Microwave Doppler reflectometer system in the Experimental Advanced Superconducting Tokamak

Zhou, Chu; Liu, A. D.; Zhang, X. H.; Hu, Jianqiang; Wang, M. Y.; Li, H.; Lan, Tao; Xie, Jinlin; Sun, Xiaofeng; Ding, Weixing; Liu, W. D.; Yu, Cong

doi:10.1063/1.4825344

Cited by 54 publications

(44 citation statements)

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“…It is shown in Fig. 5(b) that there is a sudden increase of the very edge perpendicular rotation measured by the Doppler backscattering system (DBS) [29] immediately after the application of RMPs, which indicates the change of edge topology [28]. As shown in Figs.…”

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confidence: 85%

Nonlinear Transition from Mitigation to Suppression of the Edge Localized Mode with Resonant Magnetic Perturbations in the EAST Tokamak

et al. 2016

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Evidence of a nonlinear transition from mitigation to suppression of the edge localized mode (ELM) by using resonant magnetic perturbations (RMPs) in the EAST tokamak is presented. This is the first demonstration of ELM suppression with RMPs in slowly rotating plasmas with dominant radio-frequency wave heating. Changes of edge magnetic topology after the transition are indicated by a gradual phase shift in the plasma response field from a linear magneto hydro dynamics modeling result to a vacuum one and a sudden increase of three-dimensional particle flux to the divertor. The transition threshold depends on the spectrum of RMPs and plasma rotation as well as perturbation amplitude. This means that edge topological changes resulting from nonlinear plasma response plays a key role in the suppression of ELM with RMPs. DOI: 10.1103/PhysRevLett.117.115001 Magnetic reconnection and the resultant topological change play an important role in plasma dynamics in both laboratory and space plasma physics research. The formation of an edge stochastic magnetic field caused by resonant magnetic perturbations (RMPs) is believed to be the reason for the suppression of periodic crash events near the plasma edge known as the edge localized mode (ELM) observed in the DIII-D tokamak [1]. The ELM causes transient heat loads to the plasma facing components and may degrade them on the next generation fusion device like ITER [2]. The reduction of free energy in the edge pressure gradient and current because of field stochasticity moves the plasma into a stable regime against the ELM [3]. This successful experiment motivated ELM control using RMPs in many other tokamaks [4][5][6][7]. However, the plasma response effect usually shields the external applied RMPs and may significantly reduce the magnetic field stochasticity [8][9][10][11], which makes this mechanism questionable. Different from topological change, the linear peelinglike magneto hydro dynamics (MHD) response has been found to play an important role in ELM control [12][13][14]. Nonlinear plasma response has been observed in the JET totamak [15]. The possible formation of a magnetic island near the plasma edge [16] with a toroidal Fourier mode number n ¼ 1 during ELM suppression by using n ¼ 2 RMP has been recently observed on DIII-D [17]. However, the key difference between ELM suppression and mitigation and the different roles of linear and nonlinear plasma response on ELM suppression are still not clear.In this Letter, we report the first observation of full ELM suppression using low n RMPs in slowly rotating plasmas with dominant radio-frequency (rf) wave heating, which is potentially important for the application of this method for a future fusion device. This is the first observation of full ELM suppression using RMPs in the medium plasma collisionality regime in EAST, and it expands beyond the previous observations of ELM suppression on DIII-D [1,3] and KSTAR [7]. It is found that not only the formation of a magnetic island near the edge [17] but also a critical leve...

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confidence: 85%

Nonlinear Transition from Mitigation to Suppression of the Edge Localized Mode with Resonant Magnetic Perturbations in the EAST Tokamak

et al. 2016

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“…2012; Zhou et al. 2013) can access wavenumbers between the high ion scale and the low- electron scale, . At the highest wavenumbers, relevant to ETG-scale turbulence, density fluctuations can be measured with high coherent scattering diagnostics (Rhodes et al.…”

Section: Turbulence Measurements In the Core Of Fusion Plasmasmentioning

confidence: 99%

“…Beam emission spectroscopy (BES) diagnostics (McKee et al 2007;Field et al 2014), and standard reflectometry (Nazikian, Kramer & Valeo 2001) are used to probe long-wavelength or low-k turbulence (typically k θ ρ s < 0.5), relevant for ITG/TEM type turbulence or MTM type turbulence. In the intermediate wavelength range, Doppler reflectometer (also known as Doppler backscattering) (Holzhauer et al 1998;Hirsch et al 2001;Conway et al 2004;Hennequin et al 2004;Happel et al 2009;Hillesheim et al 2009;Rhodes et al 2010;Tokuszawa et al 2012;Zhou et al 2013) can access wavenumbers between the high ion scale k θ ρ s ∼ 0.5 and the low-k electron scale, k θ ρ s ∼ 5. At the highest wavenumbers, relevant to ETG-scale turbulence, density fluctuations can be measured with high k coherent scattering diagnostics (Rhodes et al 2007;Smith et al 2008;Qing et al 2010).…”

Section: Turbulence Measurements In the Core Of Fusion Plasmasmentioning

confidence: 99%

Validation of nonlinear gyrokinetic transport models using turbulence measurements

White

2019

J. Plasma Phys.

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This tutorial covers validation of gyrokinetic turbulent-transport models via comparison of measured turbulence with realistic simulations of fusion plasmas. It presents a brief history of validation of gyrokinetic simulations, the principal challenges encountered, a limited survey of common turbulence diagnostics used on tokamaks and stellarators, an overview of the fundamentals of synthetic diagnostic models and a discussion of frontiers in turbulent-transport model validation.

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“…Hence, the extracted velocity against time at the measurement point reflects the velocity distribution of the wake. The Doppler reflectometer has been widely used on tokamak facilities as a general approach to measure the rotation velocity of plasma [11]- [13]. Since the signals received are in time domain, in order to extract the corresponding Doppler frequency shift it is necessary to convert them into frequency domain.…”

Section: Operation Principle and Data Analysis Algorithmmentioning

confidence: 99%

Contactless Measurement of Hypervelocity Projectile Wake Velocity Distribution

Jiang

Chen

et al. 2019

IEEE Access

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This paper presents a microwave approach to investigate the wake velocity distribution of hypervelocity projectile. The ballistic range measurement is carried out to model the transport of hypervelocity object on the ground. An X-band horn antenna sends a continuous sinusoidal wave with f c = 8.7 GHz to the hypervelocity object and detects the reflected signal. The continuous wavelet transform is utilized to obtain the Doppler frequency shift, and the wake velocity is calculated based on the theory of the Doppler effect. The validity of this experiment is confirmed by comparing the measured projectile velocity with that achieved by a laser-based velocity meter. As a contactless method, this approach does not interfere with the wake flow field. Therefore, the velocity distribution achieved in this paper exhibits better accuracy compared with that obtained from other contact approaches. INDEX TERMS Contactless, hypervelocity projectile, wake, velocity.

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Microwave Doppler reflectometer system in the Experimental Advanced Superconducting Tokamak

Cited by 54 publications

References 23 publications

Nonlinear Transition from Mitigation to Suppression of the Edge Localized Mode with Resonant Magnetic Perturbations in the EAST Tokamak

Nonlinear Transition from Mitigation to Suppression of the Edge Localized Mode with Resonant Magnetic Perturbations in the EAST Tokamak

Validation of nonlinear gyrokinetic transport models using turbulence measurements

Contactless Measurement of Hypervelocity Projectile Wake Velocity Distribution

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