Preparation method of small pulse broadening drift tube for ultrafast diagnosis and pulse broadening drift tube thereof

Abstract

The invention discloses a preparation method of a small pulse broadening drift tube for ultrafast diagnosis and the pulse broadening drift tube thereof. The method comprises the following steps: 1) brazing a front shell and a rear shell, and carrying out indium filling, indium melting and indium turning operation on the front shell; 2) performing spot welding to obtain a first grid mesh assembly, a second grid mesh assembly and a third grid mesh assembly; 3) preparing a substrate, a conductive film layer and a sealing film layer, and assembling to obtain a cathode input window; (4) sealing the metal anode flange, the frit ring and the optical fiber panel at high temperature, and plating a metal layer on the small surface of the optical fiber panel to prepare an anode assembly; (5) the first grid mesh assembly and the second grid mesh assembly are assembled on the front shell to obtain the front shell provided with the front assembly; and 6) preparing a cathode input window and a cathode at the rear end, degassing at high temperature, electronically brushing and sealing indium at high vacuum degree to obtain the small pulse broadening drift tube which can meet the requirements of the technical fields of nuclear detection, high-energy physics and the like on ultrafast diagnosis equipment.

Description

Technical Field

[0001] This application relates to the field of ultrafast diagnostic technology, and in particular to a method for fabricating a small pulse-broadening drift tube for ultrafast diagnostics and the pulse-broadening drift tube itself. Background Technology

[0002] Diagnostic techniques for physical processes on ultrafast timescales are at the forefront of modern physics, particularly significant in nuclear fusion research, materials science, and chemical reaction kinetics. The core technologies include: 1. Ultrafast electron beam diagnostic methods achieving picosecond or even femtosecond time resolution, including techniques such as double-deflection achromatic compression and chirped pulse amplification; 2. Diagnostic methods for extreme conditions during nuclear fusion evolution, such as laser scattering diagnostics and plasma imaging. These techniques enable the capture of ultrafast dynamic processes that are unobservable by traditional methods.

[0003] Ultrafast performance indicators are important factors affecting experimental accuracy and results, such as the time characteristics of ultrafast electron beams (picosecond resolution) and the diagnosis of nuclear fusion evolution processes. Ultrafast diagnostic equipment is the core device for realizing the measurement of ultrafast indicators.

[0004] Existing ultrafast diagnostic equipment is a streak camera, which can achieve femtosecond-level resolution through time-space conversion. Although it has high temporal resolution, it is not suitable for high repetition rate scenarios, and the equipment is expensive, has a low dynamic range, and is complex to maintain.

[0005] In recent years, with the development of ultrafast optics and electronics technology, Dr. RD Prosser of Imperial College London proposed time stretching technology in 1976 to solve the problem that low-bandwidth oscilloscopes cannot record fast signals, and this technology has been applied. In 2018, SG Gales of AWE Laboratory in the UK, H. Geppert-Kleinrath of LLNL Laboratory in the US, and others, in collaboration with Kentech Instruments in the UK, developed a 20 ps resolution pulse-stretched photomultiplier tube (PD-PMT), demonstrating that the PD-PMT can replace streak cameras for ultrafast diagnostics. Currently, research on PD-PMTs is mainly theoretical, and no fabrication technology for visible light / X-ray PD-PMTs has been publicly disclosed.

[0006] Existing ultrafast diagnostic devices with high accuracy have extremely high procurement and maintenance costs, and their technology self-sufficiency is low, making them vulnerable to embargoes and blockades in practical applications.

[0007] The information disclosed in the background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] This application addresses the aforementioned technical problems by providing a method for fabricating a small pulse-stretching drift tube for ultrafast diagnostics and the same pulse-stretching drift tube. The small pulse-stretching drift tube obtained by this method can meet the requirements of ultrafast diagnostic equipment in fields such as nuclear detection and high-energy physics. The linear stretching factor under physical design is 50, and the time resolution is better than 10 ps. It features high performance, low system construction cost, and simplified system design. At the same time, it is low in cost and simple to fabricate.

