A PROTOTYPE COIL FOR THE SUPERCONDUCTING SEPARATED SECTOR CYCLOTRON SuSe

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A PROTOTYPE COIL FOR THE

SUPERCONDUCTING SEPARATED SECTOR CYCLOTRON SuSe

U. Trinks, W. Czech, G. Hinderer, E. Kellner, P. Kienle, J. Labedzki, A.

Mitwalsky, F. Nolden, U. Schneider, W. Schott, et al.

To cite this version:

U. Trinks, W. Czech, G. Hinderer, E. Kellner, P. Kienle, et al.. A PROTOTYPE COIL FOR THE SU-

PERCONDUCTING SEPARATED SECTOR CYCLOTRON SuSe. Journal de Physique Colloques,

1984, 45 (C1), pp.C1-217-C1-220. �10.1051/jphyscol:1984143�. �jpa-00223699�

JOURNAL DE PHYSIQUE

Colloque C1, suppl6ment au n o I, Tome 45, janvier 1984 page Cl-217

A PROTOTYPE COIL FOR THE SUPERCONDUCTING SEPARATED SECTOR CYCLOTRON SuSe

U. T r i n k s , W. Czech, G. Hinderer, E . K e l l n e r , P . K i e n l e , J . Labedzki, A. Mitwalsky, F. Nolden, U. Schneider, W. S c h o t t , E . Smolic, W. Wiedemann and C.H. ~ustmann'

Phys. D e p t . of Techn., Univ. Wnchen,

8046

Garching, F.R.G.

'BBC, 6800

Mannheim, F.R. G.

R6sum6

-

L1@tude du p r o j e t d ' u n c y c l o t r o n d f o c a l i s a t i o n p a r q u a t r e s e c t e u r s skpar6s (SuSe) pour p r o t o n s e t i o n s l o u r d s d ' u n e knergie maximale de 450 MeV e t 300 MeV/u respectivement (pour l e s i o n s avec Q/A = 0 . 5 ) e t avec une q u a l i - t 6 e x c e l l e n t e du f a i s c e a u e s t en c o u r s . Les aimants d e s s e c t e u r s comprennent deux grandes bobines supra-conductrices ( a n g l e du s e c t e u r 50 degrgs, rayon e x t g r i e u r 2 , 8 m ) , deux couches de b o b i n e s c o r r e c t r i c e s , des p d l e s e n f e r r e - f r o i d l s e t un c i r c u i t m a g n B t i q u e c h a u d (300 t n ) . Le champ m a x i m a l s e r a 4 , 8 T.

D a n s l e c a d r e d ' u n e Btudeexpdrimentaleun p r o t o t y p e d e b o b i n e d e s e c t e u r a dtB c o n s t r u i t .

A b s t r a c t

-

A p r o j e c t s t u d y on a superconducting s e p a r a t e d f o u r s e c t o r cyclo- t r o n (SuSe) f o r p r o t o n s and heavy i o n s with maximum e n e r g i e s of 450 MeV r e - s p e c t i v e l y 300 MeV/u ( f o r i o n s with Q/A = 0 . 5 ) and e x c e l l e n t beam p r o p e r t i e s i s under way. The s e c t o r magnets c o n s i s t o f two l a r g e superconducting s e c t o r c o i l s ( s e c t o r a n g l e -50°, o u t e r r a d i u s 2.8 m ) , two l a y e r s of superconducting t r i m c o i l s , c o l d i r o n p o l e p i e c e s and a warm i r o n yoke (-300 t n ) . The maximum f i e l d w i l l be 4.8 T. A s p a r t of a f e a s i b i l i t y s t u d y a p r o t o t y p e s e c t o r c o i l has been b u i l t .

I

-

INTRODUCTION

A t t h e Munich A c c e l e r a t o r Laboratory a p r o j e c t s t u d y on a superconducting s e p a r a t e d s e c t o r c y c l o t r o n (SuSe) f o r t h e e x i s t i n g 13 MV-tandem i s under way / I / . SuSe s h a l l a c c e l e r a t e p r o t o n s and heavy i o n s t o s p e c l f i c e n e r g i e s o f up t o 450 MeV and 300 MeV/u r e s p e c t i v e l y with e x c e l l e n t beam p r o p e r t i e s . SuSe c o n s i s t s of f o u r superconducting s e c t o r magnets and two a c c e l e r a t i n g c a v i t i e s

-

p o s i t i o n e d i n two opposing intermedzate s e c t o r s . The mean i n j e c t i o n r a d i u s i s r l = 40 cm, t h e mean e x t r a c t i o n r a d i u s i s r2 = 240 cm ( w i t h

;

= circumference/2?i). A p l a n view of SuSe i s given i n f i g . 1 , t h e main f e a t u r e s of t h e c y c l o t r o n a r e summarized i n t a b . 1.

Table 1: Main f e a t u r e s of SuSe I n j e c t i o n r a d i u s rl

-

E x t r a c t i o n r a d i u s - r 2 Maximum f i e l d a t 52 Average f i e l d a t r2 S e c t o r a n g l e p e r magnet 2 a c c e l e r a t i n g c a v i t i e s Resonant frequency range Harmonic o p e r a t i o n modes Max. a c c e l . v o l t . p e r t u r n a t

il

Max. a c c e l . v o l t . p e r f u r n a t r2 Beam s e p a r a t i o n a t

Beam s e p a r a t i o n a t r2

0.4

m

2.4

m

4.8 T 2.25 T

-50"

TElOl mode 59. .74 MHz 5 . , 6 .

, .

^.16.

500 kV 2 MV

>

9

mm

> 2 . 5

mm

Fig.1 Top view of SuSe. Sc: supercond.coi1, Y: i r o n yoke, RF: a c c e l . c a v i t y .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984143

(21-218 JOURNAL DE PHYSIQUE

Compared t o a superconducting compact c y c l o t r o n , s e p a r a t e d s e c t o r c y c l o t r o n s a s SuSe have s e v e r a l advantages, two of them we mention h e r e : f i r s t l y , due t o t h e f a c t , t h a t p a r t of t h e r e t u r n i n g magnetic f l u x can be l e d through t h e i n t e r m e d i a t e s e c t o r s by p r o p e r adjustment of t h e c r o s s s e c t i o n of t h e i r o n yoke, t h e azimuthal f i e l d v a r i - a t i o n can be made l a r g e enough t o provide e a s i l y t h e a x i a l f o c u s i n g f o r c e s even f o r t h e f a s t e s t p a r t i c l e s . Secondly, t h e open d e s i g n a l l o w s t h e i n s t a l l a t i o n o f l a r g e ca.

v i t i e s w i t h extreme high a c c e l e r a t i n g v o l t a g e s , t h u s p r o v i d i n g c l e a n i n j e c t i o n and e x t r a c t i o n , which a r e e s s e n t i a l i n o r d e r t o achieve t h e good beam p r o p e r t i e s .

I n t h i s paper t h e superconducting magnets a r e d e s c r i b e d . Another paper of t h i s confe- rence d e a l s with superconducting channel magnets without s t r a y f i e l d s a s i n j e c t i o n elements f o r SuSe / 2 / .

I1

-

THE SECTOR MAGNETS

Each of t h e f o u r s e c t o r magnets c o n s i s t s of a p a i r of superconducting main c o i l s w i t h two l a y e r s of superconducting t r i m c o i l s i n between, c o l d i r o n p o l e p i e c e s i n - s i d e t h e c o i l cases of t h e main c o i l s , and a l a r g e warm i r o n yoke. Fig. 2 shows two c r o s s s e c t i o n s o f t h e magnets, t a b . 2 g i v e s some d a t a of t h e magnets.

Table 2: Some d a t a of t h e magnets -300 t n

S t o r e d energy 5 2 5 MJ

Max.field a t r=2.5m, z=y=O 4.8 T

" " "

t h e conductor 6 . 6 , T

T o t a l weight -2 t n

C o i l c a s e AlSi9Mg

T o t a l h e i g h t Active h e i g h t

"

width

O v e r a l l c u r r e n t d e n s i t y Ampere t u r n s

Number of t u r n s C u r r e n t i n t h e c a b l e Average t u r n l e n g t h Min.bending r a d i u s of cond

-

M a g ~ e t i c p r e s s u r e , r a d i a l

5

a x i a l

(Im I

Fig.2 Cross s e c t i o n s of a magnet. S: main c o i l , Y: yoke, T: t r i m c o i l , P: c o l d i r o n p o l e p i e c e

A l l f i e l d c a l c u l a t i o n s were performed u s i n g t h e computer code GFUN3D f o r magnets with t h r e e dimensional c o i l s w i t h i r o n

/ 3 / .

Each

s e t

of superconducting c o i l s , c o n s i s t i n g of

a

main and a

t r i m

c o i l , i s enclosed by a s e p a r a t e d , w e l l f i t t i n g c r y o s t a t . The gap f o r t h e i o n s between t h e upper and lower c r y o s t a t i s 8 cm high.

I11

-

THE MAIN COILS

The width of t h e c r o s s s e c t i o n of t h e main c o i l s i s l i m i t e d t o b = 6 . 5 cm f o r two reasons. F i r s t l y t h e minimum bending r a d i u s of t h e conductor ( i n t h e c e n t r a l t i p of t h e s e c t o r ) should n o t be l e s s t h a n 7 cm. Secondly t h e d i s t a n c ' e between two magnets i n t h e c e n t r a l r e g i o n h a s t o be a t l e a s t 10 cm i n o r d e r t o g e t enough space f o r t h e a c c e l e r a t i n g c a v i t i e s . I n f i r s t o r d e r approximation t h e number of n e c e s s a r y Ampere

t u r n s ( a s w e l l a s t h e s t o r e d energy) i s p r o p o r t i o n a l t o t h e gap h e i g h t of t h e i r o n yoke and t h u s t o t h e t o t a l h e i g h t of t h e c o i l s . From

-

j a h _gap

.

