FEL2015 - List of Keywords (experiment)

Paper	Title	Other Keywords	Page
MOP012	Present Status of Source Development Station at UVSOR-III	laser, radiation, undulator, electron	54
	N.S. Mirian, K. Hayashi, M. Katoh, J. Yamazaki UVSOR, Okazaki, Japan M. Hosaka, Y. Takashima Nagoya University, Nagoya, Japan T. Konomi, N. Yamamoto KEK, Ibaraki, Japan H. Zen Kyoto University, Kyoto, Japan
	Construction and development of a source development station are in progress at UVSOR-III, a 750 MeV electron storage ring. It is equipped with an optical klystron type undulator system, a mode lock Ti:Sa Laser system, a dedicated beam-line for visible-VUV radiation and a parasitic beam-line for THz radiation. New light port to extract edge radiation was constructed recently. An optical cavity for a resonator free electron laser is currently being reconstructed. Some experiments such as coherent THz radiation, coherent harmonic radiation, laser Compton Scattering gamma-rays and optical vortices are in progress.
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MOP013	The Fermi Seeded FEL Facility: Operational Experience and Future Perspectives	FEL, laser, electron, photon	57
	L. Giannessi, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Manfredda, C. Masciovecchio, M. Milloch, F. Parmigiani, E. Pedersoli, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are available for users, down to the shortest wavelength of 4 nm. We report on the completion of the commissioning of the high energy FEL line, FEL-2, on the most recent progress obtained on FEL-1 and on the operational experience for users, in particular those requiring specific FEL configurations, such as two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered based on our experience, aiming to maintain as well as to constantly improve the performance of the facility for our user community.
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MOP014	Status of the Soft X-Ray FEL User Facility FLASH	photon, electron, operation, FEL	61
	K. Honkavaara, B. Faatz, J. Feldhaus, S. Schreiber, R. Treusch, M. Vogt DESY, Hamburg, Germany
	Since 10 years FLASH at DESY (Hamburg, Germany) has provided high brilliance FEL radiation at XUV and soft X-ray wavelengths for user experiments. Recently FLASH has been upgraded with a second undulator beamline, FLASH2, whose commissioning takes place in parallel of the user operation on FLASH1. This paper summarizes the performance of the FLASH facility during the last user period from January 2014 to April 2015.
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MOP047	The BINP HLS to Measure Vertical Changes on PAL-XFEL Buildings and Ground	timing, survey, operation, alignment	133
	H. J. Choi, K.H. Gil, H.-S. Kang, S.H. Kim, K.W. Seo PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL is being installed and will be completed by December of 2015 so that users can be supported beginning in 2016. PAL-XFEL equipment should continuously maintain the bunch beam parameter. To this end, PAL-XFEL equipment has to be kept precisely aligned. As a part of the process for installing PAL-XFEL, a surface geodetic network and the installation of a tunnel measurement network inside buildings is in preparation; additionally, the fiducialization of major equipment is underway. After PAL-XFEL equipment is optimized and aligned, if the ground and buildings go through vertical changes during operation, misalignment of equipments will cause errors in the electron beam trajectory, which will lead to changes to the beam parameter. For continuous and systemic measurement of vertical changes in buildings and to monitor ground subsidence (sinks) and uplift, the BINP Ultrasonic-type Hydrostatic Levelling System (HLS) is to be installed and operated in all sections of PAL-XFEL for linear accelerator, undulator and beam line. This study will introduce the operation principle, design concept and advantages (self-calibration) of BINP ULS Sensor, and will outline its installation plan and operation plan.
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MOP054	Wake Field Potentials of 'Dechirpers'	wakefield, FEL, focusing, electron	157
