Time-Dependent Simulation Times Setup

When time-dependent atomic level populations are being computed, SPECT3D computes level populations using a simulation time grid that is separate from the times contained in the hydro output file. In this case, at each time step of the SPECT3D simulation, the hydro plasma parameters (temperature, density, ...) are obtained by interpolating between times contained in the hydro data file.

When setting up the time grid for a SPECT3D simulation in which time-dependent atomic level populations are computed, the hydro simulation times are shown on the left side of the Simulation Times setup widget, and are shown for information only.

Simulation times for the SPECT3D calculation are shown in the box at the right. To set up or edit the list of times, click the Setup button (see also Entering Table Data). SPECT3D computes the atomic level populations at each time step of the SPECT3D simulation time grid.

When setting up the time grid, it is recommended that a logarithmic spacing is used. This will put more time points at the beginning of a simulation where conditions are likely to be changing rapidly.

Images and spectra can be computed at each time in the SPECT3D time grid, or at a subset of these times. Check the box to the left of each simulation time for which imaging and spectral calculations are desired.

Several widgets to assist in setting multiple check boxes for the simulation times are at the lower right. Times can be selected or de-selected using any of the methods below:

• Click on the check box by the time.
• All times can be selected by clicking on the Select All button.
• A range of times can be selected by highlighting the range and clicking on the Select Range button.
• The last time can be selected by clicking on the Add Last Time button.
• Every Nth time within a highlighted range can be selected by entering a number in the N: edit box and clicking on the Select Every Nth Time button.
• All times can be de-selected by clicking on the Clear All button.

For a time-dependent calculation, the temperature and density distributions used in the SPECT3D calculation are obtained by interpolating between simulation times of the hydro output file. If the time between adjacent time steps in the SPECT3D simulation is too large, the calculation may fail to advance to the next time step. This may occur if plasma conditions are changing rapidly. If the calculation fails to advance, a warning message is written to the log file. If this occurs, it is recommended that the simulation is re-run using smaller time steps.

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