Discrete Convolution-Based Energy Spectrum Configuring Method for the Analysis of the Intrinsic Radiation of 176Lu

There has been considerable interest in inorganic scintillators based on lutetium due to their favorable physical properties. Despite their advantages, lutetium-based scintillators could face issues because of the natural occurring radioisotope of 176Lu that is contained in natural lutetium. In order to mitigate its potential shortcomings, previous works have studied to understand the energy spectrum of the intrinsic radiation of 176Lu (IRL). However, few studies have focused on the various principal types of photon interactions with matter; in other words, only the full-energy peak according to the photoelectric effect or internal conversion have been considered for understanding the energy spectrum of IRL. Thus, the approach we have used in this study considers other principal types of photon interactions by convoluting each energy spectrum with combinations for generating the spectrum of the intrinsic radiation of 176Lu. From the results, we confirm that the method provides good agreement with the experiment. A significant contribution of this study is the provision of a new approach to process energy spectra induced by mutually independent radiation interactions as a single spectrum.

Upper limits on the temperature of inspiraling astrophysical black holes

We present a method to constrain the temperature of astrophysical black holes through detecting the inspiral phase of binary black hole coalescences. At sufficient separation, inspiraling black holes can be regarded as isolated objects, hence their temperature can still be defined. Due to their intrinsic radiation, inspiraling black holes lose part of their masses during the inspiral phase. As a result, coalescence speeds up, introducing a correction to the orbital phase. We show that this dephasing may allow us to constrain the temperature of inspiraling black holes through gravitational-wave detection. Using the binary black-hole coalescences of the first two observing runs of the Advanced LIGO and Virgo detectors, we constrain the temperature of parental black holes to be less than about $$ 10^9 $$ 10 9 K. Such a constraint corresponds to luminosity of about $$ 10^{-16} M_{\odot }~\mathrm{s}^{-1} $$ 10 - 16 M ⊙ s - 1 for a black hole of $$ 20 M_{\odot } $$ 20 M ⊙ , which is about 20 orders of magnitude below the peak luminosity of the corresponding gravitational-wave event, indicating no evidence for strong quantum-gravity effects through the detection of the inspiral phase.

Research of Heat Losses of Solar Collectors and Heat Accumulators

The article discusses the features of heat losses by convection and radiation of flat solar collectors on the basis of a non-stationary thermal model and program. The connection of heat losses with the generalized heat loss coefficient of solar collectors is shown. The article also deals with the problem of determining the distribution of temperatures and heat losses by convection and radiation of a thermal insulation system – accumulating body (water) for a spherical heat accumulator under symmetric boundary conditions. The problem is solved numerically according to the program developed on the basis of the proposed “gap method.” The method and program for the numerical calculation of heat losses and temperatures in time in a spherical two-layer heat accumulator with symmetric boundary conditions, taking into account both incident and intrinsic radiation, have been developed. The program has been developed for a “long” two-layer cylindrical heat accumulator of solar collectors.

DYNAMICS OF THERMAL LOSSES BY CONVECTION AND RADIATION OF THE SPHERICAL HEAT ACCUMULATOR OF SOLAR PLANTS

There are needed energy (heat) accumulators to increase the efficiency of solar installations, including solar collectors (water heaters, air heaters, dryers). One of the tasks of designing heat accumulators is to ensure its minimal heat loss. The article considers the problem of determining the distribution of temperatures and heat losses by convection and radiation of the heat insulation-accumulating body (water) system for a ball heat accumulator under symmetric boundary conditions. The problem is solved numerically according to the program developed on the basis of the proposed «gap method». (Research purpose) The research purpose is in determining heat losses by convection and radiation of a two-layer ball heat accumulator with symmetric boundary conditions. (Materials and methods) Authors used the Fourier heat equation for spherical bodies. The article presents the determined boundary and initial conditions for bodies and their surfaces. (Results and discussion) The thickness of the insulation and the volume of the heat accumulator affect the dynamics and values of heat loss. The effect of increasing the thickness of the thermal insulation decreases with increasing its thickness, starting with a certain volume of the heat accumulator or with R > 0.3 meters, the heat losses change almost linearly over time. The dynamics of heat loss decreases with increasing shelf life, but the losses remain large. (Conclusions) Authors have developed a method and program for numerical calculation of heat loss and temperature over time in a spherical two-layer heat accumulator with symmetric boundary conditions, taking into account both falling and intrinsic radiation. The proposed method allows to unify the boundary conditions between contacting bodies.

Nature of Degradation in Semiconductor Lasers with Electronic Energy Pumping. Theoretical Background

. Catastrophic degradation takes place in case of reaching critical values of laser radiation density power in semiconductor lasers with electronically pumped energy made from single crystals of some compounds. It has been accompanied by mechanical destruction of the surface at resonator ends, an irreversible decrease in radiation power and an increase in generation threshold. Moreover, during the catastrophic degradation of semiconductor lasers under the action of intrinsic radiation, significant changes in the crystal structure occur within the single crystal: dislocation density reaches a value more 1012–1015 cm–2. It has been shown that initial density of dislocations and critical power density of the intrinsic radiation are inversely proportional. Thus, the degradation process of semiconductor lasers is directly related to generation and multiplication of dislocations during laser operation. Mechanical destruction of a crystal lattice occurs at critical values of laser radiation power and dislocation density. To clarify the proposed mechanism for the degradation of semiconductor lasers, it is necessary to take into account an effect of dislocations on optical properties of semiconductors. Typically, this effect is considered as follows: dislocations cause an appearance of a local deformation field and, in addition, form space-charge regions that surround a dislocation core in the form of a charged tube. The paper proposes a model of the phenomenon under study: large stresses arise in the dislocation core, leading to a displacement of individual atoms and deformation of the crystal lattice. Lattice deformation in the dislocation core leads to a local change in the width of a forbidden band. This change value is about 10–2 eV for a screw dislocation and 10–1 eV for a boundary dislocation. The mechanism of this change is that aforementioned deformation leads to a multiple rupture of electronic bonds and an increase in the electron concentration in the dislocation core to approximately value 1018 cm–3. The developed analytical model of the degradation mechanism allows to perform selection of a semiconductor and estimation of a laser operating mode under conditions of increased radiation power.

Спекл-интерферометрическая методика исследования пламени

Methods are described for recording and automated processing of the data obtained from phase-modulated speckle interferometry of optically dense (opaque to the intrinsic radiation) flames containing a condensed phase. The use of a high-speed single-frame measurement technique and special processing procedures makes it possible to determine the spatiotemporal distribution of the refractive index, based on which the flame structure can be identified. As an example, the results of investigation of the torch formed by burning a stationary medical paraffin droplet are presented.