Diagnostics of a converging strong shock wave generated by underwater explosion of spherical wire array

Abstract

The results of experimental studies of the convergence of shock waves (SWs) generated by the underwater electrical explosion of a spherical wire array supplied by a current pulse with an amplitude ∼300 kA and rise time ∼1.1 μs are reported. In the experiments, the power and spectrum of the light emission from an optical fiber, the explosion of a copper tube, and the time-dependent resistance of a resistor placed in the equatorial plane of the spherical wire array were measured. A comparison of the experimental data with the results of numerical simulations of SW convergence shows that the SW keeps its uniformity along the major part of the convergence towards the implosion origin.

Spectroscopy of a plasma formed in the vicinity of implosion of the shock wave generated by underwater electrical explosion of spherical wire array

“…A detailed analysis of the processes of the capillary compression by converging SW was presented in Ref. 27, showing the energy density concentration in the vicinity of the implosion and agreement with the value of pressure obtained by HD simulations in which symmetrical convergence of the SW was assumed. Here, let us note that in a few generator shots the capillary was specially moved offaxis from the origin of the sphere, which led to the damage shown in Fig.…”

“…II, when the capillary was filled by He or Ar gas, only continuous spectra were obtained (Ref. 27). Assuming that these spectra correspond to the Planckian radiation, a temperature of $3300 K was estimated as a best fit with experimental data.…”

“…27, total destruction of the copper capillary having an outer diameter of 0.9 mm placed approximately at the location of the origin of the sphere (tolerance of 60.5 mm) was obtained. A typical zoomed image of the capillary damage shown in Fig.…”

“…27. To explode spherical wire arrays having a diameter of 30 mm and consisting of 40 copper wires each with a diameter of 100 lm, a high-current generator (stored energy of $3.6 kJ, current amplitude and rise time of $300 kA and $1.1 ls, respectively) was used (see Fig.…”

“…In addition, similarly to the case of a cylindrical SW implosion, the simulations assume uniformity of the converging SW. In a recent study, 27 to investigate the uniformity of the converging SW additional diagnostics were applied; namely, the power and spectrum of the light emission from an optical fiber, the explosion of a copper capillary tube, and the time-dependent resistance of a carbon resistor placed in the equatorial plane of the spherical wire array were measured. A comparison of the results with those of numerical simulations showed that the SW should keep its uniformity along the major part of the convergence toward the implosion origin.…”