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| MOPPH020 |
FEL with Orotron Type Feedback
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electron, coupling, radiation, 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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| MOPPH025 |
Three-dimensional Theory of the Cerenkov Free-Electron Laser
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electron, laser, free-electron-laser, radiation |
73 |
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- C. A. Brau, H. L. Andrews
Vanderbilt University, Nashville, Tennessee
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We present an analytical theory for the operation of a Cerenkov free-electron laser which includes diffraction of the optical mode in the direction transverse to the electron beam. Because the width of the optical mode depends on the gain, the usual cubic dispersion relation is replaced by a 5/2-power dispersion relation, however, only two of these roots are allowed. These two roots both have positive real parts, indicating that they are slow waves. For a narrow electron beam, the optical mode is much wider than the beam, thus reducing the gain by an order of magnitude from that predicted by the two dimensional theory. In the limit of a wide electron beam, the two dimensional theory is recovered.
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| MOPPH060 |
The Drive Laser System for CFEL
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laser, electron, gun, radio-frequency |
146 |
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- Y. C. Chen, W. Li
CAEP/IAE, Mianyang, Sichuan
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A reliable and compact drive system is one of the key components for the stable operation of FEL. We have developed a solid-state drive laser system to meet the requirements of the CFEL(CAEP FEL) research. The system consisted of a passive mode-locked oscillator with a timing stabilizer,a regenerative amplifier and a frequency conversion part. After the 4-th harmonics,the duration of 15 picoseconds Gaussian pulses with wavelength 266nm at a repetition rate 54.17MHz were obtained. These micropulses were contained within a macropulses envelope as long as 1 to 6μmicroseconds,which was emitted from the drive laser at a repetition rate at 3Hz,6Hz or 12Hz,one single micropulse energy as large as 4μmicroJoules was achieved. The design specifications, configuration and diode-pumped amplifier of the drive laser system are also described.
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| MOCAU01 |
Short Wavelength Regenerative Amplifier FELs
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simulation, electron, radiation, undulator |
182 |
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- D. J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- B. W.J. McNeil
USTRAT/SUPA, Glasgow
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In this paper we discuss the possibility of extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand.
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Slides
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| TUBAU01 |
FLASH Upgraded - Preparing for the European XFEL
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laser, electron, radiation, photon |
211 |
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- H. Schlarb
DESY, Hamburg
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Since 2005, the Free electron LASer in Hamburg, FLASH, has delivered a high brilliance photon beam to users in a wavelength range between 13 nm and 40 nm. To meet the user demands for 4 nm wavelengths, sub-50fs timing stability, and better pointing stability, the accelerator will be continuously upgraded within the next few years. The upgrade to an energy of 1.3 GeV, the transverse and longitudinal intra-train feedback system, and a 3rd harmonic cavity at 3.9 GHz are key prototype tests for the European XFEL. FLASH also serves as a test bench for an entirely new approach to accelerator facility synchronisation involving optical pulses distributed in length stabilized fibres. Increased stabilization of the electron beam peak current and its arrival time should provide the possibility to reliably seed the electron bunch with higher laser harmonics. In this paper, an overview of the planned upgrade for FLASH will be presented with respect to its usefulness for the European XFEL. The status of the XFEL project will also be briefly summarized.
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Slides
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| WEPPH033 |
Stabilization of a Klystron Voltage at 100 PPM Level for PAL XFEL
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controls, target, power-supply, klystron |
424 |
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- S. D. Jang, S. J. Kwon, Y. G. Son, J.-H. Suh, J.-S. Oh
PAL, Pohang, Kyungbuk
- E. H. Song
CNU, Changwon
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The PAL XFEL needs a stable electron beam. The stable charging of PFN (pulse forming network) of a klystron-modulator is essential to provide the stable acceleration field for an electron beam. For PAL XFEL, stabilization of klystron voltage pulses at 100 PPM level is required. Short-term stability is determined by a minimum resolution of a charging system. Long-term stability is determined by a thermal stability due to the temperature drift. This paper shows details of hardware R&D and test results to achieve the target stability.
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| WEPPH052 |
In-situ Undulator Field Measurement with the SAFALI System
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undulator, laser, vacuum, electron |
468 |
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- H. Kitamura, T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- T. Seike
JASRI/SPring-8, Hyogo-ken
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Although the in-vacuum undulators (IVUs) have many advantages over out-vacuum undulators, magnetic measurement after assembling vacuum components, i.e., final verification of magnetic performance, is not an easy task. In addition, remeasurement after installation in the accelerator beamline is not trivial. The situation is more severe for cryogenic permanent magnet undulators (CPMUs), an extension of IVUs. We have recently developed a magnetic measurement system to measure the field inside the vacuum chamber. With optical laser beams introduced into the vacuum chamber, the alignment of the Hall probe positions is dynamically carried out, which ensures a high stability and accuracy of the measurement. This system is called SAFALI for Self-Aligned Field Analyzer with Laser Instrumentation. The SAFALI system has been applied to field measurement of two different undulators. One is an IVU installed in Swiss Light Source in 2001 and had been operated for about 3 years. The other is a CPMU prototype to demonstrate the principle of CPMU. The purpose of the measurement of the former is to investigate the radiation damage during operation, while that of the latter is to check the performance variation according to the temperature change of magnets. In the conference, details of the SAFALI system are given together with the results of the field measurements.
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| THAAU03 |
Experimental Study of Volume Free Electron Laser Using a "Grid" Photonic Crystal with Variable Period
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electron, radiation, free-electron-laser, laser |
496 |
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- 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
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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
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