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2021, 33: 021002. doi: 10.11884/HPLPB202133.200305
2021, 33: 023001. doi: 10.11884/HPLPB202133.200257
Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.
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Accepted Manuscript  doi: 10.11884/HPLPB202133.200327
[Abstract](11) [PDF 1055KB](1)
Abstract:
A highly selective tunable filter with switchable bandpass (BP)-to- bandstop (BS) frequency response is designed. The frequency can be adjusted by loading a varactor diode on the end of microstrip resonator and branch; a PIN diode can be used to switch BP and BS characteristics. The filter is analyzed using the even- and odd-mode method, and constant absolute bandwidth (CABW) is achieved. Then, a source and load coupling is introduced so that there is a transmission zero (TZ) on each side of band, which can be almost kept in relative position throughout the frequency tuning range (FTR). Therefore, in the FTR, the filter achieves high selectivity and good out-of-band suppression characteristics. The FTR of the proposed filter is 5.58～5.89 GHz, measured attenuation within the stopband is greater than 14 dB with CABW of (80±5) MHz under BS state; the FTR is 5.42−5.79 GHz, CABW of (120±5) MHz, the measured return loss and insertion loss within the passband is about 13 dB and 1.69−2.25 dB under BP state, respectively. Moreover, the fabricated tunable filter has a compact size of 0.28λg×0.62λg (λg is the wavelength of the center frequency during the FTR). The experimental and simulated results are in good agreement.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200296
[Abstract](10) [PDF 1196KB](0)
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HL-2A device make use of a pulse generator set to provide the energy to thyristor power supply, phase-controlled is used to control the thyristor power supply. The quality of the synchronization signal will directly affect the control accuracy of the power supply. The synchronization signal of thyristor power supply in HL-2A device is taken from the synchronous transformer. The power supply mode of pulse generator unit with rectifier load makes the synchronization signal not only have serious distortion, but also have the characteristics of a wide frequency range of synchronization signal. Considering the characteristics of the synchronization signal of thyristor power supply in HL-2A device, point-by-point Butterworth filter is implemented to eliminate waveform distortion, and then high quality synchronization signal is obtained by real-time calculation of frequency and phase reconstruction. Based on NI CompactRIO device, a real-time processing system for synchronization signal of thyristor phase-controlled power supply is designed. The experimental results show that the system can effectively solve the problem of serious distortion of synchronization signal and wide-range frequency change.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200294
[Abstract](8) [PDF 1046KB](0)
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Accepted Manuscript  doi: 10.11884/HPLPB202133.200212
[Abstract](7) [PDF 1424KB](1)
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For investigating and tracing the multi-bunch transverse coupled instability caused by beam impedance and evaluating the suppressive effect to the instability by the new updated Transverse Feedback System during the upgrade process of SSRF PHASE II, transverse beam motion in different states were recorded by diagnostics tool of feedback processor in the system, by which the evolution of dominate instability modes were analyzed respectively in steady-state, injection process and grow-damping transient. Growth/Damp rate as well as dependence of growth rate and beam current were calculated. Also, performance of the feedback system was evaluated. These research results provide data support for machine operation optimization.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200320
[Abstract](17) [PDF 1352KB](3)
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The application of Inductive Coupled Plasma (ICP), can cause a wide range high density Plasma, and have great advantages in the application of the electromagnetic wave attenuation. By studying the process of interaction between ICP plasma and electromagnetic wave, establish the electromagnetic wave propagation in inhomogeneous plasma, Hierarchical Model is adopted for the diagnosis of the interaction of plasma and electromagnetic wave, the electromagnetic wave attenuation under the different condition of input power is studied; The experiment method of inductively coupled plasma for attenuation electromagnetic wave was proposed. Based on the model of plasma covering over the flate plate, the arch system for measurement of microwave reflectivity of plasma was established. The interaction of closed-plasma and electromagnetic wave with a bandwidth of 4 GHz～8 GHz is studied, the effect of microwave reflection characteristics based on the influence of different rf power is analyzed, and the experimental measurement and calculation results were analyzed. The experimental results show that the inductively coupled plasma attenuates the electromagnetic wave in 5.92 GHz～6.8 GHz band obviously by power regulation.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200311
[Abstract](16) [PDF 1402KB](2)
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In this article, there is a research about the vibration of SESRI scanning magnet for HIT. Using the laser displacements sensors to measure the amplitudes in the key test points. The purpose of this test is to analyze the factors that influence the vibration and how to block vibration or absorb vibration. The collected data presents that when I＝450 A, f＜140 Hz, the magnet show no obvious vibration. The main factors are current I and its frequency f, especially the f is the key point. The scanning magnet for SESRI is resin casting, coil and iron core is designed as integral structure. Compared with previously design, the vibration is obviously declined. As the conclusion, the rational design inside the magnet can block vibration, which can provides the design reference for new magnet.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200287
[Abstract](23) [PDF 1171KB](0)
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Taking advantage of the robustness of genetic algorithm and the advantage of FPGA in the aspect of parallel computing, we developed the cavity failure compensation program based on the Injector II’s Cryogenic Module IV (CM4) of China Accelerator Driven Sub-critical System (C-ADS). The beam dynamics software TRACEWIN was used to verify the results got by the FPGA program, and the FPGA program was packed as an IP core so as to be used in a more general form in the embedded Linux system. In addition, considering the requirements of independence and low latency for the future superconducting cavity failure compensation system, Linux system and EPICS components are compiled for the MicroBlaze soft core processor, and the communication function of the superconducting cavity failure compensation system was verified in the simulated communication environment built.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200316
[Abstract](20) [PDF 3613KB](0)
