High stability, high detection efficiency microchannel plate for ultraviolet light and X-ray detection and preparation method thereof

Abstract

The present invention provides a microchannel plate for ultraviolet light and X-ray detection with high stability and high detection efficiency, and a preparation method thereof. On the basis of the microchannel plate, a film material with high photoelectric conversion efficiency is plated on the input surface of the microchannel plate and at a certain depth of the channel as a reflective photocathode; after plating the photocathode material, an ultra-thin, uniformly thick, dense protective layer is prepared using atomic layer deposition technology. The protective layer material includes silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, silicon nitride, etc., which has a strong ability to block water vapor and a certain secondary electron emission capability, thereby reducing the impact on the performance of the MCP itself. The MCP prepared according to the above method can be widely used in open structure detectors and related equipment, and can withstand multiple vacuum and atmospheric environment conversions without significant changes, greatly expanding the application range of materials such as halides that are easily affected by humid air as reflective photocathodes on the input surface of the MCP.

Description

Technical Field

[0001] The present invention relates to the technical field of microchannel plates, and in particular to a microchannel plate with high stability and high detection efficiency for ultraviolet light and X-ray detection and a preparation method thereof. Background Art

[0002] The microchannel plate (MCP) is a simple and compact electron multiplier device developed in the late 1960s. It is a thin disc that is composed of millions of tiny parallel hollow glass tubes. Each hollow tube channel acts like a continuous dynode multiplier, which can detect particles, electrons, X-rays and UV photons. It has the advantages of low power consumption, self-saturation, high-speed detection and low noise, and is widely used in various detectors.

[0003] Conventional MCPs have relatively low detection efficiency for ultraviolet light and X-rays. In order to improve the detection efficiency of MCPs, a material with high conversion efficiency can be plated on the input surface of the MCP as a reflective cathode, which greatly increases the number of signal photons incident on the MCP and improves the detection efficiency. The materials used are mostly halides such as cesium iodide. Patent CN 209312708 U "A Framing Image Converter Tube for an X-ray Framing Camera" discloses a method for plating a reflective cesium iodide cathode on the surface of an MCP, using a halide material as the cathode conversion functional film layer of the MCP. However, there are the following problems: the high-conversion efficiency halide used is generally easy to deliquesce, and needs to be encapsulated in a vacuum device in situ under a vacuum state after the film layer is plated, or transferred to a vacuum device that encapsulates the vacuum device within a short time after being taken out, to avoid problems such as deliquesce of the halide film layer, resulting in decreased efficiency and increased noise. Therefore, the use scope of MCP containing this photoelectric conversion functional film layer is very limited and cannot meet the use requirements of open MCP devices. In addition, the performance of the finished MCP is greatly affected by the turnover process and the environment, and is difficult to control.

[0004] There are also many public reports on improving the stability of halide film materials such as cesium iodide in humid air environments: Patent CN 212872921 U, "A moisture-proof structure for an X-ray detector scintillator," proposes covering the scintillator of an X-ray detector with a layer of PCTFE plastic film and then sealing the four edges of the PCTFE plastic film with sealant. This method greatly improves the moisture-proof performance of the cesium iodide scintillator and effectively solves the moisture-proof problem of the X-ray detector; Patent CN109950356 B, "A cesium lead iodine-based photoelectric detector and its preparation method," proposes spin-coating polymethyl methacrylate (PMMA) on the surface as a device protective layer with a thickness of 20-50 nanometers; Patent CN 103745762 A, "Water-blocking cesium iodide scintillator screen," uses an organic thin film layer as the waterproof film layer to obtain a water-blocking cesium iodide scintillator screen with excellent water-blocking and waterproof effects, while improving the stability of the scintillator layer and extending the service life of the scintillator screen. In addition, the existing technology also attempts to use a metal aluminum film layer of about 200nm, thicker PECVD silicon oxide and PECVD silicon nitride to protect cesium iodide. The protection effect achieved by the thicker film layer is acceptable.

