1. Plan for Review of FCC- ee Optics and Beam Dynamics Frank Zimmermann FCC-ee Design Meeting 31 August 2015

2. introduction & motivation The overall planning for the FCC-ee machine design foresees to converge on the optics and beam dynamics by autumn 2015. Over the last year, the low-emittance crab-waist collision scheme has gained momentum, both at BINP and at CERN. The crab waist collisions promise better performance than the original baseline, in particular for the lower-energy working points. Various optics versions for such a scheme have been developed. Design challenges include: 1)final focus optics design with a target vertical IP beta function of 1 to 2 mm, 50 or 25 times smaller than for LEP2, incorporating sextupoles for crab-waist; 2)synchrotron radiation in the final focus systems and the arcs, with effects on the detector (background, …) and on the beam (vertical emittance blow up and dynamic aperture); 3)beam-beam effects, including single-turn and multi-turn beamstrahlung; 4)design of the interaction region with a strong detector solenoid with possible compensation solenoids, a large crossing angle and a pair of final-focusing quadrupoles; 5)compatibility of the layout with the design of the hadron collider sharing the same tunnel; 6)RF acceleration system for high voltage (ZH, tt ̅) and high current (Z, WW) with possible staging scenario; 7)impedance, HOM losses and instabilities, especially for high-current low-energy operation 8)the top-up injection scheme; 9)achieving the dynamic aperture required for adequate beam lifetime and for the top-up injection, including optimization of the arc optics; 10)vertical emittance control, including field & alignment errors, lattice nonlinearities, as well as beam-beam effects; and 11)energy calibration and transverse polarization

3. goals of the review: define a (new) baseline configuration for collision scheme, IR layout, final focus, and overall configuration; converge on beam parameters; identify critical issues

4. preliminary draft agenda / themes 1. Goals of the review, 2. Physics goals and priorities 3. Overview of proposed options and parameters 4. Beam-beam simulations & luminosity performance 92 vs 4 IPs, crab waist vs non-crab waist, optimum beta*, lifetime vs acceptance) 5. Crab waist plus local chromatic correction schemes plus solenoid compensation 6. IR synchrotron radiation 7. Arc options, phase advances, sextupole confgurations 8. Emittances with misalignments, field, chromatic effects, synchrotron radiation 9. Top-up injection 10. Energy calibration

5. confirmed reviewers: Ralph Assmann (DESY), Alain Blondel (U. Geneva), John Byrd (LBNL), Yunhai Cai (SLAC), Stephane Fartoukh (CERN), John Jowett (CERN, Chair), Jean-Pierre Koutchouk (CERN), Eugene Levichev (BINP), Pantaleo Raimondi (ESRF) date and place: Wednesday, 14 October 2015, 08:30 – 17:30 (presentations and discussions), CERN, 160-1-009