Decision making in protection against radiation from nuclear disaster; Risk trade-off and stakeholder involvement

Kanda, Reiko*; Homma, Toshimitsu*; Takahara, Shogo; Tsubokura, Masaharu*; Osako, Masahiro*; Kawaguchi, Isao*; Kato, Takaaki*

Risukugaku Kenkyu, 30(3), p.133 - 139, 2021/04

https://doi.org/10.11447/jjra.SRA-0353

Almost ten years have passed since Fukushima nuclear accident. Our experience should be used to improve current emergency protective measures and preparedness. A review of the protective measures implemented in the aftermath of Fukushima nuclear accident has revealed problems such as paternalistic intervention for inhabitants and increased health risks due to the evacuation of vulnerable groups. The risk trade-offs in environmental recovery actions are more complex and ongoing; the stakeholders are the next generation and residents outside of the prefecture. Since one of the characteristics of nuclear disasters is the distance and time dependency of the risk, countless individual cases need to be addressed. While generalization of protective measures is essential, the appropriate deployment of personnel in a variety of roles may require to really address individual cases. To improve nuclear emergency preparedness in the future, it is necessary to incorporate both a top-down approach and a bottom-up approach in a well-balanced manner.

Effect of nitrous ion on oxidation of oxidizing-metallic ion in nitric acid solution

Irisawa, Eriko; Seki, Masaharu*; Ueno, Fumiyoshi; Kato, Chiaki; Motooka, Takafumi; Abe, Hitoshi

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1108 - 1112, 2015/09

Observation and theory of X-ray mirages

Magnitskiy, S.*; Nagorskiy, N.*; Faenov, A.*; Pikuz, T.; Tanaka, Momoko; Ishino, Masahiko; Nishikino, Masaharu; Fukuda, Yuji; Kando, Masaki; Kawachi, Tetsuya; et al.

Nature Communications (Internet), 4, p.1936_1 - 1936_7, 2013/06

https://doi.org/10.1038/ncomms2923

Advent of plasma-based transient collisional excitation X-ray lasers allowed us to realize compact coherent X-ray sources, thus opening the way to a wide range of applications. Here we report the observation of unexpected concentric rings in the far-field beam profile at the output of a two-stage plasma-based X-ray laser developed in Japan Atomic Energy Agency, which can be considered as the first manifestation of a mirage phenomenon in X-rays. We have developed a method of solving the Maxwell-Bloch equations, which has allowed to find that the observed phenomenon is due to the emergence in the plasma-amplifier of X-ray mirage in the form of the phase matched coherent virtual point source. The obtained results bring a new insight into physical nature of amplification of X-ray radiation in laser-induced plasma amplifiers and open new opportunities for X-ray plasma diagnostics and extreme UV lithography.

Source development and novel applications of laser-driven plasma X-ray lasers in JAEA

Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Oba, Toshiyuki; Kaihori, Takeshi; Kishimoto, Maki; Ochi, Yoshihiro; Tanaka, Momoko; et al.

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.15 - 24, 2011/12

http://ci.nii.ac.jp/ncid/BB05543208

This paper reviews recent improvement in the source development of laser-driven X-ray lasers and the applications in the research fields of material science, laser processing, X-ray imaging, and radiation damage in biological cells. In the application for material science, we have firstly observed temporal correlation between the domain structures of ferro-electric substance under the Curie temperature. In the laser processing, new X-ray laser interferometer reveals us the nano-scale surface distortion of substance pumped by a femto-second optical pulse. In the X-ray diffraction image, we have taken several static images of micro-structure of samples: now we are trying to extend the objective to nano-scale dynamics using pump and probe method. In the radiation damage of biological cells, we observed double strand break in DNA using X-ray laser exposure; this results are compared with the case using incoherent several KeV X-ray exposure.

Spallative ablation of dielectrics by X-ray laser

Inogamov, N. A.*; Zhakhovsky, V. V.*; Faenov, A. Ya.*; Khokhlov, V. A.*; Shepelev, V. V.*; Skobelev, I. Y.*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T. A.*; Kishimoto, Maki; et al.

Applied Physics A, 101(1), p.87 - 96, 2010/10

https://doi.org/10.1007/s00339-010-5764-3

Low-threshold ablation of dielectrics irradiated by picosecond soft X-ray laser pulses

Faenov, A. Y.; Inogamov, N. A.*; Zhakhovskii, V. V.*; Khokhlov, V. A.*; Nishihara, Katsunobu*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T. A.*; Kishimoto, Maki; Ishino, Masahiko; et al.

