摘要:

Mossbauer and X-ray investigations of 3 MeV proton irradiation effects in biotite are reported. Mossbauer spectra of natural biotite samples in the temperature range from 77 K to 970 K were obtained and irreversible changes caused by heating of the biotite were investigated. Changes in the Mossbauer spectra of irradiated and heated samples were found to be similar and are interpreted as a result of oxidation of Fe2+ions to the Fe3+state. It is shown both by means of Mossbauer and X-ray spectroscopy that a heavy irradiation gives rise to a formation of Fe3O4particles of a size about 0.01 μm.

ISSN:0033-7579    

DOI:10.1080/00337577608233021

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

A computer simulation model, incorporating the combined effects of binary (nuclear) collisions, thermal displacements of the lattice atoms and electron multiple scattering effects, has been used to investigate the dechannelling of ions in single crystals. The model was tested for 1.5 MeV hydrogen, deuterium and helium ions in the (100) and (110) planes of germanium. The qualitative trends predicted and the dechannelling rates calculated for these examples indicate that the model is reasonable. A significant feature of the computer model is the depth information that is obtained from it.

ISSN:0033-7579    

DOI:10.1080/00337577608233022

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The transparency coefficient,T, of thin (2.5μ) Si single crystals relative to a well collimated 8.16 MeV He ion beam has been measured as a function of angle or between the beam direction and the [110] axis of crystals rotated in the (110) plane. CurveT(α) has been found to display minima at α = 0.15°, 0.34° and 0.5°. Computer simulation of experimental conditions has shown that the first minimum is a result of competition of two processes: increase of the radius of ring-shaped angular distribution with increasing a and ion capture in the (110) planar channel. The remaining two minima are due to particle dechannelling from channel (110) resulting from resonance enhancement of transverse particle oscillations in the channel. Similar calculations have been carried out for the transition from axial [110] to planar (001) channelling. It has been shown that in this case the difference in the conditions resonance result in spatial separation of the ion beams that have passed through channels (001) with and without displaced arrangement of rows [110].

ISSN:0033-7579    

DOI:10.1080/00337577608233023

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Because the production of Frenkel defects occurs most readily along specific crystallographic directions in fee structures, the recovery mechanism by which annihilation occurs should also be related to the same crystallographic orientations. The recovery path of a diffusing interstitial requires the formation of a temporary meta-stable state as a close-pair Frenkel defect prior to annihilation. A theoretical treatment of this scheme for interstitial-vacancy recombination shows that during theIDdiffusion there is an experimentally measurable difference if the recovery forms aIBor aICclose-pair configuration in aluminum. Experimental results are given which show a difference from the theoretical predictions, and it is concluded that the assumed analytical function describing the interstitial-vacancy distribution created by a 0.4 MeV electron irradiation should be modified.

ISSN:0033-7579    

DOI:10.1080/00337577608233024

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

A method for calculating radiation effects parameters as a function of neutron energy is described. The computer code DON is used to generate damage parameters from ENDF/B nuclear data. Both integral data such as neutron spectrum averaged cross-sections and recoil energy spectra are generated. These data were used to characterize initial defect production in Al, Cu, Nb and Au in selected fission reactor, fusion reactor and fusion simulation neutron spectra. The principal differences between fission and fusion damage are the spatial characteristics of defect production and the importance of non-elastic scattering (e.g. He production). The comparison of the damage produced in one spectrum with that produced in another is dependent on the model or parameter chosen to represent the damage. This dependency is important in analyzing simulation spectra for fission and fusion reactor radiation damage problems.

ISSN:0033-7579    

DOI:10.1080/00337577608233025

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Blistering on the surface of germanium is observed, for the first time, after 450 keV Ar+ion bombardment.

ISSN:0033-7579    

DOI:10.1080/00337577608233026

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The thermal development of the long penetration tail (supertail) observed in the implantation profile of krypton in single crystalline tungsten is investigated. The supertail is formed by diffusion and becomes detectable at temperatures above about 200 K. Its exponential shape is found to be independent of the annealing temperatureT(applied between 196 and 300 K) and annealing timet(measured between 33 sec and 31 h at 200 K). The amount of implanted atoms in the supertail increases (linearly) with annealing temperature towards an upper limit reached at about 300 K. The analysis favors a trap model with trapping levels distributed between about 0.7 and 1.0 eV and in addition much deeper (irreversible) trapping sites. The diffusion coefficient D at 200 K is estimated to be greater than 6.4 × 10−15m2/sec. WithD = DOexp(−Q/kT), the activation enthalpyQis estimated to be smaller than 0.3 eV and DO between 2.5 × 10−8m2/sec and 7 × 10−8m2/sec.

ISSN:0033-7579    

DOI:10.1080/00337577608233027

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The quantum theory of charged-particle scattering by thin single crystals is approximated by a 3(2 × 2 ×N+ 1)-component wave function, whereNis the number of crystal centres normal to the incident beam. This wave function is optimized as a solution of the 3-dimensional wave equation, and shown to describe well the true 3(N3+ 1)-dimensional solution. Calculations are described for the idealized case of a simple vibration less cubic lattice with unscreened Coulomb interaction, of emergent intensity near the crystal, and the forward intensity for rotations of the crystal. Typical flux distributions and channeling dips are found. A method is described for calculations for more realistic crystal models.

ISSN:0033-7579    

DOI:10.1080/00337577608233028

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Single and double alignment backscatterings of MeV helium ions from a silicon crystal have been simulated in a computer. Angular dependences of the backscattering yield in a (110) plane for 2 MeV helium ions along (110), (100), and (111) are calculated for regular lattice positions and various interstitial positions in single alignment. In double alignment 2.8 MeV helium ions are incident on a (100) crystal plane parallel to (110) and angular dependences of the backscattering yield for detector rotation in a (110) plane along [110], [111] and [010] are calculated. In (110) and [110] the tetrahedral (T), the hexahedral (H) and so called ytterbium atom positions (Y) show a flux peak and the split (100) and the bond-centred positions (BC) have a shallow and narrow dip. In (111) and [111] the H-and the BC-positions have a flux peak and the other positions a dip. In (100) (or [010]) the BC-, H-, Y-, S-positions (BC and H) show characteristic off axis peaks and the others a dip.

ISSN:0033-7579    

DOI:10.1080/00337577608233029

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The possibility of using the optical radiation from sputtered atoms to measure concentration distributions and sputtering yields is examined. Continuous sample surface peeling is achieved by sputter-etching with energetic Ar+ion beams. It is shown that very thin layers (∼15 A), introduced in a substrate, can be detected with this technique. Hereby recoil collision processes are investigated. Sputtering yields of Ar+ions bombarding Ag, Au, Cu and Al are determined and compared to other measurements and theory. Studies of Al ions implanted into Ag have been done for energies between 50 and 120 keV, as well as 60 keV Na ions into Si. Projected ranges and range stragglings are presented and compared to theory.

ISSN:0033-7579    

DOI:10.1080/00337577608233030

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor