| Paper | Title | Page |
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| MOPEC067 | Status of the J-PARC RFQ | 621 |
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The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a beam from the ion source to the DTL. The beam test of the linac was started in November 2006 and 181 MeV beam was successfully accelerated in January 2007. Since then, the linac has been delivered beams for commissioning of the linac itself, downstream accelerators and facilities. Trip rates of the RFQ, however, unexpectedly increased in Autumn 2008, and we have been suffering from this issue for user run operation since then. We tried to recover by tender conditioning, modification of RF control, improvement of vacuum properties and so on. By taking these measures, we manage to have 2 to 3 days continuous beam operation. In this report, we describe the status of the RFQ. |
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| TUPEA046 | LLRF Controller Upgrade for the J-PARC 400 MeV LINAC | 1434 |
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The output energy of the J-PARC LINAC will be upgraded from 181 to 400 MeV in the next two years by adding high-beta acceleration sections. The upgrade of the FPGA-based digital LLRF controller for the 400 MeV LINAC will be presented in this paper. The new LLRF control system works for both the 324 MHz low-beta and 972 MHz high-beta sections. Many functions are added into the LLRF controller, such as 1) working for different RF frequencies, 2) gradually increasing the feedback gains in the feedback loop instead of fixed ones, 3) automatic chopped-beam compensation, 4) automatically switching the beam loading compensation in accordance with the different beam operation mode, 5) input rf-frequency tuning carried out by a FPGA to match the rf cavities during the rf start-up, 6) auto-tuning of the rf cavity tuner by detecting the phase curve of the rf cavity during the field decay instead of the phase difference between the cavity input and output signals. |
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| TUPEC007 | Construction of Injector System for SPring-8 X-FEL | 1722 |
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The injector of the 8 GeV linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps. Even slight RF instability in its multi-stage bunching section fluctuates the bunch width and the peak current of an electron beam and it accordingly results in unstable laser oscillation in the undulator section. The acceptable instabilities of the RF fields in the cavities, which permit 10% rms variation of the peak beam current, are only about 0.01% rms in amplitude and 120 fs rms in phase according to beam simulation. The long-term RF variations can be compensated by feedback control of the RF amplitude and phase, the short-term or pulse-to-pulse variations, however, have to be reduced as much as possible by improving RF equipment such as amplifiers. Thus we have carefully designed and manufactured the RF cavities, amplifiers and control systems, giving the highest priority to the stabilization of the short-term variations. Components of the injector will be completed by the end of the April 2010, and the injector will be perfected in the summer 2010. We will present the performance of the completed devices in the conference. |
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| TUPE025 | Development Status of RF System of Injector Section for XFEL/SPring-8 | 2194 |
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XFEL/SPring-8 is under construction, which is aiming at generating coherent, high brilliance, ultra-short femto-second X-ray pulse at wavelength of 1Å or shorter. The injector consists of a 500kV thermionic gun (CeB6), a beam deflecting system, multi-stage RF structures and ten magnetic lenses. The multi-stage RF structures (238MHz, 476MHz, 1428MHz) are used for bunching and accelerating the beam gradually to maintain the initial beam emittance. In addition, in order to realize linearizing the energy chirp of the beam bunch at three magnetic bunch compression systems after the injector system, we prepared extra RF structures of 1428MHz and 5712MHz. It is important to stabilize the gap voltage of those RF structures because the intensity of X-ray pulse is more sensitive for a slight variation of the RF system in the injector. We developed some stable amplifiers for those RF structures, and confirmed the amplitude and phase stability of an RF signal outputted from the amplifiers. The measurement results achieved nearly the requirement of design parameters. In this paper, we describe the development status and the achieved performances of RF equipment of the injector section. |
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| MOPEB033 | Operation of Superconducting Combined Function Magnet System for J-PARC Neutrino Beam Line | 343 |
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A superconducting magnet system for the J-PARC neutrino beam line was completed at the end of 2008. The system consists of 14 doublet cryostats; each contains 2 combined function magnets (SCFM). The SCFM uses two single layer left/right asymmetric coils that produce a dipole field of 2.6 T and quadrupole of 19 T/m. By 2008, the world first SCFM had been developed and tested successfully at KEK. The mass-production was started in 2005, and completed by summer 2008. The system installation and commissioning took place from Feb. 2008 to Mar. 2009. The beam operation was started in April 2009 and the first neutrino beam was generated on April 23rd. Since then beam operation and commissioning to increase beam intensity has been performed to achieve the near term milestone of 100 kW beam operation. The paper briefly summarizes the history of SCFM development and the system construction as an introduction to a discussion on beam operation experience of the SCFM system. |