FEL 2007 - Classification:FEL operation/

FEL operation

Paper	Title	Page
MOPPH036	First Experiences with the FIR-FEL at ELBE	97
	P. Michel, W. Seidel, G. Staats, J. Teichert, R. Wuensch, U. Lehnert FZD, Dresden
	We show the design and the parameters of operation of the long-wavelength (U100) FEL of ELBE. First lasing has been shown in August, 2006. Since then, the laser has undergone thorough commissioning and is available for user experiments since fall, 2006. Besides in-house users the IR beam is available to external users in the FELBE (FEL@ELBE) program witch is a part of the integrated activity on synchrotron and free electron laser science in the EU. At the beginning of 2007 lasing in the full designed wavelength range from 20μm to 200μm was demonstrated. The laser power typically reaches several W in CW operation but drops for very long wavelengths depending on the size of the used outcoupling hole. However, there exists a serious problem with small gaps in the providable wavelength spectrum. We attribute this behaviour to the transmission characteristics of the overmoded partial waveguide used from the undulator entrance to the first mirror.
MOPPH037	Characterization of a New High-Q Talbot Effect Confocal Resonator for mm-Wave FEL
	J. Dadoun, Kh. Garb, A. Gover, O. Faingersh University of Tel-Aviv, Faculty of Engineering, Tel-Aviv B. Yu. Kapilevich, B. Litvak CJS, Ariel
	A new FEL resonator for mm- wave range was assembled and characterized before installation into the high voltage terminal of the Tandem electrostatic FEL accelerator. The measured unloaded Q-factor of the new resonator is Q=30,000. Accordingly, the round-trip losses are ~18% for the total length of the resonator about 1.5m The reflector of the new resonator utilizes in one transverse dimension the Talbot effect for imaging and splitting the radiation mode field for the purpose of the laser radiation. In the other transverse dimension optical imaging is realized by means of two confocal mirrors. A 3-wire grid assembly, remotely controlled, provides fine tuning of the laser frequency and control over the resonator out-coupling coefficient. The new resonator includes an integral e-beam profile diagnostics means installed on the safety shield. All e-beam diagnostics and tuning motors are remote controlled in a Lab View environment.
MOPPH038	Experimental and 3D Simulation Studies of the Spectral Characteristics of Electrostatic Accelerator FEL with Space Charge Dominated Transport
	A. Gover, M. Volshonok University of Tel-Aviv, Faculty of Engineering, Tel-Aviv Yu. Lurie CJS, Ariel
	One of the important properties of the FEL it is the ability to generate high power radiation within a wide frequency range. By varying the acceleration energy of the tandem electrostatic FEL in the range 1.3-1.44 MeV we tuned the FEL lasing radiation between 80GHz to 110GHz. The tuning range is limited by the resonator frequency dispersion one hand and the beam trajectories on the other hand. At low acceleration energies space charge effects make it difficult to keep the electron trajectories in the wiggler confined to the axis. Because of this and because of difficulty to keep optimal e-beam injection parameters into the wiggler, the oscillation threshold is reduced and the tuning range of the FEL is limited. The finite size of the e-beam inside the wiggler also has a reduction effect on the lasing frequency. The measured spectral tuning characteristics of the FEL matches well the results of FEL lasing 3-D simulation (with FEL3D). The electron trajectories and the beam transport were calculated with GPT simulations in the space charge dominated regime.
MOPPH039	Sideband Instability in a Compact THz Free-Electron Laser at KAERI
	P. Ahn, H. J. Cha, B. C. Lee, J. Mun, S. H. Park, Y. U. Jeong KAERI, Daejon G. M. Kazakevich Fermilab, Batavia, Illinois
	Frequency offset of a Sideband instability has been observed in a compact waveguide-mode terahertz (THz) free-electron laser (FEL). The spectra of the FEL pulses were measured by a Fabry-Perot spectrometer having a resolution of 10(-4) of the central wavelength at a 2-3 THz range. The shift of the sideband was measured to be 0.5-1.2 micrometers depending on the FEL wavelength from 110 to 165 micrometers. An increase of the sideband shift for a longer wavelength can be explained by the change of the wave’s group velocity in a plane-parallel waveguide. Mode competition between the sidebands and primary wave was observed by changing the cavity length of the FEL. We could decrease the number of the modes and reduce the linewidth of the spectra by controlling the cavity detuning. We have discussed the complexity of the sideband instability depending on the FEL wavelengths and its gain characteristics.
MOPPH040	A Study of Detection Schemes in Electro-Optic Sampling Technique	101
	J. Y. Huang, C. Kim, I. S. Ko, Y. W. Parc PAL, Pohang, Kyungbuk
	Electro-Optic Sampling (EOS) is the ingenious tool for the measurement of the electron beam or Thz radiation. There are two traditional detection schemes: one is the crossed polarizer scheme and another is balanced detection one. A new detection scheme called Near Crossed Polarizer scheme in the EOS technique is developed to increase the Signal to Noise Ratio in the experiment. The new detection scheme is studied in detail and the 3D scanning result with electron beam in FLASH is compared with the detection scheme. The new detection scheme has an analytical problem which shows two solutions for the relative phase shift for specific measurement of the electron beam. That problem is also studied through the comparative study between simulation and the analyzed data from the TEO setup in FLASH.
MOPPH041	Comparative Study of Electro-Optic Effect between Simulation and Measurement	104
	J. Y. Huang, C. Kim, I. S. Ko, Y. W. Parc PAL, Pohang, Kyungbuk
	The short, intense, and low emittance electron beams are crucial to make high quality X-ray beam for X-ray free electron laser (XFEL). Electro-Optic Sampling (EOS) is a promising method to measure the electron bunch length non-destructively. A simulation study is done with the pulse propagation method, which utilizes Fourier transform to investigate the evolution of electromagnetic pulse inside the electro-optic (EO) crystal. The experimental result measured with spatial decoding method at Free electron LASer in Hamburg (FLASH) facility in Deutsches Elektronen-Synchrotron (DESY) is analyzed in terms of the relative phase shift between the horizontal and vertical component of the laser pulse. In this report, the experimental results expressed in terms of the "Relative Phase Shift Г" are compared with the simulation result. The simulation and the experimental result show similar values within reasonable error. The way to increase the signal level is also proposed.
MOPPH042	Losses in Optical Resonator of Novosibirsk Terahertz Free Electron Laser: Theory and Experiment	107
	V. V. Kubarev BINP SB RAS, Novosibirsk
	Design of optical resonator of Novosibirsk terahertz free electron laser (NovoFEL)was made on base simple analitical theory discribed in paper. Direct comparison of the theory and many experiments on NovoFEL is presented. Kubarev V. V. Babinet principle and diffraction losses in laser resonators. Quantum Electronics 30(9)824-826(2000).
MOPPH043	Control and Diagnostic System of Novosibirsk FEL Radiation	111
	V. V. Kubarev, E. V. Makashov, K. S. Palagin, S. S. Serednyakov BINP SB RAS, Novosibirsk
	The architecture the main capabilities of control and diagnostic system of the Novosibirsk FEL coherent radiation are described. The client-server model is used for software, controlling this system. The developed software is capable to work both in client and server mode. Also it can control various equipment – from FEL optical cavity mirrors to local equipment of users stations. The mode of control program operation and controlled equipment are determinates by external configuration files. Some results of the system operation are also presented.
MOPPH044	Status of Novosibirsk ERL and FEL
	N. Gavrilov, B. A. Knyazev, E. I. Kolobanov, V. V. Kotenkov, V. V. Kubarev, G. N. Kulipanov, A. N. Matveenko, L. E. Medvedev, S. V. Miginsky, L. A. Mironenko, V. Ovchar, V. M. Popik, T. V. Salikova, M. A. Scheglov, S. S. Serednyakov, O. A. Shevchenko, A. N. Skrinsky, V. G. Tcheskidov, N. Vinokurov BINP SB RAS, Novosibirsk
	The Novosibirsk terahertz free electron laser is based on the energy recovery linac (ERL) with room-temperature radiofrequency system. Some features of the ERL are discussed. The results of emittance measurements and electron optics tests are presented. The first stage of Novosibirsk high power free electron laser (FEL) was commissioned in 2003. Now the FEL provides electromagnetic radiation in the wavelength range 110 - 230 micron. The average power is 400 W. The minimum measured linewidth is 0.3%, which is close to the Fourier-transform limit. Four user stations are in operation. The second stage of the ERL, which has four orbits, is under construction.
MOPPH045	Measurement of timing jitter based on HGHG FEL spectrum dynamics
	L.-H. Yu, T. V. Shaftan BNL, Upton, Long Island, New York
	We discuss impact of temporal shift between seed laser and electron beam on the HGHG FEL radiation spectrum. Following analysis of experimental data reveals basic properties of the time jitter in the accelerator-FEL driver at Source Development Lab (BNL).
MOPPH046	Operation of Near-infrared FEL at Nihon University	114
	A. Enomoto, S. Fukuda, K. Furukawa, S. Michizono, S. Ohsawa KEK, Ibaraki Y. Hayakawa, K. Nakao, K. Nogami, T. Tanaka, K. Hayakawa LEBRA, Funabashi M. Inagaki, T. Kuwada, T. Sakai, I. Sato Nihon University
	The near-infrared FEL at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been operated for a variety of scientific applications since 2003. The stability of the FEL power was improved appreciably by the advanced stability of the 125 MeV electron linac. Currently fundamental FEL wavelength ranges from 1 to 6 microns, which is restricted by the electron energy and the optical devices. The higher harmonics in the visible region is also available. The maximum macropulse output energy of 60 mJ/pulse has been obtained at a wavelength of 1725 nm. The short FEL resonator at LEBRA causes relatively high optical energy density on the surface of the resonator mirrors; present copper-based Ag mirrors in use at LEBRA are not durable enough for long term operation. As an alternative way of generating intense harmonics in the visible to near-UV region, second and third harmonic generation by means of non-linear optical devices has been tested for the FELs around 1.5 microns as input fundamental photons.
MOPPH047	Influence of Terahertz Electromagnetic Radiation on Neurons In-vitro
	V. M. Klementyev Institute of Laser Physics, SB RAS, Novosibirsk A. S. Kozlov, A. K. Petrov ICKC SB RAS, Novosibirsk T. A. Zapara, A. S. Ratushnyak Zapara, Novosibirsk
	Isolated neurons of mollusk in vitro at various stages of network neogenesis were studied earlier. The influence of submillimeter laser radiation (from 70 up to 418 mkm) it was investigated. 40-50 hours after laser irradiation (81.5 mkm) the formation of heterogeneities of the cell surface with the subsequent creation of arbitrarily directed process - like frames is observed in 12-15% of cells which were at the process shaping stage. In neurons which have formed processes, 15-20 hours after the exposition there is disturbance in the processes growth zones. The disturbance of formation of interneuron connections and thickening of processes terminations are observed. Similar alterations of cells are absent at smaller power density, exposition at other wavelengths, and in control neurons (without exposure). There is disturbance of cell adhesion to surface in 70-80% of neurons after irradiation at 418-mkm wavelength. Experiments on high power Novosibirsk teraherz free electron laser have shown influence of such radiation on functional characteristics alive neurons. The alterations observed can be the result of a modification of separate (possibly, individual) molecules of neuron regulation or structure-forming systems.
MOPPH072	The IR-Beam Transport System from the ELBE-FELs to the User Labs	171
	M. Justus, K.-W. Leege, D. Proehl, R. Schlenk, A. Winter, D. Wohlfarth, R. Wuensch, W. Seidel FZD, Dresden
	In the Forschungszentrum Dresden-Rossendorf, two free-electron lasers (FELs) have been put into operation. They produce laser light in the medium and the far infrared wavelength range (4-200 microns). The IR light is transported to several laboratories in the same building and to the adjacent building of the High Magnetic Field Laboratory (HLD) as well. The latter is up to 70m away from the FELs. Constructional peculiarities, the large wavelength range (a factor of 50 between the shortest and the longest wavelengths), the high average power in cw regime, and the beam property requirements of the users pose a challenge to the beam line design. The transport system includes vacuum pipes, plane and toroidal gold-covered copper mirrors, exit windows, and diagnostic elements. The designed transport system produces a beam waist at selected spots in each laboratory representing an image of the outcoupling hole. Spot size and position are independent of the wavelength. In the HLD the beam is fed into a circulare waveguide, guiding the radiation to the sample inside of a cryostat. To ensure the desired beam properties, the transport system has been analyzed by means of various ray and wave optical models.
THAAU01	Experience and Plans of the JLAB FEL Facility as a User Facility	491
	M. D. Shinn Jefferson Lab, Newport News, Virginia
	Jefferson Lab’s IR Upgrade FEL building was planned from the beginning to be a user facility, and includes an associated 600 sq. m area containing seven laboratories. The high average power capability (multikilowatt-level) in the near-infrared (1-3 microns), and many hundreds of watts at longer wavelengths, along with an ultrafast (~ 1 ps) high PRF (10’s MHz) temporal structure makes this laser a unique source for both applied and basic research. In addition to the FEL, we have a dedicated laboratory capable of delivering high power (many tens of watts) of broadband THz light. After commissioning the IR Upgrade, we once again began delivering beam to users in 2005. In this presentation, I will give an overview of the FEL facility and its current performance, lessons learned over the last two years, and a synopsis of current and future experiments.
	Slides
THAAU02	Operational Experience of FLASH
	B. Faatz, S. Schreiber DESY, Hamburg K. Honkavaara Uni HH, Hamburg
	Since summer 2005 the free electron laser FLASH at DESY is operating as a user facility. It produces 10 fs long laser like pulses from the vacuum ultraviolet to the soft X-ray wavelength range. Many successful user experiments have been carried out with this world wide unique facility. In this paper we report on operational issues of the facility.
	Slides
THAAU03	Experimental Study of Volume Free Electron Laser Using a "Grid" Photonic Crystal with Variable Period	496
	V. G. Baryshevsky, N. A. Belous, V. A. Evdokimov, A. Gurinovich, A. S. Lobko, A. V. Oskin, P. F. Safronov, P. V. Molchanov Belarussian State University, Scientific Research Institute of Nuclear Problems, Minsk
	Electrodynamical properties of a crystal-like artificial periodic structure (photonic crystal) formed by a periodically strained metallic threads were studied both theoretically and experimentally,. In the present paper operation of Volume Free Electron Laser using a "grid" photonic crystal with variable period is experimentally studied. Dependence of the generation threshold on photonic crystal length is investigated along with the frequency characteristics of generated radiation. Baryshevsky V. G. et al. NIM section B. Vol252 (2006) P.92-10¹ ** Baryshevsky V. G. et al. Proc. of the 28th FEL Conference PP.331-338
	Slides
THAAU05	Light Pulse Structure, Spectrum and Coherency of Novosibirsk Terahertz Free Electron Laser
	E. I. Kolobanov, V. V. Kotenkov, G. N. Kulipanov, A. N. Matveenko, L. E. Medvedev, V. K. Ovchar, K. S. Palagin, T. V. Salikova, M. A. Scheglov, S. S. Serednyakov, N. Vinokurov, V. V. Kubarev BINP SB RAS, Novosibirsk
	Light pulse structure and spectrum of Novosibirsk free electron laser were studied by direct independent methods. Super fast Schottky diode was used in time domain experiments. Method of vacuum Fourier spectroscopy was applied for spectral investigations. Observation of spectral stability of each light pulse was made by grating monochromator with Schottky diode. Influence of cogerency on harmonic powers is also shown.
	Slides