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To reduce damped oscillation in the existing short-arc pulsed xenon lamp power supply, this paper proposes a short-arc xenon flash lamp driving power supply design based on the flyback topology method and RC isolation trigger network. The driving power supply adopts 24 V input, the main voltage generates 700 V～1000 V continuously adjustable output through the flyback topology. the pulse trigger voltage circuit adopts a two-stage cascade boost circuit to produce 5 kV～7 kV pulse output. The main voltage and the pulse trigger voltage pass through the RC isolation trigger network to drive the pulse xenon lamp. This paper designs and implements the various modules of the drive power supply. Compare the RC isolation trigger network simulation with the actual trigger waveform, and analyze the charge and discharge waveforms of the main voltage at different voltages. The experimental results show that the designed driving power supply has a 100% success rate for lighting the short-arc pulsed xenon lamp, which verifies the feasibility of the designed driving power supply. The designed driving power supply has a longest total charge and discharge time of 5.63 ms, which can provide a high flashing frequency for short-arc xenon flash lamps. In addition, the designed driving power supply can reduce the damping oscillation range from 32.24% to 4.7%, effectively suppressing the damping oscillation caused by discharge, avoid recharging the energy storage capacitor, and effectively improve the discharge times and life of the energy storage capacitor and the short-arc xenon flash lamp.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200281
[Abstract](20) [PDF 1282KB](1)
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In the paper, the E-field distributions of horizontally polarized radiation-wave simulator with two different wire grating structures are compared. The antenna wires of one simulator are uniformly distributed on the ground; the other simulator’s antenna wires are converged to several groups at the end. Meanwhile, the influences of wire number and group number on the radiated field are discussed. Results show that the E-fields below the bicone apex are not affected by the wire grating structure. While in other positions, the E-field characteristics of the two simulators are different: when the wire number is the same, the simulator with uniform wire will increase the E-field amplitude by 5% to 20%, but its rise time increases about 10% at the same time; the simulator whose antenna wires are converged shows lower E-field amplitude, but its rise time is faster. Besides, the latter is easy to establish in practice. On the other hand, increasing the wire number and wire group is helpful to improve the radiation amplitude, but the improvement reduces gradually. If the wire number increases from 24 to 96, the rise time can be improved by about 10%, but the half width of radiated E-field shows little difference. The increase of group number will leads to slower rise time. Taking into account the variation law of the E-field and the complexity to establish, the wire number of the simulator with uniform wire can be set to 48, and for the simulator whose antenna wires are converged, the group number can be set to 16.
Accepted Manuscript  doi: 10.11884/HPLPB202133.200131
[Abstract](18) [PDF 874KB](2)
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Based on the Huygens-Fresnelintegral and Rytov’s phase structure function, we formulate the average intensity and signal-to-noise of a direction-detection imaging system in turbulent media. We have given the average intensity and signal-to-noise ratio of diffused target scattering wave through turbulent atmosphere. The analytical expressions shows that the dependence of the average intensity and SNR on imaging lens, the turbulence strength and the object size. If the target size and lens size increase, and turbulent atmosphere decrease, signal-to-noise will increase.
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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Corrected proofs  doi: 10.11884/HPLPB202133.200318
[Abstract](29) [PDF 1352KB](3)
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Synchrotron light source is one of the most powerful tools in modern science and technology. Shanghai Synchrotron Radiation Facility (SSRF), located in Shanghai, China, is an advanced 3.5 GeV 3rd-generation medium energy light source. The 3rd-generation synchrotron radiation light source will provide high brilliance and high stability synchrotron radiation to fulfill the advanced experimental conditions in frontier researches. To achieve highly stable radiation, it is important to have highly stable beam orbit. Thus we adopted machine learning method to control and feedback the orbit. Using this neural network-based orbit correction method, which doesn’t rely on the response matrix, we can establish a nonlinear mapping relationship between correctors and the orbit distortions and perform continuous online retraining. This new method can significantly improve the orbit stability of SSRF.
Corrected proofs  doi: 10.11884/HPLPB202133.200291
[Abstract](29) [PDF 1754KB](3)
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In this paper, a compact broadband Rotman lens beamforming network based on equal optical path difference is proposed. The beamforming network is intended for applications in a multi-beam antenna array of 5G millimeter-wave (mm-wave) communication. Firstly, the theoretical design of the Rotman lens is introduced in detail. A power divider is used to replace the standard single-port feeding mode to generate a high-directional beam, reducing the scattering of the lens’ internal energy and the energy loss at adjacent ports. The Chebyshev multi-stub matching converter is used to optimize the original tapered array output port. To ensure a wide frequency band, the original matching port size is reduced, and the overall size of the lens is reduced by 20%. Measurement results of the improved model, show that the working frequency band of the lens is 16.5−33.8 GHz, of which S11 is better than 15 dB at 17.2−32.0 GHz, and the scanning angle is ±30°. The lens has a simple and compact structure, can effectively provide a stable phase difference signal for adjacent array elements, and achieve the goal of 5G millimeter-wave array multi-beam.
Corrected proofs  doi: 10.11884/HPLPB202133.200322
[Abstract](21) [PDF 1706KB](0)
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Vacuum arc discharges with deuteride cathode have many applications, such as nondestructive examination, oil logging, and neutron activation analysis. Deuteride cathode releases many gases during discharge, which is quite different from metal cathode. The discharges display some unique characteristics. A maguifying lens and an ICCD camera are used to observe the luminous spots of vacuum arc discharge. The space resolution of this system is about 5 μm, and the time resolution is about 2 ns. The arc current has a full width at half maximum (FWHM) of about 0.9 μs, and its waveform is half cycle sinusoidal. The results show that the luminous spots merge together into a big one in most cases. Sometimes there are two or more luminous spots due to droplets. The area of the luminous spot grows as arc current increases. The cathode spots’ merging is helpful to increase plasma density and improve discharge efficiency.
Corrected proofs  doi: 10.11884/HPLPB202133.200263
[Abstract](40) [PDF 1176KB](0)
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To solve the problem that the data link of the unmanned aerial vehicle (UAV) is vulnerable to electromagnetic interference during the flight and cause the link interruption, we took a certain data link of UAV as our research object, and proposed an experimental method of injection effect based on front door coupling. On this basis, we developed the effect experiment for the data link of UAV. We derived the sensitivity threshold curve of the data link and determined the sensitivity threshold, analyzed the work principle of RF front end circuit of the data link and the signal transmission process of the receiver under the effect of electromagnetic interference, revealed the mechanism of combined frequency interference and out of band saturation interference on data link, and finally carried out the experimental verification. Based on the test results, we put forward the corresponding protective methods from the aspects of the circuits level and adaptive control respectively.
Corrected proofs  doi: 10.11884/HPLPB202133.200248
[Abstract](41) [PDF 882KB](4)
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A kind of energy-storage power supply using high power lithium iron phosphate batteries with good safety characteristics as energy storing elements was developed for mobile platforms. This kind of power supply has high performance battery sampling and equalizer modules as well as charging/discharging management system, which enhance its reliability and prolong its life. During the development process, a large number of engineering experiments and tests were conducted to assess its transportation safety, environmental adaptability, maintainability and reliability. As a result, the reliability of the energy storage power supply system has been verified after more than 12 months’ running of 21 energy storage power supplies in high temperature areas where the temperature exceeded 55 ℃.
Corrected proofs  doi: 10.11884/HPLPB202133.200269
[Abstract](38) [PDF 1505KB](4)
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There are formidable difficulties to generate intense pulsed hard X-ray. The lack of high fidelity high fluence X-ray source has become a restriction factor of SGEMP effect research. The method for intense large-area pulsed hard X- ray production by using a series diode and the radiation parameters are presented in this paper. Flash II accelerator was refined to generate a fast rise time voltage pulse, and a two-stage series diode was developed for coupling electrical energy of high-voltage generator to a low endpoint voltage bremsstrahlung diode via two diodes in series. The X-rays generated by each diode added in space to improve intensity. A dynamic support system was invented to solve the insulation problem of the floating electrode and double-ring cathodes were designed to improve emission uniformity. The experimental results show that the two-stage series diode can work stably under ～700 kV voltage and ～310 kA current, the average energy of X rays is 87 keV, and the fluence is about 36 mJ/cm2 over 500 cm2 area with dose uniformity 2∶1 at 5 cm from the last converter.
Corrected proofs  doi: 10.11884/HPLPB202133.200179
[Abstract](55) [PDF 1690KB](9)
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In particle-in-cell simulation of plasma, TA and Nanbu models have been widely used for Coulomb collision. Both models require all particles to collide. In this paper, a cross-section-based method is introduced to give a probability of Coulomb collision for each particle pair and accelerate the computation. To test this method, the relaxations of an electron gas due to e-e collisions were simulated. Comparing the simulated with the theoretical values of velocity distribution function, electron temperature, the ratio of electron temperature in x, y direction to electron temperature, the accuracy of the cross-section-based method was verified. The calculation efficiency of this method can be improved by more than 40% than the TA model at the same small time step. Furthermore, at a large time step, the simulations show agreement with the theoretical solutions, the efficiency is also improved than the Nanbu model. The simulation about the equilibration of electron and ion temperature showes that this method is also suitable for e-i collisions. Therefore in the acceleration of simulating Coulomb collision, this method has two advantages as follows: first, there is a small number of particles to collide within a step, and second, it is suitable for large time steps.
Corrected proofs  doi: 10.11884/HPLPB202133.200275
[Abstract](66) [PDF 988KB](8)
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The research on the diffusion behavior of tritium in zirconium alloy is a crucial problem for nuclear power plant radiation safety evaluation. Based on the basic model of tritium diffusion, a one-dimensional simulation program for the behavior of tritium diffusion was established in this work. The simulation program was verified by typical experiments, and the simulation results were in good agreement with the experimental results. The effects of different concentration and temperature distribution of tritium on the diffusion behavior of tritium in zirconium alloy cladding materials were analyzed. The results show that the increase of tritium concentration in P-C gap lead to the increase of tritium diffusion flux and permeability flux in and out of cladding. Due to the relatively low diffusion coefficient of the coated oxide layer, the existence of the coated oxide layer limits the tritium permeability greatly. The effect of temperature on the diffusion rate of tritium is exponential. The higher the temperature is, the faster the diffusion rate is. The relative low temperature of the oxide layer on the outer surface of zirconium alloy limits the rate of tritium permeation out of the cladding tube. Thermally induced diffusion due to temperature gradient is beneficial to limit the permeation flux of tritium diffusing out of the zirconium cladding.
Corrected proofs  doi: 10.11884/HPLPB202133.200286
[Abstract](39) [PDF 781KB](10)
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To further improve the temperature characteristics of magnetic modulation DCCT (Direct Current Current Transducer), the effects of various parts on the DCCT performance about temperature coefficient are found out by dividing the magnetic modulation DCCT into parts with grey correlation theory; at the same time, a comprehensive evaluation method of temperature coefficient of magnetic modulation DCCT is proposed. According to the working principle of magnetic modulation DCCT, DCCT is divided into three parts: printed circuit board (PCB), coil and sampling resistance. The temperature coefficients of them of the whole DCCT, PCB, coil and sampling resistance are measured respectively; then, temperature coefficient of each part of the 7 tested DCCT is calculated by using the grey correlation theory, and the correlation coefficients between the parts are obtained. Based on factors of the temperature characteristics and actual requirements, a concept DCCT is set as the reference. Using the grey correlation theory, the temperature comprehensive evaluation of the 7 tested magnetic modulation DCCTs is provided. The results provide a direction to reduce the temperature sensitivity of DCCT.
Corrected proofs  doi: 10.11884/HPLPB202133.200201
[Abstract](73) [PDF 1076KB](6)
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As the installation foundation of magnet support, the plinth is critical for the stability of the whole support unit. Different fabrication and installation processes of plinths make significant differences in performance of the support unit. Based on the stringent requirements of advanced synchrotron light source for the mechanical stability of magnets, the plinth installation pouring experiment was carried out. Several concrete construction techniques commonly applied in practice were tested with the plinths of uniform shape and size. The natural frequency of each plinth was measured by hammering method and its stability was evaluated. It is concluded from the test result that secondary grouting can effectively improve the stability of the plinth and the plinth of epoxy-based grouting shows better performance in stability than that of cement-based grouting. Based on the natural frequency test result, the influence of the plinth installation on the system mode is analyzed with the support system of High Energy Photon Source as an example. The experimental results have certain reference value for the plinth design of similar machines.
Corrected proofs  doi: 10.11884/HPLPB202133.200285
[Abstract](55) [PDF 1008KB](4)
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The magnetie field adjustable rod (Trim-rod) and its driving system are the important auxiliary device for beam debugging in CYCIAE-230. To get the magnetic field playing a key role in maintaining the beam alignment and extraction, 16 sets of Trim-rods and driving systems were developed. First, the precise linear actuator from Thomson of The United States was used as the mechanical actuator, whose repeated positioning accuracy is ±0.01 mm. Second, the position sensor adopted the linear displacement electronic ruler from Novotechnik of Germany. The repeated positioning accuracy of the electronic ruler is 0.002 mm. In addition, a negative feedback control loop based on PLC module and linear displacement sensor was adopted in Trim-rods movement regulation. In fact, the positioning accuracy and repeatable precision of Trim-rod drive system were 0.05 mm and ±0.02 mm, respectively. Moreover, the system weat through the electrostatic discharge test, electrical fast transient/Brust test and surge immunity test, all met the requirement of YY 0505-2012/IEC 6060 1-1-2:2004. It is proved that the developed Trim-rod driving system can get high positioning accuracy and repeatable precision in high-dose ionizing radiation, high-density magnetic field and narrow space. It is very significant for radial oscillation amplitude minimization, avoiding coherent oscillation and increasing high beam extraction efficiency.
Corrected proofs  doi: 10.11884/HPLPB202133.200292
[Abstract](69) [PDF 1462KB](12)
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This paper presents a 5.8 GHz high-efficiency dual-polarized rectenna for microwave wireless power transmission. The rectenna consists of a 5.8 GHz dual-polarized receiving antenna and a 5.8 GHz class-F rectifier. A metallic probe is used to integrate the receiving antenna and the rectifier. The receiving antenna is a 2×2 microstrip array antenna and the metal ring loading technology is adopted to improve the rectenna’s impedance bandwidth and robustness. The metal probe instead of the conventional microwave connector and cable is utilized to realize the integration of receiving antenna and rectifier circuit, thus simplifying the structure and reducing the weight, loss and cost of the rectifier antenna. A prototype of the dual-polarized rectenna is fabricated and its rectifying efficiency is measured and compared with the linear-polarized rectenna with the same aperture area. The measured results show that the maximum conversion efficiency of the dual-polarized rectifying antenna reaches 76.8% under the optimum incident power density of 1.47 mW·cm−2. Compared to the linear-polarized rectenna, when the polarization direction of the incident wave varies from 0° to 90°, the conversion efficiency of the rectenna antenna is always above 62% with stable DC output and the rectenna antenna exhibits excellent all-polarization receiving rectification performance.
Corrected proofs  doi: 10.11884/HPLPB202133.200264
[Abstract](61) [PDF 1977KB](10)
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To study the damage effects of lightning electromagnetic pulses on the UAV airborne GPS module, the understanding of the transient interference, permanent damage process and the damage threshold of GPS modules by lightning electromagnetic pulses was obtained, through a combination of simulation and experimental analysis. Based on the analysis results of lightning current, CST was used to simulate the complex electromagnetic field and coupling voltage on the GPS cable. The data communication ports of the typical airborne GPS module was subjected to a lightning pulse injection test. The research results show that: with the continuous enhancement of the injected lightning pulse, the influence on the GPS output waveform kept on increasing. And finally, the function to transmit position information was lost and physical damage occurred. The lightning impulse damage threshold of the GPS data input port is 314.5 V, the lightning impulse damage threshold of the GPS data output port is 235.2 V.
Corrected proofs  doi: 10.11884/HPLPB202133.200259
[Abstract](48) [PDF 984KB](7)
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Superconducting elliptical cavity is a thin-walled structure formed by stamping parts and electron beam welding, and there are inevitable deformations in the machining process, like cell tilt, cell off-axis and cell length deviation. Thus, the axial electric field flatness of the elliptical cavity is affected, and then the operating electric field gradient is reduced. Therefore, pre-tuning is necessary after the elliptical cavity finish processing. The pre-tuning of elliptical cavity is to improve the axial electric field flatness by reshaping the elliptical cavity, including the correction of cell tilt and off-axis, and the correction of cell length. This paper presents the simulation of possible deformation of elliptical cavity by COMSOL multiphysics software and analyzes the influence of cell deformation and tuning displacement on electric field flatness is analyzed, it can provide data reference for CSNS-II elliptical cavity pre-tuning and guide the designing and developing of pre-tuning machine. In addition, it determines the requirements of mechanical deformation to ensure the machining quality of elliptical cavity to meet the actual engineering requirements of CSNS-II.
Corrected proofs  doi: 10.11884/HPLPB202133.200251
[Abstract](91) [PDF 1104KB](7)
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To meet the demand of high-power and wide-band signal sources for G-band vacuum electronic devices, the research on G-band third harmonic amplifier is carried out. The amplifier utilizes the third harmonic current in the nonlinear beam-wave interaction of E-band TWT, and realizes G-band electromagnetic wave amplification by cascading harmonic interaction section. The design scheme of high performance and practical G-band wide-band high-power source adopts folded waveguide slow wave structure with modified circular bends, and the G-band third harmonic amplifier is simulated and optimized by using the microwave tube simulator package (MTSS) software. The result shows that the device can obtain harmonic output power greater than 3.6 W in the range of 15 GHz, with conversion gain＞33.3 dB and electronic efficiency＞0.36%. Compared with other miniaturized terahertz radiation sources in this band, it has superior performance in terms of output power and bandwidth, and thus provides a design basis for the subsequent research of G-band third harmonic amplifier.
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2021, 33: 021001.   doi: 10.11884/HPLPB202133.200309
[Abstract](126) [PDF 650KB](29)
Abstract:

To enhance the thresholds of both stimulated Raman scattering and transverse mode instability, we proposed a novel active Yb-doped fiber with a spindle-shaped core and inner-cladding. An all-fiber main oscillator power amplifier (MOPA) was experimentally established based on this homemade fiber. A maximum power of 5 kW was achieved with the optical-to-optical efficiency of 66.6%, Raman-suppression ratio of ＞45 dB and M2 factor of about 2.0. We believe that the brightness and the efficiency of the laser can be improved by optimizing the structure of the Yb-doped fiber.

