SILICON FIELD EFFECT EMITTER

Abstract

A system and method for generating X-ray radiation in a predefined spatial distribution on an anode. The system includes an anode, a first switching device, a second switching device, a control unit, and an emitter with multiple field effect emitter needles. At least one field effect emitter needle of the multiple field effect emitter needles includes a diameter of less than 1 m and silicon. A first group of the multiple field effect emitter needles may be activated or deactivated by the first switching device. A second group of the multiple field effect emitter needles may be activated or deactivated by the second switching device. The first group differs from the second group. The control unit is configured to actuate the first switching device and the second switching device.

Claims

1. An X-ray tube comprising: an anode; a first switching device; a second switching device; a control unit, the control unit configured to actuate the first switching device and the second switching device; and an emitter comprising multiple field effect emitter needles; wherein at least one field effect emitter needle of the multiple field effect emitter needles includes a diameter of less than 1 m and silicon; wherein a first group of the multiple field effect emitter needles may be activated or deactivated by the first switching device; wherein a second group of the multiple field effect emitter needles may be activated or deactivated by the second switching device; and wherein the first group differs from the second group.

2. The X-ray tube of claim 1, wherein the first group differs from the second group in an arrangement of the multiple field effect emitter needles.

3. The X-ray tube of claim 2, wherein the first group differs from the second group in a number of the multiple field effect emitter needles.

4. The X-ray tube of claim 1, wherein the first group differs from the second group in an acceleration voltage applied.

5. The X-ray tube of claim 4, wherein the first group differs from the second group in a number of the multiple field effect emitter needles.

6. The X-ray tube of claim 5, wherein the first group differs from the second group in an arrangement of the multiple field effect emitter needles.

7. The X-ray tube of claim 1, wherein the first switching device, the second switching device, or the first switching device and the second switching device are configured for activating the respective multiple field effect emitter needle such that each activated field effect emitter needle supplies a saturation current.

8. The X-ray tube of claim 1, wherein the X-ray tube is configured to function with an X-ray device configured for an imaging examination with an alternating acceleration voltage.

9. A method for generating X-ray radiation in a predefined spatial distribution on an anode, the method comprising: predefining the spatial distribution of electrons striking the anode of an X-ray tube; selecting a group of multiple field effect emitter needles of an emitter (E) of the X-ray tube as a function of an acceleration voltage; and activating the selected group of multiple field effect emitter needles; wherein as a result of the activation, X-ray radiation is generated in the predefined spatial distribution on the anode.

10. The method of claim 9, wherein activating the selected group of multiple field effect emitter needles comprises activating the selected group of multiple field effect emitter needle such that each activated field effect emitter needle supplies a saturation current.

11. A non-transitory computer implemented storage medium that stores machine-readable instructions executable by at least one processor for generating X-ray radiation in a predefined spatial distribution on an anode, the machine-readable instructions comprising: predefining the spatial distribution of electrons striking the anode of an X-ray tube; selecting a group of multiple field effect emitter needles of an emitter (E) of the X-ray tube as a function of an acceleration voltage; and activating the selected group of multiple field effect emitter needles; wherein as a result of the activation, X-ray radiation is generated in the predefined spatial distribution on the anode.

12. The non-transitory computer implemented storage medium of claim 11, wherein activating the selected group of multiple field effect emitter needles comprises activating the respective group of multiple field effect emitter needle such that each activated field effect emitter needle supplies a saturation current.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0037] FIG. 1 depicts an emitter including a first group of multiple field effect emitter needles according to an embodiment.

[0038] FIG. 2 depicts an emitter including a second group of multiple field effect emitter needles according to an embodiment.

[0039] FIG. 3 depicts trajectories of the emitted electrons as a function of the acceleration voltage applied according to an embodiment.

[0040] FIG. 4 depicts an X-ray device according to an embodiment.

[0041] FIG. 5 depicts a method for generating X-ray radiation in a predefined spatial distribution on an anode according to an embodiment.

DETAILED DESCRIPTION

[0042] FIG. 1 depicts a top view of an emitter E with a first group G1 of multiple field effect emitter needles F1, F2, FN in an embodiment. The multiple field effect emitter needles F1, F2, FN are arranged distributed in two spatial directions and in the embodiment include 810 field effect emitter needles.

