I05 Alignment protocol - drain current from the photodiode vs m1 pitch and m3mj6 pitch

The aim of the section is to make a composite motor based on m1_pitch, but including movement of slave variables (m3mj6_x, m3mj6_pitch) with a view to keeping the beam centred horizontally on the exit slit as a function while m1_pitch is changed.

At this point in the alignment, we already have nice parameters for the dependence of m3mj6_x, but we want to establish the dependence of m3mj6_pitch vs m1es_pitch.

The GDA scan command would be something like:

scan m1es_pitch -200 1600 75 m3mj6_pitch 4750 5350 8 waittime 0.1 dj7current_new

which results in data like this:

We then fit the peak at each value of m1es_pitch, and from the peak positions we fit a third order polynomial. With m1es_pitch then well established, we subsequently do the focusing scan using the gas cell.

This scan actually takes over an hour, because the step motion of the hexapod (m3mj6_pitch) is slow. In principle we could try to do it in a "fly" mode with bluesky, which could be a significant speed up.

On the HR branch we do something very similar, only with d7current rather than dj7current.