File sheath_boundary.hxx

Defines

SHEATH_BOUNDARY_H

struct SheathBoundary : public Component

#include <sheath_boundary.hxx>

Boundary condition at the wall in Y

This is a collective component, because it couples all charged species

These are based on “Boundary conditions for the multi-ion magnetized plasma-wall transition” by D.Tskhakaya, S.Kuhn. JNM 337-339 (2005), 405-409

Notes:

• The approximation used here is for ions having similar gyro-orbit sizes

• No boundary condition is applied to neutral species

• Boundary conditions are applied to field-aligned fields using to/fromFieldAligned

Public Functions

SheathBoundary(std::string name, Options &options, Solver*)

Input options

• <name> e.g. “sheath_boundary”

  • lower_y Boundary on lower y?

  • upper_y Boundary on upper y?

  • wall_potential Voltage of the wall [Volts]

  • floor_potential Apply floor to sheath potential?

  • secondary_electron_coef Effective secondary electron emission coefficient

  • sin_alpha Sine of the angle between magnetic field line and wall surface (0 to 1)

  • always_set_phi Always set phi field? Default is to only modify if already set

BoutReal ionSecondaryElectronEmissionGamma(BoutReal ion_energy) const

Ion-induced secondary electron emission yield γ(E_i)

Input energy ion_energy is in Hermes normalised units (same as used internally in src/sheath_boundary.cxx).

If ion-induced SEE is disabled (ion_ee_gamma_max < 0) then returns 0.

Private Functions

virtual void transform_impl(GuardedOptions &state) override

Inputs

• species

  • e

    • density

    • temperature

    • pressure Optional

    • velocity Optional

    • AA Optional

    • adiabatic Optional. Ratio of specific heats, default 5/3.

  • <ions> if charge is set (i.e. not neutrals)

    • charge

    • AA

    • density

    • temperature

    • pressure Optional

    • velocity Optional. Default 0

    • momentum Optional. Default mass * density * velocity

    • adiabatic Optional. Ratio of specific heats, default 5/3.

• fields

  • phi Optional. If not set, calculated at boundary (see note below)

Outputs

• species

  • e

    • density Sets boundary

    • temperature Sets boundary

    • pressure Sets boundary

    • velocity Sets boundary

    • energy_source

  • <ions>

    • density Sets boundary

    • temperature Sets boundary

    • pressure Sets boundary

    • velocity Sets boundary

    • momentum Sets boundary

    • energy_source

• fields

  • phi Sets boundary

If the field phi is set, then this is used in the boundary condition. If not set, phi at the boundary is calculated and stored in the state. Note that phi in the domain will not be set, so will be invalid data.

Private Members

BoutReal Ge

Field3D sin_alpha

bool lower_y

bool upper_y

bool always_set_phi

Set phi field?

Field3D wall_potential

Voltage at the wall. Normalised units.

bool floor_potential

Apply floor to sheath potential?

BoutReal ion_ee_gamma_max

Maximum ion induced secondary emission coefficient.

BoutReal ion_ee_E_th

Threshold energy [normalised].

BoutReal ion_ee_E_max

Peak energy [normalised].

BoutReal ion_ee_p

Shape coefficient.