EP1831911A2 - Procede de production de materiau de feuille cible pour tubes a rayons x - Google Patents

Procede de production de materiau de feuille cible pour tubes a rayons x

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Publication number
EP1831911A2
EP1831911A2 EP05854645A EP05854645A EP1831911A2 EP 1831911 A2 EP1831911 A2 EP 1831911A2 EP 05854645 A EP05854645 A EP 05854645A EP 05854645 A EP05854645 A EP 05854645A EP 1831911 A2 EP1831911 A2 EP 1831911A2
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EP
European Patent Office
Prior art keywords
ray
rays
target
housing
tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05854645A
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German (de)
English (en)
Inventor
Bruce Briant Parsons
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nanodynamics 88 Inc
Original Assignee
Nanodynamics 88 Inc
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Filing date
Publication date
Application filed by Nanodynamics 88 Inc filed Critical Nanodynamics 88 Inc
Publication of EP1831911A2 publication Critical patent/EP1831911A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/112—Non-rotating anodes
    • H01J35/116—Transmissive anodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/08—Targets (anodes) and X-ray converters
    • H01J2235/081—Target material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/16—Vessels; Containers; Shields associated therewith
    • H01J35/18—Windows
    • H01J35/186—Windows used as targets or X-ray converters

Definitions

  • the invention relates to an improved way to make metallic foil targets for x-ray tubes and various applications to use transmission x-ray tubes to detect elements of interest by x-ray fluoroscopy and for x-ray imaging. It further relates to the use of a single capillary or a bundle of capillaries coupled to a transmission x-ray tube and applications thereof.
  • transmission x-ray tubes are further limited because the melting point of the substrate onto which the target is deposited is very low and the thickness of the target materials is limited to tens of microns thickness. Hence all of the electrical heat generated by the electron beam impinging on the target must be removed through the end-window.
  • Beryllium, copper and aluminum are the most commonly used end-window materials and have melting points of 1287°C, 1084 0 C, and 66O 0 C respectively.
  • Reflective tube as well would benefit from a wider use of potential target materials with the same disadvantages those materials pose for transmission tubes.
  • Reflection tubes are used almost universally in fluoroscopy applications where the spot size of the focused electron beam impinging the target is less than about 200 microns.
  • X-radiation from such tubes does not have a very high concentration of k-alpha radiation needed for high speed and accurate fluoroscopic measurement of various elements.
  • such an application is the European Union's "Directive on the restriction of the use of certain hazardous substances" in electrical and electronic equipment (RoHS Directive).
  • What is needed is a way to make x-ray targets of a wide variety of materials whose melting points are at least higher than beryllium, which can produce a high concentration of k-alpha radiation, whose reactivity in air and moisture is not high, whose heat conductivity is adjusted to match the end-window material to provide maximum x-ray tube current, and whose rate of vaporization is low to provide long x- ray tube life.
  • What is also needed is a way to improve fluoroscopic measurements made with reflection tubes. Special efforts are needed to solve the problem of rapid and accurate fluoroscopic detection of cadmium.
  • a way to produce low energy x-rays for fluoroscopic measurements from transmission tubes is needed.
  • An x-ray tube for use with capillaries is needed whereby the capillary or bundle of capillaries can be placed very close to the point on the target where x-rays are generated.
  • Figure 1 is a representation of a typical transmission type x-ray tube.
  • Figure 2 is a representation of a typical reflection type x-ray rube.
  • Figure 3 depicts two different possible x-ray target configurations for a reflective x-ray tube and two for a transmission tube
  • Figure 4 is a graphical representation the output spectrum from a transmission tube with a target of 95% cerium 5% aluminum.
  • Figure 5 is a graphical representation of the output spectrum from a transmission tube with a target made by layering molybdenum onto a zinc telluride target foil previously sputtered onto a beryllium end-window.
  • Figure 6 is a conceptual drawing depicting a transmission x-ray tube coupled to a single capillary.
  • Figure 7 represents two configurations for using a bundle of glass capillaries to guide and focus the output from a point source of x-rays.
  • Figure 8 is a graphical representation of the output spectrum from a transmission tube with a target of molybdenum 25 microns thick.
  • Figure 9 is a graphical representation of the number of counts of x-ray photons from a transmission tube with a Rhodium target.
  • Figure 10 is a graphical representation of the flux generated by comparable reflection and transmission x-ray tubes.
  • Figure 11 is a schematic drawing of an in-line application for a transmission x-ray tube of this invention.
  • Open transmission tubes are typically used for imaging of electronic circuits as well as other high-resolution applications and may alternatively be used as the x-ray source. Closed tubes are sealed with a vacuum whereas open or "pumped down" tubes have a vacuum pump continuously attached drawing a vacuum as the tube is used usually to allow for frequent replacement of tube parts which tend to fail in operation.
  • transmission tubes include both open and closed transmission type tubes except as otherwise stated.
  • the transmission tube of Figure 1 is comprised of an evacuated housing 6, and end-window anode 1, disposed at the end of the housing exposed to atmosphere.
  • An x-ray target foil 2 is deposited on the end-window anode.
  • An electrically heated cathode emits electrons, which are accelerated along the electron beam path 4, and strike the anode target producing x-rays.
  • a power supply is connected between the cathode and anode to the accelerating force for the electron beam.
  • X-rays produced exit the x- ray tube through the end-window.
  • An optional focusing cup 5 typically negatively biased or neutral, focuses the electron beam onto a spot on the target. The largest dimension of the spot is referred to as the focal spot size or spot size.
  • the output x-rays contain both bremsstrahlung (or braking radiation) and characteristic line radiation unique to the target material. If the thickness of the target is about between about 1 and 70 microns and the applied tube voltage in kVp is more than two times the characteristic K-alpha line of the target material, output x-rays from a transmission tube have a very high concentration of K-alpha x-rays compared to reflection tubes.
  • Preferred target thickness for thin target foils from such a tube are 1-10 microns and for a thick target 20-50 microns, depending on application.
  • Chamber 16 of Figure 1 may be baked at a temperature between 3500 and 5000 C for about 9 to 12 hours to de-gas the parts making the x-ray tube, and then is sealed.
  • Figure 2 is provided for reference and schematically represents a reflection tube comprised of an evacuated housing in which the cathode (9) and anode (7) are located.
  • the anode 7 is comprised of an x-ray target deposited onto a substrate which substrate removes heat generated when x-rays impinge the anode. Electrons are emitted from the cathode 9 when the cathode is heated.
  • a power supply is connected between the cathode and the anode to provide an electric field which accelerates the electrons from the cathode along an electron beam path 10 and strikes the anode in a spot generating a beam of x-rays 8 which then exit the tube through a side window 11.
  • the reflection tube harvests produced x-rays from the same side of the target that the electron beam impinges.
  • Figure 3 represents x-ray target configurations for transmission x-ray as well as for reflective tubes.
  • Figures 3A and 3B are for reflection tubes and Figures 3C and 3D for transmission tubes.
  • Figure 3A depicts an x-ray anode target for a reflective tube comprised of a single layer foil of x-ray generating material 15 fixed to an anode substrate 14 which is used to remove heat generated when electrons impinge on the target.
  • Figure 3B depicts the same x-ray target with a second foil of target material 12 deposited on top of the single target foil 15 in Figure 3 A.
  • Figure 3C depicts an x-ray anode target for a transmission x-ray tube comprised of a single layer of x-ray material 15 deposited onto an anode substrate 14 typically made of a low atomic number metal which is virtually transparent to x-rays.
  • Figure 3D depicts the same x-ray target with a second foil of material deposited on top of the single target foil 15.
  • two different elements are mixed as alloys, eutectic alloys, intermetallic compounds, or simple compounds when one of the elements needed to produce useful x-rays has a low melting point.
  • x-ray generating elements whose melting point is below that of beryllium include but are not limited to manganese, copper, tellurium, zinc, sliver, tin, barium, lanthanum, cerium, antimony, holmium, dysprosium, bismuth, praseodymium, neodymium, samarium, europium, antimony, barium, bismuth, ytterbium, gold and uranium.
  • target materials have melting points higher than beryllium but not considerably higher and with lower heat conductivity than beryllium, causing the target foil to reach temperatures greater than 300 degrees higher than the end-window substrate.
  • Those include but are not limited to yttrium, palladium, gadolinium, terbium, erbium, and thulium.
  • tin tin of 25.270keV
  • 70% tin with a melting point of 322 0 C can be mixed with 30% nickel to provide a metal mixture with a melting point of 1230°C.
  • Nickel has a k-alpha of 7.477keV useful to fluoresce elements such as cobalt, iron, manganese, and chromium.
  • the k-alpha radiation of nickel might not be needed and the nickel used simply to increase the melting temperature of the alloy whose main function is to produce tin characteristic line x-radiation.
  • the resultant metal mixture has a melting point of 730 0 C, considerably higher than either of the components.
  • the characteristic K-lines of sodium are very low energy and not an important factor, but the K-lines or L-lines of bismuth may be used for either fluorescent measurements or for x-ray imaging.
  • Lanthanum has a k-alpha of 33.440 keV and Iodine a K-absorption of 33.164 keV making Lanthanum an ideal material to produce images with iodine being used to increase the contrast in a number of applications including angiography and mammography among others.
  • Sn has a k-alpha of 25.270 keV, well below the k-absorption edge of iodine.
  • Lanthanum melts at 918°C and tin at 232 °C.
  • An intermetallic compound comprising 60% Lanthanum and 40% Tin melts at 1575 0 C thus reducing the likelihood of target melting compared to either metal alone.
  • elements highly reactivity in air or moisture mediated by mixing these elements with another metal or non-metal including but not limited to aluminum, iron, sulfur or nickel and then depositing the resultant alloy, eutectic alloy, compound or intermetallic compound onto an anode substrate.
  • another metal or non-metal including but not limited to aluminum, iron, sulfur or nickel
  • Various deposition techniques may be used, but typically the mixture would be formed into a sputtering disc for sputtering onto the substrate.
  • Examples of reactive x-ray generating metals for potential use in transmission x-ray tubes include but are not limited to lithium, sodium, potassium, cesium, francium, lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, holmium, erbium, thulium, barium, strontium, rubidium, cesium, scandium, yttrium, zirconium, and niobium.
  • Figure 4 shows an x-ray spectrum taken from a transmission tube with a ⁇ 5 micron thick target made of a mixture of 5% aluminum and 95% cerium at an applied tube voltage of 8OkVp and tube current of 5 ⁇ A.
  • the vertical axis is number of counts and the horizontal axis is the photon energy of the x-rays produced.
  • the K-alpha characteristic line is shown as Item 21 and the K-beta by Item 22.
  • the energy of K- alpha line of aluminum 1.487keV and readily absorbed by air the beryllium end window and air. Pure cerium is too reactive to be used in a production environment and causes corruption of sputtering and vacuum instrumentation.
  • the percent of aluminum is not limited to 5%.
  • Cerium melts at 795 0 C. However, combining 18.6% sulfur by weight with cerium results in a target material with 81.4% cerium but with a melting point of 2450 0 C.
  • the k-alpha of Cerium is 34.717 and is particularly well positioned to excite fluorescence in iodine, tellurium, antimony, tin, indium and cadmium for both x-ray imaging and x-ray fluoroscopy applications among others.
  • Sulfur has a k-alpha of 2.308 keV and does not interfere with measurements of higher Z elements. 1
  • Mixing sulfur with cerium mediates its high reactivity and makes it useful as an x-ray target material.
  • Neodymium quickly tarnishes in air, forming an oxide that spalls off and exposes the metal to further oxidation. It requires costly care to use it in a manufacturing environment. Yet when mixed with tellurium with 46.9% tellurium and 53.1% neodymium by weight, the resultant metallic mixture NdTe is considerably more stable. In addition the melting points of neodymium and tellurium are 1024 0 C and 450 0 C respectively while the chemical compound NdTe has a melting point of 2025 0 C. Neodymium is particularly well positioned to measure barium in fluoroscopic applications and tellurium to measure cadmium.
  • Example 9 An alternative to using zinc telluride of Example 9 below would be to use molybdenum telluride (Mo 3 Te 4 ) which has a melting point of 1300 ⁇ 70 0 C considerably higher than the melting point of tellurium, 449.57°C.
  • Mo 3 Te 4 molybdenum telluride
  • Alternative materials to nickel include but are not limited to copper and iron. Either of those metals of a concentration by weight of between about 5 and 25% will increase the thermal conductivity of molybdenum telluride.
  • Figure 5 is a graphical representation of the spectrum of a transmission tube made with a 5 micron thick zinc telluride target foil deposited on a beryllium end- window 1 mm thick followed by depositing 1 micron of molybdenum thereon.
  • the spectrum was taken with an applied tube voltage of 8OkVp and tube current of 5 microampere and clearly shows K-alpha peaks of zinc 31, molybdenum 32 and tellurium 32. These three K-alpha peaks are particularly well positioned to measure cadmium, bromine, lead, mercury and chromium of the European RoHS directive on banned substances.
  • Zinc telluride has very poor heat conductivity and severely limits the power dissipated in the anode. Simultaneous sputtering of zinc telluride and molybdenum in about equal weights to the layered target significantly improves heat dissipation and hence useful tube power.
  • Rhodium with a melting point of 1964 0 C is often the target material of choice for x-ray fluoroscopy using reflection x-ray tubes.
  • its coefficient of heat transfer is 150 AVm- IK-I compared to 170 for the beryllium used as the anode substrate. Heat is rapidly transferred to the beryllium raising the temperature of the beryllium until it melts while the temperature of the rhodium target is still well below its melting point.
  • Simultaneous sputtering of 5 to 20% by weight of a material such as titanium with a coefficient of heat transfer of only 22 AVm- IK-I slows the transfer of heat to the substrate, increasing the temperature in the rhodium layer and subsequently the useful tube power.
  • a focused transmission tube is used to produce x-rays with a focal spot size of about 0.1 microns to 3 mm for use in fluoroscopic measurement of the presence and concentration of elements in an object to be measured.
  • Preferred spot sizes are usually between 3 microns and 200 microns.
  • the output of an x-ray tube is collimated into a small beam of x-rays impinging the object to be analyzed, utilizing only a small portion of the beam and constraining x-ray fluorescence to the radiated portion of the object. If the location of radiating x-ray beam is known and varied, a map showing presence and concentration of one or more elements of interest can be produced well known by those skilled in the art.
  • Using a transmission tube has many advantages over the use of reflection tubes. Significantly higher percentages K-alpha x-radiation of the precise energy required to excite a specific element of interest in the object can be produced at higher tube voltages than can be produced by reflection tubes.
  • the collimator can be located very close to the x- ray spot, typically within 1 or 2 millimeters compared to about 20 to 30 millimeters for reflection tubes, significantly reducing the 1/r 2 losses of x-ray beam intensity of the reflection tube.
  • Figure 9 is a representation of the output spectrum of such a transmission tube useful in x-ray fluoroscopy with a rhodium target foil 6 microns thick deposited on a 250 micron thick beryllium end-window and focused to a spot size of 40 microns with a tube voltage of 9OkVp.
  • Optimal target thickness may vary from 1 micron to as much a 70 with a preferred thickness of 2 to 30 microns and tube voltage may be varied from about 20 kVp to 300 kVp with a preferred voltage of about 40 to 150 kVp to fit specific application needs.
  • the vertical axis 41 represents the number of spectrometer counts and the horizontal axis 42 the energy of the resultant x-rays.
  • Reference numeral 43 is the K-alpha characteristic line of 20.214 keV for Rhodium. Although rhodium is the target material of choice for fluoroscopy, any number of target materials may be used to replace rhodium.
  • Example 11 the L-line radiation of Rhodium from the transmission tube has been absorbed by the thick 250 micron beryllium window and is not available for fluoroscopic measurements of elements with a low atomic number such as sulfur, phosphorous, silicon, aluminum, magnesium, sodium and others.
  • Use of a thinner beryllium end-window adds cost and increased risk of air leaking into the evacuated housing aside from reducing the heat that can be dissipated from the target.
  • a thin foil of x-ray producing material, in this case rhodium of about 0.1 microns to about 10 microns is deposited on the opposite side of the end-window where the electron beam impinges. The preferred thickness is 0.5 to 3 microns.
  • Bremsstrahlung radiation or characteristic line x-radiation generated by the x-ray target passes through the end-window, is absorbed by the thin foil on the outside of the tube, and low energy characteristic x-rays produced.
  • the thin foil on the outside of the end-window may produce K-line radiation from materials including but not limited to scandium, titanium, aluminum, silicon.
  • Another advantage of using a thin layer of target material on the outside of the end- window is that varying the thickness of the outside layer will determine the ratio of K- line radiation intensity to L-line radiation intensity, something that is not possible with current state of the art fluoroscopic x-ray tubes.
  • a similar layer may be used on the outside of the window of a reflection type tube, a transmission tube is preferred. Placing the foil within 0.25 to 1 mm, the thickness of the end- window, of the x-ray generating spot is considerably more efficient. Additionally filter blur is reduced.
  • a single target materials made from an alloy, eutectic alloy, compound or intermetallic compound of two or more elements, generally available from commercial producers is provided. It is well known that layering target materials or using multiple targets and selectively moving the electron beam from one to the other, can produce x-rays containing useful characteristic lines of more than a single element but at added cost. However mixing two or more elements into a single target avoids such cost. Examples 8 and 9 above disclose the use of zinc telluride and molybdenum telluride in a target material wherein the characteristic lines of tellurium and zinc or molybdenum and tellurium are useful in speeding measurement of multiple elements in the RoHS fluoroscopic application.
  • Iodine is often used as an imaging agent in angiography and mammography among others. After injecting a patient with an Iodine based imaging agent , taking one x-ray image with a high percentage of Lanthanum K-alpha (33.440 keV) and a second with a high percentage of tin k-alpha (25.270 keV) then subtracting the images will result in a clear image of the iodine with a K-absorption of 33.164 keV. Similarly dual imaging of the tin content in solder can be accomplished with the same two elements, Lanthanum and Tin to provide a quality control tool for soldering operations.
  • An intermetallic compound comprising 60% Lanthanum and 40% Tin provides one of any number of possible target materials with sufficient amounts of each material to produce high intensity K-line x-rays for both Tin and Lanthanum. Amount of K-alpha radiation from each element is adjusted by varying the x-ray tube voltage.
  • M is the rate of evaporation in grams per cm 2 per sec.
  • T is the temperature on the Kelvin scale.
  • the calculated amount of vaporization of a tantalum target 2 microns thick after 50,000 hours at 1600°K is still less than 0.01 microns. If the temperature is raised to 20000 K the vaporization increases to 0.1 microns. If the target material reaches 2000 0 C, an anode substrate of an x-ray tube made predominantly from beryllium, copper or aluminum would melt.
  • Another preferred embodiment of the current invention provides the deposition of a thin layer of sacrificial material on the order of 0.02 to 0.10 microns thick ( Figures 3B and 3D Reference numeral 12) of low vaporization chosen from one including but not limited to tungsten, tantalum, chromium, molybdenum, and rhodium onto a target which would otherwise suffer loss of target material and failure.
  • a preferred thickness of 40 to 500 nanometers of sacrificial material will not appreciably change tube output.
  • a transmission tube described above is coupled to a single capillary or a bundle of capillaries, typically made of specialty glass well known to those skilled in the art or any suitable material as well, which guide and focus a portion of the x-rays produced by a transmission type x-ray tube.
  • Figure 6 represents a single capillary coupled to the output of a transmission type tube 34 representing a focused electron beam of a transmission tube striking the target 36 in a focal spot.
  • the target deposited on an anode substrate 35 generates a beam of x-rays Item 38 a portion of which exit the end- window and enter a single capillary 37 to exit the opposite end of the capillary.
  • a single capillary is used to focus the x-rays from a focal spot of about 20 to 150 microns diameter to a very narrow beam of x-rays on the order of 1 - 10 microns.
  • Figure 7 represents a bundle of capillaries used to focus the spot size of an x-ray tube to produce even higher resolution of the x-ray beam useful for diffraction, fluorescence and imaging or to provide a close to parallel beam of x-rays to reduce scattering inside the object.
  • Reference numeral 44 illustrates how a bundle of capillaries can receive x-rays from a point source and guide them into a nearly parallel beam of x-rays.
  • Reference numerals 45 and 48 are graphical representations of how an individual x-ray beam travels inside a single capillary within the capillary bundle.
  • Reference numeral 46 illustrates use of a bundle of capillaries to receive x-rays and refocus them at a second point in space. However, this invention is not limited to those two uses.
  • transmission losses inside the capillary or capillaries are increased because the spot where x-rays are generated is place close to the entrance of the capillary in a transmission tube, these losses are not as great as the savings in x-ray intensity due to normal 1/r 2 losses not realized inside the capillary.
  • Using a transmission tube allows placement of the capillaries as close as about 0.075 to 2mm, the thickness of the end-window, increasing significantly the intensity of x-radiation exiting the capillary compared to that from reflection tubes where placement is limited to a minimum of about 20 to 30 mm.
  • Other advantages of transmission tubes include a high percentage of characteristic line emission compared to reflection tubes described above.
  • transmission tubes configured to provide K or L-line radiation can be significantly improved with a capillary or bundle of capillaries improvements to tubes used to produce predominantly bremsstrahlung radiation have similar benefits.
  • this invention is not limited to any particular kind of transmission x-ray tube.
  • Improving the speed and accuracy of fluoroscopic measurements can be accomplished by using a thick target foil of a transmission x-ray tube.
  • a thick target foil about 10 to 70 microns thick deposited onto the anode substrate (Reference numeral 14 of Figure 3 C or 3D) will absorb a high percentage of bremsstrahlung x-rays generated inside the foil within an energy band about 10-20 keV above the foil's K-absorption energy.
  • Making a fluoroscopic measurement of an element with a characteristic line emission within that energy band greatly reduces background bremsstrahlung improving speed and or accuracy of measuring presence or concentration of the element.
  • Any of a number of filtering schemes can be used if necessary to reduce the K-alpha output of the thick foil should its intensity be too high for delicate x-ray fluoroscopes.
  • Figure 8 demonstrates the output spectrum from a 25 micron thick molybdenum target of a transmission x-ray tube with an electron beam energy of 6OkVp.
  • the region 39, of the output energy spectrum just greater (about 20.1 to 30keV) than K-absorption energy of molybdenum, 20.002 keV, is a region where very few x-ray photons are generated by the thick molybdenum target because the energy in that region is absorbed by the target an fluoresced as K-line radiation.
  • cadmium the most difficult of the RoHS directive banned substances, has a K-alpha value of 23.172 higher than and close to the k-absorption energy of molybdenum.
  • background bremsstrahlung radiation is significantly reduced improving the signal to noise ratio for measuring cadmium.
  • an additional thin target material (Figure 3D Reference numeral 12) is deposited onto the molybdenum thick target to increase the amount of x-rays absorbed by cadmium and increase speed and or accuracy of the measurement.
  • the thin target can be about 0.5 microns to 10 microns thick and be of any target material which provides output x-rays excite cadmium but does not generating further interference from Compton Scattering.
  • target materials include but are not limited to Lanthanum, Cerium, Neodymium, Gadolinium, Thulium, Tantalum and Tungsten. Although molybdenum and cadmium were used by way of example, the underlying principle can be applied to any of a number of target materials and measured elements. It will be obvious to those skilled in the art that all of the above target configurations can be used to cover all or only a portion of the substrate onto which they are deposited. It is possible to construct an x-ray target with multiple target sections any one of which can be made according to the disclosures of this invention.
  • the electron beam 13 or beams can be made to impinge each target section selectively and can be controlled to move from impinging one of the target sections to impinging another in any of a number of different ways including scanning of the target.
  • a transmission type tube is used to provide x-rays for automated in-line inspection of objects.
  • Objects are fed into the inspection station, inspected and then removed automatically by a material handling apparatus.
  • Figure 11 represents one such an application.
  • a conveyor belt 44 feeds products 48 which can be stopped during the inspection or move continuously through the station.
  • any material handling apparatus well known to those skilled in the art can also be employed.
  • a line sensor 49 well known by those versed in the art is used to sense the image and an image processor 50 collects a series of line images and transforms them into an image of the entire object.
  • a power supply 46 provides electrical power to the x-ray tube assembly 45 conventionally containing the x-ray tube immersed in a cooling and electrically isolating fluid.
  • the x- ray tube produces x-rays 47 used to produce x-ray images of the product.
  • x-rays 47 used to produce x-ray images of the product.
  • this particular representation shows a line image sensor, various sensors, well known by anyone skilled in the art, can be used either for imaging or fluoroscopy or a combination thereof.
  • the cone angle of x-rays produced 8 is considerably wider for a transmission x-ray tube than for a reflection tube.
  • Reflection the x-ray tubes are typically placed 35 cm from the conveyor can provide the same field of inspection at distances as close as 20 cm depending on the size of product being examined, decreasing the amount of x-ray flux needed and significantly reducing the heat load on the x-ray target.
  • Figure 10 describes the amount and angular distribution of total x-ray flux produced by reflection type tubes currently in the market compared to the output flux of a closed transmission tube of the current invention.
  • Tube voltage was 60 kVp and tube current 50 microAmps for both measurements.
  • Focal spot sizes for both tube were ⁇ 100 microns.
  • the transmission tube provides considerable more output flux.
  • the preferred embodiment uses a closed transmission x-ray tube, open tubes may also be employed at more expense.
  • target material and subsequent tube voltage optimally chosen for sensor used in the in-line application can provide a three to five-fold improvement in total x-ray flux at the critical x-ray imaging energy compared to reflection tubes.
  • the target materials typically include but are not limited to tungsten, tantalum, platinum and other high Z elements producing a resultant three to four times more bremsstrahlung x-rays than a reflection tubes currently used.
  • the tube voltage, target thickness and target material may be chosen to provide a very high percentage of k- alpha radiation.
  • Such optimization of target design provides from 3 to 5 fold improvements in x-ray output at critical energies compared to reflection tubes.
  • a high percentage of monochromatic x-radiation provides even further improvements is accuracy of the inspection station as well as its speed.

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  • X-Ray Techniques (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

La présente invention concerne des cibles à rayons X faites d'une seule feuille d'alliage, d'alliage eutectique, de composé (éventuellement intermétallique) d'au moins deux éléments, pour produire des émissions de lignes séparées à partir de deux éléments différents de la feuille, pour réduire la réactivité dans l'air ou l'humidité par rapport à l'un au moins desdits éléments produisant les rayons X utiles, ou pour augmenter la production de rayons X utiles. L'invention concerne également des cibles à rayons X faites par dépôt simultané de plusieurs matériaux modifiant le coefficient de transfert thermique par comparaison à la mise en couche de ces matériaux. L'invention concerne aussi des tubes d'émission de rayons X configurés pour l'utilisation en fluoroscopie par focalisation du faisceau d'électrons sur un petit point de la cible, ou par utilisation d'une feuille cible épaisse pour réduire le bruit de fond des rayons X pour la mesure d'un élément étudié, une seconde feuille fine étant éventuellement appliquée sur la feuille cible épaisse pour produire de l'énergie d'excitation destinée à l'élément mesuré. L'invention concerne enfin des tubes d'émission de rayons X couplés à un unique capillaire ou à un faisceau de capillaires.
EP05854645A 2004-12-21 2005-12-16 Procede de production de materiau de feuille cible pour tubes a rayons x Withdrawn EP1831911A2 (fr)

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US63789004P 2004-12-21 2004-12-21
US65706705P 2005-02-28 2005-02-28
US70024205P 2005-07-19 2005-07-19
US72522805P 2005-10-12 2005-10-12
PCT/US2005/045971 WO2006069009A2 (fr) 2004-12-21 2005-12-16 Procede de production de materiau de feuille cible pour tubes a rayons x

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US8406378B2 (en) * 2010-08-25 2013-03-26 Gamc Biotech Development Co., Ltd. Thick targets for transmission x-ray tubes
KR101874029B1 (ko) 2012-06-14 2018-07-05 지멘스 악티엔게젤샤프트 Ｘ­선 소스，그 사용 그리고 ｘ­선들을 생성하기 위한 방법

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EP1044457B1 (fr) * 1998-10-21 2004-09-29 Koninklijke Philips Electronics N.V. Appareil a rayonnement x comprenant une source de rayons x dotee d'un systeme optique capillaire
US7180981B2 (en) * 2002-04-08 2007-02-20 Nanodynamics-88, Inc. High quantum energy efficiency X-ray tube and targets

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