1. technology challenges for FCC-ee Frank Zimmermann on behalf of the FCC-ee design team, input from M. Benedikt and K. Oide, FCC STP Meeting #1 7 October 2015

2. SRF cavities - Q value, gradients, technology - loss factor, impedance RF power sources - efficiency arc magnets for collider and booster - cost, ~85 km arc vacuum system / antechamber/ shielding - radiation hardness & shielding IR magnets - SC quadrupoles & solenoids other technologies

4. 1. arc magnets for collider & booster

5. Comparison between two designs of the dipole magnet 1) To produce a pure solid iron core is easier than to produce a steel-concrete core, it means that the cost of the magnet fabrication will be reduced ； 2) Although the iron material that the thin solid iron core magnet needs is almost the same as that the steel-concrete core magnet needs, the thin solid iron core magnet doesn’t need cement mortar, so its total weight is only 50% of that of the steel-concrete core magnet; 3) For a rough estimation, the new thin solid iron core magnet can save 10%-20% money. 4) However, because the design is totally new, we don’t know if there will be any vital problems that lead to the failure before a prototype magnet is developed. Pre-CDR magnets for CEPC Main Ring K. Wen

6. 2. arc vacuum system, antechamber shielding

7. FCC week, 24 March 2015R. Kersevan7 The Synchrotron Radiation in the FCC-ee Arcs Some Figures MachineCritical Energy (keV) Total Power (MW) Linear Power Density (W/m) Total Flux (ph/s) Linear Flux Density (ph/s/m) Linear Outgassing Load (*) (mbar*l/s/m) FCC-ee Z18.99507244.90E+227.10E+172.87E-8 FCC-ee W103.24507249.33E+211.35E+175.46E-9 FCC-ee H348.43507242.82E+214.08E+161.65E-9 FCC-ee tt1,080.64507249.15E+201.32E+165.34E-10 LEP166.950.31516.26.10E+193.13E+151.27E-10 LEP2804.8210.15521.02.49E+201.28E+165.18E-10 ESRF20.500.9816684.08.53E+205.81E+182.35E-7 (*) Outgassing load calculated for a photo-desorption yield  =1.0E-6 (molecule/photon) ESRF: 6 GeV; 200 mA;  = 23.366 m R. Kersevan, FCC Week 2015

8. also induced activity A. Fasso, TLEP3 workshop, January 2013

9. Pb thickness 3 or 8 mm, attenuates power by 98 to 99% Would be very ineffective at higher SR energies!!! How to mitigate? Don’t know: needs new ideas A. Fasso, TLEP3 workshop, January 2013 LEP vacuum chamber

10. Photon cross sections Compton dominated Photoelectric dominated Pair dominated  p.e. =photoelectric cross section;  incoh =Compton cross section;  coherent =Rayleigh cross section;  nuc =photonuclear cross section;  N =pair production cross section, nuclear field;  e =pair production cross section, electron field A. Fasso, TLEP3 workshop, January 2013

11. J. Billan et al., “Measurement of the LEP Coupling Source,” EPAC 1990, Nice effect of magnetized 7-  m thin layer of nickel used to clad the lead shielding onto the LEP aluminium chamber … and the devil is in the details...

12. R. Kersevan12 Ref.: “Impact of synchrotron radiation in lepton collider arcs”, F. Cerutti et al., FCC Kick-off Meeting, Univ. Geneva, Feb 2014 L. Lari et al., “Beam-machine Interaction at TLEP: First Evaluation and Mitigation of the Synchrotron Radiation Impact,” IPAC’14 10.5 m dipole Iron + plastic 25 mm 24 cm absorber Lead Impact of SR on Machine and Tunnel Components FCC week, 24 March 2015 R. Kersevan, FCC Week 2015

13. FCC week, 24 March 2015R. Kersevan13 shielding for higher-energy machines (H, tt) is challenging Differential cross section of Compton scattering, R. D. Evans, “Compton Effect”, Handbuch der Physik XXXIV, Springer-Verlag, Berlin (1958) R. Kersevan, FCC Week 2015

14. 3. IR magnets, SC quads & solenoids detector solenoid 2 T (?) antisolenoid for coupling correction shielding solenoids for SC quadrupoles

15. Main detector solenoid Quad screening solenoid Compensati ng solenoid Final quads M. Koratzinos, A. Bogomyagkov, S. Sinyatkin, K. Oide IP layout final SC quadrupoles (K. Oide): QC1: 101.8 T/m, (9 mm + beam pipe + cryo) = 14 mm? radius, 3.2 m long QC2: 68.8 T/m, (15 mm + beam pipe + cryo) = 19 mm? radius, 2.5 m long

16. prototype SC IR quadrupole at BINP Main contributors are Ivan Okunev and Pavel Vobly Two versions of the FF twin-aperture iron yoke quad prototype with 2 cm aperture and 100 T/m gradient are in production. Saddle-shaped coils, complicated in production, the first coil failed. New winding device is in development. Straight coil, successfully wound and tested (650 A instead of the nominal 400 A) “The work has low priority and small contract with CERN would help” E. Levichev

17. other FCC-ee technologies low level RF control / feedback system / timing system pulsed or dc magnets for top-up injection, kickers, septa electron cloud mitigation snakes for the booster? diagnostics / control tools for the ultra- small, ultra-thin beam beam scrapers and SR masks luminometers, polarimeters …