A.V. Gradoboev

Tomsk Polytechnic University · Отделение экспериментальной физики

This paper presents the results of computational and physical studies on the production of corium and its retention in an MR’s melt trap of the Lava-B facility. A feature of the Lava-B facility used in the IAE NNC RK to study the processes occurring during a severe accident at a nuclear reactor, is the separation of the stages of the reactor core c...

The effect of active and passive power modes on the resistance of the LEDs (LEDs) made of multilayer AlGaAs heterostructures to gamma-quantum irradiation was studied. Three characteristic stages of emission power reduction during irradiation are distinguished for the studied LEDs irrespective of the power supply mode. When irradiating LEDs in the a...

This paper presents the results of experimental studies of the interaction of helium plasma with a near-surface tungsten carbide layer. The experiments were implemented at the plasma-beam installation. The helium plasma loading conditions were close to those expected in the ITER divertor. The technology of the plasma irradiation was applied in a st...

During the development of a severe accident at nuclear power plant with a core melting, corium is formed. One of the main barriers preventing outflow of corium into the environment is a melt localization device or a melt trap. The melt trap must accept and prevent the corium parameters from exceeding critical values, ensuring its retention in a con...

The obtained results suggest that 60Co γ-irradiation with small doses (D γ ~140 Gy) has a complex impact on close AuNi/n-n+-GaN{0001} Schottky contacts. Such impact manifests itself in disappearance of current steps in the initial section of the forward current-voltage curve; improvement of average values of ideality factor n and decrease of averag...

The article presents results of the study of the effect of LED power modes based on AlGaAs heterostructures (short-circuit, open circuit, and active mode with the passage of operating current during irradiation) on the resistance to γ-n-pulse exposure. Reduction of LED emission power under the influence of γ-n-pulse occurs in two stages irrespectiv...

The size effect observed in TiAlNiAu/GaN ohmic contacts (OCs) makes itself evident in the dependence of their relative electrical characteristics R SH, R SK, ρ and geometrical parameter L T on the LTLM test line width Wk . The paper explores the geometry of relief (topography) irregularities and their interface conductivity, indicating the great si...

The manuscript proposes a method to carry out of the Impulse Graphite Reactor (IGR reactor) start-up, which increases the reactor tests safety by reducing the number of reactivity control elements (control rods) of the IGR reactor control and protection system involved in the reactor operation. Based on the experimental data, the correlations betwe...

The paper shows the influence of the power supply mode (without – ―M-B‖ and with the separation of electron-hole pairs – ―M-CC‖ generated by irradiation in the built-in electric field of the pn-junction of light-emitting diodes) on the LEDs emission power changing under gamma quanta. LEDs were based on monocrystalline gallium phosphide. The maximum...

The paper presents results of a study of the influence of active and passive power modes on the resistance to gamma-quantum irradiation of the LED manufactured on the basis of AlGaAs multilayer heterostructures. Three characteristic stages of radiation power reduction are distinguished for the studied LEDs irrespective of irradiation supply mode. I...

The paper provides data on the peculiarity of change in the structure, structural phase changes and destructions in beryllium resulting from interaction with a near-wall plasma of fusion facilities. Beryllium resistance under conditions of ITER operation was evaluated, which considers factors leading to possible partial melting and erosion of panel...

The purpose of the work presented is to study the processes of phase formation in mechanically activated Ti + Al powder mixture which was exposed to low doses of gamma radiation. A two-stage treatment of the initial powder mixture of the specified composition was conducted. At the first stage, the mixture was mechanically activated in order to achi...

The paper is devoted to the analysis of existing options of under-reactor melt traps, designs and disadvantages of these traps. A variation of its own under-reactor melt trap with a heat-resistant composite coating with a fluidized bed is proposed. The description of facility for experimental studies of the heat-resistant composite coating with the...

Рассматривается проблема сварки легированных сталей в щелевую разделку. Описаны результаты исследований микроструктуры и механических свойств многослойных сварных соединений из стали 30ХГСА, выполненных традиционным и разработанным способом сварки. Установлено, что разработанный способ сварки обеспечивает надежное качество шва с улучшенной микро! с...