[0005] Among the above-mentioned multiple existing technical designs, the protective film solutions provided are all for cesium iodide materials used as transmissive cathodes or scintillators, and can achieve good results; for reflective cathodes, the above methods are not applicable. This is because the film layer is too thick, which will directly affect the escape of photoelectrons generated by the cathode material, thereby greatly affecting the detection efficiency; the secondary electron emission performance of the film material is poor, which affects the electron multiplication function of the MCP itself. Summary of the Invention

[0006] The purpose of the present invention is to provide a microchannel plate with high stability and high detection efficiency that can be used for ultraviolet light and X-ray detection. High detection efficiency is achieved by coating a functional film layer with high conversion efficiency on the input surface of the microchannel plate and the inner wall of the channel as a reflective cathode. At the same time, after the film layer is coated, an ultra-thin, dense, waterproof protective film layer is prepared to ensure that the cathode film layer, which is easily affected by humid air, has good stability without affecting the detection efficiency and the electron multiplication function of the MCP.

[0007] According to a first aspect of the present invention, a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency is provided, comprising:

[0008] An array electron multiplier formed by arranging millions of mutually parallel channel-type electron multiplying units, each electron multiplying unit forming a microchannel structure; the array electron multiplier defines an input surface;

[0009] A reflective photocathode is formed by forming a film of a material having a photoelectric conversion function on the surface of the input surface and the inner wall of the channel of the electron multiplying unit, wherein the reflective photocathode is made of a material having a high response to ultraviolet light and X-rays; and

[0010] A dense, ultra-thin waterproof protective layer with uniform thickness is prepared on the surface of the reflective photocathode.

[0011] Preferably, the reflective photocathode comprises a single film layer or a composite film layer prepared from at least one of cesium iodide, copper iodide, potassium bromide, and potassium chloride.

[0012] Preferably, the ultra-thin waterproof protective layer comprises a single film layer or a composite film layer prepared from at least one of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, and silicon nitride.

[0013] Preferably, the coverage area of ​​the reflective photocathode is the entire input surface and a predetermined depth of the inner wall of the channel, and the depth range is controlled within 3D to 20D, where D is the aperture of each electron multiplying unit of the MCP, and the coating depth is ≥1 / tan(θ), where θ is the bevel angle of the electron multiplying unit.

[0014] Preferably, the coverage area of ​​the ultra-thin waterproof protective layer is the entire input surface and the entire inner wall of the channel.

[0015] Preferably, the thickness of the reflective photocathode is controlled within a range of 100 nm to 2000 nm, and the total thickness of the ultra-thin waterproof protective layer is controlled within a range of 0.5 nm to 20 nm.

[0016] According to a second aspect of the present invention, a method for preparing a microchannel plate for ultraviolet light and X-ray detection with high stability and high detection efficiency is provided, comprising the following steps:

[0017] On the input surface and the inner wall of the channel of the electron multiplier array electron multiplier, a film layer made of a material having a photoelectric conversion function is prepared as a reflective photocathode. The reflective photocathode is made of a material with high responsiveness to ultraviolet light and X-rays.

[0018] A dense, ultra-thin waterproof protective layer with uniform thickness is prepared on the surface of the reflective photocathode.

[0019] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below, as long as such concepts are not mutually inconsistent, can be considered part of the inventive subject matter of this disclosure. In addition, all combinations of the claimed subject matter are considered part of the inventive subject matter of this disclosure.

[0020] The foregoing and other aspects, embodiments, and features of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as features and / or beneficial effects of the exemplary embodiments, will become apparent from the following description or through practice of specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0022] Figure 1 Schematic diagram of the preparation process of a microchannel plate for ultraviolet light and X-ray detection according to an exemplary embodiment of the present invention.

[0023] Figure 2 Schematic diagram of the structure of a microchannel plate for ultraviolet light and X-ray detection according to an exemplary embodiment of the present invention.

[0024] Figure 3 This is a comparison diagram of surface morphology / grain changes of a microchannel plate for ultraviolet light and X-ray detection according to an exemplary embodiment of the present invention when stored in air.

[0025] Figure 4 FIG. 1 is a graph showing how the detection efficiency of a microchannel plate for ultraviolet and X-ray detection according to an exemplary embodiment of the present invention changes with the storage time in air.

[0026] Description of reference numerals:

[0027] 10- channel inner wall;

[0028] 20- input surface;

[0029] 31-reflective photocathode;

[0030] 32-Ultra-thin waterproof protective layer. DETAILED DESCRIPTION

[0031] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0032] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any embodiment. In addition, some aspects of the present disclosure may be used alone or in any appropriate combination with other aspects disclosed herein.

