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

https://doi.org/10.1088/1742-6596/548/1/012038

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 1035 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.

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

https://doi.org/10.1088/0741-3335/53/4/045005

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

https://doi.org/10.13182/FST10-04

Alignment creation and deviation from statistical population distribution in hydrogen =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

https://doi.org/10.1088/0741-3335/51/11/115004

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

https://doi.org/10.3807/JOSK.2009.13.1.060

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.

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

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

https://doi.org/10.3807/JOSK.2003.7.3.145

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 110 W/cm was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s2p P-1s4d D (J=1/2-3/2 and J=3/2-5/2) transition line at 129.92 の1s 2pP-1s4sS (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.

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 -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.

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, 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.

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