The blades of modern gas turbine engines are complex structures made of heat-resistant nickel alloys with a complex system of internal cavities. The article describes a method of strengthening samples of a heat-resistant Ni-Cr alloy by applying a composite coating (Cr-Al-Co + ZrO2-Y2O3). The alloy prototypes were fabricated by vacuum melting. An io...

Effects of gamma-irradiation on the process of SHS of mechanoactivated mixtures Ti-Al-C and Ti-Al-Nb were studied. Mechanical activation was performed for 7 minutes in planetary ball mill at energy intensity 40 g. SHS was initiated by induction heating with varying time of annealing. Gamma-irradiation was performed on ⁶⁰ Co isotope to absorbed dose...

In this paper we present the results of development of the optocouplers for secondary power supplies. The dies of the optical radiation emitters are based on double heteroepitaxial AlGaAs structures, and the dies of the radiation receivers are based on silicon-on-sapphire. Dies were bonded to metal-ceramic packages using the optically clear silicon...

In situ synchrotron studies of structure and phase formation dynamics in mechanically activated ( t = 7 min, power density 40 g) and mechanically activated with subsequent irradiation by γ-quanta ⁶⁰ Co powder mixture (Ti 64 wt% + Al) during high-temperature synthesis by the method of thermal explosion using induction heating are described. In situ...

Neutron degradation of LEDs based upon AlGaInP heterostructures (λ=630 nm and λ=590 nm) with multiple quantum wells are presented in the article. For the initial red LED (λ=630 nm) we can clearly distinguish three characteristic regions. In the small current region a low electron injection mode into the active region of the LEDs is observed. Furthe...

There are two distinctive regions can be identified (low (LC) and high currents (HC)) of a watt-ampere ( W-I ) characteristic of initial LEDs based upon GaP with 590 nm wavelength. The established patterns differ in the exponent. At the same time, the LC region corresponds to an increase in the efficiency of conversion of operating current into lig...

The most common technological solution for increasing the light efficiency of the LEDs based upon AlGaInP heterostructures are discussed in the paper. The creation of LEDs with the inclusion of quantum wells and quantum dots in the active region, removing the original base and placing the LED on a new substrate, the replacement of the absorbent sub...

Light-emitting diodes (LEDs) operate under conditions of ionizing irradiation. The purpose of this work is to research the action of preliminary irradiation with fast neutrons on the reliability of LEDs. The objects of research are LEDs based on double AlGaAs heterostructures. The control of the forward-bias region of the current–voltage characteri...

In this paper an experimental study of structural state changes in components of mechanically activated Ti + Al powder mixture irradiated with γ-quanta ⁶⁰Co has been carried out. As an object of study titanium powder with an average particle size of 80 μm and aluminum powder with an average size of 20 μm were selected. The initial mixture correspon...

The paper represents primary tasks, solutions of which allow to develop the exploitation modes of semiconductor devices taking into account complex and combined influence of ionizing irradiation and operation factors. The structure of the exploitation model of the semiconductor device is presented, which is based on radiation and reliability models...

The paper presents the research results of watt and volt characteristics of LEDs based upon AlGaInP heterostructures with multiple quantum wells in the active region. The research is completed for LEDs (emission wavelengths 624 nm and 590 nm) under irradiation by fast neutron and gamma-quanta in passive powering mode. Watt-voltage characteristics i...

The influence of absorbed γ-quantum irradiation doses Dγ (⁶⁰Co isotope) on the structural parameters of Ti3Al single-phase compounds is experimentally investigated. The structural characteristics are defined more accurately using X-ray diffractometry. On account of the results of structural studies, it is found that exposure to low γ-radiation dose...

In the present work, the influence of the irradiation with gamma-quanta ⁶⁰Co upon the structural and phase state of the components of the mechanically activated powder composition of Ti+Al is investigated. The phase composition, structural parameters, and crystallinity are examined by means of X-ray diffractometry. It is found out that the irradiat...

Relevance. Vermiculite is one of the representatives of geo-resources that are widely used in various industries. The expanded vermiculite is obtained by heat treating of vermiculite ore concentrates in open flame furnaces. Expanded vermiculite, due to its layered-porous structure and high reflectivity, is the base for obtaining many thermo-insulat...

We have considered the influence of preliminary irradiation by ⁶⁰Co gamma quanta on development of catastrophic failure during long-term operation of IR-LEDs based upon dual AlGaAs heterostructures. Irradiation was realized in passive power mode of the LEDs prior to aging. Two specific doses of irradiation were used. The first irradiation dose corr...

The aim of the work is studying the impact of Gunn diodes thermocompression bonding conditions upon their resistance to being radiated with protons of various energies. It was established that the tough conditions of Gunn diodes thermocompression bonding results in local mechanic stresses introduced into the active layer of the device, reduction of...

The paper presents the results obtained in the study of the change in the parameters of IR LEDs based on AlGaAs double heterostructures under ⁶⁰Co gamma irradiation with regard to irradiation temperature. The study indicated several consecutive stages of LED emissive power lowering under ionizing radiation. Increased temperature during gamma irradi...

The structural and phase state of powder samples of compounds Ti3Al and TiAl has been investigated experimentally before and after the action of small doses of gamma irradiation. To study phase and structure parameters, the X-ray diffractometry has been used. It has been established experimentally that after the same conditions of gamma irradiation...

Polyethylene terephthalate (PET) track membrane (TM) has a great opportunity to use as a bio implant in ophthalmology’s surgery due to its physical and chemical properties and biological comparability. Sterilization of medical implants can change its properties and can influence on regeneration process and success of surgical treatment. We research...

We consider the influence of preliminary irradiation by 60Co gamma quanta on emission power decrease during the operating time of IR-LEDs based upon AlGaAs double heterostructures. Irradiation was realized in passive power mode of the LEDs prior to aging. Aging under long operating time conditions was simulated by a step-stress approach. We have de...

Physical and chemical properties of the surfaces of polyethylene-terephthalate (PET) track membranes (TMs) exposed to low-temperature atmospheric plasma and to γ radiation produced by ⁶⁰Co isotopes are studied. It is established that the exposure to plasma leads to changes in the chemical composition of the surface and increases the number of polar...

This paper represents the results of investigation of preliminary fast neutron irradiation influence on reliability of IR-LEDs manufactured on the basis of AlGaAs heterostructures. It is determined that design margin of LEDs is defined by catastrophic failures that are driven by mechanical destruction of LED packages rather than their lighting tech...

At present infrared light emitting diodes are used in diverse scanning and optical security systems of nuclear and power plants. The purpose of work is research reducing radiant power during step-by-step accelerated test at higher ambient temperature. The objects of research are infrared light emitting diodes based on dual AlGaAs heterostructures....

The paper presents the results of studying characteristic deterioration of AlGaInP heterostructures with multiple quantum wells. The research was completed for light emitting diodes (emission wavelengths 623 nm and 590 nm) under fast neutron irradiation in passive mode. It has been revealed that the change in emission power and operating current un...

The results of research into degradation of volt-ampere characteristics of light emitting diodes produced on the base of AlGaInP heterostructures with multiple quantum wells are presented on the example of light emitting diodes (emission wavelengths 623 nm and 590 nm) under gamma quantum and fast neutron radiation in passive powering mode. The shif...

The paper addresses simulating technique of residual energy release inside of corium prototype based on the usage of plasmotron; describes plasmotron design and its manufacturing features; considers research results of plasmotron interaction with the corium prototype.

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 struc...

It is known that the rate of introduction of radiation defects into the Schottky barrier of GaAs and InP diodes depends on the presence of the electric field. The main aim of this research is to study the influence of the built-in electric field at the p-n junction on the resistance of dual AlGaAs heterostructure IR-LEDs under gamma rays irradiatio...

Radiation exposure and long running time cause degradation of semiconductors' structures as well as semiconductors based on these structures. Besides, long running time can be the reason of partial radiation defects annealing. The purpose of the research work is to study the “memory effect” that happens during fast neuron radiation in AlGaAs hetero...

Radiation exposure causes degradation of semiconductors' structures as well as different semiconductors based on these structures. The purpose of the research work is to study transitions in AlGaInP heterostructures with multiple quantum wells during fast neutron radiation. Objects of the research are 590 nm and 630 nm LEDs based on AlGaInP heteros...

The present work is aimed at investigation of the stability of the GaAsbased Hall sensors (pickups) to irradiation by gamma quanta. The examined objects are the gallium arsenide based Hall sensors manufactured on thin active layers by the methods of vaporphase epitaxy (VPE), molecular beam epitaxy, and ion implantation. Our research methodology inv...

At present the development of methods of layer-by-layer and line-by-line synthesis of finished prototypes and functional products made of powder materials furthers introduction of these technologies into different areas of human activities from light to heavy industry and medicine. The research has been carried out to describe how gamma radiation o...

The given paper presents the results of studying the resistance of AlGaInP heterostructures with multiple quantum wells to 60Co gamma-quantum irradiation. The research was completed for light emitting diodes (λ = 630 nm). The irradiation was completed under the passive powering mode without the imposition of the electric field while the level of ex...

The research has been carried out to describe how gamma radiation of the Co60 radioactive isotope makes an impact on the copper powder, as well as the nature of sintering by the layer-by-layer laser synthesis. The changes of the structure and properties of the powder, which generally affects the layer-by-layer laser process of products sintering, h...

Metal powders are widely used in many modern technologies, as well as they have been applied in the form of various fillers composites. Recently, in some cases, the preliminary activation of metallic powders is made to improve the compatibility of the filler and the matrix. Undertook a study describe the influence of gamma radiation radioactive iso...

The presented radiation model allows evaluating the contribution of ohmic contacts metal-semiconductor into LED radiation resistance and, thus, can be used when developing the design and the production technology of LED with required radiation resistance.

Influence of gamma radiation on sensors based on GaAs is considered. The volt-ampere characteristics and the noise spectral density of magnetic field sensors before and after irradiations were investigated. It was found stabilizing effect of gamma radiation on sensors with the dose (8-10) ·103 Gy and destroying effect at the greater doses.

Gamma degradation was investigated for AlGaInP light-emitting diodes with wavelengths in the 590 nm region. The process of degradation light output power is shown in two stages. Light-current and current-voltage characteristic of the light-emitting diodes fabricated on the basis of heterostructures with AlGaInP multiple quantum wells has possible t...

In the given article, on the basis of the standard hydrodynamic representations, the physical model of the directed destruction of metals by cutting is offered. Process of cutting of metals is considered as process of the directed destruction, i.e. process of deep plastic deformation of metal always led up to destruction on surfaces of the cutting,...

Obtained results show, that used modes of positron annealing of low-frequency (1-3 GHz) HEMT lead to rising of power and current gains (Gmax and H21 respectively). The value of cutoff frequency Ft does not decrease, and the Fmax raised. According to S-parameters of low-frequency (1-3 GHz) HEMT at high-frequency (20-40 GHz) range, one can see parame...

The electric conductivity of a laser plasma, excited at the surface of a 22KhS ceramics by a pulsed laser radiation, was studied in the presence of an external electric field oriented perpendicularly to the laser beam direction. Depending on the output laser power density, there are three characteristic regimes: (i) the absence of a laser plasma po...

The results of a study of degradation of the surface of gallium arsenide resulting from irradiation with a power excimer laser at power densities ranging from the threshold power to the power level causing local melting of the surface are presented. Two degradation mechanisms have been identified, one of which causes the formation of a thin near-s...

DLTS measurements in H+ (65 MeV)-irradiated n-GaAs reveal a broad band near 250 to 340 K which is similar to the band in neutron-irradiated samples. DLTS evaluation and the modification of this band due to post-irradiation heat treatment indicates that it is formed by two subbands superposed on each other, so the combined band cannot be resolved fu...