[A1n_d2n] To do items from today's meeting

[Xiaochao Zheng]

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
----------------------------------------------------------------------------
-------------- next part --------------
A non-text attachment was scrubbed...
Name: target_structure_edit_alternate.eps
Type: image/x-eps
Size: 6342 bytes
Desc: not available
URL: <https://mailman.jlab.org/pipermail/a1n_d2n/attachments/20180516/26daebe4/attachment-0002.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: target_structure_edit.eps
Type: image/x-eps
Size: 6311 bytes
Desc: not available
URL: <https://mailman.jlab.org/pipermail/a1n_d2n/attachments/20180516/26daebe4/attachment-0003.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 3He_ERR_Reply_to_Final_Report_May2018.docx
Type: application/vnd.openxmlformats-officedocument.wordprocessingml.document
Size: 573126 bytes
Desc: not available
URL: <https://mailman.jlab.org/pipermail/a1n_d2n/attachments/20180516/26daebe4/attachment-0001.docx>