Simulation Type Setup

The Simulation Type widget is used to specify several parameters for the type of simulation to be performed.

Parameters specified in this widget affect options and displays that are presented in later setup widgets.

For Plasma Specification, the user selects the method for specifying the plasma properties. Typically for SPECT3D simulations, Use Hydrocode Output is selected. In this case space- and time-dependent plasma conditions are read from a file. Alternatively, the user can specify that a Single Cell (i.e., single volume element) calculation be performed, in which case the user will enter the plasma parameters for the cell in the Plasma widget.

Note: the units of the simulated spectra are different for the Single Cell runs. SPECT3D computes fluxes; in the Single Cell case it displays flux on a visual detector with unit solid angle. The spectra can be interpreted as the plots of intensity, which is per sterad.

When the Use Hydrocode Output option is selected, the hydrocode file must be specified. SPECT3D is currently supported to read in the following types of hydrocode output:

• EXODUS/NetCDF-formatted files (e.g., from HELIOS, FLASH (after conversion), CTH, ALEGRA)
• PDB/SILO-formatted files (from HYDRA ; currently available on Linux and Windows 64 only)
• SDF-formatted files (from ODIN)
• HDF5-formatted files from the following hydro codes. (For additional file-specific information, see Plasma Properties Setup.)
  • DRACO (2D Cylindrical RZ geometry): when loading a DRACO file, all files in the same directory, with the same file extension, will be loaded as well, each representing its own time step (individual time steps can still be selected / de-selected in the Simulations Times tab).
  • LILAC (1D Spherical or 1D Planar geometries)
  • FLASH: FLASH output files may be loaded directly (i.e., without going through an Exodus converter), either as:
    • single time step, by selecting a single FLASH output file. The file extension filter will need to be changed to "All Files (*.*)" in order to see them in the browser.
    • multi time step, by selecting the .log file output from FLASH. This option will load all FLASH output files (time steps) from a single FLASH run, as long as they are found in the same directory as the .log file.

In addition, EXODUS-formatted files can be generated for use in SPECT3D by using the GridCONVERT application. This can be done for LSP PIC code output, as well as generating multi-timestep EXODUS files based on PlasmaGEN output.

Please contact support@prism-cs.com for information on converting other files to the NETCDF format.

Summary information contained in the Hydrocode file can be seen by selecting the menu item Display | Hydro File Info. Graphical displays of 1-D, 2-D, and 3-D plasma distributions contained in the Hydrocode file can be seen by selecting Display | Hydro Data.

For Collisional-Radiative Simulation Type, the user specifies how the atomic level populations are to be computed. Options are:

• Steady-State: Populations are computed under the assumption of steady-state. For multi-timestep calculations, populations are independent of those computed in previous time steps.
• Time-Dependent: Populations are computed by solving time-dependent atomic rate equations. Plasma conditions evolve in time, based on the contents of the Hydrocode file. A simulation time grid (a time grid which is independent of the times in the Hydrocode file) is set up in the Simulation Times widget.
  • NOTE: When performing time-dependent collisional-radiative simulations, it is expected that the mass in each volume element (and therefore DCA atomic elements) does not change with time . If changes in the either number of volume elements in the grid, or in the mass of any of the volume elements is detected, a warning message is displayed.

A two-temperature model can be used with separate variables for the electron and ion temperatures.

The fluid velocity, if present in the hydro file, can be used by checking the Utilize hydrocode fluid velocities check box.

LOS-Grid Intersection Model

• For 2D or 3D Cartesian grids there is a choice of the method used to load the grid when the intersections of the lines of sight with the plasma grid are calculated:
  • Evaluate for individual elements: The intersection of the line of sight with the grid is evaluated for each volume element individually.
  • Logically Rectangular Grid:
    • To use the new modeling, parameters specifying the number of volume elements in each dimension need to be provided in the hydro data file. (Contact Prism for information on required parameters.)
    • Supported grid geometries are (previously only 2D cylindrical r-z geometry was supported):
      • 2D Cartesian grids [with nodes at x(i,j), y(i,j)]
      • 2D Cylidrical grids [with nodes at r(i,j), z(i,j)]
      • 3D Cartesian grids [with nodes at x(i,j,k), y(i,j,k), z(i,j,k)]
      • 3D Cylidrical grids [with nodes at r(i,j,k), z(i,j,k), φ(i,j,k)]
      • 3D Spherical grids [with nodes at r(i,j,k), θ(i,j,k), φ(i,j,k)]
    • The modeling supports SPECT3D simulations with photoionization/photoexcitation processes.
  • Physcally Rectangular Grid:
    • To use the new modeling, parameters specifying the number of volume elements in each dimension need to be provided in the hydro data file. (Contact Prism for information on required parameters.)
    • Supported grid geometries are:
      • 2D Cartesian grids [with nodes at x(i), y(j)]
      • 2D Cylidrical grids [with nodes at r(i), z(j)]
      • 3D Cartesian grids [with nodes at x(i), y(j), z(k)]
      • 3D Cylidrical grids [with nodes at r(i), z(j), φ(k)]
      • 3D Spherical grids [with nodes at r(i), θ(j), φ(k)]
    • The modeling supports SPECT3D simulations with photoionization/photoexcitation processes.
• Both Logically Rectangular and Physically Rectangle Grid modeling can lead to a significant reduction in CPU time required and memory use in computing plasma grid-line of sight intersections.
  

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