1. Rossana Bonomi, Alberto Degiovanni, Marco Garlasché, Silvia Verdú Andrés 5.7 GHz high gradient test cavity 16 - 06 - 2010

2. 2 Outline - High gradient test goals and program - RF design - Structural design - Tolerances and tuning - Open issues TERA Foundation

3. TERA high gradient program 3 S-band single cellC-band single cellC-band mini-tank Why ?- find operation limit in S-band - scaling law ? - find operation limit in C-band - scaling law ? - bd craters distribution (cut 1 cavity) - test cyclinac structure with high gradient - feasibility of C-band modules Where ?- pre-test @CTF3 - precise test @PSI? -? -ADAM lab /Frascati - ? (source availability) When ?- end 2010- end 2010 ?- June 2011 ? TERA Foundation

4. Design overview 4 Accelerating cell @ 5.7 GHz (two unsymmetrical half cells) RF H-coupling system (waveguide, short circuit) Connection to data acquisition (through CF flanges) Cooling system (3 plates, in-out pipes) TERA Foundation

5. power source 5 TERA Foundation VE2098 – Tunable C-band Magnetron Output Power2.5MW Frequency5707-5717MHz Pulse duration4.0µs Duty cycle0.08%- frequency tuning2MHz/turn

6. RF Design TERA Foundation

7. Cavities comparison 7 TERA Foundation 7.47 18.8 1.5 2.0 1.0 17.39 15.8 25° All values in mm ! C-band 1 cell test: NAME NEEDED!!! β0.7163 Q0Q0 9305.7 T0.905 ZTT [MOhm/m]128.73 E 0 [MV/m]33 E s,max [MV/m]154 S c,max [MW/mm 2 ]0.708 H max [kW/mm 2 ]0.0858 E s,max / E 0 4.656 P [kW]130 r(E s,max )-r(S c,max ) [mm]0.42

8. separate E max and S c,max 8 TERA Foundation Flat Nose Inner Nose Radius Outer Nose Radius

9. separate E max and S c,max 9 TERA Foundation Power and Surface Electric Field scaling: E 0,norm =33 MV/m

10. Cavities comparison 10 TERA Foundation 8.0 18.8 1.5 3.0 1.0 3.0 1.0 17.34 15.8 20° All values in mm ! C-band 1 cell test: NAME NEEDED!!! β0.7163 Q0Q0 9245.93 T0.898 ZTT [MOhm/m]116.29 E 0 [MV/m]33 E s,max [MV/m]115 S c,max [MW/mm 2 ]0.522 H max [kW/mm 2 ]0.0888 E s,max / E 0 3.484 P [kW]142 r(E s,max )-r(S c,max ) [mm]1.93

11. Parameter list for test 11 P in [kW] T pulse [μs ] E s [MV/m] S c [MW/mm 2 ] lg(BDR) 24221500.89-13.3 43022001.58-9.5 67222502.47-6.6 96723003.55-4.3 131623504.84-2.3 171924006.32-0.5 TERA Foundation

12. mesh 12 TERA Foundation Max. element length for: Cell………………... 3 mm Coupler …………. 2 mm WG ……………….. 10 mm Max. surf. deviation for: Cell……………… 0.01 mm Coupler ……… 0.01 mm

13. cavity parameters 13 TERA Foundation Frequency [GHz] 5.712 ZTT [MOhm/m] 116 df/dR [MHz/mm] -140 Coupling coefficient  1.5 ±0.05

14. slot dimensions 14 TERA Foundation Coupler mm Length S L 17.65 Width S W 3.80 Depth S D 5 Short-circuit

15. field asymmetry 15 TERA Foundation W S N E

16. Structural Design TERA Foundation

17. 17 Struct. design: halfcells Øcell [mm]34.68mm coupling slot [mm]17.65 x 3.8 inner cavity profilegeometry tolerance = ±10 μm roughness = 0.4 Ra materialC10100 copper C_factor = 1.5 Tuning range ≈ 20 MHz Two unsymmetrical halfcells: - easier brazing - no spikes in slot Outer dimensions: 48.9 x 45.9mm TERA Foundation

18. 18 Struct. design: halfcell #1- tuning Small cell diameter and brazing position do not allow controlled dimple tuning Presence of tuners in standard linacs for med. treatment TERA Foundation Tuning done through 3 tuners diametrically inserted in cavity. Ø tuners ~ 2 - 3 - 4 mm

19. 19 Struct. design: halfcells’ brazing Enlarged flanges (CF 34/16) for structural resistance during brazing (Ø ext = 39mm) TERA Foundation

20. 20 Struct. design: waveguide+flanges Waveguide: - WR 187 thickwalled (ID : 1.872 x 0.872 in – OD: 2.122 x 1.122 in) - C10100 copper Flanges: - FDP48-FDM48 standard* - 316LN stainless steel Brazing: TERA Foundation

21. 21 Struct. design: cooling plate Pp (kW) f rep (Hz) t pulse (us) Duty cycle Pav (W) Gtot (l/min) Nº circØ eq (mm) 2000<1004<0.4‰8001135.5 TERA Foundation E s (MV/m) H max (kA/m) P peak (kW) ΔT (K) 260210700~ 20 4003301700~ 50 Pulsed Surface Heating

22. 22 Struct. design: cooling plate C10100 Copper Tuners  covering plate 316L stainless steel with Ni+Cu coating TERA Foundation

23. Tolerances and Tuning TERA Foundation

24. tolerances partdzdrdf µm kHz 1. top straight± 20± 10 -1661 2. OUTER_CORNer_radius± 20± 10 -3089 3. web± 40± 10 -7304 4. INNER_CORNer_radius± 20± 10 -727 5. nose angle± 20± 10 -191 6. OUTER_NOSE_radius± 20± 10 9496 7. flat_top± 20± 10 128 8. INNER_NOSE_radius± 20± 10 1793 9. beampipe± 20± 10 4 total ± 24 MHz 1 2 3 4 5 6 7 8 9 z r 24 TERA Foundation

25. tuning sensitivity 25 TERA Foundation

26. field asymmetries 26 TERA Foundation 3 tuners: Ø = 3-3-4 mm penetration = 3 mm Δf = + 22 MHz

27. Open Issues 27 Prototype components: any info on FDP-FDM standard Test components: advice on instrumentation needed, dimensions, weight, C to S band transition… Faraday cup Optical spectrum analyzer Thermal sensors, flowmeter, manometer.. RF pick-up Further tests: Two more prototypes brazed @ 1040˚ under Nitrogen, need support on: o geometry definition (holes, thicknesses, stresses & deformations) o production process definition (tolerances..) o brazing process definition (process sponsoring, brazing material, logistics..) TERA Foundation

28. acknowledgments Thank you for all advice, discussions and help for our project Thank you for scheduling our meeting today to be continued…. 28 TERA Foundation