JP2019050189A - X-ray tube objective and focusing lens, x-ray tube and method for operating such x-ray tube - Google Patents

Abstract

To provide an X-ray tube objective lens without using a complicated cooling mechanism.SOLUTION: An objective lens 1 comprises: an object lens inner core 10; an inner objective lens coil 12 arranged on the inner core 10; an object lens outer core 11 arranged around the inner core 10. An outer objective lens coil 13 is arranged between the inner objective lens coil 12 and the objective lens outer core 11, and the outer objective lens coil 13 has two objective lens wire portions 13a and 13b having the same number of turns.SELECTED DRAWING: Figure 1

Description

  The invention relates to an objective for an X-ray tube, a focusing lens for an X-ray tube, an X-ray tube comprising such an objective and / or such a focusing lens and a method of operating such an X-ray tube About. The X-ray tube is in particular a microfocus X-ray tube.

  During operation of the x-ray tube, the shape, size and position of the focal spot changes, which is very widely applicable to microfocus x-ray tubes. This change is due, in part, to temperature changes in the components of the x-ray tube. Such focal spot changes adversely affect imaging quality when the x-ray tube is used in an imaging method.

  As a solution to this problem, Patent Document 1 proposes that the coil of the X-ray tube be thermally stabilized by uncontrolled cooling using a cooling fluid. The x-ray tube is cooled independently of external influences by a constant volume flow of coolant. Depending on the power of the tube, the ambient temperature and the coil current, an indefinite temperature equilibrium occurs. This achieves a lower absolute temperature equilibrium as compared to an uncooled X-ray tube. As a result, temperature equilibrium can be achieved more quickly because the temperature difference with the ambient temperature is reduced. This approach is complicated by the need to introduce a flow path for the cooling fluid into the coil and the need to place the cooling circuit in a high vacuum environment or to apply cooling to the outside of the x-ray tube, so X The tube becomes very large.

German Patent Application Publication No. 102010032338

  It is therefore an object of the present invention to provide an alternative which allows the focal spot to be kept as constant as possible but without complicated cooling by the cooling fluid.

  The above object is achieved by an objective according to the features of claim 1. Since the two objective wire parts of the outer objective lens coil have the same number of turns, it is possible to supply them with currents of the same current intensity, so that the respective magnetic fields are of equal magnitude. If it is certain that these fields are aligned in the opposite direction, they cancel each other so that the total field obtained is zero. This can be achieved by essentially two designs. That is, if the windings are realized in opposite directions, a design in which two objective lens wire parts are connected in series and the current may be supplied by the same filament current source, or two objective lens wire parts are If it is not realized in the opposite direction, it is either of the designs that needs to supply current with the same current strength but in the opposite direction. The person skilled in the art understands how to make such an embodiment. Thus, the magnetic field summation of the outer objective lens coil does not affect the electron beam induction of the x-ray tube, but rather only functions to generate heat in the objective lens coil. As a result, the temperature difference decreases here as time passes, as in the state of the art. Thus, the effect of stabilizing the focus of the X-ray tube is obtained without using a cooling fluid which is complicated to introduce into the objective lens coil.

  This object is also achieved by means of a focusing lens with the features of claim 2. The design of the focusing lens according to the invention is in principle the same as the design of the objective according to the invention described immediately above, with the advantages indicated there.

  An advantageous development of the invention provides that the two objective wire portions of the outer objective lens coil of the objective lens or the two focusing lens wire portions of the outer focusing lens coil of the focusing lens are respectively wound in opposite directions. provide. As a result, it has already been mentioned above that the supply of current to the two objective lens parts or the two focusing lens parts can be done by series connection without using additional devices with the same filament current source. This is advantageous over parallel windings.

  This object is also achieved by means of a focusing lens with the features of claim 4. Since the inner focusing lens coil is divided into an even number of magnetic field wire parts, for example 2, 4, 6, 8 or 10 magnetic field wire parts, the magnetic field strength of the magnetic field generated by this inner focusing lens coil is The power input to the focusing lens coil can be changed in various ways without changing, in which case the individual magnetic field wire parts are supplied with current, so that (in parts of the individual magnetic field wire parts generated in each case) The resulting total magnetic field strength, since the magnetic fields (the magnetic fields are of equal size at the same current intensity since the number of turns is the same in each case) cancel or augment each other Is the zero at the extrema of and the sum of the individual magnetic field strengths at the other extremum. The power input to the entire inner focusing lens coil does not change even if different magnetic field strengths are generated. Thus, the power input is kept constant. As a result, there is no change in focal spot for magnetic fields of different intensities generated in the focusing lens coil due to the thermal change of the inner focusing lens coil. It goes without saying that the more magnetic wire parts are present, the finer the fragmentation between the achievable magnetic field strengths. Thus, when two magnetic field wire sections are used, it is only possible to shut off the inner focusing lens coil (the sum of the magnetic field strengths is zero) or to generate a maximum magnetic field strength. On the other hand, when six magnetic field wire sections are used, two intermediate stages (1/3 or 2/3 of the total magnetic field strength) can be selected.

