Monte Carlo Framework (Deprecated in VSim 9)

The particle interactions available as part if the “Monte Carlo Interactions” framework are still available, but we recommend that users update their simulations to use the new Reactions Framework framework. The Monte Carlo interaction will be removed in VSim 10. For more information on the Monte Carlo framework, see Monte Carlo Interactions Introduction as well as the section VSim User Guide: Simulation Concepts: Collisions: Monte Carlo Interactions in the VSim User Guide.

The Monte Carlo framework collisions are available when particles in the Basic Settings element is set to include particles and the collision framework is set to monte carlo. This will add a “Reactions” element to appear with in the “Particle Dynamics” element.

When a collision process is added to a simulation, the user must specify each of the products and reactants from the drop down menus corresponding to each species in the chemical formula. Additionally, users must add a cross-sections to determine the reaction probability as to determine how many particles to react with in each cell in a timestep.

Particle Particle Collisions

These collisions are for interactions between kinetically modeled particle species (for a process involving a background gas use the “Particle Fluid Collisions”). The following interactions are available by right-clicking the “Particle Particle Collisions” element and hovering the mouse pointer over the “Add CollisionType” menu.

  • Charge Exchange A collision of the form \(A^+ + A \rightarrow A + A^+\). Reactants must be of the same species. This is the implementation of binaryChargeExchange in the visual setup.

    Note

    Caution should be exercised when using binaryChargeExchange reactions in the Monte Carlo framework with variable-weight species kinds; the results may be unreliable. Consider using the newer Reactions framework instead.

  • Recombination A collision of the form \(A^+ + e \rightarrow A + \gamma\). The energy released in the form of a photon is not tracked. This is the implementation of binaryRecombination in the visual setup.

  • Impact Ionization A collision of the form \(A + e \rightarrow A^+ + 2e\). The neutral reactant must be a kinetically modeled species. This is the implementation of binaryIonization in the visual setup.

  • Excitation Loss A collision of the form \(A + e \rightarrow A^* + e\). Where \(A^*\) is an excited state of the \(A\) species. The excited species cannot be tracked, by the user specified excitation threshold energy will be lost from the simulation. This is the implementation of binaryExcitation in the visual setup.

    excitation threshold

    The energy to excite the incoming particles species (in eV). This energy is lost from the simulation if the process occurs.

  • Elastic A collision of the form \(A + B \rightarrow A + B\). There is an option to add an energy loss when the reaction occurs. This is the implementation of binaryElastic in the visual setup.

    Note

    Caution should be exercised when using binaryElastic reactions in the Monte Carlo framework with variable-weight species kinds; the results may be unreliable. Consider using the newer Reactions framework instead.

    energy loss

    The energy (in eV) lost when the reaction occurs. This is also a threshold energy for the process to occur.

  • Impact Dissociation A collision of the form \(e + AB \rightarrow A + B + e\). There is an option to add a threshold energy. This is the implementation of binaryDissociation in the visual setup.

    threshold energy

    Dissociation threshold energy used to calculate the energy of the secondary electron.

Particle Fluid Collisions

These collisions are for interactions between kinetically modeled particle species and a background gas. The following interactions are available by right-clicking the “Particle Fluid Collisions” element and hovering the mouse pointer over the “Add CollisionType” menu.

  • Elastic A collision of the form \(A + B \rightarrow A + B\). This is the implementation of impactElastic in the visual setup.
  • Charge Exchange A collision of the form \(A^+ + A \rightarrow A + A^+\). The neutral reactant must be a fluid species and the same species as the incoming ion. This is the implementation of chargeExchange in the visual setup.
  • Impact Excitation This is the implementation of impactExcitation in the visual setup.
  • Impact Ionization This is the implementation of impactIonization in the visual setup.
  • Electron Attachment This is the implementation of electronAttachment in the visual setup.
  • Negative Ion Detachment This is the implementation of negativeIonDetachment in the visual setup.
  • Inelastic Scattering This is the implementation of nullBgAbsorber in the visual setup. Follow the link in the previous sentence for a description of the material mass, electron temperature fluid, radiation length, atomic ratio, multiple scattering model, and energy straggling`` parameters.

Three Body Reactions

These collisions are for interactions between kinetically modeled particle species (for a process involving a background gas use the “Particle Fluid Collisions”). The following interactions are available by right-clicking the “Particle Particle Collisions” element and hovering the mouse pointer over the “Add CollisionType” menu.

  • Three Body Recombination This is the implementation of threeBodyRecombination in the visual setup. Follow the link for a description of the thermal velocity neutrals, alpha, and tempExpFactor parameters.

Field Ionization Process

  • Particle Field Ionization This is the implementation of fieldIonization in the visual setup. Follow the link for a description of the DCADK and Average ADK cross section types.
  • Fluid Field Ionization This is the implementation of nullFieldIonization in the visual setup. Follow the link for a description of the DCADK and Average ADK cross section types.

Decay Process

  • Decay This is the implementation of oneBodyDecay/oneBodyVADecay in the visual setup

    lifetime

    The lifetime (in seconds) of the unstable species.

Cross-Sections

Interpolated from 2Column Data

Import cross sections from a data file with the independent variable (either velocity or energy) in the first column and the cross-section (dependent variable) in the second column.

cross section variable
The unit of the independent variable in the first column of the data file. Either velocity, or energy.
cross section data file
The name of the cross section data file. This file must be in the run directory.

function

This can be used to set a user defined function for the cross section.

cross section variable
The unit of the independent variable in the expression for the cross section. Either velocity, or energy.
expression
The expression for the cross-section. Can be set to a constant, parameter, or SpaceTimeFunction.

LXcatFile

Use cross sections with LXCat headers. The unique headers before each set of two-column cross section data sets allows. See https://fr.lxcat.net/data/set_type.php to obtain cross sections.

cross section data file
The name of the cross section data file. This file must be in the run directory.
cross section variable
The unit of the independent variable in the first column of the data file. Either velocity, or energy.
process
A string from the LXCat header that will determine which set of cross sections from with in the cross section data file to use for the interaction. Enter the text that follows the “PROCESS:” line in the header file.

Evaluated Electron Data Library (eedl)

This option is only available for some reactions. The eedl contains cross-sections for many processes involving electrons. An electron must be involved in the collision to use this set of cross-sections. The eedl.dat file (along with many others) is installed with VSim. On Windows, it is installed into C:\Program Files\Tech-X\VSim-10.0\Contents\engine\share\data. This data file must be copied into the run directory. The inputs from the user are matched with the headers in the eedl file to determine which cross-sections to use.

cross section data file
The name of the file containing the eedl headers and cross-sections. Must be copied into run directory.