IMPROVEMENT ON THE SUPPORT STRUCTURE OF THE SUPERCONDUCTING SADDLE MAGNET SSM-3

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IMPROVEMENT ON THE SUPPORT STRUCTURE OF THE SUPERCONDUCTING SADDLE MAGNET

SSM-3

Yan Luguang, Chen Haoshu, Ye Zuxian, Wang Silian, Li Guangsui, Ma Hongda

To cite this version:

Yan Luguang, Chen Haoshu, Ye Zuxian, Wang Silian, Li Guangsui, et al.. IMPROVEMENT ON THE SUPPORT STRUCTURE OF THE SUPERCONDUCTING SADDLE MAGNET SSM-3. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-841-C1-844. �10.1051/jphyscol:19841172�. �jpa-00223647�

J O U R N A L DE PHYSIQUE

Colloque C1, suppl6ment a u no 1 , Tome 45, janvier 1984 page C1-841

IMPROVEMENT ON THE SUPPORT STRUCTURE OF THE SUPERCONDUCTING SADDLE

MAGNET SSM-3

Yan ~u~uan~', Chen Haoshu, Ye Zuxian, Wang Silian, Li Guangsui and Ma Hongda I n s t i t u t e o f EZectricaz Engineering, Academia Sinica, Beijing, China

R6sume - L e t r a v a i l pour l ' a m @ l i o r a t i o n de l a s t r u c t u r e s u p p o r t a n t e de r a i m a n t SSY-3 ( " a d i a b a t i c a l l y s t a b l e , saddle magnet") e s t r6sum6. C e t

a i m a n t a t t e i n t l a performance e n G c h a n t i l l o n c o u r t .

A b s t r a c t - The work r e l a t e d t o s u p p o r t s t r u c t u r e improvement, which a l l o w s t h e a d i a b a t i c a l l y s t a b l e saddle maqnet SSM-3 t o a c h i e v e "short-sample" p e r - formance, has been summarized.

I n o r d e r t o d e v e l o p t h e h i g h c u r r e n t d e n s i t y superconducting s a d d l e magnets f o r t h e MHD g e n e r a t o r , we have designed and c o n s t r u c t e d t h e SSY-3 magnet ( F i g . 1 and Tab. 1 ) . The magnet achieved q u i t e good performance / I / . B u t d u r i n g t e s t , when t h e magnet c u r r e n t reached 1.525 kA (4.22 T c e n t r a l f i e l d ) , t h e magnet s u p p o r t s t r u c t u r e has been damaqed. A f t e r d e t a i l e d a n a l y s i s o f t h e causes o f t h e damage, a new d e s i g n t o improve t h e s u p p o r t s t r u c t u r e has been made. The t e s t r e s u l t s show t h a t t h e magnet achieved "short-sampl e" performance.

F i g . 1 - Schematic d r a w i n g o f t h e SSM-3 magnet 1 - ANALYSIS OF THE CAUSES OF THE DAMAGE

To s u p p o r t t h e g r e a t r a d i a l e l e c t r o m a q n e t i c f o r c e o f t h e SSM-3 s a d d l e magnet, t h e r e were 12 p a i r s o f aluminium a l l o y I-beam r i n g g i r d e r s , each p a i r were clamped t o g e t h e r by 16 x "10 s t a i n l e s s s t e e l b o l t s ( F i q . 2 ) , i n t h e p r a c t i c a l c o n s t r u c t i o n o n l y 12 b o l t s have been used. D u r i n g t e s t , when t h e quench occured a t 1.525 kA maqnet c u r - r e n t , a sound spreaded o u t f r o m t h e dewar, t h e n t h e magnet quench c u r r e n t was r e - duced t o about 1 kA. When t h e magnet was t a k e n f r o m t h e dewar f o r i n s p e c t i o n , i t was observed t h a t a l l t h e b o l t s on one s i d e o f t h e r i n g g i r d e r s on t h e s t r a i g h t r e - g i o n o f t h e w i n d i n g (No. 4 - No. 9) were broken e n t i r e l y , t h e b o l t s on t h e o t h e r s i d e were a l m o s t undamaqed ( o n l y two o f them were b r o k e n ) . On t h e end r e g i o n o f t h e w i n d i n g o n l y one o f t h e t h r e e g i r d e r s on each s i d e (No. 2 and No. 10) were damaged.

on leave at Kernf orschungszentrum Karlsruhe, F .R.G.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19841172

C1-842 JOURNAL DE PHYSIQUE

T a b l e 1 - Main parameters o f SSN-3 magnet Conductor Y u l t i f i amentary t w i s t e d NbTi i n Cu-matrix.

