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Microwave tomography is a new imaging modality based on differentiation of tissue dielectric properties. The main objective of our research project is to develop a microwave tomographic approach for non-invasive assessment of functional viability of myocardial tissue, including detection of infarcted tissue. Imaging of the heart in intact, euthanized animals is the first step towards this objective. When microwave tomography is used to image the thorax of intact animals, it faces two major problems: — the structural complexity of the rib area with high reflection of electromagnetic (EM) radiation from its boundaries, and the potential for high reflection of EM radiation from the lung, filled with air. In addition, when a targeted object (a heart in our case) is located inside of a larger high scattered object (a torso), the level of EM field scattered by the internal object has to be technically detectable from the stronger EM field scattered by torso. The goal of this research study is to evaluate the degree of complexity of these problems, to understand some technical requirements for clinically applicable MWT system and to demonstrate the feasibility of microwave tomography for imaging of the heart in intact mammals using a swine model. Experiments were conducted on pigs (Yorkshire Domestic Cross/Farm Pigs) using a modified three-dimensional (3D) microwave tomographic (MWT) system operating at frequency 0.9 GHz. The presence of the heart in torso changes the amplitude of EM field by about 10–20% and changes the phase of EM field by about 7–10 degrees (mean absolute differences). Microwave tomographic images of swine torso and intact euthanized animals were obtained and discussed. Images reveal intra-torso and organ anatomy, including the heart and left ventricular chamber. [ABSTRACT FROM AUTHOR]

This paper describes the results of a laboratory experiment on the sub-Alfvén expansion of a quasi-spherical laser plasma cloud into a vacuum magnetic field in the regime of nonmagnetized ions. The role of Hall fields and currents in the anomalously fast dynamics of the magnetic field during the collapse phase of a diamagnetic cavity is considered. Detailed spatial measurements of the azimuthal Hall fields configuration are demonstrated and their relationship to diamagnetic cavity collapse is determined. As a result of the experiment, data were obtained confirming the hypothesis about the transfer of the main magnetic field by the movement of electrons associated with Hall currents. [ABSTRACT FROM AUTHOR]

The laboratory experiment on modeling a sub-Alfvénic interaction of expanding plasma cloud with vacuum magnetic field is described. We produce spherically symmetric cloud by 4-beam laser irradiation of the pellet. The presented data reveal complex dynamic of cloud deceleration and formation of two field aligned jets, development of the flute instability and rapid collapse of the diamagnetic cavity. It is shown that cavity collapse can't be explained by plasma motion or anomalous diffusion and requires for explanation a new mechanism. [ABSTRACT FROM AUTHOR]

The paper presents the results of laboratory experiment modeling the interaction between Lunar magnetic anomalies and Solar wind. To model the LMA we use quadrupole magnetic field. The main dimensionless parameter of the problem, the ion inertia length relative to the mini-magnetosphere size, well corresponds between experiment and LMA conditions. The main result is measurement of the magnetically reflected proton fluxes, which show qualitative agreement to available satellite data. [ABSTRACT FROM AUTHOR]

Magnetospheres at ion kinetic scales, or mini-magnetospheres, possess unusual features as predicted by numerical simulations. However, there are practically no data on the subject from space observations and the data which are available are far too incomplete. In this paper we describe the results of a laboratory experiment on the interaction of plasma flow with a magnetic dipole with parameters such that the ion inertial length is larger than the size of an observed magnetosphere. A detailed structure of the non-coplanar or out-of-plane component of the magnetic field has been obtained in the meridian plane. The independence of this component on dipole moment reversal, as was reported in a previous work, has been verified. In the tail distinct lobes and a central current sheet have been observed. It was found that lobe regions adjacent to boundary layer are dominated by a non-coplanar component of magnetic field. Tail-ward oriented electric current in the plasma associated with that component appears to be equal to the ion current in the upstream part of magnetosphere and in the tail current sheet implying that electrons are stationary in those regions while the ions flow by. The data obtained strongly support the proposed model of mini-magnetosphere based on two-fluid effects as described by the Hall term. [ABSTRACT FROM AUTHOR]

The initial stage of prebreakdown cathode processes is studied with the help of the shadow method and electrooptical Kerr effect with laser light exposure of ≈ 3 ns. Experiments are performed by using triangular voltage pulses with time rise of ≈ 1 μs, time decay of ≈ 0.1 μs and total width of < 2 μs. The distance between electrodes 50 mm in diameter is 3 - 5 mm. Field strength varies from 275 kV/cm up to 500 kV/cm. Initial separate optical heterogeneities of size of 50-100 μm are registered at E ≥ 380 kV/cm. Spherical density disturbances with epicenter placed over the cathode are registered when the cathode "bush" reaches the size of ≥ 100 μm. In front of the "bush" the enhancement of electric field exceeding the average field several times in the gap is registered. However, fast discharge is developed from anode. Experiments performed without restriction of voltage pulse duration at E ≈ 300 kV/cm show that within 6 - 8 μs cathode disturbances increase up to the size of 2 - 4 mm and initiate the breakdown. The EHD model of subsonic cathode streamer development is considered. [ABSTRACT FROM AUTHOR]

The paper deals with the physical and electrotechnical principles of the promising method of direct conversion of the kinetic energy of an expanding plasma cloud to electrical energy by inductive generation of currents in short–circuited load coils that enclose the plasma and are oriented across the external magnetic field. An analysis of plasma deceleration by a magnetic field and transfer of plasma energy to an inductive load gave a solution of the problem in general form and the dimensionless parameters of the problem that determine the deceleration radius, the coil current, and the theoretical conversion efficiency. The role of the basic physical effects, including parasitic ones (plasma instabilities and Joule heating), influencing the real efficiency is assessed. A comparison of the results with data of experiments with laser–produced plasma clouds on a KI–1 facility and with available numerical results shows that in the optimized version of the method for conversion of inertial confinement fusion energy, a 30% efficiency can be achieved. [ABSTRACT FROM AUTHOR]

The article presents a study on increasing the field strength in water with modified electrodes. The study intends to develop the capacitive energy storage systems to be able to increase the pulsed electrical strength of water. The stainless steel with hemispherical electrodes was used to measure the electric field strength.

The results of a laboratory experiment on the simulation of the reflection of protons over regions of the local magnetization of the lunar crust have been reported. Quadrupole and dipole sources have been used to simulate a local magnetic field. The magnetic-field-induced reflection of protons near lunar magnetic anomalies reaches 50% of the incident flow. A significant difference between the quadrupole and dipole configurations has been detected both in the structure of the mini-magnetosphere and in the reflection of protons. The data obtained are in qualitative agreement with in situ measurements by spacecrafts over lunar magnetic anomalies. [ABSTRACT FROM AUTHOR]

The results of a laboratory experiment on the simulation of the reflection of protons over regions of the local magnetization of the lunar crust have been reported. Quadrupole and dipole sources have been used to simulate a local magnetic field. The magnetic-field-induced reflection of protons near lunar magnetic anomalies reaches 50% of the incident flow. A significant difference between the quadrupole and dipole configurations has been detected both in the structure of the mini-magnetosphere and in the reflection of protons. The data obtained are in qualitative agreement with in situ measurements by spacecrafts over lunar magnetic anomalies. [ABSTRACT FROM AUTHOR]

Giant exoplanets at close orbits, or so-called hot Jupiters, are supposed to have an intensive escape of upper atmospheric material heated and ionized by the radiation of a host star. An interaction between outflowing atmospheric plasma and the intrinsic planetary magnetic dipole field leads to the formation of a crucial feature of a hot Jupiter's magnetosphere—an equatorial current-carrying magnetodisk. The presence of a magnetodisk has been shown to influence the topology of a hot Jupiter's magnetosphere and to change a standoff distance of the magnetopause. In this paper, the basic features of the formation of a hot Jupiter's magnetodisk are studied by means of a laboratory experiment. A localized central source produces plasma that expands outward from the surface of the dipole and inflates the magnetic field. The observed structure of magnetic fields, electric currents, and plasma density indicates the formation of a relatively thin current disk extending beyond the Alfvénic point. At the edge of the current disk, an induced magnetic field was found to be several times larger than the field of the initial dipole. [ABSTRACT FROM AUTHOR]

This paper presents the results of laboratory experiments with laser plasma flow around a magnetic dipole which model the extreme compression of the Earthś magnetosphere by the plasma generated by high-power coronal mass ejections. Data on the formation of an artificial magnetosphere, the boundary-layer structure, and the size of the magnetosphere as a function of the magnetic moment are given. It is shown that in the presence of a conducting dipole shell modeling the ionosphere, conditions are created for the flow of intense longitudinal currents in the polar regions. It is established that the longitudinal currents have little effect on the position of the plasma stagnation point and the transition layer but make a significant contribution to the disturbance of the magnetic field in the magnetosphere. [ABSTRACT FROM AUTHOR]

The ion composition of a plasma flow obtained by intense irradiation of a solid target is determined by methods of probing diagnostics and measuring the secondary emission rate. As the ions fly through a dense gas jet, C 5+ ions are found to recharge to C 4+ ions and then to C 3+ ions. The fraction of high-charge ions in the initial plasma flow and their concentration in the region of interaction with the jet are calculated. The concentration of atoms in the gas jet is estimated on the basis of the integral change in the charge value. Results necessary for analyzing the conditions of experiments on effective charge-transfer pumping and laser generation in the far ultraviolet spectral range are obtained. [ABSTRACT FROM AUTHOR]

Results of an experiment on the interaction of laser-produced plasma with a pulsed gas jet are reported. A resonant charge-exchange pumping of the n=3 level of the C3+ ion was observed. A spatial structure of the region of intensive interaction was obtained by a short time imaging of filtered plasma radiation. According to independent probe measurements, the interaction was realized at densities of ions and gas particles in excess of 1016 cm-3. The obtained data provide a prospect for future experiments on laser gain in the EUV spectral range based on charge-exchange pumping of the C5+ ion. [ABSTRACT FROM AUTHOR]

Experiments using a powerful CO2 amplifier were performed with the aim of developing a technique for simulating a space explosion in the magnetosphere of the Earth and other planets under laboratory conditions using laser plasma clouds. The amplifier radiation with an energy of about 300 J and a pulse duration of about 10-7 sec focused on a Caprolon target of 4 mm diameter produced an exploding plasma in a dipole magnetic field with a characteristic dimension of 15 cm and a magnetic moment of 1.1·107 Gs · cm3. The paper presents preliminary results of simulating a space explosion under quasitrapping conditions, where the energy of the explosion is much lower than the geomagnetic energy and the explosion point is located in the equatorial plane at a distance of two Earth's radii. [ABSTRACT FROM AUTHOR]