Fast reciprocating probe system on the EAST superconducting tokamak

Zhang, W.; Chang, Jinming; Wan, B. N.; Xu, G. S.; Xiao, C. J.; Li, B.; Xu, C. S.; Niu, Y.; Wang, L.; Liu, S. C.; Jiang, M.; Liu, P.

doi:10.1063/1.3499237

Cited by 66 publications

(53 citation statements)

References 23 publications

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“…3. 29 A specially designed connector is installed at the front of the FRP probe shaft to make it easy to install or change the probe head. A graphite tip measuring the floating potential is also mounted besides the RFA to determine its relative location.…”

Section: Resultsmentioning

confidence: 99%

Fast electron flux driven by lower hybrid wave in the scrape-off layer

Wang

et al. 2015

Physics of Plasmas

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The fast electron flux driven by Lower Hybrid Wave (LHW) in the scrape-off layer (SOL) in EAST is analyzed both theoretically and experimentally. The five bright belts flowing along the magnetic field lines in the SOL and hot spots at LHW guard limiters observed by charge coupled device and infrared cameras are attributed to the fast electron flux, which is directly measured by retarding field analyzers (RFA). The current carried by the fast electron flux, ranging from 400 to 6000 A/m 2 and in the direction opposite to the plasma current, is scanned along the radial direction from the limiter surface to the position about 25 mm beyond the limiter. The measured fast electron flux is attributed to the high parallel wave refractive index n jj components of LHW. According to the antenna structure and the LHW power absorbed by plasma, a broad parallel electric field spectrum of incident wave from the antennas is estimated. The radial distribution of LHW-driven current density is analyzed in SOL based on Landau damping of the LHW. The analytical results support the RFA measurements, showing a certain level of consistency. In addition, the deposition profile of the LHW power density in SOL is also calculated utilizing this simple model. This study provides some fundamental insight into the heating and current drive effects induced by LHW in SOL, and should also help to interpret the observations and related numerical analyses of the behaviors of bright belts and hot spots induced by LHW. V C 2015 AIP Publishing LLC.

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Section: Resultsmentioning

confidence: 99%

Fast electron flux driven by lower hybrid wave in the scrape-off layer

Wang

et al. 2015

Physics of Plasmas

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“…26 Floating potential fluctuations interpreted as plasma potential fluctuations are measured with a Langmuir probe array 11,27 consisting of three tips. Two tips are poloidally separated by 8 mm, a third tip is placed in the middle of them, radially sticking out by 5 mm.…”

Section: Methodsmentioning

confidence: 99%

Zonal flow triggers the L-H transition in the Experimental Advanced Superconducting Tokamak

et al. 2012

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The kinetic energy transfer between shear flows and the ambient turbulence is investigated in the Experimental Advanced Superconducting Tokamak during the L-H transition. As the rate of energy transfer from the turbulence into the shear flow becomes comparable to the energy input rate into the turbulence, the transition into the H-mode occurs. As the observed behavior exhibits several predicted features of zonal flows, the results show the key role that zonal flows play in mediating the transition into H-mode. V C 2012 American Institute of Physics. [http://dx.doi.org/ 10.1063/1.4737612] INTRODUCTION The transition from low (L-mode) to high confinement (H-mode) regime in magnetized confined fusion devices occurs very rapidly at a critical condition, similar, in a sense, to leaning slightly over the side of a canoe causing only a small tilt of the craft, but leaning slightly more may roll you and the craft into the lake. Rapid threshold transitions between distinctly different stable states then require a triggering event, akin to leaning out too far from the canoe. 1 However, the physics that triggers the transition into Hmode is not understood, and thus predictions of the conditions for the transition into the H-mode regime-which are critical for the operation of ITER in the burning plasma regime-are based on empirical scalings with a wide range of uncertainty. Relative to the conditions found in low confinement regimes, H-mode plasmas are characterized by a reduced turbulence level and strong radial electric field (E r ) shear. 2,3 Azimuthally symmetric, bandlike, time-varying, turbulent generated shear flows called zonal flows (ZFs) also appear to be associated with the L-H transition. 4,5 Therefore, the interaction between micro and macroscale turbulent fluctuations has developed into one of the most active research topics in the physics of magnetized plasmas. The main focus has been placed on the generation of zonal flows and the reduction of the ambient turbulence via the nonlinear exchange, or transfer, of energy from the smaller scaled higher frequency turbulent fluctuations into the large scale, low frequency ordered zonal flow. 6-14 SELF-REGULATION OF TURBULENCETheory predicts that the L-H transition can be explained by an intermediate, quasi-periodic transient stage, where turbulence, zonal flow, mean shear flow, and the pressure gradient are coupled. 15,16 In this model, as the input power increases the pressure gradient also increases, resulting in stronger instabilities and fluctuation levels. The turbulence level grows and begins to nonlinearly drives the zonal flow until the zonal flow drive can overcome the flow damping. A finite zonal flow then begins to grow and extract kinetic energy from the turbulence and thereby acts to suppress the turbulence amplitude. Zonal flows can trigger the transition by regulating the turbulence level and associated transport until the mean shear flow is high enough to suppress the remaining turbulence and associated transport, causing the pressure gradient to i...

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“…The experiments were performed in Experimental Advanced Superconducting Tokamak (EAST) with R 0 =1.87 m and a=0.45 m. During the 2010 experimental campaign, two fast reciprocating probe systems [28] were assembled on ports A and E in the middle plane of the EAST, and the toroidal angle between them was 89 degrees. The probe arrangements can be seen in figure 1.…”

Section: Experimental Setup and Conditionsmentioning

confidence: 99%

Zonal flow energy ratio evolution during L-H and H-L transitions in EAST plasmas

Zhao

Lan

Liu

et al. 2017

Plasma Sci. Technol.

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The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak. Two toroidally localized probe arrays are used to measure the zonal flow during L-H transition and H-L back transition. The energy ratio of the low frequency zonal flow to the total drift wave turbulence is calculated. During ELM-free H mode, the energy ratio is higher than that in L mode, which reveals the important role of zonal flows in regulating turbulence amplitude in L-H transition.

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Fast reciprocating probe system on the EAST superconducting tokamak

Cited by 66 publications

References 23 publications

Fast electron flux driven by lower hybrid wave in the scrape-off layer

Fast electron flux driven by lower hybrid wave in the scrape-off layer

Zonal flow triggers the L-H transition in the Experimental Advanced Superconducting Tokamak

Zonal flow energy ratio evolution during L-H and H-L transitions in EAST plasmas

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