06 Instrumentation, Controls, Feedback & Operational Aspects

T23 Timing and Synchronization

Paper	Title	Page
WEOCG03	RF Reference Signal Distribution System for FAIR	1935
	M. Bousonville GSI, Darmstadt P. Meissner TU Darmstadt, Darmstadt
	For the synchronisation of RF systems in the FAIR (Facility for Antiproton and Ion Research) synchrotrons and storage rings, an RF Reference Signal Distribution System is being developed. The FAIR RF cavities need signals with different phases and frequencies. Furthermore, frequency ramps with RF frequency ratios of up to 7 have to be realized in all rings. To enable this functionality, the distribution system provides two different clock signals to several locations within the facility that will be up to 1 km apart. By means of these clock signals, frequency generators can be synchronised that generate the RF signals needed for the cavities. For the transmission of the clock signals, an optical network based on the DWDM method (Dense Wavelength Division Multiplex) will be used. The delay will permanently be measured and by means of the delay data, a clock regenerator produces a phase synchronous and stable reference signal at the end of each transmission line. A delay measurement accuracy of better than 100 fs has been achieved. The presentation focuses on the design of the system as well as the performance of the prototype.
	Slides
THPC152	Electro-optic Bunch Arrival Time Measurement at FLASH	3348
	V. R. Arsov, M. Felber, E.-A. Knabbe, F. Loehl, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt, P. Schmüser, S. Schulz, B. Steffen, A. Winter, J. Zemella DESY, Hamburg
	The operation of the next generation free electron lasers such as FLASH and the planned European XFEL requires drift free synchronization and femto-second stability. For this purpose an optical synchronization system has been developed, based on a mode-locked erbium-doped fiber laser, whose pulses are distributed over length stabilized fiber links. In order to evaluate the performance of the optical distribution system and the bunch arrival time monitors (BAM) an independent reference is needed. The measurement of the electro-optic (EO) response in a GaP crystal offers such a possibility. The method is destruction free and allows simultaneous determination of the peak current and the charge center of mass arrival time with femto-second precision. The measurements are performed with a 0.175 mm thick GaP crystal using 3 ps linearly chirped pulses from a Ti:Sa oscillator. The EO signal is encoded to the chirped pulse and spectrally resolved near crossed polarizers. Comparison of the EO and BAM timings provides a check of the relative accuracy of both methods, including the accuracy of the optical timing distribution system.
THPC153	Timing System of the New Elettra Injector	3351
	S. Bassanese, A. Carniel, R. De Monte, M. Ferianis, G. Gaio ELETTRA, Basovizza, Trieste
	A new timing system has been developed to operate the new injector for the Elettra storage ring. It implements a versatile injection system to support standard and exotic fillings as well as the top-up mode of operation. Based on an in-house developed programmable counter VME board, the system provides all the needed triggers by the pre-injector LINAC, the booster injection, the booster ramping system, the booster extraction, and the SR injection. An overview of the system architecture and functionality is described and the performance of the board is reported. All the trigger signals are distributed to the timing clients by means of optical links.
THPC156	Performances of the SPARC Laser and RF Synchronization Systems	3354
	A. Gallo, D. Alesini, M. Bellaveglia, G. Gatti, C. Vicario INFN/LNF, Frascati (Roma)
	The SPARC project consists in a 150 MeV S-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been completed and the SPARC scientific program is presently in progress. The low level RF control electronics to monitor and synchronize the RF phase of the accelerating structures along the linac and the laser shot on the photocathode has been commissioned and it is now fully operative. The laser synchronization is routinely monitored and slow drifts are automatically corrected by a dedicated shot-to-shot feedback system. A similar slow automatic regulation is implemented on each linac accelerating section acting either on low level or high power sliding lines. The phase noise in the 2 RF power stations is counteracted by fast intra-pulse phase feedback systems that have been developed and put in operation. Phase stability measurements taken over the whole synchronization system are reported, and performances of different synchronization architectures, micro-wave based or laser based, are compared.
THPC157	A Simple Method for Timing an XFEL Source to High-power Lasers	3357
	G. Geloni, E. Saldin, E. Schneidmiller, M. V. Yurkov DESY, Hamburg
	We propose a technique for timing an XFEL to a high-power laser with femtosecond accuracy. The same electron bunch is used to produce an XFEL pulse and an ultrashort optical pulse that are, thus, naturally synchronized. Cross-correlation techniques will yield the relative jitter between the optical pulse (and, thus, the XFEL pulse) and a pulse from an external pump-laser with femtosecond resolution. Technical realization will be based on an optical replica synthesizer (ORS) setup to be installed after the final bunch-compressor. The electron bunch is modulated in the ORS by an external optical laser. Travelling through the main undulator, it produces the XFEL pulse. Then, a powerful optical pulse of coherent edge radiation is generated as the bunch passes through a long straight section and a separation magnet downstream of the main undulator. Relative synchronization of these pulses is preserved using the same mechanical support for X-ray and optical elements transporting radiation to the experimental area, where single-shot cross-correlation between optical pulse and pump-laser pulse is performed. We illustrate our technique with numerical examples referring to the European XFEL.
THPC158	Measurement and Stabilization of the Bunch Arrival Time at FLASH	3360
	F. Loehl, V. R. Arsov, M. Felber, K. E. Hacker, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt DESY, Hamburg W. Jalmuzna TUL-DMCS, Łódź S. Schulz, A. Winter, J. Zemella Uni HH, Hamburg J. Szewinski The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
	To fully exploit the experimental opportunities offered by the 10 - 30 fs long light pulses from FLASH, e.g. in pump-probe experiments, precise measurements and control of the electron-bunch arrival-time on the 10 fs scale are needed. A bunch arrival time monitor (BAM) which uses the optical synchronization system of FLASH as a reference has been developed for this purpose. The bunch induced signal from a GHz-bandwidth beam pick-up is guided into an electro-optical modulator in which the periodic laser pulse train of the optical synchronization system experiences an amplitude modulation. Detection of this modulation allows to determine the bunch arrival time with a resolution of better than 20 fs. The superconducting linac of FLASH generates trains of up to 800 bunches. The BAM signals can be used for an intra-bunch train feedback stabilizing the arrival time to better than 50 fs. The feedback is capable of generating well-defined arrival time patterns within a bunch train which are useful for overlap-scans in pump-probe experiments. First results from the feedback installed at FLASH will be presented.
THPC159	Timing and Event Distribution for FERMI@ELETTRA	3363
	A. Rohlev, A. O. Borga, G. D'Auria ELETTRA, Basovizza, Trieste L. R. Doolittle, A. Ratti LBNL, Berkeley, California J. Serrano, M. W. Stettler CERN, Geneva
	FERMI@ELETTRA is a 4th generation light source under construction at Sincrotrone Trieste. It will be operated as a seeded FEL driven by a warm S-band Linac which places very stringent specifications on control of the amplitude and phase of the RF stations. The local clock generation and distribution system at each station will not be based on the phase reference distribution but rather on a separate frequency reference distribution which has significantly less stringent phase stability requirements. This frequency reference will be embedded in the serial data link to each station and has the further advantage of being able to broadcast synchronous machine timing signals with sub-nanosecond temporal accuracy. The phase and amplitude of the phase reference line is measured for each pulse and used to calibrate the other measurements. This paper describes the architecture used to distribute the frequency reference along with the precision machine timing and clocking signals.
THPC160	An Optical Cross-correlation Scheme to Synchronize Distributed Laser Systems at FLASH	3366
	S. Schulz, V. R. Arsov, M. Felber, F. Loehl, B. Lorbeer, F. Ludwig, K.-H. Matthiesen, H. Schlarb, B. Schmidt, A. Winter DESY, Hamburg P. Schmüser, J. Zemella Uni HH, Hamburg B. Steffen PSI, Villigen
	The soft X-ray free-electron laser FLASH and the planned European XFEL generate X-ray light pulses in the femto-second range. For time-resolved pump-probe experiments, future operation modes by means of laser seeding and for special diagnostic measurements it is crucial to synchronize various laser systems to the electron beam with an accuracy better than 30 fs. For this purpose an optical synchronization system at the telecommunication wavelength of 1550 nm is currently being installed and tested at FLASH. We developed a background-free optical cross-correlation scheme to synchronize two mode-locked laser systems of different center wavelengths and repetition rates with an accuracy better than 10 fs. The scheme was tested by linking a commercial 81 MHz Ti:Sa oscillator (center wavelength 800 nm), used for electro-optical diagnostics at FLASH, to a locally installed 40.5 MHz erbium-doped fiber laser, operating at 1550 nm. Later, this laser will be replaced by an actively length-stabilized fiber-link distributing the pulses from the 216 MHz master laser oscillator of the machine to lock the diagnostics laser to the optical synchronization system.
THPC162	The SSRF Timing System	3369
	L. Y. Zhao, D. K. Liu, C. X. Yin SINAP, Shanghai
	In the Shanghai Synchrotron Radiation Facility (SSRF), various equipment in the 150MeV linac, the full energy booster and the 3.5GeV storage ring need to be triggered and synchronized by a low jitter timing system. An event system based on distribution network is implemented in the SSRF timing system. In this paper, the software and hardware structure of the SSRF timing system are described and the system performance is presented.