| Paper | Title | Page |
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| TUPEC010 | Development of a Thermionic RF Gun for Coherent THz Source at Tohoku University | 1731 |
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A test accelerator for the coherent terahertz source (t-ACTS) has been under development at Laboratory of Nuclear Science, Tohoku University*. Intense coherent terahertz radiation will be generated by the very short electron bunch less than 100 fs using a thermionic RF gun (ITC RF-gun). ITC RF-gun is designed to have two cells uncoupled with each other, so that it can be operated at various combinations of different rf-power level and phase difference so as to optimize the longitudinal phase space distribution of the electron beam for bunch compression**. The gun employs single-crystal LaB6 cathode with small diameter of 1.8 mm to obtain a very small initial emittance with sufficiently high current density. The RF gun has been already manufactured and the measurement of RF characteristics is now in progress. We will present the results of low-power measurement and also discuss the effect of the cathode misalignment on the beam parameters such as transverse emittance and longitudinal phase space distribution. * H. Hama et al., New J. Phys. 8 (2006) 292. |
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| THPD094 | Production of Femtosecond Electron Pulse using Alpha Magnet together with Off-crest Acceleration for Generation of Coherent THz Radiation | 4509 |
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We have studied production of the very short-bunch electron beam to generate intense coherent THz radiation*. The bunch length of 100 fs is required to produce CSR around 1 THz. The beam from the thermionic RF-gun is introduced into the bunch compression system consist of an alpha magnet and a linac. The alpha magnet is often used as a bunch compressor for electron energy of several MeV. However, for our system, the alpha magnet plays a role of the longitudinal phase space rotator and energy filter. The bunch compression is done in the linac employing velocity bunching. The beam is injected on near the zero-cross phase of the RF field in the linac, and then the beam phase slip toward the crest. The longitudinal phase space and beam phase with respect to RF field at the entrance of the linac are optimized so that the bunch length would be minimum. In current analysis using numerical simulation based on the GPT code**, an rms bunch length of 30 fs has been obtained for a bunch charge of 20 pC. We will discuss the bunch compression scheme and the beam dynamics in the system. Prospect of the coherent radiation from the beam will be also reported. * H. Hama et al, Proc. Ultrashort Electron & Photon Beam Techniques and Applications, Xian, China (2009) |