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Journal Articles

Temporal variation of density fluctuation and transport in reversed shear plasmas on JT-60U

Takenaga, Hidenobu; Oyama, Naoyuki; Bruskin, L. G.*; Mase, Atsushi*; Takizuka, Tomonori; Fujita, Takaaki

Plasma Physics and Controlled Fusion, 48(5A), p.A401 - A408, 2006/05

 Times Cited Count:6 Percentile:21.58(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Reconstruction of wavenumber spectra of plasma turbulence in microwave reflectometry

Bruskin, L. G.*; Oyama, Naoyuki; Mase, Atsushi*; Shinohara, Koji; Miura, Yukitoshi

Plasma Physics and Controlled Fusion, 46(8), p.1313 - 1330, 2004/08

 Times Cited Count:13 Percentile:42.87(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Density fluctuation measurement at edge and internal transport barriers in JT-60U

Oyama, Naoyuki; Bruskin, L. G.*; Takenaga, Hidenobu; Shinohara, Koji; Isayama, Akihiko; Ide, Shunsuke; Sakamoto, Yoshiteru; Suzuki, Takahiro; Fujita, Takaaki; Kamada, Yutaka; et al.

Plasma Physics and Controlled Fusion, 46(5A), p.A355 - A361, 2004/05

 Times Cited Count:10 Percentile:34.79(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Theoretical modeling and application of microwave reflectometry to plasma turbulence study

Bruskin, L. G.*; Oyama, Naoyuki; Mase, Atsushi*; Shinohara, Koji; Miura, Yukitoshi

Journal of Plasma and Fusion Research SERIES, Vol.6, p.318 - 321, 2004/00

We present a theoretical model of single-frequency microwave reflectometry of plasma density fluctuations with the objective of quantitative estimation of their poloidal spectrum shape and amplitude. The model is based on the analytical solution of the full-wave equation for O-mode microwave propagation inside the plasma in the Born approximation. The solution allows us to find explicitly the poloidal spectrum of weak plasma fluctuations. With the additional assumption of 2D isotropic spectrum in the r-$$theta$$ plane it is also possible to find the fluctuation amplitude. We illustrate our model by the analysis of real signals recorded by the O-mode reflectometer on the JT-60U device.

Journal Articles

Relationship between particle and heat transport in JT-60U plasmas with internal transport barrier

Takenaga, Hidenobu; Higashijima, Satoru; Oyama, Naoyuki; Bruskin, L. G.; Koide, Yoshihiko; Ide, Shunsuke; Shirai, Hiroshi; Sakamoto, Yoshiteru; Suzuki, Takahiro; Hill, K. W.*; et al.

Nuclear Fusion, 43(10), p.1235 - 1245, 2003/10

 Times Cited Count:71 Percentile:88.69(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Reflectometry study of mode coupling in fusion plasma turbulence

Bruskin, L. G.; Mase, Atsushi*; Oyama, Naoyuki; Shinohara, Koji; Miura, Yukitoshi

Plasma Physics and Controlled Fusion, 45(7), p.1227 - 1245, 2003/07

 Times Cited Count:7 Percentile:22.95(Physics, Fluids & Plasmas)

The capability of microwave reflectometry to estimate the nonlinear coupling in the plasma turbulence is theoretically investigated. The full-wave 2D model of microwave scattering in plasma is applied to simulate the reflectometer response to the turbulent fluctuations, consisting of random and coherent modes, and the simulated data ensemble is further processed to obtain the auto bicoherence function. Sensitivity of the method was analyzed for different ambient plasma profiles, geometry, fluctuation spectra and amplitudes.

Journal Articles

Measurements of density fluctuations in reflectometry of cylindrical plasmas

Bruskin, L. G.; Oyama, Naoyuki; Shinohara, Koji; Miura, Yukitoshi; Kogi, Yuichiro*; Mase, Atsushi*; Hasegawa, Makoto*; Hanada, Kazuaki*

Review of Scientific Instruments, 74(3), p.1473 - 1476, 2003/03

 Times Cited Count:5 Percentile:33.19(Instruments & Instrumentation)

An analytical model of fluctuation reflectometry is developed, which is capable of handling the plasma profiles of arbitrary shape and curvature. The experimental profiles are piece-wise approximated by the functions, which allow for the integration of the full-wave O-mode equation. The model is applied to the reflectometry of the JT-60U tokamak plasma to provide a preliminary estimation of the fluctuation amplitude and spectral width.

Journal Articles

Fluctuation reflectometry of azimuthally symmetric plasmas

Bruskin, L. G.; Mase, Atsushi*; Oyama, Naoyuki; Miura, Yukitoshi

Plasma Physics and Controlled Fusion, 44(11), p.2305 - 2325, 2002/11

 Times Cited Count:17 Percentile:48.91(Physics, Fluids & Plasmas)

The results of analytical solution of time-dependent 2D full-wave equation are presented here for the case of fluctuation reflectometry. We consider a family of plasma density profiles with cylindrical symmetry, which allow for an integration of the microwave scattering equation. Based on the results of analytical modeling, Doppler reflectometry as a method of plasma velocity measurements is investigated. It is shown that the accuracy of Doppler shift measurements is sensitive to the spectral content of the broadband turbulence, as well as to the curvature of the plasma cut-off layer. Addressing the problem of fluctuation amplitude measurements, it is suggested that a power-related parameter of the microwave signal, called fluctuation index, is suitable to quantify the plasma turbulence level provided that the fluctuation spectrum is a priori estimated.

Journal Articles

Effect of plasma profile curvature on microwave scattering in reflectometry

Bruskin, L. G.; Mase, Atsushi*

Journal of the Physical Society of Japan, 71(5), p.1274 - 1279, 2002/05

 Times Cited Count:3 Percentile:29.26(Physics, Multidisciplinary)

The results of analytical solution of the time-dependent 2D full wave equation in cylindrical coordinates are presented here with application to plasma fluctuation reflectometry. We consider a family of plasma density profiles with cylindrical symmetry, which allow for a full integrationof the microwave scattering problem in Born approximation. Based on the results of analytical modeling, the effects of beam refraction and scattering are studied taking into account possible asymmetries such as antenna misalignments and movement of plasma fluctuations. It is shown that the reflectometer sensitivity to the small radial scale fluctuations increases in the plasma with the high curvature. It is also noted that the microwave reflectometry measurements are better localized in high curvature plasmas.

Journal Articles

Analytical simulation of microwave reflectometry of a plasma cylinder

Bruskin, L. G.; Mase, Atsushi*

Review of Scientific Instruments, 72(11), p.4139 - 4144, 2001/11

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Analytical study of ultra-short pulse reflectometry

Bruskin, L. G.; Mase, Atsushi*; Yamamoto, A.*; Kogi, Yuichiro*

Plasma Physics and Controlled Fusion, 43(10), p.1333 - 1349, 2001/10

 Times Cited Count:14 Percentile:43.6(Physics, Fluids & Plasmas)

no abstracts in English

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