Faculty Profiles - Nakai Mitsuo

Papers - Nakai Mitsuo

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Second harmonic generation of focused beams on the LFEX laser facility Reviewed International journal

Y. Arikawa, Z. Hu, K. Tsubakimoto, A. Morace, R. Takizawa, H. Shiraga, M. Nakai, T. Pikuz, A. Martynenko, N. Iwata, Y. Sentoku, M. Hata, S. Kojima, T. Johzaki, Y. Nakata, S. Fujioka, A. Yogo, R. Kodama

Optics Express 32 ( 16 ) 28390 - 28401 2024.7

There is a strong demand for efficient second harmonic generation (SHG) in ultra-intense short-pulse lasers. This paper demonstrates the generation of an unconverted fundamental and second harmonics mixed laser on the LFEX laser system. The LFEX laser beams with four-beams combined energy of 222 J and a pulse duration of 1.5 ps, is successfully converted to 102 J of 2ω light and 100 J of unconverted 1ω light utilizing 0.5 mm-thick LBO crystal plates in a focusing beams implemented after an off-axis parabola.
Verification of successful SHG is confirmed through X-ray pinhole imaging and electron spectrometry. This novel technique is not limited to LFEX lasers and holds applicability for various ultra-intense lasers. Consequently, this accomplishment significantly contributes to expanding the capability for high-energy density laser-plasma experiments.

Cryogenic solid deuterium target formation to realize highly pure deuteron acceleration by high-intensity laser Reviewed International journal

T. Wei, A. Iwamoto, Z. Lan, T. Hayakawa, Y. Arikawa, D. Tanabe, T. Ishimoto, T. Mori, M.Takeshita, M. Murakami, Y. Gu, A. Morace, M. Nakai, A. Yogo

Japanese Journal of Applied Physics 63 ( 4 ) 046002 - 046002 2024.4

In recent years, laser-driven neutron sources have attracted attention for their applications such as nondestructive analysis and the production of medical radioisotopes. One of the efficient neutron production methods is the use of the ⁹Be(d, n)¹⁰B reaction on a beryllium target with deuterons accelerated by laser–plasma interactions, since this is an exothermic reaction. For efficient deuteron acceleration, we have developed a formation system for solid deuterium targets. A millimeter thick solid deuterium target can be formed with the system. Before the laser shot, the solid deuterium target in the laser chamber can be mechanically moved to the laser irradiation point. We have demonstrated deuteron acceleration by the LFEX laser, and a highly pure deuteron pulse with energies of up to 6.2 MeV was measured with a Thomson parabola ion spectrometer.

The elements of a small debris mitigation system using spaceborne laser International coauthorship

Shigeaki Uchida, Kotomi Kawakami, Hideki Okamura, Nakai Mitsuo , Kazunori Shibata, Xiao Xiao (, Yin Danqing , Keke Zhang, Zhonghao Heng

2nd International Orbital Debris Conference Papers 2023 2023.12

Demonstration of efficient relativistic electron acceleration by surface plasmonics with sequential target processing using high repetition lasers

Yasunobu Arikawa, Alessio Morace, Yuki Abe, Natsumi Iwata, Yasuhiko Sentoku, Akifumi Yogo, Kazuki Matsuo, Mitsuo Nakai, Hideo Nagatomo, Kunioki Mima, Hiroaki Nishimura, Shinsuke Fujioka, Ryosuke Kodama, Shunsuke Inoue, Masaki Hashida, Shuji Sakabe, Diego De Luis, Giancarlo Gatti, Marine Huault, José Antonio Pérez-Hernández, Luis Roso, Luca Volpe

Physical Review Research 5 ( 1 ) 2023.1

Laser-Driven Neutron Generation Realizing Single-Shot Resonance Spectroscopy Reviewed International coauthorship International journal

A. Yogo, Z. Lan, Y. Arikawa, Y. Abe, S. R. Mirfayzi, T. Wei, T. Mori, D. Golovin, T. Hayakawa, N. Iwata, S. Fujioka, M. Nakai, Y. Sentoku, K. Mima, M. Murakami, M. Koizumi, F. Ito, J. Lee, T. Takahashi, K. Hironaka, S. Kar, H. Nishimura, R. Kodama

Physical Review X 13 ( 1 ) 011011-1 - 011011-12 2023.1

Feasibility study of laser-driven neutron sources for pharmaceutical applications

Takato Mori, Akifumi Yogo, Yasunobu Arikawa, Takehito Hayakawa, Seyed R. Mirfayzi, Zechen Lan, Tianyun Wei, Yuki Abe, Mitsuo Nakai, Kunioki Mima, Hiroaki Nishimura, Shinsuke Fujioka, Ryosuke Kodama

High Power Laser Science and Engineering 2023

We predict the production yield of a medical radioisotope 67Cu using 67Zn(n, p)67Cu and 68Zn(n, pn)67Cu reactions with fast neutrons provided from laser-driven neutron sources (LDNSs). The neutrons were generated by the p+9Be and d+9Be reactions with high energy ions accelerated by laser-plasma interaction. We evaluated the yield to be (3.3±0.5)×105atoms for 67Cu, corresponding to a radioactivity of 1.0±0.2 Bq, for a Zn foil sample with a single laser shot. Using a simulation with this result, we estimated 67Cu production with a high-frequency laser. The result suggests that it is possible to generate 67Cu with a radioactivity of 270 MBq using a future laser system with a frequency of 10 Hz and 10000-s radiation in a hospital.

Super-strong magnetic field-dominated ion beam dynamics in focusing plasma devices

A. Morace, Y. Abe, J. J. Honrubia, N. Iwata, Y. Arikawa, Y. Nakata, T. Johzaki, A. Yogo, Y. Sentoku, K. Mima, T. Ma, D. Mariscal, H. Sakagami, T. Norimatsu, K. Tsubakimoto, J. Kawanaka, S. Tokita, N. Miyanaga, H. Shiraga, Y. Sakawa, M. Nakai, H. Azechi, S. Fujioka, R. Kodama

Scientific Reports 12 ( 1 ) 2022.12

Abstract

High energy density physics is the field of physics dedicated to the study of matter and plasmas in extreme conditions of temperature, densities and pressures. It encompasses multiple disciplines such as material science, planetary science, laboratory and astrophysical plasma science. For the latter, high energy density states can be accompanied by extreme radiation environments and super-strong magnetic fields. The creation of high energy density states in the laboratory consists in concentrating/depositing large amounts of energy in a reduced mass, typically solid material sample or dense plasma, over a time shorter than the typical timescales of heat conduction and hydrodynamic expansion. Laser-generated, high current–density ion beams constitute an important tool for the creation of high energy density states in the laboratory. Focusing plasma devices, such as cone-targets are necessary in order to focus and direct these intense beams towards the heating sample or dense plasma, while protecting the proton generation foil from the harsh environments typical of an integrated high-power laser experiment. A full understanding of the ion beam dynamics in focusing devices is therefore necessary in order to properly design and interpret the numerous experiments in the field. In this work, we report a detailed investigation of large-scale, kilojoule-class laser-generated ion beam dynamics in focusing devices and we demonstrate that high-brilliance ion beams compress magnetic fields to amplitudes exceeding tens of kilo-Tesla, which in turn play a dominant role in the focusing process, resulting either in a worsening or enhancement of focusing capabilities depending on the target geometry.

NMR Spectroscopy for Proof-of-Concept Experimentation on a Polarized Laser Fusion Process

Masahiko Utsuro, Mitsuo Nakai, Hideki Kohri, Takeshi Ohta, Takumi Konno, Asako Igashira, Mamoru Fujiwara

Fusion Science and Technology 78 ( 7 ) 513 - 527 2022.10

Predictive capability of material screening by fast neutron activation analysis using laser-driven neutron sources

Y. Abe, A. Nakao, Y. Arikawa, A. Morace, T. Mori, Z. Lan, T. Wei, S. Asano, T. Minami, Y. Kuramitsu, H. Habara, H. Shiraga, S. Fujioka, M. Nakai, A. Yogo

Review of Scientific Instruments 93 ( 9 ) 2022.9

Bright, short-pulsed neutron beams from laser-driven neutron sources (LANSs) provide a new perspective on material screening via fast neutron activation analysis (FNAA). FNAA is a nondestructive technique for determining material elemental composition based on nuclear excitation by fast neutron bombardment and subsequent spectral analysis of prompt γ-rays emitted by the active nuclei. Our recent experiments and simulations have shown that activation analysis can be used in practice with modest neutron fluences on the order of 105 n/cm2, which is available with current laser technology. In addition, time-resolved γ-ray measurements combined with picosecond neutron probes from LANSs are effective in mitigating the issue of spectral interference between elements, enabling highly accurate screening of complex samples containing many elements. This paper describes the predictive capability of LANS-based activation analysis based on experimental demonstrations and spectral calculations with Monte Carlo simulations.

