Annealing Of Radiation Defects Research Articles

Separation in Fe–Ni and Fe–Ni–P alloys under electron irradiation and isochronous annealing

The annealing of radiation defects in the Fe–34.7at.%Ni and Fe–34.6at.%Ni–0.1at.%P alloys irradiated with 5 MeV electrons is studied by the method of residual electrical resistivity. It is shown that, during annealing after irradiation at 80 K, vacancies become mobile in the region of 220 K with a migration energy of about 0.6 eV. In this case, vacancy-impurity complexes (clusters) are formed, and in the H36 alloy vacancy clusters are formed. Under irradiation at room temperatures, vacancy defects accumulate in the form of vacancy clusters. The dissociation of these clusters at 350–550 K results in the appearance of freely migrating vacancies and enhanced self-diffusion. This leads to radiation-accelerated ordering processes in the Fe–Ni and Fe–Ni–P alloys. At temperatures around 800 K, homogenization of the solid solution occurs. The details and stages of the dissociation of vacancy-impurity complexes are discussed.

Isothermal annealing of radiation defects in silicon bulk material of diodes from 8” silicon wafers

The high luminosity upgrade of the LHC will provide unique physics opportunities, such as the observation of rare processes and precision measurements. However, the accompanying harsh radiation environment will also pose unprecedented challenged to the detector performance and hardware. In this paper, we study the radiation induced damage and its macroscopic isothermal annealing behaviour of the bulk material from new 8” silicon wafers using diode test structures. The sensor properties are determined through measurements of the diode capacitance and leakage current for three thicknesses, two material types, and neutron fluences from 6.5· 1014 to 1 · 1016 neq/cm2.

Low-temperature radiation damage studies in single-walled carbon nanotube bundles by hopping conductance

The paper shows the results of studying radiation defects in single-walled carbon nanotube bundles at low temperatures. The data were obtained in a unique experiment that inseparably combines 1 MeV electron irradiation at a temperature of ∼10 K and electrical conductivity measurements over a wide temperature range of 5–300 K. The experiment allowed us to reveal and separate the influence of stable and unstable radiation defects on the electrical properties of SWCNTs. It is shown that the 2D Mott variable range hopping conduction regime exhibits resistance to electron irradiation. The hopping conductivity is the dominant charge transfer mechanism in the temperature range of 5–50 K in both the pristine and irradiated SWCNT samples. It was found that the parameters of hopping transport demonstrate high sensitivity to the introduction and annealing of radiation defects. The low-temperature electron irradiation revealed the possibility of the emergence of an additional conduction channel in the irradiated SWCNTs. This channel demonstrates thermally activated behavior with a low activation energy of ∼0.5 meV at temperatures of 5–50 K. The obtained data indicate that unstable radiation defects create conditions for the possibility of impurity band conduction in SWCNT bundles.

On Modification of Mismatch-Induced Stresses during Microwave Annealing of Radiation Defects Generated during the Radiation Processing of a Heterostructure

On Modification of Mismatch-Induced Stresses during Microwave Annealing of Radiation Defects Generated during the Radiation Processing of a Heterostructure

Влияние длительного отжига, моделирующего параметры сухого хранения ТВЭЛов ВВЭР-1000, на механические свойства оболочек из сплава Э110 в продольном направлении

Presented are the results of mechanical tensile tests of longitudinal (segmental) samples cut from the midsection of claddings spent as VVER-1000 FA during one- and six-year campaigns and subject to thermal tests in helium at 480 °С during 468 full days. An average burnup of these fuel rods achieved ~ 20 and ~ 70 (MW·day)/kg U, respectively. The tests followed the examinations for cladding mechanical properties performed using the tests results for ring samples cut from the specified fuel rods. These fuel rods were tested in the experiments to determine impact of long-term thermal tests that model dry storage conditions on mechanical properties of Zr E110 claddings. Based on mechanical tests results at room temperature and at 380 °С there was determined as follows: ultimate strength sв, yield strength s0,2 and total relative elongation d0 of claddings length-wise on the fuel rod segments at the fuel column midsection. The obtained characteristics were compared to corresponding values for initial (unirradiated) cladding tubes and mechanical test results of the ring samples in the transverse direction. Long-term thermal tests have led to partial return to initial (before operation) values sв, s0,2 and d0 of radiation-hardened claddings; this return was more prominent in the longitudinal direction than in the transverse one. A radiation hardening decrease was accompanied with an increase in total relative elongation values in both cladding directions. Anisotropy of yield strength has changed as well. These changes can be explained by partial annealing of radiation defects, which are obstacles to dislocation movements during cladding strain. The morphology of above radiation defects is different in various sliding planes in texturized grains of cladding material.

Thermal annealing of radiation defects in MgF2 single crystals induced by neutrons at low temperatures

Primary radiation defects in ionic solids consist of Frenkel defects – pairs of defects - anion vacancies with trapped electrons (F-type centers) and interstitial ions. Upon temperature increase after irradiation, the electronic F-type centers are annealed due to recombination with mobile interstitials. Analysis of the recombination (annealing) kinetics allows us to obtain important information on the interstitial migration. At high radiation doses more complex dimer (F2-type) centers are observed in several charge states, which are well distinguished spectroscopically. We analysed here available experimental kinetics of the F2-type center annealing in MgF2 in a wide temperature range (300–1000 K). The results of the electron, neutron and ion irradiation are compared.The phenomenological theory of the recombination kinetics of radiation defects takes into account the interstitial ion diffusion and recombination with the F2-centers as well as mutual sequential transformation with temperature growth of three types of experimentally observed dimer centers: F2 (1); F2 (2), F2 (3) (which differ tentatively by effective charges with respect to the host crystalline sites: 0, +1, +2).

Formation and annealing of radiation defects in silicon, implanted with hydrogen ions

Energy spectrum of radiation defect levels in n-type epitaxial silicon irradiated with 300 keV hydrogen ions was studied by DLTS (deep level transient spectroscopy) method. The increase in the amplitude of DLTS peak with the increase in the temperature of its registration was found. This indicates the formation of areas of defects accumulation with displacement density lower initial level of doping. After exposure of irradiated samples at room temperature for several months, these areas decay with isolated point A-, E-centers and hydrogen defects with an Ec – 0.31 eV level formation. It is shown that complexes with an Ec – 0.31 eV level are formed by attaching hydrogen atoms to A-center. At Т > 150 °С, this defect begins to anneal, and at the same time A-center concentration is increased.

Microstructure and Mechanical Properties of the Fuel Cladding in VVER-1000 after the Thermal Tests That Model Dry Storage Conditions

The mechanical properties, the dislocation structure, and the morphology of phase precipitates in the E110 alloy fuel claddings worked in the fuel assemblies of a VVER-1000 reactor to a fuel burn-out of 20 and 70 (MW day)/kgU are studied. The influence of the thermal conditions that model the fuel element dry storage conditions on the annealing of radiation defects and the recovery of the mechanical properties of the claddings is analyzed.

The Increase of the Lifetime of the Onboard Electronics of Spacecrafts By High-temperature Annealing of Radiation Defects

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Effects of impurities on the rate of radiation creep and vacancy swelling in Fe-based austenite alloys

In the framework of the model of radiation-enhanced diffusion in the systems with impurities, effects of the formation of “vacancy–impurity atom” complexes on accumulation and annealing of radiation defects, rate of the growth of vacancy voids, and radiation creep in Fe-based austenite alloys are investigated. The temperature dependences of the steady-state concentration of radiation point defects, the concentration of vacancy complexes, and the effective coefficient of mutual recombination of radiation defects in materials with impurity complexes with a different bonding energy are calculated. The possibility of the suppression of the vacancy swelling and radiation creep effects due to formation of “vacancy–impurity atom” complexes having a high bonding energy is shown.

Effect of titanium doping on accumulation and annealing of radiation defects in austenitic steel 16Cr15Ni3Mo(0-1)Ti at low temperature (80 K) electron irradiation

The effect of titanium doping on accumulation and annealing of radiation defects was investigated in austenitic stainless steel 16Cr15Ni3Mo under low temperature (80 K) electron irradiation. Steel has been taken in the quenched, aged and separation of solid solution states. The data obtained on the accumulation of radiation defects and their evolution during isochronous annealing. The types of defects and its complexes and the activation energy of the processes taking place with their participation is identified. The mechanisms of radiation- induced processes and the effect of titan doping is discussed.

Accumulation and annealing of radiation defects and the hydrogen effect thereon in an austenitic steel 16Cr15Ni3Mo1Ti upon low-temperature neutron and electron irradiation

The effect of hydrogen, accumulation and annealing of radiation defects on the physicomechanical properties of an austenitic Kh16N15M3T1 steel (16Cr15Ni3Mo1Ti) has been investigated upon low-temperature (77 K) neutron and electron irradiations. It has been shown that, when its concentration is about 300 at ppm, hydrogen reduces plasticity by 25%. The presence of helium (2.0–2.5 at ppm) introduced by the tritium-trick method exerts an effect on the yield strength and hardly affects embrittlement. Upon both electron and neutron irradiation, there is a linear relation between the increment of the yield strength and the square root of the increment of the residual electrical resistivity (the concentration of radiation defects). The annealing of vacancies occurs in the neighborhood of 300 K (energy for vacancy migration is 1.0–1.0 eV). Vacancy clusters dissociate near 480 K (energy for dissociation is 1.4–1.5 eV).

High temperature ion irradiation effects in MAX phase ceramics

The family of layered carbides and nitrides known as MAX phase ceramics combine many attractive properties of both ceramics and metals due to their nanolaminate crystal structure and are promising potential candidates for application in future nuclear reactors. This investigation examines the effects of energetic heavy ion (5.8 MeV Ni) irradiations on polycrystalline samples of Ti3SiC2, Ti3AlC2, and Ti2AlC. The irradiation conditions consisted of midrange ion doses between 10 and 30 displacements per atom at temperatures of 400 and 700 °C, conditions relevant to application in future nuclear reactors and a relatively un-explored regime for this new class of materials. Following irradiation, a comprehensive analysis of radiation response properties was compiled using grazing incidence X-ray diffraction (XRD), nanoindentation, scanning electron microcopy (SEM), and transmission electron microscopy (TEM). In all cases, XRD and TEM analyses confirm the materials remain fully crystalline although the intense atomic collisions induce significant damage and disorder into the layered crystalline lattice. X-ray diffraction and nanoindentation show this damage is manifest in anisotropic swelling and hardening at all conditions and in all materials, with the aluminum based MAX phase exhibiting significantly more damage than their silicon counterpart. In all three materials there is little damage dependence on dose, suggesting saturation of radiation damage at levels below 10 displacements per atom, and significantly less retained damage at higher temperatures, suggesting radiation defect annealing. SEM surface analysis showed significant grain boundary cracking and loss of damage tolerance properties in the aluminum-based MAX phase irradiated at 400 °C, but not in the silicon counterpart. TEM analysis of select samples suggest that interstitials are highly mobile while vacancies are immobile and that all three materials are in the so-called point defect swelling regime between 400 and 700 °C. All results are consistent with previous work involving traditional and MAX phase ceramics. Results show the aluminum MAX phases are not fit for application near 400 °C and that the silicon MAX phase is more damage tolerant at 400–700 °C.

On the electronic properties of GaSb irradiated with reactor neutrons and its charge neutrality level

The electronic properties and the limiting position of the Fermi level in p-GaSb crystals irradiated with full-spectrum reactor neutrons at up to a fluence of 8.6 × 1018 cm−2 are studied. It is shown that the irradiation of GaSb with reactor neutrons results in an increase in the concentration of free holes to p lim = (5−6) × 1018 cm−3 and in pinning of the Fermi level at the limiting position F lim close to E V + 0.02 eV at 300 K. The effect of the annealing of radiation defects in the temperature range 100–550°C is explored.

Simulation of the low-temperature stage of annealing of radiation defects in BCC iron using the molecular dynamics method

A procedure for the simulation of the low-temperature stage of annealing of irradiated α iron is suggested. Based on the method of molecular dynamics, the reaction rate constants and the energies of activation for the recombination of Frenkel pairs are calculated. For the simulation of the ID and IE stages, the coefficient of diffusion of interstitials is calculated. The calculations are performed for three different potentials of interaction of iron atoms. All three potentials give close results for the majority of the configurations of Frenkel pairs considered. A comparison of the calculated annealing curve with the experimental curve of the stage I is given. Based on this comparison, a correspondence between different configurations of close Frenkel pairs and peaks of the experimental curve has been established. It is shown that one peak can be associated with several configurations of close pairs.

Recovery of the mechanical properties of an irradiated E110 alloy

The evolution of the structure-phase state of an irradiated E110 alloy (Zr-1% Nb), which is used in the production of fuel element claddings of slow-neutron reactor, is studied. The possible influence of the structure on the deformation behavior of the E110 alloy is analyzed in the α region. An equation for calculating the degree of recovery of the mechanical properties induced by annealing of radiation defects is established. A procedure for calculating the yield strength of the E110 alloy is developed with allowance for irradiation and annealing of radiation defects.

Anomalous distribution of germanium implanted into a SOI dielectric layer after the annealing of radiation defects

The germanium-distribution profile is investigated in a Si/SiO2/Si structure after the implantation of 74Ge into SiO2 dielectric layer, bonding with the Si device layer, and high-temperature annealing. The anomalously high transport and accumulation of 74Ge atoms near the SiO2/Si interface far from the bonded boundary is found. The observed 74Ge distribution is beyond the framework of the existing model of diffusion of Ge in Si and SiO2 after postimplantation annealing. A modified model of diffusion of Ge atoms near the Si/SiO2 interface qualitatively explaining the observed features is proposed.

Influence of Overlayer and Optimization of Annealing Time on Distribution of Dopant in an Implanted-Heterojunction Rectifier

In this paper we analyzed redistribution of a dopant, which implanted in a heterostructure, during annealing of radiation defects. The annealing has been done after overgrowth of the damaged during implantation area. The analysis has been verified recently obtained effects of increasing of sharpness of implanted-junction rectifier and homogeneity of distribution of dopant in enriched by the dopant area. At the same time using of overlayer gives us possibility to additionally increase homogeneity of dopant distribution.

Electrophysical and Optical Properties of 4H-SiC Irradiated with Xe Ions

A comparative research of the cathodoluminescence and electrical characteristics of the samples 4H-SiC irradiated with high energy Xe ions (167 MeV) in wide range fluencies 4x109 –1x1011 cm-2 at temperatures 250C and 5000C are presented. After irradiation these samples were thermal annealed at 5000C for 30 min. Far-action effect at a depth of more than one order of magnitude of stopping distance was observed under Xe ions irradiation in 4H-SiC. An increase of the ion Xe fluencies increased the concentration of radiation-induced defects that resulted in rise of the compensation effect of conductivity in samples. Irradiation of 4H-SiC by Xe ions at 5000C was accompanied with "dynamic annealing" some low-temperature radiation-induced defects, which led to a partial recovery of the electrical characteristics of devices. The thermal annealing of irradiated samples led to additional partial annealing of radiation defects, which increases the radiation resource of devices based on 4H-SiC.

The Conductivity of Indium Phosphide Irradiated by Fast Electrons

In this work, studied electrical conductivity(s) and annealing of radiation defects in crystals of n-InP are irradiated by electrons energy of 6 MeV and doses of 1017 el/cm2 (centimeter) and 2 × 1017 el/cm2 (centimeter). It is shown that alongside point defects (in the form of complexes with impurity atoms in crystals of n-InP) also form the complex defects of the type of disordered areas, annealing of which proceeds at T > 300°C that binds accumulating radiation defects.