[A1n_d2n] To do items from today's meeting

[Xiaochao Zheng]

Here are minutes for yesterday's meeting:

https://hallcweb.jlab.org/experiments/A1n/meetings/A1n_hallc_minutes.html#20180515

Xiaochao

----- Original Message -----
> From: "Xiaochao Zheng" <xiaochao at jlab.org>
> To: "A1n d2n" <a1n_d2n at jlab.org>
> Cc: "Mark Jones" <jones at jlab.org>
> Sent: Wednesday, 16 May, 2018 00:07:55
> Subject: [A1n_d2n] To do items from today's meeting

> Dear All:
> 
> I have attached the draft reply from today's meeting. A few items that we could
> not reconcile today are listed below:
> 
> 1) How much beam time do we need for the optics calibration at 1-pass, for the
> fall 2019 and the spring 2020 run periods, respectively?
> (Brad, Mark, Dave, JP?)
> 
> - we think a total of 2 days is needed: 1 day (8+4 PAC hours for elastic and
> Delta), and 1 day for careful optics study. The Sp2020 optics can be shorter.
> 
> - once this is done, Xiaochao and Brad will communicate the requirement to Thia.
> 
> 2) carbon foil max current: 30 or 60 uA?
> 
> 3) how do we protect the target from possible large beam halo and mis-steering?
> 
> option 1: have two carbon hole targets. But current target design does not have
> enough space to have both the central long carbon with hole and two additional
> carbon holes at +/-z edges; So we will need to sacrifice the central single
> foil.  Do we need single-foil optics?
> 
> Also if we do have double carbon holes, steering the beam into both may require
> a shift of tuning. On the other hand this needs to be done only occasionally.
> 
> --------------------------
> Actually, I checked the target drawing, and have attached a sketch (attached).
> I don't know why we can't have the hole in the vertical middle position (below
> single- and multi-foil position) and add only one more carbon hole at either +
> or -6.7cm?  (I have attached the alternate design here.)
> 
> It may even be better to have the hole in the middle position so the single
> carbon is further away from the multi carbon:
> (a) If we take data on single foil but the beam is slightly mis-steered or for
> whatever reason it scrape the multi foils, we will have less chance to see the
> other 6 foils. (In the alternate design the beam may still scrap the 2nd long
> foil but that's only one more foil to mess with the carbon elastic x-section,
> in this worst case scenario).
> (b) If we move the hole closer to the multi foils, it may be easier to spot beam
> mis-steering or to find the hole (if hole is missing) by spotting edges due to
> beam scraping the multi foils.
> 
> --------------------------
> 
> 
> option 2: Leave the solid target design as is, and rely on a combination of:
> single carbon hole, ion chamber, upstream collimator (possibly at -200cm
> according to Jay), periodic harp scans to check beam size -- to protect the
> target?
> 
> Can we interlock more stuff with the FSD to protect the target?
> 
> Then we still have our usual to do items:
> 
> 4) Dave needs to work out a reply to get Moller to 3%;
> Dave please send me a draft reply. Plain text will be good enough.
> 
> 5) JP still working on the target installation "milestones";
> 
> 6) Silviu will continue to 12 GeV target simulation as well as solid targets
> (good progress today!);
> 
> Silviu -- if you have plots ready to be included in the document, please send me
> the EPS file (or some other format) so I can start including them and editing
> the texts.
> 
> 7) target field: Gordon/Vladimir, can you provide a set of plots to show field
> conditions for the highest Q2 configuration?  I believe you already have the
> field map to make these plots.
> 
> One last thing: Now that the mailing list is generated, when should we invite
> all polarized 3He groups to join?  After the schedule is set?  Or earlier?
> 
> I will type up a longer meeting minutes tomorrow.
> 
> 
> Thanks,
> 
> Xiaochao
> 
> 
> ----------------------------------------------------------------------------
> Associate Professor, Department of Physics, University of Virginia
> 382 McCormick Rd, Charlottesville, VA 22904
> Telephone: (434) 243-4032 (during academic year); or (757) 810-2885 (summer)
> Homepage: http://people.virginia.edu/~xz5y/Main.html
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