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Journal Articles

Zeeman splitting of laser-driven soft X-ray laser line by the enhancement of magnetic field in plasma

Kawachi, Tetsuya; Hasegawa, Noboru; Iwamae, Atsushi*; Yoneda, Hitoki*

Journal of Physics; Conference Series, 548(1), p.012038_1 - 012038_7, 2014/11

 Times Cited Count:0 Percentile:0.03

Polarization is a fundamental property of light, and the effective use provides us powerful tools for probing materials and for plasma diagnostics. In plasmas, alignment of emission shows the plasma anisotropy, and Zeeman splitting informs us the magnetic field strength. We took the plasma-based soft X-ray laser as an example and observed the Zeeman splitting under the external magnetic field. A grazing incidence spectrograph, HIREFS, with the resolution of 15000 was used to observe the X-ray laser line. A magnetic coil driven by an electrical pulsed power supply provided the external magnetic field of 10$$sim$$35 T along the direction of the plasma column, and the left-handed and right-handed circular polarization components were obtained separately. The experimental result indicated that the magnetic field was larger by a factor of 4 than that of the applied field, which implied that the magnetic field compression occurred in the dynamics of the intense laser-plasma interaction.

JAEA Reports

Bi-directional reflectance distribution function of a tungsten block for ITER divertor

Iwamae, Atsushi*; Ogawa, Hiroaki; Sugie, Tatsuo; Kusama, Yoshinori

JAEA-Research 2011-045, 11 Pages, 2012/02

JAEA-Research-2011-045.pdf:2.36MB

In order to investigate reflection properties on plasma-facing material in ITER, the bi-directional reflectance distribution function (BRDF) of a tungsten block sample has been measured. On the machining surface of the block, one-directional machining lines are engraved. Two laser diodes $$lambda$$652 nm and $$lambda$$473 nm were used to simulate H$$_{alpha}$$ and H$$_{beta}$$ emissions, respectively. The reflected light is affected by the machining surface. The reflected light traces a line when the incident light is injected in the perpendicular direction to the engraved line. On the other hand the reflected light traces an arc shape when the incident light is injected in the parallel direction to the engraved lines. Ray tracing simulation qualitatively explains the experimental results.

Journal Articles

Synthesized intensity of emission lines of hydrogen isotopes and impurities in the ITER divertor plasma

Iwamae, Atsushi; Sugie, Tatsuo; Ogawa, Hiroaki; Kusama, Yoshinori

Plasma Physics and Controlled Fusion, 53(4), p.045005_1 - 045005_17, 2011/04

 Times Cited Count:2 Percentile:11.76(Physics, Fluids & Plasmas)

Journal Articles

${it In-situ}$ spectral calibration method for the impurity influx monitor (divertor) for ITER using angled physical contact fibers

Iwamae, Atsushi; Ogawa, Hiroaki; Sugie, Tatsuo; Kusama, Yoshinori

Review of Scientific Instruments, 82(3), p.033502_1 - 033502_4, 2011/03

 Times Cited Count:3 Percentile:19.8(Instruments & Instrumentation)

Journal Articles

Investigation of the helical divertor function and the future plan of a closed divertor for efficient particle control in the LHD plasma periphery

Shoji, Mamoru*; Masuzaki, Suguru*; Kobayashi, Masahiro*; Goto, Motoshi*; Morisaki, Tomohiro*; Yamada, Hiroshi*; Komori, Akio*; Iwamae, Atsushi; Sakaue, Atsushi*; LHD Experimental Group*

Fusion Science and Technology, 58(1), p.208 - 218, 2010/07

 Times Cited Count:9 Percentile:56.9(Nuclear Science & Technology)

Journal Articles

Highly charged tungsten spectra observed from JT-60U plasmas at $$T_{mbox{e}} approx$$ 8 and 14 keV

Yanagibayashi, Jun*; Nakano, Tomohide; Iwamae, Atsushi; Kubo, Hirotaka; Hasuo, Masahiro*; Itami, Kiyoshi

Journal of Physics B; Atomic, Molecular and Optical Physics, 43(14), p.144013_1 - 144013_6, 2010/07

 Times Cited Count:23 Percentile:72.41(Optics)

We observe the vacuum ultraviolet spectra of highly charged tungsten ions in plasmas at electron temperatures of 8 keV and 14 keV. The observed emission lines in a wavelength range of 2.6 $$sim$$ 3.2 nm for the plasma at 8 keV are identified to be the $$3mbox{p}_{3/2}-3mbox{d}_{5/2}$$ transitions of $$mbox{W}^{47+}-mbox{W}^{54 +}$$. The observed emission lines at 2.0 nm and 2.3 nm at 14 keV are identified to be the $$mbox{3p}_{1/2}-mbox{3d}_{3/2}$$ transitions of $$mbox{W}^{55 +}-mbox{W}^{61+}$$ and $$mbox{3s}_{1/2}-mbox{3p}_{3/2}$$ transitions of $$mbox{W}^{60 +}-mbox{W}^{63+}$$, respectively.

Journal Articles

Alignment creation and deviation from statistical population distribution in hydrogen $$n$$=3 levels observed on MSE spectra of LHD plasma

Iwamae, Atsushi; Sakaue, Atsushi*; Atake, Makoto*; Sawada, Keiji*; Goto, Motoshi*; Morita, Shigeru*

Plasma Physics and Controlled Fusion, 51(11), p.115004_1 - 115004_15, 2009/11

 Times Cited Count:6 Percentile:26.14(Physics, Fluids & Plasmas)

Journal Articles

Journal Articles

High-resolution spectroscopy of the nickel-like molybdenum X-ray laser toward the generation of circularly polarized X-ray laser

Hasegawa, Noboru; Sasaki, Akira; Yamatani, Hiroshi; Kishimoto, Maki; Tanaka, Momoko; Ochi, Yoshihiro; Nishikino, Masaharu; Kunieda, Yuichi; Kawachi, Tetsuya; Yoneda, Hitoki*; et al.

Journal of the Optical Society of Korea, 13(1), p.60 - 64, 2009/03

 Times Cited Count:5 Percentile:31.16(Optics)

The precise knowledge about the spectral width of the X-ray laser line is important to generate the circularly polarized X-ray laser. There are three magnetic sub-levels at lower state of the collisional excitation X-ray laser transition of the nickel-like ion X-ray laser medium. The polarization of each transition is circular or linear. Therefore the circularly polarized X-ray laser could be extracted by the influence of the Zeeman effect if the X-ray laser medium was under the external magnetic field. The strength of the magnetic field required for the circularly polarized X-ray laser is determined by the spectral width of the X-ray laser. Only a few measurements of the spectral width of the laser line have been reported, because the spectral width of the X-ray laser is so narrow that the required spectral resolution is quite high. In this study, we took the nickel-like molybdenum X-ray laser as an example and succeeded the measurement of the spectral width of the X-ray laser.

Journal Articles

Spectroscopic measurements of high frequency plasma in supercritical carbon dioxide

Maehara, Tsunehiro*; Kawashima, Ayato*; Iwamae, Atsushi; Mukasa, Shinobu*; Takemori, Toshihiko*; Watanabe, Takashi*; Kurokawa, Kenya*; Toyota, Hiromichi*; Nomura, Shinfuku*

Physics of Plasmas, 16(3), p.033503_1 - 033503_5, 2009/03

 Times Cited Count:12 Percentile:46.02(Physics, Fluids & Plasmas)

Journal Articles

Development of the UV and visible impurity influx monitor (divertor) for ITER

Iwamae, Atsushi; Ogawa, Hiroaki; Sugie, Tatsuo; Kasai, Satoshi*; Kusama, Yoshinori

Proceedings of 18th International Toki Conference on Development of Physics and Technology of Stellarator/Heliotrons en route to Demo (ITC-18) (CD-ROM), p.450 - 453, 2008/12

Journal Articles

Degradation of methylene blue by RF plasma in water

Maehara, Tsunehiro*; Miyamoto, Ippei*; Kurokawa, Kenya*; Hashimoto, Yukio*; Iwamae, Atsushi; Kuramoto, Makoto*; Yamashita, Hiroshi*; Mukasa, Shinobu*; Toyota, Hiromichi*; Nomura, Shinfuku*; et al.

Plasma Chemistry and Plasma Processing, 28(4), p.467 - 482, 2008/08

 Times Cited Count:48 Percentile:88.54(Engineering, Chemical)

Journal Articles

Study of the anisotropy of electron energy distribution of optical-field ionized oxygen plasma by using polarization spectroscopy

Kim, J.*; Kim, D. E.*; Kawachi, Tetsuya; Hasegawa, Noboru; Sukegawa, Kota*; Iwamae, Atsushi*; Fujimoto, Takashi*

Journal of the Optical Society of Korea, 7(3), p.145 - 149, 2003/09

The anistropy of electron energy distribution in oxygen plasmas produced by a high intensinty laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of 1$$times$$10$$^{17}$$ W/cm$$^{2}$$ was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s$$^{2}$$2p $$^{2}$$P$$^{2}$$-1s$$^{2}$$4d $$^{2}$$D$$^{0}$$ (J=1/2-3/2 and J=3/2-5/2) transition line at 129.92 $AA  was mesured. OVI $の1s$$^{2}$$ 2p$$^{2}$$P$$^{2}$$-1s$$^{2}$$4s$$^{2}$$S$$^{2}$$ (J=1/2-1/2 and J=3/2-1/2) transition line at 132.26 AA was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circlar polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.

Oral presentation

Issues and developments of spectroscopic diagnostics for ITER

Iwamae, Atsushi; Sugie, Tatsuo; Ogawa, Hiroaki; Kasai, Satoshi*; Kusama, Yoshinori

no journal, , 

In order to evaluate the impurity influx in the divertor plasma we need the average values of the ionization rate coefficient and the excitation rate coefficient. For the impurity influx of carbon, beryllium and tungsten, the accuracy of 30% is required in specification for plasma measurements on ITER. We review the present status of atomic data for tungsten. The theoretical value of S/XB, where S and X are the ionization and excitation rate coefficient, respectively, is two times higher than experimental. A prototype of the collection optics, Cassegrain telescope and micro lens array coupled with optical fiber bundle etc. has been examined. Preliminary results are reported. Two viewing fan observing divertor gap is proposed. Computerized tomographic reconstruction is performed for the model intensity distribution with the two viewing fan. We estimate the line-of-sight integrated emission intensity of carbon impurity with simulation of B2 code on ITER divertor plasma.

Oral presentation

Optical performance verification of the Impurity Influx Monitor (Divertor) for ITER

Iwamae, Atsushi; Ogawa, Hiroaki; Sugie, Tatsuo; Kusama, Yoshinori; Kasai, Satoshi*; Katsunuma, Atsushi*; Takeyama, Norihide*

no journal, , 

We report the performance test of the trial optics of the Impurity Influx Monitor (Divertor) for ITER. The emission from the divertor plasma in UV and visible wavelength region will be collected with the head optics and the Cassegrain telescope. The focused light from the plasma is transmitted by the optical fiber to the spectrometers. Since the head optics is irradiated by the high fluxes of the $$gamma$$-ray, neutron and high energy particles from the core plasma, we use molybdenum and aluminum metallic mirrors in the head optics. These mirrors are mounted in a module equipped with cooling channels to remove the nuclear heat. We have built metallic mirrors, a Cassegrain telescope, a micro-lens array and optical fiber light distributors for the optical performance test on an ITER-equivalent geometric scale. We expand the field of view along the magnetic field direction with introducing the micro-lens array in front of the fiber core. The light collection efficiency increased by three times at maximum with the micro-lens array. We have evaluated the line-of-sight integrated intensity of the impurity emission line in the divertor plasma with the collisional-radiative model. The estimated intensity of C IV line (581 nm) will be detectable in several lines of sight with the present designed optical system.

Oral presentation

Recent progress of design and R&D of impurity influx monitor (divertor) for ITER

Ogawa, Hiroaki; Iwamae, Atsushi; Sugie, Tatsuo; Kasai, Satoshi*; Katsunuma, Atsushi*; Hara, Hirotsugu*; Takeyama, Norihide*; Kusama, Yoshinori

no journal, , 

no abstracts in English

Oral presentation

First mirror issues and measures for harsh environment of ITER

Sugie, Tatsuo; Ogawa, Hiroaki; Iwamae, Atsushi; Kawano, Yasunori; Hatae, Takaki; Kajita, Shin*; Kusama, Yoshinori

no journal, , 

Plasma facing first mirrors of ITER will experience relatively higher levels of radiation due to neutron, $$gamma$$ ray irradiation than in present devices. An additional potential damaging effect for the first mirrors is the formation of coatings of impurities, such as Be, W, C, etc. due to erosion and re-deposition of the materials of the first wall and the divertor. Issues of the first mirror are summarized and the total fluxes and energy distributions of deuterium, helium, carbon and deuterium molecule at the first mirror positions are estimated. Protective and mitigating measures to minimize the degradation of first mirror reflectivity are adopted in the system designs of diagnostics. However, the reflectivity may change due to the environmental effects. An in-situ and remote sensitivity calibration system withstanding in the strong radiation field has been developed. Finally, remaining issues are summarized.

Oral presentation

Generation of polarization control of plasma X-ray laser by strong magnetic field

Hasegawa, Noboru; Kawachi, Tetsuya; Sasaki, Akira; Kishimoto, Maki; Tanaka, Momoko; Ochi, Yoshihiro; Nishikino, Masaharu; Kunieda, Yuichi; Iwamae, Atsushi*; Yoneda, Hitoki*

no journal, , 

We tried to generate the circularly polarized X-ray laser by use of the high power pulse magnet system. There are three magnetic sub-levels at lower state of the collisional excitation X-ray laser transition. For example, nickel-like X-ray laser transition (4d (m = 0) - 4p (m = -1, 0, +1)), the polarization from each transitions are right-handed circular ($$Delta$$m = -1), left-handed circular ($$Delta$$m = +1), and linear ($$Delta$$m = 0) along to the quantization axis. If the quantization axis were decided by the magnetic field from the outside of the X-ray laser medium, the circularly polarized X-ray laser can be extracted. In this study, we tried to generate the circularly polarized X-ray laser by using the nickel-like molybdenum X-ray laser medium (18.9 nm) with 20 Tesla magnetic field generated by the pulse power magnet system.

Oral presentation

Progress in ITER diagnostics development in Japan

Kawano, Yasunori; Kondoh, Takashi; Ishikawa, Masao; Ogawa, Hiroaki; Iwamae, Atsushi; Sugie, Tatsuo; Kasai, Satoshi*; Kusama, Yoshinori; Sato, Kazuyoshi

no journal, , 

no abstracts in English

Oral presentation

Development and test on the prototype of the Impurity Influx Monitor (divertor) for ITER

Iwamae, Atsushi; Sugie, Tatsuo; Ogawa, Hiroaki; Kasai, Satoshi*; Kusama, Yoshinori

no journal, , 

no abstracts in English

32 (Records 1-20 displayed on this page)