Plasma generator manufacturer DC discharge to produce plasma theory

• Categories:Technical Support
• Author:plasma cleaning machine-surface treatment equipment-CRF plasma machine-Sing Fung Intelligent Manufacturing
• Origin:
• Time of issue:2021-03-22
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(Summary description)There are two kinds of plasma gas discharge, one is DC and the other is AC. DC discharge usually refers to low-frequency discharge. Under different pressure and current range, due to the number of electrons in gas, collision frequency, particle diffusion and heat transfer velocity are different, there will be dark current area, glow discharge area and arc discharge area. The magnitude of the current depends on the power supply load characteristic curve corresponding to the falling line of resistance R1, R2 and the discharge characteristic curve intersection (operating points A, B, C). 1. Dark current area: The electromagnetic field accelerates the electrons, so that they gain enough energy, through the collision with neutral molecules, the number of new electrons rapidly increased, when the current reaches 10-7~10-5 A, there will be a very thin layer of light near the anode. 2. Glow discharge area: When the current is increased again (10-5~10-1 ampere), the cathode will be bombarded by ions at low pressure and accelerate toward the anode direction, thus giving off electrons. Near the cathode, there is a cathode drop region with a large potential difference. In the middle part between the electrodes, there is a positive column region with a small potential gradient, and the medium is non-equilibrium plasma. When there is no gas convection, electrons and ions in the positive column diffuse towards the wall at the same speed, and combine on the wall, releasing energy. In classical theory, the distribution of electron density on the cross section is in the form of Bessel function. There is an anode potential drop region several millimeters thick near the anode, and its potential difference is basically equal to the gas ionization potential difference. 3. Arc discharge area: When the current exceeds 10-1 A and the pressure is also high, the Joule heat generated in the positive column area is greater than the heat dissipation of the particle diffusion zone to the wall, so that the temperature in the center of the positive column area increases, the gas conductivity increases, so that the current concentrates in the center of the positive column area, forming unstable contraction. The conducting positive column will shrink into an arc with higher temperature and higher current density, that is, arc discharge. The current density is 104~106 A/cm, forming "cathode spot" on the cathode, according to the mechanism of hot electron emission (hot cathode) or field emission (cold cathode), electrons are emitted. There are also "anode spots" on the cathode. Because the electrons carry their kinetic energy into the anode, they release energy equivalent to the work that was lost when they enter the anode. Combined with the heat in the falling region of the anode, the anode heats up much more than the cathode. The above is the CRF plasma generator manufacturers to DC discharge to produce plasma theory discussion, I hope to help you.