1. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG21 Experience with Vertical Electro-Polishing at CEA Saclay Comparison with Horizontal EP F. Eozénou

2. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2011 IHEP WG22 STATUS AT TTC 2011  Commissioning of the VEP set-up  First operation with 1Cell

3. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG23 IMPROVEMENT OF THE INFRASTRUCTURE IN 2012  Working area closed  Tooling for the preparation of the cavity Cathode’s insertion in 9Cells Handling of cavities w/wo He vessel

4. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG24 OPERATION IN 2012 CavityVoltage (V)Acid flow L/minduration (min)Removal rate µm/min 1C21208600.22 1C212081800.25 1AC032082930.33 1AC021281400.16 1AC02883000.15 1C2112898tbd 1AC031281100.27 1AC031281050.26 1AC01I(V)8.5 - 1130 1AC017.511960.39 1AC016.5111840.16 C1-45I(V) 611120 C1-45I(V) 617127 1AC03I(V) 7.5152700.19 1AC037.515-273600.19 TB9R10256.5>20106~0.30 TB9R10256.5>20120<0.30 1AC036243300.16 1AC1625273tbd  19 EP sequences  Running time: 55 hours, no major failure  Trend: V↓ acid flow↑

5. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG25 STANDARD PARAMETERS FOR HORIZONTAL EP  High operating voltage: 14 - 17V →Oscillating current  Acid flow rate: ~ 10L/min  Acid temperature: T<35°C  ω=1rpm  Because of ω, veq=10 -2 m.s -1 → Are these parameters suitable for VEP??? Easy removal of exhaust gases

6. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG26 VEP WITH INNAPROPRIATE PARAMETERS (1Cells) 20V - 8L/min - T<25°C  Very bright surface…  … But fine stripes at  Iris  Equator (upper half cell) 12V <V<20V - 8L/min - 30°C<T<35°C  Local pitting (crown)  Asymmetric treatment Pitting + faster removal! Bubble traces 1C21 1AC3 ! Asymmetric treatment !

7. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG27 POSSIBLE EFFECTS OF HIGH V, HIGH T, LOW ACID FLOW  O 2 generated if V>12V  If flow unsufficient:  Risk of heating (pits)  Risk of unsufficient removal of bubbles  Wider plateau with higher flow rate + low flow at cavity surface (COMSOL)

8. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG28 RF RESULTS WITH INITIAL PARAMETERS 1C21 Cavity  Eacc>30MV/m with high voltage VEP.  Must be improved with optimized parameters.

9. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG29 IMPROVEMENT OF THE PROCESS  Decrease in operating voltage: ~ 6V  No change in performance (demonstrated for HEP)  No risk of O 2. H 2 risk remains  Less sulfur generated  Increase in the acid flowrate: >20L/min  Better removal of bubbles  Less heating in the cavity  Increase in cathode’s diameter (or shaped cathode)  Higher flow at the cavity surface  More efficient bubble removal (less H2/cathode surface)

10. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG210 1Cell VEP WITH NEW PARAMETERS →VEP of 1AC1  Parameters: 6V - 25L/min – 19°C  Bright surface of both half cells  No bubble trace / No pitting  No heating of the acid  No sulfur odour Cavity assembled in Cleanroom. Waiting for VT.

11. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG211 Additional RF RESULT  Better surface achieved  Pits partially removed  In spite of pits, the cavity is tested → Quench at 34MV/m at the pit area (Standard Q-Slope before baking) 1AC3: pits due to unadapted parameters (total 250 µm VEP) → + 60 µm with optimized parameters.

12. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG212 CATHODE’S OPTIMIZATION COMSOL modeling to optimize the shape of the cathode (K. Muller)  Method: Design Of Experiment  Response evaluated: uniformity of the removal (acid flow + electric field)  Parameters:  Shape geometry: cylindrical/ellipsoidal  Shape diameter  Length of the shape  Axis diameter Acid flow modelling with optimized cathode Optimized cathode for 1Cell

13. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG213 VEP OF 9Cell CAVITY WITH OPTIMIZED PARAMETERS 6V - 24L/min - T<25°C Cathode: rod Ø40 mm  ~ 60 µm removed  Heating < +3°C  Very bright surface…  No bubble trace  Brightness improved / previous HEP Promising Result! Treatment of TB9R1025 ILC cavity from (previously H-EP)

14. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG214 TEST PREPARATION  Modification of infrastructure for 9Cell 1.3GHz testing.  Cryostat prepared for test at 1.8K  Delay: Mistake occured during initial test  Final test planned for early December Before/after baking

15. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG215 CONCLUSION  Desirable parameters for VEP are put forward:  Low voltage: 6V  High acid flow  Low temperature  Large cathode  Results observed:  No bubble trace / No pitting  Nice surface finish  Symmetric brightening in the cell  Low heating in the cavity  1Cell and 9Cell treated with new parameters: waiting for test  Eacc>30MV/m with inappropriate parameters  Outlook  increase gradually the temperature and acid flowin coming treatments to increase the removal rate  VEP of SPL cavities in early 2013

16. CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG216 THANK YOU FOR YOUR ATTENTION