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R&Ds in Asia on Large/Single Crystal Niobium after the International Niobium

Workshop 2006

R&Ds in Asia on Large/Single Crystal Niobium after the International Niobium

Workshop 2006

　　IHEP/PKU (China) R&D

　　KEK/Tokyo Denkai (Japan) R&D

　　Summary

K.Saito Niobium Ingot Workshop, 22nd –24th, Sept. 2010, Jlab

Kenji SaitoA, Fumio FurutaA, Hirotaka NakaiA, Taro KonomiA,

Hiroaki UmezawaB, Jiyuan ZhaiC, Xiangyang LuD, P.KneiselE, and R.GenE

A:KEK, B: Tokyo Denkai (TD), C:IHEP,

D: Beijing University (PKU), E: Jlab

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IHEP/PKU China Activities

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IHEP Large Grain 9-cell Cavity – IHEP01

• Ningxia large grain niobium• Low loss shape• Dumbbell and cavity

frequency and length control method same with DESY

Fabricated in Beijing in 2009

4

Surface Treatment and Pretuning

Processed and pre-tuned with the SRF facilities developed in IHEP:•CBP (tumbling) machine•Vertical BCP System•Pre-tuning machine•Large ultrasonic cleaner

Field Flatness:•As delivered: 70 %•After pre-tuning: 97.6 %•After jig fitting: 94 %•After 1st VT: 90 %

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First Vertical Test Result

0 5 10 15 20 25108

109

1010

1011

Qo Pi mode [4 K] Qo Pi mode initial [1.76 - 1.73 K] Qo Pi mode final [1.88 - 2.02 K]

Eacc, max = 8.4 MV / mQo = 3.95 * 108

Po = 164 W

CBP (190 µm), BCP (110 µm), Annealing (750oC, 3 h), Pretuning (94 %), Ultrasonic (Micro-90 2%, 50oC, 3 h), BCP (20 µm), Ultrasonic (UPW), Low Pressure Rinsing @ IHEP

Ultrasonic (Liquinox 2%, 43oC, 3 h), HPR (8.5 h), Baking (105oC, 48 h), VT @ KEK

Final: Quench (self pulse) / F.E.Eacc, max = 19.8 MV / mQt = 1.40 * 1012

Qo = 1.57 * 109

Po = 230 WHe pres. = 2.69 kPaHe temp. = 1.94 K

Initial: F.E.Eacc, max = 6.3 MV / mQt = 1.46 * 1012

Qo = 1.66 * 109

Po= 21.9 WHe pres. = 1.36 kPaHe temp. = 1.73 K

1st Vertical Test, July 1, 2010IHEP-01 Large Grain Low Loss 9-cell Cavity (without HOM couplers)

Q0

Eacc [MV/m]

Tested at KEK STF• pumping during VTBad vacuum• 2~5E-7 Pa• one order of magnitude

worse than normal caseStrong Field Emission:•processed from the initial 6 MV/m to final 20 MV/mHard Quench:•cell # 9, 270-300o equator at 20 MV/m•T-mapping and optical inspection diagnostics

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Optical Inspection of Cell #9 Equator 290°

After EBW

?quench defects

1 mm

EBW seam ending problem

After VT

72010-9-22

SRF Cavity activities in Peking University since 2006

Single crystal Large grain

Fine grain

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Single Crystal 1-cell Cavity with Ningxia

by tested P/Kneisel

9Measured by P. Kneisel, et.al, JLab

PKU activities on LG materialNingxia LG material, fabricated by PKU, tested in Jlab (P.Kneisel)

PKU Large Grain cavityafter post-purification at 1250C

1.0E+09

1.0E+10

1.0E+11

0 10 20 30 40 50

Eacc[MV/m ]

Qo

Test #5a, after 1250C+bakingTest#1BCP+baked, before 1250C

Quench

Post Purification+BCP+Baking

By P.Kneisel

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F-G Nb Cavities made by Peking UniversityIn Aug. 2009, third 9-cell cavity at Peking University，Eacc is 28.6MV/m

Vertical test at JLabBy Dr. Rongli Geng

After high-pressure rinsing and clean room assembly, the first radio frequency (RF) test was done on 30 July. The maximum accelerating gradient was 20 megavolts per metre(MV/m) at an unloaded quality factor of 2.3×109, limited by field emission. After partial disassemble, additional high-pressure water rinsing was done, followed by the second RF test on 9 August. The maximum accelerating gradient reached 28.6 MV/m at an unloaded quality factor of 4×109, limited by RF cable heating.

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Observations of As-built Surface Reported on May 9, 2010 @ 1st WebEx Meeting

Lack of full penetration at equator EBW Sharp steps at iris EBW

from Rongli’s file

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KEK/Tokyo Denkai Activities

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Large Grain Sheet Production at Tokyo DenkaiTokyo Denkai

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Multi-Wire SlicingK.Saito Single Crystal-Large Grain Niobium Technology Workshop in Brazil 2006

Nb

PressingSplay liquid abrasives

This technology is well established on silicon wafer slicing.

Slicing used very thin piano wire (0.16Φ)and liquid abrasive

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The surfaces have wire traces but no problem for cavity fabrication.

R&D of Multi-Wire Slicing @ KEK/Tokyo DenkaiThe first trial for niobium ingot slicing after small sample cuttings

108

109

1010

1011

0 10 20 3 0 40 50 60

Q o

E acc [M V/m]

E acc=42.6M V/mQ o= 8.04e9 @ 2K

N o X -ray

C B P+C P (10)+A N +C P (160)+H PR (15m in.)+B aking(48hrs)

L imited by Q -slope

20mmL

270Φ

45 hrsConventional Silicon wafer

slicing machineTokyo Denkai RRR=480

First Measurement !LL End single cell cavity

(End cell shape)

BCP , not EP

Directly formedthe sliced sheets.

No annealed the sheets.

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Step by step tests for more sheets production

6 sheets(2.8t)

270Φ　20mmL

58 sheets(3.2t for Jlab)

270Φ　201mmL

265Φ　307mmL

102 sheets(2.8t)19 sheets (2.8t)

270Φ 61mmL

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1300

1350

1400

1450

0 5 10 15 20

WeightW

eigh

t [g]

No. of sheet

1387 ± 1.2 g

Scatter 0.09%0

200

400

600

800

1000

0 5 10 15 20

Tickness

Thi

ckne

ss 2

xxx[µm

]

No. of sheet

Scatter 0.13%

0

2

4

6

8

10

0 5 10 15 20

Rz

ave.

[µm

]

Sheet No.

Rz=4.9+-1.8µm

Feature of The Multi-Wire Slicing

Very Uniform

Very Smooth

0

20

40

60

80

100

120

140

2.7 2.75 2.8 2.85 2.9 2.95Thickness[mm]

All 2.741Min.2.906Max.

1144.621Total408Poits

2.805Average2.803Center2.806RMS0.020S.T deviation

0.0004Dispersion0.001Error in S.T

KEK 102 sheets

KEK 19 sheets

Rz=4.9±1.8µm

t=2.906±0.038µm

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Simplified Nb production by this slicing method

150 sheets can be produced in 48hrs, if you have a 270φx 450L Nb ingot.

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Crystal Orientation and Cut out Samples

Ｇ１

Ｇ１Ｇ１

Ｇ２

Ｇ２

Ｇ２

Ｇ３ Ｇ３ Ｇ３

Ｇ４

Ｇ４

Ｇ４

1G1H1

1G1H2

G1

G2G3

G4

G5

G1G2

G3G4

G5G1

G2G3G4

G5[1,1,0]

[1,1,0][1,1,0]

[5,3,1][1,1,0]

[3,1,0]

[1,1,0]

[1,1,0]

#3 #42 #83

[1,1,0][1,1,0]

[1,1,0]

[1,1,0]

[1,1,0]

[1,1,0]

[1,1,0]

[1,1,0][1,1,0]

[3,2,-1][1,1,0]

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Mechanical Properties of LG niobium at RT&4.2K

Tensile becomes higher about 10 times, Young’s modulus 2 times larger, and Elongation 7 times smaller at 4.2K.

Tensile Young’s modulus

Elongation

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Fist LG 9-Cell Cavity Fabricated at KEK

Totally 96µm (in average) removed by BCPMaterial removal distribution by the vertical BCP and horizontal one.

Horizontal BCP system has been successfully developed at KEK in order to improve the none-uniform material removal with vertical BCP.

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25

Vertical BCPHorizontal BCP

Rem

oval

[µm

]

Location

1 2 3 4 5 6 7 8 9

Top Bottom

Ave.=64+-13µm

Ave.=96+-28µm

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109

1010

1011

0 5 10 15 20 25 30

Qo

Eacc [MV/m]

+HCP(65µm)+Degreasing+HPR(10hr)+Bake(120OCx48hr)

Eacc=27.1MV/mQo=1.1E+10 @ 2K

CBP+HBCP+Bake

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Improvement of crystallization at Tokyo Denkai

Single Crystal

Ultrasonic images by H.UmezawaTokyo-Denkai

Ingot No.1 Ingot No.2 Ingot No.3Ingot No.3

Improving Crystallization of Ingot at Tokyo Denkai

Grains grow column likely in

EBM.

Make a seed plate for single crystal Ingot

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Cut out large crystal piece

EBW of large crystal pieces

Trial of Single Crystal Seed for EBM Nb IngotUse nearby 9 sheets

Ultrasonic diagnosis as received

Ultrasonic diagnosis after buffingAfter BCP

280Φ

We are very much looking forward to see the EBM result, which will come out on the IPAC10 in Kyoto.

EBW H.Inoue

EDM by Y.Kobayashi

Ultrasonic investigation by H.Umezawa

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Seed plate 2.8mm thick on the EBM base-plate

First experiment was failed. We will hear more information here from Tokyo Denkai.

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Scope of the LG/Single crystal niobium material from single cellcavity R&D

Large Grain: Benefits in material and preparation costs

• TESLA shape+LG+BCP(+bake) is hopeless for the ILC baseline performance : 35MV/m @ Qo=8E+9, which has been already confirmed with 9-cell cavities at DESY.

XFEL specification is well satisfied by this scheme.

TESLA shape+LG

+[CBP or Post purification at 1250OC ]+BCP(+bake) on ILC baseline performance ?

• LL shape+LG+BCP(+bake) is hopeful for the ILC baseline performance.

• LL shape+LG+CBP+BCP(+bake) is hopeful for the ACD performance: 40MV/m @ Qo=8E+9. Need more statistics.

Single Crystal

• Single crystal will make possible the ILC ACD performance without CBP on the scheme:

LL shape+LG+BCP(+bake) .

• Single crystal has more advantage on the cavity performance.

Single crystal is trade off CBP.

• Single Crystal R&D should be kept going.

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0

10

20

30

40

50

0 100 200 300 400 500

V ertical BCP

H orizontal BCP

y = 46.451 * e^(-0.00078474x) E

acc

[MV

/m]

removal [µm]

CBP(100)+VBCP(170)

ILC Baseline

BCP material removal vs Eacc,max on LG after CBP

Enhanced grain boundary steps are problem?

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Summary

• IHEP and PKU in China keep going ILC 9-cell cavity R&D with helps other laboratories. Single crystal is already produced at Ningxia.

• Multi-wire slicing has been successfully developed at KEK/Tokyo Denkai, and now it is applied in the production phase in Tokyo Denkai..

It is ready to produce 150 sheets ILC like in 48hrs, if you bring an ingot 270φ -450mm L.

• KEK has started LL 9-cell cavity fabrication LG based, and is challenging to the ILC ACD cavity performance.

• Single crystal R&D is trade off CBP. KEK/Tokyo Denkai have started the R&D.

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Acknowledgments

We express many thanks to KEK STF people, who made vertical test for IHEP01 9-cell cavity.

We thank Drs. Y.Higashi and S.Chan, who helped a lot to measure crystal orientation of LG niobium materials.

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Niobium Workshop 2006Single cell cavity R&Ds in Asia were reported:

IHEP/KEK collaboration

Ning Xia large grain Nb material achieved Eacc ~50MV/m with electropolished LL cavities.

Jlab/Pusan University/ KEK Collaboration

CBMM large grain material also reached Eacc ~ 36MV/m with EP’ed LL cavity.

Tokyo Denkai will start large grain Nb material production.

Multi wire slicing idea was proposed for industrial large grain sheet material production.

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IHEP Further R&D for LG

• IHEP-01 is now back to IHEP, will be processed again and make 2nd vertical test early next year

• IHEP-02 Large Grain Low Loss 9-cell cavity with HOM couplers in fabrication, 1st vertical test early next year

• More IHEP cavities for ILC, ADS and ERL are coming… LG may be considered.

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Ultrasonic Imaging Machine at Tokyo Denkai

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Grain boundary appearance Test using Single Crystal Coin Samples