	A. Novokhatski SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy Contract No. DOE-AC03-76SF00515. A corrugated structure, which is used on 'dechirpers' is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultra-short bunches, which are now used in FELs, excite much higher frequency fields and the corresponding wake potentials will be very different from single-mode description. We made analyzes of these wake potentials based on a numerical solution of Maxwell's equations. The behavior of the wake fields of ultra-short bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. As we increase the bunch length, the wake potentials slowly transform to the form of a single mode. For a practical application we present results for a 'dechirper', which will be soon installed at LCLS. We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. We find very good agreement with the experimental results.
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MOP063	Transverse Emittance Measurement of KAERI Linac with Thick Lens Quadrupole Scan	emittance, quadrupole, electron, space-charge	185
	S. Setiniyaz, I.H. Baek, M.S. Chae, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, H.W. Kim, S.V. Miginsky, J.H. Nam, S. Park, N. Vinokurov KAERI, Daejon, Republic of Korea S.V. Miginsky, N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	The UED (Ultrafast Electron Diffraction) beamline of KAERI (Korea Atomic Energy Research Institute) WCI (World Class Institute) Center has been completed and successfully commissioned. Transverse emittance of the electron beam was measured at the entrance of the UED chamber with the quadrupole scan technique. In this technique, larger drift distance between the quad and screen is preferred because it gives better thin lens approximation. A space charge dominated beam however, will undergo emittance growth in the long drift caused by the space charge force. We suggest mitigating this growth by introducing quadrupole scan with short drift and without thin lens approximation. We shall discuss the measurement process and results.
	Poster MOP063 [1.287 MB]
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TUP004	Three-dimensional, Time-dependent Simulation of Free-Electron Lasers	undulator, simulation, electron, FEL	331
	P.J.M. van der Slot Mesa+, Enschede, The Netherlands H. Freund, P.J.M. van der Slot CSU, Fort Collins, Colorado, USA
	Minerva is a simulation code that models the interaction of electrons with an optical field inside an undulator. Minerva uses a modal expansion for the optical field and the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to mode, for example, FEL oscillators. As there exists a large variety of FELs ranging from long-wavelength oscillators to soft and hard X-ray FELs that are either seeded or starting from noise, a simulation code, such as Minerva, should be capable of modelling this huge variety of FEL configurations. Here we present a validation of the Minerva code against experimental data for various FEL configurations, ranging from long wavelength FEL oscillators to hard X-ray SASE FEL.
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TUP022	Measurement of Spatial Displacement of X-rays in Crystals for Self-Seeding Applications	FEL, electron, detector, radiation	405
	A. Rodriguez-Fernandez, B. Pedrini, S. Reiche PSI, Villigen PSI, Switzerland K. Finkelstein Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Free-electron laser (FEL) radiation arises from shot noise in the electron bunch, which is amplified along the undulator section and results in X-ray pulses consisting of many longitudinal modes [1]. The output bandwidth of FELs can be decreased by seeding the FEL process with longitudinally coherent radiation. In the hard x-ray region, there are no suitable external sources. This obstacle can be overcome by self-seeding. The X-ray beam is separated from the electrons using a magnetic chicane, and then monochromatized. The monochromatized X-rays serve as a narrowband seed, after recombination with the electron bunch, along the downstream undulators. This scheme generates longitudinally coherent FEL pulses.[2] have proposed monochromatization based on Forward Bragg Diffraction (FBD), which introduces a delay of the narrowband X-rays pulse of the order of femtoseconds that can be matched to the delay of the electron bunch due to the chicane. Unfortunately, the FBD process produces a small transverse displacement of the X-ray beam, which results in the loss of efficiency of the seeding process [3]. Preliminary results from an experiment performed at Cornell High Energy Synchrotron Source seem to confirm the predicted transverse displacement, which is therefore to be taken into account in the design of self-seeding infrastructure for optimizing the FEL performance. [1] J.S. Wark et al., J. Apply. Crystallogr. 32, 692 (1999) [2] G. Geloni et al., DESY report 10-053 (2010). [3] Y. Shvyd'ko et al., Phys. Rev. ST Accel. Beams 15, 100702 (2012)
