IBIC2012 - List of Keywords (FEL)

Paper	Title	Other Keywords	Page
MOCB02	A Generic BPM Electronics Platform for European XFEL, SwissFEL and SLS	electronics, FPGA, cavity, interface	11
	B. Keil, R. Baldinger, R. Ditter, W. Koprek, R. Kramert, G. Marinkovic, M. Roggli, M. Stadler, D.M. Treyer PSI, Villigen PSI, Switzerland
	Funding: Work supported by Swiss State Secretariat for Education and Research SER PSI is currently developing the 2nd generation of a generic modular electronics platform for linac and storage ring BPMs and other beam diagnostics systems. The first platform, developed in 2004 and based on a generic digital back-end with Xilinx Virtex 2Pro FPGAs, is currently used at PSI for proton accelerator BPMs, resonant stripline BPMs at the SwissFEL test injector facility, and a number of other diagnostics and detector systems. The 2nd platform will be employed e.g. for European XFEL BPMs, a new SLS BPM system, and the SwissFEL BPM system. This paper gives an overview of the architecture, features and applications of the new platform, including interfaces to control, timing and feedback systems. Differences and synergies of the different BPM and non-BPM applications will be discussed.
	Slides MOCB02 [2.440 MB]

MOCC03	The First Electron Bunch Measurement by means of DAST Organic EO Crystals	electron, laser, real-time, operation	29
	Y. Okayasu, S. Matsubara, T. Togashi JASRI/SPring-8, Hyogo-ken, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan T. Matsukawa RIKEN ASI, Sendai, Miyagi, Japan H. Minamide RIKEN Advanced Science Insititute, Sendai, Miyagi, Japan K. Ogawa, T. Sato, H. Tomizawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan E. Takahashi RIKEN, Saitama, Japan
	Pilot user experiments via the seeded FEL have been demonstrated at the Prototype Test Accelerator (VUV-FEL), SPring-8 from July, 2012. A precise measurement of the electron bunch charge distribution (BCD) is crucial key to keep spatial and temporal overlaps between high-order harmonic (HH) laser pulses and electron bunches. R&D of the 3D-BCD monitor with a single-shot detection has been extensively promoted at SPring-8. The monitor adopts a spectral decoding based Electro-Optic (EO) sampling technique that is non-destructive and enables real-time reconstruction of the 3D-BCD with a temporal resolution of 30- to 40-fs (FWHM). So far, such EO sampling based BCD monitors have been developed by utilizing inorganic EO crystals such as ZnTe and their temporal resolutions are limited to ~130 fs (FWHM). As a part of this project, the first BCD measurement with an organic EO crystal DAST has been successfully demonstrated at the facility. Signal intensities, temporal resolutions and radiation related issues via both ZnTe and DAST are discussed.
	Slides MOCC03 [3.912 MB]

MOPA17	Modular Logarithmic Amplifier Beam Position Monitor Readout System at the University of Hawai'i	electron, GUI, detector, laser	90
	B.T. Jacobson, M.R. Hadmack, J. Madey, P. Niknejadi University of Hawaii, Honolulu, HI, USA
	High brightness electron beams for inverse Compton backscatter photon sources driven by thermionic microwave guns require real-time position measurements in order to achieve the spatial and temporal coincidence necessary to ensure statistically measurable signals. True logarithmic amplifiers are more adequately suited to signal comparison than are σ-delta methods. A low-cost, modular and scalable readout and data acquisition system for strip-line beam position monitors utilizing the AD640 log-amp is being developed at University of Hawai'i MkV Linear Accelerator and Free Electron Laser Lab. Initial measurements and prototyping of the hardware is complete with commissioning and deployment of the system currently ongoing. We present the methodology and early results of this project.

MOPA20	Development of 3D EO-Sampling System for the Ultimate Temporal Resolution	laser, electron, timing, feedback	98
	K. Ogawa, H. Tomizawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan S. Matsubara, Y. Okayasu JASRI/SPring-8, Hyogo, Japan
	We have been developing three dimensional bunch charge distribution (3D-BCD) monitor for FEL seeded with high-order harmonic (HH) pulse. 3D-BCD is based on EO-sampling technique with multiple EO crystal detectors in the manner of spectral decoding. Using this 3D-EO sampling technique, the positioning and timing of electron bunch is obtained in real-time with non-destructive measurement. For obtaining the high temporal resolution, an octave broadband probe laser with linear chirp rate of 1 fs/nm is required. We are developing an EO-probe laser pulse with ~10 μJ pulse energy and the bandwidth over 300 nm (FWHM). For meet these bandwidth and pulse energy, this EO-probe pulse is using a supercontinuum generated by photonic crystal fiber (PCF) and amplified with optical parametric amplification (OPA). Especially, for amplification with maintaining octave bandwidth, non-collinear OPA (NOPA) using BBO crystal and a pump source with a wavelength of 450 nm are adopted. The EO-probe pulse energy of 10 μJ provides for high S/N ratio to each detector and the bandwidth of 300 nm with 300 fs pulse duration allows the measurement for the 30 fs electron bunch duration (FWHM).