  An advantageous development of the invention provides that the number of magnetic field wire sections is four. By dividing the field wire portion into four, the switch-off mode (the opposite field strength of the two field wire portions in each case makes the field strength zero) and the maximum field strength (four individual field strengths) In addition to the half field strength mode (three magnetic field strengths are directed in one direction and one magnetic field strength is directed in the opposite direction), as a result of the two magnetic field strengths as a whole canceling one another. Can also be set.

  This object is also achieved by an x-ray tube with the features of claim 6. Although the filament current source supplies currents of the same current intensity to the objective lens portion or the focusing lens portion, the magnetic fields cancel each other to generate heat in the respective coils because the magnetic field strength in the opposite direction is generated. Regardless of this, no magnetic field can be obtained. As a result, the advantages already mentioned above in connection with claim 1 arise. The person skilled in the art understands how it is necessary to connect the filament current source to the objective lens wire portion or the focusing lens wire portion in order to achieve the specified individual field strengths.

  An advantageous development of the invention provides that the two objective wire portions of the outer objective lens coil and / or the two focusing lens wire portions of the outer focusing lens coil are connected in series. Only a single filament current source can be used for the outer objective lens coil or the outer focusing lens coil, as the respective wire sections are wound in opposite directions and connected in series, whereby additional elements The current supply can be performed in a very simple way without using.

  A further advantageous development of the invention is that at least one of the filament current sources is connected to a control system, which is connected to a temperature sensor which measures the temperature of the objective and / or the focusing lens. Provide that. Such a control system makes it possible to change the heat output, so that it is possible to adapt the temperature of the objective and / or the focusing lens to the changed situation, which results in a further improvement of the focal spot. Stabilization can be achieved.

  This object is also achieved by an x-ray tube with the features of claim 9. Such an X-ray tube results in the advantages described above with regard to the development with claim 4 and its four magnetic field wire sections.

  The object is also achieved by a method of operating an X-ray tube having the features of claim 10. The two operating modes according to the invention (total field strength zero and maximum field strength) achieve the same advantages as already described above with regard to claim 4.

  An advantageous development of the invention provides that the magnetic fields of the individual field wire parts of the inner focusing lens coil partially cancel one another in the third operating mode. Depending on the number of magnetic wire segments present, a certain number of intermediate steps (between zero magnetic field strength and maximum magnetic field strength) can be selected to generate heat resulting from changes in the introduced power Without using it, you can use the X-ray tube more flexibly.

  Further advantages and details of the invention will be explained in more detail below with reference to the example of the embodiment represented in the drawing.

FIG. 1 is a schematic longitudinal sectional view of a focusing lens according to the present invention and an objective lens according to the present invention in an X-ray tube according to the present invention. Fig. 1 is a schematic view of a first operating mode according to the invention of an X-ray tube according to the invention; FIG. 5 is a schematic view of a third operating mode according to the invention of the X-ray tube according to the invention; FIG. 5 is a schematic view of a second operating mode according to the invention of the X-ray tube according to the invention;

  FIG. 1 shows the details of the microfocus X-ray tube according to the invention in the region of its focusing lens 2 and its objective 1 in a schematic longitudinal sectional view. The remainder of the microfocus x-ray tube is not shown but corresponds to the state of the art and is not relevant to the present invention. Instead of a microfocus x-ray tube, it is also possible to be another type of x-ray tube.

  The focusing lens 2 and the objective lens 1 are arranged around the tube for the electron beam 3. The focusing lens 2 is located in front of the objective lens 1 in the direction of the electron beam 3.

  The focusing lens 2 comprises a focusing lens inner core 20, which is realized rotationally formed symmetrically by the tube for the electron beam 3. The inner core 20 of the focusing lens also extends perpendicularly to the electron beam 3 and forms on the outside a part of the outer wall where it has a tubular shape.

  A focusing lens outer core 21 is disposed in front of the electron beam 3 in the direction of the electron beam 3. The focusing lens outer core 21 has a tubular component in addition to the front wall (with an opening for the electron beam 3 in the middle) extending perpendicularly to the electron beam 3. The tubular component is also part of the outer wall and flush with the part of the outer wall formed by the focusing lens inner core 20.

  An inner focusing lens coil 22 is arranged in the central part of the focusing lens inner core 20, which also forms a tube for the electron beam 3. The inner focusing lens coil 22 comprises four wire sections each having the same number of turns and arranged in the following order (this version is shown in FIG. 1) or sequentially in the direction of the electron beam 3 The first magnetic field wire portion 22a, the second magnetic field wire portion 22b, the third magnetic field wire portion 22c, and the fourth magnetic field wire portion 22d.

  An outer focusing lens coil 23 is disposed around the inner focusing lens coil 22. The outer focusing lens coil 23 comprises two wire sections each having the same number of turns and arranged in the following order (this version is shown in FIG. 1) or sequentially in the direction of the electron beam 3 To be: first focusing lens wire portion 23a, second focusing lens wire portion 23b. These two wire sections are wound in opposite directions.

  The objective 1 comprises an objective inner core 10, which is realized rotationally symmetrical around the tube for the electron beam 3 and is formed by it. The inner core 10 of the objective also extends perpendicularly to the electron beam 3 and forms on the outside a part of the outer wall where it has a tubular shape. A portion of the outer wall is flush with and coupled to a portion of the outer wall formed by the objective lens inner core 10.

  An objective lens outer core 11 is disposed in front of the electron beam 3 in the direction of the electron beam 3. The objective lens outer core 11 has a tubular component in addition to the front wall (having an opening for the electron beam 3 in the middle) extending perpendicularly to the electron beam 3. The tubular component is also part of the outer wall and flush with the part of the outer wall formed by the objective lens inner core 10.

  An inner objective lens coil 12 is arranged at the inner part of the objective inner core 10, which also forms a tube for the electron beam 3, as understood from the prior art.

  An outer objective lens coil 13 is disposed around the inner objective lens coil 12. The outer objective lens coil 13 comprises two wire sections each having the same number of turns and arranged in the following order (this version is shown in FIG. 1) or continuously in the direction of the electron beam 3 To be: first objective lens wire portion 13a, second objective lens wire portion 13b. These two wire sections are wound in opposite directions.

  The first focusing lens wire portion 23a and the second focusing lens wire portion 23b are both wound in opposite directions and have the same number of turns, and the same current flows through the second filament current source. It is supplied from (not shown). For this reason, both may be connected in series so that one immediately after the other. As a result, since the two magnetic fields generated by the two wire parts cancel each other out, the magnetic field strength obtained for the entire outer focusing lens coil 23 becomes zero. Therefore, the outer focusing lens coil 23 generates only heat when current is supplied, and does not generate a magnetic field that would affect the trajectory of the electron beam 3. Therefore, changing the existing current intensity of the second filament current source can affect the heat of the entire focusing lens 2. By means of a temperature sensor (not shown) for detecting the temperature of the focusing lens 2 and a control system (not shown) connected to the temperature sensor, the variation of the current intensity of the second filament current source is controlled. The temperature can be kept substantially constant, as a result of which the change of the focal spot of the microfocus X-ray tube due to the thermal influence on the focusing lens 2 does not occur. Such a device with a temperature sensor, a control system and a second filament current source is in principle understood by the person skilled in the art.

  The same applies to the outer objective lens coil 13 as the outer focusing lens coil 23 described immediately before. That is, the first objective lens wire portion 13a and the second objective lens wire portion 13b are both wound in opposite directions and have the same number of turns, and the same current flows through the first filament. It is supplied from a current source (not shown). For this reason, both can be connected in series directly in front of and behind. As a result, since the two magnetic fields generated by the two wire parts cancel each other out, the magnetic field strength obtained for the entire outer objective lens coil 13 becomes zero. Therefore, the outer objective lens coil 13 generates only heat when current is supplied, and does not generate a magnetic field that affects the trajectory of the electron beam 3. Therefore, changing the existing current intensity of the first filament current source can affect the heat of the entire objective lens 1. Thereby, the objective through the change of the current intensity of the first filament current source by the temperature sensor (not shown) for detecting the temperature of the objective lens 1 and the control system (not shown) connected to the temperature sensor. The temperature of the lens 1 can be kept substantially constant, as a result of which the change of the focal spot of the microfocus X-ray tube due to the thermal influence on the objective lens 1 does not occur. Such a device comprising a temperature sensor, a control system and a first filament current source is in principle understood by the person skilled in the art.