	Poster TUP022 [5.503 MB]
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TUP045	MTCA.4 Phase Detector for Femtosecond-Precision Laser Synchronization	laser, detector, controls, timing	474
	E. Janas, M. Felber, M. Heuer, U. Mavrič, H. Schlarb DESY, Hamburg, Germany K. Czuba Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
	For time-resolved experiments at FELs such as the European XFEL an accurate synchronization of the machine is essential. The required femtosecond- level synchronization we plan to achieve with an optical synchronization system, in which an inherent part is the master laser oscillator (MLO) locked to the electrical reference. At DESY we develop a custom rear transition module in MTCA.4 standard, which will allow for different techniques of phase detection between the optical and the electrical signal, as well as locking to an optical reference using a cross-correlator. In this paper we present the current status of the development, including two basic solutions for the detection to an RF. One of the methods incorporates an external drift free detector based on the so-called MZI setup. The other one employs the currently used downconverter scheme with subsequent improvements. The module can serve for locking a variety of lasers with different repetition rates.
	Poster TUP045 [4.010 MB]
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TUP070	Energy Jitter Minimization at LCLS	linac, timing, operation, simulation	523
	L. Wang, A.L. Benwell, A. Brachmann, W.S. Colocho, F.-J. Decker, Z. Huang, T.J. Maxwell, T. Tao, J.L. Turner SLAC, Menlo Park, California, USA
	The energy jitters of the electron beam can affects the FEL in self-seeded modes if the jitter is large compared to the FEL parameter. We work in multiple ways to reduce the jitters, including hardware improvement, optimization linac set-up. This paper discusses the optimization of linac set-up. The solutions always suggest that we can largely reduce the energy jitter from a weak compression at BC1 and a stronger compression at BC2. Meanwhile a low beam energy at BC2 also reduce the energy jitter, which is confirmed by the experiment. The results can be explained by a simple model. Experimental results are also presented, demonstrating better than 20% and 40% relative energy jitter reduction for 13.6 and 4 GeV linac operation, respectively.
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TUP074	Results from the Nocibur Experiment at Brookhaven National Laboratory's Accelerator Test Facility	laser, undulator, radiation, electron	540
	N.S. Sudar, J.P. Duris, I.I. Gadjev, P. Musumeci UCLA, Los Angeles, USA M. Babzien, M.G. Fedurin, K. Kusche, I. Pogorelsky, M.N. Polyanskiy, C. Swinson BNL, Upton, Long Island, New York, USA
	Conversion efficiencies of electrical to optical power in a Free Electron Laser are typically limited by their Pierce parameter, ρ ~0.1%. Introducing strong undulator tapering can increase this efficiency greatly, with simulations showing possible conversion efficiencies of ~40%. Recent experiments performed with the Rubicon Inverse Free Electron Laser have demonstrated acceleration gradients of ~ 100 MeV/m and high particle trapping efficiency by coupling a pre-bunched electron beam to a high power CO2 laser pulse in a strongly tapered helical undulator. By reversing the undulator period tapering and re-optimizing the field strength along the Rubicon undulator, we obtain an Inverse Free Electron Laser decelerator, which we have aptly renamed Nocibur. This tapering profile is chosen so that the change in beam energy defined by the ponderomotive decelerating gradient matches the change in resonant energy defined by the undulator parameters, allowing the conversion of a large fraction of the electron beam power into coherent narrow-band radiation. We discuss this mechanism as well as results from a recent experiment performed with the Nocibur undulator at Brookhaven National Laboratory's Accelerator Test Facility.
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TUP085	Lebra Free-Electron Laser Elicits Electrical Spikes from the Retina and Optic Nerve of the Slugs Limax Valentianus	FEL, site, electron, radiation	550
	F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan Y. Komatsuzaki Nihon University, Tokyo, Japan
	Since 2001, the Laboratory for Electron Beam Research and Application (LEBRA) has been providing tunable free-electron lasers (FELs) encompassing the near-IR region and some of the mid-IR region (0.9-6 microns), and generating visible wavelengths up to 400 nm by means of nonlinear optical crystals. We are investigating the efficiency of LEBRA-FELs for triggering photoreactions in living organisms. Last year we described the effects of LEBRA-FELs in controlling the photoreaction of lettuce seeds; red FEL (660 nm) and far-red FEL (740 nm) activate and inhibit germination, respectively. Here we used LEBRA-FEL to illuminate the retina of slugs (Limax valentianus), and determined which FEL wavelengths generate electrical spikes from the retina-optic nerve. Blue FEL light (wavelength: 470 nm) efficiently produced electrical spikes from the retina. The results are consistent with a previous study, where a xenon arc lamp with interference filters was used to produce monochromatic visible light. We plan to extend the wavelengths to the near- and mid-IR regions of LEBRA-FEL. We summarize our current results for the use of FEL in investigating the electrophysiology of the retina of slugs. We thank Mr. T. Kuwabara (a graduate of Departments of Physics, College of Science and Technolgy, Nihon University) for helpful assistance.
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WEP023	Two Bunches with ns-Separation with LCLS	laser, timing, photon, controls	634
	F.-J. Decker, S. Gilevich, Z. Huang, H. Loos, A. Marinelli, C.A. Stan, J.L. Turner, Z. Van Hoover, S. Vetter SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. The Linac Coherent Light Source (LCLS) delivers typically one bunch. Two bunches are interesting for pump / probe experiments. Two electron bunches with ps separation have been already produced using a split and delay in the laser which produces them on the gun cathode. Here we present the combination of two lasers with a combiner, this allows any time separation and is it limited to RF bucket spacing so far to about 40 ns limited by the setup of our beam containment system. Different beam energies were also provided and the most challenging part was a transverse separation of a few σs for the two beams. Although this setup was very jittery a successful user experiment was accomplished.
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WEP030	First Lasing of an HGHG Seeded FEL at FLASH	FEL, electron, laser, injection	646
	K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany S. Ackermann, Ph. Amstutz, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, T. Plath, J. Roßbach Uni HH, Hamburg, Germany S. Ackermann, R.W. Aßmann, J. Bödewadt, N. Ekanayake, B. Faatz, I. Hartl, R. Ivanov, T. Laarmann, J.M. Müller DESY, Hamburg, Germany
	Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K1GU4 and 05K10PE1 and the German Research Foundation program graduate school 1355. The free-electron laser facility FLASH at DESY operates in SASE mode with MHz bunch trains of high-intensity extreme ultraviolet and soft X-ray FEL pulses. A seeded beamline which is designed to be operated parasitically to the main SASE beamline has been used to test different external FEL seeding methods. First lasing at the 7th harmonic of a 266 nm seed laser using high-gain harmonic generation has been demonstrated. Studies of the influence of the microbunching instability are being pursued.
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WEP060	Longitudinal Electron Bunch Shaping Experiments at the PAL-ITF	laser, electron, cavity, FEL	694
	M. Chung, J.M. Seok UNIST, Ulsan, Republic of Korea J.H. Han, J.H. Hong, H.-S. Kang, C.H. Kim PAL, Pohang, Kyungbuk, Republic of Korea J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Longitudinal shaping of electron beam has received much attention recently, due to its potential applications to THz generation, dielectric wakefield acceleration, improvement of FEL performance, and controlled space-charge modulation. Using a set of alpha-BBO crystals, shaping of laser pulse and electron bunch on the order of ps is tested at the Injector Test Facility (ITF) of Pohang Accelerator Laboratory (PAL). In particular, we investigate the response of the longitudinally-modulated beam to a dechirper, which is a vacuum chamber of two corrugated, metallic plates. Initial experimental results will be presented with analytical theory and numerical simulations.
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Paper

Title

Other Keywords

Page

MOP012

Present Status of Source Development Station at UVSOR-III

laser, radiation, undulator, electron

54

N.S. Mirian, K. Hayashi, M. Katoh, J. Yamazaki
UVSOR, Okazaki, Japan
M. Hosaka, Y. Takashima
Nagoya University, Nagoya, Japan
T. Konomi, N. Yamamoto
KEK, Ibaraki, Japan
H. Zen
Kyoto University, Kyoto, Japan

Construction and development of a source development station are in progress at UVSOR-III, a 750 MeV electron storage ring. It is equipped with an optical klystron type undulator system, a mode lock Ti:Sa Laser system, a dedicated beam-line for visible-VUV radiation and a parasitic beam-line for THz radiation. New light port to extract edge radiation was constructed recently. An optical cavity for a resonator free electron laser is currently being reconstructed. Some experiments such as coherent THz radiation, coherent harmonic radiation, laser Compton Scattering gamma-rays and optical vortices are in progress.

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MOP013

The Fermi Seeded FEL Facility: Operational Experience and Future Perspectives

FEL, laser, electron, photon

57

L. Giannessi, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Manfredda, C. Masciovecchio, M. Milloch, F. Parmigiani, E. Pedersoli, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are available for users, down to the shortest wavelength of 4 nm. We report on the completion of the commissioning of the high energy FEL line, FEL-2, on the most recent progress obtained on FEL-1 and on the operational experience for users, in particular those requiring specific FEL configurations, such as two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered based on our experience, aiming to maintain as well as to constantly improve the performance of the facility for our user community.

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MOP014

Status of the Soft X-Ray FEL User Facility FLASH

photon, electron, operation, FEL

61

K. Honkavaara, B. Faatz, J. Feldhaus, S. Schreiber, R. Treusch, M. Vogt
DESY, Hamburg, Germany

Since 10 years FLASH at DESY (Hamburg, Germany) has provided high brilliance FEL radiation at XUV and soft X-ray wavelengths for user experiments. Recently FLASH has been upgraded with a second undulator beamline, FLASH2, whose commissioning takes place in parallel of the user operation on FLASH1. This paper summarizes the performance of the FLASH facility during the last user period from January 2014 to April 2015.

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MOP047

The BINP HLS to Measure Vertical Changes on PAL-XFEL Buildings and Ground

timing, survey, operation, alignment

133

H. J. Choi, K.H. Gil, H.-S. Kang, S.H. Kim, K.W. Seo
PAL, Pohang, Kyungbuk, Republic of Korea

PAL-XFEL is being installed and will be completed by December of 2015 so that users can be supported beginning in 2016. PAL-XFEL equipment should continuously maintain the bunch beam parameter. To this end, PAL-XFEL equipment has to be kept precisely aligned. As a part of the process for installing PAL-XFEL, a surface geodetic network and the installation of a tunnel measurement network inside buildings is in preparation; additionally, the fiducialization of major equipment is underway. After PAL-XFEL equipment is optimized and aligned, if the ground and buildings go through vertical changes during operation, misalignment of equipments will cause errors in the electron beam trajectory, which will lead to changes to the beam parameter. For continuous and systemic measurement of vertical changes in buildings and to monitor ground subsidence (sinks) and uplift, the BINP Ultrasonic-type Hydrostatic Levelling System (HLS) is to be installed and operated in all sections of PAL-XFEL for linear accelerator, undulator and beam line. This study will introduce the operation principle, design concept and advantages (self-calibration) of BINP ULS Sensor, and will outline its installation plan and operation plan.

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MOP054

Wake Field Potentials of 'Dechirpers'

wakefield, FEL, focusing, electron

157

A. Novokhatski
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy Contract No. DOE-AC03-76SF00515.
A corrugated structure, which is used on 'dechirpers' is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultra-short bunches, which are now used in FELs, excite much higher frequency fields and the corresponding wake potentials will be very different from single-mode description. We made analyzes of these wake potentials based on a numerical solution of Maxwell's equations. The behavior of the wake fields of ultra-short bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. As we increase the bunch length, the wake potentials slowly transform to the form of a single mode. For a practical application we present results for a 'dechirper', which will be soon installed at LCLS. We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. We find very good agreement with the experimental results.

