Normal glow discharge: comparison of calculated and experimental data

The combined numerical and physical modeling of a glow discharge between plane disk electrodes in molecular nitrogen is performed at pressures р = 3 and 5 Tor. The satisfactory description of experimental data by the drift-diffusion model is shown. The simultaneous analysis of experimental and calculated data has permitted identification of the normal burning regime of a glow discharge. However, the essential effect of model parameters such as the secondary electron emission coefficient and the first Townsend coefficient on the calculated voltage-current characteristic has been demonstrated in this case.

INVESTIGATION OF GLOW DISCHARGE`S ENERGY PARAMETERS IN SMALL DIAMETER LONG TUBES

Urgency of the research. Cleaning the interior surfaces of the pipes is a mandatory operation, preceding the application of the coating using the methods of vacuum spraying. Significant disadvantages of traditionally applied methods of chemical and electrochemical purification of such surfaces conditioned the widespread use of plasma technologies based on low-temperature plasma glow discharge. Target setting. In particular, to date, the most common way to clean surfaces from various kinds of contaminants is ion spraying using a gas-discharge plasma of glow discharge. This cleaning method allows efficient removal of major types of contaminants such as fats, adsorbed water, gases, oxides, and allows processing surfaces of different configurations. Actual scientific researches and issues analysis. It is shown that the application of the glow discharge in the processes of purification and coating on the inner surface of pipes with a diameter of 56 mm in length 120 mm with the application of transverse magnetic field is shown. However, there are a number of difficulties, mainly related to the low productivity of the process, since the cleaning of the inner surface of such pipes was carried out for 60 minutes. Identification of unexplored parts of the general problem. It is possible to increase the processing efficiency by applying a glow discharge initiated in a hollow cathode. However, for today there are no data on the distribution of the concentration of charged particles inside the product, in which L >> d. The purpose of the work. The purpose of this work is a comparative analysis of stress-strain state (NDS) in the diffusion welding of compounds from heterogeneous materials, which occurs when heated in a normal glow discharge and glow discharge, initiated in a hollow cathode. The statement of basic materials. Using the probe method, the energy characteristics of the plasma of the glow discharge initiated in the hollow cathode were studied in relation to the conditions for the cleaning of the interior surfaces of long pipes of small diameter. It is shown that with a pressure in a gas-discharge chamber of 53 Pa and a discharge current of 0.075 A, a sufficiently dense plasma with a concentration of charged particles at the level of 1.6 ∙ 1010 cm-3 is formed in the investigated geometry of the cathode cavity, which is characterized by high heterogeneity in height of the cavity (40 ... 60 %). It is also shown that an effective mechanism of influence on the distribution of plasma in the middle of the cathode, in which L >> D is the change in the distance of the cathode anode, a decrease of which from 40 to 20 mm increases the uniformity to 15 ... 20 %, and the introduction of an additional anode ring in the discharge scheme - to 8 ... 10 %. Conclusions. It has been shown that the purification of the inner surface of long pipes of small diameter (in which L = 10D) by smoldering discharge using the effect of a hollow cathode is complicated by a number of factors, mainly due to the rather high heterogeneity of the distribution of the plasma inside the cathode cavity.