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JAEA Reports

Design and safety assessment of cooling facilities for air system

Asano, Norikazu; Nishimura, Arashi; Takabe, Yugo; Araki, Daisuke; Yanai, Tomohiro; Ebisawa, Hiroyuki; Ogasawara, Yasushi; Oto, Tsutomu; Otsuka, Kaoru; Otsuka, Noriaki; et al.

JAEA-Technology 2021-045, 137 Pages, 2022/06


A collapse event of a cooling tower for secondary cooling system in the Japan Materials Testing Reactor (JMTR) was caused by the strong winds of Typhoon No.15 on September 9, 2019. As measures against the event, the working group for the renewal of the UCL (Utility Cooling Loop) cooling tower was established in the department of JMTR, and the integrity of the UCL cooling tower, which is the same type of wooden cooling tower as the secondary cooling tower in the JMTR, was investigated. As a result of this investigation, we have decided to replace the existing UCL cooling tower with a new cooling system. After investigations, in order to reduce the risk of collapse due to wood decay, the new cooling system was installed as a component of the air system to be managed as a performance maintenance facility after decommissioning. This report describes the design of and the evaluation results of the facility.

Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:11 Percentile:73.63(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Operation status of the J-PARC RF-driven H$$^{-}$$ ion source

Oguri, Hidetomo; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Shibata, Takanori*; Nammo, Kesao*; Ueno, Akira; Shinto, Katsuhiro

AIP Conference Proceedings 1869, p.030053_1 - 030053_7, 2017/08

 Times Cited Count:5 Percentile:90.98

A cesiated RF-driven negative hydrogen ion source was started to operate in September, 2014 in response to the need for upgrading J-PARC's linac beam current. The ion source mainly comprises a stainless-steel plasma chamber, a beam extractor, and a large vacuum chamber with two turbo molecular pumps of 1500 L/s for differential pumping. The ion source has been successfully providing the required beam current to the accelerator without any significant issues other than a single-incident antenna failure occurred in October, 2014. Continuous operation for approximately 1,000 h was achieved with a beam current and duty factor of 45 mA and 1.25 % (0.5 msec and 25 Hz), respectively. In this paper, we will present the some operation parameters and the beam stability through the long-term user operation.

Journal Articles

High density plasma calculation of J-PARC RF negative ion source

Shibata, Takanori*; Asano, Hiroyuki; Ikegami, Kiyoshi*; Naito, Fujio*; Nammo, Kesao*; Oguri, Hidetomo; Okoshi, Kiyonori; Shinto, Katsuhiro; Takagi, Akira*; Ueno, Akira

AIP Conference Proceedings 1869, p.030017_1 - 030017_11, 2017/08

 Times Cited Count:4 Percentile:87.28

From September 2014, operation of Cs-seeded, multi-cusp, Radio Frequency (RF), hydrogen negative ion source (J-PARC source) has been started. The operation for 1,000 hours of J-PARC source has been achieved with H$$^{-}$$ beam current 45 mA and duty factor of 1.25 % (0.5 msec and 25 Hz). In the present study, mechanisms of hydrogen plasma ramp-up and H$$^{-}$$ production/transport processes in the steady state (which lasts for few 100 us) are investigated by numerical modeling for RF plasma. In the simulation, charged particle (e, H$$^{+}$$, H$$_2^{+}$$, and Cs$$^{+}$$) transport, time variations of inductive and capacitive electromagnetic field, collision processes between charged and neutral (H, H$$_{2}$$) particles are solved simultaneously. The model is applied to KEK parallel computation System-A with 32 nodes and 256 GB memory in order to solve high density RF plasma up to around 10$$^{18}$$ m$$^{-3}$$ with adequate statisticity. In the presentation, time variations of plasma density distributions and average energy are shown with electromagnetic field variations.

Journal Articles

LEBT commissioning of the J-PARC LINAC

Shibata, Takanori*; Ikegami, Kiyoshi*; Liu, Y.*; Maruta, Tomofumi*; Naito, Fujio*; Takagi, Akira*; Asano, Hiroyuki; Kondo, Yasuhiro; Miura, Akihiko; Oguri, Hidetomo; et al.

Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.251 - 253, 2017/05

After upgrade of J-PARC Linac in 2014, Low Energy Beam Transport (LEBT) beam commissioning of the J-PARC LINAC has been made for improving H$$^{-}$$ beam intensity extracted from Linac. Currents of two solenoid coils and steering magnets in LEBT are optimized with extraction and acceleration voltages for static acceleration in ion source (IS) which decides on an initial emittance diagram of H$$^{-}$$ beam. As a result of LEBT and IS parameter optimization, beam transmission rate of RFQ has been reached up to 96% in 50 mA H$$^{-}$$ current operation. Moreover, PIC-MC (Particle-In-Cell Monte-Carlo) simulation models developed for H$$^{-}$$ transport in LEBT. Comparison between experimental and numerical results are presented to clarify beam physics from IS exit to RFQ entrance.