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MOP063

Transverse Emittance Measurement of KAERI Linac with Thick Lens Quadrupole Scan

emittance, quadrupole, electron, space-charge

185

S. Setiniyaz, I.H. Baek, M.S. Chae, B.A. Gudkov, B. Han, K.H. Jang, Y.U. Jeong, H.W. Kim, S.V. Miginsky, J.H. Nam, S. Park, N. Vinokurov
KAERI, Daejon, Republic of Korea
S.V. Miginsky, N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

The UED (Ultrafast Electron Diffraction) beamline of KAERI (Korea Atomic Energy Research Institute) WCI (World Class Institute) Center has been completed and successfully commissioned. Transverse emittance of the electron beam was measured at the entrance of the UED chamber with the quadrupole scan technique. In this technique, larger drift distance between the quad and screen is preferred because it gives better thin lens approximation. A space charge dominated beam however, will undergo emittance growth in the long drift caused by the space charge force. We suggest mitigating this growth by introducing quadrupole scan with short drift and without thin lens approximation. We shall discuss the measurement process and results.

Poster MOP063 [1.287 MB]

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TUP004

Three-dimensional, Time-dependent Simulation of Free-Electron Lasers

undulator, simulation, electron, FEL

331

P.J.M. van der Slot
Mesa+, Enschede, The Netherlands
H. Freund, P.J.M. van der Slot
CSU, Fort Collins, Colorado, USA

Minerva is a simulation code that models the interaction of electrons with an optical field inside an undulator. Minerva uses a modal expansion for the optical field and the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to mode, for example, FEL oscillators. As there exists a large variety of FELs ranging from long-wavelength oscillators to soft and hard X-ray FELs that are either seeded or starting from noise, a simulation code, such as Minerva, should be capable of modelling this huge variety of FEL configurations. Here we present a validation of the Minerva code against experimental data for various FEL configurations, ranging from long wavelength FEL oscillators to hard X-ray SASE FEL.

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TUP022

Measurement of Spatial Displacement of X-rays in Crystals for Self-Seeding Applications

FEL, electron, detector, radiation

405

A. Rodriguez-Fernandez, B. Pedrini, S. Reiche
PSI, Villigen PSI, Switzerland
K. Finkelstein
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Free-electron laser (FEL) radiation arises from shot noise in the electron bunch, which is amplified along the undulator section and results in X-ray pulses consisting of many longitudinal modes [1]. The output bandwidth of FELs can be decreased by seeding the FEL process with longitudinally coherent radiation. In the hard x-ray region, there are no suitable external sources. This obstacle can be overcome by self-seeding. The X-ray beam is separated from the electrons using a magnetic chicane, and then monochromatized. The monochromatized X-rays serve as a narrowband seed, after recombination with the electron bunch, along the downstream undulators. This scheme generates longitudinally coherent FEL pulses.[2] have proposed monochromatization based on Forward Bragg Diffraction (FBD), which introduces a delay of the narrowband X-rays pulse of the order of femtoseconds that can be matched to the delay of the electron bunch due to the chicane. Unfortunately, the FBD process produces a small transverse displacement of the X-ray beam, which results in the loss of efficiency of the seeding process [3]. Preliminary results from an experiment performed at Cornell High Energy Synchrotron Source seem to confirm the predicted transverse displacement, which is therefore to be taken into account in the design of self-seeding infrastructure for optimizing the FEL performance.
[1] J.S. Wark et al., J. Apply. Crystallogr. 32, 692 (1999)
[2] G. Geloni et al., DESY report 10-053 (2010).
[3] Y. Shvyd'ko et al., Phys. Rev. ST Accel. Beams 15, 100702 (2012)

