CUTIE

CUTIE is a quasi-neutral two-fluid computer model for turbulence in a toroidal plasma. The large aspect ratio tokamak ordering is used (R/a >> 1), and B_p << B_tor, β << 1. The plasma modelled consists of electrons and a single ion species. Quasi-neutrality (n_e ≈ n_i) is assumed. The species are locally Maxwellian, but T_e ≠ T_i . Particle and energy sources, and a radial profile of Z_eff are imposed. Conservation equations for particles, energy, and momentum are solved to obtain the electron density (n), electron and ion temperatures (T_e, T_i), the ion fluid velocty (v), the electrostatic potential (Φ) and the parallel vector potential (Ψ). The poloidal magnetic field (and consequently the safety factor, q) evolves in time.

The code solves the evolution on the meso-scale level (larger than the ion gyroradius), co-evolving the flux surface averaged quantities and the turbulence in a self-consistent manner; profile gradients interact non-linearly with the turbulence. Thus, the code is capable of modelling the following fluid-like modes: linear and non-linear shear Alfvén waves, slow magneto-acoustic modes, drift-tearing modes, ballooning modes (ideal and viscoresistive), and the fluid branch of the ion temperature gradient (ITG) instability. The code contains sufficient mechanisms for the generation of sheared flow by turbulence and produces a spontaneous confinement transition similar to the L-H transition in experimental devices.

Current installations

The code is being used at:

• Culham Centre for Fusion Energy, Culham, UK (code origin)
• Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain