1. Vertical Electro-Polishing activities at CEA Saclay
F. Eozénou
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

2. CONTEXT
Provide an efficient tool for surface treatment of different types of cavities
ILC Hi-Grade Program
Treatment and test of 9-Cell cavities
Surface treatment for large proton cavities
Ø382mm L>1430mm 1,76 m L
(Tesla: Ø=211mm L=1283mm)
β = 1 cavity Eacc = 25 MV/m
Need for an efficient surface treatment→ Choice for Electro - Polishing
+ (optionnal) EP for β = 0.65 cavity Eacc = 19 MV/m
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

3. PREVIOUS TASKS Design of the set-up
Detailed engineering study: subcontracted
Modelling of the process (COMSOL)
Acid flow
Electric field
Fluid velocity m/s
Example of fluid modelling with alternative shape
VEP WITH CIRCULATING ACID SHOULD NOT BE CELL DEPENDENT
NEED TO USE SHAPED CATHODE WITH ELECTRIC INSULATION AT IRIS
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

4. SET-UP IN JULY 2011 Almost complete but some utilities not connected
Tests with circulating water >30L/min: OK
Agreement of local safety authorities to run the system
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

5. SET-UP IN NOVEMBER 2011
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

6. COMPLETED SET-UP Ventilated cavity cabinet H2 detection
Automated process
HF scrubber
N2 blowing in cavity
Ventilated acid cabinet
Ventilated acid transfer area
H2 detection
N2 blowing in tank
AUTOMATED PROCESS PILOTED THROUGH TOUCHSCREEN
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

7. DETAILS OF THE SET-UP N2 out Acid out N2 in Level sensor Acid in
HF scrubber
N2 out
Acid out
N2 in
Level sensor
Acid in
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

8. FIRST VEP WITH 1Cell Parameters for 1st VEP sequence: - 3 hours VEP
- Shaped and masked cathode
- 8 L/min acid flowrate, Nitrogen blowing (12L/min)
- 20 V
- Temperature < 26°C
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

9. PRELIMINARY RESULTS
Current oscillations observed (similar to horizontal EP)
Brightening of the surface in all the cell achieved
No difference between upper and lower parts of the cell
No (obvious) trace due to bubbles at the cavity surface
→ HPR and cavity assembly
→ Cavity under baking at Saclay (Ar 3h-145°C)
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

10. HORIZONTAL VS VERTICAL
1Cell Horizontal EP at Saclay: Good feedback for comparison:
Benefits from VEP: operator friendly!
no flaw observed during the first VEP sequence
easy preparation of the cavity (time saved + security)
more efficient rinsing procedures
very stable process
→ Adapted to industry
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

11. OUTLOOK VEP of single-cells VEP of 9-cell cavities
Qualification of the set-up
Find optimized parameters
Impact of alternative cathode for VEP (uniformity of polishing)
VEP of 9-cell cavities
ILC Cavity from Fermilab (No He vessel)
Tesla cavity (with He vessel)
Understanding of the process
Comparison Model / achieved results (Nb removal / uniformity)
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

12. CONCLUSION Set-up ready for the chemical treatments
Operator friendly process
Adapted to industrial purpose
Stable process
Brightening of the surface achieved
RF test of cavities to be performed
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2

13. THANK YOU FOR YOUR ATTENTION
12/04/2018
- F. Eozénou TTC Meeting 2011 IHEP WG2