Global Mode Analysis of Ion-Temperature-Gradient Instabilities Using the Gyro-Fluid Model in Linear Devices

Abstract

In order to understand turbulent transport phenomena in magnetized plasmas, an excitation condition of the ion-temperature-gradient (ITG) instability is investigated in linear device PANTA. Numerical analyses using a global gyro-fluid code in linear devices are performed to obtain mode structures and parameter dependences of the ITG instability. Parameter scans of the linear growth rate show the destabilization condition of the ITG modes. The global analysis considers the boundary condition and determines the radial mode structure, which gives the values of the wavenumber in the direction perpendicular to the magnetic field. The local analysis confirms to reproduce the global analysis result by using the wavenumber obtained from the global analysis. The wavenumber is a parameter in the local model, and the global analysis of the radial mode structure is necessary for the selection of this important parameter.

Finite Larmor Radius Effect on Ion-Temperature-Gradient Instability in Cylindrical Plasmas

“…The other definitions of the parameters are described in Ref. [14]. The gyro-averaged potential Ψ is represented as Ψ ≡ Γ 0 1/2 φ with operators Γ 0 1/2 = (1 + bτ/2) −1 and b = −∇ 2 ⊥ .…”

“…2. The values of the perpendicular wavenumber, which is a parameter in local stability analyses, can be evaluated from the radial structure [14]. The mode includes several Bessel components.…”

“…For the first step, linear characteristic of the ITG instability has been investigated using the parameter set of PANTA linear device [13]. Here we have developed a global simulation code for the ITG instability in linear devices [14]. The parameter dependency is evaluated with a gyro-fluid model to identify influence of the FLR effect, and is compared with analytical expression obtained from a linear dispersion relation in this article.…”