Compression Stability of Multi-Layer Composite Close-Wound Solenoid Driven by Explosive Implosion

The tightly wound solenoid is the core component of a cascade explosive cylindrical implosion magnetic flux compression device. We designed a solenoid cylinder with composite structure, and carried out two-cascade implosion magnetic flux compression experiment. It is known that the growth of interfacial instability of the solenoid cylinder will determine the amplification of the magnetic field and/or magnetic compressive stress. In the implosion compression event, the projection images of the solenoid by high-speed photography revealed that the inner surface kept in a circle without visible collapse, but cyclic disturbances were observed on the outer surface resulting from explosive detonation. A 2D finite element model was built to study the instability growth of the solenoid under the explosive implosion. The simulation results displayed that the multi-point network detonation of the explosive played an important role on the solenoid instability. The instability growth can be effectively inhibited by both increasing the number of detonation points and introducing a 1–2 mm thick cavity between the explosive cylinder and the solenoid.