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Beiner, M.

Theory of Nuclear Structure: Trieste Lectures 1969. Lectures Presented at an International Course on Nuclear Theory

Theory of Nuclear Structure: Trieste Lectures 1969. Lectures Presented at an International Course on Nuclear Theory

AbstractAbstract

[en] Separation energies of nucleons as well as pairing properties are calculated for spherical nuclei and systematically compared with experimental data. The spherical odd-nuclei (Z or N >> 15) are represented by 31 ''mean odd-Z nuclei'', (Z, N(Z)), and by 46 ''mean odd-N nuclei'', (Z(N), N), N(Z) and Z(N) being real mean values (in general non-integer) associated with any odd number Z and N, respectively. Using a local average potential (depending on few constants) in order to obtain sets of single-particle states and introducing computed realistic pairing matrices in the gap equations we obtain theoretical predictions in good agreement with the corresponding empirical data. (author)

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Source

International Atomic Energy Agency, Vienna (Austria); International Centre for Theoretical Physics, Trieste (Italy); 976 p; Jul 1970; p. 903-930; International Course on Nuclear Theory; Trieste (Italy); 7 Jan - 31 Mar 1969; IAEA-SM--6/50; ISSN 0074-1884; ; 16 refs., 11 figs., 4 tabs.

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AbstractAbstract

[en] Fission probabilities and the angular distribution of the fission fragments have been measured for six even-even compound nuclear systems using the (t, pf) reaction. Angular correlations of fission fragments obtained in these experiments provide information about the low-lying collective excitations or transition states at the fission barrier. The (t, p) reaction in particular leads to neutron-rich residual nuclei unobtainable by other methods. The absence of spin coupling for (t, p) reactions on even-even targets provides angular distributions with well defined structure in the region of the fission barrier. The experimental data were obtained using an 18-MeV triton beam on targets of

^{242}Pu,^{240}Pu,^{238}U,^{236}U,^{232}Th and^{230}Th at Los Alamos Van-de-Graaff accelerator facility. Outgoing protons were detected at 140 deg relative to the incident triton beam. Excitation energies ranging from 3.0 to 9.0 MeV were obtained in these experiments. Fission fragment angular distributions were measured at 24 angles from 0 deg to 140 deg relative to the kinematic recoil angle. The data were fitted to a series of even Legendre polynomials W(θ) = A_{0}[1 + Σ_{L}g_{L}P_{L}(cos θ)] and the coefficients g_{2}through g_{12}and A_{0}were determined as a function of excitation energy. The fission probability P_{f}was obtained from the ratio of A_{0}to the (t, p) cross-section for the target nucleus. The results exhibit well defined structure in the angular coefficients which correlates with structure in the fission probability for most of the nuclei studied. In an attempt to interpret this observed structure the experimentally determined fitting parameters P_{f}and g are compared with calculated results of a microscopic model. This model takes into consideration the penetrability and angular dependence of fission through each member of the various transition bands at the saddle point and appropriately sums the results for comparison with the data. The effects of barrier penetration through a two-peaked deformation potential are explored in this analysis. This survey of the fission properties of several nuclei indicates some general trends relating the saddle point deformation to the character of the transition level structure. (author)Primary Subject

Source

International Atomic Energy Agency, Vienna (Austria); 1001 p; Dec 1969; p. 920-921; 2. IAEA symposium on physics and chemistry of fission; Vienna (Austria); 28 Jul - 1 Aug 1969; IAEA-SM--122/104; ISSN 0074-1884; ; Abstract only

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ANGULAR CORRELATION, ANGULAR DISTRIBUTION, COLLECTIVE EXCITATIONS, EXPERIMENTAL DATA, FISSION, FISSION BARRIER, FISSION FRAGMENTS, LEGENDRE POLYNOMIALS, PLUTONIUM 240 TARGET, PLUTONIUM 242 TARGET, PLUTONIUM 244 TARGET, THORIUM 230 TARGET, THORIUM 232 TARGET, THORIUM 234 TARGET, TRITON BEAMS, URANIUM 236 TARGET, URANIUM 238 TARGET, URANIUM 240 TARGET

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Pikelner, L.B.

