Application of CCD and CMOS devices in the millimeter and submillimeter wavelength ranges
Application of CCD and CMOS devices in the millimeter and submillimeter wavelength ranges
I. N. Nikolaeva
The terahertz (THz) frequency range in the electromagnetic radiation spectrum occupies an intermediate position between the infrared and microwave ranges and the radiation within it has the properties of both, i.e. it has a low divergence and is able to penetrate through non-metallic materials. Currently, the existing THz radiation receivers are inert, have low spatial resolution and high cost, which raises the question of finding suitable affordable analogues. The solution may be the use of matrix photodetectors based on charge-coupled structures (CCD) and metal-oxide-semiconductor (CMOS) structures operating in the mode of tunneling photoelectrons into the conduction band due to an external laser source. The paper considers the features of registration of modulated electromagnetic radiation in the extended millimeter and submillimeter wavelength ranges using CCD and CMOS matrices.
Show AbstractImprovement of the thermoregulation system of the quantum frequency standard with a rubidium gas cell
Improvement of the thermoregulation system of the quantum frequency standard with a rubidium gas cell
E. V. Isupova$^1$, S. Yu. Shvetsov$^2$, A. V. Shavshin$^1$, A. P. Valov$^3$
The necessity of increasing the metrological characteristics of the quantum frequency standard on rubium-87 atoms is substantiated. It is noted that the main destabilizing factor that reduces the accuracy of frequency determination is temperature. To control it in the quantum frequency standard, thermostating and thermoregulation are used. It is established that the currently used systems for laser and optical components cannot provide the necessary temperature stability, which is required to improve the metrological characteristics of the quantum standard. A new circuit of a quantum frequency standard temperature controller with a rubidium gas cell using a PID controller has been developed, and its operation in the Micro-Cap environment has been simulated. Transient processes in the circuit of the thermostat are analyzed. A decrease in the influence of temperature on the optical components and characteristics of the laser in the quantum frequency standard was found.
Show AbstractSimulation of gamma radiation detection by segmented scintillation detectors
Simulation of gamma radiation detection by segmented scintillation detectors
A. A. Mkrtchyan$^1$, A. S. Pozanenko$^2$, P. Yu. Minaev$^2$
Despite years of research, there are still many open questions about the model of gamma-ray generation by these sources. It is assumed that the measurement of the linear polarization of radiation can provide an answer to a number of unresolved questions in the physics of phenomena. When registering gamma radiation with scintillation detectors, the problem of dead time also arises, during which the device is not able to register a newly received quantum of radiation. It begins to play a significant role when the gamma-ray flux approaches the inverse of the dead time of the detector. Such problems arise when registering terrestrial gamma-ray flashes and the most powerful cosmic gamma-ray bursts. However, by segmenting the detector, it is possible on the one hand to reduce the effect of dead time, and on the other hand to measure the polarization of radiation. In this paper, a simulation of the registration of radiation polarization by a segmented scintillation detector using the Geant4 software package is carried out.
Show AbstractDescription of neutrino oscillations in matter in the framework of quantum field theory
Description of neutrino oscillations in matter in the framework of quantum field theory
I. P. Volobuev, V. O. Egorov
Within the framework of the perturbative quantum field-theoretical approach with the distance-dependent propagator, neutrino oscillations in matter are considered. In the approximation of two neutrino flavors, the distance-dependent propagator is constructed that describes the propagation of neutrinos in a stationary non-polarized homogeneous medium. Using this propagator, the corresponding probability of the neutrino oscillation process is found, where the neutrinos are detected through the weak charged- and neutral-current interactions. It is shown that the results coincide with those obtained in the framework of the standard quantum-mechanical description. Several specific examples of processes are considered and the MSW effect is discussed.
Show AbstractFeatures of express control of volatile hydrocarbon media and their mixtures in visible light
Features of express control of volatile hydrocarbon media and their mixtures in visible light
G. V. Stepanenkov, D. V. Vakorina
The problems that arise during the express control of hydrocarbon media and their mixtures are considered. Especially noted the problems with the control of volatile hydrocarbon media that are used as fuel (gasoline, kerosene, diesel fuel, etc.). The requirements to the methods for express control and devices for their implementation are defined. The features of control of volatile hydrocarbon media and their mixtures using small-size refractometers working on the effect of total internal reflection are considered. It is shown that when using these devices, it is impossible to obtain data to determine the state of the mixture of volatile hydrocarbon media, its composition and the concentration of the components. A new method for determining the components in the mixture of volatile hydrocarbon media and data on the ratio between the concentrations of the components in it has been developed. The design of a small-size refractometer, which makes it possible to measure the refractive index in visible light, for the implementation of this method is presented. The dependences of the density change on the temperature T for different grades of gasoline for determining the composition and concentration in a three-component mixture of volatile hydrocarbon media have been established. The results of studies of various volatile hydrocarbon media and their mixtures are presented.
