A method for enabling an open X-ray tube to have multiple operating modes

Abstract

The present invention provides a method for enabling an open X-ray tube to have multiple working modes, comprising the following steps: S1: designing a two-stage magnetic focusing lens in the open X-ray tube according to the principle of electron optics; S2: controlling the working current of the two-stage magnetic lens to control the size of the magnetic field generated by it, affecting its focusing effect on the electron beam, thereby realizing multiple different working modes, solving the problem that the traditional open micro-focus X-ray tube has a single working mode and limited application scenarios, and realizing three different working modes by using electron optics in the open micro-focus X-ray tube with the same physical structure, thereby enriching the application scenarios of the open micro-focus X-ray tube.

Description

Technical Field

[0001] The present invention relates to the technical field of X-ray tubes, and in particular to a method for enabling an open X-ray tube to have multiple working modes. Background Art

[0002] Microfocus X-ray tubes can be divided into closed microfocus X-ray tubes (closed tubes) and open microfocus X-ray tubes (open tubes) according to their physical structure. The closed tubes have been evacuated to a high vacuum and sealed when leaving the factory. Due to the limited internal space, an electrostatic lens is used to focus the electron beam to form a microfocus spot on the target surface. When the internal components are damaged, they can only be replaced as a whole. Although the open tubes need to be evacuated during use, the components are easy to replace when damaged, and because the internal space is larger, a multi-stage electromagnetic focusing system can be used to achieve a smaller focus, with higher image resolution and greater magnification. However, the traditional open tube working mode is relatively simple and the application scenarios are relatively limited. Summary of the invention

[0003] The present invention discloses a method for enabling an open X-ray tube to have multiple working modes, which solves the problem that the traditional open microfocus X-ray tube has a single working mode and limited application scenarios. In an open microfocus X-ray tube with the same physical structure, three different working modes are realized by using electron optics, thereby enriching the application scenarios of the open microfocus X-ray tube.

[0004] To achieve the above object, the technical solution of the present invention is specifically implemented as follows:

[0005] The present invention discloses a method for enabling an open X-ray tube to have multiple working modes, comprising the following steps:

[0006] S1: Design a two-stage magnetic focusing lens in an open X-ray tube based on the principle of electron optics;

[0007] S2: Control the working current of the two-stage magnetic lens to control the size of the magnetic field it generates, affecting its focusing effect on the electron beam, thereby realizing a variety of different working modes.

[0008] Furthermore, the optical path of the optical system of the two-pole magnetic focusing lens designed in the open X-ray tube must meet the following requirements:

[0009] L1+L2=L

[0010]

[0011]

[0012]

[0013] Among them, L1 is the distance from the cross spot to the first-stage magnetic lens, L2 is the distance between the first-stage magnetic lens and the second-stage magnetic lens, L is the total length of the optical system, V1 is the image distance of the first-stage magnetic lens, f0 is the focal length of the second-stage magnetic lens, f1 is the focal length of the first-stage magnetic lens, m is the total magnification of the optical system, and L0 is the distance between the second-stage magnetic lens and the target.

[0014] Furthermore, the S2 specifically includes the following steps:

[0015] S21: Calculate the electromagnetic field distribution inside an open X-ray tube using the finite element analysis method;

[0016] S22: Solve the trajectory of an electron based on its equation of motion in an electromagnetic field;

[0017] S23: according to the focusing requirements of different working modes, changing the excitation current of the two-stage magnetic lens, thereby changing the electromagnetic field distribution inside the open X-ray tube, and further changing the motion trajectory of the electron beam to achieve different focusing targets;

[0018] S24: Through electronic optical simulation calculation and combined with actual testing, the excitation current corresponding to multiple working modes under any working voltage is obtained.

[0019] Furthermore, the method can enable the open X-ray tube to operate in any one of the submicron focus mode, micro focus mode and high power mode.

[0020] Furthermore, when the open X-ray tube operates in the submicron focus mode, the two-stage magnetic lenses both operate normally, and the cross spot is first focused by the first-stage magnetic lens to form a secondary cross spot; the secondary cross spot forms an extremely small focus on the transmission target surface under the strong focusing of the second-stage magnetic lens.

[0021] Furthermore, when the open X-ray tube works in the microfocus mode, the first-stage magnetic lens does not work, while the second-stage magnetic lens works normally, and the cross spot is strongly focused by the second-stage magnetic lens to form a micrometer-level focus on the transmission target surface.

[0022] Furthermore, when the open X-ray tube operates in high power mode, both the two-stage magnetic lenses work normally, the cross spot is first formed into a parallel beam after weak focusing by the first-stage magnetic lens, and the parallel beam forms a micro-focus spot on the target surface under the focusing of the second-stage magnetic lens.

[0023] Beneficial technical effects:

[0024] 1. The present invention discloses a method for making an open X-ray tube have multiple working modes, comprising the following steps: S1: designing a two-stage magnetic focusing lens in the open X-ray tube according to the principle of electron optics; S2: controlling the working current of the two-stage magnetic lens to control the size of the magnetic field generated by it, affecting its focusing effect on the electron beam, thereby realizing multiple different working modes, solving the problem that the traditional open micro-focus X-ray tube has a single working mode and limited application scenarios, and realizing three different working modes by using electron optics in the open micro-focus X-ray tube with the same physical structure, thereby enriching the application scenarios of the open micro-focus X-ray tube;

[0025] 2. In the present invention, the open X-ray tube can work in submicron focus mode. This working mode is more suitable for detection equipment that requires extremely high resolution. The imaging accuracy is very high, and the limit resolution is below 1 micron. It has important applications in related detection of the Wiener semiconductor industry.

[0026] 3. In the present invention, the open X-ray tube can work in the micro-focus mode, which is the most widely used open tube mode at present, and is mainly used in lithium battery new energy, electronic industry, etc. Under the premise of ensuring a certain target power, the resolution is also guaranteed, and a resolution better than 2 microns can be achieved;

[0027] 4. In the present invention, the open X-ray tube can work in high-power mode, which is more suitable for detecting some high-density or thicker samples. By increasing the focus, the target power can be increased to tens of watts, and the image clarity and contrast are higher;

[0028] 5. In the present invention, three different working modes are realized by using electron optics in an open microfocus X-ray tube with the same physical structure: submicron focus mode, microfocus mode and high power mode, which enriches the application scenarios of the open microfocus X-ray tube and improves the universality of the open microfocus X-ray tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0030] Figure 1 A flowchart of the steps of a method for enabling an open X-ray tube to have multiple operating modes according to the present invention;

[0031] Figure 2 Design schematic diagram for the secondary magnetic lens system;

[0032] Figure 3 for Figure 1 Flow chart of the specific steps of S2;

[0033] Figure 4Schematic diagram of the electron optical light path in three modes. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] First of all, it should be explained that the condenser in the embodiment is the first-stage magnetic lens, and the objective lens is the second-stage magnetic lens. For simplicity, the condenser and objective lens are used to describe the embodiment.

[0037] The present invention discloses a method for enabling an open X-ray tube to have multiple operating modes, see Figure 1 , the method specifically comprises the following steps:

[0038] S1: Design a two-stage magnetic focusing lens in an open X-ray tube based on the principle of electron optics;

[0039] Specifically, the optical path of the optical system of the two-pole magnetic focusing lens designed in the open-type X-ray tube must meet the following requirements:

[0040] L1+L2=L

[0041]

[0042]

[0043]

[0044] Among them, L1 is the distance from the cross spot to the condenser (first-stage magnetic lens), L2 is the distance between the condenser and the objective lens (second-stage magnetic lens), L is the total length of the optical system, V1 is the image distance of the condenser, f0 is the focal length of the objective lens, f1 is the focal length of the condenser, m is the total magnification of the optical system, and L0 is the distance between the objective lens and the target.

[0045] Specifically, in the optimization design of electron optics, the position arrangement of the magnetic lens is a very important topic. It is necessary to determine the optimal relative position of the two magnetic lenses under certain conditions. For a two-stage magnetic focusing X-ray tube, the total magnification m of the electron optical system, the distance L0 between the objective lens and the target, and the total length L of the system are determined by human design, see Figure 2, can be considered as a known quantity in the calculation of electron optics. When the two-lens system can achieve the minimum magnification, the focus of the electron beam on the ray tube is the smallest. At this time, the optical path of the system should satisfy:

[0046] L1+L2=L

[0047]

[0048]

[0049]

[0050] At this time, the focal length of the condenser is f1, and the focal length of the objective lens is f0. The above equations are rearranged with f1 as the variable;

[0051] (L0+mf1)V1 2 -(2L0+mL)f1V1+(L0+mL)f1 2 =0

[0052] If the optimization condition f1 is maximized, then Δ of the above equation is 0. At this time:

[0053]

[0054]

[0055]

[0056]

[0057] Under the optimized condition of maximum f1, the spacing between the secondary magnetic lens systems should be equal.

[0058] Usually, the cross spot diameter produced by the tungsten filament emission cathode at 160kV is about 25μm. Assuming that the diameter of the beam spot we need to produce on the target surface is 1μm, considering the influence of spherical aberration, the Gaussian image spot diameter on the target surface should be Therefore, the magnification The position parameters of the condenser and objective lens will be determined, and the structure of the condenser and objective lens will be designed in combination with the magnification and focal length.

[0059] S2: Controlling the working current of the two-stage magnetic lens to control the magnitude of the magnetic field generated by the lens, thereby affecting the focusing effect of the lens on the electron beam, thereby realizing a variety of different working modes;

[0060] Specifically, the focal length of the magnetic lens is determined by the number of turns N of the magnetic lens coil, the current I, the aperture D of the magnetic lens pole shoe, and the gap S of the magnetic lens pole shoe. At the same time, these parameters also determine the spherical aberration of the magnetic lens. After optimization, the structure of the condenser and the objective lens will be determined, that is, the value of S / D has been fixed, and the number of turns of the magnetic lens coil will also be fixed according to the actual situation. Only the current I of the magnetic lens coil can be changed.

[0061] By controlling the working current of the two-stage magnetic lens, a variety of different working modes are realized, which specifically include the following steps: Figure 3 :

[0062] S21: Calculate the electromagnetic field distribution inside an open X-ray tube using the finite element analysis method;

[0063] S22: Solve the trajectory of an electron based on its equation of motion in an electromagnetic field;

[0064] S23: according to the focusing requirements of different working modes, changing the excitation current of the two-stage magnetic lens, thereby changing the electromagnetic field distribution inside the open X-ray tube, and further changing the motion trajectory of the electron beam to achieve different focusing targets;

[0065] By adjusting the exciting current of the magnetic lens coil, the open X-ray tube can be operated in any of the sub-micron focus mode, micro focus mode and high power mode.

[0066] When the open X-ray tube works in the submicron focus mode, both the two-stage magnetic lenses work normally, and the cross spot is first focused by the first-stage magnetic lens to form a secondary cross spot; the secondary cross spot forms a very small focus on the transmission target surface under the strong focus of the second-stage magnetic lens. In this mode, the magnification of the system is the smallest, but because the focus size is extremely small in this mode, in order to prevent the target material from being burned due to high power density, the target power that the target can withstand is the smallest; the submicron focus mode is more suitable for detection equipment that requires extremely high resolution. Although the power is small, the imaging accuracy is very high, and the limit resolution is below 1 micron, which has important applications in related detection of the Wiener semiconductor industry;

[0067] When the open X-ray tube works in the micro-focus mode, the first-stage magnetic lens does not work, while the second-stage magnetic lens works normally. The cross-spot is strongly focused by the second-stage magnetic lens to form a micron-level focus on the transmission target surface. In this mode, the system magnification is very small, and the target power is in the middle of the three modes. The micro-focus mode is also the most widely used open tube mode, mainly in lithium battery new energy, electronics industry, etc. Under the premise of ensuring a certain target power, the resolution is also guaranteed, and a resolution better than 2 microns can be achieved;

[0068] When the open X-ray tube works in high-power mode, both the two-stage magnetic lenses work normally, and the cross spot is first formed into a parallel beam after weak focusing by the first-stage magnetic lens, and the parallel beam forms a micro-focus spot on the target surface under the focusing of the second-stage magnetic lens; the high-power mode is more suitable for the detection of some high-density or thicker samples. By increasing the focus, the target power can be increased to tens of watts, and the image clarity and contrast are higher.