[0043] The first group G1 of multiple field effect emitter needles F1, F2, FN is characterized by crosses and in the embodiment includes 12 field effect emitter needles. The first number is therefore 12. The first group may contain more or fewer than 12 field effect emitter needles. If the control unit S actuates and activates a switching device not shown in FIG. 1, the first group G1 of multiple field effect emitter needles F1, F2, FN emits electrons. The electrons are accelerated by a first acceleration voltage, that for example lies between 30 kV and 150 kV, for example at 120 kV.

[0044] The first group G1 includes a first arrangement and the first number of multiple field effect emitter needles F1, F2, FN, that differs from the embodiment depicted in FIG. 2

[0045] FIG. 2 depicts a top view of an emitter E with a second group G2 of multiple field effect emitter needles F1, F2, FN in an embodiment. The second group G2 differs from the first group G1. The second group G2 has a second arrangement and a second number of multiple field effect emitter needles F1, F2, FN. The second number is 20. The second group G1 of multiple field effect emitter needles F1, F2, FN is characterized by dashed crosses.

[0046] The electrons emitted from the second group G2 are accelerated by a second acceleration voltage that, for example, lies between 30 kV and 150 kV, for example at 80 kV.

[0047] The activated field effect emitter needles in the second group G2 in FIG. 2 are more compactly arranged than the activated field effect emitter needles in the first group G1 in FIG. 1.

[0048] The groups G1, G2 of multiple field effect emitter needles shown in FIG. 1 and FIG. 2 may be activated offset in time, for example one after the other, for example in accordance with the dual-energy measuring protocol.

[0049] FIG. 3 schematically depicts trajectories of the emitted electrons as a function of the acceleration voltage applied offset in time. The electrons are emitted if the gate emitter voltage is correspondingly provided by a field effect emitter needle voltage supply not shown in FIG. 3. The electrons emitted by the emitter E are accelerated by a voltage supply V toward an anode A, for example in a vacuum.

[0050] The solid trajectories differ from the dashed trajectories in the number of emitting field effect emitter needles and thus in the effect of the physical interactions to one another. The solid trajectories show for example electrons from the configuration shown in FIG. 1 and the dashed trajectories show the configuration shown in FIG. 2, if the first number in FIG. 1 is smaller than the second number in FIG. 2. Because of the higher emission current and the associated higher space-charge density of the form of embodiment shown in FIG. 2, as a result of in which comparatively stronger physical interactions occur between the electrons, the dashed trajectories deviate more strongly from one another than the solid trajectories.

[0051] FIG. 4 depicts an X-ray tube R in an embodiment. The X-ray tube R includes an anode A, a first switching device, a second switching device, a control unit S, and an emitter E with multiple field effect emitter needles F1, F2, FN. At least one field effect emitter needle of the multiple field effect emitter needles F1, F2, FN includes a diameter of less than 1 m and silicon. A first group G1 of the multiple field effect emitter needles F1, F2, FN may be activated or deactivated by the first switching device. A second group G2 of the multiple field effect emitter needles F1, F2, FN may be activated or deactivated by the second switching device. The first group G1 differs from the second group G2. The control unit S is configured to actuate the first switching device and the second switching device. The control unit S may be part of the X-ray tube R or be arranged outside the X-ray tube R. The control unit S may include an FPGA or a processor. In this embodiment the control unit S is arranged outside the X-ray tube R and is connected to the X-ray tube for actuating the first switching device and the second switching device.

[0052] The first switching device and/or the second switching device may be configured for an activation of the respective multiple field effect emitter needles F1, F2, FN, such that each activated field effect emitter needle supplies a saturation voltage.

[0053] The X-ray device includes the X-ray tube R and an X-ray detector D. The X-ray device is configured for an imaging examination with an alternating acceleration voltage. The acceleration voltage alternates during the imaging examination, for example in accordance with the dual-energy measuring protocol. In the embodiment the X-ray device is shown as part of a single-source computed tomography system CT. A patient P is arranged on a patient couch L.

[0054] FIG. 5 depicts a flow diagram of a method for generating X-ray radiation in a predefined spatial distribution on an anode.

[0055] Method step S100 includes a predefinition of the spatial distribution of electrons striking the anode of an X-ray tube.

[0056] Method step S101 includes a selection of a group of multiple field effect emitter needles of an emitter of the X-ray tube as a function of an acceleration voltage.

[0057] Method step S102 includes an activation of the selected group of multiple field effect emitter needles, as a result of which X-ray radiation is generated in the predefined spatial distribution on the anode.

[0058] 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 disclosure. 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.

[0059] While the present disclosure 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.