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Journal Articles

The Role of collision ionization of K-shell ions in nonequilibrium plasmas produced by the action of super strong, ultrashort PW-class laser pulses on micron-scale argon clusters with intensity up to 5 $$times$$ 10$$^{21}$$ W/cm$$^{2}$$

Skobelev, I. Yu.*; Ryazantsev, S. N.*; Kulikov, R. K.*; Sedov, M. V.*; Filippov, E. D.*; Pikuz, S. A.*; Asai, Takafumi*; Kanasaki, Masato*; Yamauchi, Tomoya*; Jinno, Satoshi; et al.

Photonics (Internet), 10(11), p.1250_1 - 1250_11, 2023/11

It is challenging to clearly distinguish the impacts of the optical field and collisional ionization in the evolution of the charge state of a plasma produced when matter interacts with high-intensity laser pulses. In this work, time-dependent calculations of plasma kinetics are used to show that it is possible only when low-density gaseous targets with sufficiently small clusters are used. In the case of Ar plasma, the upper limit of the cluster radius was estimated to be $$R_0 = 0.1 mu$$m.

Journal Articles

Upgrade of seismic design procedure for piping systems based on elastic-plastic response analysis

Nakamura, Izumi*; Otani, Akihito*; Okuda, Yukihiko; Watakabe, Tomoyoshi; Takito, Kiyotaka; Okuda, Takahiro; Shimazu, Ryuya*; Sakai, Michiya*; Shibutani, Tadahiro*; Shiratori, Masaki*

Dai-10-Kai Kozobutsu No Anzensei, Shinraisei Ni Kansuru Kokunai Shimpojiumu (JCOSSAR2023) Koen Rombunshu (Internet), p.143 - 149, 2023/10

In 2019, the JSME Code Case for seismic design of nuclear power plant piping systems was published. The Code Case provides the strain-based fatigue criteria and detailed inelastic response analysis procedure as an alternative design rule to the current seismic design, which is based on the stress evaluation by elastic response analysis. In 2022, it was approved to revise the Code Case with improving the cycle counting method for fatigue evaluation to the Rain flow method. In addition, the discussion to incorporate the elastic-plastic behavior of support structures is now in progress for the next revision of the Code Case. This paper discusses the contents and background of the 2022 revision, the progress of the next revision, and future tasks.

Journal Articles

Perturbation on hyperfine-enhanced $$^{141}$$Pr nuclear spin dynamics associated with antiferroquadrupolar order in PrV$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Sakai, Akito*; Nakatsuji, Satoru*; Tsujimoto, Masaki*

Physical Review B, 92(12), p.125151_1 - 125151_5, 2015/09

 Times Cited Count:5 Percentile:23.94(Materials Science, Multidisciplinary)

JAEA Reports

Report on decontamination pilot projects to establish guidelines for environmental remediation of residential areas contaminated with radioactive materials discharged from the Fukushima Daiichi Nuclear Power Station Accident

Kihara, Shinji; Amazawa, Hiroya; Sakai, Akihiro; Nakata, Hisakazu; Kugo, Teruhiko; Matsuda, Norihiro; Oizumi, Akito; Sasamoto, Hiroshi; Mitsui, Seiichiro; Miyahara, Kaname

JAEA-Research 2013-033, 320 Pages, 2014/07

JAEA-Research-2013-033.pdf:119.17MB

JAEA performed decontamination experiments at two test sites that combined a range of buildings and different types of land use, located in Date and Minami Soma municipalities as field pilot projects in order to accumulate knowledge and data for full-scale decontamination activities performed by local governments. In the pilot projects, we established its plan using practical decontamination methods that can be easily implemented, according to decontamination targets (e.g., forests, agricultural land, residential house and roads) at each site. As a result of the decontamination, the average air dose rates were reduced to approximately one half of the values before decontamination.

