| Paper |
Title |
Page |
| MOPPH046 |
Operation of Near-infrared FEL at Nihon University
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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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| WEPPH052 |
In-situ Undulator Field Measurement with the SAFALI System
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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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| WEPPH031 |
Development of A Low Emittance DC Gun for Smith-Purcell BWO FEL
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417 |
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- K. Akiyama, H. Hama, F. Hinode, M. Kawai, T. Muto, K. Nanbu, T. Tanaka, M. Yasuda, K. Kasamsook
Tohoku University, School of Scinece, Sendai
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An electron DC gun capable for producing very low emittance beam is under developed at Laboratory of Nuclear Science, Tohoku University. The DC gun employs a high voltage of 50 kV to extract electrons, which is suitable to drive Smith-Purcell backward wave oscillator free electron laser (BWO FEL). A result of numerical simulation using a 3-D finite deference time domain (FDTD) method shows the BWO FEL oscillation at the terahertz wavelength region maybe achieved by using the electron beam with an emittance around 0.1 mmmrad. Average power is expected to be more than 100 W per square mm. In addition to which a very small cathode of LaB6 single crystal is employed for the gun, the geometrical structure is optimized to produce the lower emittance beam. A numerical calculation of the elctro-static model for the DC gun to solve equilibrated beam envelope predicts a normalized beam emittance of 0.2 mmmrad will be realized at the beam current of a couple of hundreds mA. Particularly by applying special bias voltage between the cathode and the wehnelt, the transverse distribution of electrons is possibly becoming to be an ideal Kapchinskij-Vladimirskij (K-V) beam, so that the space charge effect will be minimized. The paper will present the status of the development of the low emittance DC gun and various simulation result of the terahertz BWO FEL oscillation.
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| WEPPH054 |
Coherent THz Light Source Using Very Short Electron Bunches from a Thermionic RF Gun
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476 |
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- K. Akiyama, H. Hama, F. Hinode, K. Kasamsook, M. Kawai, K. Nanbu, T. Tanaka, M. Yasuda, T. Muto
Tohoku University, School of Scinece, Sendai
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To develop a narrowband coherent Terahertz (THz) light source, a project for producing very short electron bunch has been progressed at Laboratory of Nuclear Science, Tohoku University. Coherent synchrotron radiation is another promising source for generation of high-power THz light. Passing through a conventional undulator with a field period length of ~ 10 cm, the very short electron bunch at the energy around 15 MeV can produce coherent THz radiation. The electron beams of which the bunch length is less than 100 femto-second will be generated by a combined injector system of a thermionic RF gun and a bunch compressor. We have developed an independently-tunable-cells (ITC) RF gun consisted with two uncoupled cavities in order to manipulate the longitudinal phase space. It was found out that the ITC-RF gun is possibly quite suitable to produce such a very short bunch employing a magnetic bunch compressor. In theoretical investigation at the moment, a bunch length of less than 50 fs has been achieved in the numerical tracking simulation. Employing Lienard-Weichert potential, we have performed a 3-D simulation of the coherent THz radiation. The paper will describes the latest status of development of the ITC RF gun and tracking simulations for the bunch compressor as well. Characteristics of the coherent THz radiation resulted from the simulation will be also reported
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