CEA DSM Irfu May 28th 20121 A RD 05: SURFACE PREPARATION STUDIES FOR SUPERCONDUCTIVE CAVITIES F....

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


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


EXAMPLES OF CONTRIBUTION WITHIN TYL


LOCAL GRINDING AT KEK

CCD camera＋ LED

Head : Diamond seat

Motor (3000 rpm)

Grinding machine

Scratches on iris After grinding


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


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


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


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)


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)


NEW EQUIPMENTS, NEW CHALLENGES


VERTICAL EP (VEP) AT CEA SACLAY


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


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

CEA DSM Irfu 18

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


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


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


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


1Cell Vertically EP’ed at 12V. Improvement of the surface.


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.

24

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

26

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

28

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).

30

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)

32

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.

34


OBJECTIVE FOR FY 2012

May 28th 2012

Plan of Collaboration with Single-Cell Cavity

36

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.


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)


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


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


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CEA DSM Irfu May 28th 20121 A RD 05: SURFACE PREPARATION STUDIES FOR SUPERCONDUCTIVE CAVITIES F....

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