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Methods and results of studies of the radiation spectra of high-current Z-pinches with different elemental compositions are presented. To examine a wide spectral range (Ehν = 30–3000 eV), two diagnostics tools were used—a transmission grating and a reflecting mica crystal. The radiation characteristics of the pinch are determined by its elemental composition. For currents of 2–3 MA and low-Z elements (aluminum), the hard end of the radiation spectrum is represented by spectral lines with clearly pronounced K lines, while for high-Z elements (tungsten), the spectrum lies in the softer photon energy range and is quasi-continuous. Two methods of spectrum processing were used to determine the plasma parameters. The parameters of aluminum plasma were traditionally determined from the intensity ratios of the K lines taking into account the plasma transparency for these lines. The spectra of tungsten plasma were compared with the results of computer simulations of pinch compression with allowance for both magnetohydrodynamic and plasma radiation processes. The applicability of these methods of spectral analysis is discussed.

Results are presented from measurements of the radiation spectra of the Z-pinch tungsten plasma produced during the implosion of cylindrical wire arrays with a linear mass of 200–400 μg/cm and an initial diameter of 12–20 mm at a current of ∼3 MA in the experiments performed at the Angara-5-1 facility. The radiation spectra in the photon energy range of 50–900 eV were recorded on a UF-4 X-ray film by using a spectrograph with a transmission grating. The radiation spectrum in the photon energy range of 1–3 keV was recorded using a crystalline panoramic spectrograph. A curtain shutter was used to protect the transmission grating from fast microparticles produced due to the erosion of high-voltage electrodes. The total radiation yield was measured with a thermocouple calorimeter. It is shown that most of the tungsten plasma radiation energy is emitted in the photon energy range of 80–300 eV. Measurements of the spectral intensity of pinch radiation with a spatial resolution along the pinch radius showed that the effective transverse diameter of the pinch did not exceed 2 mm, which agrees with independent current measurements of the pinch size. The results of measurements of the spectral intensity of pinch radiation were compared with calculations per-formed under the assumption of a stationary homogeneous plasma.

Results are presented from experimental studies of the implosion of cylindrical kapron fiber arrays with addition of high- and medium-Z metal wires (tungsten, aluminum). The experiments were carried out on the Angara-5-1 facility at currents of 3–4 MA. The ablation rate in kapron fiber arrays is estimated and compared with that in tungsten wire arrays.

The results of a probabilistic analysis performed to validate the safety of AES-2006 designed for the site of the Novovoronezh nuclear power plant are presented. The requirements for the AES-2006 design are examined. The characteristic features of the AES-2006 design for the conditions at the Novovoronezh nuclear power plant site are described, including the diversity of the equipment and operating regime, passive systems, and scheduled maintenance of safety systems with the reactor operating at power. The scope of the probabilistic safety analysis performed at the development stage of the technical design is described. The important problems which must be solved in a probabilistic safety analysis for the designs of new nuclear power plants are discussed.

The results of investigations into the polarisation of line radiation of the multiple charged ion plasma of high-current Z-pinches are presented in this paper. The experiments were performed on the ‘Angara-5-1’ facility at Z-pinch currents of 2.5–3.5MA. A dense high-temperature pinch was produced by the compression of a hollow Ar gas jet injected by an electromagnetic valve with a supersonic nozzle. In the process of pinch compression, the following plasma parameters were achieved: electron density n e ∼ 1021cm−3 and electron temperature Te ∼1keV. The radiation spectrum was measured by the use of a crystal spectrograph in which mica (2d=19.9 A)served as a disperse element. The spectrum of the He-like ion of Ar was detected in reflection orders II and III. On the basis of the measurements performed, conclusions on the degree of polarisation of the plasma radiation have been drawn.

A qualitative model of the dynamics of a multiterawatt radiating Z-pinch with cold start and high rate of current rise is proposed. The model is used to analyze discharges with currents I ∼ 2–5 MA (with dI/dt > 1013 A/s) through uniform or structured plasma-producing loads, including wire arrays. The most important consequence of cold start is that spatially nonuniform plasma production is prolonged to almost the entire current rise time. Under these conditions, the Ampere force begins to play a dominant role in the plasma dynamics before the plasma-producing load is completely transformed into an accelerated plasma. The results of computations of wire-array vaporization are presented. A formula is proposed for estimating the highest attainable velocity of plasma flow into a heterogeneous liner driven by the Ampere force. It is shown that local imbalance between radial motion of the produced plasma and supply of the plasma-producing substance to be ionized leads to axially nonuniform breakthrough of magnetic flux into the liner, which precedes plasma collapse. The magnetic-flux breakthrough gives rise to a chaotic azimuthal-axial plasma structure consisting of radial plasma jets of relatively small diameter, which is called a radial plasma rainstorm. The breaking-through azimuthal magnetic flux obstructs further current flow in the breakthrough region. Analyses of Z-pinch implosion based on the theory of Rayleigh-Taylor instability or the snowplow model are incorrect under the plasma-rainstorm conditions. The processes taking place in a stagnant Z-pinch include conversion of the energy carried by the current-generated magnetic field into turbulent MHD flow of the ion component of the plasma, its convective mixing with magnetic field, heating, energy transfer from ions to electrons, and emission from the plasma. Under typical experimental conditions, emission plays a key role in the energy balance in an imploding pinch. Z-pinch is modeled by an electric-circuit component that has a time-dependent nonlinear impedance and consumes the magnetic energy supplied by a generator through a magnetically insulated transmission line (MITL). The peak power reached in the circuit is comparable to the peak soft X-ray power output emitted by the pinch in terms of magnitude and timing. Optimum matching conditions are formulated for the generator-MITL-pinch circuit.

We present our experimental results of the X-ray radiography of fast radiating Z-pinches based on cylindrical multiwire tungsten arrays. The experiments were carried out at the Angara-5-1 facility at an electrical power of up to 4 TW with a discharge current of up to 4 MA rising at a rate on the order of 5×1013 A s−1. The linear mass of single and composite arrays reached 500 µg cm−1, the initial radius was 4–10 mm, and the wire diameter was 5–8 µm. We have experimentally shown that for the current-induced implosion of multiwire tungsten arrays, significant azimuthal and axial plasma inhomogeneities result from discharge cold start and prolonged plasma production, which determine the subsequent course of the implosion. The Z-pinch structure also remains spatially inhomogeneous at the time of intense X-ray radiation. The generated inhomogeneous plasma collapses toward the array axis in the form of numerous radially elongated plasmoids with relatively small diameters. The stream of plasmoids is called a radial plasma rainstorm. As the plasmoids contract toward the array axis, they decrease in radial size and merge into isolated plasma current filaments, which are elongated mainly along the discharge axis. We critically discuss the models of a radiating Z-pinch in plasma composed of matter with a large atomic number that disregard the cold-start and prolonged plasma-production effects.

Results of experimental investigation and modeling of prolonged plasma production during implosion of cylindrical wire arrays are presented. Results of the radiography of dense cores of imploding wire array and the measurements of internal azimuthal magnetic field in wire array give new experimental evidences of prolonged plasma production phenomenon. This phenomenon is an important property of current-driven implosion of the wire arrays at current rise rates /spl sim/(0.5-1)10/sup 14/ A/s. The prolonged plasma production can determine the current and the density profiles before final stage of a Z pinch compression, and also in the moment of Z pinch stagnation. From this point of view, the requirement that residual uncompressed plasma should not shunt the current at the discharge periphery becomes of the greatest importance. The conditions exist when the prolonged plasma production isn't an obstacle for the achievement of high-power X-ray emission from Z pinch. Presented experimental results on multiwire array implosion can be explained on the basis of prolonged plasma production without referring to multiwire array azimuthal structure.

