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Fukuda, S.

Paper Title Page
THP053 The Status of Nextef; The X-band Test Facility in KEK 906
 
  • S. Matsumoto, M. Akemoto, S. Fukuda, T. Higo, N. Kudoh, H. Matsushita, H. Nakajima, T. Shidara, K. Yokoyama, M. Yoshida
    KEK, Ibaraki
 
 

Nextef is a new X-band (11.4GHz) test facility in KEK. All of the key devices of this facility are from our old X-band Test Facility(XTF). By combining the power from two klystrons, 100 MW maximum X-band rf power is produced and 75MW is available in the bunker where the high power test of the high gradient accelerator structures will be done. The commissioning of the facility for the structure testing has almost done. The status of the facilityis is reported.

 
THP054 Status of RF Sources in Super-Conducting RF Test Facility (STF) at KEK 909
 
  • S. Fukuda, M. Akemoto, H. Hayano, H. Honma, H. Katagiri, S. Kazakov, S. Matsumoto, T. Matsumoto, S. Michizono, H. Nakajima, K. Nakao, T. Shidara, T. Takenaka, Y. Yano, M. Yoshida
    KEK, Ibaraki
 
 

Phase 0.5 and Phase 1.0 of the Superconducting RF Test Facility (STF) have been developed since 2005 in KEK. We have completed the two rf-sources and they have been used for the evaluation for the components of power distribution system (PDS) and couplers which were installed in the 5m-cryomodules. We have developed some rf components which is used in the power distribution system(PDS). Phase 1.0 have been conducted now and we attempt the R&D of PDS required in ILC project. This report describes the recent status of the rf source of STF in KEK including the modulator, PDS and LLRF.

 
THP055 Characteristics of Different Materials on High-Gradient Experiments 912
 
  • K. Yokoyama, S. Fukuda, Y. Higashi, T. Higo, N. Kudoh, S. Matsumoto, Y. Watanabe
    KEK, Ibaraki
 
 

High-gradient experiments have been performed using a narrow waveguide that has a field of approximately 200 MV/m at an rf power of 100 MW. The study investigates the characteristics of different materials at high-gradient rf breakdown. This paper reports the results of high-gradient experiments and observations of the surface of stainless-steel waveguides.

 

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THP061 High Power Test of a Low Group Velocity X-Band Accelerator Structure for CLIC 930
 
  • S. Döbert, A. Grudiev, G. Riddone, M. Taborelli, W. Wuensch, R. Zennaro
    CERN, Geneva
  • C. Adolphsen, V.A. Dolgashev, L. Laurent, J.R. Lewandowski, S.G. Tantawi, F. Wang, J.W. Wang
    SLAC, Menlo Park, California
  • S. Fukuda, Y. Higashi, T. Higo, S. Matsumoto, K. Ueno, K. Yokoyama
    KEK, Ibaraki
 
 

In recent years evidence has been found that the maximum sustainable gradient in an accelerating structure depends on the rf power flow through the structure. The CLIC study group consequently designed a new prototype structure for CLIC with a very low group velocity, input power and average aperture (a/λ = 0.12). The 18 cell structure has a group velocity of 2.4% at the entrance and 1% at the last cell. Several of these structures have been made in collaboration between KEK, SLAC and CERN. A total of five brazed-disk structures and two quadrant structures have been made. The high power results of some of these structures are presented. The first KEK/SLAC built structure reached an unloaded gradient in excess of 100 MV/m at a pulse length of 230 ns with a breakdown rate below 10-6. The high-power testing was done using the NLCTA facility at SLAC.

 
THP106 High Speed Data Acquisition System Using FPGA for LLRF Measurement and Control 1042
 
  • H. Katagiri, S. Fukuda, T. Matsumoto, S. Michizono, T. Miura, Y. Yano, M. Yoshida
    KEK, Ibaraki
 
 

Recently, FPGA technology is widely used for the accelerator control owing to its fast digital processing. We have been developing several applications for LLRF control and measurement using commercial and custom-made FPGA board. XtremeDSP(the commercial FPGA board equipped two ADCs and two DACs) is mainly used for the performance evaluation of STF(Superconducting RF Test Facility) LLRF. Installing the custom-made FPGA board equipped with ten ADCs and two DACs is considering for up-grade of the rf driver and rf monitoring system in the injector linac. Development of the high-speed data acquisition system that combines commercial FPGA board ML555 and FastADC(ADS5474 14bit, 400MS/s) is carried out. Result of those data acquisition systems will be summarized.

 
THP107 Performance of Digital Low-Level RF Control System with Four Intermediate Frequencies 1045
 
  • T. Matsumoto, S. Fukuda, H. Katagiri, S. Michizono, T. Miura, Y. Yano
    KEK, Ibaraki
 
 

In a superconducting accelerator, an FPGA/DSP-based low-level rf (LLRF) system with feedback control is adopted to satisfy the requirement of stability in the accelerating field. An rf probe signal picked up from cavity is down-converted to an intermediate frequency and sampled by an analog-to-digital converter (ADC) in the digital LLRF control system. In order to decrease the number of the ADCs required for vector sum feedback operation, a digital LLRF control system using different intermediate frequencies has been developed. At STF (Superconducting RF Test Facility) in KEK, the digital LLRF system with four intermediate frequencies was operated and the rf field stability under the feedback operation was estimated using a superconducting cavity. The result of the performance will be reported.

 
THP108 Performance of Digital LLRF System for STF in KEK 1048
 
  • S. Michizono, S. Fukuda, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
    KEK, Ibaraki
 
 

RF operation has started at the STF (Superconducting RF Test Facility) in KEK. The digital feedback system, which consists of one FPGA, ten 16-bit ADCs and two 14-bit DACs, was installed in order to satisfy the rf-field regulation requirements of 0.3% rms and 0.3 deg.rms in phase. The rf field stability under various feedback parameters are presented. Various studies were also carried out such as cavity detuning measurements (microphonics, quench detection, etc.). These results will also be summarized.

 
THP109 Measurements of Feedback-Instability Due to 8/9π and 7/9π Modes at KEK-STF 1051
 
  • T. Miura, S. Fukuda, H. Katagiri, T. Matsumoto, S. Michizono, Y. Yano
    KEK, Ibaraki
 
 

In the superconducting rf test facility (STF) at KEK, high power tests of the nine-cell superconducting cavity for the international linear collider (ILC) have been performed. Although the cavity was operated in π-mode, the feedback instability due to 8/9π and 7/9π modes was observed in the STF. The intensities of 8/9π and 7/9π modes were measured by changing the feedback loop-delay and stable/unstable region appeared periodically as expected.