China
Africa
Explore chapters and articles related to this topic
Borate Phosphor
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
Gas discharge lamps are a light source that generates light by sending and electrical discharge through an ionized gas, plasma. The character of the gas discharge depends on the pressure of the gas as well as the frequency of the current. Typically, such lamps used a noble gas (argon, neon, krypton and xenon) or a mixture of these gases. Most lamps are filled with additional materials, like mercury, sodium and metal halides. In operation, the gas is ionized and free electrons are accelerated by the electrical field in the tube collide with gas and metal atoms. Some electrons in the atomic orbitals of these atoms are excited by these collisions to a higher energy state. When the excited atom falls back to a lower energy state, it emits a photon of a characteristic energy, resulting in infrared, visible light or ultraviolet radiation. Some lamps convert the ultraviolet radiation to visible light with the help of a phosphor coating on the inside of a lamp's glass surface. The gas discharge lamps are mainly classified into high-pressure and low-pressure discharge lamps.
Principles and Applications of UV Light Technology
Published in Tatiana Koutchma, Ultraviolet Light in Food Technology, 2019
A gas discharge is a mixture of non-excited atoms, excited atoms, cations, and free electrons formed when a sufficiently high voltage is applied across a volume of gas. Light is emitted from the gas discharge at wavelengths dependent upon the elemental composition of the gas discharge, and the excitation, ionization, and kinetic energy of those elements. Gas discharges are responsible for the light emitted from UV lamps. When a voltage is applied, free electrons and ions present in the gas are accelerated by the electric field formed between two electrodes. With sufficient voltage, the electrons are accelerated to high kinetic energies. Collisions of the free electrons with atoms result in a transfer of energy to the atoms and if the energy is sufficient, the atoms are ionized. This ionization results in a rapid increase in the number of electrons and cations, with a corresponding increase in lamp current, and a drop in the voltage across the lamp.
Fundamentals of Plasma
Published in Eiichi Kondoh, Micro- and Nanofabrication for Beginners, 2021
Gas discharge or simply “discharge” is a phenomenon in which electric current flows in a gas. This occurs when a gas contains charged species, such as ions and electrons; otherwise gases are non-conductive, because the gas molecules are electrically neutral. Plasmas can be easily generated thorough a discharge phenomenon.
Parametric Studies of CCRF in Ar on 1D Model: Effect of Pressure and Dielectric Layers
Published in Fusion Science and Technology, 2023
Gas discharge plasmas5–14 sustained by direct current or RF sources are used extensively in industrial and medical applications. For instance, in the medical sector dermatology treatments exploit the coherent and incoherent ultraviolet and vacuum ultraviolet radiation emitted from gas discharge plasmas. These applications include discharges enhanced by vapor deposition surface modification using different materials and plasma etching. These enhancement technologies can be applied in a capacitive geometric configuration.15 This latter approach has employed a progression technique to control the discharge by means of using a barrier dielectric16–19 in a low- and higher-pressure gas.
Modeling of Discharge Lamp Characteristics by Using Floating Memristor Circuit Emulator with Tunable Threshold
Published in Electric Power Components and Systems, 2020
Cengiz Polat Uzunoğlu, Yunus Babacan, Fırat Kaçar, Mukden Ug˘ur
In general, gas discharge means that an electric current passes through an insulating gaseous medium. In order to maintain this process, an ionized gaseous medium and hence an external electric field are required. Weakly ionized gaseous medium is called discharge plasma, which satisfies an electrical current under electrical field [34]. The current initiation is obtained by collisions of ions just after the energy transfer from electric field to gas atoms or molecules. The first ionization process of gas discharge plasma was explained by Townsend [35]: