A method of measuring the thickness of an internal scintillator of a probe

Abstract

The application discloses a kind of measurement methods of the thickness of probe internal scintillator, it includes the following steps: a. using probe to the wide energy spectrum X light that ordinary X ray light source shoots is detected, the calculation formula of count value I read out by probe;B. formula is simplified and is exposed at least twice, wherein first exposure obtains I 1, change the energy spectrum that reaches probe, and exposure is carried out for the second time to obtain I 2;C. the obtained formula is solved optimally, and the thickness of scintillator is obtained.The application can obtain the thickness of scintillator without disassembling probe;Without contacting scintillator, scintillator will not be damaged;When measuring, scintillator has been encapsulated, and there is no risk of performance degradation of scintillator caused by measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of measurement methods of the thickness of the scintillator inside detector. BACKGROUND

[0002] The thickness of the scintillator affects the absorption efficiency, MTF and other performance parameters of the detector, and is one of the most important control indicators in the production of the detector, so it is necessary to measure the thickness of the scintillator. The existing scintillator measurement methods include scanning electron microscope and micrometer measurement.

[0003] When measuring the scintillator with a scanning electron microscope, the following steps are usually taken: 1. Use a knife to cut the scintillator together with the substrate into small pieces about 1 cm in size; 2. Place the prepared sample on the test tool table and fix it; 3. Place the tool table in the evaporation chamber and evaporate a layer of gold (about 10 nm) on the surface of the sample to make the sample have good electrical conductivity; 4. Place the sample in a vacuum chamber and evacuate it to 10e-6pa; 5. Adjust the lens to the sample, observe the morphology of the sample and measure the thickness of the scintillator. This method is complicated and inefficient.

[0004] The steps for measuring the scintillator with a micrometer are as follows: 1. Use a micrometer to measure the thickness of the substrate (select the part around the sample without scintillator), measure at least 5 different positions and take the average as the thickness d0 of the substrate; 2. Use a micrometer to measure the thickness of the scintillator + substrate at different positions, measure each point at least three times and take the average, which is recorded as the thickness di of the scintillator + substrate at that point; 3. Then the thickness Di of the scintillator at each point is di-d0. The results measured by a micrometer and a caliper are inconsistent, and during the measurement process, the scintillator is contacted and pressed, so the scintillator in the contact part cannot be used.

[0005] Moreover, the existing methods require measuring the scintillator before the detector is assembled, and the scintillator is measured by contact, which may damage the scintillator. In addition, the scintillator material cannot be exposed to air for a long time, so these solutions have the risk of degradation of the performance of the scintillator. Therefore, it is necessary to design a method for measuring the thickness of the scintillator without contacting it. SUMMARY

[0006] The purpose of the present application is to provide a method for measuring the thickness of the scintillator inside a detector.

[0007] To solve the above technical problems, the present application adopts the following technical solution: a method for measuring the thickness of the scintillator inside a detector, comprising the following steps:

[0008] a. Detecting the wide-energy-spectrum X-rays emitted by a common X-ray source using a detector, and the calculation formula of the count value I read by the detector is as follows:

[0009]

[0010] Wherein, G is the gain of the detector, S(E) is the X-ray energy spectrum, μ 滤过 (E) is the absorption coefficient of the total filtering material of the X-ray source, d 滤过 is the thickness of the total filtering material of the X-ray source, μ i (E) is the absorption coefficient of other materials in the optical path system between the source exit and the detector, d i is the thickness of other materials in the optical path system between the source exit and the detector, i represents the i-th material, i=0 represents that the X-ray does not pass through other materials in the optical path, and air can be ignored, μ 闪烁体 (E) is the absorption coefficient of the detector scintillator, d 闪烁体 is the thickness of the detector scintillator;

[0011] b. Let S'(E) = S(E)·exp(-μ 滤过 (E)·d 滤过 )·exp(-∑(μ i (E)·d i )),

[0012] S'(E) is the X-ray energy spectrum reaching the detector,

[0013] at least two X-ray exposures are performed, wherein the first exposure obtains I1, the energy spectrum reaching the detector is changed, and the second exposure obtains I2,

[0014]

[0015] c. The above formula is optimized and solved to obtain the scintillator thickness:

[0016]

[0017] In another embodiment, S'(E) is the number of X-ray photons at each energy E.

[0018] In another embodiment, different S'(E) can be obtained by changing the voltage kVp loaded on the X-ray source and / or by changing the material through which the X-ray passes in the optical path system.

