Keen interest was shown in a paper by B. S. Neganov (Dubna) on a new method for polarizing protons in a ro-

tat ing cyrstal of lanthanum-magnesium nitrate binary salt. The experiment , performed at Dubna, is a further exten- sion of one of the methods in use for enhancing polar izat ion, suggested recent ly by A, Abragam and C. Jeffries (Cryogenics, 3 , 42, 1963). The exper iment is as follows: a single crystal of the lanthanum-magnesium nitrate with 0.2% Ce addit ive is brought to a temperature T = 1.4"K and is then rotated in a constant magnet ic field of 2 to 5 kOe (0.2 to 0.5 T), with a radio-frequency field of 60 to 170 Mc frequency applied at right angles to the magnet ic field. The NMR signal gain is 70. This result is a tentat ive one, and the method itself is undergoing development. The interesting feature of the method is the ext remely low requirements of s tabil i ty and homogenei ty of the magnet ic f ield, and the use of meter -wavelength range microwave frequencies instead of the shorter microwave frequencies, thereby making it possible to fabricate polar ized targets of large volume.

L. M. Soroko (Dubna) presented a theoret ica l t reatment of the effect of the motion of protons under acce le ra-

tion through polar izat ion loss. The report mentioned the requirements relat ing to inhomogeneit ies in the magnet ic fields.

Z. Tre jbal (Nuel. Res. Inst., CzSSR) told of calculat ions of the trajectories in a quadrupole magnet at zero

values of the aximuthal veloci t ies , and under different conditions governing the beam inject ion and the magnet geometry. The calculat ions were performed in accord with the thermal veloci ty distribution in the beam. The dependence of the beam dimensions on the magnet ic field intensity, as reported in his paper, is a step function, as confirmed by control calculations. A new method for coarse measurement of the beam temperature was also sug- gested in that paper.

The last paper, by K. Kult , was devoted to a description of the design of a polarized ion source for the Czech Nuclear Research Institute cyclotron located at Reze. The ionizat ion system for the a tomic beam in this project involves the use of an inverted magnetron. 100% polar izat ion is obtained with the aid of the high-frequency ar- r angemen t used to exci te adiabat ic transitions (Abragam method). The quadrupole magnet serves to sp l i t the beam of atoms, and has the best beam separation characterist ics, in the view of the authors.

L, B. Parfenov

S Y M P O S I U M ' O N N U C L E A R E L E C T R O N I C S

Translated from Atomnya ~nergiya, Vol. 16, No. 5, pp. 463-464, May, 1964

An international symposium on nuclear electronics sponsored by the French society of electronics and radio

engineering, with the par t ic ipat ion of several international research bodies (IAEA, LUPAP, CERN, etc .) , was held in Paris in November, 1963.

The symposium, which at t racted over 300 specialists from 30 countries and various international organiza- tions, took place in seven sessions. At the first session, devoted to the inauguration of the gathering with short ad- dresses, the renowned French physicist F. Perrin and the minister of state H. Palevsky were heard. The second and third sessions were devoted to research and development work and applications of various types of nuclear radiat ion detectors. The fourth and fifth sessions heard reports on the extract ion and processing of exper imental data in nu- clear electronics. The sixth and seventh sessions were devoted to the design and applications of fas t -act ing de tec- tors, circuits and instruments. 65 papers were submitted to the symposium. Part icipating from the Soviet Union were G. I. Zabiyakin , V. V. Matveev, A. G. Khabakhpashev, and I. V. Shtranikh.

The sessions were opened by the reports of leading specialists, and provided a deta i led review of the state of the art in this field of electronics.

The first working session began with a review paper presented by A. Roberts (USA); the report was devoted to the elaborat ion of a method for recording nuclear part icles by spark chambers. The u t i l iza t ion of the spark cham-

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bets as instruments for visual observation of nuclear particles was discussed. Conventional chambers in which the

point at which the particle traverses the plane of the chamber is recorded, and the so-called projection chambers in

which the traces of particles passing parallel to the chamber plates are recorded, were discussed. Light was thrown on

several aspects of this use of ancillary equipment for spark chambers (optics, pulsed high-voltage generators). Some

topics in the theory of spark chamber performance were touched upon. Three methods for extracting information were discussed: the optical method based on photographic tracks in a spark chamber; the acoustical method based on meas- uring the t ime it takes for a sound wave to pass several points of known coordinates at which acoustical sensors are

positioned; an electrical method based on measuring the difference in the resistance of portions of the plates from the

point where the spark passes to the ends of the plates. Techniques for analyzing the information obtained from spark

chambers by means of electronic computers were also discussed.

Of the other reports presented at this session, two dealt with the development and applications of spark cham-

bers, two with the mechanism of scinti l lat ion processes in liquid scintillators, and two described systems for moni-

toring high-energy particle flux, while one paper was devoted to a treatment of the possible exploitation of differences in pulse shape in a proportional counter to discriminate events where protons and fast electrons are recorded.

