CN214704019U - Multilayer fast fission chamber for measuring fission cross section of wide energy region - Google Patents

Abstract

The utility model provides a fast fission chamber of multilayer for wide energy zone fission cross section is measured, including the cavity symmetry sets up the neutron window on the cavity, the neutron window is from taking the shielding layer, the neutron window sets up two seal grooves to guarantee that the membrane is firm and sealing performance, the cavity side sets up at least one interface, the cavity is inside to set up a plurality of mutually independent fission chamber units, and a plurality of mutually independent fission chamber unit parallel is fixed in on the window cover of the neutron window of one side, and fission chamber unit inside separates each electrode through special fluorine dragon (polytetrafluoroethylene) spacer ring. The utility model discloses can adorn a plurality of fission samples, structural material is few, and simple structure has reduced the influence of scattering neutron effectively, and time response is fast, and output pulse's rise time is short, can accurately give signal, fission fragment's detection efficiency height, convenient to use, and operating condition is stable.

Description

Multilayer fast fission chamber for measuring fission cross section of wide energy region

Technical Field

The utility model relates to a wide energy region fission cross-section measurement experiment technical field especially relates to a multilayer fast fission chamber for wide energy region fission cross-section measurement.

Background

Since the first fission ionization chambers developed abroad in the fifth and sixties of the last century, until the beginning of the century, europe, the united states, russia, japan, and so on, continue to use and develop new fission ionization chambers. The research and development experience of the domestic multilayer fast fission chamber is less. Of the fission cross section measurement data that has been developed internationally, much is done by multilayer fission ionizers. The neutron source used includes a reactor neutron source and a white light source in combination with a time-of-flight method. The reactor neutron source cannot acquire high-energy region data due to the limitation of a neutron energy region. Therefore, the fission cross section measurement of the international mainstream is realized by using a pulse white light neutron source and matching with a flight time method, and the method is mature and effective.

Numerous fission cross-section measurement experiments were conducted using multi-layer fast fission chambers on the n-TOF device of European CERN. The fission cross-section measurement work carried out by n-TOF is based on two sets of multi-layer fast fission chambers FIC0 and FIC1, as shown in FIG. 1. The main body of the device is a stainless steel barrel with the diameter of 40cm and the height of 60cm, and 16 samples coaxial with the neutron beam can be placed inside the stainless steel barrel. Each sample consisted of three electrodes: the center is fission nuclide plating sheet, the spacer ring is aluminum with the diameter of 12cm and the thickness of 100 μm, and the front and back surfaces of the spacer ring are deposited with the thickness of about 450 μ g/cm with the diameter of 8cm by electroplating²Fission nuclides of; on both sides of the plated sheet, 15 μm thick aluminum electrodes as readout electrodes were disposed, respectively, and the three electrodes were in a sandwich shape. The tank is filled with P1 with an air pressure of 720mbar0 gas (90% Ar +10% CH)₄/CF₄). Through the device, n-TOF develops a large number of fission cross section measurement experiments, and simultaneously establishes first-class fission cross section measurement and analysis capability of the world, so that a large number of accurate data are obtained.

Besides n-TOF, LANL in the United states also carries out a large amount of fission cross section measurement work on a LANSCE spallation source, and the used device is mainly a multilayer fast fission chamber and acquires fission cross section measurement data comprising Np isotopes (236, 237 and 238), Pa-232 and various uranium isotopes. The multi-layered fast fission chamber used is shown in fig. 2, and its body is an aluminum can body coaxial with the neutron beam. In which 8 samples can be arranged, each sample consisting of two electrodes: the electrode close to the neutron source is a stainless steel substrate with the diameter of 15.2cm and the thickness of 13 mu m, and the surface far away from the neutron source is plated with a stainless steel substrate with the diameter of 13.3cm and the mass thickness of 400 mu g/cm²Fission nuclides of; the electrodes remote from the neutron source are stainless steel readout electrodes of the same diameter and thickness. The tank is filled with P10 gas. In addition, a large number of similar devices are developed and cross-section measurement is carried out on devices such as GELINA in Europe and ORELA/RPI in America, and more measurement results are obtained. These results ultimately support the fission cross-section data in the existing international evaluation nuclear databases.

In China, due to the limitation of a neutron source, only a few single-energy-point neutrons provided by a high-voltage multiplier, a tandem accelerator and the like can be used for a long time, the intensity is weak, a formed device and a spectrometer are hardly used, and the fission cross section measurement of too few nuclides and few energy points is only carried out by some simple methods such as activation or fission chamber measurement on a steady-state single-energy neutron source. Compared with developed countries, it is only equivalent to the level in the sixty-seven decades of the last century. In the fission chamber technology, a plurality of units are developed at home, but the fission chambers manufactured by the method are mainly used for measuring the reactor power, the neutron flux, the prompt neutron energy spectrum and the like, and a multi-layer fast fission chamber special for measuring the fission cross section on a pulse white-light neutron source is not provided. Compared with a common fission chamber, the multilayer fast fission chamber for measuring the fission cross section has higher manufacturing process requirements, and the detector precision can reach the design requirement only if a series of parameters such as effective signal discrimination, pulse rise time, coating quantitative precision and the like need to meet the high-level manufacturing requirements. Meanwhile, the high case rate caused by the high source intensity of a Chinese Spallation Neutron Source (CSNS) white-light neutron source, the neutron energy determination in a flight channel and the like also put high requirements on an electronics and data acquisition and analysis system.

Therefore, the significance of developing a multi-layer fast fission chamber for measuring the fission cross section of the wide energy region is very important.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a be used for wide energy region fission cross section measuring multilayer fast fission chamber to solve the problem that proposes in the above-mentioned background art.

In order to solve the problem, the utility model adopts the following technical scheme:

one of the technical solutions of the present invention is a multilayer fast fission chamber for measuring the fission cross section of a wide energy region, comprising a cavity, wherein neutron windows are symmetrically arranged on the cavity, at least one interface is arranged on the side surface of the cavity, a plurality of mutually independent fission chamber units are arranged inside the cavity, the plurality of mutually independent fission chamber units are parallel and fixed on the window cover of the neutron window on one side, each fission chamber unit comprises a cathode, an anode and a spacer ring, the cathode and the anode are separated by an insulating ring, the cathode and the anode are respectively pressed and fixed by a copper ring, the cathodes of the mutually independent fission chamber units are respectively connected together by a wire, each anode signal is respectively connected to the BNC interface arranged inside the cavity by a wire, different fission chamber units are separated by at least one gasket, and an opening is arranged on the insulating ring of each fission chamber unit, to allow the working gas to enter the interior of the fission chamber unit.

Preferably, 8 fission chamber units which are independent of each other are arranged inside the cavity.

Preferably, the gasket and the insulating ring are both made of polytetrafluoroethylene materials.

Preferably, the target sheet plated with the fission nuclide is used as a cathode, and the bottom lining is a stainless steel sheet with the thickness of 20 mu m; the anode was an aluminum sheet with a thickness of 100 μm.

Preferably, the plurality of independent fission chamber units are fixed to the window cover of one neutron window in parallel by three stainless steel screws.

The utility model discloses another technical scheme is a multilayer fast fission chamber for wide energy zone fission cross section is measured, including the cavity, the symmetry sets up the neutron window on the cavity, the neutron window is from taking the shielding layer, the neutron window sets up two seal grooves to guarantee that the membrane is firm and sealing performance, the cavity side sets up at least one interface, the cavity is inside to set up a plurality of mutually independent fission chamber units, a plurality of mutually independent fission chamber units are parallel to each other and are fixed in the window lid of the neutron window of one side, the fission chamber unit includes negative pole, positive pole, special fluorine dragon spacer ring, separate through special fluorine dragon spacer ring between negative pole and the positive pole, negative pole and positive pole respectively press solid with a copper ring, the negative pole of a plurality of mutually independent fission chamber units is connected through the wire altogether respectively, each way anode signal is connected through the wire respectively on the general interface that the cavity inboard set up, the different fission chamber units are separated by at least one Teflon large spacer ring, and the small Teflon spacer ring and the Teflon large spacer ring are provided with openings so that working gas can enter the fission chamber units.

Preferably, three interfaces are arranged on the side face of the cavity, and the three interfaces are all KF16 standard gas interfaces and are used for butt joint of a KF16 standard valve and an online gas pressure monitor.

Preferably, the upper layer inside the fission chamber unit is provided with an aluminum ring for supporting.

Preferably, the cavity is made of aluminum material.

Preferably, 8 fission chamber units which are independent of each other are arranged inside the cavity.

Compared with the prior art, the beneficial effects of the utility model are that:

the utility model discloses can adorn a plurality of fission samples, structural material is few, and simple structure has reduced the influence of scattering neutron effectively, and time response is fast, and output pulse's rise time is short, can accurately give signal, fission fragment's detection efficiency height, convenient to use, and operating condition is stable.

The utility model provides a neutron window has used more reasonable draw-in groove to from taking the shielding layer, make new detector shell electromagnetic shield satisfy the experiment demand, need not to carry out supplementary shielding again, promoted the accuracy of detector structure greatly.

The utility model discloses arrange three KF16 standard gas interface, replace little metal pipe interface, promoted interface fastness and commonality, docked KF16 standard valve and new online small-size atmospheric pressure monitor on this basis.

The utility model provides a cable joint has abandoned fixed joint before, has designed a general interface on the cavity to with the vacuum seal cable with the form of flange dock the interface on, be favorable to changing different joints at any time, can satisfy even from now on with the built-in inside demand of cavity of advancing of leading. The improved cavity is lighter, has smaller electromagnetic noise and is more universal.

The utility model discloses reduced interelectrode electric capacity, according to front end amplifier circuit's structure, the interelectrode electric capacity is less in the fission chamber unit, and signal pulse falling speed is faster.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the technical solutions in the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a multi-layer fast fission chamber for n-TOF use.

Fig. 2 is a multi-layered fast fission chamber on a LANSCE.

FIG. 3 is a diagram of a multi-layered fast fission chamber structure.

FIG. 4 is a graph of the effect of three common neutron beam windows on neutron flux.

FIG. 5 is a graph of fission signal rise time versus bias voltage.

FIG. 6 is²³⁸U fission plateau curveAnd (6) line drawing.

FIG. 7 is a CSNS white light source²³⁵U fission signal diagram.

FIG. 8 is a diagram of a multi-layered fast fission chamber structure.

Fig. 9 is a cable connector layout.

Fig. 10a is a schematic structural size diagram of a teflon small spacer ring in a front view.

Figure 10b is a top view of a teflon spacer ring.

Fig. 11 is a side view of the teflon spacer ring.

Fig. 12 is a schematic diagram of the front structural dimension of the teflon spacer ring.

Fig. 13 is a side view of a conductive ring (copper ring) made of brass.

Fig. 14 is a schematic structural size diagram of a brass conductive ring (copper ring) in a front view.

FIG. 15 is a side view of a Teflon spacer ring.

Fig. 16 is a schematic diagram of the front structural dimension of the teflon spacer ring.

FIG. 17 is a schematic side view of an aluminum spacer ring.

Fig. 18 is a schematic front view of the structural size of the aluminum spacer ring.

FIG. 19 is measured²³⁵U fission signal diagram.

FIG. 20 is measured using a multi-layered fast fission chamber²³⁸U/²³⁵U fission cross section ratio.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

It should be noted that all the directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiments of the present invention are only used to explain the relative position relationship between the components, the motion situation, etc. in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, descriptions in the present application as to "first", "second", and the like are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

The invention will now be further described with reference to the accompanying drawings.

The working principle is as follows: uranium nuclei on the target sheet are bombarded by neutrons and split into two fission fragments with medium mass, and the fission fragments respectively have certain kinetic energy and are released in two directions at an angle of 180 degrees. One of them enters the sensitive volume of the fission chamber, deposits self energy along its trajectory and ionizes the working gas Ar at the same time, generating free electrons and positive ions, called electron ion pairs, the more the energy of the incident charged particles is, the more the electron ion pairs are ionized. Under the action of the electric field, the electron ion pairs drift towards the anode and the cathode respectively, induced charges are generated on the collecting electrode, the induced charges change along with time to generate output current, and the current signals are integrated and amplified by the preamplifier. The rise time of the signal reflects the drift time of the electrons, while the amplitude of the signal reflects the total charge collected by the electric field, i.e. the energy information of the incident particles. CH in working gas₄The presence of (a) can increase the drift velocity of the electrons, thereby achieving a faster signal rise time.

The measurement principle is as follows: the interior of the multi-layer fast fission chamber cavity contains 8 fission chamber units which are independent of each other, so that²³⁵U、²³⁸The U fission cross section is taken as a standard fission cross section, and the fission cross section ratio measurement with other fission nuclides is realized by a relative method.

Example 1:

the conceptual design of a multilayer fast fission chamber is shown in FIG. 3, and the main structure of the fission chamber mainly consists of three parts: the cavity 1 of cask, the neutron window 2 that sets up in front and back, inside fission chamber array. The barrel cavity 1 is made of stainless steel, and has an outer diameter of 320mm, a height of 300mm and a wall thickness of 5 mm. The interior of the chamber 1 contains 8 independent fission chamber units 3, which are fixed in parallel to each other on a window cover on one side by three stainless steel screws 4. Each unit is an independent fission chamber, different fission chambers can be provided with different target discs, and signal acquisition is independently carried out. Each fission chamber unit is composed of a cathode and an anode. Wherein the target sheet plated with the fission nuclide is used as a cathode, and the bottom lining is a stainless steel sheet with the thickness of 20 mu m; the anode was an aluminum sheet with a thickness of 100 μm. The two electrodes are separated by an insulating ring made of polytetrafluoroethylene, and the distance between the electrodes is 5 mm. The cathode and anode are respectively pressed and fixed by a copper ring, and the copper ring with good conductivity is also used for reading cathode and anode signals. The eight paths of cathodes are connected with the ground through leads respectively, the eight paths of anode signals are connected to the BNC interface on the inner side of the cavity through leads respectively, and the BNC interface on the outer side of the cavity is connected to the preamplifier through a cable. The different fission chamber units were separated by three 10mm high teflon gaskets. The fission chamber is filled with working gas P10 with 0.8 atmospheric pressure, and an insulating ring of each fission chamber unit is provided with an opening so that the working gas can enter the fission chamber unit. Three KF25 interfaces 5 are designed on the cavity on the side face of the fission chamber and are respectively used for inflation, air suction and air pressure monitoring, and the air pressure monitoring is realized by externally connecting a small barometer.

The current signal generated at each anode is sent to a dedicated preamplifier for shaping and amplification. The MSI-8 preamplifier provided by Mesytec was evaluated for several preamplifier designs and selected as the FIC preamplifier according to the FIC design requirements. It has the following characteristics of sufficient magnification: the amplification of the preamplifier should be around 200 mV/. mu.A in order to amplify the particle signal to the lower limit of the DAQ system (50-100 mV). The response time is fast-the inherent rise time of the preamplifier should be less than 8 ns. Low noise: the output noise of the preamplifier must be small enough to achieve a sufficiently high signal-to-noise ratio (SNR). A digital acquisition system for the digitization and storage of preamplifier signals was developed by the university of science and technology in china. The system mainly comprises an SCM module, an FDM module, a TCM module and a data center for storing waveform data.

For the choice of neutron beam window material, its effect on neutron flux and its material strength are mainly considered. Fig. 4 shows neutron transmittance of three window materials calculated by simulation. It can be seen from the figure that the stainless steel material has a large influence on neutron flux due to its large thickness. The performance of the Kapton film is basically equivalent to that of the Mylar film, the influence on the flux of neutrons in each energy band of 1eV-20MeV is less than one percent, and the strength of the Kapton film is higher than that of the Kapton film, so that the Kapton film with the thickness of 125 mu m is used as a neutron beam window of the fission chamber, and the diameters of the front and rear beam windows are 100 mm.

According to the working principle, the incident particles ionize the working gas in the fission chamber to generate electron ion pairs, and the faster the drift velocity of the electrons is, the shorter the rising time of the generated induction signal is. The rise time of the signal has important significance for fission cross section measurement, and the faster rise time indicates that the detector has better time resolution capability and has better energy resolution in the application of measuring the incident neutron energy by using a flight time method. Therefore, the physical design of the fission chamber is such that its electron drift velocity is as fast as possible.

The electron drift velocity is related to the type of working gas, the electric field strength, and the gas pressure. When the type of the working gas is determined, the electron drift velocity and the E/p value are approximately in a linear relation, E is the electric field intensity, and p is the gas pressure. However, the drift velocity of free electrons has a saturation effect, i.e., the electron drift velocity tends to be stable after the E/p value increases to a certain extent. Such a plot of electron drift velocity versus E, p is the basis for our fission chamber physical design. Moreover, the fission chamber polar distance cannot be too small, and the excessively small polar distance can cause incomplete energy deposition of charged particles, so that the discrimination of alpha-fission is difficult. Under the existing physical design (200V bias, 5mm polar distance, air pressure 0.8atm), the E/p value is 5x10⁴V/(m atm), has reached the saturation region, not only can a faster electron drift velocity be obtained,about 6x10⁴m/s and is slightly influenced by E, p fluctuation, thereby meeting the experimental requirements of people. The law is verified through experiments, the rising time of fission signals under different biases is counted by connecting an ORTEC-142PC preamplifier into a fission chamber, and the rising edge of the signals is 10% -90%. As a result, as shown in FIG. 5, the rise time decreases sharply with increasing bias voltage and stabilizes gradually to around 100V.

And carrying out related performance test on the multilayer fast fission chamber to obtain the related parameters of the fission chamber, and carrying out related adjustment on the design and the supporting electronics of the multilayer fast fission chamber according to the experimental result so as to adapt to the experimental conditions of the white light neutron source. The PD-300 accelerator neutron source of the nuclear physics and chemistry institute of China institute of engineering and physics provides experimental conditions for the neutron source. The fission chamber and a matched electronic system have good performance and can complete experimental research on fission cross sections on a white light source through testing indexes such as waveform quality, pulse amplitude spectrum, detection efficiency, plateau curve and time resolution of the fission chamber. The detection efficiency of the fission chamber is calculated to be

95.9%（²³⁸U), the time resolution of fission chamber system is 5.7ns, has satisfied the design index of fast fission chamber, can satisfy fission cross section measurement demand.

FIG. 6 is a graph of experimental measurements²³⁸U fission plateau curve. When the bias voltage is below 150V, the electric field intensity is weak, and the counting rate gradually rises as the bias voltage gradually rises, the composite effect of electron ion pairs is reduced due to the enhanced electric field intensity. The cleavage initiation chamber enters the plateau region at about 150V, and the cleavage rate remains stable over a wide bias range. After the bias voltage rises to 850V, the secondary ionization effect causes the count rate to rise again. The long plateau at 700V and the small plateau at 1.64x10-6/alpha/V demonstrate the good performance of the fission chamber.

On a CSNS white light source by using a multilayer fast fission chamber detector²³⁸U/²³⁵A U fission cross section ratio measurement experiment is carried out, and a fission chamber pulse amplitude spectrum and detection efficiency are analyzed; using Gamma-Flash and²³⁵the 8.77eV resonance peak of U (n, f) is used for calibrating the flight distance, and a constant ratio timing method is used for neutron flightThe line time is measured and the timing precision of the system is analyzed; analyze and prepare²³⁵U、²³⁸Neutron energy-signal amplitude two-dimensional spectrum of U and neutron energy spectrum, measured²³⁵The U low-energy region is completely matched with the resonance peak position of the database; the influence of the target piece bottom lining and the collector on the experiment when neutrons are emitted is analyzed, and the influence of the white light beam flow nonuniformity and the target piece impurity isotope is analyzed and corrected; the flux attenuation of white light neutrons in the fission chamber is simulated and calculated by using an MCNP program and is measured according to actual measurement²³⁵The U fission rate calculates the neutron flux of the white light, and is basically consistent with the result measured by CSNS white light source group personnel.

FIG. 7 shows the collected²³⁵Fission fragment waveform of U. The rise time of the fission signal is about 80ns (10% -90% rising edge) and the fall time is about 200ns (no signal overshoot is accounted for).

Example 2:

the multi-layer fast fission chamber for measuring the wide energy region fission cross section in the embodiment comprehensively upgrades the fission chamber cavity, refines the material and design, uses aluminum materials, reduces the weight of the detector to the previous 30 percent, and further reduces the influence on neutrons. The design eliminates the previous thick ceramic insulating layer and optimizes the design in multiple details, particularly considering the electromagnetic shielding optimization.

Referring to fig. 8, the reactor comprises a cavity 1, wherein neutron windows 2 are symmetrically arranged on the cavity 1, the neutron windows 2 are provided with shielding layers, the neutron windows are provided with double sealing grooves 8 to ensure the stability and sealing performance of a membrane, at least one KF16 standard gas interface 6 is arranged on the side surface of the cavity 1, a plurality of mutually independent fission chamber units 3 are arranged inside the cavity 1, the mutually independent fission chamber units 3 are parallel to each other and fixed on a window cover of the neutron window 2 on one side, each fission chamber unit comprises a cathode, an anode and a teflon spacer ring, the cathode and the anode are separated by the teflon spacer ring, the cathode and the anode are respectively pressed and fixed by a copper ring, the cathodes of the mutually independent fission chamber units are respectively connected in common by leads, and each anode signal is respectively connected to a common interface 7 arranged on the inner side of the cavity by leads, the different fission chamber units are separated by at least one Teflon large spacer ring, and the small Teflon spacer ring and the Teflon large spacer ring are provided with openings so that working gas can enter the fission chamber unit 3.

Compared to example 1:

the neutron window has used more reasonable draw-in groove to from taking the shielding layer, make new detector shell electromagnetic shield satisfy the experiment demand, need not to carry out supplementary shielding again, promoted the accuracy of detector structure greatly. Referring to fig. 8, three KF16 standard gas interfaces 6 are arranged, the former small metal pipe interfaces are eliminated, the interface firmness and universality are improved, and on the basis, a KF16 standard valve and a new online small-sized gas pressure monitor are butted.

Referring to fig. 9, the cable connector abandons the fixed connector, the cavity is provided with a universal connector 7, and the vacuum-tight cable is connected to the connector 7 in a flange manner, so that different connectors can be replaced at any time, and even the requirement that the cable connector is placed in the cavity in the future can be met. The improved cavity is lighter, has smaller electromagnetic noise and is more universal.

The structure of each fission chamber unit inside is modified, mainly to reduce interelectrode capacitance. Specifically, referring to fig. 10 to 18, these figures are schematic diagrams of the structural dimensions of a teflon small spacer ring, a teflon spacer ring, a brass conductive ring (copper ring), a teflon large spacer ring, and an aluminum spacer ring, respectively, specifically, a teflon spacer ring is used in each fission chamber unit inside to separate each electrode, and an aluminum ring for supporting is disposed at the top end of the fission chamber unit. The device comprises 200 Teflon small spacing rings, 50 Teflon spacing rings, 50 brass conducting rings, 40 Teflon large spacing rings and 4 aluminum spacing rings.

According to the structure of the front-end amplifying circuit, the smaller the inter-pole capacitance in the fission chamber unit is, the faster the signal pulse falling speed is. In this regard, the area of the electrode tab was reduced from 86cm according to the capacitance formula²Reduced to 50cm²Thus, the capacitance can be reduced by about one third. Meanwhile, the volume of the inter-electrode Teflon material is reduced, thereby reducing the average dielectric constant of the medium,contributing to further reduction of capacitance.

Referring to FIG. 15, the multi-layered fission chamber of the present embodiment has been tested for cross-section measurement on a CSNS white light source, and has achieved great results. Fission typical signals are collected by the full waveform, dual cluster gamma storm and fission signals are clear, and the rising time of the waveform of the fission signals is about 30 ns. The design index is reached, and the response time is extremely fast.

Referring to FIG. 16, the 1-20MeV energy region in the single cluster mode was obtained²³⁸U/²³⁵The U fission cross section ratio and the experimental relative uncertainty are 4.1-10.7% (1-1.4 MeV) and 2.3-3.6% (1.4-20 MeV), and most measured values are consistent with the data of the ENDF/B-8.0 library in the experimental uncertainty.

The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the scope of the embodiments of the present invention, and are intended to be covered by the claims and the specification.

Claims (10)

1. A multi-layer fast fission chamber for measuring a fission section of a wide energy region is characterized by comprising a cavity, neutron windows are symmetrically arranged on the cavity, at least one interface is arranged on the side surface of the cavity, a plurality of mutually independent fission chamber units are arranged in the cavity, the mutually independent fission chamber units are parallel to each other and are fixed on a window cover of the neutron window on one side, each fission chamber unit comprises a cathode, an anode and a spacer ring, the cathode and the anode are separated by an insulating ring, the cathode and the anode are respectively pressed and fixed by a copper ring, the cathodes of the mutually independent fission chamber units are respectively connected in common through a conducting wire, each anode signal is respectively connected on a BNC interface arranged on the inner side of the cavity through a conducting wire, different fission chamber units are separated by at least one gasket, and an opening hole is arranged on the insulating ring of each fission chamber unit, to allow the working gas to enter the interior of the fission chamber unit.

2. The multi-layered fast fission chamber for wide energy region fission cross section measurement according to claim 1, wherein 8 mutually independent fission chamber units are arranged inside said cavity.

3. The multi-layered fast fission chamber for wide energy region fission cross section measurement according to claim 1, wherein the gasket and the insulating ring are both made of polytetrafluoroethylene material.

4. The multi-layered fast fission chamber for wide energy region fission cross section measurement according to claim 1, wherein the target plate plated with the fission nuclide is used as a cathode, and the spacer ring is a stainless steel layer having a thickness of 20 μm; the anode was an aluminum sheet with a thickness of 100 μm.

5. The multi-layered fast fission chamber for wide energy region fission cross section measurement according to claim 1, wherein a plurality of independent fission chamber units are parallel to each other and fixed to a window cover of a neutron window on one side by three stainless steel screws.

6. A multilayer fast fission chamber for measuring a fission cross section of a wide energy region is characterized by comprising a cavity, neutron windows are symmetrically arranged on the cavity, the neutron windows are provided with shielding layers, double seal grooves are arranged on the neutron windows to ensure the stability and the sealing performance of a film, at least one interface is arranged on the side surface of the cavity, a plurality of mutually independent fission chamber units are arranged in the cavity, the mutually parallel fission chamber units are fixed on a window cover of the neutron window on one side, each fission chamber unit comprises a cathode, an anode and a Teflon spacer ring, the cathode and the anode are separated by the Teflon spacer ring, the cathode and the anode are respectively pressed and fixed by a copper ring, the cathodes of the mutually independent fission chamber units are respectively connected together through wires, and signals of each path of anode are respectively connected on a universal interface arranged on the inner side of the cavity through wires, the different fission chamber units are separated by at least one Teflon large spacer ring, and the small Teflon spacer ring and the Teflon large spacer ring are provided with openings so that working gas can enter the fission chamber units.

7. The multi-layer fast fission chamber for wide energy region fission cross section measurement according to claim 6, wherein three interfaces are arranged on the side of the cavity, and all three interfaces are KF16 standard gas interfaces for butt joint of KF16 standard valves and online gas pressure monitors.

8. The multi-layered fast fission chamber for wide energy region fission cross section measurement according to claim 6, wherein an upper layer inside said fission chamber unit is provided with an aluminum ring for supporting.

9. The multi-layered fast fission chamber for wide energy region fission cross section measurement according to claim 6, wherein said cavity is made of aluminum material.

10. A multi-layer fast fission chamber for wide energy region fission cross section measurement according to any one of claims 6 to 9, wherein 8 mutually independent fission chamber units are arranged inside the cavity.

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