Summary of the 2 nd FCC- ee MDI workshop

1. Summary of the 2nd FCC-eeMDI workshop M. Boscolo registered participantsand speakers: M. Benedikt, A. Blondel, A. Bogomyagkov, M. Dam, D. El Khechen, A. Novokhatzki, K.Oide, P. Janot, K. Kanazawa, R. Kersevan, A. Kolano, M. Koratzinos, A. Krasnov, M. Masuzawa, M. Serluca, S. Pivovarov, S.Shiyankov,S.Sinyatkin, M. Sullivan, F. Zimmermann …plus others non-registered participants Workshop on the mechanical optimization of the FCC-ee MDI January 30- February 9 2018, CERN

2. Summary • The first week of the workshop was very useful to review the MDI design and start to discuss some details related to mechanical and technical issues • The second week, first steps doneto produce a 3D mechanical design with the aim of an assembly concept • Very interesting remote talks on Superkekb mechanical assembly and vibration studies (K. Kanazawa and M. Masuzawa) • There are some open questions in the design • Effort needed to release a mechanical design of the MDI

3. Outline • I will go through some topics discussed • Layout and SR in the IR studies • Lumical • Solenoid scheme • QC1 design • HOM design • Beam pipe, heat load and water cooling system • BPM • Vibration studies • Remote Vacuum connection • Mechanical design status • Conclusions

4. Layout screening solenoid comp. solenoid BPM pump HOM abs.

5. Local primary SR scatter points The pumping and shielding designs must be combined

6. About the IR layout • We keep as main layout for the CDR a unique and flexible designat all beam energies • We keep in mind the possibility of a smaller beam pipe radius at IP at low energies (interest from detector group and it may be studied in some detail) • Estimate of SR needs an update to last paramter table, this is underway (M. Sullivan), results will be ready soon (then updated in MDI section of the CDR as well) Fast luminosity monitor for machine tuning • Detector lumical not fast enough for machine tuning • Machine luminosity detector at zero angle for high cross-sections also at low luminosity needed, it has to be studied

7. Lumical design • Absolute measurement 10-4 • Bhabha cross section 12 nb with acceptance 65-85 mrad • The faces of the lumical are perpendicular to the outgoing beamline • The distance between the two calorimeters has to be measured to 110mm • This can be done aligning with lasers the tracker wrt IP with dimuon events, then aligning the tracker with the lumical • The design is not tapered above anymore • It fits with the HOM design, but 3d mechanical design needed to check for more realistic spaces • total weight about 65 kg • maybe extra shielding below the lumical • Support: should be supported by detector

8. Solenoid Compensation Scheme • Design was optimized at 1st MDI workshop Jan.’17: • eyblow-up 0.3 pm with: L*=2.2m, Bdet=2T, Lumicalbefore 1.25 m and 140 mradangular acceptance from beam axis • This solution increased the angular acceptance from 100 mrad to 140 mrad(only the lumical occupied this extra space) • Detector group requires the angular acceptance of 100 mrad. • This study is underway We have a preliminary solution whereey increases by 0.4 pm (SAD, K.Oidewith field map from M. Koratzinos) Study with code from BINP would be useful as comparison (tool ready, S. Sinyatkin made the study last year) design from FCC WEEK17

9. The IR 3d view with magnets and lumical Actual specifications and longitudinal position of anti-solenoids are of course related to solenoid compensation scheme layout (see previous slide), slight modifications from these numbers occurred screening solenoid radius 200 mm radius 122m Final focus quads Compensating solenoid lumical 2.00 1.99 1.190 1.25 1.074 • detector solenoid dimensions 3.76m ( inner radius) (outer radius 3.818m) × 4m (half-length) • drift chamber at z=2m with 150 mrad opening angle (IDEA design)

10. QC1 design • We have two designs • BINP design: iron yoke twin aperture (superconducting, needs cooling system) • CCT design • More or less same space • We plan to present both design in the CDR • Is design ready for CDR ? • This looks to me still an open question, more details needed especially on the BINP design to assess the feasibility for FCC-ee (questions raised during presentation on the design)

11. BINP designfor QC1 Iron SC coil Stainless vacuum chamber • Questions came mainly for the SC magnet in the warm vacuum chamber, insulation and cooling system, nitrogen screen Nitrogen screen • Pros: • Ordinary production of lenses. • Remaining solenoidal magnetic field in QС1 area is additionally screened by iron yoke of lenses. • No skew components of magnetic field created by lenses. • There is small crosstalk between apertures of lenses. • Cons: • Saturation of iron yoke (nonlinearity) at large gradient. • High order multipole components at quadrupole edges. • No way to introduce high order multipole and skew components of magnetic field to compensate lattice nonlinearity. • Gradient is not large and limited by iron yoke saturation and critical current.

