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electron tube

electron tube device consisting of a sealed enclosure in which electrons flow between electrodes separated either by a vacuum (in a vacuum tube) or by an ionized gas at low pressure (in a gas tube). The two principal electrodes of an electron tube are the cathode and the anode or plate. The simplest vacuum tube, the diode , has only those two electrodes. When the cathode is heated, it emits a cloud of electrons, which are attracted by the positive electric polarity of the anode and constitute the current through the tube. If the cathode is charged positively with respect to the anode, the electrons are drawn back to the cathode. However, the anode is not capable of emitting electrons, so no current can exist; thus the diode acts as a rectifier, i.e., it allows current to flow in only one direction. In the vacuum triode a third electrode, the grid, usually made of a fine wire mesh or similar material, is placed between the cathode and anode. Small voltage fluctuations, or signals, applied to the grid can result in large fluctuations in the current between the cathode and the anode. Thus the triode can act as a signal amplifier, producing output signals some 20 times greater than input. For even greater amplification, additional grids can be added. Tetrodes, with 2 grids, produce output signals about 600 times greater than input, and pentodes, with 3 grids, 1,500 times. X-ray tubes maintain a high voltage between a cathode and an anode. This enables electrons from the cathode to strike the anode at velocities high enough to produce X rays. A cathode-ray tube can produce electron beams that strike a screen to produce pictures as in oscilloscopes and video displays. Gas tubes behave similarly to vacuum tubes but are designed to handle larger currents or to produce luminous discharges. In some gas tubes the cathode is not designed as an electron emitter; conduction occurs when a voltage sufficient to ionize the gas exists between the anode and the cathode. In these cases the ions and electrons formed from the gas molecules constitute the current. Electron tubes have been replaced by solid-state devices, such as transistors , for most applications. However they are still widely used in high-power transmitters, some television cameras, specialty audio equipment, and as oscilloscope and video displays. A klystron is a special kind of vacuum tube that is a powerful microwave amplifier; it is used to generate signals for radar and television stations.

See also magnetron ; photoelectric cell .

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	IRAN: CHINA LIFTS LIMITS ON ANODE EXPORTS TO IRAN. Newspaper article from: IPR Strategic Business Information Database; 3/5/2007; 138 words ; ...limitations imposed on the exports of China's anode to Iran have been lifted, said an official...aluminum producer, Almahdi Aluminum Corp. Anode and alumina are the main raw material required...production of aluminum. Iran's annual imports of anode from China hit around 60,000 tons. Currently... Read more
	Welding method ignites thinking in Europe. Magazine article from: Tooling & Production; 4/1/1997; 700+ words ; ...concurrently, this cathode is raised to a high...electrically grounded gun anode. The cathode (or filament) is...cathode, grid cup, and anode. This combination...the center of the anode and traverses down...being applied to the cathode. A vacuum environment... Read more
	Humidity and pollution effects on Pb-free assemblies: a study of how metallization and operating voltage influence electrochemical migration.(Cover Story) Magazine article from: Circuits Assembly; 4/1/2007; ; 700+ words ; ...structures growing from the cathode to the anode can be observed independent...concentration gradient at the cathode (Figure 1). [FIGURE 1 OMITTED...corrosion complex created at the anode is very low, so-called staining --bridges growing from the anode to the cathode--can also be ... Read more
	NEW SACRIFICIAL CATHODE PROTECTION SYSTEM FOR STEEL IN CONCRETE. Magazine article from: Industrial Environment; 1/1/1999; 193 words ; ...easy to apply, does not require that the anode be electrically isolated from the steel...power supply. Attempts to apply sacrificial anode CP to bridge structures have met with limited...success, because conventional sacrificial anode alloys operate at a low fixed potential... Read more
	Performance Metalshas introduced Boater's Dream ANODE for larger boats.(AT A GLANCE) Magazine article from: National Fisherman; 12/1/2005; 100 words ; PERFORMANCE METALS has introduced Boater's Dream ANODE for larger boats. The anode features a high-performance design that utilizes...current than is available from a traditional zinc anode, making the Boater's Dream anode last more than twice... Read more
	Fire stalls production.(Inco investigates fire at its new copper anode refining building at its Copper Cliff smelter)(Brief Article) Magazine article from: Northern Ontario Business; 3/1/2001; 127 words ; ...during the commissioning of the new copper anode refining building at its Copper Cliff smelter...copper production. The existing copper anode casting furnace at Copper Cliff remains...believed a malfunction in the number two anode furnace resulted in a spill of blister... Read more
	Anode prevents corrosion near repairs.(PCI Exhibition Products)(Advertisement) Magazine article from: The Concrete Producer; 10/1/2003; 76 words ; ...Corrosion Technologies introduces Galvashield XP. This puck-shaped anode consists of sacrificial zinc encased in a precast shell of activated...adjacent to the completed repair, sometimes referred to as ring anode effect or patch accelerated corrosion. Vector Corrosion Technologies... Read more
	Surprisingly valuable: the hollow cathode lamp market. Newspaper article from: Instrument Business Outlook; 11/15/2001; 700+ words ; Hollow cathode lamps (HCLs) occupy a unique place in...with neon or argon at low pressure. The cathode is made of the element(s) that is to be...potential ionizes the gas atoms, hit the cathode's atoms and radiate light at the element... Read more
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