Pulse neutron generation device for cutting steady-state neutron radiation and pulse time measurement method

Abstract

The invention discloses a pulse neutron generation device for cutting steady-state neutron radiation and a pulse time measurement method. Comprising a steady-state neutron radiation source device, a shielding structure, a supporting frame, a collimator provided with a conical beam limiting diaphragm, a cutting sliding block made of neutron absorbing materials and internally provided with a penetrating beam limiting hole, a sliding block falling stabilizing device, a sliding block height adjusting device, a sliding block releasing device and a detector located on the emergent side. The cutting sliding block freely falls down along a vertical track limited by the falling stabilizing device after being released at a preset height, time cutting is carried out on a steady-state neutron beam passing through the collimator, a reference point is arranged on the supporting frame according to the pulse time measuring method, and a photoelectric probe A, a photoelectric probe B and a timer are arranged near a falling path; in the falling process of the cutting sliding block, the two photoelectric probes are sequentially shielded to trigger the timer to start / stop timing, and the time interval recorded by the timer is determined as the actual pulse width of pulsed neutron radiation.

Description

Technical Field

[0001] This invention relates to the field of ionizing radiation metrology, specifically to a pulsed neutron generating device for cutting steady-state neutron radiation and a pulse time measurement method. Background Technology

[0002] A criticality accident is an energy release event, usually caused by an accidental self-sustaining or divergent neutron chain reaction. It typically occurs at nuclear fuel plants or nuclear waste reprocessing plants, and occasionally in nuclear reactors. During a criticality accident, a large amount of neutron and gamma radiation is usually emitted, exposing workers in the vicinity to high doses of radiation, even lethal doses. The radiation type changes from pulsed radiation to continuous radiation, with the pulse width on the order of milliseconds, and the radiation type is a mixed n / gamma radiation field.

[0003] The primary function of criticality alarm equipment is to detect radiation generated by criticality accidents and issue alerts to personnel. Currently, a large number of criticality accident alarm devices exist in nuclear fuel plants and reprocessing plants. The standard GB / T 12787-2020, "Criticality Accident Alarm Equipment," stipulates that after installation, the detection alarm threshold should be able to detect the following criticality accident: within 60 seconds, the total absorbed dose of neutrons and gamma radiation in free air at a distance of 2 meters from the nuclear reactant is 0.2 Gy, and the pulse width used to test the criticality accident alarm equipment is 1 ms to 3 seconds. However, corresponding pulse testing devices are currently lacking in China. Summary of the Invention

[0004] To achieve the above and other related objectives, the present invention discloses a pulsed neutron generation device for cutting steady-state neutron radiation, comprising: A steady-state neutron radiation source device used to generate a steady-state neutron beam; The shielding structure installed outside the steady-state neutron radiation source device is used to form a standard radiation field space; A support frame is installed in front of the steady-state neutron radiation source device; A collimator fixed on the support frame, the collimator having a cylindrical structure and an internal conical beam-limiting aperture for limiting the emission direction and beam size of neutron radiation; A cutting slider made of neutron-absorbing material is disposed on the exit side of the collimator and has a through-beam limiting hole inside it. When the cutting slider completely blocks the neutron beam, the neutron dose rate is attenuated by at least 500 times relative to the unshielded state. A slider falling stabilizing device, which is connected to the support frame, is used to limit the falling trajectory of the cutting slider in the vertical direction and stabilize its attitude; A slider height adjustment device, which is connected to the cutting slider via a flexible connector, is used to raise the cutting slider to a predetermined height and maintain it at that predetermined height; A slider release device, which cooperates with the cutting slider and the slider height adjustment device, is used to detach the cutting slider from the slider height adjustment device at a predetermined height, so that it can fall freely along the trajectory defined by the slider falling stabilizing device under the action of gravity. The detector, located on the emission side of the cutting slider, is used to measure the neutron dose rate after passing through the cutting slider; When the cutting slider falls freely from a predetermined height under the action of gravity, the beam-limiting aperture on the cutting slider moves relative to the beam-limiting aperture of the collimator, thereby cutting the steady-state neutron beam passing through the collimator in time, thus forming pulsed neutron radiation with a pulse width on the order of milliseconds.

[0005] Preferably, the cutting slider comprises an inner and outer two-layer structure: the inner layer is a boron-containing polyethylene shielding layer with a thickness of 15cm, used to absorb neutrons; the outer layer is a steel cladding shell with a thickness of 2cm, used to enhance mechanical strength and provide gamma radiation shielding.