2021, 33: 021002.   doi: 10.11884/HPLPB202133.200305
[Abstract](115) [PDF 749KB](23)
Abstract:

An all-fiber supercontinuum generation system is built based on a long tapered photonic crystal fiber with small core diameter, large duty cycle and gragual core change. The system uses high power picoseconds seed source pumping to achieve 314.7 W high power supercontinuum output covering all visible light with spectrum coverage 388−2400 nm. It takes into account high power and blue shift enhancement in the shortwave direction at the same time, and it has the highest power of supercontinuum covering full visible spectrum publicly reported at home and abroad.

2021, 33: 021003.   doi: 10.11884/HPLPB202133.200241
[Abstract](113) [PDF 1022KB](14)
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To improve slow axis beam quality of diode laser (LD) and decrease slow axis divergence angle, a new package with lateral heat flow suppression was designed utilizing the difference in thermal conductivity between air and heat sink. The finite element analysis software was used to analyze the temperature distribution with lateral flow suppression package. It is shown that diode laser chip soldered on trough heat sink with width W=120 μm and length L=4000 μm can reduce slow axis divergence angle about 14%, from 12.25° to 10.49°, when working current was 15A. Correspondingly, beam parameter product (BPP) can reduce from 5.344 mm·mrad to 4.5763 mm·mrad and the brightness of slow axis increased about 5.5% than before. According to the result, the lateral flow suppression package can weaken higher order mode caused by thermal lens effect of diode laser so that decrease slow axis divergence angle effectively.
2021, 33: 021004.   doi: 10.11884/HPLPB202133.200242
[Abstract](88) [PDF 2303KB](21)
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Structured light technology is a typical method for capturing the three-dimensional point cloud data of realistic objects. Structured light images are projected on the surface of the object, which are modulated by the height of the object. Then, the modulated structured light is captured by the camera. Finally, the triangulation principle is used to calculate the three-dimensional surface shape data. To scan the high-precision three-dimensional point cloud of the object, this paper proposes a structured light technology based on Gray code and six-step phase shift method. The structured light based on Gray code is composed of 7 black and white fringe periodic images, and the image can be divided into 128 areas through the gray code decoding operation; the structured light based on six-step phase shift is composed of 6 cosine periodic images with phase difference. Phase shift decoding can subdivide each of the 128 areas into a single pixel. Compared with the cumbersome calculation of six Moiré fringes, the proposed structured light technology based on six-step phase-shift method has less calculation. In the simulation experiment and actual test, the proposed structured light technology showed excellent performance.
2021, 33: 021005.   doi: 10.11884/HPLPB202133.200182
[Abstract](126) [PDF 999KB](20)
Abstract:
To realize of passive-cooling high power fiber cladding light stripper, it is important to optimize the thermal management of both the fiber and the package. By using Teflon capillaries to make segmental etching configuration on fiber, using copper as the package material, and optimizing the package structure through finite element thermal simulations, cladding light stripper capable of handling 500 W power was designed and fabricated. It was experimentally verified that the stripping efficiency reached 23.7 dB and the temperature increase rate on the bare fiber of cladding light stripper was as low as 0.007 ℃/W. In addition, at 540 W of power injection, cladding light stripper could work continuously if mounted on water-cooled cold plate, and could work for 50 s each time if mounted on cold plate filled with phase-change material, with the maximum temperature of package being 58.7 ℃ and 80 ℃ respectively. The researches and results could provide valuable information to the design and development of high power fiber lasers.
2021, 33: 021006.   doi: 10.11884/HPLPB202133.200181
[Abstract](169) [PDF 912KB](21)
Abstract:
High power double cladding fiber Bragg grating (FBG) fabrication based on ultraviolet laser and phase mask method was introduced. A pair of chirped FBGs with 1080 nm central wavelength was made. The reflection spectrum bandwidths were 2 nm and 1 nm, respectively. We adopted these FBGs to construct a fiber oscillator. whose output signal power is up to 502 W.
2021, 33: 022001.   doi: 10.11884/HPLPB202133.200200
[Abstract](102) [PDF 935KB](10)
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The pulse power device will produce a strong electromagnetic environment in the process of discharge, which interferes with diagnostic systems in the experiment, leading to their failure to work properly. By selecting, transforming and delaying the time correlated signals, a trigger network has been established for diagnostic instruments in high energy density experiments on an 8 MA pulsed power device. The jitter of time interval between the trigger signal and the X-ray pulse is less than 2 ns, which meets the requirement to synchronize diagnostics with time resolution of nanosecond. Shielding and grounding techniques are used and effectively eliminate the jamming of strong electromagnetic environment and other stray signals produced by the discharge of the device, which also ensure the normal operation of diagnostic instruments and the quality of the experimental data.
2021, 33: 023001.   doi: 10.11884/HPLPB202133.200257
[Abstract](141) [PDF 2507KB](25)
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High-power waveguide window is a critical component of high-power klystron and accelerator. The RF breakdown of the waveguide window always cause the failure of the high-power klystron. In this paper, the research progress of high-power waveguide window in the international vacuum electronics field is introduced. The research status, manufacturing requirement, and RF breakdown mechanism of the classical pill-box window are presented at first. Then the characters of some new type waveguide windows such as the tapered window, travelling wave in ceramic window, mixed-mode window, and over-mode window are summarized. Some breakdown suppression technologies like changing the material character of the window disk, changing the surface configuration of the window disk, using the positive dielectric angle, applying DC electric field or DC magnetic field, changing the waveform of transverse electric field are emphasized at the end.

