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Journal Articles

Upgrade of the 3-MeV linac for testing of accelerator components at J-PARC

Kondo, Yasuhiro; Hirano, Koichiro; Ito, Takashi; Kikuzawa, Nobuhiro; Kitamura, Ryo; Morishita, Takatoshi; Oguri, Hidetomo; Okoshi, Kiyonori; Shinozaki, Shinichi; Shinto, Katsuhiro; et al.

Journal of Physics; Conference Series, 1350, p.012077_1 - 012077_7, 2019/12

 Times Cited Count:1 Percentile:52.4

We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac's, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.

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

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

Development of RF chopper system at J-PARC Linac, 2

Hirano, Koichiro; Kondo, Yasuhiro; Kawane, Yusuke; Shinozaki, Shinichi; Miura, Akihiko; Morishita, Takatoshi; Sawabe, Yuki; Sugimura, Takashi*; Naito, Fujio*; Fang, Z.*; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.944 - 947, 2015/09

Two RF-deflecting cavities as a chopper and a beam scraper have been used in the MEBT1 between a 324 MHz RFQ and a 50-MeV DTL of the J-PARC Linac. We replaced with a newly fabricated RF chopper to decrease beam loss for the operation with 50 mA. We installed two new scrapers to absorb the higher power of the deflected beam by the RF chopper. This paper describes the RF chopper system and beam irradiation test results of the scraper.

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:43.07(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.

Journal Articles

Present status of J-PARC linac

Oguri, Hidetomo; Hasegawa, Kazuo; Ito, Takashi; Chishiro, Etsuji; Hirano, Koichiro; Morishita, Takatoshi; Shinozaki, Shinichi; Ao, Hiroyuki; Okoshi, Kiyonori; Kondo, Yasuhiro; et al.

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.389 - 393, 2014/10

no abstracts in English

Journal Articles

Interlock system of beam line for beam current upgrade

Kawane, Yusuke*; Miura, Akihiko; Miyao, Tomoaki*; Hirano, Koichiro; Sugimura, Takashi*; Kato, Yuko; Sawabe, Yuki; Fukuda, Shimpei; Ouchi, Nobuo

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1288 - 1291, 2014/10

In the J-PARC Linac, because an upgrading of a beam current up to 50mA using an RF-driven ion source and a new RFQ Linac cavity is in progress, we have developed a new frontend equipments. In order to protect the scraper against 50 mA, we need to observe the temperature and to avoid the excess heat loading of the scraper surface and to count the irradiated beam particles. We also monitor the beam transmission between the upstream and downstream of the chopper cavity to check the chopping errors using the beam current monitors. We fabricated the interlock system for the temperature, irradiated particle numbers and beam transmission. And we tested them in the test stand with actual beam. This paper describes the interlock system and their test results.

Journal Articles

Electronic stopping power dependence of ion-track size in UO$$_{2}$$ irradiated with heavy ions in the energy range of $$sim$$1MeV/u

Ishikawa, Norito; Sonoda, Takeshi*; Sawabe, Takashi*; Sugai, Hiroyuki*; Sataka, Masao*

Nuclear Instruments and Methods in Physics Research B, 314, p.180 - 184, 2013/11

 Times Cited Count:20 Percentile:82.78(Instruments & Instrumentation)

In order to investigate electronic stopping power dependence of ion-track size in UO$$_{2}$$, ion-tracks in UO$$_{2}$$ irradiated with various ions with the specific energy in the order of 1 MeV/u have been observed by a transmission electron microscope. The ion-tracksize shows monotonic increase as a function of the electronic stopping power. Theion-track size obtained for UO$$_{2}$$ is smaller than that obtained for CeO$$_{2}$$, although these two compounds have same crystallographic structure and similar thermal properties. The ion-track sizes for irradiations with ions having relatively low energy of about1 MeV/u are smaller than those expected from the thermal spike models based on melting temperature criterion. The possible interpretations for the unusually smallion-tracks observed for UO$$_{2}$$ are discussed.

Journal Articles

X-ray study of radiation damage in UO$$_{2}$$ irradiated with high-energy heavy ions

Ishikawa, Norito; Sonoda, Takeshi*; Okamoto, Yoshihiro; Sawabe, Takashi*; Takegahara, Keisuke; Kosugi, Shinya*; Iwase, Akihiro*

Journal of Nuclear Materials, 419(1-3), p.392 - 396, 2011/12

 Times Cited Count:10 Percentile:61.04(Materials Science, Multidisciplinary)

In order to characterize the radiation damage due to ion-track formation in UO$$_{2}$$, polycrystalline samples have been irradiated with 210-MeV Xe ions, and measured with XRD (X-ray diffraction) technique using Cu X-ray. We have also tried EXAFS (extended X-ray absorption fine structure) measurement using X-ray near U L$$_{3}$$-edge. The results show that XRD technique detects damage at relatively low fluence of 10$$^{16}$$ ions/m$$^{2}$$ and higher, while the irradiation-induced change of EXAFS spectra is not observed even at highest fluence of 10$$^{19}$$ ions/m$$^{2}$$. The damage detection may be critically influenced by the depth profile of X-ray penetration.

Oral presentation

Microstructural evolution in UO$$_{2}$$ under accumulation of ion tracks by high energy fission products

Sonoda, Takeshi*; Ishikawa, Norito; Sataka, Masao; Sawabe, Takashi*; Kitajima, Shoichi*; Kinoshita, Motoyasu*

no journal, , 

Microstructural evolutions of ion-irradiated UO$$_{2}$$ were observed by use of a 300 kV FE-TEM and a FE-SEM at CRIEPI. For understanding the effects of accumulation of ion tracks in UO$$_{2}$$, 210 MeV Xe+16 ions irradiation up to a fluence of 1.5 e16 ions/cm$$^{2}$$ were done. At a fluence of 5e14 ions/cm$$^{2}$$ (overlapping num. of tracks: 1e2), elliptical changes of fabricated pores and the formation of dislocations are started. Over 1e16 ions/cm$$^{2}$$ (overlapping num. of tracks: 2e3), the grain sub-divisions are observed and the dislocation density does not tend to increase. These drastic changes in UO$$_{2}$$ indicate that the overlapping of ion tracks will cause the point defects, enhance the diffusion of point defects and dislocations, and form the sub-grains at relatively low temperature.

Oral presentation

Ion-track formation in UO$$_{2}$$ irradiated with high-energy heavy ions

Ishikawa, Norito; Sonoda, Takeshi*; Sawabe, Takashi*; Sugai, Hiroyuki; Sataka, Masao

no journal, , 

One of the intriguing characteristics of the radiation damages due to high-energy ion irradiation in UO$$_{2}$$ is the formation of continuous ion-tracks along ion-paths. It is expected that one of the determining factors of ion-track size is the electronic stopping power. If the electronic stopping power is sufficiently high exceeding a certain threshold, an ion-track can be formed by each traversing ion. In the present study, the TEM study for UO$$_{2}$$ irradiated with various high-energy ions (e.g. 100$$sim$$210 MeV Xe ions and 150$$sim$$310 MeV Au ions) has revealed that the ion-track size depends on the electronic stopping power. The dependence of ion-track size on the electronic stopping power is analyzed within the framework of thermal spike model.

Oral presentation

Ion track formation in UO$$_{2}$$ irradiated with high energy ions

Ishikawa, Norito; Sonoda, Takeshi*; Sawabe, Takashi*; Sataka, Masao

no journal, , 

High energy ions were irradiated to UO$$_{2}$$. The damage trail called ion-track is observed using transmission electron microscope. It is found that the electronic stopping power dependence of ion-track size disagrees with that predicted from preexisting ion-track formation model.

Oral presentation

Effects of ion-track formation and its overlapping in uranium dioxide ceramics irradiated by swift heavy ions

Ishikawa, Norito; Sonoda, Takeshi*; Sawabe, Takashi*; Sataka, Masao

no journal, , 

UO$$_{2}$$ is highly radiation-resistant material, and the origin of the radiation-resistance is analyzed in this study.

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