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Naoe, Takashi; Kogawa, Hiroyuki; Wakui, Takashi; Saruta, Koichi; Teshigawara, Makoto; Kinoshita, Hidetaka; Haga, Katsuhiro
no journal, ,
A liquid mercury target system for the pulsed spallation neutron source is installed in the J-PARC. A mercury target vessel made of 316L stainless steel severely damaged by cavitation which is induced by the proton beam-induced pressure waves. To mitigate the cavitation erosion, we adopted a double-walled structure with a narrow channel expects to disturb the growth of the cavitation bubbles due to the pressure gradient by the high-speed mercury flow. In addition, gas microbubbles were injected into the mercury to suppress the pressure waves that induces cavitation. During the beam operation, proton-beam induced acoustic vibration on the mercury target vessel is measured aiming to diagnose the effect of gas microbubble injection on pressure wave mitigation. Operational beam power is gradually ramping-up to the 950 kW and achieved its stable operation on the effort of the cavitation damage mitigation techniques. After the operational period, every year, cavitation erosion facing the were observed by cutting out the beam window portion using an annular cutter with semi-dry cutting technique. The result showed that the obvious damage mitigation effect by injecting gas microbubble that is predicted through the acoustic measurement was observed. Based on the damage inspection, we are discussing to extend the operational period of target vessel from one year to two years. In the workshop, present status for the cavitation damage mitigation will be discussed.
Pb(p,X) reaction with GeV-energy proton incidenceSugihara, Kenta*; Meigo, Shinichiro; Iwamoto, Hiroki; Maekawa, Fujio
no journal, ,
Estimation of residual gamma-ray dose rate is important from the viewpoint of radiation safety of accelerator driven systems (ADSs). Thus we measured the nuclide production cross sections via the Pb(p,X) reaction with GeV-energy at J-PARC. The advantage of J-PARC is that the proton intensity can be obtained with smaller uncertainty, due to a high-precision current transformer with an uncertainty of 2% (1-sigma). We present the measurement and measured excitation functions. In addition, comparison among the present data, results of nuclear reaction models, and evaluated nuclear data libraries are also reported.
Oi, Motoki; Yamaguchi, Yuji; Kinoshita, Hidetaka; Meigo, Shinichiro; Haga, Katsuhiro
no journal, ,
Material and Life science experimental facility (MLF) in J-PARC is a spallation neutron source which uses 3 GeV proton beam with 1 MW power. The neutron production target is made with mercury and the target vessel is installed in the helium vessel. On the other hands, proton beam transport line is kept in high vacuum, less than 10
Pa to reduce the beam loss. As a boundary of the helium atmosphere and the vacuum region, proton beam window (PBW) is installed. The proton beam window is made with aluminum alloy. Due to the radiation damage of the window, lifetime of the PBW is estimated 10000 MWh. In this summer maintenance period, we replace from the PBW No. 4 to PBW No. 5. In this presentation, we report about life cycle, the structure and replacement work of the PBW.
Haga, Katsuhiro; Naoe, Takashi; Wakui, Takashi; Kogawa, Hiroyuki; Saruta, Koichi; Kinoshita, Hidetaka; Teshigawara, Makoto; Harada, Masahide; Sakai, Kenji
no journal, ,
In April 2023, the pulse intensity of proton beam was raised to the highest record of 950 kW for the first time for long term user operation of Materials and Life Science Experimental Facility (MLF). The pulse intensity corresponds to the beam power at the 3GeV rapid cycle synchrotron (RCS) outlet and is the dominant factor of the pitting damage of the mercury target vessel by pressure waves. This accomplishment means that the goal of the stable operation of the neutron source with 1 MW was almost achieved. Since the proton beam pulses at RCS outlet are shared between MLF and 30GeV main ring (MR), the beam power at MLF becomes smaller than that at RCS outlet. The minimum beam share of MLF is planned to be reduced to 86.2 % in 2028. In order to achieve 1 MW operation at MLF, the pulse intensity needs to be increased to 1.16 MW, and the mercury target should endure the pulse intensity higher than 1 MW. In addition, we must cope with the serious issues of storage space and disposal of the highly radioactivated used target vessels. Now R&D of the mercury target vessel is going on to extend the target operation time and to reduce the volume of the used target vessel. Thus, more effective pitting damage mitigation technology and a new target design which can be disassembled by present remote-handling tools are going to be developed. In this presentation, present status of the neutron source of MLF and future operation plan will be shown.
-phase based titanium alloysWakai, Eiichi; Ishida, Taku*; Kano, Sho*; Shibayama, Tamaki*; Sato, Koichi*; Noto, Hiroyuki*; Makimura, Shunsuke*; Furuya, Kazuyuki*; Yabuuchi, Atsushi*; Yoshiie, Toshimasa*; et al.
no journal, ,
Titanium materials have been applied to beam window materials and beam dumps in large accelerator systems because of their low specific gravity, high corrosion resistance, strength, and other advantages. As the beam power becomes higher, further improvement of irradiation resistance is required. We have investigated further the properties of titanium alloys based on the -phase, and it was found that Ti-15-3-3-3 alloys have excellent irradiation resistance when subjected to ion irradiation. In order to investigate the cause of this, microstructures and point defects in this and related materials were evaluated by TEM, positron lifetime measurement, electrical resistivity, and stress-induced changes, among others. In addition, we have recently begun to develop a prototype of a titanium-based high-entropy alloy based on -titanium, which is attracting worldwide attention and is being developed, and have also begun to evaluate the emotional properties of this alloy. We have examined the various properties of this material and found that it has considerably higher strength than conventional iron- and titanium-based materials.
Meigo, Shinichiro
no journal, ,
Material damage index of displacement per atom (dpa) is calculated by the particle flux and the displacement cross section. Since the experimental data of the displacement cross section was scarce, the measurements using protons were conducted, and the experimental data of protons up to 30 GeV have been obtained in J-PARC. The displacement cross section was almost constant regardless of the projectile proton energy above several GeV, which is against the expectation because the heat deposition given by the proton increases as projectile energy due to the relativistic theory. The experiment with 120 GeV protons at FNAL was conducted to obtain the data for high-energy regions. To extend the energy region, the experiment with 430-GeV protons at HiRadMat is planned for the following year. Additionally, a new beam irradiation facility plan at J-PARC with 0.4-GeV protons to study material radiation damage will be presented in this talk.