ISSN:0033-7579    

DOI:10.1080/00337578408206051

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

An important facet of understanding the transport of a beam of energetic charged particles within an ideal and imperfect crystal is the knowledge of ion-lattice interaction potential distribution. Various ion-lattice potentials developed earlier in analytical forms have different constraints. The success and failure of various analytical forms of interaction potentials depend to a large extent on how arbitrary and empirical are the definitions for real dislocations. First principles three-dimensional calculations of interaction potentials were carried out using Lindhard and Pathak forms of interatomic potentials. Computations were performed at various mesh points in a unit cell taking into account interaction due to all the surrounding atoms constructed on a 3 × 3 cell Mo bcc-super lattice with and without dislocation. We find that interaction potentials are significantly influenced by contributions of the next to nearest neighbour atoms. The three dimensional potentials, produced are averaged to determine axial potentials of a Mo-crystal with and without edge dislocation. Dechanneling forces for various Thomas-Fermi screening radii, using both the potentials, are compared. Axial critical angles of channeling of 2 MeV ions in such crystals show differences, that are predicted by our calculations, and can be measured experimentally.

ISSN:0033-7579    

DOI:10.1080/00337578408206052

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A description is given of a simple vitreous carbon strip heater for transient annealing of ion- implanted semiconductors. Antimony-implanted silicon samples (0.4–5.8 × 1015cm−2at 35 or 80 keV) were annealed for 15–600 s at temperatures in the range 650–910°C. Annealing was confirmed by Rutherford backscattering and electrical measurements. Supersaturated solid solutions of Sb in Si were observed with a maximum solubility of 1.0 × 1021Sb cm−3at 650°C. Electrical measurements appear to give solubilities lower than those determined by backscattering.

ISSN:0033-7579    

DOI:10.1080/00337578408206053

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The registration properties of CR-39 plastics used as detectors for alpha particles have been studied in a temperature range between −200 and 200°C. It was found that the registration efficiency remains fairly stable up to a temperature of about 60°C. The response of the detectors varies in the region between 60 and 100°C. The maximum change occurs at around 100°C where the efficiency decreases by about 50%. Some evidence obtained from X-ray scattering suggested a possible link of these changes to the change of polymeric structure in the plastics.

ISSN:0033-7579    

DOI:10.1080/00337578408206054

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Angular blocking dips around the ⟨110⟩ axis in Al single crystal of α-particles of about 2 MeV produced at a depth of 0.2 μm are calculated for several values of the mean transverse displacement υ ⊥ τ of the decaying nucleus within the range 0 ≤ υ ⊥ τ ≤ 260 pm. Calculations have been made both by an extensive multistring Monte Carlo simulation and by a continuum model with diffusion. As far as the Monte Carlo method is concerned, the influence of the (small) solid angle of particles emission and of the “single interaction” approximation has been investigated.

ISSN:0033-7579    

DOI:10.1080/00337578408206055

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Higher-order corrections have been estimated for the Bethe stopping power formula. The Z13correction formula of Jackson and McCarthy has been modified considering the screening owing to electrons around the projectile. Instead of Z14corrections predicted by Lindhard, Z12corrections have been considered as the difference between a modified Bohr formula and a modified Bethe formula. The mean excitation energy has been estimated by using the improved Bloch relation. The calculated results of stopping power are in good agreement with experimental results for various ions and targets to within a few percent for projectile energyE≥ 1 MeV/amu and several to 10% forE< 1 MeV/amu.

ISSN:0033-7579    

DOI:10.1080/00337578408206056

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Axial channeling radiation of MeV electrons in Si have been investigated using the Doyle-Turner string potential for the electron-atom interaction potential. The energy eigenvalues are determined by the variational method with an analytic trial function, where the modified Hermite polynomial is used as a trial function. Calculated photon energies for a Si crystal show good agreements with experimental ones.

ISSN:0033-7579    

DOI:10.1080/00337578408206057

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Kinetics of a void in fcc metals is simulated by the molecular dynamics technique (MDT). A void is shown to overcome the critical size through a dendrite formed of di-vacancies. The scheme for void nucleation and growth is as follows: mobile vacancy-mobile di-vacancy-dendrite-void of a critical size-void growing by adding single vacancies. This mechanism is associated with entropy contribution (the value of which is comparable with that of inner energy) to free energy at the temperature of vacancy diffusion.

ISSN:0033-7579    

DOI:10.1080/00337578408206058

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In the present paper a system of nonlinear kinetic equations is solved which describes the kinetics of nucleation and growth of clusters of defects in materials under irradiation. The developed method of calculation is applicable for examining the kinetics of accumulation of irradiation damage in the bulk under conditions of continuous and cyclic irradiation, the latter of which corresponds to the conditions of irradiation of the “first wall” of a future fusion reactor. It is shown that the cyclic irradiation conditions for the irradiation parameters being used hardly affect the nucleation of dislocation loops. The kinetics of the growth of dislocation loops is mainly determined by the total irradiation dose obtained over the whole time interval of cyclic irradiation. As regards the stage of annealing of point defects between the irradiation cycles, this does not provide any significant contribution to the growth of dislocation loops.

ISSN:0033-7579    

DOI:10.1080/00337578408206059

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Silicon was implanted at 300 K in a Pd monocrystalline film up to a dose of 1.7 × 1017at.cm−2.In situchanneling analyses were performed after various implantations with 380 keV4He++ions delivered by the implanter itself. Amorphization occurred (and the corresponding kinetics was studied) inside the Si implantation profile. The near-surface layer was only slightly disordered by the Si nuclear stopping-induced displacements. The Si atoms clearly stabilize the amorphous state.

ISSN:0033-7579    

DOI:10.1080/00337578408206060

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor