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 electron beam in such a way that results in TAC FADC scaler rate of 10^5 Hz at very low thresholds.
- Position the V-wire into the beam using the cross-hair with the holding bar on the horizontal orientation.
- Get a stable electron beam at around 30nA (or adjust the current as needed) on the V-wire.
- Perform two horizontal scans or a 2D XY scans of the goniometer to verify the location and the angle of the V-wire and to find the X-position of the bisector for the V-wire.
- Position the X to the the determined values. Move the goniometer vertically to define the vertical range of motion within the V-wire holder by watching the halo scalers.
- Move goniometer high enough to reduce the halo counter rate while keeping the cross hair in the mounting bracket of the V-wire.
- Set TAC FADC threshold to the lowest value.
- Insert the TAC into the beamline making sure the TAC interlock does not get engaged. Set the collimator to 5mm aperture.
- Move goniometer high enough to reduce the TAC rate to nearly zero and then slowly lower the goniometer position to achieve 10^5Hz rate for TAC FADC scaler.
- Record the goniometer positions where the TAC FADC rate is 10^5Hz and put them into the EPICS GUI for goniometer targets.
- Move the V-wire position by +-0.5mm in horizontal and vertical around the newly found optimal positions to check the TAC rate sensitivity to the electron beam motion with respect to the wire using MYA archiver values.