[0006] Preferably, the slider stabilizing device includes: A small slider is disposed on one side of the cutting slider, and multiple pulleys are rotatably mounted on the small slider; A sliding groove that mates with the small slider is fixed to the support frame and is made of aluminum alloy with a concave cross-section. A pulley is engaged within the sliding groove and slides smoothly along it. The pulley of the small slider rolls in the groove, which limits and guides the cutting slider during its descent, thereby maintaining the stability of the cutting slider's posture and limiting its descent path.

[0007] Secondly, the present invention discloses a pulse time measurement method for measuring the pulse time of pulsed neutron radiation generated by the pulsed neutron generating device, characterized by comprising the following steps: A reference point is set on the support frame, such that the reference point corresponds to the position on the support frame when the limiting hole of the cutting slider passes through the starting position of the pulse interval during the falling process; A light-triggered timing system is arranged near the falling path of the cutting slider. The light-triggered timing system includes photoelectric probe A, photoelectric probe B, and a timer electrically connected to both. After the cutting slider is raised to a predetermined height, it is released through the slider release device, allowing the cutting slider to fall freely under the action of gravity. During the fall, when the cutting slider blocks the light of the photoelectric probe A, the photoelectric probe A outputs a trigger signal to the timer to start the timer. As the cutting slider continues to fall, when it blocks the light from the photoelectric probe B, the photoelectric probe B outputs a stop signal to the timer to stop the timer. The time interval between the start and stop triggering times recorded by the timer is correlated with the time when the lower edge of the beam-limiting aperture of the cutting slider reaches the reference point and the time when the upper edge of the beam-limiting aperture reaches the reference point during the movement of the cutting slider, thereby determining the time interval as the actual pulse width of the pulsed neutron radiation.

[0008] Preferably, the reference point is determined through the following steps: The cutting slider is raised to a position where the steady-state neutron beam is completely shielded, and the neutron dose rate at this time is measured using a detector to obtain the measured value M1; Adjust the cutting slider so that the center of the beam-limiting aperture of the cutting slider is at the same height as the center of the steady-state neutron radiation source; Move the cutting slider upwards until the neutron dose rate measured by the detector equals M1; The reference point is the height of the lower edge of the cutting slider's constraint hole on the support frame at this time.

[0009] Preferably, it also includes theoretical calculation steps for the pulse time: Using the pulse interval length corresponding to the pulsed neutron radiation, gravitational acceleration, and the instantaneous velocity of the cutting slider at the start of the pulse interval as parameters, the theoretical pulse width of the pulsed neutron radiation is calculated based on the uniformly accelerated linear motion relationship, and the theoretical pulse width is compared with the actual pulse width.

[0010] Preferably, the method further includes the step of measuring the pulsed neutron dose rate of the pulsed neutron radiation generated by the pulsed neutron generating device: The scintillator detector used to measure the dose rate is calibrated in a standard isotope neutron source metrology standard to obtain the calibration factor N of the scintillator detector. The sensitive volume of the scintillator detector is placed at the center of the radiation beam of the pulsed neutron generating device. The cutting slider is released at different lifting heights, and the corresponding dose rate indication value M is measured. Each indication value M is multiplied by the calibration factor N to obtain the pulsed neutron dose rate under different pulse conditions, which is then combined with the actual pulse width to characterize the pulsed neutron radiation field.

[0011] By employing the above technical solution, a cutting slider with a beam-limiting aperture is installed on the emission side of the steady-state neutron beam. The controlled free fall of the cutting slider under gravity causes relative motion between the beam-limiting aperture and the collimator's beam-limiting stop, thereby achieving time-cutting of the steady-state neutron beam and obtaining millisecond-level pulsed neutron radiation. This effectively alleviates the shortcomings of existing pulse testing devices and facilitates the construction of pulsed radiation testing / calibration radiation fields for critical alarm equipment, etc. The cutting slider uses a neutron absorption structure and achieves significant attenuation of the neutron beam when completely blocked. Combined with the shielding structure, it forms a standard radiation field space, which is beneficial for improving the radiation field's effectiveness against neutrons. Comparison and testing safety; the slider falling stabilization device achieves trajectory constraint and attitude stability through pulleys and groove guidance, improving the repeatability and consistency of the pulse formation process; the slider height adjustment device and release device work together to realize controllable operation of slider lifting, holding and releasing, which facilitates the adjustment of pulse conditions as needed; at the same time, the pulse time measurement method based on the optical trigger timing system and reference point calibration can reliably measure the actual pulse width, and can combine detector calibration and dose rate measurement to obtain pulse radiation field parameter characterization capability, thereby supporting the testing and evaluation of indicators such as fast transient response and alarm response time of related alarm devices. Attached Figure Description

[0012] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. The drawings are provided for a better understanding of the invention and are not intended to limit the scope of this disclosure. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein: Figure 1 This is a simplified schematic diagram illustrating an embodiment of the present invention; Figure 2 This is a schematic diagram of actual pulse width measurement in an embodiment of the present invention.