Journal Articles

A 3 MeV linac for development of accelerator components at J-PARC

Kondo, Yasuhiro; Asano, Hiroyuki*; Chishiro, Etsuji; Hirano, Koichiro; Ishiyama, Tatsuya; Ito, Takashi; Kawane, Yusuke; Kikuzawa, Nobuhiro; Meigo, Shinichiro; Miura, Akihiko; et al.

Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.298 - 300, 2017/05

We have constructed a linac for development of various accelerator components at J-PARC. The ion source is same as the J-PARC linac's, and the RFQ is a used one in the J-PARC linac. The beam energy is 3 MeV and nominal beam current is 30 mA. The accelerator has been already commissioned, and the first development program, laser-charge-exchange experiment for the transmutation experimental facility, has been started. In this paper, present status of this 3-MeV linac is presented.

Journal Articles

Status of the J-PARC RF ion source

Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Ueno, Akira; Shibata, Takanori*; Nammo, Kesao*; Shinto, Katsuhiro; Oguri, Hidetomo

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.940 - 943, 2016/11

In 2014 October, operation of cesium-seeded Radio Frequency (RF)-driven negative hydrogen ion (H$$^{-}$$) source was started in J-PARC LINAC. Due to the skillful RF antenna screening and the proper pre-conditioning process, long term unscheduled beam stop due to the antenna failure did not occur for more than 1 year. The continuous operation of 1,350 hours with a peak beam current of 45 mA was achieved in the recent beam run. Moreover, the fluctuation of beam current in a low energy beam transport (LEBT) is kept within $$pm$$2% of target value by application of three feedback systems. An ion source test-stand was assembled to investigate the ion source beam characteristic, for example, the emittance at the position of the RFQ entrance. In the presentation, we will report the recent status of the ion source operation and some experimental results obtained at the ion source test-stand.

Journal Articles

Development of beam scrapers using a 3-Mev linac at J-PARC

Hirano, Koichiro; Asano, Hiroyuki; Ishiyama, Tatsuya; Ito, Takashi; Okoshi, Kiyonori; Oguri, Hidetomo; Kondo, Yasuhiro; Kawane, Yusuke; Kikuzawa, Nobuhiro; Sato, Yoshikatsu; et al.

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.310 - 313, 2016/11

We have used a beam scraper with the incident angle of 65deg to reduce the beam power deposition density in the MEBT between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC linac. The 65$$^{circ}$$ scraper was irradiated by the H$$^{-}$$ beam up to particle number of 1.47E22. We observed a lot of surface projections with several hundred micrometers high in the beam irradiation damage on the scraper by using the laser microscope. In order to study the limits of scrapers, we constructed a new 3 MeV linac at J-PARC. We will conduct the scraper irradiation test at the end of this year.

Journal Articles

Fine-tuning to minimize emittances of J-PARC RF-driven H$$^-$$ ion source

Ueno, Akira; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Oguri, Hidetomo

Review of Scientific Instruments, 87(2), p.02B130_1 - 02B130_5, 2016/02


 Times Cited Count:6 Percentile:33.72(Instruments & Instrumentation)

The Japan Proton Accelerator Research Complex (J-PARC) cesiated rf-driven H$$^-$$ ion source (IS), whose requirements are a peak beam intensity of 60mA within normalized emittances of 1.5 $$pi$$mm$$cdot$$mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 $$mu$$s$$ times$$ 25 Hz) and a life-time of longer than 1month, has been successfully operated for about one year. The results of the fine-tuning to minimize the emittances of the J-PARC-IS with plasma chamber #3, which had the largest emittances with initial settings among four plasma chambers, will be presented in this paper. The rod-filter-filed will be finely tuned by selecting magnets with slightly different field strengths and/or changing gap-lengths. The dependence of the beam-hole-diameter on the emittances will be also presented. The tuning procedure to improve the emittances is one of the most important technologies for the IS of the high-energy and high-intensity accelerator.

Journal Articles

Status of the RF-driven H$$^{-}$$ ion source for J-PARC linac

Oguri, Hidetomo; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Ueno, Akira; Shibata, Takanori*

Review of Scientific Instruments, 87(2), p.02B138_1 - 02B138_3, 2016/02


 Times Cited Count:6 Percentile:33.72(Instruments & Instrumentation)

For the upgrade of the Japan Proton Accelerator Research Complex (J-PARC) linac beam current, a cesiated RF-driven negative hydrogen ion source was installed in 2014 summer shutdown period, and started to operate on September 29, 2014. The ion source has been successfully operated with a beam current and a duty factor of 33 mA and 1.25% (0.5 ms and 25 Hz), respectively. The result of recent beam operation showed that the ion source is capable of continuous operation for approximately 1,100 h. The spark rate at the beam extractor was observed to be less than once a day, which is acceptable level for the user operation. Although the antenna failure occurred during the user operation on October 26, 2014, there were no further serious troubles since then. In this conference, we will present the some operation parameters and the beam stability of the RF-driven ion source through the long-term user operation.

Journal Articles

Numerical study of plasma generation process and internal antenna heat loadings in J-PARC RF negative ion source

Shibata, Takanori*; Nishida, Kenjiro*; Mochizuki, Shintaro*; Mattei, S.*; Lettry, J.*; Hatayama, Akiyoshi*; Ueno, Akira; Oguri, Hidetomo; Okoshi, Kiyonori; Ikegami, Kiyoshi*; et al.

Review of Scientific Instruments, 87(2), p.02B128_1 - 02B128_3, 2016/02


 Times Cited Count:3 Percentile:18.07(Instruments & Instrumentation)

A numerical model of plasma transport and electromagnetic field in the J-PARC RF ion source has been developed to understand relation between antenna coil heat loadings and plasma production/transport processes. From the calculation, the local plasma density increase is observed in the region close to the antenna coil. The magnetic field line with absolute magnetic flux density 30-120 Gauss results in the magnetization of electron which leads to high local ionization rate. The results suggest that modification of magnetic configuration can be made to reduce plasma heat flux onto the antenna.

Journal Articles

Status of the J-PARC RF ion source

Okoshi, Kiyonori; Ueno, Akira; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Oguri, Hidetomo

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1040 - 1044, 2015/09

In order to satisfy the requirements of the J-PARC second stage, which will produce a 1MW beam, the Cs-free LaB$$_{6}$$-filament-driven H$$^{-}$$ ion source was replaced to a cesiated RF-driven H$$^{-}$$ ion source (RF ion source) during the summer shutdown period in 2014. By developing and testing the RF ion source on an off-line test-stand for about five years, it successfully and stably produced a peak current of more than 60mA within the acceptance of the following RFQ linac with the required beam duty-factor of more than 1.25% (500$$mu$$s $$times$$ 25Hz). For about one year, the RF ion source has been operated with a peak current of 33mA routinely, which causes low beam loss in the J-PARC operated with a 500kW beam. It has been also operated with a peak current of 55mA for a few weeks in each two months for the J-PARC beam study striving toward the 1MW beam operation. The beam current is controlled within the error of $$pm$$0.1mA by feed-backing the RF power and the Cs density during the operation. Except for the only one failure of the internal RF-antenna in the beginning of the operation, there was no serious trouble. The RF ion source with the 33mA peak current operation is successfully operated for approximately 1100 hours.

Journal Articles

High-power test of annular-ring coupled structures for the J-PARC linac energy upgrade

Tamura, Jun; Ao, Hiroyuki; Nemoto, Yasuo; Asano, Hiroyuki*; Suzuki, Takahiro*

Journal of the Korean Physical Society, 66(3), p.399 - 404, 2015/02

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

ACSs are going to increase the beam energy of the J-PARC linac from 181 to 400 MeV. The 2011 Tohoku earthquake damaged the J-PARC facilities and the cavity conditioning was interrupted for two years. After the restoration of the facility, the two ACS cavities (M01 and M11) were conditioned. They achieved to 15-20% above the designed accelerating field of 4.2 MV/m. Since M01 was conditioned six years ago, the conditioning time required for M01 was drastically reduced from that for the first time. During the high-power operation for M11, which is an unique cavity equipped with a capacitive iris in a waveguide, no significant increase of the temperature and the discharge rate around the capacitive iris was observed. The vacuum pressure was sufficiently low (4$$times$$10$$^{-6}$$ Pa) even from the view point of beam loss due to residual gas scattering. The more stable operation can be expected through one-month conditioning before beam commissioning.

Journal Articles

Resuming of ACS high-power test for J-PARC Linac Energy Upgrade

Tamura, Jun; Ao, Hiroyuki; Nemoto, Yasuo; Asano, Hiroyuki*; Suzuki, Takahiro*

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.437 - 439, 2014/06

no abstracts in English

Journal Articles

Occurrence and potential activity of denitrifiers and methanogens in groundwater at 140 m depth in Pliocene diatomaceous mudstone of northern Japan

Katsuyama, Chie*; Nashimoto, Hiroaki*; Nagaosa, Kazuyo*; Ishibashi, Tomotaka*; Furuta, Kazuki*; Kinoshita, Takeshi*; Yoshikawa, Hideki; Aoki, Kazuhiro; Asano, Takahiro*; Sasaki, Yoshito; et al.

FEMS Microbiology Ecology, 86(3), p.532 - 543, 2013/12

 Times Cited Count:14 Percentile:37.98(Microbiology)

Anaerobic microbial activity has a major influence on the subsurface environment, and should be considered in subsurface activities including the construction of radioactive waste repositories. We investigated denitrification and methanogenesis in anoxic groundwater from 140 m depth in two boreholes, where the redox potential fluctuated. The average maximum potential denitrification rates, measured under anaerobic conditions in the two boreholes using an $$^{15}$$N tracer. Methanogenesis candidates were detected by 16S rRNA gene analysis. Although the stable isotope signatures suggested that some of the dissolved methane was of biogenic origin, no potential for methane production was evident during the incubations. The groundwater at 140 m depth did not contain oxygen, had an Eh ranging from -144 to 6.8 mV, and was found to be a potential field for denitrification.

Journal Articles

Dielectric constant measurement using resonant frequencies for minimizing the reflection of pillbox RF windows

Ao, Hiroyuki; Asano, Hiroyuki; Tamura, Jun; Ouchi, Nobuo; Takata, Koji*; Naito, Fujio*

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1124 - 1126, 2013/08

In the case of the RF window operated with the standing-wave cavity coupled to waveguides using coupling apertures, the reflection of the RF window affects the total coupling factor (voltage standing wave ratio, VSWR) consisted of the RF window and the cavity. Hence, the reflection (VSWR) of the RF window should be minimized not to change the cavity VSWR optimized separately, and to prevent standing waves between the RF window and the cavity. For minimizing the VSWR of the pillbox-type RF window, this report proposes that the dielectric constant of the ceramic is measured directly using the resonant frequency in the fabrication process of the RF window. In this work, three RF windows are fabricated additionally using the same type ceramic (NTK HA95), the small VSWR $$(< 1.05)$$ could be achieved using this procedure. This result also shows that the dielectric constant increases linearly with increasing the density.

Journal Articles

Beam loss reduction by the beam duct realignment in the J-PARC linac beam transport line

Tamura, Jun; Ao, Hiroyuki; Asano, Hiroyuki; Ikegami, Masanori*; Maruta, Tomofumi; Miura, Akihiko; Morishita, Takatoshi; Oguri, Hidetomo; Ouchi, Nobuo; Sawabe, Yuki*; et al.

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.377 - 380, 2013/08

In the J-PARC linac, almost all the cavities and magnets have been precisely aligned because the accelerator tunnel has been deformed by the 2011 Tohoku Earthquake. In the beam transport line called MEBT2 and A0BT at the downstream of the drift tube linac, the beam duct has been roughly aligned after the precise alignment of the quadruple doublets. During the first beam operation after the earthquake, remarkable beam loss and residual radiation have been recognized at the MEBT2 and A0BT. As the result of the duct position measurement, the misalignement including over 10 mm shift from the beam axis was found. By conducting the beam duct realignment, the beam loss and the residual radiation were successfully decreased. In this paper, the procedure of the beam duct alignment and the beam loss due to the misalignment are described.

Journal Articles

Microprocessing of arched bridge structures with epoxy resin by proton beam writing

Takano, Katsuyoshi*; Asano, Atsushi*; Maeyoshi, Yuta*; Marui, Hiromi*; Omichi, Masaaki*; Saeki, Akinori*; Seki, Shu*; Sato, Takahiro; Ishii, Yasuyuki; Kamiya, Tomihiro; et al.

Journal of Photopolymer Science and Technology, 25(1), p.43 - 46, 2012/07

 Times Cited Count:2 Percentile:7.18(Polymer Science)

Journal Articles

Fabrication of concave and convex structure array consisted of epoxy long-nanowires by light and heavy ion beams lithography

Takano, Katsuyoshi*; Sugimoto, Masaki; Asano, Atsushi*; Maeyoshi, Yuta*; Marui, Hiromi*; Omichi, Masaaki*; Saeki, Akinori*; Seki, Shu*; Sato, Takahiro; Ishii, Yasuyuki; et al.

Transactions of the Materials Research Society of Japan, 37(2), p.237 - 240, 2012/06

Journal Articles

Fabrication of poly(9,9'-dioctylfluorene)-based nano- and microstructures by proton beam writing

Maeyoshi, Yuta*; Takano, Katsuyoshi*; Asano, Atsushi*; Marui, Hiromi*; Omichi, Masaaki*; Sato, Takahiro; Kamiya, Tomihiro; Ishii, Yasuyuki; Okubo, Takeru; Koka, Masashi; et al.

Japanese Journal of Applied Physics, 51(4R), p.045201_1 - 045201_4, 2012/04

 Times Cited Count:1 Percentile:4.68(Physics, Applied)

63 (Records 1-20 displayed on this page)