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United institute of nuclear problems
NEWS ITEMS UNITED
INSTITUTE
OF NUCLEAR
PROBLEMS
In 1949 an I n s t i t u t e of Nuclear Problems was established by the Academy of Sciences of the Soviet Union on a site n o t far from the junction of the MoskvaVolga canal with the river Volga, a b o u t 150 km from Moscow. On this site lalx~ratories and accessory plants were installed to operate a 680 MeV synchrocyclotron and a 10 GeV p r o t o n accelerator ( " s y n c h r o p h a s o t r o n " ) . These installations form the nucleus of a new city, providing the personnel and their families with u r b a n accomodation and facilities in pleasantly wooded surroundings. The e q u i p m e n t of the I n s t i t u t e is going to be considerably increased, in particular by the adjunction of a reactor of high n e u t r o n density with accessory laboratories. W i t h o u t waiting for the completion of this expansion, however, it has recently been decided to t r a n s f o r m this admirable research centre into a United I n s t i t u t e of .Nuclear Problems which will be p u t at the disposal of the physicists of a n u m b e r of countries sharing its administration. At the m o m e n t these countries are, beside the Soviet Union, Albania, Bulgaria, China, Corea, Czechoslovakia, the Democratic G e r m a n Republic, H u n g a r y , Mongolia, Poland and R u m a n i a . S t a t u t e s are being elaborated for the r u n n i n g of the new Institute, and in particular a r r a n g e m e n t s a r e being contemplated to enable guests from other countries as well to avail themselves of its facilities. The direction of the United I n s t i t u t e is shared by the participating countries. The director, D. Blokhiutzev (U.S.S.R.) is assisted by two deputy-directors, M. Danysz (Poland) and V. V o t r u b a (Czechoslow~kia). The Institute, when completed, will be divided into various research groups according to the following scheme: DIRECTION
I f I ACCELERATOR
I
COSMIC RAY ] GROUP I
I
I
HIGH NEUTRON DENSITY
GROUP
I RADIOCHEMISTRY
1 [
GROUP
I "HOT LABORATORY"
The heads of the already existing groups are: p r o t o n accelerator: ~r. j . Veksler, synchrocyclotrlm: M. G. Mescheryakov, theoretical group: M. A. Markov. A s u m m a r y description will now be given of the two large accelerators of the Institute. 1. THE 680 .~1eV PROTON SYNCHROCYCLOTRON The poles of the electromagnet are of 6000 m m diameter. The m a g n e t gap is 600 m m wide. The magnetic field intensity in the gap is equal to 16800 0e. Because of the 5 ° 5 decrease of the field intensity at the m a g n e t edge the focusing is quite strong. 676
NEWS ITEMS
677
After extensive e x p e r i m e n t a l work the radius of magnetic field used was raised to 2780 ram; the particle orbit was b r o u g h t to the median plane. This work was preceded b y the d e v e l o p m e n t of new t y p e s of m a g n e t o m e t r i c i n s t r u m e n t s of high sensitivity. The easily d e m o u n t a b l e b r a s s v a c u u m c h a m b e r has r u b b e r tape packings. The b o t t o m and the cover plates of the c h a m b e r are adjusted to the poles and are packed b y means of r u b b e r rings. The c h a m b e r volume is of the order of 30 ms. I t is evacuated by two high v a c u u m p u m p s with total p u m p i n g speed of 30000 l]sec. The pressure in the c h a m b e r during the operation is 6 X 10 -a m m Hg. The limiting pres~sure in the c h a m b e r is equal to 1--2 X 10-* m m t l g if the Hi-inlet in the ion source is stopped. In c o n t r a s t to usual p r o t o n synchrocyclotrons, the r.f. accelerating field between the edge of the dee and the grounded frame is obtained by means of half wave systems: dee resonance line frequency variator. The accelerating field frequency is varied from 26 to 13 Mc as the variator rotates. Some design peculiarities of the resonance line in the frequency variator p e r m i t to diminish considerably the r.f. c u r r e n t s t h r o u g h the variator bearings. The synchrocyclotron operation d e m o n s t r a ted the reliability and the stability of the r.f. s y s t e m design. The aggregates of r.f. s y s t e m can work for t h o u s a n d s of hours w i t h o u t repair. The synchrocyclotron e q u i p m e n t permits to t u r n o u t the r. f. supply during the idle p a r t of the cycle, to o b t a i n single accelerating cycles, to control the pulsed voltage of the ion-source and to switch on the desired nuclear research i n s t r u m e n t s and assemblies m o u n t e d along the external particle beams. All these processes are linked to the frequency change cycle of the main r.f. oscillator by m e a n s of a special system. The r. f. voltage switch on is accomplished by a photoelectric s y s t e m before the cycle begins. The light b e a m falling upon a photoelectric multiplier is interrupted by the variator rotor vanes. The total accelerator aggregate control, the high and f o r v a c u u m p u m p s and refrigerating machines included, is accomplished automatically from a special building at 400 m from the synchrocyclotron. All the s u p p l y and refrigerating aggregates are m o u n t e d in this building. So is the check and control e q u i p m e n t of those aggregates which m u s t be m o u n t e d in the close vicinity of the accelerator. The electromagnet and the v a c u u m c h a m b e r are located in a large room, where a p a r t of the physical research e q u i p m e n t is also installed. T h u s the accelerator operation and the internal targets m a n a g e m e n t is greatly simplified and the possibility is acquired to use a great n u m b e r of external particle beams, as described below. The main e q u i p m e n t is located behind a 6 m thick concrete shield. A new s y s t e m p e r m i t s to eject from the v a c u u m c h a m b e r 7 °o of accelerated protons. The following investigations are carried o u t on the synchrocyclotron: a) elastic p r o t o n - proton, n e u t r o n - n e u t r o n and n e u t r o n - p r o t o n scattering, b) neutral and charged pion production in nucleon - nucleon and nucleon d e u t e r o n collisions, c) pion - nucleon interactions. The design of the s y n c h r o c y c l o t r o n gives the possibility of obtaining a great n u m b e r of different high energy particle b e a m s emerging from any desired point of the accelerated p r o t o n orbit and consequently a high utilization of the accelerator. I n the shield of the six-meter synehrocyclotron there are sixteen collimators which are used to obtain b e a m s of unpolarized and polarized nucleons, of charged pions and also beams of g a m m a - r a y s from neutral pion decay. The collimators are placed not only in the main concrete shield b u t also in the synchrocyclotron m~gnet yoke, which in this w a y is used as a radiation shield. The accelerator c h a m b e r is supplied with four probes with the help of which it is possible to introduce in the c a m e r a samples of various substances. These can be
~78
NEV¢S ITEMS
