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78-560: In its stock configuration, the Senior Partner weighs 31 pounds (14 kg) and measures 19.75 by 13.5 by 8.25 inches (50.2 by 34.3 by 21.0 cm). Its monochrome, green- phosphor cathode-ray tube display measures nine inches diagonally and supports the CGA video mode for IBM PCs and compatibles , displaying text at up to 80 columns by 25 rows and graphics up to 640 by 200 pixels. The Senior Partner runs an Intel 8088 microprocessor clocked at

156-449: A cathode-ray tube . When a phosphor is exposed to radiation, the orbital electrons in its molecules are excited to a higher energy level ; when they return to their former level they emit the energy as light of a certain color. Phosphors can be classified into two categories: fluorescent substances which emit the energy immediately and stop glowing when the exciting radiation is turned off, and phosphorescent substances which emit

234-430: A (typically) round or rectangular format. Bulky CRTs were used in the black-and-white television (TV) sets that became popular in the 1950s, developed into color CRTs in the late 1960s, and used in virtually all color TVs and computer monitors until the mid-2000s. In the late 20th century, advanced electronics made new wide-deflection, "short tube" CRT technology viable, making CRTs more compact, but still bulky and heavy. As

312-411: 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 on the voltage on the grid. Thus, a small voltage on

390-427: A blue or ultra-violet emitter with a phosphor coating that emits at longer wavelengths, giving a full spectrum of visible light. Unfocused and undeflected cathode-ray tubes have been used as stroboscope lamps since 1958. Phosphor thermometry is a temperature measurement approach that uses the temperature dependence of certain phosphors. For this, a phosphor coating is applied to a surface of interest and, usually,

468-744: A built-in thermal printer capable of operating at up to 55 cps . The printer can feed out up to 80 inches of paper before jamming due to lacking a tractor-feed mechanism. It can print up to 132 columns of text per row. Panasonic announced the Senior Partner in November 1983 and began delivering units to customers in March 1984. The hard drive–based Super Senior Partner was unveiled in May 1984, to be available in August that year. Despite being manufactured in Japan, Panasonic did not sell

546-447: A coating of a suitable material. Cerium (III)-doped YAG ( YAG:Ce , or Y 3 Al 5 O 12 :Ce ) is often used; it absorbs the light from the blue LED and emits in a broad range from greenish to reddish, with most of its output in yellow. This yellow emission combined with the remaining blue emission gives the "white" light, which can be adjusted to color temperature as warm (yellowish) or cold (bluish) white. The pale yellow emission of

624-592: A combination of phosphors is employed. The most common combination is ZnS:Ag + (Zn,Cd)S:Cu,Al (blue + yellow). Other ones are ZnS:Ag + (Zn,Cd)S:Ag (blue + yellow), and ZnS:Ag + ZnS:Cu,Al + Y 2 O 2 S:Eu (blue + green + red – does not contain cadmium and has poor efficiency). The color tone can be adjusted by the ratios of the components. As the compositions contain discrete grains of different phosphors, they produce image that may not be entirely smooth. A single, white-emitting phosphor, (Zn,Cd)S:Ag,Au,Al overcomes this obstacle. Due to its low efficiency, it

702-449: 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

780-595: A few specialized gas discharge tubes such as krytrons . In 1906, Lee De Forest found that a small voltage on a grid of metal wires between the cathode and anode could control a current in a beam of cathode rays passing through a vacuum 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

858-431: A focused beam of electrons deflected by electric or magnetic fields to render an image on a 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 experimental cold cathode vacuum tubes in which cathode rays were discovered, called Crookes tubes , this

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936-792: A formation of three beams) across a phosphor surface, a CRT has no intrinsic "native resolution" and does not require scaling to display raster images at different resolutions; the CRT can display any raster format natively, within the limits defined by the electron beam spot size and, for a color CRT, the dot pitch of the phosphor. Because of this operating principle, CRTs can produce images using either raster and vector imaging methods. Vector displays are impossible for display techologies that have permanent discrete pixels, including all LCDs, [[Plasma display|plasma display panels], DMD projectors, and [[OLED] (LED matrix, e.g. TFT OLED) panels. The phosphors can be deposited as either thin film , or as discrete particles,

1014-404: A layer absorbing the exciting and/or radiated energy, etc. The degradation of electroluminescent devices depends on frequency of driving current, the luminance level, and temperature; moisture impairs phosphor lifetime very noticeably as well. Harder, high-melting, water-insoluble materials display lower tendency to lose luminescence under operation. Examples: Phosphor layers provide most of

1092-486: 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 at the cathode (negative electrode) and its end at the anode (positive electrode). In 1857, German physicist and glassblower Heinrich Geissler sucked even more air out with an improved pump, to

1170-404: 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 able to evacuate tubes to a lower pressure, below 10 atm. These were called Crookes tubes. Faraday had been the first to notice

1248-434: A multi-step production process, with details that vary depending on the particular phosphor. Bulk material must be milled to obtain a desired particle size range, since large particles produce a poor-quality lamp coating, and small particles produce less light and degrade more quickly. During the firing of the phosphor, process conditions must be controlled to prevent oxidation of the phosphor activators or contamination from

1326-667: 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 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) suggested in his doctoral dissertation that electrons are like photons and can act as waves . The wave-like behaviour of cathode rays

1404-503: A persistent light is needed, such as glow-in-the-dark watch faces and aircraft instruments, and in radar screens to allow the target 'blips' to remain visible as the radar beam rotates. CRT phosphors were standardized beginning around World War II and designated by the letter "P" followed by a number. Phosphorus , the light-emitting chemical element for which phosphors are named, emits light due to chemiluminescence , not phosphorescence. The scintillation process in inorganic materials

1482-556: A phosphor made of silver doped zinc sulfide (ZnS:Ag), which gave a greenish glow. The phosphor is not suitable to be used in layers thicker than 25 mg/cm , as the self-absorption of the light then becomes a problem. Furthermore, zinc sulfide undergoes degradation of its crystal lattice structure, leading to gradual loss of brightness significantly faster than the depletion of radium. ZnS:Ag coated spinthariscope screens were used by Ernest Rutherford in his experiments discovering atomic nucleus . Copper doped zinc sulfide (ZnS:Cu)

1560-559: A powder bound to the surface. Thin films have better lifetime and better resolution, but provide less bright and less efficient image than powder ones. This is caused by multiple internal reflections in the thin film, scattering the emitted light. White (in black-and-white): The mix of zinc cadmium sulfide and zinc sulfide silver, the ZnS:Ag + (Zn,Cd)S:Ag is the white P4 phosphor used in black and white television CRTs. Mixes of yellow and blue phosphors are usual. Mixes of red, green and blue, or

1638-458: 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 atoms ( ions ) naturally present in

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1716-807: A single phosphor color, typically green. Phosphors for such applications may have long afterglow, for increased image persistence. A variation of the display CRT, used prior to the 1980s, was the CRT storage tube , a digital memory device which (in later forms) also provided a visible display of the stored data, using a variation of the same electron-beam excited phosphor technology. The process of producing light in CRTs by electron-beam excited phosphorescence yields much faster signal response times than even modern (2020s) LCDs can achieve, which makes light pens and light gun games possible with CRTs, but not LCDs. Also in contrast to most other video display types, because CRT technology draws an image by scanning an electron beam (or

1794-401: A single white phosphor, can also be encountered. Red: Yttrium oxide - sulfide activated with europium is used as the red phosphor in color CRTs. The development of color TV took a long time due to the search for a red phosphor. The first red emitting rare-earth phosphor, YVO 4 :Eu , was introduced by Levine and Palilla as a primary color in television in 1964. In single crystal form, it

