Thanks to the advantages of compact, inexpensive and high conversion efficiency, high power fiber lasers are highly desired in industry applications. Recently, an all-fiber high power fiber amplifier directly pumped by laser diodes (LDs) was experimentally established. A maximum power of 20.27 kW was achieved with the optical-to-optical efficiency of 84.8%, central wavelength of 1080 nm, and Raman-suppression ratio of >50 dB. We believe that the brightness and the output power can be further improved by optimizing the design of the Yb-doped fiber and devices.

It has been experimentally proved that the intense laser-driven capacitor-coil target can generate a strong magnetic field of several hundred Tesla. The basic model of the magnetic field generated by this experimental method and its development process are introduced. Comparisons are made between three magnetic field diagnostic methods commonly used in laboratory, including: B-dot, Faraday rotation and proton backlight, it is found that the first two methods can only obtain a limited number of magnetic field values far away from the target in the experiment. The values of the magnetic field at the target obtained by the simulation tool and the value of the measurement point cover a span of several orders of magnitude, which is prone to errors; the proton backlight diagnosis can obtain the global magnetic field information in the experiment, which can better meet the needs of the magnetic field diagnosis of the coil target. Because the magnetic field of the coil target is strong and sustainable for a long time, and has a certain controllability in space-time distribution, we applied it to the study of magnetic reconnection, and have successfully obtained the reconnection characteristics, such as outflow. In addition, the coil target has also been applied in many aspects, such as the confinement of charged particles and the study of magnetohydrodynamics, which will provide new ideas for the research of related problems in laboratory.

The progress of the 105/140 GHz MW gyrotron experiment aiming for fusion application is presented. The gyrotron employs dual-frequency design in triode magnetron injection gun, cavity, quasi-optical mode converter and window. In the experiment, pulse power of 710 kW at 105 GHz and 1.057 MW at 140 GHz were achieved at 1 Hz repetitive rate. The total efficiency is 34% and 49%, respectively. The experiment has firstly demonstrated the MW-level power output in the domestic quasi-optical gyrotron tests.

The deviation of the beam orbit can be quickly corrected by the fast corrector power supply, which improves the reliability of the operation of the synchrotron radiation light source. With the further improvement of the quality of the fourth-generation Diffraction-Limited Storage Ring (DLSR) light source, the Fast Orbit FeedBack (FOFB) system places higher requirements on the performance of the corrector power supply to achieve the stability of the beam orbit. In this paper, the current research achievements of beam orbit fast corrector power supply in international fourth-generation synchrotron radiation light sources are divided into two categories: linear power supply and switching power supply. According to the requirements of the FOFB system in the advanced synchrotron radiation light source for the fast corrector power supply, the topology, control strategy and performance parameters of each scheme are briefly compared and analyzed.

The key parameters of the neutral beam, such as beam uniformity and beam divergence angle, can be obtained by analyzing the infrared images generated by the beam bombarding the target surface. Due to the camera setup angle, the IR images show geometric distortion, which affects the accurate analysis of the beam parameters. Therefore, so the images should be corrected for the distortion. The traditional Hough transform, canny lines algorithm, and probabilistic Hough transform methods are not effective in detecting straight lines on this image, and there is a problem of detecting discontinuous and incorrect line segments. In this paper, Sobel filter is used to sharpen the infrared image in the horizontal and vertical directions respectively and line segment feature is detected by line segment detector (LSD) algorithm. Then complete straight lines are obtained in the image by clustering and fitting the line segments according to the geometric and angular relationships between them. Vanishing points is calculated by the intersection points of the lines. Finally, the corrected image is obtained based on the perspective relationship. Experiment results prove that this method can achieve automatic and effective correction of neutral beam infrared images and it lays a basis for obtaining key parameters of the beam.

To explore the influencing factors of the pulsed electric field on the prevention and control of aquatic organism fouling, and to determine the minimum electric field conditions required for effective prevention and control of fouling organisms, we built a pulsed electric field test platform. Approximate square wave pulses were generated by the pulse forming network. During the experiment, we recorded the death rate and morphological structure changes of the Daphnia magna. With the help of Matlab nonlinear fitting, we obtained the functional relationship between the pulsed electric field-induced death rate and the electric field strength, the total equivalent processing time, and the pulse injection energy density. The paper takes a main canal project as an example to introduce the principle of parameter selection and platform construction method of pulsed electric field for controlling large water fleas. The results showed that the treatment effect of the pulsed electric field on the Daphnia magna is positively correlated with the electric field strength, the total equivalent treatment time and the pulse injection energy density. When the electric field strength is between 0.5 and 1.5 kV/cm, the induced mortality increases by about 35% for every 0.5 kV/cm increase in the electric field strength. When the electric field strength is higher than 2.0 kV/cm, the total equivalent processing time is higher than 900 μs, or the pulse injection energy density is higher than 80 J/L, the pulsed electric field can produce more than 80% induced mortality.

To study the thermal effect and secondary thermal radiation of infrared detection system after laser irradiation on the detector imaging, this paper uses Ansys software for thermal radiation simulation and finite element structure simulation of infrared detector. The blackbody radiation law and DO radiation calculation model are used to simulate the temperature variation with time of the optical system in the detector under different laser irradiance and the interference of the secondary thermal radiation caused by the temperature rise in the detector to the imaging of the target surface. The thermal stress and deformation in the detector are simulated by thermoelastic model. The results show that, under the condition that the detector is irradiated by 1.06 μm laser while the laser irradiance of the corrective lenses is 50 W/cm2, then, the secondary thermal irradiance of the target reaches the order of 100 μW/cm2 in 0.6 seconds, the infrared detector reaches saturation. After the detector is irradiated by laser, the maximum temperature of the system appears at the center of the corrective lenses, and the function relationship between the maximum temperature of the system and the exposure time is obtained by fitting, which can predict the damage of the heating structure of the detector. The maximum thermal deformation appeared at the center of the back of the mirror, which formed unequal additional optical path difference from the outside to the inside and interfered with the imaging effect of the detector. The maximum thermal stress appeared in the front center of the corrective lenses, and the linear relationship between the maximum thermal stress and the laser irradiance was obtained, which provide the prediction parameters for the thermal stress damage of the corrective lenses.

Laser accelerators can provide proton beams with unique qualities, such as micron size, picosecond pulse duration and high peak current, and have been demonstrated for various applications and for scientific research purposes. The effect of the space charge force in high peak current beams is strong and raises challenges for application after beam transportation. We performed two-dimensional particle-in-cell simulations and studied the influence of electrons that have velocities close to that of the protons after laser acceleration. We employed ellipsoid models with different charge distributions to estimate the effects of the space charge force. Results demonstrate that space charge will affect beam transmission, and even lead to complete transmission failure if the number of protons per pulse exceeds 1010. The influence of the space charge force diminishes greatly after 20 ps, which corresponds to approximately 1.2 mm from the target.

Positioning system is the electromagnetic sensitive part in the core unit of unmanned aerial vehicle (UAV) and the key part of UAV electromagnetic protection. To analyze the failure process and mechanism of electromagnetic interference, aiming at the positioning system of typical self-assembled UAV, the radiation coupling path is analyzed by constructing the electromagnetic topology and the radiation interference effects of different coupling paths of UAV positioning system are simulated and analyzed. The GPS enhanced forwarding system is used to provide a normal working environment for the UAV system in the anechoic chamber and the microwave irradiation interference effect experiment is carried out. Through the logging function in the UAV’s firmware, combined with the real-time monitoring data in ground station, the whole process data recording and fault mechanism analysis of the electromagnetic interference of the UAV positioning system are realized. The experimental results show that the coupling interference of the receiving antenna mainly occurs within the maximum receiving bandwidth (200 MHz) of the positioning system; Cable coupling interference mainly occurs in the frequency band below 1 GHz and reaches the maximum near 171 MHz and 511 MHz; The coupling interference of PCB circuit mainly occurs in the frequency band above 1.24 GHz and the fluctuation of coupling voltage becomes stronger with the increase of interference signal frequency.

At present, efficient time domain numerical methods used for the coupling effect analysis of electromagnetic pulse to long rails on infinite ground are still rare. An efficient time domain hybrid algorithm, consisting of the finite difference time domain (FDTD) method, the transmission line equation and the fast calculation method for the excitation fields of the long rails, is presented to realize fast electromagnetic pulse coupling simulation of the long rails with compensation capacitance in time domain. Firstly, to avoid direct modeling of the irregular structures of the rails, the rails are equivalent to the tubular conductor models based on the skin effect, and the corresponding per unit length distribution parameters are extracted. Then, the electric field distribution along the rails are calculated via the fast calculation method for the excitation fields of long rails rapidly, and the electromagnetic coupling model of the rails with compensation capacitance is constructed by the transmission line equation. Finally, the FDTD method is used to solve the transmission line equation to obtain the electromagnetic pulse coupling responses on the rails. The results show that the width of the coupling current waveform on the rails would extend, and the peak values of these currents would saturate with the rail length increasing to a certain value. This conclusion will provide important data for the electromagnetic protection design of track circuit system.

High-intensity electromagnetic pulse can easily couple into the electronic system through antenna, cavity and cable, causing transient failure or permanent damage of the sensitive electronic equipment. Installing electromagnetic pulse protection circuit can effectively improve the anti-destruction ability of electronic equipment against high-intensity electromagnetic pulse. Herein, based on LC frequency selective network and transient voltage suppressor (TVS) diodes, we develop a wideband electromagnetic pulse protection circuit with outstanding suppression capability. The operation bandwidth of the protection circuit exceeds 2 GHz, while the insertion loss is less than 0.6 dB. Moreover, the suppression capabilities of this protection circuit towards square-wave pulse, wide-band high-power microwave and narrow-band high-power microwave were systematically investigated. The results show that the protection circuit has a suppression ratio of more than 40 dB and power capacity up to 387 kW, while the response time is as low as 0.7 ns. Altogether, the protection circuit has advantages of wide operation bandwidth, excellent suppression performance, fast response time and high power capacity, which are of great importance for the electromagnetic protection reinforcement of electronic information system.

For field-to-line coupling problems, the classical transmission line theory is not applicable to obtain voltage/current responses on transmission lines irradiated by high-frequency electromagnetic disturbances. To solve this problem, a time-domain full-wave modeling method based on antenna theory and analog behavior modeling (ABM) is proposed. The Harrington method of moment is utilized to discretize the current integral equation and derive time-domain expression of the macromodel. Then, the inverse Fourier transform and time-domain convolution of the frequency-dependent parameters in the expression are realized by frequency domain function module (FREQ) of ABM. With embedding into the circuit solver, the model can directly solve the responses of high-frequency electromagnetic disturbances coupling to transmission lines with different structures above lossy ground. Compared with the traditional full-wave algorithms, the model can be applied to any circumstances of incident field and linear/nonlinear loads, and there is no need to solve the current integral equation repeatedly with time-consuming methods. The proposed method can simplify the process of the full-wave algorithm and improve the efficiency of simulation calculation. It is especially convenient to obtain statistical characteristics by performing efficient repeated simulations when the incident field and load are with uncertain parameters. Finally, taking the high frequency electromagnetic field coupling to two-conductor transmission lines above lossy ground as an example, the validity of the proposed macromodel and the limitation of the transmission line theory are verified by comparing the results with those of numerical electromagnetic code and traditional transmission line theory method. The results reveal that the macromodel based on the full-wave method can efficiently and accurately acquire the transient responses on transmission lines with any structure irradiated by high frequency electromagnetic disturbances in the time domain.

Wideband high power microwave is one of the main development directions of high power microwave in recent years. A wideband high power microwave system with small volume, working in UHF band is developed. The system powered by a 24V battery uses a Marx generator as the driving source. The wideband high power microwave is generated with a quarter wavelength switching oscillator and radiated with a high power microstrip flat plate antenna. The electromagnetic simulation model is established and the key factors are simulated and calculated. The test results show that the center frequency of the wideband high power microwave is 425 MHz, and the peak-to-peak value of the electric field radiation factor is 92kV@1m. The radiation waveform is basically consistent with the simulation results. The application prospect of wideband high power microwave in drone, robot and other platforms is expanded.

This paper presents a compact filtering patch antenna with independent controllable radiation nulls. The antenna is principally composed of a simple radiation patch antenna and two split-shaped slots. Taking the basic microstrip patch antenna as the prototype, the filtering and frequency selection function is generated by adding the segmenting slot. Two broadside radiation nulls are generated by two slots in the upper/lower band respectively. According to the circuit structure, HFSS simulation software is used to optimize the structure and adjust the feeding position, and the filtering function is obtained. Without using additional filtering circuits, this design method saves space size and reduces the loss of antenna gain. For demonstration, a prototype is fabricated and tested. The simulation results agree well with the measured ones: the proposed microstrip patch filter antenna operates at 2.40 GHz; there are two radiation nulls at 1.96 and 2.66 GHz at two band-edges of the boresight gain response for improving skirt selectivity; at the same time, the frequency of the two radiation nulls can be controlled independently by controlling the length of the two split slots, increasing the flexibility of the design; the average realized gain of this filtering antenna is about 7.0 dBi and the out-of-band suppression level is more than 39 dB.

High power traveling wave tubes (TWTs) usually use compound pipe shells to enhance the integration and heat dissipation characteristics of high frequency system. When broadband TWT adopts the compound pipe shell high frequency manufacturing process, the vane load contains ferromagnetic material (pure iron), which makes the transverse magnetic field component of the focusing system become larger, radial and angular magnetic field components being non-homogeneous, resulting in the difficulty of electron beam focusing. This paper studies the causes of transverse magnetic field generation in periodic permanent magnet (PPM) focusing system and establishes theoretical model and simulates the transverse magnetic field component’s effect on the morphology of electron beam. The simulation results are consistent with the theoretical model. The optimized combination of shape and number of vanes based on the theoretical model shows that the 9 tooth-shaped loaded vanes can maintain slow-wave circuit parameters while reducing transverse magnetic field component of the focusing system, improving the focusing performance of electron beam.

Magnetized Liner Inertial Fusion (MagLIF) is one of the possible configurations to reach ignition. For future ignition validation, it is necessary to explore key issues of MagLIF and seek an optimal design of integrated MaglIF experiments on the low current generators. In this paper, a simplified circuit model is coupled to the semi-analytical model developed by McBride et al. to investigate key issues of integrated MagLIF experiments possibly conducted on the 7-8 MA facility in China, and parameter domain to attain over 1010 neutron yield is explored. Theoretical results show that many factors together determine the final neutron yield, such as the 7-8 MA current, the liner material, the initial radius and density of D2 fuel, the load height, the preheating energy, the applied axial magnetic field, as well as the fuel mixing. As the preheating energy is increased, the fuel temperature before implosion and at stagnation becomes higher, thus generating higher neutron output. The neutron yield will increase first and then decrease with the applied axial magnetic field, mainly caused by the compromise of reducing the conduction loss and decreasing the fuel convergence. When the mass ratio of impurity is higher than 10%, the neutron yield will be decreased remarkably. If an initial fuel density of 0.7 mg/cm3, an axial magnetic field of 27 T, and a preheating energy of 200 J in the case of 7-8 MA are used, 3.5×1010 neutrons can be produced with the convergence lower than 20 considering 50% fuel mixing. It is thus anticipated that the research platform on key physics of MagLIF can be developed in the case of 7-8 MA drive current.

In the study of the transportation of low energy electrons through insulating capillaries, the experimental results are very different and depending on many conditions. This leads to some controversies on whether the mechanisms of the electron guiding exists or not . This work studies the electron beam with an energy of 1500 eV transmitting through the insulating PET capillaries of 400 nm in diameter. The capillaries have never been irradiated by any beams before. The two-dimensional angular distributions of transmitted electrons and their evolution are measured by a Mirco-channel Plate (MCP) detector with the phosphor screen. The energy distribution of the transmitted electrons is also measured by a mesh system before the MCP detector where the stepping voltages are put on and the transmitted electrons are recorded by the MCP detector accordingly. The experimental results show that the intensity of transmitted electrons increases with the charging time when the capillaries starts to be exposed to the electron beam, and a typical charging-up is observed. During the charging process, the angular distribution width of transmitted electrons increases from small to large, but the center of the angular distribution remains the same. The energy spectrum of the transmitted electrons when they reach the stationary state shows that the most transmitted electrons keep their initial energy. This work provides new experimental evidence for understanding electron transport in insulator micropores, and gives the conditions for the formation of guiding electric field in micropores that may form guiding effect.

A petal-shaped electron irradiation accelerator, recirculating coaxial accelerator (Recotron) was designed by Institute of Modern Physics, Chinese Academy of Sciences. It can produce 10 MeV energy and 10 mA current irradiation electron beam. It is under construction now and expected to become China’s first domestically produced petal-shaped electron irradiation accelerator. To guarantee the radiation safety of this facility during operation and provide a reference for the radiation shielding design of the same type of electron accelerator in the future, a study on radiation shielding for this facility was carried out using Monte Carlo code FLUKA. The proposed vault of the Recotron is a kind of semi-underground structure with the accelerator room above ground and the irradiation room below ground. According to the beam loss characteristic of the Recotron, a simple but effective radiation source input model was proposed for MC simulation. This model fully considered the main beam loss points that determine the radiation field of the Recotron. The results show that to meet the dose criterion of China, the thickness of side walls, ceiling of accelerator room and ceiling of irradiation room should be at 160-220 cm, 110-150 cm, 150 cm respectively, when ordinary concrete was used as the shielding material.

The structure design and simulation research for the water-cooled solenoid with magnetic field on the order of T are presented in this paper. The multi-layer water-cooled structure design is used for the solenoid. The solenoid structure malformation caused by different temperature rise is simulated and checked. Finally the magnetic field is calculated by POISSON code. The structure deformation is less than 0.07 mm with 60 ℃ temperature rise and the magnetic field is 1.5 T with 96.6 A current.The axial magnetic field region is 40 mm on the order of 0.01% precision and is 140 mm on the order of 0.1% precision. The results show that the water-cooled solenoid is good enough for the magnetic field calibration measurement.

The high intensity proton accelerator of China Spallation Neutron Source adopts the method of charge exchange injection. A carbon foil strips two electrons of H- into H+, and proton beams are multiturn-painted in the phase space of the rapid cycling synchrontron for acceleration to 1.6 GeV. A new-developed beam current transformer (H0CT) was installed at the I-Dump beamline to measure the incompletely stripped H- and H0 particles, for the sake of an accurate measurement of the stripping efficiency, together with a study of the service life of the foil stripper with different thicknesses. To measure such extremely weak microampere beam current, in the development of the H0CT measurement system, we took into account the external interference and the noises from probes, cables and electronics. The new design has minimized the impact of environmental noise, improved the signal-to-noise ratio, and successfully measured the microampere pulsed current.

Chinese First Quasi-Axisymmetric Stellarator (CFQS) is being constructed as an international joint project between the National Institute for Fusion Science in Japan and Southwest Jiaotong University in China. To meet the requirements of 0.1 T steady-state quasi-axisymmetric magnetic field configuration experiment, it is necessary to design and manufacture the corresponding power supply system for its magnet coil. Since the power grid capacity of the laboratory can’t achieve the power consumption required for 0.1 T operation of CFQS, the magnet coil power supply system uses 500 kVA energy storage power station, and the main circuit of the magnet coil power supply system adopts bridge thyristor rectification. In this design scheme, the line impedance is estimated according to the actual engineering situation. Considering the engineering margin, we calculate the power supply at 1.2 times of the actual load parameters, and build the Simulink simulation model of the power supply system to analyze the load current ripple and the harmonic content of the grid side. According to the simulation results, we optimize the design and reduce the output current ripple by adding a passive filter at the DC side. By this way, the output current ripple can meet the requirements of the quasi-axisymmetric magnetic field configuration.

The output waveform of capacitive voltage divider has top tilt when measuring square-wave signal with pulse width of several microsecond. To solve this problem, an improved two-end matched capacitive divider is designed. The capacitive divider with two-end matching modes is simulated in frequency domain and time domain. The simulation results show that the linearity of the amplitude-frequency characteristic of the capacitive divider is not good in the middle frequency band. And the output waveform of the divider has overshoot when it responds to square wave signals. The calculation method of the beginning resistance and the corresponding terminal series capacitance has been improved, and the two-end matched capacitive divider has been improved. The experimental results show that when the low-voltage arm capacitance of divider is 2 nF and the electric length of the signal cable is 50 ns, the output waveform of the improved two-end matched capacitive divider has no top tilt , and the overshoot is less than 2%.

The Z-pinch experiments with a reflux hood structure, exp90 or exp60, were carried out in an intense pulsed power device FP-2 and simulated and analyzed by the two-dimensional magnetically driven simulation code (MDSC2). The numerical simulations show that the measured current/loop current is not a load current of liner in the Z-pinch experiment with the reflux hood structure. There is a structure coefficient between the measured current/loop current and the load current. A new formula for the relation between the boundary magnetic field and the loop current is presented. The new boundary magnetic field formula with the structure coefficient and the MDSC2 code can correctly simulate the Z-pinch experiments with a reflux hood structure. The simulated inner diameter velocity is consistent with the measured one by Velocity Interferometry System for Any Reflector (VISAR). The structure coefficients is a constant, which is determined only by the initial structure of Z-pinch with reflux hood structure. In the Z-pinch experiments with the reflux hood structure, the structure coefficients for the 90 mm inner diameter liner and the 60 mm one are 0.87 and 0.90 respectively. When the initial thickness of liner, insulation material and other conditions are the same, the larger the inner diameter of liner, the smaller the structure coefficient of Z-pinch with reflux hood structure.

When the charger based on the high-frequency switching charging technology is used to charge the pulse power supply, due to the existence of distributed inductance in the charging circuit, during the high-frequency current charging process, overvoltage higher than the charging voltage will be generated at both ends of the T-type protection circuit of the charger, and there is a risk of damaging the semiconductor power devices of the T-type protection circuit. To solve this problem, the simulation model of charger and pulse power supply circuit is established, and the preliminary law of the influence of the distribution inductance change of charging circuit on T-type protection circuit is obtained through simulation analysis, and it is further verified through experiments. To reduce the influence a solution to reduce the distributed inductance of the charging circuit is proposed. The main method is to change the type and length of the output cable. The effectiveness of the solution is verified by simulation and experiment, which provides a reliable reference for the engineering application of the pulse power supply.

In order to meet the need of magnitude transmission of high voltage pulse amplitude, this paper develops the design of high voltage pulse amplitude calibration device with pulse amplitude of 1-20 kV and pulse width of 1-100 μs. The calibration device takes the high voltage MOSFET as the core, and builds up a multi-stage Marx structure to achieve high voltage pulse. At the same time, the truncation circuit greatly reduces the pulse fall time and realizes the output of rectangular pulse waveform. On the basis of the Marx structure, the unit is built as a whole. The pulse width and amplitude can be adjusted by triggering pulse and high voltage DC power supply voltage, and the high voltage isolation is guaranteed by isolating power module and optical signal. The device uses high-precision high voltage probe and oscilloscope to constitute the internal measurement module. The measurement value is the standard value of the calibration device. The uncertainty of the pulse amplitude of the device is evaluated, and it is verified by comparison of two measurement standards. The calibration device is tested with other types of high voltage probes. The results show that, compared with the low-voltage pulse calibration source, the high voltage pulse can effectively characterize the performance and measurement accuracy of the high voltage probe, achieve the calibration of the high voltage probe, and the device can also be applied as a high voltage pulse source for other purposes in the field of pulse power field.

The principle of triple transmission line type pulse compression device is analyzed, and a built-in high resistance spiral with three parallel winding wires is designed to improve power gain and minimize the device. The circuit simulation model and three-dimensional structure electromagnetic field simulation model are established, and the influence of high resistance spiral characteristic parameters on power gain is analyzed. Based on the optimized results, a compact high power subnanosecond pulse compression device is developed. The results show that when the input pulse width is 8 ns and the power is 1 GW, the output pulse is 1.5 ns and the power is 3.7 GW. The power gain is 3.7. After 300 000 times of operation evaluation, there is no flashover and breakdown inside the device, which verifies the reliability of the design.