Obsah obrázku text, Písmo, snímek obrazovky, řada/pruh Popis byl vytvořen automaticky 4. Glow Discharge FB242 Gas discharges: physical mechanisms and applications At certain conditions it can be stabilized also at atmospheric-pressure as the so-called Atmospheric Pressure Glow Discharge (APGD): (j/p2) = konst. (Engel a Steinbeck) (alternating 50 Hz glow discharge) nCathode – with a secondary emission coefficient γ that is very important for the operation of the GD. nAston Dark Space – A thin region to the right of the cathode with a strong electric field. The electrons are accelerated through this space away from the cathode. This region has a negative space charge, meaning that stray initial electrons together with the secondary electrons from the cathode outnumber the ions in this region. The electrons are too low density and/or energy to excite the gas, so it appears dark. nCathode layer (glow) – The the electrons are energetic enough to excite the neutral atoms they collide with and their energy is increasing. The cathode glow has a relatively high ion density. The axial length of the cathode glow depends on the type of gas and the pressure. The cathode glow sometimes clings to the cathode and masks the Aston dark space. nCathode dark space - has moderate electric field, a positive space charge and a relatively high ion density. nNegative Glow – The brightest intensity of the entire discharge. The negative glow has relatively low electric field and is the most intense on the cathode side. Electrons carry almost the entire current in the negative glow region. Electrons that have been accelerated in the cathode region to high speeds produce ionization, and slower electrons that have had inelastic collisions already produce excitations. These slower electrons are responsible for the negative glow. The electron number density in the negative glow is about 1016 electrons/m3 . As these electrons slow down, energy for excitation is no longer available and Faraday dark space begins. Výsledok vyhľadávania obrázkov pre dopyt hollow cathode negative glow The positive column is a highly non-equilibrium plasma • • • • • • •J.P. Boeuf: „Ionization waves (striations) in a low-current plasma column revisited •with kinetic and fluid models“ Physics of Plasmas 29, 022105 (2022) • •„An essential aspect of the instability leading to the development of these striations is the non-Mawellian nature •of the electron energy distribution function in the uniform electric field prior to the instability onset, resulting •In an electron diffusion coefficient in space much larger than the energy diffusion coefficient.“ featured Výsledok vyhľadávania obrázkov pre dopyt hollow cathode negative glow Non-Maxwellian electron distribution in negative glow n Výsledok vyhľadávania obrázkov pre dopyt hollow cathode negative glow n n n n1 – hollow cathode, 2 – anode, n3 – positive space charge, 4 – plasma, n5 – electron trajectory n Výsledok vyhľadávania obrázkov pre dopyt hollow cathode negative glow Výsledok vyhľadávania obrázkov pre dopyt hollow cathode negative glow Applications of the positive column plasma: -„glow discharge lamps“ - 0cArGD Glow discharge lamps https://en.wikipedia.org/wiki/Gas-discharge_lamp T014952A 2 Germicidal lamps – without the fluorescent layer: n Germicidal_UV_discharge_tube_glow Gas (gas discharge) lasers: nA laser is a coherent and highly directional radiation source. LASER stands for Light Amplification by Stimulated Emission of Radiation. nA laser consists of at least three components: na gain medium that can amplify light that passes through it nan energy pump source to create a population inversion in the gain medium ntwo mirrors that form a resonator cavity nThe gain medium can be solid, liquid, or gas and the pump source can be an electrical discharge, a flashlamp, or another laser. The specific components of a laser vary depending on the gain medium and whether the laser is operated continuously (cw) or pulsed. The following headings describe specific laser designs. Gas lasers are typically excited by gas discharges gaslaser excimer : ArF* - 248 nm, XeCl* - 308 nm (pulsed) nitrogen : 337 nm (pulsed) He-Ne : 632.8 nm (cw) Ar ion : 488, 541 nm (cw) CO2 : 10.6 µm (cw or pulsed) BlaserA Excimer lasers and lamps, energy efficiency as high as 40% ! s01_img03 EXCIM s01_img02 s01_img01 Excimers n Excimer%20Spectra Thyratron A thyatron is one kind of tube filled with gas and it is used like a controlled rectifier as well as a high power electrical switch. Applications of cathode phenomena occuring in G.D. - cathode sputtering Glow Glow1 n Magnetron nTargets: Magnetron with the hollow cathode Plasma nitridation: 0dNitridGlow Plasma nitridation: n Plasma Immersed Ion Implantation nThe plasma immersion ion implantation process is of potentially great significance for the modification of surfaces, since in principle it permits the implantation of ions into a surface without the usual line-of-sight restrictions of ion-beam techniques. piii2_e A large vacuum chamber (1m diameter & 2m length) with plasma produced by the impact ionization of neutrals by thermionic electrons. A magnetic cusp to enhance plasma density. A 50 kv DC supply with a hard tube modulator Plasma Source Ion Implantation Reactor Gliding arc (GLIDARC) in fact Gliding Glow Discharge Glidarc1 https://appliedionsystems.com/diy-vortex-stabilized-gliding-arc-discharge/ Where is the „corona“ in the parallel plane geometry ? 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