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Supported noble metal catalysts, ubiquitous in chemical technology, often undergo dynamic transformations between reduced and oxidized states-which influence the metal nuclearities, oxidation states, and catalytic properties. In this investigation, we report the results of in situ X-ray absorption spectroscopy, scanning transmission electron microscopy, and other physical characterization techniques, bolstered by density functional theory, to elucidate the structural transformations of a set of MgO-supported palladium catalysts under oxidative treatment conditions. As the calcination temperature increased, the as-synthesized supported metallic palladium nanoparticles underwent oxidation to form palladium oxides (at approximately 400 °C), which, at approximately 500 °C, were oxidatively fragmented to form mixtures of atomically dispersed palladium cations. The data indicate two distinct types of atomically dispersed species: palladium cations located at MgO steps and those embedded in the first subsurface layer of MgO. The former exhibit significantly higher (>500 times) catalytic activity for ethylene hydrogenation than the latter. The results pave the way for designing highly active and stable supported palladium hydrogenation catalysts with optimized metal utilization.

The creation of metal-metal oxide interfaces is an important approach to fine-tuning catalyst properties through strong interfacial interactions. This article presents the work on developing interfaces between Pt and CeOx that improve Pt surface energetics for the hydrogen evolution reaction (HER) within an alkaline electrolyte. The Pt-CeOx interfaces are formed by depositing size-controlled Pt nanoparticles onto a carbon support already coated with ultrathin CeOx nanosheets. This interface structure facilitates substantial electron transfer from Pt to CeOx, resulting in decreased hydrogen binding energies on Pt surfaces, and water dissociation for the HER, as predicted by the density functional theory (DFT) calculations. Electrochemical testing indicates that both Pt specific activity and mass activity are improved by a factor of 2 to 3 following the formation of Pt-CeOx interfaces. This study underscores the significance and potential of harnessing robust interfacial effects to enhance electrocatalytic reactions.

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.

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.

Atomically dispersed metals on metal oxide supports are a rapidly growing class of catalysts. Developing an understanding of where and how the metals are bonded to the supports is challenging because support surfaces are heterogeneous, and most reports lack a detailed consideration of these points. Herein, we report two atomically dispersed CO oxidation catalysts having markedly different metal-support interactions: platinum in the first layer of crystalline MgO powder and platinum in the second layer of this support. Structural models have been determined on the basis of data and computations, including those determined by extended X-ray absorption fine structure and X-ray absorption near edge structure spectroscopies, infrared spectroscopy of adsorbed CO, and scanning transmission electron microscopy. The data demonstrate the transformation of surface to subsurface platinum as the temperature of sample calcination increased. Catalyst performance data demonstrate the lower activity but greater stability of the subsurface platinum than of the surface platinum.

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.

Atomically dispersed noble metal catalysts have drawn wide attention as candidates to replace supported metal clusters and metal nanoparticles. Atomic dispersion can offer unique chemical properties as well as maximum utilization of the expensive metals. Addition of a second metal has been found to help reduce the size of Pt ensembles in bimetallic clusters; however, the stabilization of isolated Pt atoms in small nests of nonprecious metal atoms remains challenging. We now report a novel strategy for the design, synthesis, and characterization of a zeolite-supported propane dehydrogenation catalyst that incorporates predominantly isolated Pt atoms stably bonded within nests of Zn atoms located within the nanoscale pores of dealuminated zeolite Beta. The catalyst is stable in long-term operation and exhibits high activity and high selectivity to propene. Atomic resolution images, bolstered by X-ray absorption spectra, demonstrate predominantly atomic dispersion of the Pt in the nests and, with complementary infrared and nuclear magnetic resonance spectra, determine a structural model of the nested Pt.

To establish the high-pressure ionization chamber products for dose rate monitoring of the environmental level γ ray, the design from the aspects of ionization chamber shell, detector, electronic system, etc. are optimized, to improve the environmental adaptability, electromagnetic compatibility and reliability of the equipment. According to the standard method, the general quality characteristics test was carried out at a third party. The test results showed that the working and storage temperature range of the product was -10 ℃-45 ℃; Humidity range ≤93% RH; It has certain anti-vibration and impact capacity, and meets the requirements of the severity level 2M1 of transport environmental conditions in GB/T 8993—1998; Electrostatic discharge immunity and radio frequency electromagnetic field radiation immunity in electromagnetic compatibility shall meet the relevant requirements of GB/T 17626-2—2018 and GB/T 17626-3—2016; The reliability meets the requirement of MTBF≥1 000 h. The environmental adaptability, electromagnetic compatibility and reliability of this product meet the requirements of meter-level products. It can be used as a portable radiation dosimeter in climatefree places. High pressure ionization chamber can be used as a high accuracy work measuring instrument for ambient level air kerma to carry out radiation dose monitoring.

The purpose of the work is to research the planar source of 14C with large size by the absorbability of the anodizing membrane. The adsorption of 14C on the anodizing membrane with thickness of 4 to 12 μm were investigated. The adsorption of 14C and the uniformity of the planar source were investigated on the volume of 14C solution. The specific activity of 14C was investigated on adsorption of 14C. The fastness, the uniformity and the surface emission rate of the planar source of 14C were measured. The result shows that the uniformity of the planar source (100 mm×150 mm) of14C is precede 10%. The plateau length is 400 V, the slope of the plateau is 0.3% per 100 V. The threshold correction is 0.2%. The uncertainty of 14C source measurement is 2% (k=2). The technical parameters of the developed plane source 14C can meet the requirements of relevant standards.

Research on radiation protection dosimetry mainly focuses on continuous radiation in the world, but pulsed ionizing radiation has been widely used in the fields of industrial detection, X-ray diagnosis, security inspection and scientific research. The active electronic dosimeter has been widely used in the fields of environmental monitoring, regional monitoring, personal dose monitoring and emergency monitoring. The active electronic dosimeters are calibrated in continuous radiation field, and they cannot measure short pulse and high dose rate pulsed ionizing radiation accurately. The active radiation dosimeter can be divided into G-M counter type, scintillator detector type, semiconductor detector type and ionization chamber type according to different radiation detection principles. The measurement of pulsed X-ray dose is very difficult due to its short duration and high instantaneous dose rate. Taking nanosecond radiation pulse as an example, its single pulse dose usually reaches more than 1 μSv, and the instantaneous dose rate can reach more than 105 Sv/h. For G-M counter and semiconductor detector, there are problems of measurement stacking and detection dead time, so it is difficult to achieve such a high dose-rate response, and there is an over-response problem in the instrument, which will inevitably affect the accuracy of monitoring results. The measurement of pulsed radiation dose (rate) is difficult. However, pulsed ionizing radiation has been widely used in many fields, such as the development of new detector, industrial flaw detection, X-ray diagnosis, nuclear emergency response and scientific research, etc. In this paper, the reference ionizing radiation field of pulsed X-ray was established based on steady-state X-ray machine, pulsed X-ray machine and portable X-ray machine. In order to measure the dose of pulsed reference field, the theoretical calculation, Monte Carlo simulation and experiment method were used to develop a secondary standard ionization chamber for millisecond pulsed X-rays. From the experimental data, it can be seen that the mainstream active dosimeters currently sold have low pulse dose response and even give false readings, which are not suitable for short pulse and high dose rate measurement and early warning, will cause safety trouble to personal. The dosimetric characteristics, such as pulse time, pulse dose and instantaneous dose rate were studied based on pulsed X-ray secondary standard ionization chamber and pulsed time measurement system. The lower limit and upper limit of instantaneous dose rate of the established pulsed X-ray reference radiation field are 2.5×10-3 Sv/h and 6.7×105 Sv/h respectively. Pulse time is adjustable between 50 ns and 10 s. The dose rate range of pulsed X-ray reference radiation field established in this study covers environmental level, radiation protection level, diagnosis level, treatment level, emergency level and nuclear critical accident level, which can be used to calibrate the pulsed radiation dose monitoring instrument. It is helpful to further study the pulsed radiation response characteristics of active radiation dosimeter and personal radiation dosimeter.

