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Electrical Explosion of Microwires in Vacuum

#3649


Electrical Explosion of Microwires in Vacuum. Experiments and Simulations

Tech Area / Field

  • PHY-PLS/Plasma Physics/Physics

Status
3 Approved without Funding

Registration date
22.11.2006

Leading Institute
VNIITF, Russia, Chelyabinsk reg., Snezhinsk

Supporting institutes

  • Siberian Branch of RAS / Institute of High Current Electronics, Russia, Tomsk reg., Tomsk

Collaborators

  • Sandia National Laboratories, USA, NM, Albuquerque

Project summary

The goal of this project is to develop a physical model that describes processes occurring on electrical explosion of wires (EEW) in vacuum. The interest in the EEW in vacuum is associated with successful experiments on multiwire array implosions and the prospects of using wire array Z-pinches for realization of inertial controlled fusion. At the same time, at present there is no a physical model of the EEW, which, on the one hand, gives a reliable description of available experimental data, and on the other hand, can be included in the existing codes for wire array implosion simulations.

The investigations planed in the frame of this project are aimed at formation of experimental database and development of a physical model of the EEW in vacuum on the base of obtained experimental results. It is considered to be established to date that electrical explosion of wires in vacuum is characterized by formation of a vapor-liquid core surrounded by a low density plasma corona shunting the conductor. Along with a description of equilibrium processes occurring on the EEW in vacuum, the model should take into account other important phenomena peculiar to the EEW in vacuum such as development of shunting discharge along the wire surface and the process of stratum formation in a dense core.

In order to form the experimental database, the following research will be carried out:

  • Determination of the electric field strength Е, at which shunting of a conductor occurs at the EEW in vacuum. The experiments will be carried out on the installations of the Institute of High Current Electronics at the current density rise rate through a wire from 1015 A/(s∙cm2) to 1017 A/(s∙cm2). As a result of this stage of work, the empirical dependence E/n = f(n, τ) will be obtained, where E is the electric field strength at the instant of shunting, n is the number density of desorbed gas, and τ is the shunting time.
  • Obtaining of the experimental data to construct a dependence of the instant of stratum formation τstr as a function of current density rise rate through a conductor. Radiography based on an X-pinch x-ray source (radiation pulse duration – 0.1-1 ns, quantum energy – 2-7 keV, radiation power ~ 1 GW) will be used to determined the instant of stratum formation.

On the basis of obtained experimental data, the physical model of the EEW in vacuum will be developed, which will describe wire explosion dynamics at the explosion regimes realized in multiwire arrays. The model will take into account development of the shunting discharge along the wire surface and the process of stratum formation in the dense matter. The physical model will be developed taking into consideration the state-of-art conceptions on electrical explosion of wires, and it will include the following:
  • Modern data on the properties of dense non-ideal plasma forming during electrical explosion of wires, i.e., the equations of state in a wide range of thermodynamic parameters and dependence of the transport coefficients of metals on density and temperature;
  • Magnetohydrodynamics equations that describe the processes in dense matter, specifically, development of different type of MHD instabilities leading to stratum formation at wire explosions;
  • Empirical dependences based on the experimental data that describe development of shunting discharge along the wire surface and allow prediction of the instant of wire shunting during the EEW in vacuum.

The model developed in the coarse of this project will permit:
  • prediction of the instant of formation of shunting current-carrying plasma near the conductor surface (the instant of corona formation) during the EEW at the current density rise rate through a wire corresponding to that in wire array implosions (dj/dt = 1015 - 1017 A/(s∙sm2));
  • prediction of the instant of stratum formation as well as a characteristic size of stratification wavelength as a function of the current density flowing through a wire during the EEW at the current density rise rate through a wire corresponding to that in wire array implosions (dj/dt = 1015 - 1017 A/(s∙sm2));
  • take into account the EEW processes in simulations of wire array implosions.


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