[0013] Reference numerals in the attached figures: 1. Steady-state neutron radiation source device; 2. Shielding structure; 3. Collimator; 4. Cutting slider; 5. Detector; 6. Shielding material. Detailed Implementation

[0014] 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.

[0015] Reference Figure 1 This invention provides a pulsed neutron generation device for cutting steady-state neutron radiation, comprising: Steady-state neutron radiation source device 1, used to generate a steady-state neutron beam; The shielding structure 2, located outside the steady-state neutron radiation source device 1, is used to form a standard radiation field space. A support frame is installed in front of the steady-state neutron radiation source device 1; The collimator 3 is fixed on the support frame. The collimator 3 is a cylindrical structure with a conical beam-limiting aperture inside, which is used to limit the emission direction and beam size of neutron radiation. In this embodiment of the invention, the collimator 3 is 20.0 cm long, has a front opening diameter of 10.2 cm, a rear opening diameter of 9.8 cm, and a steel plate with screw holes is installed at the front end. A cutting slider 4 made of neutron-absorbing material is disposed on the emission side of the collimator 3 and has a through-beam limiting hole inside it. When the cutting slider 4 completely blocks the neutron beam, the neutron dose rate is attenuated by at least 500 times relative to the unshielded state. A slider falling stabilizing device is connected to the support frame and is used to limit the falling trajectory of the cutting slider 4 in the vertical direction and stabilize its attitude. A slider height adjustment device is connected to the cutting slider 4 via a flexible connector, used to raise the cutting slider 4 to a predetermined height and maintain it at that predetermined height; A slider release device, which cooperates with the cutting slider 4 and the slider height adjustment device, is used to detach the cutting slider 4 from the slider height adjustment device at a predetermined height, so that it can fall freely along the trajectory defined by the slider falling stabilizing device under the action of gravity. Detector 5 is located on the emission side of the cutting slider 4 and is used to measure the neutron dose rate after passing through the cutting slider 4. In this embodiment of the invention, an organic scintillator is preferably coupled to a photomultiplier tube via an optical guide to form a scintillator detector 5 to detect the radiation source, such as an EJ276 scintillator.

[0016] When the cutting slider 4 falls freely from a predetermined height under the action of gravity, the beam-limiting aperture on the cutting slider 4 moves relative to the beam-limiting aperture of the collimator 3, thereby cutting the steady-state neutron beam passing through the collimator 3 in time, thus forming pulsed neutron radiation with a pulse width on the order of milliseconds.

[0017] Preferably, the cutting slider 4 comprises an inner and outer two-layer structure: the inner layer is a boron-containing polyethylene shielding layer with a thickness of 15cm, used to absorb neutrons; the outer layer is a steel cladding shell with a thickness of 2cm, used to enhance mechanical strength and provide gamma radiation shielding.

[0018] Preferably, the slider stabilizing device includes: A small slider is located on one side of the cutting slider 4, and multiple pulleys are rotatably mounted on the small slider; The groove that cooperates with the small slider is fixed on the support frame. The groove is about 5cm wide and made of aluminum alloy. Its cross-section is concave. The pulley is engaged in the groove and slides in connection with the groove. The pulley of the small slider rolls in the groove, so that the cutting slider 4 is limited and guided during the falling process, thereby maintaining the stability of the cutting slider 4 and limiting its falling path.

[0019] In a preferred embodiment of the present invention, before constructing the pulsed neutron generating device, the thickness of the cutting slider 4 is first simulated using a Monte Carlo program. During the simulation, the thickness of the cutting slider 4 is gradually increased, and the theoretical dose rate is obtained simultaneously. The design requirements can be met when the neutron radiation dose rate is attenuated by more than 500 times due to the cutting slider 4.

[0020] Secondly, the Monte Carlo program is used to simulate the different positions of the cutting slider 4 when it is static, so as to replace the change of the dynamic radiation field when the cutting slider 4 moves, and thus obtain the pulse situation under theoretical conditions, so as to compare and analyze it with the pulse generated in reality.

