HAL Id: jpa-00223712
https://hal.archives-ouvertes.fr/jpa-00223712
Submitted on 1 Jan 1984
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
A PULSED SUPERCONDUCTING DIPOLE MAGNET FOR THE NUCLOTRON
A. Smirnov, A. Baldin, A. Donyagin, E. d’Yachkov, I. Eliseeva, H.
Khodzhibagiyan, I. Khukhareva, A. Kovalenko, Yu. Kulikov, B. Kuryatnikov, et al.
To cite this version:
A. Smirnov, A. Baldin, A. Donyagin, E. d’Yachkov, I. Eliseeva, et al.. A PULSED SUPERCON-
DUCTING DIPOLE MAGNET FOR THE NUCLOTRON. Journal de Physique Colloques, 1984, 45
(C1), pp.C1-279-C1-282. �10.1051/jphyscol:1984156�. �jpa-00223712�
JOURNAL DE PHYSIQUE
Colloque C l , suppl6ment au no 1, Tome 45, janvier 1984 page C1-279
A PULSED SUPERCONDUCTING DIPOLE MAGNET FOR THE NUCLOTRON
A.A. Smirnov, A.M. Baldin, A.M. Donyagin, E.I. D'yachkov, I.A. Eliseeva, H.G. Khodzhibagiyan, I.S. Khukhareva, A.D. Kovalenko, Yu.V. Kulikov, B.K. Kuryatnikov, E.K. Kuryatnikov, V.N. Kuzichev, L.G. Makarov, P.I. Nikitaev, N.M. Sazonov, M.A. Voevodin, A.G. Zel'dovich and A.A. Vasiliev*
Joint I n s t i t u t e for Nuclear Research, Dubna, U.S. S.R.
' s t a t e Cormnittee for U t i l i z a t i o n of Atomic Energy, Moscow, U. S. S. R.
Resume
-
On d e c r i t un aimant u t i l i s a n t u n c i r c u i t ferromagnetique e t des m s avec u n supraconducteur creux. On donne l e s premiers r e s u l t a t s experimentaux.Abstract
-
A magnet with a f i e l d formed by iron and having a winding of hollow superconductor i s described. F i r s t experimental r e s u l t s are given.I
-
INTRODUCTIONI t i s evident t h a t in the future the Dubna synchrophasotron will be changed f o r the Nuclotron superconducting accelerator of r e l a t i v i s t i c nuclei /1,2/. I t i s planned t o place a main ring of the future accelerator having a perimeter of 250 m in the existing building of the synchrophasotron which e s s e n t i a l l y reduces investments and the time of i t s construction. To choose t h e type of a Nuclotron magnetic system, the following main requirements have been imposed:
1) an agreement between parameters of the accelerator (E=6 GeV/u, i n t e n s i t y
-109 part./cycle f o r and physics problems raised. Experiments with r e l a t i v i s t i c nuclear c o l l i s i o n s have shown t h a t the onset of limiting fragmentation of nuclei occurs a t 3
-
4 GeV/u. The investigation of these phenomena has shown t h a t an energy of 4 GeV/u i s a c r i t i c a l one a t which the quark degrees of freedom of the nucleus begin t o be important ( s e e , f o r example, / 3 / ) ;2) a short period of time f o r the construction of t h e new accelerator and the repla- cement of t h e old one;
3) economy (minimal construction and operation expenses);
4 ) simplicity in making and service;
5) high r e l i a b i l i t y .
Four types of magnets were considered f o r the magnetic system:
a ) conventional "warm" magnets;
b) superconducting magnets /4/ with a large ( 5 T ) f i e l d ;
c ) immersed type superconducting magnets /5/ with a f i e l d of 2 T formed by iron;
d) magnets /6,7/ with a f i e l d of 2 T formed by iron and having a winding of hollow superconductor f o r forced cooling.