Show AbstractOn the charge distribution on the surface of a LiTaO$_3$ single crystal and its effect on the characteristics of a pyroelectric accelerator
On the charge distribution on the surface of a LiTaO$_3$ single crystal and its effect on the characteristics of a pyroelectric accelerator
P. G. Shapovalov$^{1,2}$, A. N. Oleinik$^2$, M. E. Gilts$^2$, A. S. Kubankin$^{2,3}$
The article presents the results of finite element modeling of a pyroelectric accelerator based on a single crystal of lithium tantalate. The influence of the charge distribution on the crystal surface on the characteristics of the electron flow is considered. A model using an axially symmetric charge distribution obtained by interpolating the experimental dependence leads to the expected effects of self-focusing and monoenergicity of the flow. Attention is also paid to the model "triangular"\; distribution. This distribution can be caused by the structure of the lithium tantalate domain walls when its temperature changes. Simulation results for both distributions are discussed.
Show AbstractMeasurement of NA62(CERN) sensitivity towards the search of $\pi^{0}\rightarrow3\gamma$ and $\pi^{0}\rightarrow4\gamma$ decays
Measurement of NA62(CERN) sensitivity towards the search of $\pi^{0}\rightarrow3\gamma$ and $\pi^{0}\rightarrow4\gamma$ decays
K. Yu. Gorshanov
The aim of the paper is measurement of NA62 experiment sensitivity towards the search for forbidden in Standard Model decay $\pi^{0}\rightarrow3\gamma$, that violates C-invariance principle, and allowed in Standard Model decay $\pi^{0}\rightarrow4\gamma$. Current upper limit on the probability of $\pi^{0}\rightarrow3\gamma$ ($\pi^{0}\rightarrow4\gamma$) decay is $3.1\times10^{-8}$ ($2\times10^{-8}$) with $90\%$ confidence level. In the paper $K^{+}\rightarrow\pi^{+}\pi^{0}$ decays are used as a source of $\pi^{0}$. The idea of selection of events with 3 products or 4 products after $\pi^{0}$ decay in NA62 detector was developed. NA62 detector and all physical processes were modelled with Monte Carlo method using Geant4. Single event sensitivity towards $\pi^{0}\rightarrow3\gamma$ ($\pi^{0}\rightarrow4\gamma$) decay without background events consideration is $\mathcal{O}(10^{-9})$, which is 1 order better than current upper limits. Consideration of background events for each decay leads to decline of sensitivity to the level of current limits.
Show AbstractDecomposition method in the problem of acoustic sounding of the anisotropic structure of the atmosphere
Decomposition method in the problem of acoustic sounding of the anisotropic structure of the atmosphere
M. Z. Nafisovich
The paper presents a method for decomposing a signal into components of a known shape in the form of N- and U-waves obtained by partial reflection of infrasound from thin inhomogeneous layers of the atmosphere. A mathematical model of the signal is proposed as the sum of incoming waves with different amplitudes and phases, as well as random noise. The completeness of the system of functions consisting of such waves is shown. The method allows to separate components of a known shape from the signal and determine their parameters. The proposed method can be used to search for components of arbitrary shape in the signal.
Show AbstractOn the pondermotive magnetic force of interaction between halves of a uniformly magnetized cylindrical rod
On the pondermotive magnetic force of interaction between halves of a uniformly magnetized cylindrical rod
M. A. Piatakov, M. L. Akimov, P. A. Polyakov
In this work, a theoretical study of the ponderomotive magnetic force of interaction between two halves of a long rod cylindrical magnet, uniformly magnetized perpendicular to the cylinder axis, depending on the influence of the magnetic field of two other similar magnets arranged symmetrically, is carried out. It is shown that the bonding force of these halves depends significantly on the configuration and arrangement of the magnets.
Show AbstractNUMERICAL SIMULATION OF CORRECTION OF PHASE ABERRATIONS OF LASER RADIATION BY MEANS OF TWO ADAPTIVE MIRRORS UNDER THE SPG ALGORITHM CONTROL
NUMERICAL SIMULATION OF CORRECTION OF PHASE ABERRATIONS OF LASER RADIATION BY MEANS OF TWO ADAPTIVE MIRRORS UNDER THE SPG ALGORITHM CONTROL
D. A. Salamatin
The numerical simulation of adaptive system operation with two sequentially located 18-channel adaptive mirrors with size of 46x56 mm2 in the problem of the phase correction of the laser beam in size of 15x22 mm2 has been carried out. The control of the adaptive mirrors has been realized by the stochastic parallel gradient algorithm. A set of 36 Gaussian functions with a width d=1.73 cm was used to model the response functions of adaptive mirrors. The radiation power within the diffraction angle is the criterion functional of the algorithm. Two variants of system operation have been considered: in the first variant the mirrors have the joint control unit and the criterion functional sensor, and in the second variant each mirror is situated in the independent contour. The similar adaptive systems can be applied to the correction of phase distortions of the radiation caused by strong turbulence of the atmosphere. It is shown, that the efficiency of correction of phase aberrations by such adaptive system is high in the case of the independent contours at supplying on the first adaptive mirror relatively small stochastic voltages. The mutual influence of adaptive mirrors on each other's work during correction is investigated.
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