MOPA30	Application of EMMA BPMs to the ALICE Energy Recovery Linac	pick-up, sextupole, EPICS, linac	117
	A. Kalinin, D. Angal-Kalinin, F. Jackson, J.K. Jones, P.H. Williams STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The ALICE Energy Recovery Linac arc button pickups have been recently equipped with EMMA BPM electronics. These bunch-by-bunch EPICS VME BPMs give information about charge and position, and its jitter, allowing estimates of the beam energy jitter in ALICE in different modes of operation. A Mathematica program is designed to monitor statistically individual bunches (spacing 61.54ns) as well the train as a whole (up to 1625 bunches), allowing the study of jitter and position stability of the beam through the arc. The ALICE arc has been designed to be isochronous, with the bunch compression achieved through a separate dedicated bunch compressor chicane. The arc incorporates two sextupoles for correcting non-linear longitudinal matrix terms and experimental evidence suggests that the off-centred beam in the sextupoles breaks the linear isochronicity. We present some beam measurement results collected in 2012 using these BPMs. A. Kalinin et al, MOPPR061, IPAC12

MOPA42	Measurements of Martin-Puplett Interferometer Limitations using Blackbody Source	detector, radiation, vacuum, experiment	153
	P.E. Evtushenko, J.M. Klopf JLAB, Newport News, Virginia, USA
	Frequency domain measurements with Martin-Puplett interferometer is one of a few techniques capable of bunch length measurements at the level of ~ 100 fs. As the bunch length becomes shorter, it is important to know and be able to measure the limitations of the instrument in terms of shortest measurable bunch length. In this paper we describe experiment of using blackbody source with the modified Matrin-Puplett interferometer that is routinely used for bunch length measurements at the JLab FEL, as a way to estimate the shortest, measurable with the device, bunch. The limitation comes from high frequency cut-off of the presently used wire-grid polarizer and is estimated to be 50 fs RMS. The measurements are made with the same Golay cell detector that is used for beam measurements. We demonstrate that, even though the blackbody source is many orders of magnitude less bright than the coherent transition or synchrotron radiation, it can be used for the measurements and gives a very good signal to noise ratio in a combination with lock-in detection. We also compare the measurements made in air and in vacuum to show the very strong effect of the atmospheric absorption.

MOPA45	Study of Beam Length Measurement based on TM010 Mode	simulation, cavity, coupling, impedance	162
	R.X. Yuan, Y.B. Leng, L.Y. Yu, W.M. Zhou SINAP, Shanghai, People's Republic of China
	Beam length measurement in frequency domain is a familiar method, and the resolution is seriously limited by the system signal-noise-ratio (SNR) and the beam length measured. Usually this method can only obtain the resolution about ~10ps with beam length ~30ps when using signal from button or stripline BPM. But in FEL case, the beam length is the ps or sub-ps order. The paper discusses the probability of beam length measurement based on the TM010 mode in FEL case. When adopting High Order Mode(HOM) reject and system gain control, the system SNR can arrive at 110dB and the resolution can achieve 30fs with beam length ps or sub-ps.

MOPA49	EO-sampling-based Temporal Overlap Control System for an HH Seeded FEL	laser, electron, operation, timing	176
	S. Matsubara RIKEN/SPring-8, Hyogo, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan K. Ogawa, T. Sato, H. Tomizawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan Y. Okayasu, T. Togashi, T. Watanabe JASRI/SPring-8, Hyogo-ken, Japan E. Takahashi RIKEN, Saitama, Japan
	FELs have greatly interested for the short-wavelength region. However, their temporal profile and frequency spectra have shot-to-shot fluctuation by a SASE process. One of the promising approached for the problems is a seeded FEL scheme by using a full-coherent light source. The seeded FEL has been demonstrated in the EUV region by employ the high-order harmonics (HH) generation from an external laser source at the SCSS test-accelerator in the SPring-8. It is important for the HH-seeded FEL scheme to synchronize and overlap between the seeding laser pulse and the electron bunch. Their timing difference and laser spatial pointing is drifting. Therefore, a timing feedback and non-destructive monitor are necessary to operate seeded FEL continuously. We have constructed the timing monitor based on Electro-Optic (EO) sampling which is measure the timing difference the seeded laser pulse and the electron bunch simultaneously with the seeded FEL process. The probe laser pulse for the EO-sampling system is optically split from the common external HH laser driver for the seeded FEL. The EO-sampling system is able to use timing feedback for continual operation of the HH-seededFEL.

