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Journal Articles

Quasifree neutron knockout reaction reveals a small $$s$$-Orbital component in the Borromean nucleus $$^{17}$$B

Yang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.

Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02

AA2020-0819.pdf:1.29MB

 Times Cited Count:31 Percentile:96.65(Physics, Multidisciplinary)

A quasifree ($$p$$,$$pn$$) experiment was performed to study the structure of the Borromean nucleus $$^{17}$$B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $$1s_{1/2}$$ and $$0d_{5/2}$$ orbitals, and a surprisingly small percentage of 9(2)% was determined for $$1s_{1/2}$$. Our finding of such a small $$1s_{1/2}$$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in $$^{17}$$B. The present work gives the smallest $$s$$- or $$p$$-orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of $$s$$ or $$p$$ orbitals is not a prerequisite for the occurrence of a neutron halo.

Journal Articles

Proximity factor on transformation from subsurface to surface flaw

Hasegawa, Kunio*; Li, Y.; Serizawa, Ryosuke*; Kikuchi, Masanori*; Lacroix, V.*

Procedia Materials Science, 12, p.36 - 41, 2016/00

 Times Cited Count:0 Percentile:0.01

If subsurface flaws are detected that are close to component free surfaces, flaw-to-surface proximity rule is used to determine whether the flaws should be treated as subsurface flaws as is, or transformed to surface flaws. However, specific factors for the proximity rules on transforming subsurface to surface flaws differ among fitness-for-service codes. The objective of the paper is to reveal the proximity factor from the stress intensity factor interaction between the subsurface flaw and the free surface.

Journal Articles

Beam monitors for the commissioning of energy upgraded linac

Miura, Akihiko; Maruta, Tomofumi*; Liu, Y.*; Miyao, Tomoaki*; Kawane, Yusuke; Ouchi, Nobuo; Oguri, Hidetomo; Ikegami, Masanori*; Hasegawa, Kazuo

JPS Conference Proceedings (Internet), 8, p.011002_1 - 011002_6, 2015/09

BB2014-1017.pdf:0.51MB

In the J-PARC Linac, an energy upgrade project has started since 2009 using Annular-ring Coupled Structure cavities to achieve design beam power of 1 MW at the exit of the downstream rapid cycling synchrotron. Linac beam parameters of the upgraded Linac is drastically improved especially for the beam energy from 181 to 400 MeV in the project. To meet with the significant upgrades of the Linac, beam monitors to be used for the upgraded beam line are newly designed and fabricated as well as the beam monitor layout is designed with the consideration to the beam commissioning strategies. This paper introduces the beam monitor layout in the new beam line and the commissioning results to confirm the beam monitor functioning.

Journal Articles

Bunch shape measurement of 181 MeV beam in J-PARC linac

Miura, Akihiko; Feschenko, A. V.*; Mirzojan, A. N.*; Miyao, Tomoaki*; Ouchi, Nobuo; Maruta, Tomofumi*; Liu, Y.*; Oguri, Hidetomo; Ikegami, Masanori*; Hasegawa, Kazuo

JPS Conference Proceedings (Internet), 8, p.011003_1 - 011003_6, 2015/09

BB2014-1018.pdf:0.45MB

In J-PARC Linac, an energy upgrade project has started since 2009 using Annular-ring Coupled Structure (ACS) cavities. We have decided to use the bunch shape monitors (BSM) as the monitors of the longitudinal beam width measurement in order to take the longitudinal matching using two bunchers located in the upstream of ACS cavities, where the RF frequency jumps from 324 to 972 MHz. Three BSMs were completely fabricated and installed in the beam line. The BSMs were commissioned with the beam and their operability was demonstrated. We found the vacuum degradation during the measurement. We once removed all BSMs to have a vacuum conditioning and postponed the longitudinal matching at the establishment of 400-MeV operation of the energy upgraded Linac. In this paper, we introduce the mechanism of the BSM, its operability, the measurement results with the 181 MeV beam and consistency check with the respect cavity amplitude. We also describe the operational vacuum conditions and the outline of the improvement of the vacuum system for the BSMs.

