Hollow Probe for Measuring Ion Density in a Slightly Ionized Plasma Flow

Abstract

In order to measure the number density of charged particles in a high speed flow on slightly ionized argon, the hollow electric collector probe has been shown to be useful. This work is to investigate effects of the dimension of hollow probes and the strength of applied electric field on capture of charged particles. The experimental results show that the lower aspect ratio (=the ratio of the distance between electrodes to the electrode length) and the higher applied electric field are effective for capturing all charged particles entering into the probe. Even when an ion number density is relatively high (≤10¹³ cm⁻³), the hollow probe can be used for measurement of plasma density in a flowing plasma, though there are restrictions on minimum dimensions of probes and maximum strength of applied electric field.