^B max' ( h c o i 1s

-

b . ~ , )

-

^{( 1 )}

f o l l o w s with h /h . = 1 . 5 f o r t h e o v e r a l l c u r r e n t d e n s i t y : j z 8 8 A/mm 2

,

which r u l e s o u t t h e ~ ? ~ o s ~ ~ $ ~ ? s t a b i l i s a t i o n method f o r t h e c o i l s ( B = 4.8T, b = 6.5cm).

The computer c a l c u l a t i o n s y i e l d an e f f e c t i v e heigh5 of each ma!??ixcoil of 294

mm,

which g i v e s f o r t h e maximum f i e l d with j = 84 A/mm a t o t a l c u r r e n t of Itot=1.6.10 A p e r main c o i l . The s t o r e d energy p e r magnet t h e n i s E _magn

*

^{25 M J .}

A s a worst c a s e e s t i m a t i o n t h e h o t s p o t temperature i n c a s e of a quench y i e l d s a maximum temper t u r e of T

1

0300 K, i f t h e copper c r o s s s e c t i o n of t h e conductor

i s

a t l e a s t 15

mm .

The con%$tor ( f i g . 3 )

i s

f a b r i c a t e d by c a b e l i n g 23 superconducting NbTi-strands (8 0.7 mm, Cu/Sc = 1.9 and 1.3, 1 = 11 cm) around a copper t u b e , c a l i - b r a t i n g and soldering.The conductor i n s u l a t i o n W i s a one l a y e r h a l f overlapped g l a s s / c a p t o n / g l a s s sandwich t a p e . A s a r e s u l t from s h o r t sample measurements t h e c r i t i c a l c u r r e n t i n dependence of t h e magnetic f i e l d normal t o t h e c u r r e n t

i s

given i n f i g . 4 , t o g e t h e r with t h e working r e g i o n of t h e main c o i l (shadowed). The maximum c u r r e n t needed w i l l be 2675 A.

F i g . 3 Cross s e c t i o n of t h e SuSe-cable Fig.4 I (B) of t h e SuSe-cable a t T=4.5K Each main c o i l c o n s i s t s of 23 double pancakes with 26 windings each ( t h u s 598 win- d i n g s i n t o t a l ) . The c o i l c a s e i s c a s t i n one p i e c e , made from AlSi9Mg. I t d i v i d e s t h e c o i l i n t o t h r e e p a r t s , c o n t a i n i n g 8 , 7 and 8 double pancakes a s shqwn i n f i g . 5 . The outward d i r e c t e d e l e c t r o m a g n e t i c f o r c e s (maximum p r e s s u r e -12 N/mm

1 ,

which t r y t o make t h e c o i l s more c i r c u l a r , a r e taken up by beams of aluminium a l l o y , which a r e f i x e d t o t h e c o i l former by a x i a l b o l t s . The a x i a l f o r c e s a c t i n g between t h e upper and lower s e t of c o i l s a r e r e p e l l i n g a t t h e t i p of t h e s e c t o r c o i l s . Along t h e s i d e s t h e a x i a l f o r c e s a r e i n c r e a s i n g a t t r a c t i v e w i t h t h e r a d i u s . A t t h e o u t s i d e a r c of

t h e s e c t o r c o i l s t h e a t t r a c t i v e f o r c e s ary?

Fig.5 Cross s e c t i o n of t h e s e c t o r c o i l . DP: double pancake, He: l i q u i d helium

s t r o n g e s t (maximum a x i a l p r e s s u r e -20

~ / m m ~ ) .

A t t h e t i p and a l o n g t h e o u t s i d e a r c a x i a l c o l d s u p p o r t s between t h e two s e t s of c o i l s t a k e up t h e s e f o r c e s . I n t h e c a s e of symmetri- c a l alignment t h e r e a r e no a x i a l f o r c e s b e s i - d e s t h e g r a v i t a t i o n , which i s taken up by a x i a l s u p p o r t s t o t h e warm yoke. I n azimuthal d i r e c t i o n t h e c o i l s a r e i n a s t a b l e p o s i t i o n w i t h r e s p e c t t o t h e i r o n yoke. The r a d i a l f o r - c e s a r e d i r e c t e d outward and taken up by r a - d i a l r o d s t o t h e i r o n yoke.

The i n s u l a t i o n of t h e p o t t e d c o i l s i s matched s o t h a t t h e A l - c o i l c a s e p r e s t r e s s e s t h e c o i l when cooled from 300K t o 4.5K. The c o i l c a s e i s cooled by means of p i p e s w i t h f o r c e d flow of two phase helium a t 4.5K, 1.2bar. Thus a l l h e a t from o u t s i d e

i s

screened. The helium in- s i d e t h e conductor s e r v e s a s a h e a t s i n k i n c a s e of a s m a l l h e a t i n p u t i n s i d e t h e c o i l s .

Cl-220 J O U R N A L DE PHYSIQUE

The two c i r c u i t s w i t h L ' r ~ / 4 = 2 H a r e coupled v i a t h e mutual inductance M with t h e c o u p l i n g c o e f c i c i e n f E = 1

-

( M / L ' ) 2

<

0.02. From t h ? two e q u a t i o n s /4/:

R l I l

+

L ' I I

+

MI2 = 0 R212

+

L ' I 2

+

MI1 = 0 ( 2 )

I f t h e r e i s a l a r g e r h e a t i n p u t , which d r i v e s p a r t of t h e conductor i n t o normal con- d u c t i v i t y , t h e magnets have t o be deenergized immediately. I n o r d e r t o achieve a more uniform h e a t i n g throughout t h e c o i l s , t h e double pancakes a r e connected i n se- r i e s n o t one a f t e r a n o t h e r , b u t each second, t h u s g e t t i n g two groups, t h e odd num- bered and t h e even numbered double pancakes. Both groups have t h e i r own shunt r e s i - s t a n c e s with R l z 0 . 4 f i > > R 2 ~ 0 . 0 4 f i , t h e y a r e p u t i n s e r i e s again a s shown i n f i g . 6.

and t h e s t a r t i n g c o n d i t i o n s 1 1 ( 0 ) = I 2 ( 0 )

= I, t h e development of t h e c u r r e n t s f o l - lows a s shown i n f i g . 7. During t h e f i r s t s h o r t p e r i o d t h e c u r r e n t s r e d i s t r i b u t e w i t h t h e time c o n s t a n t TSh= & ' L ' . / ( R 1 + ~ 2 ) s0.09 s e c such, t h a t 11 becomes very s m a l l , while I 2 i n c r e a s e s n e a r l y t o 2x1, t h e n d e c r e a s i n g with t h e time c o n s t a n t T 1 = L 1 / R l + ~ ' / R 2 z 5 5 s e c . The f a s t r e d i - s t r i b t u t i o n c a u s e s eddy c u r r e n t s i n t h e conductor, t h u s h e a t i n g it and s p r e a d i n g t h e quench throughout t h e c o i l s . D u e t o t h e good thermal coupling, t h e h e a t pro- duced i n t h e high c u r r e n t p a r t i s d i s t r i - buted a l s o i n t o t h e o t h e r . The maximum temperature of t h e conductor w i l l be T c 140 K .

max

To prove t h e f e a s i b i l i t y of t h e magnets one main c o i l was o r d e r e d from B~c/Mann-

2 10-

N ,.-

a

-

R,(j*+R. ^:

^I0

Fig.8 View of t h e supercond.prototype c o i l heim a t t h e end of 1980. I t was d e l i v e r e d i n December 1982 and was prepared f o r t e s t s i n our Laboratory s i n c e t h e n ( s e e f i g . 8 ) . I n J u l y it was cooled down f o r t h e

&

r---

^{, I 2}

I -- -

--

^I

-- -

t

f i r s t time. Unfortunately s e v e r a l l e a k s i n t h e helium system hindered t h e o p e r a t i o n of t h e c o i l u n t i l now. F i r s t r e s u l t s a r e expected d u r i n g t h e n e x t weeks.

Fig.6 C i r c u i t of t h e c o i l s w i t h two I W

shunt r e s i s t a n c e s

t = O t

Fig.7 The development of c u r r e n t s

Work supported by t h e Federal Government of Germany.

REFERENCES

/1/ T r i n k s U . , Daniel H . , Graw G . , Hinderer G . , Huenges E., Kienle P., Korner H . J . , Morinaga H . , Nolden F., Nolte E . , S c h e e r e r H . J . , Schneider U . , S c h o t t W . , Skorka S., Wilhelm W . , W i l l e r s H.G., Zech E., IEEE, NS-30, No4 (1983), 2108

/2/ Nolden F., Hinderer G . , Labedzki J . , T r i n k s U . , Zech E . , t h i s conference

/ 3 / Armstrong A.G.A.M., C o l l i e C . J . , Diserens N . J . , Newman M . J . , Simkin J . , Trow-

b r i d g e C.W., Proceedings of t h e F i f t h 1ntern.Conf.on Magn.Techn., Rome 1975, 168 /4/ Turowski P . , IEEE, MAG-15, No1 (1979), 864