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| #REDIRECT [[X-rays]] | | #REDIRECT [[X-rays]] |
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| ==Medical uses==
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| [[Image:X-Ray Skull.jpg|right|thumb|150px||X-Ray Image of the Paranasal Sinuses, Lateral Projection]]
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| Since Röntgen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in [[medical imaging]]. [[Radiology]] is a specialized field of [[medicine]]. Radiographers employ [[radiography]] and other techniques for [[diagnostic imaging]]. Indeed, this is probably the most common use of X-ray technology.
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| X-rays are especially useful in the detection of pathology of the [[bone|skeletal system]], but are also useful for detecting some disease processes in [[soft tissue]]. Some notable examples are the very common [[chest X-ray]], which can be used to identify lung diseases such as [[pneumonia]], [[lung cancer]] or [[pulmonary edema]], and the [[abdominal X-ray]], which can detect [[ileus]] (blockage of the [[intestine]]), free air (from visceral perforations) and free fluid (in [[ascites]]). In some cases, the use of X-rays is debatable, such as [[gallstone]]s (which are rarely [[radiopaque]]) or [[kidney stone]]s (which are often visible, but not always). Also, traditional plain X-rays pose very little use in the imaging of soft tissues such as the [[brain]] or [[muscle]]. Imaging alternatives for soft tissues are [[computed axial tomography]] (CAT or CT scanning), [[magnetic resonance imaging]] (MRI) or [[medical ultrasonography|ultrasound]]. Since 2005, X-rays are listed as a [[carcinogen]] by the U.S. government.<ref>[http://ntp.niehs.nih.gov/ntp/roc/toc11.html 11th Report on Carcinogens<!-- Bot generated title -->]</ref>
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| [[Radiotherapy]], a curative medical intervention, now used almost exclusively for [[cancer]], employs higher energies of radiation.
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| The efficiency of X-ray tubes is less than 2%. Most of the energy is used to heat up the anode.
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| ==Other uses==
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| Other notable uses of X-rays include
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| *[[X-ray crystallography]] in which the pattern produced by the [[diffraction]] of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. A related technique, [[fiber diffraction]], was used by [[Rosalind Franklin]] to discover the [[Double helix|double helical]] structure of [[DNA]]).<ref>{{cite book
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| | last = Kasai
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| | first = Nobutami
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| | authorlink =
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| | coauthors = Masao Kakudo
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| | title = X-ray diffraction by macromolecules
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| | publisher = Kodansha
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| | date = 2005
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| | location = Tokyo
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| | pages = pp291-2
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| | url =
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| | doi =
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| | id =
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| | isbn = 3540253173}}</ref>
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| *[[X-ray astronomy]], which is an observational branch of [[astronomy]], which deals with the study of X-ray emission from celestial objects.
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| *[[X-ray microscope|X-ray microscopic analysis]], which uses [[electromagnetic radiation]] in the soft X-ray band to produce images of very small objects.
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| *[[X-ray fluorescence]], a technique in which X-rays are generated within a specimen and detected. The outgoing energy of the X-ray can be used to identify the composition of the sample.
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| *Paintings are often X-rayed to reveal the [[underdrawing]] and [[pentimento|pentimenti]] or alterations in the course of painting, or by later restorers. Many [[pigment]]s such as [[lead white]] show well in X-ray photographs.
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| ==History==
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| Among the important early researchers in X-rays were Professor [[Ivan Pulyui]], Sir [[William Crookes]], [[Johann Wilhelm Hittorf]], [[Eugen Goldstein]], [[Heinrich Hertz]], [[Philipp Lenard]], [[Hermann von Helmholtz]], [[Nikola Tesla]], [[Thomas Edison]], [[Charles Glover Barkla]], [[Max von Laue]], and [[Wilhelm Conrad Röntgen]]. In a humorous case of hindsight, [[Lord Kelvin]] said "X-Rays are a hoax".
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| ===Johann Hittorf===
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| Physicist [[Johann Hittorf]] (1824 – 1914) observed [[vacuum tube|tubes]] with energy rays extending from a negative electrode. These rays produced a fluorescence when they hit the glass walls of the tubes. In 1876 the effect was named "[[cathode ray]]s" by [[Eugen Goldstein]], and today are known to be streams of [[electron]]s. Later, English physicist [[William Crookes]] investigated the effects of electric currents in gases at low pressure, and constructed what is called the [[Crookes tube]]. It is a glass cylinder mostly (but not completely) evacuated, containing electrodes for discharges of a high voltage electric current. He found, when he placed unexposed photographic plates near the tube, that some of them were flawed by shadows, though he did not investigate this effect. Crookes also noted that his cathode rays caused the glass walls of his tube to glow a dull blue colour. Crookes failed to realise that it wasn't actually the cathode rays that caused the blue glow, but the low-level X-rays produced when the cathode rays struck the glass.
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| {{clear}}
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| ===Ivan Pulyui===
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| In 1877 [[Ukrane|Ukranian]]-born [[Ivan Pulyui|Pulyui]], a lecturer in experimental physics at the [[University of Vienna]], constructed various designs of [[Geissler tube|vacuum discharge tube]] to investigate their properties.<ref name=mayo>{{cite web
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| | last = Gaida
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| | first = Roman
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| | authorlink =
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| | coauthors = et al
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| | title = Ukrainian Physicist Contributes to the Discovery of X-Rays
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| | work =
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| | publisher = [[Mayo Clinic|Mayo Foundation for Medical Education and Research]]
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| | date = 1997
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| | url = http://www.meduniv.lviv.ua/oldsite/puluj.html
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| | format =
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| | doi =
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| | accessdate =2008-04-06 }}</ref> He continued his investigations when appointed professor at the [[Czech Technical University in Prague|Prague Polytechnic]] and in 1886 he found that that sealed photographic plates became dark when exposed to the emanations from the tubes. Early in 1896, just a few weeks after [[Wilhelm Conrad Röntgen|Röntgen]] published his first X-ray photograph, Pulyui published high-quality x-ray images in journals in Paris and London.<ref name=mayo/> Although Pulyui had studied with Röntgen at the [[University of Strasbourg]] in the years 1873-75, his biographer Gaida (1997) asserts that his subsequent research was conducted independently.<ref name=mayo/>
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| The first medical X-ray made in the United States was obtained using a discharge tube of Pulyui's design. In January 1896, on reading of Röntgen's discovery, Frank Austin of [[Dartmouth College]] tested all of the discharge tubes in the physics laboratory and found that only the Pulyui tube produced X-rays. This was a result of Pulyui's inclusion of an oblique "target" of [[mica]], used for holding samples of [[fluorescent]] material, within the tube. On [[3 February]] [[1896]] Gilman Frost, professor of medicine at the college, and his brother Edwin Frost, professor of physics, exposed the wrist of Eddie McCarthy, whom Edwin had treated some weeks earlier for a fracture, to the x-rays and collected the resulting image of the broken bone on [[Photographic plate|gelatin photographic plates]] obtained from Howard Langill, a local photographer also interested in Röntgen's work.<ref>{{cite journal
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| | last = Spiegel
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| | first = Peter K
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| | authorlink =
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| | coauthors =
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| | title = The first clinical X-ray made in America—100 years
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| | journal = American Journal of Roentgenology
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| | volume = 164
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| | issue = 1
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| | pages = pp241–243
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| | publisher = American Roentgen Ray Society
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| | location = Leesburg, VA
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| | date = 1995
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| | url = http://www.ajronline.org/cgi/reprint/164/1/241.pdf
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| | doi =
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| | id = ISSN: 1546-3141
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| | accessdate = }}</ref>
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| ===Nikola Tesla===
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| In April 1887, [[Nikola Tesla]] began to investigate X-rays using high voltages and tubes of his own design, as well as [[Crookes tube]]s. From his technical publications, it is indicated that he invented and developed a special single-electrode X-ray tube <ref>Morton, William James, and Edwin W. Hammer, American Technical Book Co., 1896. Page 68.</ref> <ref>{{US patent|514170}}, ''Incandescent Electric Light'', and {{US patent|454622}}, ''System of Electric Lighting''.</ref>, which differed from other X-ray tubes in having no target electrode. The principle behind Tesla's device is called the [[Bremsstrahlung]] process, in which a high-energy secondary X-ray emission is produced when charged particles (such as electrons) pass through matter. By 1892, Tesla performed several such experiments, but he did not categorize the emissions as what were later called X-rays. Tesla generalized the phenomenon as [[radiant energy]] of "invisible" kinds.<ref>Cheney, Margaret, "[http://books.google.com/books?vid=ISBN0743215362 Tesla: Man Out of Time ]". Simon and Schuster, 2001. Page 77.</ref> <ref>Thomas Commerford Martin (ed.), "[http://books.google.com/books?vid=OCLC04049568 The Inventions, Researches and Writings of Nikola Tesla]". Page 252 "When it forms a drop, it will emit visible and invisible waves. [...]". (ed., this material originally appeared in an article by Nikola Tesla in The Electrical Engineer of 1894.)</ref> Tesla stated the facts of his methods concerning various experiments in his 1897 X-ray lecture <ref>Nikola Tesla, "The stream of Lenard and Roentgen and novel apparatus for their production", Apr. 6, 1897.</ref> before the [[New York Academy of Sciences]]. Also in this lecture, Tesla stated the method of construction and safe operation of X-ray equipment. His X-ray experimentation by vacuum high field emissions also led him to alert the scientific community to the biological hazards associated with X-ray exposure.<ref>Cheney, Margaret, Robert Uth, and Jim Glenn, "[http://books.google.com/books?vid=ISBN0760710058 Tesla, master of lightning]". Barnes & Noble Publishing, 1999. Page 76. ISBN 0760710058</ref>
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| ===Fernando Sanford===
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| X-rays were first generated and detected by [[Fernando Sanford]] (1854-1948), the foundation Professor of Physics at [[Stanford University]], in 1891. From 1886 to 1888 he had studied in the [[Hermann Helmholtz]] laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as previously studied by [[Heinrich Hertz]] and [[Philipp Lenard]]. His letter of [[January 6]], [[1893]] (describing his discovery as "electric photography") to The [[Physical Review]] was duly published and an article entitled ''Without Lens or Light, Photographs Taken With Plate and Object in Darkness'' appeared in the [[San Francisco Examiner]].<ref>{{cite journal |last= Wyman|first=Thomas |year=2005 |month= Spring |title=Fernando Sanford and the Discovery of X-rays |journal= "Imprint", from the Associates of the Stanford University Libraries |volume= |issue= |pages=pp. 5–15 |}}</ref>
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| ===Heinrich Hertz===
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| In 1892, [[Heinrich Hertz]] began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as [[aluminium]]). [[Philipp Lenard]], a student of Heinrich Hertz, further researched this effect. He developed a version of the [[Crookes tube]] and studied the penetration by X-rays of various materials. Philipp Lenard, though, did not realize that he was producing X-rays. [[Hermann von Helmholtz]] formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his discovery and announcement. It was formed on the basis of the electromagnetic theory of light (''Wiedmann's Annalen'', Vol. XLVIII). However, he did not work with actual X-rays.
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| ===Wilhelm Röntgen===
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| On [[November 8]] [[1895]], [[Wilhelm Conrad Röntgen]], a [[Germany|German]] physics professor, began observing and further documenting X-rays while experimenting with Lenard and Crookes tubes. Röntgen, on [[December 28]], [[1895]], wrote a preliminary report "''On a new kind of ray: A preliminary communication''". He submitted it to the [[Würzburg]]'s Physical-Medical Society journal.<ref>{{Citation
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| | last = Stanton
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| | first = Arthur
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| | author-link =
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| | last2 =
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| | first2 =
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| | author2-link =
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| | title = Wilhelm Conrad Röntgen On a New Kind of Rays: translation of a paper read before the Würzburg Physical and Medical Society, 1895
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| | journal = [[Nature (journal)|Nature]]
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| | volume =53
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| | issue =
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| | pages = pp 274-6
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| | date = [[1896-01-23]]
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| | year = 1896
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| | url = http://www.nature.com/nature/journal/v53/n1369/pdf/053274b0.pdf
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| | doi =10.1038/053274b0
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| | id = }}</ref> This was the first formal and public recognition of the categorization of X-rays. Röntgen referred to the radiation as "X", to indicate that it was an unknown type of radiation. The name stuck, although (over Röntgen's great objections), many of his colleagues suggested calling them '''Röntgen rays'''. They are still referred to as such in many languages, including German. Röntgen received the first [[Nobel Prize in Physics]] for his discovery.
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| There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a likely reconstruction by his biographers.<ref>{{cite web
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| |first=Peter
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| |last=Peters
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| |date=1995
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| |title=W. C. Roentgen and the discovery of x-rays
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| |work=Ch.1 Textbook of Radiology
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| |publisher=Medcyclopedia.com, GE Healthcare
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| |url=http://www.medcyclopaedia.com/library/radiology/chapter01.aspx
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| |accessdate=2008-05-05}}</ref> Röntgen was investigating cathode rays with a [[fluorescent]] screen painted with barium platinocyanide and a [[Crookes tube]] which he had wrapped in black cardboard so the visible light from the tube wouldn't interfere. He noticed a faint green glow from the screen, about 1 meter away. The invisible rays coming from the tube to make the screen glow were passing through the cardboard. He found they could also pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper translated "On a New Kind of Radiation" and gave a demonstration in 1896.
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| Röntgen discovered its medical use when he saw a picture of his wife's hand on a photographic plate formed due to X-rays. His wife's hand's photograph was the first ever photograph of a human body part using X-rays.
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| ===Thomas Edison===
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| [[Image:Roentgen-Roehre.png|thumb|Diagram of a water cooled X-ray tube. (simplified/outdated)]]In 1895, [[Thomas Edison]] investigated materials' ability to fluoresce when exposed to X-rays, and found that [[calcium tungstate]] was the most effective substance. Around March 1896, the fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903 after the death of [[Clarence Madison Dally]], one of his glassblowers. Dally had a habit of testing X-ray tubes on his hands, and acquired a [[cancer]] in them so tenacious that both arms were [[amputation|amputated]] in a futile attempt to save his life. "At the 1901 Pan-American Exposition in Buffalo, New York, an assassin shot President [[William McKinley]] twice at close range with a .32 caliber revolver." The first bullet was removed but the second remained lodged somewhere in his stomach. McKinley survived for some time and requested that Thomas Edison "rush an X-ray machine to Buffalo to find the stray bullet. It arrived ''but wasn't used'' . . . McKinley died of septic shock due to bacterial infection."<ref>National Library of Medicine. "Could X-rays Have Saved President William McKinley?" ''Visible Proofs: Forensic Views of the Body''. http://www.nlm.nih.gov/visibleproofs/galleries/cases/mckinley.html</ref>
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| ===The 20th century and beyond===
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| Before the 20th century and for a short while after, X-rays were generated in cold cathode tubes. These tubes had to contain a small quantity of gas (invariably air) as a current will not flow in such a tube if they are fully evacuated. One of the problems with early X-ray tubes is that the generated X-rays caused the glass to absorb the gas and consequently the efficiency quickly falls off. Larger and more frequently used tubes were provided with a means of restoring the air. This often took the form of small side tube which contained a small piece of mica – a substance that traps comparatively large quantities of air within its structure. A small electrical heater heats the mica and causes it to release a small amount of air restoring the tube's efficiency. However the mica itself has a limited life and the restore process was consequently difficult to control.
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| In 1904, [[Sir John Ambrose Fleming]] invented the [[thermionic valve|thermionic diode valve]] (tube). This used a heated cathode which permitted current to flow in a vacuum. The principle was quickly applied to X-ray tubes, and hard vacuum heated cathode X-ray tubes completely solved the problem of efficiency reduction.
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| Two years later, physicist [[Charles Glover Barkla|Charles Barkla]] discovered that X-rays could be scattered by gases, and that each element had a characteristic X-ray. He won the 1917 [[Nobel Prize in Physics]] for this discovery. [[Max von Laue]], Paul Knipping and Walter Friedrich observed for the first time the [[diffraction]] of X-rays by crystals in 1912. This discovery, along with the early works of [[Paul Peter Ewald]], [[William Henry Bragg]] and [[William Lawrence Bragg]] gave birth to the field of X-ray [[crystallography]]. The [[X-ray tube#Coolidge_tube|Coolidge tube]] was invented the following year by [[William D. Coolidge]] which permitted continuous production of X-rays; this type of tube is still in use today.
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| [[Image:Moon in x-rays.gif|thumb|right|222px|[[ROSAT]] image of X-ray [[fluorescence]] of, and [[occultation]] of the [[X-ray background]] by, the [[Moon]].]]
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| The use of X-rays for medical purposes (to develop into the field of [[radiation therapy]]) was pioneered by Major [[John Hall-Edwards]] in [[Birmingham]], [[England]]. In 1908, he had to have his left arm amputated owing to the spread of [[X-ray dermatitis]][http://www.birmingham.gov.uk/xray].
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| The [[X-ray microscope]] was invented in the 1950s. The [[Chandra X-ray Observatory]] launched on [[July 23]], [[1999]], has been allowing the exploration of the very violent processes in the universe which produce X-rays. Unlike visible light, which is a relatively stable view of the universe, the X-ray universe is unstable, it features stars being torn apart by [[black hole]]s, galactic collisions, and novas, [[neutron star]]s that build up layers of plasma that then explode into space.
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| An [[X-ray laser]] device was proposed as part of the [[Ronald Reagan|Reagan]] administration's [[Strategic Defense Initiative]] in the 1980s, but the first and only test of the device (a sort of laser "blaster", or [[death ray]], powered by a thermonuclear explosion) gave inconclusive results. For technical and political reasons, the overall project (including the X-ray laser) was de-funded (though was later revived by the second [[George W. Bush|Bush]] administration as [[National Missile Defense]] using different technologies).
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| ==See also==
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| <div style="-moz-column-count:4; column-count:4;">
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| * [[Neutron radiation]]
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| * [[High energy X-rays]]
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| * [[X-ray crystallography]]
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| * [[X-ray astronomy]]
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| * [[X-ray machine]]
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| * [[X-ray microscope]]
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| * [[X-ray optics]]
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| * [[Backscatter X-ray]]
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| * [[Small angle X-ray scattering (SAXS)]]
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| * [[Geiger counter]]
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| * [[N ray|N-ray]]
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| * [[Radiography]]
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| * [[X-ray vision]]
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| </div>
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| ==References==
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| {{reflist|2}}
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| *[http://imagers.gsfc.nasa.gov/ems/xrays.html NASA] Goddard Space Flight centre introduction to X-rays.
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| ==External links==
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| *[http://www.radiologyforums.com X-Ray Discussion Group]
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| *[http://www.onlinetelemedicine.com/html/product/sam_images/X-Ray.jpg An Example of a Radiograph]
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| *[http://www.iuk.edu/~koalhe/img/Equipment/xray.jpg A Photograph of an X-ray Machine]
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| *[http://www.ionactive.co.uk/multi-media_video.html?m=4 An X-ray tube demonstration (Animation)]
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| *[http://deutsche.nature.com/physics/7.pdf 1896 Article: "On a New Kind of Rays"]
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| *[http://www.bigs.de/en/shop/htm/roentgen01.html X-ray Tube in Action (Animation)]
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| *[http://members.chello.nl/~h.dijkstra19/page5.html Cathode Ray Tube Collection]
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| *[http://www.carltonbooks.co.uk/display.asp?isb=9781847960009 X-Ray Art by Nick Veasey]
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| [[Category:Radiography]]
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| [[Category:X-rays]]
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| [[Category:Electromagnetic spectrum]]
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