FCC- ee mini-workshop / review CERN, 16-26 January 2017 (chair & main organizer M. Boscolo)

1. FCC-ee mini-workshop / reviewCERN, 16-26 January 2017 (chair & main organizer M. Boscolo) Motivation anmd scope This mini-workshop for the Machine Detector Interface design of the FCC-ee collider had been triggered by the FCC-ee design review of October 2016. It aimed at revisiting/validating several open issues with worldwide experts. The main topics to be discussed before freezing the baseline MDI layoutincluded the various beam-pipe dimensions, choice of l*, final magnet parameters, space and location of luminosity monitors. Overlapping in time with the FCC-ee MDI mini-workshop, the 1st FCC Physics Workshop tookplace, in the week 16-20 January. Its agenda is available at the following link: https://indico.cern.ch/event/550509 http://indico.cern.ch/event/596695

2. Participants E. Belli (CERN) M. Benedikt (CERN) A. Bogomyagkov (BINP) M. Boscolo (INFN) H. Burkhardt (CERN) M. Dam (NBI) D. El Khechen (CNRS/LAL) K. Elsener (CERN) R. Kersevan (CERN) M. Koratzinos (U Geneva) E. Levichev (BINP) A. Novokhatski (SLAC) N. Ohuchi (KEK - remote) K. Oide (KEK) M. Sullivan (SLAC) H. ten Kate (CERN) P. Vobly(BINP) G. Voutsinas (CERN) F. Zimmermann (CERN)

3. Programme Week 1 Monday 16/1 – Relevant talks at the 1st FCC Physics Workshop : 09.10 Status of the FCC Project (M. Benedikt), 09.40 FCC accelerator parameters (F. Zimmermann) The FCC-ee MDI mini-workshop starts at 2pm – Introduction & Optics 14:00 Introduction (M. Benedikt and F. Zimmermann), 14:30 Workshop Plan (M. Boscolo) 15:00 Optics (K. Oide) , 16:00 Optics discussion Tuesday 17/1 – Trapped modes 09:00 Trapped Modes Analysis (A. Novokhatski), 09:30 Trapped Modes Analysis (E. Belli) 10:00 Optics Issues Discussion & Trapped Modes Discussion, Afternoon: Working session Wednesday 18/1 – IR layout and Synchrotron Radiation 09:00 IR Layout with SR constraints (M. Sullivan), 10:00 SR with MDISim (H. Burkhardt) 10:30 SR with SYNRAD+ (R. Kersevan), 11:00 Discussion on SR related issues Afternoon: Working session Thursday 19/1 - Luminosity Monitor 09:00 LumiCal (M. Dam),10:30 FCC-eeIR magnetic element design – an update (M. Koratzinos) 11:00 Discussion on LumiCal, 12:00 Fast Luminosoity Monitor for SuperKEKB (D. El Khechen) Afternoon: Working session Friday 20/1 – Magnetic Integration System and IR Mechanical Layout 09:00 Magnetic Integration System and IR Mechanical Layout (H. ten Kate), Discussion Afternoon: Working session

4. Programme Week 2 • Monday 23/1 – IR Quadrupole Design • 14:00 IR Quadrupole Design (P. Vobly) , Discussion • 15:30 Solenoid Compensation Scheme Optimization (S. Sinyatkin) • Tuesday 24/1 - Working • 10:00 SuperKEKB IR SC Magnets (N. Ohuchi), Discussion & additional presentations • Wednesday 25/1 – Working & Writing • 09:30 Trapped Mode Analysis - Update (E. Belli), 09:45 Trapped Mode Analysis – Update (A. Novokhatski) • Discussion & write-up • Thursday 26/1 - Working & Writing • 09:30 Luminosity Calorimeter Update (M. Sullivan), 10:00 Lumical Design Update (M. Dam) • 10:55 Solenoid compensation scheme (S. Sinyatkin), • 11:00 Effect of the FCC beampipe on flavour tagging (G.G. Voutsinas) • Discussion & write-up • Friday 27/1 – Close-out • Close-out with conclusions (K. Oide, M. Sullivan, M. Dam, A. Novokhatski, H. ten Kate, S. Sinyatkin, M. Boscolo, F. Z.)

