Ultra-fast nuclear detection method and device design for nuclear fission process and fission product thereof

Abstract

The invention discloses an ultrafast nuclear detection method and device design for a nuclear fission process and a fission product of the nuclear fission process, and belongs to the technical field of nuclear fission detection. The device comprises a pulse high-energy gamma and X-ray introduction device, an air inlet device, a low-vacuum target chamber, a high-vacuum time-of-flight spectrometer (ToF) and an X-ray detection system. The pulse high-energy gamma and X-ray introduction device generates a MeV gamma beam with femtosecond pulse width and an X-ray by using an inverse Compton scattering technology, and the MeV gamma beam is used for interacting with a target nucleus to induce nuclear fission. The X-ray is used for detecting the dynamic change of an extranuclear electron structure in the fission process, resonance absorption spectrums in different stages are measured by adjusting the time delay of the X-ray and the MeV gamma beam, and the ultrafast dynamic process of nuclear fission is inverted. According to the invention, an extranuclear electron ultrafast dynamic measurement technology is introduced into nuclear physics research for the first time, shooting of the nuclear fission process under the femtosecond time scale is realized, and a brand new means is provided for nuclear physics and related basic scientific research.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear fission process detection, and in particular to an ultrafast nuclear detection method and device design for a nuclear fission process and its fission products. Background Art

[0002] Nuclear fission is an ultrafast nuclear process that occurs when a heavy nucleus splits into two intermediate-mass nuclei, lasting tens of femtoseconds. Its timescale is on the order of fs or even shorter. Traditional nuclear detection techniques detect the products of nuclear processes, not the processes themselves. Existing technologies focus on the ultrafast dynamics of electrons outside the nucleus, but fail to integrate these processes with nuclear processes.

[0003] Therefore, the present invention proposes a new experimental concept for measuring ultrafast nuclear physics processes and a device for implementing the concept. The invention can realize ultrafast "shooting" of the nuclear fission process itself and the evolution of fission products over time on the femtosecond and sub-femtosecond time scales. Summary of the Invention

[0004] The present invention aims to provide an ultrafast nuclear detection method and device design for nuclear fission processes and their fission products. The present invention introduces mature electron ultrafast dynamics measurement technology into nuclear physics, and inverts ultrafast nuclear processes through ultrafast dynamics measurements of extranuclear electrons.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] An ultrafast nuclear detection device for nuclear fission processes and their fission products, comprising: a pulsed high-energy gamma and X-ray introduction device, an air intake device, a low vacuum target chamber, a high vacuum time-of-flight spectrometer ToF, and an X-ray detection system;

[0007] The pulsed high-energy gamma and X-ray introduction device is used to introduce high-energy gamma photons and X-rays. The pulsed high-energy gamma and X-ray introduction device includes an electron accelerator and a laser. The electron accelerator generates an electron beam, and the laser generates a laser. The laser and the electron beam undergo inverse Compton scattering to generate high-energy gamma photons and X-rays. The high-energy gamma photons form a MeV gamma beam.

[0008] The gas inlet device is arranged at the top of the low vacuum target chamber, and forms a target gas injection array through a number of evenly spaced nozzles. The number of nozzles opened determines the gas intake volume and the vacuum degree of the low vacuum target chamber. The gas inlet device is used to inject the fissile target gas to be tested into the low vacuum target chamber;

[0009] The low vacuum target chamber is used for the interaction between the MeV gamma beam and the X-ray beam and the target gas. The interaction between the MeV gamma beam and the target gas causes nuclear fission in the target gas. X-rays are used as probe rays to detect the extranuclear electronic structure of the nuclear fission target gas. The MeV gamma beam and the X-rays have a clear time correlation, and the time delay of the X-ray beam relative to the MeV gamma beam can be controlled on the femtosecond time scale, and the adjustment step size is also on the femtosecond scale.

