Design Optimization Strategies for End Harmonics (3-d)
The top-bottom symmetry is highly violated in the ends (example:RD3). In a design with “no end-spacers”, it creates very large skew harmonics in addition to normal sextupole.
Compare this to early cosine theta designs which had large sextupole in the ends.
- Must do some thing to reduce them qualitatively.
- Use spacers to reduce peak field and to minimize field harmonics (as done in a typical cosine theta design, but do it here for both normal and skew harmonics). As usual, the field harmonics are minimized in an integral sense.
- Make coils above the midplane (in the upper aperture) go further out in the ends to compensate for the higher conductor volume below the midplane.
Bz is not zero locally in an individual end. But is zero in integral sense.
Bz in the ends of two nearby magnets cancel each other. AP issues?