Ultra-high-speed response near-contact focusing phototube and preparation method thereof

Abstract

The application relates to the technical field of photoelectric tubes, in particular to an ultra-high-speed response near-focus type photoelectric tube and a preparation method thereof, which comprises a tube shell component and a cathode component connected with each other through indium sealing; the tube shell component comprises a tube shell structure, an input light window, an adsorbent and a grid structure are sequentially arranged in the tube shell structure from a light input end to a first indium sealing end direction, the tube shell structure is formed by superimposing and brazing a layered ceramic and a metal electrode ring, and at least comprises an adsorbent electrode and a grid fixed electrode. Through precise assembly and near-focus structure design, the reflective photoelectric cathode is located on a cathode surface, the distance between the cathode surface and the grid structure is controlled to be sub-millimeter, the light signal is incident on the cathode surface through the grid, the electrons are directly emitted to the grid after being excited, the difference in electron flight path is greatly reduced, the time consistency is improved, the electron transit time is greatly shortened, the photoelectric response speed is significantly improved, and the rise time of 100 picoseconds can be realized.

Description

Technical Field

[0001] This invention relates to the field of phototube technology, and more specifically to an ultra-high-speed response proximity focusing phototube and its fabrication method. Background Technology

[0002] A phototube is a detector that converts light signals into electronic signals using the external photoelectric effect. It is widely used in high-energy physics, nuclear radiation detection, analytical instruments, and industrial testing. Vacuum phototubes, due to their fast response time and wide dynamic range, have important applications in the field of photoelectric detection of intense nuclear radiation.

[0003] To further meet the demand for improved time accuracy in nuclear radiation high-intensity light detection devices, it is necessary to further improve the time response speed of phototubes. However, the time response speed of traditional phototubes is still some distance from the picosecond level, making it difficult to meet the practical application requirements of some special fields. Summary of the Invention

[0004] To address the technical problems existing in phototubes in the prior art, the first aspect of the present invention proposes an ultra-high speed response proximity focusing phototube, comprising a tube shell component and a cathode component that are indium-sealed together; The tube shell component includes a tube shell structure. Inside the tube shell structure, from the light input end to the first indium end capping direction, an input light window, a getter, and a grid structure are arranged sequentially. The tube shell structure is constructed by brazing layered ceramic and metal electrode rings together, and includes at least a getter electrode and a grid fixing electrode. The cathode component includes a cathode structure and a housing ground, with a coaxial transition using a ceramic structure between the cathode structure and the housing ground to achieve impedance matching with the back-end electronics, and the tail pin is the cathode output electrode; The cathode structure has a cathode surface on one side facing the grid structure, and the surface of the cathode surface is provided with a reflective photocathode. After the tube shell component and the cathode component are assembled together, the distance between the cathode surface and the grid structure is no more than 1 mm. The reflective photocathode is used to receive the light signal incident through the input light window and emit electrons in the direction of the grid structure to be received by the grid. The cathode structure converts the electron cloud signal lost by the cathode surface into an electrical pulse signal and outputs it to the outside of the phototube.

[0005] Preferably, the cathode component is configured as a frustum-shaped structure, the cathode surface is the bottom surface of the frustum-shaped structure, a needle-shaped electrode is provided on the side of the frustum-shaped structure away from the cathode surface, and the ceramic structure is disposed between the needle-shaped electrode and the outer casing to form a coaxial conical interface.

[0006] Preferably, the cone angle on the side of the frustum-shaped structure is between 30° and 45°.

[0007] Preferably, the outer casing, the needle electrode, and the ceramic structure form a coaxial connection structure for connecting a 50Ω coaxial cable, and the impedance between the outer casing and the cathode structure is set to 50Ω.

[0008] Preferably, the distance between the cathode surface and the grid structure is between 0.15 and 1 mm.

[0009] Preferably, the reflective photocathode is formed by pre-forming antimony on the cathode surface and then activating it with potassium cesium or by alternating antimony and alkali evaporation in a high vacuum environment.

[0010] Preferably, the first indium sealing end of the tube shell component is provided with an indium sealing groove, and an indium tin alloy is provided in the indium sealing groove. The second indium sealing end of the outer shell is a plane perpendicular to the axis of the tube shell structure. An indium sealing film layer is provided on the surface of the plane. The indium sealing film layer is connected to the indium sealing groove and is sealed by an indium tin alloy indium seal.

