FURTHER IMPROVEMENT OF GALETTE COILS

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FURTHER IMPROVEMENT OF GALETTE COILS

A. Doroshenko, Yu. Katrukhin, B. Khrustalev, T. Shulgina, K. Trojnar

To cite this version:

A. Doroshenko, Yu. Katrukhin, B. Khrustalev, T. Shulgina, K. Trojnar. FURTHER IMPROVE- MENT OF GALETTE COILS. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-59-C1-62.

�10.1051/jphyscol:1984112�. �jpa-00223589�

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JOURNAL DE PHYSIQUE

Colloque Cl, supplément au n° 1, Tome <f5, janvier 198* page Cl-59

FURTHER IMPROVEMENT OF GALETTE COILS

A.P. D o r o s h e n k o , Yu.K. K a t r u k h i n , B . P . K h r u s t a l e v , T.V. S h u l g i n a and K. T r o j n a r *

L.V. Kirensky Institute of Physics, Krasnoyarsk, U.S.S.R.

*International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw, Poland

Résumé - Dans cette publication nous présentons un procédé de collage des contacts électriques entre les galettes à l'aide d'un adhésif conducteur. Cette méthode de jonction des disques a été choisie dans le but de protéger les con- nections contre les déformations de flexion qui résultent de l'action des forces électrodynamiques. Ce procédé améliore la technologie de l'assemblage des galettes qui a déjà été décrite au cours de la conférence MT 7. La méthode de la trans- formation conforme a été employée au cours du calcul des conditions de refroi- dissement des galettes.

A b s t r a c t - T h i s p a p e r p r e s e n t s a method of g l u e i n g e l e c t r i c a l c o n t a c t s between winding d i s c s of t h e g a l e t t e c o i l s w i t h a con- d u c t i n g a d h e s i v e . T h i s way of j o i n i n g t h e d i s c s s h o u l d p r e v e n t s t h e bending d e f o r m a t i o n a r i s i n g a s t h e r e s u l t of e l e c t r o d y n a m i - c a l f o r c e s a c t i o n . The method improves t h e t e c h n o l o g y of assemb- l i n g t h e g a l e t t e c o i l s d e s c r i b e d a t Conference on Magnet Techno- l o g y MT-7. The conformal mapping method was used f o r c a l c u l a t i o n of t h e c o o l i n g c o n d i t i o n s i n t h e g a l e t t e c o i l s .

I - GLUEING OP THE GALETTES

I n a t a l k g i v e n a t t h e MT-7 Conference we p r e s e n t e d t h e t e c h n o l o g y and d e s i g n f o r g l u e d pancake c o i l s f o r s t a t i o n a r y m a g n e t i c f i e l d s [lj.

Since t h e n t h e t e c h n o l o g y improved, and t h e g a t h e r e d e x p e r i e n c e p r o - ved h i g h performance of such w i n d i n g s . The s o l e n o i d f o r 10 T d e s c r i - bed i n [1] h a s been working more t h a n 3 y e a r s w i t h o u t change of t h e w i n d i n g s . Main t e c h n o l o g i c a l improvements were aimed a t i n c r e a s i n g s t r e n g t h of t h e g a l e t t e c o i l s .

I n t h e e a r l y - s t a g e d e s i g n of t h e g a l e t t e - c o i l s p r e p a r a t i o n t h e con- t a c t s u r f a c e s have been c o p p e r - p l a t e d up t o h a l f t h e t h i c k n e s s of t h e i n s u l a t i o n and t h e n s i l v e r - p l a t e d . - I n t h e new t e c h n o l o g y t h i s o p e r a - t i o n i s u n n e c e s s a r y , and t h e c o n t a c t s u r f a c e s a r e p r e p a r e d f o r g l u e - i n g . The r o l e of t h e c o n t a c t agent i s p l a y e d by a m e t a l l i c n e t f i l l e d up w i t h a c u r r e n t - c o n d u c t i n g g l u e . I t c o n t a i n s t h e same b a s e , f i l l e d w i t h powdered n i c k e l or s i l v e r , a s t h e one used f o r i m p r e g n a t i n g f i - b e r - g l a s s .

Assembling of a g a l e t t e b e f o r e g l u e i n g i t , i s shown i n f i g . 1 . The i n - s u l a t i n g g l u e i n g f i l m h a s a s l o t which, when t h e g a l e t t e i s assembled c o i n c i d e s w i t h t h e c o n t a c t s u r f a c e . I n t h i s s l o t c u r r e n t - c o n d u c t i n g g l u e i n g f i l m of a t h i c k n e s s e q u a l t h a t of t h e i n s u l a t i n g f i l m i s p l a - c e d . Copper s i l v e r - p l a t e d s e c t o r s a r e g l u e d t o t h e o u t e r c o n t a c t s of t h e g a l e t t e s .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984112

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J O U R N A L D E PHYSIQUE

Fig.1. Galette stacking.

