# Presentation: 6HJF7EV5TBW44YKZNWRTEWCV6UYKQC44

## DESIGN OF A NEW 

**SET-UP AT CEA SACLAY FOR**
** ****VERTICAL ELECTRO-POLISHING (VEP)**

**F. Eozénou**

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## OUTLINE

- CONTEXT
- TECHNICAL CHOICES FOR VERTICAL EP SET-UP
- CHALLENGES AND R&D RELATED TASKS

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## CONTEXT

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## β = 1 cavity   Eacc = 25 MV/m 

- β = 1 cavity   Eacc = 25 MV/m
- Need for an efficient surface treatment→ Choice for Electro - Polishing

- (Tesla: Ø=211mm L=1283mm)

- Ø382mm   L>1430mm  1,76 m2     88L

- + (optionnal) EP for β = 0.65 cavity    Eacc = 19 MV/m

- ILC Hi-Grade Program
- 8 Tesla Shape cavities to be treated (final step) and tested at Saclay: Final VEP + Rinsing + Test

- Surface treatment for large proton cavity

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## WHY VERTICAL EP?

- EP PROMISING FOR HIGH GRADIENTS
- HORIZONTAL EP NON SUITED FOR LARGE CAVITIES
- SIMPLER PROCESS
- EFFICIENCY OF VERTICAL EP DEMONSTRATED FOR TESLA-SHAPE 9CELL CAVITIES (CORNELL UNIVERSITY).

- ILC-CAVITY EP PARAMETERS NON SUITED TO SPL CAVITIES?
- CAVITY FULL OF ACID (Vs HALF-FILLED for horizontal EP)
- SUPERFICY OF THE CAVITY x2
- ~15 kW TO DISSIPATE?  (17V)

- VEP Parameters must be considered carrefully...

- + see Presentation by G. Hoffstaetter and Z. Conway

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## BENEFITS FROM PREVIOUS CARE SRF PROGRAM

- ALTERNATIVE EP PARAMETERS TESTED: WP 5.1 EP ON 1-CELLS

- EP @ LOWER VOLTAGE (5V) INVESTIGATED
- NO HEATING OF THE BATH
- GOOD RF PERFORMANCE
- LESS IMPURITIES

- 5V Vs 17V on 1DE1

- Pristine 1C21 after 150 μm EP

- COMPARABLE RESULTS WITH 5V ELECTRO-POLISHING

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## + LESS IMPURITIES AT LOWER VOLTAGE

- →Two Niobium samples electro-polished at 5V and 20V for a similar heavy removal with 1-9-1 (HF-H2SO4-H2O) Mixture

- Sample A, 20 Volts:
-  9.18g removed

- Sample B, 5 Volts:
- 9.11g removed

- Visible contamination for Sample A
- → We have compared impurities found in electrolytes A & B

**+ LESS IMPURITIES AT LOWER VOLTAGE**

- ~ X2 Impurities in A Mixture

- Presented at TTC 2008 & SRF 2009

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## TECHNICAL CHOICES FOR VERTICAL EP SET-UP

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## DETAILS OF THE SET-UP

- Circulating Acid
- Acid flowrate: 0-40 L/min
- Acid cooled thanks to heat exchanger inserted in the acid tank
- Nearly all piping in PFA
- Hydrogen diluted in Nitrogen flow
- Will for set-up with two storage acid tanks
- Mix VEP and BCP
- Mix Chemical treatment and rinsing recipe
- Use different electrolytes composition
- Cathode introduced in horizontal configuration
- → need for a dedicated bench
- Automated Process
- Data Monitoring (temperature, intensity, voltage, flowrate)
- Power Supply: 0-20V 2250A  (tbc)

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## Tank Acid1

- Rinsing Cavity

- Filling for tank

- Water for cooling

- Rinsing Tank

- Nitrogen for Cavity

- Nitrogen for tank

- Gas Scrubber

**filters**

**filters**

- Tank Acid2

**20V, 2kA**

- cathode

**Q**a

**Q**g

**Q**g

**Q**g

**T**

**T**

**T**

**T****air**

**Hydrogen Sensor**

- T: Temperature Sensor
- Qg/Qa: flow meter acid/gas

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## 3D - VIEW

**3D - VIEW**

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## DETAILS CONCERNING THE DESIGN PHASE

- Engineering subcontracted
- « Auxitec Ingénierie » chosen after call for tender
- PID, materials, specifications, suppliers, 3D-drawings
- Evaluation of the cost for the set-up (+/- 20%)
- Study has been made for both 1-tank and 2-tank configurations

- FINAL CONFIGURATION WILL BE CHOSEN AFTER RECEPTION OF THE OFFERS FOR THE CALL FOR TENDER
- BUILDING IN TWO STAGES?

- 2d Call for tender under preparation...
- ... for the construction of the machine

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## DETAILED PID

- Most valves automated, sensors (T, H, acid level) integrated in safety procedures

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## DRAWINGS OF ACID STORAGE TANKS

**DRAWINGS OF ACID STORAGE TANKS**

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## VIEW OF THE SET-UP AND OF THE PREPARATION AREA

**VIEW OF THE SET-UP AND OF THE PREPARATION AREA**

- Cooling system

- Cathode insertion

- Pneumatics

- Power supply

- Pneumatics

- Cooling system

- Cooling system

- Cathode insertion

- Cooling system

- Pneumatics

- Cathode insertion

- Power supply

- Pneumatics

- Power Supply

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## CHALLENGES AND R&D RELATED TASKS

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## FLUID DYNAMICS MODELLING WITH COMSOL

- Previous study  (SRF 2007)
- → improvement by cathode shape modification

- Fluid Velocity

- Acid (HF) concentration

- Makes it possible to combine matter flux (diffusion) and fluid dynamics

- Thermal modelling with CFDesign investigated at JLab (C. Reece et al., SRF 2009)

- Improved modelling by using 2D Axi-symmetry

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## PARAMETERS TO BE INVESTIGATED

- FLUID VELOCITY
- TEMPERATURE
- CHEMICALS CONCENTRATION
- POTENTIAL DISTRIBUTION
- DESIGN OF THE CATHODE
- STUDY OF THE Nb REMOVAL (NEED TO SWITCH THE CAVITY?)
- ROUGHNESS ACHIEVED
- Etc.

- - F. Eozénou -     TTC Meeting WG4 Fermilab

## THANK YOU FOR YOUR ATTENTION!

- - F. Eozénou -     TTC Meeting WG4 Fermilab