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JAEA Reports

Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region, 4 (Joint research)

Nagai, Takayuki; Okamoto, Yoshihiro; Shibata, Daisuke*; Kojima, Kazuo*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Hatakeyama, Kiyoshi*

JAEA-Research 2024-014, 54 Pages, 2025/02

JAEA-Research-2024-014.pdf:7.02MB

XAFS measurements in the soft X-ray region are suitable for evaluating the chemical state of the surface layer of a measurement sample because the X-ray transmittance is low. In this study, the purpose of the study was to confirm the difference between the coagulated surface layer and the inside of the simulated waste glasses by measuring the K-edge of the glass constituent elements boron, oxygen, sodium, and silicon, and the L$$_{3}$$ edge of the waste component cerium. As a result, the B K-edge XANES spectra showed that the proportion of B-O tetracoordinate sp$$^{3}$$ structures (BO$$_{4}$$) on the surface layer of the coagulated glass samples was higher than that on the cut surface inside the glass samples, which is expected to improve the water resistance of the coagulated surface. On the other hand, the O K-edge XANES spectra suggested that the O abundance in the coagulated surface layer was lower than that in the cut surface inside the glass samples, and that alkali metal elements may be concentrated in the coagulated surface layer. However, no difference was observed in the Na K-edge XANES spectra between the coagulated surface layer and the cut surface, and no difference was observed in the Si K-edge XANES spectra between the solidified surface and the inside of glass samples. In addition, the Ce L$$_{3}$$-edge XANES spectra confirmed that the Ce valence in the surface layer of coagulated glass samples were oxidized compared to the inside of glass samples.

Journal Articles

Application of machine learning to spattering phenomena in laser cutting

Kusumoto, Toshiyuki*; Saruta, Koichi; Naoe, Takashi; Teshigawara, Makoto; Futakawa, Masatoshi; Hasegawa, Kazuo*; Tsuboi, Akihiko

Jikken Rikigaku, 23(4), p.310 - 315, 2023/12

Reducing spatter, i.e., melt droplets flown out of the melt pool, is one of the critical issues when laser cutting is employed as a machining tool for radioactive wastes because the ejected droplets can lead to radioactive contamination with potential human exposure. The spattering phenomena are complicated processes that involve multiple physical phenomena, causing difficulty in the determination of laser parameters to minimize the amount of spatter. Here we observe the spatter ejected from 316L stainless steel plates using a high-speed camera and apply a machine learning technique to these captured images on the basis of three distinctive behaviors appeared at specific time intervals of the process of spattering phenomena: (I) a vapor, (II) a liquid film and breakup into droplets, and (III) a liquid capillary. The numerical model established through the machine learning technique predicts the spattering phenomena with an accuracy of 89% and can be used to determine the laser power and beam diameter that reduce the spatter eruption during laser irradiation.

JAEA Reports

Structural investigation of borosilicate glasses by using XAFS measurement in soft X-ray region, 3 (Joint research)

Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Shibata, Daisuke*; Kojima, Kazuo*; Hasegawa, Takehiko*; Sato, Seiichi*; Fukaya, Akane*; Hatakeyama, Kiyoshi*

JAEA-Research 2023-004, 45 Pages, 2023/09

JAEA-Research-2023-004.pdf:6.07MB

The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, simulated waste glass samples were prepared and the chemical state regarding boron (B), silicon (Si) and waste elements of iron (Fe), cesium (Cs) were estimated by using XAFS measurement in soft X-ray region. To understand the chemical stability of simulated waste glasses, XANES spectra of B K-edge, Fe L$$_{3}$$, L$$_{2}$$-edge, and Cs M$$_{5}$$, M$$_{4}$$-edge were measured on the glass surface exposed to the leachate. As a result, it was found that the glass surface exposed to the leachate was changed and it was difficult to obtain a clear XANES spectrum. From the B K-edge XANES spectra on glass surfaces exposed to the leachate, an increase in three-coordination of B-O (BO$$_{3}$$) and a decrease in four-coordination of B-O (BO$$_{4}$$) were observed compared to the glass surfaces before immersion. The XANES spectra of Fe L$$_{3}$$, L$$_{2}$$-edge, and Cs M$$_{5}$$, M$$_{4}$$-edge show that as the exposure time in the leachate increases, the Cs present on the glass surface dissolves into the leachate. The XANES spectra of Si K-edge were measured on simulated waste glass surfaces before immersion, and it was confirmed that the change in XANES spectra given by Na$$_{2}$$O concentration had a larger effect than the waste component concentration.

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:74.40(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

The Muon linac project at J-PARC

Kondo, Yasuhiro; Kitamura, Ryo; Fuwa, Yasuhiro; Morishita, Takatoshi; Moriya, Katsuhiro; Takayanagi, Tomohiro; Otani, Masashi*; Cicek, E.*; Ego, Hiroyasu*; Fukao, Yoshinori*; et al.

Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.636 - 641, 2022/09

The muon linac project for the precise measurement of the muon anomalous magnetic and electric dipole moments, which is currently one of the hottest issues of the elementary particle physics, is in progress at J-PARC. The muons from the J-PARC muon facility are once cooled to room temperature, then accelerated up to 212 MeV with a normalized emittance of 1.5 $$pi$$ mm mrad and a momentum spread of 0.1%. Four types of accelerating structures are adopted to obtain the efficient acceleration with a wide beta range from 0.01 to 0.94. The project is moving into the construction phase. We already demonstrated the re-acceleration scheme of the decelerated muons using a 324-MHz RFQ in 2017. The high-power test of the 324-MHz Interdigital H-mode (IH) DTL using a prototype cavity was performed in 2021. The fabrication of the first module of 14 modules of the 1296-MHz Disk and Washer (DAW) CCL will be done to confirm the production process. Moreover, the final design of the travelling wave accelerating structure for the high beta region is also proceeding. In this paper, the recent progress toward the realization of the world first muon linac will be presented.

Journal Articles

Present status of the R&D of the superconducting linac for the JAEA-ADS

Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo

JPS Conference Proceedings (Internet), 33, p.011043_1 - 011043_5, 2021/03

The Japan Atomic Energy Agency (JAEA) has been working in the research and development of an Accelerator Driven Subcritical System (ADS) for the transmutation of nuclear waste. The ADS proposed by JAEA consists of a CW proton linac of 30 MW coupling with a subcritical core reactor. The accelerator will be operated with a beam current of 20 mA. Normal conducting Radio-Frequency Cavities (NRFC) and Superconducting Radio-Frequency Cavities (SRFC) will be used to achieve final energy of 1.5 GeV, and the SRFC will be employed for the main part of the acceleration: from 2 MeV to 1.5 GeV. In the first stage of the accelerator development, the focus was the design and optimization of the SRFC models and the beam optics. For the SRFC sections, the acceleration will be done by using Half Wave Resonators (HWR), Single Spokes (SS), and Elliptical cavities (Ellip) operating with a frequency of 162, 324, and 648 MHz, respectively. The beam optics were optimized satisfying the equipartitioning condition to control the emittance growth, which helped to reduce the beam halos and the beam loss.

Journal Articles

Reliability of J-PARC accelerator system over the past decade

Yamamoto, Kazami; Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*

JPS Conference Proceedings (Internet), 33, p.011016_1 - 011016_7, 2021/03

The Japan Proton Accelerator Research Complex (J-PARC) is a multipurpose facility for scientific experiments. The accelerator complex consists of a 400-MeV Linac, a 3-GeV Rapid-Cycling Synchrotron (RCS) and a 30-GeV Main Ring synchrotron (MR). The RCS delivers a proton beam to the neutron target and MR, and the MR delivers the beams to the neutrino target and the Hadron Experimental Facility. The first operation of the neutron experiments began in December 2008. Following this, the user operation has been continued with some accidental suspensions. These suspensions include the recovery work due to the Great East Japan Earthquake in March 2011 and the radiation leak incident at the Hadron Experimental Facility. In this report, we summarize the major causes of suspension, and the statistics of the reliability of J-PARC accelerator system is analyzed. Owing to our efforts to achieve higher reliability, the Mean Time Between Failure (MTBF) has been improved.

Journal Articles

Development of long pulse arc driven ion source for iBNCT

Shibata, Takanori*; Sugimura, Takashi*; Ikegami, Kiyoshi*; Takagi, Akira*; Sato, Masaharu*; Naito, Fujio*; Okoshi, Kiyonori; Hasegawa, Kazuo

JPS Conference Proceedings (Internet), 33, p.011009_1 - 011009_6, 2021/03

Upgrade of beam current in the Linac of Ibaraki Boron Neutron Capture Therapy (iBNCT) is one of the most important requirements to realize clinical trial. By 2018, the measurement of the produced neutrons characteristics and the neutron irradiation experiment for living cells have been done by producing 8-MeV proton beam current at the beryllium target with average current up to 2 mA. In order to satisfy the original clinical trial conditions, 5 mA average beam current is required at the target. For this goal, peak beam current extracted from the ion source should be increased to 60 mA from the present 30 mA with duty factor up to more than 10% (pulse width up to 1 ms and repetition rate up to more than 100 Hz). Stability of the peak current in the macro pulse is also important for the clinical application.

Journal Articles

RF design of the prototype spoke cavity for the JAEA-ADS linac

Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*

JPS Conference Proceedings (Internet), 33, p.011049_1 - 011049_6, 2021/03

Journal Articles

Development of a bunch-width monitor for low-intensity muon beam below a few MeV

Sue, Yuki*; Yotsuzuka, Mai*; Futatsukawa, Kenta*; Hasegawa, Kazuo; Iijima, Toru*; Iinuma, Hiromi*; Inami, Kenji*; Ishida, Katsuhiko*; Kawamura, Naritoshi*; Kitamura, Ryo; et al.

Physical Review Accelerators and Beams (Internet), 23(2), p.022804_1 - 022804_7, 2020/02

 Times Cited Count:2 Percentile:20.59(Physics, Nuclear)

A destructive monitor to measure the longitudinal bunch width of a low-energy and low-intensity muon beam was developed. This bunch-width monitor (BWM) employed microchannel plates to detect a single muon with high time resolution. In addition, constant-fraction discriminators were adopted to suppress the time-walk effect. The time resolution was measured to be 65 ps in rms using a picosecond-pulsed laser. This resolution satisfied the requirements of the muon linac of the J-PARC E34 experiment. We measured the bunch width of negative-muonium ions accelerated with a radio-frequency quadrupole using the BWM. The bunch width was successfully measured to be $$sigma$$ 54 $$pm$$ 11 ns, which is consistent with the simulation.

Journal Articles

Disk and washer coupled cavity linac design and cold-model for muon linac

Otani, Masashi*; Futatsukawa, Kenta*; Mibe, Tsutomu*; Naito, Fujio*; Hasegawa, Kazuo; Ito, Takashi; Kitamura, Ryo; Kondo, Yasuhiro; Morishita, Takatoshi; Iinuma, Hiromi*; et al.

Journal of Physics; Conference Series, 1350, p.012097_1 - 012097_7, 2019/12

 Times Cited Count:3 Percentile:78.48(Physics, Particles & Fields)

A disk and washer (DAW) coupled cavity linac (CCL) has been developed for a middle velocity part in a muon linac to measure muon anomalous magnetic moment and search for electric dipole moment. I will accelerate muons from $$v/c$$ = $$beta$$ = 0.3 to 0.7 at an operational frequency of 1.3GHz. In this poster, the cavity design, beam dynamics design, and the cold-model measurements will be presented.

Journal Articles

Negative muonium ion production with a C12A7 electride film

Otani, Masashi*; Fukao, Yoshinori*; Futatsukawa, Kenta*; Kawamura, Naritoshi*; Matoba, Shiro*; Mibe, Tsutomu*; Miyake, Yasuhiro*; Shimomura, Koichiro*; Yamazaki, Takayuki*; Hasegawa, Kazuo; et al.

Journal of Physics; Conference Series, 1350, p.012067_1 - 012067_6, 2019/12

 Times Cited Count:3 Percentile:78.48(Physics, Particles & Fields)

Negative muonium atom ($$mu^+$$e$$^-$$e$$^-$$, Mu$$^-$$) has unique features stimulating potential interesting for several scientific fields. Since its discovery in late 1980's in vacuum, it has been discussed that the production efficiency would be improved using a low-work function material. C12A7 was a well-known insulator as a constituent of alumina cement, but was recently confirmed to exhibit electric conductivity by electron doping. The C12A7 electride has relatively low-work function (2.9 eV). In this paper, the negative muonium production measurement with several materials including a C12A7 electride film will be presented. Measured production rate of the Mu$$^-$$ were 10$$^{-3}$$/s for all the Al, electride, and SUS target. Significant enhancement on electride target was not observed, thus it is presumed that the surface condition should be more carefully treated. There was no material dependence of the Mu$$^-$$ averaged energy: it was 0.2$$pm$$0.1keV.

Journal Articles

Development of inter-digital H-mode drift-tube linac prototype with alternative phase focusing for a muon linac in the J-PARC muon g-2/EDM experiment

Nakazawa, Yuga*; Iinuma, Hiromi*; Iwata, Yoshiyuki*; Iwashita, Yoshihisa*; Otani, Masashi*; Kawamura, Naritoshi*; Mibe, Tsutomu*; Yamazaki, Takayuki*; Yoshida, Mitsuhiro*; Kitamura, Ryo; et al.

Journal of Physics; Conference Series, 1350, p.012054_1 - 012054_7, 2019/12

 Times Cited Count:7 Percentile:94.59(Physics, Particles & Fields)

An inter-digital H-mode drift-tube linac (IH-DTL) is developed in a muon linac at the J-PARC E34 experiment. IH-DTL will accelerate muons from 0.34 MeV to 4.5 MeV at a drive frequency of 324 MHz. Since IH-DTL adopts an APF method, with which the beam is focused in the transverse direction using the rf field only, the proper beam matching of the phase-space distribution is required before the injection into the IH-DTL. Thus, an IH-DTL prototype was fabricated to evaluate the performance of the cavity and beam transmission. As a preparation of the high-power test, tuners and coupler are designed and fabricated. In this paper, the development of the tuner and the coupler and the result of the low-power measurement will be presented.

Journal Articles

Electromagnetic design of the prototype spoke cavity for the JAEA-ADS linac

Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*

Proceedings of 19th International Conference on RF Superconductivity (SRF 2019) (Internet), p.399 - 402, 2019/11

Journal Articles

Bunch size measurement with high time resolution for RF accelerated muon beam

Sue, Yuki*; Iijima, Toru*; Inami, Kenji*; Yotsuzuka, Mai*; Iinuma, Hiromi*; Nakazawa, Yuga*; Otani, Masashi*; Kawamura, Naritoshi*; Shimomura, Koichiro*; Futatsukawa, Kenta*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.55 - 60, 2019/07

The result of bunch size measurement of muon accelerated by RFQ up to 89 keV is presented in this paper. A four-stage muon linac for precise measurement of muon property is under construction in the J-PARC. The demonstration of the first muon RF acceleration with an RFQ linac was conducted and the transverse profile of the accelerated muons was measured in 2017. As one of the remaining issues for the beam diagnostic system, the longitudinal beam profile after the RFQ should be measured to match the profile to the designed acceptance of the subsequent accelerator. For this purpose, the new longitudinal beam monitor using the microchannel plate is under development. The time resolution of the monitor aims to be around 30 to 40 ps corresponding to 1% of a period of an operating frequency of the accelerator, which is 324 MHz. On November 2018, the bunch size of accelerated negative muonium ion of 89 keV with the RFQ was measured using this monitor at the J-PARC MLF. The measured bunch width is $$0.54pm0.13$$ ns, which is consistent with the simulation.

Journal Articles

Development of RF input coupler for Inter-digital H-mode drift-tube linac prototype with alternative phase focusing in muon linac

Nakazawa, Yuga*; Iinuma, Hiromi*; Iwashita, Yoshihisa*; Iwata, Yoshiyuki*; Otani, Masashi*; Kawamura, Naritoshi*; Kitamura, Ryo; Kondo, Yasuhiro; Saito, Naohito; Sue, Yuki*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.404 - 407, 2019/07

An inter-digital H-mode drift-tube linac (IH-DTL) is developed in a muon linac at the J-PARC E34 experiment. IH-DTL will accelerate muons from 0.34 MeV to 4.5 MeV at a drive frequency of 324 MHz. Since IH-DTL adopts an APF method, with which the beam is focused in the transverse direction using the rf field only, the proper beam matching of the phase-space distribution is required before the injection into the IH-DTL. Thus, an IH-DTL prototype was fabricated to evaluate the performance of the cavity and beam transmission. As a preparation of the high-power test, tuners and coupler are designed and fabricated. In the low power measurement, we decided the loop structure with witch the VSWR = 1.01 and field distortion of within 7%. In this paper, the development of the tuner and the coupler and the result of the low-power measurement will be presented.

