658 IEEE TRANSACTIONS ON MAGNETICS, VOL. MAG-15, NO. 1, JANUARY 1979 FERMILAB DOUBLER MAGNET DESIGN AND FABRICATION TECHNIQUES

K. Koepke, G. K a l b f l e i s c h , W . Hanson, A. T o l l e s t r u p , J . O'Meara, J. S a a r i v i r t a n

ABSTRACT

D u r i n g t h e l a s t y e a r , t h e F e r m i l a b D o u b l e r mag- ne t s have bene f i t ed f rom a deve lopmen t e f fo r t to up- grade the per formance of the superconduct ing magnets . T h i s p a p e r p r e s e n t s t h e r e s u l t s o f t h i s e f f o r t . The des ign ph i lo sophy and t he f ab r i ca t ion t echn iques u sed on cur ren t magnets w i l l be d i scussed , a long w i th i nno- va t ive l amina ted t oo l ing wh ich has been des igned t o g ive Fe rmi l ab a two d i p o l e a day p roduc t ion capab i l i - t y . S p e c i f i c t o p i c s t o b e d i s c u s s e d are co i l geomet ry , c o i l w i n d i n g t e c h n i q u e s , c o i l c l a m p c o l l a r s , b u s s g e o - me t ry and i n su la t ion , i n t eg ra l quench hea t e r s fo r q u e n c h p r o t e c t i o n , c o i l twist , c o i l h e l i u m i r r i g a t i o n and assembly techniques tha t assure az imutha l p re load a n d a c c u r a t e c o i l s i z e .

INTRODUCTION

I n o r d e r to minimize the construct ion and opera- t i on cos t o f t he Fe rmi l ab Ene rgy Doub le r p ro j ec t and a l s o d u e t o s p a c e l i m i t a t i o n s i n t h e e x i s t i n g 5 0 0 Gev synchro t ron t unne l , a r e l a t i v e l y s i m p l e "warm" i r o n , cold bore magnet design was a d o p t e d . T h r e e d i s t i n c t modules are sepa ra t e ly f ab r i ca t ed and a s sembled to form a c o m p l e t e m a g n e t : t h e c o l l a r e d c o i l , t h e c r y o s t a t and t h e i r o n s h i e l d y o k e .

The c o i l p a c k a g e f o r t h e d i p o l e c o n s i s t s o f a two- s h e l l d e s i g n w i t h t h e f i r s t 1 0 t u r n s of t h e i n n e r s h e l l a t t h e e n d s s e p a r a t e d w i t h . loo" s p a c e r s t o r e d u c e t h e peak f i e l d a t t h e s e l o c a t i o n s . By vary ing the az imu- t h a l c o i l a n g l e s o f t h e i n n e r a n d o u t e r s h e l l , t h e two- d i m e n s i o n a l f i e l d r e g i o n c a n b e a d j u s t e d t o c a n c e l t h e sex tapo le and decapo le t e rms p re sen t i n t he ends of t h e magnet .

By v i r t u e of i t s l o c a t i o n b e t w e e n t h e r i g i d c o i l clamp c o l l a r and t h e i r o n y o k e , t h e c r y o s t a t n e e d n o t be s e l f - suppor t ing and i s f a b r i c a t e d o u t o f t h i n s t a i n - l e s s s t ee l shee t me ta l . P rec i se a l ignmen t of t h e c o l l - a r e d c o i l a s s e m b l y r e l a t i v e to t h e i r o n y o k e i s a s su red by means of r i g i d G-10 f o r c e t r a n s f e r b l o c k s l o c a t e d p e r i o d i c a l l y w i t h i n t h e c r y o s t a t . The c r y o s t a t s come p a r t i a l l y a s s e m b l e d f r o m s e v e r a l v e n d o r s .

The m a g n e t i c s h i e l d d i f f e r s f r o m c o n v e n t i o n a l mag- n e t y o k e s o n l y i n t h e i r c r o s s s e c t i o n . They a r e assem- b l e d o u t o f l a m i n a t i o n s i n t o l e f t a n d r i g h t h a l v e s i n a s t a c k i n g f i x t u r e and j o ined a round t he co i l and cry7 os ta t assembly to comple te the magnet .

Over 100 co l l a red d ipo le a s sembl i e s have been com- p l e t ed . Rough ly ha l f o f t hese have been i n se r t ed i n c r y o s t a t s w i t h i r o n s h i e l d s a n d are i n v a r i o u s s t a g e s of i n s t a l l a t i o n i n t h e s y n c h r o t r o n t u n n e l . A s problems b e c a m e e v i d e n t d u r i n g t h e i r c o n s t r u c t i o n a n d t e s t i n g , they were corrected or improved. Laminated tool ing was designed to improve coi l accuracy and product ion r a t e . C o i l m e a s u r i n g f i x t u r e s were c o n s t r u c t e d t o mon- i t o r co i l s i ze s . Conduc to r mo t ions have been r educed wi th i nc reased p re load . A new type 5 c o i l clamp c o l l a r has been adopted which has a h i g h e r r e s i s t a n c e t o f a t i - gue and i s t o r s i o n a l l y more r i g i d . H e a t e r s h a v e b e e n i n s t a l l e d in t h e d i p o l e f o r q u e n c h p r o t e c t i o n a n d a new buss geometry has been adopted.

Manuscript received September 28, 1978.

xFermi Nat ional Accelerator Laboratory, P.O. Box 500 B a t a v i a , I l l i n o i s 6 0 5 1 0 , o p e r a t e d by U n i v e r s i t i e s Research Assoc ia t ion , Inc . under cont rac t wi th the U.S. Department of Energy.

The prototype Doubler quadrupole magnet was a "warm" i r o n , c o l d b o r e , t h r e e - s h e l l d e s i g n . S e v e n mag- ne t s o f t h i s t ype have been cons t ruc t ed and success - f u l l y t e s t e d . R e c e n t l y , a two-she l l quadrupole des ign was adopted to s impl i fy fabr ica t ion and a l low a h ighe r p roduc t ion rate.

COIL FABRICATION AND MAGNET ASSEMBLY

The sequence o f f ab r i ca t ing a c o l l a r e d d i p o l e c o i l assembly s tar ts with the winding and hot molding of two i d e n t i c a l 35 t u r n i n n e r c o i l s . Our o r i g i n a l t e c h n i q u e of "saddle" winding these co i l s was abandoned in favor of our "pancake" technique. This technique consis ts of winding a f l a t c o i l a r o u n d a n a r t i c u l a t e d k e y mounted on a .060" s t ee l r e t a i n e r s h e e t . A f t e r w i n d i n g , t h e c o i l i s covered wi th a second .060" steel r e t a i n e r and t ransverse ly compressed by means o f s ide ra i l s t o a d i m e n s i o n a p p r o x i m a t e l y e q u a l t o t h e d e s i r e d o u t e r arc l e n g t h o f t h e f i n i s h e d c o i l . The s i d e ra i l s are then f a s t e n e d t o t h e r e t a i n e r s h e e t s , r e s u l t i n g i n a "pan- cake sandwich". This i s formed around a mandre l us ing a female mold i n a 2 2 ' l ong p re s s and cu red , y i e ld ing t h e c o n v e n t i o n a l " s a d d l e " c o i l c o n f i g u r a t i o n . T h i s t echn ique has p roved t o be f a s t and accu ra t e .

The o u t e r c o i l s are "saddle" wound u s i n g t h e i n n e r p re fo rmed co i l s as a winding mandrel . This technique has r e su l t ed i n adequa te conduc to r p l acemen t accu racy d u e t o t h e s m a l l e r number o f t u rns (21) i n t h e c o i l . I n o r d e r t o p r o v i d e f o r LHe edge coo l ing , a l aye r o f .021" t h i c k i n t e r r u p t e d G-10 i s placed between the i n n e r a n d o u t e r c o i l s .

The cured two-shel led upper and lower coi l halves are placed on the assembly mandrel , covered with .030" th ick p remolded mylar g round insu la t ion ( la te r to be Kapton) and f i t t e d w i t h 4" l o n g c o l l a r s e c t i o n s . The l o o s e l y c o l l a r e d c o i l a s s e m b l y i s p l a c e d i n t o a p a i r o f mass ive channel -shaped f ix tures which provide p r e c i s e v e r t i c a l and h o r i z o n t a l c o n s t r a i n t s t o t h e c o l - l a r a s i t i s s i z e d i n a 3200 ton hydrau l i c p re s s . F in - a l ly , the assembly mandrel i s removed from t h e c o i l by means of a r a t ched-ac t ion hydrau l i c cy l inde r and t he c o l l a r i s welded on both s ides by au tomat i c we ld ing machines.

F ig . 1 Dipole lower co i l

0018-9464/79/0100-0658$00.75 0 1979 IEEE

659

i n t e g r a l m o l d s f o r f o r m i n g c o i l s a n d two 3200 ton p r e s s e s f o r s i z i n g a n d w e l d i n g c o l l a r e d c o i l s . I n a d d i t i o n , t h e r e exist s e v e r a l sets of inner and ou ter winding mandrels , assembly mandrels , and channel tool- i n g u s e d t o s i z e t h e c o l l a r s .

A l l molds , winding mandre ls and keys p resent ly in u se are made of l amina t ions . In our exper ience , 22 ' l o n g t o o l s , e v e n i n s i m p l e s h a p e s , c a n n o t b e e c o n o m i - c a l l y made t o a .0005" t o l e r a n c e . H o w e v e r , r e l a t i v e l y i n e x p e n s i v e d i e s u s i n g E l o x c u t t i n g t e c h n i q u e s c a n p r o d u c e c o m p l e x c r o s s s e c t i o n s t o .0005" t o l e r a n c e s and a l amina t ion un i fo rmi ty o f .0001" i s w i t h i n t h e p r e s e n t s t a t e of t h e a r t . Tools assembled out of s t a c k e d l a m i n a t i o n s a r e t h e r e f o r e u n i f o r m t h r u - o u t t h e i r l e n g t h a n d r e p l i c a t i o n o f t o o l i n g v e r y s i m - p l e .

P ig . 2 C o l l a r e d d i p o l e c o i l h a l f i n s e r t e d i n c r y o s t a t

F ig . 4 Oute r d ipo le mvld la -n ina t ions

To a c h i e v e t h e s , t o l e r a n c e s , t h e l a m i n a t i o n s are made ou t of mi ld s teel . A l l b e a r i n g s u r f a c e s of t h e t o o l i n g are t h e r e f o r e f i t t e d w i t h h a r d e n e d steel in - serts of s i m p l e r e c t a n g u l a r cross sec t ion wh ich can be ground t o a .0005" t o l e r a n c e . T h e s e i n s e r t s a l s o a l l o w u s to change the molded az imutha l angles o f subsequent

F ig . 3 Half yoked dipole

A magnet is completed by pushing a collared coil c o i l s t o c o m p e n s a t e f o r s y s t e m a t i c f i e l d e r r o r s meas- i n r o a prefabr ica ted c . ryos ta t , weld i .ng on t h e c r y o s t a t ured in magnets* end c l o s u r e p i e c e s and f i n a l l y f i t t i n g t h e two h a l v e s of t h e p r e f a b r i c a t e d y o k e . N o t e t h a t t h i s p r o d u , c t i o n s e q u e n c e l e n d s i t s e l f t o p r o d u c t i o n l i n e t e c h n i q u e s . Wi th t he p re sen t manpower a v a i l a b l e , a p roduc t ion ra te of 5 c o l l a r e d c o i l s p e r week has been ach ieved wi th 250 manhours r equ i r ed pe r co l l a red co i l . The i n h o u s e manpower per magnet is approximate ly 400 manhours i f we a d d t h e c r y o s t a t , y o k e a n d i n s p e c t i o n s t e p s . I t i s e x p e c t e d t h a t t h e p r o d u c t i o n rate can be doubled with t h e e f f i c i e n t u s e of a v a i l a b l e t o o l i n g a n d t h r e e f u l l y s t a f f e d s h i f t s .

The q u a d r u p o l e m a g n e t f a b r i c a t i o n u t i l i z e s t h e same p r i n c i p l e s d e v i s e d i n t h e d i p o l e d e v e l o p m e n t p r o g r a m e x c e p t t h a t t h e c o i l s a r e a l l s a d d l e wound. The f o u r sets o f c o i l s a r e wound a s d o u b l e s h e l l s , p re s sed and cu red i n t he same manner as t h e d i p o l e s . I n o r d e r t o s u p p o r t t h e f o u r i n d i v i d u a l c o i l s , t h e c o l l a r s are a p p l i e d f r o m f o u r s i d e s r a t h e r t h a n t w o , n e c e s s i t a t i n g t h e a p p l i c a t i o n o € c o l l a r s o n e a t a time.

