January 26, 2018 - Wien magnet coil discussion

(Jay, Jeff, Danny, Joe)

The purpose of the meeting is to discuss the 200kV prototype Wien magnet (modifications to coil, magnet steel, vacuum can), then form a plan to include modifications for fabricating the final coils.

Comments:

• The primary fabrication difficulties were a) the time required to bend the square wire at the ends, and b) achieving the cross-section area design spec w/ the wet epoxy method
• To address the larger cross-section area a groove was cut into the magnet steel, however, this reduced the magnetic field by about 8% (modeled and measured), thus requiring more current to make up the loss.
• Although time consuming at the end, Jeff can re-use the existing fixturing parts.
• We discussed changing the coil geometry to better accommodate the square coil, however the prototype (standard) geometry remains the best solution.
• Because the square cross section is 33% less resistive than round wire the #13 square wire remains desirable.

Plan:

• Jeff will wind next coil with two modifications
  • a) will do a dry wind (rather than wet epoxy on each turn) so that a single layer can be constructed and fixtured/press tighter into design cross section more easily and will then fix and tape a layer,
  • b) will wind as many turns as possible within the allowed cross-section specification - the design is for 13 turns, but 10 turns is required. Based on previous coil Jeff made at least 11 turns, and this time will aim for 13, but if necessary will stop at 12, and 11 seems worst case but still acceptable.
• When MIT Wien arrives, Joe will evaluate similarity to CEBAF standard Wien. If similar, will modify the vacuum can ears and provide to Jeff so he can test fit new coils.