摘要:

Natural crystals of feldspars, pyroxenes, quartz and apatite have been irradiated in the Berkeley HILAC with neon and argon ions of up to 10.2 MeV/amu with maximum doses of 1.6 × 1013argon ions/cm2and 4.0 × 1013neon ions/cm2respectively. The samples were thinned to thicknesses near 30 microns, stacked to form the target and then bathed completely in the ion beams. X-ray and optical observations revealed: (a) a crystal distortion and curvature with the argon irradiation similar to that produced in mica; (b) a lesser effect from neon bombardment; (c) a fracturing of the crystal samples which depended on the total dose and energy of the incident ion; (d) polygonized structures produced when either neon or argon ions (with sufficiently high concentration) were trapped within the crystals. The interpretation of the measurements, their correlation with the mechanism of track formation and implications concerning the alteration of the lunar surface due to solar particles and the exposure of lunar and meteoritic material in the ancient solar flare cosmic rays are discussed.

ISSN:0033-7579    

DOI:10.1080/00337577008235014

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The temperature dependence of the tensile lower yield stress of an annealed aluminium grain size controlled mild steel has been investigated in the range 23–250 °C and at a strain rate of 1.67 × 10−4sec−lbefore and after neutron irradiation to 2.3 × 1018n/cm2(fission). The yield stress of the irradiated steel decreases with increasing temperature due to thermal activation of the radiation damage and is predicted to reach asymptotically that of the unirradiated steel at ∼285 °C; the maximum test temperature was below that at which thermal annealing of the damage occurs. This implies that the athermal stress component due to irradiation is zero and hence there is negligible long range interaction between dislocations and radiation-induced defects.

ISSN:0033-7579    

DOI:10.1080/00337577008235015

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A resistometric study at 4.2 °K of the high-temperature recovery spectrum of neutron-irradiated molybdenum as a function of fast fluence and of cold-worked molybdenum as a function of the heating program, yields evidence against vacancy migration in the 0.31Tmstage for VIa b.c.c. metals.

ISSN:0033-7579    

DOI:10.1080/00337577008235016

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The techniques of computer simulation are used to generate the velocity distribution of ions emerging near close packed planes from a crystal surface. We concern ourselves in particular with protons and α-particles, 5 to 100 keV, near (100) planes in copper. The ions are initially emitted from either a lattice site-the ‘blocking case ‘or any other given point within a unit cell’ intermediate emission’. The resultant profiles are compared with an analytic model due to Andersen(6)based on the continuum approximation, and the validity of this model is thereby assessed. A simpler analytic model in which the interplanar continuum potential is approximated by a pure harmonic is also developed and compared with the previous two. Using the harmonic approximation we obtain a relatively simple relationship between the yield measured exactly parallel to a plane and the position of the original emission site. It is suggested that such a relationship could be of importance for experiments that can measure nuclear lifetimes of the order of 10−18to 10−16seconds.

ISSN:0033-7579    

DOI:10.1080/00337577008235017

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The evolution of the dimensional changes of UO2-SiO2vitroceramics with a content of 60–70 per cent mol UO2during irradiation at a low fission rate is presented.

ISSN:0033-7579    

DOI:10.1080/00337577008235018

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

In a high voltage electron microscope the intense electron beam used for imaging can cause visible aggregates of point defects to form in metals in just a few minutes. The diffraction-dependence of the defect cluster production was studied experimentally in Cu and Fe using a 1000 kV electron microscope. Also, a simple method for calculating the diffraction-dependence of the atomic displacement rate was devised from multiple-beam wave-mechanical diffraction theory. The calculations indicate that the rate of point defect production should vary at most by a factor of ∼1.7 with Bragg deviation in systematic diffraction cases, and that this variation should decrease rapidly with increasing depth in the crystal. The experimental observations are consistent with these predictions. In addition, the theory allows the diffraction-dependence of the displacement rate to be explained in terms of Bloch wave properties. Some new observations of the defect structures in electron-irradiated Cu and Fe are also described.

ISSN:0033-7579    

DOI:10.1080/00337577008235019

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

An isotopic effect recently reported by Foti and coworkers in Rutherford scattering from a silicon single crystal is ascribed to the quantum mechanical near-field effects of a positive potential. An experiment further to verify this interpretation is proposed.

ISSN:0033-7579    

DOI:10.1080/00337577008235020

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

By increasing the strength of the interaction potential for a reasonable range of values, we show that the angular pattern of the electron intensity, about a crystallographic axis, changes from one dominated by Bragg peaks to an essentially structureless curve. This retains a significant dependence onh, and by that token cannot be identified with the ‘classical envelope’.

ISSN:0033-7579    

DOI:10.1080/00337577008235021

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Two types of bombardment experiments were performed. A first series on metallic spheres, examined by replicas, and a second series on thinned crystals, examined by transmission electron microscopy. The observations lead us to propose a model for the formation of the surface microrelief. This model enables one to correlate the observation of regular dislocation networks, due to the segregation in perfect loops of the induced point-defects, to the formation of the relief structure by a preferential sputtering mechanism.

ISSN:0033-7579    

DOI:10.1080/00337577008235022

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Monomer free polystyrene samples, produced by evaporation from a solvent excluding oxygen, show by excitation with UV-light (λ=270 nm) or with β-rays besides the excimer peak at 330 nm (P-peak) an additional fluorescence peak at 390 nm (G-peak). This peak disappears by melting of the sample or admission of air. The influence of additives on the fluorescence spectra was investigated. 1,2-di-(2-pyridyl)-ethylene, an efficient quencner for the first excited singlet state of polystyrene, reduces the P-peak much more than the G-peak. Therefore it is inprobable that the states responsible for the P-and G-peak are excimers of different distance or symmetry of the segmers or excimers with more than 2 segmers participating. The intensity of the G-peak in comparison to the P-peak increases by addition of low concentrations of hexachlorocyclohexane (c<10−5mole/1). The dependence on the structure of the polymer and the influence of the electron scavenger suggests, that the appearance of the G-peak is connected with the existence of electron traps. We assume that the origin of the G-peak is a charge separate state analogous to that proposed by Janssen and Funabashi to explain the luminescence in γ-irradiated alkane glasses.

ISSN:0033-7579    

DOI:10.1080/00337577008235023

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor