| Paper | Title | Page |
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| TUPEC008 | Cavity Detuning Method to Compensate Beam Energy Decrement in Thermionic RF Gun due to Back-bombardment Effect | 1725 |
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Thermionic RF guns are compact, economical and high brightness electron sources. However, when the guns are used for a driver linac of oscillator-type Free Electron Lasers (FELs), which requires moderate bunch charge (several tens pico-coulomb) and long macro-pulse duration (several micro-seconds), the guns have been suffered from the back-bombardment effect*. The effect induces beam current increment in a macro-pulse. And consequently the current increment leads to decrement of beam energy during a macro-pulse and significantly limits the beam macro-pulse duration after some bending magnets. Our group found a new energy compensation scheme called as cavity detuning** and the method was introduced to compensate the beam energy decrement in the thermionic RF gun used for KU-FEL***. In this presentation, we will introduce the principle of the method and experimental results. Detailed analysis of the method will be also presented. * C.B. McKee et al., NIM, A296, pp. 716-719, 1990. |
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| TUPEC029 | Comparison between Hexaboride Materials for Thermionic Cathode RF Gun | 1782 |
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RF gun has been chosen as injector for Kyoto University free electron laser because it can potentially produce an electron beam with high energy, small emittance, moreover inexpensive and compact configuration in comparison with other injectors. As for the RF gun cathode, thermionic cathode is simpler, easier to treat and reliable than photocathode. On the other hand, backbombardment electrons make cathode surface temperature and current density increase within the macropulse, as a result, beam energy and macropulse duration decrease, which means, it is difficult to generate stable FEL. The heating property of cathode not only depends on physical properties of the cathode material such as work function, but also backbombardment electrons energy. We investigated the heating property of six hexaboride materials against the backbombarding electrons by numerical calculation of the range and stopping power. In this investigation, the emission property of the cathode was also taken into account, since high electron emission is required for generation of high brightness electron beam. The results will be discussed. |
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| TUPE028 | Status of the MIR FEL Facility in Kyoto University | 2203 |
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A mid-infrared free electron laser (MIR FEL) facility has been constructed for the basic research on energy materials in the Institute of Advanced Energy, Kyoto University. The MIR FEL saturation at 13.2 μm was observed in May 2008, and the construction of the FEL delivery system from accelerator room to the optical diagnostic station and experimental stations has been finished in Dec. 2009. In the conference, optical properties of the MIR FEL and research program using MIR-FEL will be introduced. |
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| WEPD029 | End Field Termination for Bulk HTSC Staggered Array Undulator | 3156 |
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Aiming at realizing a short period undulator with strong magnetic field, we have proposed a Bulk HTSC (high temperature superconductor) Staggered Array Undulator which consists of bulk high temperature superconductor magnets with a staggered array configuration. The experiment with the prototype undulator at 77 K shows this configuration can be applicable to real undulator. We also estimated the magnetic performance of real device by calculations with a loop current model based on Bean model of superconductor. Although end field termination is required for practical use, traditional methods are not applicable for the bulk HTSCs. We found that the end field termination can be realized by controlling the shape and size of bulk HTSCs at the end section by numerical calculation using the loop current model. In the conference, the calculation and experimental result of end field termination will be presented. |