| Paper |
Title |
Page |
| WEPCH172 |
Electron Beam Pulse Processing toward the Intensity Modified Radiation Therapy (IMRT)
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2334 |
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- T. Kondoh, S. Tagawa, J. Yang, Y. Yoshida
ISIR, Osaka
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Radiation therapy attracts attention as one of the cancer therapies nowadays. Toward the next generation of the intensity modified radiation therapy (IMRT), the processing of electron beam pulse is studied using a photo cathode RF gun linac. Accelerated electron pulses will be converted to x-ray pulses by a metal target bremsstrahlung method or by a laser inverse Compton scattering method. Recently, the radiation therapy of cancer is developing to un-uniform irradiation as IMRT. A photo cathode RF gun is able to generate a low emittance electron beam pulse using a laser light pulse. We thought that a photo cathode RF gun can generate intensity and shape modified electron beam by processing of incident laser light. Because of a low emittance, an electron pulse is able to accelerate keeping shape. Electron beam processing by photo masks in incident optical system and generated beams are reported here. Images on photo masks were transported to a cathode surface by optical relay imaging. Beams were monitored by Desmarquest (Cr:Al2O3) luminescence. Spatially separation of a spot to a spot is about 0.3mm. Modified electron beam has fine spatial resolution.
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| WEPLS054 |
Higher-order Effect Compensation in Magnetic Compressor for < 50 fs Electron Bunch Generation
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2502 |
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- K. Kan, T. Kondoh, J. Yang, Y. Yoshida
ISIR, Osaka
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An ultrashort electron bunch is essential for pulse radiolysis, which is a pump-probe measurement based on an ultrashort electron beam and an ultrashort light. In Osaka University, a laser photocathode electron linear accelerator with a magnetic compressor has been constructed for the femtosecond electron bunch generation. An electron beam with bunch length of 98 fs was successfully generated and used in pulse radiolysis. However, an electron beam with bunch length of < 50 fs is required for development of pulse radiolysis with time resolution of 100 fs. To generate such a short bunch, higher order disadvantage effects, which are caused by the fringing fields of the magnets in the compressor, should be compensated. In this paper, a compensation technique of higher-order effects was proposed by using a nonlinear energy modulation in the bunch produced in the linear accelerator by re-phasing the linac away from the zero-crossing of the rf (i.e., away from the linear slope). In the simulation, we compressed the electron bunch into 48 fs at bunch charge of 0.1 nC.
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| WEPLS055 |
Development of Double-decker Electron Beam Accelerator for Femto/attosecond Pulse Radiolysis
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2505 |
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- Y.K. Kuroda, T. Kondoh, J. Yang, Y. Yoshida
ISIR, Osaka
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The study of electron-induced reactions in femto/attosecond time region is very important for the next electron beam nanofabrication. Pulse radiolysis with time resolution of sub-picosecond, as a powerful method to study such reactions in materials, has been developed by using radio-frequency electron accelerators and ultrashort lasers. In Osaka University, a new concept of double-decker electron beam accelerator is proposed for opening next pulse radiolysis on femto/attosecond time scale. The double electron beams with time delay of 1.4ns (350ps x 4) and bunch charge of 0.5-0.6 nC were generated in a photocathode electron accelerator by injecting two laser pulses into the photocathode. The beam energy of the two beams was 31.7MeV. The transverse normalized emittance was 3~6 mm-mrad for both the beams. The front of them is converted to Cherenkov light and used as a probe light source, and the back is used as a pump source. Both electron pulses are generated by one accelerator, resulting in no time jitter between the pump electron bunch and the probe laser pulse.
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| WEPLS057 |
Equivalent Velocity Spectroscopy Based on Femtosecond Electron Beam Accelerator
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2511 |
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- S. Takemoto, T. Kondoh, J. Yang, Y. Yoshida
ISIR, Osaka
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A new femtosecond pulse radiolysis system, which is called as "Equivalent Velocity Spectroscopy (EVS)" based on a photocathode rf linear accelerator and a femtosecond laser, is developed in ISIR for the study of primly process and ultrafast electron-induced reactions for the nanofabrication. In order to achieve a high time resolution on femtosecond scale, a femtosecond electron beam bunch produced by a photocathode accelerator and a synchronized femtosecond laser were used. The electron bunch and laser pulse were injected with an angle determined by the refractive index of the sample. The electron bunch was also rotated with a same angle, resulting in the time resolution degradation due to the velocity difference between light and the electron in the sample is thus avoided. A jitter compensation technique with a femtosecond streak camera was used to reduce the time jitter between the electron bunch and laser pulse. Moreover, in EVS, a technique of double laser pulse injection was used to improve the signal to noise ratio due to the fluctuation of the laser intensity during the measurement.
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| WEPLS058 |
Femtosecond Single-bunch Electron Linear Accelerator Based on a Photocathode RF Gun
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2514 |
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- J. Yang, K. Kan, T. Kondoh, A. Yoshida, Y. Yoshida
ISIR, Osaka
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A femtosecond single-bunch electron linear accelerator based on a photocathode rf gun was developed in Osaka University for the study of radiation-induced ultrafast physical and chemical reactions. A 32 MeV single electron bunch with a bunch length of 98 fs in rms was generated successfully in the linear accelerator with a magnet bunch compressor. The dependences of the bunch length and the transverse emittance on the bunch charge were investigated experimentally and theoretically. The higher-order effects in the magnetic field were studied and compensated successfully by using a nonlinear energy-phase correlation in the bunch produced in the linear accelerator. By using the femtosecond electron bunch, an equivalent velocity spectroscopy with a synchronized femtosecond laser, as a new method with femtosecond time-resolution, was developed for study of the ultrafast reactions or phenomena on the femtosecond time scale.
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