MOPB80	High Dynamic Range Beam Imaging with Two Simultaneously Sampling CCDs	linac, operation, emittance, brightness	263
	P.E. Evtushenko, D. Douglas JLAB, Newport News, Virginia, USA
	Transverse beam profile measurement with sufficiently high dynamic range (HDR) is a key diagnostic to measure the beam halo, understand its sources and evolution. In this contribution we describe our initial experience with the HDR imaging of the electron beam at the JLab FEL. On contrary to HDR measurements made with wire scanners in counting mode, which provide only two or three 1D projections of transverse beam distribution, imaging allows to measure the distribution itself. That is especially important for non-equilibrium beams in the LINACs. The measurements were made by means of simultaneous imaging with two CCD sensors with different exposure time. Two images are combined then numerically in to one HDR image. The system works as an online tool providing HDR images at 4 Hz. An optically polished YAG:Ce crystal with the thickness of 100 um was used for the measurements. When tested with a laser beam images with the DR of about 10⁺⁵ were obtained. With the electron beam the DR was somewhat smaller due to the limitations in the time structure of the tune-up beam macro pulse.

MOPB87	Development and First Tests of a High Sensitivity Charge Monitor for SwissFEL	electronics, electron, operation, instrumentation	287
	S. Artinian, J.F. Bergoz, F. Stulle BERGOZ Instrumentation, Saint Genis Pouilly, France P. Pollet, V. Schlott PSI, Villigen PSI, Switzerland
	The compact X-ray free electron laser SwissFEL, which is presently under development at the Paul Scherrer Institut (PSI) in Villigen, Switzerland, will operate at comparably low charges, allowing the compression of the electron bunches to a few femto-seconds (nominal 200 pC mode) and even towards the atto-second range (short bunch 10 pC mode). A high precision charge measurement turns out to be a challenge, especially in the presence of dark currents, which may occur from high gradient RF gun and accelerating structure operation. In response to this challenge, a higher sensitivity charge transformer and new beam charge monitor electronics were developed in collaboration between Bergoz Instrumentation and PSI. The Turbo-ICT captures sub-pC bunch charge thanks to a new magnetic alloy exhibiting very low core loss. Transmission over a carrier using narrow-band cable television technique preserves the signal integrity from the Turbo-ICT to the BCM-RF. Electro-magnetic and RF interferences are strongly attenuated; the dark current signal is suppressed. First beam test results, which have been performed at the SwissFEL Test Injector Facility (STIF), are presented in this contribution.

TUPA22	Design of RF Front End for Cavity Beam Position Monitor based on ICs	cavity, simulation, embedded, FPGA	383
	B.P. Wang, Z.C. Chen, Y.B. Leng, L.Y. Yu, R.X. Yuan, W.M. Zhou SINAP, Shanghai, People's Republic of China
	RF front end has the significant impact on the performance of cavity beam position monitor (CBPM) which is indispensable beam instrumentation component in free electron laser(FEL) or linear collider facility. With many new advances in data converter and radio technology, complex RF front end design has been greatly simplified. Now based on digital intermediate frequency (IF) receiver architecture, a new RF front end for (CBPM) has been designed and fabricated using surface mount component on print circuit board (PCB). The front end contains analog-digital converter used to digitize the IF signals. The whole system would be integrated to a digital board developed by our lab to produce the dedicated signal processor for CBPM. There is an Xilinx Vertex-5 FPGA device on the digital board and relevant signal processing algorithm has been implemented on it using VHDL. The details about design and test results would be introduced blow.

TUPA41	Ultra-short Electron Bunch and X-ray Temporal Diagnostics with an X-band Transverse Deflecting Cavity	electron, photon, undulator, klystron	441
	P. Krejcik, Y. Ding, J.C. Frisch, Z. Huang, H. Loos, J.W. Wang, M.-H. Wang SLAC, Menlo Park, California, USA C. Behrens DESY, Hamburg, Germany P. Emma LBNL, Berkeley, California, USA
	Funding: This work was supported by Department of Energy Contract No. DE-AC0276SF00515 The technique of streaking an electron bunch with a RF deflecting cavity to measure its bunch length is being applied in a new way at the Linac Coherent Light Source with the goal of measuring the femtosecond temporal profile of the FEL photon beam. A powerful X-band deflecting cavity is being installed downstream of the FEL undulator and the streaked electron beam will be observed at an energy spectrometer screen at the beam dump. The single-shot measurements will reveal which time slices of the streaked beam have contributed to the FEL process by virtue of their greater energy loss and energy spread relative to the non-lasing portions of the electron bunch. Since the diagnostic is located downstream of the undulator it can be operated continuously without interrupting the beam to the users. The resolution of the new X-band system will be compared to the existing S-band RF deflecting diagnostic systems at SLAC and consideration is given to the required RF phase stability tolerances required for acceptable beam jitter on the monitor. Simulation studies show that about 1 fs (rms) time resolution is achievable in the LCLS over a wide range of FEL wavelengths and pulse lengths.

TUPA43	First Operation of the Electro-optical Sampling Diagnostics of the FERMI@Elettra FEL	laser, electron, alignment, vacuum	449
	M. Veronese, A. Abrami, E. Allaria, M. Bossi, M.B. Danailov, M. Ferianis, L. Fröhlich, S. Grulja, M. Predonzani, F. Rossi, G. Scalamera, C. Spezzani, M. Trovò, M. Tudor Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	The FERMI@Elettra seeded FEL has demanding specifications in terms of longitudinal properties of the electron beam. Several diagnostics are installed along the linac. At the entrance of the FEL1 undulator chain an electro optical sampling (EOS) station based on the spatial encoding scheme is installed. The EOS provides both time jitter and longitudinal profile measurements in a non-destructive way. The layout of this system is described and the first operational measurement results obtained are reported. The paper includes also the capability of this diagnostics to perform the temporal coarse alignment of the seed laser to the electron beam. Finally a discussion on the future developments foreseen for this system is given.

TUPB76	Intra Undulator Screen Diagnostics for the FERMI@Elettra FEL	electron, laser, undulator, radiation	519
	M. Veronese, A. Abrami, E. Allaria, M. Bossi, A. Bucconi, M. De Marco, M. Ferianis, L. Fröhlich, L. Giannessi, S. Grulja, R. Sauro, C. Spezzani, M. Tudor Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy T. Borden FRIB, East Lansing, Michigan, USA F. Cianciosi ESRF, Grenoble, France
	The FERMI@Elettra seeded FEL poses demanding requirements in terms of intra undulator diagnostics due to the short wavelength of its FEL radiation and to the coexistence of the electron and photon FEL beams. An advanced multi-beam screen system has equipped both FEL1 and FEL2. The system has been designed for transverse size and profile measurement on both the electron beam and the FEL radiation. Challenging design constrains are present: COTR suppression, seed laser suppression, FEL wavelength range and minimization of the ionizing radiation delivered to the undulators. This paper describes the novel design and the obtained performance with the FERMI intra undulator screen system (IU-FEL).

TUPB81	Design of the Beam Profile Monitors for the SXFEL Facility	controls, detector, electron, linac	534
	L.Y. Yu, J. Chen, Y.B. Leng, K.R. Ye, W.M. Zhou SINAP, Shanghai, People's Republic of China
	The Shanghai X-ray Free Electron Laser Facility will begin construction at next year. The linac electron beam energy is 0.84 GeV. Over 50 beam profile monitors with OTR and YaG screen will be installed along the linac and undulators. The profile monitor system design is a challenging task, since the system has to measure transverse electron beam sizes from millimeter down to 40μm scale with a 20μm resolution and 50μm repeat positioning accuracy. This paper describes the design of the mechanical detector , the integrated step-servo motor controlling system, the beam imaging system, as well as the software system.

WECC04	Analysis of the Electro-optical Front End for the New 40 GHz Bunch Arrival Time Monitor System	laser, pick-up, electron, timing	571
	A. Kuhl, J. Rönsch-Schulenburg, J. Roßbach Uni HH, Hamburg, Germany A. Angelovski, R. Jakoby, A. Penirschke TU Darmstadt, Darmstadt, Germany M. Bousonville, M.K. Czwalinna, H. Schlarb, C. Sydlo DESY, Hamburg, Germany S. Schnepp IFH, Zurich, Switzerland T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	The Free electron LASer in Hamburg (FLASH) is currently equipped with four Bunch Arrival time Monitors (BAMs) which achieve a time resolution of less than 10 fs for bunch charges higher than 500 pC (1). In order to achieve single spike FEL pulses at FLASH, electron bunch charges down to 20 pC are of interest. With the current 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 (2) 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 pickup system also requires a new electro-optical frontend with a 40 GHz EOM. The theoretical limits of the time resolution depending on the RF signal at different bunch charges and on the jitter of the reference laser pulses where analyzed for the new EOM. (1) M. K. Bock et al. in Proceedings of DIPAC 2011, Hamburg, Germany,2011, p. 365 (2) A. Angelovski, A. Kuhl et al. in Proceedings of IPAC 2011, San Sebastian, Spain, 2011, p. 1177 and p. 1186
	Slides WECC04 [12.560 MB]

