Vacuum tube devices

The first pn junction diode or rectifier was reported in 1949 [13]. The term "diode" comes from the vacuum-tube literature, and the new device was called a rectifier when it was used in electrical rectifier circuits. However, the term "diode" should be reserved to vacuum-tube devices, and "rectifiers" should be used for semiconductor pn junction devices. 

Solid-state controls n. Control instruments or motor-drive controls whose circuitry employs transistors and kindred elements rather than mechanical or vacuum-tube devices. Practically all modern process instruments are of this type. 

The components that connect, interface, transfer, and filter RF energy within a given system or between systems are critical elements in the operation of vacuum tube devices. Such hardware, usually passive, determines to a large extent the overall performance of the RF generator. To optimize the performance of power vacuum devices, it is first necessary to understand and optimize the components upon which the tube depends. 

Cathode ray tube (CRT) A vacuum tube device, usually glass, that is narrow at one end and widens at the other to create a surface onto which images can be projected. The narrow end contains the necessary circuits to generate and focus an electron beam on the luminescent screen at the other end. CRTs are used to display pictures in TV receivers, video monitors, oscilloscopes, computers, and other systems. 

CRT(cathode ray tube) A vacuum tube device that produces light when energized by the electron beam generated inside the tube. A CRT includes an electron gun, deflection mechanism, and phosphor-covered faceplate. 

Deflection The control placed on electron direction and motion in CRTs and other vacuum tube devices by varying the strengths of electrostatic (electrical) or electromagnetic fields. 

Electronic Applications. Electronic appHcations make up a significant sector of the cesium market. The main appHcations are in vacuum tubes, photoemissive devices, and scintillation counters (see Electronic materials). 

A family of vacuum-tube MMW sources is based on the propagation of an electron beam through a so-called slow-wave or periodic structure. Radiation propagates on the slow-wave structure at the speed of the electron beam, allowing the beam and radiation field to interact. Devices in this category are the traveling-wave tube (TWT), the backward-wave oscillator (BWO) and the extended interaction oscillator (EIO) klystron. TWTs are characterized by wide bandwidths and intermediate power output. These devices operate well at frequencies up to 100 GHz. BWOs, so called because the radiation within the vacuum tube travels in a direction opposite to that of the electron beam, have very wide bandwidths and low output powers. These sources operate at frequencies up to 1.3 THz and are extensively used in THZ spectroscopic applications [10] [11] [12]. The EIO is a high-power, narrow band tube that has an output power of 1 kW at 95 GHz and about 100 W at 230 GHz. It is available in both oscillator and amplifier, CW and pulsed versions. This source has been extensively used in MMW radar applications with some success [13]. 

In many electronic applications, e.g. vacuum tubes, an electron emitting cathode is an indispensable part of the device. For many such devices cold electron emission is favorable because of its lower energy consumption. 

Despite the many advances that have occurred in semiconductor devices, conventional photomultipler vacuum tubes are still by far the most widely used detectors of fluorescence. 

Light is strong enough to knock off electrons from cesium, which makes this phenomenon useful as a coating for photoelectric cells and electric eye devices. Cesium iodide (Csl) is used in scintillation counters (Geiger counters) to measure levels of external radiation. It is also useful as a getter to remove air molecules remaining in vacuum tubes. 

Silicon s tetravalent pyramid crystalline structure, similar to tetravalent carbon, results in a great variety of compounds with many practical uses. Crystals of sihcon that have been contaminated with impurities (arsenic or boron) are used as semiconductors in the computer and electronics industries. Silicon semiconductors made possible the invention of transistors at the Bell Labs in 1947. Transistors use layers of crystals that regulate the flow of electric current. Over the past half-century, transistors have replaced the vacuum tubes in radios, TVs, and other electronic equipment that reduces both the devices size and the heat produced by the electronic devices. 

In 1948 William Bradford Shockley (1910-1989), who is considered the inventor of the transistor, and his associates at Bell Research Laboratories, Walter Houser Brattain (1902-1987) and John Bardeen (1908-1991), discovered that a crystal of germanium could act as a semiconductor of electricity. This unique property of germanium indicated to them that it could be used as both a rectifier and an amplifier to replace the old glass vacuum tubes in radios. Their friend John Robinson Pierce (1910-2002) gave this new solid-state device the name transistor, since the device had to overcome some resistance when a current of electricity passed through it. Shockley, Brattain, and Bardeen all shared the 1956 Nobel Prize in Physics. 

Since the resistance in the circuit containing the reference electrode is approximately 10,000 ohms, an accurate measure of the cathode-reference electrode potential can only be obtained by the use of a potential measuring device with an imput impedance of at least 100,000 ohms. Although a vacuum-tube voltmeter (VTVM, typical imput impedance 11 x 10 ohms) is suitable for this purpose, a common multimeter (VOM, typical imput impedance 20,000 ohms per volt) is not a satisfactory alternative. 

Misch metal, an alloy of cerium with other lanthanides is a pyrophoric substance and is used to make gas lighters and ignition devices. Some other applications of the metal or its alloys are in solid state devices rocket propellant compositions as getter in vacuum tubes and as a diluent for plutonium in nuclear fuel. 

Other applications of niobium are in electronic and propulsion devices, in electrodes in catalysis and in vacuum tubes and high-pressure sodium vapor lamps. 

The birth of the microcomputer can actually be traced back to the development of the transistor. With early electronic devices and computers the system of storing digital information was based on the use of vacuum tubes. These were cumbersome, expensive, and used a tremendous amount of power. They were much faster than relays, however, they were considerably slower than anything produced under today s standards. With the development of the transistor a revolution in the design of computer systems ushered in the time when systems would become smaller and more capable and less costly. The transistor was faster than its predecessor, the vacuum tube, required less power and was much cheaper to develop and produce than the vacuum tube technology. 

It may vaty from a simple wire to complex devices, such as hydrogen-, calomel-, capillary-, dropping- (of Heyrovsky), glass-, etc electrodes. It may be the container of the cell itself, such.as crucible, vacuum tube or valve... 

Electronics. The branch.of physical science that deals with study of electrons, especially with reference to industrial application. The devices which are studied in electronics are electron (or vacuum) tubes, electron microscope, photo-electric devices, x-ray apparatuses, audio-amplifiers, and audio- transformers... 

Photomultipliers are vacuum tube photocells with a sealed-in set of dynodes. Each successive dynode is kept at a potential difference of 100V o that photoelectrons emitted from the cathode surface are accelerated M each step. The secondary electrons ejected from the last dynode are Collected by the anode and are multiplied so that a 10° — 107 — fold arnpli-t tfion of electron flux is achieved. This allows simple devices such as l croammeters to measure weak light intensities. Background thermal mission can be minimised by cooling the photomultiplier. The schematic... 

SEMICONDUCTORS. Materials and devices known as semiconductors have been the backbone of the electronics industry for many years. Semiconductors did not enter the industry in a major way, however, until several years after the vacuum tube (valve) had been well established. In terms of perspective, it is interesting to note that at least one. semiconductor device predated the vacuum tube in the early days of radio communication. This was the then familiar galena crystal and accompanying whisker used in early crystal set radio receivers. 

The transistor had a tremendous impact, constituting the birth of modern electronics. The transistor led to the development of almost innumerable semiconductor device configurations and ultimately to the phasing out of the vacuum tube, except for rather special and limited applications. 

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