E-rhic-ir-l mailing list

[Bill Christie <christie AT bnl.gov>]

Dear All,
    Below please find the minutes from our eRHIC IR Design meeting that 
was held on Friday, 8/24/2018. Please note that our next meeting will be 
on Friday September 7th. There was discussion at this meeting about 
moving the start time forward from 3 pm to 2:30 pm. The rational was 
that there is another eRHIC meeting, in the same room, that ends at 2:30 
pm. For people involved in both meetings, start the IR Design meeting at 
2:30 pm would mean that these people don't have to wait the extra 30 
minutes. This idea sounded OK with all parties at the meeting, but I 
will poll people on the mailing list to see if there are any objections.
    I'll be away from the lab for the next meeting date (Sept. 7th), so 
Elke has kindly agreed to run the meeting.
    Greetings,
        Bill

  Minutes from the eRHIC IR Design meeting held on 8/24/18
 
---------------------------------------------------------------------------------
* We started with a brief discussion of the agenda for the meeting.
   - A discussion was held about moving the start time from 3 pm to 
2:30 pm (logic above).

* Elke gave a brief update on the status of the impedance studies. 
Alexander, Charles, and Elke tried to get together for a meeting, but 
were unsuccessful. They plan to meet on this in early September.

* Elke gave a presentation concerning ideas being discussed about 
placing collider magnets within the volume of the particle detector. 
Link: 
https://www.dropbox.com/s/ke2mmup4kwvqpg4/eRHIC.magnetsinDetector.pptx?dl=0
   - Slide #1: Physics requirements. No changes.
   - Slide #3: Figure of optimized DIS detector.
    - Point was made in discusssion that, whereas the stay clear region 
alone the beam line is 9 m, it is not necessarily required that it be +- 
4.5 m from the center of the interaction diamond.
   - Slide #4: Sctered system kinematics
   - Slide #5: Simulation in GEANT. Low Q**2 tracker.
   - Slide #7: Simple geometric arguments.
      - Christoph asks about the radius of the HERA low beta quad. No 
one recalled, so will need to look up.
   - Slide #8: Impact of internal magnets on Q**2 acceptance
     - Shows why the idea of placing magnets inside the detector region 
is worse at RHIC than at JLAB.
   - Slide #9: Impacts beyond Physics
     - Integration issues for vertex detectors
   - Slide #10: Impacts beyond Physics
      - Backgrounds
   - Slide #11: eRHICs reach in x and Q**2
   - Slide #12: Studying non-linear effects
      - Severe Impacts on saturation studies
   - Slide #13: Shows acceptance at low x in nuclei
      - cut at Q**2 = 2 GeV**2 cuts out the saturation program.
   - Couple additional Physics impact slides shown.
   - Summary:
     - Severe negative impacts if one puts collider magnets into the 
detector region.
     - Acceptance
     - Backgrounds
     - Same issues that caused problems at HERA
  -> Elke advises against putting collider magnets into the detector 
volume.
    - Christoph makes the point that if we restrict eRHIC to the low 
energies of the JLAB accelerator concept then we can do the same Physics 
as they can.
    - Works for JLAB, not for eRHIC

* Brett makes the point that we should perhaps consider the insertion of 
a magnet in the forward direction, and the backward direction, 
separately. We may find that inserting a magnet in the forward direction 
could have a positive impact on the acceptance (backward) for the 
scattered electrons, and may be acceptable.

* Bob gives a presentation of Slides he'd sent around concerning the 
possible advantages to the collider parameters (e.g. chromaticity) if 
one inserted magnets into the detector volume. File: 
1808-quads-inside-v4.pdf
   - Elke makes the point that we can't/shouldn't make this idea of 
inserted magnets into the detector volume the default plan/concept.
   - Slide #1: Radiation fans in x, and beam parameters
   - Slide #2: Amplitudes for 105 GeV parameters
   - Slide #3: Shows whole concept/idea
    - point comes up again about perhaps only considering the forward 
magnet. Could increase the high eta electron acceptance.
   - Slide #5: Magnet parameters, forward and backward
   - Slide #6: Summary
    - There was discussion concerning whether this concept would make 
the luminosity go up or go down. After confusing discussion on what 
assumptions one had to make for the statements to be valid, minute taker 
chose not to make a statement on this. In these studies by Bob, it came 
out in discussion that only the electron lattice had been changed.
   - A slide with some rear side magnet considerations/challenges.
      - Need to worry about the stray/fringe fields
       - Discussion about using Halbach magnets. Nested quads that can 
rotate relative to one another.
       - Agreed that, at present time, this whole discussion concerning 
inserting magnets into the detector volume is for information only.

* Next meeting will be in two weeks, on September 7th. Presumably will 
start at 2:30 pm, but to be confirmed.
   - Near term it is suggested that Steve T., perhaps with help from 
Guillaume, should work on the electron lattice. Use Doug's latest design 
for the IR region.
   Agenda item for next meeting:
    - Go through Doug's slides for 6:00, and if any available, for 8:00.
    - Status update from Steve & Guillaume on the electron lattice.

       End of meeting

Attachment: 1808-quads-inside-v4.pdf
Description: Adobe PDF document