Our developments and studies performed in the l a s t few' years show t h a t a magnetic system consisting of magnets with a f i e l d formed by iron and a winding of hollow superconductor greatly conforms t o the indicated requirements.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984156
C1-280 JOURNAL DE PHYSIQUE
The main elements o f such magnets are an i r o n yoke and a superconductinq winding.
The i r o n yoke decreases ampere-turns o f t h e windinq by a f a c t o r o f two, which a r e r e q u i r e d f o r t h e formation o f a given magnetic f i e l d , and forms a f i e l d w i t h h i g h homogeneity. Magnetic f o r c e s i n t h e winding a r e supported by the i r o n yoke. The con- sumption o f e l e c t r i c a l energy i s decreased by t h e superconducting winding by a f a c - t o r o f several times (versus t h e pulsed f r e q u e n c ~ of a c c e l e r a t i o n c y c l e s ) . Due t o a h i g h s t r u c t u r a l c u r r e n t d e n s i t y (-1.2.104 A/cm ) t h e superconducting winding a l l o w s t h e area o f t h e magnet cross s e c t i o n t o be decreased by a f a c t o r o f -5 as compared t o a "warm" magnet w i t h t h e same aperture. I n a d d i t i o n , u n l i k e a "warm"
magnet, an e l e c t r i c a l power supply system o f lower power i s r e q u i r e d f o r a magnet w i t h i r o n yoke and superconducting winding because o f no a c t i v e e l e c t r i c a l r e s i s t a n - ce i n i t and lower i n d u c t i v e r e s i s t a n c e . A helium c r y o s t a t vessel i s n o t r e q u i r e d f o r magnets o f h o l l o w superconducting cable. This circumstance a l l o w s one t o s i m p l i - f y s i g n i f i c a n t l y t h e s t r u c t u r e o f a c r y o s t a t , t o provide convenient access t o a mag- n e t i c system o f t h e a c c e l e r a t o r , t o decrease t h e amount o f helium and t o improve cryogenic safety. Besides, t h e requirements f o r t h e s t r u c t u r e o f a vacuum chamber o f t h e a c c e l e r a t o r a r e decreased i f i t i s n o t needed due t o cryogenic pumping. Such magnets have h i g h mechanical and e l e c t r i c a l strength.
To i n v e s t i g a t e t h e technology o f c o n s t r u c t i o n o f magnets o f h o l l o w superconductor, t o e s t i m a t e expenses f o r t h e i r p r o d u c t i o n and t o o b t a i n experimental c h a r a c t e r i s t i c s , a f u l l - s c a l e ( 1 = 1.5 m) d i p o l e magnet has been b u i l t , and i t s t e s t s have been con- ducted.
I 1
-
MAGNET AND CRYOSTATThe magnet ( F i g . 1 ) c o n s i s t s o f two symmetric p a r t s 1.5 m l o n g and has an aperture o f 90 x 42 mm2. The dimensions o f t h e i r o n yoke 4 a r e 1400 mm x 256 mm x 166 mm. The half-yokes are made o f laminated s t e e l 0.5 mm i n thickness. The two-layer saddle- -shaped winding 8 made o f a h o l l o w superconducting cable comprises twelve t u r n s . T h i r t y one 0.5 mm diameter w i r e s a r e s p i r a l l y wound on a t i n n e d cupro-nickel p i p e 5 x 0.5 mm i n diameter w i t h a t w i s t o f 47 mm. The w i r e c o n t a i n s 1045 NbTi f i l a m e n t s 10pm i n diameter i n a copper m a t r i x . The cable i s wrapped i n f o u r l a y e r s o f mylar tape 0.02 mm t h i c k and i n two l a y e r s o f f i b r e g l a s s 0.08 mm t h i c k impregnated w i t h epoxy. The winding can be disassembled i n t h i s experimental magnet. Therefore, a f t e r mounting t h e h a l f - w i n d i n g s i n t h e yoke, t h e y a r e c l u t c h e d w i t h clamps 3. Four s t e e l clamps 8 mm i n diameter i n s t a l l e d each 300 mmlengthwise t h e magnet t i g h t e n t h e wind- i n g t o t h e i r o n yoke through i n s u l a t i n g f i l l e r p l a t e s 7.
Fig. 1 -Layout o f t h e maqnet i n t h e c r y o s t a t : 1
-
vacuum s h e l l ; 2 - c o o l i n g c o i l o f t h e yoke; 3-
clamp; 4-
i r o n yoke; 5-
thermal contact; 6-
magnet support; 7-
f i l l e r p l a t e ; 8
-
superconducting winding; 9-
support pin; 10-
n i t r o g e n s h i e l d .The h o r i z o n t a l c r y o s t a t ( F i g . 1 ) represents a vacuum c y l i n d r i c a l s h e l l 1. A copper s h i e l d 10 cooled by l i q u i d n i t r o g e n i s placed i n s i d e t h e s h e l l . The magnet i s mounted i n t h e c r y o s t a t on one support placed a t t h e center o f t h e magnet. Support 6 i s made o f c o n c e n t r i c s t a i n l e s s tubes welded w i t h one another and has a thermal con- t a c t w i t h a n i t r o g e n s h i e l d .
F i g u r e 2 shows t h e magnet a f t e r i t i s mounted i n t h e c r y o s t a t .
Fig. 2
-
The magnet a f t e r i t i s mounted i n t h e c r y o s t a t .I 1 1
-
A FLOW DIAGRAM OF THE PLANT AND FIRST EXPERIMENTAL RESULTSA f l o w diagram o f magnet r e f r i g e r a t i o n i s presented i n F i g . 3. To s i m p l i f y cryogenic operation, a Joule-Thomson s a t e l l i t e r e f r i g e r a t o r has been b u i l t . The main parame- t e r s o f t h e s a t e l l i t e r e f r i g e r a t o r are: m s 5 g/s; a = 0.15; t h e amount o f l i q u i d helium i n t h e heliym vessel i s 300 1; ap =0.02 FlPa a t i = 5 g/s.
Fig. 3 - The f l o w diagram o f magnet r e f r i g e r a t i o n : 1
-
heat exchanger; 2-
c u r r e n t leads; 3-
yoke; 4 - c o o l i n g c o i l o f t h e yoke; 5,8-
o p e r a t i o n valves; 6,7-
h a l f - -windings; 9-
he1 ium vessel o f t h e sate1 1 i t e r e f r i g e r a t o r ; 10-
supercooler.C1-282 JOURNAL DE PHYSIQUE
The l i q u i d helium from supercoaTer 10 of t h e s a t e l l i t e r e f r i g e r a t o r i s d i v i d e d i n t o two p a r t s and supplied t o t h e half-windings o f t h e magnet.Passing through t h e channels o f t h e half-windings, t h e one-phase helium converts t o t h e two-phase one.
One p a r t o f t h e f l u x w i t h mass f l o w r a t e ih-c passes successively through half-wind- i n g 6, o p e r a t i o n v a l v e 5, c o i l 4 used t o cool i r o n yoke 3 and then i s f e d t o cool c u r r e n t leads 2. Another p a r t o f t h e f l u x w i t h mass f l o w r a t e $1
-
c ) passes through h a l f - w i n d i n g 7, o p e r a t i o n v a l v e 8 and r e t u r n s t o helium vessel 9 o f t h e sa- t e l l i t e r e f r i g e r a t o r a f t e r heat removal from t h e " c o l d " ends o f c u r r e n t leads 2. The f l u x w i t h mass f l o w r a t e m(a+
C ) r e q u i r e d f o r t h e o p e r a t i o n o f t h e s a t e l l i t e r e f r i - g e r a t o r i s f e d t o t h e helium vessel from t h e t a n k o f l i q u i d helium. The mass f l o w r a t e h i s measured by means o f a gas flowmeter w i t h c a l i b r a t e d holes which a r e placed on t h e way o f t h e compressed helium fromethe compressor t o heat exchanger 1 o f t h e r e f r i g e r a t o r . The mass f l o w r a t e mc and m ( l + a ) a r e measured u s i n g gas f l o w - meters.The temperature i s measured by carbon r e s i s t a n c e thermometers TBO /8/ placedi n t h e f l u x o f helium.