1. Conductive disc.

2. Insulating adhesive film.

3. Conductive adhesive film.

4. Outer silver-platted sector.

5. Fixing rods.

a. Direction of metall rolling.

Shear tensions appearing in the contact plane depend on the overlap- ping surface, but they should not exceed the strength of the glued contact even in the uncompressed winding. Glueing the contacts not only increases the strength of the coil but also improves the electri- cal contacts between the discs.

A new experimental winding for a field up to 1 5 T is now tested at the International Laboratory. Part of the galettes is prepared following the new technology. Different technological variant, using copper-gallium glues is now worked out.

Cold-worked copper and its alloys used in preparation of the windings get anisotropic structures during rolling. The mechanical anisotropy of hardened copper depends on the deformation level of the rolling and the higher is the strength reached by hardening, the higher is the anisotropy of the material. The data presented in [2] show that for the hardened copper the elasticity modulus along and at an angel of 4 5 O to the rolling direction differ by 35%. Our investigations showed that cold-worked copper ribbon used for windings has a higher tensill strength in the direction perpendicular to the rolling than along it. Usually it is not necessary, when packing the discs into a galette, to take into account the direction of rolling. However, it could not be neglected when designing a magnet for extremely high fields. To ensure that every disc will be positioned in a given direction it is enough, before milling the radial slots, to arrange copper plate in such a way that the rolling direction is the same in all ones. Then a glued galette will resemble aviation plywood of identi- cal strength in all radial directions. Arrangements of the discs is shown in fig.1. Method of the calculations of glued galette-coils strength will be presented elsewhere.

2 - CALCULATIONS FOR THE CURRENT DENSITY DISTRIBUTION

An attempt was made in [3] to solve this problem mathematically by means of the conformal mapping. Unfortunately in view of encountered difficulties, the author has restricted to particular case

-

^{the in-}

finite conductive plane with one hole only.

We use the method of conformal mapping to calculate the current den-

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sity distribution in a disc, its resistance , magnetic field and the Fabry coefficient. We assume the same temperature in all points of the disc.

Following [3,4 let us divide the disc into a series of conducting zones joined parallely. Each zone will be treated as a two-connected domain D (p=1,2.3,.

. .

,n) in the complex plane Z=x+iy fig. 2.

P

X

Fig.2. Conducting zones. 1,2,3 are the equipotential lines.

Let

r=

,$ ( 2 ) be a conf ormal mapping of the domain

Dp on the ring in the complex plane

P .

Then the current vector

d

^could

be 'written as

i z ~ : den$tr)

- (

^{d z}

where is the voltage drop on the disc,

P

is the resistivity. From the last expression the absolute value of the current density at an arbitrary point inside the zone D is given by

P

The total current running through the zone Dp has the form

where t. is the thicness of the disc.

The resistance of the zone can be written as R : - 25p/i!

eflg

.

This expression has been used by us to calculate the distribution of the cooling channels. They should be located in such a way that every zone DD will map conformally on the same ring

f & < r (

-Resistances of the Ging and the zone do not change when one is conformally mapped into the other, and zones have equal resistances if and only if they map conformally into the same ring . - c 9 L 7

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C 1-62 JOURNAL DE PHYSIQUE

The function

( P )

which maps the ring GP ( 7 into the zone D is given by Laurent series

X,

where A-k and Ak are real coefficients evaluated numerically on a computer. This method has been used when designing a single-section solenoid for 1 5 T in the L.V.Kirensky Institute of Physics. Experien- ce gained at the International Laboratory for High Iblagnetic Fields and Low Temperatures was helpful. The results of calculations of the current density distribution in the solenoid are presented in fig.3.

Fig.3. Current density distribution along the respective equipotential lines plotted on fig.2. Y2(V)is drop of voltage on the disc. p ^(om-cm).

---

is current density in the Bitter coil without cooling holes.

The method of conformal mappings enables to make the first step in the calculations of the concentrations of heat and mechanical stres- ses. The details of the method are given in [5]

.

REFERENCES.

1

.

KATRUKHIN YU. K. , KHRUSTALEV B. P. , TROJNAR K. , IEEE Trans

.

^Map.^,^fiIa~-¹⁷

(1981) 1896.

2.FRIDMAN J.B. ,MIKLAEV P.G.,Doklady ~ k a d . ~ a u k , S S S R , ~ ( 1 9 6 6 ) , 8 0 .

3. FOURNIER J.,Rappo::t T.T.,61,Centre dtEtudes Nucleaires de Grenoble (1966).

4. BOISSIER R.,BFUCHANT F.,GOJER J.,FOURNIER J.,RICQUE R.,FERON J.L., PAUTHENET R.,PICOCHE J.C.,Proc.of the Second 1ntern.Conf.on YIag.Techn.

Oxford (19671,157.

5. DOROSHENKO A.P.,Preprint N238,L.V.Kirensky Institute of Physics, Krasnoyarsk,USSR,660036,(1983).