Journal Articles

Magnetic excitations and $$c$$-$$f$$ hybridization effect in PrTi$$_2$$Al$$_{20}$$ and PrV$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*; Harima, Hisatomo*

Physical Review B, 88(8), p.085124_1 - 085124_7, 2013/08

 Times Cited Count:29 Percentile:74.56(Materials Science, Multidisciplinary)

By means of $$^{27}$$Al NMR studies, we have investigated magnetic excitations and the hybridization effect between Pr 4$$f$$ and conduction electrons in a pair of cubic compounds Pr$$Tr$$$$_2$$Al$$_{20}$$ ($$Tr$$=Ti, V). From Knight shift measurements we have evaluated comparative strengths for the $$c$$-$$f$$ hybridization effect in these compounds and confirm a definite increase of hybridization on replacing Ti with V. Analysis of the spin-lattice relaxation rate $$1/T_1$$ reveals that the spectral width of magnetic fluctuations in crystalline electric field excited states is strongly temperature dependent. This result indicates that magnetic fluctuations are dominated by the strong $$c$$-$$f$$ exchange coupling at high temperatures and thus is nicely consistent with the Kondo picture that features ln$$T$$ dependence of resistivity over the same temperature region.

Journal Articles

Microscopic evidence for long-range magnetic ordering in the $$Gamma$$$$_{8}$$ ground quartet systems Sm$$Tr$$$$_{2}$$Al$$_{20}$$ ($$Tr$$: Ti, V, Cr)

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Sakai, Akito*; Nakatsuji, Satoru*

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB050_1 - SB050_4, 2012/12

Recently, $$RT_2$$Al$$_{20}$$ compounds ($$R$$: rare earth, $$T$$: transition metal) have attracted much attention due to interesting physical properties closely related to their caged-structure. Each $$R$$ ion is confined in a Frank-Kasper cage consisting of 16 Al atoms and the large coordination number leads to strong $$c$$-$$f$$ hybridization. In addition, the Frank-Kasper cage allows various multipole degrees of freedom for the $$f$$-electrons at low $$T$$ because of a highly symmetric crystalline-electric-field (CEF). Among the $$RT_2$$Al$$_{20}$$ series, Pr$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V) and Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) exhibit both these features. The $$Gamma_3$$ ground doublet systems Pr$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V) show a phase transition at $$T_O$$ = 2.0K (Ti) and 0.6K (V). The order parameter is believed to be an electric quadrupole active in the $$Gamma_3$$ subspace. A possibility of the quadrupole Kondo effect has been discussed based on characteristic $$T$$-dependence in specific heat, resistivity, and magnetic susceptibility. The $$Gamma_8$$ ground quartet systems Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) also exhibit a phase transition at $$T_O$$ = 6.4K (Ti), 2.3K (V), and 1.8K (Cr). A nuclear specific heat study in SmTi$$_2$$Al$$_{20}$$ suggests that the primary order parameter is a magnetic dipole in spite of field-insensitive nature of the phase boundary. A possible importance of a secondarily ordered octupole moment was discussed. We here present a microscopic study of PrTi$$_2$$Al$$_{20}$$ and Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) using muon spin relaxation. In PrTi$$_2$$Al$$_{20}$$, no additional local field was observed in the ordered phase. This strongly supports the quadrupole ordering scenario. On the other hand, an appearance of a coherent local field was observed below $$T_O$$ in Sm$$T_2$$Al$$_{20}$$. This is consistent with the primary magnetic dipole ordering. The frequency distribution suggests that the magnetic structure is possibly different between the Sm$$T_2$$Al$$_{20}$$ compounds.

Journal Articles

Quasi-monochromatic pencil beam of laser-driven protons generated using a conical cavity target holder

Nishiuchi, Mamiko; Pirozhkov, A. S.; Sakaki, Hironao; Ogura, Koichi; Esirkepov, T. Z.; Tanimoto, Tsuyoshi; Kanasaki, Masato; Yogo, Akifumi; Hori, Toshihiko; Sagisaka, Akito; et al.

Physics of Plasmas, 19(3), p.030706_1 - 030706_4, 2012/03

 Times Cited Count:6 Percentile:25.89(Physics, Fluids & Plasmas)

A 7 MeV proton beam collimated to 16 mrad containing more than $$10^6$$ particles is experimentally demonstrated by focusing a 2J, 60 fs pulse of a Ti:sapphire laser onto targets of different materials and thicknesses placed in a millimeter scale conical holder. The electric potential induced on the target holder by laser-driven electrons accelerates and dynamically controls a portion of a divergent quasi-thermal proton beam originated from the target, producing a quasi-monoenergetic "pencil" beam.

Journal Articles

$$mu$$SR evidence of nonmagnetic order and $$^{141}$$Pr hyperfine-enhanced nuclear magnetism in the cubic $$Gamma_3$$ ground doublet system PrTi$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Luetkens, H.*; Baines, C.*; Sakai, Akito*; Nakatsuji, Satoru*

Journal of the Physical Society of Japan, 80(11), p.113703_1 - 113703_4, 2011/11

 Times Cited Count:29 Percentile:78.82(Physics, Multidisciplinary)

Oral presentation

NMR study of PrTi$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Saito, Yo; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

$$mu$$SR studies of $$RTr_2$$Al$$_{20}$$ ($$R$$: Pr, Sm, $$Tr$$: Ti, V, Cr) with a cage structure

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

Highly collimated Quasi-monochromatic laser-driven proton beam generation by target holder having conical cavity

Nishiuchi, Mamiko; Pirozhkov, A. S.; Sakaki, Hironao; Ogura, Koichi; Esirkepov, T. Z.; Tanimoto, Tsuyoshi; Yogo, Akifumi; Hori, Toshihiko; Sagisaka, Akito; Fukuda, Yuji; et al.

no journal, , 

We have successfully accelerate quasi-mono-energetic collimated 7MeV proton beam bt the interaction between the 2J 60fs Ti Sappire laser pulses with the thin-foil target on the target holder with conical cavity. The focusing and energy selection is by the E-field induced along the surface of the conical cavity by the point charge brought away by the escape electrons.

Oral presentation

$$mu$$SR study of PrTi$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

Al-NMR study of PrTi$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

Al-NMR study of PrTi$$_2$$Al$$_{20}$$, 2

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

NMR study of Pr$$T_2$$Al$$_{20}$$ ($$T$$=Ti, V)

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

In this study, we have performed $$^{27}$$Al NMR/NQR measurements for Pr$$T_2$$Al$$_{20}$$ ($$T$$=Ti, V). $$^{27}$$Al NMR spectra have been measured in a temperature range between 1.4 and 300 K, and the temperature dependence of the Knight shift $$K$$ has been extracted for Al(2) and Al(3). Then, from the so-called $$K$$ vs $$chi$$ plot, the hyperfine coupling constants ($$A_{hf}$$) has been estimated for each site in each compound. A large $$A_{hf}$$ obtained for Al(3) indicates the strong hybridization between Pr and Al-cage. In addition, the stronger hybridization in PrV$$_2$$Al$$_{20}$$ than in PrTi$$_2$$Al$$_{20}$$ is confirmed from the $$A_{hf}$$ values.

Oral presentation

Proton acceleration with the thin-foil target at KPSI

Nishiuchi, Mamiko; Ogura, Koichi; Tanimoto, Tsuyoshi*; Pirozhkov, A. S.; Sakaki, Hironao; Fukuda, Yuji; Kanasaki, Masato; Kando, Masaki; Esirkepov, T. Z.; Sagisaka, Akito*; et al.

no journal, , 

We present the extension of the maximum energy of protons from the interaction between the short-pulse compact laser system and solid thin-foil target. The laser pulses with parameters of 800 nm in wavelength, 40 fs of pulse width, 7 J of energy, 10$$^{10}$$ contrast are focused onto the target with the peak intensity of more than 10$$^{21}$$ Wcm$$^{-2}$$, which is also well confirmed by the measured electron temperature of 16 MeV. We report about the acceleration mechanism as well as future prospect on the proton acceleration experiment at JAEA.

