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, 5/7/2018. Please note that our next meeting will be 
on Friday May 25, at 3 pm.
    Greetings,
        Bill

  Minutes from the eRHIC IR Design meeting held on 5/7/18
 
---------------------------------------------------------------------------------
* We started with a brief discussion of the agenda for the meeting. The 
entire agenda was to welcome Doug Holmes and Qiong Wu to the meeting, 
and start discussions on integrating the crab cavity designs and 
concerns into the IR Design.

* After brief introductions, some slides from a recent presentation by 
Bob (1804_discussion.pdf) were projected to aid in our discussions.
    - The idea about rotating the entire IR design about a vertical 
axis through the center of the IR was brought up. As far as what sort of 
rotation might be in discussion, the answer was about 7 mr.
    - Discussion of the space where the crab cavities would go in the 
present IR design and beam line layouts.
        - The current design reserved about 6.9 m along the beam line 
for the Crab Cavities to be placed. The design for the Crab cavities 
only requires about 3.2 m along the beam line, and the minute taker 
doesn't recall whether this included such things as possible pumping 
ports, gate valves, etc. associated with the Crab Cavities (aka CC).
    - Topic came up "If the crossing angle were increased, from the 
present 22 mr to 25 mr, what would the issues be?"
        - If this change was made, the voltage of the cavities would 
have to be increased from ~13 to ~15 MV.
        - The CC design is based on (minute takers recollection) having 
two RF cavities in each location, but the design left space to include a 
third RF cavity. This third cavity could act as a "hot spare", or if 
necessary used to achieve the necessary integrated RF voltage. If it is 
necessary to go up to 15 MV then the region for the spare RF cavity goes 
away (i.e. space is used by third cavity, and all three necessary for 
operation).
    - Doug mentioned that there were some figures that detail the 
current CC design geometry, and he was asked to send them to the mailing 
list. (Attached to these minutes)
    - Discussion about whether the width shown in the IR design for the 
distance available transverse to the beam line (horizontal plane) is 
representative of the actual IR magnet designs. Answer was Yes.
    - Elke brought up the point hat we need a design/layout drawing for 
the RHIC tunnel regions on either side of the existing RHIC IRs.
        - Doug kindly offered to locate some of these drawings, and 
send them to the list. (attached to these minutes)
    - Alexander and Doug agreed to talk about some of the details 
passing files of the geometrical layouts.
    - Question: "Are we designing for two IRs?"
        - Answer: Yes, that is the design philosophy.
    - Qiong points out that if we have two IRs we will have to design 
for higher harmonics.
        - This led to a brief discussion of the impact of two IRs on 
the CC design.Bob points out that thre are reasons it may be drive one 
to lower harmonics (as opposed from 6 to 8).
    - Elke asks whether the 56 (28) MHz cavity adds to these effects. 
Answer is yes, this has an impact.
    - Brett points out that the idea of only colliding a given bunch at 
a given IR (i.e. one or the other IR) allows one to avoid non-linear 
dynamics.

* Brief discussion about the task list that Ferdi sent out. Elke pointed 
out that this is a draft list at present, sent out for comment, and that 
the this (draft or wait for final?) will be sent around.

* Bob asks about changing the location of some magnets prior to the pCDR.
    - The general answer is no, not until after the pCDR.
    - Bob will send out some figures showing the magnet locations, 
following the idea that nothing changes/moves at this point.

* Doug asks how he can get information of the geometry of the current 
magnet concepts/designs?
        - Brett and Holger are the contacts for this information.

* Brief discussion about warm to cold transitions, as well as vacuum 
valves to allow for the isolation of various sections and CC components.

* Alexei pointed out that he had run some (impedance) simulations on the 
CC on a single bunch basis. He does not see any issues. Other beam line 
components contribute much more to the impedance, from a longitudinal 
point of view.

* Discussion of the next meeting data and Agenda:
    - Next meeting in two weeks (i.e. May 25th) at 3 pm.
    Draft Agenda:
        - Updated figures from Bob showing magnet locations
        - Walk through the plots sent to the list by Doug
        - Simulation update by Alexander
        - Any update available on the vacuum design (needed by Alexei)
        - Summary about changes needed for the pCDR
        - Status report on the document repository by Kyle.

Attachment: Crab Cavity and Cryomodule Concept Design and Analysis 2017-12-01.pdf
Description: Adobe PDF document

Attachment: eRHIC-6IR_Building_Layout-1.pdf
Description: Adobe PDF document