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| MOYMA03 | Status and Perspective of XFEL Projects in the World | 1 |
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| Free Electron laser at X-ray wavelength is not any more a story of science fiction. Projects at SLAC and RIKEN/SPring-8 are now under construction aiming at generating first laser X-ray radiation in a few years. Two VUV FELs are already in operation at FLASH/DESY and SCSS/RIKEN. These FELs provide new type of experimental tool with unique features: high intensity, short pulse format and coherent. It is believed that XFEL will open new science cases, that why, there are many other similar projects proposed. The talk will cover, XFEL basic, key technology, and brief status of running and proposed projects. | ||
| TUPMA042 | Beam Parameters of the SCSS Prototype Accelerator Designed by PARMELA and Comparison with Measured Values | 169 |
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The 250 MeV prototype facility of the SCSS X-FEL project was constructed in the Octorber 2005 and the machine commissioning was started in May 2006. One month later, we have succeeded in confirming the amplification of the synchrotron radiation. The electron beam parameters, such as peak current and emittance, have been designed and estimated using PARMELA. In contrast to other X-FEL projects, the SCSS injector uses a thermionic pulsed electron gun [1]. Compared with RF photocathode guns, the thermionic gun is stable and easy to handle. Its peak current, however, is smaller, and the compression of the electron bunch is necessary at early stage of the low beam energy injector. In this report, we compare the simulation and measured values, such as a bunch length and projected emittance, on the SCSS prototype accelerator. The measured beam parameters, after the bunch compression procedure and emittance degradation due to space charge, show fairly good agreement with the simulation.
[1] K. Togawa, et al., “Emittance Measurement on the CeB6 Electron Gun for the SPring-8 Compact SASE Source”, Proceedings of the 2004 FEL Conference, (2004)351-354, URL: http://www. JACoW.org. |
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| WEPMA048 | Beam Position Monitor at SCSS Prototype Accelerator | 387 |
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| The SCSS X-ray free electron laser (XFEL) project is in progress at SPring-8. The SCSS prototype accelerator for VUV-FEL has been constructed and is in operation. The required resolution of the beam position is less than 1um for XFEL (10um for VUV-FEL). A cavity RF-BPM (Radio Frequency Beam Position Monitor) was developed for the SCSS accelerator based on the past experiment in which the position resolution of several 10nm was achieved. In the prototype accelerator, the beam-based calibration method of the RF-BPM was established. An experiment to evaluate the position resolution was also performed, and the preliminary result was obtained to be less than 5um. This result is sufficient for VUV-FEL. The RF-BPM made important contributions to the tuning of the prototype accelerator such as beam optics measurements and VUV-FEL amplification. By using RF-BPM data, for example, the envelope of the beam trajectory was visualized and the beam was straightly passed through undulators. As a result, VUV-FEL amplification was observed in the wavelength region of 40-60nm. | ||
| WEPMA105 | High Power Test of C-band Accelerating System for Japanese XFEL Project | 470 |
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| ?The C-band (5712 MHz) choke-mode type accelerating structure will be used for SCSS: SPring-8 Compact SASE Source project. Since the C-band accelerator generates higher accelerating gradient than traditional S-band accelerator, it makes the machine size compact and the cost low. In order to confirm the performance of the C-band accelerating system for the 8 GeV XFEL machine, the system including the same accelerating structure and RF system have been installed in the SCSS prototype accelerator. The first SASE amplification was observed at 49 nm on June 2006. In the prototype machine, four 1.8 m long C-band accelerating structures are used to accelerate electron up to 250 MeV. The C-band accelerator?unit has one 50 MW klystron and pulse compressor, where two types of pulse compressors: SKIP and SLED were adapted. After 300-hour RF conditioning, accelerating gradient up to 32 MV/m was achieved and we confirmed there is no serious problem. Now we continue the RF conditioning to get higher accelerating gradient and find the practical limit. In this paper, we would like to report on the RF conditioning and the achieved performance of the C-band accelerator. | ||
| THPMA005 | SCSS RF Control Toward 5712 MHz Phase Accuracy of One Degree | 634 |
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| To check the feasibility of X-FEL(SCSS), the 250 MeV prototype accelerator was constructed at SPring-8. The low level RF control system with a 5712 MHz pulsed RF signal was built to achieve very-tight requirements that were phase stability and resolution of less than 1 deg.. These requirements correspond to a beam energy variation of 10-4 at the crest acceleration and time stability and resolution of less than 500 fs. To realize the requirements, IQ modulators/detectors, arbitrary wave form generators/detectors of VME modules to handle an IQ function were developed. The PID control and the adaptive control method, which the modules can manipulate, were employed to obtain the requirements. We finally achieved the phase setting and detecting resolution of the IQ detectors/modulators of ± 0.5 deg.. Decreasing the phase drift was achieved by the PID control program, and reducing the phase variation within a pulse width of 2 us was achieved by the adaptive control function on the VME modules. The unnecessary time jitters of the pulse were also automatically detected by the module function. In this paper, we describe a summary of the system and its phase control performance. |