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UBC Theses and Dissertations

Design, construction and stabilisation of a large electromagnet Aaronson, David Andrew 1950

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L £ -bft7 (1 So f\i  D E S I G N ,  C O N S T R U C T I O N  O F  A  L A R G E  A N D  S T A B I L I S A T I O N  E L E C T R O M A G N E T  b y  D a v i d  A  T H E S I S  T H E  A n d r e w  S U B M I T T E D  I N  R E Q U I R E M E N T S  M A S T E R  A a r o n s o n  P A R T I A L  F O R  O F  T H E  F U L F I L M E N T  D E G R E E  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  S e p t e m b e r ,  1 9 5 0  C O L U M B I A  O F  THE UNIVERSITY O F BRITISH C O L U M B I A VANCOUVER. CANADA DEPARTMENT OF PHYSICS  October 12,  1950.  Dr. L. W. Dunlap, Librarian, U n i v e r s i t y of B r i t i s h Columbia. Dear Dr. Dunlap: T h i s w i l l c e r t i f y that the t h e s i s o f Mr. D. A. Aaronson has been c a r e f u l l y s t u d i e d by the undersigned, and t h a t the t h e s i s meets the r e q u i r e d standards and an a b s t r a c t has been approved by the Department. Yours  sincerely,  G. M. Shrum Head o f the Department  G. G. E i c h h o l z A s s i s t a n t P r o f e s s o r of P h y s i c s GMS:1c  THE UNIVERSITY OF BRITISH COLUMBIA VANCOUVER,  /?/~<L  <^-5  3?  CANADA  A B S T R A C T  A  s e v e n  p r i m a r i l y  f  U n i v e r s i t y  W i t h  a  g a u s s  a n d  o  r  b e a m  o f  a c r o s s  a  a n  o n e  o f  i n c h  i n g  f r o m  p a r t s  i  n  t o  p e r i o d  e i g h t  t h e  l o n g  U s i n g  c h a n g e  s e c o n d s .  t h e  3 5  t h e  t o  n  c o n j u n c t i o n  f i e l d  i  n  i n c h e s  a m p e r e s  o f  b e e n  w i d e  1 9 , 9 0 0  o b t a i n e d  l o o p  i  a t  m a g n e t i s i n g  h a s  " b e e n  m a i n t a i n e d  a s  l o n g  a s  c h e c k e d  p a r t  a n d  s e v e n  s t a b i l i s i n g  n e w  t h e  g e n e r a t o r .  t h e  b e e n  o n e  o f  b u i l t  s  a  a m p e r e s .  w i t h  b e  w i t h  h a s  0 . 2  h a s  " b e e n  e x c e s s  b e i n g  p e r i o d s  a  a  h y s t e r e s i s  1 5  h a s  e l e c t r o s t a t i c  s q u a r e  a m p e r e s  p e r i o d  t o  i  T h e  m i n u t e s ,  f i e l d  e l e c t r o m a g n e t  g a p .  o f  s t a b i l i t y  s i g n a l  o v e r  r  o v e r  r e s o n a n c e  o f  i  2 5 6  s t a b i l i t y  1 0 , 0 0 0  F i e l d  o f  a  n  a m p e r e s ,  s m a l l ,  z e r o  o  C o l u m b i a  4 9  c u r r e n t  C u r r e n t  t  a n a l y s i s  a r e a  s a t i s f a c t o r i l y  m a g n e t i s i n g  h a l f  B r i t i s h  c u r r e n t  o v e r  o n e  t o  i  n  s e v e n  u s i n g  1 0 , 0 0 0  b e  c u r r e n t  t h r e e  a  o v e r  p a r t s  t o  v a r y -  a  f e w  h o u r s .  p r o t o n  a  i  s h o r t  n  1 0 , 0 0 0  h o u r s .  s y s t e m ,  s e t t i n g  t h e  i  s  t i m e  l e s s  r e q u i r e d  t h a n  t h r e e  t o  ACKNOWLEDGEMENT  Acknowledgement i s g i v e n t o t h e N a t i o n a l R e s e a r c h C o u n c i l f o r t h e i r b u r s a r y , and t o t h e Defence  Research  B o a r d f o r t h e g r a n t i n s u p p o r t o f t h i s r e s e a r c h work. Thanks a r e due t o D r . J . B. Warren o f t h e P h y s i c s Department o f t h e U n i v e r s i t y o f B r i t i s h Columbia f o r t h e h e l p and guidance  i n i n i t i a t i n g and c a r r y i n g o u t  this project.  D. A. Aaronson S ept emb e r , 1950  TABLE OF CONTENTS page Introduction Chapter 1.  1 The magnet  (a) F u n c t i o n s o f the magnet  5  (b) Pole shape  5  (c) S i z e  6  (d) S t a b i l i t y  7  (e) D e s i g n o f magnet  8  ( f ) P a r t i c u l a r s o f magnet c o n s t r u c t i o n  10  (g) The magnet c o i l s  11  (h) The water c o o l i n g system  12  ( i ) The magnetic  13  Chapter 2.  field  The power supply f o r t h e magnet c o i l s  (a) The g e n e r a t o r s Chapter 3.  The r e g u l a t i n g system  14 16  (a) O p e r a t i o n  17  (b) P r e c i s i o n o f t h e system  17  Chapter 4.  The u n i t s o f t h e r e g u l a t o r  (a) Standard r e s i s t o r  20  (b) Standard r e f e r e n c e v o l t a g e  21  (c) Brown c o n v e r t e r and a m p l i f i e r  22  (d) C u r r e n t r e g u l a t i n g tubes  23  (e) Power u n i t  24  (f) Protective devices  25  p a g e  C h a p t e r  5 .  O p e r a t i o n  o f  t h e  (a)  G e n e r a l  Ob)  T h e  m o t o r  ( c )  T h e  R u b i c o n  ( d )  M a n u a l - a u t o m a t i c  l e v e l  ( e )  c o n t r o l  s y s t e m  s w i t c h i n g  2 6  g e n e r a t o r s  2 7  p o t e n t i o m e t e r  s w i t c h  2 7  a n d  D .  C .  c o n t r o l  C u r r e n t  a n d  2 8  f i e l d  s e t t i n g  o f  t h e  m a g n e t  C h a p t e r  6 .  2 8  E x p e r i m e n t a l  (a)  D r i f t  o f  m a g n e t i c  t h e  f  i  ( b )  A m p l i f i e r  ( c )  P e r f o r m a n c e  ( d )  P r o t o n  e  r e s u l t s  m a g n e t  l  c u r r e n t  a n d  d  a n d  3 1  r e g u l a t i n g  o f  t h e  r e s o n a n c e  s y s t e m  3 2  m a g n e t  m e a s u r e m e n t  3 4  o f  f  i  e  l  d  d r i f t  3 5  ( e )  P r o t o n  r e s o n a n c e  ( f )  S i m p l e  p r o t o n  r e s o n a n c e  ( g )  F u t u r e  u s e  p r o t o n  o f  R .  P .  h e a d  3 7  t h e o r y  r e s o n a n c e  3 7  f  o  r  s t a b i l i z a t i o n  A p p e n d i x  1 .  M e a s u r e m e n t  p r o t o n  3 8  o f  f  i  e  l  d  d r i f t  u s i n g  t h e  r e s o n a n c e ^ m e t h o d  ( a )  C a l i b r a t i o n  o f  t h e  (b)  S h o r t  t i m e  t e s t  f  ( c )  S e v e n  h o u r  t e s t  o  o s c i l l o s c o p e  r  8  m i n u t e s  4 0  4 1  4 2  Appendix 2.  Thermal e f f e c t s i n the magnet  (a) E f f e c t of temperature change on the magnetic  field  (h) E s t i m a t e d time f o r magnet t o c o o l Appendix 3.  Adjustment o f t h e c o n t r o l system necessary f o r optimum o p e r a t i o n  Appendix 4 . Bibliography  Use of f l i p - c o i l s  and f l u x m e t e r  Illustrations Figure  F a c i n g page  1.  P e r s p e c t i v e Sketch o f Magnet  5  2.  Sketch o f Pancake C o i l  5  3.  Sketch o f Magnet  8  4.  The Electromagnet  10  5.  The Electromagnet  10  6.  D. C. Generator Curves  14  7.  Current R e g u l a t o r B l o c k Diagram  16  8.  A m p l i f i e r and Power Supply C i r c u i t  22  9.  R e g u l a t o r Tube C h a s s i s  23  10. Current R e g u l a t o r ; W i r i n g and power u n i t  24  11. The C o n t r o l Panel  28  12. H y s t e r e s i s Loop and M a g n e t i z a t i o n Curve  34  13. F a l l - o f f o f F i e l d  34  14. Proton Resonance R. F. Head C i r c u i t 15. Proton Resonance R. F. Head  ;  37 37  INTRODUCTION The primary c o n s i d e r a t i o n i n t h e d e s i g n o f a l a r g e electromagnet i s t o g e t t h e l a r g e s t f i e l d r e a s o n a b l y p o s s i b l e w i t h an i r o n c o r e ( upper l i m i t about 20,000 gauss ) over t h e p o l e a r e a r e q u i r e d f o r t h e l e a s t c o s t . The c o s t n a t u r a l l y depends on t h e p o l e f a c e s and s i z e of a i r gap which are chosen f o r t h e s p e c i f i c uses t o which t h e magnet w i l l be p u t . the  However, t h e s i z e o f  magnet i s governed a l s o by t h e type o f c o i l s ,  e s p e c i a l l y by t h e i r a b i l i t y t o d i s s i p a t e t h e h e a t generated i n them, as w e l l as by the k i n d o f i r o n and type o f i r o n c i r c u i t used.  These s e t t l e t h e  window a r e a r e q u i r e d f o r the c o i l which i n t u r n d i c t a t e s the  dimensions o f t h e i r o n o f t h e magnet.  Since the  c o s t o f t h e magnet i n c r e a s e s w i t h t h e s i z e and weight, w i t h due r e g a r d t o t h e r e l a t i v e c o s t o f copper and i r o n , the  b e s t d e s i g n h i n g e s on maximum weight economy.  This  economy depends on whether more i r o n and l e s s copper o r more copper and l e s s i r o n c a n be used.  A g a i n , t h e leakage  f a c t o r i n c r e a s e s w i t h i n c r e a s i n g dimensions, e s p e c i a l l y 1, 2 of the a i r gap  , t h e r e f o r e , t h e s m a l l e r the magnet,  and a i r gap, t h e l a r g e r the percentage o f u s e f u l f l u x . The minimum s i z e o f t h e magnet i s governed by t h e s a t u r a t i o n i n the i r o n used, which s a t u r a t i o n u s u a l l y  - 2 -  occurs f i r s t i n t h e i r o n j u s t b e h i n d t h e p o l e p i e c e s . P r e l i m i n a r y c a l c u l a t i o n s on t h e minimum p a t h l e n g t h and magnetomotive f o r c e f o r t h e a i r gap, w i t h a minimum window a r e a assumed from experience, g i v e a t e n t a t i v e s i z e f o r t h e magnet.  Computations  on t h e s i z e o f t h e  c o i l needed may then be made by a few s u c c e s s i v e approximations, once t h e type o f power supply has been d e c i d e d upon.  Then, i f t h e p a r t i c u l a r c o i l  cannot  r a d i a t e t h e power d i s s i p a t e d w i t h a r e a s o n a b l e  temperature  r i s e , a l a r g e r c o i l , more t u r n s , fewer amperes, b u t t h e same ampere-turns must be t r i e d .  With t h i s , t h e  c a l c u l a t i o n s a r e r e p e a t e d f o r t h e l a r g e r window a r e a and l e n g t h o f i r o n path now needed.  I t i s seen, then, t h a t  the b e s t o v e r a l l d e s i g n depends a g r e a t d e a l on adequate and e f f i c i e n t heat t r a n s f e r from t h e c o i l s .  1  There i s a c h o i c e o f a i r c o o l i n g , f o r c e d v e n t i l a t i o n ^ ) water o r o i l c o o l i n g .  D i f f e r e n t types o f i n s u l a t i o n on  the c o i l s a l s o a l l o w h i g h e r ambient working  temperatures.  Water c o o l i n g which i s t h e l e a s t expensive and conserves most space and asbestos c o v e r i n g on t h e c o i l s were f i n a l l y chosen f o r t h i s  electromagnet.  A one q u a r t e r s c a l e model was made up and i t s behaviour and f i e l d d i s t r i b u t i o n cheeked, b u t i t was n o t p o s s i b l e on such a model t o check t h e c o i l d e s i g n which  -3t h e r e f o r e was r a t h e r c o n s e r v a t i v e l y r a t e d i n r e g a r d t o heat d i s s i p a t i o n and working temperature.  However s a t -  u r a t i o n c h a r a c t e r i s t i c s were checked on the model u s i n g s h o r t p u l s e s of c u r r e n t . F o l l o w i n g t h i s , the seven and one h a l f t o n e l e c t r o magnet was designed by members o f the P h y s i c s s t a f f of the U n i v e r s i t y o f B r i t i s h Columbia a f t e r c a r e f u l c o n s i d e r a t i o n had been g i v e n t o a l l t h e above f a c t o r s .  I t was t o supply  a f i e l d o f a t l e a s t 15,000 gauss over an a r e a o f 16 i n c h e s square a c r o s s an a i r gap o f one i n c h and t o do so a t a t o t a l c o s t o f about $5,000.00.  The d e s i g n made use o f an  ingeneous method o f winding the c o i l s t o conserve space and a t the same time t o p r o v i d e adequate water c o o l i n g . The d e s i g n was found t o be q u i t e c o n s e r v a t i v e . field  A  of over 19,900 gauss was o b t a i n e d w i t h a m a g n e t i s i n g  c u r r e n t o f c l o s e t o 49 amperes and a power o f about 11 kilowatts.  The t o t a l c o s t was near the f i g u r e s t a t e d  above.  The magnet yoke and p o l e p i e c e s were made by Messrs. C o l v i l l e o f Glasgow f o r about $3,000.00; the c o i l s were made "by Canadian G e n e r a l E l e c t r i c f o r about $1,000.00. S t a b i l i z a t i o n equipment has c o s t about $1,000.00  The  #  M Dr. J . B. Warren and Mr. F. Bowers c a r r i e d out most o f the c a l c u l a t i o n s . Mr. T. Mouat a s s i s t e d i n t h e e n g i n e e r i n g aspects of t h e magnet and c o i l s .  In the f i r s t i n s t a n c e t o achieve the energy r e q u i r e d , i t was  d e c i d e d t o s t a b i l i z e the  resolution  magnetising  c u r r e n t t o the r e q u i r e d p r e c i s i o n and check the v a r i a t i o n i n the magnetic f i e l d u s i n g a p r o t o n resonance method'. F i n a l l y i t i s i n t e n d e d t o s t a b i l i z e the f i e l d i t s e l f u s i n g the p r o t o n resonance  output.  t_o •fate f>. S~.  "5-  Chapter l  t  The Magnet (a) Function of the magnet The magnet was designed t o "bend a f i v e mev. "beam of protons and deuterons through a 90 degree angle f o r energyresolution. ("b) Pole Shape I t s general.shape  i s shown i n f i g . 1 . Various  p o s s i b l e pole piece shapes were considered f o r t h i s purpose b u t i t seemed very d e s i r a b l e t o be able t o 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 t h a t two experiments might be set up together. Consequently the other most considered design, t h a t of a s i n g l e quarter c i r c l e pole piece w i t h banana c o i l s wound round the poles w i t h the whole magnet on a s w i v e l , was g i v e n up. A f t e r examining p o s s i b l e shapes of pole taper needed t o g i v e the f i e l d a c t u a l l y r e q u i r e d a t the gap, and a round yoke on which t o wind the p o l e s , 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 r e q u i r i n g a l a r g e H ^ such as spectrograph a p p l i c a t i o n s o r even f o r a cloud chamber; and p r o v i s i o n was t h e r e f o r e made f o r  -6a l t e r i n g  ( c )  t h e  g a p  a n d  p o l e  s h a p e ,  S i z e  C o n s i d e r  v e l o c i t y  I t  w i d t h  w  i  l  l  v ,  a n  i o n  o f  e n t e r i n g  h e  b e n t  i  n  a  a n  c h a r g e  e,  m a g n e t i c  a r c  o f  m a s s  f i e l d  o f  r a d i u s  H  e  m,  v  -  Hp-  p  m  w i t h  s t r e n g t h  H .  s u c h  v  m  m o v i n g  t h a t  2  v e  I n  w i t h  i s  a  c o n s i s t e n t  i  n  e .  v  e  H  t h e  l  o  m.  c  i  t  u .  y  s e t  a n d  o f  e  o f  u n i t s ,  i  e .  n  s .  m  e r a t e d  i o n  t h r o u g h  a t t a i n e d  a n  t h e  e l e c t r i c  m  t h r o u g h  a n  o f  H  e l e c t r i c  f o r  0  \  c  e .  h a v e ,  m.  u . ;  w h e r e  e  H  p r o t o n s ,  c  l  o  P  o f  c  i  t  o f  v  v  b y  b e i n g  s t r e n g t h  z  2  y  e  a c c e l -  E ,  t h e n ,  E  r  "  E  c  m  a  r e q u i r e d  f i e l d  e  = / 2 e _  V t h e r e f o r e  v  f i e l d  v  v a l u e  w e  s . ,  e  1/2  T h e  u .  v  v  t h e  g .  l i g h t ,  H p -  I f  c .  /  2  t o  f i v e  3 . 2 2  x  m  c  d e f l e c t  i o n s  m i l l i o n  v  1 0  g a u s s  o  l  t  a c c e l e r a t e d  4  s  c m .  i  s  :  for  deuterons  for  tritons  3.22 x 1 0  r—  7 3 x 3.22 x 10  5  5  - 4.55 x 1 0 = 5.6  x 10  5  5  gauss cm., and gauss cm.  Protons c o u l d "be d e f l e c t e d i n b o t h d i r e c t i o n w i t h a 5 field of: 3.22 x 10 = 16,100 gauss i n a r a d i u s o f 20 20 cms.. Deuterons i n one d i r e c t i o n with a f i e l d o f : 5 4.55 x 10 - 15,200 gauss i n a r a d i u s o f 30 30 cms.. T r i t o n s i n one d i r e c t i o n o n l y with a f i e l d o f : 5 5.6 x 10 - 16,000 gauss i n a r a d i u s o f 35 35 cm..  Therefore,  a square p o l e t i p o f s i z e 16 inches  on a s i d e , equal t o 40.6 cm. on a s i d e was d e c i d e d on. T h i s then s e t the s i z e o f the round p o l e p i e c e s and thus the yoke c r o s s s e c t i o n . (d)  Stability S i n c e t h i s molecular  beam would be r e q u i r e d f o r t h e 5 Van de G r a a f f 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 a l s o f o r energy r e s o l u t i o n o f t h r e e kev. i n f i v e we must r e q u i r e t h e A H H  t o be equal t o t h r e e p a r t s i n . —•  10,000; as from (2) p 4 H = / 2 m c  e  and  mev.,  4_H  =  j/2  1/2  _E  4_E E  H  4 I must be l e s s I than A H because o f t h e f o l l o w i n g f a c t o r s , a l l o f the H . order o f a few p a r t s i n 10 o r l e s s When c u r r e n t s t a b i l i z a t i o n i s used  g  1. The width o f the a i r gap v a r i e s due t o t h e t h e r m a l expansion o f t h e i r o n and t h e magnetic f o r c e b e n d i n g the i r o n  4'  Ma q n e t  yoke and  pole  pieces  -82. The i n c r e m e n t a l p e r m e a b i l i t y o f t h e i r o n and 6 h y s t e r e s i s v a r y w i t h t h e p r e v i o u s magnetic h i s t o r y . 3. There i s a s m a l l mechanical  h y s t e r e s i s i n the \  i r o n o f t h e p o l e p i e c e s , b o l t s and nuts. (e) D e s i g n o f Magnet The d e s i g n o f the magnet and c o i l s f o l l o w e d i n t h i s manner: Take H p as 6 x 10  gauss cm. and c o n s i d e r a maximum H o f  15,000 gauss across a one i n c h gap, a l l o w i n g a beam s i z e of one h a l f i n c h . The p o l e t i p s , t o be square, w i l l be about 40 cm. on a s i d e o r 16 inches square; t h e r e f o r e t h e p o l e t i p a r e a i s 256 square  inches.  Assume a leakage c o e f f i c i e n t o f 1.8  :  T o t a l l i n e s o f f o r c e from-pole t o p o l e H a t c e n t r e o f gap x p o l e t i p a r e a Now choose t h e round diameter  o f 16/2 - 23- inches g i v i n g  an area o f t h e round p o l e s o f 2 tTD = 415 square inches 4 With t h i s and t h e 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 o f the round p o l e s i n c r e a s e s t o : 1.8 x 15.000 x 256 = 16,650 gauss ( 11.5)* Consider t h e yoke a r e a t o be 16 x 26 = 416 square inches  -9T h e n  t h e  p e r  i n c h  a n d  a n  m a g n e t o m o t i v e  f  o  r  i r o n  1 5 , 0 0 0  p a t h  l i n e s /  l e n g t h  H  T h e r e f o r e  t h e  f o r c e  o  a  i  f  r  s q .  c m .  1 2 3  i n c h e s ,  1  a  =  1 5 , 0 0 0  =  3 8 , 1 0 0 +  =  6 3 , 1 0 0  t o t a l  TT  4  r e q u i r e d ,  x  i  f  o  r- r - H  1  x  a s s u m i n g  r  a  l o w  i  s  i r o n  -h  2 . 5 4  8 0  c a r b o n  e q u a l  1  o e r s t e d s  t  s t e e l ,  o  i r o n  8 0  x  1 2 3  x  1 0  -  2 . 5 4  2 5 , 0 0 0  e r g s  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  5 0 , 3 0 0 "  4  C o n s i d e r i n g  o f  t u r n s  a  m a x i m u m  w o u l d  c u r r e n t  b e  N  o  =  f  4 5  a m p e r e  a m p e r e s ,  5 0 . 3 0 0  =  1 1 1 8  t h e n  t h e  t u r n s  n u m b e r  t u r n s  4 5  C o p p e r  t h e  t u b i n g ,  e l e c t r i c  b o r e  c u r r e n t ,  d i a m e t e r  c h a n n e l  f  o  a b i l i t y  t  o  r  o f  c o o l i n g  f  o  r  t u b i n g  v / e l l  c a l c u l a t i o n s ,  t h e  c o u l d  b e  e a s i l y  d e c i d e d  u p o n  W i n d o w  2 8  i n c h e s  l e n g t h  o  a s  a r e a  s o  f  3 / 1 6  c o p p e r ,  x  1  w o u l d  t h a t  2  1  2 3  f  o  r  p e r  e  t  u p p e r  o  f  i  n  i  2 3  t  s u s e  w a s  1  t u r n s  3 3 7 . 5  s  e  t  i  c o i l  p e r  f e e t  r  n  n  a  i  o  l  t  s  f  a n d  w h i c h  s h a p e  e  t h e  w a t e r  b y  i  t u b i n g  8  b e  t  a s  o n  a  v a l u e  s o m e  /  w e l l  a s  p a n c a k e  a v e r a g e  w o u l d  =  l i m i t  t h e  a n  2 8  l o w e r  c o p p e r  a l l o w  x  T h e  A f t e r  d i a m e t e r ,  p a n c a k e  a s  s u i t a b l e  o u t e r  t i m e s  w a t e r  b y  a  t h e  w o u n d  t h e  l i m i t  h a v i n g  s i z e  t w o  x ^ T T  s  r e q u i r e d .  e r r o r  r e a s o n a b l y  w a s  t h e  a s  t u r n s  c a r r y  p r e f e r r e d .  w h i l e  a s  t h e  c o u l d  w a s  t h i s  b e n d ,  r e s i s t a n c e  w h i c h  r  v / a s  d i a m e t e r .  d i a m e t e r  o  f  s e c t i o n ,  t h e  F i g .  T h e  4.  E l e c t r o m a g n e t  t o  f a c e  p a g e  10.  fig. The  5  Electromagnet  To  face  page 10  -10For 24 c o i l s i n s e r i e s t h e e l e c t r i c a l r e s i s t a n c e a t 20 degrees C would be 4.48 ohms which a t 50 degrees C would be i n c r e a s e d t o f i v e ohms . 1  Thus a D. C. supply a t 45  amperes, o f v o l t a g e 5 x 45 - 225 v o l t s would be r e q u i r e d . The c o i l s would have t o d i s s i p a t e , a t t h i s c u r r e n t , a maximum power o f I  2  R = 45  2  x 5 = 10,120 watts  ( f ) P a r t i c u l a r s o f magnet c o n s t r u c t i o n The yoke and p o l e p i e c e s were made o f s o f t s t e e l , t h e former o f f i v e U s e c t i o n s b o l t e d t o g e t h e r ,  the l a t t e r o f  four* round and two square p i e c e s b o l t e d t o g e t h e r .  The  s p e c i f i c a t i o n s , o f t h e s t e e l c a l l e d f o r a carbon content o f l e s s t h a n 0 . 1 % and manganese content o f l e s s t h a n 0.4 % so t h a t f o r a f i e l d s t r e n g t h o f 15,000 gauss, t h e magnetomotive f o r c e r e q u i r e d would be l e s s than 80 ampere t u r n s per i n c h . The  o n l y w e l l machined p a r t s were t h e p o l e t i p s ,  pole  p i e c e s and t h e i n s i d e s u r f a c e s o f t h e yoke t o which t h e p o l e p i e c e s were a t t a c h e d .  These were machined t o g i v e  the one i n c h a i r gap a t o l e r a n c e o f p l u s or minus 0.010 inches.  T h i s a i r gap c o u l d be i n c r e a s e d an a d d i t i o n a l  t e n inches b y removing t h e i n n e r f i v e i n c h s e c t i o n s o f the p o l e p i e c e s .  The o u t s i d e t o l e r a n c e o f t h e magnet was  p l u s or minus 0.5 i n c h e s .  T h e  h a d  i n  s q u a r e  t w o  t w o  p o l e  i n c h  f i g u r e s  1  f o c u s s i n g  y o k e  w a s  1 6  T h e  w e i g h t  T h e  w i t h  i n  t h e  f l o o r  b a s e  w h i l e  f  o  f o u r  a n d  f i v e  ( g )  T h e  i  s  u n d e r  w i t h  r  2 6  l i k e  f o r c e  s t e e l  w h e e l s  t h e  w e r e  w h i c h  d e  r o l l e r s  G r a a f f  f o u r  f  o  f  i  t  t  e  o f  " b e t w e e n  a  s h o w n  d  f  o  r  t h e  t o  t h e  s t e e l  s t e e l  s c r e w s  r  s t e e l  a s  p o l e s .  t r o l l e y  t r a c k s  g e n e r a t o r .  p o s i t i o n i n g  p r o v i d e d  o u t  t o n s .  o n  o n  c u t  s q u a r e  s u f f i c i e n t  s h o r t  r u n n i n g  V a n  s  t o n s  r o l l e r s  i n c h e s  s e c t i o n  i  3 0  7 . 5  o n  o f  c r o s s  o f  w a s  m o u n t e d  t h e  T h e  1 6  h o l e s  p i e c e s  i n c h e s  h o r i z o n t a l  m o r e  c i r c u l a r  "by  w e r e  a c r o s s  I n  p r o v i d e d  t h e  l e v e l l i n g  (  e m b e d d e d  r  a  i  l  a t  b e d ,  f i g u r e s  f o u r  ) .  m a g n e t  T h e  c o i l s  s p e c i a l  T h e y  w e r e  t h a t  t h e  w e r e  m a d e  o u t s i d e  o f  h e a r i n g  c o n j u n c t i o n  t h e  x  i n c h e s  " b e a m .  a t t r a c t i v e  m a g n e t  r o l l e r  w i t h  t h e  i n c h e s  a n  t o t a l  3 ,  o f  w i t h s t a n d  t w o  d i a m e t e r  a n d  f i n e  t i p s  w o u n d  e n d s  o f  d e s i g n  a s  c a m e  r e s i s t i v i t y  c e n t i g r a d e .  o u t s i d e  3 3 8  f e e t .  t e x t o l i t e  w a s  T h e  a n d  d o u b l e  o u t  a s b e s t o s  d i a m e t e r ,  1 / 8  l e s s  c o i l s  p a n c a k e s  c o v e r e d  o f  a n  t h a n  w a s  p a n c a k e  i n s u l a t i n g  t h e  i  o f  t a n g e n t i a l l y  i n s i d e  d i a m e t e r  E a c h  o f  8  x  1 0 "  d i a m e t e r  3 3  w a s  r i n g .  i l l u s t r a t e d  t w o  o n  c o p p e r  i n c h  s  t i m e s  t h e  d i a m e t e r  o h m - i n c h e s  7  o f  i n c h e s ,  s p a c e d  t h e  c o i l s  m a k i n g  b y  a  3 / 1 6  1 / 3 2  a  a t  s o  o f  g  .  s o  a n  i n c h  t h e  d e g r e e s  2 3  a n  i  t h a t  5 0  t o t a l  f  T h e y  o f  w a s  n  t u r n s  o u t s i d e .  t u b i n g ,  i n s i d e  2 3  i  i n c h e s  l e n g t h  i n c h  o f  2  - 1 2 -  T h e  i n d i v i d u a l  g l y p t a l  " b e f o r e  v a r n i s h .  t u b i n g  j o i n  w a t e r  ( h )  w a t e r  a  p  t  t  t h e m  w a t e r  A t  C  h  a  a  e  r  e  j o i n  f o o t  n o  r i s e  i  t  h  e  l e n g t h s  i  n  o  t o g e t h e r  c o a t s  o  c o i l s  i  f  1 / 4  f  w i t h  i n s u l a t i n g  n  s e r i e s  i n c h  p a r a l l e l  t  o  t  s a r a n  h  e  c o o l i n g  n  n  c o o l i n g  T h e  f  t  4 5  h  e  a  3 7  l b s . / s q .  t h r o u g h  a m p e r e s .  T h i s  w a t e r  i  A  a l l o w e d  n  t h e  ,1 . 4 5  c o i l s  t  o  m a n i f o l d  i  .  i  l e s s  a n d  g a l l o n s  n  2 5  s w i t c h  b e i n g  c o i l s .  A  o b s e r v a t i o n  o  f  f  d e g r e e s  w a s  c o n n e c t e d  p o w e r  o  p a r a l l e l  t h a n  p r e s s u r e  p r e v e n t e d  w a s  n  2 6  t e m p e r a t u r e  i n t a k e  i n t o  t  h  e  a p p l i e d  l u c i t e  c o v e r  w a t e r  o n  f l o w  c o i l .  t e m p e r a t u r e  t  f  w a t e r  m a n i f o l d  e a c h  s y s t e m  f l o w i n g  o  i  o  s y s t e m .  o u t l e t  a  c o o l i n g  c u r r e n t  t h r o u g h  h o u r  t h r e e  h y d r a u l i c a l l y  m i n u t e  i n t e r l o c k  t h e  c e m e n t e d  w i t h  s t r i p  t w o  p r e s s u r e  i n c o r p o r a t e d  w h e n  b a k e d  c o p p e r  w h i l e  w e r e  m a n i f o l d s .  T h e  k e p t  " b e i n g  S h o r t  e l e c t r i c a l l y  c o i l s  c u r r e n t  o  f  r i s e  3 5  w a s  o n l y  a m p e r e s  t  e  w h e n  n  d e g r e e s  t h e  i  w a t e r  n  a  f l o w  h a l f  w a s  s t o p p e d .  T h e  r i s e ,  t h a t  m a x i m u m  w h e n  t  h  e  w a t e r  d e s i g n  c u r r e n t  c o o l e d  w a s  f l o w  w a s  q u i t e  i  f  n  o  r  a  2 5  e x c e s s  d e g r e e  o  c o n s e r v a t i v e .  f  60  C  t e m p e r a t u r e  a m p e r e s  s h o w i n g  - 1 3 -  ( i )  T h e  m a g n e t i c  T h e  a  N  m a x i m u m  c u r r e n t  n u m b e r  I  N o w  w a s  4  f i e l d  o  o  f  f  4 8 . 5  t u r n s  5 7 , 5 0 0  r r  N  f  I  -  i  e  l  d  m e a s u r e d  a m p e r e s  w a s  2  x  a m p e r e  w a s  2 3  x  i  n  j u s t  t h e  g a p  o v e r  2 6  =  1 , 1 8 6  X  x  1 2 3  a  t  t h e  1 9 , 9 0 0  a n d  c e n t r e  g a u s s .  a  t  T h e  t h e r e f o r e  t h e  t u r n s .  1 9 , 9 0 0  x  2 . 5 4  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  a m p e r e  t h e  t u r n s  l i m i t  o  t h e  p e r  f  m a g n e t i z a t i o n  d e s i g n  i n c h .  f i g u r e  T h i s  m a g n e t i z a t i o n  c u r v e  ( f i g u r e  t h a t  p o i n t  " b u t  i  1 2 ) .  t  o  t h e  f  w a s  H  i  1 9 , 9 0 0  u p  o n  s  l e s s  g a u s s  t h e  t h a n  w a s  k n e e  o  8 0  n o t  f  t h e  (0_ ro  < w L V +0  u c  3o  -  :> 0 Xo o  _ l  10  1  1  o.t,  0.4-  0  0  tl)  G-enercitor  (X)  "  C.3 )  "  /n  1  no  0.  * '  "  , Ser/es  oppo s i ± i o n  y  fc  0-8  series f i e l d ,  *  -f/e/d  <e K * / .  1°  J" K w. it>a.d  "  " i'  n  oppos!ti'tn  5 \\w.  }  load  I o <* c ( .  Ge-n e r g t o r s ' Fig.  1  I  Curves <o  to  f  QC<?  p.  j  4_,  -14-  Chapter 2.  The (a) The  Power Supply f o r t h e Magnet C o i l s  generators  Two compound-wound  D. C. generators  were made a v a i l a b l e  t o supply the t e n k i l w a t t s o f power f o r which the magnet c o i l s were designed.  One generator  was r a t e d a t 5^ k i l o -  watts a t 44 amperes while, the other was r a t e d a t 6 k i l o w a t t s at 54 amperes.  However, t h i s t o t a l power was not a v a i l a b l e  i n t h e r e g u l a t i n g system s i n c e t h e s e r i e s f i e l d c o i l s were connected i n o p p o s i t i o n t o g i v e a l i n e a r  current-current  c h a r a c t e r i s t i c t o the machines when the shunt f i e l d were s e p a r a t e l y e x c i t e d . c o n t r o l o f constant  coils  T h i s was more s u i t a b l e f o r smooth  s e n s i t i v i t y b u t caused a l o s s o f 3.5  k i l o w a t t s i n output power. ; Curves 3 and 4, f i g u r e 6 i l l u s t r a t e this  effect. Each generator  was d r i v e n s e p a r a t e l y by a t e n H. P.  t h r e e phase A. C. motor u s i n g t h r e e V b e l t s on m u l t i p l e pulleys. The  two generators  were connected i n s e r i e s t o d e l i v e r  up t o 200 - 250 v o l t s t o the magnet c o i l s .  T h e i r shunt  field  -15c o i l s  w i t h  w e r e  u p  t  o  a l s o  o n e  e o n n e c t e d  a m p e r e  o f  i  n  s e r i e s  c u r r e n t  b y  a n d  s u p p l i e d  t h e  c o n t r o l  s e p a r a t e l y  s y s t e m .  V  o  0 C  c »  3  Q  C  O  v3 """»  O  I_t  o  ux  <  or o < L  01  r UJ  •p  o o  c£ CQ D  € *» VJ  *>  O Q_  i  C XT  a:  •P •J  £ i. <u V «  •p  tro  fqce  p. 16,  - 1 6 -  Char/ter 3.  T h e  T h e  e a s i l y  h a s  o b j e c t i v e  v a r i e d  b e e n  b  u  t  o  R e g u l a t i n g  f  t h e  S y s t e m  r e g u l a t i n g  a c c u r a t e l y  s y s t e m  r e g u l a t e d  w a s  t  m a g n e t i c  o  g i v e  a n  f i e l d .  T h i s  a c h i e v e d .  T h e  t y p e  o f  r e g u l a t o r  c h o s e n  u s i n g  h i g h  v a c u u m  t u b e s ,  7 , 8 , 9 , 1 0  w a s  o f  p r e f e r r e d  o p e r a t i o n  w e r e o n l y  o v e r  a n d  o t h e r  a c c u r a c y .  t h e  s a t u r a b l e - e o r e  o n e  p a r t  i  t y p e s  n  1 , 0 0 0  b e c a u s e  T h e  o t h e r  r e a c t o r a n d  t h e  m o s t  w h i c h  f  i  a n  T h e  c u r r e n t  A  s h o w n  t y p e s  a n d  o f  g a l v a n o m e t e r  l a t t e r  m o r e  b l o c k  l  h a d  c a r e  a d e q u a t e  a n d  n  d i a g r a m  f i g u r e  l  s w i t c h e s  a n d  r a c k ,  d e  g e n e r a t o r .  G r a a f f  o  f  a s  p a r t  a m p l i f i e r ,  t h e  a b o u t  r e s i s t e r  25  u  t  •  r e q u i r e d  c o n t r o l  r e g u l a t i n g  w i t h  s y s t e m  t h e  m o u n t e d  c o n t r o l  a l s o  c e l l ,  w a s  w e r e  t h e  r e g u l a t o r  f e e t  a n d  o f  T h i s  s t a n d a r d  a n d  t h e  m e t e r s  p o t e n t i o m e t e r ,  f  l o s e  b  f i n e  l a r g e  u s e d  h e r e  i  s  7 .  r e g u l a t o r  o  c o u l d  a c c u r a c y  c h a n g e s .  i  A  g a n i n  e a s e  ' .  a d j u s t m e n t ,  t h i s  s  a c c u r a c y  8 t y p e  t  c o n s i d e r e d  h a d  p h o t o c e l l  o  o n  o n e  c o n s o l e  c o n t a i n e d  t h e  . . ^ g a l v a n o m e t e r ,  t u b e s .  m a g n e t  A  t  a  r a c k ,  o f  t h e  h  V a n  R u b i c o n  b a t t e r i e s ,  d i s t a n c e  i t s e l f  t  w i t h  s u r g e - p r o t e c t o r - r e c t i f i e r .  f r o m  t h e  m a n -  L a s t l y ,  e  -17t h e  a  D .  C .  s m a l l  ( a )  t h e  ' t h e  a c r o s s  e r r o r  f i e l d  v a r i a t i o n s  i  S l o w  g e n e r a t o r  f  w a s  s e l e c t e d  T h e  w h o s e  s i t u a t e d  i n s e r t e d  d i f f e r e n c e  t w o  o f  g e n e r a t o r s  f a i t h f u l l y  p e r i o d  b y  t h e  v o l t a g e ' b u c k e d '  r e s i s t o r  c u r r e n t  t h e  i  n  t h e s e  e  w a s  s  ,  i  t  a n d  t h r o u g h o u t  n  t h e  v o l t a g e ,  u s e d  t h r o u g h  w a s  t h a t  t w o  f o l l o w e d  t  i  t  o  t h e  a n y  c o n t r o l  r e g u l a t o r  c h a n g e  r e m a i n e d  t h e  s e t t i n g  c o n s t a n t  d a y s '  p  i  n  m a g n e t  d u e  o t h e r  a  S y s t e m  i  d  t o  c u r r e n t  w a r m i n g  a r e  t w o f o l d :  u p  o f  m a g n e t ,  t  c o m m u t a t o r  c o i l s ,  c o m p o n e n t s .  v a r i a t i o n s  d u e  o  r i p p l e  a n d  p i c k - u p .  p r e c i s i o n  m i n i m u m  c u r r e n t  o  r  n o i s e  1.  t h e  d r i f t  M o r e  f o l l o w i n g  o f  w e r e  t e m p e r a t u r e .  a n d  T h e  t h e  m o t o r s  a m p l i f i c a t i o n ,  c u r r e n t  v a r a t i o n s  1 ,  t h e  w a r m - u p  n  P r e c i s i o n  o t h e r  o f  O n c e  t h e  T h e  a f t e r  m a g n e t  t h r o u g h o u t  c u r r e n t  m a n g a n i n  l e a d s .  c u r r e n t  s e t t i n g .  2.  t h e  s i g n a l ' ,  T h e  T h e  m a g n e t  p o t e n t i o m e t e r  c u r r e n t  t u b e s .  ( b )  a n d  r o o m .  r e q u i r e d  R u b i c o n  m a g n e t  i n  g e n e r a t o r s  O p e r a t i o n  d e v e l o p e d  t h e  u n i t ,  a d j o i n i n g  T h e  o f  p o w e r  o  f  t h e  c u r r e n t  c o n t r o l  d e p e n d s  o n  t h e  p o i n t s :  v a l u e  o  f  t h e  v a r i a t i o n  p r o v i d e s  a m p l i f i e r .  a n  m a n g a n i n  t h a t  e r r o r  c a n  b e  s i g n a l  r e s i s t o r  t o l e r a t e d  a b o v e  t h e  m u s t  i  n  b e  t h e  i n p u t  s u c h  t h a t  m a g n e t  n o i s e  l e v e l  - 1 8 -  2 .  T h e  r e s i s t o r  3 .  t o  a  m u s t  T h e  b e  k e p t  i n p u t  v  A n  i n g '  )  t h a n  o n e  r  l e s s  n o i s e  a c c u r a t e l y  v o l t a g e  i  a  t  i  o  t h a n  l e v e l  n  i  n  o n e "  o f  r e s i s t a n c e  p a r t  t h e  i  n  o n  i  n  i  n  t h i s  1 0 , 0 0 0 .  a m p l i f i e r  m u s t  b e  k e p t  a v a i l a b l e ,  g a i n  t o  m u s t  a l l o w  i n p u t  o r  1 / 1 0 , 0 0 0  p a r t  s y s t e m  m u s t  o v e r s h o o t  I n  4 5  e r r o r  o r d e r  t o  a m p e r e s ,  s i g n a l ,  a  t h e  o f  t h e  C .  r e f e r e n c e  w h o s e  v  a  o n e  s o  i  o f  t o  t h e  c u r r e n t  r  i  i  n  a  t  (  i  o  n  o r  i  s  ' b u c k -  a l s o  l e s s  t h e  f o l l o w  e r r o r  a m p l i f i e r  u p  a n y  c u r r e n t  p a s s i n g ;  v a r i -  d o e s  h o w e v e r  n o t  t h e  h u n t .  o v e r  p a r t  r e s i s t o r  a v a i l a b l e  s y s t e m  o r  r e g u l a t e  t o  b e  o u t p u t  e x c e e d  n o t  D .  1 0 , 0 0 0  l o o p  t h e  c o n t r o l l e d  b e  S u f f i c i e n t  c o n t r o l  a t i o n  m u s t  p a r t  5 .  t o  a  m i n i m u m .  4 .  a n d  t e m p e r a t u r e  n  t h e  c u r r e n t  1 0 , 0 0 0 ,  a t  a n d  r a n g e  g i v e  a  f r o m  f i v e  2 5  v o l t  ji  l e a s t  Pi R  2 5  s  x 5  T h e  u p p e r  o f  h e a t  a t  4 5  i  t  B y  t h a t :  t o  t h e  t  m u s t  s  R  i  1 0 1  t  s  a t  i  s  m a n g a n i n  o<  0 . 0 0 0 0 2  i  s  h i g h  n e e d e d .  g o v e r n e d  c u r r e n t s .  b y  t h e  I n  a m o u n t  t h i s  c a s e ,  d i s s i p a t e  w a t t s ,  w h i c h  t e m p e r a t u r e  u s i n g  =  o h m s  r e s i s t o r  d i s s i p a t e  I  k e e p  0 . 0 5  4  o f  m u s t  2  =  1 0 "  l i m i t  I  c i e n t  x  a m p e r e s ,  c o o l i n g  1 0  s h u n t  p e r  a n d  s t r i p  d e g r e e  n e c e s s i t a t e s  t h u s  o f  a d e q u a t e  r e s i s t a n c e  t e m p e r a t u r e  c e n t i g r a d e ,  i  t  i  c o n s t a n t .  e e e f f i -  s  r e q u i r e d  -19A R ~R~ o now , R =  / ^ R  1 10,000 ( 14- <K t )  G  therefore  A R  =  and  = o<  A  AR R  R  <* A t  G  t  o thereforeoCn. t <  1 , 10 4  4 t < 10~  4  2x10 4  5 degrees C  When t h e manganin r e s i s t o r was made up and a t t a c h e d t o the c o o l i n g water system i t was found t h a t over an e i g h t hour p e r i o d i t s temperature d i d not v a r y more than 0.2 degrees C. fulfilled.  The above c o n d i t i o n was t h e r e f o r e  easily  -20-  Chapter 4.  The U n i t s o f t h e R e g u l a t o r (a) Standard R e s i s t o r A 0.05 ohm water c o o l e d m a n g a n i n ' r e s i s t o r was made up f o r t h e reasons g i v e n i n chaper t h r e e above.  A 3fe f o o t  l e n g t h o f one i n c h manganin 'shunt' was mounted i n a g l a s s tube and connected t o t h e magnet water c o o l i n g system. E l e c t r i c a l c o n n e c t i o n s were made through heavy b r a s s c y l i n d e r s h a v i n g separate p o t e n t i a l and c u r r e n t t e r m i n a l s . These c y l i n d e r s were s o l d e r e d t o t h e ends o f t h e manganin strip.  A f t e r a n n e a l i n g , t h e complete r e s i s t o r was s e a l e d  i n t o t h e g l a s s tube and mounted on t h e magnet frame as shown a t the bottom o f f i g u r e 4. Care was taken t o have i d e n t i c a l s h i e l d e d copper l e a d s b o t h from t h i s r e s i s t o r and from t h e r e f e r e n c e v o l t a g e source l e a d i n g t o t h e a m p l i f i e r  input.  The temperature v a r i a t i o n i n t h e r e s i s t o r throughout one day, a t c u r r e n t s up t o 15 amperes was n e g l i g i b l e .  Temperature  of t h e c o o l i n g water a v a i l a b l e was found t o v a r y from day t o day b y a degree o r two b u t remained c o n s t a n t throughout t h e  -21day, t o much l e s s t h a n one degree c e n t i g r a d e as checked  over  a two week p e r i o d . (b) Standard r e f e r e n c e v o l t a g e The s t a n d a r d r e f e r e n c e v o l t a g e was o b t a i n e d from a m o d i f i e d Rubicon type B p o t e n t i o m e t e r , w i t h i t s a s s o c i a t e d standard c e l l , galvanometer  and b a t t e r y supply.  The  m o d i f i c a t i o n c o n s i s t e d i n b r i n g i n g out an e x t r a t e r m i n a l so t h a t on t h e most used range, an u n i n t e r r u p t e d v o l t a g e was a v a i l a b l e w h i l e t h e potentiometer was b e i n g checked for calibration.  The v o l t a g e range o f t h e p o t e n t i o m e t e r  had a l s o been extended t o 6.4 v o l t s so as t o handle c u r r e n t s i n t h i s r e g u l a t i n g system up t o 128 amperes i f t h a t ever became n e c e s s a r y . The s t a n d a r d c e l l was c e r t i f i e d a c c u r a t e t o one p a r t i n 100,000 a t room temperature  and t h e p o t e n t i o m e t e r t o about  12  two p a r t s i n 100,000  .  The d e t e r m i n i n g accuracy was t h e r e -  f o r e t h e constancy o f v o l t a g e o f t h e b a t t e r y s u p p l y i n g t h e potentiometer.  A f t e r t r y i n g v a r i o u s sources o f d r y c e l l s  and s t o r a g e b a t t e r i e s , two heavy duty E x i d e l e a d and s u l f u r i c a c i d b a t t e r i e s were chosen f o r t h e f i n a l t e s t s .  On t h e 50 ma.  d r a i n r e q u i r e d , they dropped i n v o l t a g e about 0.5 JU v o l t s p e r minute a f t e r b e i n g connected c o n t i n u o u s l y f o r 13 days. Superimposed  on t h i s , however were s m a l l temperature  fluctuations. Primary c e l l s o f z i n c and carbon i n NaOH appeared t o be  -22-  the o n l y ones h a v i n g the necessary s t a b i l i t y and low temp13 e r a t u r e and v o l t a g e d r i f t on low c u r r e n t d r a i n  14 '  .  A  number o f c e l l s o f t h i s t y p e , F e r b a t c o F B 4 had been ordered from Ferguson B a t t e r y Company, Slough, England, b u t have not y e t been d e l i v e r e d . (c) Brown Converter and  amplifier 15,16,17  A Brown Converter v i b r a t o r c o n v e n t i o n a l t h r e e stage R-C  f o l l o w e d by  a  coupled a m p l i f i e r , f e e d i n g a  l o c k - i h d e t e c t o r p r o v i d e d the D. C. a m p l i f i c a t i o n w i t h h i g h g a i n and s t a b i l i t y r e q u i r e d t o f o l l o w the slow d r i f t s i n current.  An a d d i t i o n a l two  stage A. C  #  a m p l i f i e r was  added  i n p a r a l l e l t o l o o k a f t e r more r a p i d v a r i a t i o n s i n c u r r e n t . B o t h o f these were t h e n f e d i n t o one d i r e c t - c o u p l e d stage which was  then d i r e c t l y c o u p l e d t o the r e g u l a t o r tubes.  A v a i l a b l e v o l t a g e g a i n , a t 60 c y c l e s , i n the t h r e e stage A. C. s e c t i o n was  over 300,000 and i n the two  s e c t i o n , 5,000 ( a t 1,000  c y c l e s p e r second).  stage A.  C.  The power  supply f o r the whole a m p l i f i e r was b u i l t on a separate c h a s s i s t o keep the power l i n e frequency out of the system. The c i r c u i t diagram f o r the above i s shown i n f i g u r e 8  and  T O  f o l l o w s t h a t used a t Chalk R i v e r *  0 #  A 400 c y c l e Brown Converter had been d e c i d e d upon f o r reasons of lower n o i s e , l e s s phase d e l a y and g r e a t e r e f f i c i e n - cy.  The n o i s e o f the 60 c y c l e type i s about two u v o l t s due  to  the c a p a c i t i v e c o u p l i n g o f the c o n t a c t s on the v i b r a t i n g r e e d t o  —  7»  - 2 3 1 5 , 1 6 , 1 7 t h e  c  o  i  a  e x c i t i n g  l  l e a d s  p h a s e  4 0 0  c y c l e s  i s  d u e  u n t i l  t h a n  t h e  ( d )  a  i  t h e  a  a t  6 0  a  A s  l  l  t o  i  c y c l e  o u t  r e d u c e  c y c l e s .  t h a t  4 0 0  b r o u g h t  a m p l i f i e r  g a t h e r e d  s  a t  t h i s  t h e  o n  4 0 0  s e c o n d  t e s t s  4 0 0  a  c y c l e  h a v e  t h e  t h e  s i d e  o f  c o n s i d e r a b l y  L a s t l y ,  t i m e s  o n e ,  t y p e  i n f o r m a t i o n  t h e  r e g u l a t i n g  6  A  T h e s e  f i l a m e n t  s h o w n  i n t e r n a l  i  S  7  b e e n  t h r o u g h  c o u p l i n g .  l e s s  g r e a t e r  v o l t a g e  o r  c a r r i e d  d  i  o u t  a t  e f f i c i e n c y  c u r r e n t  i n s t e a d  v i b r a t o r  e x c i t i n g  d  o f  o n l y  n o t  w i t h  a r r i v e  t h e  6 0  n  w e r e  p a s s e d  9 .  h  p r o v i d e d  A t  l o w  v a r i e d  a  l  f  p a r a l l e l  o n  b y  c o n t r o l  s e p a r a t e *  a n d  a s  m u c h  n  o f  s e r i e s  t h e  c h a s s i s  t h e  a s  w i t h  d e v i c e s  b u t  l o n g e s t  f  u  l  l  m a g n e t  t o g e t h e r  i n d i v i d u a l  1 0 0 %  F o r  c u r r e n t  i  a s s o c i a t e d  c u r r e n t ,  i n c r e a s e d .  r a t e d  c o n n e c t e d  t h e  t r a n s f o r m e r  c u r r e n t  o n l y  n  m o u n t e d  s u p p l y  t h e  i  f i e l d s  f i g u r e  a s  t u b e s  t u b e s  r e s i s t a n c e  e q u a l i z e d  t u b e s  t h e  g e n e r a t o r  c u r r e n t .  a s  a n d  t h e  o n e .  E i g h t  w i t h  n  s e c o n d .  C u r r e n t  w i t h  I n  c o n n e c t o r  f a c t  s  . .  i  r e c e n t l y ,  c y c l e  l  i s o l a t e d  s h i f t  t o  t i m e s  i  c a b l e  f l u c t u a t i o n  6 0  o  a r e  s h i e l d e d  T h e  c  t u b e ' s  b e c a m e  l i f e ,  l o a d  t h e  o n  t h e  g e n e r a t o r s .  C o m p l e t e  v i d e d  b y  a  c h e c k  c i r c u i t  f u s e  a n d  b y  m i l l i a m m e t e r  a  n e o n  o n  t h e  o p e n i n g  b u l b .  o p e r a t i o n  j a c k  C a t h o d e  a n d  a s  w e l l  c u r r e n t  j a c k - p l u g .  o f  T h e  o f  e a c h  a s  a  e a c h  f u s e s ,  t u b e  w a s  p r o -  ' s l o - b l o '  t u b e  r a t e d  w a s  a t  r e a d  \  - 2 4 -  a m p e r e  p r o t e c t e d  w o u l d  t h e n  t  h  e  c i r c u i t  b e  p o i n t e d  c i r c u i t e d  t u b e  c o u l d  c u r r e n t .  I  n  f r o m  t h e  p l a t e  c o m m o n  m i l l i a m p e r e  i n s e r t e d  f r o m  i  t  h  t  s m a l l  b  b  y  a  o  g l o w i n g  f o u n d  o  t  h  b  e  f  t  h  t  o  2  t  g r i d  o  a  f  e  t  o  P o w e r  t u b e s  4 0 0  a n d  f i g u r e  c i r c u i t  i  l  t  e  r  ( p l a t e )  l i n e  a s  o  o h m  d a m p  y  a  o  2 5  o v e r l o a d  w a s  r e l a y ,  i n s e r t e d  a  i  n  o n e  s y s t e m ,  p r e v e n t  t  h  w a s  e  g r i d s  o  f  r e s i s t o r  u  t  a n y  n  e a c h  p a r a s i t i c  n e g a t i v e  o h m  i  p o w e r  g r i d  l e a d  w a s  a  o s c i l l a t i o n s .  f e e d b a c k  a s  w e l l  r e s i s t o r  i  t  n  h  e  a s  ' g r i d  F i n a l l y ,  b i a s  c o m m o n  w a s  c a t h o d e  1 0  U n i t  v o l t ,  o n e  g e n e r a t o r  u s e d  w i t h  t w o  s e c t i o n .  T h e  t r a n s f o r m e r  i  p o w e r  f i e l d s  E .  i  F  i n p u t ,  t r a n s f o r m e r  c o n n e c t e d  a m p e r e  G .  c h o k e  c e n t r e - t a p p e d  a l s o  o p e n  c a t h o d e  i n t e r l o c k  c i r c u i t  A n  *  A  f  r  c u r r e n t  l e a d .  ( e )  o  L a s t l y ,  h  w h i c h  b u l b .  a m p e r e s ,  t  t u b e s  n e o n  c h e c k i n g  t u b e s .  c o n n e c t e d  c o n t r o l  y  a b o v e ,  e  s h o r t e d  p o s i t i v e .  a m o u n t  p r o v i d e d  t  t  _ a m p e r e s  l e a d  e  1 , 0 0 0  s t o p p e r '  a  n  g o i n g  T h e  0 . 6 5  r e l a y ,  u  b e  a d d i t i o n  a d j u s t a b l e  o  a g a i n s t  G  w i t h  i  s e r i e s  1 0 5  a  i  s  t  s t w o  f  o  r t  K .  1 0 4 0  a n d  i  h  f  e  d  T h i s  b  e  t  y  a n  s t w o  i  0 . 2  A .  v o l t  h  e  6  n  a  A  f  o  i  % .  l  f  i  u  l  w i n d i n g s  1 0 4  p r i m a r y .  v o l t  T h e  l  l  S  7  s h o w n  a d d i t i o n a l  t h a n  V .  t  u n i t ,  t h y r a t r o n s  l e s s  t h r e e  s e c o n d a r y  n  s e r i e s .  f o l l o w e d  r i p p l e  w a s  n  s u p p l y  e  i  d  i  n  l  w a v e  L  C  H .  T .  p o w e r -  n  s e r i e s  w i n d i n g s  -25(f)  Protective The  devices  complete  interlocks  system  ( f i g u r e 10) was p r o t e c t e d b y  a n d an o v e r l o a d  protector-rectifier  r e l a y , as w e l l as t h e s u r g e -  across  t h e magnet c o i l s  H. T. o f t h e power u n i t was pressure  failed,  shut  themselves.  o f f i f the  cooling-water  i f t h e r e g u l a t o r t u b e s drew g r i d  o r i f t h e power u n i t c a b i n e t d o o r s were o p e n e d . current  overload  three  r e l a y i n the generators'  field  current, The  circuit  as m e n t i o n e d above a n d shown i n f i g u r e 9, w o u l d  also  i n t e r r u p t power t o t h e magnet  circuit.  Lastly,  a surge-protector  i n case o f  thyratron r e c t i f i e r ,  t h e magnet, was c o n n e c t e d i n r e v e r s e coils  to discharge  them q u i c k l y .  c o u l d pass a surge c u r r e n t The  ishort  polarity  across the  This r e c t i f i e r ,  a n F 6 105,  o f 200 amperes a t 1,000  volts.  surge t h a t c o u l d be e x p e c t e d as c a l c u l a t e d from  5 ohm r e s i s t a n c e o f F G 105 i s n o t g r e a t e r The  mounted a t  filament  such t h a t  o f t h i s t h y r a t r o n was  This  volts.  connected i n t h e system  i t h a d t o b e o n and warmed up b e f o r e  b e s u p p l i e d t o t h e magnet. chapter.  t h a n 225  a  i s described  power  could  i n the next  Chapter 5.  Operation of the control system (a) General switching The switching arrangement of a l l the units i s shown i n f i g u r e 10.  One toggle switch and one push button turn  on a l l the electronic equipment while an additional push button i s needed f o r each motor generator.  ( These may be  controlled together i f desired with a small change i n wiring, by one set of push buttons. ) switch S  The main toggle  turns power on to a l l the thyratron heaters and  Sola constant voltage transformer as w e l l as a f i v e minute time-delay-relay.  The complete amplifier and a l l heaters  but the surge-protector-rectifier are f e d from the Sola transformer.  The time-delay-relay allows the thyratron  heaters to warm up before H. T. can be applied to the power unit.  Thus, a f t e r f i v e minutes, provided a l l i n t e r l o c k  switches are closed, f i e l d e x c i t a t i o n i s applied to the generators by pressing push button S . 4  This closes relay S  which applies power to the plate transformer of the power *  -27-  unit.  H. T. can be i n t e r r u p t e d manually without r e - i n t r o -  ducing the time-delay, by means of toggle switch Sg.  All  the equipment b u t the motor generators i s switched o f f by switch S^. (b) The motor generators  )  The two motors are c o n t r o l l e d i n d i v i d u a l l y by on-off push buttons which are provided w i t h i n d i c a t o r lamps. lamps and buttons are mounted on the s w i t c h panel.  The  The  motors may a l s o be c o n t r o l l e d independently by push buttons i n the motor-generator room. (c) The Rubicon -potentiometer The Rubicon potentiometer, used as the primary c o n t r o l of the system, r e q u i r e s no e x t r a s w i t c h i n g i n checking i t s c a l i b r a t i o n when used on the main 1.6 v o l t range.  By t h i s  means, the accuracy of the c u r r e n t s e t t i n g may be kept as h i g h as p o s s i b l e i n s p i t e of any v a r i a t i o n s i n the p o t e n t i o meter b a t t e r y supply, f o r magnet c u r r e n t s up t o 32 amperes. For very s m a l l c u r r e n t s , or f o r c u r r e n t s above 32 amperes, c a l l i n g f o r the use of the 0.16 or 6.4 v o l t ranges, the c o n t r o l loop of the r e g u l a t o r system has t o be opened temporarily and the magnet c u r r e n t l e f t p a r t i a l l y u n s t a b i l i z e d during the r e - c a l i b r a t i o n of the potentiometer. This i s done by f i r s t s w i t c h i n g the 'manual-automatic *  fig.  1 1 .  The C o n t r o l Panel  to face page 28  - 2 8 -  s w i t c h  o n  c h e c k i n g  t h e  E .  t h e  o f  t h e  F.  M.  t o  S .  i s  r e t u r n e d  C .  -  s  t  i  l  l  m a g n e t  i  r  C u r r e n t  t  i  o  n  i  s w i t c h  c e l l )  o f  n  t h e  t h e  a n d  i  C a l i b r a t i o n  c a r r i e d  o u t  R u b i c o n  T h e  b y  e  l  d  f  i  e  d  o r  r e -  b y  t u r n i n g  p o t e n t i o m e t e r  r e g u l a t o r  r e v e r s i n g  i  f i g u r e  R u b i c o n  i s  i n d i c a t e d  n  v a l u e  t h e '  s h o w n  i  m a n g a n i n  s e t t i n g  a d j u s t i n g  n  l a r g e  i  s y s t e m  t h e  a b o v e  i  s  R u b i c o n  D .  C .  t h e  l o w  t h e  C .  g a i n  a m p l i -  A .  p o s i t i o n ,  c o m p l e t e  o n  C .  t h e  r a n g e ,  a m p l i f i e r .  m a g n e t  t o  b y  m o u n t e d  m a g n e t  F o r  D .  ' m a n u a l !  k n o b  l o o p  T h e  t h e  r  e  f  a t  c u r r e n t  e  i  r  o n  r e g u l a t o r  t h e  e x a m p l e ,  2 0  p o t e n t i o m e t e r  c o n t r o l  s  g  t o  t h e n  s e t  s e t t i n g  t u b e  t h e  a m p e r e s  k n o b  n  c u r r e n t  w i t h  t o  i  c o n t r o l  a p p r o p r i a t e  m a g n e t  o f  r  t h e  a c t u a l  c u r r e n t  l e v e l  t h e  o b t a i n e d  m e t e r  a  c o n t r o l  o u t  t h i s  t h e  T h e  1 0 .  n  o v e r  t u r n i n g  r e s i s t o r ,  t h e  l e a v e s  o f  1 1 .  f i g u r e  t h e  c u t s  h y s t e r e s i s  b y  l e v e l  c o n t r o l  p o t e n t i o m e t e r .  b y  C .  a l t e r e d  d e s i r e d  s h o w n  t h e  b u t  s e t t i n g  l  D .  s w i t c h  l e v e l '  t h e  o n  a s  C  o f  i n d i c a t e d  t h e n  t h e  W h i l e  b e  g r a p h  t h e  b y  .  t h e n  a n d  c i r c u i t  'D.  f  t o  o h m  1  p o s i t i o n .  s w i t c h  m a y  t h e  a s  c h a s s i s  s  o n  c i r c u i t .  m a g n e t i c  l a r g e  c h o s e n  a  s e l f - s t a b i l i z a t i o n  p a n e l ,  a n d  b  C .  c u r r e n t  a d j u s t i n g  T h e  0 . 0 5  i  ' m a n u a l  ' m a n u a l - a u t o m a t i c '  l o o p  t h e  l  M a n u a l - a u t o m a t i c  p o r t i o n  ( e )  S .  t o  f i e r  b y  a  t o  p r o c e d u r e .  T h e  t h e  c  ( s t a n d a r d  s w i t c h i n g  ( d )  a m p l i f i e r  w a s  1 . 0 0 0 0  t o  m a k e  v o l t s ,  t h e  -29b a l a n c e meter M  read at centre.  T h i s gave a magnet f i e l d  s t r e n g t h o f 11,400 gauss. The  a d d i t i o n a l meters on t h e c o n t r o l p a n e l t e l l  c i s e l y what i s happening t o t h e system.  pre-  An understanding  of t h e i r f u n c t i o n and o p e r a t i o n a i d s i n t r a c i n g any f a u l t s i n t h e system.  Ammeter Mg reads t h e g e n e r a t o r s ' shunt  field  c u r r e n t and should r e a d between 0 and 1 ampere i n d i r e c t p r o p o r t i o n t o t h e magnet c u r r e n t .  The t e r m i n a l s o f t h e  milliammeter M3 come out from the f r o n t o f t h e p a n e l t o a j a c k p l u g which may be i n s e r t e d i n t h e cathode c i r c u i t o f each 6 A S 7 tube t o check i t s o p e r a t i o n .  Ammeter  as  mentioned i n t h e p r e c e d i n g paragraph reads the magnet c u r r e n t d i r e c t l y and must f o l l o w the v o l t a g e s e t t i n g o f t h e Rubicon potentiometer  directly.  The other t h r e e meters, on t h e a m p l i f i e r c h a s s i s p a n e l , t e l l the operation of the r e s t o f the e l e c t r o n i c s o f the system.  Voltmeter M  4  when r e a d i n g c e n t r e , i n d i c a t e s t h a t  the c u r r e n t s e t t i n g agrees e x a c t l y w i t h t h e d e s i r e d v a l u e as chosen by t h e Rubicon potentiometer  setting.  A. C.  v o l t m e t e r Mg reads t h e magnitude o f t h e e r r o r s i g n a l b e i n g t r a n s m i t t e d by t h e a m p l i f i e r .  F o r b e s t o p e r a t i o n under  normal c o n d i t i o n s , t h i s should r e a d as c l o s e t o zero as possible.  T h i s may be always kept r e a d i n g zero f o r a l l  magnet c u r r e n t s e t t i n g s by r e - a d j u s t i n g the' D. C. l e v e l  i  — 3 0 -  c o n t r o l  c e n t r e  k n o b ,  a s  w h i c h  w e l l .  o b t a i n e d  u n l e s s  M g  t h e  r e a d s  r e g u l a t o r  a n d  a t  a n y  b a l a n c e  C .  t u b e s .  s e t t i n g  m e t e r  v o l t a g e  M e t e r  M  4  r e s p e c t i v e l y  M  4  t h e  o f  M g  t h e  m e t e r  o f  t h e  c u r r e n t  i  s e t  a t  a p p l i e d  a n d  b a l a n c e  s  t o  t h e  i  l  l  c e n t r e .  g r i d s  t o g e t h e r  e r r o r  w  a t  s i g n a l  t h e  t h e  i  n  b e  V o l t m e t e r  o f  g i v e  n o t  t h e  6  A  S  7  p h a s e  s y s t e m  t i m e .  I  a l  m a i n t a i n  C o r r e c t  D .  m a g n i t u d e  w i l l  n  i  t  i  a  l  s e t t i n g  a d j u s t m e n t s  a r e  u p  o f  d i s c u s s e d  t h e  i  r e g u l a t i n g  n  s y s t e m  a p p e n d i x , 3 .  a n d  a d d i t i o n -  C h a p t e r  6 .  • R v p ^ - p i m e n t a l  ( a )  D r i f t  o f  S l o w  s m a l l ,  d r i f t s  o f  m i n u t e s  t h e  t h e  a n d  u s i n g  u s i n g  t h e  c u r r e n t  o f  m a g n e t  t h e  o r d e r  u p  m e n t s  m a g n e t  t o  o f  a  s e v e n  f l i p - c o i l s  f e w  a n d  m a g n e t i c  c u r r e n t  p a r t s  h o u r s  a n d  R e s u l t s  a  a s  i  n  f i e l d  w e r e  s a t i s f a c t o r i l y -  1 0 , 0 0 0  t a k e n  f r o m  o v e r  a  f i e l d  f l u x m e t e r ( a p p e n d i x  f e w  m e a s u r e -  4 ) .  B y  j  «LQ  2 2 ,  t o  a c c u r a t e  s l o w  p a r t  o n l y  i  n  d r i f t s  1 0 , 0 0 0  t h r e e  p a r t s  P a r t  t h e r m a l  c o n t r a c t i o n  a i r  a s  t h e  g a p  " b u t  f  o  r e s i s t a n c e  t e m p e r a t u r e  n o t  j u s t i f y  d r i f t  i  t h e  r  b y  o f  d r o p  c o u l d  g e n e r a t o r  i  i  a  l  l  r e s o n a n c e  i  e  n  l  w e r e  2 0 }  2 IL ^  m e t h o d  t h i s  i r o n  h a v e  p e r i o d ,  l o n g  h e  2 .  o f  f  r  f  t h e  t w o  t h e  o  r  u p  o t h e r  a b o u t  c a n  f i v e  o f  2 5  f  s e v e n  o  b y  r  t h e  o f  t h e  m o r e  t h a n  c e n t  i  n  d e g r e e  t e s t .  h a n d ,  h e  o f  w i d t h  p e r  t h i s  a c c u r a c y  t h e  h e a t e d  o  p e r i o d  r e s t  n e a r l y  t o  i n c r e a s i n g  a c c o u n t e d  T h e  u s e d  m e n t i o n e d  o n  m e a s u r e d  d e c r e a s i n g  c o i l s  c u r r e n t  s i n c e  t h e  c a n  a p p e n d i x  m a g n e t  t h e n  m i n u t e  o v e r  d e c r e a s e  a b o v e  d  e i g h t  o f  t h e  t h e  w o u l d  f  1 0 , 0 0 0  o f  r e g u l a t o r  c o i l s  a n  n  t h e  a t  t h e  t h e  a  d i s c u s s e d  a c c o u n t e d  n  o f  o v e r  h o u r s .  b e  p r o t o n  2 3  ,  o n e  h i g h l y  T h i s  c u r r e n t  t h e  d e g r e e s  C  -32at t h e same time.  The c o r r e c t e d d r i f t , n e v e r t h e l e s s , was a  s m a l l "but a d e f i n i t e i n c r e a s e i n magnetic  field.  A s m a l l amount o f commutator r i p p l e was observed b u t was reduced s a t i s f a c t o r i l y a f t e r l a r g e condensers were connected across t h e generator  brushes.  (b) A m p l i f i e r and r e g u l a t i n g system The Brown c o n v e r t e r and t h e a m p l i f i e r and l o c k - i n d e t e c t or p r o v i d e d D. C. a m p l i f i c a t i o n w i t h a minimum i n h e r e n t  drift.  T h i s r e s u l t e d i n almost complete compensation f o r t h e thermal e f f e c t s i n t h e components o f t h e r e g u l a t i n g system. The few p a r t s i n t e n thousand d r i f t observed, a f t e r c o r r e c t ion  f o rbattery d r i f t  and p r o t o n head o s c i l l a t i o n d r i f t a r e  very i n s i g n i f i c a n t compared t o the one t o two per cent o r g r e a t e r changes i n r e s i s t a n c e o f t h e magnet and generator c o i l s due t o c o o l i n g o r warming. The g a i n and s t a b i l i t y o f the system was i n v e s t i g a t e d by t r y i n g d i f f e r e n t v a l u e s f o r t h e manganin standard or. be  resist-  With 0.05 ohms, t h e D. C. a m p l i f i e r v o l t a g e g a i n c o u l d advanced t o 600 b e f o r e low frequency  'hunting  1  o f t h e system s e t i n .  o s c i l l a t i o n or  T h i s showed up on a l l t h e  meters and i n the magnet f i e l d as shown on t h e p r o t o n resonance 'scope.  V a r i o u s other v a l u e s o f r e s i s t a n c e down  t o 0.0005 ohms were t r i e d a l l o w i n g the g a i n o f t h e a m p l i f i e r to be i n c r e a s e d t o about 30,000, b u t w i t h t h e s t a b i l i t y o f  -33the  system decreasing  short periods. noise  to only  a few parts  With the lowest  value  Part  of this  noise  was  t h e 60  this  was  would to  a smaller  of  c y c l e Brown converter  most  probably  with  a separate  i t and t h e l o c k - i n  error voltage.  stability  and t h e f i e l d  a step voltage  of the f i e l d  over  i n 20  a five  was  or  response  cycle  and t e s t e d b u t  obtained  using the  Repeatability of the  small.  day p e r i o d  current  was w i t h i n  error, but this gain  Repeatability  as measured w i t h Momentary  on a p p l i c a t i o n o f a  i fthe voltage  below a few hundred.  detector  t h e system.  a m p e r e s , a b o u t 1%.  was n o t a c o n t i n u o u s  400  supply  was g o o d a n d o v e r s h o o t o n a p p l i c a t i o n  and f l u x m e t e r  w a s 4" a m p e r e  into  t o t h e i n p u t was  shoot of the current  i n value  stabilized  and accuracy  manganin r e s i s t o r .  flip-coil  A  a n d p o w e r a m p l i f i e r was b u i l t  not y e t been incorporated  setting  due  The r e s t o f  a l l o w use o f a smaller manganin r e s i s t o r  Best 0.05  .  tube c i r c u i t ,  c y c l e power f e e d i n g  oscillator has  c y c l e hum  heater.  T h e 400 o f 400  60  c y c l e Brown converter due t o t h e f i r s t  from the  as l a r g e as t h e  ,17  15,16 to  oyer  of resistance the  i n t h e i n p u t t o t h e a m p l i f i e r was  error voltage.  i n 1,000  a  over-  step-voltage  This  overshoot  overshoot d i d increase  o f t h e a m p l i f i e r was  decreased  is  K i [o$avss  it  I 1.  14-  i - 1  |o 6  - /  -7 7  -V  t r -TO -4o  l "Jo  l "20  i  ,  -'O  /  /  1  O  io  | ^  0  | 3o  | 4-0  5*  -2  -  -  4-  -  6  -  8  _  le  _  _  14  -  Ifc  -  H  v s t e r es i s  Loo p  Ma<metu4ti'«n  a n A  Curve t-e. "face  p. 3 4".  K«l»jao5  down  -tram  centre  to -f«ce p. 5 4-.  -34Th e time c o n s t a n t o f the system i n response s t e p - v o l t a g e was "between one  and two  t o ,a  seconds, which  r o u g h l y the time c o n s t a n t o f the g e n e r a t o r s , b u t than t h a t of the magnet.  T h i s was  measured  was  less  independently  to be c l o s e t o t h r e e seconds u s i n g a storage b a t t e r y , meter" and stop-watch. I t was  the time taken f o r the c u r r e n t t o  r i s e t o 63% of i t s f i n a l v a l u e and t o f a l l t o 37% o f I t s i n i t i a l value. (c) Performance o f the magnet The  inductance o f the magnet was  13.9  measured from i t s time c o n s t a n t o f 3.02  h e n r i e s as  seconds.  tance of the c o i l s a t 20 degrees c e n t i g r a d e was A t a c u r r e n t o f 48.5  s a t u r a t i o n curve has  15 amperes.  fluxmeter.  amperes wide a t a c u r r e n t  These are superimposed i n f i g u r e 12.  r e t e n t i v i t y , o f the order o f 70 t o 100 gauss, was ingly small.  ohms.  i t s knee a t 18,000 gauss w h i l e  the h y s t e r e s i s l o o p i s o n l y 0.2 of  4.6  resis-  amperes i t gave a f i e l d s t r e n g t h o f  19,919 gauss as measured w i t h a f l i p - c o i l and The  The  F i g u r e 13 shows the f a l l  h o r i z o n t a l and v e r t i c a l d i r e c t i o n s .  The  surpris-  o f f o f f i e l d i n the  T h i s shows t h a t the  leakage f l u x i s s m a l l which confirms the d e s i g n d e s c r i b e d i n chapter  1.  From the c a l c u l a t i o n s g i v e n i n chapter 1 under magnetic f i e l d '  'The  i t appeared t h a t the H r e q u i r e d f o r a f i e l d  of n e a r l y 20,000 gauss a t the c e n t r e was  about 70 ampere-  -35turns per inch,  12 % b e t t e r  The temperature r i s e far  less  of the  than anticipated,  of the  that  expected.  coils  o n l y 25  was m o s t l y due t o t h e f a c t i n the basement  t h a n was  a t 60  degrees  amperes  was  centigrade.  the water pressure  This  available  P h y s i c s b u i l d i n g where the magnet  located has been h i g h ,  f r o m 35  i n c h as a g a i n s t  pounds p e r square i n c h assumed i n  design.  25  The magnet,  a n d o v e r 500 such that was  the  lbs.  of copper, has  not only to  b u t t o b r i n g the magnet of the room to five  to  b a s e d o n 50 would take  %  keep the  thermal time  amperes the  12  From  constant  at  a c u r r e n t o f 12  of f i e l d  the magnetic  field drift  (appendix  drift  i n c h a i r gap  o f the magnet  C o l l i n s was b u i l t u p t o  .  It as  was  iron  amperes,  F . head o f a p r o t o n resonance magnetometer of T. 24  it  of the  pounds per square i n c h ,  P r o t o n resonance measurement  that  some  of iron i n absorbing heat,  centigrade  inserted i n the  shown i n f i g u r e  iron  calculations  a b o u t two h o u r s f o r t h e t e m p e r a t u r e  design following that  of  down  cooling water,  lov/er.  the  cooling  temperature r i s e  of the  centigrade  a n d w a t e r p r e s s u r e o f 37  An R.  square  t e m p e r a t u r e g r a d u a l l y down f r o m  effectiveness  to d r o p one degree  (d)  a large  up to  the temperature  seven degrees  pounds per  c o n t a i n i n g s e v e n and one h a l f t o n s  at medium c u r r e n t s ,  sufficient  p o u n d s t o 40  is  of  measure one  5 so t h a t  al-  2)  - 3 6 -  though the search c o i l was i n a homogeneous part of the f i e l d the electron tubes were as f a r out of the magnetic f i e l d as possible.  A sensitive short wave receiver together  with a General Radio heterodyne frequency meter, an amplifier and' an oscilloscope were used i n conjunction with t h i s head to carry out the measurements of f i e l d d r i f t .  The  measurements taken over a one day period are given i n appendix  1.  The measurements of d r i f t were taken i n the following manner.  The magnetic f i e l d was set with the current  regulator to a value within the range of the o s c i l l a t o r for a proton sample i n the search c o i l .  The frequency of  the R. F. head o s c i l l a t o r was adjusted t i l l the proton resonance s i g n a l after amplification was observed near the centre of the trace on the cathode ray oscilloscope.  The  oscillograph trace was then c a l i b r a t e d i n gauss as described i n appendix 1.  By tuning the short wave receiver and  heterodyne frequency meter to the R. F. frequency, i t could  5 be measured to one part i n 10 beat.  by l i s t e n i n g f o r the zero  Readings of the o s c i l l a t o r frequency, heterodyne meter  c r y s t a l c a l i b r a t i o n as well as the d r i f t i n the b a t t e r i e s supplying the Rubicon potentiometer were taken during the day and were Used i n correcting the d r i f t observed i n the motion of the proton resonance s i g n a l across the oscilloscope  f i g .  P r o t o n  1 5 .  R e s o n a n c e  R .  P .  H e a d .  t o  f a c e  p a g e  37.  to f a c e  p. 3 7.  -37-  screen. (e)  Proton resonance R. F. head The c i r c u i t diagram, f i q u r e 14, shows the head t o  c o n t a i n a 'weakly o s c i l l a t i n g d e t e c t o r ' c o n s i s t i n g o f a p a i r of 6 A G 5 tubes i n p u s h - p u l l arrangement. are  oscillations  kept s m a l l "by feedback from the a d d i t i o n a l 6 A G 5 tube 24 . . . . . . .  connected up as a low g a i n a m p l i f i e r the  The  .  Only one  control,  two-gang v a r i a b l e a i r condenser, i s needed t o change the  frequency t o any v a l u e i n the range from 20 t o 42 megacycles per  second.  T h i s condenser t o g e t h e r w i t h the s e a r c h c o i l  i n s i d e o f which i s p l a c e d a 0.1 molar s o l u t i o n o f MnS04, • forms the tank c i r c u i t which i s l o o s e l y coupled t o the o s c i l l a t o r tubes. The complete R. F. head i s r i g i d l y mounted i n a heavy b r a s s box w i t h the s e a r c h c o i l p r o t r u d i n g as i l l u s t r a t e d i n f i g u r e 15.  Two 40 t u r n double pancake wound sweep c o i l s  are -cemented t o t h e o u t s i d e s h i e l d p l a t e s o f the s e a r c h c o i l for  'wobbling' .the.;.field. ;  ( f ) Simple p r o t o n resonance t h e o r y Protons, o f - s p i n I = , i , when i n a c o n s t a n t magnetic field H  q  w i l l o r i e n t themselves i n one o f the two q u a n t i z e d  energy s t a t e s ; t h e s p i n can be p a r a l l e l or a n t i p a r a l l e l the  field.  to  I f a sample o f p r o t o n s i s p l a c e d i n a c o i l be-  -38tween t h e p o l e s o f an electromagnet w i t h t h e a x i s o f t h e c o i l a t r i g h t angle t o t h e p o l e s , then t r a n s i t i o n s between the two s t a t e s w i l l h e induced; when t h e frequency o f the s i g n a l a p p l i e d t o t h e c o i l s a t i s f i e s t h e resonance c o n d i t i o n ' 2TrV« I V I H V  •  Q  1 0  where  U  H  I i s t h e r a t i o o f the  magnetic moment t o t h e angular momentum o f the n u c l e u s , -j/ and  i s t h e frequency i n c y c l e s p e r second  Ho i s t h e magnetic f i e l d i n t e n s i t y i n gauss a t  the n u c l e u s . By u s i n g t h e most r e c e n t value,  of V"and s u b s t i t u t i n g  i n t h e above equations* t h e simple r e l a t i o n i s o b t a i n e d 24 25 for  t h e magnetic f i e l d H  0  i n terms o f t h e frequency  *  H ( k i l o g a u s s ) = 0.2348 ( £ 0.0002) f ( i n mc/s) Q  The  accuracy o f t h i s e q u a t i o n i s l i m i t e d by t h a t i n t h e  known v a l u e o f Y  .  (g) F u t u r e use o f iproton resonance  for stabilization  Although up t o t h e p r e s e n t the p r o t o n resonance has been used o n l y t o measure t h e f i e l d ,  signal  i t i s intended t o  f e e d t h i s i n f o r m a t i o n d e r i v e d from t h e magnetic f i e l d  direct-  l y i n t o t h e c u r r e n t r e g u l a t o r so as t o keep t h e f i e l d 25  constant  and s t a b i l i z e d a g a i n s t a l l changes  #  The above type o f  R. F. head i s v e r y s u i t a b l e f o r t h i s when f o l l o w e d b y a d i s c r i m i n a t o r o r l o c k - i n d e t e c t o r , f o r i t has a l a r g e s i g n a l t o  -39n o i s e r a t i o , b e t t e r than t e n t o one, and has o n l y -one main frequency  control.  Three or f o u r R. F. heads may be necessary t o cover the range o f f i e l d s from a few k i l o g a u s s t o 20 k i l o g a u s s as i n d i c a t e d i n the t a b l e below: frequency o f  oscillator  H  me/s  kilogauss  8.52  2  17.04  4  42.6  10  85.2  20  The lower l i m i t of f i e l d measurements u s i n g t h i s method i s s e t by the weakness o f p r o t o n s i g n a l s below about 3,000 27 . gauss , w h i l e the upper l i m i t i s determined by the d e s i g n of a s t a b l e v a r i a b l e h i g h frequency o s c i l l a t o r w i t h a separate tank c o i l , tunable up t o 85  mc/e.  - 4 0 -  A p p e n d i x  M e a s u r e m e n t  ( a )  o  f  f  C a l i b r a t i o n  T h e  w h i c h  e a c h  d o w n  t h e  e x t r e m e  t h i s  a n d  s c o p e  d r i f t  t h e  X  ' w o b b l i n g  s o  c y c l e .  a n d  r e s u l t s  d i a l  r e a d i n g  a r e  f  o  n  f  t w o  r e s o n a n c e  r  e  w h i c h  i  n  f  f r o m  o  r  d i a l  t h e  l e f t  d  t  h  r e s o n a n c e  o s c i l l a t o r  g i v e n  i  p r o t o n  c u r r e n t  1  e x t r e m e  r e l a t i o n  t h e  w e r e  t h a t  T h e  c a l i b r a t e d  O s c i l l a t o r  p l a t e s  c o i l  r i g h t  u s i n g  m e t h o d .  o s c i l l o s c o p e  f r e q u e n c y  t h e  w a s  T h e  d  t h e  s e a r c h  o b s e r v e d  t h e  l  o s c i l l o s c o p e  t h e  a n d  e  o f  p r o v i d e d  a r o u n d  i  1 .  t h e  t h e  c h a p t e r  6 ,  s o u r c e  s w e e p  c o i l s  p e a k s  w e r e  w a s  m o v e d  r e s o n a n c e  o f  s a m e  p e a k s  s c r e e n  t h e  u p  a n d  w e r e  n o t e d .  t r a c e  o  f  a  t  F r o m  t h e  g a u s s .  s u m m a r i z e d  H e t e r o d y n e  a s  m e t e r  f r e q u e n c y  m c / s  f o l l o w s :  C r y s t a l  c h e c k  c o r r e c t i o n  C o r r e c t e d  m c / s  f r e q u e n c y  m c  p e r  7 4 . 8  1 4 . 9 3 9 5  2  - 0 . 0 4 4  x  1 4 . 8 9 5 5 =  7 4 . 6  1 4 . 8 4 3 0  2 : X  - 0 . 0 4 4  1 4 . 7 9 9 0  -  T h e  d y n e  f a c t o r  t w o  f r e q u e n c y  s e n t e d  b y  t h e  c a m e  i  m e t e r  f o u r  =  n  a s  w a s  t h e  u s e d .  i n c h e s  2 3 4 . 8  s e c o n d  o  x  f  h a r m o n i c  T h e r e f o r e  o s c i l l o s c o p e  ( 2 9 . 7 9 1 0  -  t h e  o  t h e  w i d t h ,  t r a c e  2 9 . 5 9 8 0 )  f  2 9 . 7 9 1  2 9 . 5 9 8  h e t e r o -  r e p r e -  s  - 4 1 -  - 2 3 4 . 8  -  a n d  p  e  r  1 / 1 0  x  0 . 1 0 3  2 4 . 1 8  i n c h  -  g a u s s  d i v i s i o n  2 4 . 1 8  "  4  -  0  0 . 6 0 4 6  "  •-  a  ( b )  S h o r t  t e s t  t h e  o  t i m e  t e s t  T h e  e q u i p m e n t  w a s  m a d e .  s  c  i  l  t  o  l  a  t  o  f  r  h a d  T h e  r  o  0 . 6 0  g a u s s .  e i g h t  " b e e n  r u n n i n g  b a t t e r y  i n c r e a s e d  m i n u t e s  d r i f t  0 . 0 0 0 8  f  o  w a s  m c / s  r  f  i  v  e  h o u r s  w h e n  n e g l i g i b l e .  i  n  f r e q u e n c y  t h i s  H o w e v e r  f r o m  t h e  "til z e r o  i n  f  i  e  l  d  t h e  o  m i n u t e  w h i c h  w o u l d  o b s e r v e d  x  0 . 0 0 0 8  =  0 . 1 8 8  i n  t h e  -  0 . 2  f l u c t u a t i o n  c o r r e c t i n g  f i e l d  a v e r a g e  w a s  f  f r o m  o  r  f r o m  f i e l d  -v-  a  d r o p  x  2 9 . 6 5  a  p e r i o d  v a l u e  o  f  o  t h e  w a s f  - 1  0 . 2  x  0 . 6  0 , 6  g a u s s  0 . 3  =  g a u s s  = - 0 . 6  d r o p ,  t h e  g a u s s  f l u c t u a t i o n  0 . 3  0 . 4  f i e l d  f l u c t u a t i o n  o v e r  T h e  x  t h e  -  m e a s u r e d  2 3 4 . 8  T h e r e f o r e  a s  g a u s s  w a s  t o  T h e  u p  g a u s s  t o  t h e r e f o r e  s h o w  f  2 3 4 . 8  t h e  e i g h t h  o v e r  =  g a u s s  t h e  6 , 9 6 2  . 7  f  o  r  e i g h t  e i g h t  m i n u t e s  m i n u t e s  w a s  g a u s s  =  1  p a r t  I  n  1 0 , 0 0 0  o  f  t h e  6 9 6 2 e i g h t m i n u t e s v  m a n g a n i n  r e s i s t o r  u s e d  i  n  t h e  c u r r e n t  - 4 2 -  r e g u l a t i n g  t h e  s y s t e m  R u b i c o n  m a g n e t  w a s  0 . 0 4 9 9  p o t e n t i o m e t e r  c u r r e n t  w a s  I  o h m s .  w a s  =  T h e  v o l t a g e  0 . 6 0 0 6 .  0 . 6 0 0 6  -  s e t t i n g  T h e r e f o r e ,  o n  t h e  1 2 . 0 3 2  0 . 0 4 9 9  1 2 . 0 3  =  ( c )  S e v e n  T h e  w a s  h o u r  t  o  o s c i l l o s c o p e  f  i  e  l  d  m o v e  c h a n g e s .  T h e  t  o  t a k e n .  T h e  w e r e  B a t t e r i e s  a s  d r o p p e d  o  o n  t h e  i  w a s  h a d  o t h e r  n  v o l t a g e  f o u n d  o  f  o n  l a s t e d  f  s  i  x  f r o m  a  i  s  i  n  V o l t a g e  e q u i v a l e n t  t  POP,  1 0 "  5  A t  t h e  s a m e  f r o m  t o  w h i c h  i  s  t i m e ,  2  x  2  x  y x  1  t h e  r  g  e  a n d  i  o n e  n  o  f  5 0  t  3 2 . 6  2 0 2  x  6 . 2  0 . 4 9 3  =  e  v o l t s  f i e l d .  r e a d i n g s "  m i n u t e s .  0  o  -  d r o p  6  2 0 2  =  u  u  T h e  v o l t s .  v o l t s / m i n . ) )  r  x  i  n  f  2 4 . 1 8  i  e  l  d  o  0 . 9 8  s  f  g a u s s  3  c o r r e c t e d  1 4 . 8 5 8 0  o s c i l l a t o r  t  0 . 0 0 7 8  =  f r e q u e n c y  d r o p p e d  o  a  m c / s  d r o p  i  n  f  i  e  «  t h e n  h  m a g n e t -  0 . 0 0 5  b e f o r e  a n d  f  t h e  s m a l l  t h e  h o u r  h o u r s  t  o  1 4 . 8 6 1 9  e q u i v a l e n t  c o r r e c t i o n s  o  c h a n g e  ( " 4 1 0  d r o p  t  s i d e  f o l l o w s :  ( -  T h i s  o n e  c h a n g e s  g a u s s  o  p o t e n t i o m e t e r  o r d e r  t h a t  2 4 . 1 8  b e e n  t e s t  R u b i c o n  p e a k s  s m a l l  t  t h e  r e s o n a n c e  c h a n g e  e q u i p m e n t  r e s u l t s  t  I  a  d i a l  t h e  b e t w e e n  c o r r e s p o n d e d  w e r e  v o l t a g e  s c r e e n  r e l a t i o n s h i p  i c  t e s t  s m a l l  v a r i e d  a m p e r e s .  a r e  a  f  a  l  l  o  f  l  d  o  f  1 . 8 3  2 . 8 1  2 3 4 . 8  x  g a u s s  g a u s s  0 . 0 0 7 8  :-43T h e  o b s e r v e d  s u b t r a c t i n g  f  a  l  l  t h i s  i n i f i e l d  f r o m  t  h  e  w a s  0 . 6  a b o v e  g a u s s  c o r r e c t i o n  w e  g  e  t  i  n  2 . 8 1  c o r r e c t e d  a t  a n  w h i c h  r i s e  a v e r a g e  i  s  a  i  f  i  n  e  l  f i e l d  d  v a r i a t i o n  o  2 . 2 1  f  o  6 , 9 6 2  f  g a u s s  g a u s s  2 . 2 1 6 , 9 6 2  -  t h r e e  p a r t s  1 0 , 0 0 0  -44-  Appendix 2.  Thermal e f f e c t s i n the magnet (a) E f f e c t o f temperature change on t h e magnetic f i e l d A t the b e g i n n i n g  o f the l o n g t e s t r u n the room tempera-  t u r e was 22 degrees c e n t i g r a d e w h i l e the c o o l i n g water temperature  a t t h e i n t a k e was 15.2 degrees c e n t i g r a d e .  At the  end o f t h e t e s t t h e c o o l i n g water had r i s e n t o 17 degrees centigrade. I f we assume the magnet was c o o l e d 5 degrees  centigrade  a f t e r seven hours we may c a l c u l a t e t h e decrease i n a i r gap width due t o the l i n e a r c o n t r a c t i o n o f the s t e e l o f the magnet. The n e t l i n e a r c o n t r a c t i o n w i l l be due t o a one i n c h section of s t e e l .  Taking  ok =  10.5 x 1 0 ~  6  p e r degree  c e n t i g r a d e f o r s o f t s t e e l we f i n d from  that  L  e  A L  -  therefore  L  0  (1 -h* t )  L o(4t Q  -ol At 0  - 10.5 x 1 0 "  6  x 5  - £ part i n 10 .. _ T h i s w i l l a f f e c t the f l u x d e n s i t y i n t h e a i r gap d i r e c t l y 4  -45as H  a i r  =  4TTNI  - H  l  i r o n  i  r  o  n  aiv  1  a^AHair =  -  1  /  s  2  A l  a  i  4 ^  r  H I - H  i r o n  I  i  r  0  n]  •air' therefore  A H  ftiT  .  =  - ./j l  TT  air  a  i  r  "J air  T h i s shows t h a t a n e t decrease i n a i r gap width o f % p a r t i n 10,000 w i l l cause an i n c r e a s e i n f i e l d s t r e n g t h o f the same amount. (b) Estimated  time f o r magnet t o c o o l  T h i s c a l c u l a t i o n i s n o t s t r a i g h t f o r w a r d because o f t h e unknown f a c t o r s i n heat t r a n s f e r from t h e copper c o i l s t o the c o o l i n g water and a l s o t o t h e s t e e l o f t h e magnet. However, i t can be estimated  with the help of the e m p i r i c a l  i n f o r m a t i o n g i v e n i n H. C. R o t e r s 'Electromagnetic The  Devices'.  d a t a i s as f o l l o w s :  Room temperature  22 degrees  C o o l i n g water i n t a k e temperature  15.2  C o o l i n g water o u t l e t temperature ( a f t e r 7 hours) T o t a l f l o w o f c o o l i n g water  17  Magnet c u r r e n t  centigrade  " "  92.2 c . c . / s e c . 12.03 amperes  " "  -46R e s i s t a n c e o f copper  4.6  Weight o f copper p r e s e n t  500 l b s .  Weight o f s t e e l o f magnet  7-jjr  Heat c a p a c i t y o f copper  ohms  tons.  180 j o u l e s / l b . / d e g r e e centigrade-  Heat c a p a c i t y o f s t e e l  225 j o u l e s / l b s . / d e g r e e centigrade The heat energy added by the e l e c t r i c c u r r e n t i s (12.03)  2  x 4.6 = 667 watts = 667 j o u l e s / s e e .  The heat energy t a k e n away by t h e c o o l i n g water i s 92.2 x 4.18 x 2  = 770 j o u l e s / s e c .  T h i s l e a v e s a n e t amount o f heat energy o f 103 j o u l e s / s e c . which i s t a k e n away from t h e copper and s t e e l and thus w i l l lower t h e i r temperature. C o n s i d e r i n g t h e copper alone, t o lower i t s temperature one degree c e n t i g r a d e r e q u i r e s t a k i n g away from i t o f 500 x 180 =  90,000 j o u l e s .  T h e r e f o r e , i f t h e copper i s c o n s i d e r e d f i r s t alone, t h e time t a k e n t o lower i t s temperature one degree c e n t i g r a d e i s  9Q«Q0Q 103 x 60  = 14.6 minutes.  A f t e r some time, the s t e e l becomes between 45 % and 50 % e f f e c t i v e i n a b s o r b i n g heat" *. 1  T h e r e f o r e , assuming 50 %  e f f e c t i v e n e s s , the heat energy taken away t o lower i t s temperature b y one degree c e n t i g r a d e i s  -47-. £ x 7.5 x 2,000 x 225  =  To t h i s , add t h a t o f the copper  1,690,000 j o u l e s . 90,000 j o u l e s  g i v i n g a t o t a l of  1,780,000 j o u l e s .  The time r e q u i r e d t o lower the whole magnet one degree centigrade  once heat t r a n s f e r had "been e s t a b l i s h e d between  the copper and s t e e l would be 1.780.000 103 x 60 x 60  =4.8  hours  which c o u l d o n l y account f o r a drop o f about centigrade  degrees  i n seven hours.  A complete a n a l y s i s would have t o take i n t o account the t h e r m a l c o n d u c t i v i t y o f the s t e e l o f t h e magnet f o l l o w ed by a s o l u t i o n o f F o u r i e r ' s heat e q u a t i o n f o r t h i s of s o l i d .  shape  I t can e a s i l y be seen t h a t the s t e e l o f the  p o l e p i e c e s would have t o c o o l down b e f o r e  the yoke o f the  magnet c o u l d f e e l the e f f e c t o f the c o o l i n g water. An assumption t h a t the p o l e p i e c e s formed \ o f t h e weight o f the magnet would change the time t o c o o l them one degree t o the r i g h t amount.  T h i s would change the time  t o c o o l the copper p l u s the s t e e l of the p o l e p i e c e s  only,  t o 1.4 hours f o r a one degree drop or 7 hours f o r a drop o f 5 degrees  centigrade.  -48-  Appendix 3.  Adjustment to the c o n t r o l system necessary f o r optimum operation The procedure 1.  f o r s t a r t i n g the magnet i s as f o l l o w s :  Push the main t o g g l e s w i t c h S-^ up t o apply power t o the  a m p l i f i e r and a l l h e a t e r s .  T h i s l i g h t s the amber i n d i c a t o r  A f i v e minute time d e l a y p r e v e n t s o p e r a t i n g the H . T.  "bulb. relay. 2.  A f t e r w a i t i n g f i v e minutes, ( o r a f t e r h e a r i n g the  o f the time d e l a y r e l a y ) push b u t t o n S  4  'click'  whereupon the r e d  j e w e l i n d i c a t o r shows, i n d i c a t i n g H . T. i s a p p l i e d t o the power u n i t .  I f the r e d j e w e l does not l i g h t , then one  more of the i n t e r l o c k c i r c u i t s are open.  or  These i n t e r l o c k s  are: (a) A'-toggle s w i t c h on t h i s main p a n e l marked ' H . T. interlock.  T h i s must be  i n the  'on'  position.  (b) The p r e s s u r e s w i t c h a t the i n t a k e manifold, the c o o l i n g system.  Water must be t u r n e d on and most  the water o u t l e t tap must a l s o be t u r n e d  important  on.  (c) A one m i l l i a m p e r e r e l a y on the r e g u l a t o r tube  -49chassis.  T h i s r e l a y opens i f the 6 A S 7 g r i d s "become p o s i t i v e .  (d) The push s w i t c h on the doors o f the c a b i n e t r a c k e n c l o s i n g the power u n i t . motor-generator Now,  T h i s c a b i n e t r a c k i s mounted i n the  room.  p r o v i d i n g a l l the i n t e r l o c k s are c l o s e d , and depend-  i n g on the Rubicon potentiometer  s e t t i n g and D.  C.  level  c o n t r o l , the g e n e r a t o r shunt f i e l d c u r r e n t meter 1% s h o u l d r e a d ( and the 6 A S 7 cathode c u r r e n t meter M3  i f plugged  i n t o one of the j a c k s ) . 3.  Now  the motor g e n e r a t o r s may  be switched on by  pushing  t h e two b l a c k 'on' b u t t o n s , l i g h t i n g t h e i n d i c a t o r lamps. magnet c u r r e n t meter  The  should read.  C u r r e n t i s i n c r e a s e d or decreased by moving the main v o l t a g e d i a l s on the Rubicon potentiometer.  A f t e r each change  o f s e t t i n g , the D. C. l e v e l c o n t r o l knob s h o u l d be so t h a t b a l a n c e meter M  4  reads c e n t r e .  same time cause e r r o r s i g n a l meter Mg i t does not do so, t h e n the hum  adjusted  T h i s should, a t the t o r e a d minimum.  balancing  If  potentiometer  (screw adjustment) mounted a t the back o f the D.  C.  amplifier  power supply c h a s s i s s h o u l d be a d j u s t e d f o r minimum r e a d i n g on t h i s meter w i t h no s i g n a l s coming i n ( d i s c o n n e c t e d b o t h s h i e l d e d l e a d s t o the D.  C. a m p l i f i e r c h a s s i s i n p u t and  ground the c e n t r e t e r m i n a l s ) . F o r p r e l i m i n a r y adjustment and c a l i b r a t i o n o f t h e  -50Rubicon potentiometer - see ' O p e r a t i n g d i r e c t i o n  special  Rubicon type "B" potentiometer c a t . no. 2780, s e r i a l  no.  53750.' from the Rubicon Company, P h i l a d e l p h i a , Pa., U.S.A. I f d u r i n g the above adjustments, the shunt  field  c u r r e n t meter Mg drops t o zero,'and the magnet c u r r e n t f a l l s w h i l e the meters on the a m p l i f i e r p a n e l , M 4 , M 5 and Mg,  show o f f "balance r e a d i n g s , t h e n the c u r r e n t o v e r l o a d  r e l a y ( f i g u r e 9) must have been t r i p p e d , opening the shunt field circuit  o f the g e n e r a t o r s .  T h i s may be r e s e t by  pushing the r e s e t b u t t o n on the c u r r e n t r e g u l a t i n g tube chassis.  I f i t w i l l not s t a y i n , t h e n e i t h e r t h e r e i s a  s h o r t i n the c i r c u i t which would show up by a r e a d i n g g r e a t e r t h a n one ampere i n Mg or e l s e the r h e o s t a t adjustment on the r e l a y i s s e t too low.  T h i s i s a screw  d r i v e r adjustment a t the back o f the c u r r e n t r e g u l a t i n g tube c h a s s i s .  I t s h o u l d be a d j u s t e d t o t r i p a t j j u s t above  one ampere o f shunt f i e l d  current.  -51-  Appendix 4.  Use o f f l i p - c o i l s and f l u x m e t e r F i e l d s t r e n g t h measurements were made w i t h  specially  c o n s t r u c t e d f l i p - c o i l s and a Rawson E l e c t r i c a l Co. f l u x meter.  Four c o i l s wound on l u c i t e forms were made up t o  cover t h e range from 10 gauss t o 20,000 gauss.  Each c o i l  was screwed t i g h t l y t o a long, smooth "board two i n c h e s wide and shimmed w i t h c o r r u g a t e d cardboard s t r i p s  so as t o s l i d e  i n t o and out o f the one i n c h p o l e gap without t u r n i n g . "board was rubbed l i g h t l y w i t h p a r a f f i n moved e a s i l y  The  wax so t h a t i t  though f i t t i n g t i g h t l y .  A square hardwood frame w i t h h o l e s spaced one i n c h and f i t t e d w i t h l u c i t e p l u g s was mounted over t h e magnet p o l e p i e c e s t o h o l d the f l i p - c o i l s i n any p o s i t i o n i n t h e gap between t h e p o l e s . Two o f t h e f l i p - c o i l s were c a l i b r a t e d on a magnet u s i n g a p r o t o n resonance  s i g n a l t o measure t h e f i e l d .  other two c o i l s were then c a l i b r a t e d a g a i n s t t h e s e .  The  B i b l i o g r a p h y  1 .  R o t e r s ,  S o n s ,  2 .  N .  S t a f f ,  J o h n  H .  M.  W i l e y  4 .  R o s e t t i ,  B a m e ,  P .  S .  6 .  "  N .  J .  S o n s ,  N .  S . ,  P r o .  Y . ,  a n d  G .  W i l e y  a n d  S o c .  T r a n s f o r m e r s " ,  1 5 4 A  N u c l e a r  L .  O c t .  ffi.,  7 .  C a r o ,  D .  8 .  L a w s o n ,  N .  P a r r y ,  1 ,  ( 1 9 3 6 )  P h y s i c s " ,  P r e n t i c e -  a n d  N  R i c e  6  I n s t i t u t e ,  o n r - 2 2 4 ,  T a s k  o r d e r  1 9 4 9 .  Y . ,  J .  T h e  R e p o r t  " P r i n c i p l e  M c G r a w H i l l ,  L .  R o y .  P r o g r e s s  P . ,  E . ,  a n d  1 9 4 3 .  o f  B a g g e t  i s m " ,  J .  J o h n  1 9 4 8 .  P h y s i c s ,  H a r n w e l l ,  C i r c u i t s  Y . ,  E l e m e n t s  T e x a s ,  N u c l e a r  " M a g n e t i c  M .  F . ,  H o u s t o n ,  1  T . ,  a n d  I n c . ,  D e v i c e s " ,  1 9 4 1 .  I .  B l a c k e t t ,  5 .  " E l e c t r o m a g n e t i c  Y . ,  3 .  H a l l  C . ,  o f  E l e c t r i c i t y  a n d  M a g n e t -  1 9 3 8 .  K . ,  T y l e r ,  J .  A .  S .  W.,  I . ,  2 6 ,  R e v .  S  c  1 1 ,  i  .  1 9 4 9  I n s t .  1 0 ,  3 0 4 ,  ( 1 9 3 9 ) .  9 .  R u t g e r s  o n  1 0 .  U n i v e r s i t y ,  P r o j e c t  E l e c t r o n i c  C o r p o r a t i o n  J o h n  1 1 .  W i l e y  D r i v e r  R u b i c o n  C o . ,  o f  P h y s i c s ,  P r o g r e s s  R e p o r t  4 1 .  E n g i n e e r s  o f  " I n d u s t r i a l  a n d  H a r r i s  E l e c t r i c a l  1 2 .  n o .  D e p t .  S o n s ,  C o . ,  t h e  W e s t i n g h o u s e  E l e c t r o n i c s  E l e c t r i c  R e f e r e n c e  B o o k " ,  1 9 4 8 .  " N i c h r o m e  a n d  o t h e r  H i g h  A l l o y s " .  P h i l a d e l p h i a ,  B u l l e t i n  n o .  1 0 0 .  N i c k e l  -531 3 .  C o m m u n i c a t i o n  1 4 .  M e m o  A  f r o m  E / c y e l / R  F e r g u s o n  L  M ,  B a t t e r y  p r i v a t e  C o . .  c o m m u n i c a t i o n  f r o m  T .  R .  - E * ,  1 9 4 6 .  1 5 .  G r e e n w o o d  m e n t s " ,  N .  1 6 .  I  M .  Y . ,  B a l a n c e  I  .  T .  1 9 .  J  .  .  T .  -  H o n e y w e l l  ,  M a c r a e  R a d i a t i o n  B u l l e t i n  D . / ' E l e c t r o n i c  S e r i e s  V  o  R a d i a t i o n  p a g e  4 9 8  1 8 ,  p a g e  4 0  2 1 .  p a g e s  p a g e  l  .  2 1 ,  I n s t r u -  M c G r a w  H  i  l  l  S e r i e s  4 8 7 ,  5 1 4 ,  2 0 .  P u r e e l l ,  2 1 .  B l o c h ,  2 2 .  E l o e m e r i b e r g e n ,  N . ,  5 1 5 ,  5 4 3 ,  D r .  N .  " N u c l e a r  N i j h o f f ,  T o r r e y  H a n s e n ,  E l e c t r o n i k  I n s t r u m e n t  C o n t i n u o u s  V o l u m e s .  f r o m  L a b o r a t o r i e s ,  M a r i u s  B r o w n  5 5 4  1 0 8  B l o e m e r i b e r g e n ,  H a g u e ,  " B r o w n  C o . ,  P y r o m e t e r " .  C o m m u n i c a t i o n  R i v e r  R e g u l a t i n g  1 5 - 1 6 ,  1 7 ,  P r i v a t e  C h a l k  H o l d a m  P o t e n t i o m e t e r  2 5  1 8 .  I  M i n n e a p o l i s  M.  ,  1 9 4 8 .  D i v i s i o n ,  1 7 .  .  a n d  E  l  R .  l  i  o  t  t  a n d  D r .  C .  M a g n e t i c  R e l a c a t i o n " ,  Anderson.,  2 4 .  C o l l i n s ,  T .  H .  P o u n d ,  P a c k a r d ,  P u r c e l l  L .  L . ,  P h .  P h y s .  P h y s .  a n d  P h y s .  D .  T h e  1 9 4 8 .  R e v .  R e v .  P o u n d ,  6 9 ,  6 9 ,  P h y s .  3 7 ,  1 2 7 ,  R e v .  ( 1 9 4 6 ) .  ( 1 9 4 6 ) .  7 3 ,  ( 1 9 4 8 ) .  2 3 .  F e r g u s o n  R e v .  T h e s i s ,  7 6 ,  1 4 6 4 ,  U . B . C . ,  ( 1 9 4 9 ) .  1 9 5 0 .  6 7 9 ,  - 5 4 -  2 5 .  P a c k a r d ,  2 6 .  B l o c h ,  2 7 .  H o p k i n s ,  M .  E . ,  R e v .  N i c o d e r a u s ,  N.  J  .  ,  S  c  i  .  S t a u b ,  R e v .  S  c  I n s t . ,  P h y s .  i  .  1 9 ,  4 3 5 ,  R e v .  I n s t . ,  2 0  7 4 ,  ,  4 0 1 ,  ( 1 9 4 8 ) .  1 G 2 5 ,  ( 1 9 4 8 ) .  ( 1 9 4 9 ) . .  

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