Some Promises of Magnetic Implosion of High-Velocity Liners in the ALT-3 Driver

Simulations of the ALT-3 explosive magnetic driver with modifications in its measuring unit and liner assembly are reported. They demonstrate new capabilities of the driver as applied to materials properties studies under ramp and shock compression up to ~80 and ~80 Mbar, respectively.

I. Introduction

The ALT-3 driver, similar to ALT-1,2 [1], has been designed [2]–[5] (see Fig. 1) to test the efficiency of magnetic implosion of a cylindrical Al liner as an impactor driven by a current of ~70 MA [azimuthal magnetic field MG [see Fig. 2(a)]. Such a liner can have a velocity of km/s at an impact radius of cm and generate shock pressures above 5 Mbar in Al samples. In the ALT-1,2 experiments, a similar Al liner having a thickness of 2 mm was driven to ~12 km/s ( cm) by a current of ~30 MA ( MG). Fig. 1.

Scheme of the ALT-3 driver (projected). 1—helical explosive magnetic generator (HEMG); 2—15-module disk EMG Ø0.4m (DEMG); 3 and 4—explosive closing switches (ECS): ECS-3 disconnects the HEMG to form a DEMG-FOS circuit with 7-MA current by initial time of magnetic flux compression in DEMG cavities; ECS-4 has negligibly small resistivity and connects the load at a given time forming a FOS-liner circuit with 6 nH inductance; 5—electrically exploded FOS with a Cu foil having a thickness of 0.12–15mm and a height of ~92 cm; 6 and 7—coaxial radial transmission line (TL); 8 and 9—ponderomotive unit (PU) with an Al liner of outer radius cm, thickness mm and height ~4.4 cm; 10 and 11—current probes; 12—measuring unit of radius cm with PDV [10] probes and test materials (~20 samples).

Fig. 2.

Results of 1-D MHD simulation of liner implosion in ALT-3 (see Fig. 1). (a) Current and magnetic field on the liner, (R-t)—diagrams of liner boundaries and velocity of its inner boundary. (b) Profiles of pressure , density , current density j(t), magnetic field , and temperature in the liner before its impact on the measuring unit ( cm).