are installed at the macro-pulsed SRF accelerator of the free-electron laser FLASH and at the macro-pulsed continuous wave SRF accelerator ELBE. In this paper we present an evaluation of the pickup performance by direct signal measurements with high bandwidth oscilloscopes and by use of the electro-optical arrival time monitor. | ||
| THP090 | Femtosecond Timing Distribution for the European XFEL | 945 |
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| Accurate timing synchronization on the femtosecond timescale is an essential installation for time-resolved experiments at free-electron lasers (FELs) such as FLASH and the upcoming European XFEL. To date the required precision levels can only be achieved by a laser-based synchronization system. Such a system has been successfully deployed at FLASH and is based on the distribution of femtosecond laser pulses over actively stabilized optical fibers. Albeit its maturity and proven performance this system had to undergo a major redesign for the upcoming European XFEL due to the enlarged number of stabilized optical fibers and an increase by a factor of up to 10 in length. The experience and knowledge gathered from the operation of the optical synchronization system at FLASH has led to an elaborate and modular precision instrument which can stabilize polarization maintaining fibers for highest accuracy as well as economic single mode fibers for shorter lengths. This paper reports on the laser-based synchronization system focusing on the active fiber stabilization units for the European XFEL, discusses major complications, their solutions and and the most recent performance results. | ||