Anomalous transport

NoAnom <: AnomalousTransportModel

No anomalous collision frequency included in simulation

Bohm(c) <: AnomalousTransportModel

Model where the anomalous collision frequency scales with the electron cyclotron frequency as νan = c * ωce.

Fields

• c::Float64: Nonnegative inverse Hall parameter.

TwoZoneBohm(c1, c2) <: AnomalousTransportModel

Model where the anomalous collision frequency has two values: c1 * ωce inside the channel and c2 * ωce outside it. The transition between these values is smoothed over params.transition_length.

Fields

• c1::Float64: Nonnegative inverse Hall parameter inside the channel.

• c2::Float64: Nonnegative inverse Hall parameter outside the channel.

ScaledGaussianBohm(anom_scale, barrier_scale, width, center) <: AnomalousTransportModel

Model in which the anomalous collision frequency is Bohm-like (νan ~ ω_ce), except in a Gaussian-shaped region defined centered on z = center, where the collision frequency is lower. Reparameterized version of the GaussianBohm model to make parameters non-dimensional and closer to O(1)

Fields

• anom_scale::Float64: The maximum inverse hall parameter. Must be positive.

• barrier_scale::Float64: The factor by which transport is reduced by the baseline value at the center of the trough, must be in [0,1].

• width::Float64: The standard deviation of the Gaussian trough, in channel lengths. Must be positive.

• center::Float64: The axial position of the mean of the Gaussian trough, in channel lengths. Must be positive.

GaussianBohm(hall_min, hall_max, center, width) <: AnomalousTransportModel

Model in which the anomalous collision frequency is Bohm-like (νan ~ ωce), with a Gaussian trough centered at center. The inverse Hall parameter is hall_max far from the trough and hall_min * hall_max at its center.

Fields

• hall_min::Float64: Fraction of hall_max retained at the trough center; must be in [0, 1].

• hall_max::Float64: Inverse Hall parameter far from the trough; must be positive.

• center::Float64: Finite axial position of the center of the Gaussian trough, in meters.

• width::Float64: Positive standard deviation of the Gaussian trough, in meters.

MultiLogBohm(zs, cs) <: AnomalousTransportModel

Model similar to that employed in Hall2De, where the anomalous collision frequency is Bohm-like (i.e. νan(z) = c(z) * ωce(z)) and z is in meters.

The function c(z) is defined by a sequence of nodes (z, c) provided by the user. At z = z[1], c(z) = c[1], and so forth.

At z[i] < z < z[i+1], log(c) is defined by linearly interpolating between log(c[i]) and log(c[i+1]).

For z < z[1], c = c[1] and for z > z[end], c(z) = c[end].

The zs values must be finite and strictly increasing. The cs values must be finite and positive because their logarithms are interpolated. Both arrays must be nonempty and have the same length.

Fields

• zs::Vector{Float64}: Finite, strictly increasing axial node positions in meters.

• cs::Vector{Float64}: Positive inverse Hall parameters at the axial nodes.

SimpleLogisticShift(model, shift_length, midpoint_pressure, slope)

A wrapper model that allows a transport profile to shift axially in response to changes in background pressure. As with LogisticPressureShift, the displacement/shift of the transport profile follows a logistic curve. However, the parameterization is different, so that the shift is zero when the background pressure is zero. As such, it does not have a z0 parameter.

Fields

• model::HallThruster.AnomalousTransportModel: An AnomalousTransportModel

• shift_length::Float64: Scale of the upstream displacement in response to increasing pressure, relative to the discharge channel length. The asymptotic displacement magnitude is shift_length / (1 + exp(-slope)). Must be positive.

• midpoint_pressure::Float64: The pressure at the midpoint of the shift, in Torr. Defaults to 25e-6 Torr, which gives good fits for the H9 and SPT-100.

• slope::Float64: The slope of the pressure response curve. Defaults to 2, which gives good fits for the H9 and SPT-100.

LogisticPressureShift(model, z0, dz, pstar, alpha)

A wrapper model that allows a transport profile to shift axially in response to changes in background pressure. The displacement/shift of the transport profile follows a logistic curve.

Fields

• model::HallThruster.AnomalousTransportModel: An anomalous transport model

• z0::Float64: Dimensionless shift offset, scaled by the channel length. Must be finite.

• dz::Float64: The shift amplitude, scaled by the channel length. Must be finite.

• pstar::Float64: The positive pressure scale in Torr.

• alpha::Float64: Shape parameter for the pressure-displacement response curve; must be greater than 1.

num_anom_variables(::AnomalousTransportModel)::Int

The number of variable arrays that should be allocated for the provided anomalous transport model. These arrays are used to save state beyond the anomalous collision frequency, and are useful for defining more complex anomalous transport models. If not defined by the user, this defaults to zero.