CONSTRUCTION AND TESTING OF BOBBIN-LESS SUPERCONDUCTING SOLENOID MAGNET

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CONSTRUCTION AND TESTING OF BOBBIN-LESS SUPERCONDUCTING SOLENOID MAGNET

M. Wake, M. Takasaki, H. Hirabayashi, T. Satow, O. Asai, K. Kuno, T.

Kawaguchi, M. Fukuzuka

To cite this version:

M. Wake, M. Takasaki, H. Hirabayashi, T. Satow, O. Asai, et al.. CONSTRUCTION AND TESTING

OF BOBBIN-LESS SUPERCONDUCTING SOLENOID MAGNET. Journal de Physique Colloques,

1984, 45 (C1), pp.C1-347-C1-350. �10.1051/jphyscol:1984171�. �jpa-00223727�

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CONSTRUCTION AND TESTING OF BOBBIN-LESS SUPERCONDUCTING SOLENOID MAGNET

M. Wake, M. T a k a s a k i , H. H i r a b a y a s h i , T. Satow*, 0 . A s a i * , K. Kuno*, T. Kawaguchi* and M. Fukuzuka**

KEK National Laboratory for High Energy Physics, Oho-machi, Tsukuba-gun, Ibaraki 305, Japan

*Mitsubishi Electric Co., Wadasaki-cho, Hyogo-ku, Kobe 652, Japan

**Asada Research Laboratory, Kobe Steel Ltd., Gamo, Nada-ku, Kobe 652, Japan

Résumé - On présente la construction et les résultats de test d'un solénoxde supraconducteur sans mandrin à échelle 1/4, pour le détecteur VENUS.

Abstract - We present construction and testing of the 1/4 model of the bobbin-less superconducting solenoid magnet for VENUS detector.

1. Introduction

Solenoid magnets are usually wound on bobbins. However, the electro-magnetic force which works on the coil is always toward outside and the existence of the bobbin is not always necessary for the mechanical support of a solenoid magnet. VENUS, a general purpose detector for TRISTAN e-e+ collider at KEK, is planned to be constructed with a bobbin-less superconducting thin solenoid magnet1'. In the R&D program of VENUS, a lm^xl.2m solenoid magnet, the 1/4 model of VENUS, was built to develop the construction method, to check the feasibility of the bobbin-less structure and to test the cryogenic performance of the CFRP cryostat. Whole the magnet including the horizontal cryostat was assembled as shown in the photograph of Fig.l. The main parameters of the magnet are listed in Table 1 and the cross-section of the magnet is shown in Pig.2.

2. Superconducting composite

The Superconducting composite is made of a Nb-Ti-Ta-Zr/Cu multi-filamentary superconducting monolith in a pure aluminum stabilizer. The sizes of superconducting monolith and composite are 2.1 x 3 mm and 5 x 8 wm, respectively. Figure 3 is the cross-section photograph of the composite.

The covering of pure aluminum on superconducting monolith was made by extrusion using the port-hole method. The boundary between the superconducting monolith and the stabilizer aluminum has the metallurgical bonding which has shearing strength of 3.2 ~- 4.0 kg/mm2 with no change through the heat cycles between 80K and 500K. The uniformity of the shearing strength of the boundary along longitudinal position was confirmed by tests at every 5m of a 400m sample. The critical current of the composite, Ic, was measured to be 8400A at 2.2T. The Ic characteristics of the conductor is shown in Fig.4. The joint between conductor units was made by water cooled welding. No degradation of Ic was observed at the joint. The resistance of the welding joint was 2.8 x 10-9n/100mm.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984171

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Cl-348 JOURNAL DE PHYSIQUE

3 . C o i l C a s e

T h e c o i l c a s e , o u t s i d e s u p p o r t i n g . s t r u c t u r e o f t h e c o i l , is made o f 1 2 s e g m e n t s o f e x t r u d e d a l u m i n u m p i e c e s shown i n F i g . 5.

T h e r e c t a n g u l a r h o l e s i n t h e s e g m e n t a r e t h e h e l i u m p a t h s t o cool t h e magnet. The m a t e r i a l , m o d i f i e d L55 aluminum, was c h o s e n f r o m t h e v i e w p o i n t o f e a s y e x t r u s i o n a n d h i g h s t r e n g t h . The t e n s i l e s t r e n g t h , y l e l d i n g s t r e n g t h and elongation r a t i o a r e 27.6kg/mm2, 24.5kg/mm2 a n d 1 3 . 9 % , r e s p e c t i v e l y . To f o r m t h e a c c u r a t e c i r - c u l a r s h a p e , s e g m e n t s a r e w e l d e d o n a m a n d r e l w i t h h e a t d i s s i - p a t i n g w a t e r f l o w .

4.

Coil

The c o i l i s , a t f i r s t , wound o n a m a n d r e l h a v i n g a e x p a n s i o n s e t - u p . F i g u r e 6 shows t h e s t r u c t u r e o f t h e e x p a n s i o n s e t - u p . A f t e r t h e w i n d i n g , t h e c o i l is h e a t e d t o c u r e e p o x y u n d e r a x i a l c o m p r e s s i o n w i t h r e l e a s e d t e n s i o n b y t h e r e d u c t i o n o f t h e m a n d r e l d i a m e t e r .

T h e c o i l c a s e , p r e f o r m e d i n t o h a l f s h e l l s b e f o r e t h e f i n a l w e l d i n g , was t i g h t l y f i t o n t h e c o i l a n d w e l d e d t o g e t h e r .

W a t e r c o o l e d w e l d i n g is u s e d t o a v o i d t h e damage o f t h e con- d u c t o r . The t e m p e r a t u r e a t t n e s u r f a c e o f t h e c o i l m e a s u r e d d u r i n g t h e w e l d i n g is shown i n F i g . 7. T h e c o i l was e x p a n d e d b y t h e m a n d r e l t o s e c u r e t h e f i t n e s s b e t w e e n t h e c o i l a n d t h e c o i l case. T h e n , t h e g r o u n d i n s u l a t i o n o f t h e c o i l , 7 l a y e r s o f K a p t o n w i t n B - s t a g e e p o x y , was c u r e d a t 1 4 0 Q C u n d e r c o m p r e s s i o n o f 1 5 kg/cm2. The e x p a n s i o n was made b y h y d r a u l i c p r e s s u r e u s i n g s t a i n l e s s s t e e l t u b e s l o c a t e d i n t h e e x p a n s i o n s e t - u p o f t h e m a n d r e l . T h e c o i l was s u p p o r t e d b y CFRP s u p p o r t i n g c o l u m n s f r o m t h e s t a i n l e s s s t e e l e n d r i n g s .

5. CFRP Vacuum Chamber

T h e o u t e r w a l l o f t h e c r y o s t a t is made o f 8mm t h i c k CFRP t o r e d u c e t h e m a t e r i a l t h i c k n e s s w i t h o u t c a u s i n g t h e b u c k l i n g d u e t o t h e a t m o s p h e r i c p r e s s u r e .

D i m e n s i o n s o f CFRP vacuum c h a m b e r a r e 1,186mm i n d i a m e t e r , 1,005mm i n l e n g t h and 8mm i n t h i c k n e s s .

T h e CFRP vacuum c h a m b e r was made b y c l o t h w i n d i n g u s i n g a low t e m p e r a t u r e t y p e r e s i n . The Youn 's m o d u l u s , t e n s i l e s t r e n g t h a n d volume f a c t o r a r e 4 , 1 3 0 kg/mmj, 4 2 . 1 k g / m 2 a n d 40.6%.

r e s p e c t i v e l y . The c o n n e c t i o n s b e t w e e n CFRP c h a m b e r a n d s t a i n l e s s s t e e l e n d r i n g s w e r e made b y O - r i n g s .

T h e vacuum p r o p e r t y o f t h e CFRP c h a m b e r w a s t e s t e d b y s m a l l m o d e l s p r i o r t o t h e c r y o s t a t c o n s t r u c t i o n .

T h e o u t g a s r a t e o f CFRP a f t e r b a k i n g a t 60°C was f o u n d t o b e 5 x 10-8 ~ o r r . l / s e c * c m ~ w h i c h is s u f f i c i e n t l y s m a l l .