2021, 33: 023002.   doi: 10.11884/HPLPB202133.200252
[Abstract](71) [PDF 1273KB](19)
Abstract:
High power helical array antenna fed from planar waveguide is a new type antenna to realize the directional radiation of circularly polarized microwave, which works in C-band. The complexity and the height of the feed structure are reduced by using the planar waveguide. The structure of the basic electric probe is improved, and the coupling quantity is adjusted by controlling the central angle of the sector gap, and the reflection is eliminated by the upper and lower ridge structure. A new structure of short helical antenna is designed to optimize the axial ratio and reflection by separating the parameters, and the axial ratio of the antenna is less than 0.5 dB in the range of −7° to 7°. A 20 units linear feed array is constructed to realize equal amplitude feed by coupling energy from the planar waveguide through the electric probe structure. Finally, a helical array antenna with 20×20 units working in 4.3 GHz is simulated, and the results show that the gain of the antenna is 31.6 dB, and the aperture efficiency is 74%. The reflection is less than −16 dB within the frequency band range of 4.11−4.43 GHz and the power capacity is 3.6 GW.
2021, 33: 023003.   doi: 10.11884/HPLPB202133.200233
[Abstract](66) [PDF 1408KB](11)
Abstract:
The effect of plasma on the transmission properties of electromagnetic waves and its application have always been one of the key research directions of electromagnetic theory and technology and plasma physics. The enhancement effect of collisional plasma on electromagnetic waves is a classic subject of the interaction between electromagnetic waves and plasma. Based on the transmission characteristics of electromagnetic waves in medium, this paper takes plasma as a special medium, and carries out experimental, theoretical and simulation studies on the transmission characteristics of high power microwave (HPM) atmospheric plasma and a certain range of electromagnetic waves under certain experimental conditions. The study found that the plasma formed by the S-band HPM under a vacuum of 50 Pa has a great influence on the electromagnetic wave transmission characteristics of different frequencies, and the electromagnetic wave transmission signal enhancement effect occurs regularly within a certain frequency range. A series of transmission waveforms of continuous electromagnetic waves of different frequencies passing through the HPM plasma area were obtained, and the waveforms were normalized. At 32.4 GHz, the transmission coefficient of continuous electromagnetic waves passing through the plasma area with plasma is about twice as high as that through the area without plasma. A simulation model was established, and the transmission coefficient distribution curve in the range of 31.5−32.5 GHz was obtained. The electromagnetic wave passing through the plasma showed a transmission enhancement effect, and at some frequency points, there was a transmission enhancement of about 1.9 times. The research results provides important technical support for the application of plasma in stealth, emergency communications, and black barrier communications.
2021, 33: 023004.   doi: 10.11884/HPLPB202133.200206
[Abstract](113) [PDF 1093KB](16)
Abstract:
At present, China’s Q/V band low orbit satellite internet project is being vigorously carried out, broadband communications are gradually developing. But the domestic linearization technology is generally limited to narrow band, the related research is not mature. Therefore, it is necessary to design broadband linearizer as soon as possible. In this paper, a Q-band linearizer of traveling-wave tube amplifier (TWTA) for satellite communication has been designed using an analog predistortion technique suitable for space environment. Using the new microstrip transmission structure and the Schottky diode, the ultra-wide instantaneous frequency band can be linearized in the millimeter-wave frequency band. The amplitude distortion and phase distortion of TWTA are greatly improved in the 38−43 GHz (5 GHz) instantaneous frequency band. The linearizer has an in-band amplitude gain of about 4.8−7.2 dB and a phase expansion of about 70°−88° in the input power range of −17−13 dBm. Compared with other linearizers of the same type, this linearizer has higher corresponding frequency and can realize stable linearization of TWTA in a wide instantaneous frequency band.
2021, 33: 023005.   doi: 10.11884/HPLPB202133.200198
[Abstract](116) [PDF 1232KB](12)
Abstract:
Based on the consideration of power capacity and aperture matching to extend the low-frequency operating bandwidth, an ultra-wideband TEM horn antenna with a distributed impedance end-loading structure was designed. First, the gradual coaxial-flat balun structure was optimized, which expands the working bandwidth of the feed structure and improves the feed efficiency. Secondly, the distributed impedance matching design was performed on the exponential TEM horn antenna, and its port characteristics and radiation characteristics were significantly improved. The power pattern and energy pattern were used to evaluate the radiation effect of the antenna. The experimental results show that, compared with the exponential TEM horn antenna, after the distributed impedance matching structure is loaded, the antenna low-frequency bandwidth is widened by 330 MHz, the peak-to-peak value of the antenna main axis radiated electric field is increased by 10%, and the feed efficiency is increased by 17%.
2021, 33: 023006.   doi: 10.11884/HPLPB202133.200153
[Abstract](74) [PDF 1139KB](6)
Abstract:
For the application requirements of high integration and high selectivity of balanced filters, this paper proposes a novel balanced tri-band filter with high selectivity, which is based on an improved asymmetric stepped impedance resonator structure with self-coupling. Firstly, through the differential mode and common mode equivalent circuits of the balanced filter, the resonant characteristics of the resonator structure are specifically analyzed, and the first three resonance modes under the differential mode equivalent circuit are used to form three passbands respectively. In addition, by loading capacitors and resistance elements on the symmetrical surface of the circuit, the suppression of CM signals can be improved without affecting DM signals based on the proposed multimode balanced filter structure and design method, and a balanced tri-band filter with passband frequencies of 2.75/4.46/6.21 GHz was designed, processed and tested. The results show that the structure can achieve a compact size and high selection characteristics, and has good common mode rejection characteristics.
2021, 33: 023007.   doi: 10.11884/HPLPB202133.200149
[Abstract](92) [PDF 864KB](11)
Abstract:
The interaction between space plasma and spacecraft results into the onset of spacecraft surface charging and the resultant electrostatic discharging events. The computation of spacecraft surface charging is commonly accomplished using the secondary electron yield of spacecraft surface irradiated by mono-energetic electrons. To depict the charging environment more precisely and obtain more reliable computation results, focusing the spacecraft charging problem under the worst charging condition and taking into accounts the double-Maxwellian plasma distribution, the threshold equation controlling the onset charging is derived based on the averaged secondary electron yield. This equation is useful to analyze spacecraft charging under the condition of election irradiation with a continuous energy spectrum. Besides, the adoption of double-Maxwellian plasma distribution could better model the space plasma condition in the case of magnetospheric substorm. By theoretical analysis, the ambient plasma is divided into two typical situations according to the charging characteristics of spacecraft surface charging. Through simulation computation, the trend of spacecraft surface charging versus plasma parameters fluctuations is obtained for these two typical situations. Results show that higher electron temperature corresponds to more severe charging with higher negative potential; meanwhile, the density ratio of the two electron components in double-Maxwellian plasma distribution plays an important role in spacecraft surface charging. The obtained conclusions could provide useful reference for quantitative analysis of spacecraft surface severe charging events.
