1. 1 Modular Coil Winding Keystoning Issues NCSX Technical Meeting May 29, 2003 What is the current baseline winding? What is the problem? What are the variables and issues? What tests can be done to resolve issues What is schedule?

2. 2 What was baseline geometry? (M50_256.Z01) DimensionValue Winding pack width4.10 inches Winding pack height4.67 inches Turn insulation thickness 0.054 inches Ground insulation thickness 0.030 inches “tee” width0.75 inches Copper chill plate thickness 0.040 inches Packing fraction of copper 78 % Max current in coil653 kA-turns No of turns/coil36 Net current density in copper 13825 A/cm^2 w.p. height w.p. width

3. 3 What is baseline geometry? (M50_256.Z01) DimensionValue Winding pack width4.10 inches Winding pack height4.67 inches Turn insulation thickness 0.054 inches Ground insulation thickness 0.030 inches “tee” width0.75 inches Copper chill plate thickness 0.040 inches Packing fraction of copper 78 % Max current in coil763 kA-turns No of turns/coil28 Net current density in copper 15225 A/cm^2 w.p. height w.p. width

4. 4 What are new reference scenario currents?  Reference scenario currents from Technical data posted on web  Data scaled from 36 turns to 28 turns  Current is significantly higher than originally thought for 1.7T scenario: 763 kA-t vs 653 kA-turns per coil, up to 790 kA-turns for 1.9T scenario.

5. 5 What is conductor size?  Original design used one cable per turn, 0.5 x 0.625 inches  1000 ft. of cable procured for practice  Epoxy potting samples prepared  UT coil wound and potted  Keystoning tests performed and identified as issue  Last fall we went to 4 cables per turn to reduce keystoning  0.25 x 0.3125 in cable procured  Epoxy samples prepared  Racetrack coil form procured  Practice winding fixture prepared  More keystoning tests performed  4-cable conductor rejected, since cable bunched with insulation in place  Present baseline cable size is 0.539 x 0.660 inches

6. 6 Keystone test results so far  Single conductor with dry glass only had significant keystoning 3.5 in dia.

7. 7 Keystone test results so far  Four cables/conductor did not work well due to bunching  Cables could not slide relative to each other

8. 8 What is actual conductor bend radius?  This all depends on what the meaning of radius is  For radius to winding center, we have:  From Coil-opt, Rmin = 4.15 inches  From Pro-E model = 4.15 inches  Min. radius to edge of four sides of winding pack: leftrightShell side Plasma side M11.5811.6311.3082.443 M21.8382.1113.7233.175 M31.6881.6063.9593.685 Keystoning makes pack taller Keystoning makes pack wider

9. 9 What is effect of insulation?  Keeps 4-cable conductor from sliding relative to each other within insulation wrap  Makes conductor very stiff  Adds to keystoning problem  Options:  Teflon tape – does epoxy bond to teflon? Do we care?  CREPED NOMEX – dimensional control, pinholes?  Mylar? – not any better than kapton  Spiral wrap or butt wrap, not half lap  Look at woven glass polyimide stuff 3 layers kapton,.00325 in ea 4 layers glass,.007 in ea. Total =.038 inches

10. 10 What are options?  Figure out how much keystoning we have and live with the problem  With and without insulation  With existing and new conductor  Jim will start this one now  Figure out what “reasonable” pressure is to squash pack into place  Predict winding pack growth and check interferences with VV/adjacent coils – ORNL with Jim data  Art checks field errors from predicted keystoning w/o any correction  Pre-keystone conductor ahead of taping head in opposite direction  Go back to 4-cable conductor, wrap onto form w/o insulation, clamp cables in formed position, unwind, insulate, and re-wind  Wind into groove (e.g. on pulley or tube bender) to restrain cable, unwind and rewind  Actions  Look at changing pitch of cable ala Auburn cable – Jim  Look at pretzel coil design/schedule – fits in oven, full cross section, prototypical conductor and potting features, clamps, etc.  FDR for racetrack coil June 5

11. 11 “live with the problem”  Perform keystoning tests to quantify problem, increase size of winding pack, shim between turns to fill all space I.e. “live with the problem” Look at both id and od winding forms - ORNL

12. 12 Pre-keystone conductor ahead of taping head in opposite direction  For most regions of the coils, there would be little if any reverse keystoning needed.  We can contact NEWC to see what kind of rollers they use on their turkshead, and what it would take to make a turkshead with easily adjustable rollers.  Develop an algorithm that would pre-squash the conductor appropriately. We would need to figure out a couple of things,  how much overall swelling do we get with the extra squashing?,  how much damage do we do to the wires in the process?  can the taping machine adapt to different shapes of conductor?  We would still measure every turn and possible shim between them, but we may end up with a tighter pack (i.e. lower current density and more uniform mechanical properties).

13. 13 Go back to 4-cable conductor  Wind bare cables for some distance  Clamp conductor  Carefully unwind and insulate  Put back and clamp  Comments:  Tolerance on cable doubles  Maybe set up tape machine to tape a curve  Investigate further on roller coaster with close taping - Jim

14. 14 Current density vs insul. thickness and tee width