BINP SB RAS, Novosibirsk
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
The first stage of Novosibirsk high power free electron laser (FEL) provides electromagnetic radiation in the wavelength range 120 - 230 micron. The maximum average power is 500 W. Five user stations are in operation now. Novosibirsk ERL has rather complicated magnetic system. One orbit for 11-MeV energy with terahertz FEL lies in vertical plane. Other four orbits lie in the horizontal plane. The beam is directed to these orbits by switching on of two round magnets. In this case electrons pass four times through accelerating RF cavities, obtaining 40-MeV energy. Then, (at fourth orbit) the beam is used in FEL, and then is decelerated four times. At the second orbit (20 MeV) we have bypass with third FEL. Last year two of four horizontal orbits are assembled and commissioned. The electron beam was accelerated twice and then decelerated down to low injection energy. First multi-orbit ERL operation was demonstrated successfully. In 2009 the first lasing at the second FEL, installed on the bypass of the second track, was achieved. The wavelength tunability range lays near 50 micron. Energy recovery of a high energy spread used electron beam was optimized.
SAIC, McLean
JLAB, Newport News, Virginia
Mesa+, Enschede
We describe a procedure for the simulation of free-electron laser oscillators. The simulation uses a combination of the MEDUSA simulation code for the FEL and the OPC code to model the resonator. The simulations are compared with recent observations of the oscillator at the Thomas Jefferson National Accelerator Facility and are in substantial agreement with the experiment.
CAEP/IAE, Mianyang, Sichuan
IAP, Beijing
After the first lasing in March 2005 in CAEP, the FEL-THz facility is updated ,the former thermionic cathode injector was replaced using a high brightness photo-cathode injector. The facility mainly consists of a 4.5cells photo-cathode RF-GUN injector ,a hybrid undulator and the optical oscillator cavity. Number of undulator periods is 44, the peak value of the undulator is 4900Gs ,the good aperture is 6mm .The cathode material is Cs2Te and the quadruple light is used , the width of the driving laser is 12ps， the quantum efficiency is about 1%. The commissioning of the injector is finished, the electron energy of the injector was measured and it is about 8MeV ,the energy spread is about 1% and the electron beam normalized emittance is about 9πmm.mrad. The charge is about 100pC and up to 1nC per micro-pulse , the repetition rate is 54.167MHz .The calculated wavelength of the light is about 125micron. At present ,the spontaneous emission experiment is undertaking .
IAP/RAS, Nizhny Novgorod
BINP SB RAS, Novosibirsk
USTRAT/SUPA, Glasgow
IHEP Protvino, Protvino, Moscow Region
FZ Karlsruhe, Karlsruhe
For intense oversize relativistic electron beams with sheet and annular geometry the use of two-dimensional (2D) distributed feedback is beneficial for providing spatial coherence of the radiation and increasing the total radiation power [1]. Such feedback can be realized in planar and co-axial 2D Bragg resonators having double-periodic corrugations of the metallic side walls. High selectivity of such resonators has been demonstrated for large Fresnel parameters in the frame of coupled-wave model and in direct 3D simulations. Results of theoretical analysis are validated by data obtained in “cold” microwave measurements. Modeling of nonlinear dynamics of FEL with 2D distributed feedback also demonstrates advantages of novel feedback mechanism for production of spatial coherent radiation from large size electron beams. Simulation results are confirmed by recent experimental results where narrow frequency radiation was obtained at Ka-band co-axial and W-band planar 2D Bragg FELs which were realized at Strathclyde University [2] and Budker INP [3]. To advance 2D Bragg FEL in terahertz band the methods for extension of microwave systems over second transverse coordinate are discussed.
[1] N.S. Ginzburg, et al, Opt. Comm., 1993, v.96, p.254.
[2] I.V. Konoplev, et al, PRL, 2006, v.96, p.035002.
[3] A.V. Arzhannikov, et al, JETF Lett., 2008, v.87, p.715.