Fermilab HG cavity and coupler R&D

Transcription

1 Fermilab HG cavity and coupler R&D Motivation HOM calculations Nikolay Solyak Fermilab Outline Main Coupler and HOM dumping Multipactor Lorentz Forces Single bunch beam dynamics Summary Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

2 RE & HG cavities with a new shapes: LL and RE cavities Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

3 Motivation for the cavity with gradient higher than 25 MV/m? ILC Workshop, KEK, Dec Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

4 Example LL cavity: Epeak/Eacc = 2.36 Epeak=85 MV/m at Eacc=35 MV/m; Achieved: Cornell (RE)=100 MV/m JLAB (LL)= 90 MV/m J.Sekutowicz SLAC, Jan.25,2005 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

5 TESLA vs. Reentrant cavity DESY Eacc ~ 40 MV/m Cornell Univ. Eacc = 47 MV/m Q=10 10 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

6 R&D needs for LL &RE cavity design. s s s s s s Cavity optimization for fundamental mode Monopole High Order Modes (cryogenic losses) Dipole HOM s (R/Q, field distribution, trapped modes, etc.) Multipactor studies Mechanical properties: Detuning due to Lorentz forces, stiffening rings. Mechanical resonances, Vibrations Main coupler (position, coupling,...) Fabrication, Hydroforming, Processing, Cleaning, Tuning, Testing, Cost Wake fields (incl.coupler) and beam dynamics in Linac Etc FNAL All calculation need cross-check Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

7 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

8 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

9 Trapped modes in 5 th passband TESLA cavity LOW LOSSES cavity Asymmetric ends can help to improve dump HOM s in LL cavity (as TESLA) Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

10 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

11 (from J.Sekutowicz presentation Jan,2005) Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

12 New idea for Fundamental / HOM couplers 40mm 60 mm 30mm 30mm 82 mm F, MHz Qext Rsh/Q mode E+05 Ω/m/m M E D E D E D E D E D E D E D E D E D E D E D6 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

13 1000 Hsurf H in surface 100 Log scale 10 L, mm Linear scale Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

14 AMAC SBIR Coupler Project Two prototypes were built and tested at DESY Three new concept designs for the possible use with ILC cavities and cryomoduls are being developed with Fermilab, DESY and CPI. See WG5 presentation: AMAC s R&D Efforts for ILC High RF Input Couplers and High Gradient Cavities. Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

15 TESLA cavity. Secondary electrons LL cavity. Secondary electrons Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

16 Lorentz forces LL mid-cell No stiffening Stiffening ring at R=43 mm Stiffening ring R stiff =43mm Surface deformation STRESS Surface deformation RE mid-cell R=64mm No stiffening Stiffening ring at R=64mm Stiffening ring Surface deformation Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

17 Lorentz forces (2) Lorentz force detuning vs position of stiffening ring. Lorentz force detuning vs. wall thickness KL [Hz/(MV/m)^2)] Re-entrant Low Losses TESLA Radius of stiffening ring (mm) KL [Hz/(MV/m)^2)] Re-entrant Low Losses Wall thickness (mm) TESLA(wall=2.8mm) F(wo/w ring) = - 801/-463 Hz for 25 MV/m Low Losses(2.8mm) F(wo/w ring) = - 871/-509 Hz for 25 MV/m Re-entrant(2.8mm) F(wo/w ring) = - 860/-517 Hz for 25 MV/m Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

18 Emittance Growth in Linac with HG cavities (RE or LL) Nominal conditions: Quad,cavity,BPM offset: 300 µm Quad roll 300 µrad Cavity pitch 300 µrad CM offset: 200 µrad CM pitch: 200 µrad BPM resolution 1 µm 1:1 steering DFS Emittance growth, (nm) TESLA BNS off / on RE- entrant BNS off / on Low Losses BNS off / on DFS mean (100seeds) 6.53 / / / DFS 90% 9.27 / / / :1 mean 470 / / / 472 1:1 90% 390 / / / 515 Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

19 Beam dynamics in Linac with LL cavities No bumps Specification Autophasing needs to reduce banana effect in IP Not optimized for LL and RE cavity (used the same as for TESLA) Need more optimization for HG cavities (quad spacing, nominal conditions) Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

20 Effect of cavity misalignment DFS BNS=off Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,

21 SUMMARY The first results of design studies and experimental tests on HG cavities with a new shape (LL and RE) look promising to consider one of this cavity design for ILC. Needs more detailed studies of HOMs and clear specifications for Q ext from multi-beam dynamic studies. Developing a new ideas for Fundamental and HOM Coupler for higher reliability and cost saving (?). Emittance growth is slightly over specification, but might be reduced by farther lattice optimization, using emittance bumps and revising of misalignment tolerances. Need more efforts and support in developing HG cavities. Nikolay Solyak 2 nd ILC Workshop, Snowmass, Aug 14-18,