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A compact and low-cost 1 GeV injector linac was designed and constructed to provide injection beams to the soft X-ray synchrotron radiation facility NewSUBARU instead of the SPring-8 injector system, which will be shutdown. The total length of the injector linac needs to be less than 70 m to fit into the existing tunnel. To this end, an RF electron gun with a gridded thermionic cathode directly attached to a 238 MHz RF cavity was developed and adopted. The 500 keV, 0.6 ns, 1 nC beam emitted from the cavity is compressed to 3 ps by velocity bunching driven by a 476 MHz RF cavity and a S-band RF structure. The short-pulsed beams are accelerated up to 1 GeV with 16 C-band RF structures. In the C-band accelerator section, the klystron output of 50 MW is multiplied 4 times by a pulse compressor and fed to the 4 RF structures to generate a high accelerating field of 31 MV/m. A low-level RF system consisting of a MTCA.4 based high-speed digitizers and RF frontend boards has been constructed. This injector system is used at the 3 GeV SR facility currently under construction in Sendai. In this paper, we report the design outline and the operational performance of the injector system., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The RF system of the SPring-8 storage ring has stably generated an accelerating voltage of 16 MV at a frequency of 508.58 MHz since 1997. In the upgrade of the SPring-8, a beam energy is lowered from 8 to 6 GeV and a needed voltage is 7 MV. The upgrade employs multi-bending optics, and shortens the straight sections available for RF accelerating cavities by 30%. On account of the space, the RF system is to be so rearranged that the number of cavities can be reduced to half. The analog low-level RF (LLRF) system in use controls the voltage with sufficiently small deviations of less than 0.1 % in amplitude and less than 0.1 degree in phase, but becomes out-of-dates and hard to be maintained. We plan to replace them with a compact digital LLRF system in the MTCA.4 standard and based on under-sampling scheme. The SACLA linac is used for injecting a low-emittance beam to the ring. Because we have to balance the FEL operation and the beam injection on demand, pulse-by-pulse control of beam parameters is going to be implemented to the SACLA LLRF modules. Furthermore, we build a timing system for injection to a target bucket-position in the ring within a time deviation of 3 ps., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

To equip SACLA with wide ability to provide a laser beams in EUV and soft X-ray regions to experimental users, we have constructed a new free electron laser facility for SACLA beamline-1. Injector components, such as a thermionic electron gun, two buncher cavities, a S-band standing wave accelerator, S-band travelling wave accelerator and their RF sources, were relocated from the SCSS test accelerator, which was a prototype machine of SACLA. At the downstream of a bunch compressor chicane, three C-band 40 MV/m acceleration units were newly installed to effectively boost a beam energy up to 470 MeV. Two in-vacuum undulators were remodeled by changing the period of magnet array from 15 mm to 18 mm to increase SASE intensity by a larger K-value of 2.1. Beam commissioning was started in autumn 2015. So far SASE radiation at a 33 nm wavelength driven by a 470 MeV electron beam was observed. We will install the third undulator in this winter to obtain SASE saturation and additional C-band accelerator units in the next summer to raise the maximum beam energy to 750 MeV. In this presentation, the overview of the facility and the commissioning status will be reported., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

This paper report about a control system for a dedicated accelerator for SACLA wide-band beam line (BL1), requirements, construction strategies, and present status. At the upgrade plan of SACLA BL1, it was decided to move SCSS test accelerator, which operated from 2005 to 2013, to the upstream of the BL1 in the undulator hall. The control system of the accelerator had to be operated seamlessly with SACLA, to reuse old components as much as possible, and to avoid stopping SACLA user experiments during the start up. The system was constructed with MADOCA which is already used at SACLA. In the control components, VME optical DIO cards and chassis for magnet power supplies were reused after cleaning and checking that there was no degradation of quality. The RF conditioning of the accelerator was started in in October 2014, while SACLA user experiments were going on. A data collection system was prepared, myCC, having a MADOCA compatible interface and an independent database from SACLA. It enabled efficient start up and after enough debugging, the data collection was successfully merged to SACLA in January 2015. Beam commissioning of the accelerator is planned for autumn 2015., Proceedings of the 15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2015, Melbourne, Australia

Low electro-magnetic noise interference (EMI) is required to the klystron modulator power supply for XFEL/SPring-8 project in order to realize the highly stable beam operation with aid of various feedback loops using high-performance beam monitors. The dominant noise source is the thyratron switching noise, associated with its rapid voltage swing of 50 kV maximum. To suppress the noise leakage, special care was taken to the enclosure design of klystron modulator, i.e., using thick steel plates a monocoque enclosure was fabricated, in which all of the high power circuits was installed. The rapid image current flows on the inner surface, thus EMI was minimized. A special co-axial feed-though was developed for filtering the conducted noise on power line for thyratron and klystron heaters. In this presentation, we will report the details of the devices and the results of the noise suppression., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

This paper describes the present status of a precise temperature-regulation system for the C-band accelerator at XFEL (X-ray Free Electron Laser)/SPring-8. It is essential to maintain a constant temperature of an rf cavity for stable lasing. We therefore installed a heater-assembly unit into a cooling water circuit of each rf cavity. By controlling the heater power, the temperature of the cavity can be stabilized. We constructed a prototype of this system at the SCSS (SPring-8 Compact SASE Source) test accelerator to check its feasibility for the XFEL. The prototype significantly contributes to a stable supply of SASE to users. For the XFEL, we simplified this system in consideration of cost and controllability. For example, to make one regulation system simultaneously controlling two C-band accelerating structures was tried. Keeping a temperature variation as tight as ±0.02 K at any operational mode could be achieved by this system. The preliminary test results of the system are also reported in this paper., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

XFEL/SPring-8 will use 72 line type modulator pulse-power supply for 66 C-band klystrons, 4 S-band, one L-band and pulsed 500 kV electron gun. In order to make the size smaller to fit the space available in the high gradient C-band accelerator, we have developed all in one box design of modulator. Using metal monocok design, filled with oil, it becomes possible to fit all circuitry: PFN, thyratron, pulse transformer, klyston socket, and protection circuit into a metal box of W 1m x L 1.7m x H 1m, which provides strong support for massive klystron and solenoide with lead shield and functions as superior EM shiled. We developed high precission HV charger for PFN, which has stability better than 100 ppm.pp. Modulator and PFN chargers are under mass prodution., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

C-band (5712 MHz) accelerator is used as the main accelerator of the XFEL in SPring-8. Since the C-band generates a high accelerator gradient, as high as 35 MV/m, the total length of the 8-GeV accelerator fits within 400 m, including the injector and three bunch compressors. We use 64 C-band rf units, which consists of 128 accelerating structures, 64 rf pulse compressors, 64 klystrons, waveguide components, etc. Mass-production of these high power rf components has been almost completed. Production quality is confirmed by the high power rf test. Installation of the C-band components started in August 2009. So far, about half of the components have been installed on schedule. The accelerating structures are aligned with about 0.1 mm accuracy. By the date of the IPAC’10 conference, we will almost complete the installation. In this presentation, we will report the construction status., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

We report the high power rf test results of C-band accelerator system for X-ray free electron laser (XFEL) in SPring-8 site. In XFEL main accelerator, 64 C-band systems will be used in total, whose components are under mass production at several industries in Japan. We performed high power RF test with three sets of the mass-produced components in XFEL test bunker. We operate the C-band components with the accelerating gradient, as high as 40 MV/m. We measured the high voltage breakdown rate and the dark current emission., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan