TY - CONF AU - Kondo, Y. AU - Fang, Z. AU - Fukui, Y. AU - Futatsukawa, K. AU - Hirano, K. AU - Hori, T. AU - Ikegami, K. AU - Ishiyama, T. AU - Ito, T. AU - Ito, Y. AU - Kato, Y. AU - Kikuzawa, N. AU - Kitamura, R. AU - Kobayashi, F. AU - Miyao, T. AU - Morishita, T. AU - Nanmo, K. AU - Nemoto, Y. AU - Oguri, H. AU - Ohkoshi, K. AU - Otani, M. AU - Sato, Y. AU - Sawabe, Y. AU - Shibata, T. AU - Shinozaki, S. AU - Shinto, K. AU - Takahashi, D. AU - Tasaki, R. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Upgrade of the 3-MeV LINAC for Testing of Accelerator Components at J-PARC J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - We are now upgrading a 3-MeV linac at J-PARC. The old 30-mA RFQ is replaced by a spare one of the J-PARC 50-mA RFQ. The ion source is same as the J-PARC linac’s, therefore, the peak beam current is upgraded from 30 mA to 50 mA. This 3-MeV linac will be used for development of various accelerator components, such as beam dyagnostics devices, laser charge exchange equipments, new MEBT buncher, and so on. In this paper, present status of this 3-MeV test linac is presented. PB - JACoW Publishing CP - Geneva, Switzerland SP - 960 EP - 963 KW - rfq KW - linac KW - operation KW - MMI KW - experiment DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPTS046 UR - http://jacow.org/ipac2019/papers/mopts046.pdf ER - TY - CONF AU - Tamura, J. AU - Kondo, Y. AU - Morishita, T. AU - Naito, F. AU - Nemoto, Y. AU - Otani, M. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - The First Replacement of the RF Window of the ACS Cavity J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - In 2013, the Annular-ring Coupled Structure (ACS) cavities were installed to the Japan Proton Accelerator Research Complex (J-PARC) linac. Since then, the ACS cavities have been stably running. Although any serious problem induced by the ACS RF window has not yet observed, we decided to replace the RF window of one ACS cavity, which is the eighteenth accelerating cavity in the order of beam energy (ACS18), by the newly manufactured one. The major motivations of the replacement are to check the surface condition of the RF window which have been under operation for nearly five years and to confirm the availability of the newly manufactured RF window. By making use of the summer maintenance period of 2018, we carried out the replacement. This was the first experience for us to replace the RF window installed to the ACS cavity in the linac accelerator tunnel. As for the removed RF window, there was no any abnormal warning found with the visual examination. At the starting up of the cavity’s operation after the maintenance period, we investigated how much time would be required for an RF conditioning. It took around fifty hours so that the peak RF power including the beam loading is stably input to the cavity through the new RF window. The ACS cavity with the new RF window is now stably operating. PB - JACoW Publishing CP - Geneva, Switzerland SP - 971 EP - 973 KW - cavity KW - linac KW - vacuum KW - operation KW - proton DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPTS049 UR - http://jacow.org/ipac2019/papers/mopts049.pdf ER - TY - CONF AU - Tamura, J. AU - Kondo, Y. AU - Morishita, T. AU - Naito, F. AU - Nemoto, Y. AU - Otani, M. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - VSWR Adjustment for ACS Cavity in J-PARC LINAC J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - In the Japan Proton Accelerator Research Complex (J-PARC) linac, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by twenty-one Annular-ring Coupled Structure (ACS) accelerating cavities. The input coupler of the ACS high-beta cavity, which is the 21st accelerating cavity (ACS21) in the order of beam acceleration, had a comparatively larger value of the Voltage Standing Wave Ratio (VSWR) than those of the other ACS cavities. To adjust the VSWR of the ACS21, we designed and fabricated a rectangular waveguide with a capacitive iris which conduces to a better matching between the cavity and the waveguide. In the 2018 summer maintenance period, we installed the newly fabricated waveguide to the ACS21 in the position between the input coupler and the RF window. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current. PB - JACoW Publishing CP - Geneva, Switzerland SP - 974 EP - 976 KW - cavity KW - coupling KW - GUI KW - simulation KW - linac DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPTS050 UR - http://jacow.org/ipac2019/papers/mopts050.pdf ER - TY - CONF AU - Kamiya, J. AU - Horino, K. AU - Kotoku, K. AU - Miki, N. AU - Shobuda, Y. AU - Takayanagi, T. AU - Yamamoto, K. AU - Yanagibashi, T. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - New Design of Vacuum Chambers for Radiation Shield Installation at Beam Injection Area of J-PARC RCS J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - One of the issues in the J-PARC 3 GeV rapid cycling synchrotron is the high residual radiation dose around the beam injection point. A radiation shield is necessary to reduce radiation exposure of workers when maintenance is performed there. A space to install the radiation shield should be secured by newly designing a structure of the vacuum chamber at the injection point and the alumina ceramics beam pipes for the shift bump magnets. To make the space for the shield, the chamber is lengthened along the beam line and the cross-sectional shape is changed from circle to rectangle. The displacement and inner stress of the vacuum chamber due to atmospheric pressure was evaluated to be enough small by the calculation. For the ceramics beam pipe’s rf-shield, the damping resistor was effective to reduce the induced modulation voltages by the pulsed magnetic field. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1255 EP - 1258 KW - vacuum KW - injection KW - radiation KW - damping KW - flattop DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPMP013 UR - http://jacow.org/ipac2019/papers/tupmp013.pdf ER - TY - CONF AU - Kitamura, R. AU - Futatsukawa, K. AU - Hayashi, N. AU - Hirano, K. AU - Kondo, Y. AU - Kosaka, S. AU - Miyao, T. AU - Moriya, K. AU - Nemoto, Y. AU - Oguri, H. AU - Otani, M. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Development of the Bunch Shape Monitor Using the Carbon-Nano Tube Wire J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - A bunch shape monitor (BSM) is one of the important instruments to measure the longitudinal phase space distribution. The information of the bunch length measured by the BSM is useful to tune phases of the accelerating cavities in the linear accelerator. For example, in the J-PARC linac, three BSM’s using the tungsten wire are installed and tested at the ACS section to measure the bunch shapes between the accelerating cavities. However, this conventional BSM is hard to measure the bunch shape of H⁻ beam with 3 MeV at the beam transport between the RFQ and DTL sections, because the wire is broken around the center region of the beam. The new BSM using the carbon-nano-tube (CNT) wire is being developed to be able to measure the bunch shape of the H⁻ beam with 3 MeV. One challenge to introduce the CNT wire for the BSM is the measure to the discharge. The careful attention should be paid to apply the high voltage of 10 kV to the CNT wire. The several measures are taken to suppress the discharge from the wire and operate the CNT-BSM. This presentation reports the current status of the development and future prospective for the CNT-BSM. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2543 EP - 2546 KW - electron KW - high-voltage KW - vacuum KW - operation KW - DTL DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-WEPGW033 UR - http://jacow.org/ipac2019/papers/wepgw033.pdf ER -