sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Agenda/Paul Giannotti's Powerpoint files:  https://indico.bnl.gov/conferenceDisplay.py?confId=2803


Today's meeting is probably one of the most interesting and productive Magnet biweekly meeting as we argued/discussed about a few important issues
and realized one or two important mistakes. 


1. We first discussed what material to shield the cables/wires as we've prepared to discuss.  

    --- When Piyush Joshi & Sonny makes the voltage taps, they'll use their standard kapton/TEFZEL cables, which are separate from the rest of the strain gauge,
         tie-rods and temperature sensors etc.

    --- From p. 2 of my agenda powerpoint (in the above indico link) and p. 6 & 7, we can see that BaBar has used PVC in the flat ribbon cables etc. going from
         the magnet to the valve box through the chimney have worked so far (in BaBar and in our low-field test) and we won't change those.   But nobody likes
         them or some even called it "junk" :-)

    --- There are some temperature specifications for PVC/TEFZEL in p.12/13 of Paul's power said that they're not that different -60 C vs -65 C.  But Carl Schultheiss
         said that he and I have seen lower, like < -100 for TEFZEL.
 
    --- Piyush Joshi told us that we have to use our experience to use what has proved to work even though the specification never claims that they work at 4 K or 2K.
         What has worked consistently are those ones made with kapton inside wrapped by by TEFZEL. 

    --- The consensus in the meeting was that Cryo/Tom Tallerico and Paul Giannotti are going to try to follow Piyush's recipe.


1.1  Paul Giannotti would do research into what material of those blue plastics on those connectors hanging out from the doghouse really is, as shown in p.7 of his     
       powerpoint.

1.2  During the discussion, people like David Phillips has mentioned again (for the nth time) that this may be the time to replace those (D) connectors in the 
       doghouse (=junction-box) as shown in p. 7 of Paul Giannotti's powerpoint file, which is what we've used in the low-field test.  Obviously, nobody
       likes what they see in that picture.   Piyush thought that if it's him, he'd not try to change those connectors because those cables are old and they are
       very thin/fine and very easy to break and difficult to work with.  If we get confused, we don't know which wire is what.   The consensus was again that we
       don't want to mess with it.


1.3  The label of "Teflon" on page 11 of Paul's powerpoint is most likely wrong as Mike Anerella has pointed out.   They are probably TEFZEL outside with kapton
       inside (as Piyush told me). 



2.  Then Paul Giannotti continued his talk onto the subject of "voltage taps".  He's agreed with the picture that I've sent out after learning from Piyush that
     one should place the voltage taps at both ends of the joint, outside the overlapped region.   

---  But after Paul went through his voltage tap locations on the joints (such as p. 17-24 in his powerpoint file), we suddenly got a couple "alarming" question
     from Mike Anerella and Ray Ceruti. 
     They wondered why voltage taps were placed on the copper because they should be placed on the superconductor.   Carl/Piyush thought that there was no
     exposed superconductor to put voltage taps.    Mike and Ray told us "yes, we can." (though not literally :-) 


--- The next thing that Mike and Ray told us was that what look physically like joints are not really joints (electrically).  Those joints are created for
     structural support reasons and the superconducting cable actually underneath go pass them.    So, we probably don't need 12 additional/new voltage
     taps (in addition to the original 17 taps).  Maybe, just 4 new voltage taps would be enough.  ( Carl is considering whether we may add redundancy ... )


--- So, it's said that Carl and Piyush will get together (probably this Friday I heard) and they'll make a schematic and give it to Paul Giannotti.  Then, Paul Giannotti
    will get together with Paul Kovach and mark the voltage tap locations exactly on the drawing etc.


3.  I mentioned in the meeting that P. Rosas' crew still haven't worked on the power supply and Carl was sidetracked to deal with his RHIC crisis such that he's
    got little time to deal with sPHENIX stuff.


4. Jim Mills told us the purchase order for aluminium (which was roughly cut) has been made and sent to the vendor.  Maybe, if things go well, 2 weeks from today
   we may receive the aluminium at BNL.  Then, we'll check it and send it to Florida State University (FSU) which may take a couple days (or a week if you're
  pessimistic or realistic).   Then, Jim heard/estimated that FSU may give us the first 4 brackets in 3 weeks.    To sum up, we may receive the first 4 brackets in
  less than 6 weeks from today if things go well [ which is ~Mar. 15 ].  The cost for the (roughly cut) aluminium is about ~$7000 only (less than expected).


5.  David Phillips reminded us that if the bracket manufacture goes well, then the critical part of the schedule may be the construction of the flux return
     steel,  cutting/welding and drilling/tapping.  There wasn't much progress in the last couple weeks ?!  I talked to John Hock after the meeting and
     he seemed to be frustrated with his inability  to get hold of equipment (drill) as they're not locked by a lock that he doesn't have the key to open :-(   
     David Phillips is trying to help mediate ...

    Mike/Ray told us that their technicians can help work on those flux return  and John just needs to give them a call :-)