Spectral and Image Resolution

Spectral, spatial, and temporal instrumental resolution effects can be applied to various spectral and imaging results to facilitate comparisons with experimental data.

The resolution settings are set using the Instrumental Effects dialog. On most widgets displaying spectral or imaging results, the Instrumental Effects dialog can be displayed by clicking on the Edit button found in the Resolution Parameters panel.

Parameters with can be set include:

• Spectral Resolution: The spectrum is convolved with a Gaussian with a full width at half maximum which is defined using one of the following:
  • Constant resolution power (E/ΔE or λ/Δλ)
  • Constant wavelength resolution (Δλ)
  • Constant photon energy resolution (ΔE)
    When applying either a constant wavelength resolution or a constant photon energy resolution, the units must also be specified.
• Spatial Resolution (in cm): The image is convolved in both the x and y directions with a Gaussian with a full width at half maximum equal to the spatial resolution.
• Time Resolution (in seconds): Streaked spectrum is convolved with a Gaussian with a full width at half maximum equal to the time resolution.
• Time Integration: The images or spectra are integrated in time using the following options (all time units are in seconds):
  • First gate time is the time at the center of the first gate.
  • The time between gates is the time between the centers of the gates.
  • The gate profile is chosen from the combo box. At present, the choices are square or Gaussian.
  • The width of the gate is either the full width of a square gate or the full width at half maximum of a Gaussian gate.
  • Care should be taken to keep time gate spans within the set of simulation times. If a time gate happens to extend beyond simulation times, spectral contribution from the final time will extend one more half-time-step beyond (imagine bins where each simulation time is at the bin center). If the first simulation time is greater than zero, similar additional spectral contribution will be made (if the gate extends below that first time), though it will be cut off below zero time (thus this extra contribution, below the first time, will not exist if the initial time is zero).
• Noise parameters. Random noise, based on Poisson statistics, will be added to the spectra shown on the Time Resolved Spectra display.
  • The signal to noise ratio is specified at a particular intensity.
  • The background noise can be separately specified and can vary with photon energy.

Clicking on the Apply button will cause the parameters to be applied to all open windows.

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