1872-460: A well-padded handle to ease the burden of carrying it". In the end, he called it a "fine machine with many extras—including a built printer—at a very competitive price". In July 1985, Panasonic released the Executive Partner , the successor to the Senior Partner that also features a built-in printer. The Executive Partner replaces the Senior Partner's CRT display for a gas-plasma one and adds

1950-429: A yellow variant also exists (α-SiAlON ). For white LEDs, a blue LED is used with a yellow phosphor, or with a green and yellow SiAlON phosphor and a red CaAlSiN 3 -based (CASN) phosphor. White LEDs can also be made by coating near-ultraviolet-emitting LEDs with a mixture of high-efficiency europium-based red- and blue-emitting phosphors plus green-emitting copper- and aluminium-doped zinc sulfide (ZnS:Cu,Al) . This

2028-444: Is a copper-activated zinc sulfide (ZnS) and the silver -activated zinc sulfide ( zinc sulfide silver ). The host materials are typically oxides , nitrides and oxynitrides, sulfides , selenides , halides or silicates of zinc , cadmium , manganese , aluminium , silicon , or various rare-earth metals . The activators prolong the emission time (afterglow). In turn, other materials (such as nickel ) can be used to quench

2106-546: Is a method analogous to the way fluorescent lamps work. Some newer white LEDs use a yellow and blue emitter in series, to approximate white; this technology is used in some Motorola phones such as the Blackberry as well as LED lighting and the original-version stacked emitters by using GaN on SiC on InGaP but was later found to fracture at higher drive currents. Many white LEDs used in general lighting systems can be used for data transfer, as, for example, in systems that modulate

2184-482: Is due to the electronic band structure found in the crystals . An incoming particle can excite an electron from the valence band to either the conduction band or the exciton band (located just below the conduction band and separated from the valence band by an energy gap ). This leaves an associated hole behind, in the valence band. Impurities create electronic levels in the forbidden gap . The excitons are loosely bound electron–hole pairs that wander through

2262-448: Is found in a variety of backlight and night light applications. Several groups offer branded EL offerings (e.g. IndiGlo used in some Timex watches) or "Lighttape", another trade name of an electroluminescent material, used in electroluminescent light strips . The Apollo space program is often credited with being the first significant use of EL for backlights and lighting. White light-emitting diodes are usually blue InGaN LEDs with

2340-405: 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 negative cathode and attracted to the positive anode. They travel in parallel lines through

2418-433: Is the most common phosphor used and yields blue-green light. Copper and magnesium doped zinc sulfide (ZnS:Cu,Mg) yields yellow-orange light. Tritium is also used as a source of radiation in various products utilizing tritium illumination . Electroluminescence can be exploited in light sources. Such sources typically emit from a large area, which makes them suitable for backlights of LCD displays. The excitation of

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2496-405: Is used only on very small screens. Cathode ray Cathode rays or electron beams ( e-beam ) are streams of electrons observed in discharge 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

2574-433: Is well known in solutions of phosphorescent heavy-metal complexes and doped polymers. In recent years, phosphorescence porous materials(such as Metal–organic frameworks and Covalent organic frameworks ) have shown promising oxygen sensing capabilities, for their non-linear gas-adsorption in ultra-low partial pressures of oxygen. Phosphor banded stamps first appeared in 1959 as guides for machines to sort mail. Around

2652-460: The crystal lattice until they are captured as a whole by impurity centers. They then rapidly de-excite by emitting scintillation light (fast component). In the conduction band, electrons are independent of their associated holes. Those electrons and holes are captured successively by impurity centers exciting certain metastable states not accessible to the excitons. The delayed de-excitation of those metastable impurity states, slowed by reliance on

2730-436: The 19th century, many historic experiments were done with Crookes tubes to determine what cathode rays 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

2808-505: The Ce :YAG can be tuned by substituting the cerium with other rare-earth elements such as terbium and gadolinium and can even be further adjusted by substituting some or all of the aluminium in the YAG with gallium. However, this process is not one of phosphorescence. The yellow light is produced by a process known as scintillation , the complete absence of an afterglow being one of the characteristics of

2886-601: The IBM-PC-standard 4.77 MHz. A slot for an aftermarket 8087 floating-point co-processor is included on the motherboard. The computer's base configuration is equipped with 128 KB of RAM , expandable to 256 KB via a proprietary plug-in expansion board. At the rear of the system unit is an RS-232 serial port , a Centronics-style parallel port (in a deviation from the IBM-PC-standard DB-25 parallel connector), and an RGBI port. Panasonic offered three models of

2964-608: The LED to act as a beacon . It is also common for white LEDs to use phosphors other than Ce:YAG, or to use two or three phosphors to achieve a higher CRI, often at the cost of efficiency. Examples of additional phosphors are R9, which produces a saturated red, nitrides which produce red, and aluminates such as lutetium aluminum garnet that produce green. Silicate phosphors are brighter but fade more quickly, and are used in LCD LED backlights in mobile devices. LED phosphors can be placed directly over

3042-559: The Senior Partner: one with one 5.25-inch floppy drive; another with two such drives; and the last with one 5.25-inch floppy drive and one 10 MB hard drive . Panasonic dubbed the lattermost model the Super Senior Partner. The company supplied all units with MS-DOS 2.11 , as well as a bundle of application software including GW-BASIC , WordStar , VisiCalc , pfs:File , pfs:Graph , and pfs:Report . The Senior Partner features

3120-531: The ZnS:Ag, when excited by electrons, provides strong blue glow with maximum at 450 nm, with short afterglow with 200 nanosecond duration. It is known as the P22B phosphor. This material, zinc sulfide silver , is still one of the most efficient phosphors in cathode-ray tubes. It is used as a blue phosphor in color CRTs. The phosphors are usually poor electrical conductors. This may lead to deposition of residual charge on

3198-491: The ability to use loose-leaf paper in its printer with the purchase of an ink-ribbon print head. Phosphor A phosphor is a substance that exhibits the phenomenon of luminescence ; it emits light when exposed to some type of radiant energy . The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or visible light, and cathodoluminescent substances which glow when struck by an electron beam ( cathode rays ) in

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3276-427: The afterglow and shorten the decay part of the phosphor emission characteristics. Many phosphor powders are produced in low-temperature processes, such as sol-gel , and usually require post-annealing at temperatures of ~1000 °C, which is undesirable for many applications. However, proper optimization of the growth process allows manufacturers to avoid the annealing. Phosphors used for fluorescent lamps require

3354-487: 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

3432-426: The anode. Thus the ionized air was electrically conductive and 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

3510-400: The cathode could cast a shadow on the glowing wall, and realized that something must be traveling in straight lines from the cathode. After the electrons strike the back of the tube they make their way to the anode, then travel through the anode wire through the power supply and back through the cathode wire to the cathode, so cathode rays carry electric current through the tube. The current in

3588-555: The computer domestically and instead only sold the computer in North America. By April 1984, Panasonic secured nearly 500 nationwide dealers in the United States to sell the Senior Partner. Panasonic commissioned a name-creation company to conjure the Senior Partner name; the final trademark was selected from a pool of 400 candidates. The Senior Partner received largely positive reviews from the technology press, although some criticism

3666-438: The crystal structure are created usually by addition of a trace amount of dopants , impurities called activators . (In rare cases dislocations or other crystal defects can play the role of the impurity.) The wavelength emitted by the emission center is dependent on the atom itself and on the surrounding crystal structure. Phosphors are usually made from a suitable host material with an added activator . The best known type

3744-406: The decay time is the emission parameter that indicates temperature. Because the illumination and detection optics can be situated remotely, the method may be used for moving surfaces such as high speed motor surfaces. Also, phosphor may be applied to the end of an optical fiber as an optical analog of a thermocouple. In these applications, the phosphor is directly added to the plastic used to mold

3822-536: The die or made into a dome and placed above the LED: this approach is known as a remote phosphor. Some colored LEDs, instead of using a colored LED, use a blue LED with a colored phosphor because such an arrangement is more efficient than a colored LED. Oxynitride phosphors can also be used in LEDs. The precursors used to make the phosphors may degrade when exposed to air. Cathode-ray tubes produce signal-generated light patterns in

3900-587: 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 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

3978-415: 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 these Crookes tubes when they struck the glass wall of the tube, exciting the atoms of the glass coating and causing them to emit light, a glow called fluorescence . Researchers noticed that objects placed in the tube in front of

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4056-470: The energy after a delay, so they keep glowing after the radiation is turned off, decaying in brightness over a period of milliseconds to days. Fluorescent materials are used in applications in which the phosphor is excited continuously: cathode-ray tubes (CRT) and plasma video display screens, fluoroscope screens , fluorescent lights , scintillation sensors , white LEDs , and luminous paints for black light art. Phosphorescent materials are used where

4134-421: 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 to notice that objects in the tube in front of the cathode, such as the anode, cast sharp-edged shadows on

4212-410: 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 invention of the cathode-ray tube (CRT) by Ferdinand Braun in 1897, which

4290-415: 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

4368-451: 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

4446-415: The light produced by fluorescent lamps , and are also used to improve the balance of light produced by metal halide lamps . Various neon signs use phosphor layers to produce different colors of light. Electroluminescent displays found, for example, in aircraft instrument panels, use a phosphor layer to produce glare-free illumination or as numeric and graphic display devices. White LED lamps consist of

4524-431: The low-probability forbidden mechanism , again results in light emission (slow component). In the case of inorganic scintillators , the activator impurities are typically chosen so that the emitted light is in the visible range or near-UV , where photomultipliers are effective. Phosphors are often transition-metal compounds or rare-earth compounds of various types. In inorganic phosphors, these inhomogeneities in

4602-511: The original video display technology, having no viable competition for more than 40 years and dominance for over 50 years, the CRT ceased to be the main type of video display in use only around 2010. In addition to direct-view CRTs, CRT projection tubes were the basis of all projection TVs and computer video projectors of both front and rear projection types until at least the late 1990s. CRTs have also been widely used in scientific and engineering instrumentation, such as oscilloscopes , usually with

4680-444: The peak width (in nanometers at 50% of intensity), and decay time (in seconds ). Examples: Many phosphors tend to lose efficiency gradually by several mechanisms. The activators can undergo change of valence (usually oxidation ), the crystal lattice degrades, atoms – often the activators – diffuse through the material, the surface undergoes chemical reactions with the environment with consequent loss of efficiency or buildup of

4758-783: The phosphor from ion bombardment resulting from an imperfect vacuum. To reduce the image degradation by reflection of ambient light, contrast can be increased by several methods. In addition to black masking of unused areas of screen, the phosphor particles in color screens are coated with pigments of matching color. For example, the red phosphors are coated with ferric oxide (replacing earlier Cd(S,Se) due to cadmium toxicity), blue phosphors can be coated with marine blue ( CoO · n Al 2 O 3 ) or ultramarine ( Na 8 Al 6 Si 6 O 24 S 2 ). Green phosphors based on ZnS:Cu do not have to be coated due to their own yellowish color. The black-and-white television screens require an emission color close to white. Usually,

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4836-546: The phosphor is usually achieved by application of high-intensity electric field , usually with suitable frequency. Current electroluminescent light sources tend to degrade with use, resulting in their relatively short operation lifetimes. ZnS:Cu was the first formulation successfully displaying electroluminescence, tested at 1936 by Georges Destriau in Madame Marie Curie laboratories in Paris. Powder or AC electroluminescence

4914-502: The process vessels. After milling, the phosphor may be washed to remove minor excess of activator elements. Volatile elements must not be allowed to escape during processing. Lamp manufacturers have changed compositions of phosphors to eliminate some toxic elements formerly used, such as beryllium , cadmium , or thallium . The commonly quoted parameters for phosphors are the wavelength of emission maximum (in nanometers, or alternatively color temperature in kelvins for white blends),

4992-431: The process. Some rare-earth - doped Sialons are photoluminescent and can serve as phosphors. Europium (II)-doped β-SiAlON absorbs in ultraviolet and visible light spectrum and emits intense broadband visible emission. Its luminance and color does not change significantly with temperature, due to the temperature-stable crystal structure. It has a great potential as a green down-conversion phosphor for white LEDs ;

5070-403: The screen, effectively decreasing the energy of the impacting electrons due to electrostatic repulsion (an effect known as "sticking"). To eliminate this, a thin layer of aluminium (about 100 nm) is deposited over the phosphors, usually by vacuum evaporation, and connected to the conductive layer inside the tube. This layer also reflects the phosphor light to the desired direction, and protects

5148-424: The toys, or mixed with a binder for use as paints. ZnS:Cu phosphor is used in glow-in-the-dark cosmetic creams frequently used for Halloween make-ups . Generally, the persistence of the phosphor increases as the wavelength increases. See also lightstick for chemiluminescence -based glowing items. Quenching of the triplet state by O 2 (which has a triplet ground state) as a result of Dexter energy transfer

5226-460: The tube by a process called thermionic emission . The first true electronic vacuum tubes, invented in 1904 by John Ambrose Fleming , used this hot cathode technique, and they superseded Crookes tubes. These tubes didn't need gas in them to work, so they were evacuated to a lower pressure, around 10 atm (10 Pa). The ionization method of creating cathode rays used in Crookes tubes is today only used in

5304-470: The tube itself 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

5382-452: The tube to which voltage is applied, or magnetic fields created by coils of wire ( electromagnets ). These are used in cathode-ray tubes , found in televisions and computer monitors, and in electron microscopes . After the invention of the vacuum pump in 1654 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

5460-432: The voltage between the electrodes. These were the cathode rays. When they reached the anode end of the tube, 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

5538-466: The voltage supply). They were first observed in 1859 by German physicist Julius Plücker and 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 charged particle, which was later named the electron . Cathode-ray tubes (CRTs) use

5616-489: The world many varieties exist with different amounts of banding. Postage stamps are sometimes collected by whether or not they are "tagged" with phosphor (or printed on luminescent paper). Zinc sulfide phosphors are used with radioactive materials, where the phosphor was excited by the alpha- and beta-decaying isotopes, to create luminescent paint for dials of watches and instruments ( radium dials ). Between 1913 and 1950 radium-228 and radium-226 were used to activate

5694-404: Was done by using a high electrical potential of thousands of volts between the anode and the cathode to ionize the 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 of its surface; these were the cathode rays. Modern vacuum tubes use thermionic emission , in which the cathode

5772-573: 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 in Physics for this work. Philipp Lenard also contributed a great deal to cathode-ray theory, winning the Nobel Prize in 1905 for his research on cathode rays and their properties. The gas ionization (or cold cathode ) method of producing cathode rays used in Crookes tubes

5850-516: Was reserved for the printer's output. For example, Russ Lockwood in Creative Computing wrote that, although operating at a very quiet noise level and producing overall good-quality prints, "letters with slanted and curved lines are not as sharp as they could be. Lockwood called the Senior Partner very heavy: "You will either develop bulging biceps or suffer a separated shoulder if you lug it about more than occasionally", albeit "Panasonic attaches

5928-442: 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

6006-444: Was used as an excellent polarizer and laser material. Yellow: When mixed with cadmium sulfide , the resulting zinc cadmium sulfide (Zn,Cd)S:Ag , provides strong yellow light. Green: Combination of zinc sulfide with copper , the P31 phosphor or ZnS:Cu , provides green light peaking at 531 nm, with long glow. Blue: Combination of zinc sulfide with few ppm of silver ,

6084-402: Was used in television sets and oscilloscopes . Today, electron beams are 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

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