electron) flows from plasma boundaries and comprises a metallic cylindrical receiver-cup – 1 (Fig. 1) closed with, and insulated from, a washer-type metallic electron-suppressor lid – 2 provided with the round axial through enter-hollow of an aperture with a surface area . Both the receiver cup and the electron-suppressor lid are enveloped in, and insulated from, a grounded cylindrical shield – 3 having an axial round hole coinciding with the hole in the electron-suppressor lid – 2. The electron-suppressor lid is connected by 50 Ω RF cable with the source of variable DC voltage . The receiver-cup is connected by 50 Ω RF cable through the load resistor with a sweep generator producing saw-type pulses . Electric capacity is formed of the capacity of the receiver-cup – 1 to the grounded shield – 3 and the capacity of the RF cable. The signal from enables an observer to acquire an I-V characteristic of the Faraday cup by oscilloscope. Proper operating conditions: (due to possible potential sag) and , where is the ion free path. Signal from is the Faraday cup I-V characteristic which can be observed and memorized by oscilloscope In Fig. 1: 1 – cup-receiver, metal (stainless steel). 2 – electron-suppressor lid, metal (stainless steel). 3 – grounded shield, metal (stainless steel). 4 – insulator (teflon, ceramic). – capacity of Faraday cup. – load resistor. Thus we measure the sum of the electric currents through the load resistor : (Faraday cup current) plus the current induced through the capacitor by the saw-type voltage of the sweep-generator: The current component can be measured at the absence of the ion flow and can be subtracted further from the total current measured with plasma to obtain the actual Faraday cup I-V characteristic for processing. All of the Faraday cup elements and their assembly that interact with plasma are fabricated usually of temperature-resistant materials (often these are stainless steel and teflon or ceramic for insulators). For processing of the Faraday cup I-V characteristic, we are going to assume that the Faraday cup is installed far enough away from an investigated plasma source where the flow of ions could be considered as the flow of particles with parallel velocities directed exactly along the Faraday cup axis. In this case, the elementary particle current corresponding to the ion density differential in the range of velocities between and of ions flowing in through operating aperture of