query: what did thomson discover with his cathode ray tube experiment?

title: Cathode-ray tube

text: includes discarded CRT monitors in its category of "hazardous household waste" but considers CRTs that have been set aside for testing to be commodities if they are not discarded, speculatively accumulated, or left unprotected from weather and other damage. Leaded CRT glass was sold to be remelted into other CRTs, or even broken down and used in road construction. Basics of cathode rays and discharge in low-pressure gas: Light production by cathode rays: Manipulating the electron beam: Applying CRT in different display-purpose: Miscellaneous phenomena: Historical aspects: Safety and precautions: Cathode-ray tube The cathode-ray tube (CRT) is a vacuum tube that

title: Cathode-ray tube

text: Cathode-ray tube The cathode-ray tube (CRT) is a vacuum tube that contains one or more electron guns and a phosphorescent screen, and is used to display images. It modulates, accelerates, and deflects electron beam(s) onto the screen to create the images. The images may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets, or other phenomena. CRTs have also been used as memory devices, in which case the visible light emitted from the fluorescent material (if any) is not intended to have significant meaning to a visual observer (though the visible pattern on the tube face may cryptically represent

title: Cathode ray

text: Cathode ray Cathode rays (electron beam or e-beam) are streams of electrons observed in vacuum tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the cathode (the electrode connected to the negative terminal of the voltage supply). They were first observed in 1869 by German physicist Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein "Kathodenstrahlen", or cathode rays. In 1897, British physicist J. J. Thomson showed that cathode rays were composed of a previously unknown negatively

title: Cathode ray

text: a crystal lattice by Davisson and Germer in 1927. Cathode ray Cathode rays (electron beam or e-beam) are streams of electrons observed in vacuum tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the cathode (the electrode connected to the negative terminal of the voltage supply). They were first observed in 1869 by German physicist Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein "Kathodenstrahlen", or cathode rays. In 1897, British physicist J. J. Thomson showed that

title: Cathode-ray tube

text: a cathode-ray tube used to electronically store binary data. It was used in computers of the 1940s as a random-access digital storage device. In contrast to other CRTs in this article, the Williams tube was not a display device, and in fact could not be viewed since a metal plate covered its screen. Color tubes use three different phosphors which emit red, green, and blue light respectively. They are packed together in stripes (as in aperture grille designs) or clusters called "triads" (as in shadow mask CRTs). Color CRTs have three electron guns, one for each primary color, arranged either

title: Cathode ray

text: charged particle, which was later named the "electron". Cathode ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to create the image on a television screen. Cathode rays are so named because they are emitted by the negative electrode, or cathode, in a vacuum tube. To release electrons into the tube, they first must be detached from the atoms of the cathode. In the early cold cathode vacuum tubes, called Crookes tubes, this was done by using a high electrical potential of thousands of volts between the anode and the cathode to ionize the

title: Cathode ray

text: wire (electromagnets). These are used in cathode ray tubes, found in televisions and computer monitors, and in electron microscopes. After the 1654 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with passing high voltage electricity through rarefied air. In 1705, it was noted that electrostatic generator sparks travel a longer distance through low pressure air than through atmospheric pressure air. In 1838, Michael Faraday applied a high voltage between two metal electrodes at either end of a glass tube that had been partially evacuated of air, and noticed a strange light arc with its beginning

title: Geissler tube

text: tube wall by obstructions in the tube in front of the cathode, Johann Hittorf realized that the glow was caused by some type of ray travelling in straight lines through the tube from the cathode. These were named cathode rays. In 1897 J. J. Thomson showed that cathode rays consisted of a previously unknown particle, which was named the "electron". The technology of controlling electron beams resulted in the invention of the amplifying vacuum tube in 1907, which created the field of "electronics" and dominated it for 50 years, and the cathode ray tube which was used in radar and

title: Cathode ray

text: discovered, which he originally called ""corpuscle"" but was later named "electron", after particles postulated by George Johnstone Stoney in 1874. He also showed they were identical with particles given off by photoelectric and radioactive materials. It was quickly recognized that they are the particles that carry electric currents in metal wires, and carry the negative electric charge of the atom. Thomson was given the 1906 Nobel prize for physics for this work. Philipp Lenard also contributed a great deal to cathode ray theory, winning the Nobel prize for physics in 1905 for his research on cathode rays and their properties.

title: Cathode ray

text: invention of the cathode ray tube (CRT) by Ferdinand Braun in 1897, which was used in television sets and oscilloscopes. It is today employed in sophisticated devices such as electron microscopes, electron beam lithography and particle accelerators. Like a wave, cathode rays travel in straight lines, and produce a shadow when obstructed by objects. Ernest Rutherford demonstrated that rays could pass through thin metal foils, behavior expected of a particle. These conflicting properties caused disruptions when trying to classify it as a wave or particle. Crookes insisted it was a particle, while Hertz maintained it was a wave. The debate

title: Cathode-ray tube

text: These frequencies are at the upper range of human hearing and are inaudible to many people; however, some people (especially children) will perceive a high-pitched tone near an operating television CRT. The sound is due to magnetostriction in the magnetic core and periodic movement of windings of the flyback transformer. This problem does not occur on 100/120 Hz TVs and on non-CGA (Color Graphics Adapter) computer displays, because they use much higher horizontal scanning frequencies (22 kHz to over 100 kHz). High vacuum inside glass-walled cathode-ray tubes permits electron beams to fly freely—without colliding into molecules of air or other

title: Cold cathode

text: the cathode into the gas. A cold-cathode vacuum tube does not rely on external heating of an electrode to provide thermionic emission of electrons. Early cold-cathode devices included the Geissler tube and Plucker tube, and early cathode ray tubes. Study of the phenomena in these devices led to the discovery of the electron. Neon lamps are used both to produce light as indicators and for special-purpose illumination, and also as circuit elements displaying negative resistance. Addition of a trigger electrode to a device allowed the glow discharge to be initiated by an external control circuit; Bell Laboratories developed a "trigger

title: Electron rest mass

text: mass of the electron was determined directly from combining two measurements. The mass-to-charge ratio of the electron was first estimated by Arthur Schuster in 1890 by measuring the deflection of "cathode rays" due to a known magnetic field in a cathode ray tube. This was before it was even known what cathode rays actually were! It was seven years later that J. J. Thomson showed that cathode rays consist of streams of particles, to be called electrons, and made more precise measurements of their mass-to-charge ratio again using a cathode ray tube. The second measurement was of the charge of