  Therefore, the change of the electron beam 3 is caused by the inner focusing lens coil 22 and the inner objective lens coil 12, not the outer focusing lens coil 23 and the outer objective lens coil 13. With regard to the inner objective lens coil 12, it is an objective lens coil known from the prior art, which is not essential to the invention in terms of its structure, so that its operating mode does not have to be described in more detail.

  However, the inner focusing lens coil 22 according to the invention is basically configured differently from the focusing lens coils known from the prior art (see above). In the case of the known focusing lens coils described below, it is assumed that the focusing lens coil has the same number of turns as the sum of the four wire sections in the inner focusing lens coil 22 according to the invention. Other specific features should also be addressed to enable comparison of the focusing lens coils according to the state of the art with the inner focusing lens coil 22 according to the invention.

  In the case of the known focusing lens coil, the focusing lens coil has only one continuous winding, and the adjustment of the strength of the magnetic field is performed by a change in the current of the current source connected to the focusing lens coil. If no magnetic field is present, the current intensity is 0A. Therefore, the power input to the focusing lens coil is 0 W. At this time, the temperature of the focusing lens coil is, for example, 25 ° C. If a moderate magnetic field is required, a current intensity of, for example, 1 A is used, and if a constant voltage of 15 V is applied, a power input of 15 W occurs, so that the temperature of the focusing lens coil is, for example, 35 ° C. It becomes. For a strong magnetic field, for example, a current intensity of 2 A is used, and for a voltage of 30 V, a power input of 60 W and a temperature of the focusing lens coil of, for example, 60 ° C. are obtained. When the temperature changes rapidly, the focal spot is affected.

  The structure of the inner focusing lens coil 22 according to the invention with four wire parts of the same number of turns is described in more detail below and is power input by the different interconnections of the four wire parts represented in FIGS. 2a-2d. Can be kept constant, whereby the temperature of the inner focusing lens coil 22 becomes constant. For the other boundary conditions, it is as described in the preceding paragraph with regard to the focusing lens coils known from the prior art. The four wire sections are connected to a magnetic field current source 4, which is constant at a current of 2 A, as in the case of the strong magnetic field in the case of the known focusing lens coil described in the preceding paragraph. Is working with For the same voltage as above, a 60 W power input is always present. This means that the temperature of the inner focusing lens coil is constant, for example at 60.degree. The magnetic field current source 4 comprises four wire portions (a first magnetic wire portion 22a, a second magnetic wire portion 22b, a third magnetic field) in order to enable different magnetic field strengths of the entire inner focusing lens coil 22 described later. The wire portion 22c, the fourth magnetic field wire portion 22d) are connected via circuits known to the person skilled in the art, which allow different current directions in the individual wire portions.

  In the circuit shown in FIG. 2a, current flows in the same direction in the first magnetic field wire portion 22a and the second magnetic field wire portion 22b, but in the third magnetic field wire portion 22c and the fourth magnetic wire portion 22d. The current flows in the opposite direction to the first two parts mentioned. Thus, the magnetic fields of the individual wire sections cancel one another and the resulting magnetic field is eliminated.

  In the circuit shown in FIG. 2b, current flows in the same direction in the first magnetic field wire portion 22a, the second magnetic field wire portion 22b, and the third magnetic field wire portion 22c, but in the fourth magnetic wire portion 22d. Current flows in the opposite direction to the first three parts mentioned. Thus, the two partial magnetic fields cancel each other, and the resulting magnetic field is the sum of the two wire sections. This corresponds to the weak magnetic field in the case of the known focusing lens coil, as described above.

  In the circuit shown in FIG. 2c, current flows in the same direction in all of the first magnetic wire portion 22a, the second magnetic wire portion 22b, the third magnetic wire portion 22c, and the fourth magnetic wire portion 22d. This corresponds to the strong magnetic field in the case of the known focusing lens coil, as described above.

  It is clear that a finer adjustment of the intermediate field strength between zero and the maximum field strength can be generated if the number of turns of the inner focusing lens coil 22 is further subdivided into more wire sections. Here, the maximum magnetic field strength is the magnetic field strength when the current flows in the same direction in all wire parts.

  In summary, one of the main aspects according to the invention is achieved with the circuit by only distributing the different magnetic field strengths of the inner focusing lens coil 22 at constant temperature differently in the current direction in the wire part It can be done. Even if the magnetic field intensity changes, no temperature change occurs, so that the change in focal spot due to the influence of heat is eliminated.

  It is not absolutely necessary that all the individual wire parts of the inner focusing lens coil 22 have the same number of turns. In principle, any other subdivision is also possible, as long as it is guaranteed that at least one combination in which the resulting total field strength sum is zero is possible. Therefore, for example, it is also possible to subdivide the total number of turns at a ratio of 1/4 + 1/8 + 1/8 + 1/8 + 1/8 + 1/4.

1 objective lens 2 focusing lens 3 electron beam 4 magnetic field current source

10 objective lens inner core 11 objective lens outer core 12 inner objective lens coil 13 outer objective lens coil 13a first objective lens wire portion 13b second objective lens wire portion

20 focusing lens inner core 21 focusing lens outer core 22 inner focusing lens coil 22a first magnetic wire portion 22b second magnetic wire portion 22c third magnetic wire portion 22d fourth magnetic wire portion 23 outer focusing lens coil 23a Focusing lens wire portion 23 of 1 Second focusing lens wire portion

Claims (11)

An objective lens (1) for an X-ray tube, in particular for a microfocus X-ray tube,
An objective lens inner core (10), an inner objective lens coil (12) disposed on the objective lens inner core (10), and an objective lens outer core disposed around the objective lens inner core (10) 11) and,
An outer objective lens coil (13) is disposed between the inner objective lens coil (12) and the objective lens outer core (11),
The objective lens (1), wherein the outer objective lens coil (13) comprises two objective wire parts (13a, 13b) with the same number of turns. A focusing lens (2) for an x-ray tube, in particular for a microfocus x-ray tube,
A focusing lens inner core (20), an inner focusing lens coil (22) disposed on the focusing lens inner core (20), and a focusing lens outer core (8) disposed around the inner focusing lens coil (22) 21) and,
An outer focusing lens coil (23) is disposed between the inner focusing lens coil (22) and the focusing lens outer core (21),
A focusing lens (2), wherein the outer focusing lens coil (23) comprises two focusing lens wire portions (23a, 23b) having the same number of turns.   The two said focusing of the two objective lens wire portions (13a, 13b) of the outer objective lens coil (13) of the objective lens (1) or the outer focusing lens coil (23) of the focusing lens (2) Objective lens (1) according to claim 1 or focusing lens (2) according to claim 2, wherein the lens wire portions (23a, 23b) are respectively wound in opposite directions. A focusing lens (2) for an x-ray tube, in particular for a microfocus x-ray tube,
A focusing lens inner core (20), an inner focusing lens coil (22) disposed on the focusing lens inner core (20), and a focusing lens outer core (8) disposed around the inner focusing lens coil (22) 21) and,
A focusing lens (2), wherein the inner focusing lens coil (22) comprises an even number of magnetic wire segments (22a, 22b, 22c, 22d) each having the same number of turns.   The focusing lens (2) according to claim 4, wherein the number of the magnetic field wire parts (22a, 22b, 22c, 22d) is four. An x-ray tube, in particular a microfocus x-ray tube,
An objective lens (1) according to claim 1 or 3 and a focusing lens (2) according to any one of claims 2, 4 or 5.
The outer objective lens coil (13) is connected to a first filament current source and / or the outer focusing lens coil (23) is connected to a second filament current source, The first and second filament current sources generate magnetic fields in which the two objective lens wire portions (13a, 13b) of the outer objective lens coil (13) cancel each other, and / or the outer focusing An X-ray tube, mounted such that the two focusing lens wire portions (23a, 23b) of the lens coil (23) generate magnetic fields that cancel each other.   The two objective lens wire portions (13a, 13b) of the outer objective lens coil (13) and / or the two focusing lens wire portions (23a, 23b) of the outer focusing lens coil (23) are connected in series An x-ray tube according to claim 6, in combination with claim 3.   At least one of the filament current sources is connected to a control system, which is connected to a temperature sensor which measures the temperature of the objective lens (1) and / or the focusing lens (2) An X-ray tube according to claim 6, 7 or 8.   An X-ray tube, in particular a microfocus X-ray tube, provided with a focusing lens (2) according to any one of claims 2, 4 or 5, wherein a magnetic field source (4) is present, said magnetic field An x-ray tube, wherein a source (4) is connected to the inner focusing lens coil (22).   A method of operating an X-ray tube, in particular a microfocus X-ray tube, according to any one of claims 6 to 9, wherein the individual magnetic field wire portions (22a, 22b) of the inner focusing lens coil (22) , 22c, 22d) cancel each other in the first mode of operation and are all summed together in the second mode of operation.   The method according to claim 10, wherein the magnetic fields of the individual magnetic wire segments (22a, 22b, 22c, 22d) of the inner focusing lens coil (22) partially cancel each other in a third mode of operation.

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