Fission spectrometer for independent yield measurement of fission fragments

Abstract

The invention discloses a fission spectrometer used for fission fragment independent yield measurement. The fission spectrometer comprises a flight time detector and a screen grid ionization chamber fixedly connected to an outlet of the flight time detector. The flight time detector and the screen grid ionization chamber are provided with pump interfaces used for being connected with a vacuum pump for vacuumizing, and the flight time detector and the screen grid ionization chamber are each provided with a signal interface and a high-voltage electrical interface which are used for receiving detection signals. The signal interface and the high-voltage interface are respectively connected with the data acquisition system and the high-voltage system through lines; the method is suitable for independent yield measurement of fission fragments of multiple fission nuclides and multiple neutron energy points; according to the integrated device, online measurement of neutron-induced heavy nuclear fission can be achieved, errors caused by chemical treatment and step-by-step measurement in a traditional measurement technology are avoided, the mass resolution of fission fragments can be smaller than 1 amu, and the independent yield of the fission fragments can be obtained while excellent mass resolution is obtained.

Description

Technical Field

[0001] This invention belongs to the field of nuclear physics detection technology, specifically a fission spectrometer for measuring the independent yield of fission fragments. Background Technology

[0002] Fission physics quantities play a crucial role in nuclear energy utilization and nuclear physics research. In reactor design and maintenance, fuel rod enrichment detection, control rod control procedures, and spent fuel processing, nuclear fission-related data must serve as important input parameters for simulation design. Currently, emerging nuclear energy utilization systems are placing higher demands on the accuracy of fission data with broad neutron energy spectra and multiple fuels. However, current experimental measurements of fission product yields are incomplete and subject to significant errors. The five major nuclear databases (ENDF, JENDL, JEFF, CENDL, and BROND) only provide yield data for heavy nuclear fission induced by thermal neutrons at 0.5 MeV, 2 MeV, and 14 MeV energies.

[0003] Currently, common experimental methods for measuring fission product information include radiochemical methods and mass spectrometry (Mass, direct gamma spectroscopy, dual kinetic energy method, and velocity-kinetic energy method). However, these existing methods for measuring fission product yield rely on subsequent chemical separation or independent detection systems, which makes the measurement results highly dependent on the integrity of the chemical processing and the performance of the detector. They generally suffer from problems such as complex processes, limited accuracy, or limited applicability, thus restricting the acquisition of high-precision fission data. Summary of the Invention

[0004] The purpose of this invention is to provide a fission spectrometer for measuring the independent yield of fission fragments, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a fission spectrometer for measuring the independent yield of fission fragments, comprising a time-of-flight detector and a grid ionization chamber fixedly connected to the outlet of the time-of-flight detector; the time-of-flight detector and the grid ionization chamber are provided with pump interfaces for connecting to a vacuum pump for evacuation, and both the time-of-flight detector and the grid ionization chamber are provided with signal interfaces and high-voltage interfaces for receiving detection signals, the signal interfaces and high-voltage interfaces being connected to a data acquisition system and a high-voltage system respectively via lines; an incident channel is provided at the top of the time-of-flight detector, and an incident window corresponding to the incident channel is provided at the bottom inlet of the grid ionization chamber; the top of the grid ionization chamber is connected to a gas cylinder via a pipeline, the gas cylinder containing isobutane gas; the incident window is a perforated... An empty stainless steel sheet is used, with a SiN film covering the entrance window. An annular cathode electrode is fixedly connected above the entrance window, with the center of the annular cathode electrode facing the entrance window. A cathode-gate PCB voltage equalization ring is fixedly disposed above the annular surface of the cathode electrode. An annular gate is fixedly disposed above the cathode-gate PCB voltage equalization ring. A gate-anode PCB voltage equalization ring is fixedly connected above the annular surface of the gate, and an anode electrode is fixedly connected above the gate-anode PCB voltage equalization ring. The inner diameters of the cathode electrode, the cathode-gate PCB voltage equalization ring, the gate, the gate-anode PCB voltage equalization ring, and the anode electrode are equal and larger than the outer diameter of the entrance window. The cathode electrode, the gate, and the anode electrode are connected to the signal interface and the high-voltage interface, and the cathode electrode, the gate, and the anode electrode are insulated from the shell of the grid ionization chamber.

