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Watch hand luminous paint11/25/2023 ![]() ![]() Sizes range from tiny tubes small enough to fit on the hand of a watch to ones the size of a pencil. For comparison, most consumer desktop liquid crystal displays have luminances of 200 to 300 cd/m 2. Green usually appears as the brightest color with a brightness as high as 2 cd/m 2 and red appears the least bright. The light produced by GTLSs varies in color and size. The difference between the signs is how much tritium the manufacturer installs. Tritium exit signs usually come in three brightness levels guaranteed for 10, 15, or 20 year useful life expectancies. The more tritium that is initially placed in the tube, the brighter it is to begin with, and the longer its useful life. Additionally, phosphor degradation will cause the brightness of a tritium tube to drop by more than half in that period. Being an unstable isotope with a half-life of 12.32 years, the rate of beta emissions decreases by half in that period. The average such GTLS has a useful life of 10–20 years. The GTLSs used in watches give off a small amount of light: Not enough to be seen in daylight, but visible in the dark from a distance of several meters. Some of the colors that have been manufactured in addition to the common phosphors are green, red, blue, yellow, purple, orange, and white. For example, doping zinc sulfide phosphor with different metals can change the emission wavelength. ![]() Various preparations of the phosphor compound can be used to produce different colors of light. ![]() Tritium is the only radiation source used in radioluminescent light sources today due to its low radiological toxicity and commercial availability. Promethium briefly replaced radium as a radiation source. Radium was used to make self-luminous paint from the early years of the 20th century until approximately 1970. Tritium is not the only material that can be used for self-powered lighting. These particles excite the phosphor, causing it to emit a low, steady glow. In the tube, the tritium gives off a steady stream of electrons due to beta decay. Borosilicate is preferred for its strength and resistance to breakage. The tube is then sealed at the desired length using a carbon dioxide laser. ĭuring manufacture, a length of borosilicate glass tube that has had the internal surface coated with a phosphor-containing material is filled with radioactive tritium. The tritium in a gaseous tritium light source undergoes beta decay, releasing electrons that cause the phosphor layer to phosphoresce. Such a tube is known as a "gaseous tritium light source" (GTLS), or beta light (since the tritium undergoes beta decay). Tritium lighting is made using glass tubes with a phosphor layer in them and tritium gas inside the tube. Tritium was found to be an ideal energy source for self-luminous compounds in 1953 and the idea was patented by Edward Shapiro on 29 October 1953, in the US (2749251 – Source of Luminosity). Gun sights for night use and small lights (which need to be more reliable than battery powered lights, yet not interfere with night vision or be bright enough to easily give away one's location) used mostly by military personnel fall under the latter application. As tritium illumination requires no electrical energy, it has found wide use in applications such as emergency exit signs, illumination of wristwatches, and portable yet very reliable sources of low intensity light which won't degrade human night vision. The overall process of using a radioactive material to excite a phosphor and ultimately generate light is called radioluminescence. Tritium emits electrons through beta decay and, when they interact with a phosphor material, light is emitted through the process of phosphorescence. Tritium radioluminescence is the use of gaseous tritium, a radioactive isotope of hydrogen, to create visible light. Radioluminescent 1.8- curie (67 GBq) 6-by-0.2-inch (152.4 mm × 5.1 mm) tritium vials are tritium gas-filled, thin glass vials with inner surfaces coated with a phosphor. Use of gaseous tritium to create visible light ![]()
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