Thermal Annealing Of Radiation Damage Research Articles

In situ heating high-resolution TEM observation of structural recovery in metamict titanite

Besides radiation resistance, thermal recovery of radiation damage provides another critical criterion to evaluate the host phase for immobilizing high-level waste (HLW) produced by nuclear plants. Despite the increasing investigations, a comprehensive atomic-scale understanding remains elusive on thermal annealing of radiation damage in ceramics. Here, using in situ heating high-resolution transmission electron microscopy, we investigate the thermal annealing of radiation damage in natural metamict titanite (CaTiSiO5) caused by a high alpha decay dose from the incorporated U and Th during the geologic time. The recovery of the fully amorphous titanite precursor starts at 456 ℃ from the appearances of monoclinic nanoparticles 2–5 nanometers wide, and more nanoparticles form as the temperature gradually increases. At 1000 ℃, the amorphous phase recovers through epitaxial growth with titanite nanoparticles as templates. This study provides information for a unit-cell-scale understanding of the thermal stability of radiation damage in titanite-based ceramics, having significance for immobilizing HLW.

Thermal annealing of radiation damage produced by swift 132Xe ions in MgO single crystals

The annealing kinetics of the electron-type F+ and F color centers in highly pure MgO single crystals irradiated by 0.23-GeV 132Xe ions with fluences covering three orders of magnitude (Φ = 5 × 1011 –3.3 × 1014 ions/cm2) are studied experimentally via dependence of the optical absorption on preheating temperature. The annealing data are analyzed in terms of the diffusion-controlled bimolecular reactions between F-type centers and complementary interstitial oxygen ions. The behavior of the main kinetic parameters – the migration energies and pre-exponential factors – for different irradiation fluences is discussed and compared with that for other wide-gap binary materials from previous studies.

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Widely used to study surface processes and the development of topography through geologic time, (U–Th)/He thermochronometry in apatite depends on a quantitative description of the kinetics of 4He diffusion across a range of temperatures, timescales, and geologic scenarios. Empirical observations demonstrate that He diffusivity in apatite is not solely a function of temperature, but also depends on damage to the crystal structure from radioactive decay processes. Commonly-used models accounting for the influence of thermal annealing of radiation damage on He diffusivity assume the net effects evolve in proportion to the rate of fission track annealing, although the majority of radiation damage results from α-recoil. While existing models adequately quantify the net effects of damage annealing in many geologic scenarios, experimental work suggests different annealing rates for the two damage types. Here, we introduce an alpha-damage annealing model (ADAM) that is independent of fission track annealing kinetics, and directly quantifies the influence of thermal annealing on He diffusivity in apatite. We present an empirical fit to diffusion kinetics data and incorporate this fit into a model that tracks the competing effects of radiation damage accumulation and annealing on He diffusivity in apatite through geologic time. Using time–temperature paths to illustrate differences between models, we highlight the influence of damage annealing on data interpretation. In certain, but not all, geologic scenarios, the interpretation of low-temperature thermochronometric data can be strongly influenced by which model of radiation damage annealing is assumed. In particular, geologic scenarios involving 1–2 km of sedimentary burial are especially sensitive to the assumed rate of annealing and its influence on He diffusivity. In cases such as basement rocks in Grand Canyon and the Canadian Shield, (U–Th)/He ages predicted from the ADAM can differ by hundreds of Ma from those predicted by other models for a given thermal path involving extended residence between ∼40–80 °C.

Thermal Annealing of Radiation Damage in CMOS ICs in the Temperature Range -140°C to +375°C

Annealing of radiation damage was investigated in the commercial,Z-and J-processes of the RCA CD4007A ICs in the temperature range from -140°C to +375°C. Tempering curves were analyzed for activation energies of thermal annealing, following irradiation at -140°C. It was found that at -140°C, the radiation-induced shifts in the threshold potentials were similar for all three processes. The radiation hardness of the Z-and J-processes is primarily due to rapid annealing of radiation damage at room temperature. In the region -140 to 20°C, no dopant-dependent charge trapping is seen, similar to that observed at higher temperatures. In the unbiased Z-process n-channels, after 1 MeV electron irradiation, considerable negative charge remains in the gate oxide.

Thermal annealing of radiation damage in NaCl crystals studied by positron annihilation techniques

The thermal annealing of radiation damage induced by gamma radiation in NaCl crystals is studied by positron annihilation techniques. The results show that the concentration of positron annihilation centers (A center) decreases quickly at first upon heating, but then more slowly until a very slowly decreasing region, a ``pseudoplateau'' is reached. The A-center concentrations at which these pseudoplateaus are obtained depend on the temperatures at which the annealing processes are carried out. The kinetics of the annealing as observed by the positron annihilation technique is consistent with a bimolecular reaction model. The experimentally obtained activation energy for this process is ≈ 1.2 eV; this suggests the elimination of positive ion vacancies aggregates, which act as positron annihilation centers, by migrating anion vacancies at elevated temperatures.

Oscillating Structure of Thermal Annealing of Radiation Damage revealed by Neutron Diffraction

I HAVE reported the fine structure of the isothermal annealing curves of neutron irradiated solid compounds in a series of publications1–9. The structure was confirmed later by others10–12. An oscillating structure was always found for the isotherms, irrespective of the chemical constitution of the lattice and the nuclear events which produced the recoil radionuclides. The phenomenon thus seems to be based on some general property of a radiation damaged lattice. I now describe similar annealing behaviour for radiation damage detected physically, using the neutron diffraction method with irradiated single crystals of compounds similar to those studied already by radiochemical means. Tri-ethylenediamine, cobalt nitrate and chloride in the form of single crystals were reactor irradiated for 1 h in a position where the neutron thermal and fast flux were 4.18 × 1012 and 2.6 × 1011 neutrons cm−2 s−1 respectively. The absorbed gamma dose was about 30 Mrads. After irradiation the single crystal was oriented to give an intense diffracted neutron beam at the MAN neutron spectrometer of the 1 MW nuclear reactor. The diffraction spectrum for a particular lattice plane was taken before and after reactor irradiation. The maximum was shifted about 0.15 of a degree and the new peak was used to examine the variation in the intensity; the shape of the peak did not change during annealing.

Characteristics of Thermal Annealing of Radiation Damage in MOSFET's

The thermal annealing characteristics of radiation damage in p-channel MOSFETS due to irradiation by 1.5 MeV electrons as a function of time and temperature are presented. Both isothermal and isochronal annealing curves are analyzed and it is found that the activation energy of the annealing processes has a distribution in a range of 1 eV with the peak at about 1 eV. The mechanism of radiation damage and the model of thermal annealing in the MOSFETS are discussed.