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STATUS REPORT ON THE SWISS LCT-COIL
J. Zichy, B. Jakob, C. Marinucci, J. Zellweger, G. Vécsey, H. Benz, R. Maix, J. Rauch
To cite this version:
J. Zichy, B. Jakob, C. Marinucci, J. Zellweger, G. Vécsey, et al.. STATUS REPORT ON THE SWISS LCT-COIL. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-139-C1-143.
�10.1051/jphyscol:1984130�. �jpa-00223685�
JOURNAL DE PHYSIQUE
Colloque C l , suppl6ment a u n o 1, Tome 45, janvier 1984 page C1-145
MANUFACTURING DEVELOPMENT OF T H E WESTINGHOUSE Nb3Sn C O I L FOR T H E L A R G E C O I L TEST PROGRAM*
J . L . Young, T.L. Vota and S.K. Singh
Westinghouse E l e c t r i c Corporation, East Pittsburgh, PA 15112, U.S.A.
&s& - L'aimant de Nb3Sn fabrique/ par la ~ o c i L t 6 Westinghouse pour l e
Programme Grande Bobine du L a b o r a t o i r e Oak Ridge ( t h e Oak Ridge N a t i o n a l Laboratory Large C o i l Program) (LCP) e s t b i e n engag6 dans l a phase de f a b r i c a - t i o n . Cet a r t i c l e examine l e s proc6des/ de f a b r i c a t i o n a i n s i que l e s t r a v a u x de d6veloppement e n t r e p r i s pour c e t t e bobine de c o n c e p t i o n avanc6e e t u n i q u e ( 1 ) . ABSTRACT - The Westinghouse Nb3Sn Magnet f o r t h e Oak Ridge N a t i o n a l L a b o r a t o r y Large C o i l Program (LCP) i s c u r r e n t l y w e l l i n t o t h e manufacturing phase. T h i s paper i d e n t i f i e s t h e manufacturing p r o c e s s e s and development t a s k s f o r t h i s unique, advanced c o i l . ( l )
COIL DESIGN
The g o a l o f t h e Westinghouse Large C o i l i s t o d e m o n s t r a t e t h e p o t e n t i a l o f NbgSn f o r l a r g e s c a l e a p p l i c a t i o n s t o e i t h e r h i g h f i e l d o r h i g h c u r r e n t d e n s i t y magnets. The unique modular, d i s t r i b u t e d s t r u c t u r e concept i n c o r p o r a t e d i n t h i s c o i l p r o v i d e s many manufacturing and d e s i g n advantages. The d i s t r i b u t e d s t r u c t u r e p r e v e n t s t h e accumulation o f f o r c e s which would l e a d t o h i g h conductor s t r a i n and i n s u l a t i o n s t r e s s e s . It a l s o p r o v i d e s b e t t e r d i s t r i b u t i o n o f s t r u c t u r e and conductor over t h e c r o s s - s e c t i o n o f t h e c o i l and d e l i v e r s a h i g h e r e f f e c t i v e f i e l d on plasma when a p p l i e d t o a Tokamak T o r o i d a l c o n f i g u r a t i o n . The modular c o n s t r u c t i o n p e r m i t s par- a l l e l winding o p e r a t i o n s and e l i m i n a t e s t h e need f o r heavy s t r u c t u r a l welds.
The c o i l u t i l i z e s a c a b l e d NbqSn conductor which h a s been encased i n a s t a i n l e s s s t e e l j a c k e t . The conductor - i s i n s u l a t e d w i t h Kapton t a p e and t h e n formed and i n s e r t e d i n t o s p i r a l s l o t s machined i n t o t h e 24 aluminum p l a t e s . The 48 conductor l e n g t h s a r e formed, four a t a t i m e , w i t h each s e t o f four s u f f i c i e n t l y long t o wind 2 p l a t e s ( s e e f i g u r e 1 ) . The c o i l i s wound i n 2 h a l v e s which w i l l be assembled t o g e t h e r w i t h c l o s e f i t t i n g s t a i n l e s s s t e e l s t u d s t o form a c o n s o l i d a t e d s t r u c t u r e . The conductor i s cooled by flowing l i q u i d helium i n t o a c a b l e t h r o u g h h e a d e r s which have been formed around t h e conductor j o i n t s between t h e wound p l a t e p a i r s . A f t e r t h e c o i l h a l v e s have been assembled, t h e h e a d e r s a r e connected t o t h e i n l e t and out- l e t m a n i f o l d s . During t h e c o n c e p t u a l and f i n a l d e s i g n o f t h e c o i l , e n g i n e e r s e x p e r i e n c e d i n manufacturing and manufacturing p l a n n i n g were an i n t e g r a l p a r t o f t h e d e s i g n team. Manufacturing p r o c e s s e s which were e x t r a p o l a t a b l e from normal, l a r g e e l e c t r i c a l equipment manufacture were i n c o r p o r a t e d i n t o t h e d e s i g n . For a l l key p r o c e s s s t e p s , p l a n s were e s t a b l i s h e d and implemented t o b u i l d p r o t o t y p e s , conduct q u a l i f i c a t i o n t r i a l s and t o t r a i n and q u a l i f y p e r s o n n e l .
T a b l e 1 l i s t s some o f t h e more i m p o r t a n t p r o t o t y p i c a l t a s k s . I n e v e r y c a s e , t h e completion o f t h e s e t a s k s r e s u l t e d i n p r o c e s s m o d i f i c a t i o n p r i o r t o a c t u a l commit- ment t o manufacture. Adoption o f t h i s philosophy was a n i n v a l u a b l e a i d t o a s s u r i n g t h e q u a l i t y o f t h e c o i l .
*NOTE: T h i s work was sponsored by Department o f Energy and Oak Ridge N a t i o n a l L a b o r a t o r y under Union Carbide' C o r p o r a t i o n C o n t r a c t No. 22X31747C.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984130
JOURNAL DE PHYSIQUE
/CONDUCTORHEADER REGION
I SPLITS
SUPERCONDUCTING
STAINLESS STEEL SHEATH
17.6 KA - CURRENT WESTINGHOUSE CONDUCTOR
FIGURE 1. WESTINGHOUSE COIL CONSTRUCTION
TABLE 1 MANUFACTURING DEVELOPMENT TASKS HEADER AND MANIFOLD WELDING WINDING PROCESS TRIALS
WELDER QUALIFICATION INSULATION WINDING TRIALS
CONDUCTOR BUTT WELDING COATED INSULATION CRYOGENIC TRIALS
CONDUCTOR BRAZING CROSSOVER BENDING TRIALS
CONDUCTOR JOINT PULL TESTS STRUCTURAL PLATE MACHINING X-RAY SENSITIVITY ON BUTT WELDS CONDUCTOR STRAIGHTENING
BUTT WELDER CONSISTANCY CONDUCTOR LEAK TESTING
WINDING TOOL TRIALS (SPRINGWCK) CONDUCTOR JACKET REMOVAL
MANUFACTURING SEQUENCE
The l a y o u t o f t h e manufacturing a i s l e i s shown i n f i g u r e 2. The conductor i s r e c e i v e d from Oxford-Airco r e e l e d o n 2.5M O.D. f l a t s p i r a l e d r e e l s . The f i r s t s t e p i s t o s t r a i g h t e n t h e l l O M l e n g t h s o f conductor i n a c o n v e n t i o n a l 8 r o l l s t r a i g h t e n e r . The conductor i s t h e n c l e a n e d and any s h a r p f e a t u r e s which c o u l d damage t h e i n s u l a t i o n a r e removed. Although t h e conductor i s l e a k t e s t e d by t h e s u p p l i e r a t l i q u i d Nitrogen t e m p e r a t u r e i n i t s r e e l e d c o n d i t i o n , i t i s rechecked a f t e r s t r a i g h t e n i n g t o determine i f any l e a k s have developed d u r i n g h e a t t r e a t i n g o r s t r a i g h t e n i n g . T h i s i s accomplished by e n c l o s i n g a 6M l e n g t h o f conductor i n a moveable vacuum chamber a t room t e m p e r a t u r e w h i l e helium gas s i n t r o d u c e d a t 30 atmospheres. T h i s system d e t e c t s l e a k r a t e s a s low a s 5 x LOa SCC/sec. To d a t e t h e r e l i a b i l i t y o f t h e welds h a s been loo%, and no l e a k s have developed subsequent to manufacture. A f t e r t h e l e a k check t h e c o n d u c t o r s a r e t a p e d w i t h 7 h a l f lapped l a y e r s o f Kapton t o p r o v i d e t h e t u r n t o t u r n and ground w a l l i n s u l a t i o n .
SOUTH WINDING ROOM
RUNOUT
IN$ULATINF
: : 'INSULATING
1 : : : : : : :
CONDUCTOR STRAIGHTENER DEREELING STAND
NORTH WINDING ROOM
FIGURE 2. WINDING AISLE CONFIGURATION
The winding o f t h e conductor i s accomplished by forming t h e conductors t o t h e e x a c t contour o f t h e grooves which have been m i l l e d i n t o t h e aluminum p l a t e s ( s e e f i g u r e 3). Pre-manufacturing t r i a l s were h e l d t o e s t a b l i s h t h e t o l e r a n c e s and f i n i s h e s a t t a i n a b l e . These t r i a l s a l s o v e r i f i e d t h a t warpage due t o m a t e r i a l removal would not be a problem and p l a t e t h i c k n e s s could be h e l d v e r y a c c u r a t e l y . The aluminum p l a t e s a r e t h e n f a s t e n e d t o a r o t a t i n g t a b l e . The c e n t e r o f t h e t a b l e h a s provi- s i o n s f o r t h e mounting o f t h e forming t o o l s . The conductor forming i s accomplished by clamping t h e i n s u l a t e d conductor t o t h e former and r o t a t i n g t h e t a b l e w h i l e applying a f o r c e t o t h e f r e e , extended, end o f t h e conductor through a h y d r a u l i c a l l y a c t i v a t e d r o l l e r ( s e e f i g u r e s 4 and 5).
FIGURE 3. PLATE MACHINING
FIGURE 4. WINDING TABLE FIGURE 5. CONDUCTOR FORMING
C1-148 JOURNAL DE PHYSIQUE
The winding t r a i l s , u s i n g dummy c o n d u c t o r s proved e x t r e m e l y worthwhile. W e e s t a b - l i s h e d t h e need f o r a mylar t a p e s l i p l a y e r between t u r n s , and t o adopt more t u r n s o f t h i c k e r Kapton t a p e t h a n o r i g i n a l l y planned, f o r a d d i t i o n a l p r o t e c t i o n a g a i n s t winding damage. Valuable e x p e r i e n c e was a l s o g a i n e d r e g a r d i n g t h e e f f e c t o f conduc- t o r s p r i n g b a c k on c o n d u c t o r forming. E m p i r i c a l d a t a was g e n e r a t e d t o e s t a b l i s h t h e t o o l i n g shapes which would p r o v i d e c o n g r u i t y o f t h e conductor and t h e s t r u c t u r a l s l o t c o n f i g u r a t i o n . I n a d d i t i o n t h e p r o p e r l o c a t i o n o f t o o l placement was e s t a b - l i s h e d t o a s s u r e t h e proper s t a r t and f i n i s h o f e a c h r a d i u s .
A f t e r winding each p a i r o f p l a t e s , t h e four c o n d u c t o r s a r e j o i n e d t o t h e c o n d u c t o r s f o r t h e n e x t p a i r o f p l a t e s . T e r m i n a l s have been formed on each end d u r i n g conduc- t o r manufacture by swaging copper t u b e s o v e r t h e c a b l e . These t e r m i n a l s a r e j o i n e d by an e l e c t r i c a l r e s i s t a n c e b u t t weld. A f t e r X-ray examination o f t h e b u t t weld a s p l i c e c o l l a r i s b r a z e d o v e r t h e j o i n t f o r added s t r e n g t h ( s e e f i g u r e 6 ) . The j o i n t s a r e t h e n e n c l o s e d i n a s t a i n l e s s s t e e l header box which w i l l b e connected t o t h e helium manifold. An e x t e n s i v e program o f welding t e c h n i q u e development, j o i n t t e s t i n g and welder q u a l i f i c a t i o n h a s g i v e n u s g r e a t c o n f i d e n c e i n t h e q u a l i t y o f a l l t h e s e j o i n t s .
A f t e r b o t h c o i l h a l v e s have been wound, t h e y w i l l be assembled t o g e t h e r ( s e e f i g u r e 7). Then t h e s t u d h o l e s w i l l b e l i n e reamed and t h e s t u d s w i l l be assembled and t o r q u e d . A t t h i s p o i n t t h e m a n i f o l d system w i l l be assembled, welded and l e a k checked by p r e s s u r i z i n g w i t h helium w h i l e t h e c o i l i s i n a vacuum t e s t box.
TWO HALVES ASSEMBLED
BRAZED COLLAR
FIGURE 6. CONDUCTOR JOINT FIGURE 7. FINAL COIL ASSEMBLY
CONCLUSION
During t h e development and implementation o f t h i s manufacturing p r o c e s s much was l e a r n e d about t h e manufacturing t e c h n i q u e s r e q u i r e d t o b u i l d a l a r g e advanced NbjSn f o r c e d flow c o o l e d magnet. To d a t e , we have e n c o u n t e r e d no problems which w o i l d prevent s c a l i n g t h i s concept t o t h e l a r g e r s i z e s p r e s e n t l y being planned f o r Tokamak r e a c t o r s . We have e v e r y r e a s o n t o b e l i v e we w i l l be a b l e t o c a p i t a l i z e on t h e advantages o f t h i s concept t o p r o v i d e compact, h i g h c u r r e n t d e n s i t y c o i l s .
R e f e r e n c e
( 1 ) C . Heyne, D. Hackworth, S. Singh, J. Young, Proceedings o f t h e 8 t h Symposium o n E n g i n e e r i n g Problems o f F u s i o n E n g i n e e r i n g , San F r a n c i s c o , C a l i f . Nov. 1979, p. 1148-53.