[0006] Preferably, the time-of-flight detector includes a vacuum cylinder and a starting microchannel plate secondary electronic time detector and a terminating microchannel plate secondary electronic time detector, which are respectively fixedly connected to the bottom and top of the vacuum cylinder. Flanges are provided at both ends of the vacuum cylinder. The incident channel is located on the top flange of the vacuum cylinder. The pump interface, signal interface, and high-voltage interface are located on the side wall of the vacuum cylinder. A vacuum gauge is also connected to the side wall of the vacuum cylinder for detecting the gas pressure inside the vacuum cylinder. The starting microchannel plate secondary electronic time detector and the terminating microchannel plate secondary electronic time detector are respectively fixedly connected to the bottom flange and top flange of the vacuum cylinder by bolts. Both the starting microchannel plate secondary electronic time detector and the terminating microchannel plate secondary electronic time detector are connected to the signal interface and the high-voltage interface via wiring.

[0007] Preferably, the bottom of the grid ionization chamber is bolted to a base flange, and the top of the grid ionization chamber is bolted to a top cover flange. The base flange has a first through hole coaxial with the incident channel. The incident window is bolted above the first through hole. A sealing flange is bolted to the top of the base flange. A second through hole, coaxial with the incident window and having the same outer diameter as the incident window, is provided on the sealing flange. Multiple insulating supports are fixedly connected to the top of the sealing flange. The cathode electrode is mounted on the insulating supports and fixed with insulating bolts. The pump interface on the grid ionization chamber is located on the side wall of the grid ionization chamber. The signal interface and high-voltage interface on the grid ionization chamber are located on the top cover flange.

[0008] Preferably, both the starting microchannel plate secondary electron time detector and the ending microchannel plate secondary electron time detector include a base, a secondary electron conversion film, an accelerating grid, an aluminum frame, an inner deflection grid, and an outer deflection grid connected in sequence, with a microchannel plate fixedly connected to the side wall of the aluminum frame.

[0009] Furthermore, a preamplifier is installed on the connection line between the signal interface and the data acquisition system. The preamplifier amplifies weak signals, optimizes signal quality, and improves information transmission efficiency.

[0010] Preferably, the connection voltage of the accelerating grid, microchannel plate and inner deflection grid is 2000 V, the secondary electron conversion film material is a 300 nm carbon film, the connection voltage of the secondary electron conversion film is 4000 V, and the connection voltage of the outer deflection grid is 6000 V; the aluminum frame is a copper-clad PCB board square frame with a thickness of 2 mm, and the accelerating grid, inner deflection grid and outer deflection grid are made of 0.25 μm gold-plated tungsten wires, spaced 1 mm apart, soldered onto copper electrodes.

[0011] Furthermore, a four-way adapter is fixedly connected to the pump interface of the grid ionization chamber. The other three connectors of the four-way adapter are respectively connected to the pressure relief valve, the pressure gauge and the vacuum pump, and a needle valve is installed on the connection pipeline between the vacuum pump and the four-way adapter.

[0012] Furthermore, a needle valve and a gas flow meter are installed on the connecting pipeline between the grid ionization chamber and the gas cylinder.

[0013] Compared with the prior art, the beneficial effects of the present invention are: The fission spectrometer for measuring the independent yield of fission fragments of the present invention is suitable for measuring the independent yield of fission fragments with multiple fission nuclides and multiple neutron energy points. The integrated device of the present invention can realize online measurement of neutron-induced heavy nucleus fission, avoiding the errors caused by chemical processing and step-by-step measurement in traditional measurement techniques. It can obtain a mass resolution of less than 1 amu for fission fragments, and obtain the independent yield of fission fragments while obtaining excellent mass resolution. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall connection structure of the fission spectrometer for measuring the independent yield of fission fragments provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the fission spectrometer circuit connection for measuring the independent yield of fission fragments provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the connection of the time-of-flight detector screen grid ionization chamber provided in an embodiment of the present invention; Figure 4 This is a cross-sectional view of the connection structure of the time-of-flight detector screen ionization chamber provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the internal structure of the screen grid ionization chamber provided in an embodiment of the present invention; Figure 6 This is a cross-sectional view of the microchannel plate secondary electron time detector provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the incident window structure provided in an embodiment of the present invention; Figure 8 This is the time spectrum of fission fragments in a time-of-flight detector provided in an embodiment of the present invention; Figure 9 This is a graph showing the energy detection results of fission fragments provided in an embodiment of the present invention; Figure 10 This is a two-dimensional time-energy diagram of fission fragments provided in an embodiment of the present invention; Figure 11 This is the mass yield distribution of fission fragments provided in the embodiments of the present invention; In the diagram, 1-Time-of-flight detector, 2-Grid ionization chamber, 3-Pump interface, 4-Signal interface, 5-High voltage interface, 6-Vacuum pump, 7-Data acquisition system, 8-High voltage system, 9-Preamplifier, 11-Vacuum cylinder, 12-Bottom flange, 13-Top flange, 14-Initiating microchannel plate secondary electronic time detector, 15-Terminating microchannel plate secondary electronic time detector, 16-Vacuum gauge, 21-Base flange, 22-Top cover flange, 23-First through hole, 24-Incident window, 25-Sealing flange, 26-Second through hole, 27-Insulation Support, 28-Cathode electrode, 29-Insulating bolt, 210-PCB equalizing ring between cathode and gate, 211-Gate, 212-PCB equalizing ring between gate and anode, 213-Anode electrode, 214-Four-way adapter, 215-Pressure relief valve, 216-Pressure gauge, 217-Needle valve, 218-Gas cylinder, 131-Incident channel, 1451-Base, 1452-Secondary electron conversion membrane, 1453-Accelerating grid, 1454-Aluminum frame, 1455-Inner deflection grid, 1456-Outer deflection grid, 1457-Microchannel plate. Detailed Implementation

[0015] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figures 1-7 This invention provides a technical solution: a fission spectrometer for measuring the independent yield of fission fragments, comprising a time-of-flight detector 1 and a grid ionization chamber 2 fixedly connected to the outlet of the time-of-flight detector 1; the time-of-flight detector 1 and the grid ionization chamber 2 are provided with pump interfaces 3 for connecting to a vacuum pump 6 for evacuation, and both the time-of-flight detector 1 and the grid ionization chamber 2 are provided with signal interfaces 4 and high-voltage interfaces 5 for receiving detection signals, the signal interfaces 4 and the high-voltage interfaces 5 are respectively connected to a data acquisition system 7 and a high-voltage system 8 through lines, and a preamplifier 9 is provided on the connection line between the signal interfaces 4 and the data acquisition system 7, the preamplifier 9 amplifies weak signals, optimizes signal quality, and improves information transmission efficiency.

[0017] The time-of-flight detector 1 includes a vacuum cylinder 11 and a starting microchannel plate secondary electronic time detector 14 and a terminating microchannel plate secondary electronic time detector 15, which are respectively bolted to the bottom flange 12 and the top flange 13 of the vacuum cylinder 11. An incident channel 131 is provided on the top flange 13 of the vacuum cylinder 11. The pump interface 3, the signal interface 4, and the high-voltage electrical interface 5 are provided on the side wall of the vacuum cylinder 11 through interface flanges. A vacuum gauge 16 communicating with the inside of the vacuum cylinder 11 is also connected to the side wall of the vacuum cylinder 11 for detecting the gas pressure inside the vacuum cylinder 11. The starting microchannel plate secondary electronic time detector 14 and the terminating microchannel plate secondary electronic time detector 15 are both connected to the signal interface 4 and the high-voltage electrical interface 5 through lines.

[0018] Both the starting microchannel plate secondary electron time detector 14 and the ending microchannel plate secondary electron time detector 15 include a base 1451, a secondary electron conversion film 1452, an acceleration grid 1453, an aluminum frame 1454, an inner deflection grid 1455, and an outer deflection grid 1456 connected end to end in sequence. A microchannel plate 1457 is fixedly connected to the side wall of the aluminum frame 1454, thus forming a deflection electric field. Secondary electrons excited by fission fragments are deflected by 90° under the action of the deflection electric field and enter the microchannel plate 1457 to generate a time signal. The acceleration grid 1453, microchannel plate 1457, and inner deflection grid 1455 are connected at a voltage of 2000 V. The secondary electron conversion film 1452 is made of 300 nm carbon film and is connected at a voltage of 4000 V. The outer deflection grid 1456 is connected at a voltage of 6000 V. The aluminum frame 1454 is a copper-clad PCB board square frame with a thickness of 2 mm. The acceleration grid 1453, inner deflection grid 1455, and outer deflection grid 1456 are made of 0.25 μm gold-plated tungsten wires spaced 1 mm apart. mm is made by soldering onto a copper electrode; in the actual application of the present invention, a spontaneous fission target or a neutron-induced fission target is placed at the center of the bottom flange 12 of the time-of-flight detector 1. The fission fragments generated therefrom will pass through the initial microchannel plate secondary electron time detector 14, the final microchannel plate secondary electron time detector 15, and the incident window 24 in sequence, and finally stop in the grid ionization chamber 2; wherein, the fission fragments excite secondary electrons on the surface of the secondary electron conversion film 1452. The secondary electrons undergo acceleration, drift, deflection and drift processes, and finally enter the microchannel plate 1457 to form a signal. The flight speed of the fission fragments can be calculated by the distance between the initial microchannel plate secondary electron time detector 14 and the final microchannel plate secondary electron time detector 15 and the time of signal transmission.

[0019] The bottom of the grid ionization chamber 2 is bolted to a base flange 21, and the top of the grid ionization chamber 2 is bolted to a top cover flange 22. A first through hole 23, coaxial with the incident channel, is provided on the base flange 21. An incident window 24, bolted above the first through hole 23, is provided. The incident window 24 is a perforated stainless steel sheet covered with a SiN film. The SiN film isolates the pressure difference between the grid ionization chamber 2 and the time-of-flight detector 1, and ensures that fission fragments can pass through and enter the grid ionization chamber 2 to generate a signal. A sealing flange 25 is bolted to the base flange 21. A second through hole, coaxial with the incident window 24, is provided on the sealing flange 25 at a location equal to the outer diameter of the incident window 24. 26; Multiple insulating supports 27 are fixedly connected to the upper surface of the sealing flange. An annular cathode electrode 28 is mounted above the insulating supports 27, with the center of the annular cathode electrode 28 facing the entrance window. The cathode electrode 28 is fixedly connected to the insulating supports 27 by insulating bolts 29. A cathode-gate PCB equalizing ring 210 is fixedly installed above the annular surface of the cathode electrode 28. An annular gate 211 is fixedly installed above the cathode-gate PCB equalizing ring 210. A gate-anode PCB equalizing ring 212 is fixedly connected above the annular surface of the gate 211. An anode electrode 213 is fixedly connected above the gate-anode PCB equalizing ring 212. The cathode electrode 28 and the cathode-gate P... The inner diameters of the CB equalizing ring 210, gate 211, gate-anode inter-PCB equalizing ring 212, and anode electrode 213 are equal and larger than the outer diameter of the entrance window 24. The cathode-gate inter-PCB equalizing ring 210 and the gate-anode inter-PCB equalizing ring 212 are constructed from etched single-sided copper-clad thin PCBs and connected in series using voltage divider resistors. The pump interface 3 on the grid ionization chamber 2 is located on the side wall of the grid ionization chamber 2. The signal interface 4 and high-voltage interface 5 on the grid ionization chamber 2 are located on the top cover flange 22. The cathode electrode 28, gate 211, and anode electrode 213 are connected to the signal interface 4 and high-voltage interface 5. A four-way adapter is fixedly connected to the pump interface 3 of the grid ionization chamber 2. The head 214 and the other three connectors of the four-way adapter 214 are respectively connected to the pressure relief valve 215, the pressure gauge 216 and the vacuum pump 6, and a needle valve 217 is provided on the connecting pipe between the vacuum pump 6 and the four-way adapter 214; the top of the grid ionization chamber 2 is connected to the gas cylinder 218 through a pipe, and a needle valve 217 and a gas flow meter 219 are provided on the connecting pipe between the grid ionization chamber 2 and the gas cylinder 218. The gas cylinder 218 contains isobutane gas, which is supplied to the grid ionization chamber 2 through the gas cylinder 218 and depressurized through the pressure relief valve 215, thereby forming a gas flow system in the grid ionization chamber 2. The pressure is detected by the pressure gauge 216. When measuring fission fragments, the gas pressure of the grid ionization chamber 2 is maintained at 11 kPa, and when measuring alpha particles, the gas pressure of the grid ionization chamber 2 is maintained at 13 kPa.The working gas in the grid ionization chamber 2 is isobutane. The fission fragments are ionized in the grid ionization chamber 2. Due to the strong electric fields between the grid and cathode and between the anode and grid, cations and electrons are formed and drift towards the two electrodes. Each electrode plate collects the induced charge signal. The height of the anode signal pulse is the energy of the fission fragment.

[0020] In this embodiment, the device is powered by a high-voltage system 8 (CAEN, DT1470ET 4ch×±8 kV). Due to the significant difference in signal length between the microchannel plate secondary electron time detector and the grid ionization chamber 2, the preamplifier 9 connected to the time-of-flight detector 1 is an ORTEC 9306 1 GHz preamplifier used to process the signals from the starting and ending microchannel plate secondary electron time detectors 14 and 15. The preamplifier 9 connected to the grid ionization chamber 2 is an ORTEC 142 PC charge-sensitive preamplifier used to process the signals from the grid ionization chamber 2. The data acquisition system 7 uses a PXIe-62590 chassis with PXIe-1022 (3.2 GS / s 12bit 2ch) and PXIe-1073 (1 GS / s 16bit 4ch) modules to convert analog signals into digital signals. Through data processing, the flight time and energy of the fission fragments can be obtained, and the mass of the fission fragments can be calculated using the kinetic energy theorem. The mass distribution of fission fragments was obtained through statistical analysis; Figures 8-11 These are experimental data obtained during the measurement of spontaneous fission targets in embodiments of the present invention, wherein... Figure 8 This represents the time spectrum of fission fragments within a time-of-flight detector. Figure 9 The black spectrum represents the energy deposition data (black energy spectrum) obtained by measuring fission fragments in the grid ionization chamber. The red spectrum represents the flight energy obtained by the final analysis using data acquisition system 7. Figure 10 A two-dimensional diagram of the flight time-energy of fission fragments. Figure 11 The distribution of mass yield of fission fragments. Figure 11 The black lines represent ENDF-BVII data, while the red lines represent the measurement results from the device of this invention. By comparison, the measurement results of this invention are consistent with the NDF-BVII data, proving the accuracy of the fission spectrometer used for measuring the independent yield of fission fragments in this invention.

[0021] It should be noted that the vacuum pump 6, high-pressure system 8, and data acquisition system 7 used in this invention are commercially available components purchased from the market. The specific model and specifications of the vacuum pump 6 need to be selected and determined according to the actual specifications of the device. The selection calculation method adopts the existing technology in the field. The connection and use of the vacuum pump 6 are clear to those skilled in the art, so they will not be described in detail.

[0022] 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 fission spectrometer for fission fragment independent yield measurement, characterized by: The time-of-flight detector and the fixed grid ionization chamber are connected with a pump interface for connecting a vacuum pump for vacuumizing, and the time-of-flight detector and the fixed grid ionization chamber are both provided with a signal interface and a high-voltage electric interface for receiving a detection signal, which are connected with a data acquisition system and a high-voltage system through lines respectively; the time-of-flight detector is provided with an incident channel at the top, the fixed grid ionization chamber is provided with an incident window corresponding to the incident channel at the bottom inlet, the fixed grid ionization chamber is connected with a gas cylinder through a pipeline, and the gas cylinder contains isobutane gas; the incident window is a hollow stainless steel sheet, and a SiN film is covered on the incident window; a ring-shaped cathode electrode is fixedly connected above the incident window, and the center of the ring-shaped cathode electrode is opposite to the incident window; a cathode-grid PCB voltage-equalizing ring is fixedly arranged above the ring-shaped surface of the cathode electrode; a ring-shaped grid electrode is fixedly arranged above the cathode-grid PCB voltage-equalizing ring; a grid-anode PCB voltage-equalizing ring is fixedly connected above the grid electrode; and an anode electrode is fixedly connected above the grid-anode PCB voltage-equalizing ring; the inner diameters of the cathode electrode, the cathode-grid PCB voltage-equalizing ring, the grid electrode, the grid-anode PCB voltage-equalizing ring and the anode electrode are equal, and the inner diameters are larger than the outer diameter of the incident window; the cathode electrode, the grid electrode and the anode electrode are connected with the signal interface and the high-voltage electric interface, and the cathode electrode, the grid electrode and the anode electrode are insulated from the shell of the fixed grid ionization chamber.

2. The fission spectrometer for independent yield measurement of fission fragments according to claim 1, characterized in that: The time-of-flight detector comprises a vacuum cylinder and a starting micro-channel plate secondary electron time-of-flight detector and a terminal micro-channel plate secondary electron time-of-flight detector fixedly connected to the bottom and the top of the vacuum cylinder respectively; the two ends of the vacuum cylinder are provided with flanges, the incident channel is arranged on the top flange of the vacuum cylinder, the pump interface, the signal interface and the high-voltage electric interface are arranged on the side wall of the vacuum cylinder, and a vacuum gauge is further connected to the side wall of the vacuum cylinder for detecting the air pressure in the vacuum cylinder; the starting micro-channel plate secondary electron time-of-flight detector and the terminal micro-channel plate secondary electron time-of-flight detector are fixedly connected to the bottom flange and the top flange of the vacuum cylinder through bolts respectively, and the starting micro-channel plate secondary electron time-of-flight detector and the terminal micro-channel plate secondary electron time-of-flight detector are connected with the signal interface and the high-voltage electric interface through lines.

3. The fission spectrometer for independent yield measurement of fission fragments according to claim 1, characterized in that: The bottom of the parallel-plate ionization chamber is bolted with a base flange, and the top of the parallel-plate ionization chamber is bolted with a top cover flange; the base flange is provided with a first through hole coaxial with the incident channel, the incident window is bolted above the first through hole, a sealing flange is fixedly connected above the base flange, the sealing flange is provided with a second through hole corresponding to the incident window and coaxial with the incident window, the second through hole has an outer diameter equal to that of the incident window, a plurality of insulating supports are fixedly connected above the sealing flange, the cathode electrode is arranged on the insulating supports and fixed by insulating bolts, the pump interface of the parallel-plate ionization chamber is arranged on the side wall of the parallel-plate ionization chamber, and the signal interface and the high-voltage electric interface of the parallel-plate ionization chamber are arranged on the top cover flange.

4. The fission spectrometer for independent yield measurement of fission fragments according to claim 2, characterized in that: The starting micro-channel plate secondary electron time detector and the ending micro-channel plate secondary electron time detector both comprise, in sequence, a base, a secondary electron conversion film, an acceleration grid, an aluminum frame, an inner layer deflection grid and an outer layer deflection grid, and the aluminum frame is fixedly connected with a micro-channel plate on the side wall thereof.

5. The fission spectrometer for independent yield measurement of fission fragments according to claim 4, characterized in that: A preamplifier is arranged on the connection line of the signal interface and the data acquisition system.

6. The fission spectrometer for independent yield measurement of fission fragments according to claim 4, characterized in that: The connection voltage of the acceleration grid, the micro-channel plate and the inner layer deflection grid is 2000 V, the secondary electron conversion film is made of a 300-nm carbon film, the connection voltage of the secondary electron conversion film is 4000 V, and the connection voltage of the outer layer deflection grid is 6000 V; the aluminum frame is a square frame of a copper-coated PCB plate with a thickness of 2 mm, the acceleration grid, the inner layer deflection grid and the outer layer deflection grid are made of 0.25-um gold-plated tungsten wires, and the tungsten wires are welded on the copper electrodes with a 1-mm interval by using soldering tin.

7. The fission spectrometer for independent yield measurement of fission fragments according to claim 3, characterized in that: A four-way adapter is fixedly connected to the pump interface of the parallel-plate ionization chamber, the other three connectors of the four-way adapter are connected with a pressure relief valve, a pressure gauge and a vacuum pump respectively, and a needle valve is arranged on the connection pipeline of the vacuum pump and the four-way adapter.

8. The fission spectrometer for independent yield measurement of fission fragments according to claim 7, characterized in that: A needle valve and a gas flow meter are arranged on the connection pipeline of the parallel-plate ionization chamber and the gas cylinder.

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