IBIC2013 - List of Keywords (DESY)

Paper	Title	Other Keywords	Page
MOPC32	Development Status of Optical Synchronization for the European XFEL	XFEL, laser, coupling, shielding	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.

TUPC31	New Design of High Order Modes Electronics in MTCA.4 Standard for FLASH and the European XFEL	XFEL, beam-position, monitoring, alignment	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]

TUPC34	Precision Synchronization of Optical Lasers Based on MTCA.4 Electronics	laser, feedback, monitoring, XFEL	451
	U. Mavrič, L. 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	pick-up, XFEL, beam-position, SNR	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.

TUPF32	A Cryogenic Current Comparator for FAIR with Improved Resolution	pick-up, cryogenics, shielding, longitudinal	590
	R. Geithner, W. Vodel HIJ, Jena, Germany R. Geithner, R. Neubert, P. Seidel FSU Jena, Jena, Germany F. Kurian, H. Reeg, M. Schwickert GSI, Darmstadt, Germany
	A Cryogenic Current Comparator is a highly sensitive tool for the non-destructive online monitoring of continuous as well as bunched beams of very low intensities. The noise-limited current resolution of such a device depends on the ferromagnetic material embedded in the pickup coil of the CCC. Therefore, the main focus of research was on the low temperature properties of ferromagnetic core materials. In this contribution we present first results of the completed Cryogenic Current Comparator for FAIR working in a laboratory environment, regarding the improvements in resolution due to the use of suitable ferromagnetic core materials.
	Poster TUPF32 [3.868 MB]

WEPC21	Design and Beam Test Results of Button BPMs for the European XFEL	pick-up, BPM, XFEL, controls	723
	D.M. Treyer, R. Baldinger, R. Ditter, B. Keil, W. Koprek, G. Marinkovic, M. Roggli PSI, Villigen PSI, Switzerland D. Lipka, D. Nölle, S. Vilcins DESY, Hamburg, Germany
	Funding: Swiss State Secretariat for Education, Research and Innovation The European X-ray Free Electron Laser (E-XFEL) will use a total ~300 button BPMs along the whole accelerator, as well as 160 cavity BPMs. The pickups for the button BPMs have been designed by DESY, whereas the electronics has been developed by PSI. This paper gives an overview of the button BPM system, with focus on the RF front end electronics, signal processing, and overall system performance. Measurement results achieved with prototypes installed at FLASH/DESY and at the SwissFEL Injector Test Facility (SITF) are presented. The position noise obtained with button pickups in a 40.5 mm aperture beam pipe is as low as ~11 um at 20 pC bunch charge.
	Poster WEPC21 [1.595 MB]

WEPC31	New Design of the 40 GHz Bunch Arrival Time Monitor Using MTCA.4 Electronics at FLASH and for the European XFEL	laser, XFEL, pick-up, diagnostics	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	laser, electron, controls, FEL	753
	S. Schulz, M. Bousonville, M.K. Czwalinna, M. Felber, M. Heuer, T. Lamb, J.M. 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	pick-up, simulation, laser, resonance	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)

WEPF03	Scintillating Screen Monitors for Transverse Electron Beam Profile Diagnostics at the European XFEL	electron, XFEL, OTR, transverse	807
	Ch. Wiebers, M. Holz, G. Kube, D. Nölle, G. Priebe, H.-Ch. Schröder DESY, Hamburg, Germany
	Transverse beam profile diagnostics in modern electron linear accelerators like FELs or injector LINACs are mainly based on optical transition radiation (OTR) as standard technique which is observed in backward direction when a charged particle beam crosses the boundary between two media with different dielectric properties. The experience from modern LINAC based 4th generation light sources shows that OTR diagnostics might fail because of coherence effects in the OTR emission process. As a consequence, for the European XFEL which is currently under construction in Hamburg, transverse beam profile measurements are based on scintillating screen monitors. The LYSO:Ce screens are oriented such that coherent OTR generated at the screen boundaries will be geometrically suppressed. An additional advantage is that the imaging optics operate in Scheimpflug condition thus adjusting the plane of sharp focus with respect to the CCD chip and significantly increasing the apparent depth of field. This report gives an overview of the measuring principle and the monitor setup together with results of laboratory test measurements and a first prototype test at FLASH (DESY, Hamburg).