2021, 33: 024001.   doi: 10.11884/HPLPB202133.200216
[Abstract](106) [PDF 1306KB](17)
Abstract:
Vertical tests are very important for superconducting cavity after its post-processing. The aim is to obtain the quality factor versus accelerating gradient curve to evaluate a cavity’s performance. Because of its narrow bandwidth, the superconducting cavity should work stably in the resonant state during the vertical tests. The digital self-excited loop system for the vertical test stand of Peking University is introduced in this paper. The methods of avoiding crosstalk during multi-cell superconducting cavity test were brought out. The influence of deviation from quadruple frequency sampling on amplitude and phase was analyzed. The system is stable and reliable, can effectively distinguish \begin{document}${\text{π}}$\end{document} mode from \begin{document}$8{\rm{{\text{π}}}}/9$\end{document} mode of the 1.3 GHz 9-cell superconducting cavity, and solve the problem of mode crosstalk in multi-cell superconducting cavity test.
2021, 33: 024002.   doi: 10.11884/HPLPB202133.200162
[Abstract](143) [PDF 1221KB](12)
Abstract:
Hybrid bunching-accelerating structure (HBaS) is a novel RF structure integrating a standing-wave(SW) pre-buncher (PB), a traveling-wave (TW) buncher (B) and a standard accelerating structure together. This paper presents the design results, including beam dynamic optimization, microwave design and the cold test of the S-band HBaS prototype, and explicates the reason of transverse emittance increasement caused by the hybrid structure. The low RF power results are in good agreement with the RF design. The measured S11 at operation frequency is less than −45 dB, the phase shift deviation is less than ±2° and the bandwidth is more than 5 MHz (VSWR≤1.2). The axis field distribution fully meets the dynamic requirements.
2021, 33: 024003.   doi: 10.11884/HPLPB202133.200197
[Abstract](111) [PDF 747KB](12)
Abstract:
In one high repetition frequency X-ray free electron laser (XFEL) equipment, the electron gun and compensate solenoid have special structure in the photoinjector, thus the electric field and the magnetic field overlaps near the cathode. The thermal emittance of the cathode should be measured in the experiment. The solenoid scan method used to measure the thermal emittance is not suitable for the overlapping field, because it works effectively only when the rms emittance keeps constant. As the normalized phase space can avoid the influence of the electric field, we tried to use the solenoid scan method in normalized phase space. Using simulation code to do simulations and analysis, we finally demonstrate that this method is feasible for measurement of thermal emittance of the photoinjector which has overlapping field.
2021, 33: 024004.   doi: 10.11884/HPLPB202133.200107
[Abstract](85) [PDF 769KB](5)
Abstract:
By studying the principle of characteristic impedance mismatch of uniform transmission line, it is found that the characteristic impedance mismatch of transmission cable will lead to the distortion of excitation current amplitude of load terminal. The key parameters of main circuit for power supply are analyzed, the amplitude and rise time of the excitation current at the magnet are decreased, when the matching impedance of the uniform transmission line is mismatched. By establishing the equivalent model of barrier point in uniform transmission line, the reflection coefficient at the barrier point of the uniform transmission line is derived. Based on the analysis of series resistance and parallel resistance at the barrier, it is found that the mismatch of transmission line characteristic impedance will lead to the decrease of active power at matching load. It is verified by the breakdown of high voltage cable.
2021, 33: 024005.   doi: 10.11884/HPLPB202133.200229
[Abstract](100) [PDF 1138KB](7)
Abstract:
To study the influence of ion beam perveance condition on the grids erosion velocity for 30 cm diameter ion thruster, we established a beam perveance model and calculated the grids erosion velocity caused by CEX (charge exchange) ions by PIC-MCC method, and then compared and analyzed the calculation results with 1500 h short time life test results. The results show that under the normal beam perveance condition, the mass erosion velocity of the accelerator grid and the decelerator grid are (1.11−1.72)×10−15 kg/s and (1.22−1.26)×10−17 kg/s in 3 kW and 5 kW working modes, respectively. Under 5 kW working mode, when the upstream plasma density of the screen grid reaches 4.03×1017 m−3, the beam is under perveance condition, and the maximum ion erosion velocity of the accelerator grid and the decelerator grid is about 4.33×10−15 kg/s and 4.02×10−15 kg/s respectively. Under 3 kW working mode, when the upstream plasma density of the screen grid reaches 0.22×1017 m−3, the beam is in over perveance condition. Meanwhile, the maximum ion erosion velocity of the accelerator grid and the decelerator grid is about 3.24×10−15 kg/s and 5.01×10−15 kg/s respectively. The life test results show that the calculation value of mass erosion velocity of the accelerator grid hole has a small error to the test value. However, the calculation results of erosion velocity of the decelerator grid hole differ greatly from the test results, which is mainly because of the direct bombardment of the beam ions on the decelerator grid hole. From the current research conclusions, it is considered that the variable aperture design for the screen grid hole is an effective measure to reduce the erosion velocity of the accelerator grid hole and the decelerator grid hole caused by CEX ions when the beam is in under or over perveance condition. In addition, variable aperture design of the grids can significantly improve the working life of the thruster.
