THE

300-MeV

TOMSK V. V. B. V. V.

ELECTRON

POLYTECHNIC P. N. N. N. I.

Anokhin, A. Eponeshnikov, Kalinin, L. Kuz'min, G. Tolmachev,

SYNCHROTRON

OF

THE

INSTITUTE G. Vlasov, A . A. V o r o b ' e v , I. A . G a b r u s e n k o , G. K o s i t s y n , V. A. K o c h e g u r o v , A. S i p a i l o v , B. A. S o l n t s e v , a n d I. P . C h u c h a l i n

UDC 621.384.612

In March 1966 a 3 0 0 - M e V ' e l e c t r o n s y n c h r o t r o n was put into s e r v i c e at the Nuclear P h y s i c s R e s e a r c h Institute of the T o m s k Polytechnic Institute: it was subsequently found convenient to use it for r e s e a r c h in n u c l e a r physics. The work envisaged in this field f o r the n e a r future falls into two c a t e g o r i e s : investigation of the c r o s s sections of n u c l e a r photo-effects, and of the photoproduction of p i - m e s o n s f r o m light nuclei. F i g u r e 1 shows a g e n e r a l view of the equipment. A c h a r a c t e r i s t i c feature of the s y n c h r o t r o n is the deep frequency modulation of the a c c e l e r a t i n g voltage, as the e l e c t r o n s are injected with an e n e r g y of 250 keV. The e l e c t r o m a g n e t of the s y n c h r o t r o n c o n s i s t s of four quadrants s e p a r a t e d by l i n e a r gaps of length 0.6 m. The magnetic c i r c u i t c o n s i s t s of 24 blocks with C - s h a p e d c r o s s section, with the gap on the outer side. The radius of the orbit in the quadrants is 0.95 m, and the coefficient of d e c r e a s e of the field is 0.65. The total weight of steel in the magnet is 14.7 tons, that of copper is 1.5 tons. The s y n c h r o t r o n operates in pulses with r e c u r r e n c e frequency 1 sec -1. The e l e c t r o m a g n e t is excited by d i s c h a r g e of a

Fig.1. General view of 300-MeV synchrotron. T r a n s l a t e d f r o m Atomnaya ]~nergiya, Vol.21, No.6, pp.502-503, D e c e m b e r , 1966. Original l e t t e r submitted August 1, 1966.

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b a t t e r y of c a p a c i t o r s . The c u r r e n t amplitude in the winding is 758 A for a 8.7-kV voltage. The potential a c r o s s the c a p a c i t o r b a t t e r y is stabilized to within • 0.5%. To reduce power consumption, provision is made for r e c h a r g i n g the c a p a c i t o r b a t t e r y f r o m the electromagnet. The injector is a t w o - e l e c t r o d e a c c e l e r a t o r tube fed by pulses f r o m a 250-kV t r a n s f o r m e r . t r a n s f o r m e r pulses a r e r e c t a n g u l a r , the stability of the flat part being not w o r s e than 0.07%.

The

F r o m the a c c e l e r a t o r tube, the beam p a s s e s through the injection channel to the vacuum c h a m b e r , and is extracted parallel to the orbit by means of an electrostatic inftector located in the linear gap. Owing to the relatively low injection energy, the frequency of the accelerating field at the beginning of an a c c e l e r a t i o n cycle has to v a r y f r o m 28.2 to 37.5 Mc/sec in about 300 psec. To this end the entire hf channel is divided into two. The f i r s t channel operates during s y n c h r o p h a s o t r o n acceleration, and changes the a c c e l e r a t i n g voltage frequency f r o m 28.2 to 37 Mc/sec. Since the operating time of this f i r s t channel is short, it is based on GI-14B pulse tubes which can develop sufficient power in the r e quired frequency band. The f i r s t channel c o n s i s t s of a f r e q u e n c y - m o d u l a t e d g e n e r a t o r of about 3 kW power, and an amplifier which gives an output power of the o r d e r of 6 kW. F r e q u e n c y modulation is achieved by varying the inductance of the g e n e r a t o r coil. This coil is wound on a f e r r i t e ring and placed in the gap of a special e l e c t r o m a g n e t The value and f o r m of the excitation c u r r e n t of this electromagnet determines the modulation p r o g r a m . This scheme yields a m a r k e d reduction in modulating c u r r e n t and simplifies the c i r c u i t s for shaping it. Both stages of the f i r s t channel are modulated by a r e c t a n g u l a r anode pulse: the output stage is switched in later, so as to attenuate t r a n s i e n t s o c c u r r i n g when the autogenerator is switched in. The second channel is operative during the g r e a t e r part of the acceleration cycle, and gives an accelerating voltage with an amplitude of 1100 V and a frequency of 37.5 Mc/sec. P a r t i c l e l o s s e s during the transition f r o m s y n c h r o p h a s o t r o n to s y n c h r o t r o n acceleration are negligible. The accelerating s t r u c t u r e consists of paired toroidal r e s o n a t o r s . The t r a n s m i s s i o n band of one of these is broadened by shunting its r e s i s t a n c e . To reduce the sizes of the r e s o n a t o r s , each of them has lumped c a p a c i t o r s . wide-band r e s o n a t o r is 4,that of the n a r r o w - b a n d r e s o n a t o r is 160.

The Q - f a c t o r of the

The r e s o n a t o r s are close together, and t h e r e f o r e , to reduce coupling between them, their f r e quencies are widely s e p a r a t e d (30 and 37.5 Mc/sec). To avoid e n e r g y l o s s e s by the electrons owing to interaction with the n a r r o w - b a n d r e s o n a t o r during the transition f r o m s y n c h r o p h a s o t r o n to s y n c h r o t r o n conditions, a frequency change is provided f r o m 37 to 37.5 Mc/sec. At present the individual units of the s y n c h r o t r o n are being developed and their stability improved. In future it is hoped to i n c r e a s e the pulse r e c u r r e n c e frequency.

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