Raster and Bull's Eye Scan Procedure
This
is required for beam position calibration. Once the beam position is
established by doing raster scan on a carbon-hole target by observing
the hole at the center of the raster pattern, do this Bull's eye scan.
- General info, applies to both raster and bull's eye scans:
- Target: carbon hole target <- Do this first!
- Beam current: <5 uA. Beam raster:
ON. [Raster ON is required to see the hole, no raster, no hole. To see
a better hole, use a clock trigger (T8), prescale away all physics
triggers.]
- Take
both HRS CODA runs. Establish the center of the target by doing raster
scan and seeing the hole and centering it.
- Raster scan procedure:
- start from raster size 2x2mm2.
- Run spot++ and try to find the hole.
- if cannot see the hole, increase raster size by 1mm in each direction, goto step 2.
- if raster size has reached the maximum (perhaps 6x6mm2) and you still cannot see the hole, call RC.
- if
at a particular raster size you can see the hole, check if it is at the
center of the raster pattern. If not, ask the MCC to change the beam
position at both BPMA and BPMB (the 2 BPMs must have the same changes
to ensure a straight beam) and repeat, until the hole is seen at the
center of the raster pattern. Write down the beam position. This will be the one to use for all productions runs.
- Bull's eye scan procedure:
- One run at the nominal beam center as established above.
- One run at (x,y) of both BPM A and B at
(+3.0, +3.0). (if it takes more than 5-10 minutes for MCC to set it up,
settle with (+2.5, +2.5) or lower values)
- One run at (x,y) of both BPM A and B at (+3.0, -3.0).
- One run at (x,y) of both BPM A and B at (-3.0, -3.0).
- One run at (x,y) of both BPM A and B at (-3.0, +3.0).
- Make a halog entry saying wich runs correspond to which conditions.
- End of Bull's eye scan