Poster TUP022 [5.503 MB]

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TUP045

MTCA.4 Phase Detector for Femtosecond-Precision Laser Synchronization

laser, detector, controls, timing

474

E. Janas, M. Felber, M. Heuer, U. Mavrič, H. Schlarb
DESY, Hamburg, Germany
K. Czuba
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

For time-resolved experiments at FELs such as the European XFEL an accurate synchronization of the machine is essential. The required femtosecond- level synchronization we plan to achieve with an optical synchronization system, in which an inherent part is the master laser oscillator (MLO) locked to the electrical reference. At DESY we develop a custom rear transition module in MTCA.4 standard, which will allow for different techniques of phase detection between the optical and the electrical signal, as well as locking to an optical reference using a cross-correlator. In this paper we present the current status of the development, including two basic solutions for the detection to an RF. One of the methods incorporates an external drift free detector based on the so-called MZI setup. The other one employs the currently used downconverter scheme with subsequent improvements. The module can serve for locking a variety of lasers with different repetition rates.

Poster TUP045 [4.010 MB]

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TUP070

Energy Jitter Minimization at LCLS

linac, timing, operation, simulation

523

L. Wang, A.L. Benwell, A. Brachmann, W.S. Colocho, F.-J. Decker, Z. Huang, T.J. Maxwell, T. Tao, J.L. Turner
SLAC, Menlo Park, California, USA

The energy jitters of the electron beam can affects the FEL in self-seeded modes if the jitter is large compared to the FEL parameter. We work in multiple ways to reduce the jitters, including hardware improvement, optimization linac set-up. This paper discusses the optimization of linac set-up. The solutions always suggest that we can largely reduce the energy jitter from a weak compression at BC1 and a stronger compression at BC2. Meanwhile a low beam energy at BC2 also reduce the energy jitter, which is confirmed by the experiment. The results can be explained by a simple model. Experimental results are also presented, demonstrating better than 20% and 40% relative energy jitter reduction for 13.6 and 4 GeV linac operation, respectively.

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TUP074

Results from the Nocibur Experiment at Brookhaven National Laboratory's Accelerator Test Facility

laser, undulator, radiation, electron

540

N.S. Sudar, J.P. Duris, I.I. Gadjev, P. Musumeci
UCLA, Los Angeles, USA
M. Babzien, M.G. Fedurin, K. Kusche, I. Pogorelsky, M.N. Polyanskiy, C. Swinson
BNL, Upton, Long Island, New York, USA

Conversion efficiencies of electrical to optical power in a Free Electron Laser are typically limited by their Pierce parameter, ρ ~0.1%. Introducing strong undulator tapering can increase this efficiency greatly, with simulations showing possible conversion efficiencies of ~40%. Recent experiments performed with the Rubicon Inverse Free Electron Laser have demonstrated acceleration gradients of ~ 100 MeV/m and high particle trapping efficiency by coupling a pre-bunched electron beam to a high power CO2 laser pulse in a strongly tapered helical undulator. By reversing the undulator period tapering and re-optimizing the field strength along the Rubicon undulator, we obtain an Inverse Free Electron Laser decelerator, which we have aptly renamed Nocibur. This tapering profile is chosen so that the change in beam energy defined by the ponderomotive decelerating gradient matches the change in resonant energy defined by the undulator parameters, allowing the conversion of a large fraction of the electron beam power into coherent narrow-band radiation. We discuss this mechanism as well as results from a recent experiment performed with the Nocibur undulator at Brookhaven National Laboratory's Accelerator Test Facility.

