THz and Long Wavelength FELs
Paper Title Page
WEOC02
 Status of the KAERI Table-Top THz Free-Electron Laser Development  
 
  • Y.U. Jeong, S. Bae, B.H. Cha, B.A. Gudkov, K.H. Jang, K.N. Kim, K. Lee, S.V. Miginsky, J. Mun, S. H. Park, N. Vinokurov
    KAERI, Daejon, Republic of Korea
  • S. Park
    Kyungpook National University, Daegu, Republic of Korea
  
  Funding: This work was supported by the World Class Institute (WCI) Program of the NRF funded by the MEST (NRF Grant Number: WCI 2011-001).
Korea Atomic Energy Research Institute is under development of a table-top terahertz (THz) free electron laser (FEL) driven by a conventional microtron accelerator. The THz FEL is composed of a compact variable-period helical undulator and a cylindrical-waveguide resonator with a mesh outcoupling mirror to achieve a small scale. The target wavelength and average power of the system are 400-600 um and 1 W. The energy and peak current of the microtron is designed to be 6.5 MeV and 1 A. We fabricated a compact microtron accelerator including a thermionic RF gun, a magnetron and a modulator having a maximum repetition rate of 200 Hz. We fabricated a variable-period helical undulator having tunable periods of 23-26 mm while keeping the on-axis field strength of 1 T, and total length of 700-800 mm. A compact beamline with two 45-degree bending magnets and 6 permanent-magnet quadrupoles has been designed to transport optimal electron beams to the variable-period helical undulator. A cylindrical-waveguide resonator having a mesh outcoupling mirror and a full mirror with the function of beam dump will decrease the size of the FEL. The size of the FEL is expected to be 2.3 m x 1.6 m. 		 
slides icon Slides WEOC02 [6.856 MB]  
 
WEOC03 The Novosibirsk Terahertz FEL Facility - Current Status and Future Prospects 361
 
  • O.A. Shevchenko, V.S. Arbuzov, K.N. Chernov, E.N. Dementyev, B.A. Dovzhenko, Ya.V. Getmanov, E.I. Gorniker, B.A. Knyazev, E.I. Kolobanov, A.A. Kondakov, V.R. Kozak, E.V. Kozyrev, V.V. Kubarev, G.N. Kulipanov, E.A. Kuper, I.V. Kuptsov, G.Y. Kurkin, L.E. Medvedev, L.A. Mironenko, V.K. Ovchar, B.Z. Persov, A.M. Pilan, V.M. Popik, V.V. Repkov, T.V. Salikova, M.A. Scheglov, I.K. Sedlyarov, G.V. Serdobintsev, S.S. Serednyakov, A.N. Skrinsky, S.V. Tararyshkin, V.G. Tcheskidov, N. Vinokurov, M.G. Vlasenko, P. Vobly, V. Volkov
    BINP SB RAS, Novosibirsk, Russia
  
  The Novosibirsk terahertz FEL facility is based on the normal conducting CW energy recovery linac (ERL) with rather complicated lattice. This is the only multiorbit ERL in the world. It can operate in three different modes providing electron beam for three different FELs. The first FEL works for users since 2003. This FEL radiation is used by several groups of scientists which include biologists, chemists and physicists. Its maximum average and peak powers are 500 W and 1MW and wavelength can be tuned from 110 up to 240 microns. The high peak and average powers are used in experiments on material ablation and biological objects modification. The second FEL is installed on the second orbit. The first lasing of this FEL was achieved in 2009. Its radiation has almost the same average and peak powers and is delivered to the same user stations as the first FEL one, but its tunability range lies between 35 and 80 microns. The third FEL will be installed on the fourth orbit. In this paper we report the latest results obtained from the operating FELs as well as our progress with the commissioning of the two remaining ERL orbits. We also discuss possible options for the future upgrade.  
slides icon Slides WEOC03 [5.364 MB]  
 
WEOC04 Accelerator Beamline Performance for the IR FEL at the Fritz-Haber-Institut, Berlin 365
 
