@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Science, Faculty of"@en, "Physics and Astronomy, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Aaronson, David Andrew"@en ; dcterms:issued "2012-03-05T17:55:27Z"@en, "1950"@en ; vivo:relatedDegree "Master of Arts - MA"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """A seven and one half ton electromagnet has been built primarily for beam analysis in conjunction with the University of British Columbia electrostatic generator. With a current of 49 amperes, a field in excess of 19,900 gauss over an area of 256 square inches has been obtained across a one inch air gap. The hysteresis loop is satisfactorily small, being 0.2 amperes wide at a magnetising current of 15 amperes. Current stability with the magnetising current varying from zero to 35 amperes has "been maintained to a few parts in 10,000 over periods as long as seven hours. Field stability has been checked using a proton resonance signal to be one part in 10,000 over a short period of eight minutes, and to be three parts in 10,000 over the long period of seven hours. Using the stabilising system, the time required to change the field to a new setting is less than three seconds."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/41136?expand=metadata"@en ; skos:note "L £ -b ft 7 (1 So f\\i D E S I G N , C O N S T R U C T I O N A N D S T A B I L I S A T I O N O F A L A R G E E L E C T R O M A G N E T b y D a v i d A n d r e w A a r o n s o n A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R O F A R T S i n P H Y S I C S • T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A S e p t e m b e r , 1 9 5 0 T H E U N I V E R S I T Y O F BRITISH C O L U M B I A VANCOUVER. CANADA D E P A R T M E N T O F P H Y S I C S October 12, 1950. Dr. L. W. Dunlap, L i b r a r i a n , University of B r i t i s h Columbia. Dear Dr. Dunlap: This w i l l c e r t i f y that the thesis of Mr. D. A. Aaronson has been c a r e f u l l y studied by the undersigned, and that the thesis meets the required standards and an abstract has been approved by the Department. Yours sincerely, G. M. Shrum Head of the Department GMS:1c G. G. Eichholz Assistant Professor of Physics THE UNIVERSITY OF BRITISH COLUMBIA V A N C O U V E R , C A N A D A /?/~. S~. \"5-Chapter l t The Magnet (a) Function of the magnet The magnet was designed to \"bend a f i v e mev. \"beam of protons and deuterons through a 90 degree angle f o r energy-resolution. (\"b) Pole Shape I t s general.shape i s shown i n f i g . 1 . Various possible pole piece shapes were considered f o r t h i s pur-pose but i t seemed very desirable to be able to bend the i o n beam to the l e f t or to the r i g h t without s h i f t i n g the magnet so that two experiments might be set up together. Consequently the other most considered design, that of a single quarter c i r c l e pole piece with banana c o i l s wound round the poles with the whole magnet on a swivel, was given up. After examining possible shapes of pole taper needed to give the f i e l d a c t u a l l y required at the gap, and a round yoke on which to wind the poles, a square pole t i p was chosen. This gave a very conventional design which i s e a s i l y adapted f o r other experiments requiring a large H ^ such as spectrograph applications or even f o r a cloud chamber; and provision was therefore made f o r -6-a l t e r i n g t h e g a p w i d t h a n d p o l e s h a p e , ( c ) S i z e C o n s i d e r a n i o n o f c h a r g e e, m a s s m , m o v i n g w i t h v e l o c i t y v , e n t e r i n g a m a g n e t i c f i e l d o f s t r e n g t h H . I t w i l l h e b e n t i n a n a r c o f r a d i u s p s u c h t h a t H e v - m v 2 H p - m v e I n a c o n s i s t e n t s e t o f u n i t s , c . g . s . , e . m . u . ; w i t h H i n e . m . u . a n d e i n e . s . u . w e h a v e , w h e r e e i s t h e v e l o c i t y o f l i g h t , H p - m v c v e I f t h e i o n a t t a i n e d t h e v e l o c i t y v b y b e i n g a c c e l -e r a t e d t h r o u g h a n e l e c t r i c f i e l d o f s t r e n g t h E , t h e n , 1/2 m c v 2 z e E r \" v = / 2 e _ V m c E t h e r e f o r e H P a / 2 m c T h e v a l u e o f H 0 r e q u i r e d t o d e f l e c t i o n s a c c e l e r a t e d \\ 4 t h r o u g h a n e l e c t r i c f i e l d o f f i v e m i l l i o n v o l t s i s : f o r p r o t o n s , 3 . 2 2 x 1 0 g a u s s c m . f o r deuterons 3.22 x 10 5 - 4.55 x 10 5 gauss cm., and r— 5 5 f o r t r i t o n s 7 3 x 3.22 x 10 = 5.6 x 10 gauss cm. Protons could \"be deflected i n both d i r e c t i o n with a 5 f i e l d o f : 3.22 x 10 = 16,100 gauss i n a radius of 20 20 cms.. Deuterons i n one d i r e c t i o n with a f i e l d of : 5 4.55 x 10 - 15,200 gauss i n a radius of 30 30 cms.. Tritons i n one d i r e c t i o n only with a f i e l d o f: 5 5.6 x 10 - 16,000 gauss i n a radius of 35 35 cm.. Therefore, a square pole t i p of size 16 inches on a side, equal to 40.6 cm. on a side was decided on. This then set the size of the round pole pieces and thus the yoke cross section. (d) S t a b i l i t y Since t h i s molecular beam would be required f o r the 5 Van de Graaff e l e c t r o s t a t i c generator s t a b i l i z a t i o n , and also f o r energy r e s o l u t i o n of three kev. i n f i v e mev., we must require the A H to be equal to three parts i n H . — • 10,000; as from (2) p 4 H = / 2 m c 1/2 _E e and 4_H = j/2 4_E H E When current s t a b i l i z a t i o n i s used 4 I must be less I than A H because of the following f a c t o r s , a l l of the H . g order of a few parts i n 10 or less 1. The width of the a i r gap varies due to the thermal expansion of the i r o n and the magnetic force bending the i r o n 4' Ma q n et yoke and pole p i e c e s -8-2. The incremental permeability of the i r o n and 6 hysteresis vary with the previous magnetic h i s t o r y . 3. There i s a small mechanical hysteresis i n the \\ i r o n of the pole pieces, b o l t s and nuts. (e) Design of Magnet The design of the magnet and c o i l s followed i n t h i s manner: Take H p as 6 x 10 gauss cm. and consider a maximum H of 15,000 gauss across a one inch gap, allowing a beam siz e of one h a l f inch. The pole t i p s , to be square, w i l l be about 40 cm. on a side or 16 inches square; therefore the pole t i p area i s 256 square inches. Assume a leakage c o e f f i c i e n t of 1.8 : T o t a l l i n e s of force from-pole to pole H at centre of gap x pole t i p area Now choose the round diameter of 16/2 - 23- inches g i v i n g an area of the round poles of 2 tTD = 415 square inches 4 With t h i s and the leakage c o e f f i c i e n t , the i n t e n s i t y i n the i r o n of the round poles increases t o : 1.8 x 15.000 x 256 = 16,650 gauss ( 11.5)* Consider the yoke area to be 16 x 26 = 416 square inches -9-T h e n t h e m a g n e t o m o t i v e f o r c e r e q u i r e d , a s s u m i n g 8 0 o e r s t e d s p e r i n c h f o r 1 5 , 0 0 0 l i n e s / s q . c m . f o r a l o w c a r b o n s t e e l , a n d a n i r o n p a t h l e n g t h o f 1 2 3 i n c h e s , i s e q u a l t o H a i r 1 a i r - r - H i r o n 1 i r o n = 1 5 , 0 0 0 x 1 x 2 . 5 4 - h 8 0 x 1 2 3 x 2 . 5 4 = 3 8 , 1 0 0 + 2 5 , 0 0 0 = 6 3 , 1 0 0 e r g s T h e r e f o r e t h e t o t a l 4 TT N I = 6 3 , 1 0 0 1 0 a n d t h e a m p e r e t u r n s r e q u i r e d , N I = 6 3 . 1 0 0 x 1 0 - 5 0 , 3 0 0 \" 4 a m p e r e t u r n s C o n s i d e r i n g a m a x i m u m c u r r e n t o f 4 5 a m p e r e s , t h e n t h e n u m b e r o f t u r n s w o u l d b e N = 5 0 . 3 0 0 = 1 1 1 8 t u r n s 4 5 C o p p e r t u b i n g , w h i c h c o u l d c a r r y t h e w a t e r a s w e l l a s t h e e l e c t r i c c u r r e n t , w a s p r e f e r r e d . T h e l o w e r l i m i t o n t h e b o r e d i a m e t e r o f t h i s t u b i n g w a s s e t b y i t s u s e a s a w a t e r c h a n n e l f o r c o o l i n g w h i l e t h e u p p e r l i m i t w a s s e t b y i t s a b i l i t y t o b e n d , a s v / e l l a s h a v i n g a s u i t a b l e v a l u e o f r e s i s t a n c e f o r t h e t u r n s r e q u i r e d . A f t e r s o m e t r i a l a n d e r r o r c a l c u l a t i o n s , t h e s i z e o f t h e c o p p e r t u b i n g w h i c h c o u l d b e r e a s o n a b l y e a s i l y w o u n d i n t h e p a n c a k e s h a p e v / a s d e c i d e d u p o n a s 3 / 1 6 1 1 o u t e r d i a m e t e r , 1 / 8 i n n e r d i a m e t e r . W i n d o w a r e a w o u l d a l l o w a n a v e r a g e c o i l d i a m e t e r o f 2 8 i n c h e s s o t h a t f o r t w o t i m e s 2 3 t u r n s p e r s e c t i o n , t h e l e n g t h o f c o p p e r , p e r p a n c a k e w o u l d b e 2 x 2 3 x ^ T T x 2 8 = 3 3 7 . 5 f e e t F i g . 4 . T h e E l e c t r o m a g n e t t o f a c e p a g e 10. f i g . 5 The E l e c t r o m a g n e t To f a c e page 10 -10-For 24 c o i l s i n series the e l e c t r i c a l resistance at 20 degrees C would be 4.48 ohms which at 50 degrees C would be increased to f i v e ohms1. Thus a D. C. supply at 45 amperes, of voltage 5 x 45 - 225 v o l t s would be required. The c o i l s would have to di s s i p a t e , at t h i s current, a maximum power of I 2 R = 45 2 x 5 = 10,120 watts (f) P a r t i c u l a r s of magnet construction The yoke and pole pieces were made of so f t s t e e l , the former of f i v e U sections bolted together, the l a t t e r of four* round and two square pieces bolted together. The specifications, of the s t e e l c a l l e d f o r a carbon content of less than 0.1% and manganese content of less than 0.4 % so that f o r a f i e l d strength of 15,000 gauss, the magneto-motive force required would be less than 80 ampere turns per inch. The only well machined parts were the pole t i p s , pole pieces and the inside surfaces of the yoke to which the pole pieces were attached. These were machined to give the one inch a i r gap a tolerance of plus or minus 0.010 inches. This a i r gap could be increased an ad d i t i o n a l ten inches by removing the inner f i v e inch sections of the pole pieces. The outside tolerance of the magnet was plus or minus 0.5 inches. T h e s q u a r e p o l e t i p s t w o i n c h e s \" b y 1 6 i n c h e s s q u a r e h a d t w o t w o i n c h d i a m e t e r c i r c u l a r h o l e s c u t o u t a s s h o w n i n f i g u r e s 1 a n d 3 , w i t h l i k e p i e c e s o f s t e e l f i t t e d f o r f i n e f o c u s s i n g o f t h e \" b e a m . T h e c r o s s s e c t i o n o f t h e y o k e w a s 1 6 i n c h e s x 2 6 i n c h e s w h i c h i s s u f f i c i e n t t o w i t h s t a n d a n a t t r a c t i v e f o r c e o f 3 0 t o n s \" b e t w e e n t h e p o l e s . T h e t o t a l w e i g h t o f s t e e l w a s 7 . 5 s h o r t t o n s . T h e m a g n e t i s m o u n t e d o n r o l l e r s o n a s t e e l t r o l l e y w i t h r o l l e r h e a r i n g w h e e l s r u n n i n g o n s t e e l t r a c k s e m b e d d e d i n t h e f l o o r u n d e r t h e V a n d e G r a a f f g e n e r a t o r . I n c o n j u n c t i o n w i t h t h e r o l l e r s f o u r s c r e w s w e r e p r o v i d e d a t t h e b a s e f o r h o r i z o n t a l p o s i t i o n i n g a c r o s s t h e r a i l b e d , w h i l e f o u r m o r e w e r e p r o v i d e d f o r l e v e l l i n g ( f i g u r e s f o u r a n d f i v e ) . ( g ) T h e m a g n e t c o i l s T h e s p e c i a l d e s i g n o f t h e c o i l s i s i l l u s t r a t e d i n f i g . 2 T h e y w e r e w o u n d a s d o u b l e p a n c a k e s o f t w o t i m e s 2 3 t u r n s s o t h a t t h e e n d s c a m e o u t t a n g e n t i a l l y o n t h e o u t s i d e . T h e y w e r e m a d e o f a s b e s t o s c o v e r e d c o p p e r t u b i n g , 3 / 1 6 o f a n i n c h o u t s i d e d i a m e t e r , 1 / 8 o f a n i n c h i n s i d e d i a m e t e r s o t h a t t h e r e s i s t i v i t y w a s l e s s t h a n 8 x 1 0 \" 7 o h m - i n c h e s a t 5 0 d e g r e e s c e n t i g r a d e . T h e i n s i d e d i a m e t e r o f t h e c o i l s w a s 2 3 i n c h e s a n d o u t s i d e d i a m e t e r w a s 3 3 i n c h e s , m a k i n g a t o t a l l e n g t h o f 3 3 8 f e e t . E a c h p a n c a k e w a s s p a c e d b y a 1 / 3 2 o f a n i n c h t e x t o l i t e i n s u l a t i n g r i n g . - 1 2 -T h e i n d i v i d u a l c o i l s w e r e c e m e n t e d t o g e t h e r w i t h g l y p t a l \" b e f o r e \" b e i n g b a k e d w i t h t h r e e c o a t s o f i n s u l a t i n g v a r n i s h . S h o r t c o p p e r s t r i p j o i n t h e c o i l s i n s e r i e s e l e c t r i c a l l y w h i l e t w o f o o t l e n g t h s o f 1 / 4 i n c h s a r a n t u b i n g j o i n t h e m h y d r a u l i c a l l y i n p a r a l l e l t o t h e c o o l i n g w a t e r m a n i f o l d s . ( h ) T h e w a t e r c o o l i n g s y s t e m A t a p r e s s u r e o f 3 7 l b s . / s q . i n . , 1 . 4 5 g a l l o n s o f w a t e r p e r m i n u t e f l o w i n g t h r o u g h 2 6 c o i l s i n p a r a l l e l k e p t t h e r i s e i n w a t e r t e m p e r a t u r e t o l e s s t h a n 2 5 d e g r e e s C a t a c u r r e n t o f 4 5 a m p e r e s . A p r e s s u r e s w i t c h w a s i n c o r p o r a t e d i n t h e i n t a k e m a n i f o l d a n d c o n n e c t e d i n t o t h e i n t e r l o c k s y s t e m . T h i s p r e v e n t e d p o w e r b e i n g a p p l i e d w h e n n o c o o l i n g w a t e r w a s i n t h e c o i l s . A l u c i t e c o v e r o n t h e o u t l e t m a n i f o l d a l l o w e d o b s e r v a t i o n o f w a t e r f l o w t h r o u g h e a c h c o i l . T h e t e m p e r a t u r e r i s e w a s o n l y t e n d e g r e e s i n a h a l f h o u r a t a c u r r e n t o f 3 5 a m p e r e s w h e n t h e w a t e r f l o w w a s s t o p p e d . T h e m a x i m u m c u r r e n t f l o w f o r a 2 5 d e g r e e C t e m p e r a t u r e r i s e , w h e n w a t e r c o o l e d w a s i n e x c e s s o f 60 a m p e r e s s h o w i n g t h a t t h e d e s i g n w a s q u i t e c o n s e r v a t i v e . - 1 3 -( i ) T h e m a g n e t i c f i e l d T h e m a x i m u m f i e l d m e a s u r e d i n t h e g a p a t t h e c e n t r e a t a c u r r e n t o f 4 8 . 5 a m p e r e s w a s j u s t o v e r 1 9 , 9 0 0 g a u s s . T h e n u m b e r o f t u r n s w a s 2 x 2 3 x 2 6 = 1 , 1 8 6 a n d t h e r e f o r e t h e N I w a s 5 7 , 5 0 0 a m p e r e t u r n s . N o w 4 r r N I - 1 9 , 9 0 0 x 2 . 5 4 X x 1 2 3 x 2 . 5 4 1 0 t h e r e f o r e X = 7 2 . 2 0 0 - 5 0 . 5 0 0 3 1 2 = 2 1 . 7 0 0 = 6 9 . 5 a m p e r e t u r n s / i n c h 3 1 2 T h i s c o n f i r m s t h e d e s i g n f i g u r e t h a t t h e H i s l e s s t h a n 8 0 a m p e r e t u r n s p e r i n c h . T h i s p o i n t o f 1 9 , 9 0 0 g a u s s w a s n o t t h e l i m i t o f m a g n e t i z a t i o n \" b u t i t w a s u p o n t h e k n e e o f t h e m a g n e t i z a t i o n c u r v e ( f i g u r e 1 2 ) . (0_ ro 0 3o -o _ l Xo 10 0 1 1 1 I 1 0 o.t, 0.4- 0. fc 0-8 1 ° tl) G - e n e r c i t o r no series f i e l d , J\" K w. it>a.d (X) \" * \" \" \" C.3 ) \" * ' , Ser/es -f/e/d i ' n oppos!ti'tn } 5 \\\\w. load / n o p p o s i ± i o n y O £ i. Q _ i