A new method for determining the plasma density by a RF twin probe

A Twin Probe which consists of a large 'reference' probe (RP) and a small 'sounding' probe (SP) placed in the boundary layer of the RP has been used for determining the space potential of the plasma. This paper proposes a new method for determining the plasma density by using a RF Twin Probe superimposed a RF voltage on the d.c. potential of the RF. A good agreement of measured values of the plasma density by using the present method with those by using a resonance probe method and a Langmuir probe method is obtained. (Auth.)