 Background¶

pd cwl tof neut xray

A background describes the smooth intensity beneath the diffraction peaks.

Choose a background representation¶

The application supports line-segment backgrounds, represented by points, and polynomial or Chebyshev backgrounds, represented by terms. The Background group shows the values for the current experiment.

Changing the background type replaces its representation; review the confirmation before removing points or terms you want to keep.

Estimate the background¶

On Experiment, choose Estimate in the Background group. The estimate replaces the current points or terms. Undo brings the previous values back. Estimate needs measured data: until data are loaded into the experiment, the button is disabled and its tooltip says why.

The estimation mode controls what happens next:

• Manual keeps the current values for editing. Estimate runs when you ask for it.
• Auto estimates again when the measured data or estimation settings change. The table shows the estimated values; choose manual to edit them.

You can still free or fix a value through its context menu.

A practical sequence¶

1. Load the data and estimate the background while the model is still rough.
2. Fit the structure and profile, keeping the background fixed or freeing selected background values.
3. Inspect the residual and estimate again if the improved model makes the background clearer.