In some embodiments, an X-ray target includes a target cap formed of a substrate material and a focal track layer of emitting material, and at least one of the substrate material and the emitting material has a density greater than about 95.0% of theoretical density. In some embodiments, a method of manufacturing an X-ray target includes forming an intermediate target cap form of substrate material and a focal track layer of emitting material, and compacting the intermediate target cap form by application of gas pressure at elevated temperature to form a final target cap form, and at least the substrate material is dense substrate material having a final density greater than an intermediate density or the emitting material is dense emitting material having a final emitting material density greater than an intermediate emitting material density.

FIELD OF THE INVENTION

The disclosure relates generally to X-ray imaging systems, X-ray apparatus and X-ray targets. The disclosure also relates to methods for manufacturing X-ray systems, X-ray apparatus and X-ray targets.

BACKGROUND OF THE INVENTION

X-ray imaging systems typically include an X-ray apparatus operable to generate a beam of X-rays, a detection apparatus, and a control system connected to the X-ray apparatus and detection apparatus. The X-ray apparatus produces a beam of X-rays which interact with a subject and are detected by operation of the detection apparatus. One typical example of an X-ray imaging system is a high performance computed tomography (CT) X-ray imaging system, which accommodates a human subject for medical imaging. Medical X-ray imaging systems typically include a gantry which is movable in relation to the human subject.

X-ray apparatus typically include an X-ray tube which is operable to generate a beam of X-rays. A typical X-ray tube includes a housing which forms an evacuated chamber. The housing supports inside the chamber a cathode assembly with a cathode filament. A high voltage electrical circuit is formed between the cathode and an anode assembly supported inside the housing. The anode assembly includes an X-ray target spaced from the cathode filament. The X-ray target includes a generally disk-shaped target cap. The target cap is formed of a high conductivity refractory metal, such as an alloy of molybdenum. An annular focal track on the front surface of the target cap includes a suitable X-ray emitting material, such as a chemical species of high atomic weight, of a type which interacts with high energy electrons to emit X-rays. The X-ray target also includes a heat sink affixed to a rear surface of the target cap. The heat sink receives intense heat conducted away from the focal track and substrate. Typically, the heat sink is formed of an annular block of graphite brazed to the rear surface of the target cap. The target cap is supported for rotation about a longitudinal axis. High speed rotation of the X-ray target is driven by a rotor connected to a drive motor.

For an imaging scan, the electrical circuit energizes the cathode filament to generate high energy electrons which impinge upon the focal track of the X-ray target. Interactions between the electrons and high atomic weight species in the focal track emit high frequency electromagnetic waves, or X-rays. X-rays directed through a window in the chamber housing are focused on a subject for imaging purposes. The electron interactions release intense heat into the focal track and target cap. The X-ray target is rotated by the motor at high speed in order to avoid overheating. Heat is also conducted out of the focal track into the substrate, and then into the heat sink. Heat dissipates from the heat sink through evacuated space in the chamber and into the housing. The housing is cooled by immersion in an external fluid bath.

Conventional X-ray targets presently possess material densities ranging from about 90.0% to about 95.0% of theoretical density. X-ray targets possessing material densities ranging from about 90.0% to about 95.0% of theoretical density are hindered by remaining porosity and porosity variation. X-ray targets can be produced by a “PSF” method by cold pressing (P) a form of substrate material and X-ray emitting material, sintering (S) the cold pressed form, and forging (F) the sintered form to desired shape. X-ray targets produced by the PSF method can possess material densities ranging from about 90.0% to about 95.0% of theoretical density. X-ray targets produced by the PSF method can be hindered by limited density, density variations, remaining porosity, porosity variations, limited mechanical strength properties, variation of mechanical strength properties, limited thermal conductivity, limited thermo-mechanical properties, limited thermal loading capacity, limited mechanical loading capacity. Examples of specific properties limited by the foregoing include: resistance to creep, tensile strength, compressive strength, thermal conductivity, bulk modulus, yield strength, mass per unit diameter, X-ray target diameter, thermal durability per unit of mass, mechanical durability per unit of mass, fatigue resistance, resistance to fatigue crack growth, resistance to crack growth, focal track life, and focal track performance. X-ray apparatus including X-ray targets having the foregoing limitations are hindered by limited capacity to operate at peak power, limited X-ray target rotation speed, limited gantry rotation speed, limited X-ray output at peak power, limited frequency of exposures at peak power, longer cooling periods between exposures, and limited cycle rate.

The specified limitations of X-ray targets produced by the PSF method can worsen as diameter of the X-ray target increases. Targets produced by the PSF method can suffer CTE mismatched bending stress or warpage because of differences between material properties of the focal track and the substrate material supporting the focal track. X-ray targets produced by the PSF method are hindered by the limitation that microstructure of the substrate and focal track materials is not highly controlled and, thus, variations of material properties such as microstructure and variation of microstructure are not optimal and are subject to great variation.

For reasons stated above and for other reasons which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improved X-ray targets, X-ray apparatus, and X-ray imaging systems, and for improved methods of manufacturing the same.

BRIEF DESCRIPTION OF THE INVENTION

The above-mentioned shortcomings, disadvantages and problems are addressed herein, as will be understood by those skilled in the art upon reading and studying the following specification.

In one aspect, systems, apparatus, and methods are provided through which X-ray imaging systems, X-ray apparatus, X-ray tubes, anode assemblies, and X-ray targets include a target cap formed of substrate material and a focal track layer formed of emitting material, and at least one of the substrate material and the emitting material has a density greater than about 95.0% of theoretical density.

In one aspect, systems, apparatus and methods are provided through which an X-ray target includes a target cap formed of substrate material and a focal track layer of emitting material, and at least one of the substrate material is dense substrate material having a final density greater than an intermediate density, or the emitting material is dense emitting material having a final emitting material density greater than an intermediate emitting material density.

Apparatus, systems, and methods of varying scope are described herein. In addition to the aspects and advantages described in this summary, further aspects and advantages will become apparent by reference to the following drawings, detailed description and claims.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and disclosure. It is to be understood that other embodiments may be utilized, and that logical, mechanical, electrical, and other changes may be made without departing from the scope of the embodiments and disclosure. In view of the foregoing, the following detailed description is not to be taken as limiting the scope of the embodiments or disclosure.

Illustrated inFIG. 1is a simplified block diagram of an X-ray imaging system100according to an embodiment. It is to be understood that an X-ray imaging system100according to embodiments of the disclosure can have different arrangements other than the specific representation illustrated inFIG. 1. One example of an X-ray imaging system100according to an embodiment is a computed tomography (CT) X-ray imaging system for imaging a human subject. Other specific arrangements of an X-ray imaging system100according to embodiments are contemplated. Examples of other embodiments include arrangements for various medical imaging uses and for examination of baggage, containers and other objects.

X-ray imaging system100includes a control system120. X-ray imaging system100also includes an X-ray apparatus140. X-ray apparatus140is connected to control system120and is operable to generate a beam of X-rays for imaging a subject (not shown). X-ray imaging system100also includes a detection apparatus160. Detection apparatus160is connected to control system120and is operable to detect X-rays which can interact with the subject (not shown). In some specific arrangements, the X-ray apparatus140may include a movable gantry (not shown) connected to the control system120and operable for movement along a prescribed path.

Illustrated inFIG. 2is a partial perspective view of an X-ray apparatus140according to an embodiment, with parts broken away, parts in section, and parts omitted. It is to be understood by those skilled in the art that, for clarity, various elements have been omitted fromFIG. 2. X-ray apparatus140can have different arrangements other than the specific representation illustrated inFIG. 2. In the specific arrangement illustrated inFIG. 2, the X-ray apparatus140includes an X-ray tube200. It is to be understood that X-ray apparatus140according to an embodiment can include, in addition to the illustrated X-ray tube200, additional elements (not shown inFIG. 2) known by those skilled in the art and which cooperate with X-ray tube200to generate X-rays for imaging a subject.

