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| TUPMA035 |
SCSS Prototype Accelerator Timing System
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154 |
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- N. Hosoda, T. Ohata, T. Ohshima
JASRI/SPring-8, Hyogo-ken
- H. Maesaka, Y. Otake
RIKEN Spring-8 Harima, Hyogo
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SPring-8 Compact SASE-FEL Source (SCSS) project is in progress. To verify its feasibility, the 250MeV SCSS prototype accelerator (SPA) was constructed and beam commissioning started in October 2005. We observed first lazing of 49nm wave length in June 2006. In this paper, we describe the timing system of SPA. The target time jitter was selected under 1ps. To achieve this, A master trigger generator unit (MTU), a master trigger distribution unit, a 5712MHz synchronous trigger delay unit (TDU) and a level converter unit were newly developed. The MTU generates a 1-120Hz master trigger to drive all accelerator components synchronously from 60Hz AC line and 238MHz RF. The TDU is an 8ch 24bit delay counter to generate required timing signals for each component using the master trigger from the MTU. The TDU uses 238MHz RF as a counter clock and uses 5712MHz RF to recover the circuit jitter and to synchronize to the electron beam. The time jitter of 0.71ps in the TDU was achieved. We measured the time jitter between an electron beam and a 5712MHz RF that is a main acceleration RF frequency, and obtained 0.34ps. This demonstrates good stability of SPA.
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| WEPMA048 |
Beam Position Monitor at SCSS Prototype Accelerator
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387 |
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- H. Maesaka, Y. Otake, T. Shintake, K. Togawa
RIKEN Spring-8 Harima, Hyogo
- H. Ego, T. Fukui, N. Hosoda, T. Ohshima
JASRI/SPring-8, Hyogo-ken
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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.
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| THPMA005 |
SCSS RF Control Toward 5712 MHz Phase Accuracy of One Degree
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634 |
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- Y. Otake, M. Kitamura, H. Maesaka, T. Shintake
RIKEN Spring-8 Harima, Hyogo
- T. Fukui, N. Hosoda, T. Ohata, T. Ohshima
JASRI/SPring-8, Hyogo-ken
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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.
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