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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