TOOLING

The equ ipmen t ava i l ab le t o p roduce co l l a red d ipo le c o i l a s s e m b l i e s c o n s i s t s o f t h r e e 2 2 ' long winding ma- c h i n e s f o r p r o d u c i n g c o i l s , two 22 ' long presses wi th

CONDUCTOR PLACEMENT ACCURACY

I n o r d e r t o r e d u c e t h e AC l o s s i n h e r e n t i n ramped magne t s , t he supe rconduc t ing cab le adop ted fo r t he Doubler magnets was a Ru the r fo rd t ype cab le made by t w i s t i n g 23 s t r a n d s , e a c h o f .027" d i a m e t e r , i n t o a (.044" - .055") x . 307" keys toned c ros s s ec t ion i n a Turkshead die . The keys toned shape a l lows fo r p rope r c o n d u c t o r s t a c k i n g i n t h e c y l i n d r i c a l c o i l g e o m e t r y and is p o r o u s t o a l l o w f o r LHe i r r i g a t i o n . The poro- s i t y of c o i l s i s main ta ined by the use o f a non-adhe- s i v e 7 / 1 2 l a p l a y e r o f .001" x .375" Kapton for elec- t r i c a l i n s u l a t i o n f o l l o w e d by a .125" gap h e l i c a l wrap of .007" x .25" B-stage epoxy impregnated glass t ape fo r bond ing .

The t y p i c a l mean a z i m u t h a l a r c l e n g t h v s . a p p l i e d p res su re behav io r o f a d i p o l e i n n e r c o i l i s p l o t t e d i n F i g . 5. Rig id and accura te conductor p lacement o f t h e s e p o r o u s c o i l s i s ob ta ined by compact ing the c o i l s d u r i n g a s s e m b l y i n t o a s p l i t c o l l a r . The c o l l a r p r e s e n t s a r i g i d , p r e c i s e r a d i a l and az imutha l ou ter b o u n d a r y t o t h e c o i l s .

To t h e e x r e n t t h a t t h e c o i l s a c t l i k e p i e c e

660 than .001".

30 MIN CREEP

LL 0 0 0 0 0 0 0 0 0 0 uo 0 0 0 0 0 0 0 0 0 0 g o o 0 0 @ J m , l o s c = 2 a

AZIMUTHAL PRESSURE (LBS./SO.IN.)

Fig. 5 I n n e r d i p o l e c o i l s i z e m e a s u r e d relative t o 2.145", t h e mold dimension.

wise l i n e a r s p r i n g s i n t h e a z i m u t h a l d i r e c t i o n , t h e upper t o l o w e r c o i l b o u n d a r y w i t h i n t h e c o l l a r a t a g i v e n a z i m u t h a l f o r c e is de termined by ha l f the d i f f e r e n c e i n a z i m u t h a l c o i l s i z e m e a s u r e d a t t h a t f o r c e . T h e s e c o i l s i z e s ( F i g . 6) are r e g u l a r l y measured as p a r t o f our ongoing qua l i ty cont ro l p ro- gram. Al though the co i l s izes vary wi th in a .020" r a n g e , r e s u l t i n g i n a v a r i a b l e p r e l o a d , t h e c o i l b o u n d a r i e s f o r c o l l a r e d c o i l s are on the ave rage w i th - i n .001" of

W

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Lz W

2 -.010

a

L

: h e i r c a l c u l a t e d p o s i t i o n .

I I

UPPER COIL LEFT SIDE i LOWER COIL LEFT SIDE

I IO 115 120 I25 I30 MAGNET NUMBER

F i g . 6 The i n n e r d i p o l e c o i l s were measured a t an az imutha l p ressure o f 4780 l b s . / s q . i n . The e r r o r b a r s r e p r e s e n t the s t a n d a r d d e v i a t i o n o f 11 measurements t aken a long the l ength of t h e c o i l

The bore dimension of the magnet is determined by t h e w a l l t h i c k n e s s of t h e c o i l s , w h i c h r e p r o d u c e w i t h i n .001" d u e t o t h e small c u m u l a t i v e t o l e r a n c e i n t h i s d i r e c t i o n . S t r a i n g a u g e m e a s u r e m e n t s on t h e OD of t h e c o l l a r a n d t h e I D (bo re ) o f t he co i l s have shown t h a t t h e r a d i a l c o m p r e s s i o n o f t h e c o i l s i s less

The azimuthal conductor placement within individ- u a l c o i l s is h a r d e r t o c o n t r o l . The conduc to r d i s t r i - b u t i o n w i t h i n t h e i n n e r d i p o l e l a y e r , t h e l a y e r w h o s e c o n d u c t o r d i s t r i b u t i o n i s m o s t d i f f i c u l t t o c o n t r o l , has been op t ica l ly measured on c r o s s s e c t i o n s of c o l l - a r e d d i p o l e s . The measurements ind ica te tha t the con- duc tors have a mean p o s i t i o n e r r o r re la t ive t o t h e c o r - rect p o s i t i o n o f less than .001" w i t h a s t anda rd dev i - a t i o n of .003". F o r t h e o u t e r d i p o l e c o i l s a n d t h e q u a d r u p o l e c o i l s , t h i s e r r o r is e x p e c t e d t o b e less d u e t o t h e smaller number of conductors present.

C a l c u l a t i o n s and measu remen t s i nd ica t e t ha t t he conductor placement o f t h e magnet ends are a n o r d e r of magnitude less c r i t i c a l t h a n t h e two d imens iona l p a r t of the magnet . I n t h i s case, the con tour o f t h e e n d s i s a s s u r e d by mold ing prec is ion G-10 s p a c e r s t o t h e e n d s d u r i n g t h e c o i l c u r i n g s t a g e . T h e s e space r s r ema in w i th t he co i l du r ing a s sembly .

CONDUCTOR MOTION AND PRELOAD

Measurements performed on 1 f t . l o n g p r o t o t y p e s of t he Doub le r supe rconduc t ing d ipo le s i nd ica t ed t ha t t he az imutha l compac t ion o f co i l s i n ene rg ized magne t s c a n b e l i m i t e d t o a few thousands of an inch with a d e q u a t e a z i m u t h a l p r e l o a d . E a r l y a t t e m p t s t o s i z e c o i l s s u c h t h a t t h i s p r e l o a d i s t r a p p e d i n t h e c o l l a r on f u l l s i z e d m a g n e t s f a i l e d f o r t h e f o l l o w i n g r e a s o n s : The c o i l clamp c o l l a r u s e d t o b e bonded a t 200°F w i t h hea t cu re epoxy . Dur ing t h i s p rocess , t he t r apped c o i l s u n d e r t h e combined e f f e c t of hea t and p re s su re c o l l a p s e d . T h i s e f f e c t h a s b e e n m e a s u r e d t o s tar t a t 1 2 5 ' ~ .

2

The p re load t ha t r ema ined was fu r the r r educed b y t h e d i f f e r e n t i a l c o i l t o c o l l a r s h r i n k a g e f r o m room t o LHe t empera tu re . The d i f f e rence i n az imutha l c o i l s i z e A R (P) measured at room temperature and LN t empera tu re bo th a t az imutha l p re s su re P has been measured t o f o l l o w t h e e q u a t i o n :

where PO e q u a l s t h e p r e s s u r e a t w h i c h t h e s a m p l e is cooled . All p r e s s u r e s a r e e x p r e s s e d i n l b s . / sa . i n . The (P-Po) term a c c o u n t s f o r t h e d i f f e r e n c e i n Young's modulus a t t h e two tempera tures .

I n o r d e r t o a s s u r e a d e q u a t e p r e l o a d , t h e i n n e r a n d o u t e r c o i l s o f t h e s u p e r c o n d u c t i n g d i p o l e h a v e t o b e molded .040" and .005" o v e r s i z e i n t h e a z i m u t h a l d i r e c t i o n . The c o l l a r s a r e now we lded t o e l imina te t e m p e r a t u r e i n d u c e d c o i l y i e l d i n g . Upon c o o l down, a t least 4700 l b s . / sq . i n . o f az imutha l p re load r ema ins i n t h e i n n e r c o i l . T h i s h a s b e e n v e r i f i e d by s l i t t i n g t h e c o l l a r a t the median p lane o f the d ipole and m e a s u r i n g t h e f o r c e r e q u i r e d t o r e t u r n t h e s p r u n g c o l l a r b a c k t o i t s nominal dimension a t room tempera- t u r e and LN tempera ture .