Paper

Title

Other Keywords

Page

MOCB02

A Generic BPM Electronics Platform for European XFEL, SwissFEL and SLS

electronics, FPGA, cavity, interface

11

B. Keil, R. Baldinger, R. Ditter, W. Koprek, R. Kramert, G. Marinkovic, M. Roggli, M. Stadler, D.M. Treyer
PSI, Villigen PSI, Switzerland

Funding: Work supported by Swiss State Secretariat for Education and Research SER
PSI is currently developing the 2nd generation of a generic modular electronics platform for linac and storage ring BPMs and other beam diagnostics systems. The first platform, developed in 2004 and based on a generic digital back-end with Xilinx Virtex 2Pro FPGAs, is currently used at PSI for proton accelerator BPMs, resonant stripline BPMs at the SwissFEL test injector facility, and a number of other diagnostics and detector systems. The 2nd platform will be employed e.g. for European XFEL BPMs, a new SLS BPM system, and the SwissFEL BPM system. This paper gives an overview of the architecture, features and applications of the new platform, including interfaces to control, timing and feedback systems. Differences and synergies of the different BPM and non-BPM applications will be discussed.

Slides MOCB02 [2.440 MB]

MOCC03

The First Electron Bunch Measurement by means of DAST Organic EO Crystals

electron, laser, real-time, operation

29

Y. Okayasu, S. Matsubara, T. Togashi
JASRI/SPring-8, Hyogo-ken, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
T. Matsukawa
RIKEN ASI, Sendai, Miyagi, Japan
H. Minamide
RIKEN Advanced Science Insititute, Sendai, Miyagi, Japan
K. Ogawa, T. Sato, H. Tomizawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
E. Takahashi
RIKEN, Saitama, Japan

Pilot user experiments via the seeded FEL have been demonstrated at the Prototype Test Accelerator (VUV-FEL), SPring-8 from July, 2012. A precise measurement of the electron bunch charge distribution (BCD) is crucial key to keep spatial and temporal overlaps between high-order harmonic (HH) laser pulses and electron bunches. R&D of the 3D-BCD monitor with a single-shot detection has been extensively promoted at SPring-8. The monitor adopts a spectral decoding based Electro-Optic (EO) sampling technique that is non-destructive and enables real-time reconstruction of the 3D-BCD with a temporal resolution of 30- to 40-fs (FWHM). So far, such EO sampling based BCD monitors have been developed by utilizing inorganic EO crystals such as ZnTe and their temporal resolutions are limited to ~130 fs (FWHM). As a part of this project, the first BCD measurement with an organic EO crystal DAST has been successfully demonstrated at the facility. Signal intensities, temporal resolutions and radiation related issues via both ZnTe and DAST are discussed.

Slides MOCC03 [3.912 MB]

MOPA17

Modular Logarithmic Amplifier Beam Position Monitor Readout System at the University of Hawai'i

electron, GUI, detector, laser

90

B.T. Jacobson, M.R. Hadmack, J. Madey, P. Niknejadi
University of Hawaii, Honolulu, HI, USA

High brightness electron beams for inverse Compton backscatter photon sources driven by thermionic microwave guns require real-time position measurements in order to achieve the spatial and temporal coincidence necessary to ensure statistically measurable signals. True logarithmic amplifiers are more adequately suited to signal comparison than are σ-delta methods. A low-cost, modular and scalable readout and data acquisition system for strip-line beam position monitors utilizing the AD640 log-amp is being developed at University of Hawai'i MkV Linear Accelerator and Free Electron Laser Lab. Initial measurements and prototyping of the hardware is complete with commissioning and deployment of the system currently ongoing. We present the methodology and early results of this project.

MOPA20

Development of 3D EO-Sampling System for the Ultimate Temporal Resolution

laser, electron, timing, feedback

98

K. Ogawa, H. Tomizawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
S. Matsubara, Y. Okayasu
JASRI/SPring-8, Hyogo, Japan

We have been developing three dimensional bunch charge distribution (3D-BCD) monitor for FEL seeded with high-order harmonic (HH) pulse. 3D-BCD is based on EO-sampling technique with multiple EO crystal detectors in the manner of spectral decoding. Using this 3D-EO sampling technique, the positioning and timing of electron bunch is obtained in real-time with non-destructive measurement. For obtaining the high temporal resolution, an octave broadband probe laser with linear chirp rate of 1 fs/nm is required. We are developing an EO-probe laser pulse with ~10 μJ pulse energy and the bandwidth over 300 nm (FWHM). For meet these bandwidth and pulse energy, this EO-probe pulse is using a supercontinuum generated by photonic crystal fiber (PCF) and amplified with optical parametric amplification (OPA). Especially, for amplification with maintaining octave bandwidth, non-collinear OPA (NOPA) using BBO crystal and a pump source with a wavelength of 450 nm are adopted. The EO-probe pulse energy of 10 μJ provides for high S/N ratio to each detector and the bandwidth of 300 nm with 300 fs pulse duration allows the measurement for the 30 fs electron bunch duration (FWHM).

MOPA30

Application of EMMA BPMs to the ALICE Energy Recovery Linac

pick-up, sextupole, EPICS, linac

117

A. Kalinin, D. Angal-Kalinin, F. Jackson, J.K. Jones, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The ALICE Energy Recovery Linac arc button pickups have been recently equipped with EMMA BPM electronics*. These bunch-by-bunch EPICS VME BPMs give information about charge and position, and its jitter, allowing estimates of the beam energy jitter in ALICE in different modes of operation. A Mathematica program is designed to monitor statistically individual bunches (spacing 61.54ns) as well the train as a whole (up to 1625 bunches), allowing the study of jitter and position stability of the beam through the arc. The ALICE arc has been designed to be isochronous, with the bunch compression achieved through a separate dedicated bunch compressor chicane. The arc incorporates two sextupoles for correcting non-linear longitudinal matrix terms and experimental evidence suggests that the off-centred beam in the sextupoles breaks the linear isochronicity. We present some beam measurement results collected in 2012 using these BPMs.
*A. Kalinin et al, MOPPR061, IPAC12

MOPA42

Measurements of Martin-Puplett Interferometer Limitations using Blackbody Source

detector, radiation, vacuum, experiment

153

P.E. Evtushenko, J.M. Klopf
JLAB, Newport News, Virginia, USA

Frequency domain measurements with Martin-Puplett interferometer is one of a few techniques capable of bunch length measurements at the level of ~ 100 fs. As the bunch length becomes shorter, it is important to know and be able to measure the limitations of the instrument in terms of shortest measurable bunch length. In this paper we describe experiment of using blackbody source with the modified Matrin-Puplett interferometer that is routinely used for bunch length measurements at the JLab FEL, as a way to estimate the shortest, measurable with the device, bunch. The limitation comes from high frequency cut-off of the presently used wire-grid polarizer and is estimated to be 50 fs RMS. The measurements are made with the same Golay cell detector that is used for beam measurements. We demonstrate that, even though the blackbody source is many orders of magnitude less bright than the coherent transition or synchrotron radiation, it can be used for the measurements and gives a very good signal to noise ratio in a combination with lock-in detection. We also compare the measurements made in air and in vacuum to show the very strong effect of the atmospheric absorption.

MOPA45

Study of Beam Length Measurement based on TM010 Mode

simulation, cavity, coupling, impedance

162

R.X. Yuan, Y.B. Leng, L.Y. Yu, W.M. Zhou
SINAP, Shanghai, People's Republic of China

Beam length measurement in frequency domain is a familiar method, and the resolution is seriously limited by the system signal-noise-ratio (SNR) and the beam length measured. Usually this method can only obtain the resolution about ~10ps with beam length ~30ps when using signal from button or stripline BPM. But in FEL case, the beam length is the ps or sub-ps order. The paper discusses the probability of beam length measurement based on the TM010 mode in FEL case. When adopting High Order Mode(HOM) reject and system gain control, the system SNR can arrive at 110dB and the resolution can achieve 30fs with beam length ps or sub-ps.

MOPA49

EO-sampling-based Temporal Overlap Control System for an HH Seeded FEL

laser, electron, operation, timing

176

S. Matsubara
RIKEN/SPring-8, Hyogo, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
K. Ogawa, T. Sato, H. Tomizawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
Y. Okayasu, T. Togashi, T. Watanabe
JASRI/SPring-8, Hyogo-ken, Japan
E. Takahashi
RIKEN, Saitama, Japan

FELs have greatly interested for the short-wavelength region. However, their temporal profile and frequency spectra have shot-to-shot fluctuation by a SASE process. One of the promising approached for the problems is a seeded FEL scheme by using a full-coherent light source. The seeded FEL has been demonstrated in the EUV region by employ the high-order harmonics (HH) generation from an external laser source at the SCSS test-accelerator in the SPring-8. It is important for the HH-seeded FEL scheme to synchronize and overlap between the seeding laser pulse and the electron bunch. Their timing difference and laser spatial pointing is drifting. Therefore, a timing feedback and non-destructive monitor are necessary to operate seeded FEL continuously. We have constructed the timing monitor based on Electro-Optic (EO) sampling which is measure the timing difference the seeded laser pulse and the electron bunch simultaneously with the seeded FEL process. The probe laser pulse for the EO-sampling system is optically split from the common external HH laser driver for the seeded FEL. The EO-sampling system is able to use timing feedback for continual operation of the HH-seededFEL.