The possibility of the propagation of a thermonuclear detonation wave in a deuterium pinch with a small (∼0.5%) tritium admixture is considered. The required pinch parameters and the necessary value of the current produced by a high-power pulsed current generator are estimated.

Prolonged plasma creation in heterogeneous liners, in which the liner substance is separated into two phase states (a hot plasma and a cold skeleton), is investigated both experimentally and theoretically. This situation is typical of multiwire, foam, and even gas liners in high-current high-voltage facilities. The main mechanisms governing the rate at which the plasma is created are investigated, and the simplest estimates of the creation rate are presented. It is found that, during prolonged plasma creation, the electric current flows through the entire cross section of the produced plasma shell, whose thickness is comparable with the liner radius; in other words, a current skin layer does not form. During compression, such a shell is fairly stable because of its relatively high resilience. It is shown that, under certain conditions, even a thick plasma shell can be highly compressed toward the discharge axis. A simplified numerical simulation of the compression of a plasma shell in a liner with prolonged plasma creation is employed in order to determine the conditions for achieving regimes of fairly compact and relatively stable radial compression of the shell.

Work on Z-pinches, that is under way at the SRC RF TRINITI, is aimed at the resolution of two basic problems: to investigate the problem of physics of X-ray generation in a Z-pinch scheme with the goal of its application for ICF at the "Angara-5-1" facility to develop the engineering aspects of multimegampere facilities intended for using them in a Z-pinch scheme for ICF and making the "Baikal" project. At the "Angara-5-1 facility" the measurements of plasma production rates for the wire and foam liners were taken. It has been shown that for Mo, W, Cu, Fe, and Al a current sheath with a radial thickness much larger than the skin- layer forms. The value of the plasma production rate for these metals was obtained. In the case of the liner from agar-agar foam no formation of such a layer was observed. The spectral measurements taken in hybrid Al-W liners make it possible to estimate the electron temperature and concentration from the spectrum of Al ions. It is also shown that an addition of tungsten into the array compound at a constant mass leads to a decrease of not only the electron temperature but also the final radius of stagnation. The measurements of the hard X-radiation appearing at the moment close to a peak of the X-ray pulse are likely to indicate the formation of an several kiloamperes electron beam. The experiments with conical arrays consisting of tungsten wires demonstrate the effects which arise when the wire array is imploded both in radial and axial directions. For large cone angles there appear two separate radiating regions. The corresponding X-ray pulses have a double-peak structure. Calculations of such liner compression are used to test the programs describing both radial and axial plasma compression. The results obtained at the IMM RAS fairly well provide a quantitative description of the X-ray pulse structure. Such conical liners prove to be a promising tool to test complicated RMHD codes. A pulse generation scheme relevant to the "Baikal" project is under development at the MOL facility. A 30-fold reliable current multiplication in the inductive storage has been obtained. The storage energy was effectively transferred to the subsequent stage of formation, i.e. a magnetic amplifier. The current in the latter was multiplied by a factor of 1.55. At the "Angara-5-1" facility the MEVL code reporting the process of magnetic insulation arising in the in-parallel- connected magnetically insulated vacuum lines has been tested.

In SRC RF TRINITI the physics of radiating Z pinches for application as a source of x-ray for ICF target ignition are under investigation. Simultaneously the works on a designing the module of the generator “Baikal” [1] which should deliver the current pulse up to 50 MA as a driver for radiating Z pinch are designed by co-operation of the RRC the Kurchatov Institute, the SRC RF TRINITI, the SUE NIIFA and RFNC VNIITF. Experiments for study of the wire array compression are conducted on the largest in Russia laboratory source of pulsed electric power “Angara-5-1” installation.

