FEL2011 - List of Keywords (controls)

Paper	Title	Other Keywords	Page
MOPA02	Development of a Microscopic Irradiation Technique for Delivering VIS-FELs to Single Cells through a Fine-tapered Glass Rod	FEL, laser, electron, free-electron-laser	16
	F. Shishikura Nihon University School of Medicine, Tokyo, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka LEBRA, Funabashi, Japan
	The first lasing of LEBRA* succeeded in 2001 to produce near infrared FELs, by which the higher harmonics generated by means of the non-linear optical crystals now covered with visible and near infrared regions from 0.35 to 6 microns. The VIS-FELs are of particular interest and are expected to reveal photochemical reactions of single cells, even those in living organisms. To do this, it is a prerequisite to develop a micro-irradiation technique for targeting a single cell without photochemical effect to neighboring cells. We have established a microscopic irradiation technique with VIS-FELs through a fine glass rod. The FEL delivered through a fine-tapered glass rod with a diameter of about 5 microns has two major advantages compared with conventional microscope irradiation systems. The first is to deliver the FEL directly into targeted single cells in accordance with standard microinjection techniques used in developmental biology. The second is the ability to irradiate specific areas of the cytoplasm including cell organelle without severely damaging targeted cells. Using this technique, we also report micro-irradiation experiments on targeted single cells in living organisms. *Laboratory for Electron Beam Research and Application, Nihon University

MOPB25	Improvement of the Crossed Undulator Design for Effective Circular Polarization	undulator, polarization, radiation, electron	61
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	The production of X-ray radiation with a high degree of circular polarization constitutes an important goal at XFEL facilities. A simple scheme to obtain circular polarization control with crossed undulators has been proposed so far. In its simplest configuration the crossed undulators consist of pair of short planar undulators in crossed position separated by an electromagnetic phase shifter. An advantage of this configuration is a fast helicity switching. A drawback is that a high degree of circular polarization (over 90%) can only be achieved for lengths of the insertion devices significantly shorter than the gain length, i.e. at output power significantly lower than the saturation power level. Here we propose to use a setup with two or more crossed undulators separated by phase shifters. This cascade crossed undulator scheme is distinguished, in performance, by a fast helicity switching, a high degree of circular polarization (over 95%) and a high output power level, comparable with the saturation power level in the baseline undulator at fundamental wavelength. We present feasibility study and exemplifications for the LCLS baseline in the soft X-ray regime.

MOPB27	Circular Polarization Control for the LCLS Baseline in the Soft X-ray Regime	undulator, radiation, electron, polarization	69
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Several schemes have been discussed to obtain soft-polarization control in the context of the LCLS. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. As in previously proposed methods, the microbunching of the planar undulator is used here as well. After the baseline undulator, the electron beam is sent through a 40 m long straight section, and subsequently through a short helical (APPLE II) radiator. The microbunching is easily preserved, and intense coherent radiation is emitted in the helical radiator. The background radiation from the baseline undulator can be suppressed by letting radiation and electrons through horizontal and vertical slits upstream the helical radiator, where the radiation spot size is about ten times larger than the electron bunch transverse size. Thin Be foils for the slits will preserve from electron losses. Other facilities e.g. LCLS II or the European XFEL may benefit from this work as well, due to availability of sufficiently long free space at the end of undulator tunnel.

MOPC02	Improvement of Termination Field of Bulk HTSC Staggered Array Undulator	undulator, electron, simulation, solenoid	96
	N. Kimura, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	We have proposed a bulk High Temperature Superconductor Staggered Array Undulator (Bulk HTSC SAU) to achieve higher undulator field, shorter period, and variable K-value without changing gap[1]. The purpose of this study is to revise the controversial point, that bulk HTSC SAU generates strong wicked magnetic field on its terminations, which scatters electron beam. Therefore we studied a new method to correct the field. We developed a physical model which based on Bean model to deal with the bulk superconducting material and then constructed a simulation code. By using the calculation results, we developed the correction method by adding bulk material on the edge of undulator. Measurement of the magnetic field of a prototype of bulk HTSC SAU with this method has been performed. We confirm that the numerical calculation well describe the experimental results. In this conference, numerical and experimental results of our end field termination method will be presented. [1] R. Kinjyo, T. Kii, H. Zen, K Higashimura, K Masuda, K. Nagasaki, H. Ohgaki, Y.U. Jeong "Bulk High-TC Super Conductor Staggered Array Undulator" Proceedings of FEL2008

