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TUC04 |
Image Charge Effect on Emittance Reduction Phenomenon in Electron Gun | |
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Development of next generation light sources requires reduction of beam emittance. The emittance can be influenced in the vicinity of a cathode, where electron energy is low and the beam dynamics is dominated by space charge and image charge effect. Recently it was discovered that for ideal DC acceleration emittance rises near cathode and subsequently decreases due to self-linearization force caused by space charge effect [*]. This phenomenon occurs for accelerating field, which is lower than usually applied at conventional electron guns. It is an issue that this concept is feasible for electron gun configuration of real injectors. In this research we numerically investigate the transverse emittance and its dependence on parameters such as current density, accelerating field and the distance from the cathode. As a result, the position of minimal emittance was found to be correlated to perveance. This position can be varied by proper settings of parameters. In this conference, we will present these phenomena seen numerically in the SCSS thermionic gun geometry.
* A. Mizuno, et al., Nucl. Instr. Meth. Phys. Res. A 774 (2015) 51-59. |
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Slides TUC04 [1.604 MB] | |
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| WEP010 | Development of Phonon Dynamics Measurement System by MIR-FEL and Pico-second Laser | 615 |
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| Coherent control of a lattice vibration in bulk solid (mode-selective phonon excitation: MSPE) is one of the attractive methods in the solid state physics because it becomes a powerful tool for the study of ultrafast lattice dynamics (e.g. electron-phonon interaction and phonon-phonon interaction). Not only for that, MSPE can control electronic, magnetic, and structural phases of materials. In 2013, we have directly demonstrated MSPE of a bulk material with MIR-FEL (KU-FEL) by anti-Stokes Raman scattering spectroscopy. For the next step, we are starting a phonon dynamics measurement to investigate the difference of physical property between thermally excited phonon (phonon of equilibrium state) and optically excited phonon (phonon of non-equilibrium state) by time-resolved method in combination with a pico-second VIS laser. By using pico-second laser, we also expect to perform the anti-Stokes hyper-Raman scattering spectroscopy to extend MSPE method to the phonon mode which has Raman inactive . As the first step, we have commissioned the time-resolved phonon measurement system and started measurement on 6H-SiC. In this conference, we will present the outline of measurement system, and experimental results. | ||
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