The results of the experiments on Z‐pinch produced from wire arrays performed on the facility Angara‐5‐1 are presented. The models of liner implosion, i.e. prolonged plasma production have found their confirmation. Estimation based on our experimental data show that W wire cores are heterogeneous. The velocity of core expansion is determined by energy deposited at the first nanoseconds after current start. The effect of the inner array on the current distribution in the region between the arrays has been revealed. The «lost mass » was measured at initial radius of array at the moment of X‐ray pulse maximum.

The results of the experiments performed on the Angara-5-1 facility of Z-pinch produced from wire arrays are presented. The models of liner implosion, i.e. prolonged plasma production and "plasma rainstorm" have found their confirmation. The effect of the inner array on the current distribution in the space between the arrays has been revealed.

Spatial distributions of mass and current inside current-driven wire array during implosion were investigated on Angara-5-1 facility. Radiography of dense cores of imploding wire array, measurements of internal azimuthal magnetic field in wire array and electron density measurements on the periphery of initial array position at the moment of stagnation give new experimental evidences of prolonged plasma production phenomenon. The measurement of current density inside the array shows that about half the current flows on the liner periphery at the moment of maximum compression. At this time up to 10% of the liner mass is present on the periphery of the initial wire array.

Results of first experiments on powerful plasma focus PF-1000 (IFPiLM), loaded by low mass foam liners, produced for "Angara" (TRINITI) liner implosion program, are presented in this report. An interaction of PF current plasma shell and the liner was the problem of main interest in our joint experiment. The main goal is to elaborate new method of plasma liner production for its compact implosion using multiterawatt pulsed power driver.

The X-ray spectrograph based on mica crystal (2d=19.9/spl Aring/) for spectrum analysis is described. The device construction (/spl theta/-2/spl theta/ scheme) is suited for radiation detectors: film, charge coupled device (CCD) and microchannel plate (MCP). X-ray film is used for spectrum measurements in the working range of the device (3/spl Aring/-18/spl Aring/). The device working range is measured by CCD. The CCD length is 3 cm. It correspond to the /spl Delta//spl lambda/=4/spl Aring/ range of the X-ray spectrum. An analog CCD signal is transformed to digital form and is sent to an IBM PC. The computer software has codes for plasma parameter determination (T/sub e/,n/sub e/). The CCD characteristics in the X-ray region have been initially researched. Some of these results are given. There are two time resolved detectors for plasma dynamic measurements. The construction of these detectors is based on microchannel plates. The X-ray range of the MCP detector is /spl Delta//spl lambda/=0.1/spl Aring/. Some results of this device application at the pulsed power facilities ANGARA-5 and GAEL are given.

The results of spectroscopy measurements of a composite Z-pinch on ANGARA-5-1 installation are presented. The composite Z-pinch was created with the help of a hollow Ar or methane gas jet which collapsed onto a solid foam cylinder doped with salts of KCl or NaCl. The dependence of the line radiation intensities and plasma parameters on linear mass of the gas jet (3-60 mkg/cm) was investigated.

The experiment on the 22 mm liner implosion on ANGARA-5-1 (4.5 MA, 90 ns) have been accomplished. The foam preionization by imploding low density gas corona and exploded wires has been investigated. It was found the foam-plasma transition by current pulse without preionization accompanied by sharp azimuthal nonuniformities. The implosion of rare gas corona onto a foam liner improved significantly the uniformity when specific corona mass m/sub c/ with diameter 55 mm was of 0.05 m/sub 1/. However the soft X-ray yield in the double liner scheme was not increased in comparison with gas-puff-foam liner combination investigated in previous research. The first experiment on currentless preionization by soft X-ray radiation of exploded wires have been performed. The improving of azimuthal uniformity and stability was observed.

Brief review of our recent results concerning prolonged plasma production (P3) in multiwires arrays and its influence on their dynamics in pulse power facilities is presented. P3 means that owing to overheating effects hot plasma with high conductivity is being produced from the relatively cold material almost during the whole period of current rising. P3 results in formation of a plasma shell with a low aspect ratio and without any skin effect. It means that magnetic flux and electric current are distributed more or less uniformly along the shell and there is no magnetic piston. The latter fact is responsible for the more stable implosion of the plasma. P3 is unavoidable effect for initially cold liners of all types in pulse power facilities, and it is useful for production of high power X-ray pulses with multiwires arrays because the process of P3 leading to more stable implosion is well controlled in this case due to well defined periodic structure of the array. Theoretical evaluation of rate of plasma production is obtained, and it is compared with experiments. Simple simulation of plasma dynamics during implosion of multiwire arrays with P3 is presented. Combining of such simulation with probe magnetic measurements inside cylindrical liners we obtain a certain information about dependence of the plasma production rate on time and about characteristics of depletion of plasma source. It appears that process of the depletion may be rather gradual, so that some amount of plasma is being placed at initial array position even till the moment of X-ray pulse maximum. It may lead to partial shunting of electric current and to some depression of X-ray pulse intensity. These results discover new opportunities to control plasma implosion and X-ray pulse parameters.

The study of the wire array implosion on installation Angara-5-1 is devoted. Magnetic probes and the x-ray backlighting technique were used to investigate a current and mass distribution during the implosion. The experimental data confirm the concept of prolonged plasma production: the long time of implosion the hot plasma flows from dense fixed wire cores and is accelerated by the Lorentz force to the array center together with frozen magnetic field.

Appearance of generators of electric power of pulse duration of about 100 ns opened new possibilities in classic Z- pinches. First, it is connected with new level of power of this generators. Second, it has become possible to use loads of another size and densities. One of the new tasks studied on powerful installations is generation is generation of pulses of soft x-ray radiation for thermonuclear fusion research. The models of target ignition, developed on systems of laser initiation, determined the nanosecond time as a characteristic time scale of radiation pulse. A program of fast liner compression is developing in TRINITI on Angara 5-1 installation- an 8 module pulse generator of max power of 9TW, pulse rise time of 90 ns, load peak current of 4 MA. The main aim of the program was to investigate a way to create a source of soft x-ray radiation of high intensity for thermonuclear fusion and fundamental research work. A conception of double liner were proposed as a perspective way to ensure a dynamic hohlraum for thermonuclear target irradiation.

Results of first experiments on powerful plasma focus PF-1000 (IFPiLM) [1], loaded by low mass foam liners, produced for “Angara” (TRINITI) liner implosion program [2], are presented in this report. An interaction of PF current plasma shell and the liner was the problem of main interest in our joint experiment. The main goal is to elaborate new method of plasma liner production for its compact implosion using multiterawatt pulsed power driver.

Recent development of soft X-ray sources based on super-fast Z-pinch implosion has demonstrated the great promise of pulsed power for ICF physics study. The main direction of the “Angara-5-1” program is oriented toward using the double liner scheme to confine radiation inside a cavity in order to enhance its intensity significantly. Collision of the external liner shell onto the inner leads to radiation penetration through the inner liner and a decrease in the radiation pulse duration to 3–5 ns. Testing this scheme on “Angara-5-1” with current 3.5–5 MA demonstrates a flux intensity up to 3 TW/cm2. In spite of the fact that results of the experiment and a 1D-simulation are close, there are many issues with external liner stability during current sheath formation and implosion. Recent experimental efforts on Angara-5-1 focused on the “cold start” problem and on the Rayleigh-Taylor instability for thick (gas-puff) and thin (doped foam) shells. Preionization makes the liner’s plasma more homogeneous. The meth...

A method is presented for determining the spatial and energy distribution of thermal neutrons within the cells of a heterogeneous reactor. If the effect of the asymmetric part of the scattering cross section on the change in neutron energy is neglected, the problem of determining the integral parameters of a cell may, in many cases, be reduced to the solution of monoenergetic Boltzmarm equations for a certain set of energy values with a subsequent determination of the neutron energy spectrum. The possibility of using an iterative process for refining the results of the first approximation is investigated.