TAC V-wire commissioning

The purpose of the commissioning of the V-wire is to identify the position of the goniometer that exposes the V-wire to the beam in a way that produces TAC FADC scaler rate of 10^5 Hz at very low thresholds.

1. Position the V-wire into the beam using the cross-hair with the holding bar on the horizontal orientation.
2. Get a stable electron beam at around 30nA on the V-wire.
3. Perform two horizontal scans using halo counters from MYA as detectors at two different Y-position of the goniometer to verify the angle of the V-wire and to find the X-position of the bisector for the V-wire.
4. Move the goniometer vertically to define the vertical range of motion within the V-wire holder.
5. Move goniometer low enough to reduce the halo counter rate while keeping the cross hair in the mounting bracket of the V-wire.
6. Set TAC FADC threshold to the lowest value.
7. Insert the TAC into the beamline making sure the TAC interlock does not get engaged. Set the collimator to 5mm.
8. Move goniometer low enough to reduce the TAC rate to nearly zero and then slowly raise the goniometer position to achieve 10^5Hz rate for TAC FADC scaler.
9. Record the position where the rate is 10^5Hz and put into the EPICS GUI for goniometer targets.
10. Move the V-wire position by +-0.5mm in horizontal and vertical around the determined optimal position to check the TAC rate sensitivity to the electron beam motion with respect to the wire using MYA archiver values.