Materials

Materials in charging simulations are a critical part of the simulation initialization process. Materials are key features that affect the potential, fields, charge and currents in charging simulations. EMA3D® materials used for arcing in air are described in the EMA3D section of this manual. The capabilities and features associated to materials applicable to surface and internal charging simulation are introduced in this section of the manual.

Charging Materials

To accommodate the various solvers and workflows, there are three types of charging material available in EMA3D Charge:

Isotropic (EMA3D) – for the FDTD and arcing in air,
Surface charging (CHARGE) – for the surface charge balance equations and the charging of surfaces from plasmas, friction electrification, precipitation static, etc…, and
Internal charging (CHARGE) – for the FEM and the charging of bulk material by high-energy particles, analytical sources, boundary conditions, etc….

Depending on the charging environment, some or all of the material properties will contribute to the calculations.

Assigning a surface or internal charging to a geometry will automatically define if the mesh will be a surface or a volumetric mesh, respectively. All three materials draw from the same set of material properties described in the table below.

List of Material Properties and Their Respective Workflow

Property	Description	Type
Relative permittivity	Material dielectric constant used for quasi-static and full-wave solutions	Isotropic, Surface, Internal
Relative permeability	Material relative permeability used for the full-wave solutions	Isotropic, Internal
Bulk conductivity (S/m)	Material electric conductivity, value of -1 can be used for perfect conductors and numerical stability	Isotropic, Surface, Internal
Atomic mass (amu)	Average atomic mass of material in amu	Internal
Atomic number		Surface, Internal
Photoemission (A/sq. m)	Release of electrons from a material when exposed to EM radiation	Surface
Surface resistivity (Ohm/square)	Material current resistivity at the surface, value of -1 can be used for perfect conductors	Surface
Density (kg/cu. m)	Material volumetric density	Surface, Internal
RIC	Radiation induced conductivity	Surface
Thickness (mm)	Material thickness for material used	Surface
Delta max	Maximum SEY for electron impact at normal incidence	Surface, Internal
E-max (keV)	Primary electron energy to produce maximum yield at normal incidence	Surface
Range 1	R₁E^e₁ + R₂E^e₂	Surface
Exponent 1	R₁E ^e₁* + R₂*E^e₂	Surface
Range 2	R₁E^e₁ + R₂E^e₂	Surface
Exponent 2	R₁E^e₁ + R₂E ^e₂	Surface
Proton yield	Secondary electron yield for normal incident 1keV protons	Surface
Proton max (keV)	Proton energy to produce maximum secondary electron yield	Surface
Breakdown threshold (V/m)	Electric field threshold at which dielectric breakdown is initiated, also activates breakdown simulation	Internal
Affects particle transport	Decision to use the material properties as part of the particle transport, else it assumes vacuum	Internal
Permittivity (F/m)	Absolute permittivity	Isotropic
Permeability (H/m)	Absolute permeability	Isotropic
Magnetic conductivity	Material magnetic conductivity	Isotropic

The secondary electron yield (SEY) parameters are parametrized with a Bi-Exponent Range Law, or Fully Reduced Extended Power law, as described in the technical section of the manual.

Material Library

The material library of EMA3D Charge consists of materials with properties that were sourced from published documents. Coming Soon: exclusive material properties will be obtained from EMA SERE test facility, which has a dedicated plasma environment chamber (https://www.ema3d.com/sere/).

The current materials, their description, and the source of the properties are listed in the table below.

List of Materials and the Source of their Properties

Name	Description	Source
GOLD	Gold plate	NASA CR-165348; NIST STAR (density); doi:10.1515/pac-2015-0305 (atomic weight)
SOLAR	Coated fused silica	NASA CR-165348; http://mpg.physics.usu.edu/range/ (density, atomic weight); https://accuratus.com/fused.html (breakdown)
WHITEN	Non-conductive white paint	NASA CR-165348
SCREEN	Fictitious conductive screen which absorbs but does not emit charged particles	NASA CR-165348
BLACKC	Conductive black or yellow paint	NASA CR-165348
GOLDPD	88% gold and 12% conductive paint in polka dot pattern	NASA CR-165348
YGOLDDC	50% gold and 50% conductive paint	NASA CR-165348
POLYIMIDE	Polyimide film, 1-mil	NASA CR-165348; NIST STAR (density, atomic weight); doi:10.1109/tdei.2010.5411997 (breakdown)
ASTROQ	Si02 fabric	NASA CR-165348; https://www.azom.com/properties.aspx?ArticleID=764 (breakdown); https://www.sciencedirect.com/topics/engineering/glass-fibre (density)
PTFE	a synthetic fluoropolymer of tetrafluoroethylene	NASA CR-165348; ISBN 9780367417246 (breakdown); http://mpg.physics.usu.edu/range/ (atomic weight); NIST STAR (density)
INDOX	Indium oxide	NASA CR-165348; https://www.americanelements.com/indium-iii-oxide-1312-43-2 (density)
ALUMIN	Aluminum plate	NASA CR-165348; doi:10.1515/pac-2015-0305 (atomic weight); NIST STAR (density)
BOOMAT	Platinum banded polyimide film	NASA CR-165348
VACUUM	Vacuum properties

If you have access to material properties that are published and that you would like to see them as part of the EMA3D Charge library, please reach out to your software provider.

This material list is defined in ChargingMaterials.xml as part of the installation directory of EMA3D Charge. Users can edit this file, following the template of already defined materials, and the newly added materials will be automatically loaded in the GUI.