Energy conversion efficiency of electrical exploding foil accelerators

Abstract

We evaluate the energy conversion efficiency of an electrical exploding foil accelerator that accelerates a thin dielectric foil (called the flyer) to more than 1 km/s, which is propelled by electrically exploded bridge material. The effective flyer mass ejected from the accelerator is estimated by impulse measurements obtained using a gravity pendulum as well as by time-resolving flyer velocity measurements obtained using a photonic Doppler velocimetry system. For two different bridge sizes (0.2 and 0.4 mm), the flyer velocity and impulse increase with the input energy at the bridge section. The maximum flyer velocity and impulse, that is, 4.0 km/s and 67 µN s, respectively, are obtained by supplying 0.33 J of input energy. Upon increasing the input energy, the effective flyer mass also increases and exceeds the designed-bridge mass for both bridge sizes. The energy conversion efficiency from input electrical energy to flyer kinetic energy is calculated based on the effective flyer mass, velocity, and input energy. Both bridge sizes show comparable efficiencies: 27% and 30% for 0.2 and 0.4 mm bridges, respectively. The efficiency increases with increasing specific input energy at least up to 15 MJ/kg for the 0.4 mm bridge, whereas the efficiency of the 0.2 mm bridge above 30 MJ/kg decreases. This is owing to the excessively high input energy density in the 0.2 mm bridge, which causes the effective flyer mass to increase by including surrounding materials. These results indicate that the specific input energy should be optimized for obtaining maximum efficiency.

Optimizing cure temperature of polyimide flyer for exploding foil initiator applications

“…A reliable flyer material needs to be robust, able to withstand an impulsive launch, and remain intact at speed approaching supersonic velocity. Various materials such as silicon, 3 polymethyl methacrylate (PMMA), 7 Mylar, 8 SU-8, 9 polyimide (PI), [10][11][12] parylene C (PC), 13 and PC/metal alloy 14,15 have been used for the preparation of FFI flyer. Compared with other materials, PI is a more commonly used flyer material that has several distinct advantages such as favorable dielectric properties and high thermal stability.…”

Preparation and Performance Characterization of Exploding Foil Initiator Based on ODPA-ODA Polyimide Flyer

“…To study the electrical explosion performance of the in situ prepared polyimide flyer, a photo doppler velocity (PDV) measurement system, based on the doppler frequency shift effect, is used to measure the velocity of the polyimide flyer [ 4 , 17 ]. The explosion current and voltage of the exploding foil were measured by a homemade device, whose schematic diagram is shown in Figure 3 .…”

“…Under the action of high pressure and heavy current, exploding foil generates high-temperature and high-pressure plasma to drive high-speed flyer to detonate explosives. So far, a range of materials such as polyimide [ 2 , 4 , 5 ], parylene C [ 6 ], polymethyl methacrylate [ 7 ], polyester [ 8 ], silicon [ 9 ], and PC/metal alloy [ 10 ] have been designed as flyer plate. Of the flyer materials mentioned above, polyimide is the most attractive engineering polymer [ 11 ], which exhibits thermal stability, outstanding mechanical properties, high radiation resistance, and excellent dielectric properties.…”

“…PMDA-ODA polyimide is commonly used for the flyer in EFI, probably because of its excellent engineering performance and commercial availability. For example, Ichihara [ 4 ] recently evaluated the energy conversion efficiency of an EFI that accelerates a flyer of polyimide film. Borman and Dowding [ 5 ] demonstrated the use of numerical simulation to predict the mass of plasma formed and subsequent mass ejected from an EFI with polyimide flyer during various initial circuit conditions.…”