title: Hot cathode

text: require heating. There are two types of hot cathode. In a "directly heated cathode", the filament is the cathode and emits the electrons. In an "indirectly heated cathode", the filament or "heater" heats a separate metal cathode electrode which emits the electrons. From the 1920s to the 1960s, a wide variety of electronic devices used hot-cathode vacuum tubes. Today, hot cathodes are used as the source of electrons in fluorescent lamps, vacuum tubes, and the electron guns used in cathode ray tubes and laboratory equipment such as electron microscopes. A cathode electrode in a vacuum tube or other vacuum system

title: Cathode

text: produce electrons by thermionic emission. The filament is a thin wire of a refractory metal like tungsten heated red-hot by an electric current passing through it. Before the advent of transistors in the 1960s, virtually all electronic equipment used hot-cathode vacuum tubes. Today hot cathodes are used in vacuum tubes in radio transmitters and microwave ovens, to produce the electron beams in older cathode ray tube (CRT) type televisions and computer monitors, in x-ray generators, electron microscopes, and fluorescent tubes. There are two types of hot cathodes: In order to improve electron emission, cathodes are treated with chemicals, usually compounds

title: Teltron tube

text: this we get the amount of specific electron charge The determination of the velocity is performed using the energy conservation law This is finally followed by The specific electron charge has the value Since the charge of an electron is available from the Millikan experiment, the study of electrons in an magnetic field is the determination of its mass in accordance with: Similar concepts for the weighing of charged particles can be found in the mass spectrometer. Teltron tube A teltron tube (named for Teltron Inc., which is now owned by 3B Scientific Ltd.) is a type of cathode ray

title: X-ray tube

text: technology of switching power supplies (aka switch mode power supply), and allowed for more accurate control of the X-ray unit, higher quality results, and reduced X-ray exposures. Electrons from the cathode collide with the anode material, usually tungsten, molybdenum or copper, and accelerate other electrons, ions and nuclei within the anode material. About 1% of the energy generated is emitted/radiated, usually perpendicular to the path of the electron beam, as X-rays. The rest of the energy is released as heat. Over time, tungsten will be deposited from the target onto the interior surface of the tube, including the glass surface.

title: Franck–Hertz experiment

text: governing the impact of an electron upon an atom". Franck and Hertz's original experiment used a heated vacuum tube containing a drop of mercury; they reported a tube temperature of 115 °C, at which the vapor pressure of mercury is about 100 pascals (and far below atmospheric pressure). A contemporary Franck–Hertz tube is shown in the photograph. It is fitted with three electrodes: an electron-emitting, hot cathode; a metal mesh grid; and an anode. The grid's voltage is positive relative to the cathode, so that electrons emitted from the hot cathode are drawn to it. The electric current measured in

title: Cold cathode

text: External circuitry limits the discharge current. Cold-cathode discharge lamps use higher voltages than hot-cathode ones. The resulting strong electric field near the cathode accelerates ions to a sufficient velocity to create free electrons from the cathode material. Another mechanism to generate free electrons from a cold metallic surface is field electron emission. It is used in some x-ray tubes, the field-electron microscope (FEM), and field-emission displays (FEDs). Cold cathodes sometimes have a rare-earth coating to enhance electron emission. Some types contain a source of beta radiation to start ionization of the gas that fills the tube. In some tubes, glow

title: Cathode ray

text: tube. His invention, called the triode, was the first device that could amplify electric signals, and revolutionized electrical technology, creating the new field of "electronics". Vacuum tubes made radio and television broadcasting possible, as well as radar, talking movies, audio recording, and long distance telephone service, and were the foundation of consumer electronic devices until the 1960s, when the transistor brought the era of vacuum tubes to a close. Cathode rays are now usually called electron beams. The technology of manipulating electron beams pioneered in these early tubes was applied practically in the design of vacuum tubes, particularly in the

title: Cathode-ray tube

text: in a straight line or in an equilateral triangular configuration (the guns are usually constructed as a single unit). (The triangular configuration is often called "delta-gun", based on its relation to the shape of the Greek letter delta Δ.) A grille or mask absorbs the electrons that would otherwise hit the wrong phosphor. A shadow mask tube uses a metal plate with tiny holes, placed so that the electron beam only illuminates the correct phosphors on the face of the tube; the holes are tapered so that the electrons that strike the inside of any hole will be reflected back,

title: Cathode-ray tube

text: the stored data). In television sets and computer monitors, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In all modern CRT monitors and televisions, the beams are bent by "magnetic deflection", a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although electrostatic deflection is commonly used in oscilloscopes,

title: Crookes tube

text: to find out what cathode rays were. There were two theories: British scientists Crookes and Cromwell Varley believed they were particles of 'radiant matter', that is, electrically charged atoms. German researchers E. Wiedemann, Heinrich Hertz, and Eugen Goldstein believed they were 'aether vibrations', some new form of electromagnetic waves, and were separate from what carried the current through the tube. The debate continued until J.J. Thomson measured their mass, proving they were a previously unknown negatively charged particle, the first subatomic particle, which he called a 'corpuscle' but was later renamed the 'electron'. Julius Plücker in 1869 built an anode

title: Geer tube

text: tubes and a 2-dimensional version of his pyramids. The vertical channels reflected the light in two directions, providing different images for each eye. Geer tube The Geer tube was an early single-tube color television cathode ray tube, developed by Willard Geer. The Geer tube used a pattern of small phosphor-covered three-sided pyramids on the inside of the CRT faceplate to mix separate red, green and blue signals from three electron guns. The Geer tube had a number of disadvantages, and was never used commercially due to the much better images generated by RCA's shadow mask system. Nevertheless, Geer's patent was

title: Teltron tube

text: Teltron tube A teltron tube (named for Teltron Inc., which is now owned by 3B Scientific Ltd.) is a type of cathode ray tube used to demonstrate the properties of electrons. There were several different types made by Teltron including a diode, a triode, a Maltese Cross tube, a simple deflection tube with a fluorescent screen, and one which could be used to measure the charge-to-mass ratio of an electron. The latter two contained an electron gun with deflecting plates. The beams can be bent by applying voltages to various electrodes in the tube or by holding a magnet close

title: Cathode-ray tube

text: are intrinsic to the unadjusted tube. Typically there are two or three pairs of two magnets in the form of rings made of plastic impregnated with a magnetic material, with their magnetic fields parallel to the planes of the magnets, which are perpendicular to the electron gun axes. Each pair of magnetic rings forms a single effective magnet whose field vector can be fully and freely adjusted (in both direction and magnitude). By rotating a pair of magnets relative to each other, their relative field alignment can be varied, adjusting the effective field strength of the pair. (As they rotate

title: Cathode-ray tube

text: than atoms, the first "subatomic particles", which were later named "electrons". The earliest version of the CRT was known as the "Braun tube", invented by the German physicist Ferdinand Braun in 1897. It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. The first cathode-ray tube to use a hot cathode was developed by John B. Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922. In 1925, Kenjiro Takayanagi demonstrated a CRT television that received images with a 40-line resolution.

title: Cathode-ray tube amusement device

text: public, so it had no effect on the future video game industry. Under most definitions, the device is not considered a video game, as while it had an electronic display it did not run on a computing device. Therefore, despite its relevance to the early history of video games, it is not generally considered a candidate for the title of the first video game. The cathode-ray tube amusement device consists of a cathode ray tube connected to an oscilloscope with a set of knobs and switches. The device uses purely analog electronics and does not use any digital computer or

title: Cathode-ray tube amusement device

text: Cathode-ray tube amusement device The cathode-ray tube amusement device is the earliest known interactive electronic game. The device simulates an artillery shell arcing towards targets on a cathode ray tube (CRT) screen, which is controlled by the player by adjusting knobs to change the trajectory of a CRT beam spot on the display in order to reach plastic targets overlaid on the screen. Thomas T. Goldsmith, Jr. and Estle Ray Mann constructed the game from analog electronics and filed for a patent in 1947, which was issued the following year. The gaming device was never manufactured or marketed to the

title: Cathode-ray tube

text: flat panels are available in and larger sizes. Cathode rays were discovered by Johann Wilhelm Hittorf in 1869 in primitive Crookes tubes. He observed that some unknown rays were emitted from the cathode (negative electrode) which could cast shadows on the glowing wall of the tube, indicating the rays were traveling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, and William Crookes showed they could be deflected by magnetic fields. In 1897, J. J. Thomson succeeded in measuring the mass of cathode rays, showing that they consisted of negatively charged particles smaller

title: Cathode-ray tube amusement device

text: purely analog hardware and did not run on a computing device; some loose definitions may still consider it a video game, but it is still usually disqualified as the device was never manufactured. Nevertheless, it is the earliest known interactive electronic game as well as the first to incorporate an electronic display, thus making it a forerunner to other games in the early history of video games. As the device was never manufactured or widely shown it did not directly inspire any other games and had no impact on the future video game industry. Cathode-ray tube amusement device The cathode-ray

title: Cathode-ray tube

text: be displayed by a conventional tube only while it actually occurs. The use of a long persistence phosphor may allow the image to be observed after the event, but only for a few seconds at best. This limitation can be overcome by the use of a direct view storage cathode-ray tube (storage tube). A storage tube will continue to display the event after it has occurred until such time as it is erased. A storage tube is similar to a conventional tube except that it is equipped with a metal grid coated with a dielectric layer located immediately behind the

title: Cathode-ray tube

text: By 1927, he improved the resolution to 100 lines, which was unrivaled until 1931. By 1928, he was the first to transmit human faces in half-tones on a CRT display. By 1935, he had invented an early all-electronic CRT television. It was named in 1929 by inventor Vladimir K. Zworykin, who was influenced by Takayanagi's earlier work. RCA was granted a trademark for the term (for its cathode-ray tube) in 1932; it voluntarily released the term to the public domain in 1950. The first commercially made electronic television sets with cathode-ray tubes were manufactured by Telefunken in Germany in 1934.

title: Cathode-ray tube

text: gas. If the glass is damaged, atmospheric pressure can collapse the vacuum tube into dangerous fragments which accelerate inward and then spray at high speed in all directions. The implosion energy is proportional to the evacuated volume of the CRT. Although modern cathode-ray tubes used in televisions and computer displays have epoxy-bonded face-plates or other measures to prevent shattering of the envelope, CRTs must be handled carefully to avoid personal injury. To accelerate the electrons from the cathode to the screen with sufficient velocity, a very high voltage (EHT or Extra High Tension) is required, from a few thousand volts

title: Cathode-ray tube amusement device

text: care". The cathode-ray tube amusement device was invented by physicists Thomas T. Goldsmith, Jr. and Estle Ray Mann. The pair worked at television designer DuMont Laboratories specializing in the development of cathode ray tubes that used electronic signal outputs to project a signal onto television screens. Goldsmith, who had received a Ph.D. in physics from Cornell University in 1936 with a focus on oscilloscope design, was at the time of the device's invention the director of research for DuMont Laboratories in New Jersey. The two inventors were inspired by the radar displays used in World War II, which Goldsmith had

title: Cathode-ray tube amusement device

text: did not work on games after the invention of the device; he was promoted to vice president in 1953 and left DuMont—by then split up and sold to other firms—to become a professor of physics at Furman University in 1966. Goldsmith kept the device and brought it with him to Furman; in a 2016 interview fellow physics professor Bill Brantley recalled Goldsmith demonstrating the game to him. Despite being a game that used a graphical display, the cathode-ray tube amusement device is generally not considered under most definitions to be a candidate for the first video game, as it used

title: Cathode ray

text: began to glow. What was happening was that as more air was pumped from the tube, the electrons knocked out of the cathode when positive ions struck it could travel farther, on average, before they struck a gas atom. By the time the tube was dark, most of the electrons could travel in straight lines from the cathode to the anode end of the tube without a collision. With no obstructions, these low mass particles were accelerated to high velocities by the voltage between the electrodes. These were the cathode rays. When they reached the anode end of the tube,

title: Cathode ray

text: were. There were two theories. Crookes and Arthur Schuster believed they were particles of "radiant matter," that is, electrically charged atoms. German scientists Eilhard Wiedemann, Heinrich Hertz and Goldstein believed they were "aether waves", some new form of electromagnetic radiation, and were separate from what carried the electric current through the tube. The debate was resolved in 1897 when J. J. Thomson measured the mass of cathode rays, showing they were made of particles, but were around 1800 times lighter than the lightest atom, hydrogen. Therefore, they were not atoms, but a new particle, the first "subatomic" particle to be