  • H. Bluem, D. Dowell, J.H. Park, A.M.M. Todd, L.M. Young
    AES, Princeton, New Jersey, USA
  • S. Gewinner, W. Schöllkopf
    FHI, Berlin, Germany
  • H. Loos
    SLAC, Menlo Park, California, USA
  
  An electron accelerator and beamline for an IR and THz FEL with a design wavelength range from 4 to 500 μm has been commissioned by Advanced Energy Systems at the Fritz-Haber-Institut (FHI) in Berlin, Germany, for applications in, i.a., molecular and cluster spectroscopy as well as surface science. The linac comprises two S-band standing-wave copper structures and was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (<50 keV-psec) and transverse emittance (<20 μm), at more than 200 pC bunch charge with aμpulse repetition rate of 1 GHz. First lasing was achieved February 2012. Operational experience and measured electron beam performance will be presented.  
slides icon Slides WEOC04 [12.785 MB]  
 
WEOCI01
 The Infrared and THz User Facility FELIX in Nijmegen  
 
  • G. Berden, B. Redlich
    FOM Rijnhuizen, Nieuwegein, The Netherlands
  • R.T. Jongma, F.J.P. Wijnen, A.F.G. van der Meer, W.J. van der Zande
    Radboud University, Nijmegen, The Netherlands
  
  The infrared and THz user facility FELIX at the Radboud University Nijmegen will comprise two free electron lasers - namely FLARE, the recently commissioned THz laser at Nijmegen, as well as the FELIX and FELICE laser beam lines, currently relocated from the FOM Institute to Nijmegen. The FELIX (Free Electron Lasers for Infrared eXperiments) facility will offer the international user community a unique wavelength range covering the mid- and far-infrared as well as the THz range from 3 to 1500 micron (3300 - 6 cm-1 or 100 THz - 0.2 THz). We will discuss the layout of this new facility including the user laboratories as well as some of the special features offered to the users including: (i) the FLARE high spectral resolution mode, (ii) the FELICE intra-cavity configuration for extreme infrared intensities and (iii) the connection of the facility with the adjacent high magnetic field laboratory (HFML). The timeline for the integration of the facility foresees a start of operation in the summer of 2013 and full operation is expected for the beginning of 2014.  
slides icon Slides WEOCI01 [3.952 MB]  
 
WEPD48 Development of Intense Terahertz-wave Coherent Synchrotron Radiations at LEBRA 480
 
  • N. Sei, H. Ogawa
    AIST, Tsukuba, Ibaraki, Japan
  • K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
    LEBRA, Funabashi, Japan
  
  Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696.
Nihon University and AIST have jointly developed intense terahertz-wave coherent synchrotron radiations at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. Because a bunch length is short and a charge is large in an electron beam of a linac to saturate free-electron laser (FEL) power, the electron beam of the linac in an FEL facility is suitable for generating intense coherent radiations generally. Therefore, we launched a development of a THz-wave source with using an upstream bending magnet located in the FEL beam line. Recently, Nihon University developed 'burst mode operation', in which two or three electron bunches were included at an interval of 22.4 or 44.8 ns [1]. The electric charge in the micropulse was high (several hundreds pC) in the burst mode, so generation and observation of the coherent synchrotron radiation became easy. We have already measured the intense THz-wave from LEBRA and confirmed it to be the coherent synchrotron radiation (CSR). It was also found that CSR might have serious influence on a high-energy electron beam. In the presentation, we will report the characteristics of the CSR at LEBRA.
E-mail address: sei.n@aist.go.jp
1. K. Nakao et al., Lasing of near infrared FEL with the burst-mode beam at LEBRA, Proceedings of FEL11, Shanghai, China, (2011). 		 
 