[0033] Combine Figure 1 、 2 The high-stability, high-detection-efficiency microchannel plate for ultraviolet and X-ray detection of the embodiment shown includes: an array electron multiplier, a reflective photocathode prepared on the input surface and in the channel of the array electron multiplier, and an ultra-thin waterproof protective layer prepared on the surface of the reflective photocathode.

[0034] Among them, the array electron multiplier is an array electron multiplier composed of millions of mutually parallel channel electron multiplier units, and has an input surface and an output surface.

[0035] As an optional embodiment, an array electron multiplier refers to an array electron multiplier composed of millions of parallel channel electron multiplier units. It is usually made of skin glass and core glass as raw materials, and is an MCP background made through wire drawing, multi-filament drawing, screen arrangement, screen pressing, screen cutting, polishing, corrosion, and hydrogen reduction processes, and is in a state without any functional film layer coating.

[0036] Each electron multiplying unit constitutes a microchannel structure.

[0037] Combine Figure 1 The figure shows an example of a microchannel structure of an array electron multiplier, or MCP background, wherein reference numeral 10 represents the inner wall of the channel, the area between the two inner walls of the channel constitutes the microchannel, and reference numeral 20 represents the input surface of the array electron multiplier.

[0038] Combine Figure 1 、 2 As shown, a reflective photocathode 31 is prepared on the surface of the input surface 20 and the surface of the inner wall 10 of the channel of the electron multiplying unit, respectively. The reflective photocathode refers to a film layer prepared by a material having a photoelectric conversion function.

[0039] Preferably, the reflective photocathode is made of a material that has a high response to ultraviolet light and X-rays, for example, a single film layer prepared from one of cesium iodide, copper iodide, potassium bromide, and potassium chloride.

[0040] In another embodiment, the reflective photocathode 31 includes a first composite film layer prepared from at least two of cesium iodide, copper iodide, potassium bromide, and potassium chloride.

[0041] In the aforementioned embodiment, no matter it is a single film layer or a composite film layer, the total layer thickness of the reflective photocathode 31 is controlled to be 100-2000 nm.

[0042] The preparation process of the reflective photocathode can be carried out by using physical vapor deposition methods such as thermal evaporation, electron beam evaporation, magnetron sputtering, ion plating, etc.

[0043] In an embodiment of the present invention, the reflective photocathode 31 covers the entire input surface and a predetermined depth of the inner wall of the channel, and the coverage depth range is controlled to be 3D to 20D, where D is the aperture of each electron multiplying unit of the MCP, and the coating depth is ≥1 / tan(θ), where θ is the bevel angle of the electron multiplying unit.

[0044] Combine Figure 1 、 2 As shown, a dense, uniformly thick ultra-thin waterproof protective layer 32 is formed on the surface of the reflective photocathode 31. The ultra-thin waterproof protective layer 32 covers the entire input surface 20 and the entire channel inner wall 10.

[0045] In another optional embodiment, the coverage area of ​​the ultra-thin waterproof protective layer 32 is the entire surface of the input surface 20 , the surface of the output surface and the entire channel inner wall 10 .

[0046] like Figure 1 、 2 In the example shown, the preparation of the ultra-thin waterproof protective layer can be prepared by atomic layer deposition technology. The prepared film layer has a high water vapor blocking ability and a certain secondary electron emission ability. The material types include silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, silicon nitride, etc.

[0047] In an optional embodiment, the ultra-thin waterproof protective layer 32 includes a film layer prepared from one of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, and silicon nitride, or a composite film layer prepared from at least two of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, and silicon nitride.

[0048] Regardless of being a single film layer or a composite film layer, the total film thickness of the ultra-thin waterproof protective layer 32 is controlled to be between 0.5 nm and 20 nm.

[0049] According to an example disclosed in the present invention, a method for preparing a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency comprises the following steps:

[0050] On the input surface and the inner wall of the channel of the electron multiplier array electron multiplier, a film layer made of a material having a photoelectric conversion function is prepared as a reflective photocathode. The reflective photocathode is made of a material with high responsiveness to ultraviolet light and X-rays.

[0051] A dense, ultra-thin waterproof protective layer with uniform thickness is prepared on the surface of the reflective photocathode.

[0052] As an optional embodiment, the reflective photocathode 31 can be deposited by physical vapor deposition methods such as thermal evaporation, electron beam evaporation, magnetron sputtering, ion plating, etc., using a single film layer or a composite film layer prepared from at least one of cesium iodide, copper iodide, potassium bromide, and potassium chloride. The parameters of the MCP substrate used, such as the aperture, bevel angle, and size, are not limited. The coverage depth range is controlled to be 3D to 20D, where D is the aperture of each electron multiplying unit of the MCP, and the coating depth is ≥ 1 / tan(θ), where θ is the bevel angle of the electron multiplying unit.

[0053] Among them, the film material coating process parameter range of the reflective photocathode 31 can be selected as: film thickness 100nm~2000nm, tooling speed 1r / min~100r / min, coating rate 0.5nm / s~5nm / s; baking before coating: temperature 50~200℃, time 10min~60min.

[0054] As an optional embodiment, the ultra-thin waterproof protective layer 32 includes a single film layer or a composite film layer prepared from at least one of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, and silicon nitride.

[0055] As an optional embodiment, the ultra-thin waterproof protective layer 32 is deposited using atomic layer deposition technology. The resulting film has a high water vapor barrier capability and a certain secondary electron emission capability. The ultra-thin waterproof protective layer evenly covers the entire surface of the MCP input surface and the inner wall of the through-channel. The film thickness ranges from 0.5nm to 20nm, and the film deposition temperature ranges from 150°C to 300°C.

[0056] Next, we take Examples 1 and 2 and a microchannel plate coated with only a reflective photocathode as examples to assemble the same MCP assembly for a 2KeV X-ray detection test.

[0057] Example 1:

[0058] Step 1: Using physical vapor deposition method to plate the photoelectric conversion reflective cathode film layer:

[0059] 1) Prepare MCP with NiCr electrode: pore size 12 μm, diameter 50 mm, bevel angle 12°;

[0060] 2) Prepare cesium iodide coating material;

[0061] 3) Place the MCP into a special fixture that can correct the bevel angle, and place it on the coating machine with the coating angle adjusted so that the coating depth is 10D;

[0062] 4) Set appropriate coating parameters: film thickness 1000nm, tooling speed 5r / min, coating rate 1nm / s; pre-coating baking: temperature 150℃, time 30min; automatically run the coating process to complete the coating process.

[0063] Step 2: Prepare the protective film layer using atomic layer deposition technology

[0064] 1) Prepare the precursor for depositing silicon oxide: SiH2(NEt2)2+O3;

[0065] 2) The MCP coated with a reflective photocathode film is directly transferred to the ALD device through a sample transfer channel connected to the vacuum device, where the MCP is suspended in the ALD device.

[0066] 3) Depositing a film layer at a deposition temperature of 280° C. with a film deposition thickness of 1 nm.

[0067] 4) After the protective film layer is deposited, the gas is released to obtain MCP sample 1.

[0068] Step 3: Encapsulate the MCP sample 1 into an MCP assembly and perform detection efficiency and moisture resistance tests.

[0069] Example 2:

[0070] Step 1: using physical vapor deposition to deposit a photoelectric conversion reflective cathode film layer: the same as in Example 1.

[0071] Step 2: Prepare the protective film layer using atomic layer deposition technology

[0072] 1) Prepare the precursor for depositing silicon oxide: SiH2(NEt2)2+O3;

[0073] 2) The MCP coated with a reflective photocathode film is directly transferred to the ALD device through a sample transfer channel connected to the vacuum device, where the MCP is suspended in the ALD device.

[0074] 3) Depositing a film layer at a deposition temperature of 280° C. with a film thickness of 20 nm;

[0075] 4) After the protective film layer is deposited, the gas is released to obtain MCP sample 2.

[0076] Step 3: Encapsulate the MCP sample 2 into an MCP assembly and perform detection efficiency and moisture resistance tests.

[0077] The test results of Example 1, Example 2 and the unplated ultra-thin waterproof protective film layer are compared as follows

[0078] * Humid air conditions: temperature 22-25℃, relative humidity ~60%.

[0079] * See attached SEM pictures of actual grain morphology changes Figure 3 .

[0080] Combine Figure 4 The curve of detection efficiency changing with storage time in the air is shown. According to the comparison test results of the above-mentioned embodiments, it can be seen that as the thickness of the ultra-thin waterproof protective film layer increases, the detection efficiency of X-rays is more and more obviously affected; the thicker the ultra-thin waterproof protective film layer, the more stable the storage in the air, and the more stable the detection efficiency as the storage time increases. Therefore, in the embodiment of the present invention, the thickness of the ultra-thin waterproof protective film layer is selected to be 0.5-20nm, which not only ensures that there is basically no effect on the detection efficiency of X-rays and ultraviolet rays, but also ensures that the cathode film layer that is easily affected by humid air has good stability. It can be widely used in open structure detectors and related equipment, and can withstand multiple vacuum and atmospheric environment conversions without obvious changes, which greatly expands the application range of materials such as halides that are easily affected by humid air as MCP input surface reflective photocathodes.

[0081] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency, characterized in that: include: An array electron multiplier formed by arranging millions of mutually parallel channel-type electron multiplying units, each electron multiplying unit forming a microchannel structure; the array electron multiplier defines an input surface; A reflective photocathode is formed by a film of a material having a photoelectric conversion function formed on the surface of the input surface and the inner wall of the channel of the electron multiplying unit. The reflective photocathode is made of a material having a high response to ultraviolet light and X-rays. as well as A dense, uniformly thick ultra-thin waterproof protective layer is prepared on the surface of the reflective photocathode; the total thickness of the ultra-thin waterproof protective layer is controlled to be 0.5 nm to 20 nm; The reflective photocathode covers the entire input surface and a predetermined depth of the inner wall of the channel, and the coverage depth range is controlled to be 3D to 20D, where D is the aperture of each electron multiplying unit of the MCP, and the coating depth is ≥1 / tan(θ), where θ is the bevel angle of the electron multiplying unit.

2. The microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 1, characterized in that: The reflective photocathode comprises a single film layer prepared from one of cesium iodide, copper iodide, potassium bromide and potassium chloride.

3. The microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 1, characterized in that: The reflective photocathode comprises a first composite film layer prepared from at least two of cesium iodide, copper iodide, potassium bromide, and potassium chloride.

4. The microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 2 or 3, characterized in that: The ultra-thin waterproof protective layer comprises a film layer prepared from one of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide and silicon nitride.

5. The microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 2 or 3, characterized in that: The ultra-thin waterproof protective layer includes a second composite film layer prepared from at least two of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, and silicon nitride.

6. The microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 1, characterized in that: The ultra-thin waterproof protective layer covers the entire input surface and the entire channel inner wall.

7. The microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 1, characterized in that: The thickness of the reflective photocathode is controlled to be between 100 nm and 2000 nm.

8. A method for preparing a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency, characterized in that: The following steps are involved: On the input surface and the inner wall of the channel of the electron multiplier array electron multiplier, a film layer made of a material having a photoelectric conversion function is prepared as a reflective photocathode. The reflective photocathode is made of a material with high responsiveness to ultraviolet light and X-rays. A dense, uniformly thick ultra-thin waterproof protective layer is prepared on the surface of the reflective photocathode; the total thickness of the ultra-thin waterproof protective layer is controlled to be 0.5 nm to 20 nm; The reflective photocathode covers the entire input surface and a predetermined depth of the inner wall of the channel, and the coverage depth range is controlled to be 3D to 20D, where D is the aperture of each electron multiplying unit of the MCP, and the coating depth is ≥1 / tan(θ), where θ is the bevel angle of the electron multiplying unit.

9. The method for preparing a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 8, characterized in that: The reflective photocathode comprises a single film layer or a composite film layer prepared from at least one of cesium iodide, copper iodide, potassium bromide, and potassium chloride.

10. The method for preparing a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 8, characterized in that: The ultra-thin waterproof protective layer includes a single film layer or a composite film layer prepared from at least one of silicon oxide, hafnium oxide, aluminum oxide, titanium oxide, and silicon nitride.

11. The method for preparing a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 8, characterized in that: The ultra-thin waterproof protective layer covers the entire input surface and the entire channel inner wall.

12. The method for preparing a microchannel plate for ultraviolet and X-ray detection with high stability and high detection efficiency according to claim 9, characterized in that: The thickness of the reflective photocathode is controlled to be between 100 nm and 2000 nm.

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