[0021] Preferably, the steady-state neutron radiation source device 1 contains a Cf-252 isotope neutron source with an activity of 20 mCi inside the source container, and the neutron fluence at 1 m is 827 cm⁻¹. -2 ∙s -1 .

[0022] The shielding structure is constructed of 21.5m thick concrete, with indoor dimensions of 12.8m long × 7.5m wide × 9.0m high. The support frame is positioned 23cm in front of the steady-state neutron radiation source device 1 to maintain the stability of the entire pulsed neutron radiation device and provide installation positions for other components. In this embodiment, the support frame includes a main support, a base, and a top support. The top support is T-shaped and welded to the main support, with screw holes on its protruding portion for mounting the motor of the lifting and cutting slider 4. The main support consists of two U-shaped square steel frames, 300.0cm high, with a 30.0cm distance between the two supports. Screw holes for mounting related equipment are provided on the main support. The base is a thick steel plate with four supports, on which triangular supports are welded to the main support to ensure its stability. Furthermore, a buffer zone is defined on the base to accommodate cushioning material and prevent its movement.

[0023] Preferably, in this embodiment of the invention, the slider height adjustment device is used to lift the cutting slider 4 and mainly consists of two parts. The first part consists of a motor, a reducer, and a steel wire rope, used to adjust the height of the cutting slider 4. The second part consists of a plastic circular plate, a lever, and a switch, used to prevent damage to the motor and reducer. The motor is a PA400 mini electric hoist, which can lift a maximum weight of 200 kg. The reducer is used to adjust the lifting speed, and its attached cylinder is the location for installing the steel wire rope. The steel wire rope has a diameter of 3 mm and can withstand a maximum tensile force of 1 t, which is much greater than the weight of the cutting slider 4 itself, ensuring sufficient redundancy. The specific composition and structure of the slider height adjustment device are not limited, as long as it can complete the height adjustment of the cutting slider 4.

[0024] Preferably, the slider release device is operated remotely by a pull-type release device, which can release the cutting slider 4 from a predetermined height. When the spring of the pull-type release device is not pulled open, it acts as a hook for the cutting slider 4. When the cutting slider 4 is raised to a specified height, the spring is pulled open to release the cutting slider 4.

[0025] Secondly, embodiments of the present invention provide a pulse time measurement method for measuring the pulse time of pulsed neutron radiation generated by the pulsed neutron generating device, characterized by comprising the following steps: A reference point is set on the support frame so that the reference point corresponds to the position on the support frame when the limiting hole of the cutting slider 4 passes through the starting position of the pulse interval during the falling process. Reference Figure 2 When measuring the actual pulse width, an optical trigger timing system is arranged near the falling path of the cutting slider 4. The optical trigger timing system includes a photoelectric probe A, a photoelectric probe B, a reflector, and a timer electrically connected to both. A light shield 6 is provided at the front end of the cutting slider 4 to block the signal between the photoelectric probe A, the photoelectric probe B, and the reflector. When the cutting slider 4 is not blocked, the reflector reflects the signals of photoelectric probe A and photoelectric probe B. At this time, no counting is performed. After the cutting slider 4 is raised to the predetermined height, it is released through the slider release device, allowing the cutting slider 4 to fall freely under the action of gravity. During the fall, when the cutting slider 4 blocks the light of photoelectric probe A, photoelectric probe A outputs a trigger signal to the timer to start the timer. As the cutting slider 4 continues to fall, when the cutting slider 4 blocks the light from the photoelectric probe B, the photoelectric probe B outputs a stop signal to the timer to stop the timer. The time interval between the start triggering time and the stop triggering time recorded by the timer is correlated with the correspondence between the time when the lower edge of the beam-limiting aperture of the cutting slider 4 reaches the reference point and the time when the upper edge of the beam-limiting aperture reaches the reference point during the movement of the cutting slider 4, thereby determining the time interval as the actual pulse width of the pulsed neutron radiation.

[0026] Preferably, the reference point is determined through the following steps: Raise the cutting slider 4 to a position that completely shields the steady-state neutron beam, and use detector 5 to measure the neutron dose rate at this time to obtain the measured value M1; Adjust the cutting slider 4 so that the center of the beam-limiting aperture of the cutting slider 4 is at the same height as the center of the steady-state neutron radiation source; Move the cutting slider 4 upwards until the neutron dose rate measured by the detector 5 equals M1; The reference point is the corresponding height of the lower edge of the limiting hole of the cutting slider 4 on the support frame.

[0027] Preferably, it also includes theoretical calculation steps for the pulse time: Using the pulse interval length corresponding to the pulsed neutron radiation, gravitational acceleration, and the instantaneous velocity of the cutting slider 4 at the start of the pulse interval as parameters, the theoretical pulse width of the pulsed neutron radiation is calculated according to the uniformly accelerated linear motion relationship. The theoretical pulse width is then compared with the actual pulse width, and the specific comparison method is not limited here.

[0028] Preferably, the method further includes the step of measuring the pulsed neutron dose rate of the pulsed neutron radiation generated by the pulsed neutron generating device: The scintillator detector 5 used for dose rate measurement is calibrated in a standard isotope neutron source metrology standard device to obtain the calibration factor N of the scintillator detector 5. The sensitive volume of the scintillator detector 5 is placed at the center of the radiation beam of the pulsed neutron generating device. The cutting slider 4 is released at different lifting heights, and the corresponding dose rate indication value M is measured respectively. Each indication value M is multiplied by the calibration factor N to obtain the pulsed neutron dose rate under different pulse conditions, which is combined with the actual pulse width to characterize the pulsed neutron radiation field.

[0029] Preferably, determining the pulse interval length includes: The reference point is used as the starting point of the pulse interval; Move the cutting slider 4 downwards until the neutron dose rate measured by the detector 5 is equal to M1. Take the corresponding height of the lower edge of the beam-limiting aperture of the cutting slider 4 on the support frame at this time as the end point of the pulse interval. The distance between the starting point and the ending point is taken as the length of the pulse interval.

[0030] When measuring the theoretical pulse width, the following method is used: Under ideal conditions, the falling process of cutting slider 4 is a uniformly accelerated fall, and the motion of cutting slider 4 is governed by the following formula: Where v0 is the velocity of the slider cutting just before the pulsed gamma radiation is generated, t is the theoretical pulse width, s is the length of the interval where the pulsed radiation is generated, and a = g, where g is the acceleration due to gravity. v0 in the above formula can be calculated using the following formula: v0 = (2gd) a ) 0.5 Where v0 is the velocity of the slider 4 cutting just before the pulse radiation is generated, g is the acceleration due to gravity, and d is the velocity of the slider 4 cutting just before the pulse radiation is generated. a Let t be the acceleration distance of the slider, from which the theoretical value of the theoretical pulse width t can be obtained.

[0031] Preferably, after setting up the pulsed neutron generator, the device can also measure the fast transient response coefficient and alarm response time of the fixed critical alarm equipment, specifically including: When measuring the fast transient response coefficient, the fixed critical alarm device is placed in the radiation field of the reference radiation field, the pulse width is selected in different millisecond ranges, the dose rate is ±10% of the alarm threshold, and the ratio of the dose rate measurement value k1 of the fixed critical alarm device to the agreed true value k is the fast transient response coefficient R.

[0032] When testing the alarm response time, place the fixed critical alarm device and the decibel meter in the radiation field simultaneously, adjust the pulse width to 1 second, set the dose rate to twice the alarm threshold of the fixed critical alarm device, connect the decibel meter and the fixed critical alarm device to the oscilloscope simultaneously, and take the time interval between the values ​​measured by the decibel meter and the fixed critical alarm device as the alarm response time of the fixed critical alarm device.

[0033] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0034] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0035] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pulsed neutron generation device for cutting steady-state neutron radiation, characterized in that, include: A steady-state neutron radiation source device used to generate a steady-state neutron beam; The shielding structure installed outside the steady-state neutron radiation source device is used to form a standard radiation field space; A support frame is installed in front of the steady-state neutron radiation source device; A collimator fixed on the support frame, the collimator having a cylindrical structure and an internal conical beam-limiting aperture for limiting the emission direction and beam size of neutron radiation; A cutting slider made of neutron-absorbing material is disposed on the exit side of the collimator and has a through-beam limiting hole inside it. When the cutting slider completely blocks the neutron beam, the neutron dose rate is attenuated by at least 500 times relative to the unshielded state. A slider falling stabilizing device, which is connected to the support frame, is used to limit the falling trajectory of the cutting slider in the vertical direction and stabilize its attitude; A slider height adjustment device, which is connected to the cutting slider via a flexible connector, is used to raise the cutting slider to a predetermined height and maintain it at that predetermined height; A slider release device, which cooperates with the cutting slider and the slider height adjustment device, is used to detach the cutting slider from the slider height adjustment device at a predetermined height, so that it can fall freely along the trajectory defined by the slider falling stabilizing device under the action of gravity. The detector, located on the emission side of the cutting slider, is used to measure the neutron dose rate after passing through the cutting slider; When the cutting slider falls freely from a predetermined height under the action of gravity, the beam-limiting aperture on the cutting slider moves relative to the beam-limiting aperture of the collimator, thereby cutting the steady-state neutron beam passing through the collimator in time, thus forming pulsed neutron radiation with a pulse width on the order of milliseconds.

