A large-area cathode small-size streak tube and a preparation method thereof

Abstract

The application discloses a large-area cathode small-size streak tube and a preparation method thereof. The streak tube comprises, in sequence along an electron beam transmission direction, a curved surface photocathode, a grid electrode, a first focusing electrode, a second focusing electrode, an anode, a drift region and a fluorescent screen. The photocathode is a continuous surface cathode, the effective working diameter is not less than 30 mm, and the total length is not more than 300 mm, so that miniaturization is realized. By replacing the photocathode material and the input window material, the streak tube can work in multiple wave bands such as visible light, X-rays or ultraviolet light according to different cathode materials. The preparation method adopts a transfer indium sealing process, separates cathode manufacturing from tube shell assembly, avoids electrode pollution, and improves device performance and yield. The application has the advantages of large detection area, high spatial resolution, picosecond-level time resolution, wave band expansion, reliable preparation process and the like, and is suitable for fields of ultrafast diagnosis, plasma physics, nuclear detection and the like.

Description

Technical Field

[0001] This invention relates to the field of ultrafast diagnostic device technology, specifically to a large-area cathode miniature stripe tube and its fabrication method, which is suitable for high temporal and spatial resolution diagnosis in visible light, X-ray, ultraviolet and other bands. Background Technology

[0002] A stripe tube (or stripe image converter tube) is a high-end optoelectronic device with ps or even fs-level time resolution and μm-level spatial resolution. It is widely used in synchrotron radiation sources, electron-positron colliders, high-temperature and high-density plasma diagnostics, biomedical fluorescence lifetime measurement and other fields. Its working principle is that the light signal to be measured irradiates the photocathode to generate photoelectrons. After the electrons are accelerated, focused and deflected, the time change information is converted into spatial change information, and finally imaged on the fluorescent screen.

[0003] Traditional striped tubes often employ slit cathode structures (such as the ST-Y type from Photek in the UK, with a cathode size of 35 mm × 5 mm) to achieve time-space conversion. However, the detection area of ​​slit cathodes is limited and insufficient for large-area two-dimensional spatial resolution imaging requirements. Existing striped tubes are typically designed for a single wavelength band (visible light or X-ray), resulting in poor versatility. In terms of fabrication processes, traditional non-transfer system fabrication methods involve cathode fabrication and device assembly within the same housing, which easily leads to electrode contamination, resulting in high-voltage arcing, increased noise, decreased dynamic range, and low vacuum sealing success rate. Some patents have adopted transfer sealing technology, but these are mostly for slit cathode structures and primarily for the visible light band, without addressing large-area cathode (continuous surface cathode) structures, miniaturized designs, or fabrication methods compatible with multiple wavelength bands.

[0004] Therefore, developing a striped tube with a large cathode area, miniaturization, compatibility with multiple wavelengths, and reliable fabrication process has significant application value. Summary of the Invention

[0005] This invention aims to solve the problems of existing striped tubes, such as small detection area, inability to directly perform two-dimensional imaging, large size, single wavelength range, and performance degradation due to electrode contamination during fabrication. It provides a striped tube and its fabrication method with a working area of ​​not less than 35 mm in diameter or an equivalent large-area cathode, miniaturized (total length not exceeding 300 mm, outer diameter not exceeding 65 mm), compatible with multiple wavelength ranges (visible light, X-rays, ultraviolet), and with a reliable fabrication process. Simultaneously, it avoids electrode contamination during cathode fabrication, improves device performance and yield, and ultimately achieves a sealing vacuum level better than 1×10⁻⁶. -7 Pa.

[0006] This invention provides a large-area cathode miniature stripe tube, which, along the electron beam transmission direction, sequentially comprises: a curved photocathode, a grid electrode, a first focusing electrode, a second focusing electrode, an anode, a drift region, and a fluorescent screen. All electrodes are encapsulated within a vacuum tube shell.

[0007] The CST software was used to model and simulate a small striped tube with a large cathode. The structural parameters of each electrode are as follows: The photocathode is located at an axial coordinate of 0 to 5.25 mm, with a spherical structure, a radius of curvature of not less than 90 mm, an axial arc length of 4.5–5.5 mm, a radial arc length of 25–35 mm, and an applied voltage of 0 V. The grid electrode is located at an axial coordinate of 15 mm to 30 mm, with an inner radius of 30 mm, and an applied voltage of 0.7–1 kV. The first focusing electrode is located at an axial coordinate of 37.5 mm to 52.5 mm, with an inner radius of 27 mm, and an applied voltage of 1.9–2.5 kV. The second focusing electrode is located at an axial coordinate of 60 mm to 90 mm, with an inner radius of 27 mm, and an applied voltage of 4.5–6.5 kV. The anode is located at an axial coordinate of 82.5 mm to 90 mm, with an inner radius of 15 mm, and a central aperture with a radius of 7.5 mm or 5 mm, and an applied voltage of 13–15 kV. The drift region is located at an axial coordinate of 135 mm to 250 mm, with an inner radius of 30 mm, and an applied voltage of 13 to 15 kV. The fluorescent screen is located at an axial coordinate of 250 mm, with an applied voltage of 13 to 15 kV. The applied potential at each location can be increased or decreased synchronously to ensure a voltage difference. The total length of the entire casing is no more than 300 mm, and the outer diameter is no more than 65 mm, achieving miniaturization.

[0008] The photocathode is a continuous surface cathode with an effective working diameter of not less than 30 mm (actual designs can reach 35 mm). The cathode material is not predetermined: for the visible light band, a multi-alkali cathode (chemical formula Na₂KSb(Cs)) is used; for the X-ray band, CsI, Au, or other high atomic number cathode materials are used; for the ultraviolet band, CsTe, etc., are used. By changing the cathode material and the input window material (borosilicate glass for visible light, Be film for X-rays, and quartz or MgF₂ for ultraviolet), cross-band applications of the same electron optical structure can be achieved.

[0009] The present invention also provides a method for preparing the large-area cathode miniature stripe tube, which employs a transfer indium sealing process and includes the following simplified steps:

[0010] a) Component preparation: Prepare metal parts, ceramic parts and optical parts respectively, and conduct incoming inspection, cleaning and annealing leak detection; prepare cathode evaporation source and indium tin alloy.

[0011] b) Component assembly and adjustment: The metal electrodes, ceramic insulators and optical components are grouped and coaxially assembled and welded with high precision, and vacuum leak testing is performed; the components are assembled by laser welding or spot welding to form a striped tube single tube for cathode preparation, and vacuum leak testing is performed again.

[0012] c) Cathode fabrication: The striped tube to be fabricated and the cathode evaporation source are assembled into the cathode transfer fabrication system. In the cathode fabrication chamber of the cathode transfer fabrication system, photocathode material is deposited according to the target wavelength.

[0013] d) Transfer of Indium Sealing (Indium Sealing): Indium-tin alloy is heated and melted in the indium sealing chamber. The input end, after cathode preparation, is transferred and sealed onto the tube shell. After cooling, it is sealed to ensure a vacuum level better than 1×10⁻⁶. -7 Pa.

[0014] e) Performance testing (optional): Based on the target wavelength, use a corresponding light source to illuminate the cathode input window and measure the spatial resolution, temporal resolution, deflection sensitivity, and other indicators on the fluorescent screen.

[0015] Preferably, in step a), the specific process for cleaning the metal parts is as follows: ultrasonic cleaning in acetone solution for 5 minutes, ultrasonic cleaning in 1% to 3% alkaline detergent solution at room temperature for 5 minutes, rinsing in running tap water for 5 minutes, rinsing in running deionized water for 5 minutes, ultrasonic cleaning in 1% to 3% acidic detergent solution at room temperature for 5 minutes, rinsing in running tap water for 5 minutes, rinsing in running deionized water for 5 minutes, dehydrating with alcohol, and then drying in a 50 °C oven.

[0016] Preferably, in step a), the dried metal parts are subjected to hydrogen annealing (hydrogen atmosphere annealing) in a tube furnace, with the H2 flow rate set to 8 L / min, the N2 flow rate set to 8 L / min, the N2 flow rate set to 55 L / min when the furnace is started, the heating temperature to 400 °C to 1000 °C, and the holding time to 15 min to 30 min.

[0017] Preferably, in step a), the ceramic parts are ultrasonically cleaned for 10 minutes each in degreasing agent, alcohol, and deionized water, and then dried. The ceramic parts that need to be metallized are treated with the molybdenum-manganese method or the active metal method.

[0018] Preferably, in step a), after the cathode input window of the optical component is high-frequency sealed to the Kovar metal disk and then subjected to high-temperature annealing, the vacuum leak detection leak rate is less than 10%. -10 Pa·L / s.

[0019] Preferably, in step a), the grid electrode is a nickel grid with a thickness of 5 μm to 7 μm, a line width of 8 μm to 12 μm, and a grid size of 40 μm to 50 μm; the effective working diameter of the grid electrode is not less than 35 mm, and there are no holes with a diameter greater than 0.08 mm or wrinkles with a diameter greater than 0.5 mm in the working area.

[0020] Preferably, in step a), the indium sealing material is an In-Sn alloy (melting point 118 °C), which is pre-melted and formed at 600 °C after cleaning.

[0021] Preferably, in step b), after the high-precision coaxial assembly, spot welding, and laser welding processes between various parts and solders, the coaxiality must be better than 0.05 mm, and the leak detection vacuum degree must be better than 5×10⁻⁶ mm. -7 Pa.

[0022] Preferably, in step b), the cathode ring, grid electrode, first focusing electrode, second focusing electrode, anode, and drift electrode are placed on a special mounting fixture according to the designed axial position to ensure coaxiality better than 0.05 mm; different tube shells are laser welded in segments.

[0023] Preferably, in step b), when assembling the grid assembly, a clamp is used to position the grid ring, place the grid and pressure ring, apply the assembly load, spot weld power of 10 W·s to 25 W·s, pulse time of 2 ms, and rotate and install after spot welding.

[0024] Preferably, in step b), the image quality is adjusted using a metal photocathode in the electron optical simulation assembly system; after assembly, a vacuum leak test is performed, and the leak rate is less than 10%. -10 Pa·L / s.

[0025] Preferably, in step c), the assembled tube shell (excluding the input end) is placed into the indium sealing chamber of the transfer system, and the input end and cathode evaporation source are placed into the cathode fabrication chamber, baked at 350 °C for more than 10 h, with a vacuum degree better than 1×10⁻⁶. -7 Pa.

[0026] Preferably, in step c), an electric current is slowly applied to the cathode evaporation source for degassing.

[0027] Preferably, in step c), the cathode is deposited according to the target wavelength: for visible light multi-alkali cathodes, Sb, K, Na, and Cs are evaporated in sequence, and the photocurrent is monitored to the maximum value; for X-ray cathodes, CsI or Au films are deposited by thermal evaporation or electron beam evaporation with a thickness of 100 nm to 300 nm and a rate of 0.5 nm / s; for ultraviolet cathodes, Te and Cs are evaporated alternately.

[0028] Preferably, in step d), the heating temperature is 120 °C to 130 °C, the melting point of the indium-tin alloy is 118 °C, and it is sealed in a vacuum with a degree better than 1 × 10⁻⁶. -7 The experiment was conducted under the condition of Pa.

[0029] Preferably, in step d), the indium-sealed chamber is heated to 120 °C to 130 °C to melt the In-Sn alloy. The input end of the prepared cathode is transferred to the indium-sealed chamber through a magnetic transfer rod. After aligning the upper and lower indium-sealed structures, the tube is slowly lowered into the liquid alloy, allowed to cool and solidify naturally, and then the entire tube is removed.

[0030] Preferably, in step e), a USAF 1951 resolution plate is attached to the light input window, illuminated by a white LED array, and the focusing voltage is adjusted to make the fluorescent screen image clear. The image is acquired by a CCD, and the spatial resolution is calculated by modulating the transfer function. The slit cathode is replaced, a voltage is applied to one side of the deflection electrode, and the slit image displacement is measured to calculate the deflection sensitivity. The temporal resolution is calculated based on the transit time dispersion simulation and the deflection sensitivity, scanning voltage slope, and dynamic spatial resolution.

[0031] The beneficial effects of this invention are:

[0032] (1) Large-area cathode and two-dimensional imaging capability. The effective working area of ​​the cathode is not less than 30 mm in diameter (up to 35 mm). It is a continuous surface cathode and can be directly used for two-dimensional spatial resolution imaging, overcoming the limitation of small detection area of ​​slit cathode.

[0033] (2) Miniaturization and structural versatility. The total length of the tube shell is no more than 300 mm and the outer diameter is no more than 65 mm, making it compact in size. The electron optical structure is versatile, and by changing the cathode material and the input window material, it can be applied to different bands such as visible light, X-ray, and ultraviolet light, meeting various ultra-fast diagnostic needs.

[0034] (3) High-reliability manufacturing process. The transfer indium sealing technology is employed, separating cathode fabrication from shell assembly, avoiding electrode contamination, reducing high-voltage arcing, improving dynamic range, and ultimately achieving a sealing vacuum degree better than 1×10⁻⁶. -7 Pa.

[0035] (4) Excellent performance indicators. The coaxiality is better than 0.05 mm, the measured static spatial resolution is 52 lp / mm (@MTF5%), the deflection sensitivity is 258.6 V / cm, and the temporal resolution is 38 ps, which meets the requirements of ultra-fast diagnosis. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for fabricating a small striped tube with a large cathode.

[0037] Figure 2This is a schematic diagram (axial section) of a large-area cathode miniature stripe tube structure.

[0038] Figure 3 This is a diagram of the electric field distribution in the CST simulation.

[0039] Figure 4 This is a graph showing the spatial resolution test results of the USAF 1951 resolution board. Detailed Implementation

[0040] Combined with appendix Figure 1 Through the detailed description of the embodiments of the present invention, the above and other objects, features, and advantages of the present invention will become clearer. It should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0041] Example 1: Fabrication of a large-area cathode miniature stripe tube in the visible light band

[0042] See Figure 1 As shown, this embodiment illustrates a method for fabricating a large-area cathode miniature stripe tube, employing a transfer indium sealing process, and includes the following steps:

[0043] a) Component Preparation and Incoming Material Inspection. Based on the designed electro-optical structure, metal components (including cathode rings, grid electrodes, first focusing electrode, second focusing electrode, anode, and drift electrode), ceramic components (including segmented insulators and support rings), and optical components (including cathode input windows and anode panels) are prepared. All components undergo incoming material inspection. Metal components are sequentially subjected to ultrasonic treatment with acetone, alkaline detergent, and acidic detergent, followed by rinsing with deionized water. They are then dehydrated with alcohol and dried in a 50°C oven, followed by hydrogen annealing at 400°C–1000°C in a tube furnace. Optical components are ultrasonically cleaned with deionized water, then high-frequency sealed to a Kovar metal disc and annealed at high temperature. Ceramic components are ultrasonically cleaned for 10 minutes each with degreasing agent, alcohol, and deionized water. Ceramic components requiring metallization are treated using the molybdenum-manganese method. Additionally, cathode evaporation source materials (such as Sb, K, Na, Cs, etc.) with a purity of not less than 99.99% and indium-tin alloy solder with a melting point of 118°C are prepared.

[0044] b) Component assembly and vacuum leak testing. The components processed in step a) are placed on a dedicated high-precision assembly fixture and assembled in groups according to the axial design position. They are then fixed using laser welding or spot welding, with the coaxiality of each electrode strictly controlled to be better than 0.05 mm. The welded components undergo a first helium mass spectrometry leak test to ensure a leak rate of less than 5 × 10⁻⁶. -7Pa·L / s; then the components are assembled into a "single striped tube for cathode fabrication" (i.e., a semi-finished tube shell without a photocathode installed), and a second vacuum leak test is performed to confirm that the tube shell itself has qualified vacuum sealing, providing a clean vacuum environment for subsequent cathode fabrication.

[0045] c) High-vacuum cathode preparation. The qualified semi-finished tube shell (excluding the input end) from step b) is placed in the indium-sealed chamber of the cathode transfer preparation system. The input end assembly with the cathode input window and the evaporation source are placed in the cathode fabrication chamber. The system chambers are then baked at 350°C for more than 10 hours to ensure that the vacuum level of both chambers is better than 1×10⁻⁶. -7 Pa; depending on the target operating wavelength, material deposition is performed in the cathode fabrication chamber: for the visible light band, Sb, K, Na, and Cs are evaporated in sequence, and the photocurrent is monitored in real time until it reaches its peak value (e.g., above 500 nA); for the X-ray band, Au or CsI thin films are deposited by thermal evaporation; for the ultraviolet band, CsTe cathodes are prepared by alternating evaporation of Te and Cs to ensure that the cathode has the best quantum efficiency.

[0046] d) Transferring the indium seal to the casing. Maintaining the high vacuum environment of step c), the indium seal chamber is heated to 120℃~130℃ to completely melt the pre-placed indium-tin alloy solder. The input end assembly, with the cathode already prepared, is smoothly transferred from the fabrication chamber to the indium seal chamber using a magnetic transfer rod. A high-precision positioning mechanism precisely aligns the indium seal groove at the input end with the cutting edge of the main casing, and then it is slowly pressed into the liquid alloy. Heating is stopped, and the alloy is allowed to cool and solidify naturally in a vacuum environment, forming a dense, high-strength weld. This achieves a high-vacuum, high-reliability seal between the input end and the casing, maintaining an overall tube vacuum level better than 1×10⁻⁶. -7 Pa.

[0047] e) Single-tube testing and overall tube sealing. Preliminary performance testing is performed on the sealed single tubes from step d). A USAF1951 resolution board and a white LED light source are used to illuminate the cathode input window. The voltages of each electrode are adjusted, and images are acquired on the fluorescent screen via CCD. Key indicators such as spatial resolution, deflection sensitivity, and temporal resolution are tested. After passing the tests, the entire tube undergoes final sealing treatment (such as venting or ion pump welding) to complete the overall device fabrication. Finally, comprehensive testing of the entire tube is conducted to verify its imaging quality and ultrafast diagnostic capabilities in the target wavelength band, ensuring that the device meets design requirements.

[0048] This embodiment is performed according to steps a) to e) above, with the specific parameters as follows:

[0049] The incident window is made of borosilicate glass with a diameter of 35 mm and a thickness of 2 mm. The photocathode is a polyalkali Na2KSb(Cs), which is evaporated in the order of Sb, K, Na, and Cs. The substrate temperature is maintained at 200 °C, and the final photocurrent reaches more than 500 nA (white light source), with a spectral response range of 400 to 800 nm.

[0050] Electrode voltage settings: photocathode -15 kV, grid electrode -14.2 kV, first focusing electrode -14.2 kV, second focusing electrode -3.22 kV, anode 0 V (refer to the actual operating voltage in the test report; the polarity is opposite to the simulation voltage, but the absolute value is equivalent). The total tube length is approximately 256 mm, and the maximum outer diameter is 65 mm. During assembly, ensure coaxiality better than 0.05 mm and leak detection vacuum better than 5 × 10⁻⁵ kV. -7 Pa.

[0051] Spatial resolution test: The USAF 1951 resolution board was tightly attached to the cathode input window and uniformly illuminated with a white LED array. Operating voltages were applied to each electrode of the stripe tube (e.g., photocathode -15 kV, grid electrode -14.2 kV, first focusing electrode -14.2 kV, second focusing electrode -3.22 kV, anode 0 V), and the focusing voltage was adjusted to achieve the clearest image of the resolution board on the fluorescent screen. Images of the fluorescent screen were acquired using a CCD camera, and the modulation transfer function (MTF) was calculated. When the MTF value reached 5% (the limit of human visual resolution), the corresponding line pair values ​​were read. In this embodiment, the measured limit of spatial resolution reached 52 lp / mm. Figure 4 As shown, this proves that the large-area cathode and electron optical design of the present invention successfully achieve high-definition two-dimensional imaging, effectively solving the problem that the traditional slit cathode has a small detection area and cannot directly perform two-dimensional imaging.

[0052] Deflection sensitivity test: The cathode was replaced with a 100 μm wide slit, and a voltage of -100 V was applied to the deflection electrode (the other side was grounded). The displacement of the slit image on the fluorescent screen was measured. Combined with the downscaling of the optical imaging system, the deflection sensitivity was calculated to be 258.6 V / cm. This high sensitivity value is a prerequisite for achieving picosecond-level time resolution.

[0053] Temporal resolution calculation: Based on the electron transit time dispersion simulated by CST software (less than 1 ps) and the above-mentioned measured deflection sensitivity, combined with the scanning voltage slope (75 V / ns) and dynamic spatial resolution (conservatively taken as 30% of the static value of 52 lp / mm, approximately 9 lp / mm), the total temporal resolution was calculated to be approximately 38 ps using the formula. This result confirms that the miniaturized stripe tube of this invention possesses picosecond-level temporal resolution capability, meeting the requirements for use in the field of ultrafast diagnostics.

[0054] Dimensioning and Vacuum Verification: The entire tube was measured using vernier calipers. The total length was 255–256 mm, and the maximum outer diameter was 65 mm, meeting the miniaturization design goal of a total length not exceeding 300 mm and an outer diameter not exceeding 65 mm. Simultaneously, the vacuum level inside the tube was maintained by an ion pump, consistently better than 1×10⁻⁶. -7 Pa demonstrates the reliability of the transfer indium sealing process, avoiding the problems of high-voltage arcing and vacuum reduction caused by electrode contamination in traditional processes.

[0055] Example 2: Performance testing of the striped tube prepared in Example 1

[0056] The main results are as follows:

[0057] Spatial resolution: A USAF 1951 resolution board (groups 0-7) is attached to the light input window, illuminated by a white LED array. The focusing voltage is adjusted to ensure clear imaging on the fluorescent screen, and the image is acquired by a CCD. Calculations based on the modulation transfer function show that when the modulation depth is taken as 5% of the human visual resolution limit, the limiting spatial resolution is 52 lp / mm.

[0058] Spatial magnification: By comparing the linewidth of the resolution board with the image width, the measured spatial magnification is 1.0.

[0059] Deflection sensitivity: Replace the cathode with a 100 μm wide slit, apply a -100 V voltage to one side of the deflection electrode and ground the other side, and measure the slit image displacement. Considering the optical lens magnification (0.5), the calculated deflection sensitivity is 258.6 V / cm.

[0060] Time resolution: based on the formula Calculation, where the physical time resolution T p The total transit time dispersion obtained from CST simulations is less than 1 ps, indicating a technical time resolution. (P is the deflection sensitivity, S is the scanning voltage slope of 75 V / ns, and R is the dynamic spatial resolution, conservatively taken as 30% of the static value, i.e., 9 lp / mm). The calculated T... t ≈38ps, therefore the total time resolution is approximately 38 ps.

[0061] Temporal magnification: The temporal magnification was calculated to be 0.8 by comparing the width of the slit image before and after deflection.

[0062] Bare pipe dimensions: Measured with vernier calipers, pipe length 255~256 mm, maximum pipe diameter 65 mm.

[0063] Vacuum level: After indium transfer sealing, the vacuum level inside the tube is maintained by an ion pump, which is better than 1×10⁻⁶. -7 Pa.

[0064] The above test data shows that the large-area cathode miniature stripe tube prepared by this invention achieves high spatial resolution, high deflection sensitivity and picosecond-level temporal resolution in the visible light band, and is compact in size with excellent vacuum performance, meeting the needs of ultrafast diagnosis.

[0065] Example 3: Fabrication of a small striped tube with a large-area cathode in the X-ray band

[0066] The main difference between this embodiment and Embodiment 2 is:

[0067] The incident window is made of quartz glass, 0.5 mm thick and 35 mm in diameter. The photocathode is a thermally evaporated Au thin film, 150 nm thick, deposited at a rate of 0.5 nm / s, with the substrate kept at room temperature. Instead of an alkali metal evaporation source, an Au evaporation source was used during cathode fabrication, with a vacuum level better than 1 × 10⁻⁶ before evaporation. -7 Pa. Other electrode structures, voltage settings, and assembly processes (coaxiality better than 0.05 mm, leak detection vacuum better than 5 × 10⁻⁶) -7 The vacuum level after indium transfer sealing is exactly the same as in Example 1. -7 Pa.

[0068] Performance testing (expected): For 8 keV X-rays, the spatial resolution can reach more than 25 lp / mm, and the temporal resolution is better than 10 ps.

[0069] Example 4: Fabrication of a small striped tube with a large-area cathode in the ultraviolet band

[0070] The difference between this embodiment and Embodiment 2 is as follows:

[0071] The incident window material is MgF2 (or quartz), with a diameter of 35 mm and a thickness of 2 mm. The photocathode is CsTe, and the evaporation sequence is Te first, followed by Cs, with ultraviolet photocurrent (wavelength 254 nm) monitored. The remaining electrode structure, voltage settings, and assembly process are the same as in Example 2. The vacuum level is better than 1×10⁻⁶. -7 Pa.

[0072] Performance testing (expected): Under 254 nm ultraviolet light irradiation, the spatial resolution can reach more than 25 lp / mm, and the temporal resolution is better than 10 ps.

Claims

1. A small striped tube with a large cathode surface, characterized in that: The striped tube comprises a photocathode, a grid electrode, a first focusing electrode, a second focusing electrode, an anode, a drift region, and a fluorescent screen arranged sequentially along the electron beam transmission direction; the photocathode is a continuous surface cathode with an effective working diameter of not less than 30 mm; the total length of the striped tube shell is not greater than 300 mm and the outer diameter is not greater than 65 mm; the photocathode is spherical with a radius of curvature of not less than 90 mm, an axial arc length of 4.5 mm to 5.5 mm, and a radial arc length of 25 mm to 35 mm; an aperture is provided at the center of the anode; the striped tube is suitable for visible light, X-rays, or ultraviolet light bands.

2. The large-area cathode miniature stripe tube according to claim 1, characterized in that: The voltage of the grid electrode is 0.7 kV to 1 kV, the voltage of the first focusing electrode is 1.9 kV to 2.5 kV, the voltage of the second focusing electrode is 4.5 kV to 6.5 kV, and the voltage of the anode and drift region is 13 kV to 15 kV.

3. The large-area cathode miniature stripe tube according to claim 1, characterized in that: The photocathode material is selected from visible light polyalkali materials, X-ray sensitive materials, or ultraviolet sensitive materials; The visible light-sensitive material is Na2KSb(Cs), the X-ray-sensitive material is CsI or Au, and the ultraviolet-sensitive material is CsTe.

4. The large-area cathode miniature stripe tube according to claim 1, characterized in that: The radius of the aperture is 7.5 mm or 5 mm.

5. The large-area cathode miniature stripe tube according to claim 1, characterized in that: The grid electrode is made of nickel mesh with a thickness of 5μm to 7μm, a line width of 8μm to 12μm, and a grid size of 40μm to 50μm; the effective working diameter of the grid electrode is not less than 35 mm, and there are no holes with a diameter greater than 0.08 mm or wrinkles with a diameter greater than 0.5 mm in the working area.

6. A method for preparing a large-area cathode miniature stripe tube, comprising the following steps: a) Component preparation: Prepare metal parts, ceramic parts and optical parts respectively, and conduct incoming material inspection, cleaning and annealing leak detection; prepare cathode evaporation source and indium tin alloy; b) Component assembly and adjustment: The metal electrodes, ceramic insulators and optical components are grouped and coaxially assembled and welded with high precision, and vacuum leak testing is performed; the components are assembled by laser welding or spot welding to form a striped tube single tube for cathode preparation, and vacuum leak testing is performed again. c) Cathode fabrication: The striped tube single tube to be prepared for cathode fabrication and the cathode evaporation source are assembled into the cathode transfer preparation system. In the cathode fabrication chamber of the cathode transfer preparation system, photocathode material is deposited according to the target wavelength. d) Transfer of indium seal: Indium-tin alloy is heated and melted in the indium seal chamber, and the input end of the cathode preparation is transferred and sealed on the tube shell. After cooling, it is sealed.

7. The preparation method according to claim 6, characterized in that, In step a), the metal parts include a cathode ring, a grid electrode, a first focusing electrode, a second focusing electrode, an anode, a drift electrode, and a lead ring; the ceramic parts include a segmented insulator and a support ring; the optical parts include a cathode input window and an anode panel / fluorescent screen window; the cleaning of the metal parts adopts acetone ultrasonic, alkaline detergent ultrasonic, acidic detergent ultrasonic, deionized water rinsing, alcohol dehydration, drying, and hydrogen annealing processes.

8. The preparation method according to claim 6, characterized in that: In step b), for the high-precision coaxial assembly, spot welding, and laser welding processes between various parts and solders, the coaxiality must be better than 0.05 mm, and the leak detection vacuum degree must be better than 5×10⁻⁶ mm. -7 Pa.

9. The preparation method according to claim 6, characterized in that: In step c), for visible light multi-alkali cathodes, evaporation is performed in the order of Sb, K, Na, and Cs, and the photocurrent is monitored to its maximum value; for X-ray cathodes, CsI or Au films are deposited by thermal evaporation or electron beam evaporation; for ultraviolet cathodes, Te and Cs are evaporated alternately.

10. The preparation method according to claim 6, characterized in that: In step d), the heating temperature is 120 ℃~130 ℃, the melting point of indium tin alloy is 118 ℃, and it is sealed in a vacuum with a degree better than 1×10 -7 The experiment was conducted under the condition of Pa.

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