[0011] Preferably, the casing structure includes a getter ceramic ring, a positioning ceramic ring, a grid ceramic ring, and an indium-sealed ceramic ring arranged sequentially from the light input end toward the first indium-sealed end; The first end of the getter ceramic ring is connected to the first getter electrode, the second end is connected to the second getter electrode, and the getter connected between the first getter electrode and the second getter electrode includes a metal filament getter. The first end of the positioning ceramic ring is connected to the second getter electrode, and the second end is connected to the grid fixing electrode. The first end of the grid ceramic ring is connected to the grid fixing electrode, and the second end is connected to the grid output electrode. The first end of the indium-sealed ceramic ring is connected to the grid output electrode, and the second end is connected to the indium-sealed groove.

[0012] Preferably, the grid fixing electrode is provided with multiple limiting plates and a supporting ring. The inner surfaces of the multiple limiting plates form a first limiting surface for radially limiting the grid structure, and the upper surface of the supporting ring forms a second limiting surface for axially limiting the grid structure. The inner side of the grid output electrode is provided with an arc-shaped limiting plate, and the inner side of the arc-shaped limiting plate is provided with a pressure ring. The pressure ring makes the grid structure fit tightly against the second limiting surface.

[0013] The second aspect of the present invention provides a technical solution, such as the above-mentioned method for preparing an ultra-high speed response proximity focusing phototube, including the assembly of the tube shell component, the assembly of the cathode component, and the encapsulation of the tube shell component and the cathode component. The assembly of the shell component includes the following steps: Step Sa1: The first getter electrode, getter ceramic ring, second getter electrode, positioning ceramic ring, grid fixing electrode, grid ceramic ring, grid fixing electrode, indium sealing ceramic ring and indium sealing groove are stacked and assembled in sequence, and brazed in a high temperature vacuum environment to form a tube shell structure with high airtightness. Step Sa2: Use laser welding technology to weld the two ends of the metal wire getter to the first getter electrode and the second getter electrode; Step Sa3: Install the grid structure onto the surface of the support ring and achieve radial positioning through multiple circumferentially arranged limiting pieces. Then, place a shim on top of the grid structure, and then use a special tool to clamp the pressure ring, causing it to shrink and be placed on top of the shim. After releasing the tool, the pressure ring opens and is locked inside the arc-shaped limiting piece to complete the assembly of the grid structure. The assembly of the cathode component includes the following steps: Step Sb1: A reflective photocathode is formed on the cathode surface of the cathode structure by pre-fabricating antimony and then activating it with potassium cesium or by performing an alternating antimony-alkali co-evaporation process in a high vacuum environment. Step Sb2: The cathode structure is assembled with the ceramic structure and the outer shell using vacuum laser welding to form a cathode component with impedance matching characteristics. The encapsulation of the shell component and the cathode component includes the following steps: Step Sc1: Deposit a Cr / Cu / Ag indium sealing film layer on the mating surface between the outer casing and the indium sealing tank; Step Sc2: Place the indium tin alloy in the indium sealing tank and heat it to the melting temperature of the indium tin alloy in a vacuum or protective atmosphere to wet and fill the sealing interface, thus completing the airtight indium sealing connection between the shell component and the cathode component. After the shell component and the cathode component are assembled together, the distance between the cathode surface and the grid structure is not greater than 1 mm.

[0014] Compared with the prior art, the advantages of the present invention are as follows: This application employs a precision assembly and close-fitting focusing structure design, placing the reflective photocathode on the cathode surface. The distance between the cathode surface and the grid structure is controlled at the sub-millimeter level. The light signal is incident on the cathode surface through the grid, exciting electrons which are then directly emitted towards the grid. This significantly reduces the difference in electron flight paths, improves time consistency, greatly shortens electron transit time, and significantly enhances photoelectric response speed, achieving a rise time on the order of hundreds of picoseconds. In addition, this application uses a frustum-shaped cathode structure and a coaxial transition ceramic dielectric layer to achieve 50Ω characteristic impedance matching, effectively suppressing signal reflection and waveform distortion, ensuring distortion-free transmission of high-speed electrical signals, thereby enabling the entire tube to achieve rapid response capability. Attached Figure Description

[0015] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the ultra-high speed response proximity focusing phototube shown in this invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the ultra-high speed response proximity focusing phototube shown in this invention; Figure 3 This is a schematic diagram of the grid structure shown in this invention; Figure 4 This is a schematic diagram of the tubular shell structure shown in this invention; Figure 5 This is a schematic diagram of the structure of the cathode component shown in this invention; Figure 6 This is a schematic diagram illustrating the principle of converting optical signals into electrical signals as shown in this invention; Figure 7 This is a schematic diagram of the structure of the grid-fixed electrode shown in this invention; Figure 8 This is a schematic diagram of the structure of the pressure ring fixed to the grid power supply electrode as shown in this invention; Figure 9 This is a test diagram of the rise time of the phototube shown in this invention; Figure 10 This is a waveform diagram of the phototube shown in this invention. Detailed Implementation

[0016] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0017] Combination Figure 1 and Figure 2 As shown, the first aspect of the present invention provides an ultra-high speed response proximity focusing phototube, comprising a housing component 10 and a cathode component 20 connected to each other by indium sealing.

[0018] The housing component 10 includes a housing structure 11. Inside the housing structure 11, an input light window 12, a getter 13, and a grid structure 14 are arranged sequentially from the light input end 101 toward the first indium end 102. The housing structure 11 is constructed by brazing layered ceramic and metal electrode rings together, and includes at least a getter electrode and a grid output electrode 114.

[0019] The cathode component 20 includes a cathode structure 21 and a housing ground 23, with a coaxial transition using a ceramic structure 22 between the cathode structure 21 and the housing ground 23 to achieve impedance matching with the back-end electronics.

[0020] In an optional embodiment, the ceramic structure 22 is made of alumina or aluminum nitride. To reduce the accumulation effect of high-voltage charge in the ceramic, chromium may be doped into the ceramic material. Furthermore, the cathode structure 21 and the outer casing 23 are made of Kovar materials such as 4J29 or 4J33, and the solder used for assembling the cathode components 20 is silver-copper or oxygen-free copper solder.

[0021] The getter electrode is used to power the getter 13, the grid output electrode 114 provides a first voltage V1 to the grid structure 14, and the needle electrode 213 at the tail provides a second voltage V2 to the cathode structure 21.

[0022] The cathode structure 21 has a cathode surface 211 on the side facing the grid structure 14, and a reflective photocathode 24 is provided on the surface of the cathode surface 211.

[0023] Traditional photocathodes use transmission cathodes, and the cathode is usually placed on the inner surface of the light window. After light enters from one side of the light window, electrons are emitted from the other side and fly towards the cathode structure. In this application, a reflective photocathode 24 is placed on the surface of the cathode surface 211. Light passes through the grid structure 14 and irradiates the reflective photocathode 24 on the cathode surface 211. The excited photoelectrons are emitted towards the grid structure 14 under the action of the electric field. After the electrons are collected by the grid structure 14, the electrons lost by the cathode surface 211 form a current pulse. Through the design of impedance matching with the back-end electronics, distortion-free transmission is achieved.

[0024] In an optional embodiment, a reflective photocathode 24 is formed on the cathode surface 211 by pre-fabricating antimony followed by potassium cesium activation or by an alternating antimony-alkali co-evaporation process in a high vacuum environment.

[0025] Specifically, firstly, an antimony layer with a thickness of 100-400 nm is deposited on the cathode surface 211 using thermal evaporation, electron beam, or magnetron sputtering. Then, it is transferred to a vacuum chamber to activate potassium and cesium sources to form a reflective paper photocathode 24. Alternatively, antimony spheres, potassium sources, and cesium sources are simultaneously installed in a vacuum chamber, and antimony, potassium, and cesium are evaporated onto the cathode surface 211 using an electric current evaporation method to form a K2SbCs photocathode material.

[0026] Specifically, the reflective photocathode 24 receives the light signal incident through the input light window 12 and emits electrons towards the grid structure 14. The grid output electrode 114 provides a first voltage V1 to the grid structure 14, and the needle electrode 213 provides a second voltage V2 to the cathode structure 21. To achieve stable signal output, the cathode structure 23 is grounded, meaning the second voltage V2 is at zero potential, and the power supply potential of the grid output electrode 114 is positive.

