An ultrafast reciprocating probe

Liu, Wenbin; Tan, Yidong; Wang, Wenhao; Gao, Zhe

doi:10.1063/1.4962060

“…The spatial resolution of the HRS system for temperature fluctuation measurement is about 1-2 cm [30]. As shown in figure 1(b), POINT has 11 channels, all of which are parallel to the mid-plane and uniformly distributed from down to up (Z from −42.5 cm to 42.5 cm) in the same poloidal crosssection [31]. The ECE diagnostic has 48 channels, one or two of which covers the pedestal region depending on the pedestal parameters.…”

Section: Methodsmentioning

confidence: 99%

Impact of coherent mode on divertor particle and heat flux in a type I ELMy H mode plasma on EAST tokamak

Long

¹

,

Zhang²,

Ming³

et al. 2022

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The paper investigates the effect of pedestal turbulence, i.e. coherent mode (CM), on the divertor total particle flux, the particle flux distribution and heat flux distribution, and their decay lengths in the scrape-off layer (SOL) region on EAST tokamak. The experimental evidence indicates the coherence between the pedestal CM and the divertor particle flux fluctuation, which implies that the pedestal CM can affect the divertor plasma behavior. The increase of the particle flux decay length ( λ j s ) correlates with the density radial decay length (λ n,SOL) in the SOL region where the λ n,SOL is largely affected by the change of pedestal CM amplitude. A quantitative statistical analysis shows that the divertor total particle flux and λ j s in the SOL region increase with increasing amplitude of the electron density fluctuation and the electron temperature fluctuation induced by the pedestal CM. The temporal decay process of the total particle flux is interrupted by the appearance of CM at the pedestal. Meanwhile, the spatial distributions of the divertor particle flux and heat flux are enhanced when the pedestal CM appears, which are observed in both the upper single null and lower single null configurations.

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“…AEs in this work are excited by NBI in the presence of strong high-Z impurities. The main equilibrium profiles, such as safety factor, pressure and current, are reconstructed from kinetic-EFIT with magnetic/current constraints from Faraday angles measured by polarimeter-interferometer (POINT) diagnostics [48][49][50]. In addition, pressure is constrained from electron density (n e ) and electron temperature (T e ) is measured by Thomson scattering (TS) diagnostics [51].…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

Investigation of Alfvén eigenmodes and Energetic Particle Modes in EAST with neutral beam injection

Xu¹,

Shen²,

Ren³

et al. 2021

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Alfvén eigenmodes (AEs) and energetic particle modes (EPMs) have been observed in EAST neutral beam injection plasma with the presence of heavy tungsten impurity in the core region. The AEs are identified as toroidal Alfvén eigenmodes (TAEs) with roughly constant frequency f TAE ∼ 100 kHz and a special set of AEs with frequency chirping up from frequency f AE ∼ 70 kHz to f AE ∼ 100 kHz. The frequency of EPMs is around f EPM ∼ 60 kHz, exhibiting with frequency chirping down feature. A transition from EPMs to AEs is found, and the location and mode numbers are measured by experimental diagnostics. Hybrid simulations with the global kinetic-magnetohydrodynamic code M3D-K have been carried out to investigate the observed AEs and EPMs, and linear simulations find the EPM with toroidal mode number n = 2 and poloidal mode number m = 3. Nonlinear simulations show that the EPM frequency chirps down nonlinearly, and then two modes emerge with frequencies around 72.7 kHz and 88.0 kHz: the mode with higher frequency is a TAE, and the other mode is an EPM. Afterward, the TAE disappears quickly with the frequency almost unchanged, and the EPM with lower frequency chirps down continuously. The mode frequencies and locations of the simulated EPM and TAE, as well as the chirping down feature of the EPM frequency, are consistent with the experimental measurements. The transition from EPM to TAE is found to be a self-consistent dynamic of nonlinear evolution with the expel of energetic ions due to EPM.

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“…Moreover, the profiles of electron temperature (T e ) and plasma density (n e ) are measured by Thomson scattering (TS) [36] and reflectometer [37]. The line-averaged electron density (n e ) is measured by either the hydrogen cyanide (HCN) far-infrared interferometer [38] or the polarimeter interferometer [39]. The poloidal or toroidal views of these diagnostics are all shown in figure 1.…”

Section: Main Diagnostics and Divertor Gas-puff Systemmentioning

confidence: 99%

Divertor plasma behaviors with neon seeding at different locations on EAST with ITER-like divertor

Meng¹,

Wang²,

Wang³

et al. 2022

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For the problem of excessively high divertor heat flux, active impurity seeding is an effective method to radiate the plasma energy reaching the divertor and thus achieve the divertor detachment. Neon is a very effective radiation impurity on many current tokamaks, which is also a candidate species to be applied on ITER. In the EAST 2019 experimental campaign, a series of experiments were performed by seeding a mixture of neon and deuterium (Ne-D2) for detachment and core-edge-divertor integration in H-mode plasmas. The divertor partial detachment with high-confinement core plasma has been achieved by using Ne-D2 seeding in EAST with ITER-like tungsten divertor. Both the plasma stored energy and H_(98,y2)>1.1 are maintained, with the divertor electron temperature, heat flux and the surface temperature near the strike point being all significantly reduced. The differences between Ne-D2 seeding at the scrape-off layer (SOL) upstream and downstream have been experimentally investigated in detail. It is found that impurity seeding at SOL downstream is more beneficial to reducing the divertor electron temperature and peak heat flux. By comparison with experiments using divertor D2 fueling, it is further demonstrated that gas seeding in the SOL downstream will enrich more particles near the strike point, while the seeding in the SOL upstream will influence the entire outer target more evenly. Furthermore, in most of the experiments, gas seeding does not cause obvious toroidal asymmetry in the divertor plasma. However, when D2 is injected in an amount similar to that used to build the plasma, it causes the particle flux near the gas-puff to increase locally, i.e., much more than that at the toroidal location far from the gas-puff location. It is a competition between particle source and transport. When the particle source is stronger, it will naturally increase the local particles. In addition, dedicated experiments with different poloidal distances between impurity seeding and strike point on the radiation ability were carried out. Both experimental results and SOLPS simulation show that the seeding close to the strike point is more conducive to neon ionization and energy radiation.

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An ultrafast reciprocating probe

Cited by 7 publications

References 9 publications

Impact of coherent mode on divertor particle and heat flux in a type I ELMy H mode plasma on EAST tokamak

Impact of coherent mode on divertor particle and heat flux in a type I ELMy H mode plasma on EAST tokamak

Investigation of Alfvén eigenmodes and Energetic Particle Modes in EAST with neutral beam injection

Divertor plasma behaviors with neon seeding at different locations on EAST with ITER-like divertor

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