12. Iron yoke twin-aperture quadrupole 2D model BINP design Main parameters: • Max.gradient 100 T/m Length 120 cm • Aperture 4.2 cm • Clear aperture 3cm • NbTi1.4 x 0.8 Saddle-type coils • Permendureiron yoke 70 mm 66 mm Edge of quad close to IP 152 mm

13. QC1 : CCT approach • Pros: • The design can have embedded correctors (x and y dipole correctors, skew quadrupole correctors, etc.) Distance from IP (mm) IP A2 corrector A1 corrector B1 corrector 0.5mm wire, critical current @3T is 300A, physical length ~20cm

14. Orbit errors at the FCC-ee due to the FF quadrupoles displacements (S. Sinyatkin) COD excited by FF quads misalignments correction scheme

15. 3d model of IR pipe Useful design developed for HOM analysis Starting point for the mechanical design, CATIA file imported by S. Pivovarov

17. Concept of HOM absorber

18. SuperkekB HOM estimate much lower (even if higher beam current and lower vacuum chamber)

19. Beam pipe Warm beam pipe could be supported by the detector itself (as CMS) • MATERIAL • Be from about +/-80 cm to accommodate LumiCal • Cuafterwards Be and Cu pipes may be welded togetherbut similar solution to Superkekb using also Ti being considered • DIMENSION • Central beam pipe has 3 cm dia. • Entering and exiting beam pipe through QC1 (3cm dia.) • Pipe size increases to 4cm dia. in QC2 • Size outside QC2 is 7 cm dia. (but 6 cm in plot) • HORIZONTAL MASK TIPS • +/-12 mm radius at Z= +/-2.1 m and +/-5.44 m • +/-18 mm radius at Z= +/- 8.27 m • Vert. 1cm; 5 mm thickness

20. Heat load and Cooling system updated estimate with latest parameter table foreseen We have estimates for previous parameter table (i.e. 2.5 ns bunch spacing): • resistive wall: for copper, ~ 100 W/m • direct SR does not arrive close at IR (stopped before) • e-cloud: for SEY=1.1 ~20W/m, for SEY=1.2 ~200W/m We need cooling system of the beam pipe: • The central Be pipe will be cooled by liquid (paraffineas Superkekb?) • Inside QC1 water cooling within the copper vacuum chamber • SR mask tips will be water cooled • HOM absorbers water cooled • Also ~5mm Gold coating in the central Be pipe discussed and still an open question (coating to enhance conductivity and optimized with detector group), but water cooling necessary in any case

21. Superkekb case

22. Superkekb

23. BPM • 3 BPMs in the IR: • 1 before QC1 • 1 between first and second section of QC1 • 1 between QC1 and QC2 • Special BMPs in IR needed due to space constraint: smaller than standard ones (~1 cm long instead of 4-5cm) BPM-bellows tube • SuperkekbBPMs transversly fixed to the beam pipe, but longitudinally free to move with temperature variations

24. Vibration studies • We have heard what has been done in LAPP for CLIC, ATF2 and plans for studies for FCC-ee • We have heard experience from Superkekb • vibration measurements/model of cryostat • cultural noise • collision and orbit feedback • For FCC-ee similar approach to Superkekb, feedback needed • Vibration motion should be identified for FCC-ee

25. Presented by R. Deng (SINAP)@GM2017@IHEP FCC-ee MDI workshop

26. R&D ACTIVITIES – Vibration control for CLIC takenfrom Lau Gatignon, MDI Status and Plans CLIC Workshop 2017

27. R&D ACTIVITIES – Vibration control for CLIC • Beam trajectory control & mechanical stabilization: 4 nm @ 4 Hz Support tubes Stabilization + prealignement 0,2 nm @ 4 Hz • At the Interaction Point (beam feedback: IPFB +mechanical stabilization), • We aim at 0,2 nm at 0,1 Hz

28. Superkekb Purpose of the vibration measurements To characterize the vibrations • Where is it that vibrates? • Magnets • Magnet supporting table • Floor • Especially in the interaction region (IR) • At which frequency? • Characteristic frequencies • With what amplitude? Will it cause a serious degradation in the machine performance? • Collision tuning (Luminosity), feedback FCC-ee MDI workshop

29. Superkekb Review of what we did at KEKB Vertical: “iBump” system Feedback based on beam-beam deflection, calculated from BPM readings and a set of steering magnets to create a bump at the IP : called “iBump” system Horizontal: “iSize” system Feedback based on LER beam size measured by SRM and a set of steering magnets to create a size (dispersion) bump in an arc section sy ~ 1mm Both 1. and 2. FB systems were looped ~ 1Hz FCC-ee MDI workshop

30. Superkekb SuperKEKB collision feedback • Vertical (offset and vertical angle) • Same as KEKB iBump (beam-beam deflection) • But needs to be a lot faster, up to ~100Hz • Why? Because the beam size is so small, that vibrations could be critical. • Horizontal offset • Beam-beam kick will not be a sensitive parameter for monitoring collision as xx is so small: xx~ 0.0028(e+), 0.0017(e-) • We will adopt “luminosity dither” system such was used by PEP-II. • Size? May be. Especially IF LER & HER vibrate incoherently. FCC-ee MDI workshop

31. IR Vacuum System • Experience from Superkekb discussed • One NEG pump foreseen in the MDI region, between the HOM absorber and the BMP, before QC1. • Remote vacuum connection for FCC-ee has to be worked out Open question yet, need effort

32. 3d Mechanical design • Mechanical design is being started • One week if course not enough to design such a challenging MDI region • More effort is needed, not only to implement the elements, but also to understand how to assemble it, to make it feasible • Also cryostat and remote vacuum connection is to be designed • Superkekb experience is very important for us • The mechanical design provided by BINP will eventually be used also for impedance studies and more realistic simulations • It will be very useful to prove the feasibility of the FCC-ee MDI

33. Conclusions • Last year in 1st MDI workshop main design layout was made: • L*, lumical space, opening angle acceptance, solenoid compensation scheme, vacuum chamber dimension and profile, hom design, … This year we added important elements to the MDI design: • BPMs, vacuum pump, flanges, bellows, water cooling system, vibration studies, orbit correction, luminosity feedback, fast luminosity monitor for machine tuning, cryostat, remote vacuum connection, … • We have a feasible design of the MDI for FCC-ee, consistent for all the operating energies

34. Conclusions-II • There are still some open points being updated, under study or that need to be studied like: • angular acceptance of detector (solenoid compensation scheme) • QC1 design • update on SR and heat load with new parameters • zero angle luminometer for machine tuning • vibration studies (vibration motion should be identified) • special BPMs • shielding outside beam pipe • coating of Be pipe in central region • Effort needed to produce a 3d mechanical design with assembly concept jus started (also to study e.m. forces) • main elements to be added in the design • cryostat to be designed yet (space constraints) • water cooling system • ….

35. Back-up

36. Concerns • Assembly • Remote vacuum connection (ala Belle II)? • Bellows between Central chamber and cryostat chambers (at least 1-2 convolutions) • Central chamber support • Cable and cooling pipe space for central detectors • Vibration control • Cryostat support • Magnetic forces • Anti-solenoids have strong expulsion forces? • Compensating solenoids have strong expulsion force near detector field edge • Overlapping Z space • LumiCal • Cryostat • Remote vacuum assembly • NEG pump • HOM absorbers • Shielding

37. Latest Parameter table D. Shatilov, 19 Jan 2018

38. Scatter rate normalization table

39. Table again with preliminary detector hits * No shielding. With some shielding ~600 † Over 1400 xings ‡ Over 45000 xings From A. Kolano