Studies on the Measuring Method of Number Density of Ions in the High Speed Flow Field

At present, the method of using a parallel-plate probe to measure the number density of ions at atmosphere has some limitations such as big size of probe, low velocity of gas flow allowed to measure, and low accuracy. In this paper, a detector with a spherical probe is fabricated and is used to measure the number density of ions. The diameter of probe can be reduced to 6 mm. The highest velocity that can be measured is extended to 28 m/s, and the collecting rate is up to 100%. The spatial distribution diagram of ion number density is also given, with a cross section of 0.36 $hbox{m}^{2}$. Then, an effective method is provided to measure the number density of ions generated from the miniature ion source or in the gas flow with high velocity.