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Building Langmuir Probes and Emissive Probes for Plasma Potential Measurements in Low Pressure, Low Temperature Plasmas
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Zero-turbulence manifold in a toroidal plasma.

E G Highcock1, A A Schekochihin, S C Cowley

  • 1Magdalen College, Oxford OX1 4AU, United Kingdom. edmund.highcock@physics.ox.ac.uk

Physical Review Letters
|February 2, 2013
PubMed
Summary
This summary is machine-generated.

Reducing the magnetic field pitch to inverse aspect ratio (q/ϵ) in tokamak plasmas is key to achieving higher temperature gradients. This control parameter helps prevent turbulence, enabling states with zero turbulent transport, similar to experimental transport barriers.

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Area of Science:

  • Plasma Physics
  • Fusion Energy
  • Turbulence Dynamics

Background:

  • Sheared toroidal flows in tokamak plasmas can lead to bifurcations into states with zero turbulent transport.
  • Subcritical turbulence, driven by the parallel velocity gradient, limits the maximum achievable temperature gradients.

Purpose of the Study:

  • To investigate the role of the magnetic field pitch to inverse aspect ratio (q/ϵ) as a critical control parameter for sheared tokamak turbulence.
  • To determine if reducing q/ϵ allows for higher temperature gradients without inducing turbulence.

Main Methods:

  • Mapping the zero-turbulence manifold in the zero-magnetic-shear limit.
  • Analyzing the parameter space including perpendicular flow shear (γ(E)), q/ϵ, and normalized inverse temperature gradient scale (R/L(T)).

Main Results:

  • Demonstrated that q/ϵ is a critical control parameter for sheared tokamak turbulence.
  • Showed that reducing q/ϵ enables significantly higher temperature gradients without triggering turbulence.
  • Observed temperature gradients comparable to those in experimental transport barriers.

Conclusions:

  • The parameter q/ϵ is crucial for controlling turbulence and achieving high-gradient states in tokamaks.
  • Reducing q/ϵ offers a pathway to access improved confinement regimes, potentially relevant for fusion energy.
  • The study maps the accessible parameter space for zero-turbulence states and discusses the role of linear theory.