x-ray tube

n. A vacuum tube containing electrodes that accelerate electrons and direct them to a metal anode, where their impacts produce x-rays.

X-ray tube

n (General Physics) an evacuated tube containing a metal target onto which is directed a beam of electrons at high energy for the generation of X-rays

x-ray tube

n. an electronic tube for producing x-rays, essentially a cathode-ray tube in which a metal target is bombarded with high-energy electrons. [1905–10]

Thesaurus

Noun

X-ray tube - a vacuum tube containing a metal target onto which a beam of electrons is directed at high energy for the generation of X rayselectron tube, thermionic tube, thermionic vacuum tube, thermionic valve, vacuum tube, tube - electronic device consisting of a system of electrodes arranged in an evacuated glass or metal envelopeX-ray machine - an apparatus that provides a source of X rays

X-Ray Tube

X-ray tube

An electronic device used for the generation of x-rays. X-rays are produced in the x-ray tube by accelerating electrons to a high velocity by an electrostatic field and then suddenly stopping them by collision with a solid body, the so-called target, interposed in their path. The x-rays radiate in all directions from the spot on the target where the collisions take place. The x-rays are due to the mutual interaction of the fast-moving electrons with the electrons and positively charged nuclei which constitute the atoms of the target. Depending upon the method used in generating the electrons, x-ray tubes may all be classified in two general groups, gas tubes and high-vacuum tubes. See X-rays

In gas tubes electrons are freed from a cold cathode by positive ion bombardment. For the existence of the positive ions a certain gas pressure is required without which the tube will allow no current to pass. Metals, such as platinum and tungsten, are placed in the path of the electron beam to serve as the target. Concave metal cathodes are used to focus the electrons on a small area of the metal target and increase the sharpness of the resulting shadows on the fluorescent screen or the photographic film. Many designs of gas tubes have been built for useful application, particularly in the medical field.

The operational difficulties and erratic behavior of gas x-ray tubes are inherently associated with the gas itself and the positive ion bombardment that takes place during operation. The high-vacuum x-ray tube eliminates these difficulties by using other means of emitting electrons from the cathode. The original type of high-vacuum x-ray tube had a hot tungsten-filament cathode and a solid tungsten target. This tube permitted stable and reproducible operation with relatively high voltages and large masses of metals. A modern commercial hot-cathode high-vacuum x-ray tube is built with a liquid-cooled, copper-backed tungsten target.

X-Ray Tube

an electron tube used to generate X-radiation. The X rays are produced when the electrons emitted by the cathode are retarded or stopped by the anode, or anticathode. When electrons accelerated by the strong electric field in the space between the anode and the cathode strike the anode, their energy is partially converted into the energy of X-radiation. The radiation of an X-ray tube consists of bremsstrahlung and the characteristic radiation of the substance composing the anode.

X-ray tubes can be classified in various ways. With respect to the method used to produce the electron stream, there are distinguished hot-cathode tubes, which are based on thermionic emission; point-cathode tubes, which make use of field emission; tubes whose cathodes are bombarded with positive ions; and tubes containing a radioactive (β) source of electrons. Depending on the method of evacuation, X-ray tubes are classed as sealed-off or continuously evacuated. With respect to radiation time, X-ray tubes can be divided into continuous-action and pulse types. X-ray tubes can be classified according to the type of cooling used for the anode: water cooling, oil cooling, air cooling, or radiant cooling. Large-focus, small-focus, and microfocus X-ray tubes are distinguished according to the size of the focal spot, that is, the area of the anode that is bombarded by the electron beam. With respect to shape, X-ray tubes are classed as toroidal, circular, or linear. X-ray tubes with electrostatic, magnetic, and electromagnetic focusing are distinguished on the basis of the method used to focus the electrons on the anode.

Figure 1. Schematic of an X-ray tube for X-ray diffraction analysis: (1) metallic anode block (usually grounded); (2) beryllium window for exit of X-radiation; (3) hot cathode; (4) glass envelope insulating the anode part of the tube from the cathode part; (5) cathode leads, to which the filament voltage and high (with respect to the anode) voltage are supplied; (6) electrostatic electron-focusing system; (7) anode (anticathode); (8) inlet and outlet pipes for the flowing water that cools the anode block

X-ray tubes are used in X-ray diffraction analysis, X-ray spectral analysis, flaw detection, roentgen diagnosis, roentgenotherapy, X-ray microscopy, and microradiography. The type of X-ray tube used most widely in all fields is the sealed-off hot-cathode tube with a water-cooled anode and an electrostatic electron-focusing system (Figure 1). The hot cathode of an X-ray tube is usually a spiral or straight filament of tungsten wire that is heated to a high temperature by an electric current. The target surface of the anode is a mirrorlike metallic surface positioned perpendicular or at an angle to the electron stream. In order to obtain a continuous spectrum of high-energy and high-intensity X-radiation, anodes made of Au and W are used. X-ray tubes with anodes made of Ti, Cr, Fe, Co, Ni, Cu, Mo, and Ag are used in X-ray diffraction analysis.

The maximum permissible accelerating voltage of X-ray tubes varies from 1 to 500 kilovolts. The electron current ranges from 0.01 milliampere to 1 ampere. The specific power dissipation of the anode varies from 10 to 10⁴ watts /mm², and the total power consumption varies from 0.002 watt to 60 kilowatts. The focal spot can have dimensions ranging from 1 micrometer to 10 mm. The efficiency of X-ray tubes is between 0.1 and 3 percent.

REFERENCES

Taylor, A. Rentgenovskaia metallografiia. Moscow, 1965. (Translated from English.)
Umanskii, Ia. S. Rentgenografiia metallov i poluprovodnikov. Moscow, 1969.
Shmelev, V. K. Rentgenovskie apparaty. Moscow, 1973.

V.G. LIUTTSAU

x-ray tube

[′eks ‚rā ‚tüb] (electronics) A vacuum tube designed to produce x-rays by accelerating electrons to a high velocity by means of an electrostatic field, then suddenly stopping them by collision with a target.

x-ray tube

tube

[to̳b] a hollow cylindrical organ or instrument. adj., adj tu´bal.auditory tube eustachian tube.Blakemore-Sengstaken tube Sengstaken-Blakemore tube.chest tube see chest tube.Dobhoff tube a small-lumen tube" >feeding tube that can be advanced into the duodenum.drainage tube a tube used in surgery to facilitate escape of fluids.Drieling tube a double-lumen tube having a metal weight at one end to carry it past the stomach into the duodenum. At the other end are two tails, one used to collect gastric specimens and the other to collect specimens from the duodenum. The tube is used in the secretin test for pancreatic exocrine function.Durham's tube a jointed tube" >tracheostomy tube.endobronchial tube a single- or double-lumen tube inserted into the bronchus of one lung and sealed with an inflatable cuff, permitting ventilation of the intubated lung and complete deflation of the other lung; used in anesthesia and thoracic surgery.endotracheal tube see endotracheal tube.esophageal tube stomach tube.eustachian tube see eustachian tube.Ewald tube a large lumen tube used in gastric lavage.fallopian tube see fallopian tube.feeding tube one for introducing high-caloric fluids into the stomach; see also tube feeding.tube feeding a means of providing nutrition via a tube" >feeding tube inserted into the gastrointestinal tract; it may be done to maintain nutritional status over a period of time or as a treatment for malnutrition. It can be used as the only source of nutrition or as a supplement to oral feeding or parenteral nutrition.
Patients who may require tube feeding include those unable to take in an adequate supply of nutrients by mouth because of the side effects of chemotherapy or radiation therapy, those with depression or some other psychiatric disorder, and those suffering from severe hypermetabolic states such as burns or sepsis, or malabsorption syndromes. Other conditions that may require tube feeding include surgery or trauma to the oropharynx, esophageal fistula, and impaired swallowing such as that which occurs following stroke or that related to neuromuscular paralysis.
There are commercially prepared formulas for tube feeding. Some contain all six necessary nutrients (carbohydrates, fats, proteins, vitamins, minerals, and trace elements) and need no supplement as long as they are given in sufficient volume to meet nutritional and caloric needs. Other types of tube feeding formulas are incomplete and therefore will require some supplementation. Choice of formula is based on the patient's particular needs, presence of organ failure or metabolic aberration, lactose tolerance, gastrointestinal function, and how and where the feeding is to be given, that is, via nasogastric, gastrostomy, or enterostomy tube.Patient Care. In addition to frequent and periodic checking for tube placement and monitoring of gastric residuals to prevent aspiration, other maintenance activities include monitoring effectiveness of the feeding and assessing the patient's tolerance to the tube and the feeding. Special mouth care is essential to maintain a healthy oral mucosa. A summary of the complications related to tube feeding, their causes and contributing factors, and interventions to treat or prevent each complication is presented in the accompanying table.fermentation tube a U-shaped tube with one end closed, for determining gas production by bacteria.Levin tube a gastroduodenal catheter of sufficiently small caliber to permit transnasal passage; see illustration.

Two types of nasogastric tubes. From Ignatavicius et al., 1995.Linton tube a triple-lumen tube with a single balloon used to control hemorrhage from esophageal varices. Once it is positioned under fluoroscopic control and inflated, the balloon exerts pressure against the submucosal venous network at the cardioesophageal junction, thus restricting the flow of blood to the esophageal varices.Miller-Abbott tube see miller-abbott tube.Minnesota tube a tube with four lumens, used in treatment of esophageal varices; having a lumen for aspiration of esophageal secretions is its major difference from the sengstaken-blakemore tube.nasogastric tube see nasogastric tube.nasotracheal tube an endotracheal tube that passes through the nose.neural tube the epithelial tube produced by folding of the neural plate in the early embryo.orotracheal tube an endotracheal tube that passes through the mouth.otopharyngeal tube eustachian tube.Rehfuss tube a single-lumen oral tube used to obtain specimens of biliary secretions for diagnostic study; it is weighted on one end so that it can be passed through the mouth and positioned at the point where the bile duct empties into the duodenum. See also biliary drainage test.Salem sump tube a double-lumen nasogastric tube used for suction and irrigation of the stomach. One lumen is attached to suction for the drainage of gastric contents and the second lumen is an air vent. See illustration.Sengstaken-Blakemore tube see sengstaken-blakemore tube.stomach tube see stomach tube.T-tube one shaped like the letter T and inserted into the biliary tract to allow for drainage of bile; it is generally left in place for 10 days or more in order to develop a tract through which bile can drain after the tube is removed. A T-tube cholangiogram is usually performed prior to removal of the tube in order to determine that the common duct is patent and free of stones. If stones are found they can be removed through the tube tract by instruments inserted under x-ray guidance.test tube a tube of thin glass, closed at one end; used in chemical tests and other laboratory procedures.thoracostomy tube a tube inserted through an opening in the chest wall, for application of suction to the pleural cavity; used to drain fluid or blood or to reexpand the lung in pneumothorax. See also chest tube.tracheal tube endotracheal tube.tracheostomy tube a curved endotracheal tube that is inserted into the trachea through a tracheostomy; see discussion under tracheostomy.tympanostomy tube ventilation tube.uterine tube fallopian tube.ventilation tube a tube inserted after myringotomy in chronic cases of middle ear effusion, such as in secretory or mucoid otitis media; it provides ventilation and drainage for the middle ear during healing, and is eventually extruded. Called also tympanostomy tube.

Tympanostomy (ventilation) tube. Polyethylene tubes are inserted surgically into the eardrum to relieve middle ear pressure and promote drainage of chronic or recurrent middle ear infections. Tubes extrude spontaneously in 6 months to 1 year. From Jarvis, 1996.Wangensteen tube a small nasogastric tube connected with a special suction apparatus to maintain gastric and duodenal decompression.Whelan-Moss T-tube a t-tube whose crossbar tube is larger in diameter than the tube" >drainage tube.x-ray tube a glass vacuum bulb containing two electrodes; electrons are obtained either from gas in the tube or from a heated cathode. When suitable potential is applied, electrons travel at high velocity from cathode to anode, where they are suddenly arrested, giving rise to x-rays.

x-ray

(eks'rā), 1. The ionizing electromagnetic radiation emitted from a highly evacuated tube, resulting from the excitation of the inner orbital electrons by the bombardment of the target anode with a stream of electrons from a heated cathode. Synonym(s): roentgen ray Compare: glass rays, indirect rays. 2. Ionizing electromagnetic radiation produced by the excitation of the inner orbital electrons of an atom by other processes, such as nuclear delay and its sequelae. 3. Synonym(s): radiograph

x-ray tube

(rā tūb) Vacuum tube containing electrodes that are directed onto a metal target to produce an x-ray.
See also: x-ray

x-ray tube

x-ray tube

X-ray tube

x-ray tube

X-Ray Tube

X-ray tube

X-Ray Tube

REFERENCES

x-ray tube

x-ray tube

tube

x-ray

x-ray tube

X-ray tube

Words related to X-ray tube

noun a vacuum tube containing a metal target onto which a beam of electrons is directed at high energy for the generation of X rays

Related Words