2021, 33: 025001.   doi: 10.11884/HPLPB202133.200223
[Abstract](225) [PDF 1468KB](36)
Abstract:
With the wide application of all-solid-state high-voltage pulse generators in the fields of material modification, biomedicine and industry, all-solid-state pulse generators are developing in the direction of miniaturization, intelligence and modularization. To further reduce the volume and cost of the power supply, this paper proposes a positive self-triggering all-solid-state Marx generator topology. It only needs to provide an isolated signal to control the turn-on and turn-off of discharging switch in the first stage, and the gates of the adjacent-stage discharging switches will be automatically charged and discharged through the inter-stage capacitors, so that they turn on and off one by one. This topology makes the driving circuit of the multiple switches in the Marx generators much simpler and does not need to provide a multi-channel driving power supply with isolated power supplies, and also avoids the dynamic and static voltage balancing problems of the switches. Based on this topology, a 17-stage positive polarity Marx generator prototype is built, and the voltage amplitudes and pulse widths are continuously adjustable. It outputs 10 kV positive high-voltage pulses at a repetition frequency of 100 Hz over a 10 kΩ resistive load. The leading edge is approximately 328 ns. The prototype is small in size and stable in work, which verifies the feasibility of this topology.
2021, 33: 025002.   doi: 10.11884/HPLPB202133.200142
[Abstract](56) [PDF 1333KB](5)
Abstract:
Aiming at the arc-drawing problem of rail gun armature at muzzle exit, a muzzle arc suppression scheme based on shunt is proposed in this paper. Taking solid armature as the research object, the simulation model of electromagnetic rail launching system with arc suppression device is established by using Simulink software. The purpose is to achieve the best match between the electrical parameters of the arc suppression device and the electrical parameters of the launch system through the simulation calculation of the different impedance values of the arc suppression device, so as to reduce the influence of the arc suppression branch on the speed of the armature outlet, and at the same time effectively restrain the arc of the muzzle. By optimizing the parameters of resistance and inductance of the arc suppression device, the impedance of the arc suppression branch is far greater than that of the armature branch in bore, and the launch current mostly flows through the armature, which has the least effect on the armature speed. After the armature is out of the muzzle, the impedance of the arc suppression branch is less than that of the arc, thus a reasonable arc rapid elimination is established. The residual energy of the launching system can be released by the arc suppression device to reduce the influence of the muzzle arcing on the launching performance. After the calculation and analysis of the multi parameter values of the resistance and the inductance of the arc suppression device, it is determined that the arc suppression resistance matching the transmission system in this paper is about 1 mΩ, and the inductance is about 1 μH. Combined with the structure of the launching device, the resistance and inductance of the arc suppression device are 1.32 mΩ and 0.124 μH respectively. In the simulation model of the launching system, the launching simulation calculation of the charging voltage 3 kV is carried out. Under the energy level of the charging voltage 3 kV, the arc suppression launching test is carried out. The simulation results are in good agreement with the test results, and the arc suppression effect is good.
2021, 33: 026001.   doi: 10.11884/HPLPB202133.200168
[Abstract](103) [PDF 1035KB](22)
Abstract:
Aiming at the radiation protection and safety requirements of HLS-II (HLS-Ⅱ), a neutron monitor based on embedded EPICS was developed for neutron monitoring of radiation field and environment. The control system of HLS-II is based on EPICS (Experimental Physics and Industrial Control System) architecture. In order to reduce the middle link of the radiation monitoring system and improve the reliability of the personal safety chain of HLS-II, a neutron monitor based on embedded EPICS control system was developed. The key component of the neutron monitor-detector is the BF3 proportional counter tube. By adding a 2 kV positive high voltage bias to the weak electrical signal generated by the proportional counter tube, the AC coupling intervenes in the preamplifier for amplification, and then outputs a pulse signal with a fixed width. The signal is counted by the CORTEX-M3 circuit, and then processed by the CORTEX-A8 circuit to publish the data to the local area network. The performance of the developed monitor has been preliminarily tested by using Am-Be neutron source and on-site radiation environment of HLS-II. The results show that the monitor meets the design requirements and can be used for neutron monitoring.
2021, 33: 026002.   doi: 10.11884/HPLPB202133.200152
[Abstract](57) [PDF 1141KB](6)
Abstract:
The 4.6 GHz low hybrid current drive (LHCD) system is an important part in the EAST tokamak auxiliary heating system. Its cathode high voltage dc power supply is based on pulse stepped modulation (PSM) technology. 64 DC modules are used to output 50 kV dc voltage in series. As the modulation frequency of PSM single module is 50 Hz, the regulation speed of system is limited. In the face of the interference caused by the voltage fluctuation of the network side in the actual operation, the power supply cannot make more rapid response and feedback regulation. It leads to large fluctuation of the output voltage and affects the output performance. To improve the regulation speed and anti-interference capability of system, the high-frequency PSM module with 1 kHz modulation frequency capability was designed to replace some of the original low-frequency modules. The fluctuation of output voltage was suppressed by the rapid regulation capability of the high frequency module. The experimental results show that the output voltage fluctuation of the upgraded power supply is reduced by 50%, which better meets the control requirements of klystron for voltage accuracy and stability, and guarantees the reliability of the system operation.
2021, 33: 029001.   doi: 10.11884/HPLPB202133.200221
[Abstract](178) [PDF 1403KB](9)
Abstract:
Compared with a point laser scanning method, a surface exposure laser melting has advantages of high forming efficiency and low residual stress, which has become a promising new generation selective laser melting of additive manufacturing technology. In this paper, a principle device platform of new generation surface exposure selective laser melting were developed with a light source of 915 nm diode laser, combined with an electrically addressed reflective pure phase liquid crystal spatial light modulator. Its principle experimental verification of surface exposure selective laser melting were implemented. A sample of surface exposure selective laser melting with a “○”-shaped pattern were obtained by using a low melting point metal powder.
2021, 33: 029002.   doi: 10.11884/HPLPB202133.200224
[Abstract](67) [PDF 1405KB](10)
Abstract:
To achieve high-power white LED system with high uniformity and narrow beam, an optical system composed of Chips On Board (COB), compound parabolic reflector, Fresnel lens and aspheric lens is designed. In the design, based on the COB light distribution curve, the light source simulation model of the optical system is built firstly. Then the light source beam is converged by the compound parabolic reflector, and the spill light is controlled by the Fresnel lens. finally, an aspheric lens is used for collimating light source beam. The TracePro software is used for ray tracing simulation. According to the simulated results, an experimental setup is developed for experimental testing. The testing results show that the divergence angle of the optical system is ±7.9°, and the circular uniformity is 96% with the distance of 0.7 m, and the overall light efficiency reaches 60%.

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