TUPA08	The Control System for CAEP FEL	FEL, EPICS, power-supply, vacuum	206
	D. Zhang, M. Li, H.B. Wang, X. Yang CAEP/IAE, Mianyang, Sichuan, People's Republic of China
	It describes a control system of CAEP Free Electron Laser (FEL), which is a distributed control system based on EPICS and Visual C++6.0. EPICS is popular in large accelerator laboratories in the world. It is a software toolkit for building process control system for a wide variety of experiment and industrial applications. The software tools in the kit provide independent and expandable modules for system configuration, distributed process control, run-time database, alarm manager, etc. It gives detailed description of the magnet power supply system , beam diagnostic system, including the hardware structure and software design. Other subsystems are also described in the paper. The control system has standard module, interoperability, and repeatability are available. The control system is simple direct, and stable.

TUPA21	Optical Synchronization of the SwissFEL 250 Mev Test Injector Gun Laser With the Optical Master Oscillator	laser, FEL, cathode, gun	243
	V.R. Arsov, S. Hunziker, M.G. Kaiser, V. Schlott Paul Scherrer Institut, Villigen, Switzerland F. Löhl CLASSE, Ithaca, New York, USA
	Funding: This work is partly supported by IRUVX-PP, an EU co-funded project under FP7 (Grant Agreement 211285) The SwissFEL gun laser stability is crucial for stable SASE operation in the hard X-ray regime. In 10 pC mode in which sub-10 fs photon pulses will be delivered for the users, the gun laser arrival time jitter at the cathode shouldn't exceed 30 fs (rms). In the present design it is foreseen that the gun oscillator is optically stabilized. It is also necessary to check the stability of the combination laser oscillator and transfer line with an optical reference. For this, the Ti:Sa oscillator was used as a master laser and its pulses were delivered through a ca. 5 m long free space transfer line to optically synchronize an Er-fiber oscillator via two color balanced optical cross correlator with a BBO crystal. The two lasers were placed on different optical tables, which didn't have a mechanical connection through the transfer line. Stable optical lock for at least 60 minutes was demonstrated with an in-loop stability in the range 3.7-17.6 fs. In the range 10 Hz-1 kHz the phase noise stability of the optically locked Er-fiber oscillator varied between 76.5 fs and 118.5 fs rms, 76 fs of which was the contribution of the 1.5 GHz PLO, to which the Ti:Sa oscillator was RF-locked.

WEPA19	Report on the Redesign of the Fibre Link Stabilisation Units at FLASH	laser, optics, alignment, free-electron-laser	370
	M.K. Bock, M. Bousonville, M. Felber, P. Gessler, T. Lamb, H. Schlarb, B. Schmidt, S. Schulz DESY, Hamburg, Germany M. Kuntzsch HZDR, Dresden, Germany
	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.

WEPA22	Development of Insertion Devices Measurement System at IHEP	undulator, alignment, insertion, insertion-device	381
	W. Chen, X. Feng, H.H. Lu, C. Shi, Y. Yang, J.C. Zhang IHEP, Beijing, People's Republic of China
	In the cooperation between IHEP and EXFEL, prototype undulator U48 for EXFEL is developed by IHEP. In order to meet, maintain and verify the ID’s magnetic performance, a magnetic measurement system has been developed. The development status of the system at IHEP is described in this paper. A 6.5 m long measurement bench with hall probe and small coil is used to measure the vertical and horizontal components of the Insertion Device magnetic field. The measurement system includes a precise granite bench to position and move the magnetic sensors, motion control part and data acquisition part. The characteristics and performances of the magnetic measurement system are presented.

WEPB04	Position Stability Monitoring of the LCLS Undulator Quadrupoles	undulator, quadrupole, ground-motion, monitoring	398
	H.-D. Nuhn, G.L. Gassner, F. Peters SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 In the era of SASE FELs, the demand for position stability of undulator components scales down to the range of sub-micrometers per day. Simultaneously, the undulator length increases significantly, in order to reach X-ray wavelengths. To minimize the impact of the outside environment, the LCLS undulator is placed underground, but reliable data about ground motion inside such a tunnel were not available in the required stability range. Therefore, a new position monitor system has been developed and installed for the LCLS undulator. That system is capable to measure X-, Y- and Roll positions of each of the 33 undulator quadrupoles, with respect to stretched wires. Instrument resolution is about 20 nm and instrument drift is negligible small. Position data of individual quadrupoles can be correlated along the entire undulator, which has a length of 132 m. The system is under continuous operation since 2009. The report describes long term experience with the running system and the observed position stability of the undulator quadrupoles.

WEPB05	Experiments on Femtosecond Stabilization of Fiber Link for Shanghai Soft-XFEL	laser, FEL, electron, LLRF	402
	X.P. Ma IHEP, Beijing, People's Republic of China B. Liu SINAP, Shanghai, People's Republic of China
	The Shanghai Soft X-ray Free Electron Laser (SXFEL) facility will be constructed in the Shanghai Synchrotron Radiation Facility (SSRF) campus. SXFEL will operate in the HGHG and/or EEHG mode and require a femtosecond timing distribution system as well as the synchronization between femtosecond pulsed lasers, femtosecond pulsed X-rays, CW microwave signals and electron bunches with 10 fs precision. The pulsed fiber laser based femtosecond T&S system which has been proposed by the MIT/DESY team is adopted. In this paper the status of the femtosecond T&S system for SXFEL is introduced. Some initial progress of the phase stabilization by electronics control when laser pulses transport though long optical fibers is presented.

WEPB18	Development of the First U48 Undulator Prototype for the European X-ray Free Electron Laser	undulator, alignment, FEL, laser	420
	H.H. Lu, W. Chen, X. Feng, X.M. Jiang, C. Shi, S.C. Sun, M.T. Wang, Z.X. Wang, Y.F. Yang IHEP, Beijing, People's Republic of China Y. Li, J. Pflüger European XFEL GmbH, Hamburg, Germany
	Funding: MOST973 Program The European XFEL will be a user facility consisting of three beamlines named SASE1/2/3 at the first stage. The first undulator prototype U48 for the European XFEL SASE2 beamline has been developed and tested by IHEP, China. Its magnetic design and specifications are briefly given. Development of U48, including magnetic material, mechanical structure, control system and assembly, are introduced. Magnetic tuning and test results are presented and discussed.

THPA18	Operation of the FLASH Photoinjector Laser System	laser, electron, gun, cathode	507
	S. Schreiber, M. Görler, K. Klose, T. Schulz, M. Staack DESY, Hamburg, Germany G. Klemz, G. Koss DESY Zeuthen, Zeuthen, Germany I.H. Templin, I. Will, H. Willert MBI, Berlin, Germany
	The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate thousands of electron bunches per second in burst mode. This puts special demands on the design of the electron source, especially the laser system. The fully diode pumped laser system is based on Nd:YLF and produces a train of 2400 UV pulses in a burst of 0.8 ms length with a repetition rate of 5 Hz and 800 pulses with 10 Hz. The single pulse energy is up to 25 μJ per pulse at 262 nm. The laser uses a pulsed oscillator synchronized to the master RF with a stability of better than 200 fs in arrival time at the RF gun. Special care has been taken to produce a uniform and stable pulse train in terms of pulse energy, shape, and phase. Since FLASH is a free-electron laser user facility, the laser is designed to operate for more than 8000 h per year without operator intervention and little maintenance. We report on operational experience with the new system brought in operation in spring 2010.

THPA26	Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs	feedback, electron, laser, beam-loading	531
	Ch. Schmidt, M.K. Bock, W. Koprek, S. Pfeiffer, H. Schlarb DESY, Hamburg, Germany W. Jałmużna TUL-DMCS, Łódź, Poland
	Highly precise regulation of accelerator RF fields is a prerequisite for a stable and reproducible photon generation at Free Electron Lasers such as FLASH. Due to major improvements of the RF field controls during 2010 and 2011 the FEL performance and the beam stability was significantly improved. In order to facilitate femtosecond precision pump-probe and seeding experiments at FLASH a combination of RF and beam based feedback loops are used. In this paper, we present the achieved stabilization of the arrival time and the pulse compression at FLASH using intra-pulse train feedbacks. Current limitations and future steps toward sub-10fs rms jitter are discussed.

THPA32	Femtosecond Stable Laser-to-RF Phase Detection Using Optical Modulators	laser, coupling, feedback, free-electron-laser	551
	T. Lamb, M.K. Bock, M. Bousonville, M. Felber, P. Gessler, F. Ludwig, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz DESY, Hamburg, Germany E. Janas Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	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.

THPB01	Optical Comb and Interferometer Development for Laser Synchronization in Femtosecond FELs	laser, FEL, optics, feedback	561
	R.B. Wilcox, J.M. Byrd LBNL, Berkeley, California, USA R. Holzwarth Menlo Systems GmbH, Martinsried, Germany
	Funding: This work supported by the U.S. Department of Energy under contract DE-AC02-05CH11231 We describe a method of synchronizing lasers in FELs to potential sub-femtosecond precision using interferometry and optical clock techniques, and show supporting experimental results. This precision is needed for pump/probe experiments in ultrafast FELs. The proposed system consists of carrier/offset phase stabilized, pulsed lasers synchronized via a single optical frequency delivered over fiber, analogous to RF oscillators synchronized with a reference frequency, but at 200 to 400THz. Our tests of modelocked lasers, interferometers and stabilized CW lasers show that subsystems can perform to the required precision. We have synchronized fiber lasers to less than 10fs jitter using two different frequency comb line locking schemes, and demonstrated interferometers in a working FEL with less than 100as jitter over 150m fiber. Based on these tests and published work by others, we calculate the performance of an optimized, integrated timing system to be less than 1fs in the short term. Long term stability is maintained by feedback from X-ray/optical cross-correlation at the experiment.

FROAI1	State-of-the-Art RF Distribution and Synchronization Techniques	laser, cavity, electron, klystron	633
	Y. Otake RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	In a recent FEL accelerator, the temporal stability of an accelerated electron beam is the most crucial problem to achieve stable lasing. The demanded temporal stability is less than several ten fs (rms) to stably keep an extremely high peak current formed at a bunch compressor, as well as attaining required temporal resolution of a pump-probe experiment. To realize this stability, elaborate rf distribution and synchronization system for the accelerator are strongly needed. One of the most promising methods to realize the system is unified instruments of laser technology and electrical technology. Because the system can control an rf phase based on optical wavelength resolution and reduce effects of environmental perturbations arising from temperature variation, vibration and electrical noise. Many institutes already employed the unified system comprising instruments, such as optical fiber signal transmission and in-phase and quadrature rf vector manipulation. We recently obtained less than 30 fs (rms) temporal fluctuation of electron beams at XFEL/SPring-8 “SACLA” by using this kind system. This paper reviews state of the art timing systems using the unified technology for FEL.

Paper

Title

Other Keywords

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Development of a Microscopic Irradiation Technique for Delivering VIS-FELs to Single Cells through a Fine-tapered Glass Rod

FEL, laser, electron, free-electron-laser

16

F. Shishikura
Nihon University School of Medicine, Tokyo, Japan
K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
LEBRA, Funabashi, Japan

The first lasing of LEBRA* succeeded in 2001 to produce near infrared FELs, by which the higher harmonics generated by means of the non-linear optical crystals now covered with visible and near infrared regions from 0.35 to 6 microns. The VIS-FELs are of particular interest and are expected to reveal photochemical reactions of single cells, even those in living organisms. To do this, it is a prerequisite to develop a micro-irradiation technique for targeting a single cell without photochemical effect to neighboring cells. We have established a microscopic irradiation technique with VIS-FELs through a fine glass rod. The FEL delivered through a fine-tapered glass rod with a diameter of about 5 microns has two major advantages compared with conventional microscope irradiation systems. The first is to deliver the FEL directly into targeted single cells in accordance with standard microinjection techniques used in developmental biology. The second is the ability to irradiate specific areas of the cytoplasm including cell organelle without severely damaging targeted cells. Using this technique, we also report micro-irradiation experiments on targeted single cells in living organisms.
*Laboratory for Electron Beam Research and Application, Nihon University

MOPB25

Improvement of the Crossed Undulator Design for Effective Circular Polarization

undulator, polarization, radiation, electron

61

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

The production of X-ray radiation with a high degree of circular polarization constitutes an important goal at XFEL facilities. A simple scheme to obtain circular polarization control with crossed undulators has been proposed so far. In its simplest configuration the crossed undulators consist of pair of short planar undulators in crossed position separated by an electromagnetic phase shifter. An advantage of this configuration is a fast helicity switching. A drawback is that a high degree of circular polarization (over 90%) can only be achieved for lengths of the insertion devices significantly shorter than the gain length, i.e. at output power significantly lower than the saturation power level. Here we propose to use a setup with two or more crossed undulators separated by phase shifters. This cascade crossed undulator scheme is distinguished, in performance, by a fast helicity switching, a high degree of circular polarization (over 95%) and a high output power level, comparable with the saturation power level in the baseline undulator at fundamental wavelength. We present feasibility study and exemplifications for the LCLS baseline in the soft X-ray regime.

MOPB27

Circular Polarization Control for the LCLS Baseline in the Soft X-ray Regime

undulator, radiation, electron, polarization

69

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Several schemes have been discussed to obtain soft-polarization control in the context of the LCLS. We propose a novel method to generate 10 GW level power at the fundamental harmonic with 99% degree of circular polarization from the LCLS baseline. Its merits are low cost, simplicity and easy implementation. As in previously proposed methods, the microbunching of the planar undulator is used here as well. After the baseline undulator, the electron beam is sent through a 40 m long straight section, and subsequently through a short helical (APPLE II) radiator. The microbunching is easily preserved, and intense coherent radiation is emitted in the helical radiator. The background radiation from the baseline undulator can be suppressed by letting radiation and electrons through horizontal and vertical slits upstream the helical radiator, where the radiation spot size is about ten times larger than the electron bunch transverse size. Thin Be foils for the slits will preserve from electron losses. Other facilities e.g. LCLS II or the European XFEL may benefit from this work as well, due to availability of sufficiently long free space at the end of undulator tunnel.

MOPC02

Improvement of Termination Field of Bulk HTSC Staggered Array Undulator

undulator, electron, simulation, solenoid

96

N. Kimura, M. A. Bakr, Y.W. Choi, H. Imon, K. Ishida, T. Kii, R. Kinjo, K. Komai, K. Masuda, H. Ohgaki, M. Omer, S. Shibata, K. Shimahashi, T. Sonobe, K. Yoshida
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

We have proposed a bulk High Temperature Superconductor Staggered Array Undulator (Bulk HTSC SAU) to achieve higher undulator field, shorter period, and variable K-value without changing gap[1]. The purpose of this study is to revise the controversial point, that bulk HTSC SAU generates strong wicked magnetic field on its terminations, which scatters electron beam. Therefore we studied a new method to correct the field. We developed a physical model which based on Bean model to deal with the bulk superconducting material and then constructed a simulation code. By using the calculation results, we developed the correction method by adding bulk material on the edge of undulator. Measurement of the magnetic field of a prototype of bulk HTSC SAU with this method has been performed. We confirm that the numerical calculation well describe the experimental results. In this conference, numerical and experimental results of our end field termination method will be presented.
[1] R. Kinjyo, T. Kii, H. Zen, K Higashimura, K Masuda, K. Nagasaki, H. Ohgaki, Y.U. Jeong "Bulk High-TC Super Conductor Staggered Array Undulator" Proceedings of FEL2008

TUPA08

The Control System for CAEP FEL

FEL, EPICS, power-supply, vacuum

206

D. Zhang, M. Li, H.B. Wang, X. Yang
CAEP/IAE, Mianyang, Sichuan, People's Republic of China

It describes a control system of CAEP Free Electron Laser (FEL), which is a distributed control system based on EPICS and Visual C++6.0. EPICS is popular in large accelerator laboratories in the world. It is a software toolkit for building process control system for a wide variety of experiment and industrial applications. The software tools in the kit provide independent and expandable modules for system configuration, distributed process control, run-time database, alarm manager, etc. It gives detailed description of the magnet power supply system , beam diagnostic system, including the hardware structure and software design. Other subsystems are also described in the paper. The control system has standard module, interoperability, and repeatability are available. The control system is simple direct, and stable.

TUPA21

Optical Synchronization of the SwissFEL 250 Mev Test Injector Gun Laser With the Optical Master Oscillator

laser, FEL, cathode, gun

243

V.R. Arsov, S. Hunziker, M.G. Kaiser, V. Schlott
Paul Scherrer Institut, Villigen, Switzerland
F. Löhl
CLASSE, Ithaca, New York, USA

Funding: This work is partly supported by IRUVX-PP, an EU co-funded project under FP7 (Grant Agreement 211285)
The SwissFEL gun laser stability is crucial for stable SASE operation in the hard X-ray regime. In 10 pC mode in which sub-10 fs photon pulses will be delivered for the users, the gun laser arrival time jitter at the cathode shouldn't exceed 30 fs (rms). In the present design it is foreseen that the gun oscillator is optically stabilized. It is also necessary to check the stability of the combination laser oscillator and transfer line with an optical reference. For this, the Ti:Sa oscillator was used as a master laser and its pulses were delivered through a ca. 5 m long free space transfer line to optically synchronize an Er-fiber oscillator via two color balanced optical cross correlator with a BBO crystal. The two lasers were placed on different optical tables, which didn't have a mechanical connection through the transfer line. Stable optical lock for at least 60 minutes was demonstrated with an in-loop stability in the range 3.7-17.6 fs. In the range 10 Hz-1 kHz the phase noise stability of the optically locked Er-fiber oscillator varied between 76.5 fs and 118.5 fs rms, 76 fs of which was the contribution of the 1.5 GHz PLO, to which the Ti:Sa oscillator was RF-locked.

WEPA19

Report on the Redesign of the Fibre Link Stabilisation Units at FLASH

laser, optics, alignment, free-electron-laser

370

M.K. Bock, M. Bousonville, M. Felber, P. Gessler, T. Lamb, H. Schlarb, B. Schmidt, S. Schulz
DESY, Hamburg, Germany
M. Kuntzsch
HZDR, Dresden, Germany

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.

WEPA22

Development of Insertion Devices Measurement System at IHEP

undulator, alignment, insertion, insertion-device

381

W. Chen, X. Feng, H.H. Lu, C. Shi, Y. Yang, J.C. Zhang
IHEP, Beijing, People's Republic of China

In the cooperation between IHEP and EXFEL, prototype undulator U48 for EXFEL is developed by IHEP. In order to meet, maintain and verify the ID’s magnetic performance, a magnetic measurement system has been developed. The development status of the system at IHEP is described in this paper. A 6.5 m long measurement bench with hall probe and small coil is used to measure the vertical and horizontal components of the Insertion Device magnetic field. The measurement system includes a precise granite bench to position and move the magnetic sensors, motion control part and data acquisition part. The characteristics and performances of the magnetic measurement system are presented.

WEPB04

Position Stability Monitoring of the LCLS Undulator Quadrupoles

undulator, quadrupole, ground-motion, monitoring

398

H.-D. Nuhn, G.L. Gassner, F. Peters
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
In the era of SASE FELs, the demand for position stability of undulator components scales down to the range of sub-micrometers per day. Simultaneously, the undulator length increases significantly, in order to reach X-ray wavelengths. To minimize the impact of the outside environment, the LCLS undulator is placed underground, but reliable data about ground motion inside such a tunnel were not available in the required stability range. Therefore, a new position monitor system has been developed and installed for the LCLS undulator. That system is capable to measure X-, Y- and Roll positions of each of the 33 undulator quadrupoles, with respect to stretched wires. Instrument resolution is about 20 nm and instrument drift is negligible small. Position data of individual quadrupoles can be correlated along the entire undulator, which has a length of 132 m. The system is under continuous operation since 2009. The report describes long term experience with the running system and the observed position stability of the undulator quadrupoles.

WEPB05

Experiments on Femtosecond Stabilization of Fiber Link for Shanghai Soft-XFEL

laser, FEL, electron, LLRF

402

X.P. Ma
IHEP, Beijing, People's Republic of China
B. Liu
SINAP, Shanghai, People's Republic of China

The Shanghai Soft X-ray Free Electron Laser (SXFEL) facility will be constructed in the Shanghai Synchrotron Radiation Facility (SSRF) campus. SXFEL will operate in the HGHG and/or EEHG mode and require a femtosecond timing distribution system as well as the synchronization between femtosecond pulsed lasers, femtosecond pulsed X-rays, CW microwave signals and electron bunches with 10 fs precision. The pulsed fiber laser based femtosecond T&S system which has been proposed by the MIT/DESY team is adopted. In this paper the status of the femtosecond T&S system for SXFEL is introduced. Some initial progress of the phase stabilization by electronics control when laser pulses transport though long optical fibers is presented.

WEPB18

Development of the First U48 Undulator Prototype for the European X-ray Free Electron Laser

undulator, alignment, FEL, laser

420

H.H. Lu, W. Chen, X. Feng, X.M. Jiang, C. Shi, S.C. Sun, M.T. Wang, Z.X. Wang, Y.F. Yang
IHEP, Beijing, People's Republic of China
Y. Li, J. Pflüger
European XFEL GmbH, Hamburg, Germany

Funding: MOST973 Program
The European XFEL will be a user facility consisting of three beamlines named SASE1/2/3 at the first stage. The first undulator prototype U48 for the European XFEL SASE2 beamline has been developed and tested by IHEP, China. Its magnetic design and specifications are briefly given. Development of U48, including magnetic material, mechanical structure, control system and assembly, are introduced. Magnetic tuning and test results are presented and discussed.

THPA18

Operation of the FLASH Photoinjector Laser System

laser, electron, gun, cathode

507

S. Schreiber, M. Görler, K. Klose, T. Schulz, M. Staack
DESY, Hamburg, Germany
G. Klemz, G. Koss
DESY Zeuthen, Zeuthen, Germany
I.H. Templin, I. Will, H. Willert
MBI, Berlin, Germany

The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate thousands of electron bunches per second in burst mode. This puts special demands on the design of the electron source, especially the laser system. The fully diode pumped laser system is based on Nd:YLF and produces a train of 2400 UV pulses in a burst of 0.8 ms length with a repetition rate of 5 Hz and 800 pulses with 10 Hz. The single pulse energy is up to 25 μJ per pulse at 262 nm. The laser uses a pulsed oscillator synchronized to the master RF with a stability of better than 200 fs in arrival time at the RF gun. Special care has been taken to produce a uniform and stable pulse train in terms of pulse energy, shape, and phase. Since FLASH is a free-electron laser user facility, the laser is designed to operate for more than 8000 h per year without operator intervention and little maintenance. We report on operational experience with the new system brought in operation in spring 2010.

THPA26

Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs

feedback, electron, laser, beam-loading

531

Ch. Schmidt, M.K. Bock, W. Koprek, S. Pfeiffer, H. Schlarb
DESY, Hamburg, Germany
W. Jałmużna
TUL-DMCS, Łódź, Poland

Highly precise regulation of accelerator RF fields is a prerequisite for a stable and reproducible photon generation at Free Electron Lasers such as FLASH. Due to major improvements of the RF field controls during 2010 and 2011 the FEL performance and the beam stability was significantly improved. In order to facilitate femtosecond precision pump-probe and seeding experiments at FLASH a combination of RF and beam based feedback loops are used. In this paper, we present the achieved stabilization of the arrival time and the pulse compression at FLASH using intra-pulse train feedbacks. Current limitations and future steps toward sub-10fs rms jitter are discussed.

THPA32

Femtosecond Stable Laser-to-RF Phase Detection Using Optical Modulators

laser, coupling, feedback, free-electron-laser

551

T. Lamb, M.K. Bock, M. Bousonville, M. Felber, P. Gessler, F. Ludwig, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz
DESY, Hamburg, Germany
E. Janas
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

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.

THPB01

Optical Comb and Interferometer Development for Laser Synchronization in Femtosecond FELs

laser, FEL, optics, feedback

561

R.B. Wilcox, J.M. Byrd
LBNL, Berkeley, California, USA
R. Holzwarth
Menlo Systems GmbH, Martinsried, Germany

Funding: This work supported by the U.S. Department of Energy under contract DE-AC02-05CH11231
We describe a method of synchronizing lasers in FELs to potential sub-femtosecond precision using interferometry and optical clock techniques, and show supporting experimental results. This precision is needed for pump/probe experiments in ultrafast FELs. The proposed system consists of carrier/offset phase stabilized, pulsed lasers synchronized via a single optical frequency delivered over fiber, analogous to RF oscillators synchronized with a reference frequency, but at 200 to 400THz. Our tests of modelocked lasers, interferometers and stabilized CW lasers show that subsystems can perform to the required precision. We have synchronized fiber lasers to less than 10fs jitter using two different frequency comb line locking schemes, and demonstrated interferometers in a working FEL with less than 100as jitter over 150m fiber. Based on these tests and published work by others, we calculate the performance of an optimized, integrated timing system to be less than 1fs in the short term. Long term stability is maintained by feedback from X-ray/optical cross-correlation at the experiment.

FROAI1

State-of-the-Art RF Distribution and Synchronization Techniques

laser, cavity, electron, klystron

633

Y. Otake
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

In a recent FEL accelerator, the temporal stability of an accelerated electron beam is the most crucial problem to achieve stable lasing. The demanded temporal stability is less than several ten fs (rms) to stably keep an extremely high peak current formed at a bunch compressor, as well as attaining required temporal resolution of a pump-probe experiment. To realize this stability, elaborate rf distribution and synchronization system for the accelerator are strongly needed. One of the most promising methods to realize the system is unified instruments of laser technology and electrical technology. Because the system can control an rf phase based on optical wavelength resolution and reduce effects of environmental perturbations arising from temperature variation, vibration and electrical noise. Many institutes already employed the unified system comprising instruments, such as optical fiber signal transmission and in-phase and quadrature rf vector manipulation. We recently obtained less than 30 fs (rms) temporal fluctuation of electron beams at XFEL/SPring-8 “SACLA” by using this kind system. This paper reviews state of the art timing systems using the unified technology for FEL.