[0069] In short, for the three working modes of the two-stage magnetic lens, the working state of the condenser and the objective lens under a certain tube voltage is determined by the coil current. By applying a suitable coil current, the focal length and performance of the magnetic lens can reach the designed state, thereby realizing the rapid switching of the three modes, see Figure 4 , two groups of magnetic lenses work at the same time, and the focal size is the smallest, which corresponds to the submicron focus mode. However, since the large divergence angle electrons generated after two strong focusing will increase the aberration, it is necessary to set an aperture to limit the electron beam half angle, but this will lose the beam current, the number of electrons reaching the target will be reduced, and the target power will be greatly reduced; when a higher beam current is required, the micro focus mode can be used, that is, only the objective lens works. At this time, the beam current that can reach the target is increased, and the focal size is increased compared with mode 1; when a larger target power is required for imaging, the condenser can focus the electron book into a parallel beam to ensure that a large number of electrons can pass through the aperture, and finally the objective lens is focused on the target. This mode corresponds to the high power mode. Although the focus is the largest among the three modes, the target power is also the highest.

[0070] S24: Through electronic optical simulation calculation and combined with actual testing, the excitation current corresponding to multiple working modes under any working voltage is obtained.

[0071] Specifically, an open X-ray tube has three operating modes at any operating voltage: submicron focus mode, micro focus mode and high power mode. When the operating voltage changes, the lens control parameters (excitation current) corresponding to each mode change accordingly, and the changes can be obtained through electronic optical calculations.

[0072] The present invention discloses a method for making an open X-ray tube have multiple working modes. In an open X-ray tube with the same physical structure, different working modes, namely, submicron focus mode, micro focus mode and high power mode, are realized by using electron optics, thereby enriching the application scenarios of the open X-ray tube. The same open X-ray tube can work in three different modes, thereby reducing the application cost from the side.

[0073] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0074] The above embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for enabling an open X-ray tube to have multiple operating modes, characterized in that: The following steps are involved: S1: Design a two-stage magnetic focusing lens in an open X-ray tube based on the principle of electron optics; S2: Control the working current of the two-stage magnetic focusing lens to control the size of the magnetic field it generates, thereby affecting its focusing effect on the electron beam, thereby achieving a variety of different working modes.

2. A method for enabling an open X-ray tube to have multiple operating modes according to claim 1, characterized in that: The optical path of the optical system of the two-pole magnetic focusing lens designed in the open X-ray tube must meet the following requirements: Among them, L1 is the distance from the cross spot to the first-stage magnetic lens, L2 is the distance between the first-stage magnetic lens and the second-stage magnetic lens, L is the total length of the optical system, V1 is the image distance of the first-stage magnetic lens, f0 is the focal length of the second-stage magnetic lens, f1 is the focal length of the first-stage magnetic lens, m is the total magnification of the optical system, and L0 is the distance between the second-stage magnetic lens and the target.

3. The method for enabling an open X-ray tube to have multiple operating modes according to claim 1, characterized in that: The S2 specifically includes the following steps: S21: Calculate the electromagnetic field distribution inside an open X-ray tube using the finite element analysis method; S22: Solve the trajectory of an electron based on its equation of motion in an electromagnetic field; S23: according to the focusing requirements of different working modes, changing the excitation current of the two-stage magnetic focusing lens, thereby changing the electromagnetic field distribution inside the open X-ray tube, and further changing the motion trajectory of the electron beam to achieve different focusing targets; S24: Through electronic optical simulation calculation and combined with actual testing, the excitation current corresponding to multiple working modes under any working voltage is obtained.

4. The method for enabling an open X-ray tube to have multiple operating modes according to claim 1, characterized in that: The method can enable the open X-ray tube to operate in any one of the submicron focus mode, micro focus mode and high power mode.

5. The method for enabling an open X-ray tube to have multiple operating modes according to claim 4, characterized in that: When the open X-ray tube works in the submicron focus mode, the two-stage magnetic focusing lenses both work normally, and the cross spot is first focused by the first-stage magnetic lens to form a secondary cross spot; the secondary cross spot forms an extremely small focus on the transmission target surface under the strong focusing of the second-stage magnetic lens.

6. The method for enabling an open X-ray tube to have multiple operating modes according to claim 4, characterized in that: When the open X-ray tube works in the microfocus mode, the first-stage magnetic lens does not work, while the second-stage magnetic lens works normally. The cross spot is strongly focused by the second-stage magnetic lens to form a micrometer-level focus on the transmission target surface.

7. The method for enabling an open X-ray tube to have multiple operating modes according to claim 4, characterized in that: When the open X-ray tube works in high power mode, both the two-stage magnetic focusing lenses work normally, and the cross spot is first formed into a parallel beam after weak focusing by the first-stage magnetic lens, and the parallel beam forms a micro-focus spot on the target surface under the focusing of the second-stage magnetic lens.

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