摘要:

A system of equations describing the production of electron-hole pairs in semiconductors by energetic electrons and holes is given for the low energy region. It is assumed that electron-phonon interaction and interband Auger transitions constitute the dominant slowing-down mechanisms. Quantitative estimates are obtained for the influence of parameters characterizing both the band structure and the interactions under consideration on the mean numbergof electrons and holes created. Also, the second order momentg2and the Fano factor Fare calculated. Furthermore, the problem of energy transfer to the crystal lattice is discussed in detail. The radiation-ionization energy ε and the corresponding phonon-loss part εphare estimated for several typical band structure models.

ISSN:0033-7579    

DOI:10.1080/00337577008234988

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

We have studied the thermal annealing of fossil tracks stored in hypersthene crystals of the Johnstown meteorite. We have observed that the annealing of the tracks depend on their initial length and therefore of the charge of the incident ions. The shortest tracks are annealed at a lower temperature than the longer ones. These long tracks in turn have been found to be less thermally stable on the average than fission fragment tracks.

ISSN:0033-7579    

DOI:10.1080/00337577008234989

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Lexan plastic prints are formed when a rock section is irradiated, with a sheet of plastic held against it, in a predominantly thermal neutron flux. The print texture is made up of varying densities of tiny etch pits, which are formed when the plastic is chemically etched after irradiation. The pits are formed from short trails caused by the passage of either α-particles or recoil ions from the rock material. Observed pit densities are correlated with the mineral phases producing them, and calculations of the elemental concentration of B, Li and O required to produce them are made. The present ideas of the print formation are compared with a previous suggestion that they are produced by recoiling OH ions.

ISSN:0033-7579    

DOI:10.1080/00337577008234990

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

La théorie de la cinétique chimique est reprise et développée pour plusieurs schémas d'agglomération de défauts ponctuels dans les métaux. En particulier, il est trouvé que la forme exacte du noyau influe peu sur le grossissement ultérieur, mais que l'instabilité d'une des formes conduisant au noyau modifie beaucoup l'agglomération. D'autre part, les conditions de validité de cette théorie sont discutées. Il en résulte que la théorie s'appliquera bien lorsque le nombre de paires de Frenkel créées Par choc avec la Particule incidente est voisin de 1. Plus ce nombre est grand, plus la probabilité d'obtenir une nucléation inhomogène est grande.

ISSN:0033-7579    

DOI:10.1080/00337577008234991

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Le mica est utilisé pour la mesure du parcours moyen des fragments de fission de l'uranium 235 dans différents métaux. Cette détermination a pour but le dosage d'éléments fissiles dans les alliages au moyen des traces dans le mica. On trouve, pour l'état écroui, en mg cm−2:

ISSN:0033-7579    

DOI:10.1080/00337577008234992

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

We have determined the response of plastic track detectors to heavy charged particles from the HILAC at Berkeley, California. The rates of track etching as a function of particle charge and velocity are presented for cellulose tri-acetate and cellulose acetate butyrate plastic and are compared to previously measured response curves of Lexan polycarbonate and cellulose nitrate plastics. Application of these data to the determination of nuclear charges by the method proposed by Price and co-workers(3)are discussed. A variant of this method based on measurements of track diameters will also be presented. Finally, we present data on the change in calibration for plastics exposed to different environmental conditions prior to etching. No effect of gamma irradiation is observed up to a total dose of 18 000 roentgen. In contrast, there is a marked effect on the rate of track etching between samples stored in air at different temperatures after irradiation.

ISSN:0033-7579    

DOI:10.1080/00337577008234993

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A latent track in a plastic detector can be etched to a visible track, if the ratio of the track etching ratevtto the bulk etching ratevbis greater than 1. The etching rate in a specific material for a given particle depends on the particle's energy. For a given particle the critical energyEcis defined byvt(Ec) =vbThe track etching rate approaches the bulk etching rate near the critical energy in an asymptotic manner.

ISSN:0033-7579    

DOI:10.1080/00337577008234994

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The formation of point defect dusters, i.e. sinks for point defects in α-copper-zinc alloys during irradiation with 2 MeV electrons was studied by means of a decrease of the diffusion rate during prolonged irradiation. It was found that the free migrating interstitials are rate determining for the diffusion process during irradiation. Their activation energy gave 0.7 eV. With increasing electron dose the diffusion rate decreases due to the formation of sinks which cause a reduction of the concentration of interstitials with respect to the concentration in virgin Specimens.

ISSN:0033-7579    

DOI:10.1080/00337577008234995

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The existence of the ternary photofission of232Th,238U and239Pu induced with the bremsstrahlung of a 27.5 MeV electron beam has been looked for simultaneously with track detectors of different thresholds. In sandwiches prepared from both muscovite mica and plastic (Melinex O) altogether about 1.5 million binary fission events have been scanned. Data are given for the frequency of (1) three-prong events, (2) two-prong events with a space angle smaller than 180°, and (3) recoil events produced by the fission fragment scattered on39K and16O occurring in the material of the mica and plastic detectors, respectively. In the case of (1) and (2) range and angular distributions are also presented. Results obtained in mica and plastic are compared.

ISSN:0033-7579    

DOI:10.1080/00337577008234996

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The track diameter of particles entering the track detectors at right angles shows a strong dependence on the energy and type of particles. Some general features of this effect are discussed. It is shown that, even in glass, different heavy nuclei can be distinguished according to their track diameters. New data are presented for α-particles registrated in Makrofol E. Using the correlation between α-particle energy and track diameter, detailed investigations have been carried out to measure angular distributions of α-groups from nuclear reactions. Preliminary experimental results obtained for reaction19F(d, α) and27Al(d, α) at very low bombarding energies are presented.

ISSN:0033-7579    

DOI:10.1080/00337577008234997

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor