SchottkyEmissionBC

The electron flux boundary condition due to field ehanced thermionic emission (Schottky emission) (Based on Go (2012))

Overview

SchottkyEmissionBC is an outflow boundary condition that assumes the electron current density is defined by field ehanced thermionic emission, Schottky emission.

Using a Richardson equation for the field emission, the electron current density is defined as

Where is the electron current density, is the Richardson coefficient, is the temperature of the cathode, is Boltzmann constant in units of eV/K, is the local work function, is the difference in the work funtion due to the electric field, is the local field, is the normal vector of the boundary, is the field enhancement factor, and is the potential. is defined such that the outflow is only defined when the drift velocity is directed towards the wall and zero otherwise. With the electron current density, the outward electron flux is defined as

Where is the outflow normal to the boundary, is the mobility coefficient of the ions, indicates the advection behavior ( for positively charged species and for negatively charged species), is the ion density, is the diffusion coefficient of ions, is the elemental charge, and is the ion induced secondary electron emission coefficient. is defined as the fraction of particles reflected by the surface.

When converting the density to logarithmic form and applying a scaling factor of the mesh and voltage, the strong form is given by

Where is the molar density of the specie in logarithmic form, is Avogadro's number, is the scaling factor of the potential, and is the scaling factor of the mesh.

Example Input File Syntax

[BCs]
  [Emission_left]
    type = SchottkyEmissionBC
    #               type = SecondaryElectronBC
    variable = em
    boundary = 'left'
    potential = potential
    ions = Arp
    electron_energy = mean_en
    r = 1
    position_units = ${dom0Scale}
    tau = ${relaxTime}
    relax = true
    emission_coeffs = 0.02
  []
[]
(test/tests/1d_dc/NonlocalPotentialBCWithSchottky.i)

Input Parameters

  • boundaryThe list of boundary IDs from the mesh where this object applies

    C++ Type:std::vector<BoundaryName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The list of boundary IDs from the mesh where this object applies

  • electron_energyThe mean electron energy density in log form

    C++ Type:std::vector<VariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The mean electron energy density in log form

  • emission_coeffsA list of species-dependent secondary electron emission coefficients for each species in `ions`

    C++ Type:std::vector<std::string>

    Unit:(no unit assumed)

    Controllable:No

    Description:A list of species-dependent secondary electron emission coefficients for each species in `ions`

  • ionsA list of ion densities in log form

    C++ Type:std::vector<VariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:A list of ion densities in log form

  • position_unitsUnits of position.

    C++ Type:double

    Unit:(no unit assumed)

    Controllable:No

    Description:Units of position.

  • potentialThe electric potential

    C++ Type:std::vector<VariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The electric potential

  • potential_unitsThe potential units.

    C++ Type:std::string

    Unit:(no unit assumed)

    Controllable:No

    Description:The potential units.

  • rThe reflection coefficient

    C++ Type:double

    Unit:(no unit assumed)

    Controllable:No

    Description:The reflection coefficient

  • variableThe name of the variable that this residual object operates on

    C++ Type:NonlinearVariableName

    Unit:(no unit assumed)

    Controllable:No

    Description:The name of the variable that this residual object operates on

Required Parameters

  • displacementsThe displacements

    C++ Type:std::vector<VariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The displacements

  • prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

    C++ Type:MaterialPropertyName

    Unit:(no unit assumed)

    Controllable:No

    Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.

  • relaxFalseUse relaxation for emission.

    Default:False

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:Use relaxation for emission.

  • tau1e-09The time constant for ramping the boundary condition.

    Default:1e-09

    C++ Type:double

    Unit:(no unit assumed)

    Controllable:No

    Description:The time constant for ramping the boundary condition.

  • use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

    Default:False

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Optional Parameters

  • absolute_value_vector_tagsThe tags for the vectors this residual object should fill with the absolute value of the residual contribution

    C++ Type:std::vector<TagName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The tags for the vectors this residual object should fill with the absolute value of the residual contribution

  • extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

    C++ Type:std::vector<TagName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The extra tags for the matrices this Kernel should fill

  • extra_vector_tagsThe extra tags for the vectors this Kernel should fill

    C++ Type:std::vector<TagName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The extra tags for the vectors this Kernel should fill

  • matrix_tagssystemThe tag for the matrices this Kernel should fill

    Default:system

    C++ Type:MultiMooseEnum

    Unit:(no unit assumed)

    Options:nontime, system

    Controllable:No

    Description:The tag for the matrices this Kernel should fill

  • vector_tagsnontimeThe tag for the vectors this Kernel should fill

    Default:nontime

    C++ Type:MultiMooseEnum

    Unit:(no unit assumed)

    Options:nontime, time

    Controllable:No

    Description:The tag for the vectors this Kernel should fill

Tagging Parameters

  • control_tagsAdds user-defined labels for accessing object parameters via control logic.

    C++ Type:std::vector<std::string>

    Unit:(no unit assumed)

    Controllable:No

    Description:Adds user-defined labels for accessing object parameters via control logic.

  • diag_save_inThe name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

    C++ Type:std::vector<AuxVariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

  • enableTrueSet the enabled status of the MooseObject.

    Default:True

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:Yes

    Description:Set the enabled status of the MooseObject.

  • implicitTrueDetermines whether this object is calculated using an implicit or explicit form

    Default:True

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:Determines whether this object is calculated using an implicit or explicit form

  • save_inThe name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

    C++ Type:std::vector<AuxVariableName>

    Unit:(no unit assumed)

    Controllable:No

    Description:The name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

  • seed0The seed for the master random number generator

    Default:0

    C++ Type:unsigned int

    Unit:(no unit assumed)

    Controllable:No

    Description:The seed for the master random number generator

  • use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

    Default:False

    C++ Type:bool

    Unit:(no unit assumed)

    Controllable:No

    Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Advanced Parameters

Input Files

References

  1. David B Go. Theoretical analysis of ion-enhanced thermionic emission for low-temperature, non-equilibrium gas discharges. Journal of Physics D: Applied Physics, 46(3):035202, 2012. doi:10.1088/0022-3727/46/3/035202.[BibTeX]