摘要:

The quantum mechanical formalism for anomalous transmission of particles through perfect crystals using Debye model for lattice vibrations as described in an earlier work is applied to the case of Born-Mayer potential as the interaction between the incident particles and the lattice atoms. The results have been compared with those obtained by using the screened Coulomb potential in the earlier work. The dependence of the process on the incident particle energy and the temperature of the crystal has been established and is found to be similar to that obtained earlier. The channeling parameter (1 - ϵ) has been found to depend upon the charge numberz1of the incident particle (decreases with increasingz1) in contrast to the results obtained with the screened Coulomb potential where (1 - ϵ) depends only upon the screening properties of the electrons in the crystal.

ISSN:0033-7579    

DOI:10.1080/00337577208232016

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

To assess the total radiation damage caused as a consequence of (n, γ) reactions of iodine in hydrocarbons, the extent of added scavenger I2consumption per nuclear event has been sought to be estimated in the systems CH2I +I2+ hydrocarbon and I2+hydrocarbon, using131I labelled I2, gas chromatographic analysis of the product iodides and by spectrophotometry. The results conclusively show that a fantastically large number (1 × 1010) of I2molecules are consumed for every (n, γ) event on127I. Neutron irradiation of the frozen matrix at 77 °K result in the chemical reaction of 2 × 108molecules of I2for every (n, γ) event. On neutron irradiation of CH3I alone, I2is produced at the rate of 1010molecules per (n, γ) event. The various sources of energy deposition in the system as a result of the nuclear reaction have been assessed and it is suggested that an ionic chain reaction is involved in the chemical fixation of such a large number of iodine molecules.

ISSN:0033-7579    

DOI:10.1080/00337577208232017

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

With a view to assess the extent of radiation damage caused in hydrocarbon media by nuclear reactions of halogens and thus understand the physicochemical processes preceding the chemical fixation of the radioactive atom, results are reported of nuclear reactions of iodine [127I(n, 2n)126I and130mI(I.T.)130I] and bromine [80mBr(I.T.)80Br] in cyclohexane, hexane and heptane. From the extent of scavenger I2(labelled with131I) and Br2(labelled with82Br) consumed as a result of the nuclear transformations, as monitored by the121I and82Br activity in the organic form, the number of scavenger molecules taking part in chemical reactions for every (I.T.) or (n, 2n) reaction have been determined. The values for the iodine and bromine nuclear reactions are 5 × 108and 2 × 104molecules respectively. Reaction products like iodocyclohexane, monobromo and dibromo cyclohexane have been identified by gas chromatography. The importance of these results in understanding chemical effects of nuclear transformation has been stressed.

ISSN:0033-7579    

DOI:10.1080/00337577208232018

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

The effects which may accompany radioactive decay in irradiated metals can be described in terms of five mechanisms. Two are responsible for the production of defects, and two can annihilate existing defects. The fifth mechanism is the formation of transmutations. The relative importance of each mechanism is dependent upon the nuclear properties and damage state of the metal. The experimental observation of the effects of some of these mechanisms is made by means of resistivity change measurements in thermal neutron-irradiated Cu, W, Re, and Au. The observation of those effects which produce compensating changes is accomplished through the use of post-irradiation annealing procedures and control of defect concentration.

ISSN:0033-7579    

DOI:10.1080/00337577208232019

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

A liquid nitrogen irradiation loop was installed at the Research Reactor of N.R.C. 'Democritus' in Athens. This facility allows to irradiate metals with fast neutrons at 78 °K, where the electrical resistivities of these metals can be measured during irradiation. The irradiation facility as well as the electrical resistivity measuring cryostat, which allows annealing of the samples in the temperature range of 78 to 650 °K, are described in this paper. The annealing spectra of neutron irradiated Cu, Ni, Al, Fe and Fe(Si, C) were measured in order to prove the performance of the system and to get new recovery data mainly in the high temperature range. The details of these spectra are discussed with more emphasis of the fine structure to be seen. Stage II of Cu and Ni shows four well separated sub-stages indicating a rather complex recovery process.

ISSN:0033-7579    

DOI:10.1080/00337577208232020

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

Irradiation of three partially ordered alpha-copper-zinc alloys containing 20, 30 and 36 per cent Zn with 2 MeV electrons in the temperature region between 40 and 140°C caused an increase of the degree of short range order. The equilibrium state of order obtained thus depends slightly on the irradiation temperature. For the activation energy of the ordering process during irradiation an activation energy of 0.29±0.03 eV was found for all three alloys. After a prolonged irradiation of the 20 per cent alloy a temperature independent enhancement of diffusion was found. For the temperature-dependent diffusion a square root dependence, while for the temperature-independent diffusion a linear dependence, of diffusion rate on the electron flux was observed.

ISSN:0033-7579    

DOI:10.1080/00337577208232021

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

Recovery data in the temperature range of stage II are presented for nominally pure Pt samples and dilute Pt(Au)-alloys. The dilute alloys exhibit three well defined substages near 28, 42 and 90 K. Evidence is presented which points towards a rearrangement of trapped interstitials at Au-atoms in the substages at 28 and 42K and to dissociation of interstitials from Au-atoms at 90 K. At low initial defect densities the nominally pure samples exhibit substages near 120K and in the temperature range between 200 and 500K. Probably most of these substages are not of intrinsic character but are related to residual impurities. At high initial defect densities a gradual and continuous intrinsic stage II recovery is observed.

ISSN:0033-7579    

DOI:10.1080/00337577208232022

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

The annealing in stage III and IV of irradiated, and quenched plus irradiated Pt samples has been studied in detail. At low defect densities the observed activation energy is equal and constant in both stages and amounts to 1.4 eV. At higher irradiation induced and quenched in defect densities, a systematic variation of the effective activation energy is observed in both stages. A model which assumes vacancy migration in stage III and stage IV and which allows for partial formation and more rapid migration of divacancies is able to account for these experimental observations. Model calculations using physically reasonable values for the relevant physical parameters are able to reproduce quantitatively the experimental recovery curves and activation energies.

ISSN:0033-7579    

DOI:10.1080/00337577208232023

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

The radiolysis of gaseous 1,3-butadiene has been investigated using80Co γ-rays. The yields of C1to C4hydrocarbons are reported for both scavenged and unscavenged systems.

ISSN:0033-7579    

DOI:10.1080/00337577208232024

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor

摘要:

Transmission electron microscopy and immersion density measurements were used to characterize radiation damage and postirradiation annealing effects in annealed 1100 aluminum irradiated at 45 °Cin an aqueous environment to maximum fluences of 3.2 × 1022n/cm2(> 0.1 MeV) and 3.1 × 1022n/cm2(thermal). Radiation-induced swelling from voids was first detected at 7 × 1021n/cm2and reached a value of 1.5 per cent at 3.2 × 1022n/cm2with a void concentration of 1.8 × 1014/cm3. Transmutation-produced silicon, from thermal neutron reactions with27Al, formed fine precipitate particles of approximately 5 × 1015/cm3, uniformly distributed throughout the matrix.

ISSN:0033-7579    

DOI:10.1080/00337577208232025

出版商:Taylor & Francis Group    

年代:1972

数据来源: Taylor