Time function triple Langmuir probe measurements in low frequency pulsed DC discharge plasma

Abstract

286 1 Different plasma parameters including the electron temperature (T e ), electron number density (n e ), float ing potential, electron energy distribution function (EEDF), etc. can reliably be investigated with Lang muir probes [1,2]. From the time when Langmuir probe was invented, several physicists have derived theories and published the work to solve the difficulties in explaining the probes data for their applications as power full plasma diagnostics [1][2][3][4]. The triple Lang muir probe has several benefits over standard single and double Langmuir probes. It allows immediate measurements of plasma parameters in pulsed DC plasmas without requirement of the sweep voltage [5,6]. The pulsed DC discharges have many advantages over simple DC discharges. In DC discharge, ions in the plasma gain more and more energy with rise in input power. As a result, temperature of the cathode increases by causing transition from abnormal glow discharge to an arc [7]. This transition to an arc region can be suppressed effectively by using pulsed DC dis charge instead of a simple DC discharge [2,8]. In plasma processing, the substrate temperature can be Abstract-This study investigated the temporal profiles of electron temperature and number density in rec tified DC air discharge generated with a 50 Hz step up transformer. An in house built triple Langmuir probe and circuitry were used to diagnose the plasma parameters as a function of input voltage and filling gas pres sure. A tungsten metal wire capable of withstanding the high temperatures was used as probe tip material. The temporal profiles revealed an increase in electron temperature with input voltage in the range of 380 to 450 V, whereas, an inverse relation between number density and input voltage was evident in the given work. The observed trend in the plasma parameters was absolutely reversed in case of the filling gas pressure. The elec tron temperature linearly decreased with an increase in pressure from 1 to 4 mbar, whereas a linear increase in number density with pressure was seen in the temporal profiles. Finally, it was concluded that the results for the tested plasma parameters were consistent and the in house built probe functioned well in DC dis charge for the used range of voltage and filling pressure.

Study of High-Density Polyethylene (HDPE) Kinetics Modification Treated by Dielectric Barrier Discharge (DBD) Plasma

“…The Langmuir Triple probe is a disseminated technique for the diagnosis of plasma, which can provide the electronic temperature, i.e., the average energy of the electrons [ 56 , 57 ]. Then, it is possible to correlate the average energy of the electrons with the energy of the chemical bond, estimating the functional groups generated superficially during the plasma treatments [ 58 , 59 , 60 , 61 ].…”