[en] Diagnostics of downstream plasma generated in a microwave ECR plasma chemical vapour deposition (CVD) facility (a 2.45 GHz, 1.5 KW) is done using a Langmuir probe. The probe is inserted near the substrate location (640 mm away from main ECR zone). The objective is to see the extent of uniformity in the plasma parameters of generated plasma near the substrate location. For this purpose I-V probe characteristics were recorded at four different operating pressures for four different power levels for each pressure to cover the operating range of parameters that are used during thin film deposition. Data was analysed to obtain the radial electron energy distribution function (EEDF) and radial variation of plasma parameters such as electron number density (n_e), average electron energy (< E>), and plasma potential (V_p). Ion number density (n_i) was also estimated by Orbital Motion Limited Theory (OML) using a Graphical User Interface (GUI) developed for this purpose and compared with n_e calculated from electron energy distribution function (EEDF). The results obtained by the different methods are compared and observed differences are explained.