Study of shock-compressed argon plasma using microwave diagnostics

A microwave diagnostics method and radio interferometers with wavelengths of 3.2 and 2.1 mm are used to study the kinematic and electrophysical characteristics of shock-compressed argon plasma, which is initially at atmospheric pressure. This research study is carried out at pressures of 12–56 MPa, shock wave velocities of 3.1–6.2 km/s, temperatures 9 000–19 000 K, and densities 0.006–0.012 g/cm$^3$ for powers of Coulomb nonideality from 10$^{-4}$ to 0.2. The data obtained on the shock-wave compressibility of argon are consistent with the known measurement results and calculations using the modified Van der Waals model and the chemical plasma model. A set of values of the reflection coefficient of electromagnetic radiation from the shock wave front at wavelengths of 3.2 and 2.1 mm is obtained, which serves as a basis for estimating the conductivity and electron concentration behind the shock wave front. The experimental data are consistent with calculation results in a wave velocity range of 3.1–3.6 km/s. It is established that with a further increase in the velocity has no effect on the reflection coefficient.