Journal Articles

Design and delivery of beam monitors for the energy-upgraded linac in J-PARC

Miura, Akihiko; Ouchi, Nobuo; Oguri, Hidetomo; Hasegawa, Kazuo; Miyao, Tomoaki*; Ikegami, Masanori*

Journal of the Korean Physical Society, 66(3), p.364 - 372, 2015/02

 Times Cited Count:2 Percentile:20.53(Physics, Multidisciplinary)

In J-PARC Linac, an energy upgrade project has started to achieve the design beam power of 1 MW at the exit of downstream synchrotron. To meet with significant upgrades of the beam parameters, beam monitors used for the beam commissioning are modified and fabricated. We discuss how to design and assemble the beam monitors for the upgraded Linac. We delivered them for the new upgraded beam line periodically and newly fabricated monitors for the longitudinal matching are also delivered because of the frequency jump between original RF cavity and newly developed cavity. Finally we suppose the commissioning plans to support the monitor check.

Journal Articles

Installation and performance check of beam monitors for energy upgraded J-PARC linac

Miura, Akihiko; Ouchi, Nobuo; Oguri, Hidetomo; Hasegawa, Kazuo; Maruta, Tomofumi*; Liu, Y.*; Miyao, Tomoaki*; Ikegami, Masanori*

Proceedings of 27th International Linear Accelerator Conference (LINAC 2014) (Internet), p.1059 - 1061, 2014/12

An energy upgrade project has started in the J-PARC Linac since 2009. In the upgraded project, beam energy in the Linac has increased from original 181 MeV to 400 MeV using the additional 21 Annular-ring Coupled Structure Linac (ACS) cavities. The new beam monitors as the beam current monitors, the phase monitors, the beam position monitors and the transverse profile monitors (wire scanner monitors) were designed and fabricated. By the end of November, 2013, all beam monitors were completely installed. From the middle of December, we started the beam commissioning to achieve the beam energy as 400 MeV, as well as to confirm the beam monitor functioning. We achieved the 400 MeV beam acceleration at the middle of January, 2014 using newly installed beam monitors. This paper describes the beam monitor installation and the beam commissioning results of beam monitor functioning.

Journal Articles

Bunch shape monitor for J-PARC linac

Miura, Akihiko; Feschenko, A. V.*; Mirzojan, A. N.*; Miyao, Tomoaki*; Ouchi, Nobuo; Oguri, Hidetomo; Hasegawa, Kazuo; Ikegami, Masanori*

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.705 - 708, 2014/06

In J-PARC linac, a project for energy and intensity upgrade has been progressed since 2009 using Annular-ring Coupled Structure (ACS) cavities. Because the longitudinal matching of the injection beam to the ACS cavities is required as well as the transverse matching, we decided to employ the bunch shape monitors (BSM's) to measure the longitudinal beam profile. We developed three BSM's in collaboration with INR (Institute for Nuclear Research: Russia) for the upstream part of the ACS section. We introduce the structure of BSM and mention the measured results taken during the commissioning of BSM.

Journal Articles

Development of $$^{99}$$Mo-$$^{rm 99m}$$Tc domestic production with high-density MoO$$_{3}$$ pellets by (n,$$gamma$$) reaction

Tsuchiya, Kunihiko; Tanase, Masakazu*; Takeuchi, Nobuhiro*; Kobayashi, Masaaki*; Hasegawa, Yoshio*; Yoshinaga, Hideo*; Kaminaga, Masanori; Ishihara, Masahiro; Kawamura, Hiroshi

Proceedings of 5th International Symposium on Material Testing Reactors (ISMTR-5) (Internet), 10 Pages, 2012/10

As one of effective uses of the JMTR, JAEA has a plan to produce $$^{99}$$Mo by (n, $$gamma$$) method, a parent nuclide of $$^{rm 99m}$$Tc. In case of Japan, the supplying of $$^{99}$$Mo depends only on imports from foreign countries. The R&D on production method of $$^{99}$$Mo -$$^{rm 99m}$$Tc has been performed with Japanese industrial users under the cooperation programs. The main R&D items for the production are (1) Fabrication of irradiation target such as the sintered MoO$$_{3}$$ pellets, (2) Separation and concentration of $$^{rm 99m}$$Tc by the solvent extraction from Mo solution, (3) Examination of $$^{rm 99m}$$Tc solution for a medicine, and (4) Mo recycling from Mo generator and solution. In this paper, the status of the R&D is introduced for the production of $$^{99}$$Mo -$$^{rm 99m}$$Tc.

