Double Langmuir Probe Analysis Freeware: DLPGUI

Double Langmuir probe (DLP) is an important diagnostic tool that can be used to characterize various types of plasmas. Unlike the single Langmuir probe (SLP), DLP withdraws no net current from the plasma; therefore, it can be used to do measurements on plasmas that are small and time-varying. However, DLP can measure fewer parameters than SLP. With appropriate data analysis, electron temperature ($T_{e})$, positive ion density ($n_{i})$ and the local field can be determined using DLP measurements. For the analysis of measured I-V curves, one must choose an electron energy distribution function (EEDF) \textit{a priori}, and in literature, the methods of analysis generally assume a Maxwellian EEDF. In this work, we review and discuss available theories to reliably evaluate $T_{e}$ and $n_{i}$ from DLP I-V curves and incorporate those theories into a new and free analysis software named DLPGUI. DLPGUI acts both as a theoretical compendium and a flexible analysis tool. With a graphical user interface, DLPGUI allows the user to choose from a list of ion flux models of varying collisionality and different EEDFs before performing analysis of I-V data. The software also provides an approach to extract $n_{i}$ from measurements conducted in gas mixtures.