CEA DSM Irfu May 28th 2012 1 A RD 05: SURFACE PREPARATION STUDIES FOR SUPERCONDUCTIVE CAVITIES F. Eozénou, T. Saeki - F. Eozenou / T. Saeki - A_RD_05
Dec 28, 2015
CEA DSM IrfuMay 28th 2012 1
A RD 05:
SURFACE PREPARATION
STUDIES
FOR SUPERCONDUCTIVE CAVITIES
F. Eozénou, T. Saeki
- F. Eozenou / T. Saeki - A_RD_05
CEA DSM Irfu 2May 28th 2012 - F. Eozenou / T. Saeki - A_RD_05
CONTEXT
CEA DSM Irfu 3May 28th 2012 - F. Eozenou / T. Saeki - A_RD_05
Members
Irfu KEKLeader: Eozénou Fabien
Leader: Takayuki Saeki
Visentin Bernard Hitoshi Hayano
Berry Stéphane Ken Watanabe
Antoine Claire Shigeki Kato
Masashi Yamanaka
Motoaki Sawabe
PARTICIPANTS
Visit Saeki San & Yamanaka San @ Saclay in March 2012
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 4
SURFACE TREATMENTS FOR LARGE SCALE CAVITY PRODUCTION
International Linear Collider
~16000 Superconductive Niobium cavities > 31.5 MV/m
Improvement of the preparation of the SC Nb cavities Cleaning of the surface Reparation of defects Increase in the reprocubility of the process Cost reduction Industrialization
Cavity tratment/exchange program Sample treatments/analysis
CEA DSM Irfu 5May 28th 2012 - F. Eozenou / T. Saeki - A_RD_05
EXAMPLES OF CONTRIBUTION WITHIN TYL
CEA DSM Irfu 6May 28th 2012 - F. Eozenou / T. Saeki - A_RD_05
LOCAL GRINDING AT KEK
CCD camera+ LED
Head : Diamond seat
Motor (3000 rpm)
Grinding machine
Scratches on iris After grinding
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 7
1.E+08
1.E+09
1.E+10
1.E+11
0 5 10 15 20 25 30
Eacc (MV/m)
Qo
électrons
D1 DE1 H1 T=1.7K D1 DE1 I3 T = 1,7K
1.E+08
1.E+09
1.E+10
1.E+11
0 5 10 15 20 25 30 35 40Eacc (MV/m)
Qo
QUENCH
processingélectrons
Recovery of the cavity after local grinding of the defects at iris.
grinding
IMPROVEMENT AFTER GRINDING OF DAMAGED CAVITY
RF test of damaged 1Cell Test after grinding and EP
CEA DSM Irfu 8May 28th 2012 - F. Eozenou / T. Saeki - A_RD_05
Poly-Ethylene (PE) sponge
wipe handle
Sponge mechanicsInsertion
Sponge ExpansionandWipe by rotation
UPW + detergent inlet
UPW + detergent outlet
PE sponge
SET-UP FOR SPONGE WIPING ON SINGLE-CELL
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 9
RESULTS ACHIEVED WITH SINGLE-CELL
• Test with a good cavity (Eacc>35 MV/m, no FE)• Sponge wipe at KEK• VT at Saclay
• The performance of the cavity is maintained• The process do not deteriorate performance
• Tests in challenging conditions (FE limited cavity)• No improvement achieved• But suspicious cleaning sequence• Experiment will be repeated
CEA DSM Irfu 10May 28th 2012 - F. Eozenou / T. Saeki - A_RD_05
Field flatness degradation experimentally observed at KEK after electropolishing,
How can modelling help us understand (and solve) the problem?
Fluid velocity
[HF] at 4 000 s
[HF] at 20 000 s
• Good electropolishing of central cell #5
• Electro-polishing will depend on the cell location for others
→Electropolishing needs to be improved in the other cells
HF
mol/m3
Velocity m/s
TESLA Cavities
MODELLING OF ELECTRO-POLISHING (Saclay)
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 11
SURFACE CONTAMINATION ANALYSIS OF SAMPLES
• Samples EP’ed at KEK & Saclay• Analysis at KEK• Same contaminants found (S, F, C)• More sulfur @ KEK• Influence of anode-cathode distance?
→ Experiments to be continued
Surface Analyses (XPS)Surface Analyses (Auger/AES)Surface Analyses (SIMS)
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 12
NEW EQUIPMENTS, NEW CHALLENGES
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 13
VERTICAL EP (VEP) AT CEA SACLAY
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 14
3 cm
EVOLUTION OF EP @ CEA SACLAY
2004: Experiments on flat samples:
2006: Operation of 1Cell Horizontal EP set-up
2011: Operation of Vertical EP Set-up
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 15
September 2011: Commissioning, Tests with waterOctober 2011: Connections to exhausts, tests with acid in novemberJanuary 2012: Area closed. Final configuration.