The X-ray tube200includes a glass or metal envelope or housing210. Inside the housing210exists a vacuum or evacuated space having a reduced pressure of about 10.sup.−5 to about 10.sup.−9 torr. A cathode assembly220including a cathode filament230is supported inside the housing210. The cathode filament230is connected to a selectively operable electrical circuit (not shown). The electrical circuit is connected to an anode assembly240supported inside the housing210. The anode assembly240includes an X-ray target250spaced a fixed distance from the cathode assembly220along a longitudinal axis255(seeFIG. 3). Referring toFIG. 4, the electrical circuit is selectively operable to cause a voltage potential between the cathode filament230and anode assembly240which generates high energy electrons directed at the X-ray target250. X-ray target250includes a target cap260having a disk portion265and a rear surface277, as further described below. A heat sink270is affixed to the rear surface277of target cap260to dissipate heat. X-ray target250and target cap260also include a stem280supporting the disk portion265, as further described below. The stem280is connected to a rotor300by a rotor hub320. Rotor300is connected to a motor (not shown) and drives rotation of the target cap260about longitudinal axis255. Target cap260is secured to a rotational shaft330by a fastener340. Rotational shaft340is operatively supported by a front bearing350and rear bearing360. A preloaded spring370is positioned about the rotational shaft330between the front bearing350and rear bearing360for maintaining load on the bearings350,360during thermal expansion and contraction of the anode assembly240.

FIG. 3is a front elevation view of the X-ray target250(shown generally inFIG. 2) according to an embodiment. The X-ray target250includes the generally disk-shaped target cap260. Viewed along longitudinal axis255, target cap260includes a disk portion265having a circular front surface400facing the cathode assembly220and cathode filament230(not shown inFIG. 3). The front surface400has therein a center420at longitudinal axis255. The front surface400has therein a central hole440concentric with the center420. The front surface400is symmetrical about center420and includes a continuous outer edge460. Outer edge460is spaced outwardly from the center420in a radial direction and thus defines an outer radius. The front surface400includes an annular focal track480. The focal track480has a continuous outer focal track edge482. In the illustrated arrangement, the outer focal track edge482is defined by the outer edge460. The outer focal track edge482is spaced outwardly from the center420in the radial direction and thus defines an outer focal track radius. The focal track480also has a continuous inner focal track edge484intermediate the center420and outer focal track edge482. The inner focal track edge484is spaced outwardly from the center420in the radial direction and thus defines an inner focal track radius. The focal track480defined between the inner focal track edge484and outer focal track edge482is an annulus. In the illustrated arrangement, the inner focal track edge484is closer to the outer edge460than the center420, such that the annular focal track480is adjacent the outer edge460.

FIG. 4is a cross section of X-ray target250taken generally along line4-4inFIG. 3. Referring toFIG. 4, X-ray target250includes the target cap260formed of substrate material486. In an embodiment, substrate material486is a suitable high conductivity refractory metal. For example, in an embodiment, substrate material486is formed of molybdenum, compositions including molybdenum, alloys of molybdenum, compositions including alloys of molybdenum, tungsten or alloys of tungsten. In one embodiment, the substrate material486is formed of TZM molybdenum alloy containing small amounts of titanium, zirconium and carbon, oxide-dispersion strengthened molybdenum alloy (ODS-Mo), or other carbide-dispersion strengthened alloys. In one embodiment, the substrate material486includes a high conductivity refractory metal selected from molybdenum, compositions including molybdenum, alloys of molybdenum, compositions including alloys of molybdenum, tungsten, compositions including tungsten, alloys of tungsten, and compositions including alloys of tungsten.

According to one embodiment, the substrate material486is dense substrate material488. According to an embodiment, dense substrate material488has a density greater than or equal to about 95.0% of theoretical density. According to one embodiment, dense substrate material488has a density greater than or equal to about 96.0% of theoretical density. According to one embodiment, dense substrate material488has a density greater than or equal to about 97.0% of theoretical density. According to one embodiment, dense substrate material488has a density greater than or equal to about 98.0% of theoretical density. According to one embodiment, dense substrate material488has a density greater than or equal to about 99.0% of theoretical density. As used herein, “density” means the minimum density within the subject material.

Referring toFIG. 4, the focal track480is formed of emitting material490. Emitting material490is suitable material known to emit X-rays upon interacting with high energy electrons. According to one embodiment, emitting material490is one of a group of chemical species of high atomic number and high melting temperature, which are known to emit X-rays. Examples of suitable emitting material490include tungsten and alloys of tungsten. In one specific embodiment, the emitting material490is a tungsten-rhenium alloy.

The focal track480is formed of emitting material490in a focal track layer620on the front surface400of the substrate material486. Focal track layer492extends between the inner focal track edge484and outer focal track edge482in an annulus on the front surface400. The focal track layer492of emitting material490is formed on the front surface400of the dense substrate material488in a suitable manner. In one embodiment, the focal track layer492is formed by depositing the emitting material490on the substrate material486by powder coating, plasma spraying, electroplating, chemical vapor deposition or physical vapor deposition.

According to one embodiment, the emitting material490is dense emitting material494. According to one embodiment, dense emitting material494has a density greater than or equal to about 95.0% of theoretical density. According to one embodiment, dense emitting material494has a density greater than or equal to about 96.0% of theoretical density. According to one embodiment, dense emitting material494has a density greater than or equal to about 97.0% of theoretical density. According to one embodiment, dense emitting material494has a density greater than or equal to about 98.0% of theoretical density. According to one embodiment, dense emitting material494has a density greater than or equal to about 99.0% of theoretical density. As used herein and specified above, “density” means the minimum density within the subject material.

Referring toFIG. 4, central hole440in the front surface400is defined by intersection of continuous inner wall495with front surface400. Inner wall495extends along longitudinal axis255in parallel spaced relation thereto and thus defines an open cavity497. Open cavity497accommodates the rotational shaft340. Inner wall495reduces diameter in stem280and terminates at stem hub498. Stem280has an outer stem wall499which returns from the stem hub498and intersects the rear surface277. In the embodiment illustrated inFIG. 4, stem280is integrally and continuously formed of the same substrate material486forming target cap260. In one embodiment, stem280is integrally formed of the same dense substrate material488forming target cap260. In one embodiment (not shown), the stem280is initially formed of separate material from the substrate material486, and is then joined with the substrate material486by a known method, such as welding. According to an embodiment, welding includes friction welding, inertia welding, and brazing.

The rear surface277of target cap260is generally parallel and in spaced opposition to front surface400. Heat sink270is integrally affixed to rear surface277in thermal communication with dense substrate material488. The heat sink270receives intense heat conducted away from the focal track480and front surface400through the dense substrate material488. In one embodiment, the heat sink270is formed of an annular block of graphite275. In one embodiment, the heat sink270is formed of suitable material having sufficiently high heat capacity and thermal emission to rapidly dissipate intense heat and sufficient mechanical strength to endure high speed rotation through repeated heating and cooling cycles. In one embodiment, the heat sink270is integrally affixed to the rear surface277by brazing. In one embodiment, the heat sink270is integrally affixed to the rear surface277by diffusion bonding.

An embodiment of the disclosure provides various improvements, benefits, advantages, features and solutions which will be described in further detail, as follows. X-ray targets in X-ray imaging systems such as computed tomography (CT) systems can be formed with a relatively large diameter target cap and focal track in order to accommodate increased peak power loads and thus provide increased X-ray output and image resolution. The diameter of X-ray targets can be limited by mechanical factors, such as limitations of the mechanical strength, thermal conductivity, and thermo-mechanical durability of the target cap substrate material and emitting material. In X-ray imaging systems such as computed tomography (CT) systems, a gantry rotates at approximately three revolutions per second around a patient and an anode assembly including the X-ray target rotates at approximately 100 to 200 revolutions per second. These rotations create large forces on the X-ray target and target cap that increase exponentially as the diameter and mass of the target cap and X-ray target increase. X-ray targets in X-ray imaging systems can also have a limiting mechanical factor in the thermal conductivity of the target cap substrate material and emitting material. The target cap substrate material and emitting material must be able to conduct heat at specified rates in order to be capable of emitting X-ray energy at a related minimum rate. Limits on the rate of emitting X-ray energy in turn limits the maximum number of imaging scans per unit of time, or usage rate, at which X-ray images can be made by the X-ray imaging system, and thus limits the usefulness of such X-ray imaging systems. During periods of continuous usage of some systems, the maximum usage rate at peak power can also be limited by the length of time required between exposures to adequately dissipate heat from the anode assembly. Operating an X-Ray system repeatedly or continuously at or in excess of the maximum usage rate can cause premature failure of X-ray tube components, especially the X-ray target. Temperatures reached in adjoining components decreases as those components are located increasingly distant from the focal track. Additionally, in order to rapidly dissipate heat from the heat sink, it is effective to rotate the X-ray target at high speed. However, other limitations frequently are prohibitive of continuously rotating the X-ray target in order to dissipate heat. In ordinary use, if the X-ray target and rotor were allowed to continue to rotate between exposures, the bearings would wear rapidly and fail prematurely. Thus, under certain circumstances of ordinary use dictating an excessive time delay between exposures, the X-ray system control system rapidly slows or stops the rotor and X-ray target in a period of seconds. When ready to initiate a scan, the control system returns the rotor and X-ray target to operational rotation speed as quickly as possible. Rapid acceleration and rapid deceleration are utilized because, among other reasons, there are a number of resonant frequencies that must be avoided during acceleration and braking. During such rapid acceleration and rapid braking, mechanical stresses and thermal stresses impact the components of the anode assembly. Embodiments of the disclosure provide X-ray imaging systems, X-ray apparatus, anode assemblies, X-ray targets, target caps, and methods for producing the same, having improvements, benefits, advantages, features and solutions which address the foregoing issues.

Method Embodiments

In the previous section, apparatus embodiments were described. In the present section, and by reference to the accompanying series of flowcharts, are described methods for manufacturing X-ray targets according to embodiments of the disclosure. It is to be understood that embodiments other than those specifically described herein are possible. It is to be understood that methods according to embodiments provide X-ray imaging systems, X-ray apparatus, X-ray tubes, anode assemblies, and X-ray targets having the same features, improvements and benefits described above in reference to the apparatus embodiments. It will be understood by those skilled in the art that X-ray targets are readily manufactured using target caps produced by methods according to the embodiments. It is to be understood that methods according to the embodiments can readily be adapted by one skilled in the art to produce target caps, X-ray targets, anode assemblies, X-ray tubes, X-ray apparatus and X-ray imaging systems.

FIG. 5is a flowchart illustrating a method500to manufacture an X-ray target according to an embodiment. Method500includes forming502an intermediate target cap form of substrate material having an intermediate density and a focal track layer of emitting material having an intermediate emitting material density. As used herein, “form” includes an arrangement of layers of substrate material and emitting material, irregardless of whether the arrangement is forged to desired shape. Suitable substrate materials and emitting materials were previously described above. According to one embodiment, only one of the substrate material and the emitting material is present during forming502. The intermediate target cap form can be formed in any suitable manner. According to one embodiment, the intermediate target cap form is formed by sequentially cold pressing, sintering and forging a target cap form. As used herein, “cold pressing” means uniaxially compacting materials of a form at pressures ranging from an initial pressure to a final pressure at about ambient temperature in the presence of atmospheric air. According to an embodiment, the intermediate target cap form can be formed of the substrate material by powder metallurgy techniques, plasma spraying, electroplating, chemical vapor deposition, or physical vapor deposition, as previously described herein. According to an embodiment, the focal track layer of emitting material is formed on the front surface of the substrate material in a suitable manner, such as by powder coating or plasma spraying. As used herein, intermediate density means the density of the substrate material in the resulting intermediate target cap form formed in forming502. As used herein, intermediate emitting material density means density of the emitting material in the resulting intermediate target cap form formed in forming502. As previously explained above, “density” means the minimum density within the subject material.

Method500also includes compacting504the intermediate target cap form of substrate material and the focal track layer of emitting material by application of gas pressure at elevated temperature for a time period to form a final target cap form of dense substrate material having a final density greater than the intermediate density and a focal track of dense emitting material having a final emitting material density greater than the intermediate emitting material density. According to an embodiment, at least one of the substrate material and the emitting material is densified. As used herein, “densified” means that the subject material has a final density greater than a preceding intermediate density. According to one embodiment, at least one of the substrate material is dense substrate material having a final density greater than the intermediate density or the emitting material is dense emitting material having a final emitting material density greater than the intermediate emitting material density. According to one embodiment, only one of the substrate material and the emitting material is present during compacting504. As used herein, “dense substrate material” means a dense substrate material formed in compacting504and which has a final density greater than the intermediate density. As used herein, “dense emitting material” means a dense emitting material formed in compacting504and which has a final emitting material density greater than the intermediate emitting material density. Suitable gases are inert gases or reducing gases. The ranges of gas pressure, temperature and time period may vary, as further described below.

According to an embodiment, the final density of the substrate material and final emitting material density are greater than or equal to about 95.0% of theoretical density. According to an embodiment, the final density and final emitting material density are greater than or equal to about 96.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 97.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 98.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 99.0% of theoretical density. According to one embodiment, at least one of the substrate material and the emitting material has a respective final density or final emitting material density as specified in the preceding.

In one embodiment, compacting504includes hot isostatic pressing. As used herein, hot isostatic pressing means compacting a form of substrate material and emitting material by application of gas pressure, at homologous temperature, for a time period to form dense substrate material having a final density greater than an intermediate density and dense emitting material density having a final emitting material density greater than an intermediate emitting material density. As used herein, “homologous temperature” means the ratio, on an absolute temperature scale, of process temperature to the melting point of a material. According to one embodiment, only one of the substrate material and the emitting material is present during hot isostatic pressing. According to one embodiment, either or both of the substrate material and the emitting material are in the form of powder before compacting504. According to one embodiment, compacting504includes: compacting the intermediate target cap form of substrate material and emitting material by application of gas pressure between about 35 MPa and about 500 MPa, at homologous temperature (Th) between about 0.3 of the lowest melting point component and about 0.8 of the highest melting point component, for a time period. In one embodiment, the time period ranges from at least about 1 minute to at least about 100 hours. In one embodiment, the time period ranges from at least about 1 minute to about 100 hours. In one embodiment, the time period ranges from at least about 30 minutes to about 100 hours. In one embodiment, the time period ranges from at least about 4 hours to about 100 hours. It is to be understood that the ranges of pressure, temperature and time period can vary in embodiments.

According to one embodiment, method500includes mechanically working506the final target cap form to impart work into the dense substrate material and the dense emitting material. Imparting mechanical work into the dense substrate material and dense emitting material forms or influences desired properties, such as desired grain size and more uniform grain size distribution.

According to one embodiment, method500also includes final machining508the final target cap form to predetermined dimensions.

FIG. 6is a flowchart illustrating a method600to manufacture an X-ray target according to an embodiment. Method600includes forming602an intermediate target cap form of substrate material having an intermediate density and a focal track layer of emitting material having an intermediate emitting material density. As used herein, “form” includes an arrangement of layers of substrate material and emitting material, irregardless of whether the arrangement is forged to desired shape. Method600includes compacting604the intermediate target cap form of substrate material and emitting material material by application of gas pressure between about 35 MPa and about 500 MPa, at homologous temperature (Th) between about 0.3 of the lowest melting point component and about 0.8 of the highest melting point component, for a time period to form a final target cap form of dense substrate material having a final density greater than the intermediate density and dense emitting material having a final emitting material density greater than the intermediate emitting material density. Suitable materials and conditions were previously described above. In an embodiment, compacting604includes hot isostatic pressing. Method600includes mechanically working606the final target cap form to impart work into the dense substrate material and dense emitting material. Method600includes final machining608the final target cap form to predetermined dimensions.

According to an embodiment, the final density of the substrate material and final emitting material density are greater than or equal to about 95.0% of theoretical density. According to an embodiment, the final density and final emitting material density are greater than or equal to about 96.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 97.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 98.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 99.0% of theoretical density. According to one embodiment, at least one of the substrate material and the emitting material has a respective final density or final emitting material density as specified in the preceding.

