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In order to verify the design specifications of in-hospital neutron irradiator (IHNI), the neutron fluence rates at the exit of its thermal and epithermal neutron beams were measured by using the method of cadmium difference. The radial distribution of the different components of the treatment beam exit was measured using a scanning device with a diamond detection unit. The results show that the thermal neutron fluence rates are 1.75×109 cm-2·s-1 and 6.57×107 cm-2·s-1 at the center of the thermal and epithermal neutron beams, respectively, and the epithermal neutron fluence rates are 1.41×107 cm-2·s-1 and 3.14×108 cm-2·s-1 at 30 kW full power operation; The vast majority of the treatment beam components are distributed within the beam aperture, with an exponential drop-off near the beam edges. The measurement results provide parameter support for subsequent related testing and experiments of In-Hospital Neutron Irradiators.

Aiming at the characteristics of short pulse time and high instantaneous dose rate of pulsed X-ray, a TLD-based few-channel spectrometer is studied. In this paper, the basic structure and principle of the spectrometer are introduced, the absorption plates and detectors of the spectrometer are selected. The energy response matrix of the few-channel spectrometer for single energy photons of different energies is simulated by Monte Carlo method and its influence on the energy resolution of the spectrometer is analyzed. The maximum entropy method is used to verify the pulsed X-ray spectrum resolution. The results show that the TLD-based few-channel spectrometer can be used to measure short pulse and high dose rate pulse X-ray energy spectrum, and it is also suitable for other high dose rate radiation fields.

Pulsed radiation field is characterized by short duration and high instantaneous dose rate compared with steady state radiation field, and has been widely used in the development of new detectors, radiological examination, X-ray diagnosis, nuclear accident emergency response and scientific research. Traditional nuclear radiation detectors in the pulsed radiation field often have problems such as signal stacking, ion composite, dead time, etc., which makes it difficult to realize the accurate measurement of pulsed radiation dose. Diamond detectors have the advantages of large bandwidth, high carrier mobility, strong anti-irradiation ability, fast time response, etc. In this paper, we utilize millisecond and nanosecond pulsed X-ray reference radiation field, high dose rate γ irradiation device to carry out the pulsed radiation field response test of single crystal diamond detector TW60019 produced by German PTW company, and we conclude that: the single-pulse response of diamond detector decreases with the increase of pulsed dose, and the single-pulse response of the single-pulse detector decreases with the increase of pulsed dose, and the single-pulse response of the single-pulse detector increases with the increase of pulse dose. It is concluded that the single-pulse response of the diamond detector decreases with the increase of the pulse dose, and similar to the ion complex effect in the ionization chamber in the pulsed radiation field, the diamond detector also suffers from the phenomenon of unsaturated collection in the measurement of large-dose and short-time pulsed radiation, and the detector's collection efficiency decreases with the increase of the single-pulse dose. Based on the experimental phenomenon, the influence of impurities and defects in the synthetic diamond film on the collection efficiency of the detector is analyzed, the impact of back-end electronics systems on collection efficiency during diamond detector signal collection is discussed and it is verified that the diamond detector can meet the requirements of fast response and high instantaneous dose rate of pulsed radiation measurements, which provides a basis for the further realization of the real-time monitoring of the pulsed radiation dose and the solution of the widely existed technical needs of the pulsed radiation dose monitoring in the fields of medical diagnosis and industrial flaw detection. The detector has been used in the following fields: medical diagnosis, industrial flaw detection, etc.

A water calorimeter based on thermistor is developed in this paper, and for the correction of chemical thermal defects in the absolute measurement of absorbed dose to water from proton beam, the design of gas saturated ultrapure water system is completed. By filling the ultrapure water inside the calorimeter core with high purity gas to form saturation condition, the effect of radiation chemical reaction is minimized. And the irradiation reaction of O2 in the ultrapure water is fully occurred through pre-irradiation experiment after the encapsulation of the calorimeter core, so that the water environment inside reaches a stable state without heat loss,which successfully developed a stable zero heat loss water calorimeter and the influence of heat loss on the absolute measurement of absorbed dose to water is minimized, which provides an important basis for the subsequent absolute measurement of absorbed dose to water.

After a major nuclear accident occurs in a nuclear facility, it is of great significance to quickly enter the accident area to obtain the radiation distribution of the site of nuclear leakage and radioactive contamination. In order to overcome the traditional nuclear emergency monitoring methods, which are prone to radiation damage to personnel, poor mobility and low efficiency, this paper designs and implements a UAV radiation monitoring system, which can quickly enter the sky over radioactive contaminated areas for radiation monitoring. The UAV radiation monitoring system mainly includes wide-range G-M counter tube, cerium bromide scintillator detector, data acquisition system and data transmission system. The above devices can be built on the UAV to measure the real-time radiation dose rate and energy spectrum at 0-100 m low altitude.

BackgroundThe physical quantity concerned in the clinical application of 125I particle source brachytherapy is the 1 cm water absorbed dose rate D˙w,1 cm. However, there is no corresponding standard for this physical quantity in China. It is planned to develop an ionization chamber for the absolute measurement of the water absorbed dose rate of the 125I particle source as a standard device, hence the internal electric field of the ionization chamber must first be analyzed to obtain the most reasonable design scheme to satisfy the condition that the electric field intensity is uniformly distributed in the ionization chamber.PurposeThis study aims to simulate the internal electric field of the ionization chamber for the design of particle source water absorbed dose absolute measurement device.MethodsFirstly, the internal model of the ionization chamber was established by Maxwell software to simulate the distribution of electric field intensity under the six variables of the ionization chamber: with or without a protective electrode, different protective electrode ring width, different insulation ring width, different grid number, different grid shape and different grid thickness. Then, qualitative and quantitative analysis were carried out using finite element method. Finally, the influence of different variables on the distribution of electric field intensity in the ionization chamber of the absolute measurement of water absorbed dose of 125I particle source was obtained.ResultsAnalysis results show the ratio of the width of the guard electrode to the radius of the collector electrode must be not less than 2 for design of the ionization chamber. The edge effect at the edge of the collector is increased with width increment of the insulator ring, hence the width of the insulator ring should be reduced as much as possible. When the number of grid electrodes is 15, the variation of the electric field intensity can be reduced to about 1%. When the grid section is rectangular, the variation in electric field intensity is small compared with the circular and triangular grid sections. The larger the thickness of the grid, the more severe the edge effect at the edge of the grid, and the thickness of the grid should be reduced as much as possible.ConclusionsThe uniformity of the electric field can be effectively improved by increasing the number of grid electrodes. Results of this study is helpful to optimal design of the standard device for measuring the absolute water absorbed dose of 125I particle source.

The in-situ experimental study of the microstructure of materials under thermodynamic coupling under near-working conditions is very important for in-depth understanding of the evolution mechanism of material service performance. The microscopic distribution of nanostructures on the sample can be given. Based on the advantages of small-angle neutron scattering method with good statistics and large sampling volume, in-situ experiments can be carried out, based on the small-angle neutron scattering spectrometer of China Advanced Research Reactor, an in-situ experimental device with simultaneous loading of high temperature and tensile force was designed and developed, and the morphological changes of materials at the nanoscale were measured online at high temperature and high pressure. The test results of the inspection and calibration experiment show that the maximum load of the device can reach 20 kN, the maximum temperature is 800℃, and the temperature control accuracy is better than ±1℃. The device was used to carry out in-situ small-angle neutron scattering experiments on nickel-based single crystal superalloy samples, and the obvious changes in the internal nanostructure of the samples under temperature tension conditions were obtained, indicating that the device could carry out the experimental research ability of in-situ thermodynamic coupling loading small-angle neutron scattering. The device and its corresponding experimental methods can also be used for in-situ experimental research of various high-temperature structural materials such as nuclear power stainless steel to provide microstructure evolution data.

