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RSS2018 Vol. 30, No. 7
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2018,
30: 1-2.
2018,
30: 071001.
doi: 10.11884/HPLPB201830.170153
Abstract:
RIXS, Resonant Inelastic X-ray Scattering, is an x-ray spectroscopy technique used to investigate the electronic structure of molecules and materials. The requirement of it for source and spectrometer is extremely strict. Mastering its design idea, application method, performance, and so on is of great significance for future research. Through analyzing the design ideas of RIXS spectrometer, using LPF of theory analysis and calculating the varied-line-spacing grating parameters, this paper analyzes each aberration effect on the result of the energy resolution. The relationship between motor encoder and accurate angle of each part of spectrometer is needed during setting up and operating. Thus a non-contact measurement using visible laser was applied and it has been proved to be effective. Before the first commissioning of XFEL, the spectrometer was calibrated by X-ray in synchrotron end station for its energy resolution. The SHADOW program simulation shows that the performance of spectrometer meets the requirement of design and experiment.
RIXS, Resonant Inelastic X-ray Scattering, is an x-ray spectroscopy technique used to investigate the electronic structure of molecules and materials. The requirement of it for source and spectrometer is extremely strict. Mastering its design idea, application method, performance, and so on is of great significance for future research. Through analyzing the design ideas of RIXS spectrometer, using LPF of theory analysis and calculating the varied-line-spacing grating parameters, this paper analyzes each aberration effect on the result of the energy resolution. The relationship between motor encoder and accurate angle of each part of spectrometer is needed during setting up and operating. Thus a non-contact measurement using visible laser was applied and it has been proved to be effective. Before the first commissioning of XFEL, the spectrometer was calibrated by X-ray in synchrotron end station for its energy resolution. The SHADOW program simulation shows that the performance of spectrometer meets the requirement of design and experiment.
2018,
30: 071002.
doi: 10.11884/HPLPB201830.170404
Abstract:
When a vortex beam is generated by liquid crystal spatial light modulator (LCSLM), the polarization direction of the incident light has a significant effect on generating the vortex. Based on the physical principle of the spatial light modulator, the influence of the polarization directions of the incident light on the output beam is calculated and analyzed, and the calculation is compared with the experimental results. The results show that, the modulation error of the LCSLM increases with the angle between the polarization direction of the incident light and the optical axis of the liquid crystal molecule, and the quality of vortex beam is worse. In particular, the quality of the vortex beam is significantly worse when the angle of the angle is greater than 4.725°. As the angle continues to increase, the modulation effect of LCSLM on the incident light is weakened, and the vortex beam can not be generated.
When a vortex beam is generated by liquid crystal spatial light modulator (LCSLM), the polarization direction of the incident light has a significant effect on generating the vortex. Based on the physical principle of the spatial light modulator, the influence of the polarization directions of the incident light on the output beam is calculated and analyzed, and the calculation is compared with the experimental results. The results show that, the modulation error of the LCSLM increases with the angle between the polarization direction of the incident light and the optical axis of the liquid crystal molecule, and the quality of vortex beam is worse. In particular, the quality of the vortex beam is significantly worse when the angle of the angle is greater than 4.725°. As the angle continues to increase, the modulation effect of LCSLM on the incident light is weakened, and the vortex beam can not be generated.
Characterization and optical properties investigation of pulsed laser deposited MgxNi1-xO alloy film
2018,
30: 071003.
doi: 10.11884/HPLPB201830.180068
Abstract:
A series of MgxNi1-xO alloy films were prepared by pulsed laser deposition.In the procedure, the laser energy density was fixed at 5 J/cm2, while the temperature of heated substrate varied from 300 ℃ to 700 ℃.The composition and microstructure of the as deposited films were characterized by atomic force microscopy(AFM), transmission electron microscopy(TEM) and X -ray photoelectron spectroscopy(XPS). The influence of annealing on the sample was also studied. UV-VIS spectrophotometer was used to analyse the transmittance of the films. Some interesting results were obtained. The as deposited MgxNi1-xO film was found constituted by crystalline component and amorphous one. The ultraviolet absorption edge were located at about 290 nm, near the superior limit of solar-blind wavelength. It is also found that the film prepared at 5 J/cm2-500 ℃ have strong absorption within short wave range, but scarce absorption in infrared and visible wave band, which is useful to ultraviolet detection.The annealing treatment was very effective to improve the surface quality of the film, but had little effect on the optical band gap.
A series of MgxNi1-xO alloy films were prepared by pulsed laser deposition.In the procedure, the laser energy density was fixed at 5 J/cm2, while the temperature of heated substrate varied from 300 ℃ to 700 ℃.The composition and microstructure of the as deposited films were characterized by atomic force microscopy(AFM), transmission electron microscopy(TEM) and X -ray photoelectron spectroscopy(XPS). The influence of annealing on the sample was also studied. UV-VIS spectrophotometer was used to analyse the transmittance of the films. Some interesting results were obtained. The as deposited MgxNi1-xO film was found constituted by crystalline component and amorphous one. The ultraviolet absorption edge were located at about 290 nm, near the superior limit of solar-blind wavelength. It is also found that the film prepared at 5 J/cm2-500 ℃ have strong absorption within short wave range, but scarce absorption in infrared and visible wave band, which is useful to ultraviolet detection.The annealing treatment was very effective to improve the surface quality of the film, but had little effect on the optical band gap.
2018,
30: 072001.
doi: 10.11884/HPLPB201830.170529
Abstract:
Reflector system is an important part of the laser facility, whose rotation stability has a direct effect on the beam's propagation. Aiming at the stability problem of large-scale precision mirror mount caused by ground random vibration, the formula about the root mean square (RMS) of mirror's rotation angle is deduced. The finite element (FE) model of a reflector system is built in ANSYS, the modal analysis and the micro-vibration calculations are done on the FE model. The RMS rotation angle of the mirror is calculated according to the simulation result. At the same time, another engineering approach to calculate the RMS rotation angle of the mirror is presented by FE simulation. The results of the two approaches are consistent, which shows that the approaches to calculate rotation angle of mirror are effective and reasonable.
Reflector system is an important part of the laser facility, whose rotation stability has a direct effect on the beam's propagation. Aiming at the stability problem of large-scale precision mirror mount caused by ground random vibration, the formula about the root mean square (RMS) of mirror's rotation angle is deduced. The finite element (FE) model of a reflector system is built in ANSYS, the modal analysis and the micro-vibration calculations are done on the FE model. The RMS rotation angle of the mirror is calculated according to the simulation result. At the same time, another engineering approach to calculate the RMS rotation angle of the mirror is presented by FE simulation. The results of the two approaches are consistent, which shows that the approaches to calculate rotation angle of mirror are effective and reasonable.
2018,
30: 072002.
doi: 10.11884/HPLPB201830.170512
Abstract:
Measurement of fusion reaction history by detecting the 16.7 MeV gamma-rays needs high neutron yield. For this reason, simulation study for fusion reaction history diagnosis with inelastic gammas generated by 14 MeV neutron interacting with the puck in front of (Gas Cherenkov Detector, GCD) was carried out. Material and thickness of the puck were determined by calculating energy spectrum of the secondary gamma and yield of gammas above the Cherenkov threshold. Cherenkov signal of the inelastic gammas through the GCD generated by interaction of 14 MeV neutron with the puck was simulated. Noises of gammas, electrons and positrons at the photo-electric conversion device were analyzed. Relation of the statistical fluctuations of the Cherenkov detection system and the fusion neutron yield was ascertained. Fusion neutron yield for fusion reaction history diagnosis by detecting 14 MeV neutron can decrease by two magnitudes in comparison with that by directly detecting 16.7 MeV gamma rays.
Measurement of fusion reaction history by detecting the 16.7 MeV gamma-rays needs high neutron yield. For this reason, simulation study for fusion reaction history diagnosis with inelastic gammas generated by 14 MeV neutron interacting with the puck in front of (Gas Cherenkov Detector, GCD) was carried out. Material and thickness of the puck were determined by calculating energy spectrum of the secondary gamma and yield of gammas above the Cherenkov threshold. Cherenkov signal of the inelastic gammas through the GCD generated by interaction of 14 MeV neutron with the puck was simulated. Noises of gammas, electrons and positrons at the photo-electric conversion device were analyzed. Relation of the statistical fluctuations of the Cherenkov detection system and the fusion neutron yield was ascertained. Fusion neutron yield for fusion reaction history diagnosis by detecting 14 MeV neutron can decrease by two magnitudes in comparison with that by directly detecting 16.7 MeV gamma rays.
2018,
30: 073001.
doi: 10.11884/HPLPB201830.170469
Abstract:
Pulse compression is an effective means for increasing the output peak power of microwave sources, the coupling coefficient characterizes the coupling strength between the input waveguide and the storage cavity. In order to change the coupling coefficient in different stages of active SLED compression experiment, a pulse compressor system with adjustable coupling coefficient was designed by the adapter function of H-T waveguide junction and shorting piston. The adjustment capability of the waveguide H-T was analyzed based on the scattering matrix theory. The passive SLED pulse compression experiment was carried out by single storage cavity when the 3dB coupler was replaced by a high power waveguide circulator. The experiment results show that the adjustment capability of the waveguide junction agrees with that of the theoretical analysis.
Pulse compression is an effective means for increasing the output peak power of microwave sources, the coupling coefficient characterizes the coupling strength between the input waveguide and the storage cavity. In order to change the coupling coefficient in different stages of active SLED compression experiment, a pulse compressor system with adjustable coupling coefficient was designed by the adapter function of H-T waveguide junction and shorting piston. The adjustment capability of the waveguide H-T was analyzed based on the scattering matrix theory. The passive SLED pulse compression experiment was carried out by single storage cavity when the 3dB coupler was replaced by a high power waveguide circulator. The experiment results show that the adjustment capability of the waveguide junction agrees with that of the theoretical analysis.
2018,
30: 073002.
doi: 10.11884/HPLPB201830.170491
Abstract:
This paper studies a high efficiency X-band over-mode relativistic backward wave oscillator (RBWO), which is composed of a dual-cavity reflector, a 7-periods trapezoid SWS and extraction cavity. The ratio of D to λ of the generator is 2.6, and the electron beam interacts with the TM01 near π mode of the structure wave. In the SWS region the TM01 mode surface wave mainly transfers to the TM02 mode body wave, the primary mode of the output microwave is TM02 mode with the proportion 81%, and the remainder is TM01 mode. A method to design the resonant reflector under over-mode condition is proposed, a dual-cylindrical cavity reflector is optimized by using the mode-matching method, and the reflection coefficients for the TM01 and TM02 modes are larger than 0.99, hence good insulation between the SWS and the diode is achieved. Simultaneously, the longitudinal electric field of the resonant reflector could pre-modulate the electron beam sufficiently, which would promote the beam-wave interaction in the SWS. Furthermore, the transfer coefficient is increased by loading the extraction cavity after the SWS. Simulation results indicate that microwave output power of 6.6 GW is achieved, the diode voltage is 900 kV and beam current is 14.3 kA, and the transfer efficiency is 51%.
This paper studies a high efficiency X-band over-mode relativistic backward wave oscillator (RBWO), which is composed of a dual-cavity reflector, a 7-periods trapezoid SWS and extraction cavity. The ratio of D to λ of the generator is 2.6, and the electron beam interacts with the TM01 near π mode of the structure wave. In the SWS region the TM01 mode surface wave mainly transfers to the TM02 mode body wave, the primary mode of the output microwave is TM02 mode with the proportion 81%, and the remainder is TM01 mode. A method to design the resonant reflector under over-mode condition is proposed, a dual-cylindrical cavity reflector is optimized by using the mode-matching method, and the reflection coefficients for the TM01 and TM02 modes are larger than 0.99, hence good insulation between the SWS and the diode is achieved. Simultaneously, the longitudinal electric field of the resonant reflector could pre-modulate the electron beam sufficiently, which would promote the beam-wave interaction in the SWS. Furthermore, the transfer coefficient is increased by loading the extraction cavity after the SWS. Simulation results indicate that microwave output power of 6.6 GW is achieved, the diode voltage is 900 kV and beam current is 14.3 kA, and the transfer efficiency is 51%.
2018,
30: 073003.
doi: 10.11884/HPLPB201830.170436
Abstract:
The structure and working principle of a Ka-band RBWO operating at TM02 mode with low guiding magnetic field was introduced, and mechanism of the TM02 mode selection was analyzed. The PIC (particle-in-cell) simulation shows the output power and frequency of the RBWO were 493 MW and 29.3 GHz respectively with guiding magnetic field of 1 T. The operating mode and frequency were corresponding to the theoretic design. The experiment study was done based on the parameters in simulation. A 29.3 GHz millimeter wave with an output power of 286 MW and pulse width of 10 ns was obtained at guiding magnetic field, diode voltage and current of 1 T, 580 kV and 3.56 kA respectively. The frequency of microwave in experiment was in accordance with that in simulation. However, the output power in experiment was much lower, and the pulse width was shortened at post end evidently, which was considered as a result of electrons bombarding at the post cascaded resonators.
