Refine your search:     
Report No.
 - 
Search Results: Records 1-11 displayed on this page of 11
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Mitigation of cavitation damage in J-PARC mercury target vessel

Naoe, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Wakui, Takashi; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi

JPS Conference Proceedings (Internet), 28, p.081004_1 - 081004_6, 2020/02

The beam window of the mercury target vessel in J-PARC is severely damaged by the cavitation. The cavitation damage is a crucial factor to limit lifetime of the target because it increases with the beam power. Therefore, mitigating cavitation damage is an important issue to operate the target stably for long time at 1 MW. At J-PARC, to mitigate the cavitation damage: gas microbubbles are injected into mercury for suppressing pressure waves, and double-walled structure with a narrow channel of 2 mm in width to form high-speed mercury flow ($$sim$$4m/s) has been adopted. After operation, the beam window was cut to inspect the effect of the cavitation damage mitigation on inner wall. We optimized cutting conditions through the cold cutting tests, succeeding in cutting the target No.2 (without damage mitigation technologies) smoothly in 2017, and target No.8 with damage mitigation technologies. In the workshop, progress of cavitation damage observation for the target vessel will be presented.

Journal Articles

Pulsed pressure induced cavitation erosion in mercury narrow channel under flowing conditions

Naoe, Takashi; Kogawa, Hiroyuki; Tanaka, Nobuatsu*; Futakawa, Masatoshi

Advanced Experimental Mechanics, 4, p.17 - 21, 2019/08

We have introduced the following two techniques to mitigate the pressure wave-induced cavitation damage in the mercury target. One is the gas microbubble injection into the flowing mercury, and the other is the double-walled structure with a narrow gap channel at the proton beam entrance portion of the mercury vessel. The latter is expected to mitigate the cavitation damage due to the high-speed liquid flow ($$sim$$ 4 m/s) and the narrow gap boundary (2 mm). To quantitatively investigate the effect of double-walled structure on cavitation damage, cavitation damage tests were conducted by parametrically changing mercury flow velocity and gap width of the channel wall. The results showed that the damage evaluated as a surface roughness was reduced by increasing the flow velocity. By contrast, the effect of gap width on cavitation damage was hardly observed under flowing conditions.

Journal Articles

Pitting damage evaluation by liquid/solid interface impact analysis

Naoe, Takashi; Futakawa, Masatoshi; Oi, Toshiyuki; Ishikura, Shuichi*; Ikeda, Yujiro

Zairyo, 54(11), p.1184 - 1190, 2005/11

High power spallation targets for neutron sources are being developed in the world. Mercury target will be installed at the material science and life facility in J-PARC, which will promote innovative science. The mercury target is subject to the pressure wave caused by the proton bombarding in the mercury. The pressure wave propagation induces the cavitation in mercury that imposes localized impact damage on the target vessel. The impact erosion is a critical issue to decide the lifetime of the target. The electro Magnetic IMpact Testing Machine, MIMTM, was developed to reproduce the localized impact erosion damage and evaluate the damage formation. Additionally, droplet impact analysis was carried out to investigate the correlation between isolate pit profile and micro-jet velocity. We confirmed that value of depth/radius was able to estimate micro jet-velocity. And the velocity at 560W in MIMTM was estimated to be 225$$sim$$325 m/s. Furthermore, surface-hardening treatments were inhibited pit formation in plastic deformation.

Journal Articles

Micro-impact damage caused by mercury bubble collapse

Futakawa, Masatoshi; Naoe, Takashi*; Kogawa, Hiroyuki; Date, Hidefumi*; Ikeda, Yujiro

JSME International Journal, Series A, 48(4), p.234 - 239, 2005/10

Mercury target will be installed at the material science and life facility in J-PARC, which will promote innovative science. The mercury target will be subjected to the pressure wave caused by proton bombarding in the mercury. The pressure wave propagation induces the cavitation in mercury that imposes localized impact damage on the target vessel. The impact erosion is a critical issue to decide the lifetime of target. An electromagnetic impact testing machine, MIMTM, was developed to reproduce the localized impact erosion damage and evaluate the damage formation. Additionally, droplet impact analyses were carried out to investigate the correlation between isolate pit profile and micro-jet velocity. We confirmed that the value of depth/radius was applicable to estimate micro-jet velocity, and the velocity at 560 W in MIMTM equivalent to 1MW proton beam injection was 300 m/s approximately.

Journal Articles

Erosion damage evaluation using acoustic vibration induced by micro-bubble collapse

Naoe, Takashi*; Futakawa, Masatoshi; Koyama, Tomofumi*; Kogawa, Hiroyuki; Ikeda, Yujiro

Jikken Rikigaku, 5(3), p.280 - 285, 2005/09

no abstracts in English

Journal Articles

Damage diagnostic of localized impact erosion by measuring acoustic vibration

Futakawa, Masatoshi; Naoe, Takashi*; Kogawa, Hiroyuki; Ikeda, Yujiro

Journal of Nuclear Science and Technology, 41(11), p.1059 - 1064, 2004/11

 Times Cited Count:11 Percentile:40.92(Nuclear Science & Technology)

High power spallation targets for neutron sources are developing in the world. Mercury target will be installed at the material and life science facility in J-PARC, which will promote innovative science. The mercury target is subject to the pressure wave caused by the proton bombarding mercury. The pressure wave propagation induces the cavitation in mercury that imposes localized impact damage on the target vessel. The impact erosion is a critical issue to decide the lifetime of the target. The electric Magnetic Impact Testing Machine, MIMTM, was developed to produce the localized impact erosion damage and evaluate the damage formation. Acoustic vibration measurement was carried out to investigate the correlation between damage and acoustic vibration. It was confirmed that the acoustic vibration is useful to predict the damage due to the localized impact erosion and to diagnose the structural integrity.

