E-rhic-ir-l mailing list

[Bill Christie <christie AT bnl.gov>]

    Minutes from eRHIC IR Design mtg held on September 8, 2017.
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* The meeting started with a discussion of Holger's presentation from 
the previous meeting. We walked through the slides, with some questions.
    - Question about which directions the protons bend in the figures, 
Answer, "Always away from the Electron beam".
    - We discussed the question, from the perspective of the Physics 
program, which design for the B0 magnet would work.
        - Experimental program would be OK with either the Septum or 
Holbach designs. However, given the flexibility that one gets with the 
Septum design (ability to vary the B0 field strength) the preference is 
the Septum design for B0.
        - There was a discussion about the acceptance necessary for the 
eRHIC experimental program. Elke showed a few plots illustrating that 
the vast majority of the particles of interest were within an acceptance 
of about 4 mr or so. The 20 mr acceptance of the current Baseline design 
was thus felt to be more than sufficient for the physics program. Also 
discussion that we shouldn't over design the acceptance.
    - The question came up whether achieving the necessary precision in 
the positioning of the conducting coils for the Septum design would 
present a technical problem. Holger did not see this as an issue, but 
indicated that he'd look into it.
      - After discussion, the Septum design is adopted as baseline 
design for B0.

* The next question that we had in the queue for discussion (before the 
Septum adoption above) was to the Accelerator Physicists, it was "Could 
the entire eRHIC physics program be run with a single, fixed magnetic 
field strength for the B0 magnet?" Given the decision to go with the 
variable field Septum design for B0, this question became less topical, 
and it was not discussed.

* We then moved on to a discussion of some slides that Bob had put together.
    - Bob showed that, by rotating the beams in the IR design by 7 mr 
(essentially by rotating the entire IR region as a rigid body) one ends 
up with something that is easier to match to the eRHIC lattice, and it 
allows one to reduce the needed field strengths for some of the IR 
region magnets. Both positive effects.
    - Steve Tepikian indicated that a 7 mr rotation of the IR region 
may present challenges, but that a rotation by something on the order of 
3 mr may be possible. It would take some time and effort to investigate. 
Consensus that even the 3 mr rotation would make the matching between 
the IR and lattice easier, and allow some of the IR magnet field 
strength requirements to be relaxed, but to a lesses degree that the 7 
mr. Christoph brought up the point that having Steven investigate this 
modification (3 mr rotation) would be a diversion from the current 
baseline lattice effort and timeline. How far to pursue this was going 
to be discussed by Christoph and others outside this meeting.
    - Next iteration is for Bob to look into a design with the 3 mr 
rotation.
    - Decided that this discussion was our update on the status of the 
effort t match the IR to te rest of the eRHIC lattice.

* Agenda for the next meeting:
    - Decided to keep every two week schedule for future meetings, 
rather han try to pick dates when all could attend.
    - Update on 3 mr rotation and matching to lattice.
    - Holger on Septum B0 precision question.

            End of meeting.