Comparative studies of cold/hot probe techniques for accurate plasma measurements

Abstract

The emissive probe technique and the cold Langmuir probe technique for the plasma potential measurement are compared in microwave electron cyclotron resonance plasmas. With different results of plasma potential, discrepant results of electron temperature and electron density are obtained from a hot emissive probe I–V curve and a cold Langmuir probe I–V curve, respectively. A comparison of the experimental data shows that the plasma parameters obtained from the cold Langmuir probe I–V curve are always grossly underestimated, while the results determined from the hot emissive probe I–V curve are much more reliable. Additionally, based on the experimental results, a novel emissive probe technique named the hot probe with zero emission limit method is proposed to easily obtain the accurate plasma potential and other reliable plasma parameters.