Energy Estimation of Plasma Induced by High-Speed Impact at Impact Point

Abstract

Pressure and temperature are important physical quantities for understanding high speed impact phenomena. The pressure caused by high speed impact can be measured with a PVDF gauge. But measurement method of the temperature generated by high speed impact has not been established. So, we focused on the plasma induced by the impact. By grasping the energy of the plasma induced by the impact, it is a clue to estimate the temperature change at the impact point. In the experiment, the plasma was generated by colliding a tip hemispherical projectile of A5052 with same material plate at 630 m/s. Triple probe method was used for measurement of plasma induced by impact. A measuring device was placed at 12 mm from the impact point. The electron density calculated from experimental results decreased with time. This showed that plasma was diffused. As a result of fitting to the time history of electron density using the diffusion equation, it was found that 6.7×10¹³ electrons are generated at the impact point. Assuming that all the ionized atoms are monovalent ions or trivalent ion, the energy at the impact point was estimated from the number of electrons and the ionization energy and it was 10^-4-10^-5 J. In the future, we will pay attention to atmospheric diffusion phenomena and ionization degree and confirm the validity of the obtained value.