Method for supervising the flux of white neutrons and quasi-monochromatic neutrons

Abstract

The present application relates to a kind of white light neutron and quasi-monochromatic neutron fluence supervision method, comprising the following steps: (1) neutron fluence supervisor is placed in neutron radiation field appropriate position;(2) the ratio of neutron fluence supervisor counting rate and incident proton flow intensity is scaled;(3) obtain the neutron spectrum of the position of irradiation device when incident proton flow intensity is I, and calculate the neutron fluence rate in the energy region [E1,E2] of interest: (4) carry out neutron irradiation experiment, neutron is measured using neutron fluence supervisor during experiment, record the change of measured counting rate with experimental time t, obtain the cumulative count D of neutron fluence supervisor during experiment;(5) calculate the neutron fluence in [E1,E2] energy region irradiated to device when incident proton flow intensity is I during experiment.The present application realizes the effective supervision of neutron fluence, so as to obtain accurate and reliable device neutron SEE cross section.

Description

Technical Field

[0001] This invention relates to neutron irradiation experimental techniques, specifically to a method for monitoring the fluence of white light neutrons and quasi-monoenergetic neutrons in single-event effect experiments. Background Technology

[0002] Neutrons are a major component of the atmospheric radiation environment, and the single-event effects (SEE) they induce in microelectronic devices can jeopardize the reliable operation of aircraft, drawing widespread attention and concern from the international aviation community. On Earth, evidence already exists that atmospheric neutrons can cause SEE in electronic devices such as large computers, high-end servers, routers, electronic voting systems, and mobile phones. Other industries with high reliability requirements for electronic equipment also face potential risks from neutron SEE.

[0003] Single-event effect experiments using white-light neutrons and quasi-monoenergetic neutrons generated by high-energy proton bombardment from accelerators are crucial for studying neutron SEE mechanisms, verifying radiation hardening techniques, and evaluating the resistance of electronic devices to atmospheric neutron radiation. A key physical quantity obtained from neutron SEE experiments is the neutron SEE cross section. Obtaining an accurate neutron SEE cross section requires accurate neutron fluence irradiated onto the device; therefore, research on neutron fluence monitoring methods is of great significance for neutron single-event effect studies.

[0004] Currently, the method for calculating the neutron fluence irradiated onto the device during experiments is to multiply the neutron fluence rate by the irradiation time. This ignores the fluctuations in the neutron fluence rate over time during irradiation, which may introduce significant errors into the calculation of the neutron SEE cross section. Therefore, a more accurate and reliable method for monitoring neutron fluence is needed. Summary of the Invention

[0005] The purpose of this invention is to address the problem of large errors in the calculation of neutron SEE cross sections in current single-event effect experiments, and to provide a method for monitoring the fluence of white light neutrons and quasi-monoenergetic neutrons, so as to achieve effective monitoring of neutron fluence and thus obtain accurate and reliable device neutron SEE cross sections.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons includes the following steps:

[0008] (1) Place the neutron fluence monitor at an appropriate location in the neutron radiation field;

[0009] (2) The ratio of the neutron fluence monitor count rate to the incident proton flux intensity is calibrated;

[0010] (3) Obtain the neutron energy spectrum at the location of the irradiation device in the neutron irradiation experimental system when the incident proton flux is I. The neutron flux rate within the energy region of interest [E1, E2] is calculated using the following formula:

[0011]

[0012] (4) Conduct neutron irradiation experiments. During the experiments, a neutron flux monitor was used to measure neutrons and record the count rate. The cumulative count D of the neutron fluence monitor during the experiment varies with experimental time t as follows:

[0013]

[0014] (5) Calculate the neutron flux irradiated onto the device in the [E1,E2] energy region when the incident proton flux is I during the experiment using the following formula:

[0015]

[0016] Furthermore, in the white light neutron and quasi-monoenergetic neutron fluence monitoring method described above, the count rate of the neutron fluence monitor in step (1) is proportional to the incident proton flux or neutron fluence rate, and it can record the change of the count rate over time.

[0017] Furthermore, as a specific implementation, the neutron flux monitor can be a neutron ambient dose equivalent (rate) meter, and the count rate of the neutron flux monitor is the neutron dose rate measured in real time by the neutron ambient dose equivalent (rate) meter.

[0018] Furthermore, in the white light neutron and quasi-monoenergetic neutron fluence monitoring method described above, in step (1), the neutron fluence monitor is placed in front of the irradiation device, off the beam center, at a position that can detect neutrons but does not have a significant impact on the neutron radiation field irradiated to the device.

[0019] Furthermore, in the white-light neutron and quasi-monoenergetic neutron fluence monitoring method described above, in step (2), a detector is used to measure the incident proton flux intensity I provided by the accelerator, and the count rate of the neutron fluence monitor under this incident proton flux intensity is recorded simultaneously.

[0020] Furthermore, in the white light neutron and quasi-monoenergetic neutron fluence monitoring method described above, in step (3), the neutron energy spectrum at the location of the irradiation device is obtained by simulating the generation process of white light neutrons or quasi-monoenergetic neutrons using a Monte Carlo program; or the neutron energy spectrum is obtained through actual experimental measurement.

[0021] The beneficial effects of this invention are as follows: This invention selects an appropriate neutron fluence monitor to perform online monitoring of the neutron radiation field. Its count rate is proportional to the incident proton flux or neutron fluence rate, thus the count rate during the experiment reflects the change in the neutron fluence rate during that period. Ultimately, the neutron fluence rate obtained by this method is more reliable, avoiding the problem that multiplying the neutron fluence rate by the irradiation time might introduce significant errors in the calculation of the neutron SEE cross section. Besides using this method to determine the neutron fluence in neutron single-event effect experiments, it can also be used in neutron irradiation experiments in biology, materials science, and other fields. Attached Figure Description

[0022] Figure 1 This is a flowchart of the white light neutron and quasi-monoenergetic neutron fluence monitoring method of the present invention;

[0023] Figure 2 The neutron energy spectrum at the DUT location simulated by the Geant4 program in a specific embodiment of the present invention;

[0024] Figure 3 This is a specific embodiment of the invention showing the change in dose rate over time as recorded by a neutron dose equivalent (rate) meter during a neutron SEE experiment. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] The method of the present invention will be specifically described below using the white light neutron or quasi-monoenergetic neutron SEE experiment as an example.

[0027] First, the setup work for the white-light neutron or quasi-monoenergetic neutron SEE experiment is carried out, and the electronic devices and their testing systems, as well as other related experimental instruments and equipment, are set up in place. Then, as... Figure 1 As shown, the white light neutron and quasi-monoenergetic neutron fluence monitoring method of the present invention is carried out according to the following steps:

[0028] 1. Select an appropriate neutron fluence monitoring instrument that meets the following conditions: its count rate should be proportional to the incident proton flux or neutron fluence rate, and it should be able to record the change in count rate over time. For example, a neutron ambient dose equivalent (rate) meter is such an instrument. Place the instrument in front of the electronic device, off-center from the beam center, in a location that can detect neutrons but will not significantly affect the neutron radiation field irradiating the device, so as to monitor the proton flux or neutron fluence rate during device irradiation experiments.

[0029] 2. Calibrate the ratio of the neutron fluence monitor count rate to the incident proton flux. Measure the proton flux I provided by the accelerator and applied to the target using a Faraday cage or similar detector, and simultaneously record the neutron fluence monitor count rate under this incident proton flux condition.

[0030] 3. Simulate the generation process of white-light neutrons or quasi-monoenergetic neutrons using a Monte Carlo simulation program to obtain the neutron energy spectrum at the device location, or obtain the neutron energy spectrum through experimental measurement, and then deduce the neutron energy spectrum at the device location when the incident proton flux is I. The unit is cm -2 s -1 MeV -1 The neutron fluence rate within the energy region of interest [E1, E2] was calculated.

[0031]

[0032] Its unit is cm -2 s -1 The neutron energies in white light or quasi-monoenergetic neutron fields produced by conventional accelerators typically range from thermal neutrons to near-incident proton energies, while neutron single-particle effect experiments generally focus on energy ranges above 1 or 10 MeV.

[0033] 4. Conduct white light or quasi-monoenergetic neutron SEE experiments on the device. During this period, a neutron fluence monitor is used to measure neutrons and record the measured count rate. The change over time. Assuming the neutron fluence monitor count rate is proportional to the proton flux, if the neutron SEE experiment duration is t, the cumulative count of the neutron fluence monitor during this period is:

[0034]

[0035] 5. During white light or quasi-monoenergetic neutron SEE experiments, when the incident proton flux is I, the neutron fluence irradiated onto the device in the [E1,E2] energy region should be:

[0036]

[0037] Its unit is cm -2 .

