KR101767724B1

KR101767724B1 - X-Ray Detector

Info

Publication number: KR101767724B1
Application number: KR1020150072790A
Authority: KR
Inventors: 강정원; 김종석
Original assignee: 단국대학교 산학협력단
Priority date: 2015-05-26
Filing date: 2015-05-26
Publication date: 2017-08-16
Also published as: KR20160139083A

Abstract

Disclosed is an electrode structure of a plasma display panel-based X-ray detector for detecting an X-ray as an electrical signal to increase the acquisition efficiency. In this case, four electrode structures including one electrode on the upper substrate and three electrodes on which the negative electrode is added to the lower substrate are applied, and protrusions on both sides of the positive electrode are provided, An X-ray detector capable of enhancing the signal acquisition efficiency by enhancing the electric field around and increasing the electron amplification.

Description

X-ray detector {X-ray Detector}

The present invention relates to an X-ray detector, and more particularly, to an electrode structure of an X-ray detector based on a plasma display panel capable of detecting an X-ray by an electrical signal to improve the acquisition efficiency.

Generally, a digital X-ray imaging apparatus, which is frequently used, includes a direct conversion system that directly receives an electrical signal of a photoconductor and generates an image, and an indirect conversion system that converts an induced phosphor light into an electrical signal by using a light- There is a conversion method. However, in general semiconductor-based detectors, it is not easy to increase the size, and it has disadvantages such as high cost per unit area and durability in which pixels are easily damaged due to radiation.

In order to overcome the above-mentioned problems, development of a different type of digital image device has been demanded. In this case, a PDP (Plasma Display Panel) method has been suggested as a detector of an X-ray image device.

An apparatus based on a plasma display panel has a structure in which a discharge voltage is applied after sealing a penning gas such as Xe or Ne on two substrates coated with a plurality of electrodes and by ultraviolet rays generated in a plasma generated by the discharge voltage, Refers to an image device that implements numbers, characters, or images by utilizing visible light generated by exciting phosphors formed in a predetermined pattern.

Such a plasma display panel-based X-ray detector has advantages such as low cost, large size, less damage by radiation, simple manufacturing process and long lifetime compared to a semiconductor-based detector.

1 is a schematic diagram of a conventional X-ray detector.

Referring to FIG. 1, a conventional X-ray detector 100 includes an upper substrate 101, a lower substrate 102, an upper electrode 103, a cathode 104, (105), and a gas layer (106).

Initial charges are generated in the detector 100 due to the incident X-rays, and an electric field is generated due to the voltage applied between the upper substrate 101 and the lower substrate 102. As a result, The positive electrode 105 is moved to the lower substrate 102 where the positive electrode 105 is located and then moved to the positive electrode 105 by the voltage applied to the lower substrate 102 when approaching the lower substrate 102. Electron multiplication occurs in which additional electrons are generated due to collision of electrons and neutral gas particles generated during the movement, so that a charge larger than that generated due to X-ray absorption at the beginning occurs in the detector 100 So that the acquisition signal also increases.

The conventional X-ray detector 100 generally includes an upper electrode 103 disposed on the lower surface of the upper substrate 101 and a negative electrode 104 and a positive electrode 105 disposed on the upper surface of the lower substrate 102, Electrode structure.

Korean Patent Publication No. 10-2010-0052074

The present invention relates to an electrode structure of a plasma display panel-based X-ray detector capable of improving signal acquisition efficiency. That is, it is an object of the present invention to provide an X-ray detector capable of increasing the acquisition efficiency detected by an electrical signal of an X-ray by applying four electrode structures including one electrode on the upper substrate and three electrodes on the lower substrate.

According to an aspect of the present invention, there is provided a plasma display panel comprising: an upper electrode formed on an upper substrate; a plurality of lower electrodes formed on a lower substrate facing the upper substrate; and a lower electrode formed between the upper electrode and the plurality of lower electrodes And a gas layer filled with a mixed gas, and formed on at least one electrode of the plurality of lower electrodes, and at least one protrusion for strengthening an electric field between the plurality of lower electrodes.

The plurality of lower electrodes may include a positive electrode and a first negative electrode and a second negative electrode disposed adjacent to the positive electrode.

The positive electrode may be disposed between the first negative electrode and the second negative electrode.

The protrusion may be formed on both sides of the positive electrode.

The protrusion may be triangular.

The protrusion may be made of the same material as the positive electrode.

The width of the positive electrode may be equal to or smaller than the width of the first negative electrode or the width of the second negative electrode.

The first negative electrode and the second negative electrode may be respectively bent to be spaced apart from the protrusion by a predetermined distance.

According to the present invention, a total of four electrode structures including one electrode on the upper substrate and three electrodes on the lower substrate are applied, and a triangular protrusion is formed on the positive electrode formed on the lower substrate, And the electric field around the negative electrode can be enhanced to improve the signal acquisition efficiency.

In addition, an X-ray detector based on a plasma display panel has many advantages such as a low price, a large size, a low radiation damage, a simple manufacturing process and a low defect rate compared to a semiconductor-based detector Which has the potential to replace semiconductor-based detectors in the future.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a schematic diagram of a conventional X-ray detector.
2 is a schematic diagram of an X-ray detector according to a preferred embodiment of the present invention.
3 (a) to 3 (c) are views for explaining the electrode structures of Example 1, Example 2 and Comparative Example of the present invention.
Figs. 4 (a) to 4 (c) are diagrams showing simulation results of an electronic drift line according to the electrode structures of Example 1, Example 2 and Comparative Example of the present invention.
5 (a) to 5 (c) are diagrams showing the results of the equal-potential simulation according to the electrode structures of the first, second and comparative examples of the present invention.
6 is a diagram showing the results of charge multiplication simulation according to the electrode structures of Examples 1, 2 and Comparative Example of the present invention.
7 is a view showing an electrode structure for an experimental example according to an embodiment of the present invention.
8 and 9 are graphs showing test results according to an experimental example of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Referring to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, .

FIG. 2 is a schematic view of an X-ray detector according to a preferred embodiment of the present invention, and FIGS. 3A to 3C are views for explaining the electrode structures of Examples 1, 2 and Comparative Example of the present invention to be.

2, an X-ray detector 200 according to a preferred embodiment of the present invention includes an upper substrate 201, a lower substrate 202, A lower electrode 203, a plurality of lower electrodes 204, 205, 206, and a gas layer 207.

The outside of the detector 200 may be formed using a partition wall (not shown) or may be integrally formed, and may be formed in a closed structure so that gas may be filled therein. The detector 200 includes an upper substrate 201 and a lower substrate 202 disposed opposite to each other and includes an upper electrode 203 on the lower surface of the upper substrate 201 and a plurality of lower electrodes 202 on the upper surface of the lower substrate 202, 204, 205, and 206, respectively.

The conventional electrode structure of a conventional X-ray detector has a three-electrode structure including one upper electrode on the lower surface of the upper substrate and a negative electrode and a positive electrode on the upper surface of the lower substrate. The electrode structure of the X-ray detector 200 according to the present invention includes one upper electrode 203 on the lower surface of the upper substrate 201 and a plurality of lower electrodes 204, 205, 206). The lower electrodes 204, 205, and 206 may preferably include a first negative electrode 204, a positive electrode 205, and a second negative electrode 206. That is, four electrodes including one upper electrode 203 and three lower electrodes 204, 205, and 206 may be disposed in the detector 200.

The upper electrode 203 may be an address electrode, and may be formed as a front electrode on the lower surface of the upper substrate 201. The first negative electrode 204, the positive electrode 205 and the second negative electrode 206 which are the plurality of lower electrodes 204, 205 and 206 may be spaced apart from each other by a predetermined distance, Preferably, the positive electrode 205 may be disposed between the first negative electrode 204 and the second negative electrode 206. That is, the first negative electrode 204 and the second negative electrode 206 may be spaced apart from each other by a predetermined distance around the positive electrode 205. The width Wa of the positive electrode 205 is preferably equal to or smaller than the width Wc of the first negative electrode 204 or the width Wc of the second negative electrode 206 Lt; / RTI >

The space between the upper electrode 203 and the plurality of lower electrodes 204, 205, and 206 may include a gas-filled gas layer 207. For example, the gas in the gas layer 207 may be any one selected from the group consisting of xenon, krypton, argon, neon, helium, carbon dioxide, and methane, or two or more of these gases .

The gas layer 207 acts to convert electrons into incident X-rays. That is, the X-rays transmitted through the human body are incident through the upper substrate 201, and the X-rays passing through the upper substrate 201 reach the gas layer 207 through the upper electrode 203, The X-rays reaching the electron gun 207 ionize the gas to generate electron and electron pairs. The electrons are moved toward the lower electrode by the electric field generated by the voltage applied to the upper electrode 203 and the lower electrodes 204, 205 and 206, and the moved electrons are transmitted to the lower electrodes 204 205, and 206, respectively, due to the applied voltage. During movement, electron multiplication occurs in which additional electrons are generated due to collision between the charge generated in the movement and the neutral gas particles, so that more charge than the charge generated due to the X-ray absorption at the beginning is generated in the detector 200 So that the acquisition signal is increased.

The positive electrode 205 of the plurality of lower electrodes 204, 205 and 206 according to the present invention includes at least one protrusion 208 for enhancing the electric field between the electrodes as shown in FIGS. 3 (a) and 3 (b) May be included. The protrusion 208 has a triangular shape having a pointed shape and one protrusion 208 is formed on both sides of the positive electrode 205 or two or more protrusions 208 are formed on both sides of the positive electrode 205 And can be arranged side by side from the central portion. In addition, the material of the protrusion 208 may be the same material as the positive electrode 205, but is not limited thereto.

The positive electrode 205 has the triangular protruding portion 208 having the pointed shape on both sides of the positive electrode 205 and the first negative electrode 204 by the edge effect of the electric field, And the second negative electrode 206 can be strengthened. This can generally enhance the electric field of the protruding portion 208 due to the increased charge density because the charge is gathered at a portion that is taller than the portion where the surface is a surface.

The first negative electrode 204 and the second negative electrode 206 spaced apart from the positive electrode 205 by a predetermined distance from the protruding portion 208 of the positive electrode 205, A part of the electrode may be bent in a direction opposite to the protruding portion 208, respectively.

As described above, the electrode of the X-ray detector 200 according to the present invention includes four electrodes composed of one upper electrode 203 and three lower electrodes 204, 205, and 206 in the detector 200 , It is possible to increase the electron amplification of the electrons moving to the positive electrode 205. A triangular protrusion 208 is additionally formed on both sides of the positive electrode 205 so that the electric field between the positive electrode 205 and the negative electrode can be obtained by using the edge effect of the electric field by the protrusion 208 It is possible to improve the signal acquisition efficiency of the X-ray detector 200 by increasing the amount of electrons collected at the positive electrode 205 by further amplifying the electrons.

3 (a) to 3 (c), a detailed description of the first embodiment, the second embodiment and the comparative example of the present invention and the result of the simulation according to the first embodiment, the second embodiment and the comparative example will be described in detail below.

Example 1

3 (a), the lower electrode structure of the first embodiment includes a first negative electrode 204, a positive electrode 205, and a second negative electrode 206, The first negative electrode 204 and the second negative electrode 206 are disposed on both sides of the electrode 205 at a predetermined distance. In order to enhance the edge effect of the electric field, two triangular protrusions 208 are formed side by side in the center of both sides of the positive electrode 205, and a first negative electrode 204 and a second negative electrode 206, A part of the electrode is formed in a bent shape so as to be spaced apart from the protrusion 208 by a predetermined distance in a direction opposite to the protrusion 208 of the positive electrode 205. That is, in Embodiment 1, two protrusions 208 are formed on both sides of the positive electrode 205 in a four-electrode structure composed of one upper electrode 203 and three lower electrodes 204, 205, and 206.

The width Wa of the positive electrode 205 of Example 1 is 80 占 퐉 and the width Wc of the first negative electrode 204 and the second negative electrode 206 is 100 占 퐉, The height Hr of the projection 208 formed on the base 205 is 80 占 퐉 and the length Br of the base is 100 占 퐉.

Example 2

3 (b), the lower electrode structure of the second embodiment includes a first negative electrode 204, a positive electrode 205, and a second negative electrode 206, The first negative electrode 204 and the second negative electrode 206 are disposed on both sides of the electrode 205 at a predetermined distance. On both sides of the positive electrode 205, a triangular protrusion 208 is formed one by one to enhance the edge effect of the electric field, and the first negative electrode 204 and the second negative electrode 206 form positive A part of the electrode is formed in a bent shape so as to be spaced apart from the protrusion 208 by a predetermined distance in a direction opposite to the protrusion 208 of the electrode 205. That is, the second embodiment is similar to the first embodiment in that it has a four electrode structure composed of one upper electrode 203 and three lower electrodes 204, 205 and 206, but only the number of the protrusions 208 is changed .

The width Wa of the positive electrode 205 of Example 2 is 100 占 퐉 and the width Wc of the first negative electrode 204 and the second negative electrode 206 is 100 占 퐉 and the positive electrode The height Hr of the protrusion 208 formed on the base 205 is 50 mu m and the length Br of the base is 600 mu m.

In Examples 1 and 2, one or two protrusions 208 are included to confirm the effect of the protrusions 208 formed on the positive electrode 205. However, the protrusions 208 of the X- 208) is not limited thereto.

Comparative Example

Referring to FIG. 3C, the lower electrode structure of the comparative example includes a conventional lower electrode structure, in which the lower electrode includes a negative electrode 209 and a positive electrode 205 spaced apart from each other by a predetermined distance, But does not include protrusions 208 formed on the positive electrode 205 as in the second embodiment. That is, the electrode structure of the comparative example does not include the projecting portion 208 but is formed in a three-electrode structure composed of one upper electrode 203 and two lower electrodes 205 and 209.

The width Wa of the positive electrode 205 and the negative electrode width Wc of the comparative example are both set to 100 mu m.

The sizes of the electrodes and protrusions 208 according to the first, second, and comparative examples are summarized in Table 1.

Electrode structure Positive electrode
Width Wa (μm) Negative electrode
Width Wc (μm) projection part
Height Hr (μm) Base of protrusion
Length Br (μm) Example 1 80 100 80 100 Example 2 100 100 50 600 Comparative Example 100 100 - -

4 (a) to 4 (c) are graphs showing simulation results of an electronic drift line according to the electrode structures of Example 1, Example 2 and Comparative Example of the present invention, and Figs. 5 (c) are graphs showing the results of an equal-potential simulation according to the electrode structures of Examples 1, 2 and Comparative Example of the present invention.

Referring to Figures 4 (a) -4 (c) and 5 (a) -5 (c), Figures 4 (a) (b) is a simulation result for each of the comparative examples, and FIG. 4 (c) and FIG. 5 (c) are simulation results for the case where the same voltage is applied to each electrode structure, The results of the simulation are compared. The simulated result view shows simulation results for an electron drift line and an equal-potential distribution in a plane located 0.1 mm above the upper surface of the lower electrode.

The increase in the electron drift line indicates that the multiplication of electrons in the region is further increased. As shown in Figs. 4 (a) to 4 (c), it is confirmed that the largest electron multiplication in the electrode structure of Example 1 is activated And it can be confirmed that the smallest electron multiplication is activated in the electrode structure of the comparative example.

This means that, at the same applied voltage, the number of electrons in Example 1 and Example 2, which are four electrode structures according to the present invention, is larger than that of the conventional three electrode structure, which is the electrode structure of the comparative example. That is, it can be confirmed that a strong electric field due to the edge effect is formed around the protruding portion 208 formed on both sides of the positive electrode 205 to increase the number of electrons. In the structure of Embodiment 1 in which two protrusions 208 are formed on both sides of the positive electrode 205 than the electrode structure of Embodiment 2 in which only one protrusion 208 is formed on both sides of the positive electrode 205, And the electron multiplication is further increased.

5 (a) to 5 (c), it can be seen that a stronger electric field is formed around the protruding portion 208 of the first and second embodiments than the electrode structure of the comparative example, It is confirmed that a stronger electric field is formed in the two protrusions 208 of the first embodiment.

6 is a diagram showing the results of charge multiplication simulation according to the electrode structures of Examples 1, 2 and Comparative Example of the present invention.

Referring to FIG. 6, simulation results of FIG. 6 show simulation results of charge multiplication according to Example 1, Example 2, and Comparative Example. As a result, the initial charges generated by the incident X- To increase the charge in the detector 200 due to multiple collisions.

Simulation results for the average multiplication calculated by simulation show 6074 in the four electrode structure of Example 1, 2766 in the four electrode structure of Example 1, and 1073 in the three electrode structure of the comparative example. It can be seen that this is 2.6 times higher than that of the conventional three electrodes and 2.6 times higher than that of the conventional three electrodes and 3.6 times higher than that of the three electrodes in the case of the four electrode structure of Example 1. Further, In the electrode structure, it can be seen that Example 1 is increased 2.2-fold compared to Example 2 due to the difference in the structure of the protrusion 208.

Experimental Example

In order to evaluate the performance of the electrode structure according to Example 1 and Example 2 of the present invention, the electrode structure of Example 1 and the electrode structure of Example 2 were designed and tested.

FIG. 7 is a view showing an electrode structure for an experimental example according to an embodiment of the present invention, and FIGS. 8 to 9 are graphs showing test results according to an experimental example of the present invention.

7, the width of the electrodes of the X-ray detector 200 according to the present example is 0.1 mm, and the positive electrode 205, the first negative electrode 204, and the second negative electrode 206 were 0.1 mm respectively. The distance between the upper substrate 201 and the lower substrate 202 is 2.8 mm, and the structure of the triangular projection 208 of the first and second embodiments is designed as shown in Table 1.

The mixed gas of Xe 80% + He 20% was used as the gas of the gas layer 207. The negative electrode was fixed at -400 V, the voltage of the upper electrode 203 was applied from -500 V to -1500 V, (X-ray on) and when not irradiated (X-ray off).

8 (a) and 8 (b) show the results of the charge amount measurement according to Example 1 and Example 2, respectively, when X-ray is irradiated in the detector 200 between 3 seconds and 4.57 seconds. Measurement Results The results for the protruding portion 208 of Example 1, which is shown in FIG. 8 (a), are about twice as large as those of the protruding portion 208 of Example 2 shown in FIG. 8 (b) .

Further, a formula for calculating the detection sensitivity of X-ray through the measured amount of charge is shown in Equation (1).

Here, Sensitivity is the detection sensitivity of the X-ray, Exposed Dose is the dose at the X-ray exposure, Exposed Detection Area is the irradiation area of the X-ray, and Charges during X-ray ON is the amount of charge when the X-ray is irradiated.

9 shows the detection sensitivity of X-rays calculated using Equation (1) as a comparative example of a conventional three-electrode structure and the calculation results of the four-electrode structure of the first and second embodiments of the present invention.

9, the X-ray detection sensitivity according to the electrode structure of Example 2 is 1.5 times higher than that of the electrode structure of the comparative example. In Example 1, the X- It can be confirmed that the line detection sensitivity has an improved detection performance of 3.8 times as compared with the electrode structure of the comparative example and 2.5 times as much as that of the electrode structure of the second embodiment.

As described above, the electrode structure of the X-ray detector 200 of the present invention has one upper electrode 203 on the upper substrate 201, a first negative electrode 204 on the lower substrate 202, Electrode structure including three electrodes including a first negative electrode 205 and a second negative electrode 206 and a protruding portion 208 having a triangular shape on the positive electrode 205, The electric field around the positive electrode 205 and the negative electrode is strengthened to increase the electron amplification, thereby improving the signal acquisition efficiency.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

201: upper substrate 202: lower substrate
203: upper electrode 204: first negative electrode
205: Positive electrode 206: Second negative electrode
207: gas layer 208:

Claims

An upper electrode formed on the upper substrate;
A plurality of lower electrodes formed on a lower substrate facing the upper substrate; And
And a gas layer formed between the upper electrode and the plurality of lower electrodes and filled with a mixed gas,
The plurality of lower electrodes may include a plurality of lower electrodes,
A positive electrode including at least one protrusion on each side thereof for enhancing an electric field between the plurality of lower electrodes; And
And a first negative electrode and a second negative electrode arranged to be spaced apart from each other by a predetermined distance about the positive electrode,
Wherein the first negative electrode and the second negative electrode each have a bent shape so as to be spaced apart from the protruding portion.

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The method according to claim 1,
Wherein the protrusion is triangular in shape.

The method according to claim 1,
Wherein the protrusion is made of the same material as the positive electrode.

The method according to claim 1,
Wherein the width of the positive electrode is equal to or smaller than the width of the first negative electrode or the width of the second negative electrode.

delete