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Title |
Other Keywords |
Page |
| MOPPH019 |
Optimized Designs for CAEP IR Free-electron Laser
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simulation, free-electron-laser, laser, electron |
58 |
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- Y. H. Dou, X. J. Shu
IAP, Beijing
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The characteristics of CAEP IR free-electron laser are estimated and the optimized designs of the resonator parameters such as radius of output hole, the size of mirror, the resonator length is carried out using our 3D FEL oscillator code. Based on the appropriate parameters, the saturated power, output power, gain and construction of optical modes are calculated.
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| MOPPH020 |
FEL with Orotron Type Feedback
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electron, radiation, feedback, undulator |
61 |
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- R. Ando, K. Kamada
Kanazawa University, Kanazawa
- N. S. Ginzburg, N. Yu. Peskov, R. M. Rozental, A. Sergeev, V. Yu. Zaslavsky, A. Malkin
IAP/RAS, Nizhny Novgorod
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In microwave electronics orotron is widely used as a source of RF radiation in millimeter and submillimeter wavebands. In this device an electron beam is coupled to a mode of quasi-optical resonator by means of the periodical grating one of the resonator mirror. In our paper we discuss a relativistic modification of such a device. A novel FEL scheme is suggested in which the slow wave structure of orotron is replaced by shallow Bragg corrugation which provides the coupling of the transverse (with respect to direction of beam propagation) mode of a two-mirror cavity with longitudinally propagating wave. The latter can be excited by the electron beam wiggling in undulator field. Described scheme allows to combine selective properties of an orotron with relativistic frequency conversion of a free electron laser. The transverse mode provides the feedback in the system thus leading to self-excitation, while the propagating wave is responsible for energy extraction in the steady-state regime of operation. The discussed system was investigated both analytically and numerically using direct codes and averaged equations approach.
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| MOPPH022 |
A Description of Guided FEL Radiation Using Dielectric Waveguide Eigenmodes
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radiation, undulator, electron, bunching |
65 |
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| MOPPH042 |
Losses in Optical Resonator of Novosibirsk Terahertz Free Electron Laser: Theory and Experiment
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laser, electron, free-electron-laser, radiation |
107 |
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| MOPPH046 |
Operation of Near-infrared FEL at Nihon University
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electron, linac, undulator, klystron |
114 |
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- 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
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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.
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| TUPPH002 |
High Order Mode Analyses for the Rossendorf SRF Gun
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gun, emittance, resonance, focusing |
228 |
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- D. Janssen
FZD, Dresden
- V. Volkov
BINP SB RAS, Novosibirsk
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High Order Modes (HOM) excited by the beam in a superconducting RF gun (SRF gun) could destroy the quality of the electron beam. This problem is studied on the base of frequency domain description by considering of the equivalent RLC circuit contour for each HOM, periodical excited by a pulsed current source. Expression for the voltage, the field amplitude and the phase of the excited HOM has been obtained. The equations for the coupling impedances of monopole TM-HOM and TE-HOM in the RF gun cavity has been derived. In this calculation the change of the particle velocity due to acceleration is taken into account. Resonance frequencies, coupling impedances, unloaded and external quality factors, excitation voltages and field distributions for each HOM including trapped HOM are calculated for Rossendorf SRF gun up to the frequency of 7.5 GHz, using the complex field solver CLANS. The dependence of the calculated parameters from a cavity deformation has been studied. The influence of the seven most dangerous HOM on the beam quality has been estimated by particle tracking using the ASTRA code.
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| WEPPH019 |
Determination of the Wakefield Budget for the FERMI FEL Undulator System
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vacuum, undulator, impedance, electron |
374 |
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- C. Bontoiu, P. Craievich, L. Rumiz
ELETTRA, Basovizza, Trieste
- M. Castronovo
Università degli Studi di Trieste, Trieste
- R. Vescovo, A. A.G. Lutman
DEEI, Trieste
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The FERMI project aims to achieve very high-brightness photon beam pulses of minimum bandwidth. These goals can be marred by the presence of large wakefields generated along the length of the undulator small-gap vacuum chamber. Estimations of the induced energy-spread caused by the resistive wall and surface roughness wakefields along the length of the vacuum chamber of the FERMI FEL undulator are presented. The energy spread and losses induced by the resistive wall wakefield are determined for three possible transverse geometries of the vacuum chamber, namely circular, rectangular and elliptical cross-section, while the energy spread and losses induced by the surface roughness wakefields are obtained for the circular cross-section case. In this last case in-house surface profile measurements are used to provide realistic estimates.
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| WEPPH026 |
Design Study of the Triode-Type Thermionic RF Gun
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cathode, gun, electron, emittance |
398 |
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- K. Kanno, E. Tanabe
AET Japan, Inc., Kawasaki-City
- T. Kii, K. Masuda, H. Ohgaki, S. Sasaki, H. Zen, T. Shiiyama
Kyoto IAE, Kyoto
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We use a 4.5-cell RF gun with a thermionic cathode as the injector for our KU-FEL facility, having taken its advantageous features compared with photocathode guns, such as high averaged current, low cost and easy operation, while we suffer from the limited macro-pulse duration and peak current by the back-bombardment effect. To mitigate these adverse effects, we proposed the triode-type thermionic RF gun with an additional small cavity providing the accelerating phase nearby the cathode independent of the main cavity phase*. Results from PIC simulations show that the back-bombardment power can be reduced drastically by more than 80%, and in addition the peak current of the output electron beam will be improved greatly by supplying a moderate RF power of tens kW to the RF triode structure. The RF system of up to 100 kW capabilities has been prepared and tested. Also the prototype design of the triode-type thermionic RF gun was completed. The cavity parameters, namely the quality factor, shunt impedance, and the coupling coefficient with the RF feed coaxial cable were designed taking into account both the available maximum field on the cathode and the phase and amplitude stability against the expected variations of the beam loading and cavity temperature. We will also present PIC simulation prediction on the output beam characteristics promising the first FEL lasing.
* K. Masuda, et al., Proceedings of the 2006 FEL conference, (2006)
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| WEPPH041 |
7th Harmonic Buncher Experiment at Neptune Laboratory
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laser, undulator, electron, bunching |
441 |
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- R. Tikhoplav, S. Tochitsky, P. Musumeci
UCLA, Los Angeles, California
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Since typically FEL undulator magnets have period length in the cm range, and the normalized magnetic field strength K is maintained close to unity to guarantee a good coupling, a very high energy electron beam is needed to access the far UV and x-ray region of the electromagnetic spectrum. One way to reduce the beam energy necessary for short wavelength light sources consists of exploiting the FEL harmonic interaction. An experiment aimed at demonstrating the efficiency of harmonically coupled schemes is proposed for the Neptune Laboratory at UCLA. We plan to inject the 12.4 MeV beam from the split photoinjector in an already available undulator with period = 3.3 cm and K = 1.8. The FEL resonant wavelength with these parameters is 74.2 um. A copropagating high power 10.6 um CO2 laser bunches the beam via 7th harmonic FEL/IFEL interaction. Preliminary calculations show that even though the interaction is weakened by the high harmonic number, it is required to use only 5 -10 MW of power in order to induce full bunching on the beam in the 10 period long undulator.
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| WEPPH043 |
The UCSB MM-FEL Injection Locking System
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injection, laser, free-electron-laser, electron |
445 |
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| THBAU04 |
Millimeter Waves Sensing Behind Walls - Feasibility Study with FEL Radiation
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radiation, polarization, controls, survey |
501 |
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- M. Einat, M. Kanter, B. Litvak, A. Yahalom, B. Yu. Kapilevich
CJS, Ariel
- A. Gover
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
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The existing through-wall imaging (TWI) systems operate in 1 – 10 GHz, basically, in order to reduce an attenuation caused by building material. However, the spatial resolution is drastically degraded when the operating frequency is relatively low. On the other hand, a majority of building materials demonstrate increased losses as the frequency increases. As a result, higher RF power from the source is required. The Israeli mm-wave FEL provides unique opportunity to solve the above TWI problem permitting to deliver output power 100-1000W at 85-105 GHz. Design of TWI system operating on mm-waves needs comprehensive study of constitutive parameters of different building materials. This paper describes systematic measurements of effective attenuation constant of typical building materials such as concrete bricks, wood, tiles, sand, gypsum, etc. on mm-waves using powerful FEL radiation. Since the Rayleigh criterion for surface roughness cannot be satisfied for some of measured materials, scattering and depolarization effects lead to increasing measured attenuation in comparison with bulky material. Additional experiments were performed to estimate a contribution of these effects into the measured attenuation.
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Slides
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