The high sensitivity of traditional diagnostic methods hinders their application in inertial confinement fusion with the pulsed radiation power of target plasma being as high as 1013–1014 W. Different methods of attenuating the incident radiation flux either alter its characteristics or are too complicated. The results of tests of a new detector, where quartz glass is used as a sensing element, at the Angara-5-1 facility are presented. It is demonstrated experimentally that the detector sensitivity is ~2 V/(MW cm 2 ) and the time resolution is ~1 ns. The mechanism of formation of the response signal, where the temperature of electrons produced under irradiation plays a significant part, is discussed.

The concept of layout synthesis of optimal configurations is introduced in the article. Under the tasks of layout synthesis it means the formation of a set of geometric objects in such a mutual arrangement that would satisfy the given relations (constraints, properties) and would deliver an extremum to a certain quality criterion. One problem of finding the optimal configuration of geometric objects of spherical shape is considered. The problem is to find such an arrangement of set of spheres without their mutual overlaps, so that their spherical shell is minimal. For this problem, several equivalent mathematical models are given. Since the problem is NP-complete, methods are considered for solving it, based on the search and improvement of local minima. To find one local minimum, it can be used any method of non-linear optimization. In this paper it is used an open system IPOPT for solving optimization problems, using the methods of internal points to search for a local minimum. To search for a local minima, there are used several approaches. The first of them is based on the application of the space expansion method. This method consists in finding a local minimum for a problem with constant radii, and then at the resulting point, a transition to a model with variable radii is made, in which the initial values of the radii of the circles change in a certain range in a random way. After that, the local search is performed again, and so many times. This approach allows for a directed search of a local minima, improving the solution. The second approach is based on a multiple search for a local minima using a genetic algorithm. The third approach is an interactive and uses human intuition. After obtaining some solution, the result is displayed in a graphical editor and the researcher can change the mutual position of objects, after which one of the automatic methods is applied. It is necessary that initial position objects do not be feasible. When solving a problem, it is necessary to ensure interaction between different stages of the solution. To do this, it is need to repeatedly convert geometric information from one form to another. Information technologies for the transformation of geometric information in the process of solving the problem are proposed. An example of a numerical solution is given.

Computer modeling of measuring devices that contains matrix of electrodes are examined. Method of local weighted approximation is applied. Special location of the measurement nodes that forms a matrix structure (grid pattern) is applied for quadratic basis. It is shown that in this case either calculation of scalar or estimation of scalar derivatives in the central pattern node can be produced uniformly by prior finding of resolvent. Examples of usages of given method for finding the minimum of a function of two variables are considered. The possibility of using considered method for finding minimums of functions with discontinuities derivatives is specified.

The concept of layout synthesis of optimal configurations is introduced in the article. Under the tasks of layout synthesis it means the formation of a set of geometric objects in such a mutual arrangement that would satisfy the given relations (constraints, properties) and would deliver an extremum to a certain quality criterion. One problem of finding the optimal configuration of geometric objects of spherical shape is considered. The problem is to find such an arrangement of set of spheres without their mutual overlaps, so that their spherical shell is minimal. For this problem, several equivalent mathematical models are given. Since the problem is NP-complete, methods are considered for solving it, based on the search and improvement of local minima.To find one local minimum, it can be used any method of non-linear optimization. In this paper it is used an open system IPOPT for solving optimization problems, using the methods of internal points to search for a local minimum.To search for a local minima, there are used several approaches. The first of them is based on the application of the space expansion method. This method consists in finding a local minimum for a problem with constant radii, and then at the resulting point, a transition to a model with variable radii is made, in which the initial values of the radii of the circles change in a certain range in a random way. After that, the local search is performed again, and so many times. This approach allows for a directed search of a local minima, improving the solution.The second approach is based on a multiple search for a local minima using a genetic algorithm.The third approach is an interactive and uses human intuition. After obtaining some solution, the result is displayed in a graphical editor and the researcher can change the mutual position of objects, after which one of the automatic methods is applied. It is necessary that initial position objects do not be feasible. When solving a problem, it is necessary to ensure interaction between different stages of the solution. To do this, it is need to repeatedly convert geometric information from one form to another. Information technologies for the transformation of geometric information in the process of solving the problem are proposed.An example of a numerical solution is given.

Computer modeling of measuring devices that contains matrix of electrodes are examined. Method of local weighted approximation is applied. Special location of the measurement nodes that forms a matrix structure (grid pattern) is applied for quadratic basis. It is shown that in this case either calculation of scalar or estimation of scalar derivatives in the central pattern node can be produced uniformly by prior finding of resolvent. Examples of usages of given method for finding the minimum of a function of two variables are considered. The possibility of using considered method for finding minimums of functions with discontinuities derivatives is specified.

ДИЭЛЕКТРИЧЕСКИЙ ДЕТЕКТОР ИНТЕНСИВНЫХ ПОТОКОВ РЕНТГЕНОВСКОГО ИЗЛУЧЕНИЯИ.А

An X-ray detector with a dielectric (KU1 optical glass) used as a sensitive element is described. Operation of the detector is based on the discovered effect of electric-field generation in a dielectric under exposure to radiation. The measurements were taken at the Angara-5-1 facility, at which the radiation source is megaampere Z-pinch plasma. It is shown that when the radiation power incident on the detector is approximately 1 MW/cm2, the detector response is a few volts with a time resolution of 1–2 ns. This effect is thought to be caused by “hot” electrons induced by radiation in the dielectric. The estimates for these experimental conditions are presented.

Исследуется эффект, наблюдающийся при взаимодействии электромагнитного излучения (энергия квантов 25-1000 eV) с диэлектриком, имеющим металлическое покрытие. Источником излучения служил мегаамперный Z-пинч. Измерения, проведенные с образцами оптического стекла, показали, что под действием излучения (мощность ~106 W/сm2) в электрической цепи, включающей металлизированный диэлектрик, возникает ток. Авторы считают, что причиной данного гальванического эффекта является генерация в диэлектрике горячих" электронов.

The effect observed upon interaction between the electromagnetic radiation with quantum energy of 25–1000 eV and a dielectric with metal coating is investigated. The radiation source was a megampere Z-pinch. Measurements performed on optical glass samples showed that radiation with a power of ~106 W/cm2 in the electric circuit switching on the metalized dielectric induces the current. It is shown that the observed galvanic effect originates from the generation of hot electrons in the dielectric.

A study is made of the Z-pinch plasma expansion after the current is switched off. Measurements were carried out in experiments on the implosion of tungsten wire arrays in the Angara-5-1 facility. It is found experimentally that, at a distance of 2 m from the pinch, the ion velocity in the expanding Z-pinch plasma is about (2.5–4.0) × 107 cm/s, which substantially exceeds the thermal velocity of tungsten ions. A model describing the plasma expansion process is proposed that is based on the ambipolar acceleration mechanism. The results of numerical simulations are compared with the experimental data.

The process of Z-pinch decay upon current termination is considered. The experimental data obtained for the Angara-5-1 facility on compression of multiwire tungsten liners are discussed. It is shown that among the decay products there are microparticles of the eroded liner construction material and plasma fluxes. It was determined that the plasma flow velocities exceeded the ‘thermal’ velocities of the Z-pinch plasma. A model for the description of the process of ion acceleration based on an ambipolar mechanism is suggested. Precautions for protection of the peripheral equipment against the decay products of Z-pinch are discussed and protective components are studied. A fast electromagnetic shutter is used for protection from microparticles.

The results of spectral measurements of radiation from microsecond gas Z-pinch are presented. The pinch current is 250 kA with a rise time of 1 μs. At the maximum nitrogen-pinch compression, the radiation spectrum corresponds to the emission of helium-, lithium-, and beryllium-like ions. The spectral-intensity peak lies within the spectral range 15–25 nm, which corresponds to the 2s-3p transitions of Li-and Be-like ions and to higher-energy transitions of these ionization states (2s-4p, 2s-5p, and 2s-6p). The spectra are measured in the first, second, and third diffraction orders. The total yield of X rays measured by a thermocouple-based calorimeter was 45 J at a 2-kJ electric energy stored in the capacitor bank. The pinch-radiation intensity and the spectra obtained experimentally are compared to the results of two-dimensional simulation of the emitting-plasma plasma dynamics using the ZETA radiation-magnetic hydrodynamic code.

The spectral characteristics of the plasma radiation of a gas Z-pinch with arise time of 1 mu s and a current amplitude of 250kA have been measured. The measurements were performed in the range of X-ray energy quanta from 30eV to 600eV. A spectrograph with a transmission grating and a polychromator on the basis of multilayer X-ray mirrors served as the diagnostic device. Absolutely calibrated semiconducting detectors AXUV-5 were used as radiation detectors in the polychromator. The full pinch radiation loss was measured with a thermocouple calorimeter. The radiation of He-, Li- and Be-like ions has been shown to dominate at the stage of maximum compression of the nitrogen Z-pinch. The results of the spectral measurements were employed for the absolute calibration of various X-ray detectors. Some of these calibration results are presented in this paper.

The pulsed power technology is being used for generation of intense x-ray and charged particle beams (electron, light ions), inertial confinement fusion researches, high current z-pinch experiments. The main part of the pulsed power facility is the generator with parameters: power >10(13) Wt, current >10(6) A, output pulse time duration approximate to 10(-7) sec. The operation of pulsed power facilities have specific features, namely, a small number experiments (shot) per day, short time duration of processes in generator (<10(-6) sec), hundreds of measuring parameters during shot.According to specific operation, the control equipment of facility contain several types of systems. One of them is the system for the technological preparation of the installation for a shot. Because technological parameters are changed slowly it is possible to realize on-line operation of this system. Second one is the data acquisition system for acquiring data during a shot. This system includes fast ADC of different types. Part of them have the time step of waveform measurements <10(-9) sec. The special timing system provides the synchronization of all systems operation in the wide time scale of events. In this paper control systems of pulsed power Angara-5 facility as an example is given.

This work deals with the problem of optimal allocation of objects of a so-called irregular form. The objects are allocated on a strip of given width and with defects. This problem is insufficiently studied, but it is typical for many industries and is also interesting for developing the theory of solving cutting and packing problems. An analytical model of the problem using only continuous variables is written in terms of classical mathematical programming, and it is constructed on the basis of the original theory of φ-functions and structures of linear inequalities. The presented theory allows one to easily describe the conditions of mutual non-overlapping of objects and their allocation in the stock region. The exact method for searching a local minimum of the problem from any feasible initial point is based on the application of the active set strategy ideas. A number of examples of solving practical problems are considered.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.