[Show abstract][Hide abstract] ABSTRACT: 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 (E hν = 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.
Full-text · Article · Feb 2015 · Plasma Physics Reports
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Oct 2012 · Plasma Physics Reports
[Show abstract][Hide abstract] ABSTRACT: To verify the codes which describe implosion of wire conical wire arrays with a mass of 200-400μg and large and small radii of cone 12-20mm and 5-10mm, correspondingly, were used. In spite of the fact that these liners produce a less powerful pulse of X-radiation than cylindrical ones, they have some features especially important to verify codes. For a cone angle of >; 20° the X-pulse has three peaks. Comparison of their relative magnitude and duration obtained by experiment and in calculations allows us to more reliably verify some assumptions introduced into the code than would be the case of cylindrical liners. At the Angara-5-1 facility due to the electrostatic stretching of the cylindrical wire array occurred by an additional electrode the quasi-spherical arrays of 30-6- tungsten wires 6μm thick are formed with a radius of 8-12mm and a mass of 200-400μg. The implosion of Z pinches formed with such liners was effected by 3-4 MA current with a rise front of 100ns at the Angara-5-1 facility. It was shown that the central part of such a liner forms a hotter area compared with its edges and a hotter one than in the case of cylindrical liners.
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Jun 2010 · Plasma Physics Reports
[Show abstract][Hide abstract] ABSTRACT: Results are presented from experimental studies of Z-pinches produced by implosion of aluminum and tungsten cylindrical wire
arrays in the Angara-5-1 facility. The electron temperature T
and density n
of the high-temperature pinch plasma have been determined by analyzing line emission from multicharged ions. For the same
mass and radius of the array and the same number of wires in it, the intensity of line emission of H- and He-like Al ions
from an imploded Al + W wire array containing even a small amount of tungsten (7 wt %) is one order of magnitude lower than
that from an Al array. As the W content increases, the total soft X-ray (SXR) yield increases, while the duration of the SXR
pulse decreases. For the 30% W content in the array, the power and duration of the SXR pulse are nearly the same as those
recorded during the implosion of a W array with the same linear mass and radius and the same number of wires. Results are
also presented from experiments with nested wire arrays in which the outer and inner shells were made of Al and W wires, respectively.
It is found that, in this case, the effect of tungsten on the line emission of aluminum is much weaker than that in experiments
with arrays in which tungsten and aluminum wires were placed in the same shell, even if the mass of the inner (tungsten) shell
was larger than that of the outer (aluminum) one. At the same time, the inner W shell plays a significant role in the implosion
dynamics of a nested wire array, reducing the duration of the SXR pulse and increasing the SXR power.
No preview · Article · Mar 2010 · Plasma Physics Reports
[Show abstract][Hide abstract] ABSTRACT: In the work presented are the results of the investigations into the physics of implosion of multiple wire arrays from various elements carried out on the Angara-5-1 facility. To study the process of prolonged plasma production for such arrays some microprobes placed inside the liner were applied. As a result a dependence of the time taken by a magnetic field to penetrate the half radius of the liner on its wire substance type has been found. Study into the process of compression both along the pinch radius and axis was carried out in experiments with conic arrays. Such experiments along with calculations permit clarifying 3-D effects arising in compressing these wire arrays. We describe the results produced by a MEVL code for simulation magnetically insolated vacuum transmission lines (MIVL), which are connected in parallel. This simulation has been tested on the Angara-5-I installation. The results of experiments performed on MOL installation for Baikal project about energy transfer at millisecond time scale are presented.
[Show abstract][Hide abstract] ABSTRACT: 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" proj- - ect 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.
[Show abstract][Hide abstract] ABSTRACT: Summary form only given. 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 which should deliver the current pulse up to 50 MA as a driver for radiating Z pinch are conducted. 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. In recent experiments on installation "Angara-5-1" the quantitative distinction in initiation of wire liners from various materials was shown. Using the set of modified 0-dimensional equations the description of electrical characteristics of Z-pinch discharge at stagnation is developed. Modes of multiwire array compression in which there are a significant excess of the measured sizes of pinch as in visible and in x-ray radiation above the minimal size of pinch, obtained in modeling without taking into account ohmic resistance of plasma, are found out. It is shown, that rate of average current radius change which is calculated from electrical current and voltage profiles has a sharp peak at a moment of start of X-ray output. The image of stagnated Z-pinch in hard X-ray quanta was recorded. The difference of images obtained in soft (~0.5 keV) and hard (6-50 keV) X-rays is presented. Time delay of hard X-ray power peak relatively soft X-ray power peak was recorded. The possible mechanisms of hard X-ray production are discussed. The features of conical multiwire arrays implosion is discussed. Dependence of the height of radiating pinch on a cone angle is obtained. For development of multimegaampere generators for IFE the comparison of intensity of plasma production on a surface of electrodes from lead and stainless steel under action of current with high linear density and high intensity of X-ray is executed. On installation "MOL" intended for developing the scheme of "Baikal" generator- the tests of energy transfer from the inductive store to the magnetic amplifier were executed. Improvement of design of explosive electrical switch type RV-50/1000 is executed. The scheme of a magnetic flux compressor without use of the additional source of initial magnetic flux is proposed.
[Show abstract][Hide abstract] ABSTRACT: 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”  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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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 ne∼ 10cm and electron temperature Te ∼1keV. The radiation spectrum was measured by the use of a crystal spectrograph in which mica (2d=19.9 Å)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.
No preview · Article · Jun 2005 · Plasma Devices and Operations
[Show abstract][Hide abstract] ABSTRACT: 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 Ampére 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 Ampére 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.
No preview · Article · Jan 2004 · Journal of Experimental and Theoretical Physics
[Show abstract][Hide abstract] ABSTRACT: Measurements of spatial shape of wire array produced Z-pinch is described. Nonsymmetry of the cathode and anode regions of pinch was observed. According to different spectra of X-ray emission emissive aria separates on two zones. For a single array an analogue of a ≪zipper effect- is observed: a hot zone appears at the cathode and expands towards the anode.
[Show abstract][Hide abstract] ABSTRACT: The results of the investigations into polarization of line radiation of multiple charged ion plasma of high-current Z-pinches are presented in the work. The experiments were performed on the ≪Angara-5-1≫ facility at Z-pinch currents of 2.5 to 3.5 MA. A dense high temperature pinch was produced by compresson 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 have been achieved: electron density ne∼1021 cm−3 and electron temperature Te∼1 keV. The radiation spectrum was measured by use of a crystal spectrograph where mica (2d=19.8 A) served as a dispersive element. The spectrum of He-like ion of Ar was detected in reflection orders II and III. On the basis of the measurements performed the conclusions on the polarization degree of plasma radiation have been drawn. The work has been supported by Grant RFBR # 02-02-16832.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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
No preview · Article · Jan 2003 · Journal of Experimental and Theoretical Physics
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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 ∼(0.5-1)10<sup>14</sup> 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.
No preview · Article · May 2002 · IEEE Transactions on Plasma Science