[0009] This application provides a method for fabricating a small pulse-stretching drift tube for ultrafast diagnostics, and the pulse-stretching drift tube itself, comprising the following steps: 1) After brazing the front and rear housings, the front housing is filled with indium, indium-treated and indium-machined, and the parallelism difference between the end faces of the front and rear housings is corrected to ensure the coaxiality between the front and rear housings. 2) After assembling the grid, pressure ring, and fixing ring, spot weld them to obtain the first grid assembly, the second grid assembly, and the third grid assembly; 3) The substrate, conductive film, and sealing film are prepared and assembled to obtain the cathode input window; 4) High-temperature sealing of metal anode flange, glass ring and optical fiber panel, and metal layer plating on small facet of optical fiber panel to prepare anode assembly; 5) The first grid assembly and the second grid assembly are assembled on the front housing to obtain the front housing for installing the front assembly. The third grid assembly and the microchannel plate are assembled in the rear housing to obtain the rear housing for installing the rear assembly. They are laser welded together in the following order: the front housing for installing the front assembly, the drift cylinder, the rear housing for installing the rear assembly, and the anode assembly. Leak detection is performed after each laser weld to prepare the cathode assembly to be prepared. 6) The cathode assembly to be prepared is placed in the exhaust station equipment for cathode input window and rear cathode preparation, high temperature degassing, electronic cleaning and high vacuum indium sealing tube fabrication, insulation treatment, power supply connection and assembly of magnetic lens assembly to obtain the small pulse broadening drift tube.

[0010] Preferably, when assembling the grid, pressure ring, and fixing ring, the grid is laid on the central through hole of the fixing ring; a protruding ring is provided on the periphery of the central through hole; the periphery of the grid extends out of the protruding ring and is pressed and fixed in the receiving groove of the fixing ring by the pressure ring.

[0011] Preferably, the shell brazing method is as follows: 1.1) After assembling the lower clamp and positioning cylinder, the handle rod at the top of the lower clamp passes through each component of the housing, and the outer diameter of each component and the solder ring matches and positions the inner diameter of the positioning cylinder; 1.2) Load the load at the top opening of the positioning cylinder. After each component is extruded and formed, lift the handle to lift the formed front shell and load from the positioning cylinder to obtain the formed assembly. 1.3) The obtained molded components are placed on a belt furnace for brazing. After the welding is completed, leak detection is performed to obtain the front shell.

[0012] Preferably, during the brazing of the front housing, a cathode ring, a first ceramic cylinder, a first grid mounting ring, a second ceramic cylinder, a second grid mounting ring, a first ceramic cylinder, and a spacer ring are placed in the positioning cylinder in sequence from top to bottom, and a solder ring is placed between any two adjacent components. During the brazing of the rear housing, the following components are placed in the positioning cylinder in sequence from top to bottom: rear housing isolation ring, rear housing first ceramic cylinder, rear housing grid mounting ring, rear housing first ceramic cylinder, rear housing assembly ring, rear housing second ceramic cylinder, rear housing contact ring, rear housing third ceramic cylinder, rear housing getter ring, rear housing fourth ceramic cylinder, and rear housing isolation ring. A solder ring is placed between any two adjacent components.

[0013] Preferably, the positioning cylinder includes: a cylinder body and a first pair of through slots, a second pair of through slots, and a limiting slot that are spaced apart on the circumferential sidewall of the cylinder body; a boss is provided in the central axis area on the bottom surface of the cylinder body; the lower clamp includes: a snap-fit ​​groove, a handle, and a support base; a snap-fit ​​groove is provided in the central area of ​​the bottom surface of the support base, and the snap-fit ​​groove is fitted onto the boss, so that the positioning cylinder and the lower clamp are coaxial. A through hole is made along the central axis of the load; a convex ring is provided on the bottom surface of the load; the convex ring matches and abuts against the cathode ring of the front housing or the isolation ring of the rear housing, and the handle rod is set through the through hole.

[0014] Preferably, the components used to fabricate the small pulse broadening drift tube include: metal parts, ceramic parts, and optical parts; after the metal parts pass inspection, they are subjected to pickling, degreasing, cleaning, drying, and annealing treatment. After the ceramic parts pass inspection, they are cleaned, dried, and annealed. After the optical components pass inspection, they are cleaned and dried.

[0015] Preferably, the annealing operation of the metal parts includes: releasing N2 for at least 15 minutes before starting hydrogen combustion, setting the H2 flow rate during hydrogen combustion to 8 L / min, setting the N2 flow rate for dispersing gas to 8 L / min, setting the N2 flow rate to 55 L / min when starting the furnace, setting the heating temperature range to 400℃~1000℃, and holding time to 15 minutes~30 minutes. The cleaning process for ceramic parts includes: ultrasonic cleaning in 3% to 5% neutral detergent for 5 minutes, then cleaning in deionized water for 10 minutes, changing the water twice, repeating the cleaning for 10 minutes after each water change, ultrasonic cleaning in alcohol for 5 minutes, and then drying in an oven. The cleaning process for optical components includes: ultrasonic cleaning in alcohol for 5 minutes, then cleaning in deionized water for 15 minutes, ultrasonic cleaning in alcohol for 5 minutes, and then drying in an oven.

[0016] Preferably, leak detection is performed after brazing, laser welding, and electric welding operations; the leak detector is activated to evacuate the components until the vacuum level reaches 1. ~1 Once the reading is within the specified range and stable, use an air gun to blow helium into the component and observe the change in the vacuum reading. If there is a change, it is determined that there is a leak, and the leak needs to be repaired; if there is no change, it is determined that there is no leak.

[0017] Preferably, the conductive layer and sealing layer of the cathode input window are any one of a Cr film, a Cu film, or an Ag film; the thickness of the Cr film used is 2000 μm. , the Cu film thickness used is 4500 , the Ag film thickness used is 4500 ; The high-temperature sealing operation involves placing the metal anode flange, glass ring, and fiber optic panel in a high-temperature furnace for high-temperature sealing at a temperature of 1000℃.

[0018] Another aspect of this application provides a pulse broadening drift tube obtained by the method described above, comprising: a drift tube, a front housing, a rear housing, an anode assembly, a cathode input window, a first grid assembly, a second grid assembly, a third grid assembly, and a microchannel plate; the two ends of the drift tube are respectively connected to the front housing and the rear housing; A first grid mounting ring and a second grid mounting ring are provided at intervals inside the front housing; a first grid assembly is sleeved on the first grid mounting ring and installed inside the front housing; a second grid assembly is sleeved on the second grid mounting ring and installed inside the front housing; A microchannel plate and a third grid assembly are installed inside the rear housing; a rear housing grid mounting ring is provided inside the rear housing, and the third grid assembly is sleeved on the rear housing grid mounting ring and installed inside the rear housing through the mounting ring; The anode assembly is mounted on the outside of the third grid assembly; The cathode input window is installed on the outside of the first grid assembly.

[0019] The beneficial effects that this application can produce include: 1) The method for fabricating a small pulse broadening drift tube for ultrafast diagnostics provided in this application has a stable process, simple and controllable process parameters, and can realize the regulation of the internal structure and physical parameters of the fabricated pulse broadening drift tube.

[0020] 2) The miniature pulse-stretching drift tube for ultrafast diagnostics provided in this application has a bare tube length ≤190mm and a bare tube outer diameter ≤100mm. It can achieve linear stretching with a stretching factor of not less than 40 times, and the physical design value of this drift tube can reach 50 times. The time resolution is 10ps, which is a significant improvement compared to the 20-fold stretching factor of existing devices, achieving an order-of-magnitude improvement in device time resolution. Currently, using picosecond lasers, with the drift tube under DC operating voltage, the unstretched waveform time resolution obtained by testing is ≤300ps. Attached Figure Description

[0022] Figure 1 This application provides at least one embodiment of brazing fixtures for the front and rear housings; a) front sectional view of the upper fixture; b) top view of the upper fixture; c) the upper fixture holding the front housing in use; d) front view of the lower fixture; e) front view under load; Figure 2 This application provides a process flow diagram of a method for fabricating a small pulse broadening drift tube for ultrafast diagnostics in at least one embodiment; Figure 3 This application provides a schematic diagram of the main cross-sectional view of a single miniature pulse drift tube prepared according to at least one embodiment; Figure 4 The present application provides a physical image of a small pulse drift tube prepared according to at least one embodiment. The external magnetic lens, external driving power supply and pulse broadening power supply module are not shown.

[0023] Figure 5 This application provides photographs of the grid assembly in at least one embodiment; Figure 6 This application provides photographs of the fixing rings in at least one embodiment; Legend: Cathode input window 101, first grid assembly 102, second grid assembly 103, drift cylinder 104, microchannel plate 105, third grid assembly 106, anode assembly 107, positioning cylinder 2, first pair of through slots 21, second pair of through slots 22, boss 24, limiting groove 23, snap-fit ​​groove 212, handle rod 211, support base 213, load 3, through hole 31, convex ring 32, cathode ring 11, first ceramic cylinder 12, first grid mounting ring 13, second ceramic cylinder 14, second grid mounting ring 13, isolation ring 15, pressure ring 222, grid, fixing ring 221, receiving groove 224. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0026] Technical means not detailed in this application and not used to solve the technical problems of this application are all set according to common general knowledge in the field, and multiple common general knowledge setting methods can be implemented.

[0027] See Figures 1-6 This application provides a method for fabricating a small pulse broadening drift tube, comprising the following steps: a) The components required for fabricating a small pulse broadening drift tube include: metal parts, ceramic parts and optical components. Upon entry into the company, the inspection items include: external structural dimensions, end face parallelism, cleanliness of the inner wall of the ceramic tube and optical performance of the optical components. b) Metal parts are pickled, degreased, cleaned, and annealed; ceramic parts are cleaned and annealed; optical parts are cleaned and dried. c) Employing group welding processes and using, for example Figure 1 The brazing fixture shown in figures a-e includes a positioning cylinder 2 and a lower fixture. The positioning cylinder 2 includes a cylinder body and a first pair of through slots 21, a second pair of through slots 22, and a limiting groove 23 spaced apart along the circumferential sidewalls of the cylinder body. The first pair of through slots 21 includes through slots symmetrically arranged in pairs on opposite sidewalls of the positioning cylinder 2. The second pair of through slots 22 includes through slots symmetrically arranged in pairs on opposite sidewalls of the positioning cylinder 2. The limiting groove 23 is located away from the first pair of through slots 21 and the second pair of through slots 22 on one side of the positioning cylinder 2. A boss 24 is provided in the central area of ​​the inner bottom surface of the positioning cylinder 2. The lower fixture is disposed in the inner cavity of the positioning cylinder 2 and is coaxially arranged with the positioning cylinder 2. The protrusions on the periphery of the front housing components can pass through the limiting groove 23 for positioning.

[0028] The lower clamp includes: a snap-fit ​​groove 212, a handle 211, and a support base 213; the snap-fit ​​groove 212 is opened in the center area of ​​the bottom surface of the support base 213, and the snap-fit ​​groove 212 is sleeved on the boss 24. The support base 213 is in contact with the bottom surface of the positioning cylinder 2; the handle 211 is set in the center area of ​​the support base 213 and extends from the top surface of the positioning cylinder 2, so that after positioning, the entire front housing can be extracted from the positioning cylinder 2 while ensuring that the positioning positions of each component do not move relative to each other.

[0029] A through hole 31 is made longitudinally through the load 3 along its central axis; a convex ring 32 is provided in the central area of ​​the bottom surface of the load 3; the convex ring 32 matches and abuts against the concave ring on the cathode ring 11, thereby applying pressure evenly to all components of the front housing. The handle rod 211 of the lower clamp is provided through the through hole 31.

[0030] During positioning, the lower clamp is placed into the positioning cylinder 2, and the snap-fit ​​groove 212 is fitted onto the boss 24. After assembly, the lower clamp and the positioning cylinder 2 are coaxial. Then, the various components of the front housing are placed into the positioning cylinder 2 through the handle rod 211 of the lower clamp. The placement order of the various components of the front housing in the positioning cylinder 2 is as follows: cathode ring 11, first ceramic cylinder 12, first grid mounting ring 13, second ceramic cylinder 14, second grid mounting ring 13, first ceramic cylinder 12, and isolation ring 15 are placed from the top to the bottom of the positioning cylinder 2. The outer periphery of each component is in positioning contact with the inner wall of the positioning cylinder 2, thereby achieving accurate positioning based on the outer diameter of each component and the inner diameter of the positioning cylinder 2. After the through hole 31 of the load 3 is passed through the handle rod 211 of the lower clamp, the load 3 is placed on the top surface of the positioning cylinder 2, applying downward pressure to the entire front housing. After all parts are positioned, the lifting handle 211 is lifted, thereby removing the lower clamp, load 3, and front housing together from the positioning cylinder 2 to obtain the formed positioning assembly. Both the front and rear housings include: metal parts, ceramic parts, and solder (placed between the metal and ceramic parts). A solder ring is placed between any two adjacent parts. Using the above brazing method, the positioning accuracy of each component in the front and rear housings is high, which is beneficial for achieving a better expansion effect.

[0031] During the assembly of the rear housing, the following components are sequentially placed in the upper fixture from top to bottom: the rear housing isolation ring, the first ceramic cylinder of the rear housing, the rear housing grid mounting ring, the second ceramic cylinder of the rear housing, the contact ring of the rear housing, the third ceramic cylinder of the rear housing, the getter ring of the rear housing, the fourth ceramic cylinder of the rear housing, and the rear housing isolation ring. A solder ring is placed between any two adjacent components. All ceramic cylinders used are of the same model. The remaining operations are the same as those for the front housing and will not be described in detail here.

[0032] The obtained molded components and brazing material are assembled and placed on a belt furnace for brazing. After the welding is completed, leak detection is performed to obtain the front shell and the rear shell. d) Fabrication of the substrate, conductive film, and sealing film of the cathode input window 101; e) The metal anode flange, glass ring and fiber optic panel are sealed from top to bottom at high temperature, and a metal layer is plated on the small side of the fiber optic panel to prepare the anode assembly 107; the small side of the fiber optic panel refers to the end face of the anode assembly 107 that protrudes from the third grid assembly 106.

[0033] f) such as Figure 3 , 5 The first grid assembly 102, the second grid assembly 103, and the third grid assembly 106 shown in ~6 have the same structure. The grid assembly includes: a pressure ring 222, a grid, and a fixing ring 221. The fixing ring 221 has a through hole in its central area, a protruding ring 223 on the periphery of the through hole, and a receiving groove 224 on the outer side of the disc of the protruding ring 223. The preparation method is as follows: the grid is laid on the central through hole of the fixing ring 221, the periphery of the grid is hung down, the pressure ring 222 is set on the other side of the grid, the pressure ring 222 is sleeved on the outside of the protruding ring 223, and the part of the grid extending out of the protruding ring 223 is pressed under the pressure ring 222. After spot welding the pressure ring 222 and the fixing ring 221, the first grid assembly 102, the second grid assembly 103, and the third grid assembly 106 are obtained. g) Perform indium filling, indium melting and indium machining operations on the front housing obtained in step c), and correct the parallelism difference between the end faces of the front and rear housings to ensure the coaxiality between the front and rear housings; h) Assemble the first grid assembly 102 and the second grid assembly 103 obtained in step f) onto the front housing obtained in step g), as shown in the figure. Figure 3 The getter filament, microchannel plate 105, and the third grid assembly 106 obtained in step f) are assembled into the rear housing obtained in step g) in the order shown, i.e., from left to right, to obtain the front and rear assemblies to be laser welded; the front assembly installed in the front housing includes: the first grid assembly 102 and the second grid assembly 103; the rear assembly installed in the rear housing includes: the third grid assembly 106 and the microchannel plate 105; each grid assembly is connected to the front and rear housings through mounting rings on the front and rear housings. The first grid assembly (102) is sleeved on the outside of the first grid mounting ring (13) and installed; the second grid assembly (103) is sleeved on the outside of the second grid mounting ring (16) and installed; the third grid assembly 106 is sleeved on the outside of the grid mounting ring of the rear housing and installed through the mounting ring.

[0034] i) As follows Figure 3 After assembly in the order shown, the specific assembly sequence is as follows: the front housing with the front component is installed at one end of the drift cylinder 104, the rear housing with the rear component is installed at the other end of the drift cylinder 104, and then the anode component 107 is installed on the other end face of the rear housing with the rear component. After assembling the components in the above order and positioning them, the front housing with the front component installed, the rear housing with the rear component installed, the anode component 107 and the drift cylinder 104 are laser welded, and leak detection is performed after each laser welding to prepare the cathode component to be prepared. j) Assemble the cathode assembly to be prepared on the exhaust stage. d) Assemble the cathode input window 101 obtained in step d on the cathode hook on the exhaust stage. Perform cathode preparation, high-temperature degassing, electronic cleaning and high-vacuum indium sealing tube preparation on the exhaust stage equipment to prepare a drift tube single tube. k) The drift tube obtained after insulation treatment is connected to the power supply and assembled with an external magnetic lens assembly to obtain a small pulse broadening drift tube, such as... Figure 4 As shown.

[0035] The resulting miniature pulse broadening drift tube includes: a drift cylinder 104, a front housing, a rear housing, an anode assembly 107, a cathode input window 101, a first grid assembly 102, a second grid assembly 103, a third grid assembly 106, and a microchannel plate 105. The front and rear housings are respectively connected to the two ends of the drift cylinder 104. The first grid assembly 102 and the second grid assembly 103 are installed at intervals inside the front housing. The microchannel plate 105 and the third grid assembly 106 are installed inside the rear housing. The anode assembly 107 is installed outside the third grid assembly 106. The cathode input window 101 is installed outside the first grid assembly 102. The device installation sequence from left to right in the miniature pulse broadening drift tube is: cathode input window 101, first grid assembly, second grid assembly, drift cylinder 104, microchannel plate 105, third grid assembly, and anode assembly 107.

[0036] Preferably, the materials used in the devices of this invention include: metal or ceramic, and the drying temperature of the metal parts and ceramic parts is 40℃~50℃, and the drying time is 4h~8h. The ceramic parts include: a first ceramic cylinder, a ceramic cylinder, and a second ceramic cylinder; the metal parts include: a grid pressure ring, a grid ring, a grid mounting ring, and a drift cylinder; the optical parts include: a cathode window, an anode screen, and a microchannel plate.

[0037] Preferably, metal and ceramic parts should be rinsed in deionized water for 3 to 5 minutes.

[0038] Preferably, in step a) of the present invention, according to the structural dimensions on the design drawings, calibrated dial indicators, vernier calipers, contour projectors and other measuring devices and equipment are used to conduct in-situ inspections on metal parts, ceramic parts and optical components to ensure the high performance of the parts.

[0039] Preferably, in step b) of the present invention, the metal parts are first ultrasonically cleaned in acetone solution for 5 minutes, then ultrasonically cleaned in 1% to 3% alkaline detergent solution at room temperature for 5 minutes, then rinsed in running tap water for 5 minutes, then rinsed in running deionized water for 5 minutes, then ultrasonically cleaned in 1% to 3% acidic detergent solution at room temperature for 5 minutes, then rinsed in running tap water for 5 minutes, then rinsed in running deionized water for 5 minutes, then dehydrated with alcohol and then dried in an oven.

[0040] Preferably, in step b) of the present invention, after the metal parts have completed pickling, degreasing, and cleaning, they need to be annealed in a tubular furnace using hydrogen. Before starting hydrogen annealing, N2 should be released for at least 15 minutes to purge air from the furnace. The boat containing the metal parts is placed in the heating zone of the furnace, the furnace door is closed, and then the N2 valve is closed. The H2 flow rate during hydrogen annealing is set to 8 L / min, the N2 flow rate for dispersing gas is set to 8 L / min, and the N2 flow rate when starting the furnace is set to 55 L / min. The heating temperature range is 400℃~1000℃, and the holding time is 15min~30min. Strict control and attention to the safety of the process steps are required.

[0041] Preferably, in step b) of the present invention, the ceramic part is first ultrasonically cleaned in 3% to 5% neutral detergent for 5 minutes, then cleaned in deionized water for 10 minutes, with the water changed twice during the process. After each water change, the cleaning is repeated for 10 minutes. Then, it is ultrasonically cleaned in alcohol for 5 minutes and placed in an oven to dry. Care should be taken to prevent damage to the end face of the ceramic cylinder.

[0042] Preferably, in step b) of the present invention, the optical component is first ultrasonically cleaned in alcohol for 5 minutes, then cleaned in deionized water for 15 minutes, then ultrasonically cleaned in alcohol for 5 minutes, and then placed in an oven to dry. Care should be taken to prevent damage to the optical component.

[0043] Preferably, in step c) of the present invention, the order of placement of the parts should follow the sequence of housing metal ring (metal) - solder - housing ceramic ring - solder - housing metal ring.

[0044] Preferably, in step c) of the present invention, the front and rear components (high coaxiality) without grid, microchannel plate and getter wire after the fixture is fixed are brazed in a belt furnace. The N2 flow rate of the air curtain at the inlet is set to at least 40 L / min, the N2 flow rate of the air curtain at the outlet is set to at least 50 L / min, the belt speed of the belt furnace is 20 cm / min, and the temperature is determined according to the solder, generally 750℃~1000℃.

[0045] Preferably, in this invention, all components and brazed or laser-welded components need to be leak-tested using a leak detector. The component to be leak-tested is placed on the leak detector base using the appropriate connector, and the leak detector is activated to evacuate the component until the vacuum level reaches 1. ~1 Once the reading is within range and stable, use an air gun to blow helium into the component and observe the change in the vacuum reading to determine if the component is leaking. If it is leaking, appropriate measures must be taken to repair the leak.

[0046] Preferably, in step d) of the present invention, the cathode input window is cleaned in flowing deionized water for 15 minutes, and at the same time, corresponding grinding and polishing processes are required.

[0047] Preferably, in step d) of the present invention, the conductive layer and sealing layer of the cathode input window are metals Cr, Cu, or Ag, and the Cr film thickness is 2000 μm. The Cu film thickness is 4500 mm. , Ag film thickness 4500 .

[0048] Preferably, in step e) of the present invention, the metal anode flange, glass ring and optical fiber panel are placed in a high-temperature furnace for high-temperature sealing at a sealing temperature of 1000°C.

[0049] Preferably, in step e) of the present invention, the thickness of the metal layer plated on the small facet of the optical fiber panel is 3000 mm. .

[0050] Preferably, the spot welding process in this invention needs to be adjusted according to factors such as the cleanliness of the parts and the thickness and type of metal. The commonly used spot welding power can be set to 10W·sec to 25W·sec, and the spot welding pulse time is 2ms.

[0051] Preferably, nitrogen gas is used as the shielding gas during laser welding in this invention, and the shielding gas flow should continue for at least 10 seconds after welding. Depending on the welding material, the welding laser operating frequency is 200Hz, the current range is 50A to 150A, the single-point energy is 10J to 25J, and the rotation speed is 10rpm to 15rpm.

[0052] See Figure 4 The method provided in this application can be used to fabricate a small pulse-stretching drift tube as shown in the figure. This device is the first of its kind among drift tube devices, with a stretching factor of 50 and a time resolution of 10 ps according to the physical design values. Currently, using picosecond lasers and applying a DC operating voltage to the drift tube, the time resolution of the unstretched waveform obtained by testing is ≤300 ps.

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a small pulse broadening drift tube for ultrafast diagnostics, characterized in that, Includes the following steps: 1) After brazing the front and rear housings, the front housing is filled with indium, indium-treated and indium-machined, and the parallelism difference between the end faces of the front and rear housings is corrected to ensure the coaxiality between the front and rear housings. 2) After assembling the grid, pressure ring (222) and fixing ring (221), spot weld to obtain the first grid assembly, the second grid assembly, and the third grid assembly; 3) The substrate, conductive film, and sealing film are assembled to obtain the cathode input window (101). 4) The metal anode flange, glass ring and optical fiber panel are sealed at high temperature, and a metal layer is plated on the small side of the optical fiber panel to prepare the anode assembly (107). 5) The first grid assembly (102) and the second grid assembly (103) are assembled on the front housing to obtain the front housing for installing the front assembly. The third grid assembly and the microchannel plate (105) are assembled in the rear housing to obtain the rear housing for installing the rear assembly. They are laser welded together in the following order: the front housing for installing the front assembly, the drift cylinder (104), the rear housing for installing the rear assembly, and the anode assembly (107). After each laser welding, a leak test is performed to prepare the cathode assembly to be prepared. 6) The cathode assembly to be prepared is placed in the exhaust platform equipment for cathode input window (101) and the cathode preparation at the back end, high temperature degassing, electronic cleaning and high vacuum indium sealing tube, insulation treatment, power supply connection and magnetic lens assembly to obtain the small pulse broadening drift tube.

2. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 1, characterized in that, When assembling the grid, pressure ring (222) and fixing ring (221), the grid is laid on the central through hole of the fixing ring (221); a protruding ring (223) is provided on the periphery of the central through hole; the periphery of the grid extends out of the protruding ring (223) and is pressed and fixed in the receiving groove (224) of the fixing ring (221) by the pressure ring (222).

3. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 1, characterized in that, Brazing method for the casing: 1.1) After assembling the lower clamp and positioning cylinder (2), the handle rod (211) on the upper part of the lower clamp passes through each component of the housing, and the outer diameter of each component and the solder ring matches and positions the inner diameter of the positioning cylinder (2); 1.2) Load (3) is installed at the top opening of the positioning cylinder (2). After each component is extruded and formed, the handle rod (211) is lifted to lift the formed front shell and load (3) from the positioning cylinder (2) to obtain the formed assembly. 1.3) The obtained molded components are placed on a belt furnace for brazing. After the welding is completed, leak detection is performed to obtain the front shell.

4. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 3, characterized in that, During the brazing of the front housing, the cathode ring (11), the first ceramic cylinder (12), the first grid mounting ring (13), the second ceramic cylinder (14), the second grid mounting ring (16), the first ceramic cylinder (12), and the isolation ring (15) are placed in the positioning cylinder (2) in sequence from top to bottom, and a solder ring is placed between any two adjacent components; During the brazing of the rear housing, the rear housing isolation ring, the first ceramic cylinder of the rear housing, the rear housing grid mounting ring, the first ceramic cylinder of the rear housing, the rear housing assembly ring, the second ceramic cylinder of the rear housing, the contact ring of the rear housing, the third ceramic cylinder of the rear housing, the getter ring of the rear housing, the fourth ceramic cylinder of the rear housing, and the rear housing isolation ring are placed in the positioning cylinder (2) in sequence from top to bottom, and a solder ring is placed between any two adjacent components.

5. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 3, characterized in that, The positioning cylinder (2) includes: a cylinder body and a first pair of through slots (21), a second pair of through slots (22), and a limiting slot (23) spaced apart on the circumferential side wall of the cylinder body; a boss (24) is provided in the central axis area on the bottom surface of the cylinder body; the lower clamp includes: a snap-fit ​​groove (212), a handle (211), and a support base (213); the support base (213) has a snap-fit ​​groove (212) in the central area of ​​the bottom surface, and the snap-fit ​​groove (212) is fitted onto the boss (24), so that the positioning cylinder (2) and the lower clamp are coaxial; A through hole (31) is opened along the central axis of the load (3); a convex ring (32) is provided on the bottom surface of the load (3); the convex ring (32) matches and abuts against the cathode ring (11) of the front housing or the isolation ring of the rear housing, and the handle rod (211) is set through the through hole (31).

6. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 2, characterized in that, The components used in the fabrication of the small pulse broadening drift tube include: metal parts, ceramic parts, and optical parts; after the metal parts pass inspection, they undergo pickling, degreasing, cleaning, drying, and annealing. After the ceramic parts pass inspection, they are cleaned, dried, and annealed. After the optical components pass inspection, they are cleaned and dried.

7. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 6, characterized in that, The annealing operation of the metal parts includes: releasing N2 for at least 15 minutes before starting hydrogen combustion, setting the H2 flow rate to 8 L / min during the hydrogen combustion process, setting the N2 flow rate to 8 L / min for the dispersing gas, setting the N2 flow rate to 55 L / min when starting the furnace, setting the heating temperature range to 400℃~1000℃, and holding time to 15 minutes~30 minutes. The cleaning process for ceramic parts includes: ultrasonic cleaning in 3% to 5% neutral detergent for 5 minutes, then cleaning in deionized water for 10 minutes, changing the water twice, repeating the cleaning for 10 minutes after each water change, ultrasonic cleaning in alcohol for 5 minutes, and then drying in an oven. The cleaning process for optical components includes: ultrasonic cleaning in alcohol for 5 minutes, then cleaning in deionized water for 15 minutes, ultrasonic cleaning in alcohol for 5 minutes, and then drying in an oven.

8. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 1, characterized in that, Leak testing is performed after brazing, laser welding, and electric welding operations; the leak detector is activated to evacuate the components until the vacuum level reaches 1. ~1 Once the reading is within the specified range and stable, use an air gun to blow helium into the component and observe the change in the vacuum reading. If there is a change, it is determined that there is a leak, and the leak needs to be repaired; if there is no change, it is determined that there is no leak.

9. The method for fabricating a miniature pulse broadening drift tube for ultrafast diagnostics according to claim 1, characterized in that, The conductive layer and sealing layer of the cathode input window (101) are any one of Cr film, Cu film or Ag film; the thickness of the Cr film used is 2000 mm. , the Cu film thickness used is 4500 , the Ag film thickness used is 4500 ; The high-temperature sealing operation involves placing the metal anode flange, glass ring, and fiber optic panel in a high-temperature furnace for high-temperature sealing at a temperature of 1000℃.

10. A pulse broadening drift tube obtained by the method according to any one of claims 1 to 9, characterized in that, include: The drift tube (104), front housing, rear housing, anode assembly (107), cathode input window (101), first grid assembly (102), second grid assembly (103), third grid assembly (106), and microchannel plate (105) are respectively connected to the two ends of the drift tube (104). A first grid mounting ring (13) and a second grid mounting ring (16) are provided at intervals inside the front housing; a first grid assembly (102) is sleeved on the first grid mounting ring (13) and installed inside the front housing; a second grid assembly is sleeved on the second grid mounting ring (16) and installed inside the front housing; A microchannel plate (105) and a third grid assembly (106) are installed inside the rear housing; a rear housing grid mounting ring is provided inside the rear housing, and the third grid assembly (106) is sleeved on the rear housing grid mounting ring and installed inside the rear housing through the mounting ring; The anode assembly (107) is mounted on the outside of the third grid assembly (106); The cathode input window (101) is installed on the outside of the first grid assembly (102).

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