1.81 x 3.28 mm', Cu/s.c = 2, 500 f i l a m e n t s , 50 rnm t w i s t p i t c h . T o t a l l e n g t h 1389 m, t o t a l w e i q h t 64.6 kg.

40 urn p o l y i m i d e t a p e i n s u l a t i o n .

Winding 45O c i r c u l a r saddle, d o u b l e pancake. 10 l a y e r s , 932 t u r n s . - - T E - r n m i n n e r d i a m e t e r , 302 mm o u t e r d i a m e t e r , 625 mm l e n g t h .

I n t e r l a y e r i n s u l a t i o n : 0 . 4 - 1.5 mm e p o x y - f i b e r q l a s s banding.

S u p p o r t s t r u c t u r e

Bore tube: S t a i n l e s s s t e e l , 190 mm i n n e r diameter, 215 mm o u t e r diameter, 790 mmilength.

G i r d e r s : Aluminium a l l o y , 12 p a i r s , 50 mm w i d t h , 312 mm i n n e r diameter, 500 mm o u t e r d i a m t e r . Magnet C e n t r a l f i e l d B / I = 27.9 G/A, Peak f i e l d B / I = 38.6 6/A

R e s i s t a n c e ~ & ~ = 6 . 4 o h m , I n d u c t a n c e ~ ~ = 0 . 2 9 7 H .

"Short-sample" performance

C r i t i c a l c u r r e n t I = 1.69 kA, C e n t r a l f i e l d Boco = 4.72 T, Peak f i e l d Bmc = 6?52 T, S t o r e d energy !$+-, = 424 k j , O v e r a l l c u r r e n ? d e n s i t y joco = 17.8 kA/cm .

F i g . 2 - R a d i a l s u p p o r t s t r u c t u r e

F i g . 3 - Damaqe o f t h e s u p p o r t s t r u c t u r e

As i t can be seen f r o m F i q . 3, t h a t t h e break o f b o l t s was b r i t t l e . The measurements o f t h e c o m p o s i t i o n and mechanical n r o p e r t i e s o f t h e demounted b o l t s a f t e r t e s t a l s o proved t h a t t h e r e was a m i s t a k e d u r i n g m a n u f a c t u r i n g t o use t h e 2Cr13 s t a i n l e s s s t e e l i n s t e a d o f t h e designed l C r l 8 N i 9 T i . A t 4.2 K, i t h s no y i e l d and t h e measured v a l u e o f i t s u l t i m a t e s t r e n g t h i s between 84 - 108 kg/mmq, t h a t means t h e b r e a k f o r c e f o r one b o l t i s 4.4 - 5.6 t.

The magnet r a d i a l e l e c t r o m a g n e t i c f o r c e per u n i t l e n g t h F R / l on t h s t r a i g h t r e g i o n o f t h e w i n d i n g c a l c u l a t e d by t h e simp1 i f i e d f o r m u l a e F q / l = 8/3 (Bo/2u0)R0 7s 5

2 . 1 t/cm, where Bo i s t h e c e n t r a l f i e l d and Ro i s t h e i n n e r r a d i u s o f t h e wlnding.

So t h e r a d i a l f o r c e a c t i n g on each p a i r o f g i r d e r s w i t h t h e w i d t h o f 5 cm i s 10.5 t, i t i s a l m o s t equal t o t h e sum o f b r e a k f o r c e s f o r one b o l t on each s i d e . I t i s c l e a r t h a t t h e damage o f b o l t s i s a l s o due t o t h e u n u n i f o r m l o a d i n g . T h i s u n u n i f o r m i t y i s c r e a t e d by t h e clamping w i t h a l o t o f b o l t s ( 6 ) i n p a r a l l e l and due t o a l a r g e number ( 6 ) o f g i r d e r s i n p a r a l l e l , i t was d i f f i c u l t t o c o n t r o l t h e i r clamping s t a t e d u r i n g assembly.

2 - IMPROVEMENT OF THE SUPPORT STRUCTURE

Based on t h e p r e c e d i n g a n a l y s i s i t was decided t o use t h e o l d aluminium a l l o y r i n g g i r d e r s and t o improve t h e s u p p o r t s t r u c t u r e i n f o l l o w i n g t h r e e aspects, namely:

( I ) u s e t h e s u i t a b l e m a t e r i a l s w i t h good l o w t e m p e r a t u r e mechanical p r o p e r t i e s ; ( 2 ) r e d e s i g n t h e clamping s t r u c t u r e c o n s i s t i n g o f l a r g e c r o s s - s e c t i o n s t a i n l e s s s t e e l p i n s and aluminium a l l o y n l a t e s t o r e p l a c e t h e o l d b o l t s ; ( 3 ) improve t h e assembly t e c h n o l o g y t o ensure r e l a t i v e l y u n i f o r m l o a d i n g between t h e g i r d e r s . F i g u r e 4 shows t h e new d e s i g n o f t h e clamping s t r u c t u r e . The two h a l v e r i n g g i r d e r s a r e connected by two 79 mm wide and 15 mm t h i c k aluminium a l l o y p l a t e s on each s i d e , t h e c o n n e c t i o n between g i r d e r s and p l a t e s a r e made w i t h two 0 24 l C r l 8 N i 9 T i s t a i n - l e s s s t e e l ? i n s . Assuming t h a t t h e e l e c t r o m a g n e t i c f o r c e i s supported o n l y by one p l a t e and one p i n on each s i d e , t h e c a l c u l a t e d maximal s r e s s e s f o r t h e magn t "short-sample" c r i t i c 1 c u r r e n t (1.69 kA) a r e 13.9 kg/mm

2 .

F i g . 4 - New d e s i g n o f t h e s u p p o r t s t r u c t u r e

F i g . 5 - Preassembly

F i g . 6 - D r i l l i n g t h e p i n - h o l e s F i g . 7 - Assembled magnet

Cl-844 JOURNAL DE PHYSIQUE

To ensure t h e t i q h t compression o f e v e r y p a i r o f r i n q g i r d e r s on t h e magnet w i n d i n g d u r i n g assembly and t o reduce t h e p o s s i b l e u n u n i f o r m i t y o f l o a d i n g between d i f f e r e n t g i r d e r s , t h e e n t i r e assembly process c o n s i s t s o f t h r e e s t e p s : preassembly, d r i l l i n g t h e p i n - h o l e s and f i n a l assembly. D u r i n g preassembly ( F i g . 5), w i t h a s i m p l e d e v i c e t h e r i n g g i r d e r s a r e pressed a g a i n s t t h e magnet winding, a f t e r c h e c k i n g t h e t h i g h t - ness o f c o n t a c t between w i n d i n g and g i r d e r s t h e p o s i t i o n o f p l a t e s r e l a t e d t o g i r d e r s i s f i x e d w i t h s e v e r a l small p i n s . Then a f t e r demounting f r o m t h e magnet w i n d i n g t h e p i n - h o l e s a r e d r i l l e d ( F i g . 6 ) , t h e h o l e s a r e machined t o t h e r e q u i r e d t o l e r a n c e w i t h a reamer. F i n a l l y t h e g i r d e r s a r e reassembled on t h e w i n d i n g , t h e p i n s a r e p u t

i n t o t h e h o l e s w i t h a wood hammer. F i g u r e 7 shows t h e assembled magnet.

3 - TEST RESULT

The magnet was t e s t e d i n a v e r t i c a l Damage of dewar. The quench c u r r e n t s i n se- support

quence a r e : 1395, 1550, 1553, 1600, structure

1622, 1623 and 1633 ( F i g . 8 ) . The h i g h e s t magnet performance achieved i s 4.56 T c e n t r a l f i e l d , 6.3 T peak f i I d , 396 k j s t o r e d energy and 27.2 kA/cm 5

c o n d u c t o r c u r r e n t d e n s i t y . I t i s 96.6%

of t h e maqnet "short-samnl?" performan- 1 . 2

c e and t h e c r r e ponding j WM v a l u e

$2 2 4

i s 2.93 x 10 j A /m . F o r comparison t h e F i g . 8 a l s o shows t h e t e s t r e s u l t s o f magnet b e f o r e and a f t e r t h e s u p p o r t s t r u c t u r e damage.

F i g . 8 - T e s t r e s u l t 4 - CONCLUSION

The s u p p o r t s t r u c t u r e improvement a l l o w s t h e SSV-3 magnet t o a c h i e v e t h e " s h o r t - sample" performance and demonstrates t h e f e a s i b i l i t y o f , c o n s t r u c t i o n h i g h p e r f o r - mance, close-packed, wax-f ill ed m i d d l e - s i z e s a d d l e magnets.

ACKNOWLEDGEMENTS

Chang Hong, L i Huidong, Yao Hai and Q i n g J i e t o o k p a r t i n t h e magnet t e s t . Xu L i t o o k p a r t i n t h e maqnet assembly. Wang Baomu and Yue Q i n g x i u o f t h e south-west

i n s t i t u t e o f p h y s i c s measured t h e mechanical p r o p e r t i e s o f t h e used m a t e r i a l s . REFERENCES

/1/ Yan Luquanq e t a l : "Development and t e s t o f a h i g h c u r r e n t d e n s i t y supercon- d u c t i n g s a d d l e magnet SSY-3", IEEE Trans. on Magnetics, v o l . MAG-19, No. 3, p. 1381 (May, 1983).