The structure and working principle of a Ka-band RBWO operating at TM02 mode with low guiding magnetic field was introduced, and mechanism of the TM02 mode selection was analyzed. The PIC (particle-in-cell) simulation shows the output power and frequency of the RBWO were 493 MW and 29.3 GHz respectively with guiding magnetic field of 1 T. The operating mode and frequency were corresponding to the theoretic design. The experiment study was done based on the parameters in simulation. A 29.3 GHz millimeter wave with an output power of 286 MW and pulse width of 10 ns was obtained at guiding magnetic field, diode voltage and current of 1 T, 580 kV and 3.56 kA respectively. The frequency of microwave in experiment was in accordance with that in simulation. However, the output power in experiment was much lower, and the pulse width was shortened at post end evidently, which was considered as a result of electrons bombarding at the post cascaded resonators.
2018,
30: 073004.
doi: 10.11884/HPLPB201830.170441
Abstract:
In this paper, a real-time vacuum measurement system is designed for the static vacuum maintaining and repetition frequency operation of Magnetically Insulated Transmission Line Oscillator(MILO). By optimizing the conventional vacuum measurement method, this system realizes the real-time monitoring of vacuum and data acquisition. Experiments of real-time vacuum measurement in the MILO were carried out on a 30 GW pulse power driver. Results show that this system has good anti-electromagnetic interference ability. Meanwhile, accurate pressures and pulse deflation characteristics can be well obtained. Under repetition frequency operation, this vacuum measurement system can provide technical support for parameter diagnosis of HPM sources.
In this paper, a real-time vacuum measurement system is designed for the static vacuum maintaining and repetition frequency operation of Magnetically Insulated Transmission Line Oscillator(MILO). By optimizing the conventional vacuum measurement method, this system realizes the real-time monitoring of vacuum and data acquisition. Experiments of real-time vacuum measurement in the MILO were carried out on a 30 GW pulse power driver. Results show that this system has good anti-electromagnetic interference ability. Meanwhile, accurate pressures and pulse deflation characteristics can be well obtained. Under repetition frequency operation, this vacuum measurement system can provide technical support for parameter diagnosis of HPM sources.
2018,
30: 073005.
doi: 10.11884/HPLPB201830.170532
Abstract:
High power microwave research is moving into the high rep-rate regime and it will be common that an electron beam accelerator operates more than a million shots per year. As a result, accumulated bremsstrahlung X-ray produced by the electron beam collector is no longer negligible, and shielding is necessary for personnel safety. By using the BEAMnrc Monte-Carlo code, a typical collector for a ring beam usually used in HPM tube is simulated, which has beam voltage 1 MV, beam current 10 kA, pulse duration 100 ns and rep-rate 100 Hz. The results show the spectrum and spatial distribution of the X-ray generated at the collector. The attenuation factor of the X-ray is estimated from the simulation. The estimation of the skyshine radiation is also considered for the roof of the building.
High power microwave research is moving into the high rep-rate regime and it will be common that an electron beam accelerator operates more than a million shots per year. As a result, accumulated bremsstrahlung X-ray produced by the electron beam collector is no longer negligible, and shielding is necessary for personnel safety. By using the BEAMnrc Monte-Carlo code, a typical collector for a ring beam usually used in HPM tube is simulated, which has beam voltage 1 MV, beam current 10 kA, pulse duration 100 ns and rep-rate 100 Hz. The results show the spectrum and spatial distribution of the X-ray generated at the collector. The attenuation factor of the X-ray is estimated from the simulation. The estimation of the skyshine radiation is also considered for the roof of the building.
2018,
30: 073006.
doi: 10.11884/HPLPB201830.170530
Abstract:
Without the power scanning function, the traditional Particle-in-Cell simulation software needs to perform many times in order to achieve multipactor threshold prediction. Therefore, an adaptive scanning method is proposed without considering the self-consistent field generated by electrons. Under the effect of the electromagnetic field distribution calculated by MSAT, the electron motion is tracked and updated with leapfrog algorithm. Secondary electrons are released once electrons reach the boundaries of the simulation region. The criterion for determining multipactor occurrence is established according to the particle number curve via the multipactor simulation. Meanwhile, the power input is adaptively adjusted by the bisection method so that the multipactor threshold can be automatically determined with a given initial power. For verification, multipactor thresholds of stepped impedance transformer and coaxial cavity filters obtained with adaptive-scanning method are compared with experiments. And the simulation results accord well with the experimental data.
Without the power scanning function, the traditional Particle-in-Cell simulation software needs to perform many times in order to achieve multipactor threshold prediction. Therefore, an adaptive scanning method is proposed without considering the self-consistent field generated by electrons. Under the effect of the electromagnetic field distribution calculated by MSAT, the electron motion is tracked and updated with leapfrog algorithm. Secondary electrons are released once electrons reach the boundaries of the simulation region. The criterion for determining multipactor occurrence is established according to the particle number curve via the multipactor simulation. Meanwhile, the power input is adaptively adjusted by the bisection method so that the multipactor threshold can be automatically determined with a given initial power. For verification, multipactor thresholds of stepped impedance transformer and coaxial cavity filters obtained with adaptive-scanning method are compared with experiments. And the simulation results accord well with the experimental data.
2018,
30: 073007.
doi: 10.11884/HPLPB201830.170302
Abstract:
This article presents a measurement on the testing environment of an airship lifting platform in real test range scene and moderate weather condition. The results show that the heading azimuth of the airship is more stable under fixed orientation flying mode than under fixed flight path mode, while the elevation and rolling angular stabilities under the two flying modes are almost undistinguishable. Statistical analysis proves that the equipped antenna stabilizing platform can isolate the carrier's angular shake as high as ±10° and continuously control the antenna beam axis to aim at the ground target with error within ±1°. The 20-40 km distance tests show that the airship carried receiving antenna with 4.5° beam width suffered a 1 dB gain loss and ±1 dB signal level fluctuation under head-on flying path, while the results degenerate to 2.3 dB gain loss and ±3 dB signal level fluctuation in lateral flying path. The article also presents some testing results about the airship lifting platform's EM scattering environment rooting from its metal structure as well as the test range's rough ground.