[0027] Combination Figure 6As shown, the light signal passing through the input light window 12 is irradiated onto the surface of the reflective photocathode 24 by the grid structure 14, and electrons are excited by the reflective photocathode 24 and emitted in the direction of the grid structure 14.

[0028] As mentioned above, compared to the traditional method of placing the photocathode on the surface of the input light window, this application places the reflective photocathode 24 on the surface of the cathode surface 211. During the process of electrons generated by the photocathode and collected by the cathode surface 211, the electrons have a short movement path, so the electron transit time is extremely short and the transit time of all electrons is very small, which is the basis for achieving a rise time on the order of hundreds of picoseconds.

[0029] Furthermore, after the shell component 10 and the cathode component 20 are assembled together, the distance between the cathode surface 211 and the grid structure 14 is no greater than 1 mm. Preferably, the distance between the cathode surface 211 and the grid structure 14 is between 0.15 and 1 mm.

[0030] Thus, by reducing the distance between the cathode surface 211 and the grid structure 14, close-range focusing and ultra-high-speed response can be achieved. In the prior art, the path from the cathode to the electron collection surface is relatively long, resulting in differences in the time it takes for all electrons to reach the cathode, which slows down the rise time of the pulse signal. In this application, the distance between the cathode surface 211 and the grid structure 14 is compressed to the sub-millimeter level, so that all electrons are instantly accelerated under the action of the electric field, and the signal rise time is reduced to the level of hundreds of picoseconds.

[0031] Combination Figures 2 to 5 As shown, the cathode structure 21 is constructed as a frustum-shaped structure, the cathode surface 211 is the bottom surface of the frustum-shaped structure, and a needle-shaped electrode 213 is provided on the side of the frustum-shaped structure away from the cathode surface 211. The ceramic structure 22 is disposed between the needle-shaped electrode 213 and the outer shell ground 23.

[0032] By constructing the cathode structure 21 as a frustum shape, the area of ​​the cathode surface 211 at the bottom is made larger, which can effectively increase the electron collection area and optimize the electric field distribution between the cathode surface 211 and the grid structure 14.

[0033] Furthermore, a coaxial connection structure 202 is formed by the outer shell 23, the needle electrode 213, and the ceramic structure 22.

[0034] The coaxial connection structure 202 is used to connect a 50Ω coaxial cable. Therefore, the back-end electronics are a 50Ω coaxial cable, and the impedance between the outer casing ground 23 and the cathode structure 21 is set to 50Ω.

[0035] Thus, by using a coaxial structure design to achieve characteristic impedance matching of the coaxial cable and reduce signal reflection, it is possible to ensure that the high-speed electrical signal collected by the cathode surface 211 is transmitted without distortion and to suppress waveform distortion.

[0036] Preferably, the cone angle of the frustum-shaped structure side 212 is between 30° and 45°.

[0037] Thus, the bottom and top surfaces of the cathode structure 21 transition from a large diameter to a small diameter, with the large-diameter bottom surface serving as the signal input terminal and the small-diameter top surface serving as the signal output terminal. This design ensures that the impedance between the entire transition area and the outer casing ground remains stable at 50Ω.

[0038] Combination Figure 2 As shown, the first indium sealing end 102 of the tube shell component 10 is provided with an indium sealing groove 115, and an indium tin alloy 17 is provided in the indium sealing groove. The second indium sealing end 201 of the outer shell ground 23 is a plane perpendicular to the axis of the tube shell structure 11. An indium sealing film layer is provided on the surface of the plane. The indium sealing film layer is connected to the indium sealing groove 115 and is sealed by indium tin alloy 17.

[0039] Thus, when the second indium sealing end 201 of the outer casing 23 is attached to the surface of the indium sealing groove 115, the cathode surface 211 of the cathode structure 21 is kept parallel to the grid structure 14, ensuring that the electric field between the cathode structure 21 and the grid structure 14 is uniform.

[0040] Furthermore, the edge of the outer casing 23 is plated with a Cr / Cu / Ag indium sealing film layer.

[0041] In this layer, Cr serves as the underlayer, exhibiting strong adhesion to the oxides of ceramic or metal shells, providing a firm bond. Cu acts as a transition and barrier layer, bonding well with the Cr layer while preventing the diffusion of Ag or In from the upper layers to the underlayer; copper itself is also easy to solder. Ag serves as a brazing layer or indium capping layer, where silver forms a good metallurgical bond with the molten indium-tin alloy, achieving a reliable and hermetic seal.

[0042] Optionally, the thickness of the indium sealing film can be selected from 200nm to 1000nm. This ensures that the film is continuous and free of pinholes, effectively achieving its functions of adhesion, barrier, and solderability, while avoiding excessive thickness that could lead to excessive internal stress and peeling.

[0043] Combination Figure 4 As shown, the tube shell structure 11 includes a getter ceramic ring 11a, a positioning ceramic ring 11b, a grid ceramic ring 11c, and an indium-sealed ceramic ring 11d arranged sequentially from the light input end 101 toward the first indium-sealed end 102.

[0044] The first end of the getter ceramic ring 11a is connected to the first getter electrode 111, and the second end is connected to the second getter electrode 112. The getter 13 connected between the first getter electrode 111 and the second getter electrode 112 includes a metal filament getter.

[0045] The first end of the positioning ceramic ring 11b is connected to the second getter electrode 112, and the second end is connected to the grid fixing electrode 113.

[0046] The first end of the grid ceramic ring 11c is connected to the grid fixed electrode 113, and the second end is connected to the grid output electrode 114.

[0047] The first end of the indium-sealed ceramic ring 11d is connected to the grid output electrode 114, and the second end is connected to the indium-sealed groove 115.

[0048] As described above, the tube shell structure 11, from the light input end 101 to the first indium sealing end 102, is a layered ceramic and metal electrode ring superimposed and brazed connection structure consisting of a first getter electrode 111, a getter ceramic ring 11a, a second getter electrode 112, a positioning ceramic ring 11b, a grid fixing electrode 113, a grid ceramic ring 11c, a grid output electrode 114, an indium sealing ceramic ring 11d, and an indium sealing groove 115. This structure can achieve a vacuum airtightness leakage rate ≤1×10⁻⁶. -4 pa.cm 3 / s, to ensure a high vacuum environment for the phototube, enabling collision-free electron flight and a long cathode lifespan.

[0049] In a specific embodiment, combined with Figure 7 and Figure 8 As shown, the grid fixing electrode 113 is provided with multiple limiting pieces 113a and a supporting ring 113b. The inner surfaces of the multiple limiting pieces 113a form a first limiting surface that radially limits the grid structure 14, and the upper surface of the supporting ring 113b forms a second limiting surface that axially limits the grid structure 14. The inner side of the grid output electrode 114 is provided with an arc-shaped limiting piece 114a, and the inner side of the arc-shaped limiting piece 114a is provided with a pressure ring 16, which makes the grid structure 14 fit tightly against the second limiting surface.

[0050] Thus, the assembly structure and assembly sequence described above are designed to ensure the planarity and positional accuracy of the grid structure 14, and to strictly control the distance between the cathode surface 211 and the grid structure 14 to the sub-millimeter level. This is the key to achieving close-fit focusing and ultra-short electron transit time.

[0051] In an optional embodiment, the input window 12 is made of borosilicate glass, quartz, or sapphire. The input window 12 is made of borosilicate glass, quartz, or sapphire using glass metallization technology to achieve the transition of the borosilicate glass, quartz, or sapphire window to a metal Kovar edge.

[0052] Combination Figure 6 As shown, the photoelectric conversion principle and transmission path of the phototube are as follows: The cathode structure 21 is connected to zero potential via the tail needle electrode 213, the cathode structure shell is grounded, and the grid structure 14 is positively charged. Light enters the reflective photocathode 24 through the input light window 12 for photoelectric conversion. The converted electrons are accelerated towards the grid structure 14 under the action of the electric field and are eventually collected by the grid structure 14. The electrons lost by the reflective photocathode 24 form a waveform as shown in the waveform diagram. Figure 9 , Figure 10 The positive signal shown.

[0053] Appendix Figure 9 The image shows the signal waveform of the phototube directly tested using a high-speed oscilloscope. The rise time of the phototube, calculated by fitting, can reach 137 ps, as read from the oscilloscope.

[0054] When photoelectrons are collected, the resulting current signal is an ultrafast pulse on the order of picoseconds. For such a rapidly changing signal, the external high-voltage power supply and circuit can be regarded as short-circuited to ground. At this time, the reference ground of the signal is no longer the absolute ground at the far end, but the nearest low-impedance return path - i.e., the outer casing ground 23.

[0055] The cathode surface 211 serves as the signal end for collecting electrons, and the outer casing 23 serves as the signal return end. Together with the ceramic structure 22 between them, they constitute a standard coaxial transmission line.

[0056] As described above, by precisely designing the structure of the cathode 21, the inner diameter of the outer casing 23, and the dielectric constant of the ceramic structure 22, the characteristic impedance of the transmission line is precisely controlled at 50Ω. The entire cathode component 20 can be equivalent to a coaxial transmission line with an impedance of 50Ω, matching the coaxial line impedance of the downstream measurement system. Therefore, the ultrafast electrical signal generated by the reflective photocathode 24 can be transmitted to the output interface without reflection or distortion through the equivalent 50Ω coaxial transmission line, and finally accurately captured by the external measurement equipment.

[0057] {Example 2} The second aspect of the present invention provides a technical solution, such as the above-mentioned method for preparing an ultra-high speed response proximity focusing phototube, including the assembly of the tube shell component 10, the assembly of the cathode component 20, and the encapsulation of the tube shell component 10 and the cathode component 20. The assembly of the shell component 10 includes the following steps: Step Sa1: The first getter electrode 111, getter ceramic ring 11a, second getter electrode 112, positioning ceramic ring 11b, grid fixing electrode 113, grid ceramic ring 11c, grid output electrode 114, indium sealing ceramic ring 11d and indium sealing groove 115 are stacked and assembled in sequence, and brazed in a high temperature vacuum environment to form a tube shell structure 11 with high airtightness.

[0058] Thus, by stacking and vacuum brazing multiple ceramic-metal electrode rings, a high-vacuum sealed, structurally robust, and reliably insulated tubular shell is constructed, achieving a vacuum leak rate ≤1×10⁻⁶. -4 pa.cm 3 / s, to ensure a high vacuum environment for the phototube, enabling collision-free electron flight and a long cathode lifespan.

[0059] Step Sa2: The two ends of the metal wire getter 13 are welded to the first getter electrode 111 and the second getter electrode 112 using laser welding technology. Laser welding can achieve local rapid heating of the getter 13, avoid overheating damage to the surrounding ceramics or electrodes, ensure reliable electrical connection of the getter 13 and subsequent activation to maintain the vacuum in the tube.

[0060] Step Sa3: Install the grid structure 14 onto the surface of the support ring 113b, and achieve radial positioning through multiple circumferentially arranged limiting pieces 113a. Then, place the shim 15 on top of the grid structure 14, and then clamp the pressure ring 16 with a special tool to shrink it and place it on top of the shim 15. After releasing the tool, the pressure ring 16 opens and is locked inside the arc-shaped limiting piece 114a to complete the assembly of the grid structure 14. This assembly sequence ensures the flatness and positional accuracy of the grid and strictly controls the distance between the cathode surface 211 and the grid structure 14 to the sub-millimeter level, which is the key to achieving close-fit focusing and ultra-short electron transit time.

[0061] The assembly of the cathode component 20 includes the following steps: Step Sb1: A reflective photocathode 24 is formed on the cathode surface 211 of the cathode structure 21 by pre-fabricating antimony and then activating it with potassium cesium or by performing an alternating antimony-alkali co-evaporation process in a high vacuum environment.

[0062] In a specific embodiment, an antimony layer with a thickness of 100-400 nm is first deposited on the cathode surface 211 using thermal evaporation, electron beam, or magnetron sputtering. Then, it is transferred to a vacuum chamber where potassium and cesium sources are activated to form a reflective paper photocathode 24. Alternatively, an antimony sphere, potassium source, and cesium source are simultaneously installed in a vacuum chamber, and antimony, potassium, and cesium are evaporated onto the cathode surface 211 using an electric current evaporation method to form a K2SbCs photocathode material.

[0063] Step Sb2: The cathode structure 21 is assembled with the ceramic structure 22 and the outer shell 23 using vacuum laser welding to form a cathode component 20 with impedance matching characteristics.

[0064] Thus, welding in a vacuum environment can prevent parts from oxidizing and ensure connection quality. The coaxial transition design of the ceramic structure 22 and laser welding can ensure that the cathode output impedance is precisely matched to 50Ω and reduce high-speed signal reflection.

[0065] The encapsulation of the housing component 10 and the cathode component 20 includes the following steps: Step Sc1: Deposit a Cr / Cu / Ag indium sealing film layer on the mating surface of the outer casing 23 and the indium sealing tank 115; In this layer, Cr serves as the underlayer, exhibiting strong adhesion to the oxides of ceramic or metal shells, providing a firm bond. Cu acts as a transition and barrier layer, bonding well with the Cr layer while preventing the diffusion of Ag or In from the upper layers to the underlayer; copper itself is also easy to solder. Ag serves as a brazing layer or indium capping layer, where silver forms a good metallurgical bond with the molten indium-tin alloy, achieving a reliable and hermetic seal.

[0066] Step Sc2: Place the indium tin alloy 17 in the indium sealing groove 115 and heat it to the melting temperature of the indium tin alloy in a vacuum or protective atmosphere to wet and fill the sealing interface, thus completing the airtight indium sealing connection between the shell component 10 and the cathode component 20. After the shell component 10 and the cathode component 20 are assembled together, the distance between the cathode surface 211 and the grid structure 14 is no more than 1 mm.

[0067] Thus, by using a low-temperature indium tin alloy and sealing it in a controlled atmosphere, thermal damage to the photocathode and assembled components can be avoided by high temperature. At the same time, a high-airtightness package can be achieved to ensure that the high vacuum required for long-term operation inside the phototube is maintained. Furthermore, the extremely close-patch spacing control has reduced the electron trajectory path, and the coaxial conical cathode structure enables ultra-high-speed electronic output, thereby enabling the entire tube to achieve rapid response capability.

[0068] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A high-speed response proximity focusing phototube, characterized in that, Includes a housing component (10) and a cathode component (20) that are indium-sealed together. The housing component (10) includes a housing structure (11). Inside the housing structure (11), an input light window (12), a getter (13), and a grid structure (14) are arranged sequentially from the light input end (101) to the first indium end (102). The housing structure (11) is constructed by brazing layered ceramic and metal electrode rings, and includes at least a getter electrode and a grid output electrode (114). The cathode component (20) includes a cathode structure (21) and a housing ground (23), with a coaxial transition using a ceramic structure (22) between the cathode structure (21) and the housing ground (23) to achieve impedance matching with the back-end electronics; The cathode structure (21) has a cathode surface (211) facing the grid structure (14), and the surface of the cathode surface (211) is provided with a reflective photocathode (24). After the tube shell component (10) and the cathode component (20) are assembled together, the distance between the cathode surface (211) and the grid structure (14) is no more than 1 mm. The reflective photocathode (24) is used to receive the light signal incident through the input light window (12) and emit electrons in the direction of the grid structure (14) to be received by the grid structure (14). The reflective photocathode (24) converts the electron cloud signal lost by the cathode surface (211) into an electrical pulse signal and outputs it to the outside of the phototube.

2. The ultra-high-speed response proximity focusing phototube according to claim 1, characterized in that, The cathode component (20) is constructed as a frustum-shaped structure, the cathode surface (211) is the bottom surface of the frustum-shaped structure, and a needle electrode (213) is provided on the side of the frustum-shaped structure away from the cathode surface (211). The ceramic structure (22) is disposed between the needle electrode (213) and the outer shell (23).

3. The ultra-high-speed response proximity focusing phototube according to claim 2, characterized in that, The cone angle of the side (212) of the frustum-shaped structure is between 30° and 45°.

4. The ultra-high-speed response proximity focusing phototube according to claim 2, characterized in that, A coaxial connection structure (202) is formed by the outer casing (23), the needle electrode (213) and the ceramic structure (22), the coaxial connection structure (202) is used to connect a 50Ω coaxial cable, and the impedance between the outer casing (23) and the cathode structure (21) is set to 50Ω.

5. The ultra-high-speed response proximity focusing phototube according to claim 1, characterized in that, The distance between the cathode surface (211) and the grid structure (14) is between 0.15 and 1 mm.

6. The ultra-high-speed response proximity focusing phototube according to claim 1, characterized in that, The reflective photocathode (24) is formed on the cathode surface (211) by pre-preparing antimony and then activating it with potassium cesium or by alternating antimony and alkali evaporation in a high vacuum environment.

7. The ultra-high-speed response proximity focusing phototube according to claim 1, characterized in that, The first indium sealing end (102) of the shell component (10) is provided with an indium sealing groove (115), and an indium tin alloy (17) is provided in the indium sealing groove. The second indium sealing end (201) of the outer shell ground (23) is a plane perpendicular to the axis of the shell structure (11). An indium sealing film layer is provided on the surface of the plane. The indium sealing film layer is connected to the indium sealing groove (115) and is sealed by indium tin alloy (17).

8. The ultra-high-speed response proximity focusing phototube according to claim 1, characterized in that, The casing structure (11) includes a getter ceramic ring (11a), a positioning ceramic ring (11b), a grid ceramic ring (11c) and an indium-sealed ceramic ring (11d) arranged sequentially from the light input end (101) to the first indium-sealed end (102). The first end of the getter ceramic ring (11a) is connected to the first getter electrode (111), and the second end is connected to the second getter electrode (112). The getter (13) connected between the first getter electrode (111) and the second getter electrode (112) includes a metal filament getter. The first end of the positioning ceramic ring (11b) is connected to the second getter electrode (112), and the second end is connected to the grid fixing electrode (113). The first end of the grid ceramic ring (11c) is connected to the grid fixed electrode (113), and the second end is connected to the grid output electrode (114). The first end of the indium-sealed ceramic ring (11d) is connected to the grid output electrode (114), and the second end is connected to the indium-sealed groove (115).

9. The ultra-high-speed response proximity focusing phototube according to claim 8, characterized in that, The grid fixing electrode (113) is provided with multiple limiting pieces (113a) and a supporting ring (113b). The inner surfaces of the multiple limiting pieces (113a) form a first limiting surface that radially limits the grid structure (14), and the upper surface of the supporting ring (113b) forms a second limiting surface that axially limits the grid structure (14). The inner side of the grid output electrode (114) is provided with an arc-shaped limiting piece (114a), and the inner side of the arc-shaped limiting piece (114a) is provided with a pressure ring (16). The pressure ring (16) makes the grid structure (14) fit tightly against the second limiting surface.

10. The method for fabricating an ultra-high-speed response proximity focusing phototube according to claim 1, characterized in that, This includes the assembly of the housing component (10), the assembly of the cathode component (20), and the encapsulation of the housing component (10) and the cathode component (20); The assembly of the shell component (10) includes the following steps: Step Sa1: The first getter electrode (111), getter ceramic ring (11a), second getter electrode (112), positioning ceramic ring (11b), grid fixing electrode (113), grid ceramic ring (11c), grid output electrode (114), indium sealing ceramic ring (11d) and indium sealing groove (115) are stacked and assembled in sequence, and brazed in a high temperature vacuum environment to form a tube shell structure (11) with high airtightness. Step Sa2: Use laser welding process to weld the two ends of the metal wire getter (13) to the first getter electrode (111) and the second getter electrode (112). Step Sa3: Install the grid structure (14) onto the surface of the support ring (113b) and achieve radial positioning through multiple circumferentially arranged limiting pieces (113a). Then place a shim (15) on top of the grid structure (14), and then clamp the pressure ring (16) with a special tool to shrink it and place it on top of the shim (15). After releasing the tool, the pressure ring (16) opens and is locked inside the arc-shaped limiting piece (114a) to complete the assembly of the grid structure (14). The assembly of the cathode component (20) includes the following steps: Step Sb1: A reflective photocathode (24) is formed on the cathode surface (211) of the cathode structure (21) by pre-preparing antimony and then activating it with potassium cesium or by performing an alternating antimony-alkali co-evaporation process in a high vacuum environment. Step Sb2: The cathode structure (21) is assembled with the ceramic structure (22) and the outer shell (23) using vacuum laser welding to form a cathode component (20) with impedance matching characteristics. The encapsulation of the housing component (10) and the cathode component (20) includes the following steps: Step Sc1: Deposit a Cr / Cu / Ag indium sealing film layer on the mating surface of the outer casing (23) and the indium sealing tank (115); Step Sc2: Place the indium tin alloy (17) in the indium sealing tank (115) and heat it to the melting temperature of the indium tin alloy in a vacuum or protective atmosphere to wet and fill the sealing interface, thus completing the airtight indium sealing connection between the shell component (10) and the cathode component (20). After the shell component (10) and the cathode component (20) are assembled together, the distance between the cathode surface (211) and the grid structure (14) is not greater than 1 mm.

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