Third Harmonic Cavity Status

Transcription

1 Third Harmonic Cavity Status General parameters Cavity design Main coupler calculation HOM analysis and HOM coupler design Lorentz Forces and Stress analysis Summary

2 General parameters Third harmonic cavity (3.9GHz) was proposed to compensate nonlinear distortion of the longitudinal phase space due to cosin-like voltage curvature of 1.3 GHz cavities. Parameter List for 3.9 GHz 9-cell cavity: Number of cavities Active Length Gradient Phase R/Q E peak / E acc B peak (E acc =15 MV/m) Qext BBU limit for HOM, Q Total energy Beam current m 14 MV/m -179 deg 780(750) Ω T 9.5e+5 <1.e+5 20 MeV 9 (12) ma Steps to build 3 rd harmonic cavity: Cu model Main Coupler HOM coupler Nb model He vessel with tuner Cryostat

3 Cavity with increased end-cell iris (30 40mm) Axis E z -field

4 Cups production and QC measurements Dies for mid-cell (Rutgers Univ) Dies for end-cell (delaed) 2+6 (+20) Cu cups 4 (+2) Nb cups Mechanical and RF QC done on each step

5 Dumbells Carbon support is used for aligning and brazing of cups Two dumbells brazed in vacuum furnace (65Cu/35Au)

6 Nb cups production 36 Profile of Nb #1 cup NB#1_A design NB#1_D Produced 4 Nb cups 2.8mm thickness for welding test (Oct.11,2002) Blanks for 2 more cups to check profile and RF QC, then anneal and re-stamp.

7 Mechanical and RF quality control CELL BA Design Measured profile of Cu cell#b vs. design Copper Cups #A,#B, # Stamped and coined 2. Mechanical and RF QC 3. #1-6 Annealed, re-stamped, re-coined 4. Mech and RF QC, facing 5. Brazed 2 dumbbells: (1-2) and (4-5) R, mm Cell_1, annealed and re-stamp Cell_1A design cell_1c Z, mm Results of RF measurements Design F0= F π =3900 #B Stamped, Coined F0= F π = HFSS calculation F0= F π = #1 Annealed St&Coined F π = F0= HFSS calculation F0= F π = Brazed dumbbells: (#1-#2) F0= F π = (#4-#5) F0= F π = (1-2)+(4-5) F0= F π =3883.2

8 RF and mechanical QC RF set-ups Cups and dumbell RF QC, (fundamental and HOM modes) Plunger measurement and cavity tuning (CKM set-up upgrading) Bead-pull measurements (NLC set-up) Frequency tuner

9 Main Coupler Design P=12.5 kw DESY type window in coax 30mm/13mm S11=0.01 S11=0.03

10 Coaxial coupler (HFSS simulation) Designed value: Q_ext = 9.5 e+5 Coax geometry: =30mm, Z=50 Ω, antenna -5mm inside tube. Second antenna (from right) is used as pick-up. Most calculations for 3cell geometry. After optimization checked for 9-cell. (Q 9cell = 3*Q 3cell ). Cylindrical antenna provides designed Q ext for L=20mm Capacitive antenna can reduce Q. L=20mm Q_ext=4.8e+5 L 7 Qext for DESY (red) and FNAL(blue) designs S12 (Tip = 1 mm) Freq, GHz Qext, 10^ Q ext vs. antena tip (9 cell cavity) Tip, mm Q ext, E Q ext, E Distance from cavity, mm

11 Waveguide type coupler HFSS model dw opt =20mm

12 High Order Modes (HFSS simulation) 50 Transverse (R/Q) (HFSS) R/Q,[Ohm/cm^2] EE-boundaries MM-boundaries Frequency, MHz

13 HOM coupler design HOM coupler design proposed by J.Sekutowich (scaling of TTF design). FNAL re-calculate and optimized this design (Initial design had 3.32 rejection frequency) Rejection 3.9GHz

14 Cavity excited by the beam (2mm off-set) Qext=1e+6 Monopole, Q=2.5e4 2 nd dipole band Qext<1.e+4 3 nd dipole band Qext<1.e+4 Tube

15 Frequency shift due to Lorentz forces HFSS simulation of half cell P= (µ 0 Η 2 ε 0 E 2 )/4 data exchange (HFSS- ANSYS) ANSYS simulation of stresses in half cell different wall thickness Yung modulus, Poisson's ratio Frequency shift due to Lorentz force (Slater s Theorem) 2 2 F = 1/(4W) F ( ε 0 E µ H ) dv V 0 Thickness (mm) F (Hz) Displacement of the cell wall due to Lorentz force. Wall thickness T=1.5 mm.

16 Summary Cavity design Start production of cups, dumbells, tubes, couplers Mechanical and RF QC for production feed-back Tooling and RF set-ups in progress Main coupler Calculation done Design in progress HOM analysis and HOM coupler design HOM analisys in progress HOM coupler model designed, procurement in progress (delivery Nov, 2002) Lorentz Forces and Stress analysis done. Thanks our team: H.Edwards, T.Khabibouline, I.Gonin, M.Foley, D.Mitchell, L.Simmons, E.Borrisov, I.Terechkin. For help: V.Yarba, D.Finley,L.Bellantoni,D.Snee, T.Arkan, H.Carter, C.Boffo, B.Smith, A.Rowe, T.Nicol.