摘要:

Present work deals with atomic and electronic alterations of the quartz structure by high energy ion irradiation. The atomic structure of irradiated quartz is probed by means of X-ray absorption spectroscopies (XANES, EXAFS). Electronic structure modifications are investigated by XPS and bulk paramagnetic point defects by ESR. The experimental data suggest that for light ions (O), irradiated quartz targets preserve their long range order.E'point defects, i.e. oxygen vacancy defects, are created along the ion path with a poor efficiency (2 GeV/E'), close to the efficiency of y rays. For heavier ions (Kr, Pb), irradiation damage consists of a trail of extended defects. These extended defects are composed of an amorphous SiO2state. The density of these amorphized regions is about 4% larger than the common relaxed silica. This poorly densified silica appears similar to that obtained by neutron irradiation of quartz. E’ defects are mostly located inside these amorphous zones (>85%).

ISSN:1042-0150    

DOI:10.1080/10420159208228862

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A multi-string model is given for the computer simulation of radiation characteristics (spectral and angular densities, radiation energy losses) for axial electron channeling in crystals. The spectral and angular distributions of the radiation in the channeling and above-barrier motion regimes are obtained by simulation of the trajectories of axially channeled electrons. Besides, the simulated data on the passage of electrons through axial channels of single crystals are presented. The results are compared with experiments.

ISSN:1042-0150    

DOI:10.1080/10420159208228863

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

CR-39, a polymer widely used for nuclear track detectors, was bombarded with 500 keV protons and Ar ions, and with 2.8 MeV He ions. A mass analysis of the gas ejected during bombardment yielded CO2, CO, and H2. In the case of He ions, the amount of hydrogen was monitored during the bombardment by using elastic recoil analysis. The hydrogen spectrum was unchanged in spite of the gas loss, and it was concluded that the bombarded volume was being continuously replaced by new material, with very little carbon buildup. Since the bombardment leaves a clearly visible depression on the surface, the volume of gas ejected could be measured using a profile measuring apparatus. From this it was calculated that each 2.8 MeV He ion produces 23,000 ejected atoms. Since the range of these ions is 12.8μm, an ejection rate of one atom every 0.5 nm is determined, essentially half the atoms that the ion encounters. For 500 keV protons and argon ions, there are one atom ejected every 0.9nm and one atom every 0.16nm, respectively. We therefore propose that this gas ejection will contribute in an important way to the formation of etchable tracks.

ISSN:1042-0150    

DOI:10.1080/10420159208228864

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The change in electrical properties of TGS crystals due to induced defects created by fast neutron irradiation of two different energies (2 and 14 MeV) and different integrated neutron fluxes have been studied in the vicinity of phase transition. It is observed that the electrical conductivity increases with increase of neutron fluence up to 1.7 × 1010n · cm−2and the values of the relative change of electrical conductivity in case of 2 MeV are higher than that of 14 MeV neutrons at the same neutron fluence ()

ISSN:1042-0150    

DOI:10.1080/10420159208228865

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Two series of TeO2-P2O5And Bi2O3-TeO2-P2O5glass systems have been prepared for the present investigation. Measurements of the dc electrical conductivity in the temperature range of 300-573k for unirradiated and y-irradiation glass samples are reported. The dc electrical conductivity are found to increase with increasing y-irradiation doses. The observed increase in conductivity is attributed to the relative increase in the charge carriers that produced by y-rays. The radiation induced change in dc conductivity is found to be sensitive to temperature and glass composition.

ISSN:1042-0150    

DOI:10.1080/10420159208228866

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The kinetics of radiation defect accumulation and subsequent recovery during/after electron irradiation below 273 K, at 323 K and 373 K were investigated for the Fe-15.7 at.% Cr using positron annihilation measurements at room temperature. Formation of vacancy clusters was observed at all of the irradiation temperatures. The formation of clusters and kinetics of their accumulation point to mobility of vacancies at least at room temperature. The cluster rearrangement and variations in the cluster configuration take place during annealing.

ISSN:1042-0150    

DOI:10.1080/10420159208228867

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Temperature dependence of EPR of copper doped Cadmium Maleate Dihydrate has been studied in detail. Cupric ion is found to form a square planar complex with oxygens, at a unique interstitial site in the host lattice. The hyperfine interaction andgtensors are co-axial and temperature dependent. The temperature dependence of linewidth indicates a rapid relaxation at room temperature as compared to low temperatures. A detailed analysis of EPR data places the unpaired electron in the |x2-y2⟩ ground state orbital. The bonding parameters indicate that for the copper complex in question, the in-plane σ and π bondings are covalent in nature, whereas the out-of-plane π bonding is essentially ionic.

ISSN:1042-0150    

DOI:10.1080/10420159208228868

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Point defects produced by neutron, electron or γ-ray irradiation were studied by electrical measurements. The defect levels were analyzed by DLTS technique. Annealing of radiation induced defects at about 260°C was obtained in 20 min isochronal annealings. Annealed fraction of the 260°C stage was obtained to be 85% in arsenic-doped crystals and independent of the species of irradiating particle. The value in antimony-doped and oxygen-doped specimens were 25 and 70%, respectively. The activation energy was found to be 1.6 eV and the annealing kinetics were first order. A tentative model for the defect responsible at the 260°C stage is a vacancy complex.

ISSN:1042-0150    

DOI:10.1080/10420159208228869

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The thermoluminescence and thermo-dynamic parameters of LiKSO4: Nd were investigated. The effect of Nd dopant concentration in the range 0.1-1% as well as that of γ-irradiation dose in the range 56.3-3.24 × 105Gy were studied. The glow curves of the material are characterized by a double peak; each behaving seperately with radiation dose. The highest TL enhancement was obtained for Nd concentration of 0.5%; while irradiation dose of few hundreds Gy gave the best TL response. The thermodynamic parameters of LiKSO4doped with 0.5% Nd decreased with radiation dose up to about 5000 Gy.

ISSN:1042-0150    

DOI:10.1080/10420159208228870

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor