摘要:

Nickel samples have been irradiated at two different dose rates with the same dose of 2.8-MeV58Ni+to a peak damage level of 13 dpa. The peak damage dose rates were ∼7 × 10−2dpa sec−1(HDR) and ∼7 × 10−4dpa sec−1(LDR). An upward shift of ∼75°C in the low-temperature limit for swelling has been observed for this increase of a factor of 100 in dose rate. The HDR results showed a peak swelling of 1.2% at 625°C, while the LDR results gave a peak swelling of 2.4% at 550°C. The LDR samples contained larger voids at lower densities than the HDR samples at all temperatures at which voids were observed. The results were compared with models for void nucleation and growth from which it was concluded that the HDR and LDR swelling curves both exhibited a low temperature regime which was void- growth-limited and a high temperature regime which was void-nucleation-limited. When temperature independent void and dislocation parameters were employed, the Brails ford and Bullough (BB) void growth model predicted that both LDR and HDR swelling would extend to much higher temperatures than was observed. When the experimentally measured parameters were employed at each point, the temperature dependence of the calculated swelling rate and that of the observed swelling agreed well for the LDR data but the resulting curves differed by ∼50°C for the HDR results. Thus, the BB theory has little quantitative predictive capacity because at present the temperature and dose rate variations of the void and dislocation parameters must be determined experimentally and even the use of these data does not necessarily give quantitative agreement. The various BB temperature shift models similarly lack quantitative predictive value since similar void and dislocation parameters enter these expressions. The temperature dependences of the void number density, the mean void diameter, and the dislocation density were only qualitatively similar when compared for the two dose rates, and a simple temperature shift did not produce reasonable coincidence between the values of these quantities obtained at the two different dose rates. This direct measurement of dose rate effects in nickel-ion-irradiated nickel indicates that, for the present, experimental measurement of dose rate effects appear to be needed in a given material before reasonably accurate predictions of swelling behavior as a function of damage dose rate can be made; further evaluation and improvement of theories of swelling is called for.

ISSN:0033-7579    

DOI:10.1080/00337577508237413

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Carbon ions have been implanted intop-type silicon at energies in the range 1.5–4.3 MeV in order to examine the doping effects of the damage. Carbon was chosen since it does not produce impurity doping and hence damage effects alone could be observed. Capacitance-voltage doping profiles showed that initially two p-type doping peaks were produced. On annealing to 400°C thep-type activity increased, then disappeared completely after a 700°C anneal. The deeper peak disappeared at a lower annealing temperature.

ISSN:0033-7579    

DOI:10.1080/00337577508237414

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Our previous model on dimer sputtering is extended to the formation of larger clusters. The general formalism for the calculation of the momentum distribution function of these clusters is given. A simple analytical expression is obtained for the distribution function of any cluster in the high energy limit. Comparison of this expression with experimental data on the energy and angle distribution of Wk+clusters at high energies shows good agreement. The experimental results on K2and KI sputtering with low energies are recompared with the theory. For the ionic crystal KI, evidence is obtained that sputtering of non adjacent K and I atoms from the lattice gives an important contribution to dimer formation. The role of the binding energyEb, of the particles with respect to the surface is discussed.

ISSN:0033-7579    

DOI:10.1080/00337577508237415

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Defects in annealed P+ion-implanted silicon (ptype), implanted to below the critical dose to form a continuous “amorphous” layer, were found to be faulted hexagonal Frank loops (∼1016/cm3, 200 Å in diameter) on the four {111} planes. A few unfaulted loops and linear defects (∼1013/cm3, ∼800 Å in length) along the ⟨110⟩ directions were also present. The loops showed contrast effects indicative of solute segregation within the loop. The displacement vectors are then of the typea/x[111] withxslightly greater than three. The loops were all interstitial suggesting that they form from the conversion and growth of small interstitial clusters formed during implantation. Segregation of dopants to these interstitial clusters could account for the poor electrical activity of phosphorus in foils implanted to below the critical dose and annealed in the 500–700° range. Studies ofn-type (P and Sb doped) foils show that defect morphology varies with foil type (n-or p-) and dopant species present prior to implantation. Evidence that the linear defects are interstitial type, that they anneal from the end near the free surface and that boron is necessary for their formation is also presented.

ISSN:0033-7579    

DOI:10.1080/00337577508237416

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The lyoluminescence response of sodium chloride to radiations of different nature and energy is discussed. Irradiation with60Co or137Cs γ-rays and90Sr/90Y β-particles gave results suggesting equal sensitivity to these radiations, whilst the response to alpha particles from241Am was only 20% of that for β-rays.

ISSN:0033-7579    

DOI:10.1080/00337577508237417

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A classical theory ′of channeling of heavy charged particles in crystal has been developed. The kinetic equations of the Focker-Plank type and their solutions for the axial and planar channeling with allowance for the inelastic scattering of particles from electrons have been obtained. A detailed analysis of the distribution of particle flux across the channel has been made. The characteristic depths at which statistical equilibrium is established have been determined.

ISSN:0033-7579    

DOI:10.1080/00337577508237418

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Electron and positron transmission experiments have been performed on MgO and Si single crystals with energies between 5 and 45 MeV. The measured axial directional effects can be interpreted in terms of the classical continuum model of positive ion channeling, if particle deflections caused by string scattering are taken into account. The influence of crystal thickness and particle energy are understood qualitatively by these classical theoretical considerations. Computer calculations were performed to give a quantitative comparison of the classical theory with experimental electron transmission profiles. Fine structure due to diffraction effects has been observed in angular distributions of electrons and positrons up to particle energies of 15 MeV.

ISSN:0033-7579    

DOI:10.1080/00337577508237419

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Studied in the present work is the focusing of parallel ion beam by a pair of close packed atomic chains of a crystal. The focal length of this system has been calculated to the approximation of continuous potential of chain in the general form and also for a number of specific potential of ion-atom interaction. Ar ion beam focusing by a ⟨110⟩ Cu chain pair has been discussed in details. For this case, the focal length has been calculated as a function ion energy using the method of computer simulation of ion trajectories in the chain field. The calculations were made on the basis of the Born-Mayer potential with various constants. A pronounced dependence of focal length on the constant in this potential has been found.

ISSN:0033-7579    

DOI:10.1080/00337577508237420

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Thin foils of niobium single crystals containing long screw dislocations with b =a/2 ⟨111⟩ have been irradiated at 900 keV in a high voltage electron microscope at room temperature. Climb of the dislocations under the electron beam lead to the formation of helical dislocations. In situ observations of their nucleation and growth are performed, and their nature is shown to be of interstitial type.

ISSN:0033-7579    

DOI:10.1080/00337577508237421

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

An anomalous penetration of oxygen can be observed in certain neutron irradiated metallic samples. A strong oxygen diffusion occurs in niobium or iron but not in nickel, molybdenum or platinum. This diffusion can only be observed when the samples are water immersed during neutron irradiation. Different initial concentrations of oxygen in the samples do not yield significantly different results. The surface state or the crystalline state of samples are of negligible importance. The oxidation products, the nature of the radiations and the penetration of hydrogen were also studied.

ISSN:0033-7579    

DOI:10.1080/00337577508237422

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor