ss medium beta prototype cavities CEA SaclayESS ECCTD WU Cavités Enrico Cenni S Berry on b ehalf of E Cenni PAGE 2 Cavities status Latest results RF tests Preparation BCP and tuner test ID: 1015766
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1. Progress and status on ess medium beta prototype cavitiesCEA Saclay/ESS ECCTD WU Cavités| Enrico CenniS. Berry on behalf of E. Cenni
2. | PAGE 2Cavities statusLatest results (RF tests)Preparation (BCP and tuner test)Manufacturing Lessons learnedSummaryOUTLINE
3. Cavities statusCavitiesStatusDetailsMP01Ready for string assemblyIn clean room assembled with power couplerMP02Ready for string assemblyIn clean room assembled with power couplerMP03Final vertical testEquipped with helium tankMP04Final BCP-Vertical testEquipped with helium tankMP05Ready to test BCP with different setupWill be sent to Zanon for integrationMP06Sent to Zanon for BCP and integrationWe need the tank and bellow borrowed to LASA to finish the integration4 cavities equipped with helium tank, 2 cavities already equipped with power coupler.Soon we will be ready for the first string assembly. See T. TRUBLET on Tuesday
4. Latest results (Q-E)D. RoudierL. Maurice
5. Q versus E and X rayMultipacting or FECav P01 and Cav P02 : same MP barrier behaviourCalculation gives MP activities from 8-12 MV/mNeed for HPR nozzle optimization (act.Hb)| PAGE 5
6. Latest results (RS)P01P02R0 [nΩ]3.16Δ [K]18.5819.01Eg [eV]1.61.63 Fitted withD. RoudierL. Maurice@ 1MV/m
7. Latest results (cavities+ FP couplers)2 cavities assembled with input couplersMP01MP02A. BouyguesC. Boulch
8. Influence of the cavity ends@ 1MV/mCav P01 : 2 beam pipe extensionsCav P02 : 1 beam pipe extension & 1 blind flangeCav P03 : 2 blind flangesNo field on the ends for cav P01 lower Rs| PAGE 8D. RoudierL. Maurice
9. temperature curve features (naked cavity) no exterior coolingWater rinsingAcid flow stop and pumped out Acid touch the cavity surface ~ 2 °C/min~0.2 °C/minAcid tank temperature~0.2 °C/minBCP reaction produces about 2kW, we are able to cool down only 1kW in the acid tank.X. HanusC. Servouin
10. | PAGE 10Bcp with helium tank and water coolingAcid enter the cavityAcid fill up the cavityBCP finishedCavity emptyCavity full of waterWe are able to limit the temperature increase during BCP.Same duration but T < 12°C
11. Tuning| PAGE 11Passband mode frequencies in vacuum while moving the tunerBlue 10 turns pull (~1mm)Orange 0 turn (blocked before pumping)Tuning sensitivity:PullingReleasingComputation predict 211kHz/mm measured value is between 210-212 kHz/mmD. RoudierE. Jacques
12. Field flatness and HOMsCavity Field flatness are consistently brought to 95%, heat treatment and tank integration can change the field flatness about 1-2% depending on the accumulated stress on the cavity.HOMs are monitored during manufacturing and they are away from machine lines as designed (typically more than 20MHz)TE modesNote: each BCP moves the dangerous TM mode more away from machine lineTM mode
13. Lessons learned| PAGE 13Manufacturing process looks to be reproducible and reliable (learning curve shall be took into account), still there is space for improvement non rotatable flange : safe because Maximum angular displacement 0.5° (average is 0.2°))Tuner blocks on helium tank: make the fabrication simple to get reproducible tolerancesBCP temperature shall be monitored, water cooling proof to be effective with integrated cavity (recently we were able to obtain very low Rs)Frequency change rate with BCP is about 2.9kHz/µm and the average etching rate is about 1µm/min with 1:1:2.4 mix (FNP)Heat treatment at 600°C for 10 hours works fine to remove the hydrogen (US rinsing and/or Ethanol cleaning give same results)
14. Summary and outlook| PAGE 14We have successfully manufactured 6 medium cavities, 4 of them are now equipped with helium tank.Two cavities has been successfully assembled with power couplers, they are ready for the string assembly.Q-E curves are above specifications even with field emission. We are improving HPR procedure in order to avoid future issues.Finally we identified a preparation procedure for medium beta cavities (still some minor improvement is needed for HPR)§Cavity MP03 with tank is on the vertical insert and will be tested this weekSee also “Prototype Experience SRF Cavities for ESS” by Christine DARVE
15. | PAGE 15THANK YOU FOR YOUR ATTENTIONThanks to: D. Roudier, L. Maurice, X. Hanus, F. Peauger, P. Bosland, C. Madec, F. Eozenou, C. Servouin, Y. Boudigou, G. Monnereau, E. Jacques, G. Devanz .
16. Commissariat à l’énergie atomique et aux énergies alternativesCentre de Saclay | 91191 Gif-sur-Yvette CedexT. +33 (0)1 69 08 xx xx | F. +33 (0)1 69 08 99 89Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019| PAGE 16BACK UP SLIDES
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18. Medium beta Cavity parametersLFD [Hz/(MV/m)^2]ZanonIDEAL*Fixed ends-0.7796-0.735Free ends-21.98-23.35Stiffness [kN/mm]ZanonIDEAL*1.3621.286Tuning sensitivity [kHz/mm]ZanonIDEAL*211.26214.83Pressure sensitivity [Hz/mbar]ZanonIDEAL* (1 mbar applied)FIXED ENDS18.0123.08FREE ENDS-417.35-364.94
19. One cell temperature distributionX. Hanus54321ΔT≈10°CΔT≈15°CAcid Flow
20. Fluid dynamics Simulation resultsAcid speed [mm/s]Acid speed and velocity [mm/s]Inflow 20 l/minTemperature [°C]
21. Vertical test resultsTargetLeak+field emission
22. Surface resistance| PAGE 22ProcessRs @2K [nΩ]BCP ~200µm205Heat treatment+HPR20HT+BCP ~20µm10BCP 200µmHT+HPRHT+BCP 20µm
23. Cavities details| PAGE 23 MediumHighGeometrical beta - bgeom0.670.86Frequency [MHz]704.42Number of cells65Operating temperature [K]2Maximum surface field in operation [MV/m]4044Nominal Accelerating gradient Eacc [MV/m] 16.719.9Accelerating length Lacc = (ncell.bgeom.l/2) [m]0.8550.915Nominal Accelerating Voltage Vacc = (Eacc x Lacc) [MV] 14.318.2Theoretical RBCS (1) at operating temperature [nW]3.2G [W]196.6241Q0 at operating temperature for RBCS6.14x10107.53x1010Q0 at nominal gradient> 5 x109Cavity dynamic RF heat load [W]4,96,5Qext7.5x1057.6x105Iris diameter [mm]94120Beam tube diameter [mm]136140Cell to cell coupling k [%]1.221.8p and 5p/6 or 4p/5 mode separation [MHz]0.541.2Epk/Eacc at bopt2.362.2Bpk/Eacc [mT/(MV/m)] at bopt4.794.3Maximum r/Q [W] at bopt394477r/Q [W] at bgeom367435Optimum beta bopt0.7050.92Stored energy [J] at nominal Eacc and bopt 117.3156.9RF Power Pfwd [kW] with power coupler at Qext and bgeom (2)185250
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25. Manufacturing (medium betas)We have created a dimension control plan on each subparts300 points on each halfcells and dumbbells RF surfaces with CMM On the integrated cavity we put about 80 dimensional controls (this will be optimized after string assembly feedback)Some number related to the first 4 integrated cavities:Maximum displacement between beam flanges 1mm (average is 0.6mm)Maximum angular displacement 0.5° (average is 0.2°)optional
26. Frequencies (simulation)Calculation agrees well with measurements Tuner system is very close to fix ends conditionoptional
27. Manufacturing (high beta)High beta manufacturing has started, we plan to receive the first cavity in AugustWe tried to simplify the manufacturing process along with the preparationTank integration will be done with closed cavity in order to preserve RF surface and possibly avoid the final BCPHelium tank preparation showed to be challenging especially on the tuner side, we are putting in place a new procedure with the manufacturer to make the process more reliable Out of scope