Broadband superluminescent diodes based on quantum wells
Broadband superluminescent diodes based on quantum wells
A. A. Mikheeva$^1$, A. A. Turkin, A. A. Marmalyuk
Today, amplified spontaneous emission (superluminescence) is an important effect both in injection lasers and in superluminescent diodes. In the latter, this phenomenon allows achieving the widest emission spectrum of the device at a sufficiently high output power, which is an undeniable advantage for a wide class of practical applications. Due to the relevance of the problem of creating broadband superluminescent diodes (SLDs), it seems promising to analyze the best way to broaden the spectrum of these devices depending on the design of their active region. To do this, it is necessary to carry out theoretical modeling of optical gain in various designs of SLD active regions, as well as to study the behavior of the spontaneous radiative recombination rate with increasing wavelength in these structures. When constructing the gain spectrum, it is possible to draw a conclusion about which optical transitions in the quantum well make the greatest contribution to the gain at a certain injection current. The analysis of such important effects allows to construct the calculated spectra of the SLD output power and to calculate the width of each spectrum at half-height at different injection currents. In addition, in order to understand which of the active media designs allows to create an effective broadband superluminescent diode, it is necessary to analyze the magnitude of the spectral dip between the maxima in the corresponding emission spectrum. The work shows that the broadest SLD with a small spectral dip can be created on the basis of one quantum well, in which two optical transitions are involved in the emission process.
Show AbstractExcited states of triply heavy tetraquarks
Excited states of triply heavy tetraquarks
V. O. Galkin$^1$, E. M. Savchenko$^{1,2}$
Masses of ground and radially and orbitally excited states of triply heavy tetraquarks with a pair of open and hidden heavy flavors (charm, bottom) were calculated within the relativistic quark model, based on the quasipotential approach and QCD. A tetraquark is considered as a bound state of a diquark with an antidiquark. Diquarks are treated as color--triplet states. Calculations take into account all relativistic effects (spin--independent and spin--dependent) and finite size of diquarks. Obtained results are compared with the strong fall--apart decay thresholds into a pair of heavy and heavy--light mesons. Tetraquark states that are most promising candidates for experimental searches are identified.
Show AbstractProblems of temperature control in laser metalworking using a thermal imager
Problems of temperature control in laser metalworking using a thermal imager
A. A. Gajna$^1$, A. A. Mozhaiko$^2$
The paper investigated the accuracy of temperature measurements during laser hardening of structural steel using a thermal imager operating in the mid-infrared range (8-14 microns). Experiments were conducted on installations equipped with fiber lasers, LENS 750 and ЛС-10. Several factors have been identified that affect the accuracy of measurements. These include the reflection of laser radiation, the camera resolution, incorrectly adjusted emission coefficients, and the interaction between laser radiation and air during discharge. In order to improve the accuracy, several methods have been proposed. These methods include the use of optical filters, optimization of the observation distance, and correction of emission coefficients. The study's results indicated the need for comprehensive calibration of the system in order to ensure accurate surface temperature measurement.
Show AbstractAmplitude-phase characteristics of images of fractal structures
Amplitude-phase characteristics of images of fractal structures
P. V. Korolenko$^{1,2}$, R. T. Kubanov$^1$, A. Yu. Mishin$^1$
Based on numerical modeling, the scaling (scale invariance) of spatial spectra of amplitude and phase images of fractal structures in a general optical system was estimated. The relevance of the study is due to the key role of spatial radiation spectra in the processes of optical information perception and processing. Particular attention is paid to the properties of stochastic light structures, which are widely used in art therapy and ophthalmology. For their construction, the properties of the two-dimensional Mandelbrot-Weierstrass function, as well as the properties of the stochastic model of constructive fractals, were used. Despite the disordered (speckle-like) nature of the field distribution in the generated structures, their spatial spectra had a fractal shape with clearly expressed scaling. After passing through the optical system of the initial field distribution, the spectrum contrast decreased, but the shape of the distribution of low-frequency components had a certain stability. Both amplitude and phase images had this property. With the growth of the fractal dimension of radiation, the region of stable arrangement of spectral components expanded, and with the broadening of the scattering function of the optical system, it sharply decreased. The scaling characteristics in images formed in coherent and incoherent light were compared. Their comparison showed that due to the wider transfer function of the optical system, distortions of spatial spectra in incoherent light are less significant. The study indicates the prospects of using fractal speckle distributions in medicine during light therapy sessions.
Show AbstractAtomic H over crystal surface: a variational approach
Atomic H over crystal surface: a variational approach
A. V. Tolokonnikov, P. K. Silaev
We study the behavior of the lowest electron level of a hydrogen atom confined in the semi-infinite space with a plane surface applying variational methods. The properties of the adsorbent are modeled by the parameter of the Robin boundary condition imposed on the electron wave functions at the boundary. We consider the case of crystalline adsorbent, so we assume that the parameter in Robin condition is a periodoc function. It is shown that the periodicity of the parameter should be taken into account when choosing a trial function. Trial wave funtion should provide the correct relationship between the normal derivative and the wave function value at each point of the boundary and have an antinode at the vicinity of the atomic nucleus. We perform a сomparison of the results obtained via the variational approach and via direct numerical calculations.
Show AbstractGravitational bremsstrahlung by electromagnetic interaction
Gravitational bremsstrahlung by electromagnetic interaction
Yu. V. Grats, P. -. Spirin
We revisit the problem of classical gravitational bremsstrahlung which occurs by collisions of ultra-relativistic charges. The collision is characterized by the Lorentz-factor~$\gamma$ and the impact parameter~$b$. Within the perturbation theory, we compute the total energy, radiated as a gravitational wave, as well as numerous spectral, angular and polarization distributions. The most of radiation is emitted into a beaming cone with linear angle of order~$1/\gamma$. The average frequency is of order~$\gamma^2/b$.
Show AbstractDevelopment of a graphical shell for the ion beam therapy planning system
Development of a graphical shell for the ion beam therapy planning system
E. V. Parmenova, O. P. Yushchenko
A description of the graphical shell is presented. It was developed for the planning system of the projected ion radiation therapy center on the basis of the operating Accelerator complex U-70 of the NRC “Kurchatov Institute” - IHEP in Protvino. The graphical interface is implemented in Qt. Its functionality is based on the modular base of the ion beam therapy planning system. The current version of the shell is related to the implementation of the module for working with DICOM files.
Show AbstractDevelopment of a setup for calibration of ionization chambers and feedback sensors of the extracted carbon ion beam with activation detectors
Development of a setup for calibration of ionization chambers and feedback sensors of the extracted carbon ion beam with activation detectors
A. G. Vasilyeva$^1$, M. Yu. Kostin$^1$, V. A. Pikalov$^1$, A. A. Yanovich$^1$
This paper presents a radiometric experimental setup operating on the γ-γ-coincidence principle for calibration of ionization chambers and feedback sensors of the extracted carbon ion beam with activation detectors. In this case, an activation detector made of pure carbon with a natural isotope mixture and the 12C(12C,X)11C reaction are used. The setup ensures the measurement of sample activity with an error of about 3%. A block diagram of the setup and its description are provided, as well as a description of the process of measuring its registration efficiency using a control reference source 22Na. The registration efficiency of the radiometric setup was measured and is estimated at 60.1%. The working prototype of this radiometric setup has already been used for several sessions of operation of the U-70 accelerator complex when working with carbon ions with an energy of 400-450 MeV/nucleon to calibrate the plane-parallel ionization chamber developed and manufactured by IHEP. A manual for the operation of the setup and a technique for performing measurements are being prepared.
Show AbstractThe effect of proton radiation on K-208 glass
The effect of proton radiation on K-208 glass
I. S. Kuznetsov
As a result of the experimental study of the effect of protons with energies of 20 and 30 keV, typical for hot magnetospheric plasma (HMP), on the protective glass for K-208 solar batteries, carried out using an atomic force microscope, it was found that gas-filled bubbles and microcracks are formed in the glass in the case when the proton energy is 30 keV. The initial hypothesis is that the specified structural changes occur due to the field migration of sodium ions in the field of protons injected into the glass. In this paper, the passage of proton radiation with energies of 20 and 30 keV is simulated using the Geant4 package. It was found that the depths corresponding to the peak concentrations of protons injected into the K-208 glass are 240 and 350 nm, respectively, and the overwhelming majority of protons settle in a thin layer near these depths. The paper also presents the energy release curves for protons with the specified energies. It has been established that the main mechanism of energy loss by protons is ionization braking, which occurs intensively from the very beginning of proton movement through glass. Based on the results obtained using Geant4, the electric field inside the glass is calculated in cases where the sample is on a dielectric substrate and on a grounded metal substrate.
Show AbstractNumerical modeling of temperature field in the system of graphite crucibles during electric arc synthesis of metal carbides and borides
Numerical modeling of temperature field in the system of graphite crucibles during electric arc synthesis of metal carbides and borides
D. E. Stovpets$^1$, G. A. Bleykher$^1$, A. Y. Pak$^2$
The increasing demand for materials with unique physical properties creates the need for new methods of obtaining such materials. One of the most promising is the method of synthesis of substances using energy of arc discharge generated in atmospheric conditions, in this way it is possible to obtain carbides and borides of various metals. This method is distinguished by the possibility of realization in open air environment and relatively short duration of working process. One of the problems that arise in the development of technologies based on this method is to find the most appropriate operating parameters of the set. The solution of this problem only by experiment is very resource-consuming. It is advisable to use numerical modeling here. The proposed paper describes a numerical model of thermal processes in an electric arc reactor based on the heat conduction equation with a surface heat source. Using experimental measurements the heat transfer coefficient between the reactor elements is determined. The operability of the developed numerical model and the method of setting the surface heat source is demonstrated. The numerical model will be used to optimize the parameters of the arc plasma source in the practical implementation of materials synthesis using the method described here.
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