Both a UVA coarse alignment check and an FNAL Dock Survey (with target insert) have previously been performed. The in-cave survey is likely not valid anymore due to the disassembly and reassembly of the magnet. A quality beam pipe alignment on the target end was never performed outside of what was done by the target group.
Coarse alignment has been previously achieved. This procedure was accomplished with the nose and nitrogen shield off so that it's possible to configure the location of the target in the central beam location. Hand-held lasers were used to check the horizontal alignment which demonstrated that the insert horizontal position is good to within 1 mm level. The approximate location (1 mm >) vertically was also checked but this is without the actuator to pinpoint this position with the required reproducibility. After this very coarse and basic target team survey the target insert was given to the FNAL alignment group. This insert was scanned and fiducials on the cups were temporarily installed and coupled to fiducials on the top of the insert. These fiducials were then tied into the fiducial network during the initial target-magnet cryostat. This scan is probably not that helpful since the target stick ladder is quite flexible and will not be in the same location once inserted and sitting in LHe.
This alignment information will change when the target insert is fully cold, but only on a scale of ~0.3 mm. The twist and rotation from contraction is a concern and it would be good to follow up with a beam scanning procedure based on rates to understand beam target positioning better.
Cross-hair and pencil targets that can be loaded into the existing inserts for tests of target-beam alignment. Cross-hair targets can be made out of a standard target cell with CuNi wire or bands running vertically and horizontally. We have fine control of the y-direction with the target actuator. We can also make a pencil target machined SS or lead of the length of the target cell (8 cm) with a circular profile coming to a point dead center of the target cell to help determine this location with scalars.
It is not anticipated to be needed but an x-alignment device can be made as well. If a tool is necessary for central course alignment in x we can make a cylindrical insert of around 0.7" wide with a solid wire (of various thicknesses) running vertically. Rotation of the insert would change the position of the vertical wire. Such a thing can be made to rotate a fraction of a degree with a stepper motor if needed.
Previous Survey Information:
The following image shows the cross-hair cell. The cell structure is made out of PCTFE and the middle plates are from CuNi as described above.
The following image shows the Pencil beam cell. The CuNi pencil rod is mounted by two PCTFE structures to keep the rod in the center of the cup.
