ABSTRACT: A method for measuring the gradient of the magnetic field in the plasma of an imploding wire array is described. Results from
measurements of the magnitude and gradient of the magnetic field in a tungsten wire array on the Angara-5-1 facility at currents
of ∼3 MA are presented. A novel method for calculating the velocity of the current-carrying plasma in the framework of MHD
equations from data on the magnitude and gradient of the magnetic field at a certain point inside the array is proposed. It
is demonstrated that a gradient magnetic probe can be used to investigate the plasma current sheath in plasma focus facilities.
Plasma Physics Reports 05/2012; 37(7):586-602. · 0.65 Impact Factor
ABSTRACT: By means of the electrostatic expansion of a cylindrical wire array by an additional electrode, quasi-spherical arrays with
a radius of 8–12 mm and a mass of 200–400 μg consisting of 30–60 tungsten wires 6 μm in thickness are formed. The compression
of Z pinches formed by these arrays was performed by a current of 3–4 MA with a rise time of 100 ns in the Angara-5-1 facility.
It has been shown that the central part of this array forms a region hotter than its edges and that for cylindrical arrays.
JETP Letters 04/2012; 89(7):315-318. · 1.35 Impact Factor
ABSTRACT: One of the main problems in Z-pinch experiments is to transport power and energy from the generator to the load. As the pulse
produced in a double forming line propagates to the load along a water-vacuum insulator, its power and energy decrease due
to current leakage in the plasma shortening the gap and during the establishment of magnetic self-insulation in regions with
a zero magnetic field. Only a fraction of the delivered energy is spent on the load implosion, whereas the rest of the energy
goes on creating the magnetic field around the load. In this work, an analysis is made of what is the fraction of the generator
energy that reaches the liner, what fraction is radiated, and what are losses of energy and current in different stages of
transporting the electromagnetic pulse to the load of the Angara-5-1 facility.
Plasma Physics Reports 10/2008; 34(11):911-919. · 0.65 Impact Factor
ABSTRACT: Results are presented from experimental studies and numerical simulations of three-dimensional dynamics of the plasma produced
in the Angara-5-1 facility by the electrical implosion of conical wire arrays at currents of up to 3 MA. The arrays were made
of 6-to 8-μm-diameter tungsten wires, the inclination angle of the generatrix with respect to the axis being from 15° to 42°.
The results of two-dimensional MHD simulations are compared with experimental data. The formation dynamics of the plasma precursor
is found to be different for cylindrical and conical arrays. As the cone angle increases, the duration of the X-ray pulse
increases, while the height of the pinch radiating zone decreases.
Plasma Physics Reports 09/2008; 34(10):815-829. · 0.65 Impact Factor
ABSTRACT: Results of experimental studying of cylindrical multiwire arrays compression in Z-pinch discharge at a current up to 3.5 MA are submitted. The purpose of work has consisted in finding-out of influence of initial characteristics of arrays on efficiency of electric energy transfer from the generator of high-voltage pulses of a current in energy of plasma. The power and duration of X-ray pulse were used as indicators of efficiency of energy transfer from generator to plasma at stagnation. For analysis of experiments modified 0-D system of equations was applied. Application of the modified system of the equations allows predicting prominent features of experimental profiles of a current and a voltage, the minimal size of pinch and a characteristic time scale of its stagnation. Comparison of the electric power enclosed in Z-pinch with the power of x-ray output is carried out. It is shown, that during stagnation there is an effective plasma movement braking which correlates with increase of output x-ray power. Peaks of hard X-ray with energy of quanta more 50 keV which are detained relatively to peak of soft X-ray were observed. The evidence of development of accompanying phenomenon which can be connected to development of processes of conversion of magnetic energy in energy of plasma is revealed have been registered. Possibility of output X-ray power profiling by means of application induced longitudinal magnetic field and mix substance arrays is observed.
Pulsed Power Conference, 2007 16th IEEE International; 07/2007
ABSTRACT: Results are presented from experimental and theoretical studies of the interaction of intense X-ray pulses with different
types of plane targets, including low-density (∼10 mg/cm3) ones, in the Angara-5-1 facility. It is found experimentally that a dense low-temperature plasma forms on the target surface
before the arrival of the main heating X-ray pulse. It is demonstrated that the contrast of the X-ray pulse can be increased
by placing a thin organic film between the target and the discharge gap. The expansion velocity of the plasma created on the
target surface irradiated by Z-pinch-produced X rays was found to be (3–4) × 106 cm/s. A comparison between the simulation and experimental results confirms the validity of the physical-mathematical model
Plasma Physics Reports 05/2007; 33(6):444-454. · 0.65 Impact Factor
ABSTRACT: Characteristic properties of the plasma production process have been considered for the case of megampere currents flowing through hollow cylindrical wire arrays of the Angara-5-1 facility. In 3-4 nanoseconds after voltage applying to the wire surfaces there appear a plasma layer. The system becomes heterogeneous, i.e. consisting of a kernel of metal wires and a plasma layer. In several nanoseconds the current flow goes from metal to plasma, which results in reducing the electric field strength along the wire.The Joule heat energy delivered to the metal before the moment of complete current trapping by plasma is insufficient for the whole mass transition to a hot plasma state. The X-ray radiography techniques made it possible to detect and study dense clusters of substance of ∼1g/cm3 at a developed discharge stage. The radial expansion velocity of ∼104 cm/s measured at the 70-th nanosecond after the current start allows treating the dense core at a late stage in the form of a submicron heterogeneous structure from its liquid and slightly ionized gas phase. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Beiträge aus der Plasmaphysik 11/2005; 45(8):553 - 567.
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.
Pulsed Power Conference, 2005 IEEE; 07/2005
ABSTRACT: Knowledge of spatial mass distribution is important for understanding the physics of implosion of megaampere-current wire
arrays. The paper presents results from studying the electron density distribution at the periphery of a tungsten wire array
near the instant of maximum compression by using laser interferometry at λ=0.69 µm. It is found that, at the instant of maximum
compression (∼100 ns after the beginning of the discharge), the estimated maximum local electron density inside the wire array
reaches ∼1018 cm−3 at a distance of 0.3–3 mm from the initial wire positions. Assuming the average tungsten ion charge to be 10, the local linear
mass density in this region turns out to be 3 µg/cm, which amounts to about 10% of the total linear mass density of the liner.
A fraction of the generator current flows through this plasma. The duration of the soft X-ray pulse is 5–8 ns, which indicates
the achievement of a fairly high compression ratio.
Plasma Physics Reports 02/2004; 30(3):218-227. · 0.65 Impact Factor
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.
Journal of Experimental and Theoretical Physics 01/2004; 99(6):1150-1172. · 1.03 Impact Factor
ABSTRACT: The features are studied of plasma production in the initial stage of implosion of hollow cylindrical wire arrays at electric-field
growth rates of 1012 V/(cm s). The results are presented from the analysis of both UV emission from the wire plasma and the discharge parameters
in the initial stage of the formation of a Z-pinch discharge. It is found that, a few nanoseconds after applying voltage to
a tungsten wire array, a plasma shell arises on the wire surface and the array becomes a heterogeneous system consisting of
metal wire cores and a plasma surrounding each wire (a plasma corona). As a result, the current switches from the wires to
the plasma. A further heating and ionization of the wire material are due primarily to heat transfer from the plasma corona.
A model describing the primary breakdown along the wires is created with allowance for the presence of low-Z impurities on the wire surface.
Plasma Physics Reports 11/2003; 29(12):1034-1040. · 0.65 Impact Factor
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
Journal of Experimental and Theoretical Physics 01/2003; 97(4):745-753. · 1.03 Impact Factor
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.
IEEE Transactions on Plasma Science 05/2002; · 1.17 Impact Factor
ABSTRACT: Fast compression of liners is under consideration as a possible approach to electric energy conversion into X-ray pulse at the energy scale of dozens of megajoules. Scientific cooperation including TRINITI, Kurchatov institute, Efremov institute, and VNIITF develops the "Baikal" project in which an inductive storage has to be used which in the case of successive transformation procedure could produce an electric pulse with parameters adequate for these purposes. On the S-300 pulsed power generator, experiments is being carried out studying promising schemes of output devices for the next generation of machines. In particular, a device similar to the plasma flow switch is being investigated aimed to sharpening the current ns. The results of experiments on a current implosion of multi-wire arrays on Angara-5-1 facility are presented. There are given experimental proofs that the formation of Z-pinch takes place at temporally spread plasma production. The phenomena of temporally spread plasma production determines mode and quality of final stage of a pinch. The temporally spread plasma formation is not a hindrance to obtain high power of X-radiation output at compression and heating of a Z-pinch.
Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers; 02/2001
ABSTRACT: Large achievements in soft X-ray production were obtained by
Sandia with multiwire array implosion. The efficiency of the generator
energy conversion to radiation strongly depends upon the quality of the
plasma shell. Thus the investigation of the initial stage of wire
explosion and the method of plasma shell creation are very important. To
study the different processes of plasma creation at the initial stage of
wire explosion the precision voltage on the wire array axis and current
measurements have been carried out
High-Power Particle Beams, 1998. BEAMS '98. Proceedings of the 12th International Conference on; 02/1998