High spatial and temporal resolution charge exchange recombination spectroscopy on the HL-2A tokamak

Wei, Y. L.; Yu, D.L.; Liu, L.; Ida, K.; Hellermann, M. von; Cao, Jianyong; Sun, A.P.; Ma, Qianli; Chen, W. J.; Liu, Yi; Yan, Lei; Qi, Yang; Duan, X.R.; Liu, Yong

doi:10.1063/1.4897186

Cited by 37 publications

(23 citation statements)

References 12 publications

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“…A 32/64-channel charge exchange recombination spectroscopy (CXRS) diagnostic system is developed at the HL-2A tokamak, monitoring plasma ion temperature and toroidal rotation velocity simultaneously with spatial and temporal resolutions up to ~1 cm and 5 ms [12,13]. A 32-channel (now it is around 45 channels) fast electron cyclotron emission (ECE) system provides the electron temperature (T e ) with temporal and spatial resolutions up to 0.8 μs and 1 cm [14].…”

Section: Introductionmentioning

confidence: 99%

Ion internal transport barrier in neutral beam heated plasmas on HL-2A

Wei

Liu

et al. 2016

Nucl. Fusion

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Ion internal transport barriers (iITBs) are first observed in neutral beam injection (NBI) heated plasmas at the HL-2A tokamak. The position of the barrier foot, in the stationary state, coincides with the q = 1 surface within its uncertainty of measurement. iITBs can develop more easily at the beginning of NBI heating. Also, iITBs are unstable for the sawtooth plasma. Simulations reveal that the thermal diffusivity of ions (χ i) inside the barrier can be as low as the neoclassical level. It is observed that the flow shear in the stationary iITB state reaches the level required for suppressing the ion temperature gradient mode instability, which indicates the important role of flow shear in sustaining the iITB.

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Section: Introductionmentioning

confidence: 99%

Ion internal transport barrier in neutral beam heated plasmas on HL-2A

Wei

Liu

et al. 2016

Nucl. Fusion

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“…Besides, Mirnov coils, soft-x-ray (SXR) detectors and Doppler reflectometer were used to measure MHD instabilities and turbulence at a sampling rate of 1 MHz. The toroidal plasma rotation was detected by a charge exchange recombination spectroscopy (CXRS) with a spatial resolution ≈1.5 cm23.…”

Section: Methodsmentioning

confidence: 99%

On the interplay between neoclassical tearing modes and nonlocal transport in toroidal plasmas

Hidalgo³

et al. 2016

Sci Rep

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This Letter presents the first observation on the interplay between nonlocal transport and neoclassical tearing modes (NTMs) during transient nonlocal heat transport events in the HL-2A tokamak. The nonlocality is triggered by edge cooling and large-scale, inward propagating avalanches. These lead to a locally enhanced pressure gradient at the q = 3/2 (or 2/1) rational surface and hence the onset of the NTM in relatively low β plasmas (β N < 1). The NTM, in return, regulates the nonlocal transport by truncation of avalanches by local sheared toroidal flows which develop near the magnetic island. These findings have direct implications for understanding the dynamic interaction between turbulence and large-scale mode structures in fusion plasmas.Over the past years, a number of experiments which study transient transport events in magnetically confined plasmas have revealed a provocative phenomenon [1][2][3][4][5][6][7] . A rapid change of local thermal transport in response to a change of plasma parameters occurs at a location distant from the perturbation, i. e., the so-called "nonlocal" transport, which cannot be explained just by the standard diffusive local transport paradigm. Although several theoretical models [8][9][10][11][12] have been proposed which try to interpret this nonlocal effect, the underlying physical mechanisms remain unclear, due to limited experimental data.On the other hand, to achieve economic viability for a future fusion reactor, a crucial task is to operate the plasma at relatively high β values, where β is the ratio of plasma pressure p to the magnetic field (B) pressure defined as β = p/(B 2 /2μ 0 ). However, the maximum achievable β can be limited by resistive MHD instabilities, in particular, the neoclassical tearing mode (NTM) [13][14][15][16][17] . The NTM is driven by a loss of a large bootstrap current related to a large plasma pressure gradient within a magnetic island. The occurrence of NTMs may considerably increase parallel heat transport across the width of the island, degrade energy confinement and even cause plasma disruptions. Thus, the NTM will prevent plasmas moving into a high-β state if it appears in the low-β case. As a consequence, understanding the physical processes for the onset of NTMs, as well as their prevention, is also one of major challenges for fusion.In this Letter, we present the first experimental observation of self-regulation of nonlocal transport events by NTMs generated during transient nonlocal transport events. The nonlocal effect is excited by edge cooling and propagates inward by avalanche events. These cause a local increase of the pressure gradient at the inversion surface, and thus the onset of the NTM in relatively low β plasmas (β N < 1). The presence of the NTM, results in the development of sheared flows at the magnetic island. The dual role of low-order rationals as both damping 18 and drive mechanism of steady-state 19 and fluctuating 20 E r × B flows has been identified, thus the magnetic topology is an important regulator of radial ...

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“…The shape of the electron density profile is assumed to be the same as that of the similar discharge #25733. [12] The electron and thermal ion temperature profiles are measured through electron cyclotron emission [15] and charge exchange recombination [16] diagnosis systems, respectively. Fast ion profiles are output from NUBEAM [17] calculation.…”

Section: Physical Model In the Gene Code And Numerical Setupmentioning

confidence: 99%

Gyrokinetic simulation of low-n Alfvénic modes in tokamak HL-2A plasmas

Lin¹,

Li²,

García³

et al. 2023

Chinese Phys. B

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Turbulence characteristics of plasmas with the internal transport barriers in HL‐2A tokamak are analyzed by means of linear gyrokinetic simulations. It is found that turbulence is dominated by the Ion Temperature Gradient (ITG) mode together with large scale modes characterized by high‐frequency electromagnetic fluctuation, which are destabilized by the steep ion temperature gradient in weak magnetic shear regime. Comparison with solutions of analytical dispersion relations shows that their linear features match well with the beta‐induced Alfven eigenmode (BAE) branch of shear Alfvenic spectrum. It is further clarified that the large population of fast ions in these plasmas play a stabilization role through the dilution mechanism in high‐n ITG mode regimes.

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High spatial and temporal resolution charge exchange recombination spectroscopy on the HL-2A tokamak

Cited by 37 publications

References 12 publications

Ion internal transport barrier in neutral beam heated plasmas on HL-2A

Ion internal transport barrier in neutral beam heated plasmas on HL-2A

On the interplay between neoclassical tearing modes and nonlocal transport in toroidal plasmas

Gyrokinetic simulation of low-n Alfvénic modes in tokamak HL-2A plasmas

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