The aerospace vehicles will encounter the radiation of space electrons when they are operating in extraterrestrial space. Establishing an electronic source on the ground to simulate the electronic environment, which is encountered by the aerospace vehicle in space, and to study the damage caused by related effects and the effectiveness of protective measures is an important method to ensure the safe and stable operation of aerospace vehicles. The ground simulation facility of the space electronic environment directly provides electrons in the energy range of 1.5 MeV by an electron linac, followed by a transport system to expand the electron beam size. The large energy range demands higher requirements for the design and operation of the accelerator. This paper mainly investigated the design and implementation process of the accelerator. The energy switching technology was adopted and the beam loading effects were considered. The energy switch accelerating tube consists one bunching cavity and five light speed cavities. When the energy switch is turned on, there are acceleration fields in all six cavities. When the energy switch is turned off, there are acceleration fields in the first three cavities. The beam dynamics calculation was carried out using PARMELA. The dynamic shows the electron beam can be effectively accelerated in two states, with high energy of 5.05 MeV and low energy of 0.98 MeV. The emission angle at output is less than 140 mrad, which meets the subsequent transmission requirements. Coupling characteristics under different conditions were studied. Based on the analysis and calculation of beam loading effect, input power and coupling coefficient, the coupling coefficient is determined to be 3 at the low energy level, and corresponding pulse beam current is 300 mA. The coupling coefficient of high energy level is 1.5, and corresponding beam load is 300 mA. Meantime, the magnetron-based power source output parameters were analyzed and the corresponding experimental research was carried out. The output pulse power of magnetron is adjusted from 0.7 MW to 1.8 MW, and the stability and energy spectrum of high power output can meet the demand. After the installation and commissioning of the accelerator, the energy was measured by the polyethylene dose depth distribution method. The results show that the test energy reaches 5 MeV when the pulse current is 94 mA, and the energy is 0.9 MeV when the pulse current is 334 mA. The experimental test results of the accelerator show that the electron beam meets the requirements and provides an effective and reliable electron source for the simulation device.

To study the new type of dosimeter with a dose up to the ultra-high dose range of MGy, the electron spin resonance (ESR) method is used to measure the signal intensity of the sample irradiated by gamma rays or electron beams. Preliminary studies have been carried out through the selection of sensitive materials, linearity after irradiation, and stability. The results showed that the quartz can be used as a raw material for ultra-high dosimeters. After 15 min 300 ℃ proper heat treatment, the signal intensity of the irradiated quartz sample can maintain good stability within one year with a change of less than 3%. The radiation dose and the E′ signal intensity of quartz are proportional to the dose range of 10-103 kGy. The fitting coefficient is above 0.99. Compared with the high-purity quartz sample without heat treatment, the stability and R2 of fitting function of quartz sample are significantly improved. Therefore, the quartz dosimeter is suitable as a working dosimeter in the ultra-high dose range.

Achieving a pre-designed scattering pattern from an ultra-compact platform is highly desired for on-chip integration optics, but conventional techniques suffer from the limitations of bulky size, wavelength-scale modulation and low efficiency. Here, we propose a new strategy to efficiently generate arbitrary spin-polarized scattering far-field patterns from surface-wave (SW) excitations on a designer Pancharatnam–Berry (PB) metasurface. We find that a PB meta-atom serves as a subwavelength scatter to decouple impinging SW to a spin-polarized propagating wave (PW) with tailored amplitude and phase, and thus interference among PWs generated by scatterings at different PB meta-atoms can generate a tailored far-field pattern. As a proof of concept, we design and fabricate a series of PB metasurfaces in the microwave regime and experimentally demonstrate that they can generate desired radiation patterns within a broad frequency band, including unidirectional radiation, line/point focusing, vortex beam and hologram. These findings may stimulate important applications in on-chip integrated photonics.