E-rhic-ir-l mailing list

[Bill Christie <christie AT bnl.gov>]

Dear All,
    Please find the minutes from the March 3, 2017 eRHIC IR design mtg 
below. I'll try to get out the minutes from the March 8th mtg soon.

    Meeting on the eRHIC IR design
        Mtg date: March 3, 2017.

We had a brief discussion of the synchrotron radiation calculation and 
plots that Christoph had done. He'd modifed the units used for the 
radiation fluxes, and was looking for feedback on whether these levels 
were "acceptable". The answer was that, whether acceptable or not will 
depend on the specific detector technologies that will be selected for 
the eRHIC detector, and the various beam monitors.

Brett brought up that he'd taken a look at the other side (i.e. on side 
where e beam exits the IR). Suggests that he and Christoph get together 
to look into any integration issues with fitting Christoph's masks with 
the magnet and beam line locations.

We then moved onto Richard's presentation.
    - details the magnet geometries and fields used.
    - Discussion that it is likely advantageous to combine geometry 
files with beam parameter files into a single file. N.B. that this idea 
seems to run counter to the configuration management discussion we'd had 
at a previous mtg, where the two file types were to be version 
controlled separately. Vadim indicated that he would take care of this 
new scheme.
    - pointed out that in subsequent files we must either specify more 
explicitly whether the emittances listed are normalized or not, or pick 
one choice and then used it exclusively.
    - pointed out that in a recent decision it was decided that the 
proton and ion beams had to be in the Yellow beam.
    - Point made that Richard's results agree reasonably well with 
Bob's calculations.
    - The acceptances, as shown from the simulation, are not acceptable 
for the physics program needs. SOme discussion on what is acceptable. 
Pointed out that one can lose the low Pt acceptance some, but from a Pt 
of ~ 600 MeV/c and above one needs at least 60% acceptance.
    - Discussion of the effect on the results if one includes 
dispersion (not included in the simulation results shown at this mtg). 
Richard will get the information needed to include dispersion into the 
simulation and include it.
    - The current Pt reconstruction algorithm requires a position and a 
vector at the Roman pot stations.
    - The reconstructed Pt resolution is not great. Elke explained a 
bit why it is not easy to use the momentum of the scattered electron to 
correct the proton momentum.
    - one has to unfold the effect of the beam divergence on the 
reconstructed momentum.
    - "Step 2" will be to get the formula for the beam emittance and 
look at the impact n the beam size at the location of the Roman Pots. 
This ended the presentation.

Discussion about what comes next. As mentioned already, the beam 
emittance will get included, and it will be seen how it distorts the 
spectra. A question on how Jlab deals with these issues in their design.

We moved on to a quick walk through of the "other sdie" of the IR by Brett.
    - Brett needs to discuss this with Christoph and figure out the 
aperature and collimator integration needs.
    - Brett needs to meet with Steve T. to match his design onto the 
ring lattice.

Finally, a discussion of when we could fit in a mtg to discuss Bob's 
talk a bit and help him prepare for his dry run on March 15th. We settle 
to try to set up a meeting on Wednesday afternoon, after the 3 pm eRHIC 
R&D mtg. We'll also get an update at this mtg from Richard on his "Step 
2" progress. Note that the actual eRHIC review date is April 5th and 6th.
                                End of mtg