HAL Id: jpa-00223582
https://hal.archives-ouvertes.fr/jpa-00223582
Submitted on 1 Jan 1984
HAL
is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire
HAL, estdestinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
INFLUENCE OF AN INNER SHORT-CIRCUIT ON THE BEHAVIOUR OF THE SUPERCONDUCTING
MAGNET
F. Žížek
To cite this version:
F. Žížek. INFLUENCE OF AN INNER SHORT-CIRCUIT ON THE BEHAVIOUR OF THE SU- PERCONDUCTING MAGNET. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-555-C1-559.
�10.1051/jphyscol:19841113�. �jpa-00223582�
JOURNAL DE PHYSIQUE
Colloque C1, supplbment au n o 1 , Tome 45, janvier 1984 page Cl-555
INFLUENCE OF AN INNER SHORT-CIRCUIT ON THE BEHAVIOUR OF THE SUPERCONDUCTING MAGNET
Rgsunik
-
Au c o u r s de l l e x c i t a t i o n d e l ' u n d e s a i ~ . a n t s q u a d r u - p o T g i ? e s s u p e r c o n d ~ c t e u r s , d e s p o i n t e s d e t e n s i o n o n t e t 6 ob- s e r v k e s s u r l e s b o r n e s d e s o r t i e . L o r s q u e u n c e r t a i n n i v e a u d e c o u r a n t e s t o b t e n u , l e s p o i n t e s d e t e n s i o n d i s p a r a i s s e n t e t on c o n s t a t e l a t r a n s i t i o n de l l a i m a n t & l ' k t a t n o r m a l . L ' a n a l y s e f a i t c a n o n t r k que c e phknonEne e s t c a u s k p a r l ' i n f l u e n c e du c o u r t - c i r c u i t d e s s p i r e s a 1 1 i r i t 6 r i e u r d e l ' u n e d e s b o b i n e s q u a d r u p o l a i r e s . L o s p o i n t e s 2e t e n s i o n o n t 6 t 6 c a u s g e s p a r l e s t r a n s i t i o n s r 6 p 6 t k e s de l a p a r t i e d e l l e n r o u l e m e n t c o u r t - c i r - c u i t k eB
1 ' 6 t a t n o r m a l . Au c o u r s du l e n t a c c r o i s s e m e n t d u c o u - r a n t , l e phknomsne m e n t i o n n 6 ne s e n a n i f e s t e p a s .A b a t ~ a c t - On e x c i t i n g one of t h e s u p e r c o n d u c t i n g q u a d r u p o l e
iiagnzs;
v o l t a g e p u l s e s w e r e o b s e r v e d on t h e w i n d i n g o u t l e t s . Over a c e r t a i n c u r r e n t l e v e l t h e p u l s e s d i s a p p e a r e d a n d a q u e n c h o l t h e n i s g n e t was r e g i s t e r e d . A s u b s e q u e n t a n a l y s i s p r o v e d t h a t pbenomanon was c a u s e d by s h o r t - c i r c u i t i n g of t h e t u . r n s i n s i d e one of t h e q u a d r u p o l e c o i l s . The v o l t a g e p u l s e s 7.vere c a u s e d by r e p e a t e d q u e n c h e s of t h e s h o r t - c i r c u i t e d p a r t o f t h e v i n d i n g . The a b o v e e f f s c t d i d n o t a p p e a r u n t i l a c e r - t a i n r a t e o f r i s e o r t h e c u r r e n t w a s a t t a i n e d .TYO s u p e r c o n d u c t i n g f o c u s i c g m a g n e < s , e a c h w i t h a warm c y l i n d r i c a l h o l e o f 2 0 3 mm i n d i a m e t e r e n d w i t h a m a g n e t i c l e n g t h of 700 m w e r e m a n u f a c t u r e d a t ~ K O D A f a c t o r y . The n u l t i f i l m e n t a r y s u p e r c o n d u c t o r
i n a c o p p e r m a t r i x o f r e c t a n g u l a r s h a p e was p r o v i d e d w i t h a v a r n i s h - b o n t e d g l a s s c o v e r e d t y p e of i n s u l a t i o n . The w i n d i n g , i m p r e g n s t e d w i t h e p o x y r e s i n , was o p e r a t e d i n e l i q u i d h e l i u m b a t h .
A s r e g a r d s bhe f i r s t q u a d r u p o l e m a g n e t , t h e c u r r e n t r e a c h e d q u i c k l y i t s r a t e 2 v r l u e 1 3 5 0 A . A s t h e s e c o n d m a g n e t s t a r t e d t o g e t e x c i t e d , a s e n s i t i v e e l e c t r o n i c p r o t e c t i o n d e v i c e d i s c o n n e c t e d t h e power s o u r c e a t e l o w c u r r e n t l e v e l . A f t e r d e c r e a s i n g t h e s e n s i t i v i t y of t h e p r o t e c t i o n d e v i c e , v o l t a g e p u l s e s w e r e o j s e r v e d on t h e m e a s u r i n g o u t l e t s f r o m p a r t i c u l a r c o i l s ( P i g s . l , 2 )
.
The f r e q u e n c y o f t h e p u l - s e s was s t r i c t l y r e g u l a r a n d p r o p o r t i o n a l t o t h e r a t e o f r i s e o f t h e c u r r e n t . The a m p l i t u d e s of t h e p u l s e s w e r e d e c r e a s i n g f r o m t h e i n i - t i a l p e a k v a l u e o f a b o u t 1 V u n t i l , o v e r a c e r t a i n c u r r e n t l e v e l , t h e p u l s e s d i s a p p e a r e d a n d a q u e n c h of t h e m a g n e t was r e g i s t e r e d . Frorc a l l o s c i l l o g r a ~ s i t i s o b v i o u s t h a t t h e p o l a r i t y o f p u l s e s mea-s u r e d on t h e c o i l number 3 was o p p o s i t e t o a l l o t h e r s . T h i s c o i l h a d a l s o a c o n s i d e r a b l y l o w e r i n d u c t i v i t y a s f o l l o w s f r om a c o m p a r i s o n of t h e i n i t i a l v o l t a g e j u n p s r e l a t i n g 6 0 t h e p a r t i c u l a r c o i l s a t t h e i n s t a n t o f c o n n e c t i n g t h e m a g n e t t o t h e power s u p p l y ( F i g . 1 ) . The i n d u c t i v i t i s of t h o c o i l s were a l s o m e a s u r e d d u r i n g t h e s u b s e q u e n t t e m p e r a t u r e r i s e of t h e K a g n e t , b u t t h e d r o ~ i n i n d u c t i v i t y of t h e
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19841113
J O U R N A L DE PHYSIQUE
F i g . 1
-
V o l t a g e p u l s e s r e l a t i n g t o t h e i n c r e a s e a n d d e c r e a s e o f t h e c u r r e n t ( b t r a n s n o r t c u r r e n t , l , 2 , 3 , 4 s e r i a l numbers of t h e c o i l s )Fig.2
-
A t a c e r t a i n c u r r e n t l e v e l the p u l s e s d i s e p e a r a n d a q u e n c h i s r e g i s t e r e dc o i l number 3 was by f a r n o t s o l a r g e a s i n t h e s u p e r c o n d u c t i n g s t a t e .
I t was a s s u m e d t h n t t h e d e s c r i b e d b e h a v i o u r o r t h e m a g n e t was c a u s e d by s h o r t - c i r c u i t e d t u r n s i n s i d e o f t h e c o i l number 3 . The f o l l o w i n g a n a l y s i s was d i r e c t e d a t v e r i f i c a t i o n o f t h i s h y p o t h e s i s . Among o t h e r e x p e r i m e n t s , t h e e f f e c t o f a r t i f i c i a l i n s i d e s h o r t - c i r c u i t s on t h e i n d u c t i v i t y was i n v e s t i g a t e d on a m o d e l of t h e same s i z e . The r e g u l t s o f t h e e x p e r i m e n t s show t h a t t h e a b o v e L r o p i n i n d u c t i v i t y i s c s u s e d by s h o r t - c i r c u i t i n g o f a b o u t ; 13 t o 2 0 'turns.
The t e m p e r a t u r e d e p e n d e n c e of t h e i n d u c t i v i t y o f t h e d e f e c t i v e c o i l is r e l a t e d t o t h e c h a n g e i n t h e r e s i s t a n c e o f t h e s h o r t - c i r c u i t e d p a r t o f t h e w i n d i n g . Under some s i m p l i f i e d c o n s i d e r e t i o n s , t h e i n - d u c t i v i t y o f t h e d e f e c t i v e c o i l r e a d s
.c/ (1)
0
=
where L i s i n c i u c t i v i t y of a good.
c o i l , I!.,
, R,
i n d u c t i v i t y a n d r e s i s t a n c e of t h e s h o r t - c i r c u i - t e d p a r t o f t h e c o i l . P t e r e s i s - t a n c e R, r e p r e s e n t s t h e p r o F e r - t i e s o f t h e c o n t z c t p o i n t of t h e s h o r t - c i r c u i t . I c t h e f i u p e r c o n - d u c t i c g s t a t e Rn = 3 , and. r e l a - t i n g d r o p i n i n d u c t i v i t y i s l a r g e . A t t h e a 3 b i e n t t e m p e r a t u - r e , on t h e o t h e r h s n d , t h e r e - s i s t a n c eR,,
m u s t be c o n s i d e r e d F i g . 3-
S i m ? l i f i e d c i r c u i t d i a -(
R,,,
) , I nRyan o f a d e f e c t i v e c o i l
-
t h e c o n d i t i o n ( 1 ) a t t h e a m b i e n tt e m p e r a t u r e , i t i s n e c e s s a r y t o c h o o s e t h e number o f t h e s h o r t - c i r c u i t e d t u r n s /urn a a p r o x i m a t e l y 8.
T a k i n g i n t o a c c o u n t t h e w i n d i n g t e c h n o l o g y , h o w e v e r , MY, = 11 s e e m s t o be m o s t p r o b a b l e .
L e t u.s f i r s t a s s u n e a s i m p l e m a t h e m a t i c a l m o 5 e l w i t h t h e w i n d i n g i n t h e s u p e r c o n d u c t i n g s t s t e ( F i g . 3 )
.
The b e h a v i o u r of t h i s c i r c u i t c o n n o x i o n may be c h a r a c t e r i z e d by t h s f o l l o w i n g e q u a t i o nw h e r e t h e tirile c o n 2 t a n . l .
r = 1 ,
/R,
a n 3 du/& i s t t c g l v e r . c o n s t a n t r a t e 3f r i s e of t h e c u r r e r . t r e l a t i n g t o t h e t i m eA
2 0. F o r t h e i n i - t i a l c o n d i t i o n s &=Lo,
A/, = O we c a n g e tThe c u r r e n t i n t h e s h o r t - c i r c u i t e d p a r t of t h e c o i l
A/,
=A/, -
A/. I f t h e r a t e of t h e c u r r e n t r i s e&/dL
i s l o w , t h e h e a t g e n e r a t e d by t h e c u r r e n t f l o w i n g t h r o u g h t h e c o n t a c t p o i n t c a n be d i s s i p a t e d a n d n o e x c e e d i n g of t h e s u p e r c o n d u c t o r c r i t i c a l t e m p e r a t u r e o c c u r s ( F i g . 4 ) . The c u r r e n t NA i c t h e s h o r t - c i r c u i t e d p a r t o f t h e c o i l r e a - c h e s t h e maximum, t h e n b e g i n s t o d e c r e a s e a n d e v e n t u a l l y c h a n g e s t h e p o l a r i t y .F i g . 4 - Time b e h a v i o u r of c u r r e n t s a t a l o w r a t e of t h e c u r r e n t r i s e
JOURNAL DE PHYSIQUE
F i g . 5
-
Time b e h a v i o u r o f c u r r e n t s a t a h i g h e r r a t e o f t h e c u r r e n t r i s eThe s i t u a t i o n i s d i f f e r e n t , a t a h i g h e r r a t e o f t h e c u r r e n t r i s e ( F i g . 5 ) . When t h e c u . r r e n t h a s r e a c h e d a c e r t a i n c u r r e n t E m i t t h e n o r m a l c o n d u c t i n g s t a t e b e g i n s t o p r o p e g a t e f r o n t h e c o n t a c t p o i n t i n t o tAe a r e a of a l a r g e r c u r r e n t , i . e . i n t o t h e s h o r t - c i r c u i - t e d p a r t , o f t h e c o i l . The r e s i s t a n c e of t h i s p a r t i n c r e a s e s a n d c u r r e l i t A/*q u i c k l y d i m i n i s h e s . F o r atl i n s t a n t a l l t h e t r a n s p o r t c u r r e n t ,& f13ws t h r o u . g h t h e c o n t a c t p o i n t t i l l t h e s h o r t - c i r c u i t e d p a r t o f t h e w i n d i n g r e t u r n s s p o n t a n e ou.sly b a c k t o t h e s u 2 e r c o n d u c t i n g s t a t e . A l l t h i s d i s c h e r g e p r o c e s s r e s u l t s i n a v o l t a g e p u l s e t h a t n a y be m e a s u r e d on t h e c o i l .
The t i m e d u r a t i o n o f t h e p u l s e i s r e l a t i v e l y s h o r t . Any c h a n g e i n t h e t r a n s p o r t c u r r e n t A/ c a n be n e g l e c t e d a n d t h e d i s c h a r g e p r o c e s s may b e d e s c r i b e d by t h e f o l l o w i n g d i f f e r e n t i a l e q u a t i o n
dk
w h e r e
R,
i 3 t h e t i m e - d e p e n d e n t r e s i s t a n c e of' t h e s h o r z - c i r c u i t e d p a r t of t h e c o i l . The e n l a r g e m e n t of t h e n o r m a l c o n d u c t i n g zone c a n be r e s p e c t e d byR*
=&Arn
C o n s i d e r i n g .the i n i t i a l c o n d i t i o n A& ( 0 )
=/UcL-k ,
we c a n g e t t h e s o l u t i o nD u r i n g t h e d i s c h a r g e p r o c e s s t h e v o l t a g e , w o n t h e o u t l e t s o f t h e d e - f e c t i v e c o i l w i l l be
n a g n i l-ude n
T h e r o f .the c o n t a c t c u . r r e n t l i m i t A/,pcan be d e r i v e d f r o m ( 1 ) . I n v i e w of t h e a b o v e e x > e r i n e n t s , t h e i n p u * d a t a n e e d e d f o r t h e c a l c u l a t i o n o f b C d a r e a s f o l l o w s : / & = 1 5 2 , /UA= 11,
LA
= 0 , l mH,T =
2 0 s ( d e r i - ved f r o n t h e p u l s e p e r i o d ) . The minimum r a t e of t h e c u r r e n t r i s e n e e d e d f o r g e n e r a t i n g t h e v o l t a g e p u l s a s i s a b o u t '2 A / s . The r e l a - t i n g c o q t a c t c u r r e n t l i m i t at t i m e4 4 0 0
o b t a i n e d by m e a n s of Eqn.( 2 ) i s 4,4= 550 A . The c o n s t a n t & i n E q n . ( 3 ) s h o u l d be c h o s e n s o a s
t o e n s u r e t % e a g r e e m e n t b e t ~ i e e n th e c a l c u - l a t e d p u l s e w i d t h a n d i t s r e a l va1u.e. The
!vid.th of t h e m e a s u r e d p u l s e was a b o u t 1 s , f r o m w h i c h f o l l o w s
A / ( ( & +
1 ) L A ) = 1.The c a l c u l a t e d p u l s e s h s p e f o r w - 1 ar.d 2
I. i s shown i n F i g . 6 . The a m p l i t u d e s of t h e
? u l s e s r e l a t i ! ! g t o A)= O a r e 0 , 9 V ar_d 1 , 2 V , r e s p e c : ; i v e l y , w h i c k i s I n g o o d a g r e e m e n t w i t h t h e measu-red v a l u e s .
,
L m t l y , t h e q u e s t i o t i of w h e t h e r t h e h e a t g e n e r a t e d i n t h e c o n t a c t p o i n t i s s u f f i c i - F i g . 6-
C a l c u l a t e d s h a - e n t t o c ~ x s c t h e e n l a r g e m e n t of t h e n o r m a l pe o f t h e v o l t a g e p u l s e c o n d u c t i n g z o n e s h o u l d be c o n s i d e r e c . Thel o s s o f e n e r g y i~ t h e r e s i s t a n c e d u r i c g t h e t i m e i n t e r v a l ( 0 , k ) caz be o b t e i n e d by means of E q n . ( l )
. 2 &-a5
E =
JR,+&
=R , T ~ ( ~ ~ ) ~ . x
70
w h e r e
X
i s a f u n c t i o n of t h c r e l a t i v e t i z e &-/L/C ( F i g . ? ) .The h e a t f r o m t h e c o n t a c t p o i n t p r o . ? a g a t c s a b o v e a l l i n t h e d i r e c t i - on a l o n g t h e s u o e r c o n d u c t o r s . The v e l o c i t y of n r o p a g a t i o n i s g i v e n by t h e t i n e c o n s t a n t of t h e h e a t c o n d u . c t i o n . L e t us a s s u m e t h a t a t t h e t i m e A the b e a k d i s t u r b a n c e e x t e n d s LXD t o t h e d i s t a n c e
where C, i s t h e s p e c i f i c beet ol" t h e c o n d u c t o r a t i t s i n i t i a l tempe- r a t u r e
<
= 4,2 K . The h o a t d i s t u ~ b e n c e a f f e c t s t h e t w o n e i g h b o u r i n g s a p e r c o n d u c t o r s , whose n a s s i s M = 4 L S w . The e n e r g y r:eeded f o r a d i a - b a t i c h e a t i n g of t h e mans Pf r e a d s4 fl
E
= M J ~ = M&,
J f 1 3 d b 9 a n d t h e r e s u l t i n g mean t e m 5 e r a t u r e of t h i s m a s s9
i sfl = y m
e M
The c z l c u l a t e d i n c r e a s e o f t h e mean t e m p e r a t u r e i n t h e v i c i n i t y of t h e c o n t a c t p o i n t ( F i g . 7 ) i s s t r o n g l y d e p e n d e n t on t h e r a t e of t h e c u r r e n t r i s e . F o r .tile r a t e s o v e r 1 A / s t h e c u r r e n t MA i s l i k e l y t o e x c e e d t h e c r i t i c a l v ~ l u e w h i c h r e s u l t s i n s d i s c h a r g e o t t h e magne- t i c e n e r g y . D e p e n d i n g on i h e m e g n i t u d c o r t h e t r a n s p o r t c u r r e n t , t k e s u p e r c o n d u c t i n g s t a t e i s e i t h e r r e s t o r e d , w h i c h i s n a n i f e s t e d by a
v o l t e g e p c l s e , o r a q u e n c h a p p e - a r s . U n l e s s t h e r a t e of t h e c u r -
f5.- r e n t r i s e r e a c h e s t h e a b o v e v a -
l u e ( 1 A / s ) , t h e f u l l r a t e d c u r - r e ? t car? be o b t a i n e d . T h i s f a c t h a s b e e n e x p e r i c e n t a l l y c h e c k e d .
Re= 5 . 1 0 - ~ J 2 c o = O , l J/kg/K
% = 2 0 s ,,&a= 1.10-3 ~ / h g / ~ '
w = 1 5 2
2
= 1000 W/S/X /1?;= 11s
= 7 . 1 0 - ~ r2ac
o w = 8 9 0 0 kg/m 3F i g . 7