This article presents a measurement on the testing environment of an airship lifting platform in real test range scene and moderate weather condition. The results show that the heading azimuth of the airship is more stable under fixed orientation flying mode than under fixed flight path mode, while the elevation and rolling angular stabilities under the two flying modes are almost undistinguishable. Statistical analysis proves that the equipped antenna stabilizing platform can isolate the carrier's angular shake as high as ±10° and continuously control the antenna beam axis to aim at the ground target with error within ±1°. The 20-40 km distance tests show that the airship carried receiving antenna with 4.5° beam width suffered a 1 dB gain loss and ±1 dB signal level fluctuation under head-on flying path, while the results degenerate to 2.3 dB gain loss and ±3 dB signal level fluctuation in lateral flying path. The article also presents some testing results about the airship lifting platform's EM scattering environment rooting from its metal structure as well as the test range's rough ground.
2018,
30: 073008.
doi: 10.11884/HPLPB201830.170531
Abstract:
In this paper, a high power planar antenna without phase shifter is designed. This antenna realizes the function of space beam scanning through the phase distribution change of the aperture field via strata radiatum self-rotating, and realizes the requirements of light weight, and low profile integration. The gain of the antenna is 36 dB, the beam scanning range is from -30° to +30°, the power capability level is GW, the frequency range is Ku. We fabricated the antenna and tested its parameters, the results indicate that the antenna has high technical index in beam scanning and high aperture radiation efficiency. Compared with the traditional phased array antennae, this antenna can realize phase regulation, change the beam pointing without phase-shifted feed network, and it has the advantages such as simple servo, compact structure, low profile and low weight. This antenna can be applied to the surface conformal emission technique of the airborne, vehicular, shipboard high power weapon system.
In this paper, a high power planar antenna without phase shifter is designed. This antenna realizes the function of space beam scanning through the phase distribution change of the aperture field via strata radiatum self-rotating, and realizes the requirements of light weight, and low profile integration. The gain of the antenna is 36 dB, the beam scanning range is from -30° to +30°, the power capability level is GW, the frequency range is Ku. We fabricated the antenna and tested its parameters, the results indicate that the antenna has high technical index in beam scanning and high aperture radiation efficiency. Compared with the traditional phased array antennae, this antenna can realize phase regulation, change the beam pointing without phase-shifted feed network, and it has the advantages such as simple servo, compact structure, low profile and low weight. This antenna can be applied to the surface conformal emission technique of the airborne, vehicular, shipboard high power weapon system.
2018,
30: 073009.
doi: 10.11884/HPLPB201830.170490
Abstract:
In this paper, the nonlinear characteristics of the amplitude and phase of a single Schottky diode and series and parallel analog pre-distortion circuit are analyzed. The simulation results show that the diode can be used as an adjustable core component of an analog pre-distortion circuit. By using the transmission matrix, it is found that connecting the Schottky diodes in different positions of the predistortion circuit and selecting serial or parallel modes can improve the amplitude and phase compensation curves. The simulation results show that connecting a Schottky diode in series or in parallel at different positions of the circuit can effectively change the position and slope of the curve, so as to obtain an ideal target curve shape.
In this paper, the nonlinear characteristics of the amplitude and phase of a single Schottky diode and series and parallel analog pre-distortion circuit are analyzed. The simulation results show that the diode can be used as an adjustable core component of an analog pre-distortion circuit. By using the transmission matrix, it is found that connecting the Schottky diodes in different positions of the predistortion circuit and selecting serial or parallel modes can improve the amplitude and phase compensation curves. The simulation results show that connecting a Schottky diode in series or in parallel at different positions of the circuit can effectively change the position and slope of the curve, so as to obtain an ideal target curve shape.
2018,
30: 073101.
doi: 10.11884/HPLPB201830.180029
Abstract:
A dual-band microstrip antenna operating in the terahertz band is proposed. Two rectangular patches are loaded at 45° and 135° on the antenna's radiating patch to increase the radiation area and the impedance bandwidth at the high frequency resonance point. By introducing a defected ground structure(DGS), the current path of the antenna at the ground plate is changed and coupled with the radiation patch so as to realize dual frequency characteristics. In order to increase the gain of the antenna, several parasitic rectangular patches are loaded on the edge of the radiating patch. To further improve the antenna gain, the thickness of the substrate at the parasitic patch is increased, so that the antenna can simultaneously operate well at two bands, namely 520 GHz (508-532 GHz) and 680 GHz (581-766 GHz). The corresponding maximum gains are 3.54 dB and 4.11 dB respectively. One of the relative bandwidth at high frequency reached 27.5%. The dual-band antenna has the characteristics of simple structure and stable performance, and it has the application value for terahertz communications and wireless transmission systems.
A dual-band microstrip antenna operating in the terahertz band is proposed. Two rectangular patches are loaded at 45° and 135° on the antenna's radiating patch to increase the radiation area and the impedance bandwidth at the high frequency resonance point. By introducing a defected ground structure(DGS), the current path of the antenna at the ground plate is changed and coupled with the radiation patch so as to realize dual frequency characteristics. In order to increase the gain of the antenna, several parasitic rectangular patches are loaded on the edge of the radiating patch. To further improve the antenna gain, the thickness of the substrate at the parasitic patch is increased, so that the antenna can simultaneously operate well at two bands, namely 520 GHz (508-532 GHz) and 680 GHz (581-766 GHz). The corresponding maximum gains are 3.54 dB and 4.11 dB respectively. One of the relative bandwidth at high frequency reached 27.5%. The dual-band antenna has the characteristics of simple structure and stable performance, and it has the application value for terahertz communications and wireless transmission systems.
2018,
30: 073201.
doi: 10.11884/HPLPB201830.180047
Abstract:
Thin slots with complex configurations used in practical engineering make the evaluation of electromagnetic shielding effectiveness(SE) for metallic enclosure increasingly challenging. The contour path (CP) method is adopted to deal with the complex thin slots in order to keep the coarse gridding in FDTD programming. An equivalent model with simple configuration is presented to replace the complex nested slits, and as a result, the programming and calculation efficiency of the CP-FDTD method is improved when dealing with thin slots with complex configurations. The equivalent model and CP-FDTD are used to calculate the SE of metallic enclosure with two typical kinds of thin slot configurations at the wide frequency range respectively. Results are in good agreements with those obtained by using fine-gridded FDTD, and high calculation efficiency is achieved at the same time.
Thin slots with complex configurations used in practical engineering make the evaluation of electromagnetic shielding effectiveness(SE) for metallic enclosure increasingly challenging. The contour path (CP) method is adopted to deal with the complex thin slots in order to keep the coarse gridding in FDTD programming. An equivalent model with simple configuration is presented to replace the complex nested slits, and as a result, the programming and calculation efficiency of the CP-FDTD method is improved when dealing with thin slots with complex configurations. The equivalent model and CP-FDTD are used to calculate the SE of metallic enclosure with two typical kinds of thin slot configurations at the wide frequency range respectively. Results are in good agreements with those obtained by using fine-gridded FDTD, and high calculation efficiency is achieved at the same time.
2018,
30: 073202.
doi: 10.11884/HPLPB201830.180048
Abstract:
The feasibility of mode stirred reverberation chambers(MSRCs) constructed by using flexible shielding materials is investigated, whose uneven walls enable them easily meet the requirements of the statistic characteristics of isotropic, uniform distribution and random polarization. The field uniformity and the probability density function(PDF) of normalized electric field are measured, and the results are in accordance with the standard IEC 61000-4-21-2011 and the PDF of ideal MSRC model. Then the influence of the stirrer rotation speed, antenna height and position on PDF of normalized electric field is analyzed experimentally. Finally, the flexible shielding material based reverberation chamber is used to measure the shielding effectiveness(SE) of an electrically large cavity with and without water load, demonstrating a good feasibility.
The feasibility of mode stirred reverberation chambers(MSRCs) constructed by using flexible shielding materials is investigated, whose uneven walls enable them easily meet the requirements of the statistic characteristics of isotropic, uniform distribution and random polarization. The field uniformity and the probability density function(PDF) of normalized electric field are measured, and the results are in accordance with the standard IEC 61000-4-21-2011 and the PDF of ideal MSRC model. Then the influence of the stirrer rotation speed, antenna height and position on PDF of normalized electric field is analyzed experimentally. Finally, the flexible shielding material based reverberation chamber is used to measure the shielding effectiveness(SE) of an electrically large cavity with and without water load, demonstrating a good feasibility.
2018,
30: 073203.
doi: 10.11884/HPLPB201830.170401
Abstract:
In order to meet the requirements of anti EMP performance test of the difference size effect test compounds, and to generate the simulated EMP environments with more comprehensive coverage and more ideal waveform, in the paper, the basic composition and working principle of the EMP-simulator diver with one-stage pulse sharpening and based on the Marx generator are introduced. According to the actual experiences of design and debugging of this kind of devices, some problems that may be encountered when using the ideal principle to design these drivers are analyzed, and some targeted solutions are provided. In addition, some drivers for the small-and-middle scale EMP simulator with rated output voltage of 100-600 kV are developed. With the development of super compact Marx generator, compact flat-form film capacitor and low inductance output switch, the optimization of the connection structure, and the selection of reasonable parameters, these drivers connected with the load of 120-180 Ω can produce the ideal double exponential waveforms with the rise time of 1.2-2.7 ns and the half width of 32-41 ns.
In order to meet the requirements of anti EMP performance test of the difference size effect test compounds, and to generate the simulated EMP environments with more comprehensive coverage and more ideal waveform, in the paper, the basic composition and working principle of the EMP-simulator diver with one-stage pulse sharpening and based on the Marx generator are introduced. According to the actual experiences of design and debugging of this kind of devices, some problems that may be encountered when using the ideal principle to design these drivers are analyzed, and some targeted solutions are provided. In addition, some drivers for the small-and-middle scale EMP simulator with rated output voltage of 100-600 kV are developed. With the development of super compact Marx generator, compact flat-form film capacitor and low inductance output switch, the optimization of the connection structure, and the selection of reasonable parameters, these drivers connected with the load of 120-180 Ω can produce the ideal double exponential waveforms with the rise time of 1.2-2.7 ns and the half width of 32-41 ns.
2018,
30: 073204.
doi: 10.11884/HPLPB201830.170465
Abstract:
The electromagnetic field simulation software CST based on the finite integral method was used to simulate and analyze the influence of the metal plate on the distribution of the available test volume and external radiated field in the large-scale parallel wire-grid bounded-wave simulator. First of all, the simulation model of the parallel wire-grid bounded-wave simulator was established, and its rationality was proved according to GJB 8848. Then the influence of the metal plate on the electric field distribution of the available test volume inside the simulator was analyzed in detail, and the effect of the location, thickness, height, and length of the metal plate were listed through detailed data. Moreover, the shielding effect of the metal plate on the external radiated electric field of the simulator was discussed. Finally, several suggestions for setting the metal protection plate were proposed. The conclusion is a good reference for effectively shielding the external radiation field without affecting the internal electric field distribution of the bounded-wave simulator.
The electromagnetic field simulation software CST based on the finite integral method was used to simulate and analyze the influence of the metal plate on the distribution of the available test volume and external radiated field in the large-scale parallel wire-grid bounded-wave simulator. First of all, the simulation model of the parallel wire-grid bounded-wave simulator was established, and its rationality was proved according to GJB 8848. Then the influence of the metal plate on the electric field distribution of the available test volume inside the simulator was analyzed in detail, and the effect of the location, thickness, height, and length of the metal plate were listed through detailed data. Moreover, the shielding effect of the metal plate on the external radiated electric field of the simulator was discussed. Finally, several suggestions for setting the metal protection plate were proposed. The conclusion is a good reference for effectively shielding the external radiation field without affecting the internal electric field distribution of the bounded-wave simulator.
2018,
30: 073205.
doi: 10.11884/HPLPB201830.170475
Abstract:
A conformal leapfrog alternating direction implicit finite-difference time-domain (CLeapfrog ADI-FDTD) method based on conformal technique was proposed in the article. Compared with the conventional FDTD method, the proposed method decreased the step approximation error, it was used to simulate the irregular object whose boundary couldn't match the orthogonal grid; at the same time, this method could have a high efficiency because leapfrog alternating direction implicit finite-difference time-domain (Leapfrog ADI-FDTD) is a method with unconditional stability. However, CLeapfrog ADI-FDTD method may lose the stability expected with the Leapfrog ADI-FDTD schemes, and instability factor in CLeapfrog ADI-FDTD was analyzed through eigenvalue of the growth matrix, then a new method named improved conformal leapfrog alternating direction implicit finite-difference time-domain (ICLeapfrog ADI-FDTD) with a modified conformal technique was proposed, which could improve the stability without losing the calculation accuracy. The accuracy and efficiency of the proposed ICLeapfrog ADI-FDTD method were verified by numerical results.