WEPD49 The Terahertz FEL Facility Project at CAEP 484
 
  • X. Yang, M. Li, Z. Xu
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  • Y.H. Dou, X.J. Shu
    Institute of Applied Physics and Computational Mathematics, People's Republic of China
  • W.-H. Huang
    TUB, Beijing, People's Republic of China
  • X.Y. Lu
    PKU, Beijing, People's Republic of China
  
  To meet the requirement of material and biomedicine study, a terahertz FEL user facility project was proposed by China Academy of Engineering Physics(CAEP), at present the project has been approved and the facility will be constructed within 5 years. The facility will operate in the quasi CW mode and the average power is about 10W. The wavelength of the light can be regulated between 100μm/3THz to 300μm/1THz according to the user necessary by changing the electron energy and the magnetic field of the wiggler. In order to achieve the high brightness beam, the photocathode DC gun will be used as the electron source. The electron energy after a superconducting accelerator is about 8MeV, which is suitable to obtain the terahertz light. The facility will be a useful tool to the science.  
 
WEPD51 The parameter study of terahertz Free-Electron Laser Oscillator based on Electrostatic Accelerator 488
 
  • A.L. Wu, Q.K. Jia
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • F.W. Wang, J. Wu
    SLAC, Menlo Park, California, USA
  
  Free-Electron Laser Oscillator based on Electrostatic Accelerator (EA-FELO) is one of the best methods to realize the powerful terahertz source, which can not only produce high power, but also obtain coherent and tunable wavelength. In this paper, we investigate the effects of the main parameters in this scheme, including the initial electron-beam energy spread, emittance and beam current. Besides, the influence of the radius of the mirrors and the position of the undulator on FEL performance is also studied. The numerical results from 1D FEL Oscillator simulation code FELO are presented, and show that this compact device could achieve the terahertz light with the peak output power is about 5.3kW.  
 
WEPD52 THz Radiation Sources based on RF-linac at Chiang Mai University 492
 
  • C. Thongbai, P. Boonpornprasert, S. Chunjarean, K. Kusoljariyakul, S. Rimjaem, J. Saisut, S. Suphakul
    Chiang Mai University, Chiang Mai, Thailand
  
  A THz radiation source in a form of coherent radiation from short electron bunches has been constructed at the Plasma and Beam Physics (PBP) research facility, Chiang Mai University. The accelerator system consists of an RF-gun with a thermionic cathode, an alpha-magnet as a magnetic bunch compressor, and a SLAC-type linear accelerator. Coherent transition radiation emitted from short electron bunches passing through an Al-vacuum interface was used as the THz radiation source. This THz radiation can be used as a source of the THz imaging system and THz spectroscopy. Details of the accelerator system and THz radiation production will be presented. A plan for extension to accommodate Free Electron Lasers (FEL) optimized for mid-infrared and far-infrared/THz radiation will also be discussed.  
 
WEPD53 Linac-based THz Imaging at Chiang Mai University 496
 
  • J. Saisut, S. Rimjaem
    Chiang Mai University, Chiang Mai, Thailand
  • P. Boonpornprasert, K. Kusoljariyakul, M.W. Rhodes, C. Thongbai
    ThEP Center, Commission on Higher Education, Bangkok, Thailand
  • P. Thamboon
    IST, Chiang Mai, Thailand
  
  Funding: the Thailand Center of Excellence in Physics (ThEP), the National Research Council of Thailand (NRCT) and the Thailand Research Fund (TRF)
At the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University, intense THz radiation is generated in a form of coherent transition radiation from femtosecond electron bunches. The THz radiation is used as a source of THz imaging system which was successfully setup and tested. The radiation is focused onto a sample which will be scanned using an xy-translation stage. The transmission or reflection at different points of the sample are recorded to construct a THz image. Details of the setup and the experimental results from the system will be presented. The THz imaging to accommodate a future IR-THz Free Electron Laser (FEL) will also be discussed. 		 
 
WEPD54 Characterization of Single-cycle THz Pulses at the CTR Source at FLASH 500
 
  • S. Wunderlich, S. Schefer, B. Schmidt, S. Schulz, S. Wesch
    DESY, Hamburg, Germany
  • M.C. Hoffmann
    SLAC, Menlo Park, California, USA
  
  At the coherent transition radiation source at the free-electron laser in Hamburg (FLASH) at DESY, single-cycle THz pulses with electric field strengths exceeding one MV/cm are generated. We present the temporal and spatial characterization of this source with the technique of electro-optic sampling using a laser system synchronized with the accelerator to better than 100 fs. This method offers a quantitative detection of the electric field of the THz pulses in the time domain. Compared to other electron-accelerator driven sources like undulator radiation, the transition radiation source provides pulses with a high bandwidth and durations shorter than one picosecond. This enables time-resolving and non-destructive experiments with radiation in the THz regime including THz pump / THz probe experiments. Broadband and intense THz pulses are expected to be valuable tools for the study of dynamics of excitation of complex materials in transient electric and magnetic fields.  
 
