Orbits

Example of how to generate guiding-center and particle orbits using SOFT.

Example of orbits computed using SOFT. The left figure shows guiding-center orbits, while the right figure shows particle orbits.

Important points

SOFT always calculates orbits, but to explicitly output the orbits calculated, the @Orbits module must be used.

One-file example

The following is a one-file example of a configuration file that will generate the guiding-center orbits in the figure at the top of this page:

# Simulate orbits in a circular tokamak
# magnetic field.
##############################

magnetic_field     = mf;
tools              = orbits;
include_drifts     = yes;

# Configuration of EAST-like magnetic equilibrium
@MagneticField mf (analytical) {
    B0     = 5;     # On-axis field strength (T)
    Rm     = 0.68;  # Major radius (m)
    rminor = 0.22;  # Minor radius (m)

    # Safety-factor
    qtype  = linear;
    qa1    = 2;
    qa2    = 1;
    sigmaB = ccw;
}

# Phase space grid
@ParticleGenerator PGen {
    a      = 0.1, 0.9, 9;  # Minor radius
    gamma  = 10, 10, 1;    # Energy (mc^2) (approx. 30 MeV)
    xi     = 0.3, 0.3, 1;  # Cosine of pitch angle

    position = guiding-center;
}

# Orbit generator
@ParticlePusher PPusher {
    nt       = 100;        # Number of timesteps per orbit (resolution parameter)
}

@Orbits orbits {
    output = "data/guiding-center.mat";
}

Configuration scripts

The following configuration scripts are available in the SOFT2 GitHub repository and will generate the two figures at the top of this page.

File	Description
baseline	Baseline configuration applied to all simulations.
gc	Simulate guiding-center orbits.
particle	Simulate particle orbits.