A conformal leapfrog alternating direction implicit finite-difference time-domain (CLeapfrog ADI-FDTD) method based on conformal technique was proposed in the article. Compared with the conventional FDTD method, the proposed method decreased the step approximation error, it was used to simulate the irregular object whose boundary couldn't match the orthogonal grid; at the same time, this method could have a high efficiency because leapfrog alternating direction implicit finite-difference time-domain (Leapfrog ADI-FDTD) is a method with unconditional stability. However, CLeapfrog ADI-FDTD method may lose the stability expected with the Leapfrog ADI-FDTD schemes, and instability factor in CLeapfrog ADI-FDTD was analyzed through eigenvalue of the growth matrix, then a new method named improved conformal leapfrog alternating direction implicit finite-difference time-domain (ICLeapfrog ADI-FDTD) with a modified conformal technique was proposed, which could improve the stability without losing the calculation accuracy. The accuracy and efficiency of the proposed ICLeapfrog ADI-FDTD method were verified by numerical results.
2018,
30: 074101.
doi: 10.11884/HPLPB201830.180007
Abstract:
There are many initial design methods for microstrip interdigital filter with tapped-line but the design methods are not complate, concise and accurate enough, so a set of initial design flow with completeness and conciseness is given. The design steps are as follows: index "standardization", determine the low-pass prototype filter, determine the order of the filter, determine the normalized conductance value, design tapped line length and width, design resonator width, design non-input/output resonator length, design adjacent resonator spacing, design input/output resonator length and tapped line position, integral modeling and simulation of interdigital filter. Finally, taking the initial design of Ka-band filter as an example, the initial design results show that the center frequency is about 30.19 GHz, the passband range is slightly larger than 29.40-31.00 GHz, the maximum insertion loss is 4.21 dB, the minimum return loss is 9.35 dB, the stopband rejection of 27.00 GHz and 33.40 GHz is more than 30.00 dB, which basically meet the design indexes, only a little optimization is needed to fully meet the design indexes, and the feasibility and high accuracy of the design flow are verified.
There are many initial design methods for microstrip interdigital filter with tapped-line but the design methods are not complate, concise and accurate enough, so a set of initial design flow with completeness and conciseness is given. The design steps are as follows: index "standardization", determine the low-pass prototype filter, determine the order of the filter, determine the normalized conductance value, design tapped line length and width, design resonator width, design non-input/output resonator length, design adjacent resonator spacing, design input/output resonator length and tapped line position, integral modeling and simulation of interdigital filter. Finally, taking the initial design of Ka-band filter as an example, the initial design results show that the center frequency is about 30.19 GHz, the passband range is slightly larger than 29.40-31.00 GHz, the maximum insertion loss is 4.21 dB, the minimum return loss is 9.35 dB, the stopband rejection of 27.00 GHz and 33.40 GHz is more than 30.00 dB, which basically meet the design indexes, only a little optimization is needed to fully meet the design indexes, and the feasibility and high accuracy of the design flow are verified.
2018,
30: 074102.
doi: 10.11884/HPLPB201830.180026
Abstract:
To meet the requirements of co-phase diffraction limit imaging, a high resolution tip/tilt mirror(TM) for multi-mirror ground-based telescope is proposed and designed. Three dumbbell-shaped flexible hinges and rhombus attenuated displacement structures (RADSs) were used in the TM system as the moving transmission devices, and three piezoelectric stack actuators (PSAs) were applied as driving components. The structure parameters of the flexible hinges and RADSs were optimized by theoretical, experimental and simulative methods. The experimental results show that the TM has an extreme high angular resolution of 0.017″, and the mechanical excursion angle is larger than 0.24′ with a natural frequency of 136.97 Hz, which accord well with the results of the theoretical estimation and finite element analyzing (FEA) simulation. The high angular resolution property indicates the multi-mirror telescope can achieve the imaging in diffraction limit.
To meet the requirements of co-phase diffraction limit imaging, a high resolution tip/tilt mirror(TM) for multi-mirror ground-based telescope is proposed and designed. Three dumbbell-shaped flexible hinges and rhombus attenuated displacement structures (RADSs) were used in the TM system as the moving transmission devices, and three piezoelectric stack actuators (PSAs) were applied as driving components. The structure parameters of the flexible hinges and RADSs were optimized by theoretical, experimental and simulative methods. The experimental results show that the TM has an extreme high angular resolution of 0.017″, and the mechanical excursion angle is larger than 0.24′ with a natural frequency of 136.97 Hz, which accord well with the results of the theoretical estimation and finite element analyzing (FEA) simulation. The high angular resolution property indicates the multi-mirror telescope can achieve the imaging in diffraction limit.
2018,
30: 074103.
doi: 10.11884/HPLPB201830.180055
Abstract:
The experimental equipment used for synthesizing nanopowders via the electrical explosion of wire was designed and built based on the high-voltage breakdown method. Equipped with current and voltage measuring system, the equipment could conveniently prepare nanoparticles and record the current and voltage of the electric explosion process in real time. Electrical explosion experiments were carried out on zirconium wires, and the deposition energy of Zr wire in the process of electric explosion and the change of the state were analyzed. The influence of charging voltage on deposition energy and nanoparticles properties was studied. Component analysis of the produced nanoparticles was completed by X-ray diffraction (XRD) and energy spectrometer (EDS). The particle morphology of the nanopowders was observed by the transmission electron microscope (TEM).The particle size and distribution of the nanoparticles were obtained based on the statistics and observation of TEM images. The results show that the increase of voltage increased the deposition energy and shortened the evaporation time of zirconium wire. Higher charging voltage could significantly reduce nanopowder particle size distribution, and get a smaller average diameter of particles. The products of Zirconium wire electrical explosion were ZrO2 nanoparticles, based on the structures of the monoclinic crystal(m-ZrO2) and the cubic crystal (c-ZrO2), and the particles were perfectly spherical, smooth and clear, and the particle size distribution of nanoparticles was concentrated between 10 and 40 nm.
The experimental equipment used for synthesizing nanopowders via the electrical explosion of wire was designed and built based on the high-voltage breakdown method. Equipped with current and voltage measuring system, the equipment could conveniently prepare nanoparticles and record the current and voltage of the electric explosion process in real time. Electrical explosion experiments were carried out on zirconium wires, and the deposition energy of Zr wire in the process of electric explosion and the change of the state were analyzed. The influence of charging voltage on deposition energy and nanoparticles properties was studied. Component analysis of the produced nanoparticles was completed by X-ray diffraction (XRD) and energy spectrometer (EDS). The particle morphology of the nanopowders was observed by the transmission electron microscope (TEM).The particle size and distribution of the nanoparticles were obtained based on the statistics and observation of TEM images. The results show that the increase of voltage increased the deposition energy and shortened the evaporation time of zirconium wire. Higher charging voltage could significantly reduce nanopowder particle size distribution, and get a smaller average diameter of particles. The products of Zirconium wire electrical explosion were ZrO2 nanoparticles, based on the structures of the monoclinic crystal(m-ZrO2) and the cubic crystal (c-ZrO2), and the particles were perfectly spherical, smooth and clear, and the particle size distribution of nanoparticles was concentrated between 10 and 40 nm.
2018,
30: 074104.
doi: 10.11884/HPLPB201830.170403
Abstract:
To monitor the environment in high peak laser system inline, the method to sense containments by using optical microfiber(OM) was proposed. To realize precise control of the OM diameter, we firstly analyzed the OM fabrication process, obtained the relationship between the deviation of the OM shape and the errors of heating length and stretching length, then simulated the deviation in different situation, finally got the optimal parameter to fabricate OM with the length of 10 mm and the diameter of 1.5 μm. We have proved the simulation results by measuring the shape of the drawn OMs. According to our research, precise control of OM shape can be achieved by tuning the OM fabrication parameters, and the results lay the foundation for practical application of OM contaminants sensor.
To monitor the environment in high peak laser system inline, the method to sense containments by using optical microfiber(OM) was proposed. To realize precise control of the OM diameter, we firstly analyzed the OM fabrication process, obtained the relationship between the deviation of the OM shape and the errors of heating length and stretching length, then simulated the deviation in different situation, finally got the optimal parameter to fabricate OM with the length of 10 mm and the diameter of 1.5 μm. We have proved the simulation results by measuring the shape of the drawn OMs. According to our research, precise control of OM shape can be achieved by tuning the OM fabrication parameters, and the results lay the foundation for practical application of OM contaminants sensor.
2018,
30: 075001.
doi: 10.11884/HPLPB201830.180008
Abstract:
Based on the experimental data, this paper presents the pulsed magnetization characteristic of magnetic cores made of 25 μm metglass 2605TCA, 25 μm metglass 2605SA1 and 50 μm electric steel DG6. The characteristic parameter, the slope of the voltage pulse per unit area of magnetic core, is proposed to standardize the condition of exciting the core. It indicates that the magnetic flux density swing (ΔB) keeps nearly constant as the parameter is changed, the ΔB values of 2605TCA and DG6 are about 3.1 T, while the ΔB value of 2605SA1 is only 2.4 T. When the characteristic parameter is increased from 67 to 129, the relative permeability of 2605SA1 is decreased from 1800 to 1200, while the relative permeability of 2605TCA is decreased from 1100 to 400. Hence, the relative permeability of metglass varies evidently as the characteristic parameter is different. The DG6 performs not well under fast rise time pulse, which shows that the maximum of the relative permeability is only 130 and the relative permeability drops sharply as the magnetic core tends to be saturated. These experimental results are useful to the choice of the magnetic cores for fast linear transformer driver stage.
Based on the experimental data, this paper presents the pulsed magnetization characteristic of magnetic cores made of 25 μm metglass 2605TCA, 25 μm metglass 2605SA1 and 50 μm electric steel DG6. The characteristic parameter, the slope of the voltage pulse per unit area of magnetic core, is proposed to standardize the condition of exciting the core. It indicates that the magnetic flux density swing (ΔB) keeps nearly constant as the parameter is changed, the ΔB values of 2605TCA and DG6 are about 3.1 T, while the ΔB value of 2605SA1 is only 2.4 T. When the characteristic parameter is increased from 67 to 129, the relative permeability of 2605SA1 is decreased from 1800 to 1200, while the relative permeability of 2605TCA is decreased from 1100 to 400. Hence, the relative permeability of metglass varies evidently as the characteristic parameter is different. The DG6 performs not well under fast rise time pulse, which shows that the maximum of the relative permeability is only 130 and the relative permeability drops sharply as the magnetic core tends to be saturated. These experimental results are useful to the choice of the magnetic cores for fast linear transformer driver stage.
2018,
30: 075002.
doi: 10.11884/HPLPB201830.170453
Abstract:
A series of compact repetitive pulsed power systems on the basis of fast Marx generator were developed in Institute of Fluid Physics, China Academy of Engineering Physics. They are mainly composed of a fast Marx generator and a repetitive high voltage charging device. There are polypropylene film capacitors with plastic shell, miniaturized gas switches, isolated inductors and SF6 gas insulation in these fast Marx generators. An 8-stage Marx generator was designed and tested. It can output repetitively 5 pulses with peak power of beyond 10 GW, rising-time of 50 ns, pulse width of 150 ns at frequency of 10 Hz. An 18-stage Marx generator has the same structure as the 8-stage Marx generator. It can generate a single pulse with peak power of more than 33 GW and pulse duration of about 160 ns on a resistor load of 18 Ω. Its peak power density is up to 150 GW/m3. But its output pulse has an obvious reverse pulse in the falling time, which is not helpful to drive a diode load. So, a 16-stage coaxial Marx generator was designed, there are four capacitors in parallel in one stage. The coaxial Marx generator has a low inductance and a low output impedance. It can generate a pulse with peak power of 28 GW and pulse duration of 130 ns without reverse pulse on an 12 Ω load. This work is useful for the development of high power compact pulsed power. There are also some work to do in order to enhance the working life and repetitive operation stability of high power compact Marx generator.
A series of compact repetitive pulsed power systems on the basis of fast Marx generator were developed in Institute of Fluid Physics, China Academy of Engineering Physics. They are mainly composed of a fast Marx generator and a repetitive high voltage charging device. There are polypropylene film capacitors with plastic shell, miniaturized gas switches, isolated inductors and SF6 gas insulation in these fast Marx generators. An 8-stage Marx generator was designed and tested. It can output repetitively 5 pulses with peak power of beyond 10 GW, rising-time of 50 ns, pulse width of 150 ns at frequency of 10 Hz. An 18-stage Marx generator has the same structure as the 8-stage Marx generator. It can generate a single pulse with peak power of more than 33 GW and pulse duration of about 160 ns on a resistor load of 18 Ω. Its peak power density is up to 150 GW/m3. But its output pulse has an obvious reverse pulse in the falling time, which is not helpful to drive a diode load. So, a 16-stage coaxial Marx generator was designed, there are four capacitors in parallel in one stage. The coaxial Marx generator has a low inductance and a low output impedance. It can generate a pulse with peak power of 28 GW and pulse duration of 130 ns without reverse pulse on an 12 Ω load. This work is useful for the development of high power compact pulsed power. There are also some work to do in order to enhance the working life and repetitive operation stability of high power compact Marx generator.
