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A draft of Interaction Region with Crab Waist. Bogomyagkov, E. Levichev, P.Piminov , I.Okunev Budker Institute of Nuclear Physics. Why Crab Waist. http://arxiv.org/abs/1311.1580. Crab Waist ( P.Raimondi 2006 ).
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A draft of Interaction Regionwith Crab Waist Bogomyagkov, E. Levichev, P.Piminov, I.Okunev Budker Institute of Nuclear Physics FCC Kickoff Meeting, 12-15 February 2014
Why Crab Waist http://arxiv.org/abs/1311.1580
Crab Waist (P.Raimondi 2006) • Large Piwinski’s angle (z/x∙tan()) – to decrease the overlapping area • Low y – luminosity increase • Crab waist – to suppress betatron resonances (sextupoles in phase with IP)
Crab Waist Optics requirements • Sextupole at x=m, y=(2n+1)/2 • Sextipole is strong, therefore Wx=0, Wy=0. • Local chromaticity correction: two “–I” pairs of sextupoles at m from FF quadrupoles.
Final focus D0=0.7 m Q0: L=4.6 m, G=95 T/m @ 175 GeV D1=0.4 m Q1: L=2 m, G=96 T/m @ 175 GeV
QD0 • Compact SC iron yoke • twin aperture magnet • Single aperture 2 cm • Gradient 110 T/m
Optics CRAB Y2 X1 X2 Y1
Optics CRAB Y2 X1 X2 Y1 FFT YXCCS CRAB
Chromatic functions Fine phase adjustment of sextupole pairs will help to reduce even more.
Phase advance variation • Sextupole at the end of FFT controls Qy’’’ • Additional sextupoles an octupoles will compensate higher order chromaticity.
Effect of sextupole length http://arxiv.org/abs/0909.4872 A.Bogomyagkov, S.Glykhov, E.Levichev, P.Piminov
Dynamic aperture 153 x 461 y 1000 y Left: black -- sextupoles, kinematic, fringes. Left: blue -- sextupoles and compensators. Left: red -- sextupoles and compensators, kinematic, fringes. Right: plus two octupoles to compensate kinematic, fringes.
Things to look at • Kinematic term at IP (will increase drastically with larger L*, see Oide-san FF of SuperKEKB). • FF quadrupoles fringes (will increase drastically with larger L*, see Oide-san FF of SuperKEKB). • Sextupole length (Effect of the Sextupole Finite Length on Dynamic Aperture in the Collider Final Focus, 2009, http://arxiv.org/abs/0909.4872).
Conclusion • A first draft of IR with crab waist is ready. • We do not see any reason to make L*>0.7m. • Design of Q0, adjust length, distance from IP. • Bending angle of dipoles, of whole IR. • Quadrupole, Sextupole strengths. • Nonlinear optimization: chromaticity, dynamic aperture.