Electron energy distribution of the discharge plasma in a cusped ion thruster plays an important role for its discharge chamber performance. Accurate electron energy distribution measurement, particularly in the energy range above the ionization potential, is required to estimate the discharge performance correctly. This Note presents measurement system that is composed of a low-noise detector circuit with a logarithmic amplifier, digital data acquisition and computer system for data analysis. This system enables us to accurately measure the energy distribution even when the measurement is done in noisy environments. The accuracy of the experimental technique and measurement system is discussed. Using the discharge plasma in a cusped thruster, an example demonstrating the measurement system is given.
The Japan Society for Aeronautical and Space Sciences