WEPF04	A New Compact Design of a Three-Dimensional Ionization Profile Monitor (IPM)	IPM, laser, simulation, beam-position	811
	H.F. Breede, H.-J. Grabosch, M. Sachwitz, L.V. Vu DESY Zeuthen, Zeuthen, Germany
	FLASH at DESY in Hamburg is a linear accelerator, which uses superconducting technology to produce soft x-ray laser light ranging from 4.1 to 45 nm. To ensure the operation stability of FLASH, monitoring of the beam is mandatory. Two Ionization Profile Monitors (IPM) detect the lateral x and y position changes. The functional principle of the IPM is based on the detection of particles, generated by interaction of the beam with the residual gas in the beam line. The newly designed IPM enables the combined determination of the horizontal and vertical position as well as the profile. This is made possible by a compact monitor, consisting of a cage in a vacuum chamber, two micro-channel plates (MCP) and two repeller plates with toggled electric fields at the opposite sides of the MCPs. The particles created by the FEL beam, drift in a homogenous electrical field towards the respective MCP, which produces an image of the beam profile on an attached phosphor screen. A camera for each MCP is used for evaluation. This indirect detection scheme operates over a wide dynamic range and allows the detection of the center of gravity and the shape of the beam. The final design is presented.
	Poster WEPF04 [3.643 MB]

WEPF06	A Fast Switching Mirror Unit at FLASH	vacuum, laser, site, free-electron-laser	818
	F. Perlick, J.D. Good, N. Leuschner, A.S. Ontoso, M. Sachwitz, L.V. Vu DESY Zeuthen, Zeuthen, Germany H. Schulte-Schrepping DESY, Hamburg, Germany
	The Free Electron Laser (FLASH) at DESY Hamburg is a linac providing unique experimental opportunities to investigate the atomic structure and the properties of materials, nanoparticles, viruses and cells. At the experimental hall, the incoming FEL beam can be deflected towards five test sites by silicon mirrors mounted into vacuum vessels, of which one is operated in permanent switching mode, allowing the simultaneous use of the light at two different test sites. So far, the entire vacuum vessel with the mirror inside is moved into the beam by a linear motor. This results in high translatory inertia and, to compensate the vessel motion, requires vacuum bellows, which have a limited lifetime especially at higher switching frequencies. Therefore, in the recent design the mirror is shifted by piezo motors operated inside the vessel under ultra-high vacuum conditions. However, temperature measurements revealed that during continuous operation the motor reaches up to 90°C only when exposed to air, necessitating long breaks to allow it to cool. Therefore suitable cooling methods are being investigated to guarantee continuous operation of the motor under ultra-high vacuum conditions.
	Poster WEPF06 [2.431 MB]

WEPF24	Charge Monitors at the Relativistic Electron Gun for Atomic Exploration – REGAE	electron, laser, diagnostics, gun	868
	H. Delsim-Hashemi, K. Flöttmann, M. Seebach DESY, Hamburg, Germany S. Bayesteh Uni HH, Hamburg, Germany
	A new linac is commissioned at DESY mainly as the electron source for femtosecond electron diffraction facility REGAE (Relativistic Electron Gun for Atomic Exploration). REGAE comprises a photo-cathode gun followed by normal conducting 1.5 cell rf-cavity to provide sub pC charge electron-bunches of 2-5 MeV with a coherence length of 30nm. In order to produce and maintain such electron bunches, sophisticated single-shot diagnostics are desired e.g. emittance, energy, energy-spread and bunch-length measurement. There are three methods at REGAE for charge measurement. The most routine method is based on Faraday-cups that are distributed along machine and can provide charge reading down to ~50 fC. The second method, which is non-destructive, is a cavity based antenna that measures beam induced fields. A third method is based on beam-profile measurement diagnostics. By proper calibration of integral intensity that arrives at detector one can measure charges down to fC level. The last method has the potential to reach the limit of few electrons charge when state-of-the-art intensifiers are used in profile monitors.

WEPF25	Resonator for Charge Measurement at REGAE	controls, XFEL, PITZ, LEFT	872
	D. Lipka, J. Lund-Nielsen, M. Seebach DESY, Hamburg, Germany
	A resonator has been developed for the diagnostics of dark current and charge measurements at the European XFEL, FLASH and PITZ. The first induced monopole mode TM01 at 1.3 GHz from charged bunches is used to detect the dark current and charge with high resolution at these accelerators. At REGAE this resonator with electronics is installed to detect the bunch charge because charges below pC are used and this device can resolve it non-destructively. The same electronics as for the dark current and charge measurement is used and the resolution is measured to be 2.3 fC for 200 fC.
	Poster WEPF25 [0.822 MB]

Paper

Title

Other Keywords

Page

MOPC32

Development Status of Optical Synchronization for the European XFEL

XFEL, laser, coupling, shielding

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.

TUPC31

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

XFEL, beam-position, monitoring, alignment

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]

TUPC34

Precision Synchronization of Optical Lasers Based on MTCA.4 Electronics

laser, feedback, monitoring, XFEL

451

U. Mavrič, L. 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

pick-up, XFEL, beam-position, SNR

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.

TUPF32

A Cryogenic Current Comparator for FAIR with Improved Resolution

pick-up, cryogenics, shielding, longitudinal

590

R. Geithner, W. Vodel
HIJ, Jena, Germany
R. Geithner, R. Neubert, P. Seidel
FSU Jena, Jena, Germany
F. Kurian, H. Reeg, M. Schwickert
GSI, Darmstadt, Germany

A Cryogenic Current Comparator is a highly sensitive tool for the non-destructive online monitoring of continuous as well as bunched beams of very low intensities. The noise-limited current resolution of such a device depends on the ferromagnetic material embedded in the pickup coil of the CCC. Therefore, the main focus of research was on the low temperature properties of ferromagnetic core materials. In this contribution we present first results of the completed Cryogenic Current Comparator for FAIR working in a laboratory environment, regarding the improvements in resolution due to the use of suitable ferromagnetic core materials.

Poster TUPF32 [3.868 MB]

WEPC21

Design and Beam Test Results of Button BPMs for the European XFEL

pick-up, BPM, XFEL, controls

723

D.M. Treyer, R. Baldinger, R. Ditter, B. Keil, W. Koprek, G. Marinkovic, M. Roggli
PSI, Villigen PSI, Switzerland
D. Lipka, D. Nölle, S. Vilcins
DESY, Hamburg, Germany

Funding: Swiss State Secretariat for Education, Research and Innovation
The European X-ray Free Electron Laser (E-XFEL) will use a total ~300 button BPMs along the whole accelerator, as well as 160 cavity BPMs. The pickups for the button BPMs have been designed by DESY, whereas the electronics has been developed by PSI. This paper gives an overview of the button BPM system, with focus on the RF front end electronics, signal processing, and overall system performance. Measurement results achieved with prototypes installed at FLASH/DESY and at the SwissFEL Injector Test Facility (SITF) are presented. The position noise obtained with button pickups in a 40.5 mm aperture beam pipe is as low as ~11 um at 20 pC bunch charge.

Poster WEPC21 [1.595 MB]

WEPC31

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

laser, XFEL, pick-up, diagnostics

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

laser, electron, controls, FEL

753

S. Schulz, M. Bousonville, M.K. Czwalinna, M. Felber, M. Heuer, T. Lamb, J.M. 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

pick-up, simulation, laser, resonance

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)

WEPF03

Scintillating Screen Monitors for Transverse Electron Beam Profile Diagnostics at the European XFEL

electron, XFEL, OTR, transverse

807

Ch. Wiebers, M. Holz, G. Kube, D. Nölle, G. Priebe, H.-Ch. Schröder
DESY, Hamburg, Germany

Transverse beam profile diagnostics in modern electron linear accelerators like FELs or injector LINACs are mainly based on optical transition radiation (OTR) as standard technique which is observed in backward direction when a charged particle beam crosses the boundary between two media with different dielectric properties. The experience from modern LINAC based 4th generation light sources shows that OTR diagnostics might fail because of coherence effects in the OTR emission process. As a consequence, for the European XFEL which is currently under construction in Hamburg, transverse beam profile measurements are based on scintillating screen monitors. The LYSO:Ce screens are oriented such that coherent OTR generated at the screen boundaries will be geometrically suppressed. An additional advantage is that the imaging optics operate in Scheimpflug condition thus adjusting the plane of sharp focus with respect to the CCD chip and significantly increasing the apparent depth of field. This report gives an overview of the measuring principle and the monitor setup together with results of laboratory test measurements and a first prototype test at FLASH (DESY, Hamburg).

WEPF04

A New Compact Design of a Three-Dimensional Ionization Profile Monitor (IPM)

IPM, laser, simulation, beam-position

811

H.F. Breede, H.-J. Grabosch, M. Sachwitz, L.V. Vu
DESY Zeuthen, Zeuthen, Germany

FLASH at DESY in Hamburg is a linear accelerator, which uses superconducting technology to produce soft x-ray laser light ranging from 4.1 to 45 nm. To ensure the operation stability of FLASH, monitoring of the beam is mandatory. Two Ionization Profile Monitors (IPM) detect the lateral x and y position changes. The functional principle of the IPM is based on the detection of particles, generated by interaction of the beam with the residual gas in the beam line. The newly designed IPM enables the combined determination of the horizontal and vertical position as well as the profile. This is made possible by a compact monitor, consisting of a cage in a vacuum chamber, two micro-channel plates (MCP) and two repeller plates with toggled electric fields at the opposite sides of the MCPs. The particles created by the FEL beam, drift in a homogenous electrical field towards the respective MCP, which produces an image of the beam profile on an attached phosphor screen. A camera for each MCP is used for evaluation. This indirect detection scheme operates over a wide dynamic range and allows the detection of the center of gravity and the shape of the beam. The final design is presented.

Poster WEPF04 [3.643 MB]

WEPF06

A Fast Switching Mirror Unit at FLASH

vacuum, laser, site, free-electron-laser

818

F. Perlick, J.D. Good, N. Leuschner, A.S. Ontoso, M. Sachwitz, L.V. Vu
DESY Zeuthen, Zeuthen, Germany
H. Schulte-Schrepping
DESY, Hamburg, Germany

The Free Electron Laser (FLASH) at DESY Hamburg is a linac providing unique experimental opportunities to investigate the atomic structure and the properties of materials, nanoparticles, viruses and cells. At the experimental hall, the incoming FEL beam can be deflected towards five test sites by silicon mirrors mounted into vacuum vessels, of which one is operated in permanent switching mode, allowing the simultaneous use of the light at two different test sites. So far, the entire vacuum vessel with the mirror inside is moved into the beam by a linear motor. This results in high translatory inertia and, to compensate the vessel motion, requires vacuum bellows, which have a limited lifetime especially at higher switching frequencies. Therefore, in the recent design the mirror is shifted by piezo motors operated inside the vessel under ultra-high vacuum conditions. However, temperature measurements revealed that during continuous operation the motor reaches up to 90°C only when exposed to air, necessitating long breaks to allow it to cool. Therefore suitable cooling methods are being investigated to guarantee continuous operation of the motor under ultra-high vacuum conditions.

Poster WEPF06 [2.431 MB]

WEPF24

Charge Monitors at the Relativistic Electron Gun for Atomic Exploration – REGAE

electron, laser, diagnostics, gun

868

H. Delsim-Hashemi, K. Flöttmann, M. Seebach
DESY, Hamburg, Germany
S. Bayesteh
Uni HH, Hamburg, Germany

A new linac is commissioned at DESY mainly as the electron source for femtosecond electron diffraction facility REGAE (Relativistic Electron Gun for Atomic Exploration). REGAE comprises a photo-cathode gun followed by normal conducting 1.5 cell rf-cavity to provide sub pC charge electron-bunches of 2-5 MeV with a coherence length of 30nm. In order to produce and maintain such electron bunches, sophisticated single-shot diagnostics are desired e.g. emittance, energy, energy-spread and bunch-length measurement. There are three methods at REGAE for charge measurement. The most routine method is based on Faraday-cups that are distributed along machine and can provide charge reading down to ~50 fC. The second method, which is non-destructive, is a cavity based antenna that measures beam induced fields. A third method is based on beam-profile measurement diagnostics. By proper calibration of integral intensity that arrives at detector one can measure charges down to fC level. The last method has the potential to reach the limit of few electrons charge when state-of-the-art intensifiers are used in profile monitors.

WEPF25

Resonator for Charge Measurement at REGAE

controls, XFEL, PITZ, LEFT

872

D. Lipka, J. Lund-Nielsen, M. Seebach
DESY, Hamburg, Germany

A resonator has been developed for the diagnostics of dark current and charge measurements at the European XFEL, FLASH and PITZ. The first induced monopole mode TM01 at 1.3 GHz from charged bunches is used to detect the dark current and charge with high resolution at these accelerators. At REGAE this resonator with electronics is installed to detect the bunch charge because charges below pC are used and this device can resolve it non-destructively. The same electronics as for the dark current and charge measurement is used and the resolution is measured to be 2.3 fC for 200 fC.

Poster WEPF25 [0.822 MB]