irradiated in the internal p r o t o n beam at a n y desired energy up to 680 MeV. The overall shielding and collimation system is designed in such a w a y as to widely utilize the possibility of simultaneous carrying o u t of m a n y e x p e r i m e n t s on various particle beams used in "parallel" work, either of the same kind as, /or example, in the case of mesons with different energies, or of different kinds, as in the case of n e u t r o n s and polarized proton beams. For the purpose of increasing the synchrocyclotron utilization wide use is made of a u t o m a t i c and remote control of e q u i p m e n t located in rooms where, for biological reasons, h u m a n beings are not allowed to s t a y when the accelerator is working. l:or the same purpc;se multi-channel electronic s y s t e m s for registration of nuclear processes are widely used. 2. THE 10 Go\: PROTON ACCELERATOR The l0 GeV proton synchrocyclotron is built to s t u d y the n a t u r e of the nuclear forces, the properties of mesons, of h y p e r o n s and of antiprotons, the nuclear cascades and so on. I t is so far the m o s t powerful accelerator of this type. Principal characteristics of the accelerator: M a x i m u m particle energy E n e r g y of injection Orbit radius N u m b e r of s t r a i g h t sections L e n g t h of a straight section E l e c t r o m a g n e t weight I)uration nf the accelerating cycle N u m b e r of cycles per minute I n n e r dimensions of the v a c u u m c h a m b e r M a x i m u m field s t r e n g t h ill the gap Operation pressure in the c h a m b e r I n t e n s i t y of the accelerated particle beam
I0 GeV 7.5 MeV 28 in 4
8 m 35000 tons 3.3 sec 5 0.4 × 2.0 m ~ 13 000 Oe
2 - - 3 × 1 0 -e m m Fig 10'--101° particles in a pulse
Injection of particles into the c h a m b e r is carried o u t by means of a system consisting of a 570 keV formjector, a 7.,5 MeV linear accelerator and an ion optic a r r a n g e m e n t which includes beam focusing and position correcting units as well as of an electromagnet and ajusting capacitors guiding the beam and fitting it to the orbit with an angular precision of 3. The electromagnet having a []q-shape consists of 48 demontable blocks assembled of steel plates l0 to 40 m m thick. "/'he electromagnet coil is supplied by 11 kV voltage pulses; m a x i m u m coil current is a b o u t 13 000 A. The coil is cooled by water. The v a c u u m c h a m b e r has double walls. Pressure of the order of 1 m m Hg is maintained in the fore v a c u u m chamber. The h i g h - v a c u u m c h a m b e r is built of thin stainless steel sheets; the junctions between the sheets are packed by means of a special rubber. The operating zone extension coils as well as the inductance coil of the integrating field m e a s u r e r and some o t h e r devices are placed on the upper and on the lower wallsides of the chamber. The h i g h - v a c u u m c h a m b e r is evacuated by 56 5000 1/see h i g h - v a c u u m p u m p s . The liquid nitrogen supply of p u m p to t r a p s to freeze out the oil v a p o u r s is accomplished by means of a tube system with v a c u u m heat isolation. The v a c u u m s y s t e m valves have pneumo-hydraulic remote control. The electromagnet supply is accomplished by 4 chains of ignitron transformers, 24 igni lions each, fed by a.c. generators with a nominal power of a b o u t 150 000 k\VA.
NEWS YrEMS
679
T h e g e n e r a t o r s are supplied with h e a v y flywheels to store t h e e n e r g y d u r i n g tim ignitron t r a n s f o r m e r inversion cycle. T h e acceleration is a c c o m p l i s h e d in two s t r a i g h t sections b y m e a n s of 7 m long electrodes. T h e f r e q u e n c y of 20 kV s u p p l y of t h e electrodes varies from 0.18 to 1,45 Mc d e p e n d i n g on t h e m a g n e t i c field. To t u n e t h e o u t p u t cascades t h e perm e a b i l i t y of t h e territe cores of i n d u c t a n c e coils is a u t o m a t i c a l l y c h a n g e d by m e a n s of direct current. A s y s t e m of linkage b e t w e e n t h e f r e q u e n c y of t h e r.f. accelerating field a n d t h e m a g n e t i c field i n t e n s i t y H e n s u r e s t h e n e c e s s a r y d e p e n d e n c e /(H) with 0.1'~,'o accuracy. To control t h e processes of injection a n d of acceleration a special s y s t e m was developed f o r m i n g t h e control pulses related to t h e m a g n e t i c field i n t e n s i t y w i t h 4 × 10 -~ accuracy. A special precision m e a s u r i n g e q u i p m e n t a c c o m p l i s h e d t h e m e a s u r e m e n t of i n s t a n t a n e o u s values of accelerating field f r e q u e n c y with 5 × 10-* accuracy, of m a g n e t i c field i n t e n s i t y with 10 -3 accuracy, etc. T h e e l e c t r o m a g n e t w i t h t h e v a c u u m c h a m b e r a n d e q u i p m e n t which m u s t be located in t h e close p r o x i m i t y of t h e c h a m b e r (injector, v a c u u m p u m p i n g s y s t e m , o u t t m t r.f. c a s c a d e s a n d so on) art'. s i t u a t e d in a special building. An e x p e r i m e n t a l installation building is s i t u a t e d n e a r b y behind a 8 m concrete shielding. All t h e o t h e r e l e m e n t s of t h e accelerator - - t h e e l e c t r o m a g n e t s u p p l y s y s t e m , t h e electronics, t h e aperiodical r.f. amplifiers etc. - - are located in a n o t h e r building s i t u a t e d 100 m from t h e first; in t h e s a m e building t h e principal control panel of r e m o t e control of all t h e accelerator s y s t e m s is s i t u a t e d . THE MOSCOW
CONFERENCE ON THE PHYSICS OF PARTICLES H I G H E N E R G Y ( 1 4 - - - 2 2 M A Y 1956)
OF
An All-Union Conference on t h e p h y s i c s of particles of high energy, organized by t h e A c a d e m y of Sciences of t h e IJ.S.S.R., was held in Moscow from t h e 14th to t h e 22rid May, 1!156. T h e conference was a t t e n d e d b y a b o u t a t h o u s a n d Soviet p h y s i c i s t s a n d a b o u t 60 foreign g u e s t s (including a b o u t 15 from t h e people's democracies, 14 from t h e L'nited S t a t e s a n d s m a l l e r g r o u p s from m o s t E u r o p e a n countries, A u s t r a l i a a n d C a n a d a ) . T h e conference was divided into t h r e e sections, w h o s e sessions m o s t l y overlapped: (a) e l e m e n t a r y particles a n d t h e i r i n t e r a c t i o n s (96 s c h e d u l e d c o m m u n i c a t i o n s ) , (b) h i g h - e n e r g y accelerators of e l e m e n t a r y particles (79 c o m m u n i c a t i o n s ) , (c) theoretical i n v e s t i g a t i o n s on h i g h - e n e r g y p h y s i c s (25 c o m m u n i c a t i o n s ) . Meetings were held a l m o s t e v e r y d a y in t h e m o r n i n g a n d t h e late a f t e r n o o n a n d were often prolonged, w i t h u n r e l e n t i n g energy, for a n indefinite time. Additional i n f o r m a l m e e t i n g s were held by t h e theoretical physicists. Discussions were m o s t s t i m u l a t i n g a n d at t i m e s very lively, especially t h o s e of t h e Soviet p h y s i c i s t s a m o n g t h e m s e l v e s . Altogether, t h e c o n t a c t s , scientific a n d other, between t h e foreign p h y s i c i s t s a n d their h o s t s were m a r k e d b y g r e a t cordiality. T h e foreign guests, received w i t h o v e r w h e h n i n g hospitality, h a d a m p l e o p p o r t u n i t y of visiting v a r i o u s laboratories a n d i n s t i t u t i o n s b o t h in a n d a r o u n d Moscow a n d at L e n i n g r a d a n d Kiev. P a r t i c u l a r l y i m p r e s s i v e was t h e inspection of t h e I n s t i t u t e of Nuclear P r o b l e m s on t h e river Vnlga. In section (a), m a n y new e x p e r i m e n t a l d a t a a n d s o m e theoretical c o n s i d e r a t i o n s were presented, b e a r i n g on t h e i n t e r a c t i o n s b e t w e e n nucleons, a - m e s o n s a n d nuclei; especially s c a t t e r i n g processes, m e s o n production, a n t i p r o t o n p r o d u c t i o n a n d a n n i h i l a t i o n , p h o t o n u c l e a r r e a c t i o n s were e x t e n s i v e l y discussed. Besides, h e a v y m e s o n s a n d h y p e r o n s received d u e a t t e n t i o n .
6~0
NEWS ITEMS
In section (c). there was a great variety of topics to which the Soviet groups made i m p o r t a n t and highly original contributions. L. D. L a n d a u and his collaborators, especially I. Y. l ' o m e r a n c h u k , developeci with great vigour their a r g u m e n t s tending to establish the inconsistency of the present form of q u a n t u m field theory. Other groups presented new developments of the dispersion relations and of various aspects of meson theory. Section (b), although mainly concerned with technical problems, had to consider also interesting questions of a more f u n d a m e n t a l nature, connected with the stability of particle orbits in the accelerators. In the opening session were presented not only descriptions of the large accelerators already completed in the Soviet Union, b u t also accounLs of projected proton accelerators of still larger energies: the 15 (;eV proton synchroton of Argonne National I . a b o r a t o r y and the U.S.S.R. Academy of Sciences strong focusing 50--60 GeV proton accelerator, with the a c c o m p a n y i n g s t u d y of a 6 --7 (;eV accelerator on the same principle. Here is a s u m m a r y account of the Soviet project, according to V. V. Vladimirsky, F. G. K o m a r and A. L. Minz. 1)REJECT
OF
A
RING PROTON ACCELERATOR FOR 6.--7 (~eV
The main p a r a m e t e r s of the accelerator are the following: M a x i m u m accelerated particles energy Injection energy Mean orbit radius N u m b e r of m a g n e t s N u m b e r of c o m p e n s a t i n g m a g n e t s N u m b e r of radial and vertical oscillations per revolution C h a m b e r width Chamlrer height Magnetic s y s t e m weight Magnetic field energy stock
7 GeV 4 MeV 40 m 112 14 12.75 11 cm 8 cm 2700 tons 10 ~ joule
In the project a s y s t e m of c o m p e n s a t i n g the length of the orbit with rise of particle m o i n e n t u m is adopted. The use of c o m p e n s a t i n g m a g n e t s has s o m e w h a t increased the mean accelerator radius, b u t led to some allay of tolerances. In the c o m p e n s a t i n g m a g n e t are placed the span tubes of the accelerating s y s t e m working on the 7th harmonics of the revolution frequency. The v a c u u m c h a m b e r is a thinwalled (0.2 mm) corrugated tube of oval section made of stainless steel. 16 compensating m a g n e t s have a X-shape type yoke, the o t h e r m a g n e t s are of C-shape type with a separate neutral pole. The foundation of the m a g n e t s y s t e m is a massive solid concrete ring. I t has a sufficient rigidity to suppress all dangerous harmonical displacements of the accelerator arising from irregular ground settling. THE MAIN CItARACTERISTICS OF TIlE PROJECTFD STRONG FOCUSING 5 0 . - 6 0 (~eV PROTON ACCELERATOR In performing the project of the 50---60 GeV proton-accelerator the v a r i a n t with the elimination of the critical energy by introduction into the magnetic system of c o m p e n s a t i n g m a g n e t s with inverse magnetic field was chosen. The rnagnetic s y s t e m of the accelerator will consist of 105 guiding-field m a g n e t s with alternating radial and vertical focusing, and of 15 c o m p e n s a t i n g magnets. Each eighth m a g n e t will be a cornpensating one. The length of the orbit will be 1480 in, the initial field-intensity at the injection will be 90 Oe, the m a x i m u m field-intensity will reach 10.000--12.000 Oe. The weight of the iron in the yokes will reach a b o u t 17 t h o u s a n d tons; the whole weight of the magnets, including design-elements of the magnets, will be a b o u t 22 t h o u s a n d tons. The main characteristics of the orbit, the tolerances of the magnetic field distribution and of the m o m e n t u m value and the characteristics of the p o w e r - s u p p l y of the accelerator are listed below.
681
NEXVS I T E M S
A 10 s eV l i n e a r a c c e l e r a t o r will serve as the i n j e c t o r device. The a c c e l e r a t i n g s y s t e m will be s u p p l i e d w i t h h i g h - f r e q u e n c y p o w e r a t a f r e q u e n c y 30 t i m e s t he r e v o l u t i o n f r e q u e n c y of t h e particles. T h e e n e r g y the p r o t o n s get d u r i n g one r e v o l u t i ( m will a m o u n t to a b o u t I(/8 eV. T r a n s f o r m e r s w i t h Ierrite cores will be used as a c c e l e r a t i n g units. The pow e r of th e h i g h - f r e q u e n c y o s c i l l a t o r s will be a b o u t 500 kXV. The m a i n p a r a m e t e r s of t h e h i g h - f r e q u e n c y s y s t e m are g i v e n below.
1. The main parameters o/ the orbit N u m b e r of o s c i l l a t i o n s per r e w ) l u t i o n radial vertical R a d i u s of c u r v a t u r e of t h e o r d i n a r y m a g n e t s R a d i u s of c u r v a t u r e of t h e c o m p e n s a t i n g m a g n e t s I , e n g t h of the r a d i a l focusing m a g n e t L e n g t h of t h e v e r t i c a l focusing m a g n e t s U t i l i z a t i o n coefficient of t h e m a g n e t i c field L o g a r i t h m i c d e r i v a t i v e of l e n g t h of ()rl)it b y m o m e n t u m Angle a p e r t u r e of t h e b e a m
13.752 12.744 166.67 m 297.6 m 10.99 m 10.69 m 0.8050 - - 3 . 2 × 10--' 2 × 10 -3
2. The tolerances o[ the magnetic ]ield, momentum and magnet assemblage E r r o r s in tile m o m e n t u m D e v i a t i o n s in t h e field i n t e n s i t y D e v i a t i o n s in tile m a g n e t i c field g r a d i e n t D e v i a t i o n s in t h e m a g n e t a s s e m b l a g e M a x i m u m v a l u e of t h e a m p l i t u d e of tile l"]th h a r m o n i c of t h e v e r t i c a l d i s p l a c e m e n t of t h e m a g n e t
0.5 % 0.25 ° o 0.5 o~, 1 mm 0.05 m m
3. The main data o[ the power-supply system T h e rising t i m e of t h e m a g n e t i c field N u m b e r of cycles per m i n u t e Maximum current value Maximum voltage R e s i s t a n c e of t h e m a g n e t coils a t 15 ° C M a x i m u m v a l u e of t h e i n d u c t a n c e of t h e coils The peak power
:1.8 sec tl 12 000 A 8 000 V 0.31 O h m 1.8 l i e 96 000 kVA
4. The main parameters o/ the high-/requency system T h e f r e q u e n c y of t h e a c c e l e r a t i n g field a t the b e g i n n i n g of t h e a c c e l e r a t i o n a t t h e end of t h e a c c e l e r a t i o n Tile errors in t h e f r e q u e n c y a t tile b e g i n n i n g of t h e a c c e l e r a t i o n a t t h e end of t h e a c c e l e r a t i o n T h e c o r r e s p o n d i n g a c c u r a c y of t h e m a g n e t i c field m e a s u r e m e n t s a t t h e b e g i n n i n g of t h e a c c e l e r a t i o n a t the end of t h e a c c e l e r a t i o n The n u m b e r of s y n c h r o t o n o s c i l l a t i o n s a t file b e g i n n i n g of t h e a c c e l e r a t i o n a t t h e end of t h e a c c e l e r a t i o n T o l e r a n c e s on t h e r e s o n a n c e f r e q u e n c y a t t h e b e g i n n i n g of t h e a c c e l e r a t i o n a t F ~ 50 Hz a t t h e end of the a c c e l e r a t i o n T o l e r a n c e s on t h e n o i s e - m o d u l a t i o n
2.624 Mc 6.063 Me 2x 2,'<
I0 -s 10 -6
2 . 5 × 10 -a 10 -2 5150 l.tz 24 H z 31 4
× 10 -~ ×10
*
12.5× 10 -0 4 < 1O "~Hz2/FIz
6,11')
.'~E ~.vs ITEMS
CERN SYMPOSIUM
AT GENEVA
(11~22
JUNE
1956)
An i n t e r n a t i o n a l s y m p o s i u m o n particle accelerators, detection t e c h n i q u e s a n d high e n e r g y p h y s i c s was a r r a n g e d b y C E R N between 11 a n d 22 J u n e 1956. T h e m e e t i n g s were held a t t h e I n s t i t u t de P h y s i q u e of G e n e v a U n i v e r s i t y , which had been placed at t h e disposal of t h e organisers b y t h e local authorities. T h e following c o u n t r i e s were r e p r e s e n t e d at t h e conference: Australia, Belgium, C a n a d a , Czechoslovakia, D e n m a r k , France, Federal Republic of G e r m a n y , Greece, India, Italy, J a p a n , N e t h e r l a n d s , Norway, Spain, Sweden, Switzerland, U.S.S.R., United K i n g d o m , U.S.A., a n d Yugoslavia. U N F S C O also sent an observer. T h e first week of t h e s y m p o s i u m was d e v o t e d entirely to high e n e r g y partiele accelerators, l ) u r i n g t h a t period, a b o u t fifty papers were given on t h e m a i n p r o b l e m s raised by t h e c o n s t r u c t i o n of m o d e r n accelerators, s u c h as t h e theoretical a s p e c t s of t h e question, t h e stud}, of m a g n e t s , t h e r a d i o f r e q u e n c y accelerating s y s t e m , t h e injection a n d ejection of particles, t h e o p e r a t i o n of the m a c h i n e s , etc. Moreover, t h e technical features of the large accelerators n o w in operation or in t h e course of b u i h t i n g were explained in detail. Finally, entirely new principles were p u t forward, whose practical application would considerably i m p r o v e t h e a l r e a d y s p e c t a c u l a r l)erformanee of e x i s t i n g accelerators. l l u r i n g t h e second week of t h e S y m p o s i u m , a t t e n t i o n was focused on detection metllods a n d on tile theoretical a s p e c t s a n d e x p e r i m e n t a l t e c h n i q u e s of t h e p h y s i c s of e l e m e n t a r y particles. T h e s e v e n t y p a p e r s given dealt with a wide v a r i e t y of questions, s u c h as Wilson c h a m b e r s , bubble c h a m b e r s , o v e r - c o m p r e s s i o n a n d c o u n t i n g t e c h n i q u e s , e x p e r i m e n t a l a n d theoretical p h y s i c s c o n c e r n i n g mesons, nucleons a n d a n t i p r o t o n s , q u a n t u m Iiehl theories, t h e s t r u c t u r e of t h e proton, mesic a t o m s , etc. T h e e x c h a n g e s of views t h a t took place between participants, both in a n d o u t s i d e t h e conference room. proved e x t r e m e l y fruitful, a n d the f r a n k n e s s s h o w n b y all concerned bodes well for t h e possibility of f u t u r e i n t e r n a t i o n a l cooperation in physics.
INTERNATIONAL
CONFERENCE
(AMSTERDAM,
2~7
ON NUCLEAR JULY
REACTIONS
1956)
T h e A m s t e r d a m conference, t h e full p r o g r a m m e of which m a y be f o u n d in No. 2 of this journM (this volume, p. 136), proceeded according to this p r o g r a m m e with g r e a t p u n c t u a l i t y a n d success. T h e r e were m o r e t h a n 500 p a r t i c i p a n t s : t h e cont i n g e n t s from France, G r e a t B r i t a i n a n d t h e U n i t e d S t a t e s were of t h e order of 70 each, t h e Soviet g r o u p was a b o u t 30. This well-planned a n d well-organised conference m a d e possible a full s u r v e y of t h e r a p i d l y a c c u m u l a t i n g d a t a from t h e v a s t am! diversified field of n u c l e a r reactions; t h e theoretical i m p l i c a t i o n s of this i n f o r m a t i o n were also e x t e n s i v e l y discussed. A general conclusion which e m e r g e d from t h e c o n f r o n t a t i o n of all t h e i n f o r m a t i o n is t h a t t h e optical model of t h e n u c l e u s is capable to a surprising e x t e n t of p r o v i d i n g a c o n s i s t e n t f r a m e w o r k for t h e analysis of n u c l e a r s t a t e s over tile whole r a n g e of so-called 'low' energies. T h e m o r e fund a m e n t a l p r o b l e m s oI d e r i v i n g n u c l e a r s t r u c t u r e s a n d collective m o d e s of e x c i t a t i o n from a m a n y - b o d y t h e o r y received d u e consideration, b u t t h e s e q u e s t i o n s are still in an early s t a g e of d e v e l o p m e n t .
INSTITUTE
OF NUCLEAR
PROBLEMS
In 1949 an I n s t i t u t e of Nuclear Problems was established by the Academy of Sciences of the Soviet Union on a site n o t far from the junction of the MoskvaVolga canal with the river Volga, a b o u t 150 km from Moscow. On this site lalx~ratories and accessory plants were installed to operate a 680 MeV synchrocyclotron and a 10 GeV p r o t o n accelerator ( " s y n c h r o p h a s o t r o n " ) . These installations form the nucleus of a new city, providing the personnel and their families with u r b a n accomodation and facilities in pleasantly wooded surroundings. The e q u i p m e n t of the I n s t i t u t e is going to be considerably increased, in particular by the adjunction of a reactor of high n e u t r o n density with accessory laboratories. W i t h o u t waiting for the completion of this expansion, however, it has recently been decided to t r a n s f o r m this admirable research centre into a United I n s t i t u t e of .Nuclear Problems which will be p u t at the disposal of the physicists of a n u m b e r of countries sharing its administration. At the m o m e n t these countries are, beside the Soviet Union, Albania, Bulgaria, China, Corea, Czechoslovakia, the Democratic G e r m a n Republic, H u n g a r y , Mongolia, Poland and R u m a n i a . S t a t u t e s are being elaborated for the r u n n i n g of the new Institute, and in particular a r r a n g e m e n t s a r e being contemplated to enable guests from other countries as well to avail themselves of its facilities. The direction of the United I n s t i t u t e is shared by the participating countries. The director, D. Blokhiutzev (U.S.S.R.) is assisted by two deputy-directors, M. Danysz (Poland) and V. V o t r u b a (Czechoslow~kia). The Institute, when completed, will be divided into various research groups according to the following scheme: DIRECTION
I f I ACCELERATOR
I
COSMIC RAY ] GROUP I
I
I
HIGH NEUTRON DENSITY
GROUP
I RADIOCHEMISTRY
1 [
GROUP
I "HOT LABORATORY"
The heads of the already existing groups are: p r o t o n accelerator: ~r. j . Veksler, synchrocyclotrlm: M. G. Mescheryakov, theoretical group: M. A. Markov. A s u m m a r y description will now be given of the two large accelerators of the Institute. 1. THE 680 .~1eV PROTON SYNCHROCYCLOTRON The poles of the electromagnet are of 6000 m m diameter. The m a g n e t gap is 600 m m wide. The magnetic field intensity in the gap is equal to 16800 0e. Because of the 5 ° 5 decrease of the field intensity at the m a g n e t edge the focusing is quite strong. 676
NEWS ITEMS
677
After extensive e x p e r i m e n t a l work the radius of magnetic field used was raised to 2780 ram; the particle orbit was b r o u g h t to the median plane. This work was preceded b y the d e v e l o p m e n t of new t y p e s of m a g n e t o m e t r i c i n s t r u m e n t s of high sensitivity. The easily d e m o u n t a b l e b r a s s v a c u u m c h a m b e r has r u b b e r tape packings. The b o t t o m and the cover plates of the c h a m b e r are adjusted to the poles and are packed b y means of r u b b e r rings. The c h a m b e r volume is of the order of 30 ms. I t is evacuated by two high v a c u u m p u m p s with total p u m p i n g speed of 30000 l]sec. The pressure in the c h a m b e r during the operation is 6 X 10 -a m m Hg. The limiting pres~sure in the c h a m b e r is equal to 1--2 X 10-* m m t l g if the Hi-inlet in the ion source is stopped. In c o n t r a s t to usual p r o t o n synchrocyclotrons, the r.f. accelerating field between the edge of the dee and the grounded frame is obtained by means of half wave systems: dee resonance line frequency variator. The accelerating field frequency is varied from 26 to 13 Mc as the variator rotates. Some design peculiarities of the resonance line in the frequency variator p e r m i t to diminish considerably the r.f. c u r r e n t s t h r o u g h the variator bearings. The synchrocyclotron operation d e m o n s t r a ted the reliability and the stability of the r.f. s y s t e m design. The aggregates of r.f. s y s t e m can work for t h o u s a n d s of hours w i t h o u t repair. The synchrocyclotron e q u i p m e n t permits to t u r n o u t the r. f. supply during the idle p a r t of the cycle, to o b t a i n single accelerating cycles, to control the pulsed voltage of the ion-source and to switch on the desired nuclear research i n s t r u m e n t s and assemblies m o u n t e d along the external particle beams. All these processes are linked to the frequency change cycle of the main r.f. oscillator by m e a n s of a special system. The r. f. voltage switch on is accomplished by a photoelectric s y s t e m before the cycle begins. The light b e a m falling upon a photoelectric multiplier is interrupted by the variator rotor vanes. The total accelerator aggregate control, the high and f o r v a c u u m p u m p s and refrigerating machines included, is accomplished automatically from a special building at 400 m from the synchrocyclotron. All the s u p p l y and refrigerating aggregates are m o u n t e d in this building. So is the check and control e q u i p m e n t of those aggregates which m u s t be m o u n t e d in the close vicinity of the accelerator. The electromagnet and the v a c u u m c h a m b e r are located in a large room, where a p a r t of the physical research e q u i p m e n t is also installed. T h u s the accelerator operation and the internal targets m a n a g e m e n t is greatly simplified and the possibility is acquired to use a great n u m b e r of external particle beams, as described below. The main e q u i p m e n t is located behind a 6 m thick concrete shield. A new s y s t e m p e r m i t s to eject from the v a c u u m c h a m b e r 7 °o of accelerated protons. The following investigations are carried o u t on the synchrocyclotron: a) elastic p r o t o n - proton, n e u t r o n - n e u t r o n and n e u t r o n - p r o t o n scattering, b) neutral and charged pion production in nucleon - nucleon and nucleon d e u t e r o n collisions, c) pion - nucleon interactions. The design of the s y n c h r o c y c l o t r o n gives the possibility of obtaining a great n u m b e r of different high energy particle b e a m s emerging from any desired point of the accelerated p r o t o n orbit and consequently a high utilization of the accelerator. I n the shield of the six-meter synehrocyclotron there are sixteen collimators which are used to obtain b e a m s of unpolarized and polarized nucleons, of charged pions and also beams of g a m m a - r a y s from neutral pion decay. The collimators are placed not only in the main concrete shield b u t also in the synchrocyclotron m~gnet yoke, which in this w a y is used as a radiation shield. The accelerator c h a m b e r is supplied with four probes with the help of which it is possible to introduce in the c a m e r a samples of various substances. These can be
~78
NEV¢S ITEMS
irradiated in the internal p r o t o n beam at a n y desired energy up to 680 MeV. The overall shielding and collimation system is designed in such a w a y as to widely utilize the possibility of simultaneous carrying o u t of m a n y e x p e r i m e n t s on various particle beams used in "parallel" work, either of the same kind as, /or example, in the case of mesons with different energies, or of different kinds, as in the case of n e u t r o n s and polarized proton beams. For the purpose of increasing the synchrocyclotron utilization wide use is made of a u t o m a t i c and remote control of e q u i p m e n t located in rooms where, for biological reasons, h u m a n beings are not allowed to s t a y when the accelerator is working. l:or the same purpc;se multi-channel electronic s y s t e m s for registration of nuclear processes are widely used. 2. THE 10 Go\: PROTON ACCELERATOR The l0 GeV proton synchrocyclotron is built to s t u d y the n a t u r e of the nuclear forces, the properties of mesons, of h y p e r o n s and of antiprotons, the nuclear cascades and so on. I t is so far the m o s t powerful accelerator of this type. Principal characteristics of the accelerator: M a x i m u m particle energy E n e r g y of injection Orbit radius N u m b e r of s t r a i g h t sections L e n g t h of a straight section E l e c t r o m a g n e t weight I)uration nf the accelerating cycle N u m b e r of cycles per minute I n n e r dimensions of the v a c u u m c h a m b e r M a x i m u m field s t r e n g t h ill the gap Operation pressure in the c h a m b e r I n t e n s i t y of the accelerated particle beam
I0 GeV 7.5 MeV 28 in 4
8 m 35000 tons 3.3 sec 5 0.4 × 2.0 m ~ 13 000 Oe
2 - - 3 × 1 0 -e m m Fig 10'--101° particles in a pulse
Injection of particles into the c h a m b e r is carried o u t by means of a system consisting of a 570 keV formjector, a 7.,5 MeV linear accelerator and an ion optic a r r a n g e m e n t which includes beam focusing and position correcting units as well as of an electromagnet and ajusting capacitors guiding the beam and fitting it to the orbit with an angular precision of 3. The electromagnet having a []q-shape consists of 48 demontable blocks assembled of steel plates l0 to 40 m m thick. "/'he electromagnet coil is supplied by 11 kV voltage pulses; m a x i m u m coil current is a b o u t 13 000 A. The coil is cooled by water. The v a c u u m c h a m b e r has double walls. Pressure of the order of 1 m m Hg is maintained in the fore v a c u u m chamber. The h i g h - v a c u u m c h a m b e r is built of thin stainless steel sheets; the junctions between the sheets are packed by means of a special rubber. The operating zone extension coils as well as the inductance coil of the integrating field m e a s u r e r and some o t h e r devices are placed on the upper and on the lower wallsides of the chamber. The h i g h - v a c u u m c h a m b e r is evacuated by 56 5000 1/see h i g h - v a c u u m p u m p s . The liquid nitrogen supply of p u m p to t r a p s to freeze out the oil v a p o u r s is accomplished by means of a tube system with v a c u u m heat isolation. The v a c u u m s y s t e m valves have pneumo-hydraulic remote control. The electromagnet supply is accomplished by 4 chains of ignitron transformers, 24 igni lions each, fed by a.c. generators with a nominal power of a b o u t 150 000 k\VA.
NEWS YrEMS
679
T h e g e n e r a t o r s are supplied with h e a v y flywheels to store t h e e n e r g y d u r i n g tim ignitron t r a n s f o r m e r inversion cycle. T h e acceleration is a c c o m p l i s h e d in two s t r a i g h t sections b y m e a n s of 7 m long electrodes. T h e f r e q u e n c y of 20 kV s u p p l y of t h e electrodes varies from 0.18 to 1,45 Mc d e p e n d i n g on t h e m a g n e t i c field. To t u n e t h e o u t p u t cascades t h e perm e a b i l i t y of t h e territe cores of i n d u c t a n c e coils is a u t o m a t i c a l l y c h a n g e d by m e a n s of direct current. A s y s t e m of linkage b e t w e e n t h e f r e q u e n c y of t h e r.f. accelerating field a n d t h e m a g n e t i c field i n t e n s i t y H e n s u r e s t h e n e c e s s a r y d e p e n d e n c e /(H) with 0.1'~,'o accuracy. To control t h e processes of injection a n d of acceleration a special s y s t e m was developed f o r m i n g t h e control pulses related to t h e m a g n e t i c field i n t e n s i t y w i t h 4 × 10 -~ accuracy. A special precision m e a s u r i n g e q u i p m e n t a c c o m p l i s h e d t h e m e a s u r e m e n t of i n s t a n t a n e o u s values of accelerating field f r e q u e n c y with 5 × 10-* accuracy, of m a g n e t i c field i n t e n s i t y with 10 -3 accuracy, etc. T h e e l e c t r o m a g n e t w i t h t h e v a c u u m c h a m b e r a n d e q u i p m e n t which m u s t be located in t h e close p r o x i m i t y of t h e c h a m b e r (injector, v a c u u m p u m p i n g s y s t e m , o u t t m t r.f. c a s c a d e s a n d so on) art'. s i t u a t e d in a special building. An e x p e r i m e n t a l installation building is s i t u a t e d n e a r b y behind a 8 m concrete shielding. All t h e o t h e r e l e m e n t s of t h e accelerator - - t h e e l e c t r o m a g n e t s u p p l y s y s t e m , t h e electronics, t h e aperiodical r.f. amplifiers etc. - - are located in a n o t h e r building s i t u a t e d 100 m from t h e first; in t h e s a m e building t h e principal control panel of r e m o t e control of all t h e accelerator s y s t e m s is s i t u a t e d . THE MOSCOW
CONFERENCE ON THE PHYSICS OF PARTICLES H I G H E N E R G Y ( 1 4 - - - 2 2 M A Y 1956)
OF
An All-Union Conference on t h e p h y s i c s of particles of high energy, organized by t h e A c a d e m y of Sciences of t h e IJ.S.S.R., was held in Moscow from t h e 14th to t h e 22rid May, 1!156. T h e conference was a t t e n d e d b y a b o u t a t h o u s a n d Soviet p h y s i c i s t s a n d a b o u t 60 foreign g u e s t s (including a b o u t 15 from t h e people's democracies, 14 from t h e L'nited S t a t e s a n d s m a l l e r g r o u p s from m o s t E u r o p e a n countries, A u s t r a l i a a n d C a n a d a ) . T h e conference was divided into t h r e e sections, w h o s e sessions m o s t l y overlapped: (a) e l e m e n t a r y particles a n d t h e i r i n t e r a c t i o n s (96 s c h e d u l e d c o m m u n i c a t i o n s ) , (b) h i g h - e n e r g y accelerators of e l e m e n t a r y particles (79 c o m m u n i c a t i o n s ) , (c) theoretical i n v e s t i g a t i o n s on h i g h - e n e r g y p h y s i c s (25 c o m m u n i c a t i o n s ) . Meetings were held a l m o s t e v e r y d a y in t h e m o r n i n g a n d t h e late a f t e r n o o n a n d were often prolonged, w i t h u n r e l e n t i n g energy, for a n indefinite time. Additional i n f o r m a l m e e t i n g s were held by t h e theoretical physicists. Discussions were m o s t s t i m u l a t i n g a n d at t i m e s very lively, especially t h o s e of t h e Soviet p h y s i c i s t s a m o n g t h e m s e l v e s . Altogether, t h e c o n t a c t s , scientific a n d other, between t h e foreign p h y s i c i s t s a n d their h o s t s were m a r k e d b y g r e a t cordiality. T h e foreign guests, received w i t h o v e r w h e h n i n g hospitality, h a d a m p l e o p p o r t u n i t y of visiting v a r i o u s laboratories a n d i n s t i t u t i o n s b o t h in a n d a r o u n d Moscow a n d at L e n i n g r a d a n d Kiev. P a r t i c u l a r l y i m p r e s s i v e was t h e inspection of t h e I n s t i t u t e of Nuclear P r o b l e m s on t h e river Vnlga. In section (a), m a n y new e x p e r i m e n t a l d a t a a n d s o m e theoretical c o n s i d e r a t i o n s were presented, b e a r i n g on t h e i n t e r a c t i o n s b e t w e e n nucleons, a - m e s o n s a n d nuclei; especially s c a t t e r i n g processes, m e s o n production, a n t i p r o t o n p r o d u c t i o n a n d a n n i h i l a t i o n , p h o t o n u c l e a r r e a c t i o n s were e x t e n s i v e l y discussed. Besides, h e a v y m e s o n s a n d h y p e r o n s received d u e a t t e n t i o n .
