FIT Scan - What is a Fit Scan for and When do Instrument Scientists Use it?

[JackEAllen]

I noticed an Instrument scientists running a fit scan using a command similar to:
Fit scan command: x=g.cget(b.SMOFFSET)["value"];fit=scan(b.SMOFFSET, x-2, x+2, 15, frames=80,det=280, mon=2,pixel_range=0,fit=Erf)

Does anyone know what a Fit scan does and is able to describe what is going on exactly in the above command?
I would also like to know how this fits into an instrument scientist workflow if anyone knows?

[Tom-Willemsen]

scan comes from the scans library.

Fundamentally it is attempting to plot a graph of detector intensity against b.SMOFFSET, and then fit a particular model to this graph.

• It's scanning the value of b.SMOFFSET around it's current value (plus or minus 2), counting for 80 frames per measurement.
• The fit function being used is Erf, implying that the scientists are looking for some kind of "edge" in their data. Another common fit would be a Gaussian, where they want to find the position that will maximise their beam intensity at the detector. They would then use this to optimise the positions on their beamline.