Picosecond snapshot imaging of electric fields induced on a cone guide target designed for fast ignition scenario Reviewed

Binghe Shi, Akifumi Yogo, Kazuki Okamoto, Daniil Golovin, Seyed Reza Mirfayzi, Alessio Morace, Yasunobu Arikawa, Kohei Yamanoi, Yuki Abe, Masakatsu Murakami, Yanjun Gu, Kunioki Mima, Yasuhiko Sentoku, Mitsuo Nakai, Hiroyuki Nishimura, Hiroyuki Shiraga, Shinsuke Fujioka, Tomoyuki Johzaki, Akifumi Iwamoto, Hitoshi Sakagami, Ryosuke Kodama

Journal of Plasma Physics 88 ( 4 ) 905880404 2022.8

In this study, we experimentally evaluate the ion transportation through a cone guide target, which accelerates ions up to MeV energies via target normal sheath acceleration, and transports them onto the position of imploding fuel in the fast ignition scenario of nuclear fusion. We measured the electric and magnetic fields (EM-fields) induced by return current streaming along the cone wall by proton radiography, and we report that the EM-fields are predominantly induced within a temporal window up to 30 ps after the laser injection. The magnitude of the electric field is maximized around 13 ps, reaching $4.0\times 10^{10} \mathrm {V}\ \mathrm {m}^{-1}$, when the magnetic field is below 200 T. The present scheme provides insights on the EM-fields evaluation in the time region that is difficult to treat with simulations due to the computing resources.

Thermal neutron fluence measurement using a cadmium differential method at the laser-driven neutron source

Takato Mori, Akifumi Yogo, Takehito Hayakawa, Seyed R. Mirfayzi, Zechen Lan, Tianyun Wei, Yuki Abe, Yasunobu Arikawa, Mitsuo Nakai, Kunioki Mima, Hiroaki Nishimura, Shinsuke Fujioka, Ryosuke Kodama

Journal of Physics G: Nuclear and Particle Physics 49 ( 6 ) 2022.6

We produced high-energy neutrons by p + Be and d + Be reactions with protons and deuterons with continuous energies of up to 30 and 10 MeV/u, respectively, provided from laser-plasma interactions. Thermal neutrons were subsequently generated through deceleration by a small moderator with conjunction on the Be target. Here, we report the measurements on the thermal neutron fluence using the activation method with/without Cd filters. The unstable isotopes of 198Au, 56Mn, 60Co, and 181Hf were produced through (n, γ) reactions by a single laser shot. The nuclear reaction fractions were evaluated by measuring the γ-rays emitted from these unstable isotopes. The thermal neutron fluences from the four nuclides are consistent within their experimental uncertainties. The fluence is evaluated to be (2.2 ± 0.4) × 105 neutrons cm-2 at the distance of approximately 9 mm at 90° against the laser axis. The present result shows that the method to generate thermal neutrons from a compact neutron source with a diameter of 44 mm and length of 46 mm is expected to be a useful tool for various nuclear experiments and applications.

Non-destructive inspection of water or high-pressure hydrogen gas in metal pipes by the flash of neutrons and x rays generated by laser

Tianyun Wei, Akifumi Yogo, Takehito Hayakawa, Yasunobu Arikawa, Yuki Abe, Maiko Nakanishi, Seyed Reza Mirfayzi, Zechen Lan, Takato Mori, Kunioki Mima, Shinsuke Fujioka, Masakatsu Murakami, Mitsuo Nakai, Hiroaki Nishimura, Satyabrata Kar, Ryosuke Kodama

AIP Advances 12 ( 4 ) 045220 - 045220 2022.4

The thermal and epithermal neutrons are powerful probes to inspect water or high-pressure hydrogen gas because of their large scattering cross-sections with protons. Laser-driven neutron source, which is able to simultaneously emit different types of radiations such as x rays, can be used for neutron and x-ray radiography in the same laser shot. In this paper, we report the demonstration of non-destructive inspection for H<sub>2</sub>O contained within a stainless steel pipe using a laser-driven thermal neutron source, where water and stainless containers are detected by neutrons and x rays, respectively. The simulation result indicates that this method can also provide the capability to measure the hydrogen density in high-pressure hydrogen gas in metal containers.

Author Correction: Proof-of-principle experiment for laser-driven cold neutron source (Scientific Reports, (2020), 10, 1, (20157), 10.1038/s41598-020-77086-y)

S. R. Mirfayzi, A. Yogo, Z. Lan, T. Ishimoto, A. Iwamoto, M. Nagata, M. Nakai, Y. Arikawa, Y. Abe, D. Golovin, Y. Honoki, T. Mori, K. Okamoto, S. Shokita, D. Neely, S. Fujioka, K. Mima, H. Nishimura, S. Kar, R. Kodama

Scientific Reports 11 ( 1 ) 2021.12

The original version of this Article contained errors. In Figure 3b, where “Deutron” now reads: “Deuteron” In addition, in Figure 4d, where the x-axis “10–4, 10– 3, 10– 2, 10– 1, 10, 102, 103” now reads: “10–4, 10– 3, 10– 2, 10– 1, 1, 101, 102” The original Figures 3 and 4 and accompanying legends appear below. Finally, the Author Contributions section, “The moderator and experiment was developed by S.R.M. with support from A.I. and funded by A.Y. to and led by S.R.M. S.R.M., A.Y., Z.L. and T.I. executed the experiment with support from, AI, KM, MNag, MNak, YAr, YAb, D.G., Y.H., T.M., S.S. and K.O. contributed both to the experimental setup and diagnostics. S.R.M. and Z.L., T.I. performed data analysis.” now reads: “The moderator and experiment were developed by S.R.M. with support from A.I. The experiment funded by A.Y. and led by S.R.M. S.R.M., A.Y., Z.L. and T.I. executed the experiment with support from A.I., K.M., M.Nag, M.Nak, Y.Ar., Y.Ab., D.G., Y.H., T.M., S.S. and K. contributed both to the experimental setup and diagnostics. S.R.M., Z.L. and T.I. performed the data analysis. The manuscript was prepared by S.R.M., D.N., S.F., K.M., H.N., S.K. and R.K. were involved in discussions and preparation.” The original Article has been corrected. (Figure presented.).

Preliminary Cryogenic Layering by the Infrared Heating Method Modified with Cone Temperature Control for the Polystyrene Shell FIREX Target

Keisuke IWANO, Akifumi IWAMOTO, Kohei YAMANOI, Yasunobu ARIKAWA, Hideo NAGATOMO, Mitsuo NAKAI, Takayoshi NORIMATSU

Plasma and Fusion Research 16 1404099 - 1404099 2021.11

Single shot radiography by a bright source of laser-driven thermal neutrons and x-rays

Akifumi Yogo, Seyed Reza Mirfayzi, Yasunobu Arikawa, Yuki Abe, Tianyun Wei, Takato Mori, Zechen Lan, Yuki Hoonoki, Daniil O. Golovin, Keisuke Koga, Yosuke Suzuki, Masato Kanasaki, Shinsuke Fujioka, Mitsuo Nakai, Takehito Hayakawa, Kunioki Mima, Hiroaki Nishimura, Satyabrata Kar, Ryosuke Kodama

APPLIED PHYSICS EXPRESS 14 ( 10 ) 2021.10

Thermal neutron (similar to 25 meV) beam is a powerful tool for investigating the structure and properties of materials used in science and technology. A laser-driven neutron source generating 10(10) neutrons within 1 ns duration is utilized to a single shot radiography with a dual beam of thermal neutrons and X-rays. As a proof of principle, we show the non-destructive inspection of hazardous substances (Cadmium) contained in a typical battery, when the cadmium anode thickness is evaluated from the transmittance of thermal neutrons. The fact that the neutron inspection above is performed with a single laser shot, i.e. with a single bunch of neutrons leads to a safer neutron source that is optically controlled on/off, and provides a novel tool for science and engineering.

Direct evaluation of high neutron density environment using reaction induced by laser-driven neutron source

Takato Mori, Akifumi Yogo, Takehito Hayakawa, Seyed R. Mirfayzi, Zechen Lan, Yuki Abe, Yasunobu Arikawa, Daniil Golovin, Tianyun Wei, Yuki Honoki, Mitsuo Nakai, Kunioki Mima, Hiroaki Nishimura, Shinsuke Fujioka, Ryosuke Kodama

Physical Review C 104 ( 1 ) 2021.7

We demonstrate that reactions are induced by a high-flux pulse of fast neutrons ( neutrons in ) provided from a laser-driven neutron source (LDNS). The maximum energy of the broadband neutrons reaches a few tens MeV. Several kinds of metal targets are exposed to the fast neutrons. As a result, unstable isotopes, such as , and are produced by reactions and , and are produced by reactions. We evaluate the neutron fluence and energy spectrum using the activation method in conjunction with a time-of-flight measurement. The neutron fluence is determined to be in the energy range from approximately 8 to 20 MeV at 8-mm downstream of the neutron source. The present scheme provides a method to evaluate high-density neutrons seen in stellar environments, which are expected to be generated from future LDNSs.

Dosimetric calibration of GafChromic HD-V2, MD-V3, and EBT3 films for dose ranges up to 100 kGy

Y. Abe, A. Morace, Y. Arikawa, S. R. Mirfayzi, D. Golovin, K. F.F. Law, S. Fujioka, A. Yogo, M. Nakai

Review of Scientific Instruments 92 ( 6 ) 2021.6

Surface structure on diamond foils generated by spatially nonuniform laser irradiation Reviewed

Hiroki Kato, Hideo Nagatomo, Mitsuo Nakai, Tatsuhiro Sakaiya, Hidenori Terasaki, Tadashi Kondo, Yoichiro Hironaka, Katsuya Shimizu, Keisuke Shigemori

Scientific Reports 10 ( 1 ) 2020.12

© 2020, The Author(s). Here we report on the effects of material strength factors on the generation of surface structure due to nonuniform laser irradiation. The influence of material strength on the generation of perturbation on a diamond surface subjected to nonuniform laser irradiation was experimentally investigated. Our previous investigations suggested that stiffer and denser materials reduce surface perturbation due to spatially nonuniform laser irradiation, which was reproduced well by calculations with multi-dimensional hydrodynamic simulation code. In this work, we found that local fractures due to yield strength failure are generated by high degrees of irradiation non-uniformity. A characteristic crack-like surface structure was observed, which was not reproduced by the 2D simulation code calculations at all. The 2D simulations showed that the pressure at the diamond surface locally exceeds the Hugoniot elastic limit due to nonuniform irradiation, implying the potential for development of surface perturbations. We also measured the areal-density distribution of perturbations for single-crystal diamond and diamond with a thin high atomic number (high-Z) coating on its surface. The experimental results imply that the combination of a stiff material and thin high-Z coating can suppress the solid-strength effects caused by large irradiation non-uniformity. The knowledge given here is applicable to inertial confinement fusion target design, laser material processing, and universal problems involving solids and high-energy-density plasmas.

Proof-of-principle experiment for laser-driven cold neutron source

S. R. Mirfayzi, A. Yogo, Z. Lan, T. Ishimoto, A. Iwamoto, M. Negata, M. Nakai, Y. Arikawa, Y. Abe, D. Golovin, Y. Honoki, T. Mori, K. Okamoto, S. Shokita, D. Neely, S. Fujioka, K. Mima, H. Nishimura, S. Kar, R. Kodama

SCIENTIFIC REPORTS 10 ( 1 ) 2020.11

The scientific and technical advances continue to support novel discoveries by allowing scientists to acquire new insights into the structure and properties of matter using new tools and sources. Notably, neutrons are among the most valuable sources in providing such a capability. At the Institute of Laser Engineering, Osaka, the first steps are taken towards the development of a table-top laser-driven neutron source, capable of producing a wide range of energies with high brightness and temporal resolution. By employing a pure hydrogen moderator, maintained at cryogenic temperature, a cold neutron (similar to 25 meV) flux of similar to 2 x 10(3) n/cm(2)/pulse was measured at the proximity of the moderator exit surface. The beam duration of hundreds of ns to tens of mu s is evaluated for neutron energies ranging from 100s keV down to meV via Monte-Carlo techniques. Presently, with the upcoming J-EPoCH high repetition rate laser at Osaka University, a cold neutron flux in orders of similar to 1 x 10(9) n/cm(2)/ s is expected to be delivered at the moderator in a compact beamline.

Relativistic magnetic reconnection in laser laboratory for testing an emission mechanism of hard-state black hole system

K. F.F. Law, Y. Abe, A. Morace, Y. Arikawa, S. Sakata, S. Lee, K. Matsuo, H. Morita, Y. Ochiai, C. Liu, A. Yogo, K. Okamoto, D. Golovin, M. Ehret, T. Ozaki, M. Nakai, Y. Sentoku, J. J. Santos, E. D'Humières, Ph Korneev, S. Fujioka

Physical Review E 102 ( 3 ) 2020.9

Magnetic reconnection in a relativistic electron magnetization regime was observed in a laboratory plasma produced by a high-intensity, large energy, picoseconds laser pulse. Magnetic reconnection conditions realized with a laser-driven several kilotesla magnetic field is comparable to that in the accretion disk corona of black hole systems, i.e., Cygnus X-1. We observed particle energy distributions of reconnection outflow jets, which possess a power-law component in a high-energy range. The hardness of the observed spectra could explain the hard-state x-ray emission from accreting black hole systems.

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Papers - Nakai Mitsuo