X and γ ray reference radiation field is a necessary facility for the calibration of X and γ radiation dosimeter. The dosimetric parameters of radiation field directly affects the reliability of the transmission of numerical values. To measure the dosimetric parameters of the radiation field rapidly, a new automatic measuring system of dosimetric parameters for radiation field has been investigated, which enables remote control of the positioning of the manipulator and the measurement of the ionization chamber. It features preset measurement paths, automated measurements, readout and recording data, and the ability to derive measurement results. The dose-rate distribution, scattered radiation characteristics and uniformity of 137Cs γ-ray reference radiation field, 60Co γ-ray reference radiation field, low-energy, medium-energy and high-energy X-ray reference radiation field were measured by an automated measurement system. The results show that the air kerma rates at 1-6 m away from the 137Cs multi-source irradiation device and the 60Co single-source irradiation device are 0.67-25.61 mGy/h and 0.19-7.25 Gy/h, respectively. For the 137Cs multi-source irradiation device, the 60Co single-source irradiation device, the low energy X-ray machine and the medium and high energy X-ray machine, the scattered radiation are all less than 4%, and the radiation field diameter of radiation field at the distance of 1 m is 22 cm, 14 cm, 16 cm and 7 cm, respectively. The automated measurement system can achieve fast and accurate measurements of the radiation field, which can greatly reduce the workload of the operator and implement radiation protection optimization principles.

Metallic magnetic calorimetry holds significant promise in critical defense applications such as nuclear proliferation prevention, radionuclide classification, nuclear safety and anti-terrorism. Metallic magnetic calorimetry realizes energy resolution in the order of a few electron Volts by utilizing the significant contribution of heat capacity of a magnetic origin at milli-Kelvin temperatures in rare-earth doped Au films. For detecting gamma-ray photons with an energy of around 100 keV, the energy resolution is better than 0.1%, 10 times better than the high-purity germanium (HPGe) gamma spectrometer with the highest energy resolution. The metallic magnetic calorimeter can detect other radiation types than gamma rays such as alpha and beta emissions. Metallic magnetic calorimetry can also be used for precise measurement of astrophysical phenomena, cosmic rays and other high-energy physics phenomena. As an critical part of the metallic magnetic calorimeter, the pick-up coil plays a dual role in the sensor unit. It is not only responsible for converting magnetic flux changes into electrical signals, which is subsequently picked up by the SQUID chip, but also responsible for generating persistent excitation magnetic field and magnetizing the rare-earth doped sensor thin-film. The design configuration and electromagnetic parameters of pick-up coil can directly influence the energy resolution of the sensor. In the paper the influences of various parameters (e.g., number of turns of soil, duty ratio) on the electromagnetic characteristics using the finite element method was calculated. The actual pick-up coil size is in the order of micrometers. As direct measurement of such tiny devices is extremely difficult with conventional means and such measurements suffer high errors, in this paper scaled-up samples were measured, and the validity of the simulation model and parameters through comparison with measurement results was verified to provide a reliable foundation for design work of pick-up coils. The calculation results show that the influence of turn number of pick-up meander coil on inductance is more significant than other parameters such as duty ratio and loop pitch. With the increase of the duty ratio, the inductance shows a monotonic decrease trend. When the duty ratio increases from 30% to 70%, the inductance decreases by about 76.4%. On the other hand, with the increase of the turn number, the inductance shows an obvious increasing trend. When the turn number increases from 15 to 75, the inductance increases by about 253%. The simulation result also reveals the magnetic field distribution inside the metal magnetic calorimeter sensor pick-up coil, which provides critical information for the design of the sensor thin film.

Proton beam therapy (PBT) can achieve the effect of precision radiotherapy due to its unique Bragg peak. In the process of proton therapy, the peak can be accurately located to the tumor area, which can give the tumor a larger dose of irradiation, reduce the damage to normal tissues and organs, and reduce the occurrence of side effects. Therefore, it is very important to locate the Bragg peak of proton beam in real time in proton therapy. In this paper, a cyclotron is used to generate proton beam, and a diamond detector is used to test the radiation characteristics of proton beam, and the Bragg peak and the beam spot center are measured (0, 35 mm). Thus, accurate Bragg peak value of proton beam was obtained, which guaranteed the accuracy of proton therapy.

