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

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

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

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 1C C AC AC AC C tbd 1AC AC AC01I(V) AC AC C1-45I(V) C1-45I(V) AC03I(V) AC TB9R >20106~0.30 TB9R >20120<0.30 1AC AC tbd  19 EP sequences  Running time: 55 hours, no major failure  Trend: V↓ acid flow↑

CEA DSM Irfu 11/06/2016- F. Eozénou - TTC Meeting 2012 JLab WG25 STANDARD PARAMETERS FOR HORIZONTAL EP  High operating voltage: V →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

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 !

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)

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.

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)

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.

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.

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

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)

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

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

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