Patent Application
20170345611
Embodiments relate to a metal jet x-ray.
In stationary or rotary anode tubes, or metal jet x-ray tubes, there is the problem of a power density at a point of incidence of the electron beam on the anode component. High power losses are generated for given luminous intensities and focal spot luminances. Strong background magnetic fields, for example, caused in conjunction with magnetic resonance imaging scanners cause a problem. It is impossible to focus the electron beam using electrostatic in magnetic fields of such strength.
The problem of maintaining the solid or liquid aggregate state of the anode material in the focal point of the electron beam in rotation anode tubes and in metal jet x-ray tubes may be solved by virtue of the material of the rotary anode or of the metal jet being transported sufficiently quickly through the focal spot at the focal point of the electron beam. In the process, the electrons are decelerated to a standstill, even though only high-energy electrons cause the desired short-wave x-ray radiation. In view of the focal spot power deposition, and also in view of the efficiency, a drawback is the complete deceleration.
The scope of the present invention is defined solely by the appended claims and is not affected to any degree by the statements within this summary. The present embodiments may obviate one or more of the drawbacks or limitations in the related art.
Embodiments provide a metal jet x-ray tube that is affected less than conventional stationary or rotary anode tubes, or previous metal jet x-ray tubes, by the problem of the power density at the point of incidence of the electron beam on the anode component.
In an embodiment, in a vacuum chamber, the metal jet x-ray tube includes a cathode component for extracting an electron beam and a provision for extracting the electron beam by the cathode component. The metal jet x-ray tube further includes an anode component formed by a liquid metal jet as a target for the emitted electron beam of the cathode component and a provision for accelerating the electron beam emitted by the cathode component within a vacuum path in the direction and with a target of the anode component. The metal jet x-ray tube includes a thin metal jet as an anode component, by which the electrons of the electron beam incident thereon are only partly decelerated. The metal jet x-ray tube includes a blade cathode as the cathode component. The blade cathode includes a cathode blade directed with a slight inclination downward in the direction of the liquid metal jet of the anode component.
A metal jet x-ray tube is provided with fast primary electrons that are accelerated along a first vacuum path in electrostatic or electrodynamic manner, and are only partly decelerated in a thin, relatively electron-transparent target medium.
However, the thin light-producing anode material may only absorb very little energy. At the end there is, at first, substantially the same power limit as in the case of a thick anode material. Physically very thin anode materials are required (e.g., with a thickness of 0.1 to 10 μm).
It may be very difficult to realize liquid metal jets in a form that differs from a round one. Hence, the focal spot diameter is likewise restricted to a very small size.
Further, the presence of a strong, homogeneous background magnetic field (e.g., in the case of use in a magnetic resonance imaging scanner) renders focusing the electrons by electrostatic impossible.
Therefore, in combination with the thin metal jet of the anode component, a blade cathode that produces a flat electron beam with a thickness that fits to the metal jet diameter such that a sufficiently large portion of the electrons emerging from the cathode are incident on the metal jet is provided.
In an embodiment, a further vacuum path is provided downstream of the anode component for the electrons of the electron beam that have not yet been completely decelerated. Within the further vacuum path, the electrons are decelerated at least virtually to standstill.
If this decelerating of the electrons is carried out together with an energy recuperation provision, the light production efficiency is increased.
An additional increase in the efficiency is provided by a metal jet of the anode component that is embedded in a second material or is dissolved in the second material. The second material passes electrons relatively well and is heat absorbing.
By way of example, the dissolution may be brought about in the form of an alloy or a mix. In contrast to previous metal jet x-ray tubes, an alloy or a mix facilitates physically relatively thick but electron-optically thin anodes with a large specific energy absorption capacity. Overall, the metal jet may have the cylindrical form with a diameter of the order of the electron beam diameter (e.g., 10 to 100 μm), while nevertheless having sufficient transmissivity from an electron-kinetic point of view. The mix or the alloy has a low melting point in order to facilitate the liquid jet formation. The improved energy absorption capacity of the anode material reduces the necessary anode beam speed and/or facilitates a higher power deposition and hence luminance of the focal spot.
The metal jet 6 is configured as a thin metal jet. The electrons of the electron beam 4 are only partly decelerated by the metal jet 6. The cathode component 3 has a cathode blade 10 such that the cathode component 3 may also be referred to as a blade cathode. The cathode blade 10 is directed with a slight inclination downward in the direction of the liquid metal jet 6 of the anode component 7.
There is a further vacuum path 11 downstream of the anode component 7 for the electrons of the electron beam 4 that have not yet been decelerated completely. The vacuum path 11 serves to decelerate the only partly decelerated electrons downstream of the anode component 7 to a standstill. In an embodiment, the system also includes an energy recuperation provision 12.
While not depicted, the metal jet 6 of the anode component 7 is at least embedded or dissolved in a single second material 13 that passes electrons well and is heat absorbing.
In an embodiment, a blade cathode that is slightly inclined in relation to possibly present magnetic field lines is used. Additionally, in an embodiment according to
The metal jet 6 is, for example, injected into the electron beam 4 by an injector such that bremsstrahlung and characteristic radiation are produced in the interaction zone 14. The transmitted and scattered electrons are decelerated in an electrostatic collector by way of a counteracting E-field with recuperation of energy and caught at a low velocity.
Easily melting metal alloys tend to have a high vapor pressure in the case of elevated temperatures, which promotes the deposition of conductive surface layers (e.g., on insulators). The metal jet 6 is guided through the discharge chamber for only a minimum length required for the interaction with the electron beam 4 and thereafter let to enter a wall-cooled condensation and collection container.
It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.
While the present invention has been described above by reference to various embodiments, it may be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 226 813.3 | Dec 2014 | DE | national |
The present patent document is a §371 nationalization of PCT Application Serial Number PCT/EP2015/080504, filed Dec. 18, 2015, designating the United States, which is hereby incorporated by reference. This patent document also claims the benefit of DE 102014226813.3, filed on Dec. 22, 2014, which is also hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/080504 | 12/18/2015 | WO | 00 |