EVOLUTION OF THE VEP SET-UP
CEA DSM Irfu - F. Eozenou / T. Saeki - A_RD_05 16
HORIZONTAL VS VERTICAL
Pros:- Good evacuation of gases (cavity
half filled)- Demonstrated efficiency- Large range of parameters
Cons:- Complicated process- Rotary seals- Switching of the cavity- Low removal rate
Pros:- Simple process- Low floor surface- Improved safety- Higher removal rate
Cons:- Sensitive to fluid dynamics- Proper parameters to be determined…
…Voltage and fluid velocityMay 28th 2012
CEA DSM Irfu
r
Z
VERTICAL CONFIGURATION AND MODELLING
Cathode
Fz
Configuration simpler in VEP case:Symmetry according to z-axis
→ 2D axisymmetry model
Fluid velocity
[HF] at 4 000 s
[HF] at 20 000 s
Modelling of horizontal EP:• Difficult: no symmetry• Hints for non uniform polishing
- F. Eozenou / T. Saeki - A_RD_05May 28th 2012
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EXAMPLE OF MODELLING
• Modelling (COMSOL) with rod cathode• Area close to the cell poorly swept with SPL cavities• Needs improvement
Electrolyte velocity: m/s
Flow profile from the cathode to the cavity:
Fluid velocity m/s Vs x
Flu
id v
elo
city
m/s
- F. Eozenou / T. Saeki - A_RD_05May 28th 2012
CEA DSM Irfu 19
Modified Cathode Shape (SPL cavity)
• VEP WITH CIRCULATING ACID SHOULD NOT BE CELL DEPENDENT• SHAPED CATHODE MAKE IT POSSIBLE TO IMPROVE THE FLOW
Example of fluid modelling with alternative shape
Fluid velocity m/s
Fluid velocity m/s Vs x
Flu
id v
elo
city
m/s
- F. Eozenou / T. Saeki - A_RD_05May 28th 2012
CEA DSM Irfu 20
Parameters for 1st VEP sequence:
- 3 hours VEP- Shaped and masked cathode- 8 L/min acid flowrate, Nitrogen blowing- 20 V- Temperature < 26°C
FIRST VEP WITH 1Cell
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
- F. Eozenou / T. Saeki - A_RD_05May 28th 2012
CEA DSM Irfu
• Bright Surface• Brighter on top half-cell• … but bubble traces
→ 20 V = Oxygen generation
RESULTS AFTER EPV A 20V
Acid flow (8L/min) not sufficient to stir the gas
- F. Eozenou / T. Saeki - A_RD_05
+Ar Baking 3hx145°C
May 28th 2012
CEA DSM Irfu 22
EPV WITH LOWER VOLTAGE (12V)
• No obvious bubble trace at the upper cell• Brightening of the surface• Promising Voltage
→ Waiting for the RF Test of the cavity
- F. Eozenou / T. Saeki - A_RD_05May 28th 2012
1Cell Vertically EP’ed at 12V. Improvement of the surface.
CEA DSM Irfu - F. Eozenou / T. Saeki - A_RD_05 23
NEW CAVITY FABRICATION FACILITY AT KEK
May 28th 2012
Introduction of KEK activities• The fabrication-cost reduction of superconducting
cavity is not enough for future project like ILC. We have constructed a new superconducting Cavity Fabrication Facility (CFF) at KEK for the study of cost-effective mass-production of cavity.
• All the necessary equipment for the cavity fabrication were installed in the CFF at KEK.
• We have fabricated 9-cell cavity KEK-00 (without HOM) in CFF. The fabrication process of KEK-00 and the vertical test result of KEK-00 will be shown.
• Future plan of CFF will shown as well as the plan of FJPPL collaboration between Saclay and KEK.
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25
Main Equipments of Cavity Fabrication Facility
Inspection equipment for Nb surface
EBW room
Installation of EBW machine started from April 2011.
Vertical lathePress machine (servo control)
Measuring system for half cell shape (Under developing)
Chemical Polishing room
30 June 2011
4 – Dumbbell, 8 – Dumbbell EBW at Job-shop (June 2011 – July 2011)
Beam
Beam
8 July 2011
6 July 2011
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Fabrication of KEK-00 Cavity (w/o HOM)
Center cells (Nb) / EBW at job shopDumb-bell (Nb)
Beam-pipe (Nb)
End-cells (Nb)
Input-port pipe (Nb)
End-Plates (Ti) + Nb ring
Beam-pipe (Nb)
End-Plates (Ti) + Nb ring
Flanges (Nb-Ti alloy)
27
Final EBW at Equator of End-Cell at Job Shop
1 Dec. 2011
Failure in the EBW at the equator of end-cell (cell#1)/ 120 kV, 30 – 29 mA.
