It seems that the critical rate of primary ionization for track registration must also depend on the etching conditions. Simple experimental methods are presented to show a possible change in registration sensitivity as a function of the chemical parameters. It was proved, from investigations of a-particle tracks, that the sensitivity of a cellulose acetate detector can considerably depend on the concentration and type of etching reagent. Quantitative data are given on the ratio of the rate of chemical etching along the track and on the detector surface as a function of concentration of NaOH solution for tracks of fission fragments registered in plastics of cellulose acetate, polycarbonate and polyethylene-terephthalate.
Thick-layered Be was bombarded with a-particles of a small-diameter Po preparation. The distribution of neutron-emission energy associated with the Be 9 (a, n) C 12 nuclear process was determined by the measurement of recoil-proton tracks incident in the nuclear emulsion. The energy spectrum obtained by the measurement of more than 12 000 tracks showed three maxima (1,3 ; 4,4 ; 6,9 MeV) and the observed upper limit of neutron energy was 10,7 MeV.The distribution of energy observed showed considerable disagreement with results known from literature. This can be accounted for by the fact that the number of measurements contributing to the present result exceeds by far the number of measurements carried out by other authors. Furthermore the divergence of irradiation geometry offers a very favourable opportunity for observation when a source of small diameter is used.Of the neutron sources produced by natural radioactive alpha rays itis the Beg(a, n)C 12 nuclear process which is associated with the most intensive neutron emission. In many cases polonium is preferred as ah alpha source, by reason of its y radiation having considerably smaller intensity than Ra of Rn. Furthermore its alpha energy is more homogeneous.This fact explains why studies dealing with the investigation of the energy spectrum of neutrons from a Po-Be source abound in the literature. The subject has not lost its significance even at the present time. The various results [11,12,13 ] so lar obtained agree in putting the highest limit of radiation at 11 MeV. The maximum of intensity has been determined in general as ranging from 2 to 5 MeV. However, as to the number and locus of maxima, as well as the proportion of intensities ate considerable discrepancies.The purpose of this study is to examine the energy distribution of fast neutrons, as they emerge from a Po-Be neutron source of small dimensions, with the photographic emulsion method.
Presentcd by A. Szalay. --Receivcd 11. XI. 1960) By measuring the range-energy curve of recoil protons produced in the nuclear emulsion by reactions H2(d, n) He a and Ha(d, n) He 4, calibration points were obtained to determine the range-energy relation of the Agfa K2 emulsion. The measured ranges showed good agreement within the error limits with results of calculations for Agfa K2 emulsion containing 60~o relative humidity [1].The photoemulsion method cannot be applied to determine the energy of particles without precise knowledge of their range-energy relation. Therefore it is not surprising that in the literature such a great number of both calculated and measured data can be found on emulsions of different make and type.The range-energy relation of Agfa K2 emulsions was investigated by LxNIvs [2] and BEBEL [1]. Both authors carried out calculations for protons, and obtained the calibration points by measuring and reducing the range of alpha-particles from the decay series of Th. Experimental data on protons were reported only by LANIus, who measured the range of 0,58 MeV protons from the reaction N 14 (n,p) C 14. Both measurements were made in air of 60~ relative humidity, and the calculations were also made for emulsions of this kind. There is a substantial difference in the atomic composition reported by the two authors and accordingly also in the density of emulsions. According to BEBEL'S recerit data the latter is 3,38 gcm --3 as against the previous 3,84 gcm -3. LANIUS carried out the calculations as described by C•[3], while BEBEL made them with the method developed by VIGNERON [4] using --in addition to the composition of the emulsion --new data also for the average ionization potential value.On the basis of the above it can be expected and also understood that the discrepancy in the range of protons with identical energy is considerably greater between the data of the two authors referred to than the usual error in measurement. The data of measurement and calculated values of both authors --on the other hand --show good agreement. The reason for this, besides the use of emulsions with different stopping power, is to be found in the fact that
Kodak Fast Neutron Monitoring Films of different ages were irradiated for calibration with fast neutrons of the reaetions (D + D) and (D + T). The energy distributions of the neutrons were also measured using Ilford K2 nuclear plates irradiated simultaneously.Aecording to the resuhs the density of the "traeks" eontaining less than five grains is independent of the dosis on a wide range; the track-counting was performed with ah aeeuracy of • under a realistic scanning time; ageing tendeney was not observed.The fast n e u t r o n personal d o s i m e t r y of those working with n e u t r o n generators is m a i n l y based on nuclear t r a c k counting, and even t o d a y ir is performed with the aid of a nuclear emulsion. Several comprehensive works have been published as to the description of the m e t h o d e.g. [1,2]. The K o d a k Personal N e u t r o n Monitoring Films of t y p e A ate m o s t widely used. I t is the above t y p e of film t h a t has been used in this I n s t i t u t e since 1964.A n u m b e r of papers h a v e been published relating to the calibration of the K o d a k F a s t N e u t r o n Monitoring Films [3 --10]. W i t h i n the scope of the present article no systematic s t u d y of the factors determining the calibration of the films is given. Here, we only a t t e m p t to draw a t t e n t i o n to a few phen o m e n a and conditions t h a t were observed during the s t u d y of the films used for the calibration. I t should also be added t h a t our investigations, in m a n y aspects, c a n n o t be regarded as complete.A s a rule, in every series calibration exposures were m a d e with b o t h neutrons originating from the D -4-T and D -k D nuclear reactions of known yield. The films to be irradiated were placed at 90 ~ to the direction of the deuteron beato a n d a t 0 ~ in other cases. I n each case the badges were irradiated on a n o r m a l front.The t i m e -i n t e g r a t e d neutron flux received was m e a s u r e d with a long aounter, which was calibrated b y using P o --B e of R a --B e neutron sources. The conditions of irradiation were chosen in such a w a y t h a t the error of distance m e a s u r e m e n t could be regarded as negligible. The films were always irradiated simultaneously at different distances. * Dedieated to Prof. A. SZALXY on his 60th birthday.
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