摘要:

The use of various approximations in calculating proton projected ranges has been studied by the analytical and the Monte Carlo methods. A correction is presented for the projected ranges given in the compilation (Andersen and Ziegler: Hydrogen Stopping Powers and Ranges in All Elements). The greatest correction factors at 1, 10, 100 and 1000 keV are 3.5, 2.1, 1.4 and 1.2, respectively. The corrections result from the inclusion of the tabulated electronic stopping power values in the calculation of the projected ránge to the total range ratio and from the estimation of the effect of the reflection. The Monte Carlo calculations show the electronic straggling to be a remarkable factor in the width of the proton range distributions at reduced energies larger than of the order of 100.

ISSN:0033-7579    

DOI:10.1080/00337578208237493

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The angular distribution of 2.8 MeV helium ions backscattered from silicon crystals containing self-interstitials has been calculated by channeling computer simulations for a double alignment channeling configuration. The structures of the self-interstitial defects are assumed to be the split <110> interstitial and the split <100> di-interstitial with various inter-atomic distances. The obtained profiles of the backscattering yield are found to show shapes characteristic for each structure which can be used for differentiating between these structures. When comparing these profiles with experimental profiles obtained with the same double alignment channeling configuration in a previous study one finds reasonable agreement for the split <110> interstitial defect with an inter-atomic distance of 1.76 Å.

ISSN:0033-7579    

DOI:10.1080/00337578208237494

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Studies relating to the development of microstructure using pulsed electron and cyclotron beams are very useful in understanding damage effects in pulsed fusion reactors. In this paper we give some exact results to link the evolution of micro-structure during pulsing with that during continuous irradiation, since the effects in the latter case are relatively well understood. Two pulsing time regimes are considered: pulsing times (a) smaller and (b) larger. than microstructural evolution time constants. In both these cases the adiabatic approximation can be used to decouple the point defect variables from the microstructural variables. In case (a) for pulsed electron irradiation and for relatively small pulsing times in cyclotron irradiation the evolution of the microstructure can be exactly simulated by continuous irradiation using an appropriately determined dose rate. A similar analysis is made for case (b) and several effects encountered in continuous irradiation are shown to manifest themselves in pulsed irradiation. A general formalism is developed to determine the equivalent continuous irradiation parameters like dosc rate which will simulate the microstructural development under pulsing. Our treatment is semiquantitative and is based on the analysis of the trajectories in the phase space. The results presented provide a simple practical approach for interpreting and understanding experimental observations.

ISSN:0033-7579    

DOI:10.1080/00337578208237495

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Nous avons étudié pardes mesures de résistivité é lectrique effé ctué es pendant Irradiation aux neutrons rapides i 20 K, la creation de difauts dans des alliages Cu3Au et CuAu ordonnés et dé sordonnés. Lés résistivités moyennes des paires de Frenkel, less volumes de recombinaison, les taux de production d'atomes deplaces et de defauts d'antistructure sont estimes.L'extrapolation des courbes de production suggere que I'on obtient i saturation I'etat totalement desor-donne, quel que soit I'etat de depart, pour nos conditions d'irradiation. Un dkbut de mise en ordre se produit lors de recuits a 300 K pour I'alliage CuAu. Les caracteristiques de migration de I'interstitiel semblent tres differentes dam les alliages ordonnes et desordonnes.

ISSN:0033-7579    

DOI:10.1080/00337578208237496

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The effect of nuclear reactions upon the formation of energy spectra of primary knocked-on atoms (PKA) and the rate of primary radiation defect formations under irradiation by protons, neutrons and a-particles is considered. Calculations were performed by using the original technique which correctly accounted the peculiarities of different nuclear reaction channels within the frame of the statistical theory. As an example the considerable differences of separate reaction channels and their influence upon the defect formation processes are shown by irradiation of Cu. The summary contribution of nuclear reaction to the radiation damage of Cu has been analysed. It is shown that it may become a dominant one at neutron energies more than 4 MeV and proton ones more than 27 MeV.

ISSN:0033-7579    

DOI:10.1080/00337578208237497

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A detailed study of dechanneling by dislocations has been carried out. Dechanneling measurements on dislocations produced by ion implantation in silicon were performed as a function of incident energy, charge number of particles, target temperature, and channeling direction. Concentration and structure of dislocations were determined by TEM The theoretical dependences of the dechanneling by dislocations from ion energy and charge number are confirmed experimentally. The results show, that Quërts model overestimates the dechanneling in the axial case by a factor of about 4–5. A better consistence between experimental and theoretical results is received using van Vliet's model which also describes the measured temperature dependence of axial dechanneling. For planar dechanneling a good agreement is found between experimental and theoretical results. The detection limit for dislocations is determined to about 2 × 109dislocations per cm2in the axial case, whereas for planar channeling 2–4 × 108dislocations per cm2should be still detectable.

ISSN:0033-7579    

DOI:10.1080/00337578208237498

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In their theory Meyer, Klein and Wedell consider the electronic stopping in an insufficient way, since both the nuclear and electronic energy loss in a single collision are assumed to be proportional to the square of the scattering angle. This assumption, however, is only fulfilled for the nuclear energy loss (in the small-angle approximation). In this paper, energy-angle distributions are calculated using more realistic distributions for the electronic energy loss-a Gaussian distribution and a distribution, calculated by means of the Landau-Vavilov equation and Firsov's formula for the electronic energy loss in a single collision.

ISSN:0033-7579    

DOI:10.1080/00337578208237499

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In the present work, anomalous shapes of free radical (FR) accumulation curves Found under PMMA copolymers irradiation in the T ≥ 300°K temperature range have been studied. With the irradiation dose increase the FR concentration in PMMA increases up to a definite maximal value and then starts falling. It is stated that appearance of slopes on the FR accumulation curves is not associated with possible changes of the FR relaxation characteristics. The second order of the FR decay reactions is estimated with the activation energy E = 8.3 kcal/mol. It is suggested that the FR decay processes in the irradiation temperature range T ≥ 300°K are due to the fast decay of macrochains according to the “unzipping” mechanism.

ISSN:0033-7579    

DOI:10.1080/00337578208237500

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A Penning type ion source has been developed for the application in definite sputtering experiments and surface etching. The source produces ion currents up to 200μA for energies between 2.5 and 50keV. By electrostatic ion optics the beam diameter can be varied From 0.3 to 20 mm by changing the focusing conditions.

ISSN:0033-7579    

DOI:10.1080/00337578208237501

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The interaction of migrating Al self-interstitials with Co atoms has been investigated in the same dilute AlCo alloys which were used previously for Mössbauer spectroscopy experiments. Resistivity damage rate and recovery experiments were performed in the temperature range 50 K to 150 K. The effective capture radius of Co for migrating Al self-interstitials was found to be so large that correction terms had to be applied in the analysis of the damage rate data. The capture radius decreases slightly with increasing irradiation temperature. The resistivity contribution of a Co-Al interstitial complex was found to be considerably less than the sum of the resistivity contributions of an isolated solute Co atom and an Al self-interstitial. The results are explained by a model, which assumes that Al self-interstitials are trapped both at deep and shallow traps, and are compared with Mössbauer data of the same alloys.

ISSN:0033-7579    

DOI:10.1080/00337578208237502

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor