IBIC2013 - List of Authors (Schlarb, H.)

Paper

Title

Page

Electron Bunch Diagnostic at the Upgraded ELBE Accelerator: Status and Challenges

23

M. Kuntzsch, S. Findeisen, M. Gensch, B.W. Green, J. Hauser, S. Kovalev, U. Lehnert, P. Michel, F. Röser, Ch. Schneider, R. Schurig
HZDR, Dresden, Germany
A. Al-Shemmary, M. Bousonville, M.K. Czwalinna, T. Golz, H. Schlarb, B. Schmidt, S. Schulz, N. Stojanovic, S. Vilcins
DESY, Hamburg, Germany
E. Hass
Uni HH, Hamburg, Germany

Within the ELBE upgrade towards a Center for High Power Radiation Sources (HSQ), a mono energetic positron, a liquid lead photo neutron source and two new THz sources have been installed at the superconducting electron linac at ELBE. A variety of established as well as newly developed electron beam diagnostics were installed and tested. In this paper we want to present first results achieved with the currently existing prototype beam arrival time and bunch compression monitors (BAM, BCM) as well as one versatile EOS set-up. Based on these future developements and upgrades are discussed.

Slides MOBL3 [3.578 MB]

MOPC32

Development Status of Optical Synchronization for the European XFEL

135

C. Sydlo, M.K. Czwalinna, M. Felber, C. Gerth, T. Lamb, H. Schlarb, S. Schulz, F. Zummack
DESY, Hamburg, Germany
S. Jabłoński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

Precise timing synchronization on the femtosecond timescale is crucial for time resolved experiments at modern free-electron lasers (FELs) like FLASH and the upcoming European XFEL. The required precision can only be achieved by a laser-based synchronization system. The pulsed laser-based scheme at FLASH, based on the distribution of femtosecond laser pulses over actively stabilized optical fibers, has evolved over the years from a prototype setup to a mature and reliable system. At the same time, the present implementation serves as prototype for the synchronization infrastructure at the European XFEL. Due to a factor of ten increase of the length of the accelerator and an increased number of timing-critical subsystems, new challenges arise. This paper reports on the current development progress of the XFEL optical synchronization, discusses major complications and their solutions.

MOPC33

Status of the Fiber Link Stabilization Units at FLASH

139

F. Zummack, M.K. Czwalinna, M. Felber, T. Lamb, H. Schlarb, S. Schulz, C. Sydlo
DESY, Hamburg, Germany
S. Jabłoński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

State-of-the-art X-ray photon science with modern free-electron lasers (FEL) like FLASH and the upcoming European X-ray Free-Electron Laser Facility (XFEL) requires timing with femtosecond accuracy. For this purpose a sophisticated pulsed optical synchronization system distributes precise timing via length-stabilized fiber links throughout the entire FEL. Stations to be synchronized comprise bunch arrival time monitors, RF stations and optical cross-correlators for external lasers. The different requirements of all those stations have to be met by one optical link-stabilization-unit (LSU) design, compensating drifts and jitter in the distribution system down to a fs-level. Five years of LSU operation at FLASH have led to numerous enhancements resulting in an elaborate system. This paper presents these enhancements, their impact on synchronization performance and the latest state of the LSUs.

MOPC38

Overview on Electron Bunch and Photon Beam Diagnostic Techniques for CW Linear Accelerators Using the Example of ELBE

158

R. Schurig, S. Findeisen, M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, F. Röser, Ch. Schneider
HZDR, Dresden, Germany
A. Al-Shemmary, M. Bousonville, M.K. Czwalinna, T. Golz, H. Schlarb, B. Schmidt, S. Schulz, N. Stojanovic, S. Vilcins
DESY, Hamburg, Germany
E. Hass
Uni HH, Hamburg, Germany

For future light sources a continuous wave mode of operation enables perspectives for high precision time-resolved experiments. In order to ensure steady experimental conditions, various elements for electron bunch and photon beam diagnostics are used. Bunch Arrival Time Monitors (BAM), Bunch Compression Monitors (BCM), Electro-optical Sampling (EOS) and new types of THz-diagnostic are essential for the understanding of the machine’s behavior to generate stable secondary radiation. The detector readout benefits from the high repetition rate and allows data acquisition in frequency domain with enhanced sensitivity. The contribution will give an overview on CW Diagnostic elements at ELBE which are currently in commissioning state and first measurement results which have been carried out.

TUPC03

Commissioning and Diagnostics Development for the New Short-Pulse Injector Laser at FLASH

353

T. Plath, J. Rönsch-Schulenburg, J. Roßbach
Uni HH, Hamburg, Germany
H. Schlarb, S. Schreiber, B. Steffen
DESY, Hamburg, Germany

In order to extend the parameter range of FLASH towards shorter electron pulses down to a few fs SASE pulses, shorter bunches with very small charges of a few tens of picocoulombs are necessary directly at the photo injector. Therefore a new injector laser delivering pulses of 1 to 5 ps has been installed and commissioned. The influence of the laser parameters on the electron beam was studied theoretically. In this paper we discuss the required laser beam diagnostics and present measurements of critical laser and electron beam parameters.

Poster TUPC03 [1.076 MB]

TUPC31

New Design of High Order Modes Electronics in MTCA.4 Standard for FLASH and the European XFEL

443

S. Bou Habib, A. Abramowicz
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
N. Baboi, H. Schlarb
DESY, Hamburg, Germany

At free-electron linear accelerators, various High Order Modes (HOM) - both monopole and dipole - are excited. Extensive studies at DESY have shown that monitoring and analysis of some of these modes can be used for different applications including Beam Position Monitors (BPMs) and the reduction of wake-fields, the measurement of the beam phase with-respect-to RF signal in cavities, and the measurement of cavity alignment in the 1.3 GHz cryo-modules. Three frequencies were chosen for further experiments: the 1.3 GHz base frequency from the klystron, the 1.7 GHz dipole mode and the 2.4 GHz monopole mode. In order to realize the monitoring and analysis requirements, very high resolution measurements in amplitude, phase and shape (time resolution) are required for all three frequencies simultaneously. In this paper, we present the new HOM electronics prototype including a microstrip and stripline RF tri-passband filter design and measurements and the specialized MTCA.4 Rear Transition Module for HOM measurements with an ultra-fast high-resolution AMC digitizer.

Poster TUPC31 [1.226 MB]

TUPC33

Femtosecond Stable Laser-to-RF Phase Detection for Optical Synchronization Systems

447

T. Lamb, M.K. Czwalinna, M. Felber, C. Gerth, H. Schlarb, S. Schulz, C. Sydlo, M. Titberidze, F. Zummack
DESY, Hamburg, Germany
E. Janas
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
J. Szewiński
NCBJ, Świerk/Otwock, Poland

Optical reference distributions have become an indispensable asset for femtosecond precision synchronization of free-electron lasers. At FLASH and for the future European XFEL, laser pulses are distributed over large distances in round-trip time stabilized fibers to all critical facility sub-systems. Novel Laser-to-RF phase detectors will be used to provide ultra phase stable and long-term drift free microwave signals for the accelerator RF controls. In this paper, we present the recent progress on the design of a fully integrated and engineered version of the L2RF phase detector, together with first experimental results demonstrating so-far unrivaled performance.

Poster TUPC33 [18.910 MB]

TUPC34

Precision Synchronization of Optical Lasers Based on MTCA.4 Electronics

451

U. Mavrič, Ł. Butkowski, H.T. Duhme, M. Felber, M. Fenner, C. Gerth, P. Peier, H. Schlarb, B. Steffen
DESY, Hamburg, Germany
T. Kozak, P. Predki
TUL-DMCS, Łódź, Poland

Optical laser have become an integral part of free-electron laser facilities for the purposes of electron bunch generation, external seeding, diagnostics and pump-probe experiments. The ultra-short electron bunches demand a high timing stability and precision synchronization of the optical lasers. In this paper, we present the proof-of-principle for a laser locking application implemented on a MTCA.4 platform. The system design relies on existing MTCA.4 compliant off-the-shelf modules that are available on the market or have been developed for other applications within the particle accelerator community. Besides performance and cost, we also tried to minimize the number of out-of-crate components. Preliminary measurements of laser locking at the FLASH and REGAE particle accelerators are presented, and an outlook for further system development in the area of laser-to-RF synchronization is given.

TUPC35

Upgrade of the Read-out Electronics for the Energy Beam Position Monitors at FLASH and European XFEL

454

U. Mavrič, C. Gerth, H. Schlarb
DESY, Hamburg, Germany
A. Piotrowski
TUL-DMCS, Łódź, Poland

The dispersive sections of magnetic bunch compressor chicanes at free-electron lasers are excellent candidates for beam energy measurements. In the rectangular beamline sections of the bunch compressors at FLASH, energy beam position monitors (EBPM) with transversely mounted stripline pickups are installed. In this paper, we present the upgrade of the read-out electronics for signal detection of the EBPM installed at FLASH. The system is based on the MTCA.4 standard and reuses already available MTCA.4 compliant modules. This is also true for gateware and software development which fits into standard MTCA.4 framework development. The performance of the instrument was studied at FLASH during user operation and the results are presented.

WEPC31

New Design of the 40 GHz Bunch Arrival Time Monitor Using MTCA.4 Electronics at FLASH and for the European XFEL

749

M.K. Czwalinna, C. Gerth, H. Schlarb
DESY, Hamburg, Germany
S. Bou Habib
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
S. Korolczuk, J. Szewiński
NCBJ, Świerk/Otwock, Poland
A. Kuhl
Uni HH, Hamburg, Germany

At free-electron lasers, today's pump-probe experiments and seeding schemes make high demands on the electron bunch timing stability with an arrival time jitter reduction down to the femtosecond level. At FLASH and the upcoming European XFEL, the bunch train structures with their high bunch repetition rates allow for an accurate intra-train stabilisation. To realise longitudinal beam-based feedbacks a reliable and precise arrival time detection over a broad range of bunch charges, which can even change from 1 nC down to 20 pC within a bunch train, is essential. Benefitting from the experience at FLASH, the current bunch arrival time monitors (BAMs), based on detection of RF signals from broad-band pick-ups by use of electro-optic modulators, are further developed to cope with the increased requirements. In this paper, we present the new BAM prototype, including an adapted electro-optical front-end and the latest development of the read-out electronics based on the MTCA.4 platform.

WEPC32

Past, Present and Future Aspects of Laser-Based Synchronization at FLASH

753

S. Schulz, M. Bousonville, M.K. Czwalinna, M. Felber, M. Heuer, T. Lamb, J. Müller, P. Peier, S. Ruzin, H. Schlarb, B. Steffen, C. Sydlo, F. Zummack
DESY, Hamburg, Germany
T. Kozak, P. Predki
TUL-DMCS, Łódź, Poland
A. Kuhl
Uni HH, Hamburg, Germany

Free-electron lasers, like FLASH and the upcoming European XFEL, are capable of producing XUV and X-ray pulses of a few femtoseconds duration. For time-resolved pump-probe experiments and the externally seeded operation mode it is crucial not only to stabilize the arrival time of the electron bunches, but also to achieve a synchronization accuracy of external lasers on the same timescale. This can only be realized with a laser-based synchronization infrastructure. At FLASH, a periodic femtosecond laser pulse train is transmitted over actively stabilized optical fibers to the critical subsystems. In this paper we report on the present status and performance of the system, as well as its imminent upgrades and new installations. These include the connection of FLASH2, electron bunch arrival time monitors for low charges, a new master laser pulse distribution scheme, all-optical synchronization of the pump-probe laser and arrival time measurements of the UV pulses on the e-gun photocathode. Along with the coming connection of the acceleration modules to the master laser and the switch of the low-level hardware to the uTCA platform, an outlook to improved feedback strategies is given.

WEPC40

Pickup Signal Improvement for High Bandwidth BAMs for FLASH and European - XFEL

778

A. Angelovski, R. Jakoby, A. Penirschke
TU Darmstadt, Darmstadt, Germany
M.K. Czwalinna, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

In order to measure the arrival time of the electron bunches in low (20 pC) and high (1 nC) charge operation mode, new high bandwidth pickups were developed as a part of the Bunch Arrival-time Monitors (BAMs) for FLASH at DESY *. The pickup signal is transported via radiation resistant coaxial cables to the electro-optic modulator (EOM) **. Due to the high losses of the 40 GHz RF front-end the signal in the RF path is attenuated well below the optimal operation voltage of the EOM. To improve the overall performance, the signal strength of the induced pickup signal needs to be increased and at the same time the losses in the RF front-end significantly reduced. In this paper, the analysis towards improving the induced pickup signal strength is presented. Simulations are performed with the CST STUDIO SUITE package and the results are compared with the state of the art high bandwidth pickups.
* A. Angelovski et al., Phys. Rev. ST Accel. Beams 15, 112803 (2012)
** A. Penirschke et al., Proc. of IBIC2012, Tsukuba, Japan (2012)

WEPC41

Comparative Analysis of Different Electro-Optical Intensity Modulator Candidates for the New 40 GHz Bunch Arrival Time Monitor System for FLASH and European XFEL

782

A. Kuhl, J. Rönsch-Schulenburg, J. Roßbach
Uni HH, Hamburg, Germany
M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany
S. Schnepp
ETH Zurich, Institute of Electromagnetic Fields (IFH), Zurich, Switzerland
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: The work is supported by Federal Ministry of Education and Research of Germany (BMBF) within FSP 301 under the contract numbers 05K10GU2 and 05K10RDA.
The currently installed Bunch Arrival time Monitors (BAMs) at the Free electron LASer in Hamburg (FLASH) achieved a time resolution of less than 10 fs for bunch charges higher than 500 pC. In order to achieve single spike FEL pulses at FLASH, electron bunch charges down to 20 pC are of interest. With these BAMs the required time resolution is not reachable for bunch charges below 500 pC. Therefore new pickups with a bandwidth of up to 40 GHz are designed and manufactured*. The signal evaluation takes place with a time-stabilized reference laser pulse train which is modulated with an Electro-Optical intensity Modulator (EOM). The new BAM system also requires new EOMs for the electro-optical frontend. The available selection of commercial EOM candidates for the new frontend is very limited. In this paper we present a comparison between different EOM candidates for the new electro optical frontend.
* A. Angelovski et al. Proceedings Phys. Rev ST AB, DOI:10.1103/PhysRevSTAB.15.112803

Poster WEPC41 [0.619 MB]

Paper	Title	Page
MOBL3	Electron Bunch Diagnostic at the Upgraded ELBE Accelerator: Status and Challenges	23
	M. Kuntzsch, S. Findeisen, M. Gensch, B.W. Green, J. Hauser, S. Kovalev, U. Lehnert, P. Michel, F. Röser, Ch. Schneider, R. Schurig HZDR, Dresden, Germany A. Al-Shemmary, M. Bousonville, M.K. Czwalinna, T. Golz, H. Schlarb, B. Schmidt, S. Schulz, N. Stojanovic, S. Vilcins DESY, Hamburg, Germany E. Hass Uni HH, Hamburg, Germany
	Within the ELBE upgrade towards a Center for High Power Radiation Sources (HSQ), a mono energetic positron, a liquid lead photo neutron source and two new THz sources have been installed at the superconducting electron linac at ELBE. A variety of established as well as newly developed electron beam diagnostics were installed and tested. In this paper we want to present first results achieved with the currently existing prototype beam arrival time and bunch compression monitors (BAM, BCM) as well as one versatile EOS set-up. Based on these future developements and upgrades are discussed.
	Slides MOBL3 [3.578 MB]

MOPC32	Development Status of Optical Synchronization for the European XFEL	135
	C. Sydlo, M.K. Czwalinna, M. Felber, C. Gerth, T. Lamb, H. Schlarb, S. Schulz, F. Zummack DESY, Hamburg, Germany S. Jabłoński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	Precise timing synchronization on the femtosecond timescale is crucial for time resolved experiments at modern free-electron lasers (FELs) like FLASH and the upcoming European XFEL. The required precision can only be achieved by a laser-based synchronization system. The pulsed laser-based scheme at FLASH, based on the distribution of femtosecond laser pulses over actively stabilized optical fibers, has evolved over the years from a prototype setup to a mature and reliable system. At the same time, the present implementation serves as prototype for the synchronization infrastructure at the European XFEL. Due to a factor of ten increase of the length of the accelerator and an increased number of timing-critical subsystems, new challenges arise. This paper reports on the current development progress of the XFEL optical synchronization, discusses major complications and their solutions.

MOPC33	Status of the Fiber Link Stabilization Units at FLASH	139
	F. Zummack, M.K. Czwalinna, M. Felber, T. Lamb, H. Schlarb, S. Schulz, C. Sydlo DESY, Hamburg, Germany S. Jabłoński Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	State-of-the-art X-ray photon science with modern free-electron lasers (FEL) like FLASH and the upcoming European X-ray Free-Electron Laser Facility (XFEL) requires timing with femtosecond accuracy. For this purpose a sophisticated pulsed optical synchronization system distributes precise timing via length-stabilized fiber links throughout the entire FEL. Stations to be synchronized comprise bunch arrival time monitors, RF stations and optical cross-correlators for external lasers. The different requirements of all those stations have to be met by one optical link-stabilization-unit (LSU) design, compensating drifts and jitter in the distribution system down to a fs-level. Five years of LSU operation at FLASH have led to numerous enhancements resulting in an elaborate system. This paper presents these enhancements, their impact on synchronization performance and the latest state of the LSUs.

MOPC38	Overview on Electron Bunch and Photon Beam Diagnostic Techniques for CW Linear Accelerators Using the Example of ELBE	158
	R. Schurig, S. Findeisen, M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, F. Röser, Ch. Schneider HZDR, Dresden, Germany A. Al-Shemmary, M. Bousonville, M.K. Czwalinna, T. Golz, H. Schlarb, B. Schmidt, S. Schulz, N. Stojanovic, S. Vilcins DESY, Hamburg, Germany E. Hass Uni HH, Hamburg, Germany
	For future light sources a continuous wave mode of operation enables perspectives for high precision time-resolved experiments. In order to ensure steady experimental conditions, various elements for electron bunch and photon beam diagnostics are used. Bunch Arrival Time Monitors (BAM), Bunch Compression Monitors (BCM), Electro-optical Sampling (EOS) and new types of THz-diagnostic are essential for the understanding of the machine’s behavior to generate stable secondary radiation. The detector readout benefits from the high repetition rate and allows data acquisition in frequency domain with enhanced sensitivity. The contribution will give an overview on CW Diagnostic elements at ELBE which are currently in commissioning state and first measurement results which have been carried out.

TUPC03	Commissioning and Diagnostics Development for the New Short-Pulse Injector Laser at FLASH	353
	T. Plath, J. Rönsch-Schulenburg, J. Roßbach Uni HH, Hamburg, Germany H. Schlarb, S. Schreiber, B. Steffen DESY, Hamburg, Germany
	In order to extend the parameter range of FLASH towards shorter electron pulses down to a few fs SASE pulses, shorter bunches with very small charges of a few tens of picocoulombs are necessary directly at the photo injector. Therefore a new injector laser delivering pulses of 1 to 5 ps has been installed and commissioned. The influence of the laser parameters on the electron beam was studied theoretically. In this paper we discuss the required laser beam diagnostics and present measurements of critical laser and electron beam parameters.
	Poster TUPC03 [1.076 MB]

TUPC31	New Design of High Order Modes Electronics in MTCA.4 Standard for FLASH and the European XFEL	443
	S. Bou Habib, A. Abramowicz Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland N. Baboi, H. Schlarb DESY, Hamburg, Germany
	At free-electron linear accelerators, various High Order Modes (HOM) - both monopole and dipole - are excited. Extensive studies at DESY have shown that monitoring and analysis of some of these modes can be used for different applications including Beam Position Monitors (BPMs) and the reduction of wake-fields, the measurement of the beam phase with-respect-to RF signal in cavities, and the measurement of cavity alignment in the 1.3 GHz cryo-modules. Three frequencies were chosen for further experiments: the 1.3 GHz base frequency from the klystron, the 1.7 GHz dipole mode and the 2.4 GHz monopole mode. In order to realize the monitoring and analysis requirements, very high resolution measurements in amplitude, phase and shape (time resolution) are required for all three frequencies simultaneously. In this paper, we present the new HOM electronics prototype including a microstrip and stripline RF tri-passband filter design and measurements and the specialized MTCA.4 Rear Transition Module for HOM measurements with an ultra-fast high-resolution AMC digitizer.
	Poster TUPC31 [1.226 MB]

TUPC33	Femtosecond Stable Laser-to-RF Phase Detection for Optical Synchronization Systems	447
	T. Lamb, M.K. Czwalinna, M. Felber, C. Gerth, H. Schlarb, S. Schulz, C. Sydlo, M. Titberidze, F. Zummack DESY, Hamburg, Germany E. Janas Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland J. Szewiński NCBJ, Świerk/Otwock, Poland
	Optical reference distributions have become an indispensable asset for femtosecond precision synchronization of free-electron lasers. At FLASH and for the future European XFEL, laser pulses are distributed over large distances in round-trip time stabilized fibers to all critical facility sub-systems. Novel Laser-to-RF phase detectors will be used to provide ultra phase stable and long-term drift free microwave signals for the accelerator RF controls. In this paper, we present the recent progress on the design of a fully integrated and engineered version of the L2RF phase detector, together with first experimental results demonstrating so-far unrivaled performance.
	Poster TUPC33 [18.910 MB]

TUPC34	Precision Synchronization of Optical Lasers Based on MTCA.4 Electronics	451
	U. Mavrič, Ł. Butkowski, H.T. Duhme, M. Felber, M. Fenner, C. Gerth, P. Peier, H. Schlarb, B. Steffen DESY, Hamburg, Germany T. Kozak, P. Predki TUL-DMCS, Łódź, Poland
	Optical laser have become an integral part of free-electron laser facilities for the purposes of electron bunch generation, external seeding, diagnostics and pump-probe experiments. The ultra-short electron bunches demand a high timing stability and precision synchronization of the optical lasers. In this paper, we present the proof-of-principle for a laser locking application implemented on a MTCA.4 platform. The system design relies on existing MTCA.4 compliant off-the-shelf modules that are available on the market or have been developed for other applications within the particle accelerator community. Besides performance and cost, we also tried to minimize the number of out-of-crate components. Preliminary measurements of laser locking at the FLASH and REGAE particle accelerators are presented, and an outlook for further system development in the area of laser-to-RF synchronization is given.

TUPC35	Upgrade of the Read-out Electronics for the Energy Beam Position Monitors at FLASH and European XFEL	454
	U. Mavrič, C. Gerth, H. Schlarb DESY, Hamburg, Germany A. Piotrowski TUL-DMCS, Łódź, Poland
	The dispersive sections of magnetic bunch compressor chicanes at free-electron lasers are excellent candidates for beam energy measurements. In the rectangular beamline sections of the bunch compressors at FLASH, energy beam position monitors (EBPM) with transversely mounted stripline pickups are installed. In this paper, we present the upgrade of the read-out electronics for signal detection of the EBPM installed at FLASH. The system is based on the MTCA.4 standard and reuses already available MTCA.4 compliant modules. This is also true for gateware and software development which fits into standard MTCA.4 framework development. The performance of the instrument was studied at FLASH during user operation and the results are presented.

WEPC31	New Design of the 40 GHz Bunch Arrival Time Monitor Using MTCA.4 Electronics at FLASH and for the European XFEL	749
	M.K. Czwalinna, C. Gerth, H. Schlarb DESY, Hamburg, Germany S. Bou Habib Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland S. Korolczuk, J. Szewiński NCBJ, Świerk/Otwock, Poland A. Kuhl Uni HH, Hamburg, Germany
	At free-electron lasers, today's pump-probe experiments and seeding schemes make high demands on the electron bunch timing stability with an arrival time jitter reduction down to the femtosecond level. At FLASH and the upcoming European XFEL, the bunch train structures with their high bunch repetition rates allow for an accurate intra-train stabilisation. To realise longitudinal beam-based feedbacks a reliable and precise arrival time detection over a broad range of bunch charges, which can even change from 1 nC down to 20 pC within a bunch train, is essential. Benefitting from the experience at FLASH, the current bunch arrival time monitors (BAMs), based on detection of RF signals from broad-band pick-ups by use of electro-optic modulators, are further developed to cope with the increased requirements. In this paper, we present the new BAM prototype, including an adapted electro-optical front-end and the latest development of the read-out electronics based on the MTCA.4 platform.

WEPC32	Past, Present and Future Aspects of Laser-Based Synchronization at FLASH	753
	S. Schulz, M. Bousonville, M.K. Czwalinna, M. Felber, M. Heuer, T. Lamb, J. Müller, P. Peier, S. Ruzin, H. Schlarb, B. Steffen, C. Sydlo, F. Zummack DESY, Hamburg, Germany T. Kozak, P. Predki TUL-DMCS, Łódź, Poland A. Kuhl Uni HH, Hamburg, Germany
	Free-electron lasers, like FLASH and the upcoming European XFEL, are capable of producing XUV and X-ray pulses of a few femtoseconds duration. For time-resolved pump-probe experiments and the externally seeded operation mode it is crucial not only to stabilize the arrival time of the electron bunches, but also to achieve a synchronization accuracy of external lasers on the same timescale. This can only be realized with a laser-based synchronization infrastructure. At FLASH, a periodic femtosecond laser pulse train is transmitted over actively stabilized optical fibers to the critical subsystems. In this paper we report on the present status and performance of the system, as well as its imminent upgrades and new installations. These include the connection of FLASH2, electron bunch arrival time monitors for low charges, a new master laser pulse distribution scheme, all-optical synchronization of the pump-probe laser and arrival time measurements of the UV pulses on the e-gun photocathode. Along with the coming connection of the acceleration modules to the master laser and the switch of the low-level hardware to the uTCA platform, an outlook to improved feedback strategies is given.

WEPC40	Pickup Signal Improvement for High Bandwidth BAMs for FLASH and European - XFEL	778
	A. Angelovski, R. Jakoby, A. Penirschke TU Darmstadt, Darmstadt, Germany M.K. Czwalinna, H. Schlarb, C. Sydlo DESY, Hamburg, Germany T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	In order to measure the arrival time of the electron bunches in low (20 pC) and high (1 nC) charge operation mode, new high bandwidth pickups were developed as a part of the Bunch Arrival-time Monitors (BAMs) for FLASH at DESY . The pickup signal is transported via radiation resistant coaxial cables to the electro-optic modulator (EOM) . Due to the high losses of the 40 GHz RF front-end the signal in the RF path is attenuated well below the optimal operation voltage of the EOM. To improve the overall performance, the signal strength of the induced pickup signal needs to be increased and at the same time the losses in the RF front-end significantly reduced. In this paper, the analysis towards improving the induced pickup signal strength is presented. Simulations are performed with the CST STUDIO SUITE package and the results are compared with the state of the art high bandwidth pickups. A. Angelovski et al., Phys. Rev. ST Accel. Beams 15, 112803 (2012) ** A. Penirschke et al., Proc. of IBIC2012, Tsukuba, Japan (2012)

WEPC41	Comparative Analysis of Different Electro-Optical Intensity Modulator Candidates for the New 40 GHz Bunch Arrival Time Monitor System for FLASH and European XFEL	782
	A. Kuhl, J. Rönsch-Schulenburg, J. Roßbach Uni HH, Hamburg, Germany M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo DESY, Hamburg, Germany S. Schnepp ETH Zurich, Institute of Electromagnetic Fields (IFH), Zurich, Switzerland T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: The work is supported by Federal Ministry of Education and Research of Germany (BMBF) within FSP 301 under the contract numbers 05K10GU2 and 05K10RDA. The currently installed Bunch Arrival time Monitors (BAMs) at the Free electron LASer in Hamburg (FLASH) achieved a time resolution of less than 10 fs for bunch charges higher than 500 pC. In order to achieve single spike FEL pulses at FLASH, electron bunch charges down to 20 pC are of interest. With these BAMs the required time resolution is not reachable for bunch charges below 500 pC. Therefore new pickups with a bandwidth of up to 40 GHz are designed and manufactured. The signal evaluation takes place with a time-stabilized reference laser pulse train which is modulated with an Electro-Optical intensity Modulator (EOM). The new BAM system also requires new EOMs for the electro-optical frontend. The available selection of commercial EOM candidates for the new frontend is very limited. In this paper we present a comparison between different EOM candidates for the new electro optical frontend. A. Angelovski et al. Proceedings Phys. Rev ST AB, DOI:10.1103/PhysRevSTAB.15.112803
	Poster WEPC41 [0.619 MB]