Seamless RF Cavities

Activities of DESY, KEK, INFN, JLabPresented by W. Singer

• Introduction• Fabrication technique

• NbCu clad cavities• Conclusion

W. Singer SRF 2005

Hydroforming, DESY, KEKSpinning (V.Palmieri,INFN Legnaro)

Fixed MatrixMovable MatrixTube

Pcyl sensor Lsensor

Oil Hydr system

Water Hydr. system

Rsensor

Ptube sensor

W. Singer SRF 2005

10.00E+8

1.00E+10

1.00E+11

0 5 10 15 20 25 30 35 40 45

Qo

Eacc [MV/m]

­ 250 µm bcp, Test #1

-100 µm e-pol., Test #2

DESY Seamless Cavity 1K2 T=1,99K

The best Q(Eacc) result of by

hydroformingproduced single cell

cavity

The best Q(Eacc) result of by spinning

produced single cell cavity

W. Singer SRF 2005

Significant progress was achieved in last years in development of seamless cavities.

It was shown that the high accelerating gradient ca. 40 MV/m can be achieved in seamless cavities

The main technical problems of the fabrication of seamless single cell and multi cell (by spinning or hydroforming)

are solved.

The main remaining task is improvement of the fabrication technique to the industrially applicable level.

Fabrication technique

W. Singer SRF 2005

Spinning (V. Palmieri, INFN)

Spinning from diskSpinning from tube

Spun 3-cell cavityW. Singer SRF 2005

First spun 9-cell cavity

W. Singer SRF 2005

New spinning machine. The two spinning

turrets (revolver heads) work one against each other. A 9-cell cavity

can be spun in 4 hours.Poster TuP68

Spinning (V. Palmieri,

INFN)

Two and three cell cavities hydroformed at DESY

Not uniform necking at the iris area done at company HTI ( hole appeared during barrel

polishing).

Improvement of the necking procedure was necessaryW. Singer SRF 2005

Reduction mechanism.

Principle of tube diameter reduction in the iris area

Seamless technique by hydroforming: step 1- necking

DESY Necking machine: new PC controlled necking procedure

Tubes after reduction in the iris areas

All steps of hydroforming optimized and checked on the Cu dummies

W. Singer SRF 2005

Seamless technique by hydroforming: step 2- expansion

DESY hydroforming machine

Principle of the tube expansion in the equator region

Rather uniform wall thickness distribution is achievable

Example of hydroformed

3 cells

W. Singer SRF 2005

DESY high pressure device for cavity

calibration. Pressure ca. 1 kbar

Seamless technique by hydroforming: step 3- calibration

W. Singer SRF 2005

1 0 0 .0 0

0 .0 0

2 0 .0 0

4 0 .0 0

6 0 .0 0

8 0 .0 0

2 5 3 61 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0 2 0 0 0 2 2 0 0 2 4 0 0

0 .e n d 1 0 0 0 .5 0 2 8 .5 7

b e g 3 9 9 .3 7 1 8 .2 7

gr1

6 5 .0

4 1 .7

4 5 .0

4 7 .5

5 0 .0

5 2 .5

5 5 .0

5 7 .5

6 0 .0

6 2 .5

2 5 .8-0 .1 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 1 4 .0 1 6 .0 1 8 .0 2 0 .0 2 2 .0 2 4 .0

m e a s

c a lc u

C u r 1 1 .6 9 5 0 .5 4

gr2

Init. LoadSaveZero

Stop ResetCut

Load Dcalc. ShowdataSave Dcalc.

0.5P in tube

8Feb2000Date

2:20 Time

D :\ 1 c e ll h yd ro fo rm in g \ D a ta \ N io b iu m D 8 3 m m P r1 .s toPath

Niobium 137*83.0*2.6mm. L0=51.6.Drossel=300, kran on -8, kran off 135.Niobium tube Pr1. During of hydroforming (18-6mm of length) the shape was conical, dD=5mm). Smooth surface, inside and outside. Calibrated at 560bar. Thickness at equator =2.2mm.

C o m m e n ta ry

P in cylindery1

Lengthx2 Radiusy2

25.76Length, mm

0 .8 4 .3 2 5 .8 4 1 .7 3 .1

2 .8 4 .6 2 5 .8 4 1 .7 3 .1

0

0

Data

PROCESS START

5 2 2 6 6 8t0

1 4 .9P ze ro

7 2 .1 6L z e ro

2 4 .7 0

6 5 .0 0 2 4 .1 7

7 0 .5 0 2 3 .6 5

7 5 .5 0 2 3 .1 2

8 3 .5 0 2 2 .0 7

9 0 .0 0 2 1 .0 2

9 7 .5 0 1 8 .9 2

0 1 .5 0 1 6 .8 2

0 4 .0 0 1 4 .7 1

0 6 .5 0 1 2 .6 1

0 7 .0 0 1 0 .5 1

0 6 .0 0 8 .4 1

0 5 .0 0 6 .3 1

0 3 .0 0 4 .2 0

0 1 .0 0 2 .1 0

9 9 .0 0 0 .0 0

0 .0 0 0 .0 0

0 .0 0 0 .0 0

0 .0 0 2 5 .7 5

4 2 .0 0 2 5 .2 2

5 6 .5 0

0

0

D c a lc

41.70Radius, mm

1 0 7 .8

0 .0

2 0 .0

4 0 .0

6 0 .0

8 0 .0

1 0 0 .0

2 5 .8-0 .1 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 1 4 .0 1 6 .0 1 8 .0 2 0 .0 2 2 .0 2 4 .0

m e a s

c a lc uC u r 1 8 .9 2 9 7 .5 0

gr3

P in tubey3Lengthx3

41.70R 1 41.70R 2

0.00d R

93.6Pstab

0.10dL

25.66L teor

4.4Pcylinder

-1 9 .6P c y lz e ro

0.80Pscale170P tu b e m a x

130P c yl m a x

4 1 .7 5R te o r

0 .9 4K Pstart

0 .9 9K P sta b

5 0 0 0T p a u se , m se c

0 .0d P c o r.%

T im e P tu b e L , m m R ,m m P c y l

Front panel of the software for hydroforming - machine

FEM simulations: reasonable at the beginning

Front panel of the software for necking - machine

PC control allows reproducibly repeat

the forming parameters

W. Singer SRF 2005

Pot with thick wall by spinning (or deep drawing)

Flow forming

Fabrication technique: seamless Nb tubes

Appropriate microstructure and rather high strain before onset of necking. Tubes of 1,4 m

long and ID ca. 200 mm for spinning have been build by V. Palmieri

Nb tubes,ID=150 mm

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30 35 40 45

dL/L0*100

F/S0

, N/m

m2

Nb-1B1-1 780C 1h Nb-1B1-2 780C 1h Nb-1B3-1 800C 1h Nb-1B3-2 800C 1h Nb-1T1-1 780C 1h Nb-1T1-2 780C 1h Nb-1T3-1 800C 1h Nb-1T3-2 800C 1h

W. Singer SRF 2005

Fabrication steps of 9 cell cavity by hydroforming as option 3x3 is in work

Barrel polishing, 800°C annealing, EP (KEK recipe) seams to be a most appropriate treatment for seamless cavities

W. Singer SRF 2005

Hydroforming of 9 cell cavity from one piece tube can be done on the same way (three cells simultaneously in three steps)

Hydroforming of cells can be done or as three cells simultaneously or cell by cell

W. Singer SRF 2005

NbCu clad cavitiesFabrication of cavity from bimetallic bonded NbCu tube

by seamless technique (spinning or hydroforming).

Combination of the seamless technique with NbCubonding gives to bimetallic option new opportunity.

W. Singer SRF 2005

Advantages • cost effective: allows saving a lot of Nb (ca. 4 mm cavity wall has only ca. 1 mm of Nb and 3 mm Cu). Especially significant for large projects like ILC • bulk Nb microstructure and properties (the competing sputtering technique does not have such advantages)• the treatment of the bulk Nb BCP, EP, annealing at 800°C, bake out at 150°C, HPR, HPP can be applied (excluding only post purification at 1400°C).• high thermal conductivity of Cu helps for thermal stabilization• stiffening against Lorentz - force detuning and microphonics can be easily done by increasing of the thickness of Cu layer.• fabrication by seamless technique allows elimination of the critical for the performance welds especially on equator

W. Singer SRF 2005

The bonding takes place by an explosively driven, high-velocity angular impact of two metal surfaces.

Explosively bonded NbCu tube

Fabrication of bimetallic NbCu tubes. Two options considered.

Flow forming of NbCu tubeAfter flow forming

Structure of Nb/Cu interface

Explosively bonded NbCu tubes:-Explosive bonding of seamless Nb tube ca. 4 mm wall thickness (RRR=250) with

Cu tube of wall thickness 12 mm- Flow forming into NbCu tube, wall thickness ca. 1mm Nb, 3 mm Cu

W. Singer SRF 2005

NbCu cavities hydroformedfrom explosively bonded tubes

at DESY. NbCu single cell cavity 1NC2 produced

at DESY by hydroforming from explosively bonded tube. Preparation and

HF tests at Jeff. Lab: 180 µm BCP, annealing at 800°C, baking at 140°C for

30 hours, HPR (P. Kneisel).

1,00E +09

1,00E +10

1,00E +11

0 5 10 15 20 25 30 35 40 45

Eacc [MV/m]

Q0

T=2K T=2K - M easured after quenches

40 MV/m without EP

Difficult to get reproducibly high bonding

quality. Hot bonding fabrication procedure of NbCu tubes seems to be

more promising

W. Singer SRF 2005

Fabrication principle of sandwiched hot rolled Cu-Nb-Cu tube (KEK and Nippon Steel Co.)

• Hot bonded NbCu tubes

Hot roll bonded Cu-Nb-Cu tube produced at Nippon Steel Co.

Fabrication principle of sandwiched

coextruded Cu-Nb-Cu tube (KEK)

W. Singer SRF 2005

NSC-3: Barrel polishing, CP(10 mµ), Annealing 750oC x 3h, EP(70 µm)

K.Saito

One NbCu sandwiched cavity was tested NSC-3.

Hot roll bonded tube fabrication at Nippon Steel Co., hydroforming at

DESY, Preparation and RF tests at KEK

Single cell NbCu cavities produced at DESY by hydroforming from

KEK sandwiched tube.

Not enough statistic for comparison of explosive bonding and hot

bonding. Quality of hot bonding is more reliable; better statistic is to

expect

W. Singer SRF 2005

4 NbCu clad tube of KEK

Four 2 cell NbCu clad cavities recently produced at DESY from KEK tubes (no cracks on the inside surface)

Multicell NbCu clad cavities (Poster TuP59)

4,14,24,34,44,54,64,74,84,9

0 100 200 300 400 500

Distance along tube axis, mm

Wal

l thi

ckne

ss, m

m

2NC4

2NC3

2NC2

2NC1

Wall thickness distribution

W. Singer SRF 2005

1305

1306

1307

1308

1309

1310

1311

2NC1 2NC2 2NC3 2NC4

Cavity

Freq

uenc

y, M

Hz

cell 1

cell 2

-0,10-0,050,000,050,100,150,200,250,300,350,40

-2,50 -2,00 -1,50 -1,00 -0,50 0,00 0,50

Frequency deviation MHz

Leng

th d

evia

tion

mm

Before trimming

Frequency measurement (G. Kreps)

Frequency distribution in cells

Example of dumb bells frequency for standard

cavity fabrication

Small frequency deviation between the cells can be

achieved. Warm tuning seems to be unavoidable

W. Singer SRF 2005

Cost comparison of Nb and NbCu clad cavity of TESLA shape (pessimistic estimation)

9 cell Nb cavity cost = (disc weight • Nb disc cost per kg • 18) + (costs of not cell parts like flanges, end tubes etc.)+ (standard cavity fabrication costs)

9 cell NbCu clad cavity cost = (tube weight for 9 cells • 0.25•8.4/8.96• Nb cost in tube per kg) + (tube weight for 9 cells • 0.75•8.96/8.4• Cu cost in tube per kg) + (costs of not cell parts like

flanges, end tubes etc.)+ (cavity fabrication costs by hydroforming)Assumed:

• Cavity fabrication costs by hydroforming and standard fabrication roughly the same (industrial studies)• Fabrication costs for bimetallic NbCu clad tubes are by factor of two higher as for Nb discs.• Costs of not cell parts like flanges, end tubes etc. the same for Nb and NbCu clad cavities (prices based on TTF experiences)• Contribution for Nb disc fabrication is 20 % of total Nb cost

NbCu clad cavity cost /Nb cavity cost = 70.5 %W. Singer SRF 2005

Two ways to defeat the cracks*a) Sandwiched tube (Nb is between two Cu layers. Cu layer on both sides

prevent creating of cracks in Nb); removing of inside Cu layer on the cavity after forming (K.Saito). The option was checked, it works

Difficulties in NbCu technology1. Dangerous of cracks appearance in iris area during fabrication

(because of big difference in recrystallization temperature of Nb and Cu)

Microstructure of Cu and Nb after annealing at 560°C for 2 hours. Nb is not recrystallysed (hard).

* Improvement of the necking technique allows reducing the cracks dangeW. Singer SRF 2005

0

50

100

150

200

250

0 5 10 15 20 25 30 35 40 45

dL/L0, %

Sigm

a, N

/mm

2

CuZr0.15, 800C 2h S.1 CuZr0.15, 800C 2h S.2

Microstructure of Cu0.15%Zr and Nbafter annealing at 800°C for 2 hours.

Possible solutions

b) Cu only outside: Cu0.15%Zr special Cu with high recrystallization temperature

The Cu0.15%Zr shows a high elongation after annealing at 800°C, small and rather uniform grain and can be a good candidate for replacing of pure Cu in NbCu clad tubes

Thermal conductivity can be recovered by aging at ca.

400°C/one hour. Zr leaved the solid solution and

creates precipitates Cu5Zr finely distributed in Cu

matrix

Stress –strain behavior and thermal

conductivity of Cu0,15%Zr after

annealing at 800°C for 2 hours compared

with Cu and Nb.

10

100

1000

3 8Temperature, K

Ther

mal

con

duct

ivity

, W/m

K

99.98%Cu Cu0,15%Zr, anneal. 800C, 2h RRR270

W. Singer SRF 2005

NbCu0.15%Zr tube

2. Q degradation during fast cool down, RF processing or quench (trapping of magnetic flax

caused by thermo - coupling effect).

• Is not completely understood, more work is necessary. Similar effect was observed on Nb3Sn

cavities (M.Peiniger). Similar effect is to expect in sputtered NbCu cavities.

• The Q degradation is relatively moderate especially for rather thick Nb layers of ca. 1 mm thickness

(less than one order of magnitude). Can be cured by warm up over Tc and slow cool down.

Q degradation in a seam less single cell cavity from NbCu

explosively bonded tube (K.Saito)

Additional surface resistance after quenches at ca 40 MV/m (P.Kneisel)

• It seems that annealing and hot bonding (due to

diffusion) should contribute to reduction

of the thermal coupling effect

NbCu phase diagramW. Singer SRF 2005

Conclusion

On laboratory level the most work is done.

Industrialization of seamless technique is the main

remaining task W. Singer SRF 2005

KEK present activity towards the industrialization is very worthwhile

W. Singer SRF 2005

Poster TuP59

Connection of end tubes to NbCu cells

Microstructure of CGDS Cu coating on Nb, small porosity ca. 1%, small oxidation. electr. conduct. ca.80%

of bulk Cu (top: spraying by Nitrogen, bottom- by Helium)

Cu layer on Nb tube. Small purity degradation of Nb

during spraying: from RRR=300 to RRR=250

Principle of the welding of 0,7-1 mm thick Nb layer of the cavity with 2 mm thick wall of Nb end tube.

New Cold Gas Dynamic Spray System. Warms up the particles by only ca.

300°C and accelerate to velocities of 600-1500m/s (H.Kreye, University of

the Federal Armed Forces in Hamburg)W. Singer SRF 2005