1. LHC Cryostat evaluation Nikolay Solyak Thanks Rama Calaga, Tom Peterson, Slava Yakovlev, Ivan Gonin C11 workshop. FNAL, Oct 27-28, 2008

2. Agenda Possible CC design for phase I Cryostat location Using LHC 400 MHz cavity cryostat –problems? SBIR phase-I proposal for CC cryostat Helium Temperature 2K vs. 4K LHC requirement for cryostat/cavity

4. Coupler design constrains All couplers are mounted in Horizontal plane (FPC and HOM coupler) or Vertical plane (SOM, LOM) Only one horizontal direction is available for couplers (other is occupied by second beam). It fixes the beam line for CC For ILC-like HOM coupler with side power extraction coaxial line there is no room in cryostat. Need straight line coaxial design like in LHC 400 MHz cavity HOM coupler. Need LHe cooling for all couplers Power coupler : –Power ~ 50kW CW, available from IOT –No needs for tunable design (small beam loading)

5. LHC standard beam-beam distance: 20 cm around P4: special 42 cm (for main RF!), not easy (dog-leg) - Transverse Space: 800 MHz | * OK (*) 800 MHz will NOT do for the real thing:too crooked bunches

6. LHC IP4 location (RF) CC location CC location (second beam)

7. Global Option Location: P4 at (staged) ACN location

8. Tunnel cross-section Coupler position limitations FPC & HOM ??? FPC & HOM Do we have room available for couplers from the wall side?

9. CM Layout (400 MHz cavity) 1496 mm 1130 mm

10. Sub-unit for one 400 MHz cavity Side view Top view WG Variable input coupler Narrow band HOM coupler Broad band HOM coupler Needs 2 cavities (2 units) Port locations are different

11. Flange ports Cover plates Easy access for cavity assembly inside cryostat Cryostat frame

12. Helium circuit in one cavity Gas collector (box) He heater & He level Liquid He Inlet or Gas He Outlet ??? Emergency outlet Coupler Gas He cooling

13. Problems with using of LHC cryostat Port locations not fit present CC design Cryogenic ports not fit as well (?) 2K option is not possible (shielding, cryosystem). Need redesign: support system, alignment, tuner (hopefully partial), … Needs at least 2 sub-units and 2 end-cups  not available. New order is costly  cryostat has complex design and expensive in production. New design probably is more preferable option –SBIR phase-I proposal with AES is under preparation

14. New design constrains Most constrains are defined by CERN requirements and safety regulations (see talk of J. Tückmantel “LHC Integration of a Crab Cavity” an CC mini workshop, CERN, Aug. 21,2008) –CERN Standards –Compatibility –Safety, –Materials for CM and components –Cryogenic and protection from accidents –Vacuum, bake-out, –Radiation –RF components, cables etc. –Alignment –Transportation –Other

15. Questions: Operating temperature: 2  K versus 4  K. 4  K problems: Neither magnetic shield no a heat shield are necessary ! - higher losses in the cavity; - Microphonics from bubles - lower gradient ?  higher number of cavities? Need to be investigated – cavity design, available place for them. 2  K problems: - high pressure; - possible cavity deformation in the case of an accident. Need to be investigated – robust cavity design, helium input, fast valves, etc.

16. SNS experience (805 MHz, pulse regime)

17. 2. Available components? -coaxial lines for the (1-10) kW monopole mode extraction; -Coaxial lines for other couplers ? -Cables and loads for LOMs/HOMs -Frequency tuner. 3. Environment limitations: - position of the dampers and input coupler (vertical, above the cavity, below the cavity; horizontal?) - limitation for longitudinal position of the couplers.

18. Cavity Mechanical Tuner Stepping motor Thermal Shielding (super isolation only) 800 MHz Crab cavity needs Tuner design. Can we adopt an existing design for CC? Is it available from CERN, including control system ?

19. End Cups Super isolation Flanges for beam pipe (in horizontal plane)

20. Cavity Support / Alignment Top View Side View Horizontal Vertical Longitudinal

21. FNAL CRAB CAVITY WITH QUARTEWAVE COUPLERS (alternative compact design) LOM Couplers HOM and FP Couplers Notch-filter for 800 MHz

22. 2D optimization L gap a b R cavity R ap A B FIXED: R cavity =175mm R ap =60mm a, b, A, B, L gap are optimized. H s /H eff L gap, mm

23. V * ┴, MV 2.5 Bpeak, mT 77.4 Epeak MV/m 31.7 R ┴ /Q, Ohms 52.5 * V ┴ = Δp ┴ c/e a 50 b 60 A 50 B 45 L gap 125 D1/D2 147/175 Dimensions (in mm) and main parameters of FNAL Crab cavity D1 D2 F, MHzQR/Q, Ohm 661.238186 664.63712.9 105215001.2 1055151035.2 RESULTS OF FIRST 3D OPTIMIZATION Monopole modes P<2kW P=2.5 kW