cavities CEA SaclayESS ECCTD WU Cavités Enrico Cenni E Cenni on behalf of the CEAESS group temperature data from XHanus PAGE 2 BCP system setup Motivation Temperature measures ID: 1015767
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1. Buffer chemical polishing study on ESS medium beta cavitiesCEA Saclay/ESS ECCTD WU Cavités| Enrico CenniE. Cenni on behalf of the CEA-ESS group(temperature data from X.Hanus)
2. | PAGE 2BCP system setupMotivationTemperature measuresVertical test resultsSummaryOUTLINE
3. ESS MEDIUM BETA PROTOTYPES2 medium beta prototype (fine grain high purity Niobium)Cavity dataSurface1.8 m2Volume67 litersLength1258 mmEquator diameter370 mmIris diameter94 mm# cells6Frequency704.42 MHzCEA is involved in the design and prototyping for ESS medium and high beta elliptical cavities.The cavities will be installed into a prototype cryomodule.
4. BCP SetupBCP integrated system:200 liters acid tankHF/HNO3/H3PO4 1:1:2.4Flow: 20 l/minAcid flow
5. J. Halbritter, P. Kneisel, K. Saito. SRF93.Motivation Q-disease Still present after warm up No difference with faster cooling rateHydrogen diffusion during BCP? Need to optimize the BCP process for the pre-series
6. Some improvementIncreased the length of the acid tank cooling line.External tube to pre-cool the cavity.Temperature sensors on the external surface.
7. temperature curve featuresWater 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 remove only 1kW in the acid tank.Viscous layer formation?
8. One cell temperature distributionX. Hanus54321ΔT≈10°CΔT≈15°CAcid Flow
9. Thickness measurements Average removal ≈50µmRatio between top/bottom removal≈ 3-4Max=110µm, min=20µmAcid FlowThickness measurements performed by ultrasoundF. EozenouC. Servouin
10. Fluid dynamics Simulation resultsAcid speed [mm/s]Acid speed and velocity [mm/s]Inflow 20 l/minTemperature [°C]
11. Vertical test resultsTargetLeak+field emission
12. Surface resistance| PAGE 12ProcessRs @2K [nΩ]BCP ~200µm205Heat treatment+HPR20HT+BCP ~20µm10BCP 200µmHT+HPRHT+BCP 20µm
13. Summary and outlook| PAGE 13 We can’t control the temperature rise during the BCP without an external cooling Equip the cavity with a water tank? External tube? Bigger acid tank?We have observed a temperature gradient across the cell (looking for explanation).Viscous layer formation?Gas bubble formation? ~~~Analysis of polished and treated sample (similar to cavity) by SIMSTest of the second prototype (BCP with acid temperature <15°C)
14. 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 14THANK YOU FOR YOUR ATTENTIONThanks to: X. Hanus, F. Peauger, P. Bosland, D. Roudier, C. Madec, F. Eozenou, C. Servouin, Y. Boudigou, G. Monnereau, T. Hemelin, J.P. Poupeau, Y. Gasser.
15. 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 15BACK UP SLIDES
16. Vertical testsTargetQ disease curves
17. Medium beta cavity| PAGE 17 ParameterValueGeometrical beta - bgeom0.67Frequency [MHz]704.42Number of cells6Operating temperature [K]2Maximum surface field in operation [MV/m]44Nominal Accelerating gradient Eacc [MV/m] at bopt 16.7Accelerating length Lacc = (ncell.bgeom.l/2) [m]0.855Q0 at nominal gradient>5.109Cavity dynamic heat load [W]4,9Qext7.5 105Cell to cell coupling k [%]1.22p and 5p/6 (or 4p/5) mode separation [MHz]0.54Epk/Eacc 2.36Bpk/Eacc [mT/(MV/m)]4.79Maximum r/Q [W] at bopt394Optimum beta bopt0.705G [W]196.63 6 prototypes will be built, 4 will installed in the cryomodule 2 cell shapes (central cells and end groups)
18. SIMS surface analysis (Argon beam)| PAGE 18Ar+Nb+NbO+NbO2+Na+Ti+TiO+Fe+FeH+Ar++Ca++