Author: Iwashita, Y.
Paper Title Page
MOPO085 Prototype of an Inter-digital H-mode Drift-tube Linac for Muon Linac 180
 
  • Y. Nakazawa, H. Iinuma
    Ibaraki University, Ibaraki, Japan
  • K. Hasegawa, Y. Kondo, T. Morishita
    JAEA/J-PARC, Tokai-mura, Japan
  • N. Hayashizaki
    RLNR, Tokyo, Japan
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • Y. Iwata
    NIRS, Chiba-shi, Japan
  • N. Kawamura, T. Mibe, M. Otani, T. Yamazaki, M. Yoshida
    KEK, Ibaraki, Japan
  • R. Kitamura, H.Y. Yasuda
    University of Tokyo, Tokyo, Japan
  • N. Saito
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • Y. Sue
    Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
 
  An inter-digital H-mode (IH) drift-tube linac (DTL) is developed for a low velocity part in a muon linac at the J-PARC E34 experiment. It will accelerate muons from v/c = 0.08 to 0.28 at an operational frequency of 324 MHz. In order to achieve higher acceleration efficiency and make cost lower, an alternative phase focusing (APF) scheme is adopted. A prototype with 6 cells of 0.45 m length was manufactured. The prototype accelerates muons from v/c = 0.08 to 0.15 stage. We conducted frequency measurement and bead-pull measurement as a low-power measurement, in order to evaluate the prototype product. In this paper, the results of the low-power measurement for prototype cavity will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO085  
About • paper received ※ 10 September 2018      issue date ※ 18 January 2019  
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MOPO125 Steering Magnets with Permanent Magnets 264
 
  • Y. Iwashita, M. Abe, T. Yako
    Kyoto ICR, Uji, Kyoto, Japan
  • Y. Fuwa
    Kyoto University, Research Reactor Institute, Osaka, Japan
  • N. Terunuma
    KEK, Ibaraki, Japan
 
  Funding: This work was supported by the Collaborative Research Program of Institute for Chemical Research, Kyoto University (grant #2018-10)
Dipole magnet using permanent magnet technology is under investigation for correction magnets in beamline. It can reduce cost of electricity of coil excitation and cooling water pump, thick electric cabling and water piping, power supply, and their maintenance cost. The structure and the field adjustment scheme whith bipolar variable range will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO125  
About • paper received ※ 20 September 2018      issue date ※ 18 January 2019  
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TUPO030 Precise Evaluation of Characteristic of the Multi-layer Thin-film Superconductor Consisting of NbN and Insulator on Pure Nb Substrate 391
TUOP03   use link to see paper's listing under its alternate paper code  
 
  • R. Katayama, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • C.Z. Antoine
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Four
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  In recent years, it has been pointed out that the maximum accelerating gradient of a superconducting RF cavity can be pushed up by coating the inner surface of the cavity with a multilayer thin-film structure that consists of alternating insulating and superconducting layers. In this structure, the principal parameter that limits the performance of the cavity is the critical magnetic field or effective Hc1 at which vortices start penetrating into the superconductor layer, and it is predicted to depend on the combination of the film thickness. We made samples that have NbN/SiO2 thin-film structure on pure Nb substrate with several thicknesses of NbN film deposited using DC magnetron sputtering method. Here, we report the measurement results of effective Hc1 of the NbN sample with a thickness of 200 nm by using the third-harmonic voltage method. In addition, we report the preliminary results to evaluate the dependence of the effective Hc1 on the thickness of the NbN film in the range 50 nm-200 nm.  
slides icon Slides TUPO030 [0.305 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO030  
About • paper received ※ 18 September 2018      issue date ※ 18 January 2019  
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TUPO050 Construction of Thin-film Coating System Toward the Realization of Superconducting Multilayered Structure 445
 
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • H. Ito
    Sokendai, Ibaraki, Japan
  • Y. Iwashita, R. Katayama
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  Although S-I-S (superconductor-insulator-superconductor) multilayered structure is expected to increase the maximum acceleration gradient of SRF cavities, in order for it to function in reality, it is necessary to develop a coating processing that can realize high purity and quality superconducting thin-films. We launched the co-sputtering system to create superconducting alloy thin-films such as Nb3Sn and to research how the characteristics of them change depending on the coating conditions. The deposition rate of two elements was optimized by adjusting each input power, so we successfully obtained an alloy thin-film having appropriate composition ratio. In addition, we developed another experimental equipment for coating on the inner surface of the 3GHz TESLA type small cavities. A cylindrical shape Nb in which some permanent magnets are inserted was adopted as the sputtering target. Glow discharge of the target was confirmed, and the inner-sputtering test was conducted. This presentation reports the specifications of the two sputtering apparatuses and the results of the coating test.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO050  
About • paper received ※ 18 September 2018      issue date ※ 18 January 2019  
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TUPO066 Lower Critical Field Measurement of Thin Film Superconductor 484
 
  • H. Ito
    Sokendai, Ibaraki, Japan
  • C.Z. Antoine
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Four
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • H. Hayano, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • R. Ito, T. Nagata
    ULVAC, Inc, Chiba, Japan
  • Y. Iwashita, R. Katayama, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
 
  Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
Superconducting thin film is the promising technology to increase the performance of SRF cavities. The lower critical field Hc1, which is one of the important physical parameters characterizing a superconducting material, will be enhanced by coating Nb with thin film superconductor such as NbN. To investigate the Hc1, we developed the Hc1 measurement system using the third harmonic response of applied AC magnetic field. The measurement system consists of helium cryostat with two of GM refrigerators, sample Cu stage, solenoid coil Cu mount, solenoid coil, temperature sensors, and liquid helium level meter. AC magnetic field is produced by a coil which is driven by function generator and power amplifier at around 1 kHz. In order to control the temperature of the sample, we installed heaters and thermal anchors which could be moved by the motor. By this temperature control the sample state can be easily transferred from Meissner state to mixed state. So that the measurement is repeated for various applied magnetic field, and the transition curve can be made. In this report, measurement result of the bulk Nb sample and NbN-SiO2 multilayer thin film sample will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO066  
About • paper received ※ 19 September 2018      issue date ※ 18 January 2019  
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THPO126 Compact H+ ECR Ion Source with Pulse Gas Valve 955
SPWR037   use link to see paper's listing under its alternate paper code  
 
  • Y. Takeuchi, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
 
  We are developing a compact ECR H+ ion source with pulse gas valve. In the case of high current ion linac, the distance between the ion source and the first accelerating tube such as RFQ must be as short as possible to reduce the space charge effect, while operating in a high electric field a good vacuum condition is desirable. Since hydrogen gas always flows out from ion sources if the plasma chamber is filled with the gas, vacuum pumping systems have to evacuate the gas enough before the first accelerating tube. The pulse gas injection system achieved by a fast piezo gas valve can reduce the gas load on the vacuum evacuation system and is suitable for installing the ion source close to the RFQ.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO126  
About • paper received ※ 19 September 2018      issue date ※ 18 January 2019  
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