As built locations in the Mu2e Hall

[kutschke]

On December 29, 2023 George Ginther sent the following email.

We decided that these changes are small enough that we do not need to implement any of them for the shielding assessment. Doing everything right may require significant change on how we specify the geomettry.

On the time scale of mid to late 2025 we need to evaluate what as-built specs need to be in the Mu2e Offline geometry description and then plan the work to get it done.

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Jeff Brandt is in the process of preparing to finalize the locations of the
transport solenoids to accommodate the as-built shapes of the TS cryostats.
The plan is to shift the TSu and TSd north as needed to aim at maintaining
the design Z axis of the DS positioned down the center of the detector hall in
the north-south direction. Now that the welding of the TS cryostats is
complete, a likely consequence is that the north-south location of the
interface between the TSu and TSd cryostats (the antiproton window) will be
shifted north by ~5 mm relative to the nominal location (as determined by the
floor pads) in the detector hall. The PS axis will shift north by ~10 mm.
Jeff proposes to attempt to maintain the east-west position of the line through
the downstream end of TSu and the upstream end of TSd (the COL3u and COL3d axis)
in the design location. So, in addition, to accommodate the shapes of the as-built
TS cryostats, this is likely to shift the PS west by ~5 mm, and the DS east by ~5 mm.
Please note that the estimates of the specific shifts are not final, but are
intended to provides insight into the anticipated scale of the shifts.

This plan to shift the locations of the TS and PS as necessary to maintain
the DS on the centerline of the detector hall has been around for many years,
but we are approaching implementation time. I highlight this topic because
I believe the offline Mu2e coordinate system origin is nominally tied to the
location of the interface between the TSu and the TSd, and this plan will shift
the as-built location of that interface relative to fixed features in the building.
I am curious as to whether this might have implications with respect to
implementations in simulation and/or analysis geometries.