Applied Physics Letters, 94(23), p.231107_1 - 231107_3, 2009/06

https://doi.org/10.1063/1.3152290

Direct measurement of the temporal profile of the amplification gain of the transient collisional excitation neonlike manganese X-ray laser medium

Hasegawa, Noboru; Kawachi, Tetsuya; Sasaki, Akira; Kishimoto, Maki; Sukegawa, Kota; Tanaka, Momoko; Tai, R. Z.*; Ochi, Yoshihiro; Nishikino, Masaharu; Nagashima, Keisuke; et al.

Physical Review A, 76(4), p.043805_1 - 043805_5, 2007/10

https://doi.org/10.1103/PhysRevA.76.043805

We firstly demonstrated the measurement of temporal profile of the amplification gain of the transient collisional excitation (TCE) X-ray laser with the solid target by use of X-ray diagnostic beam injection technique. In this experiment, higher-order harmonic light at a wavelength of 26.9 nm was injected into the neon-like manganese plasma as X-ray laser medium, and the amplified signal was observed. The obtained buildup time of the amplification gain was 23 ps measured from the time of the main pumping laser pulse, and the lifetime of the amplification gain was 27 ps. This result was in good agreement with the theoretical simulation by using an atomic kinetics code.

Analysis of gain generation of the TCE X-ray laser through temporal duration

Ochi, Yoshihiro; Kawachi, Tetsuya; Sasaki, Akira; Nagashima, Keisuke; Hasegawa, Noboru; Tanaka, Momoko; Kishimoto, Maki; Nishikino, Masaharu; Kato, Yoshiaki

X-Ray Lasers 2004; Institute of Physics Conference Series, Vol.186, p.111 - 114, 2005/06

We have measured the temporal duration of the TCE X-ray laser (XRL) with Ni-like silver (Ag; Z = 47), palladium (Pd; Z = 46), and molybdenum (Mo; Z = 42). The pumping pulse was derived from Nd:glass laser system with the chirped pulse amplification at the wavelength of 1053 nm. The duration of the main pulse and prepulse were set to be 4.8 ps and 400 ps respectively. The pulse separation between the pulses was typically 500 ps. A quasi-traveling wave pumping using 6-step mirror was adopted in the focusing system. The X-ray laser outputs were measured by use of an X-ray streak camera coupled with a flat field spectrometer. The observed durations were 9.3 ps, 6.2 ps, and 3.9 ps for Ag, Pd, and Mo XRLs respectively, resulting in the longer duration for the higher atomic number material. We will discuss the gain generation in the plasma medium with the help of numerical simulation and atomic code.

Development of a full spatial coherent X-ray laser at 13.9 nm and its applications

Nagashima, Keisuke; Tanaka, Momoko; Nishikino, Masaharu; Kishimoto, Maki; Kado, Masataka; Kawachi, Tetsuya; Hasegawa, Noboru; Ochi, Yoshihiro; Sukegawa, Kota*; Tai, R.; et al.

Applied Physics B, 78(7), p.927 - 932, 2004/05

We have succeeded in developing a laser-pumped X-ray laser with full spatial coherence at 13.9 nm. A highly directed X-ray laser beam with the divergence of 0.2 mrad was generated from the double target experiment, where a seeding light from the first laser medium was amplified in the second medium. The observed divergence is close to the diffraction limit value within a factor of two. The seeding light was amplified in the second medium without refraction influence and the gain coefficient was about 8 cm-1. From the measurement of visibility, it was found that the spatial coherent length is longer than the beam diameter. As an application of this coherent X-ray laser, we observed a surface microstructure of ferroelectric material, BaTiO and clarified a change of the microstructure near the Curie temperature.

X-ray laser beam with diffraction-limited divergence generated with two gain media

Tanaka, Momoko; Nishikino, Masaharu; Kawachi, Tetsuya; Hasegawa, Noboru; Kado, Masataka; Kishimoto, Maki; Nagashima, Keisuke; Kato, Yoshiaki

Optics Letters, 28(18), p.1680 - 1682, 2003/09

https://doi.org/10.1364/OL.28.001680

We have demonstrated an x-ray laser at a wavelength of 13.9 nm with a beam divergence of 0.2 mrad, which is 1.8 times the diffraction limit. The x-ray laser is generated using two gain media, where the seed x-ray pulse from the first medium is amplified in the second medium. The effect of refraction on x-ray propagation is reduced by spatially and temporally controlling the injection of the seed x-ray to the second medium.