Fast movable remotely controlled Langmuir probe system

Pedrosa, M. A.; López-Sánchez, Almudena; Hidalgo, C.; Montoro, A.; Gabriel, A. H.; Encabo, J.; Gama, J. de la; Martínez, Laura Marqués; Sánchez, E.; Perez, R. V.; Sierra, C.

doi:10.1063/1.1149350

Cited by 38 publications

(17 citation statements)

References 3 publications

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“…The data are taken with a reciprocating probe system sampling at 2 MHz, described in more detail in [13]. The probe head contains three probe sets, each set consisting of three pins (figure 1).…”

Section: Experimental Set-up and Methodsmentioning

confidence: 99%

Bicoherence during confinement transitions in the TJ-II stellarator

2008

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Bicoherence was computed for a number of discharges having confinement transitions, either induced by biasing or spontaneous, at the TJ-II stellarator. The bicoherence was computed for a variety of signals obtained using a reciprocating Langmuir probe system, but the main emphasis here is on the analysis of the poloidal electric field (E θ). During biasing, the auto-bicoherence of E θ was significant only in a narrow radial range, in contrast to the fluctuation level of E θ and the linear coherence between E θ and E r (the radial electric field), which were affected over a very broad radial extension. With spontaneous transitions, significant bicoherence was again detected only in a narrow radial range, associated with the position of the flow shear layer. The observations are consistent with the standard sheared flow model for confinement transitions. The temporal asymmetry A of E θ was also computed. During biasing, the region of strongly modified asymmetry was located inwards from the bicoherence maximum. This suggests that the detected bicoherence is not merely due to a change in the temporal shape of the signal.

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Section: Experimental Set-up and Methodsmentioning

confidence: 99%

Bicoherence during confinement transitions in the TJ-II stellarator

2008

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“…Experiments were carried out in the TJ-II stellarator (B T = 1 T, <R> = 1.5 m, <a> 0.22 m, ι(a)/2π ≈ 1.5 -1.9), in Electron Cyclotron Resonance (ECR) heated plasmas (P ECRH 400 kW) and in Neutral Beam Injection (NBI) heated plasmas (P NBI port through ≈ 450 kW, ECRH target plasmas) with Li-coated wall conditions [14]. A full set of plasma diagnostics has been used to characterize plasma parameters, including two sets of Langmuir probes installed on fast reciprocating drives working simultaneously (at approximately 1 m/s) [17].…”

Section: Experimental Set-upmentioning

confidence: 99%

Long‐Range Correlations During Plasma Transitions in the TJ‐II Stellarator

Pedrosa¹,

Hidalgo²,

Silva

et al. 2010

Contrib. Plasma Phys.

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The mechanism underlying the development of edge transport barriers is still one of the fundamental issues confronting the magnetic fusion community. The results presented show the importance of long-range correlation as approaching plasma bifurcations in different plasma scenarios, including biasing induced and spontaneous edge transport bifurcations in ECRH and NBI plasmas. These findings are consistent with the theory of zonal flows, pointing out the importance of both mean and fluctuating electric fields during the development of edge plasma transitions.

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“…The plasma density was modified in the range (0.35-1) × 10 19 m −3 . Different edge plasma parameters were characterized using a multi-Langmuir probe system, installed on a fast reciprocating drive (approximately 1 m s −1 ) that allows one to obtain radial profiles in a single shot [15].…”

Section: Experimental Set-upmentioning

confidence: 99%

Sheared flows and turbulence in fusion plasmas

Pedrosa¹,

Carreras²,

Hidalgo³

et al. 2007

Plasma Phys. Control. Fusion

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The universality of the observed characteristics of sheared flows points to a general ingredient to explain the damping/driving mechanisms responsible for the development of these flows in the plasma boundary region of fusion devices. Experiments in the TJ-II stellarator showing that the generation of spontaneous sheared flows at the plasma edge requires a minimum plasma density or density gradient, open a unique possibility to characterize the dynamics of sheared flow development in fusion plasmas. The effective viscosity at the plasma edge can be deduced by means of the decay rate of the perpendicular flow measurement once the driving force has been removed. Changes in the plasma rotation and turbulence have been studied when an electric field is externally applied at the plasma edge. The relaxation of flows and radial electric fields has been compared in the edge plasma region of TJ-II stellarator and CASTOR tokamak showing a striking similarity. The findings can help to test neoclassical and anomalous damping mechanisms in fusion plasmas. Finally, the emergence of the plasma edge sheared flow as a function of plasma density can be explained using a simple second-order phase transition model that reproduces many of the features of the TJ-II experimental data while capturing the qualitative features of the transition near the critical point.

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Fast movable remotely controlled Langmuir probe system

Cited by 38 publications

References 3 publications

Bicoherence during confinement transitions in the TJ-II stellarator

Bicoherence during confinement transitions in the TJ-II stellarator

Long‐Range Correlations During Plasma Transitions in the TJ‐II Stellarator

Sheared flows and turbulence in fusion plasmas

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