WEPD55 Tunable IR/THz Source for Pump Probe Experiments at the European XFEL 503
 
  • M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  We present a concept of an accelerator based source of powerful, coherent THz radiation for pump-probe experiments at the European XFEL. The electron accelerator is similar to that operating at the PITZ facility. It consists of rf gun and warm accelerating section (energy up to 30 MeV). The radiation is generated in a 5 meter long APPLE-type undulator with a period length of 4 cm, thus providing polarization control. Radiation with wavelength below 200 micrometers is generated using the mechanism of SASE FEL. Powerful coherent radiation with wavelength above 200 micrometers is generated in the undulator by a tailored (compressed) electron beam. Properties of the radiation are: wavelength range is 10 to 1000 micrometers (30 THz - 0.3 THz), radiation pulse energy is up to a few hundreds microjoles, peak power is 10 to 100 MW, spectrum bandwidth is 2 - 3%. It is important to note that the time structure of the THZ source ideally matches with the time structure of the x-ray pulses since the THZ source is based on the same technology as the injector of the European XFEL. A similar scheme can be also realized at LCLS, SACLA, or SWISS FEL with S-band rf accelerator technology.  
 
WEPD58 Emission of Coherent T-rays from Trains of Ultrashort Electron Pulses in a Pulsed Helical Undulator 507
 
  • W.K. Lau, M.C. Chou, J.-Y. Hwang, A.P. Lee
    NSRRC, Hsinchu, Taiwan
  • N.Y. Huang
    NTHU, Hsinchu, Taiwan
  
  Sub-100 fsec electron pulses are produced from the 30 MeV NSRRC thermionic rf gun injector by beam selection in the alpha magnet as well as velocity bunching in the rf linac. The coherent infrared radiation from a pulsed helical undulator driven by such high rep.-rate electron beam being investigated theoretically. Recent progress of the installation of the injector will also be presented.  
 
WEPD59 FLUTE, a Compact Accelerator-based Source for Coherent THz Radiation 511
 
  • S. Naknaimueang, E. Huttel, A.-S. Müller, M.J. Nasse, R. Rossmanith, M. Schuh, M. Schwarz
    KIT, Karlsruhe, Germany
  • M.T. Schmelling
    MPI-K, Heidelberg, Germany
  • P. Wesolowski
    FZK, Karlsruhe, Germany
  
  FLUTE is a test facility for a compact accelerator-based THz source in the final design phase at the Karlsruhe Institute of Technology (KIT) in cooperation with Paul Scherrer Institute (PSI), Switzerland. The design is based on a 7 MeV photo injector, an S-band linac with a maximum energy of 50 MeV and a bunch compressor. The machine will be operated in a wide range of bunch charges, from 10 pC up to 3 nC. The final bunch length after the compressor is dominated by space charge effect in the photo injector and the coherent synchrotron radiation (CSR) in the compressor. This paper gives an overview over the status of the project and presents results of simulations for the different operating regimes. In addition, THz spectra generated by different processes (CSR, coherent transition radiation and coherent edge radiation) for different, charge dependent, bunch shapes will be discussed.  
 