Oral presentation

Laser-driven proton generation from a thin-foil target with a high-intensity laser

Sagisaka, Akito; Nishiuchi, Mamiko; Pirozhkov, A. S.; Ogura, Koichi; Sakaki, Hironao; Maeda, Shota; Pikuz, T.; Faenov, A. Ya.*; Fukuda, Yuji; Yogo, Akifumi; et al.

no journal, , 

High-intensity laser and thin-foil interactions produce high-energy particles, hard X-ray, high-order harmonics, and terahertz radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical and other applications. We have performed several high intensity laser-matter interaction experiments using a thin-foil target irradiated by Ti:sapphire laser (J-KAREN) at JAEA. The pulse duration was typically $$sim$$ 40 fs (FWHM). The electron density profiles of the preformed plasma were observed with the interferometer. The high temporal contrast laser system could reduce the preformed plasma. The maximum proton energy gradually increased as the laser performance improved and finally protons of $$sim$$ 40 MeV energy were observed at the peak laser intensity of $$sim$$ 1 $$times$$ 10$$^{21}$$ W/cm$$^{2}$$.

Oral presentation

Laser driven ion acceleration experiment by high contrast high intensity laser J-KAREN system

Nishiuchi, Mamiko; Sakaki, Hironao; Sagisaka, Akito; Maeda, Shota; Pirozhkov, A. S.; Pikuz, T.; Faenov, A. Ya.*; Ogura, Koichi; Fukuda, Yuji; Matsukawa, Kenya*; et al.

no journal, , 

no abstracts in English

Oral presentation

Measurement of electron spectrum generated by irradiating thin-Foil target with Ultra-intense Ultra-short pulse laser

Maeda, Shota; Nishiuchi, Mamiko; Sakaki, Hironao; Sagisaka, Akito; Pirozhkov, A. S.; Pikuz, T.; Faenov, A. Ya.*; Ogura, Koichi; Fukuda, Yuji; Matsukawa, Kenya*; et al.

no journal, , 

In JAEA, the high energy ions generated by the interaction between Ultra-intense Ultra-Short pulse laser and thin-foil target is being studied. Irradiating condition must be optimized to generate higher energy ions while suppress the becoming gigantic of laser. It is necessary to know the physical phenomenon in plasma to determine the parameter to optimize from the information on the electron and neutron, X-rays, which are generated simultaneously with ion. In this study, in order to measure electron temperature accurately, an electron spectrometer was developed which have broad range (1-200 MeV). The detector is comprised of permanent magnets and a fluorescent plate, CCD camera. In the presentation, the result of the calibration experiment carried out using 4, 9, 12, 15 MeV quasi-monoenergetic electron beam in HIBMC will be reported. Moreover, response analysis method was inspected using PHITS which is particle transporting Monte Carlo simulation code, and will also report the result.

Oral presentation

Laser-driven proton acceleration with a thin-foil target

Sagisaka, Akito; Nishiuchi, Mamiko; Pirozhkov, A. S.; Ogura, Koichi; Sakaki, Hironao; Maeda, Shota; Pikuz, T.; Faenov, A. Y.*; Fukuda, Yuji; Kanasaki, Masato; et al.

no journal, , 

High-intensity laser and thin-foil interactions produce high-energy particles, hard X-ray, high-order harmonics, and terahertz radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical and other applications. We have performed several high intensity laser-matter interaction experiments using a thin-foil target irradiated by Ti:sapphire laser (J-KAREN) at JAEA. The pulse duration was typically $$sim$$40 fs (FWHM). The high-order harmonics (2nd$$sim$$4th) were observed with the spectrometer in the reflected direction. The maximum proton energy of $$sim$$40 MeV energy were observed at the peak laser intensity of $$sim$$1$$times$$10$$^{21}$$W/cm$$^{2}$$.

23 (Records 1-20 displayed on this page)