[0010] The high vacuum time-of-flight spectrometer (ToF) is an ion detection unit that uses a small-aperture conical port design to connect to the low vacuum target chamber. The high vacuum time-of-flight spectrometer (ToF) is three-dimensionally adjustable, making it easier to find the intersection area of ​​the MeV gamma beam and X-rays and obtain high-quality ion spectra.

[0011] The X-ray detection system is used to measure the absorption spectrum of X-rays after they pass through the target.

[0012] Furthermore, the pulse width of the MeV gamma beam and the X-ray beam is controlled at the femtosecond scale. An electron beam of several hundred MeV to GeV is generated by an electron accelerator, and a laser with a pulse width of ~fs and a wavelength of 800nm ​​is generated by a laser. The above laser and the electron beam undergo inverse Compton scattering to produce high-energy gamma photons and X-rays with a pulse width of ~fs.

[0013] Furthermore, the ion detector in the high vacuum time-of-flight spectrometer ToF uses a microchannel plate. The microchannel plate detector has a special material coating that can achieve a higher ion signal response gain.

[0014] A method for using an ultrafast nuclear detection device for nuclear fission processes and their fission products: by adjusting the delay time of X-rays to MeV gamma beams, measuring the resonance absorption spectra of X-rays at different delay times, and comparing them with the resonance absorption spectra of different fission stages calculated theoretically, the ultrafast fission process of the target gas target nucleus to be measured can be obtained.

[0015] The principle of this technical solution is that gamma photons, or MeV gamma beams, in the present device react with a target nucleus within a low-vacuum target chamber to produce a fissile nucleus C. X-rays passing through the target region are resonantly absorbed by the extranuclear electrons of the C nucleus and its fission products, nuclei A and B, forming a resonance absorption spectrum. During the fission of nucleus C into nuclei A and B, their extranuclear electronic structures gradually change, resulting in different resonance absorption spectra at different stages of fission. Therefore, by adjusting the delay time between the MeV gamma beam and the X-rays, measuring the resonance spectra at different delay times, and comparing them with theoretically calculated resonance absorption spectra at different fission stages, the ultrafast fission process of nucleus C can be experimentally determined.

[0016] Advantages of this technical solution: The present invention can measure the ultrafast dynamics of nuclear fission. Previous research has been limited to the ultrafast dynamics of extranuclear electrons, and the ultrafast dynamics of extranuclear electronic structures have never been incorporated into nuclear detection. This invention uses ultrafast dynamics of extranuclear electrons to extract ultrafast nuclear dynamics. The equipment used in this invention has a compact structure, high integration, and is safe and simple to operate. This device not only enables the "filming" of ultrafast nuclear fission processes but also has a significant impact on the development of nuclear physics and even related basic sciences. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the design of the detection device of the present invention; DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0019] like Figure 1 As shown in the figure, it is a design diagram of the ultrafast nuclear detection device for nuclear fission process and its fission products of the present invention. The device of the present invention includes a pulsed high-energy gamma and X-ray introduction device, an air intake device, a low vacuum target chamber, a high vacuum time-of-flight spectrometer ToF and an X-ray detection system. The molecular pump in the figure is used for vacuum adjustment, and the data acquisition card is used for collecting high vacuum time-of-flight spectrometer ToF data.

[0020] The pulsed high-energy gamma and X-ray introduction device includes an electron accelerator and a laser. The electron accelerator generates an electron beam of several hundred MeV to GeV, and the laser generates a laser with a pulse width of 800 nm and a wavelength of 800 nm. The laser and the electron beam undergo inverse Compton scattering to generate high-energy gamma photons and X-ray pulses with a pulse width of 800 nm. The high-energy gamma photons form a MeV gamma beam. Through inverse Compton scattering, 800 nm photons gain energy when colliding with high-energy electrons. By changing the energy of the electron beam or the scattering angle between the laser photons and the electron beam, high-energy photons with continuously adjustable energy in the range of 800 keV to 800 MeV can be obtained. The intensity of the high-energy photon beam depends on the intensity of the electron beam and the intensity of the laser, and the pulse width is consistent with the pulse width of the laser.

[0021] The gas inlet device is located at the top of the low-vacuum target chamber, forming a target gas jet array through several evenly spaced nozzles. The number of nozzles opened in the gas inlet device determines the gas intake volume and the vacuum level of the low-vacuum target chamber. A pulsed gamma beam (MeV gamma) and a beam of keV photons (X-rays) interact with the target gas within the low-vacuum target chamber, where the vacuum level is maintained at tens of millibars. The MeV gamma beam interacts with the target gas, causing it to fission. X-rays are used as probe rays to detect the structure of the extranuclear electrons in the fissioned target gas. The gas inlet device is designed to provide a longer path for the MeV gamma beam and X-ray pulses to interact with the target gas, while also allowing the X-ray pulses to escape the interaction region without being blocked by the gas target chamber.

[0022] The high vacuum time-of-flight spectrometer ToF is an ion spectrum detection unit, which is connected to the low vacuum target chamber using a small-diameter conical port design. Under the premise of ensuring the introduction of ions, the vacuum in the ToF cavity is maintained at 10 -6 mbar level. The ion detector in the high-vacuum time-of-flight spectrometer (ToF) utilizes a microchannel plate (MCP), which features a special material coating that achieves high ion signal response gain. Furthermore, the ToF unit is three-dimensionally adjustable, facilitating the identification of the region where the MeV gamma beam intersects with X-rays and the acquisition of high-quality ion spectra.

[0023] The X-ray detection system is used to measure the absorption spectrum of X-rays after they pass through the target. The absorption spectrum corresponds to the extranuclear electronic structure of the elements encountered during the propagation of X-rays.

[0024] The specific implementation process of using the detection device of the present invention to achieve "photography" of the ultrafast process of nuclear fission is as follows: MeV gamma beams and X-rays are introduced through a pulsed high-energy gamma and X-ray introduction device, and the target gas to be measured is input into the low vacuum target chamber through the air intake device. The MeV gamma beam with a pulse width of ~fs reacts with the target nucleus in the low vacuum target chamber to generate fissionable nuclei C. The C nuclear fission process can be simply described as follows: In the first stage, the incident gamma rays react with the target nucleus C to form excited nuclides C*. In the second stage, the nuclide C* fissions into two independent daughter nuclei A and B. In the third stage, under the action of Coulomb repulsion, the internuclear distance between nuclei A and B becomes larger and larger. When the internuclear distance between nuclei A and B reaches the internuclear distance of a diatomic molecule, (AB) can be regarded as a molecule. In the fourth stage, as the internuclear distance between nuclei A and B continues to increase, the (AB) molecule gradually evolves into two independent atoms A and B. That is, the C nuclear fission process can be described as C +q →(AB) +q →A +m +B +n(q is the charge state of the atomic ion with atomic nucleus C and the AB molecular ion, m and n are the charge states of the A atomic ion and the B atomic ion respectively). At different stages of fission, the extranuclear electronic structure of the fission system will be different, and the resonance absorption spectrum will also be different. The X-ray detection system can obtain the absorption spectrum after the X-ray passes through the target. Therefore, by adjusting the time delay of the X-ray relative to the MeV gamma and measuring the resonance absorption spectrum of the fission system under different time delays, we can detect the entire process of the C nucleus fissioning into A and B nuclei.

[0025] Analyze the correlation between X-ray absorption spectrum and ToF ion spectrum, further reduce the interference on X-ray absorption spectrum, establish the dependence of X-ray absorption spectrum of different ions and different charge states of the same ion on the delay time of X-ray relative to MeV gamma beam, so as to extract the nuclear fission evolution dynamics process.

[0026] During implementation, it is important to note that:

[0027] 1. The energy of the gamma photon should be high enough. When a single gamma photon is absorbed by the target nucleus, the fission energy of the excited compound nucleus C is higher than the fission barrier, allowing the C nucleus to fission within a femtosecond or even shorter time. Using this method, the present invention can enable the fission of numerous C nuclei within a femtosecond or even shorter time.

[0028] 2. The X-ray energy distribution range should match the energy range of the extranuclear electron resonance absorption in the nuclear fission process.

[0029] 3. After the target gas is input into the air intake device, the vacuum degree of the low vacuum target chamber is maintained at tens of mbar. The number of nozzles opened determines the air intake volume and the vacuum degree of the low vacuum target chamber. Gradually increase the air intake volume and reduce the vacuum degree of the target chamber until a clear X-ray resonance absorption spectrum can be measured.

[0030] 4. After the target gas is input into the air inlet device, the vacuum degree of the free flight zone of ToF is less than 2×10 -4 Pa, the working vacuum of the ToF ion detector area is less than 2×10 -4 Pa, so the balance between the target gas intake volume per unit time and the vacuum pump speed is critical.

[0031] 5. In the low vacuum target chamber, the ionized fission target gas should be introduced into the ToF detection device as much as possible.

[0032] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. For those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. An ultrafast nuclear detection device for nuclear fission processes and their fission products, characterized in that: include: Pulsed high-energy gamma and X-ray introduction device, air intake device, low vacuum target chamber, high vacuum time-of-flight spectrometer ToF and X-ray detection system; The pulsed high-energy gamma and X-ray introduction device is used to introduce high-energy gamma photons and X-rays. The pulsed high-energy gamma and X-ray introduction device includes an electron accelerator and a laser. The electron accelerator generates an electron beam, and the laser generates a laser. The laser and the electron beam undergo inverse Compton scattering to generate high-energy gamma photons and X-rays. The high-energy gamma photons form a MeV gamma beam. The gas inlet device is arranged on the top of the low vacuum target chamber, and forms a target gas injection array through a plurality of evenly spaced nozzles. The number of nozzles opened determines the gas intake volume and the vacuum degree of the low vacuum target chamber. The gas inlet device is used to inject the fissile target gas to be tested into the low vacuum target chamber; The low vacuum target chamber is used for the interaction between the MeV gamma beam and the X-ray beam and the target gas. The interaction between the MeV gamma beam and the target gas causes nuclear fission of the target gas. The X-rays are used as detection rays to detect the extranuclear electronic structure of the nuclear fission target gas. The MeV gamma beam and the X-rays have a clear time correlation. The time delay of the X-ray beam relative to the MeV gamma beam can be controlled on a femtosecond time scale, and the adjustment step size is also on a femtosecond scale. The high vacuum time-of-flight spectrometer (ToF) is an ion detection unit that uses a small-aperture conical port design to connect to a low vacuum target chamber. The high vacuum time-of-flight spectrometer (ToF) is three-dimensionally adjustable, making it easier to find the region where the MeV gamma beam and X-rays intersect, thereby obtaining high-quality ion spectra. The X-ray detection system is used to measure the absorption spectrum of X-rays after they pass through the target.

2. The method for using the ultrafast nuclear detection device for nuclear fission process and its fission products according to claim 1, characterized in that: By adjusting the delay time of X-rays to MeV gamma beams, measuring the resonance absorption spectra of X-rays at different delay times, and comparing them with the resonance absorption spectra of different fission stages calculated theoretically, the ultrafast fission process of the target gas target nucleus to be measured can be obtained.

3. The ultrafast nuclear detection device for nuclear fission process and its fission products according to claim 1, characterized in that: The pulse width of the MeV gamma beam and the X-ray beam is controlled at the femtosecond scale. An electron beam of several hundred MeV to GeV is generated by an electron accelerator, and a laser with a pulse width of 800 nm and a wavelength of 800 nm is generated by a laser. The laser and the electron beam undergo inverse Compton scattering to generate high-energy gamma photons and X-rays with a pulse width of 1.5 fs.

4. The ultrafast nuclear detection device for nuclear fission process and its fission products according to claim 1, characterized in that: The ion detector in the high vacuum time-of-flight spectrometer ToF adopts a microchannel plate. The microchannel plate detector has a special material coating, which can achieve a higher ion signal response gain.

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