UPDATE ON ERING LOW EMITTANCE CHROMATICITY CORRECTION STUDY
- Slides: 9
UPDATE ON E-RING LOW EMITTANCE CHROMATICITY CORRECTION STUDY Y. Nosochkov August 2, 2016
August 2, 2016 2 Description • Design a CCB based on Super. B scheme, but with extra cells between x and y sextupole pairs for easier match • Adjust CCB bending angle to approximately produce the same average angle per length as in the arc • Study three optics versions differed by beta functions at the sextupoles, total CCB length and dipole length & angle
3 August 2, 2016 Scheme-1 • Length = 134. 2 m • Seven 5. 4 m dipoles with bending angle = 2. 286*q 0 • b = 300 m / 600 m at x/y sextupoles match Y Y X X
4 August 2, 2016 Scheme-2 (reduced b) • Length = 134. 0 m • Seven 5. 4 m dipoles with bending angle = 2. 286*q 0 • Reduced b = 200 m / 400 m at x/y sextupoles Y Y X X
5 August 2, 2016 Scheme-3 (reduced b & dispersion, short dipole) • 50% shorter CCB dipoles for a smaller bending angle • Reduced length = 88. 1 m • Seven 2. 7 m short dipoles with reduced bending angle = 1. 429*q 0 • b = 200 m / 400 m at x/y sextupoles • 6 extra cells in arcs compared to schemes 1 & 2 due to shorter CCB Y Y X X
August 2, 2016 6 Ring beta match • • CCB match on the arc side using quadrupoles CCB match on the IR side using matrix element No dispersion suppressor on the IR side due to zero CCB dispersion Total bending angle is approximately matched, but the overall geometry is not closed
7 August 2, 2016 Emittance at 5 Ge. V e ~ E 2 I 5 / I 2 ~ E 2 q 3, (1) e = 29. 3 nm I 5 = Hds/r 3, I 2 = ds/r 2, (2) e = 22. 8 nm H-function I 5 [10 -3] (at bend exit) H = gh 2+2 ahh +bh 2 (3) e = 12. 2 nm
August 2, 2016 Chromaticity correction • • Using scheme-3 CCB sextupoles at exactly 90° from IP Correction comparable to the previously studied –I schemes Could be improved with fine tuning of phase advance 8
August 2, 2016 9 Comments • Realized that the CCB bending angle should be higher for more accurate scaling: × 2. 52 in schemes 1&2, and × 1. 66 in scheme-3 higher emittance • Strong emittance dependence on bending angle small angles are needed • Assuming that angle scales with CCB length, a small angle requires a short CCB hence, shorter bends since they determine the CCB cell length • But dipole field in a shorter bend may be too high • Chromaticity correction is comparable to the previously studied –I schemes
