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Title |
Page |
| MOPPH041 |
Development of THz Light Source Using Pre-Bunched FEL
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71 |
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- M. Yasuda, H. Hama, F. Hinode, K. Kasamsook, M. Kawai, A. Kurihara, K. Nanbu, Y. Shibasaki, S. Takahashi
Tohoku University, School of Scinece, Sendai
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A project of pre-bunched FEL as a Terahertz (THz) light source using short electron bunch less than 100 fs has been progressed at Laboratory of Nuclear Science, Tohoku University. We expect that FEL with shorter electron beam (comparing with FEL wavelength) may generate shorter light pulse than conventional FEL with longer electron beam. By choosing an appropriate initial electron phase, the FEL gain will be higher. Since seed light of coherent synchrotron radiation is added in each round trip, the FEL will be saturated quickly so that long macro pulse won’t be required. In order to produce very short electron bunch around 100 fs, we have been developing an independently-tunable-cells (ITC) RF gun with a small thermionic cathode and a bunch compressor employing α magnet. We have made a numerical simulation code based on 1-D FEL equations. This code can calculate interaction between short the electron bunch and the FEL field. We will report on characteristics such as a time structure and spectrum of pre-bunched FEL resulted from the simulations.
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| TUPPH026 |
Emittance Measurement of a DC Gun for Smith-Purcell Backward Wave Oscillator FEL
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294 |
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- K. Kasamsook, H. Hama, F. Hinode, M. Kawai, K. Nanbu, M. Yasuda
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). From numerical simulation usings a 3-D finite deference time domain (FDTD) method, it has been found the BWO FEL oscillation at the terahertz wavelength region maybe achieved by using the electron beam with a normalized emittance around 1 mmmrad. A double-slit method has been employed to measure the phase space distribution of the beam. By applying special bias voltage between the cathode and the wehnelt, the equi-potential surface around the cathode, which is very crucial for emittance growth, is able to be manipulated. We have observed the change of the phase space distribution due to the bias voltage. Applying an appropriate bias voltage, the normalized emittance has been deduced to be less than 1 mmmrad. The paper will present the emittance measurements of the beam from the DC gun and the status of the terahertz BWO FEL project as well.
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| TUPPH029 |
Space Charge Effect for Short Electron Bunches in an Alpha Magnet
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305 |
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- H. Hama, F. Hinode, K. Kasamsook, M. Kawai, K. Nanbu, M. Yasuda
Tohoku University, School of Scinece, Sendai
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To develop a coherent Terahertz (THz) light source, a project for producing very short electron bunch has been progressed at Laboratory of Nuclear Science, Tohoku University. We have developed an independently-tunable-cells (ITC) RF gun consisted with two cavities and thermionic cathode in order to produce bunch length of several tens femto-second. Though the alpha magnet has been often used for the bunch compressor, beam dynamics including the space charge effect has been not well studied. To evaluate the both longitudinal and transverse phase space of the short electron bunch, we have developed a simulation code employing a 3-D finite deference time domain (FDTD) method for solving the Maxwell’s equations. From the simulations it was found out that the field strength of the alpha magnet should be considerably increased as increasing the bunch charge to obtain the shortest bunch length. The transverse emittance is also significantly growing up. The paper will describe characteristics of the beam quality after passing through the alpha magnet.
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