Journal Articles

Development of the longitudinal beam profile monitor with high time resolution for realization of low-emittance muon beam in the J-PARC E34 muon g-2/EDM experiment

Yotsuzuka, Mai*; Iijima, Toru*; Iinuma, Hiromi*; Inami, Kenji*; Otani, Masashi*; Kawamura, Naritoshi*; Kitamura, Ryo; Kondo, Yasuhiro; Saito, Naohito; Shimomura, Koichiro*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.814 - 817, 2019/07

The J-PARC E34 experiment aims to measure the muon anomalous magnetic moment and the electric dipole moment with a high precision. In this experiment, thermal muonium is produced and ionized by laser resonance to generate ultra-slow muons, which are then accelerated in a multistage muon linac. In order to satisfy the experimental requirements, suppression of the emittance growth during the acceleration is necessary. Because the main cause of the emittance growth is beam mismatching between the accelerating stages, the transverse and longitudinal beam monitoring is important. The longitudinal beam monitor has to measure the bunch length with the resolution equivalent to tens of picoseconds, which is 1% of the acceleration phase of 324 MHz. In addition, it should be sensitive to single muon because the beam intensity is limited during the commissioning phase. To realize above requirements, we are developing a longitudinal beam monitor with a micro channel plate, and the test bench to evaluate the monitor performance. So far, the time resolution of the beam monitor was obtained to be 65 ps in RMS including the jitter on the test bench. We also succeeded in measuring the longitudinal bunch size of the muon beam accelerated by RFQ using the beam monitor. In this paper, the results of the performance evaluation for this beam monitor are reported.

Journal Articles

Status of J-PARC accelerators

Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*; Yamamoto, Noboru*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1235 - 1239, 2019/07

After the summer shutdown in 2018, the J-PARC restarted user operation in late October. While beam power to the Materials and Life Science Experimental Facility (MLF) was 500 kW as before the summer shutdown, linac beam current was increased from 40 to 50 mA. Operation of the Main Ring (MR) was suspended due to the modification and/or maintenance of the Superkamiokande (neutrino detector) and Hadron experimental facility. The user operation was resumed in the middle of February for the Hadron experimental facility at 51 kW. But on March 18, one of the bending magnets in the beam transport line to the MR had a failure. It was temporary recovered and restored beam operation on April 5, but the failure occurred again on April 24 and the beam operation of the MR was suspended. In the fiscal year of 2018, the availabilities for the MLF, neutrino and hadron facilities are 94%, 86%, and 74%, respectively.

Journal Articles

Cavity and optics design of the accelerator for the JAEA-ADS project

Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.107 - 111, 2019/07

Journal Articles

Development of the longitudinal beam monitor with high time resolution for a muon linac in the J-PARC E34 experiment

Yotsuzuka, Mai*; Iijima, Toru*; Inami, Kenji*; Sue, Yuki*; Iinuma, Hiromi*; Nakazawa, Yuga*; Saito, Naohito; Hasegawa, Kazuo; Kondo, Yasuhiro; Kitamura, Ryo; et al.

Proceedings of 10th International Particle Accelerator Conference (IPAC '19) (Internet), p.2571 - 2574, 2019/06

The J-PARC E34 experiment aims to measure the muon anomalous magnetic moment and the electric dipole moment with a high precision. In this experiment, thermal muonium is produced and ionized by laser resonance to generate ultra-slow muons, which are then accelerated in a multistage muon linac. In order to satisfy the experimental requirements, suppression of the emittance growth during the acceleration is necessary. Because the main cause of the emittance growth is beam mismatching between the accelerating stages, the transverse and longitudinal beam monitoring is important. The longitudinal beam monitor has to measure the bunch length with the resolution equivalent to tens of picoseconds, which is 1% of the acceleration phase of 324 MHz. In addition, it should be sensitive to single muon because the beam intensity is limited during the commissioning phase. To realize above requirements, we are developing a longitudinal beam monitor with a micro channel plate, and the test bench to evaluate the monitor performance. So far, the time resolution of the beam monitor was obtained to be 65 ps in RMS including the jitter on the test bench. We also succeeded in measuring the longitudinal bunch size of the muon beam accelerated by RFQ using the beam monitor. Further improvement of the measurement system is needed to guarantee the required accuracy. In this paper, the results of the performance evaluation for this beam monitor are reported.

271 (Records 1-20 displayed on this page)