[0019] The present application has the advantages that the present application can obtain the thickness of the scintillator without disassembling the detector, does not contact the scintillator and does not cause damage to the scintillator, and the scintillator has been encapsulated during measurement, and there is no risk of performance degradation of the scintillator caused by measurement. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings are provided for the present application; Figure 1 is a flowchart of the present application;

[0021] Appendix Figure 2 This is a schematic diagram of the first measurement I during the invention (without a known sample);

[0022] Appendix Figure 3 This is a schematic diagram of the second measurement I of the present invention (with a known sample set). Detailed Implementation

[0023] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings:

[0024] like Figure 1 As shown, the method for measuring the thickness of the scintillator inside the detector includes the following steps:

[0025] a. Using a detector to detect the broad-spectrum X-rays emitted from a common X-ray source, the formula for calculating the count value I read by the detector is as follows:

[0026]

[0027] Where G is the detector gain, S(E) is the X-ray energy spectrum, and μ 滤过 (E) is the absorption coefficient of the total filter material of the X-ray source, d 滤过 The total thickness of the filter material for the X-ray source is μ. i (E) represents the absorption coefficient of other materials within the optical path system between the source exit and the detector, d i Let μ be the thickness of other materials within the optical path system between the source exit and the detector, where i represents the type of material, i = 0 indicates that the X-rays do not pass through other materials within the optical path, and air is negligible. 闪烁体 (E) is the absorption coefficient of the detector scintillator, d 闪烁体 The thickness of the detector scintillator; In the above formula 1(1), the S(E) X-ray energy spectrum for commonly used tungsten targets, combined with the kVp measured by the dosimeter, can be given by simulation calculation. The filtered material and thickness are generally expressed by equivalent aluminum in the industry. The absorption coefficient of aluminum can be obtained by looking up the table, and the equivalent thickness can be measured by the dosimeter; The thickness of other materials in the optical path can be freely selected and controlled, and is also a known quantity; The absorption coefficient of the scintillator can also be obtained by looking up the table according to the scintillator material selected in the detector; In formula (1), the detector gain G involves the X-ray-visible light conversion efficiency and visible light absorption efficiency inside the detector, which cannot be obtained directly; Therefore, in formula (1), there are two unknowns, and the required scintillator thickness information cannot be obtained by one X-ray detection. Therefore, the thickness of the scintillator can be calculated by using at least two X-ray exposures.

[0028] b. Let S′(E) = S(E)·exp(-μ 滤过 (E)·d 滤过) · exp(-∑(μ i (E) · d i )),

[0029] S'(E) is the X-ray spectrum reaching the detector, i.e. the number of X-ray photons at each energy E,

[0030] X-ray exposure is performed, where the first exposure obtains I1, the spectrum reaching the detector is changed, the second exposure is performed to obtain I2,

[0031]

[0032] c. The above formula is optimized by using the conjugate gradient descent method to obtain the scintillator thickness:

[0033]

[0034] Different S'(E) can be obtained by changing the voltage kVp loaded on the X-ray source and / or by changing the material through which the X-ray passes in the optical system.

[0035] Embodiment one

[0036] In this embodiment, the distance between the X-ray source and the detector is set to 1.5 meters, the beam collimator is adjusted so that the X-ray area reaching the detector is about 1 cm x 1 cm, a 1 mm aluminum filter is placed at the outlet of the source, the parameters of the X-ray source are set to 90 kV and 10 mAs, and a dose meter produced by RTI in Sweden, model Piranha R / F, is used to measure the total filter and kVp of the source.

[0037] Without changing the above settings, the first X-ray exposure is performed to obtain the first reading I1 of the detector.

[0038] Without changing the above settings, a known sample, for example, a 1 mm thick copper sheet, is placed in the X-ray optical path, the second X-ray exposure is performed to obtain the second reading I2 of the detector, and the formula (3) is solved to obtain the scintillator thickness d 闪烁体 .

[0039] The above embodiments are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit of the present application shall be covered within the protection scope of the present application.

Claims

1. A method of measuring the thickness of an internal scintillator of a probe, characterized by, It comprises the following steps: a. Detecting the wide energy spectrum X-ray emitted by the common X-ray source by using the detector, and calculating the count value I read by the detector according to the Beer-Lambert law and the energy deposition of the detector as follows: （1） where G is the gain of the detector, S(E) is the X-ray spectrum, is the absorption coefficient of the total filtration material of the X-ray source, is the thickness of the total filtration material of the X-ray source, is the absorption coefficient of other materials in the optical path system between the source exit and the detector, is the thickness of other materials in the optical path system between the source exit and the detector, i indicates the i-th material, i = 0 indicates that the X-rays do not pass through other materials in the optical path, and air can be ignored, is the absorption coefficient of the detector scintillator, is the thickness of the detector scintillator; b. Let , S'(E) is the X-ray energy spectrum reaching the detector, Performing at least two X-ray exposures, wherein the first exposure obtains I1, the energy spectrum reaching the detector is changed, the second exposure obtains I2, (2)； c. Optimizing and solving the above formula to obtain the thickness of the scintillator: (3)。 2. The method of measuring the thickness of an internal scintillator of a probe according to claim 1, characterized in that: S'(E) is the number of X-ray photons at each energy E.

3. The method of measuring the thickness of an internal scintillator of a probe according to claim 1, wherein: Different S'(E) can be obtained by changing the voltage kVp loaded on the X-ray source and / or by changing the material through which the X-ray passes in the optical path system.

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