Plasma confinement in the GAMMA 10 tandem mirror

Impurity spectra have been measured and identified using a newly designed ultraviolet and visible ͑UV/visible͒ spectroscopic system in the tandem mirror GAMMA 10. It is constructed using two spectrometers to obtain an entire wavelength range of UV/visible impurity spectra with a high wavelength resolution in one plasma shot. We successfully obtained the emission intensities of the radiation spectra in detail and information on the time-varying population densities of the impurities. We evaluate radiation loss from the GAMMA 10 plasma in the UV/visible range; further we estimate the electron density and temperature after applying the measured spectral intensity to a collisional-radiative model.

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“…[8][9][10] Plasma is produced and heated by the ion cyclotron range of frequency power deposition. The plasma duration is 200 ms.…”

Section: Plasma Spectroscopymentioning

confidence: 99%

Measurements of impurity spectra using UV/visible spectroscopic system in a GAMMA 10 plasma

Matama

Yoshikawa

Kobayashi

et al. 2006

Review of Scientific Instruments

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“…2 together with the locations of the heating systems [5]. In order to produce the main plasma and heat the ions, ion-cyclotron range of frequency (ICRF) waves are injected into the target plasma in the central cell, which is injected along the magnetic-field line from both ends of the machine.…”

Section: Tandem Mirror Configurationmentioning

confidence: 99%

Transport of the ion bounced by the plug potential caused by radial electric field in the tandem mirror

et al. 2005

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In the tandem mirror, plug potentials are created in the plug/barrier cells by microwave injection, and also anchor cells with a minimum B magnetic field configuration are installed in order to reduce the MHD instability. Existence of the ion bounced by the plug potential (PP-bounced ion) is essential for the ion confinement in the tandem mirror. We study the transport of the PP-bounced ion on the assumption that the cross-sectional shape of the magnetic flux tube is slightly different from the cross-sectional shape of the equi-potential surface at the mirror throats of the anchor cell as a small deviation from the equilibrium state. The radial-potential profile of the core plasma is adjusted by controlling the electrostatic potentials of the coaxially separated end plates. We find that the spread type of radial-potential profile is effective for the confinement of the plug-potentialbounced ion.

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“…A nearly axisymmetric potential profile was produced by the axisymmetrization of the ECRH pattern. In addition to the adjustment of the heating patterns of ECRH and ICRH, conducting plates have been installed in anchor transition regions to fix the potential at the plasma boundary, thereby reducing possible irregular electric fields, which are considered to be a cause of the radial loss [1]. The radial loss has been much reduced with these procedures and a density increase of 125% due to the potential confinement was attained [2].…”

Section: Introductionmentioning

confidence: 99%

High-Pressure H2O Vapor Heat Treatment Used to Fabricate Poly-Si Thin Film Transistors

Watakabe¹,

Sameshima²

2002

Jpn. J. Appl. Phys.

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The improvement of potential confinement reported at the last IAEA Fusion Energy Conference in 1998 was attained by axisymmetrization of the heating pattern of ECRH. It was experimentally shown that the axisymmetrization of ECRH actually produced an axisymmetric potential profile. GAMMA 10 experiments on potential confinement have advanced in the direction of longer sustainment and higher density. Experiments to achieve long sustainment of potential confinement were carried out in order to study problems of steady state operation of a tandem mirror reactor. A confining potential was sustained for 150 ms by sequentially injecting two ECRH pulses into the plug region. It had previously been difficult to increase the central cell density to higher than about 2.5 × 10 12 cm −3 with or without potential confinement, owing to some density limiting mechanism. In order to overcome this problem, a new, higher frequency ICRF system (RF3: 36-76 MHz) has been installed. A higher density plasma has been produced with RF3. In addition to RF3, NBI in the anchor cells was recently made more effective through the reduction of neutral gas from the beam injectors. Potential confinement experiments have advanced to higher central cell densities of up to 4 × 10 12 cm −3 with RF3 and NBI. A 35% density increase due to the potential confinement was obtained in the high density experiments.

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Plasma confinement in the GAMMA 10 tandem mirror

Cited by 59 publications

References 5 publications

Measurements of impurity spectra using UV/visible spectroscopic system in a GAMMA 10 plasma

Measurements of impurity spectra using UV/visible spectroscopic system in a GAMMA 10 plasma

Transport of the ion bounced by the plug potential caused by radial electric field in the tandem mirror

High-Pressure H2O Vapor Heat Treatment Used to Fabricate Poly-Si Thin Film Transistors

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