T. Yorita

Osaka University, Suika, Ōsaka, Japan

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Publications (86)169.05 Total impact

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    ABSTRACT: Recently, several developments of low energy beam transport line and its beam diagnostic systems have been performed to improve the injection efficiency of ion beam to azimuthally varying field cyclotron at Research Center for Nuclear Physics, Osaka University. One of those is the fast emittance monitor which can measure within several seconds for the efficient beam development and a Pepper-Pot Emittance Monitor (PPEM) has been developed. The PPEM consists of pepper-pot mask, multichannel plate, fluorescent screen, mirror, and CCD camera. The CCD image is taken via IEEE1394b to a personal computer and analyzed immediately and frequently, and then real time measurement with about 2 Hz has been achieved.
    No preview · Article · Feb 2016 · Review of Scientific Instruments
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    ABSTRACT: An 18 GHz superconducting electron cyclotron resonance ion source is installed to increase beam currents and to extend the variety of ions especially for highly charged heavy ions which can be accelerated by cyclotrons of Research Center for Nuclear Physics (RCNP), Osaka University. The beam production developments of several ions from B to Xe have been already done [T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 79, 02A311 (2008) and T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 81, 02A332 (2010)] and the further studies for those beam extraction and its transport have been done in order to increase the beam current more. The plasma electrode, extraction electrode, and einzel lens are modified. Especially extraction electrode can be applied minus voltage for the beam extraction and it works well to improve the extracted beam current. The extraction voltage dependences of transmission and emittance also have been studied for beam current improvement which is injected into azimuthally varying field cyclotron at RCNP.
    No preview · Article · Feb 2014 · The Review of scientific instruments
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    ABSTRACT: A laser-Compton backscattering beam, which we call a `Laser-Electron Photon' beam, was upgraded at the LEPS beamline of SPring-8. We accomplished the gains in backscattered photon beam intensities by factors of 1.5--1.8 with the injection of two adjacent laser beams or a higher power laser beam into the storage ring. The maximum energy of the photon beam was also extended from 2.4 GeV to 2.9 GeV with deep-ultraviolet lasers. The upgraded beams have been utilized for hadron photoproduction experiments at the LEPS beamline. Based on the developed methods, we plan the simultaneous injection of four high power laser beams at the LEPS2 beamline, which has been newly constructed at SPring-8. As a simulation result, we expect an order of magnitude higher intensities close to 10$^7$ sec$^{-1}$ and 10$^6$ sec$^{-1}$ for tagged photons up to 2.4 GeV and 2.9 GeV, respectively.
    Full-text · Article · Aug 2013 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: A search for $K^-pp$ bound state (the lightest kaonic nucleus) has been performed using the $\gamma d \rightarrow K^+ \pi^- \rm{X}$ reaction at E$_\gamma$=1.5-2.4 GeV at LEPS/SPring-8. The differential cross section of $K^+ \pi^-$ photo-production off deuterium has been measured for the first time in this energy region, and a bump structure was searched for in the inclusive missing mass spectrum. A statistically significant bump structure was not observed in the region from 2.22 to 2.36 GeV/$c^2$, and the upper limits of the differential cross section for the $K^-pp$ bound state production were determined to be 0.1$-$0.7 $\mu$ b (95$%$ confidence level) for a set of assumed binding energy and width values.
    Full-text · Article · Jun 2013
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    ABSTRACT: We report the measurement of differential cross sections for $\omega$ and $\eta'$ photoproduction from protons at backward angles ($-1.0<\cos\Theta_{C.M}^{X}<-0.8$) using linearly polarized photons at $E_{\gamma}=$$1.5-3.0$ GeV. Differential cross sections for $\omega$ mesons are larger than the predicted $u$-channel contribution in the energy range $2.0\leq\sqrt{s}\leq2.4$ GeV. The differential cross sections for $\omega$ and $\eta'$ mesons become closer to the predicted $u$-channel contribution at $\sqrt{s}>2.4$ GeV. A bump structure in the $\sqrt{s}$ dependence of the differential cross sections for $\eta'$ mesons was observed at $\sqrt{s}\sim$2.35 GeV.
    Full-text · Article · Jun 2013 · Progress of Theoretical and Experimental Physics
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    ABSTRACT: A three-pole 10-T superconducting wiggler was installed in the 8-GeV electron storage ring at SPring-8 for generating high-energy synchrotron radiation. Beam tests were carried out to check its performance and to investigate the effects on a stored beam. A beam was successfully stored at magnetic fields of the wiggler up to 9.7 T. The beam current was limited to 1 mA to avoid unnecessarily high heat-load on photon absorbers and radiation damage to accelerator components. Beam parameters such as a horizontal beam size, a bunch length, betatron tune shifts were measured. A spectrum of high-energy synchrotron radiation from the wiggler was also measured with the NaI scintillator at an extremely low beam current of about 8 pA.
    Full-text · Conference Paper · Feb 2013
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    ABSTRACT: At RCNP, we have been developing magnets utilizing high-temperature superconducting (HTS) wires for this decade. Recently we fabricated a cylindrical magnet for a practical use which polarizes ultracold neutrons. It consists of 10 double pancakes and the field strength at the center is larger than 3.5 T which is required to fully polarize 210 neV neutrons. Design and performance of the magnet are described.
    No preview · Article · Jan 2013
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    ABSTRACT: As the upgrade program of the azimuthally varying field (AVF) cyclotron is at the cyclotron facility of the RCNP, Osaka University for the improvement of the quality, stability, and intensity of accelerated beams, an 18 GHz superconducting (SC) ECR ion source has been installed to increase beam currents and to extend the variety of ions, especially for highly charged heavy ions which can be accelerated by RCNP AVF cyclotron. The production development of several ions such as B, O, N, Ne, Ar, Ni, Kr, and Xe has been performed by Yorita et al. [Rev. Sci. Instrum. 79, 02A311(2008); 81, 02A332 (2010)]. Further studies for the beam transport have been done in order to improve the beam current more for injection of cyclotron. The effect of field leakage of AVF main coil is not negligible and additional steering magnet has been installed and then beam transmission has been improved. The emittance monitor has also been developed for the purpose of investigating correlation between emittance of beam from ECR ion sources and injection efficiency. The monitor consists with BPM82 with rotating wire for fast measurement for efficient study.
    No preview · Article · Feb 2012 · The Review of scientific instruments
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    ABSTRACT: We have been developing mgnets utilizing hightemperature superconducting (HTS) wiresfor a decade. We have investigated the performance of HTS wires excited by alternatingcurrents as well as direct currents. A scanning magnet was designed, fabricated, and testedfor its suitability as a beam scanner. After successful cooling tests, the magnetperformance was investigated in AC mode. The magnet was operated at frequencies of 10- 20Hzand 20K. The power loss dissipated in the coils was measured and compared with the modelcalculations. In order to check feasibilities of pulse magnet using HTS wire, we havefabricated a super-ferric dipole magnet to be operated by lumping currents. Preliminaryperformance is described.
    No preview · Article · Jan 2012
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    ABSTRACT: An upgrade program for increase of beam intensity and improvement of beam quality is in progress at the cyclotron facility of Research Center for Nuclear Physics(RCNP). A 2.45 GHz ECR proton source was modified to increase 392 MeV proton beam intensity. Rated output power of a microwave power supply was increased from 200 W to 2 kW. A water-cooled waveguide system for high power microwave transfer is being installed for the proton source. A 15 keV proton beam with intensity of 0.6 mA was stably produced for output microwave power of 200 W. Emittance of 50 to 100  mm-mrad was obtained for 0.05 to 0.1 mA proton beams in the LEBT system. Beam transmission, defined by the ratio of the beam intensity between a Faraday cup placed in the axial injection beam line and an inflector electrode of the AVF cyclotron, was improved from 25 % for a 0.07 mA proton beam to more than 90 % for 0.03 mA, which indicated that the beam transmission was limited by the acceptance of the axial injection beam line. A new active gradient corrector is being designed for horizontal beam focusing in the extraction region of the AVF cyclotron and for reducing a beam loss at the vacuum chamber in the extraction region. An asymmetric dee voltage distribution at an acceleration gap is being analyzed for improvement of a flat-top acceleration system of the AVF cyclotron.
    Preview · Article · Jan 2011
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    ABSTRACT: The RCNP cyclotron cascade system consists of K140 AVF cyclotron and K400 ring cyclotron and is providing high quality beams for various experiments. There are increasing demands for high intensity beams and even to improve the quality. In order to increase the physics research opportunities, a new injector cyclotron is recently proposed, which has four separated sector magnets and two accelerating cavities. Sector magnets are designed to use High Temperature Superconducting (HTS) wire. At RCNP we have been developing magnets with HTS wires for a decade. In this paper, we will report recent results of developed HTS magnets and the design of sector magnets for the new injector SSC.
    Preview · Article · Jan 2011
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    ABSTRACT: The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for γp→ϕp, γd→ϕpn, and γd→ϕd at forward production angles. A linearly polarized photon beam at Eγ=1.6–2.4 GeV was used for the production of ϕ mesons. The natural-parity Pomeron exchange processes remain dominant near threshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from the nucleons but is greatly reduced in the coherent production from deuterons. There is no strong Eγ dependence, but there is some dependence on momentum transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the t-channel is observed.
    Full-text · Article · Jul 2010 · Physical Review C
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    ABSTRACT: Differential cross sections and photon-beam asymmetries for the gamma p -> K+ Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6<cos(theta)<1. A new bump structure was found at W=2.11 GeV in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with J<=3/2. This result suggests that the bump might be produced by a nucleon resonance possibly with J>=5/2 or by a new reaction process, for example an interference effect with the phi photoproduction having a similar bump structure in the cross sections.
    Full-text · Article · Apr 2010 · Physical Review Letters
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    ABSTRACT: A scanning magnet using high-temperature superconductor (HTS) wire was designed, built, and tested for its suitability as a beam scanner. After successful cooling tests, the magnet performance was studied using DC and AC currents. With DC current the magnet was successfully operated to generate designed field distributions and effective length. In AC mode, the magnet was operated at frequencies of 30–59 Hz and a temperature of 77 K as well as 10–20 Hz and 20 K. The power losses dissipated in the coils were measured and compared with the model calculations. The observed losses per cycle were independent of the frequency and the scaling law of the transport current was consistent with theoretical predictions for hysteretic losses in HTS wires.
    Preview · Article · Apr 2010 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: An 18 GHz superconducting electron cyclotron resonance ion source has been installed as a subject of the azimuthally varying field cyclotron upgrade project (K. Hatanaka et al., in Proceedings of the 17th International Conference on Cyclotrons and Their Applications, Tokyo, Japan, 18-22 October 2004, pp. 115-117), in order to increase beam currents and to extend the variety of ions. The production development of several ions has been performed since 2006 and some of them have already been used for user experiments [T. Yorita et al., Rev. Sci. Instrum. 79, 02A311 (2008)]. Further optimizations for each component such as the material of plasma electrode, material, and shape of bias probe and mirror field have been continued and more intense ion beams have been obtained for O, N, and Ar. For the purpose of obtaining highly charged Xe with several microamperes, the optimization of position and shape of plasma electrode and bias disk has also been done and highly charged Xe(32+) beam has been obtained successfully.
    Preview · Article · Feb 2010 · The Review of scientific instruments
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    ABSTRACT: We have been developing mgnets utilizing high-temperature superconducting (HTS) wire. A scanning magnet was designed, fabricated, and tested for its suitability as beam scanner. After successful cooling tests, the magnet performance was studied using DC and AC currents. In AC mode, the magnet was operated at frequencies of 30-59Hz and a temperature of 77K as well as 10-20Hz and 20K. The power loss dissipated in the coils was measured and compared with the model calculations. The observed loss per cycle was independent of the frequency and the scaling law of the excitation current was consistent with theoretical predictions for hysteretic losses in HTS wires. As the next step, a 3T dipole magnet is under construction now.
    No preview · Article · Jan 2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: A scanning magnet using high-temperature superconductor (HTS) wire was designed, fabricated, and tested for its suitability as beam scanner. After successful cooling tests, the magnet performance was studied using DC and AC currents. In AC mode, the magnet was operated at frequencies of 30-59 Hz and a temperature of 77 K as well as 10-20 Hz and 20K. The power loss dissipated in the coils was measured and compared with the model calculations. The observed loss per cycle was independent of the frequency and the scaling law of the excitation current was consistent with theoretical predictions for hysteretic losses in HTS wires.
    No preview · Article · Jan 2010
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    ABSTRACT: At Research Center for Nuclear Physics (RCNP), Osaka Univ., An 18 GHz superconducting ECRIS has been installed to increase beam currents and to extend the variety of ions, especially for highly charged heavy ions which can be accelerated by RCNP AVF cyclotrons. The production development has been performed and several ions like B, C ~ Xe have been obtained successfully by gas mixing or MIVOC. In order to extend the variety of ions more, metal viper or spatter system has also been installed to 10GHz NEOMAFIOS with minimum modifications and ion beams of Li and Mg also have been successfully obtained.
    Preview · Article · Jan 2010
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    ABSTRACT: An upgrade program of the RCNP cyclotron facility for increase of beam intensity and improvement of beam quality is in progress to meet requirements from research in nuclear physics and industrial applications using secondarily produced particles such as neutrons, muons and radioisotopes. A 2.45 GHz ECR proton source using a set of permanent magnets was developed for high intensity proton beam production. The proton beam intensity more than 0.5 mA at an extraction energy of 15 keV has been obtained with a high proton ratio more than 80 %. The quality of the pre-accelerated beam from the K140 injector AVF cyclotron has been improved by a flat-top acceleration system using the 7 th harmonic voltage to enhance the beam transmission to the K400 ring cyclotron. Transversal resonant mode of a dee electrode with a span angle of 180 degrees was also investigated to confirm feasibility of the 4 th harmonic FT acceleration in the frequency region from 50 to 60 MHz.
    Preview · Article · Jan 2010
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    ABSTRACT: SPring-8 storage ring has been available for user operation with low emittance and extreme stability for over 10 years. However there occurred some problems in the components of the storage ring due to high-brightness synchrotron radiation (SR) and low-emittance operation. On the vacuum system of the storage ring, an accurate pressure could not be measured near the photon absorber due to scattered high-energy SR to the gauge head. High-energy SR activated dissolved oxygen in cooling water, and the activated dissolved oxygen corroded the inside of the photon absorbers in SR irradiation part. Air leakage occurred at an injection chamber due to impact by a small-size electron beam produced by low-emittance operation.We investigated the cause of the aforementioned difficulties with the vacuum system and prescribed the treatments described in this paper. In addition, we are making continual efforts at further system upgrades such as developing an RF shield that suppresses temperature increase in the shield in possible high-current operation.
    No preview · Article · Dec 2009 · Vacuum

Publication Stats

837 Citations
169.05 Total Impact Points

Institutions

  • 2001-2014
    • Osaka University
      • Research Center for Nuclear Physics
      Suika, Ōsaka, Japan
  • 2005-2010
    • Japan Synchrotron Radiation Research Institute (JASRI)
      Tatsuno, Hyōgo, Japan
  • 2006
    • Chubu University
      Касугай, Aichi, Japan
  • 1997-2000
    • Tohoku University
      • Department of Physics
      Sendai, Kagoshima, Japan