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In order to meet the power source requirements of C-band linear accelerators for industrial applications, a C-band high power klystron operating at a frequency of 5 712 MHz was developed. For this klystron, the development objective of the output power is no less than 3.5 MW and the efficiency is no less than 35%. During the entire design process, the output power was optimized to over 4 MW and the power efficiency over 40% to compensate for the disadvantage effects caused by manufacturing and testing errors in the development processes. Firstly, the electron optics system with a Pierce gun and a combination of five forward and one reverse focusing coils was designed. The Pierce gun with a perveance of 2 μP was adopted and the beam voltage and current were chosen as 120 kV and 83.3 A. By iteratively calculating the structure of the electron gun with EGUN code and optimizing the magnetic field between the electron gun and the beam-wave interaction section, the final electron beam pass rate reaches 100% and the fluctuation of the beam envelop is only 4.8%. Secondly, the efficiency optimization and PIC simulation of the beam-wave interaction section were carried out using the one dimensional AJDISK code, 1.5 dimensional KlyC code and three dimensional CST code. The scheme of six resonant cavities was ultimately determined and the basic cavity parameters were optimized based on the principles of stagger tuning. The simulation results of different codes all indicate that the efficiency can reach above 46.5%, and the output power can all reach above 4.650 MW. And the influence of frequency errors and output external quality factor on efficiency was also analyzed to guide the manufacturing process. After that, the mechanical structure of cavities was designed and all cavities were manufactured with oxygen free copper. The cold test and tuning of all cavities were carried out and the frequency error is mostly within the range of ±5 MHz, which basically does not affect the output power. Finally, the electron gun, the beam-wave interaction section and the collector were welded together. And the high power test was conducted immediately after the first high power C-band klystron protype was completed. When the electron gun operates at the voltage of 115 kV and current of 79.6 A, the klystron peak output power reaches 3.52 MW, the gain reaches 45.5 dB and the efficiency reaches about 38.5%. The high power test results show that this C-band high power klystron achieves the expected development goals.

BackgroundLower hybrid current drive (LHCD) is one of the main auxiliary heating and current driving methods for Tokamak, and studies have shown that the boundary parasitics effect of lower hybrid (LH) wave in scrap-off layer (SOL) significantly decreases current drive efficiency of LH wave. Among these, wave scattering caused by density fluctuation at the boundary results in spectral changes within the SOL, which changes the power deposition location and current drive efficiency.PurposeThis study aims to explore the lower hybrid scattering caused by density fluctuation in the scrap-off layer on the Experimental Advanced Superconducting Tokamak (EAST) device.MethodsBased on the cold plasma dispersion theory and the blob density fluctuation theory, COMSOL Multiphysics was employed to establish a full-wave solution model of lower hybrid scattering in the SOL. Based on the parameters of the EAST device, the influence of low-frequency electron density fluctuation with different characteristics on wave scattering was analyzed.ResultsThe simulation results show that the backscattering direction caused by the density wave packet "blob" is more obvious than the forward scattering, and scattering induced by blob leads to the change of spatial structure of low hybrid power flow. The density fluctuation in the blob mainly affects the amplitude of the wave field disturbance, the radius of the blob mainly affects the spatial range of the wave scattering, the full-field disturbance caused by multiple blobs increases significantly.ConclusionsThe full-wave solution model of the SOL established in this study is reliable. The simulation results using this model show that the density fluctuation will cause lower hybrid scattering, which will change the spatial structure of the power flow.

The 25 MeV wastewater treatment electron linear accelerator uses a 15 MW klystron as the microwave power source, which provides a microwave power no less than 13 MW at the entrance of the traveling wave tube, and accelerates the electron beam to 25 MeV/5 kW in a traveling wave tube with length of 76 cm. The operating frequency of the accelerator is 2 856 MHz in the Sband. The traveling wave tube adopts a diskloaded waveguide structure, which is simple and stable. To ensure that the beam can reach sufficient energy and power, the traveling wave tube is composed of a variable phase velocity bunching section, a constant phase velocity bunching section, and a light velocity section. The physical design of the traveling wave tube was introduced in detail. Using SUPERFISH, a two-dimensional cavity model was established, effective shunt impedance, attenuation constant, cavity wall loss, and other key parameters were calculated, and the traveling wave tube field distribution was obtained based on the power loss. Using numerical calculation methods, the phase oscillation equation and the beam envelope equation were solved, the capture efficiency of longitudinal motion is about 50% and the beam energy spread is about 72% with optimizing the length of the constant phase velocity bunching section. The solenoid magnetic field that was calculated by the SUPERFISH software was substituted, and magnetic field distribution to make the beam envelope smaller than the beam aperture of the accelerating tube was optimized. Finally, the design was verified with PARMELA. When 10 000 particles are injected, 6 106 particles can be accelerated to the exit of the acceleration tube, that is, the capture efficiency is about 61%. Good consistency is obtained. Then, the threedimensional RF structure model was established. The accelerating cavity model in the simulation software was calculated using the principle of the probe method. The coupler model was calculated by using three frequency methods, and the coupling degree was optimized by adjusting the size of the coupling port and the inner diameter of the cavity. The field distribution of traveling wave tube was analyzed by timedomain method, and cavity inner diameter was adjusted to optimize field distribution. The simulation field distribution is consistent with the beam dynamics design. Voltage standing wave ratio of operating frequency is 101, and bandwidth of accelerator tube is 2 MHz. The design of 2.5 MeV traveling wave accelerator tube is completed, providing a reference for its research and development.

In order to develop a compact electron linear accelerator, a C-band on-axis coupled standing wave accelerating tube operating at the frequency of 5 712 MHz was developed in this paper. The designed beam energy is 6 MeV, and the designed pulse beam current intensity is greater than 80 mA. Firstly, in order to achieve the compact goal, the beam dynamics design was carried out based on the RF phase focusing theory. By designing the phase velocity distribution and electric field distribution in the whole tube reasonably, the longitudinal bunching and transverse focusing of the electron beam were realized simultaneously without external focusing magnetic field. Secondly, the structure of this C-band accelerating tube was optimized after establishing the equivalent circuit model to obtain the required electric field distribution. This accelerating tube adopted π/2 mode onaxis coupled standing wave structure and was composed of three bunching cavities and nine uniform accelerating cavities with a total length of about 284 mm. Through the analysis of the equivalent model, the relationship between the cavity parameters and the coupling coefficient between adjacent cavities were revealed. After adjusting the basic parameters of each cavity, the structure of this tube was determined and the required electric field distribution was obtained. Then the input coupler was designed to match the coupling requirement and the RF field got from the simulation of the whole tube was used in the beam dynamics validation calculation. At last, cavities were brazed together after tuned to the designed frequency and the cold test and highpower test of this tube were carried out. The reflection parameters of this tube were tested in the vacuum condition. The test results show that the operating frequency is 5 7136 MHz, the reflection coefficient at the operating frequency is -16.5 dB, and the corresponding input coupling is 1.35, which meets the designed requirements. The electric field distribution was tested according to the bead-pull measurement method and it’s consistent with the designed field distribution. In the high-power test, the tube was driven by a C-band magnetron which delivered a 2.5 MW peak power, 4 μs width pulse with a repetition rate of 250 Hz. An X-ray target was placed at the beam exit and the maximum dose rate at 1 m behind the target is 845 cGy/min, which indicates that the beam pulse current is 84.5 mA. Based on the half-value-layer measurement methods, the test result shows the electron beam energy can reach 6 MeV. These test results verify the validity of the development process of C-band 6 MeV on-axis coupled standing wave accelerating tube.

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.

Nowadays, global warming caused by the increasing levels of CO2 has become a serious environmental problem. Membrane separation technology has demonstrated its promising potential in carbon capture due to its easy operation, energy-efficientness and high efficiency. Interfacial polymerization process, as a facile and well-established technique for preparing membranes with a thin selective layer, has been widely used for fabricating commercial reverse osmosis and nanofiltration membranes in water treatment domain. To push forward such an interfacial polymerization process in the research of CO2 separation membranes, herein we make a review on the regulation and research progress of the interfacial polymerization membranes for CO2 separation. First, a comprehensive and critical review of the progress in the monomers, nanoparticles and interfacial polymerization process optimization for preparing CO2 separation membrane is presented. In addition, the potential of molecular dynamics simulation and machine learning in accelerating the screen and design of interfacial polymerization membranes for CO2 separation are outlined. Finally, the possible challenges and development prospects of CO2 separation membranes by interfacial polymerization process are proposed. It is believed that this review can offer valuable insights and guidance for the future advancement of interfacial polymerization membranes for CO2 separation, thereby fostering its development. [ABSTRACT FROM AUTHOR]

Sarcopenia is a systemic skeletal muscle disease characterized by a decline in skeletal muscle mass and function. Originally defined as an age‐associated condition, sarcopenia presently also encompasses muscular atrophy due to various pathological factors, such as intensive care unit‐acquired weakness, inactivity, and malnutrition. The exact pathogenesis of sarcopenia is still unknown; herein, we review the pathological roles of the neuromuscular junction and mitochondria in this condition. Sarcopenia is caused by complex and interdependent pathophysiological mechanisms, including aging, neuromuscular junction impairment, mitochondrial dysfunction, insulin resistance, lipotoxicity, endocrine factors, oxidative stress, and inflammation. Among these, neuromuscular junction instability and mitochondrial dysfunction are particularly significant. Dysfunction in neuromuscular junction can lead to muscle weakness or paralysis. Mitochondria, which are plentiful in neurons and muscle fibers, play an important role in neuromuscular junction transmission. Therefore, impairments in both mitochondria and neuromuscular junction may be one of the key pathophysiological mechanisms leading to sarcopenia. Moreover, this article explores the structural and functional alterations in the neuromuscular junction and mitochondria in sarcopenia, suggesting that a deeper understanding of these changes could provide valuable insights for the prevention or treatment of sarcopenia. [ABSTRACT FROM AUTHOR]

Bismuth chloride oxide (BiOCl) is a typical V-VI-VII ternary oxide material, which is one of the widely studied metal oxides due to its unique surface, electronic and photocatalytic properties. However, the broad bandgap and the large number of photogenerated electron-hole pair complexes of BiOCl limit its photocatalytic efficiency. Since the photocatalytic performance of BiOCl is highly dependent on its exposed crystallographic facets, research attention has increasingly focused on the different structures and properties possessed by different crystallographic facets of BiOCl. This article reviews the basic principles of using different crystalline surfaces of BiOCl materials to enhance photocatalytic activity, summarizes the applications of BiOCl single-crystal catalysts and composite catalysts in the environmental field, and provides an outlook on the challenges and new research directions for future development in this emerging frontier area. It is hoped that the crystalline surface-related photocatalysis of BiOCl can be used to provide new guidance for the rational design of novel catalysts for various energy and environment-related applications. [ABSTRACT FROM AUTHOR]