Journal Articles

Predictive analysis of the radiation exposure for the primary cooling system of the rated power operation of MONJU

Matsuo, Yoichiro; Hasegawa, Masanori; Maegawa, Yoshiharu; Miyahara, Shinya

Hoken Butsuri, 46(4), p.304 - 313, 2011/12

Radioactive corrosion products (CP) are main source of personal radiation exposure during maintenance without fuel-failure accident in the liquid-metal fast breeder reactor (LMFBR) plants. In order to establish the techniques of radiation dose estimation for personnel, program system DORE has been developed. The DORE system is constructed by PSYCHE code and QAD code system. The density of each deposited CP of primary coolant system in MONJU was estimated by using the PSYCHE. Moreover, the QAD-CGGP2R code is applied to dose rate calculations for the primary coolant system in MONJU. The predicted values were estimated to be saturated at 2-3 mSv/h in twenty years after the start of operation, and the dose rate reaches 4 mSv/h in domains near the IHX and the cold-leg piping.

Journal Articles

Beam monitor deformation by Tohoku Earthquake and its recovery project

Miura, Akihiko; Hasegawa, Kazuo; Oguri, Hidetomo; Ouchi, Nobuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*

Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2328 - 2330, 2011/09

On March 11, 2011, the great earthquake occurred off the Pacific coast of Tohoku. This earthquake and related ones caused the big damage of the J-PARC accelerators. As for the beam monitors in J-PARC linac, some commissioning tools had damage and the vacuum leakage was observed. In the recovery work, we inspected the damage and put the emergency steps for the vacuum equipment. In this paper, detailed inspection results of beam monitors are described and also the recovery work is introduced.

Journal Articles

Beam loss detected by scintillation monitor

Miura, Akihiko; Maruta, Tomofumi; Sako, Hiroyuki; Hasegawa, Kazuo; Ouchi, Nobuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*

Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1257 - 1259, 2011/09

Ar-CO$$_{2}$$ gas proportional beam loss monitors (BLMs) have measured the beam loss through operations, but they are also sensitive to background noise of X-ray emitted from RF cavities. For the future energy upgrade of J-PARC linac, because 21 RF cavities are additionally installed in the beam line, the background noise would be serious problem. We employed the scintillation monitors to measure the beam loss which would bring more accurate beam loss measurements with suppression of X-ray noise. As the measurement results, a good signal to noise ratio is observed for the scintillation monitor with quite low sensitivity to the background X-ray. In addition, the availability of the scintillation monitor is also confirmed at the low energy part. This paper describes the beam loss measurement system using a scintillation monitor.

Journal Articles

Beam loss detected by scintillation monitor

Miura, Akihiko; Maruta, Tomofumi; Sako, Hiroyuki; Hasegawa, Kazuo; Ouchi, Nobuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*

Proceedings of 10th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators (DIPAC 2011) (Internet), p.149 - 151, 2011/08

Ar-CO$$_{2}$$ gas proportional beam loss monitors (BLMs) have measured the beam loss through operations, but they are also sensitive to background noise of X-ray emitted from RF cavities. For the future energy upgrade of J-PARC linac, because 21 RF cavities are additionally installed in the beam line, the background noise would be serious problem. We employed the scintillation monitors to measure the beam loss which would bring more accurate beam loss measurements with suppression of X-ray noise. As the measurement results, a good signal to noise ratio is observed for the scintillation monitor with quite low sensitivity to the background X-ray. This paper describes the beam loss measurement system using a scintillation monitor.

Journal Articles

Beam loss detection by scintillation monitor

Miura, Akihiko; Maruta, Tomofumi; Sako, Hiroyuki; Hasegawa, Kazuo; Ouchi, Nobuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*

Proceedings of 8th Annual Meeting of Particle Accelerator Society of Japan (Internet), 3 Pages, 2011/08

Ar-CO$$_{2}$$ gas proportional beam loss monitors (BLMs) have measured the beam loss through operations, but they are also sensitive to background noise of X-ray emitted from RF cavities. For the future energy upgrade of J-PARC linac, because 21 RF cavities are additionally installed in the beam line, the background noise would be serious problem. We employed the scintillation monitors to measure the beam loss which would bring more accurate beam loss measurements with suppression of X-ray noise. As the measurement results, a good signal to noise ratio is observed for the scintillation monitor with quite low sensitivity to the background X-ray. This paper describes the beam loss measurement system using a scintillation monitor.

Journal Articles

Transport of radioactive corrosion products in primary system of sodium-cooled fast breeder reactor "MONJU"

Matsuo, Yoichiro; Hasegawa, Masanori; Maegawa, Yoshiharu; Miyahara, Shinya

Journal of Power and Energy Systems (Internet), 5(1), p.96 - 107, 2011/01

Radioactive corrosion products (CP) are primary cause of personal radiation exposure during maintenance work at FBR plants with no breached fuel. The PSYCHE code has been developed based on the solution-precipitation model for analysis of CP transfer behavior. We predicted and analyzed the CP solution and precipitation behavior of MONJU to evaluate the applicability of the PSYCHE code to MONJU, using the parameters verified in the calculations for JOYO. From the calculation result pertaining to the MONJU system, distribution of $$^{54}$$Mn deposited in the primary cooling system over 20 years of operation is predicted to be approximately 7 times larger than that of $$^{60}$$Co. In particular, predictions show a notable tendency for $$^{54}$$Mn precipitation to be distributed in the primary pump and cold-leg. The calculated distribution of $$^{54}$$Mn and $$^{60}$$Co in the primary cooling system of MONJU agreed with tendencies of measured distribution of JOYO.

Journal Articles

Electron compound nature in a surface atomic layer of a two-dimensional hexagonal lattice

Matsuda, Iwao*; Nakamura, Fumitaka*; Kubo, Keisuke*; Hirahara, Toru*; Yamazaki, Shiro*; Choi, W. H.*; Yeom, H. W.*; Narita, Hisashi*; Fukaya, Yuki; Hashimoto, Mie*; et al.

Physical Review B, 82(16), p.165330_1 - 165330_6, 2010/10

 Times Cited Count:9 Percentile:40.75(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Development of fast beam-stop system using RF chopper

Kikuzawa, Nobuhiro; Suzuki, Takahiro; Ito, Yuichi; Miura, Akihiko; Fukuta, Shimpei; Ikegami, Masanori*; Sako, Hiroyuki; Kobayashi, Tetsuya; Suzuki, Hiroyuki; Hasegawa, Kazuo

Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.677 - 679, 2010/08

To avoid heat damage and radioactivation by beam loss of the J-PARC accelerator, Machine Protection System (MPS) has been developed. Actually, high responsibility and high reliability have been achieved in J-PARC. Beam-stop method in addition to a way of RFQ OFF has been requested in order to avoid damage to the RFQ. Therefore, we have been developing a fast beam-stop system by using a RF chopper. The fast beam-stop system, including beam test, is described in this paper.

Journal Articles

MEBT-chopper tuning procedure and its tolerance

Miura, Akihiko; Kobayashi, Tetsuya; Hasegawa, Kazuo; Sako, Hiroyuki; Ikegami, Masanori*

Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.939 - 941, 2010/08

MEBT-Chopper tuning procedure was proposed using a downstream wire scanner monitor and this has been employed for the beam commissioning of the J-PARC Linac. This paper introduces the results obtained by several tuning experiences and its tendencies. Finally, tolerance depending on the tank level of RFQ (Radio-Frequency Quadrupole Linac) is introduced.

Journal Articles

Prediction of radioactive corrosion product transfer in primary systems of Japanese prototype fast breeder reactor Monju

Matsuo, Yoichiro; Hasegawa, Masanori; Maegawa, Yoshiharu; Miyahara, Shinya

Proceedings of 18th International Conference on Nuclear Engineering (ICONE-18) (CD-ROM), 8 Pages, 2010/05

Radioactive corrosion products are main cause of personal radiation exposure during maintenance with no breached fuel in FBR plants. CP is produced in the core region by activation of fuel cladding and sub-assembly wrappers, and they are transported to the primary circuit with sodium flow and deposited on the wall of the primary piping and components. In order to establish the techniques of radiation dose reduction for of personnel, program system for corrosion hazard evaluation code PSYCHE has been was developed. The PSYCHE code is based on the solution-precipitation model. The density of each deposited CP and dose rate of primary coolant system in Monju was estimated by using the PSYCHE and QAD-CG code.

Journal Articles

Tuning of MEBT-Chopper by using wire scanner monitor

Sato, Susumu; Miura, Akihiko; Igarashi, Zenei*; Ikegami, Masanori*; Ueno, Akira; Sako, Hiroyuki; Morishita, Takatoshi; Yoshikawa, Hiroshi; Hasegawa, Kazuo; Kobayashi, Tetsuya

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.298 - 300, 2010/03

no abstracts in English

Journal Articles

Design of beam diagnostic systems for energy upgraded linac

Miura, Akihiko; Sato, Susumu; Sako, Hiroyuki; Yoshikawa, Hiroshi; Hasegawa, Kazuo; Igarashi, Zenei*; Ikegami, Masanori*

Proceedings of 6th Annual Meeting of Particle Accelerator Society of Japan (CD-ROM), p.733 - 735, 2010/03

no abstracts in English

53 (Records 1-20 displayed on this page)