Coherence-imaging spectroscopy for 2D distribution of ion temperature and flow velocity in a laboratory magnetosphere

Nakamura, K.; Nishiura, M.; Takahashi, N.; Yoshida, Zensho; Kinoshita, Naoki; Sugata, T.; Katsura, Seiichiro; Howard, J.

doi:10.1063/1.5037124

Cited by 5 publications

(6 citation statements)

References 14 publications

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“…Coherence imaging spectroscopy (CIS) [17] was newly implemented to understand the heating mechanism and its effect on a poloidal cross section. In helium plasmas, the CIS measured the spectral intensity, the ion temperature, and the flow velocity of He + in FIG.…”

Section: Icrf Heating and Its Effect In Dipole Confinementmentioning

confidence: 99%

“…The ion temperature was increased in the confinement region, while the ion flow is enhanced near the levitation magnet [12]. CIS [17] was newly implemented to understand the heating mechanism and its effect on a poloidal cross-section. In helium plasmas, the CIS measured the spectral intensity, ion temperature and flow velocity of He + in figure 6.…”

Section: Icrf Heating and Its Effect In Dipole Confinementmentioning

confidence: 99%

“…To understand the transport of self-organized plasmas and the heating effect in magnetospheric plasmas, a Thomson scattering (TS) for the electron temperature and density [15], and the coherence imaging spectroscopy (CIS) [16] have recently been implemented in the RT-1 [17]. The existing diagnostics can explain the local and entire plasma dynamics.…”

Section: Introductionmentioning

confidence: 99%

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Experimental analysis of self-organized structure and transport on the magnetospheric plasma device RT-1

Nishiura¹,

Yoshida²,

Kinoshita³

et al. 2019

Nucl. Fusion

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The dipole plasma exhibits strong heterogeneities in field strength, density, temperature, and other parameters, while maintaining the holistic balance. Enquiring into the internal structures, we reveal the fundamental self-organizing mechanisms operating in their simplest realization (as commonly observed in astronomical systems). Three new findings are reported from the RT-1 experiment: Creation of a high-energy electron core (similar to the radiation belts in planetary magnetospheres) is observed for the first time in a laboratory system. Highenergy electrons (3 -15 keV), produced by an electron cyclotron heating (ECH), accumulate in a "belt" located in the low-density region (high-beta value ~ 1 is obtained by increasing the high-energy component up to 70% of the total electrons). The dynamical process of the "uphill diffusion" (a spontaneous mechanism of creating density gradient) has been analyzed by perturbing the density by gas injection. The spontaneous density formation in laboratory 2 magnetosphere eluciates the self-organized plasma transport relevant to planetary magnetosphere. The coherence-imaging spectroscopy visualized the two dimensional profiles of ion temperature and flow velocity in the ion cyclotron resonance frequency (ICRF) heating.The ion temperature and flow were enhanced globally, and particularly along the magnetic field lines near the levitation magnet. These results advance our understanding of transport and self-organization not only in dipole plasmas, but also in general magnetic confinement systems relevant to fusion plasmas.

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Section: Icrf Heating and Its Effect In Dipole Confinementmentioning

confidence: 99%

Section: Icrf Heating and Its Effect In Dipole Confinementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental analysis of self-organized structure and transport on the magnetospheric plasma device RT-1

Nishiura¹,

Yoshida²,

Kinoshita³

et al. 2019

Nucl. Fusion

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“…To understand self-organized plasmas in a dipole confinement device Ring-Trap 1 (RT-1), Doppler spectroscopy is utilized in high-beta plasmas to study the heat and particle transports, which imitate a planetary magnetospheric plasma in the laboratory 1,2 . To understand the role of ion flow in self-organized plasmas, coherence imaging spectroscopy (CIS) has been developed in the RT-1 3 .…”

Section: Introductionmentioning

confidence: 99%

Calibration of coherence imaging spectroscopy using spectral line sources

Uéda

Nishiura

Kinoshita

et al. 2021

Review of Scientific Instruments

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Coherence imaging spectroscopy (CIS) measures the two-dimensional profiles of both ion temperature and ion velocity in plasmas. The interferometric technique is realized by a certain relation between a phase and a wavelength of light emerging from the birefringent crystal. The calibration for the CIS system requires monochromatic and tunable light sources near He II line (468.6 nm) or C III line (465 nm) where the CIS measures. In this research, the CIS system has been upgraded by implementing an electron multiplier CCD (EM-CCD) and a CIS cell. A monochromator validates the linearity of the phase relation on the wavelength near the He II line. As an in-situ calibration at Ring Trap 1 (RT-1) plasma device, two spectral lines of Ti and Zn lamps obtain the accurate dispersion function of phase. It is found that the simple method with two spectral lines is reliable and sufficient for the calibration.

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“…We applied this reconstruction technique to the He II 468.6 nm imaging diagnostic of Coherence Imaging Spectroscopy (CIS) [4] from RT-1, a laboratory magnetosphere created by levitating a superconducting ring magnet [5]. To train the network to reconstruct images, we generated pairs of local-intensity profiles and line-integrated images that simulate the optics of the CIS system.…”

mentioning

confidence: 99%

Tomographic Reconstruction of Imaging Diagnostics with a Generative Adversarial Network

Kinoshita

Nishiura

Nakamura

et al. 2019

Plasma and Fusion Research

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We have developed a tomographic reconstruction method using a conditional Generative Adversarial Network to obtain local-intensity profiles from imaging-diagnostic data. To train the network we prepared pairs of local-emissivity and line-integrated images that simulate the experimental system. After validating the accuracy of the trained network, we used it to reconstruct a local image from a measured line-integrated image. We applied this procedure to the He II-emission imaging diagnostic for RT-1 magnetospheric plasmas, including the effects of stray light within the measured image to remove reflections from the chamber walls in the reconstruction. The local intensity profiles we obtain clearly elucidate the effect of ion-cyclotron-resonance heating. This method is a powerful tool for systems where it is difficult to solve the inversion problem due to the involved contributions of nonlocal optical effects or measurement restrictions.

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Coherence-imaging spectroscopy for 2D distribution of ion temperature and flow velocity in a laboratory magnetosphere

Cited by 5 publications

References 14 publications

Experimental analysis of self-organized structure and transport on the magnetospheric plasma device RT-1

Experimental analysis of self-organized structure and transport on the magnetospheric plasma device RT-1

Calibration of coherence imaging spectroscopy using spectral line sources

Tomographic Reconstruction of Imaging Diagnostics with a Generative Adversarial Network

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