MOPB80

High Dynamic Range Beam Imaging with Two Simultaneously Sampling CCDs

linac, operation, emittance, brightness

263

P.E. Evtushenko, D. Douglas
JLAB, Newport News, Virginia, USA

Transverse beam profile measurement with sufficiently high dynamic range (HDR) is a key diagnostic to measure the beam halo, understand its sources and evolution. In this contribution we describe our initial experience with the HDR imaging of the electron beam at the JLab FEL. On contrary to HDR measurements made with wire scanners in counting mode, which provide only two or three 1D projections of transverse beam distribution, imaging allows to measure the distribution itself. That is especially important for non-equilibrium beams in the LINACs. The measurements were made by means of simultaneous imaging with two CCD sensors with different exposure time. Two images are combined then numerically in to one HDR image. The system works as an online tool providing HDR images at 4 Hz. An optically polished YAG:Ce crystal with the thickness of 100 um was used for the measurements. When tested with a laser beam images with the DR of about 10⁺⁵ were obtained. With the electron beam the DR was somewhat smaller due to the limitations in the time structure of the tune-up beam macro pulse.

MOPB87

Development and First Tests of a High Sensitivity Charge Monitor for SwissFEL

electronics, electron, operation, instrumentation

287

S. Artinian, J.F. Bergoz, F. Stulle
BERGOZ Instrumentation, Saint Genis Pouilly, France
P. Pollet, V. Schlott
PSI, Villigen PSI, Switzerland

The compact X-ray free electron laser SwissFEL, which is presently under development at the Paul Scherrer Institut (PSI) in Villigen, Switzerland, will operate at comparably low charges, allowing the compression of the electron bunches to a few femto-seconds (nominal 200 pC mode) and even towards the atto-second range (short bunch 10 pC mode). A high precision charge measurement turns out to be a challenge, especially in the presence of dark currents, which may occur from high gradient RF gun and accelerating structure operation. In response to this challenge, a higher sensitivity charge transformer and new beam charge monitor electronics were developed in collaboration between Bergoz Instrumentation and PSI. The Turbo-ICT captures sub-pC bunch charge thanks to a new magnetic alloy exhibiting very low core loss. Transmission over a carrier using narrow-band cable television technique preserves the signal integrity from the Turbo-ICT to the BCM-RF. Electro-magnetic and RF interferences are strongly attenuated; the dark current signal is suppressed. First beam test results, which have been performed at the SwissFEL Test Injector Facility (STIF), are presented in this contribution.

TUPA22

Design of RF Front End for Cavity Beam Position Monitor based on ICs

cavity, simulation, embedded, FPGA

383

B.P. Wang, Z.C. Chen, Y.B. Leng, L.Y. Yu, R.X. Yuan, W.M. Zhou
SINAP, Shanghai, People's Republic of China

RF front end has the significant impact on the performance of cavity beam position monitor (CBPM) which is indispensable beam instrumentation component in free electron laser(FEL) or linear collider facility. With many new advances in data converter and radio technology, complex RF front end design has been greatly simplified. Now based on digital intermediate frequency (IF) receiver architecture, a new RF front end for (CBPM) has been designed and fabricated using surface mount component on print circuit board (PCB). The front end contains analog-digital converter used to digitize the IF signals. The whole system would be integrated to a digital board developed by our lab to produce the dedicated signal processor for CBPM. There is an Xilinx Vertex-5 FPGA device on the digital board and relevant signal processing algorithm has been implemented on it using VHDL. The details about design and test results would be introduced blow.

TUPA41

Ultra-short Electron Bunch and X-ray Temporal Diagnostics with an X-band Transverse Deflecting Cavity

electron, photon, undulator, klystron

441

P. Krejcik, Y. Ding, J.C. Frisch, Z. Huang, H. Loos, J.W. Wang, M.-H. Wang
SLAC, Menlo Park, California, USA
C. Behrens
DESY, Hamburg, Germany
P. Emma
LBNL, Berkeley, California, USA

Funding: This work was supported by Department of Energy Contract No. DE-AC0276SF00515
The technique of streaking an electron bunch with a RF deflecting cavity to measure its bunch length is being applied in a new way at the Linac Coherent Light Source with the goal of measuring the femtosecond temporal profile of the FEL photon beam. A powerful X-band deflecting cavity is being installed downstream of the FEL undulator and the streaked electron beam will be observed at an energy spectrometer screen at the beam dump. The single-shot measurements will reveal which time slices of the streaked beam have contributed to the FEL process by virtue of their greater energy loss and energy spread relative to the non-lasing portions of the electron bunch. Since the diagnostic is located downstream of the undulator it can be operated continuously without interrupting the beam to the users. The resolution of the new X-band system will be compared to the existing S-band RF deflecting diagnostic systems at SLAC and consideration is given to the required RF phase stability tolerances required for acceptable beam jitter on the monitor. Simulation studies show that about 1 fs (rms) time resolution is achievable in the LCLS over a wide range of FEL wavelengths and pulse lengths.