Nuclear Structure: Dubna Symposium 1968. Invited Papers from the International Symposium on Nuclear Structure

Nuclear Structure: Dubna Symposium 1968. Invited Papers from the International Symposium on Nuclear Structure

AbstractAbstract

[en] A review is given of some recent work on neutron spectroscopy of non-fissionable nuclei, performed on the pulsed reactor, Dubna. Neutron transmission and radiative capture were measured for separated isotopes of rare earths - neodymium, gadolinium and erbium - and for isotopes of germanium and selenium. Parameters of the considerable number of levels of these isotopes were obtained, by which strength functions, average level spacings, and single-particle state density near the Fermi energy were calculated. Strength functions of rare earths have a weak maximum at A ≃ 160, in addition to two main peaks at A ≃ 145 and A ≃ 180 associated with nuclear deformation in this mass number region. Strength functions of germanium and selenium isotopes are in satisfactory agreement with the calculations from the optical model, which take into account nuclear dynamic deformation. The detailed experimental data on nuclear level density in the rare earth region made it possible to determine reliably a peak of the density g of single-particle states near the Fermi level at A ≃ 150. As was shown by the calculations of Furman and Popov, the experimental results are in satisfactory agreement with theoretical g

_{shell}(N) calculated from single-particle level schemes in the deformed well. Level spacings versus neutron excess in a nucleus (N - Z) in the region of light nuclei are discussed and comparison is made with the experimental data. (author)[ru]

Da etsja obzor rabot po nejtronnoj spektroskopii nedeljashhihsja jader, vypolnennyh v poslednee vremja na impul'snom reaktore OIJaI. Izmerenija propuskanija i r a diacionnogo zah vata nejtronov byli provedeny dlja razdelennyh izotopov redkozemel'nyh jelementov neodima, gadolinija i jerbija, a takzhe dlja izotopov germanija i selena. Polucheny parametry znachitel'nogo chisla urovnej jetih izotopov, po kotorym rasschitany si lovye funkcii, srednie rasstojanija mezhdu urovnjami, plotnost' odnochastichnyh sostojanij vblizi jenergii Fermi. Silovye funkcii redkozemel'nyh jelementov imejut slabo vyrazhennyj maksimum pri A ≃ 160 pomimo dvuh osnovnyhpikov pri A ≃ 145 i A ≃ 180, svjazannyh s deformaciej jader v jetoj oblasti massovyh chisel. Silovye funkcii izotopov germanija i s e l e na udovletvoritel'no soglasujutsja s raschetami po opticheskoj modeli, v kotoryh uchityvae tsja dinamicheskaja deformacija jader. Podrobnye jeksperimental'nye dannye o plotnosti urovnej jader v oblasti redkozemel'nyh jelementov povolili nadezhno prosledit' pik plotnosti g odnochastichnyh sostojanij vblizi poverhnosti Fermi pri A ≃1 5 0. Kak pokazali r a s chety Popova i Furmana, jeksperimental'nye r e zul' taty udovletvoritel'no soglasujutsja s teoreticheski poluchennoj g_{06on}(N), vychislennoj iz shem odnochastichnyh urovnej v deformirovannoj jame. Obsuzhdaetsja zavisimost' plotnosti urovnej ot izbytka nejtronov v jadre (N — Z) v oblasti legkih jader i provoditsja sravnenie s jeksperimental'nymi dannymi. (author)

Original Title

Plotnosti urovnej i silovye funktsii yader vblizi ehnergii svyazi nejtrona

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Source

International Atomic Energy Agency, Vienna (Austria); International Union of Pure and Applied Physics, London (United Kingdom); 658 p; Dec 1968; p. 349-359; Symposium on Nuclear Structure; Dubna (Russian Federation); 4-11 Jul 1968; ISSN 0074-1884; ; 32 refs., 5 figs., 2 tabs.

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Nörenberg, W.

Physics and Chemistry of Fission. Proceedings of the Second IAEA Symposium on the Physics and Chemistry of Fission

Physics and Chemistry of Fission. Proceedings of the Second IAEA Symposium on the Physics and Chemistry of Fission

AbstractAbstract

[en] A first step towards a unified theory of fission is proposed in a simple model which allows the mass yield, the kinetic energies, and the fragment excitation energies to be described as functions of the compound excitation energy. The main assumptions of this model are: (1) a full statistical equilibrium of all degrees of freedom at the saddle point, and (2) strong coupling between collective degrees of freedom and weak coupling to non-collective degrees of freedom on the way from saddle to scission. The dependence of the various features: of fission on the compound excitation energy comes in through the number of quasi-particle (qp) excitations at the saddle point and the collective temperature which characterizes the assumed statistical equilibrium of the collective degrees of freedom at the scission point. In particular the so-called molecular model of fission is .used. In this model the compound nucleus is described by two interacting fragments. The centre-to-centre distance of the fragments is assumed to be large enough to treat the compound nucleus as a ''molecule'' bound by the outer nucleons. From the above assumptions for the motion from the saddle to the scission point the eigenenergies of the mass-asymmetry motion are a linear function of the number of (qp)-excitations at the saddle point. From a simple Boltzmann distribution one obtains the energy dependence of the ratio of symmetric-to-asymmetric mass yield. This ratio increases with increasing compound excitation energy. The mean kinetic energies of the fragments are determined by the Coulomb energy at the scission point. The scission-point distance depends on the deformability of the fragments which, in turn, is a function of the number of quasi-particle excitations. The difference of the mean kinetic energy at two different compound excitation, energies turns out to be approximately zero for symmetric fission and linear in the difference of the number of (qp)-excitations for asymmetric fission. For increasing compound excitation energies the mean kinetic energies of the fragments in asymmetric fission decreases. The loss in kinetic energy mainly appears as excitation energy of the heavier fragment which is nearly magic. The dependence of the mean number of (qp)-excitations on the compound excitation is explicitly given in a simple statistical model of level densities. Some experimental data are analysed according to the theory and found to be in rather good agreement with the theory. (author)

Primary Subject

Source

International Atomic Energy Agency, Vienna (Austria); 1001 p; Dec 1969; p. 51-64; 2. IAEA Symposium on the Physics and Chemistry of Fission; Vienna (Austria); 28 Jul - 1 Aug 1969; IAEA-SM--122/30; ISSN 0074-1884; ; 29 refs., 4 figs., 1 tab.

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Malmskog, S.G.

AB Atomenergi, Nykoeping (Sweden)

AB Atomenergi, Nykoeping (Sweden)

AbstractAbstract

[en] The knowledge of the half-lives of excited states is often a valuable information in the investigation of the nuclear level structure. The present paper contains a collection of such half-lives being published in the current literature over the period 1967-1970. The data is arranged in increasing order of mass number

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Source

Jul 1970; 40 p; tabs.

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Report

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Cabral, J.; Hopman, H.J.; Insinger, F.G.; Ott, W.

Plasma Physics and Controlled Nuclear Fusion Research. Proceedings of the Third International Conference on Plasma Physics and Controlled Nuclear Fusion Research. Vol. II

Plasma Physics and Controlled Nuclear Fusion Research. Proceedings of the Third International Conference on Plasma Physics and Controlled Nuclear Fusion Research. Vol. II

AbstractAbstract

[en] Cyclotron instability and its harmonics appear under certain conditions in injection machines, whether the injection is parallel to the axial magnetic field B

_{0}(Demirkhanov and Alexeff at the Culham Conference) or perpendicular to B_{0}(DCX, Phoenix experiments). The paper describes measurements on these instabilities, around the transition from the first to the second regime. This experiment is characterized by a rapid alternation of different instabilities and plasma-density and temperature changes with each instability. Investigations of these variations have only recently been forthcoming (Kharchenko, Seidl, Hopman at the Conference on Ionized Gases, Vienna, 1967). Main results of this paper are the distribution functions of the beam electrons, correlated with the different types of instabilities. Drastic changes in the distribution function are found. In the second regime the distribution function of axial energies jumps between a narrow plateau between 0.6 and 1.1 eV_{b}, and a wide plateau extending from 0 to 1.4 eV_{b}. These plateaus develop in about 100 ns. The wide plateau is found in correlation with an instability whose frequency is twice the electron cyclotron frequency. The narrow plateau is established by the electron cyclotron instability. Only the plateau belonging to the electron plasma instability is symmetric around eV_{b}; it has a width of 0.1 eV_{b}. In all three cases the plateaus are found to be flat, independent of their width, and of the radius on which they are measured. In correlation with the cyclotron instability are found beam electrons with transverse energies of the order of 0.3 eV_{b}, indicating the possibility to build up a high-energy electron plasma, directly from beam electrons, in cases where a magnetic bottle is applied. In connection with the experimental data, numerically calculated dispersion diagrams are presented for bounded beam-plasma systems including temperature effects. (author)Primary Subject

Source

International Atomic Energy Agency, Vienna (Austria); 852 p; Mar 1969; p. 749-762; 3. international conference on plasma physics and controlled nuclear fusion research; Novosibirsk, USSR (Russian Federation); 1-7 Aug 1968; IAEA-CN--24/L-6; ISSN 0074-1884; ; 11 refs., 9 figs., 1 tab.

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AbstractAbstract

[en] The thermal and hydrodynamic phenomena occurring during a power excursion were studied in an out-of-pile loop with a water cooled channel at low pressure (1 to 4 atm. abs. ). Circular and rectangular test sections with electrically heated walls of two different thermal diffusivity materials(aluminium and stainless steel) were used. The rectangular test sections were 600 mm long, 35 mm wide and had a 2, 9 mm gap; they simulate two half plates of the M.T.R. fuel element. Natural or forced convection are possible in the test section; the water height above it can be varied from 2.8 to 8 meters and the maximum allowed pressure at its outlet is 4 atm. abs.The heating source is a series of lead batteries which is able to generate, for short periods of time, 85 volts and 25000 amperes; linear, square or exponential power rise versus time can be realized. A 14 channels tape recorder (0-10 000 Hz bandwidth; is used for the measurements of temperature (8/100 mm diameter thermocouple), pressure ('Statham' pressure transducers) and void fraction (X rays). More than 500 tests have been carried out. The influence of the initial water temperature, flow rate, pressure, water height on the water ejections, pressure variations and void fraction in the test section were studied. Tests with energies up to 3000 W/cm in 50 milliseconds were attempted. The energy above which the instabilities appear was determined. An interpretation of the observed phenomena and a simplified theoretical model are presented

[fr]

Les phenomenes thermiques et hydrodynamiques qui apparaissent au cours d'une excursion de puissance ont ete etudies sur un canal refroidi par de l'eau a basse pression situe sur une installation hors pile. On a utilise des sections d'essais de geometrie cylindrique ou parallipedique dont les parois chauffees par effet Joule sont constituees de materiaux de diffusivite calorifique differente (aluminium et acier inoxydable). La section d'essais parallipedique a 600 mm de long, 35 mm de large et 2,9 mm d'entrefer; elle simule deux demi-plaques d'un element combustible M.T.R. II est possible de realiser dans la section d'essais un ecoulement d'eau en convection forcee ou sans convection, la hauteur d'eau surmontant le canal peut etre reglee entre 2.8 et 8 metres et la pression maximale admissible a sa sortie est de 4 atm. abs. La source de puissance est un ensemble de batteries au plomb montees en serie, capable de fournir pendant de courts instants un courant de 25000 A sous 85 V; il est possible de realiser, en fonction du temps, des montees en puissance lineaires, exponentielles ou sous forme de creneaux. Un enregistreur magnetique a 14 pistes (bande passante 0, 10000 Hz) permet d'enregistrer les mesures de temperature (thermocouples de 8/100 mm de diametre), de pression et de taux de vide (par absorption de rayons X). Le dispositif experimental a permis d'effectuer plus de 500 essais; certains ont ete realises avec une puissance de 3000 W/cm dissipee pendant 50 millisecondes. On a etudie l'influence de la temperature initiale de l'eau, du debit, de la pression et de la hauteur de la colonne d'eau surmontant le canal, sur les ejections d'eau, les variations de pression et de taux de vide dans le canal. L'energie au-dessus de laquelle des instabilites apparaissent dans le canal a ete determinee; une interpretation des phenomenes observes ainsi qu'un modele theorique simplifie les representant est propose. (auteur)Original Title

Etude des phenomenes thermiques et hydrauliques accompagnant une excursion rapide de puissance sur un canal chauffant

Primary Subject

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1969; Sep 1967; [153 p.]; These sciences

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Report

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Thesis/Dissertation; Numerical Data

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Zakharova, S.M.; Stavinskij, V.S.; Shubin, Yu.N.

Nuclear data for reactors. Proceedings of the second international conference. Vol. II

Nuclear data for reactors. Proceedings of the second international conference. Vol. II

AbstractAbstract

[en] The behaviour of the average radiation width is studied as a function of the number of nucleons in a nucleus. Nuclear level density is calculated in terms of the Fermi-gas model, allowance for residual interactions being made on a phenomenological basis. It is shown that the ratio of the average radiation width obtained from the experimental data on neutron resonances in the low-energy range to the average radiation width calculated with the Weisskopf model depends on the shell structure and correlates with the behaviour of the width of a dipole giant resonance. Analytical treatment of the data yielded a semi-empirical expression for the average radiation width which can be used for calculating this quantity, in the case of a nuclear excitation energy of the order of neutron binding energy, to within ± 40% in the range of A = 60 to A = 200. (author)

[ru]

V rabote issleduetsya povedenie srednej radiatsionnoj shiriny v zavisimosti ot chisla nuklonov v yadre. Plotnost' yadernykh urovnej rasschityvaetsya v ramkakh modeli fermigaza s fenomenologicheskim uchetom ostatochnykh vzaimodejstvij. Pokazano, chto otnoshenie srednej radiatsionnoj shiriny, poluchennoj iz ehksperimental'nykh dannykh po nejtronnym rezonansam v oblasti nizkikh ehnergij, k srednej radiatsionnoj shirine, rasschitannoj v ramkakh modeli Vajskopfa, zavisit ot obolochechnoj struktury i korreliruet s povedeniem shiriny dipol'nogo gigantskogo rezonansa. Na osnovanii provedennogo analiza polucheno poluehmpiricheskoe vyrazhenie dlya srednej radiatsionnoj shiriny, pozvolyayushchee vychislit' ehtu velichinu pri ehnergii vozbuzhdeniya yadra poryadka ehnergii svyazi nejtrona s tochnost'yu ne khuzhe 40% v oblasti massovykh chisel ot A = 60 do A = 200. (author)Original Title

Srednie radiatsionnye shiriny pri ehnergii vozbuzhdeniya poryadka ehnergii svyazi nejtrona

Primary Subject

Source

International Atomic Energy Agency, Vienna (Austria); 976 p; Oct 1970; p. 909-917; 2. international conference on nuclear data for reactors; Helsinki (Finland); 15-19 Jun 1970; IAEA-CN--26/82; ISSN 0074-1884; ; 6 refs, 4 figs; Presented by A.I. Abramov

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AbstractAbstract

[en] Experimental measurements of the neutron flux elastically scattered from medium and high mass nuclei have yielded excellent cross section data over a wide range of neutron energies. The moderated bomb spectrum which comprises our neutron source function provides ample flux for cross section measurements between energies of 60 eV and 3 MeV. Analyses of the compound elastic scattering data show that the time dependence of the neutron source function contributes to a time-of-flight energy distribution which is approximately Poisson. The full width of the distribution at half the peak value exceeds one percent of the time-of-flight energy. Area analyses of the measured elastic cross sections yield resonance parameters for energies up to the 100 keV region, A careful study of the applicability of shape analysis to these data reveals that a reduction in the width of the neutron source function would be highly advantageous and has led to additional calculations of moderator design. Results of some data analysis, moderator design and shielding calculations will be presented. (author)

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American Nuclear Society, Hindsdale, IL (United States); United States Atomic Energy Commission (United States); 935 p; May 1970; p. 1257-1268; Symposium on engineering with nuclear explosives; Las Vegas, NV (United States); 14-16 Jan 1970; 4 refs, 6 figs

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AbstractAbstract

[en] A study has been made of the types and relative frequencies of chromatid aberrations induced by doses of 16.3 and 48.2 rad of 14.1-MeV neutrons in the primary root meristem cells of Vicia faba. Fixations were made at hourly intervals from 3 to 9 hours post irradiation to cover cells which were in G2 and late S at the time of treatment. Frequency changes with time show similar trends to those found after X-rays in this material under similar conditions, most aberrations types showing a definite peak of sensitivity in early to mid G2 and a decline in S. A detailed cytological analysis of the Revell intra-change types provides evidence of the importance of the high LET particles (which result from inelastic collisions) in the production of chromosomal aberrations with this quality of neutrons. The findings give further support to the theory that the effective LET of 14.1-MeV neutrons in biological materials is higher than one would expect from a consideration of recoil proton energies alone. (author). 32 refs, 5 figs, 7 tabs

Primary Subject

Source

Joint FAO/IAEA Div. of Nuclear Techniques in Food and Agriculture, Vienna (Austria); Technical reports series; (No.92); 183 p; Oct 1968; p. 9-28; IAEA; Vienna (Austria); FAO/IAEA meeting on co-ordination of research on the use of neutrons in seed irradiation; Vienna (Austria); 11-15 Dec 1967

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BARYONS, BIOLOGICAL EFFECTS, BIOLOGICAL RADIATION EFFECTS, CELL DIVISION, DATA, ELECTROMAGNETIC RADIATION, ELEMENTARY PARTICLES, ENERGY RANGE, ENERGY TRANSFER, FERMIONS, GENETIC EFFECTS, HADRONS, INFORMATION, IONIZING RADIATIONS, MEV RANGE, NEUTRONS, NUCLEONS, NUMERICAL DATA, RADIATION EFFECTS, RADIATIONS

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