NEO
Quick links
NEO [BC08, BC09, BC12] is a multi-species drift-kinetic solver was developed by the ESL project as a practical tool for high accuracy neoclassical calculations. NEO is an Eulerian code that solves the first-order (in the drift-ordering parameter \(\rho_*=\rho_i/a \ll 1\)) drift-kinetic-Poisson equations. In NEO, no approximations beyond the drift-ordering are made. The full linearized Fokker-Planck collision operator is used for the collision dynamics, with complete cross-species collisional coupling for arbitrary mass ratio and an arbitrary number of species. General flux-surface shape, including up-down asymmetry, is treated. In addition, full sonic rotation and centrifugal terms are retained. NEO has been extensively benchamarked with analytic theories, as well as with NCLASS, over a wide range of parameters and in various asymptotic limits.
The equations solved in NEO complement those solved in gyrokinetic codes such as GYRO and CGYRO insofar as together they represent the complete first-order deviation of the plasma from a local Maxwellian.
Data input
The primary NEO input file is input.neo. Profile data can be optionally captured from input.gacode.
NEO can also be run using a subroutine interface. In this case, inputs and outputs are contained in a monolithic module file named neo_interface. The interface parameter name is formed by prepending neo_ and appending _in to the name of the corresponding input.neo parameter.
use neo_interface
call neo_init
! Set neo_interface inputs (e.g. neo_n_species_in = 2 ...)
call neo_run
! Get neo_interface outputs (e.g. jbs = neo_jpar_dke_out ...)
Data output
A description of the NEO output files and output subroutine parameters is here.
Normalization
When run in local profile mode, the NEO normalizing length \(a\), normalizing mass \(m_{\rm norm}\), normalizing density \(n_{\rm norm}\), normalizing temperature \(T_{\rm norm}\), and normalizing velocity \({\rm v}_{\rm norm} = \sqrt{T_{\rm norm}/m_{\rm norm}}\) are arbitrary, since the input.neo parameters are set with respect to these and the output parameters are defined with respect to these. For experimental profiles, the normalizations are set as follows:
Quantity |
Unit |
Description |
|---|---|---|
Length |
\(a\) |
Minor radius |
Mass |
\(m_{\rm norm} = m_{\rm D}\) |
Mass of deuterium (3.3452e-27 kg) |
Density |
\(n_{\rm norm}(r)=n_{0,{\rm species 1}}\) |
Local density of species 1 |
Temperature |
\(T_{\rm norm}(r)=T_{0,{\rm species 1}}\) |
Local temperature of species 1 |