Rossana Bonomi, Alberto Degiovanni, Marco Garlasché, Silvia Verdú Andrés 5.7 GHz high gradient test cavity

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

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 ?- - precise -? -ADAM lab /Frascati - ? (source availability) When ?- end end 2010 ?- June 2011 ? TERA Foundation

Design overview 4 Accelerating 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

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

RF Design TERA Foundation

Cavities comparison 7 TERA Foundation ° All values in mm ! C-band 1 cell test: NAME NEEDED!!! β Q0Q T0.905 ZTT [MOhm/m] E 0 [MV/m]33 E s,max [MV/m]154 S c,max [MW/mm 2 ]0.708 H max [kW/mm 2 ] E s,max / E P [kW]130 r(E s,max )-r(S c,max ) [mm]0.42

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

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

Cavities comparison 10 TERA Foundation ° All values in mm ! C-band 1 cell test: NAME NEEDED!!! β Q0Q T0.898 ZTT [MOhm/m] E 0 [MV/m]33 E s,max [MV/m]115 S c,max [MW/mm 2 ]0.522 H max [kW/mm 2 ] E s,max / E P [kW]142 r(E s,max )-r(S c,max ) [mm]1.93

Parameter list for test 11 P in [kW] T pulse [μs ] E s [MV/m] S c [MW/mm 2 ] lg(BDR) TERA Foundation

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

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

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

field asymmetry 15 TERA Foundation W S N E

Structural Design TERA Foundation

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 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 ~ mm

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

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

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‰ TERA Foundation E s (MV/m) H max (kA/m) P peak (kW) ΔT (K) ~ ~ 50 Pulsed Surface Heating

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

Tolerances and Tuning TERA Foundation

tolerances partdzdrdf µm kHz 1. top straight± 20± OUTER_CORNer_radius± 20± web± 40± INNER_CORNer_radius± 20± nose angle± 20± OUTER_NOSE_radius± 20± flat_top± 20± INNER_NOSE_radius± 20± beampipe± 20± 10 4 total ± 24 MHz z r 24 TERA Foundation

tuning sensitivity 25 TERA Foundation

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

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 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

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