[A1n_d2n] To do items from today's meeting

[Jian-Ping Chen]

Xiaochao,

The position below the multifoil target is the empty target position for 
beam tuning.

Jian-ping

On 5/16/18 12:07 AM, Xiaochao Zheng wrote:
> 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
> 
> 
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