An X-ray measurement spot collimation system

Abstract

The present invention discloses an X-ray measurement spot collimation system, which relates to the field of X-ray collimation. The system includes: an X-ray source, a transmitting end collimator, a receiving end collimator, and a ray detector. When the collimation system is in operation, first, after the cone beam of rays emitted by the X-ray source passes through the transmitting end collimator with a funnel-shaped window cross section, the X-rays are initially collimated so that the light spot on the sample to be measured has the desired shape. Secondly, after passing through the sample to be measured, the rays will pass through the receiving end collimator with a trapezoidal window cross section to shield scattered rays. Finally, the collimated ray beam reaches the X-ray detector to obtain the final ray intensity. The present invention can control the size and shape of the light spot measured by the system, ensure the spatial resolution of the system measurement, and minimize the influence of scattered rays while ensuring that the collimated main beam of rays is received by the ionization chamber as much as possible after passing through the pole piece, thereby improving the ray utilization rate and thus improving the measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of X-ray collimation, and in particular to an X-ray measurement spot collimation system. Background Art

[0002] The X-ray transmission measurement method can be used to measure the thickness or surface density of an object. During the measurement process, X-rays are irradiated on the surface of the sample to be measured. Their intensity will be attenuated when passing through the sample to be measured. The intensity of the attenuated rays is measured using the corresponding detector. The thickness or surface density of the sample to be measured can then be calculated based on the known initial intensity of the rays.

[0003] X-ray transmission thickness measuring equipment has a simple structure and strong anti-interference ability. Compared with beta-ray thickness measuring equipment, its radiation dose is lower, and it is more suitable for measuring items such as thin films and pole pieces with lower thickness, for example, the surface density detection of the positive electrode coating of lithium batteries. Through the X-ray transmission measurement method, the surface density of the positive electrode coating of lithium batteries can be measured, so as to detect its coating uniformity. However, in this scheme, due to the cone beam shape of the X-ray measurement beam itself, there is a situation where the measurement spot is large, resulting in a low measurement spatial resolution, especially when measuring the surface density of the coating edge, there are relevant requirements for the size and shape of the measurement spot. In addition, the scattered rays generated when the rays interact with the air and the sample to be measured will have a certain impact on the measurement results, thereby affecting the accuracy of the measurement results. Summary of the Invention

[0004] The present invention aims to address the deficiencies of the above-mentioned prior art and provides an X-ray measurement spot collimation system, which is intended to control the size of the measurement spot by collimating and shielding the X-rays, thereby improving the measurement spatial resolution while reducing the impact of scattered rays on the measurement results and improving the measurement accuracy.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical solutions:

[0006] The X-ray measurement spot collimation system of the present invention is characterized by comprising:

[0007] An X-ray source, used for emitting X-rays of intensity required for corresponding measurement;

[0008] An emitting end collimator is provided at a certain distance below the beryllium window of the X-ray source, and the window shape of the emitting end collimator is the light spot shape required by the sample to be tested, and the window cross section is funnel-shaped; and is used to collimate the cone beam of X-rays and then incident on the sample to be tested, so that the light spot on the sample to be tested is collimated into the required shape;

[0009] The receiving end collimator is set at a certain distance below the transmitting end collimator. The window shape of the receiving end collimator is the light spot shape required by the sample to be tested. The cross section of the window is trapezoidal. It is used to shield the scattered rays generated by the X-rays after the initial collimation after passing through the sample to be tested, and receive the X-rays that have been re-collimated after passing through the sample to be tested;

[0010] The X-ray detector has a detection window located below the collimator at the receiving end and is used to measure the intensity of the re-collimated X-rays.

[0011] The X-ray measurement spot collimation system of the present invention is also characterized in that the cross section of the emission end collimator is funnel-shaped, the exit wall is perpendicular to the exit window, and the angle between the incident wall and the exit wall is , the exit window is the spot shape required by the sample to be tested; and the incident window of the collimator at the emitting end is larger than the exit window;

[0012] When the light spot shape required by the sample to be tested is rectangular, the opening length of the exit window of the collimator at the emission end is ,width ;in, 、 are the length and width of the light spot required for the sample to be tested, is the distance from the focus of the X-ray source to the exit window of the collimator at the emission end, is the distance from the focus of the X-ray source to the sample to be measured;

[0013] When the light spot shape required by the sample to be tested is circular, the exit window of the collimator at the emission end is circular, and its opening radius is ,in, The radius of the light spot required for the sample to be measured;

[0014] When the light spot required by the sample to be tested is rectangular, the length of the incident window of the emitting end collimator is ,width ;in, is the thickness of the collimator at the transmitting end, is the thickness of the exit wall of the collimator at the emitting end;

[0015] When the light spot required by the sample to be tested is circular, the radius of the incident window of the collimator at the emitting end is .

[0016] Furthermore, the incident window of the collimator at the receiving end is in the shape of a light spot required by the sample to be measured;

[0017] When the light spot shape required by the sample to be tested is rectangular, the incident window of the receiving end collimator is rectangular, and its opening length is , width ;in, 、 are the length and width of the exit window of the collimator at the transmitting end, is the distance from the focus of the X-ray source to the incident window of the collimator at the receiving end;

[0018] When the light spot shape required by the sample to be measured is circular, the incident window radius of the receiving end collimator is .

[0019] Furthermore, the exit window of the collimator at the receiving end is in the shape of a light spot required by the sample to be measured; and the size of the exit window of the collimator at the receiving end is larger than the size of the incident window;

[0020] When the light spot shape required by the sample to be tested is rectangular, the opening length of the exit window of the collimator at the receiving end is ,width ,in, is the thickness of the collimator at the receiving end;

[0021] When the light spot shape required by the sample to be tested is circular, the exit window radius of the collimator at the receiving end is .

[0022] Furthermore, the photon energy of the scattered rays shielded by the collimator at the receiving end is obtained using formula (1): :

[0023] (1)

[0024] In formula (1), is the photon energy of the X-ray after initial collimation; is the static energy of the electron; is the angle between the collimated X-ray direction and the scattered ray direction.

[0025] Furthermore, the intensity of the X-ray after re-collimation is obtained using formula (2): :

[0026] (2)

[0027] In formula (2), is the intensity of the X-ray after initial collimation; is the mass absorption coefficient of the sample to be tested, is the thickness of the sample to be tested.

[0028] Compared with the prior art, the present invention is beneficial in that:

[0029] 1. The present invention uses a two-stage collimation structure to collimate X-rays through a collimating window at the emission end with a funnel-shaped window cross-section, so that the light spot on the sample to be measured is collimated into a long strip. While controlling the size and shape of the measurement spot, the utilization rate of the X-rays is ensured, and the accuracy of the measurement results is improved while ensuring the spatial resolution of the system measurement.

[0030] 2. During the actual measurement process, X-rays will generate scattered rays in the air and when passing through the sample to be measured. The present invention designs a receiving-end collimator located between the X-ray detector and the sample to be measured based on the shape of the X-ray measurement beam after being collimated by the transmitting-end collimator during the measurement process. This shields the scattered rays generated during the measurement process while ensuring that the measurement beam of the rays is completely absorbed by the X-ray detector as much as possible, reducing the impact of scattered rays on the measurement results and improving measurement accuracy.

[0031] 3. The receiving end collimator of the present invention not only shields scattered rays but also avoids direct exposure of the detection window to the external environment, plays a dust-proof role, reduces the influence of the external environment on the measurement results, and improves the anti-interference ability of the measurement system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a structural diagram of the X-ray transmission measurement method system used in the present invention;

[0033] Figure 2 Schematic diagram of the two-stage collimation structure of the present invention;

[0034] Figure 3a A diagram showing the simulation results of the particle distribution on the sample to be tested and the detector window surface in the X-ray collimation system constructed according to the present invention and based on the Monte Carlo method simulation (broadside);

[0035] Figure 3b A diagram showing the simulation results of the particle distribution on the sample to be tested and the detector window surface in the X-ray collimation system constructed according to the present invention and simulated based on the Monte Carlo method (narrow edge);

[0036] Figure 4a A graph showing the particle spatial distribution simulation results of an X-ray collimation system constructed according to the present invention and simulated based on the Monte Carlo method (broadside);

[0037] Figure 4b A graph showing the particle spatial distribution simulation results of an X-ray collimation system constructed according to the present invention and simulated based on the Monte Carlo method (broadside);

[0038] Figure numerals: 1, X-ray source; 2, transmitting end collimator; 3, transmitting end housing; 4, sample to be measured; 5, receiving end collimator; 6, X-ray detector; 7, receiving end housing. DETAILED DESCRIPTION

[0039] In this embodiment, in order to solve the problems of large measurement spot, low spatial resolution and the influence of scattered rays on the measurement results when using the X-ray transmission method, an X-ray measurement spot collimation system is designed. The system includes an X-ray source, a transmitting end collimator, a receiving end collimator and an X-ray detector. In the actual measurement process, each component is arranged in sequence from top to bottom in the vertical direction, such as Figure 1 As shown:

[0040] The X-ray source is used to emit X-rays of the intensity required for the corresponding measurement. It is a tungsten target ultrasoft X-ray source with a tube voltage of 5 kV, a target angle of 20°, a focal spot size of 0.6 × 0.6 mm, and a distance from the focal spot to the beryllium window of 20 mm;

[0041] The emission end collimator is arranged at a certain distance below the beryllium window of the X-ray source, and the window shape of the emission end collimator is the light spot shape required by the sample to be tested, and the window cross section is funnel-shaped; and is used to collimate the cone beam of X-rays and then incident on the sample to be tested, so that the light spot on the sample to be tested is collimated into the required shape;

[0042] The receiving end collimator is set at a certain distance below the transmitting end collimator. The window shape of the receiving end collimator is the light spot shape required by the sample to be tested. The cross section of the window is trapezoidal. It is used to shield the scattered rays generated by the X-rays after the initial collimation after passing through the sample to be tested, and receive the X-rays that have been re-collimated after passing through the sample to be tested;

[0043] The X-ray detector, with its detection window located below the collimator at the receiving end, is used to measure the intensity of the re-collimated X-rays. In this embodiment, the ionization chamber used can measure the intensity of X-rays with energies above 4 keV, with a sensitivity of 0.6 nA / GBq and a leakage current of less than 0.1 pA.

[0044] The X-rays emitted by the X-ray source will first pass through the collimator at the transmitting end. After being collimated, the rays will form a long strip of measurement spot on the sample to be measured, so as to control the size and shape of the measurement spot. After being attenuated by the sample to be measured, the X-rays will pass through the collimator at the receiving end. At this time, the scattered rays not required for measurement will be shielded, and the main beam of rays required for measurement will be received by the X-ray detector below the collimator at the receiving end, and the intensity of the main beam after attenuation by the sample to be measured will be obtained.

[0045] In this embodiment, the cross section of the emitting end collimator is funnel-shaped, and its exit wall is perpendicular to the exit window, and the angle between the incident wall and the exit wall is , the exit window is the spot shape required by the sample to be tested;

[0046] When the light spot shape required by the sample to be tested is rectangular, the opening length of the exit window is ,width ;in, 、 are the length and width of the light spot required for the sample to be tested, is the distance from the focus of the X-ray source to the exit window of the collimator at the emission end, is the distance from the focus of the X-ray source to the sample to be measured;

[0047] When the light spot shape required by the sample to be measured is circular, the exit window is circular, and its opening radius is ,in, The radius of the light spot required for the sample to be measured;

[0048] The incident window of the collimator at the transmitting end is larger than the exit window. When the light spot required by the sample to be tested is rectangular, the incident window length is ,width ;in, is the thickness of the collimator at the transmitting end, is the thickness of the collimator exit wall at the transmitting end;

[0049] When the light spot required for the sample to be measured is circular, the incident window radius .

[0050] In this embodiment, if Figure 2 As shown in the figure, the thickness of the emitter collimator is 3 mm, the incident window is rectangular, the opening size is 12×5 mm, the incident wall is at an angle of 45° to the horizontal direction of the window, and the thickness is 2 mm; the exit window is rectangular, the opening size is 8×1 mm, the exit wall is perpendicular to the window, and the thickness is 1 mm. The emitter collimator is made of lead and is used to collimate and shield the X-rays emitted by the ray source, so that the spot irradiated on the sample to be tested is collimated into a rectangle. The simulation results of the spot size after collimation by the emitter collimator are shown in the figure. Figure 3a and Figure 3b As shown in Figure 1, the spot size of the ray on the sample to be tested is about 10×1.2mm. The simulation results of the spot size after collimation by the collimator at the transmitting end are shown in Figure 1. Figure 3a and Figure 3b As shown in the figure, the spot size of the ray on the sample to be measured is about 1.2×10 mm.

[0051] The incident window of the collimator at the receiving end is the spot shape required by the sample to be tested. When the spot shape required by the sample to be tested is rectangular, the incident window is rectangular and its opening length is , width ;in, 、 are the length and width of the exit window of the collimator at the transmitting end, is the distance from the focus of the X-ray source to the incident window of the collimator at the receiving end;

[0052] When the spot shape required by the sample to be measured is circular, the radius of the incident window of the collimator at the receiving end is .

[0053] The exit window of the collimator at the receiving end is the spot shape required by the sample to be tested. When the spot shape required by the sample to be tested is rectangular, the opening length of the exit window is ,width ,in, is the thickness of the collimator at the receiving end;

[0054] When the spot shape required by the sample to be measured is circular, the radius of the collimator exit window at the receiving end is .

[0055] In this embodiment, the exit window size of the receiving end collimator is larger than the incident window size. The receiving end collimator is 3 mm thick and made of lead. The entrance window opening size is 11.2×1.4 mm, and the exit window opening size is 12.16×1.52 mm. The photon spatial distribution of the X-ray collimation system during the measurement process is shown in the figure. Figure 4a and Figure 4b shown.

[0056] X-rays will scatter when they are in the air and when they pass through the sample to be measured. For photons with energy less than 1.02MeV, the main forms of interaction between X-rays and matter are: photoelectric effect, Compton effect and electron pair effect. Among them, the electron pair effect will only occur when the ray energy is greater than 1.02MeV. For photons with energy less than 1.02MeV, the main forms of interaction with matter are photoelectric effect and Compton effect. Among them, the Compton effect will produce scattered rays that are not required for measurement. Scattered rays are the inevitable product of the interaction between photons and matter. They have no fixed radiation direction, and compared with primary rays, their energy is reduced and the wavelength is longer. The photon energy of the scattered rays shielded by the collimator at the receiving end is obtained using formula (1): :

[0057] (1)

[0058] In formula (1), is the photon energy of the X-ray after initial collimation; is the static energy of the electron; is the angle between the collimated X-ray direction and the scattered ray direction.

[0059] The intensity of the X-ray after re-collimation is obtained using formula (2): :

[0060] (2)

[0061] In formula (2), is the intensity of the X-ray after initial collimation; is the mass absorption coefficient of the sample to be tested, is the thickness of the sample to be measured. In the actual measurement process, it is necessary to first The value of is calibrated, and then the thickness or surface density of the sample to be tested is calculated according to formula (2).

Claims

1. An X-ray measurement spot collimation system, characterized in that: include: An X-ray source, used for emitting X-rays of intensity required for corresponding measurement; An emitting end collimator is provided at a certain distance below the beryllium window of the X-ray source, and the window shape of the emitting end collimator is the light spot shape required by the sample to be tested, and the window cross section is funnel-shaped; and is used to collimate the cone beam of X-rays and then incident on the sample to be tested, so that the light spot on the sample to be tested is collimated into the required shape; The cross section of the emission end collimator is funnel-shaped, and its exit wall is perpendicular to the exit window, and the angle between the incident wall and the exit wall is , the exit window is the spot shape required by the sample to be tested; and the incident window of the collimator at the emitting end is larger than the exit window; A receiving-end collimator is disposed at a certain distance below the transmitting-end collimator, and the shape of the window of the receiving-end collimator is the light spot shape required by the sample to be tested. The cross-section of the window is trapezoidal, and is used to shield the scattered rays generated by the X-rays after the initial collimation after passing through the sample to be tested, and to receive the X-rays that are collimated again after passing through the sample to be tested; the incident window of the receiving-end collimator is the light spot shape required by the sample to be tested; the exit window of the receiving-end collimator is the light spot shape required by the sample to be tested; and the size of the exit window of the receiving-end collimator is larger than the size of the incident window; The X-ray detector has a detection window located below the collimator at the receiving end and is used to measure the intensity of the re-collimated X-rays.

2. The X-ray measurement spot collimation system according to claim 1, characterized in that: When the light spot shape required by the sample to be tested is rectangular, the opening length of the exit window of the collimator at the emission end is ,width ;in, 、 are the length and width of the light spot required for the sample to be tested, is the distance from the focus of the X-ray source to the exit window of the collimator at the emission end, is the distance from the focus of the X-ray source to the sample to be measured; When the light spot shape required by the sample to be tested is circular, the exit window of the collimator at the emission end is circular, and its opening radius is ,in, The radius of the light spot required for the sample to be measured; When the light spot required by the sample to be tested is rectangular, the length of the incident window of the emitting end collimator is ,width ;in, is the thickness of the collimator at the transmitting end, is the thickness of the exit wall of the collimator at the emitting end; When the light spot required by the sample to be tested is circular, the radius of the incident window of the collimator at the emitting end is .

3. The X-ray measurement spot collimation system according to claim 2, characterized in that: When the light spot shape required by the sample to be tested is rectangular, the incident window of the receiving end collimator is rectangular, and its opening length is , width ;in, 、 are the length and width of the exit window of the collimator at the transmitting end, is the distance from the focus of the X-ray source to the incident window of the collimator at the receiving end; When the light spot shape required by the sample to be measured is circular, the incident window radius of the receiving end collimator is .

4. The X-ray measurement spot collimation system according to claim 3, characterized in that: When the light spot shape required by the sample to be tested is rectangular, the opening length of the exit window of the collimator at the receiving end is ,width ,in, is the thickness of the collimator at the receiving end; When the light spot shape required by the sample to be tested is circular, the exit window radius of the collimator at the receiving end is .

5. The X-ray measurement spot collimation system according to claim 1, characterized in that: The photon energy of the scattered rays shielded by the collimator at the receiving end is obtained using formula (1): : (1) In formula (1), is the photon energy of the X-ray after initial collimation; is the static energy of the electron; is the angle between the collimated X-ray direction and the scattered ray direction.

6. The X-ray measurement spot collimation system according to claim 1, characterized in that: The intensity of the X-ray after re-collimation is obtained using formula (2): : (2) In formula (2), is the intensity of the X-ray after initial collimation; is the mass absorption coefficient of the sample to be tested, is the thickness of the sample to be tested.

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