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Journal Articles

Development of semiconductor switches for high-power crowbar circuits for J-PARC accelerator

Ono, Ayato; Takayanagi, Tomohiro; Fuwa, Yasuhiro; Shinozaki, Shinichi; Ueno, Tomoaki*; Horino, Koki*; Sugita, Moe; Yamamoto, Kazami; Kinsho, Michikazu; Ikoma, Naoya*; et al.

Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.871 - 876, 2023/11

In J-PARC, an ignitron is used for the crowbar device of the klystron power supply to excite the RF acceleration voltage in a Linac cavity. Mercury, that is used in the ignitron, would be prohibition of use in the future due to environmental protection. Therefore, we designed a semiconductor crowbar switch for short-circuit protection of klystron using a MOS gate thyristor. We have manufactured an oval-type board module that realizes an operating output of 3kV, 40kA, and 50us per board. Because a high voltage of 120 kV is applied on each board, we adopted a self-power supply method to supply a electricity for the control system. This method can create the electricity from a high-voltage DCDC converter. We confirmed the operating performance on a 1/2 scale (60 kV, 40 kA) of the voltage in the existing ignitron system (120 kV, 40 kA). We also studied a test circuit in a higher voltage range of more than 90 kV. Our latest result is well promising for an alternative system of ignitron.

Journal Articles

Development of semiconductor switches for high-power crowbar circuits

Ono, Ayato; Takayanagi, Tomohiro; Fuwa, Yasuhiro; Shinozaki, Shinichi; Ueno, Tomoaki*; Horino, Koki*; Sugita, Moe; Yamamoto, Kazami; Kinsho, Michikazu; Ikoma, Naoya*; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.395 - 399, 2023/01

At J-PARC, an ignitron is used for the crowbar device of the klystron power supply for high-frequency acceleration of a linear accelerator. Ignitron uses mercury, which is of limited use worldwide, and is expected to be discontinued in the future. Therefore, we designed a semiconductor crowbar switch for short-circuit protection of klystron using a MOS gate thyristor. We have manufactured an oval-type board module that realizes an operating output of 3 kV, 40 kA, and 50 $$mu$$s per board. For the control power supply to each board module assuming a high voltage of 120 kV, we adopted a self-power supply method that creates a control power supply with a high-voltage DCDC converter from the voltage shared and charged by each board module. It was possible to confirm the operating performance on a 1/2 scale (60 kV, 40 kA) against the voltage of the existing equipment (120 kV, 40 kA) by connecting twenty oval board modules in series. The output test result will be reported.

Journal Articles

Semiconductor pulse power supplies for accelerators at J-PARC

Takayanagi, Tomohiro; Ono, Ayato; Fuwa, Yasuhiro; Shinozaki, Shinichi; Horino, Koki*; Ueno, Tomoaki*; Sugita, Moe; Yamamoto, Kazami; Oguri, Hidetomo; Kinsho, Michikazu; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.242 - 246, 2023/01

At J-PARC, semiconductor short pulse power supplies to replace kicker power supplies and semiconductor long pulse power supplies to replace klystron power supply systems are under construction. We have fabricated a 40kV/2kA/1.2$$mu$$s unit power supply that employs a linear transformer drivers (LTD) system for kickers. Currently, we are working on a high voltage insulating cylinder insulator that suppresses corona discharges using only the insulator structure, without using insulating oil. In addition, the MARX system was adopted for klystron power supply system. A main circuit unit for 8kV/60A/830$$mu$$s rectangular pulse output and an 800V/60A correction circuit unit that improves the flat top droop from 10% to 1% were manufactured. Furthermore, a 2.2kV/2.4kW high voltage SiC inverter charger has been fabricated for this MARX power supply. The presentation will report the evaluation results of each test and prospects for semiconductor pulse power supplies.

Journal Articles

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.

Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09

 Times Cited Count:7 Percentile:72.25(Nuclear Science & Technology)

In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.

Journal Articles

Time dependence of corrosion behavior on Ta in NaOH solutions

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

Materials Transactions, 63(4), p.538 - 544, 2022/04

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

The time dependence of the corrosion behavior of tantalum (Ta), which is used in nuclear fuel reprocessing equipment, in sodium hydroxide (NaOH) solutions was investigated by immersion tests, and the mechanism of the time dependence was examined via surface observations and electrochemical measurements. The immersion tests were conducted at room temperature with NaOH concentrations ranging from 1 to 7 mol/L for immersion periods of 24 to 168 h. The corrosion rate increased with the NaOH concentration but peaked with the immersion period and then decreased. The time to peak of the corrosion rate was shorter with higher NaOH concentration. The X-ray diffraction (XRD) patterns and Raman spectra of the surfaces of the specimens immersed in the 7 mol/L NaOH solution for more than 48 h showed Na$$_{8}$$Ta$$_{6}$$O$$_{19}$$ formation. The polarization resistance decreased with immersion time for all NaOH concentrations up to about 24 h after immersion. Thereafter, the polarization resistance increased with immersion time in 7 mol/L NaOH solution and remained almost constant in the other NaOH concentrations. Findings suggested that the change in the corrosion rate was affected by the film formation during immersion, since the time dependence of the polarization resistance and the sum of film resistance and charge transfer resistance had the same tendencies. The precipitation film was mainly Na$$_{8}$$Ta$$_{6}$$O$$_{19}$$ formed by the dissolution of the passivity film on Ta.

Journal Articles

Positron annihilation lifetime spectroscopy investigation of thermal aging effect for the mechanical properties of hydrogen-absorbed tantalum

Ishijima, Yasuhiro; Yokoyama, Kenichi*; Ueno, Fumiyoshi; Abe, Hitoshi

Materials Transactions, 63(4), p.592 - 599, 2022/04

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

The effect of thermal aging on the behavior of vacancy-hydrogen (H) cluster generation and the mechanical properties of tantalum (Ta) were investigated by positron annihilation lifetime spectroscopy (PALS) and tensile tests. Based on the PALS results, vacancy clusters that included 8-15 vacancies were generated after aging at and above 200$$^{circ}$$C, and vacancy-H clusters were generated in 3 and 6 h-charged specimens after aging at 300$$^{circ}$$C. The loss of ductility in Ta and crack generation were observed by conducting tensile tests in 6 h H-charged specimens after aging at 200$$^{circ}$$C for 2000 h and in 3 and 6 h H-charged specimens aged at 300$$^{circ}$$C for 2000 h. The reduction of ductility due to thermal aging of Ta was also observed under these thermal aging conditions. These results suggested that vacancy-H cluster generated by dissolved H during thermal aging induced the ductility loss by reducing the dislocation migration during deformation.

Journal Articles

Dynamical response of transition-edge sensor microcalorimeters to a pulsed charged-particle beam

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I.-H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

IEEE Transactions on Applied Superconductivity, 31(5), p.2101704_1 - 2101704_4, 2021/08

 Times Cited Count:1 Percentile:8.46(Engineering, Electrical & Electronic)

A superconducting transition-edge sensor (TES) microcalorimeter is an ideal X-ray detector for experiments at accelerator facilities because of good energy resolution and high efficiency. To study the performance of the TES detector with a high-intensity pulsed charged-particle beam, we measured X-ray spectra with a pulsed muon beam at the Japan Proton Accelerator Research Complex (J-PARC) in Japan. We found substantial temporal shifts of the X-ray energy correlated with the arrival time of the pulsed muon beam, which was reasonably explained by pulse pileup due to the incidence of energetic particles from the initial pulsed beam.

Journal Articles

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.

Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08

 Times Cited Count:16 Percentile:84.07(Optics)

Journal Articles

Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic $$K$$ X rays

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07

 Times Cited Count:15 Percentile:79.06(Physics, Multidisciplinary)

We observed electronic $$K$$X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic $$K$$$$alpha$$ and $$K$$$$beta$$ X rays together with the hypersatellite $$K$$$$alpha$$ X rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the $$L$$-shell electrons, accompanied by electron side-feeding. Assisted by a simulation, this data clearly reveals the electronic $$K$$- and $$L$$-shell hole production and their temporal evolution during the muon cascade process.

Journal Articles

Time dependence of corrosion behavior on Ta in NaOH solutions

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

Zairyo To Kankyo, 70(6), p.192 - 198, 2021/06

The time dependence of corrosion behavior on tantalum used in nuclear fuel reprocessing equipment in sodium hydroxide solution was investigated by immersion corrosion tests, and the mechanism of aging change was discussed from surface observations and electrochemical measurements. The immersion tests were carried out at room temperature with NaOH concentrations ranging from 1 to 7 mol/L and immersion times ranging from 24 to 168 hr, respectively. The corrosion rate increased with NaOH concentration, but peaked with immersion time and then decreased. The time to peak of corrosion rate was shorter with higher NaOH concentration. The SEM observations and Raman analysis at the surface of the specimens that were cleaned and weighed after the immersion test did not show any film formation. On the other hand, the polarization resistance showed a constant value or an increase after a decrease immediately after immersion. It is suggested that the change in corrosion rate is affected by the formation of film by immersion, since the value of polarization resistance is almost the same as the sum of film resistance and charge transfer resistance. The film was considered to be mainly Na$$_{8}$$Ta$$_{6}$$O$$_{19}$$ formed by the dissolution of Ta.

Journal Articles

Consideration on stress corrosion cracking evaluation of zirconium for Fuel Reprocessing Facilities

Hashikura, Yasuaki*; Ishijima, Yasuhiro; Nakahara, Masaumi; Sano, Yuichi; Ueno, Fumiyoshi; Abe, Hitoshi

Hozengaku, 19(3), p.95 - 102, 2020/10

A plutonium concentrator was selected, and constant load tensile tests with controlled applied potentials and electrochemical tests were conducted in nitric acid and sodium nitrate solutions. From the results, a map which shows the effect of nitric acid concentration to crack initiation potential was drawn. And, it was pointed out that not only the nitric acid but also the nitrate ion coordinated to the nitrate must be considered in evaluating the possibility of stress corrosion cracking.

Journal Articles

Short- and middle-ranges order structures of KNbO$$_3$$ nanocrystals

Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Fujii, Ichiro*; Nagata, Hajime*; Ohara, Koji*; Wada, Satoshi*

Japanese Journal of Applied Physics, 58(SL), p.SLLA03_1 - SLLA03_7, 2019/11

 Times Cited Count:5 Percentile:24.70(Physics, Applied)

Journal Articles

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

 Times Cited Count:13 Percentile:98.66(Quantum Science & Technology)

Journal Articles

Local structure analysis of KNbO$$_3$$ nanocrystals with cubic shape

Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Ohara, Koji*; Wada, Satoshi*

Transactions of the Materials Research Society of Japan, 43(2), p.93 - 96, 2018/04

KNbO$$_3$$ nanocrystals were grown by solvothermal technique assisted by a microwave treatment. We performed high-energy X-ray diffraction to extract average and local structural parameters. The particle size can be evaluated by the Scherrer's equation. The unit cell size was reduced as the particle size increased. The local structure was found to be a rhombohedral structure, which was similar to that of the bulk KNbO$$_3$$.

Journal Articles

New precise measurement of muonium hyperfine structure interval at J-PARC

Ueno, Yasuhiro*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

 Times Cited Count:3 Percentile:85.27(Physics, Atomic, Molecular & Chemical)

Journal Articles

Hydrogen absorption behavior on zirconium under $$gamma$$-radiolysis of nitric acid solution

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(2), p.100 - 106, 2017/05

Zirconium (Zr) has been used as a structural material at the spent nuclear fuel reprocessing plant in Japan because of its excellent corrosion resistance against nitric acid solution. And the radiolytic hydrogen is known to be generated in the spent nuclear fuel solution. Zr is known to be highly susceptible to hydrogen embrittlement. Therefore, evaluating the radiolytic hydrogen absorption behavior of Zr in nitric acid solution (HNO$$_{3}$$) is essential. In this study, immersion tests were conducted on Zr in nitric acid solutions under $$gamma$$-ray irradiation to evaluate its radiolytic hydrogen absorption behavior. Results showed that hydrogen concentration on Zr increased both in 1-3 mol/L HNO$$_{3}$$ and pure water at 5 and 7 kGy/h after immersion. The amount of hydrogen absorption on Zr under $$gamma$$-ray irradiation had a direct correlation with the radiolytic hydrogen generation value in HNO$$_{3}$$. The results of glow discharge optical emission spectrometry, thermal desorption spectroscopy, and X-ray diffraction result shows that the absorbed radiolytic hydrogen generated a hydride on the surface of Zr.

Journal Articles

New muonium HFS measurements at J-PARC/MUSE

Strasser, P.*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12

 Times Cited Count:7 Percentile:90.23(Physics, Atomic, Molecular & Chemical)

Journal Articles

The Effect of crystal textures on the anodic oxidization of zirconium in a boiling nitric acid solution

Kato, Chiaki; Ishijima, Yasuhiro; Ueno, Fumiyoshi; Yamamoto, Masahiro

Journal of Nuclear Science and Technology, 53(9), p.1371 - 1379, 2016/09

AA2015-0626.pdf:1.2MB

 Times Cited Count:5 Percentile:41.31(Nuclear Science & Technology)

The effects of crystal textures and the potentials in the anodic oxidation of zirconium in a boiling nitric acid solution were investigated to study the stress corrosion cracking of zirconium in nitric acid solutions. The growth of the zirconium oxide film dramatically changed depending on the applied potential at a closed depassivation potential (1.47 V vs. SSE). At 1.5 V, the zirconium oxide film rapidly grows, and its growth exhibits cyclic oxidation kinetics in accordance with a nearly cubic rate law. The zirconium oxide film grows according to the quantity of electric charge, and the growth rate does not depend on the crystal texture in the pretransition region before the cyclic oxidation kinetics. However, the growth and cracking under the thick oxide film depend on the crystal texture in the transition region. On the normal direction side, the oxide film thickness decreases on average since some areas of the thick oxide film are separated from the specimen surface owing to the cracks in the thick oxide. On the rolling direction side, cracks are found under the thick oxide film, which deeply propagate along the RD without an external stress. The cracks under the thick oxide film propagate to the center of the oxide layer. The cracks in the oxide layer propagate in the (0002)Zr plane in the zirconium matrix. The oxide layer consists of string-like zirconium oxide and zirconium hydride. The string-like zirconium oxide contains orthorhombic ZrO$$_{2}$$ in addition to monoclinic ZrO$$_{2}$$. As one assumption for the mechanism of crack initiation and propagation without an external stress, it is considered that the oxidizing zirconium hydrides precipitate in the (0002)Zr and then the phase transformation from orthorhombic ZrO$$_{2}$$ to monoclinic ZrO$$_{2}$$ in the oxide layer causes the crack propagation in the (0002) plane.

Journal Articles

Thermal aging effect for creep properties on Ni base refractory alloys

Ishijima, Yasuhiro; Ueno, Fumiyoshi

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 4 Pages, 2015/05

In this study, to evaluate the effect of thermal aging on creep properties of Alloy 625, we carried out creep tests on aged and solution-treated Alloy 625 at 1073 K. According to the creep test results, time-to-rupture decreased by thermal aging when test stress was more than 100 MPa, but did not change when test stress was less than 100 MPa for any specimens. In the solution-treated alloy, creep deformation behaviors changed over 100 MPa. These results show that time-to-rupture was constant because intermetallic compounds precipitated when the test stress was less than 100 MPa in solution-treated alloy. The observed relationship between creep strain rate and test time showed that the precipitation started after 100 hr for solution treated alloys. These results suggest that intermetallic compounds precipitate immediately after furnace operation. And it is appropriate to use creep data of thermal-aged Alloy 625 for the reducing roasting furnace lifetime prediction.

Journal Articles

Beam test of a new radio frequency quadrupole linac for the Japan Proton Accelerator Research Complex

Kondo, Yasuhiro; Morishita, Takatoshi; Yamazaki, Saishun; Hori, Toshihiko; Sawabe, Yuki; Chishiro, Etsuji; Fukuda, Shimpei; Hasegawa, Kazuo; Hirano, Koichiro; Kikuzawa, Nobuhiro; et al.

Physical Review Special Topics; Accelerators and Beams, 17(12), p.120101_1 - 120101_8, 2014/12

 Times Cited Count:6 Percentile:41.95(Physics, Nuclear)

We performed a beam test of a new radio frequency quadrupole linac (RFQ III) for the beam current upgrade of the Japan Proton Accelerator Research Complex. First, the conditioning of RFQ III was conducted, and after 20 h of conditioning, RFQ III became very stable with a nominal peak power and duty factor of 400 kW and 1.5%, respectively. An off-line beam test was subsequently conducted before installation in the accelerator tunnel. The transmission, transverse emittance, and energy spread of the 50-mA negative hydrogen beam from RFQ III were measured and compared with simulation results. The experiment and simulation results showed good agreement; therefore, we conclude that the performance of RFQ III conforms to its design.

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