E-rhic-ir-l mailing list

[Bill Christie <christie AT bnl.gov>]

Dear All,
    Below please find the very brief minutes from today's impromptu ir 
Design mtg., as well as two questions it seems we need to address to 
make a baseline selection for the B0 Spectrometer Magnet design.
    Greetings,
        Bill

                                 eRHIC IR Design Meeting
                                   August 25, 2017.

* The meeting topic was a presentation which Holger had put together, 
giving the three options for the B0 Spectrometer magnet.
  - Septum Magnet
  - Halbach Magnet
  - Super Conducting compensating coil Magnet
  - Holger introduced each of the three options for the B0 magnet, and 
then presented the Pros and Cons for each design. He then ends with a 
Summary table that rates semi quantitatively, in Holger's opinion, the 
relative strengths and minuses of the three designs, and a final 
Conclusion slide.

* Given Holger's very nice summary of the options for the B0 
Spectrometer Magnet design, the next step is for the group to choose a 
baseline design for the IR. In addition to updates on matching the IR 
optics to the rest of the lattice, this seems to present two questions 
for us to address in our next one or two meetings, depending on who can 
attend which meeting.

First Question:
    The Septum Magnet design has strength in the majority of the issues 
rated. It also doesn't push technology frontiers, would take little 
further time to flesh out the design, and would have a modest cost. The 
one possible issue has to do with the size and thickness of the Septum 
magnet iron, and whether this shadowing of the downstream (exiting) 
region for the protons prevents needed acceptance for any part of the 
experimental program. This seems like a questions for Elke, Alexander, 
and Sasha.
    So, assuming they agree with this idea, we'd want to have this 
question on the agenda when they have had a chance to consider the 
question, and are ready to address it.

Second Question:
    The Halbach Design has one possibly big minus in that it can only 
work for one value of magnetic field strength. One could consider 
building separate Halbach magnets if deemed necessary to run at 
different field strengths, but this would have complications in 
exchanging the magnets. So, the idea for this question is that the 
Accelerator Physicists (e.g. Bob, Vadim, Christoph, Dejan, Gulliame, ..) 
address the question of whether everything works for the various eRHIC 
beam energies if the B0 magnet can only have one field strength.
    So, assuming they agree with this idea, we'd want to have this 
question on the agenda when they have had a chance to consider the 
question, and are ready to address it.

      Now that we've broken phase again with our every two week 
schedule for these meetings, I'll send out an e-mail early next week 
seeking input on when we should hold our next meeting.