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Submitted on 1 Jan 1984
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NIOBIUM-3-TIN INTERNALLY COOLED CABLED SUPERCONDUCTOR (ICCS) TECHNOLOGY I
M. Hoenig, M. Steeves, C. Cyders
To cite this version:
M. Hoenig, M. Steeves, C. Cyders. NIOBIUM-3-TIN INTERNALLY COOLED CABLED SUPER-
CONDUCTOR (ICCS) TECHNOLOGY I. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-403-
C1-406. �10.1051/jphyscol:1984182�. �jpa-00223738�
JOURNAL DE PHYSIQUE
Colloque C l , supplément au n° 1, Tome 45, janvier 1984 page C1-403
NI0B1UM-3-TIN INTERNALLY COOLED CABLED SUPERCONDUCTOR (iCCS) TECHNOLOGY I
M.O. Hoenig, M.M. Steeves and C.J. Cyders*
Massachusetts Institute of Technology, Plasma Fusion Center, Cambridge, Massachusetts 02139, U.S.A.
Résumé - De récents travaux utilisant une gaine de tantale et d'Incoloy 903 ont démontré que les supraconducteurs câblés à refroidissement interne
(ICCS/SCRI) peuvent être compactés sans dégradation du courant. Ce rapport compare la gaine d'Inconel 617 aux résultats précédents L'inconel 617 est un matériau pratique pour la construction mécanique avec une contraction thermique située entre celles de l'acier inoxydable et de l'Incoloy 903.
Abstract - Recent work, using tantalum and Incoloy 903 sheathing has demon- strated that internally cooled, cabled superconductors (ICCS) can be com- pacted without current degradation. This paper compares Inconel 617 sheath- ing to previous results. Inconel 617 is a practical engineering material with a thermal contraction lying between stainless steel and Incoloy 903.
INTRODUCTION
Initial work using 27 strand ICCS conductors sheathed in stainless steel demon- strated substantial degradation of current density due to compaction. /I/ In more recent work /2/ stainless steel sheathing was replaced with Incoloy 903 and tantalum.
As can be seen in (Fig. 1 and 3 ) , Incoloy 903 and tantalum sheathed conductors have demonstrated current densities, which are essentially independent of compaction. To complement this work Inconel 617 has now been tested as a sheathing material.
EXPERIMENT
Procedures used in these experiments have been consistent with practice. /1/2/ A typical test sample is illustrated in (Fig. 2 ) .
EXPERIMENTAL RESULTS
Critical current densities (J
c) of Inconel 617 sheathed conductors, compacted to various degrees have been measured at flux densities of 8 to 12 T at 4.2 K. These results are listed in Table I and are compared with equivalent current densities for test conductors sheathed in stainless steel, tantalum and Incoloy 903. Compaction is defined as the ratio of solid area to total area inside the sheath. Noncopper critical current density for all four sheathing materials has also been plotted in Fig. 1 for conductors compacted to 68% void. All test specimens were reacted for 30 hours at 750 C. Figure 3 shows the effect of sheathing material on current den- sity as a fraction of single strand current density. Thus for 12 T stainless steel, Inconel 617, Incoloy 903 and tantalum sheathed conductors have current densities of 68, 82, 99 and 107% of that of single strands of wire.
*Supported by U.S. DOE/DMFE and partially by the MIT-FBNML under its NSF Grant.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984182
JOURNAL DE PHYSIQUE
P i g . 1 - N o n c o p p e r c r i t i c a l c u r r e n t d e n s i t y ( J c ) ~ / m m ~ a s f u n c t i o n o f f l u x d e n s i t y (E) T , f o r v a r i o u s s h e a t h i n g m a t e r i a l s .
Sheath Swaged to Given Compact~on
27 Strand Cable I
Term~nolion Swaged i n Copper to 99%
Solld i
Airco Bronze Matrix Wire 0 . 0 6 8 mm Dla 6 4 % Pure Copper
F i g . 2 - T e s t s p e c i m e n .
TABLE I
NONCOPPER CRITICAL CURRENT DENSITY FOR 27 STRAND Nb3Sn ICCS CONDL'CTORS AT 4 . 2 K , REACTED FOR 30 HRS AT 750 C
SHEATH
FLUX DENSITY (T) 8 1 0 1 2
VOLIME NONCOPPER CRITICAL CURRENT DENSITY ( ~ / m m ~ )
1 FugIoN 1
COMPACTION (% SOLID) 58 6 8 79 1 0 0
SHEATH SINGLE WIRE
TANTALUM INCOLOY 9 0 3
INCONEL 617 .68
DISCUSSION
58 6 8 79 100
The above b e h a v i o r of d i f f e r e n t s h e a t h i n g m a t e r i a l s i s c o n s i s t e n t w i t h a u n i a x i a l i n t r i n s i c s t r a i n model. For a s i n g l e s t r a n d o r f o r a f u l l y compacted ICCS t h e con- d u c t o r i s m o n o l y t h i c . The s t r a i n o n t h e Nb$n,unreacted niobium and t a n t a l u m b a r - r i e r can be c a l c u l a t e d from volume f r a c t i o n s , e l a s t i c m o d u l i , y i e l d s t r e s s e s and t h e r m a l c o n t r a c t i o n s from 1000 t o 4.2 K. The i n t r i n s i c f i l a m e n t a r y s t r a i n (&f) i s t h e n g i v e n by Eq. 1. / 3 /
58 6 8 79 100
where and ab, r e p r e s e n t l o n g i t u d i n a l s t r e s s f o r copper s t a b i l i z e r and b r o n z e i n y i e l d e d c o n d i t l o ~ Y The c o n d u i t i s assumed t o remain e l a s t i c . Vc, Vcu and Vbz a r e volume f r a c t i o n s of c o n d u i t , c o p p e r and b r o n z e r e s p e c t i v e l y . / 2 / S i m i l a r l y AL/Lc and A L / L ~ a r e thermal. c o n t r a c t i o n s o f c o n d u i t and f i l a m e n t . E i s Youngs modulus.
The e f f e c t o f i n t r i n s i c u n i a x i a l s t r a i n o n n o r m a l i z e d c u r r e n t d e n s i t y ( J c / J c m ) can b e c a l c u l a t e d from E q . 2. / 3 /
F i g u r e 4 i s a p l o t of J c / J c m v s
& ff o r Nb3Sn a t 1 2 T and 4 . 2 K , c a l c u l a t e d from Eqs. 1 and 2 above. D a t a f o r p a r t i a l l y compacted c o n d u c t o r s h a v e been added on t h e b a s i s of t h e i r noncopper c r i t i c a l c u r r e n t d e n s i t i e s (J,).
I t s h o u l d b e n o t e d t h a t f o r I n c o n e l 617 and e s p e c i a l l y s t a i n l e s s s t e e l t h e volume
f r a c t i o n Vc h a s a c o n t r o l l i n g e f f e c t . The u s e of t h i c k e r t u b i n g w i l l r e s u l t i n a
h i g h e r Vc and h e n c e a h i g h e r c o m p r e s s i v e s t r a i n
( - E ~ ) .The c o r r e s p o n d i n g Jc/Jc,
s h o u l d b e e v e n l o w e r .
J O U R N A L DE PHYSIQUE
u
8 10 12 Flux Oens~ty ( T )
F i g . 3 - C r i t i c a l c u r r e n t d e n s i t y f o r s h e a t h e d con- d u c t o r s a s f r a c t i o n o f s i n g l e s t r a n d c u r r e n t d e n s i t y ; a l l r e a c t e d f o r 30 h o u r s a t 750 C.
58% Camp
68% COmD 100% Camp*
+
c a l ~ u l o t e d and Measured D a t a P o i n t sl I I L I I I I ' I I 1 ~ l
V -