6. T e s t O p e r a t i o n

T h e p r e l i m i n a r y c o o l d o w n was made down t o 4.8K a t t h e m i d d l e p a r t o f t h e c o i l . The c o o l d o w n t i m e o f t h e m a g n e t w a s a b o u t 5 0 h r s as shown i n F i g . 8. Due t o t h e u n e x p e c t e d h e a t l e a k s , t h e f i x e d e n d o f t h e c o i l was n o t c o l d e n o u g h t o e x c i t e t h e m a g n e t t o t h e f u l l c u r r e n t . So f a r , t h e m a g n e t was e x c i t e d u p t o 2600A

(5kG=VENUS minimum f i e l d ) . Vacuum l e a k o r m e c h a n i c a l b r e a k down h a s n o t b e e n o b s e r v e d u p t o t h i s c u r r e n t .

7. C o n c l u s i o n

T h e b o b b i n - l e s s s t r u c t u r e is f e a s i b l e f o r VENUS s u p e r c o n - d u c t i n g t h i n s o l e n o i d magnet. T h e c o n s t r u c t i o n method w i t h e x p a n d a b l e m a n d r e l a n d w a t e r c o o l e d w e l d i n g was f o u n d t o b e v e r y u s e f u l . The u s e o f CFRP i n t h e o u t e r w a l l o f t h e c r y o s t a t d i d n o t c a u s e a n y vacuum p r o b l e m o r b u c k l i n g o f t h e w a l l . The t h e r m a l p r o p e r t i e s w i l l b e s t u d i e d f u r t h e r more.

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f o r t h e i r s u p p o r t and e n c o u r a g e m e n t . We would l i k e t o t h a n k D r s . T . l l a t s u i , T.Kondo a n d N . I s h i h a r a f o r t h e i r h e l p f u l d i s c u s s i o n s .

R e f e r e n c e

1 ) Y. Nagashima e t ^{d l . ,} P r o p o s a l f o r S t u d y o f e + e - R e a c t i o n s w i t h a L a r g e A p e r t u r e S p e c t r o m e t e r , TRISTAN-EXP-001 KEK

( 1 9 8 3 ) .

F i g . 1 C o m p l e t e d magnet

Table 1. Parameters of Bobbin-less

superconducting S o l e n o i d Model Magnet Conductor

Bare w i r e

cu/sc CuRRR A1RRR r (Al/cul Filament dia.

p i t c h C r i t i c a l C u r r e n t C o i l

-

I D (Innder d i a . I L (Length) Number of Turns O p e r a t i o n a l C u r r e n t Center F i e l d s I n s u l a t i o n S t r e n g t h

: NbTi/Cu w i t h p u r e aluminum s t a b i l i z e r 5.0 x 8.Omm : 1.0 : 205 : 1500 : 3.2 *. 4.0kg/m2 : 35pmm : 50mm

: 12000A ( a t 4.2K, 1Tl : iooomm

: 1200mm : 237 ( 1 l a y e r

s o l e n o i d c o i l ) : 5000A

: 1.OT : 15oov C r y o s t a t

OD (Outer d i a . : 1186mm

I D ( I n n e r d i a . I : 896mm

L (Length) : 1 3 8 0 ~

Outer Wall : C m , 8mm i n

t h i c k n e s s

I n n e r Wall : Al, 3mm i n t h i c k n e s s

Heat leakage : c2Ow

F i g . 2 C r o s s - s e c t i o n o f t h e m o d e l m a g n e t

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C1-350 JOURNAL DE PHYSIQUE

-

2 0 0 - -

-

L

-

100..

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

0 6 1 2 18 2 4 ^I 3 0 36 4 2 4 8 5 4

c o m p o s i t e T I M E (Hr)

F i g . 8 C o o l down c u r v e

F i g . 7 T e m p e r a t u r e d u r i n g w e l d i n g

F i g . 4 S h o r t s a m p l e c h a r a c t e r i s t i c s o f t h e c o n d u c t o r

F i g . 6 E x p a n d a b l e m a n d r e l

F i g . 5 S e g m e n t o f t h e c o i l c a s e