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TUP085

Lebra Free-Electron Laser Elicits Electrical Spikes from the Retina and Optic Nerve of the Slugs Limax Valentianus

FEL, site, electron, radiation

550

F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
Y. Komatsuzaki
Nihon University, Tokyo, Japan

Since 2001, the Laboratory for Electron Beam Research and Application (LEBRA) has been providing tunable free-electron lasers (FELs) encompassing the near-IR region and some of the mid-IR region (0.9-6 microns), and generating visible wavelengths up to 400 nm by means of nonlinear optical crystals. We are investigating the efficiency of LEBRA-FELs for triggering photoreactions in living organisms. Last year we described the effects of LEBRA-FELs in controlling the photoreaction of lettuce seeds; red FEL (660 nm) and far-red FEL (740 nm) activate and inhibit germination, respectively. Here we used LEBRA-FEL to illuminate the retina of slugs (Limax valentianus), and determined which FEL wavelengths generate electrical spikes from the retina-optic nerve. Blue FEL light (wavelength: 470 nm) efficiently produced electrical spikes from the retina. The results are consistent with a previous study, where a xenon arc lamp with interference filters was used to produce monochromatic visible light. We plan to extend the wavelengths to the near- and mid-IR regions of LEBRA-FEL. We summarize our current results for the use of FEL in investigating the electrophysiology of the retina of slugs.
We thank Mr. T. Kuwabara (a graduate of Departments of Physics, College of Science and Technolgy, Nihon University) for helpful assistance.

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WEP023

Two Bunches with ns-Separation with LCLS

laser, timing, photon, controls

634

F.-J. Decker, S. Gilevich, Z. Huang, H. Loos, A. Marinelli, C.A. Stan, J.L. Turner, Z. Van Hoover, S. Vetter
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) delivers typically one bunch. Two bunches are interesting for pump / probe experiments. Two electron bunches with ps separation have been already produced using a split and delay in the laser which produces them on the gun cathode. Here we present the combination of two lasers with a combiner, this allows any time separation and is it limited to RF bucket spacing so far to about 40 ns limited by the setup of our beam containment system. Different beam energies were also provided and the most challenging part was a transverse separation of a few σs for the two beams. Although this setup was very jittery a successful user experiment was accomplished.

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WEP030

First Lasing of an HGHG Seeded FEL at FLASH

FEL, electron, laser, injection

646

K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany
S. Ackermann, Ph. Amstutz, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, T. Plath, J. Roßbach
Uni HH, Hamburg, Germany
S. Ackermann, R.W. Aßmann, J. Bödewadt, N. Ekanayake, B. Faatz, I. Hartl, R. Ivanov, T. Laarmann, J.M. Müller
DESY, Hamburg, Germany

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K1GU4 and 05K10PE1 and the German Research Foundation program graduate school 1355.
The free-electron laser facility FLASH at DESY operates in SASE mode with MHz bunch trains of high-intensity extreme ultraviolet and soft X-ray FEL pulses. A seeded beamline which is designed to be operated parasitically to the main SASE beamline has been used to test different external FEL seeding methods. First lasing at the 7th harmonic of a 266 nm seed laser using high-gain harmonic generation has been demonstrated. Studies of the influence of the microbunching instability are being pursued.

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WEP060

Longitudinal Electron Bunch Shaping Experiments at the PAL-ITF

laser, electron, cavity, FEL

694

M. Chung, J.M. Seok
UNIST, Ulsan, Republic of Korea
J.H. Han, J.H. Hong, H.-S. Kang, C.H. Kim
PAL, Pohang, Kyungbuk, Republic of Korea
J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Longitudinal shaping of electron beam has received much attention recently, due to its potential applications to THz generation, dielectric wakefield acceleration, improvement of FEL performance, and controlled space-charge modulation. Using a set of alpha-BBO crystals, shaping of laser pulse and electron bunch on the order of ps is tested at the Injector Test Facility (ITF) of Pohang Accelerator Laboratory (PAL). In particular, we investigate the response of the longitudinally-modulated beam to a dechirper, which is a vacuum chamber of two corrugated, metallic plates. Initial experimental results will be presented with analytical theory and numerical simulations.

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