crooks - seamless cavities
TRANSCRIPT
RRR Niobium Seamless Cavities
Roy Crooks1
Waldemar Singer2
1Black Laboratories, L.L.C., Newport News, Virginia, U.S.A.
2Deutsches Elektronen‐Synchrotron (DESY), Hamburg, Germany
The Fourth International Workshop onTHIN FILMS AND NEW IDEAS FOR
PUSHING THE LIMITS OF RF SUPERCONDUCTIVITYOctober 4 – 6, 2010
Legnaro National Laboratories, Padua, Italy
Support for R. Crooks under DOE SBIR Grant No. DE‐FG02‐04ER83909, and from Fermilab and Jefferson Lab
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Advantages of seamless tube cavity production•
No RRR degradation in the welding seam •
No pits associated with the HAZ•
No weld contamination•
Lower production costs in large production runs•
Less scatter in performance compared to welded cavities
Approach:Seamless tubes produced by:•
Drawing or Spinning from sheet and flow forming (DESY)• Extrusions were not adequate due to large grain size
•
Heavily deformed and recrystallized fine‐grain billet, Back extrusion,
forward extrusion and flow‐forming (BL/AWC)
Rationale and Approach, applications for ILC 1.3 GHz SRF Cavities
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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W. Singer, DESY
Tube Making Necking Hydroforming
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Successful fabricationof tube and hydroformedcavities
Tube is good for 3‐cells
W. Singer, DESY
DESY: Tube Making from sheet
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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W. Singer, DESY
DESY: Necking by Profile Ring
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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W. Singer, DESY
DESY: Hydroforming
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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W. Singer, DESY
DESY: Assembled 3x3‐cell ILC Cavity
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Extruded Tube
Advantages:
•
The metal is exposed to steady‐state conditions for most of
the extrusion length.
•
Results in a uniform structure and axisymmetric properties.
Requires a billet with a fine‐grain, randomly oriented starting
microstructure.
Tubes shaped at DESY by spinning and hydroforming.
BL/AWC
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Billet Processing Results (3 deformation methods) 50 mm diameter sub‐scale billet, Inverse Pole Figures of radial sections,
grain boundary number fraction vs. misorientation, texture intensity
surface t/4 t/2c
surface t/4 t/2 bsurface t/4 t/2a
Scaled
up to
165 mm
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
10 20 30 40 50 60
Num
ber F
ract
ion
Misorientation Angle [degrees]
Misorientation Angle
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
10 20 30 40 50 60
Num
ber F
ract
ion
Misorientation Angle [degrees]
Misorientation Angle
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
10 20 30 40 50 60
Num
ber F
ract
ion
Misorientation Angle [degrees]
Misorientation Angle
a
c
b
05
10152025
Texture IntensityODF Max
A B CProcess
Texture Intensity vs. Distance from Surface, inches
00.250.5
from t/4
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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BL/AWC Tube Processing & TestingThicknessFlow Forming
RxRxRx
B1BB2B
B1C
YS, MPa vs 1/sqrt(d)
50
60
70
80
90
100
0 0.1 0.2 0.3
Inverse square root of (d)
YS, M
Pa
Hall-Petch
Limiting dome height testfrom flattened tube100mm dome5mm/min
Huang and CaoNorthwestern UniversityNovember 2009
Tensile Tests/ Roughening
DESY
BL/AWCB1B
50-60% elongattion40% needed
90% Rx
Recrystallization
14 μmODF max 7
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0 10 20 30 40 50 60 70
Num
ber F
ract
ion
Misorientation Angle [degrees]
Misorientation Angle
Correlated Random
Mackenzie (random)
Formability Test
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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BL/AWC Tube (B2B) Forming at DESY December 2009
Hydroforming
Final HydroformingStage
First Stage
Spinning
Spinning of irises Second Stage
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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BL/AWC Hydroforming Results at DESY
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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DESY Coarse Grain SRF Test 3‐cell
at JLab (Peter Kneisel)
(9‐cell testing has started at DESY)
3-cell seamless cavity #3, Test #1
1.0E+09
1.0E+10
1.0E+11
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
Eacc [MV/m]
Q0
Q-drop. No quench
BL/AWC Fine Grain SRF Test 3‐cell
at JLab (Peter Kneisel)
(9‐cell prepped for testing at JLab)
Superfluid
Helium leak
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Assembly of BL/AWC 9‐cell (best of lot)
Welded, stiffener ringsBCP, no leaks warm or cold
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Remaining Issues
•
Optimum Grain Size–
Small for smoothness–
Larger for more elongation? (we are forming near the ductility limit
for Nb)
•
Optimum Crystallographic Texture–
What target other than random? (guidelines from bcc sheet forming?)–
Changes with higher T anneal•
Intermediate Anneals (work to‐date has been at RT)?–
During flow‐forming of tube–
During spinning/hydroforming of cavities•
Increase total elongation•
Modification of hydroforming approach (Bob Rimmer, JLab)
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Grain size optimum? Smoother surface vs. lower ductility
YS, MPa vs 1/sqrt(d)
50
60
70
80
90
100
0 0.1 0.2 0.3
Inverse square root of (d)
YS, M
Pa
Hall-Petch Plot
AA7075Zhao et al Act mater; 52 (2004) 4859Coarse vs fine grain Nb tube
YS vs inverse sq rt grain size
RRR Niobium Seamless Cavities; Crooks, Singer TFSRF 2010, Legnaro, October 4 – 6, 2010
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Summary
•
Nine‐cell ILC geometry ILC cavities can be assembled from seamless tube
given room temperature necking and hydroforming procedures used at
DESY.
•
The tube from spinning or deep‐drawing requires a 3x3 cell assembly, with
iris welds between 3‐cell sections.
•
Heavily deformed and recrystallized billet has been shown to allow
production of a fine‐grain, weakly textured tube.
•
The BL/AWC fine‐grain extruded tube is capable of fabrication into a 9‐cell
cavity without welds, although the proper machine will have to be built.
•
The consistent microstructure of the fine‐grain extruded tube should
reduce the scatter in srf
performance with production scale operations.•
Tube process optimization studies are in progress.