What is LRDFIT?
LRDFIT is an LR (inductanceresistance) 2D axisymmetric circuit model of a tokamak which can be constrained to fit various combinations of diagnostic data.
In short: LRDFIT = LR circuit model with Data FITting capabilities
LRDFIT is most commonly used for equilibrium reconstructions, but can also be used to predict timedependent vacuum field evolution.
(1) Equilibrium Reconstructions  in this mode, the LRDFIT is run in 2 steps:
Step 1  SVD fit to magnetics data to determine all toroidal currents in system

All toroidal currents in the system are determined consistent with the LR circuit model and a "bestfit" to the timedependent magnetics data.

The toroidal plasma current density is treated as unknown, and is allowed to flow anywhere inside the limiter boundary.

Regularization (smoothing) of the plasma current density is utilized to produce an overconstrained system of equations.

The GradShafranov equilibrium force balance constraint is NOT enforced at this stage.

The solution of this step provides a good estimate of all toroidal currents in passive conducting structures (vessel, passive plates, etc.)

These passive structure currents are commonly treated at "known" in subsequent GradShafranov constrained equilibrium fits

Treating these currents as known: (a) produces similar results to fully timedependent equilibrium fits, and (b) enables parallelization of the equilibrium fits


The solution of this step also provides an initial poloidal flux distribution for the GradShafranov constrained equilibrium fits
Step 2  GradShafranov equilibrium (GSE) fit to the magnetics and other data

The passive conductor currents are treated as known and the coil currents are fit

The magnetics data, MSE data, electron temperature isosurfaces, etc. are used as constraints on the equilibrium fit

Basis functions for the p' and FF' profiles are specified, and the "bestfit" weighting of the basis functions is determined

The results for individual timeslices are written to files

The code can be run interactively, or in parallel/batch mode

In batch mode, after multiple timeslices have been computed, time dependent quantities are computed, and the results are archived in MDS+