title: J. J. Thomson

text: one side, out of the direct path of the cathode rays. Thomson could trace the path of the ray by observing the phosphorescent patch it created where it hit the surface of the tube. Thomson observed that the electrometer registered a charge only when he deflected the cathode ray to it with a magnet. He concluded that the negative charge and the rays were one and the same. In May–June 1897, Thomson investigated whether or not the rays could be deflected by an electric field. Previous experimenters had failed to observe this, but Thomson believed their experiments were flawed because

title: Cathode ray

text: to notice that objects in the tube in front of the cathode, such as the anode, cast sharp-edged shadows on the glowing back wall. In 1869, German physicist Johann Hittorf was first to realize that something must be traveling in straight lines from the cathode to cast the shadows. Eugen Goldstein named them "cathode rays" (German "kathodenstrahlen"). At this time, atoms were the smallest particles known, and were believed to be indivisible. What carried electric currents was a mystery. During the last quarter of the 19th century, many historic experiments were done with Crookes tubes to determine what cathode rays

title: Crookes tube

text: paddle. This was proven in 1903 by J. J. Thomson who calculated that the momentum of the electrons hitting the paddle wheel would only be sufficient to turn the wheel one revolution per minute. All this experiment really showed was that cathode rays were able to heat surfaces. Jean-Baptiste Perrin wanted to determine whether the cathode rays actually carried negative charge, or whether they just accompanied the charge carriers, as the Germans thought. In 1895 he constructed a tube with a 'catcher', a closed aluminum cylinder with a small hole in the end facing the cathode, to collect the cathode

title: Crookes tube

text: Heinrich Hertz, Philipp Lenard, Kristian Birkeland and others to discover the properties of cathode rays, culminating in J.J. Thomson's 1897 identification of cathode rays as negatively charged particles, which were later named "electrons". Crookes tubes are now used only for demonstrating cathode rays. Wilhelm Röntgen discovered X-rays using the Crookes tube in 1895. The term "Crookes tube" is also used for the first generation, cold cathode X-ray tubes, which evolved from the experimental Crookes tubes and were used until about 1920. Crookes tubes are cold cathode tubes, meaning that they do not have a heated filament in them that releases

title: X-ray tube

text: produce X-rays. These were the first X-ray tubes. These first generation "cold cathode" or "Crookes" X-ray tubes were used until the 1920s. Crookes tubes generated the electrons needed to create X-rays by ionization of the residual air in the tube, instead of a heated filament, so they were partially but not completely evacuated. They consisted of a glass bulb with around 10 to 5×10 atmospheric pressure of air (0.1 to 0.005 Pa). An aluminum cathode plate at one end of the tube created a beam of electrons, which struck a platinum anode (for economy, made from nickel or copper with

title: Cathode ray

text: The gas ionization (or cold cathode) method of producing cathode rays used in Crookes tubes was unreliable, because it depended on the pressure of the residual air in the tube. Over time, the air was absorbed by the walls of the tube, and it stopped working. A more reliable and controllable method of producing cathode rays was investigated by Hittorf and Goldstein, and rediscovered by Thomas Edison in 1880. A cathode made of a wire filament heated red hot by a separate current passing through it would release electrons into the tube by a process called thermionic emission. The first

title: Cathode ray

text: able to evacuate tubes to a lower pressure, below 10 atm. These were called Crookes tubes. Faraday had been the first to notice a dark space just in front of the cathode, where there was no luminescence. This came to be called the "cathode dark space", "Faraday dark space" or "Crookes dark space". Crookes found that as he pumped more air out of the tubes, the Faraday dark space spread down the tube from the cathode toward the anode, until the tube was totally dark. But at the anode (positive) end of the tube, the glass of the tube itself

title: Cathode ray

text: lines from the cathode. After the electrons reach the anode, they travel through the anode wire to the power supply and back to the cathode, so cathode rays carry electric current through the tube. The current in a beam of cathode rays through a vacuum tube can be controlled by passing it through a metal screen of wires (a grid) between cathode and anode, to which a small negative voltage is applied. The electric field of the wires deflects some of the electrons, preventing them from reaching the anode. The amount of current that gets through to the anode depends

title: Cathode-ray tube

text: Flat panel displays dropped in price and started significantly displacing cathode-ray tubes in the 2000s, with LCD screens exceeding CRTs in 2008. The last known manufacturer of (in this case, recycled) CRTs ceased in 2015. In oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with television and other large CRTs. The beam is deflected horizontally by applying an electric field between a pair of plates to its left and right, and vertically by applying an electric field to plates above and below. Televisions use magnetic rather than electrostatic deflection because the deflection plates obstruct the

title: Cathode ray

text: negative cathode and attracted to the positive anode. They travel in straight lines through the empty tube. The voltage applied between the electrodes accelerates these low mass particles to high velocities. Cathode rays are invisible, but their presence was first detected in early vacuum tubes when they struck the glass wall of the tube, exciting the atoms of the glass and causing them to emit light, a glow called fluorescence. Researchers noticed that objects placed in the tube in front of the cathode could cast a shadow on the glowing wall, and realized that something must be travelling in straight

title: Cathode ray

text: residual gas atoms in the tube. The positive ions were accelerated by the electric field toward the cathode, and when they collided with it they knocked electrons out if its surface; these were the cathode rays. Modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament which is heated by a separate electric current passing through it. The increased random heat motion of the filament knocks electrons out of the surface of the filament, into the evacuated space of the tube. Since the electrons have a negative charge, they are repelled by the

title: J. J. Thomson

text: When the upper plate was connected to the negative pole of the battery and the lower plate to the positive pole, the glowing patch moved downwards, and when the polarity was reversed, the patch moved upwards. In his classic experiment, Thomson measured the mass-to-charge ratio of the cathode rays by measuring how much they were deflected by a magnetic field and comparing this with the electric deflection. He used the same apparatus as in his previous experiment, but placed the discharge tube between the poles of a large electromagnet. He found that the mass-to-charge ratio was over a thousand times

title: The Cathode Ray

text: The Cathode Ray The Cathode Ray are an alternative band based in Edinburgh, Scotland. The current line-up is Jeremy Thoms (lead vocals/guitar/keyboards), Steve Fraser (guitar/backing vocals), Phil Biggs (guitar/backing vocals), Neil Baldwin (bass), and David Mack (drums & percussion). Originally based on a loose concept of forging late 70’s New York, with late 70’s Manchester, The Cathode Ray started life in 2006, initially as a song-writing collaboration and “a bit of fun” between Jeremy Thoms and his friend ex-Josef K frontman Paul Haig. The songs written were swift to adopt their own unique stamp and personality, so a band was

title: Anode ray

text: Anode ray An anode ray (also positive ray or canal ray) is a beam of positive ions that is created by certain types of gas-discharge tubes. They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886. Later work on anode rays by Wilhelm Wien and J. J. Thomson led to the development of mass spectrometry. Goldstein used a gas-discharge tube which had a perforated cathode. When a high electrical potential of several thousand volts is applied between the cathode and anode, faint luminous "rays" are seen extending from the holes in the back

title: X-ray tube

text: The anode is usually made out of tungsten or molybdenum. The tube has a window designed for escape of the generated X-ray photons. The power of a Coolidge tube usually ranges from 0.1 to 18 kW. Any vacuum tube operating at several thousand volts or more can produce X-rays as an unwanted byproduct, raising safety issues. The higher the voltage, the more penetrating the resulting radiation and the more the hazard. CRT displays, once common in color televisions and computer displays, operate at making them the main concern among household appliances. Historically, concern has focused less on the cathode ray

title: X-ray tube

text: a thin platinum face) target at the center generating X-rays. The anode surface was angled so that the X-rays would radiate through the side of the tube. The cathode was concave so that the electrons were focused on a small (~1 mm) spot on the anode, approximating a point source of X-rays, which resulted in sharper images. The tube had a third electrode, an anticathode connected to the anode. It improved the X-ray output, but the method by which it achieved this is not understood. A more common arrangement used a copper plate anticathode (similar in construction to the cathode)

title: X-ray tube

text: the increased power density level for the metal-jet X-ray tube is the possibility to operate with a smaller focal spot, say 5 µm, to increase image resolution and at the same time acquire the image faster, since the power is higher (15-30 W) than for solid-anode tubes with 10 µm focal spots. As with any vacuum tube, there is a cathode, which emits electrons into the vacuum and an anode to collect the electrons, thus establishing a flow of electrical current, known as the beam, through the tube. A high voltage power source, for example 30 to 150 kilovolts (kV),

title: J. J. Thomson

text: debated whether cathode rays were immaterial like light ("some process in the aether") or were "in fact wholly material, and ... mark the paths of particles of matter charged with negative electricity", quoting Thomson. The aetherial hypothesis was vague, but the particle hypothesis was definite enough for Thomson to test. Thomson first investigated the magnetic deflection of cathode rays. Cathode rays were produced in the side tube on the left of the apparatus and passed through the anode into the main bell jar, where they were deflected by a magnet. Thomson detected their path by the fluorescence on a squared

title: X-ray tube

text: This will slowly darken the tube and was thought to degrade the quality of the X-ray beam. Vaporized tungsten condenses on the inside of the envelope over the "window" and thus acts as an additional filter and decreases the tubes ability to radiate heat. Eventually, the tungsten deposit may become sufficiently conductive that at high enough voltages, arcing occurs. The arc will jump from the cathode to the tungsten deposit, and then to the anode. This arcing causes an effect called "crazing" on the interior glass of the X-ray window. As time goes on, the tube becomes unstable even at

title: Hot cathode

text: reaction between these. The material has to be resistant to high temperatures, have high melting point and very low vapor pressure, and be electrically conductive. Materials used can be e.g. tantalum diboride, titanium diboride, zirconium diboride, niobium diboride, tantalum carbide, zirconium carbide, tantalum nitride, and zirconium nitride. A "cathode heater" is a heated wire filament used to heat the cathode in a vacuum tube or cathode ray tube. The cathode element has to achieve the required temperature in order for these tubes to function properly. This is why older electronics often needs some time to "warm up" after being powered

title: History of television

text: last mechanical television broadcasts ended in 1939 at stations run by a handful of public universities in the United States. In 1897, J. J. Thomson, an English physicist, in his three famous experiments was able to deflect cathode rays, a fundamental function of the modern Cathode Ray Tube (CRT). The earliest version of the CRT was invented by the German physicist Karl Ferdinand Braun in 1897 and is also known as the "Braun tube". It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. A cathode ray tube was successfully demonstrated as a displaying device

title: Hot cathode

text: on; this phenomenon can still be observed in the cathode ray tubes of some modern televisions and computer monitors. The cathode heats to a temperature that causes electrons to be 'boiled out' of its surface into the evacuated space in the tube, a process called thermionic emission. The temperature required for modern oxide-coated cathodes is around . The cathode is usually in the form of a long narrow sheet metal cylinder at the center of the tube. The heater consists of a fine wire or ribbon, made of a high resistance metal alloy like nichrome, similar to the heating element

title: X-ray tube

text: is the cathode of the tube. The high voltage potential is between the cathode and the anode, the electrons are thus accelerated, and then hit the anode. There are two designs: end-window tubes and side-window tubes. End window tubes usually have "transmission target" which is thin enough to allow X-rays to pass through the target (X-rays are emitted in the same direction as the electrons are moving.) In one common type of end-window tube, the filament is around the anode ("annular" or ring-shaped), the electrons have a curved path (half of a toroid). What is special about side-window tubes is

title: The Cathode Ray

text: 2010 – 2011 at Gold Star Studios in Fife. 2010 also saw The Cathode Ray making their live debut with well received shows in Edinburgh and Glasgow. They have since built up a solid live reputation with more gigs in and around Scotland including an appearance at the Wickerman Festival in 2012. The debut album “The Cathode Ray” was finally released in April 2012, through Stereogram Recordings to high critical acclaim. The album featured high in the end of year roundups on the Manic Pop Thrills, Penny Black Music, The Sound Project and Jocknroll websites. The single “Dispersal” was Track

title: Cathode ray

text: was resolved when an electric field was used to deflect the rays by J. J. Thomson. This was evidence that the beams were composed of particles because scientists knew it was impossible to deflect electromagnetic waves with an electric field. These can also create mechanical effects, fluorescence, etc. Louis de Broglie later (1924) showed in his doctoral dissertation that electrons are in fact much like photons in the respect that they act both as waves and as particles in a dual manner as Einstein had shown earlier for light. The wave-like behaviour of cathode rays was later directly demonstrated using

title: The Cathode Ray

text: Of The Month in April 2012 on the influential Janice Forsyth Show on BBC Radio Scotland. Three tracks, “Train”, “Around” and “Dispersal” were lifted from the album as singles to much acclaim and worldwide radio exposure. The Cathode Ray released their second album entitled “Infinite Variety” on Stereogram Recordings in April 2015. Accompanied by the singles ‘Resist’, ‘Buck The Trend’ and ‘This Force Of Nature’, it has garlanded ecstatic praise from all corners of the music press. The Cathode Ray returned on 6 April 2018, after a three-year recording hiatus, with “Another World”, the lead track from their forthcoming third

title: The Cathode Ray

text: album “Heightened Senses” which is due for release early in 2019. "Another World" marks the recording debut of guitarist Phil Biggs with the band, plus production assistance, cover art and video direction from Alex Thoms, the son of lead singer Jeremy Thoms. Steve Fraser (lead guitar), Neil Baldwin (bass) and David Mack (drums) still complete the current line-up. The Cathode Ray The Cathode Ray are an alternative band based in Edinburgh, Scotland. The current line-up is Jeremy Thoms (lead vocals/guitar/keyboards), Steve Fraser (guitar/backing vocals), Phil Biggs (guitar/backing vocals), Neil Baldwin (bass), and David Mack (drums & percussion). Originally based on

title: Crookes tube

text: more X-rays, and was tilted at an angle to the cathode, so the X-rays would radiate through the side of the tube. The cathode had a concave spherical surface which focused the electrons into a small spot around 1 mm in diameter on the anode, in order to approximate a point source of X-rays, which gave the sharpest radiographs. These cold cathode type X-ray tubes were used until about 1920, when they were superseded by the hot cathode Coolidge X-ray tube. During the last quarter of the 19th century Crookes tubes were used in dozens of historic experiments to try

title: Vacuum tube

text: analog scopes (dependent upon CRTs) continue to be produced, are economical, and preferred by many technicians. At one time many radios used "magic eye tubes", a specialized sort of CRT used in place of a meter movement to indicate signal strength, or input level in a tape recorder. A modern indicator device, the vacuum fluorescent display (VFD) is also a sort of cathode ray tube. The X-ray tube is a type of cathode ray tube that generates X-rays when high voltage electrons hit the anode. Gyrotrons or vacuum masers, used to generate high-power millimeter band waves, are magnetic vacuum tubes

title: Crookes tube

text: made in the form of a concave spherical dish, the cathode rays would be focused to a spot in front of the dish. This could be used to heat samples to a high temperature. Heinrich Hertz built a tube with a second pair of metal plates to either side of the cathode ray beam, a crude CRT. If the cathode rays were charged particles, their path should be bent by the electric field created when a voltage was applied to the plates, causing the spot of light where the rays hit to move sideways. He did not find any bending,

title: Crookes tube

text: pressure of residual gas in the tube. Over time the gas was absorbed by the walls of the tube, reducing the pressure. This reduced the amount of cathode rays produced and caused the voltage across the tube to increase, creating more energetic cathode rays. In Crookes X-ray tubes this phenomenon was called "hardening" because the higher voltage produced "harder", more penetrating X-rays; a tube with a higher vacuum was called a "hard" tube, while one with lower vacuum was a "soft" tube. Eventually the pressure got so low the tube stopped working entirely. To prevent this, in heavily used tubes

title: X-ray tube

text: called the "tube voltage", is connected across cathode and anode to accelerate the electrons. The X-ray spectrum depends on the anode material and the accelerating voltage. In many applications, the current flow (typically in the range 1 mA to 1 A) is able to be pulsed on for between about 1 ms to 1 s. This enables consistent doses of X-rays, and taking snapshots of motion. Until the late 1980s, X-ray generators were merely high-voltage, AC to DC variable power supplies. In the late 1980s a different method of control was emerging, called high speed switching. This followed the electronics

title: Cathode ray

text: on the voltage on the grid. Thus, a small voltage on the grid can be made to control a much larger voltage on the anode. This is the principle used in vacuum tubes to amplify electrical signals. The triode vacuum tube developed between 1907 and 1914 was the first electronic device that could amplify, and is still used in some applications such as radio transmitters. High speed beams of cathode rays can also be steered and manipulated by electric fields created by additional metal plates in the tube to which voltage is applied, or magnetic fields created by coils of

title: Cathode-ray tube

text: on the storage mesh. One way of allowing the image to be retained for longer is temporarily to turn off the flood gun. It is then possible for the image to be retained for several days. The majority of storage tubes allow for a lower voltage to be applied to the storage mesh which slowly restores the initial charge state. By varying this voltage a variable persistence is obtained. Turning off the flood gun and the voltage supply to the storage mesh allows such a tube to operate as a conventional oscilloscope tube. The Williams tube or Williams-Kilburn tube was

title: Video camera tube

text: equipment was optimized for tube-sourced video. Video camera tube Video camera tubes were devices based on the cathode ray tube that were used to capture television images prior to the introduction of charge-coupled devices (CCDs) in the 1980s. Several different types of tubes were in use from the early 1930s to the 1980s. In these tubes, the cathode ray was scanned across an image of the scene to be broadcast. The resultant current was dependent on the brightness of the image on the target. The size of the striking ray was tiny compared to the size of the target, allowing

title: Cold cathode

text: tube" cold-cathode device in 1936. Many types of cold-cathode switching tube were developed, including various types of thyratron, the krytron, cold-cathode displays (Nixie tube) and others. Voltage regulator tubes rely on the relatively constant voltage of a glow discharge over a range of current and were used to stabilize power-supply voltages in tube-based instruments. A Dekatron is a cold-cathode tube with multiple electrodes that is used for counting. Each time a pulse is applied to a control electrode, a glow discharge moves to a step electrode; by providing ten electrodes in each tube and cascading the tubes, a counter system

title: Video camera tube

text: in the NTSC format, or 576 lines in PAL. Any vacuum tube which operates using a focused beam of electrons, "cathode rays", is known as a cathode ray tube (CRT). These are usually seen as display devices as used in television receivers and computer displays. The camera pickup tubes described in this article are also CRTs, but they display no image. In June 1908, the scientific journal "Nature" published a letter in which Alan Archibald Campbell-Swinton, fellow of the Royal Society (UK), discussed how a fully electronic television system could be realized by using cathode ray tubes (or "Braun" tubes,

title: Cathode-ray tube

text: video voltage and beam intensity). In better quality old-fashioned tube radio sets, a tuning guide consisting of a phosphor tube was used to aid the tuning adjustment. This was also known as a "Magic Eye" or "Tuning Eye". Tuning would be adjusted until the width of a radial shadow was minimized. This was used instead of a more expensive electromechanical meter, which later came to be used on higher-end tuners when transistor sets lacked the high voltage required to drive the device. The same type of device was used with tape recorders as a recording level meter, and for various

title: Video camera tube

text: Video camera tube Video camera tubes were devices based on the cathode ray tube that were used to capture television images prior to the introduction of charge-coupled devices (CCDs) in the 1980s. Several different types of tubes were in use from the early 1930s to the 1980s. In these tubes, the cathode ray was scanned across an image of the scene to be broadcast. The resultant current was dependent on the brightness of the image on the target. The size of the striking ray was tiny compared to the size of the target, allowing 483 horizontal scan lines per image

title: Vacuum tube

text: tube is often used in videocassette recorders, DVD players and recorders, microwave oven control panels, and automotive dashboards. Rather than raster scanning, these vacuum fluorescent displays (VFD) switch control grids and anode voltages on and off, for instance, to display discrete characters. The VFD uses phosphor-coated anodes as in other display cathode ray tubes. Because the filaments are in view, they must be operated at temperatures where the filament does not glow visibly. This is possible using more recent cathode technology, and these tubes also operate with quite low anode voltages (often less than 50 volts) unlike cathode ray tubes.

title: Cathode ray

text: they were traveling so fast that, although they were attracted to it, they often flew past the anode and struck the back wall of the tube. When they struck atoms in the glass wall, they excited their orbital electrons to higher energy levels. When the electrons returned to their original energy level, they released the energy as light, causing the glass to fluoresce, usually a greenish or bluish color. Later researchers painted the inside back wall with fluorescent chemicals such as zinc sulfide, to make the glow more visible. Cathode rays themselves are invisible, but this accidental fluorescence allowed researchers

title: Cathode ray

text: an electric current flowed through the tube. Geissler tubes had enough air in them that the electrons could only travel a tiny distance before colliding with an atom. The electrons in these tubes moved in a slow diffusion process, never gaining much speed, so these tubes didn't produce cathode rays. Instead, they produced a colorful glow discharge (as in a modern neon light), caused when the electrons struck gas atoms, exciting their orbital electrons to higher energy levels. The electrons released this energy as light. This process is called fluorescence. By the 1870s, British physicist William Crookes and others were

title: Cathode ray

text: at the cathode (positive electrode) and its end are at the anode (negative electrode). In 1857, German physicist and glassblower Heinrich Geissler sucked even more air out with an improved pump, to a pressure of around 10 atm and found that, instead of an arc, a glow filled the tube. The voltage applied between the two electrodes of the tubes, generated by an induction coil, was anywhere between a few kilovolts and 100 kV. These were called Geissler tubes, similar to today's neon signs. The explanation of these effects was that the high voltage accelerated free electrons and electrically charged

title: Vacuum tube

text: use in radar, microwave ovens and industrial heating. Traveling-wave tubes (TWTs) are very good amplifiers and are even used in some communications satellites. High-powered klystron amplifier tubes can provide hundreds of kilowatts in the UHF range. The cathode ray tube (CRT) is a vacuum tube used particularly for display purposes. Although there are still many televisions and computer monitors using cathode ray tubes, they are rapidly being replaced by flat panel displays whose quality has greatly improved even as their prices drop. This is also true of digital oscilloscopes (based on internal computers and analog to digital converters), although traditional

title: X-ray tube

text: side of the main tube contained a mica sleeve or chemical that released a small amount of gas when heated, restoring the correct pressure. The glass envelope of the tube would blacken in use due to the X-rays affecting its structure. The Crookes tube was improved by William Coolidge in 1913. The Coolidge tube, also called hot cathode tube, is the most widely used. It works with a very good quality vacuum (about 10 Pa, or 10 Torr). In the Coolidge tube, the electrons are produced by thermionic effect from a tungsten filament heated by an electric current. The filament

title: X-ray tube

text: in line with the anode such that the anode was between the cathode and the anticathode. To operate, a DC voltage of a few kilovolts to as much as 100 kV was applied between the anodes and the cathode, usually generated by an induction coil, or for larger tubes, an electrostatic machine. This created and then accelerated a small number of ions from the low pressure gas in the tube. These struck further gas atoms, knocking electrons off them, creating more positive ions in a chain reaction. All the positive ions were attracted to the cathode. When they struck it,

title: Cathode ray

text: atoms (ions) naturally present in the air of the tube. At low pressure, there was enough space between the gas atoms that the electrons could accelerate to high enough speeds that when they struck an atom they knocked electrons off of it, creating more positive ions and free electrons, which went on to create more ions and electrons in a chain reaction, known as a glow discharge. The positive ions were attracted to the cathode and when they struck it knocked more electrons out of it, which were attracted toward the anode. Thus the ionized air was electrically conductive and

title: Cathode bias

text: inevitable differences between vacuum tubes nor does it protect against run-away conditions caused by tube or circuit malfunctions. He also asserted that most tube specialists consider fixed bias operation to be dangerous. Despite this stance, fixed bias is commonly used in tube amplifiers today. Tomer identified the trend toward fixed bias designs in 1960 but was not certain about the reasons for it. Cathode bias In electronics, cathode bias (also known as self-bias, or automatic bias) is a technique used with vacuum tubes to make the direct current (dc) cathode voltage positive in relation to the negative side of the

title: X-ray tube

text: X-ray tube An X-ray tube is a vacuum tube that converts electrical input power into X-rays. X-ray tubes evolved from experimental Crookes tubes with which X-rays were first discovered on November 8, 1895, by the German physicist Wilhelm Conrad Röntgen. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast to other sources of ionizing radiation, X-rays are only produced as long as the X-ray tube is energized. X-ray tubes are also used in CT scanners, airport luggage scanners, X-ray crystallography, material and structure analysis, and

title: Cold cathode

text: discharge around the cathode is usually minimized; instead there is a so-called positive column, filling the tube. Examples are the neon lamp and nixie tubes. Nixie tubes too are cold-cathode neon displays that are in-line, but not in-plane, display devices. Cold-cathode devices typically use a complex high-voltage power supply with some mechanism for limiting current. Although creating the initial space charge and the first arc of current through the tube may require a very high voltage, once the tube begins to heat up, the electrical resistance drops, thus increasing the electric current through the lamp. To offset this effect and

title: Cathode bias

text: unbypassed cathode resistor. Degeneration will not occur because, if the grid voltage versus plate current characteristics of the two tubes are matched, the current through the cathode resistor will not vary during the 360 degrees of the signal cycle. Cathode bias, as a solution, is often the alternative to using fixed bias. Robert Tomer, in his 1960 book about vacuum tubes, which mainly concerned itself with strategies for improving tube lifespan, condemned fixed bias designs in favor of cathode bias. He said that fixed bias, unlike cathode bias, does not provide a margin for error that protects the system from

title: X-ray generator

text: X-ray generator An X-ray generator is a device that produces X-rays. Together with an X-ray detector, it is commonly used in a variety of applications including medicine, fluorescence, electronic assembly inspection, and measurement of material thickness in manufacturing operations. In medical applications, X-ray generators are used by radiographers to acquire x-ray images of the internal structures (e.g., bones) of living organisms, and also in sterilization. An X-ray generator generally contains an X-ray tube to produce the X-rays. Possibly, radioisotopes can also be used to generate X-rays. An X-ray tube is a simple vacuum tube that contains a cathode, which directs

title: J. J. Thomson

text: their tubes contained too much gas. Thomson constructed a Crookes tube with a better vacuum. At the start of the tube was the cathode from which the rays projected. The rays were sharpened to a beam by two metal slits – the first of these slits doubled as the anode, the second was connected to the earth. The beam then passed between two parallel aluminium plates, which produced an electric field between them when they were connected to a battery. The end of the tube was a large sphere where the beam would impact on the glass, created a glowing

title: Crookes tube

text: Lenard was awarded the Nobel Prize in Physics in 1905 for his work. Crookes tube A Crookes tube (also Crookes–Hittorf tube) is an early experimental electrical discharge tube, with partial vacuum, invented by English physicist William Crookes and others around 1869-1875, in which cathode rays, streams of electrons, were discovered. Developed from the earlier Geissler tube, the Crookes tube consists of a partially evacuated glass bulb of various shapes, with two metal electrodes, the cathode and the anode, one at either end. When a high voltage is applied between the electrodes, cathode rays (electrons) are projected in straight lines from

title: X-ray tube

text: lower voltages, and must be replaced. At this point, the tube assembly (also called the "tube head") is removed from the X-ray system, and replaced with a new tube assembly. The old tube assembly is shipped to a company that reloads it with a new X-ray tube. The X-ray photon-generating effect is generally called the bremsstrahlung effect, a contraction of the German "bremsen" for braking, and "strahlung" for radiation. The range of photonic energies emitted by the system can be adjusted by changing the applied voltage, and installing aluminum filters of varying thicknesses. Aluminum filters are installed in the path

title: X-ray

text: had a limited life, and the restoration process was difficult to control. In 1904, John Ambrose Fleming invented the thermionic diode, the first kind of vacuum tube. This used a hot cathode that caused an electric current to flow in a vacuum. This idea was quickly applied to X-ray tubes, and hence heated-cathode X-ray tubes, called "Coolidge tubes", completely replaced the troublesome cold cathode tubes by about 1920. In about 1906, the physicist Charles Barkla discovered that X-rays could be scattered by gases, and that each element had a characteristic X-ray spectrum. He won the 1917 Nobel Prize in Physics

title: Cathode-ray tube

text: used to strictly limit, for instance, television receivers to 0.5 milliroentgens per hour (mR/h) (0.13 µC/(kg·h) or 36 pA/kg) at a distance of from any external surface; since 2007, most CRTs have emissions that fall well below this limit. Older color and monochrome CRTs may have been manufactured with toxic substances, such as cadmium, in the phosphors. The rear glass tube of modern CRTs may be made from leaded glass, which represent an environmental hazard if disposed of improperly. By the time personal computers were produced, glass in the front panel (the viewable portion of the CRT) used barium rather

title: Video camera tube

text: after its inventor, Karl Braun) as both imaging and display devices. He noted that the "real difficulties lie in devising an efficient transmitter", and that it was possible that "no photoelectric phenomenon at present known will provide what is required". A cathode ray tube was successfully demonstrated as a displaying device by the German Professor Max Dieckmann in 1906, his experimental results were published by the journal "Scientific American" in 1909. Campbell-Swinton later expanded on his vision in a presidential address given to the Röntgen Society in November 1911. The photoelectric screen in the proposed transmitting device was a mosaic

title: Crookes tube

text: electrons themselves. Since the atoms are thousands of times more massive than the electrons, they move much slower, accounting for the lack of Doppler shift. Philipp Lenard wanted to see if cathode rays could pass out of the Crookes tube into the air. See diagram. He built a tube with a "window" "(W)" in the glass envelope made of aluminum foil just thick enough to hold the atmospheric pressure out (later called a "Lenard window") facing the cathode "(C)" so the cathode rays would hit it. He found that something did come through. Holding a fluorescent screen up to the

title: X-ray tube

text: voltages in the event of failure. The hazard associated with excessive voltages was eliminated with the advent of all solid state TVs, which have no tubes beside the CRT. Since 1969 the FDA has limited TV X-ray emission to 0.5 mR (milliroentgen) per hour. The flat screens used today do not have any vacuum tubes capable of emitting X-rays. X-ray tube An X-ray tube is a vacuum tube that converts electrical input power into X-rays. X-ray tubes evolved from experimental Crookes tubes with which X-rays were first discovered on November 8, 1895, by the German physicist Wilhelm Conrad Röntgen. The

title: Williams tube

text: Williams tubes were made from radar-type cathode ray tubes with a phosphor coating that made the data visible, while other tubes were purpose-built without such a coating. The presence or absence of this coating had no effect on the operation of the tube, and was of no importance to the operators, since the face of the tube was covered by the pickup plate. If a visible output was needed, a second tube connected in parallel with the storage tube, with a phosphor coating, but without a pickup plate, was used as a display device. Developed at the University of Manchester

title: J. J. Thomson

text: screen in the jar. He found that whatever the material of the anode and the gas in the jar, the deflection of the rays was the same, suggesting that the rays were of the same form whatever their origin. While supporters of the aetherial theory accepted the possibility that negatively charged particles are produced in Crookes tubes, they believed that they are a mere by-product and that the cathode rays themselves are immaterial. Thomson set out to investigate whether or not he could actually separate the charge from the rays. Thomson constructed a Crookes tube with an electrometer set to