[0038] Example

[0039] The following describes the specific implementation of this invention using the neutron fluence monitoring process during a neutron SEE experiment conducted using a white-light neutron beamline at a 100MeV proton cyclotron accelerator. A SIM-MAX N3020 neutron ambient dose equivalent (rate) meter is used as the neutron fluence monitor and is positioned appropriately within the neutron radiation field. The SIM-MAX N3020 neutron ambient dose equivalent (rate) meter can provide the neutron dose rate in real time. (i.e., the count rate of the neutron flux monitor) and the cumulative dose D (μSv) over the measurement time. Simultaneously, the instrument can also record the dose rate change over time and provide corresponding documentation. Clearly, the dose rate... It should be proportional to the incident proton flux I. As long as the position of the dose equivalent (rate) meter around the neutron remains unchanged during the experiment, although the proton flux may vary, the ratio will remain the same. It should be constant.

[0040] During the experiment, when the incident proton flux I was 3.1 μA, the dose rate was... The neutron energy density is 3257.7 μSv / h. Monte Carlo simulations using Geant4 were performed to obtain the neutron energy spectrum at the device irradiation location above 1 MeV when I is 3.1 μA. The results are shown in […]. Figure 2 From equation (1), the neutron fluence in this energy region is 1.93 × 10⁻⁶. 5 cm -2 s -1 During the single-event effect experiment, the neutron dose rate recorded by the SIM-MAX N3020 neutron ambient dose equivalent (rate) meter changed over time as follows: Figure 3 As shown, the total cumulative dose during this period is 3976.54 μSv, obtained from equation (2). Finally, the neutron fluence with energies above 1 MeV irradiated onto the device during the experiment is 8.49 × 10⁻⁶, obtained from equation (3). 8 cm -2 .

[0041] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. Thus, the invention also intends to include such variations and adaptations if they fall within the scope of the claims and their equivalents.

[0042] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of protection of the present invention should be defined by the claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons, characterized in that, Includes the following steps: (1) Place the neutron fluence monitor at an appropriate location in the neutron radiation field; (2) The ratio of the neutron fluence monitor count rate to the incident proton flux intensity is calibrated; (3) Obtain the neutron energy spectrum at the location of the irradiation device in the neutron irradiation experimental system when the incident proton flux is I. The neutron flux rate within the energy region of interest [E1, E2] is calculated using the following formula: (4) Conduct neutron irradiation experiments. During the experiments, a neutron flux monitor was used to measure neutrons and record the count rate. The cumulative count D of the neutron fluence monitor during the experiment varies with experimental time t as follows: (5) Calculate the neutron flux irradiated onto the device in the [E1,E2] energy region when the incident proton flux is I during the experiment:

2. The method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons as described in claim 1, characterized in that, The count rate of the neutron fluence monitor described in step (1) is proportional to the incident proton flux or neutron fluence rate, and it can record the change of the count rate over time.

3. The method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons as described in claim 2, characterized in that, The neutron fluence monitor is a neutron ambient dose equivalent meter, and the count rate of the neutron fluence monitor is the neutron dose rate measured in real time by the neutron ambient dose equivalent meter.

4. The method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons as described in claim 1, characterized in that, In step (1), the neutron fluence monitor is placed in front of the irradiation device, off the beam center, at a position that can detect neutrons but does not have a significant impact on the neutron radiation field irradiated to the device.

5. The method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons as described in claim 1, characterized in that, In step (2), the incident proton flux intensity I provided by the accelerator is measured using a detector, and the count rate of the neutron fluence monitor under this incident proton flux intensity is recorded.

6. The method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons as described in claim 5, characterized in that, The detector used to measure proton flux is the Faraday tube.

7. The method for monitoring the fluence of white-light neutrons and quasi-monoenergetic neutrons as described in claim 1, characterized in that, In step (3), the neutron energy spectrum at the location of the irradiation device is obtained by simulating the generation process of white light neutrons or quasi-monoenergetic neutrons using a Monte Carlo program; or by obtaining the neutron energy spectrum through actual experimental measurements.

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