Voltage
BeamCurrent
Position of hole
Cell#1
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The setup of EBW of KEK-00 to repair the hole of cell#1.
Repair of 9-cell cavity KEK-00 by EBW
30 Jan. 2012 (Mon.)
Small Nb piece was made and it was set into the hole.
EBW
29
EBW with 120kV, 20mA, and 5 mm/s.
EBW beadEBW bead
Observation of repaired part and local grindingA picture of repaired part: inner surface of cell#1-equator, theta=237 deg. (1st Feb. 2012)
EBW bead
EBW bead
Area of EBW for repairing the hole of cell#1
Observation by Kyoto camera
Local grinding was done for the inner surface of the repaired part of cell#1 by hand in order to make a smooth surface. (3 Feb. 2012).
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31
Surface treatment of 9-cell cavity (KEK-00)
Bulk EP (100 um), Degreasing (50 0C, 30 min), HPR (1.5 h), Annealing(4 h, 750 0C), and final EP (20 um).
HPR (7 hours)
Brushing of beam-pipe and HOM antenna.Degreasing with detergent (FM-20 2%) in hot bath (500C, 30 min).
Brushing
Vertical Test Result of 9-cell cavity w/o HOM (KEK-00)
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Cell#1 (repaired cell) reached to 42.7 MV/m in the 6pi/9 mode. Limitation in the pi mode might be quench at cell#8, because the T-mapping sensor detected higher temperature in cell#8 in coincidence with the quench at 29 MV/m.
Eacc = 29 MV/mQ0 = 9 x 10^9
33
Future Plan of Cavity Fabrication Facility (CFF)
Activities
FY 2011 FY2012
9-cell cavity: KEK-00 without HOM
April
9-cell cavity: KEK-01 with HOM
Machining of all parts by KEK
EBW of all seams at CFF(KEK)
April
Fabrication
9-cell cavities: KEK-02 with HOM
Single-cell cavity for FJPPL collaboration
Surface preparation and VT
Surface preparation and VT
Study for the high-pressure code application
This cavity will be used for the vertical EP test at Saclay.
Fabrication
Fabrication
Summary of KEK activities• All equipment (press machine, CP room, EBW machine,
etc) were installed in Cavity Fabrication Facility (CFF).
• 9-cell cavity KEK-00 (w/o HOM) was fabricated. Center cells were EBW’ed at job shop and end-groups were EBW’ed in CFF(KEK).
• Final EBW of KEK-00 cavity at the equator of end-cell was failed, but it was repaired. After surface preparation at KEK, KEK-00 reached to Eacc = 29 MVm in vertical test.
• 9-cell cavity KEK-01 and -02 (w/ HOM) will be fabricated
where all seams will be EBW’ed at CFF(KEK) in FY2012.
• We will fabricate a single-cell cavity in CFF at KEK. This cavity will be used for the study of vertical EP at Saclay in the frame-work of FJPPL collaboration.
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CEA DSM Irfu - F. Eozenou / T. Saeki - A_RD_05 35
OBJECTIVE FOR FY 2012
May 28th 2012
Plan of Collaboration with Single-Cell Cavity
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Fabrication of a single-cell cavity at CFF(KEK). This cavity will be used for the study of vertical EP at Saclay in the frame-work of FJPPL collaboration.
Fabrication of single-cell cavity at CFF(KEK).
Vertical EP of the cavity and vertical test at Saclay.
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 37
ON-GOING SAMPLES EXPERIMENTS
Same contaminants observed Quantities differ (Sulfur) More sulfur found at iris at KEK Electrodes’ configuration incriminated
EP @ KEK. Rotating Nb samples. EP @ Saclay. static Nb samples.
Samples measurements on cavities @ KEK.
4 samples will be EP’ed, 4 different anode-cathode distance (Saclay) Packing in Cleanroom in dedicated box Analysis of samples (KEK)
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 38
COMPARISON HEP/VEP
HEP @ KEK VEP @ Saclay
2 advanced equipments Efficiency of HEP demonstrated Experience necessary for VEP Unique opportunity for fruitful comparison
KEK HEP’ed cavity shipped to Saclay VEP @ Saclay VT @ Saclay Comparison
CEA DSM IrfuMay 28th 2012 - F. Eozenou / T. Saeki - A_RD_05 39
ON-GOING GRIDING/WIPING EXPERIMENTS
KEK Grinder makes it possible to treat equator and iris New head under development to reach any part of a cell
Saclay Cavity with pits sent to KEK Local grinding of the defects Cavity shipped back to Saclay for VT
Additional sponge-wiping of contaminated cavity
Saclay cavity with pits
Saclay cavity with FE
KEK grinding system
KEK wiping system
CEA DSM Irfu 40
THANK YOU FOR YOUR ATTENTION
- F. Eozenou / T. Saeki - A_RD_05May 28th 2012