Conductor motion i n t h e s u p e r c o n d u c t i n g d i p o l e s has been l imi t ed t o less than .003" i n b o t h t h e a z i m u t h a l a n d r a d i a l d i r e c t i o n a t 45 KG. The a x i a l motion a t t h i s f i e l d h a s b e e n m e a s u r e d f o r E22-43 and e q u a l s .050". The m o t i o n r e l a t e d f i e l d p e r t u r b a t i o n s as a func t ion o f cu r ren t are the re fo re domina ted by the two-dimensional par t of the magnet.

COLLARS

F a t i g u e tests performed on 1" s e c t i o n s o f t h e t y p e 4 c o l l a r p r e v i o u s l y u s e d on t h e d i p o l e s p r e d i c t e d

t h e i r f a i l u r e a f t e r 10 magnet cycles. Furthermore, t h e c o l l a r was u n a b l e t o c o n t a i n t h e c o i l p r e l o a d wi thou t excess ive de fo rma t ion and had i n su f f i c i en t r e s i s t a n c e t o a x i a l t o r q u e s .

6

A new "so l id" t ype 5 c o l l a r d e s i g n h a s b e e n adopted that overcomes these problems. The f a t i g u e p o i n t h a s b e e n r a i s e d t o l o 8 cyc le s , an o rde r o f m a g n i t u d e g r e a t e r t h a n t h e a n t i c i p a t e d l i f e of t h e a c c e l e r a t o r . Any t w i s t p r e s e n t i n t h e c o l l a r e d c o i l a s sembly a f t e r we ld ing i s m e a s u r e d r e l a t i v e t o a s u r f a c e p l a t e and reduced t o less than 3 m i l l i r a d i a n s w i t h a t o r q u e f i x t u r e . The c o l l a r i s t h e n s u r f a c e c o a t e d i n p l a c e w i t h l o w v i s c o s i t y room cure epoxy. It p e n e t r a t e s .1" a n d e f f e c t i v e l y r e s u l t s i n a t u b e of t h i s wall t h i c k n e s s t o c o u n t e r a c t a n y t o r q u e s p r e s e n t

COIL FATIGUE

The p rema tu re f a i lu re of t h e t y p e 4 c o l l a r u n d e r r e p e a t e d small motions prompted a test o f t h e i n n e r d i p o l e c o i l u n d e r similar c o n d i t i o n s . The c y c l i c a l az imutha l p re s su re and t h e r e s u l t a n t c o n d u c t o r m o t i o n t h a t t h e c o i l e x p e r i e n c e s d u r i n g a magnet current c y c l e was approximated by applying an azimuthal v a r i a b l e p r e s s u r e a t a ra te of 2 cyc le s pe r s econd . The test was performed with the sample immersed in LN, A compar ison of the az imutha l co i l s ize measured a t t h e s tar t o f t h e test and a f t e r t h e s a m p l e experienced lo6 p r e s s u r e c y c l e s showed no measurable s i z e r e d u c t i o n o r a n y o t h e r v i s i b l e s i g n s o f damage;

BUSS LEAD

Unl ike t he o the r conduc to r s i n t he magne t , t he b u s s e l e c t r i c a l i n s u l a t i o n h a s t o w i t h s t a n d 3 KV. To o b t a i n t h e r a d i a l c l e a r a n c e i n t h e magnet f o r t h e a d d i t i o n a l i n s u l a t i o n , t h e b u s s c a b l e wa$ fash ioned out o f unders ized .025" d i a m e t e r s t r a n d s t o a c r o s s sec t ion of ( .043" - .049") x .286". This buss is i n s u l a t e d w i t h 4 l a y e r s of 7 /12 lap .,001" x .375" Kapton followed by an armor layer composed of a l t e r n a t i n g d r y and B-stage impregnated .007" x .25" Kev la r t ape he l i ca l ly wrapped w i th a b u t t l a p .

HEATERS

Two hea te r s , one r edundan t , have been i n s t a l l ed i n t h e d i p o l e s as p a r t o f a proposed quench protec- t i o n c i r c u i t f o r t h e D o u b l e r . The purpose o f the h e a t e r s i s t o i n i t i a t e a uni form longi tudina l quench i n t h e s u p e r c o n d u c t i n g t u r n i m m e d i a t e l y a d j a c e n t t o t h e h e a t e r . T h i s q u e n c h r a p i d l y p r o p o g a t e s i n the t r a n s v e r s e d i r e c t i o n f r o m t u r n t o t u r n , p e r m i t t i n g t h e magnet t o a b s o r b i t s s to red ene rgy w i thou t damage.

Each h e a t e r c o n s i s t s o f a .005" x .200" s t a i n l e s s s teel s t r i p wound unde r t he g l a s s t ape o f t he comple t e f i r s t t u r n o f a n o u t e r c o i l . It f a c e s away f rom the c o i l a n d is i n s u l a t e d f r o m t h e t u r n by a .010" s t r i p o f K a p t o n .

QA QUADRUPOLES

The p r o t o t y p e QA quadrupole was a 3..25" b o r e , 3 - s h e l l d e s i g n . T h e t o o l i n g f o r t h i s m a g n e t was des igned fo r accu racy and s u f f i c i e n t p r e l o a d i n g c a p a b i l i t y , b o t h o f w h i c h were a t t a i n e d .

The f i r s t several q u a d s d M n o t a t t a i n , a p r e l o a d i n t e r n a l l y . The l o s s of preload w a s t r a c e d t o t h e h e a t c u r e c y c l e o f b o n d i n g t h e c o l l a r s . The l as t two quads were then bonded with room tempera tu re cu re epoxy. They d id ach ieve az imutha l p re load . The v e r i f i c a t i o n of p re load was obtained by magnet ic f i e ld measu remen t s unde r exc i t a t ion . The 12-pole

661

component is s e n s i t i v e t o c h a n g e i n t h e c o i l s i z e . 3 y ' c a l c u l a t i o n , t h e r a t i o o f t h e 1 2 - p o l e t o t h e & p o l e component ( i . e . quadrupo le ) a t 1 inch r ad ius changes by 1 p a r t i n 10,000 f o r a 0.001 inch az imutha l squeeze . Adequa te ly p re loaded co i l s w i l l t h e n show a c o n s t a n t 1 2 - p o l e r a t i o w i t h v a r y i n g e x c i t a t i o n c u r r e n t ; a change w i l l i nd ica t e mo t ion . The h e a t c u r e d c o l l a r e d a s s e m b l i e s show a 12-po le r a t io chang ing w i th exc i t a - t i o n ( F i g . 7A). The magnitude of the observed change i n t h i s r a t i o a g r e e s well wi th independent mechanica l measu remen t s o f t he co i l mo t ion unde r exc i t a t ion . The room t e m p e r a t u r e c u r e d c o l l a r e d a s s e m b l i e s ( F i g . 7B) show a c o n s t a n t v a l u e f o r t h i s r a t i o , i n d i c a t i n g a motion of less than 0.001".

QB QUADRUPOLE

The product ion QB quadrupole i s a 3 .5" bore , two- s h e l l d e s i g n . D i p o l e t o o l i n g t e c h n i q u e s h a v e b e e n i n c o r p o r a t e d t o p r o d u c e t o o l i n g t h a t w i l l a l l o w a h i g h product ion rate. A s p a c e r h a s b e e n i n c o r p o r a t e d i n t h e inne r co i l wh ich r educes t he 20 -po le a f a c t o r o f 5 o v e r t h e QA d e s i g n . The f i r s t QB magnet tes ted reached 5400 A (22KG/in.) i n t h r e e q u e n c h e s . A pre l iminary harmonic p robe ana lys i s i nd ica t e s no conduc to r mo t ion i n t he c o i l s .

X I I I I I

t 4 a) HEAT CURE

I 2 5 - 0

0

0

s 5 -2 LY - " F- b) ROOM C U R E

u -7 E Z 1 i / , I I I

4 0 I 0 CURRENT (KILOAMPERES)

2 3 4 5

F i g . 7 QBA Magnet 12 P o l e t o 4 P o l e R a t i o s .

ACKNOWLEDGEMENT

The teamwork of t h e F e r m i l a b s t a f f is r e s p o n s i b l e fo r t he success o f t he Doub le r magne t p roduc t ion p ro - gram. The a u t h o r s w i s h t o s p e c i f i c a l l y a c k n o w l e d g e t h e c o n t r i b u t i o n o f S . Bara th , J. Carson, J. Humbert, J. Jagger , G. J u g e n i t z , D. Smith and the remaining s t a f f o f t h e F e r m i l a b Magnet F a c i l i t y .

References

1. P. Livdahl , IEEE, Trans. Nucl . Sci . , N S - 2 4 , No. 3, 1218 (1977)

2. A. T o l l e s t r u p , e t . a l . , I E E E , Trans. Nucl . Sci . , NS-24 NO. 3 , 1331 (1977)