FIG. 7is a flowchart illustrating a method700to manufacture an X-ray target according to an embodiment. Method700includes: cold pressing702a target cap form of substrate material and a focal track layer of emitting material to form a pressed target cap form of pressed substrate material having a pressed density and pressed emitting material having a respective pressed emitting material density. Method700includes sintering704the pressed target cap form to form a sintered target cap form of sintered substrate material having a sintered density and sintered emitting material having a sintered emitting material density. Method700includes forging706the sintered target cap form to form a forged target cap form of forged substrate material having a forged density and forged emitting material having a forged emitting material density. Method700includes compacting708the forged target cap form of forged substrate material and forged emitting material by application of gas pressure between about 35 MPa and about 500 MPa, at homologous temperature (Th) between about 0.3 of the lowest melting point component and about 0.8 of the highest melting point component, for a time period to form a final target cap form of dense substrate material having a final density greater than the forged density and dense emitting material having a final emitting material density greater than the forged emitting material density. Suitable materials and conditions were previously described above. According to an embodiment, compacting708includes hot isostatic pressing. Method700includes mechanically working710the final target cap form to impart work into the dense substrate material and dense emitting material. Method700includes final machining712the final target cap form to predetermined dimensions.

According to an embodiment, the final density of the substrate material and final emitting material density are greater than or equal to about 95.0% of theoretical density. According to an embodiment, the final density and final emitting material density are greater than or equal to about 96.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 97.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 98.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 99.0% of theoretical density. According to one embodiment, at least one of the substrate material and the emitting material has a respective final density or final emitting material density as specified in the preceding.

FIG. 8is a flowchart illustrating a method800to manufacture an X-ray target according to an embodiment. Method800includes cold pressing802a target cap form of substrate material and a focal track layer of emitting material to form a pressed target cap form of pressed substrate material having an initial pressed density and pressed emitting material having a respective pressed emitting material density. Method800includes sintering804the pressed target cap form to form a sintered target cap form of sintered substrate material have a sintered density and sintered emitting material having a respective sintered emitting material density. Method800includes forging806the sintered target cap form to form a forged target cap form of forged substrate material having a forged density and forged emitting material having a respective forged emitting material density. Method800includes compacting808the forged target cap form by application of gas pressure between about 35 MPa and about 500 MPa, at homologous temperature (Th) between about 0.3 of the lowest melting point component and about 0.8 of the highest melting point component, for a time period to form a final target cap form of dense substrate material having a final density greater than the forged density and dense emitting material having a respective final emitting material density greater than the forged emitting material density. Method800includes welding810the disk portion of the final target cap form to a stem. In an embodiment, welding810includes friction welding, inertia welding, or brazing. Method800includes stress relieving812the final target cap form. It is to be understood that, according to an embodiment, stress relieving can be performed more than once and can be performed at different or additional points in method800. For example, stress relieving can be performed after forging806. Method800includes final machining814the final target cap form. Method800includes cleaning816the target cap. Method800includes vacuum firing818the target cap. According to one embodiment, welding810is omitted when the final target cap form includes a disk portion and stem integrally formed of the dense substrate material, because further joining disk portion and stem is not required. Suitable materials and conditions were previously described above.

According to an embodiment, the final density of the substrate material and final emitting material density are greater than or equal to about 95.0% of theoretical density. According to an embodiment, the final density and final emitting material density are greater than or equal to about 96.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 97.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 98.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 99.0% of theoretical density. According to one embodiment, at least one of the substrate material and the emitting material has a respective final density or final emitting material density as specified in the preceding.

FIG. 9is a flowchart illustrating a method900to manufacture an X-ray target according to an embodiment. Method900includes cold pressing902a target cap form, the target cap form including substrate material integrally forming a stem and a disk portion, the disk portion having a front surface with an outer edge, the target cap form including a focal track layer of emitting material on the front surface, the focal track layer defining an annular focal track on the front surface adjacent the outer edge, and thus forming a pressed target cap form of pressed substrate material having a cold pressed density and pressed emitting material respectively having a cold pressed emitting material density. Method900includes sintering904the pressed target cap form to create a sintered target cap form of sintered substrate material having a sintered density and sintered emitting material having a respective sintered emitting material density. Method900includes forging906the sintered target cap form to create a forged target cap form of forged substrate material having a forged density and forged emitting material having a respective forged emitting material density. Method900includes compacting908by hot isostatic pressing the forged target cap form by application of gas pressure between about 35 MPa and about 500 MPa, at homologous temperature (Th) between about 0.3 of the lowest melting point component and about 0.8 of the highest melting point component, for a time period to form a final target cap form of dense substrate material having a final density greater than the forged density and dense emitting material having a respective final emitting material density greater than the forged emitting material density. Method900includes stress-relieving910the final target cap form. It is to be understood that, according to an embodiment, stress relieving can be performed more than once and can be performed at different or additional points in method900. For example, stress relieving can be performed after forging906. It is to be understood that, according to alternative arrangements wherein the final target cap form does not include a stem integrally formed of the substrate material, before stress relieving910, the disk portion of the final target cap form is joined to a stem in a suitable manner, such as welding. According to an embodiment, welding can include, for example, friction welding, inertia welding, or brazing. Method900includes final machining912the final target cap form. Method900includes cleaning914the target cap. Method900includes vacuum firing916the target cap. Suitable materials and conditions were previously described herein.

According to an embodiment, the final density of the substrate material and final emitting material density are greater than or equal to about 95.0% of theoretical density. According to an embodiment, the final density and final emitting material density are greater than or equal to about 96.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 97.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 98.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 99.0% of theoretical density. According to one embodiment, at least one of the substrate material and the emitting material has a respective final density or final emitting material density as specified in the preceding.

FIG. 10is a flowchart illustrating a method950to manufacture an X-ray target according to an embodiment. Method950includes: cold pressing952a target cap form of substrate material and a focal track layer of emitting material to form a pressed target cap form of pressed substrate material having a pressed density and pressed emitting material having a respective pressed emitting material density. As used herein and previously explained above, “form” includes an arrangement of layers of substrate material and emitting material, irregardless of whether the arrangement is forged to desired shape. Method950includes sintering954the pressed target cap form to form a sintered target cap form of sintered substrate material having a sintered density and sintered emitting material having a sintered emitting material density. Method950includes compacting956the sintered target cap form of sintered substrate material and sintered emitting material by application of gas pressure between about 35 MPa and about 500 MPa, at homologous temperature (Th) between about 0.3 of the lowest melting point component and about 0.8 of the highest melting point component, for a time period to form a final target cap form of dense substrate material having a final density greater than the sintered density and dense emitting material having a final emitting material density greater than the sintered emitting material density. Suitable materials and conditions were previously described above. According to an embodiment, compacting956includes hot isostatic pressing. Method950includes forging958the final target cap form to desired shape. Method950includes mechanically working960the final target cap form to impart work into at least one of the dense substrate material and dense emitting material. It is to be understood that working906can be performed to refine the dense substrate material and dense emitting material at any desired point, such as before forging958. Method950includes final machining962the final target cap form to predetermined dimensions.

According to an embodiment, the final density of the substrate material and final emitting material density are greater than or equal to about 95.0% of theoretical density. According to an embodiment, the final density and final emitting material density are greater than or equal to about 96.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 97.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 98.0% of theoretical density. According to one embodiment, the final density and final emitting material density are greater than or equal to about 99.0% of theoretical density. According to one embodiment, at least one of the substrate material and the emitting material has a respective final density or final emitting material density as specified in the preceding.

CONCLUSION

X-ray targets, X-ray apparatus, and X-ray imaging systems according to embodiments of the disclosure are described. Although specific embodiments are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose can be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the embodiments and disclosure. For example, although described in terminology and terms common to the field of X-ray imaging systems, X-ray apparatus and X-ray targets, one of ordinary skill in the art will appreciate that implementations can be made for other systems, apparatus or methods that provide the required function.

In particular, one of ordinary skill in the art will readily appreciate that the names of the methods and apparatus are not intended to limit embodiments or the disclosure. Furthermore, additional methods, steps, and apparatus can be added to the components, functions can be rearranged among the components, and new components to correspond to future enhancements and physical devices used in embodiments can be introduced without departing from the scope of embodiments and the disclosure. One of skill in the art will readily recognize that embodiments are applicable to future X-ray imaging systems, X-ray apparatus, anode assemblies, X-ray targets, target caps, different substrate materials, and different emitting materials.

Terminology used in the present disclosure is intended to include all environments and alternate technologies which provide the same functionality described herein.