At the second session, the audience listened with keen interest to a review report by J, Mayer (USA) on sem-

iconductor radiation detectors. After briefly discussing the latest achievements in the field of the development and applications of surface-barrier detectors and diffusion type semiconductor detectors, the author centered his main

at tention on progress achieved in the field of the design and use of p - i - n type diffusion drift detectors. He also cited

some general relationships characterizing the l ink-up between the electrical and the counting parameters of these

detectors, examined the reduction in "dead layer," and the enhanced energy resolution of the detectors, and presented

the findings and the methods for employing diffusion-drift detectors in spectrometry, The report covered the use of detectors to record charged particles. The use of diffusion-drift type detectors in beta-ray spectrometry was charac- terized by the author in terms of the spectra of Cs 137 and Bi 2~ internal conversion electrons. In the case of cesium,

the energy resolution of the K-l ine was 3.8 keV, and 14 KeV in the case of bismuth. This section of the report placed the main emphasis on gamma-ray spectrometry.

The author turned his attention to the importance of introducing substances of high atomic number into the composition of the detector materials, with the object of enhancing the role of the photoelectric effect and obtaining simpler amplitude distributions from the detector. A whole series of gamma-ray spectra of Bi z37, Co 6~ , Am 242, and

Cs is7 acquired in the experiments by using detectors of different thickness (2,5:, and 8 ram) was also reported. The

energyresolut ion was 21 keV (1.6~ in the case of cobalt, 3 keV in the case of americium (the 59.6 keV line), and

9 keV in that of cesium.

The overwheh-ning majority of the remaining papers heard at this session (10 of the 11 papers) also dealt with

the development and applications of semiconductor detectors, preponderantly diffusion drift-compensated detectors,

for recording and spectrometry of nuclear radiations, A fast-response dE/dx- scinti l lation counter was described in

one paper.

The sessions dealing with electron devices, and with the automation and processing of results of measure-

ments, were opened with a review report presented by R, Chase (USA), analyzing the achievements of the develop- ment of nuclear electronics, discussing the principal methods used to solve problems, and citing data on the prog-

ress attained in the field of nucleonic instrumentation, as well as data on instruments fabricated by industrial es-

tablishments. Some problems of importance demanding the attention of nuclear electronics experts were delineated

and formulated in the concluding section of the report.

8ome of the reports delivered at these sessions dealt with the design of various electronic instruments for recording and spectrometry of nuclear radiations with the aid of scinti l lation chambers and spark chambers. Of these

reports, we draw the attention of the reader to one by R. Dudley and R. Scaghetitti (IAEA), proposing a method for

automatic and continuous stabilization of scinti l lation counters by means of a reference source emit t ing correlated

8- and y-radia t ion, The instrument described performed several months' rel iable service for calibrating a spec- trometer, within 0.02% accuracy over that t ime. Some other papers were devoted to the techniques of measurement and eon=ol of flux intensity from nuclear reactors. Several papers touched on the design of pulse height analyzers and t ime analyzers.

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Most of the reports at these sessions were devoted to computer applications in exper imental nuclear physics. The requirements imposed on physics experiments have been stepped up to such an exacting degree in recent years that currently avai lab le analyzers barely differ from computers in the amount of equipment and hardware and in the

complexi ty of the logic switching operations. And, while two years ago at the Belgrade conference computer appli- cations had been only discussed and a very few unique cases of computer applications in experiments were on record, at this symposium there was a fairly large number of reports in which experience in the use of standard computers for mult idimensional and mult ichannel analysis was described, and i t can be stated with confidence today that thistrend

is becoming increasingly predominant.

The sessions devoted to ul trahigh-speed (nanosecond) electronics were opened with a review paper by/ . Pieser

(CERN). On the basis of inferences drawn from published work over the past decade, he made an analysis of the progress achieved in at taining higher speeds in the basic e lectronic devices in use: amplifiers, coincidence circuits, scalers, t ime analyzers , photomult ipl ier tubes, etc. The slope of the cl imb in the speed of response is roughly the same for all of these devices: a rapid growth in the first five to seven years followed by a pronounced slackening in the rate of growth in the ensuing years and an asymptotic approach to some " l imi t , " equal to units or fractions of a nanosecond. Even though the author singled out the important role of new types of modular systems in this progress, with which there can be no disagreement , the transition from vacuum tube devices to semiconductor de= vices failed to show any not iceable breaks in the curve of growth.

The papers submitted at these sessions may be divided up into two distinct groupings: reports devoted to the development of fast radiat ion detectors and papers touching direct ly on circuit soluti0ns of instrumentation and de=

vices in the nanosecond range.

As far as can be judged from the papers presented, semiconductor detectors are increasingly dominating the field in nanosecond devices. In the c i rcui t solutions, papers deal ing with the development of t ime analyzers, rapid amplif iers , discriminators, sealers, etc. contrasted with the papers presented at the ear l ier Belgrade conference in

the improved speed of response and increase in the number of channels reported. Most of the devices are complete= ly transistorized; the number of instruments based on tunnel diodes is increasing, and some based on thin magnet ic f i lm memories are making their appearance. Plans call for publishing the proceedings of the symposium in the first

half of 1964 for distribution in the countries which sent delegates to the symposium.

As part of the conference program, symposium delegates were invited to visit the French scientif ic research centers at Orsay and Saclay. The Soviet delegat ion also visited the industrial concern Intertechnique responsible

for the production of a l ine of e lect ronic hardware including mult ichannel analyzers of up to 4,000 channels , radiom- eter instruments, and pulsed grid ionizat ion chambers (of up to 0.8o]0 resolution for a - r ad ia t ion ) . This concern is selling its products to a variety of nations. With the object of expanding trade ties with the USSR, the firm is now

planning an exhibit of its wares at the Polyteehnical Museum in Moscow, in May, 1964.

V. Matveev

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