TUPA43

First Operation of the Electro-optical Sampling Diagnostics of the FERMI@Elettra FEL

laser, electron, alignment, vacuum

449

M. Veronese, A. Abrami, E. Allaria, M. Bossi, M.B. Danailov, M. Ferianis, L. Fröhlich, S. Grulja, M. Predonzani, F. Rossi, G. Scalamera, C. Spezzani, M. Trovò, M. Tudor
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

The FERMI@Elettra seeded FEL has demanding specifications in terms of longitudinal properties of the electron beam. Several diagnostics are installed along the linac. At the entrance of the FEL1 undulator chain an electro optical sampling (EOS) station based on the spatial encoding scheme is installed. The EOS provides both time jitter and longitudinal profile measurements in a non-destructive way. The layout of this system is described and the first operational measurement results obtained are reported. The paper includes also the capability of this diagnostics to perform the temporal coarse alignment of the seed laser to the electron beam. Finally a discussion on the future developments foreseen for this system is given.

TUPB76

Intra Undulator Screen Diagnostics for the FERMI@Elettra FEL

electron, laser, undulator, radiation

519

M. Veronese, A. Abrami, E. Allaria, M. Bossi, A. Bucconi, M. De Marco, M. Ferianis, L. Fröhlich, L. Giannessi, S. Grulja, R. Sauro, C. Spezzani, M. Tudor
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
T. Borden
FRIB, East Lansing, Michigan, USA
F. Cianciosi
ESRF, Grenoble, France

The FERMI@Elettra seeded FEL poses demanding requirements in terms of intra undulator diagnostics due to the short wavelength of its FEL radiation and to the coexistence of the electron and photon FEL beams. An advanced multi-beam screen system has equipped both FEL1 and FEL2. The system has been designed for transverse size and profile measurement on both the electron beam and the FEL radiation. Challenging design constrains are present: COTR suppression, seed laser suppression, FEL wavelength range and minimization of the ionizing radiation delivered to the undulators. This paper describes the novel design and the obtained performance with the FERMI intra undulator screen system (IU-FEL).

TUPB81

Design of the Beam Profile Monitors for the SXFEL Facility

controls, detector, electron, linac

534

L.Y. Yu, J. Chen, Y.B. Leng, K.R. Ye, W.M. Zhou
SINAP, Shanghai, People's Republic of China

The Shanghai X-ray Free Electron Laser Facility will begin construction at next year. The linac electron beam energy is 0.84 GeV. Over 50 beam profile monitors with OTR and YaG screen will be installed along the linac and undulators. The profile monitor system design is a challenging task, since the system has to measure transverse electron beam sizes from millimeter down to 40μm scale with a 20μm resolution and 50μm repeat positioning accuracy. This paper describes the design of the mechanical detector , the integrated step-servo motor controlling system, the beam imaging system, as well as the software system.

WECC04

Analysis of the Electro-optical Front End for the New 40 GHz Bunch Arrival Time Monitor System

laser, pick-up, electron, timing

571

A. Kuhl, J. Rönsch-Schulenburg, J. Roßbach
Uni HH, Hamburg, Germany
A. Angelovski, R. Jakoby, A. Penirschke
TU Darmstadt, Darmstadt, Germany
M. Bousonville, M.K. Czwalinna, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany
S. Schnepp
IFH, Zurich, Switzerland
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

The Free electron LASer in Hamburg (FLASH) is currently equipped with four Bunch Arrival time Monitors (BAMs) which achieve a time resolution of less than 10 fs for bunch charges higher than 500 pC (1). In order to achieve single spike FEL pulses at FLASH, electron bunch charges down to 20 pC are of interest. With the current 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 (2) 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 pickup system also requires a new electro-optical frontend with a 40 GHz EOM. The theoretical limits of the time resolution depending on the RF signal at different bunch charges and on the jitter of the reference laser pulses where analyzed for the new EOM.
(1) M. K. Bock et al. in Proceedings of DIPAC 2011, Hamburg, Germany,2011, p. 365
(2) A. Angelovski, A. Kuhl et al. in Proceedings of IPAC 2011, San Sebastian, Spain, 2011, p. 1177 and p. 1186

Slides WECC04 [12.560 MB]