6~0
NEWS ITEMS
In section (c). there was a great variety of topics to which the Soviet groups made i m p o r t a n t and highly original contributions. L. D. L a n d a u and his collaborators, especially I. Y. l ' o m e r a n c h u k , developeci with great vigour their a r g u m e n t s tending to establish the inconsistency of the present form of q u a n t u m field theory. Other groups presented new developments of the dispersion relations and of various aspects of meson theory. Section (b), although mainly concerned with technical problems, had to consider also interesting questions of a more f u n d a m e n t a l nature, connected with the stability of particle orbits in the accelerators. In the opening session were presented not only descriptions of the large accelerators already completed in the Soviet Union, b u t also accounLs of projected proton accelerators of still larger energies: the 15 (;eV proton synchroton of Argonne National I . a b o r a t o r y and the U.S.S.R. Academy of Sciences strong focusing 50--60 GeV proton accelerator, with the a c c o m p a n y i n g s t u d y of a 6 --7 (;eV accelerator on the same principle. Here is a s u m m a r y account of the Soviet project, according to V. V. Vladimirsky, F. G. K o m a r and A. L. Minz. 1)REJECT
OF
A
RING PROTON ACCELERATOR FOR 6.--7 (~eV
The main p a r a m e t e r s of the accelerator are the following: M a x i m u m accelerated particles energy Injection energy Mean orbit radius N u m b e r of m a g n e t s N u m b e r of c o m p e n s a t i n g m a g n e t s N u m b e r of radial and vertical oscillations per revolution C h a m b e r width Chamlrer height Magnetic s y s t e m weight Magnetic field energy stock
7 GeV 4 MeV 40 m 112 14 12.75 11 cm 8 cm 2700 tons 10 ~ joule
In the project a s y s t e m of c o m p e n s a t i n g the length of the orbit with rise of particle m o i n e n t u m is adopted. The use of c o m p e n s a t i n g m a g n e t s has s o m e w h a t increased the mean accelerator radius, b u t led to some allay of tolerances. In the c o m p e n s a t i n g m a g n e t are placed the span tubes of the accelerating s y s t e m working on the 7th harmonics of the revolution frequency. The v a c u u m c h a m b e r is a thinwalled (0.2 mm) corrugated tube of oval section made of stainless steel. 16 compensating m a g n e t s have a X-shape type yoke, the o t h e r m a g n e t s are of C-shape type with a separate neutral pole. The foundation of the m a g n e t s y s t e m is a massive solid concrete ring. I t has a sufficient rigidity to suppress all dangerous harmonical displacements of the accelerator arising from irregular ground settling. THE MAIN CItARACTERISTICS OF TIlE PROJECTFD STRONG FOCUSING 5 0 . - 6 0 (~eV PROTON ACCELERATOR In performing the project of the 50---60 GeV proton-accelerator the v a r i a n t with the elimination of the critical energy by introduction into the magnetic system of c o m p e n s a t i n g m a g n e t s with inverse magnetic field was chosen. The rnagnetic s y s t e m of the accelerator will consist of 105 guiding-field m a g n e t s with alternating radial and vertical focusing, and of 15 c o m p e n s a t i n g magnets. Each eighth m a g n e t will be a cornpensating one. The length of the orbit will be 1480 in, the initial field-intensity at the injection will be 90 Oe, the m a x i m u m field-intensity will reach 10.000--12.000 Oe. The weight of the iron in the yokes will reach a b o u t 17 t h o u s a n d tons; the whole weight of the magnets, including design-elements of the magnets, will be a b o u t 22 t h o u s a n d tons. The main characteristics of the orbit, the tolerances of the magnetic field distribution and of the m o m e n t u m value and the characteristics of the p o w e r - s u p p l y of the accelerator are listed below.
681
NEXVS I T E M S
A 10 s eV l i n e a r a c c e l e r a t o r will serve as the i n j e c t o r device. The a c c e l e r a t i n g s y s t e m will be s u p p l i e d w i t h h i g h - f r e q u e n c y p o w e r a t a f r e q u e n c y 30 t i m e s t he r e v o l u t i o n f r e q u e n c y of t h e particles. T h e e n e r g y the p r o t o n s get d u r i n g one r e v o l u t i ( m will a m o u n t to a b o u t I(/8 eV. T r a n s f o r m e r s w i t h Ierrite cores will be used as a c c e l e r a t i n g units. The pow e r of th e h i g h - f r e q u e n c y o s c i l l a t o r s will be a b o u t 500 kXV. The m a i n p a r a m e t e r s of t h e h i g h - f r e q u e n c y s y s t e m are g i v e n below.
1. The main parameters o/ the orbit N u m b e r of o s c i l l a t i o n s per r e w ) l u t i o n radial vertical R a d i u s of c u r v a t u r e of t h e o r d i n a r y m a g n e t s R a d i u s of c u r v a t u r e of t h e c o m p e n s a t i n g m a g n e t s I , e n g t h of the r a d i a l focusing m a g n e t L e n g t h of t h e v e r t i c a l focusing m a g n e t s U t i l i z a t i o n coefficient of t h e m a g n e t i c field L o g a r i t h m i c d e r i v a t i v e of l e n g t h of ()rl)it b y m o m e n t u m Angle a p e r t u r e of t h e b e a m
13.752 12.744 166.67 m 297.6 m 10.99 m 10.69 m 0.8050 - - 3 . 2 × 10--' 2 × 10 -3
2. The tolerances o[ the magnetic ]ield, momentum and magnet assemblage E r r o r s in tile m o m e n t u m D e v i a t i o n s in t h e field i n t e n s i t y D e v i a t i o n s in tile m a g n e t i c field g r a d i e n t D e v i a t i o n s in t h e m a g n e t a s s e m b l a g e M a x i m u m v a l u e of t h e a m p l i t u d e of tile l"]th h a r m o n i c of t h e v e r t i c a l d i s p l a c e m e n t of t h e m a g n e t
0.5 % 0.25 ° o 0.5 o~, 1 mm 0.05 m m
3. The main data o[ the power-supply system T h e rising t i m e of t h e m a g n e t i c field N u m b e r of cycles per m i n u t e Maximum current value Maximum voltage R e s i s t a n c e of t h e m a g n e t coils a t 15 ° C M a x i m u m v a l u e of t h e i n d u c t a n c e of t h e coils The peak power
:1.8 sec tl 12 000 A 8 000 V 0.31 O h m 1.8 l i e 96 000 kVA
4. The main parameters o/ the high-/requency system T h e f r e q u e n c y of t h e a c c e l e r a t i n g field a t the b e g i n n i n g of t h e a c c e l e r a t i o n a t t h e end of t h e a c c e l e r a t i o n Tile errors in t h e f r e q u e n c y a t tile b e g i n n i n g of t h e a c c e l e r a t i o n a t t h e end of t h e a c c e l e r a t i o n T h e c o r r e s p o n d i n g a c c u r a c y of t h e m a g n e t i c field m e a s u r e m e n t s a t t h e b e g i n n i n g of t h e a c c e l e r a t i o n a t the end of t h e a c c e l e r a t i o n The n u m b e r of s y n c h r o t o n o s c i l l a t i o n s a t file b e g i n n i n g of t h e a c c e l e r a t i o n a t t h e end of t h e a c c e l e r a t i o n T o l e r a n c e s on t h e r e s o n a n c e f r e q u e n c y a t t h e b e g i n n i n g of t h e a c c e l e r a t i o n a t F ~ 50 Hz a t t h e end of the a c c e l e r a t i o n T o l e r a n c e s on t h e n o i s e - m o d u l a t i o n
2.624 Mc 6.063 Me 2x 2,'<
I0 -s 10 -6
2 . 5 × 10 -a 10 -2 5150 l.tz 24 H z 31 4
× 10 -~ ×10
*
12.5× 10 -0 4 < 1O "~Hz2/FIz
6,11')
.'~E ~.vs ITEMS
CERN SYMPOSIUM
AT GENEVA
(11~22
JUNE
1956)
An i n t e r n a t i o n a l s y m p o s i u m o n particle accelerators, detection t e c h n i q u e s a n d high e n e r g y p h y s i c s was a r r a n g e d b y C E R N between 11 a n d 22 J u n e 1956. T h e m e e t i n g s were held a t t h e I n s t i t u t de P h y s i q u e of G e n e v a U n i v e r s i t y , which had been placed at t h e disposal of t h e organisers b y t h e local authorities. T h e following c o u n t r i e s were r e p r e s e n t e d at t h e conference: Australia, Belgium, C a n a d a , Czechoslovakia, D e n m a r k , France, Federal Republic of G e r m a n y , Greece, India, Italy, J a p a n , N e t h e r l a n d s , Norway, Spain, Sweden, Switzerland, U.S.S.R., United K i n g d o m , U.S.A., a n d Yugoslavia. U N F S C O also sent an observer. T h e first week of t h e s y m p o s i u m was d e v o t e d entirely to high e n e r g y partiele accelerators, l ) u r i n g t h a t period, a b o u t fifty papers were given on t h e m a i n p r o b l e m s raised by t h e c o n s t r u c t i o n of m o d e r n accelerators, s u c h as t h e theoretical a s p e c t s of t h e question, t h e stud}, of m a g n e t s , t h e r a d i o f r e q u e n c y accelerating s y s t e m , t h e injection a n d ejection of particles, t h e o p e r a t i o n of the m a c h i n e s , etc. Moreover, t h e technical features of the large accelerators n o w in operation or in t h e course of b u i h t i n g were explained in detail. Finally, entirely new principles were p u t forward, whose practical application would considerably i m p r o v e t h e a l r e a d y s p e c t a c u l a r l)erformanee of e x i s t i n g accelerators. l l u r i n g t h e second week of t h e S y m p o s i u m , a t t e n t i o n was focused on detection metllods a n d on tile theoretical a s p e c t s a n d e x p e r i m e n t a l t e c h n i q u e s of t h e p h y s i c s of e l e m e n t a r y particles. T h e s e v e n t y p a p e r s given dealt with a wide v a r i e t y of questions, s u c h as Wilson c h a m b e r s , bubble c h a m b e r s , o v e r - c o m p r e s s i o n a n d c o u n t i n g t e c h n i q u e s , e x p e r i m e n t a l a n d theoretical p h y s i c s c o n c e r n i n g mesons, nucleons a n d a n t i p r o t o n s , q u a n t u m Iiehl theories, t h e s t r u c t u r e of t h e proton, mesic a t o m s , etc. T h e e x c h a n g e s of views t h a t took place between participants, both in a n d o u t s i d e t h e conference room. proved e x t r e m e l y fruitful, a n d the f r a n k n e s s s h o w n b y all concerned bodes well for t h e possibility of f u t u r e i n t e r n a t i o n a l cooperation in physics.
INTERNATIONAL
CONFERENCE
(AMSTERDAM,
2~7
ON NUCLEAR JULY
REACTIONS
1956)
T h e A m s t e r d a m conference, t h e full p r o g r a m m e of which m a y be f o u n d in No. 2 of this journM (this volume, p. 136), proceeded according to this p r o g r a m m e with g r e a t p u n c t u a l i t y a n d success. T h e r e were m o r e t h a n 500 p a r t i c i p a n t s : t h e cont i n g e n t s from France, G r e a t B r i t a i n a n d t h e U n i t e d S t a t e s were of t h e order of 70 each, t h e Soviet g r o u p was a b o u t 30. This well-planned a n d well-organised conference m a d e possible a full s u r v e y of t h e r a p i d l y a c c u m u l a t i n g d a t a from t h e v a s t am! diversified field of n u c l e a r reactions; t h e theoretical i m p l i c a t i o n s of this i n f o r m a t i o n were also e x t e n s i v e l y discussed. A general conclusion which e m e r g e d from t h e c o n f r o n t a t i o n of all t h e i n f o r m a t i o n is t h a t t h e optical model of t h e n u c l e u s is capable to a surprising e x t e n t of p r o v i d i n g a c o n s i s t e n t f r a m e w o r k for t h e analysis of n u c l e a r s t a t e s over tile whole r a n g e of so-called 'low' energies. T h e m o r e fund a m e n t a l p r o b l e m s oI d e r i v i n g n u c l e a r s t r u c t u r e s a n d collective m o d e s of e x c i t a t i o n from a m a n y - b o d y t h e o r y received d u e consideration, b u t t h e s e q u e s t i o n s are still in an early s t a g e of d e v e l o p m e n t .