Study of Irradiation Temperature Effect on Change of Structural, Optical and Strength Properties of BeO Ceramics When Irradiated With Ar8+ and Xe22 Heavy Ions

This paper presents the results of the study of the effect of irradiation temperature on structural and optical distortions and deformations, as well as the strength properties of BeO ceramics as a result of irradiation with Ar8+ and Xe22+ ions at a radiation dose of 5х1013 cm-2. The choice of radiation dose is due to the effect of overlapping defective areas arising along the trajectories of ions in ceramics, which makes it possible to model radiation damage caused by the effect of accumulation as a result of cascade collisions and overlapping damaged areas. The temperature range of 300-1000 K was chosen to simulate different operating conditions, as well as the possibility of simulating partial annealing of defects during irradiation at high temperatures. During the research it was established that high-temperature radiation reduces influence of size of electronic and nuclear power losses of ions of Ar8+ and Xe22+ with energy of 70 MeV and 231 MeV, respectively, on extent of radiation damage of ceramics of BeO. Irradiation at a temperature of 1000 K results in an equal 14% change in dislocation density for these particles, a comparable decrease in the yield intensity of optically stimulated luminescence by 5% and 15%, as well as microhardness by 25% and 30%, respectively.

Thermal Annealing of Implanted ²⁵²Cf Fission-1 Tracks in Monazite

A series of isochronal heating experiments were performed to constrain monazite fission-track thermal annealing properties. 252Cf fission-tracks were implanted into monazite crystals from the Devonian Harcourt Granodiorite (Victoria, Australia) on polished surfaces oriented parallel and perpendicular to (100) prismatic faces. Tracks were annealed over 1, 10, 100 and 1000 hour schedules at temperatures between 30 °C and 400 °C. Track lengths were measured on captured digital image stacks, and then converted to calculated mean lengths of equivalent confined fission tracks which progressively decreased with increasing temperature and time. Annealing is anisotropic, with tracks on surfaces perpendicular to the crystallographic c-axis consistently annealing faster than those on surfaces parallel to c. To investigate how the mean track lengths decreased as a function of annealing time and temperature, one parallel and two fanning models were fitted to the empirical dataset. The temperature limits of the monazite partial annealing zone (MPAZ) were defined as length reductions to 0.95 (lowest) and 0.5 (highest) for this study. Extrapolation of the laboratory experiments to geological timescales indicates that for a heating duration of 107 years, estimated temperature ranges of the MPAZ are −44 to 101 °C for the parallel model and −71 to 143 °C (both ~ 6–21 °C, 2 standard errors) for the best fitting linear fanning model (T0 = ∞). If a monazite fission-track closure temperature is approximated as the mid-point of the MPAZ, these results, for tracks with similar mass and energy distributions to those involved in spontaneous fission of 238U, are consistent with previously estimated closure temperatures (calculated from substantially higher energy particles) of

The Influence of Power Mode on Ir-Leds Resistance to the Irradiation with Fast Neutrons

In this paper we present the results of investigation of the power mode influence on the resistance to fast neutron irradiation of IR-LEDs based on AlGaAs heterostructures. The investigation shows that there are 2 stages of LED emissive power lowering. At the first stage the emissive power decreases due to reorganization of existing defective structure. At the second stage it happens as the result of radiation defects introduction. The rate of defects introduction that influences the emissive power lowering at the first stage in the space charge region of the embedded p-n junction is higher than in the neutral region. The forward current flowing under irradiation results in partial annealing of introduced defects and consequently to resistance growth at the first stage of emissive power lowering. The LED power mode doesn’t contribute essentially to the power lowering at the second stage while observed difference is due to decrease of contribution of the first stage to the whole process of emissive power lowering.

Thermal history of the Podhale Basin in the internal Western Carpathians from the perspective of apatite fission track analyses

The thermal history of the Paleogene Podhale Basin was studied by the apatite fission track (AFT) method. Twenty four Eocene-Oligocene sandstone samples yielded apparent ages from 13.8 ± 1.6 to 6.1 ± 1.4 Ma that are significantly younger than their stratigraphic age and thus point to a post-depositional resetting. The thermal event responsible for the age resetting is interpreted as a combination of heating associated with mid-Miocene volcanism and variable thickness of Oligocene and potentially also Miocene sediments. Extending the mid-Miocene thermal event found in the Inner Carpathians into the Podhale Basin as a likely heat source suggests that the amount of denudation in the Podhale Basin determined only on the basis of heat related to the thickness of sedimentary sequence might have be significantly overestimated. Two samples from the western part of the basin that yielded 31.0 ± 4.3 and 26.9 ± 4.7 Ma are interpreted as having mixed ages resulting from partial resetting in temperature conditions within the AFT partial annealing zone. This observation agrees very well with reported vitrinite reflectance and illite-smectite thermometry, which indicate a systematic drop of the maximum paleotemperatures towards the western side of the basin.

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.