WEPD64 FEL Gain Measurement with a Novel Method 515
 
  • M. Fujimoto, A. Irizawa, G. Isoyama, F. Kamitsukasa, R. Kato, K. Kawase, H. Ohsumi, M. Yaguchi
    ISIR, Osaka, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • S. Yamamoto
    KEK, Tsukuba, Japan
  
  The FEL gain is an important factor characterizing performance of the FEL. We used to derive the gain of the THz-FEL at Osaka University from the macropulse shape measured using a Ge:Ga detector with the time resolution of ~10 ns. The method was recently found faulty because the response of the detector shows strong non-linearity in amplitude at a high intensity level. We, therefore, have developed a new method for the gain measurement using a silicon bolometer, which has a very high linearity over the wide intensity range. The detector has the time resolution of ~1 ms, which is much longer than the FEL macropulse of a few microseconds, so that it measures energy in the macropluse. In order to derive the temporal revolution of FEL power, the number of amplifications is varied by changing the macropulse length of the electron beam. The sensitivity of the detector is also high, so that we could measure the energy development of the FEL over 6~7 orders of magnitude at a wavelength ~100 micrometers in combination with appropriate absorbers. We will report results of the measurement and analysis of the FEL gain.  
 
WEPD65 Design and Numerical Simulation of THz-FEL Amplifier in Kyoto University 519
 
  • M. A. Bakr, Y.W. Choi, T. Kii, R. Kinjo, K. Masuda, H. Negm, H. Ohgaki, M. Omer, K. Shimahashi, K. Yoshida, H. Zen
    Kyoto University, Institute for Advanced Energy, Kyoto, Japan
  • M. A. Bakr
    Assiut University, Assiut, Egypt
  
  Design of a compact and economic THz free-electron laser (FEL) amplifier, which consists of a BNL-type 1.6 cells photocathode radio frequency gun, Solenoid, transport line and short undulator, has been studied at Kyoto University. The electron beam energy to obtain FEL with a wavelength of the range 150~400 μm was calculated to be 4.1~7.0 MeV for a bunch charge of 1.0 nC/bunch. The numerical calculations of the electron beam from the RF gun up to the undulator entrance are carried out using Parmela code and the FEL properties from the undulator will be simulated using GENESIS 1.3. The expected FEL spectral was estimated using 4~5 undulator periods with ~30 cm length and 0.3 T magnetic field. Details of the design concept, numerical calculations and results will be presented in the conference.  
 
WEPD66 Phase Space Manipulation with Laser-generated Terahertz Pulses 523
 
  • S.P. Jamison, B.D. Muratori, Y.M. Saveliev, R.J. Smith, T.T. Thakker
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • M.J. Cliffe, W.R. Flavell, D.M. Graham
    The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
  • D.J. Holder, D. Newton, A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
  
  Ultrafast lasers are able to generate THz pulses with >1MV/m field strengths, and with controllable electric field temporal profiles. We report on an experiment to demonstrate the use of laser generated THz pulses to manipulate the γ-z correlation of a  ∼  20MeV electron bunch on a sub picosecond time scale. The manipulation is achieved in free space, without external magnetic fields or undulators, by the interaction of the bunch with the longitudinal electric field of a co-propagating THz pulse in a TEM10*-like mode. We discuss the potential for arbitrary phase space control, including the possibility of correcting temporal jitter and driving electron beams into synchronisation with the laser.  
 
WEPD68 UCLA Seeded THz FEL Undulator Buncher Design 527
 
  • S.C. Gottschalk, R.N. Kelly
    STI, Washington, USA
  • C. Joshi, S. Tochitsky
    UCLA, Los Angeles, California, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  UCLA is planning to build a THz user facility. One is a seeded THz FEL tunable in the range of 0.5 - 3 THz or even 3-9 THz in an optical klystron configuration. Another* relies on microbunching at 340 micron using a 3.3 cm undulator or even driving the FEL with an electron beam from a laser-plasma accelerator. These FEL's make use of a 2.1m long pre-buncher, chicane and shorter, 110cm long radiator. Chicane requirements are modest. A round copper waveguide with 4.8mm ID will be used. We will describe the magnetic design and measured performance of the gap tunable undulators, mechanical design of the entire system, vacuum boxes, waveguides and expected operational approaches. Both undulators have 33mm periods and curved poles for two-plane focusing. Discussions will be included on issues associated with fabricating, sorting and shimming curved pole undulators. A new optimization method will be described that was used to meet magnetic requirements with a minimum volume of magnetic material.
*S. Tochitsky et al, "Seeded FEL Microbunching Experiments at the UCLA Neptune Laboratory", Advanced Accelerator Conference 2010