The h a l f - w i n d i n g s o f t h e magnet were r e f r i g e r a t e d by means o f the f l u x o f two-phase helium w i t h t h e f o l l o w i n g parameters: a mass vapour content o f 0
-
1, a s p e c i f i c mass f l o w r a t e o f 12-260 kg/mZs and a maximum t e m p e r a t i r e o f 4.5-
5 K.The c r i t i c a l c u r r e n t i n t h e magnet i s 6 kA a t a temperature o f 4.5 K. I n t h i s case t h e magnetic f i e l d a t t h e d i p o l e center i s 2 T.
A harmonic a n a l y s i s o f t h e magnetic f i e l d has been performed by f l a t i n d u c t i o n c o i l s r o t a t i n g i n t h e magnet aperture. I n t e r a l r e l a t i v e inhomogeneity o f t h e magnetic
2
f i e l d i n t h e a p e r t u r e was AB/Bo=4.10- a t a l e v e l o f 2 T on a 20 mm r a d i u s .
The heat released i n t h e magnet was determined from t h e equation o f energy balance.
The f l u x e s i n t h e half-windings were r e g u l a t e d so t h a t t h e helium was i n t h e one- -phase ( l i q u i d o r gaseous) s t a t e a t t h e p o i n t o f measuring enthalpy. The s t a t i c heat l e a k t o t h e magnet, i n c l u d i n g t h e heat l e a k along t h e support, was 3.3 !4. The heat l e a k t o each o f t h e o p e r a t i o n valves was 0.8 14.
The magnet was e x c i t e d by a continuous stream o f c u r r e n t pulses o f t r i a n g u l a r shape.
The dynamic heat released i n t h e magnet was -30 W a t a f i e l d sweep r a t e o f B=5 T/s.
Approximately h a l f t h e dynamic heat r e l e a s e was i n t h e i r o n yoke. I f t h e a c c e l e r a t o r operates a t a f i e l d sweep r a t e o f 4 T/s and a pulsed frequency o f a c c e l e r a t i o n c y c l e s 0.2 Hz, t h e t o t a l heat l e a k t o helium i s 5 W f o r a 1 m l e n g t h o f t h e magnet. Dynamic heat r e l e a s e can be p r i m a r i l y decreased due t o decreasing heat r e l e a s e i n t h e i r o n yoke. T h i s a l l o w s t h e pulsed frequency o f a c c e l e r a t i o n c y c l e s t o be increased a t t h e
same t o t a l heat leak.
The pressure losses i n t h e magnet, measured a t a s p e c i f i c mass f l o w r a t e o f 38 kg/m2s, an average pressure o f 0.16 MPa i n t h e channel and t h e change o f vapour c o n t e n t s from 0 a t t h e i n p u t t o . 1 a t t h e output, were equal t o 6 kPa.
I V
-
REFERENCES:1. ALEKSEEV V.P. e t a l . JINR, 9-7148 (1973).
2. BALDIN A.M. e t a l . Proc. I V m n i o n Meeting on Charged Part.Accelerators,
2
(1975) 4.
3. BALDIN A.M. Proc. o f t h e 1981 CERN-JINR School o f Physics (1982) 1.
4. BALDIN A.M. e t a l . Proc. V A l l - U n i o n Meeting on Charged Part.Accelerators,
2
(1977) 63.
5. AVERICHEV S.A. e t s a l . JINR, P8-11700 (1978).
6. AGAPOV N.N. e t a l . PTE, 2 (I-;
AGAPOV N.N. e t a l . Cryogenics, 20 (1980) 345.
7. D'YACHKOV E . I . e t a l . JINR, 8-8T169 (1982).
8. DATSKOV V.1: PTE,