Journal Articles

Estimation of incubation time of cavitation erosion for various cavitating conditions

Soyama, Hitoshi*; Futakawa, Masatoshi

Tribology Letters, 17(1), p.27 - 30, 2004/07

 Times Cited Count:17 Percentile:41.32

Estimation have been made, resulting in a general method for the prediction of the incubation time for cavitation erosion using various cavitating conditions and materials. From a single erosion test, the incubation time can be estimated for various conditions and materials by plotting the mass loss as a function of exposure time to cavitation on a log-log scale.

Journal Articles

Pitting damage formation up to over 10 million cycles; Off-line test by MIMTM

Futakawa, Masatoshi; Naoe, Takashi; Kogawa, Hiroyuki; Tsai, C.-C.*; Ikeda, Yujiro

Journal of Nuclear Science and Technology, 40(11), p.895 - 904, 2003/11

 Times Cited Count:50 Percentile:4.9(Nuclear Science & Technology)

A liquid-mercury target system for the MW-scale target is being developed in the world. The pitting damage induced by pressure wave propagation gets to be one of critical issues to estimate the life of the target structure with mercury and to evaluate its structural integrity. The off-line test on the pitting damage at high cycles over 10 millions was carried out using a novel device, the MIMTM which drives electromagnetically to impose pulse pressure into the mercury. It was found that from the pitting damage data obtained by the MIMTM that the pitting damage can be characterized in two steps, an incubation period that can extend to more than 106 cycles in 316SS and 107 cycles in surface hardening treated one and steady state erosion where mass loss scales with the number of cycles to approximately the 1.27 power for mercury. The length of the incubation period is primarily a function of the material and the intensity of the pressure. This observation provides a simple model for estimating lifetime for different materials and beam power.

JAEA Reports

Off-line tests on pitting damage in mercury target

Futakawa, Masatoshi; Kogawa, Hiroyuki; Tsai, C.-C.*; Ishikura, Shuichi*; Ikeda, Yujiro

JAERI-Research 2003-005, 70 Pages, 2003/03

JAERI-Research-2003-005.pdf:12.08MB

A liquid-mercury target system for the MW-scale target is being developed in the world. The moment the proton beams bombard the target, stress waves will be imposed on the beam window and pressure waves will be generated in the mercury by the thermally shocked heat deposition. Provided that the negative pressure generates through its propagation in the mercury target and causes cavitation in the mercury, there is the possibility for the cavitation bubbles collapse to form pits on the interface between the mercury and the target vessel wall. In order to estimate the cavitation erosion damage due to pitting, two types of off-line tests were performed: Split Hopkinson Pressure Bar (SHPB), and Magnetic IMpact Testing Machine (MIMTM). The data on the pitting damage at the high cycle impacts up to 10 million were given by the MIMTM. As a result, it is confirmed that the mean depth erosion is predictable using a homologous line in the steady state with mass loss independently of testing machines and the incubation period is very dependent on materials and imposed pressures.

Oral presentation

Flow effect on cavitation bubble behaviors in narrow channel

Kawamura, Shunsuke; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi

no journal, , 

In the mercury target for the pulsed spallation neutron source at J-PARC, cavitation damage at the beam window of the mercury target vessel is a key factor to decide lifetime of target because the damage degrade the vessel structural integrity. A double-walled structure with a narrow channel was adopted to the vessel for expecting to reduce cavitation damage. In this study, the cavitation bubble behaviors of the growth and collapse under water flow field were investigated to determine the effective factor for mitigating cavitation damage in narrow channel. We measured the equivalent diameter and wall vibration due to the cavitation bubble collapse with parametrically changing flow velocity. It was found that the maximum equivalent diameter of the cavitation bubble and the response vibrational acceleration of the wall are decreased with the increasing velocity. As the results, it was found that cavitation bubble collapse pressure was affected by flowing condition in the narrow channel.

Oral presentation

Effect of wall boundary on growing and collapsing behaviors of cavitation bubble

Kawamura, Shunsuke; Naoe, Takashi; Tanaka, Nobuatsu*; Futakawa, Masatoshi

no journal, , 

A mercury target for spallation neutron source has been in operation at the J-PARC. When the high-intense proton beams hits the mercury to produce spallation neutrons, pressure waves are generated due to the abrupt heat deposition of mercury. Mercury enclosure vessel made of stainless steel with a thin wall thickness of 3 mm is severely damaged by pressure wave-induced cavitation erosion. Recently a double-walled structure with narrow gap channel at the front part of the vessel has been developed to mitigate the cavitation damage. In this study, we observed experimentally the growth and collapse behavior of cavitation bubbles in the narrow channel by using a technique of spark discharge in water and a high-speed video camera. Furthermore, the effects of flow velocity and gap width on collapsing pressure were investigated with focusing on the ratio of the projection radius to the gap width. The relationship between the narrow gap and the collapsing pressure will be discussed.

11 (Records 1-11 displayed on this page)
  • 1