In many real-world settings, it is crucially vital for agents to learn to communicate and cooperate. Different cooperation models have been proposed to represent cooperative relations among agents. However, the intensity of the cooperative relation has not received much attention. In particular, how it varied with spatial-temporal information has not been studied deeply. In this paper, we propose a temporal dynamic weighted graph convolution based multi-agent reinforcement learning framework (TWG-Q). We design a weighted graph convolutional network to capture cooperative information among agents. On top of that, a temporal weight learning mechanism is introduced to characterize intensities of cooperations. We design a novel temporal convolutional network in the temporal dimension to extract effective features for the multi-agent reinforcement learning. Extensive experiments show that our method significantly improves the performance of multi-agent reinforcement learning on the public benchmark of micromanagement tasks in StarCraft II.

The dose rate constant, radial dose function, one-dimensional anisotropy function and two-dimensional anisotropy function of domestic 6711 particle source were simulated by MCNP software. The error between the dose rate constant and the recommended value reported by TG 43-U1 was -0.83%. The radial dose function in the range of 0.05-10 cm was obtained, and the fifth-order polynomial fitting of the data in the range of 0.25-10 cm was proposed to improve the accuracy of the fitting function. The one-dimensional anisotropy function and the two-dimensional anisotropy function in the range of 0.25-7 cm are obtained, and compared with the relevant literature, it can be seen that the difference of the structure of the domestic type 6711 particle core will cause the phenomenon of the one-dimensional anisotropy function and the two-dimensional anisotropy function.

Background COVID-19 may impair the central nervous system, but the prevalence and related factors of very early cognitive impairment in discharged COVID-19 convalescents are still unclear. Objective To assess the prevalence of very early cognitive impairment in discharged COVID-19 convalescents, and to identify its influencing factors. Methods This study included 574 COVID-19 convalescents from August 28 to September 30, 2020, including individuals who were discharged from designated hospitals for treating COVID-19 in Wuhan from December 2019 to April 2020 randomly selected from the hospital information system, and those with informed consent recruited through news media. According to the Eight-item Informant Interview to Differentiate Aging and Dementia (AD8) score, the subjects were divided into a very early cognitive impairment group (AD8≥2) and a non-very early cognitive impairment group (AD8

Abstract: The H-8 horizontal channel of CARR is an experimental channel to provide neutrons, which can provide a stable radiation field. For different neutron experiments, the required neutron energy spectrum shapes are often different, so accurate measurement of neutron energy spectrum is of great significance. A passive single sphere neutron spectrometer with gold foils as thermal neutron detector is developed to measure the neutron energy spectrum of H-8 horizontal channel. The neutron energy response in 10-11-15 MeV is calculated by MCNP and the rationality of the energy response is analyzed. The single sphere spectrometer was tested in the conduit hall of CARR, the activity of each gold foil was measured by high-purity germanium detector, and the experimental data were calculated by UGA (unfolding based on genetic algorithm). The results show that the neutron energy range emitted from the conduit hall is 10-9-10-6 MeV and the single sphere neutron spectrometer can give accurate neutron energy spectrum data, and can be applied to the measurement and research of neutron energy spectrum in H-8 horizontal channel of CARR.

To introduce 3D printing technology into the field of radiation source preparation and make up for the lack of precision special-shaped radiation source preparation technology at home and abroad. The photosensitive resin for 133Cs 3D printing was prepared by studying the phase transfer method and detected by ICP-MS to explore the preparation conditions. Then, the photosensitive resin material for 137Cs 3D printing was prepared and detected by lanthanum bromide detector. The results show that the uneven distribution of cesium in three photosensitive resins for 133Cs 3D printing and 137Cs 3D printing prepared by phase transfer method was less than 5%. As a simple and mild method, phase transfer method can be used to prepare photosensitive resin for 3D printing containing cesium, and has certain universality.

The value of activity concentration of tritium standard source is very important for the monitor and calibration of tritium. The length compensation method is applied for measuring activity of tritium. The analysis and uncertainty evaluation results of measuring uncertainty is given based on internal inflatable proportional counter The uncertainty of the activity concentration of tritium mainly came from the statistical fluctuation of background and count, volume measurement, dead time correction, wall effect correction, and measurement repeatability and stability. The results show that the standard uncertainty of synthesis is 1.6% for 7×103 Bq/L tritium gas.