2. The pulsed neutron generating device for cutting steady-state neutron radiation according to claim 1, characterized in that, The cutting slider comprises an inner and outer two-layer structure: the inner layer is a 15cm thick boron-containing polyethylene shielding layer for absorbing neutrons; the outer layer is a 2cm thick steel cladding for enhancing mechanical strength and providing gamma radiation shielding.

3. The pulsed neutron generating device for cutting steady-state neutron radiation according to claim 1, characterized in that, The slider stabilization device includes: A small slider is disposed on one side of the cutting slider, and multiple pulleys are rotatably mounted on the small slider; A sliding groove that mates with the small slider is fixed to the support frame and is made of aluminum alloy with a concave cross-section. A pulley is engaged within the sliding groove and slides smoothly along it. The pulley of the small slider rolls in the groove, which limits and guides the cutting slider during its descent, thereby maintaining the stability of the cutting slider's posture and limiting its descent path.

4. A pulse time measurement method, characterized in that, A method for measuring the pulse time of pulsed neutron radiation generated using the pulsed neutron generating device according to any one of claims 1 to 3, characterized in that it comprises the following steps: A reference point is set on the support frame, such that the reference point corresponds to the position on the support frame when the limiting hole of the cutting slider passes through the starting position of the pulse interval during the falling process; A light-triggered timing system is arranged near the falling path of the cutting slider. The light-triggered timing system includes photoelectric probe A, photoelectric probe B, and a timer electrically connected to both. After the cutting slider is raised to a predetermined height, it is released through the slider release device, allowing the cutting slider to fall freely under the action of gravity. During the fall, when the cutting slider blocks the light of the photoelectric probe A, the photoelectric probe A outputs a trigger signal to the timer to start the timer. As the cutting slider continues to fall, when it blocks the light from the photoelectric probe B, the photoelectric probe B outputs a stop signal to the timer to stop the timer. The time interval between the start and stop triggering times recorded by the timer is correlated with the time when the lower edge of the beam-limiting aperture of the cutting slider reaches the reference point and the time when the upper edge of the beam-limiting aperture reaches the reference point during the movement of the cutting slider, thereby determining the time interval as the actual pulse width of the pulsed neutron radiation.

5. The method according to claim 4, characterized in that, The reference point is determined through the following steps: The cutting slider is raised to a position where the steady-state neutron beam is completely shielded, and the neutron dose rate at this time is measured using a detector to obtain the measured value M1; Adjust the cutting slider so that the center of the beam-limiting aperture of the cutting slider is at the same height as the center of the steady-state neutron radiation source; Move the cutting slider upwards until the neutron dose rate measured by the detector equals M1; The reference point is the height of the lower edge of the cutting slider's constraint hole on the support frame at this time.

6. The method according to claim 4, characterized in that, It also includes the theoretical calculation steps for the pulse time: Using the pulse interval length corresponding to the pulsed neutron radiation, gravitational acceleration, and the instantaneous velocity of the cutting slider at the start of the pulse interval as parameters, the theoretical pulse width of the pulsed neutron radiation is calculated based on the uniformly accelerated linear motion relationship, and the theoretical pulse width is compared with the actual pulse width.

7. The method according to claim 4, characterized in that, The method also includes the step of measuring the pulsed neutron dose rate of the pulsed neutron radiation generated by the pulsed neutron generating device. The scintillator detector used to measure the dose rate is calibrated in a standard isotope neutron source metrology standard to obtain the calibration factor N of the scintillator detector. The sensitive volume of the scintillator detector is placed at the center of the radiation beam of the pulsed neutron generating device. The cutting slider is released at different lifting heights, and the corresponding dose rate indication value M is measured. Each indication value M is multiplied by the calibration factor N to obtain the pulsed neutron dose rate under different pulse conditions, which is then combined with the actual pulse width to characterize the pulsed neutron radiation field.

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