5. Optics Summary Katsunobu Oide

6. Mike Sullivan

7. Mike’s summary • The LumiCal looks OK at the Z running • We need a Be beam pipe for the LumiCal window in order to minimize the RL to the LumiCal and to minimize the HOM power in this region • The LumiCal window will cause central detector SR backgrounds to increase at the Top running because of the high energy of the scattered photons Mike Sullivan

8. For the Top running • 1.9109 photons incident on the mask tip every beam bunch • 3.87% scatter through the mask tip • About 1% can scatter through 2 cm of Ta • This means about 700,000 photons go into the central detector region every beam crossing – too many • We will need to add as much shielding as we can in order to cut this rate down Mike Sullivan

9. Detector Magnets Herman ten Kate

10. Quadrupole Magnets Herman ten Kate

11. Compensation & shielding solenoius, etc. Herman ten Kate

12. Model 2 E. Belli 25/01/2017 – FCCee MDI Workshop

13. Wake potential 10 mm 5 mm E. Belli 25/01/2017 – FCCee MDI Workshop

14. HOM power estimate IR power loss (two beams) Positrons Electrons Excitation of a cavity by electron and positron currents depends upon the difference in the arrival time and frequency of the cavity. The power may vary from 0 to 4. In average we assume to be 2. B-side BPM A good HOMs absorber in IP will solve the problem with resonant modes. Alexander Novokhatski

15. A trapped mode in FCC IR Electric field lines in this place Perpendicular to the beam trajectory And image currents Alexander Novokhatski

16. A screen with longitudinal slots Alexander Novokhatski

17. HOM absorber for FCC IR water pipe cupper absorbing tiles screen screen Alexander Novokhatski

18. Layout 1.2 m Luminometer QC1R1_1 QC1R1_2 Compensating Solenoid 1 m Screening Solenoid 1.25 m Defocusing Quads 2.01 m 1.84 m 2.16 m 2.2 m QC1R1_1: L= 0.7 m, K1=-75 / -75 T/m, R = 0.015 m QC1R1_2: L= 1.4 m, K1=-173 / -166 T/m, R = 0.0175 m Sergey Sinyatkin

19. Layout Sergey Sinyatkin

20. Field distribution with detector iron yoke Transverse half size: - main solenoidfield - Lgeom = 1.25 m, Bs = 2 T - compensating solenoid - R = 0.176/ 0.243 m, Lgeom= 0.756 m, Bs~ 3.3 T - screening solenoid - R = 0.245 m , Lgeom = 1.838 m Sergey Sinyatkin

21. Field distribution with detector iron yoke Edge field in quad area: Bs<0.01 T Bx<0.002 T It is necessary to introduce additional corrections in the screening area and at the detector’s yoke end cap. Sergey Sinyatkin

22. Beam Orbit at IR Sergey Sinyatkin

23. Emittance calculation • I2 = 5.65*10-4 m-1 • I5 = 1.99*10-11 m-1 For 2 IP Sergey Sinyatkin

24. Field distribution Bs_no iron Bs • Nonuniformity: • No iron: Bs ~ 1 kGs • With iron: Bs ~ 50 Gs • Insert of distributed screening solenoid coils • Screening area up to 6 – 10 m by distributed screening solenoids Sergey Sinyatkin

25. Sergey’s Summary • Vertical emittance for current geometry is small. • Residual magnetic field in FF area is less than 50 - 100 Gs. • Absence of detector’s solenoid iron yoke requires distributed solenoid coils. Sergey Sinyatkin

26. my personal highlights • enormous progress, all questions were answered (l*, HOMs, lumical, chamber dimension, material…) • some otherconclusions/observations: • no need for full final quadrupole prototypes • structural design of compensating solenoid does not yet exist • new questions: • do we need LumiCal for the H? • can we make the final part of soft bend even softer? • SR from solenoid fringe field • where are the draftsmen making detector specification drawings? • option for second detector with 0.5 T field? – which detail in CDR? • do we really need a no-yoke magnet for FCC-ee? • beta_x* at Z? SR emittance limits?electron cloud in IR?! • new requests: • 3D CAD computer model of IR region (now already pursued by vacuum group!) as input for realistic impedance calculations • need cryostat designer