2018,
30: 075101.
doi: 10.11884/HPLPB201830.180034
Abstract:
The Beam Current Transformers (BCTs) were designed to measure beam macro-pulse current in China Spallation Neutron Source (CSNS) Linear Accelerator (Linac). The BCT design was based on the CSNS Linac beam parameters, the transverse and longitudinal spaces of the accelerator pipe, etc. Now the BCTs have measured the beam macro-pulse current successfully in commissioning and providing support for operation of the Linac.
The Beam Current Transformers (BCTs) were designed to measure beam macro-pulse current in China Spallation Neutron Source (CSNS) Linear Accelerator (Linac). The BCT design was based on the CSNS Linac beam parameters, the transverse and longitudinal spaces of the accelerator pipe, etc. Now the BCTs have measured the beam macro-pulse current successfully in commissioning and providing support for operation of the Linac.
2018,
30: 075102.
doi: 10.11884/HPLPB201830.170098
Abstract:
The Dragon-Ⅱ injector is a strong current pulse electron beam source, it is an inductive adder with thermal cathode and provides three pulse beams with adjustable pulse interval for Dragon-Ⅱ LIA. The way with cross validation and mutual promotion of PIC simulations and experiments is adopted during the injector beam tuning. First, the magnetic field loading range of the leading solenoid is determined approximately by the beam spot measurements. Second, the magnetic field configuration of every solenoid installed in the anode beam line is simulated by PIC step by step, and then confirmed by the beam spot measurements. By this means, three kinds of magnetic field configurations which can keep the pulse flat-topped completely are obtained in order to meet the different requirements of the downstream beam transportation. Finally, the factors affecting the effects of beam tuning are discussed and the key to the injector performance improvement is considered to be further improving the emission uniformity of the large area thermal cathode.
The Dragon-Ⅱ injector is a strong current pulse electron beam source, it is an inductive adder with thermal cathode and provides three pulse beams with adjustable pulse interval for Dragon-Ⅱ LIA. The way with cross validation and mutual promotion of PIC simulations and experiments is adopted during the injector beam tuning. First, the magnetic field loading range of the leading solenoid is determined approximately by the beam spot measurements. Second, the magnetic field configuration of every solenoid installed in the anode beam line is simulated by PIC step by step, and then confirmed by the beam spot measurements. By this means, three kinds of magnetic field configurations which can keep the pulse flat-topped completely are obtained in order to meet the different requirements of the downstream beam transportation. Finally, the factors affecting the effects of beam tuning are discussed and the key to the injector performance improvement is considered to be further improving the emission uniformity of the large area thermal cathode.
2018,
30: 079001.
doi: 10.11884/HPLPB201830.180023
Abstract:
It is a new path to achieve hyperspectral imaging of objective area by employing the wavelength selectivity of thick volume Bragg gratings(VBGs). Based on the rigorous coupled wave theory, grating structures were optimally designed, fabricating craft were explored, the imaging system was constructed and the imaging ability of the VBG was verified. The results showed that: to obtain narrow filtered bandpass, we should improve the ratio of grating thickness and period, as well as strictly control the divergence angle of incident beam. For the beam quality of writing laser beams, vibration and polarization will all have large effect on the grating's fringe homogeneity, it is necessary to optimize the writing process by adopting vibration-proof measures, optimizing writing light to uniform beam and tuning polarization directions parallel of both writing light beams to promote grating's diffraction efficiency and quality. The two-dimensional spatial imaging ability of VBG were validated. Under transmission incidence of wide spectral light source, the filtered bandpass was about 5 nm and spatial resolution was about 4 lines/mm; under diffuse reflection incidence, spatial resolution was about 4.9 lines/mm by adopting grating pair to compensate the dispersion.
It is a new path to achieve hyperspectral imaging of objective area by employing the wavelength selectivity of thick volume Bragg gratings(VBGs). Based on the rigorous coupled wave theory, grating structures were optimally designed, fabricating craft were explored, the imaging system was constructed and the imaging ability of the VBG was verified. The results showed that: to obtain narrow filtered bandpass, we should improve the ratio of grating thickness and period, as well as strictly control the divergence angle of incident beam. For the beam quality of writing laser beams, vibration and polarization will all have large effect on the grating's fringe homogeneity, it is necessary to optimize the writing process by adopting vibration-proof measures, optimizing writing light to uniform beam and tuning polarization directions parallel of both writing light beams to promote grating's diffraction efficiency and quality. The two-dimensional spatial imaging ability of VBG were validated. Under transmission incidence of wide spectral light source, the filtered bandpass was about 5 nm and spatial resolution was about 4 lines/mm; under diffuse reflection incidence, spatial resolution was about 4.9 lines/mm by adopting grating pair to compensate the dispersion.
2018,
30: 079002.
doi: 10.11884/HPLPB201830.170500
Abstract:
For preparing micro-sized spherical alumina powder, the micro-sized η phase irregular alumina powders with large pore volume were spheroidized in laminar plasma jet generated by a segmented anode non-transferred arc laminar plasma torch using nitrogen as plasma gas. The effect of different working parameters of the plasma torch and a powder feeder on the spheroidization rate of the treated powders was investigated. The spheroidization rate was obtained by counting the number of the spherical particles over the total particles shown in images taken by an optical microscope, using reflection method. The spheroidization rate of the treated powders was close to 100%, showing a good performance of the laminar plasma torch. The alumina powders with high spheroidization rate, high dispersion and uniform particle size can be obtained using different combinations of the working parameters of the plasma torch and the powder feeder. In addition, it was shown that high spheroidization rate of the alumina powders can be achieved with the laminar plasma torch working at low power. The main phases of the raw and treated alumina are η and α, respectively, characterized by the XRD based on PDF card matching method.
For preparing micro-sized spherical alumina powder, the micro-sized η phase irregular alumina powders with large pore volume were spheroidized in laminar plasma jet generated by a segmented anode non-transferred arc laminar plasma torch using nitrogen as plasma gas. The effect of different working parameters of the plasma torch and a powder feeder on the spheroidization rate of the treated powders was investigated. The spheroidization rate was obtained by counting the number of the spherical particles over the total particles shown in images taken by an optical microscope, using reflection method. The spheroidization rate of the treated powders was close to 100%, showing a good performance of the laminar plasma torch. The alumina powders with high spheroidization rate, high dispersion and uniform particle size can be obtained using different combinations of the working parameters of the plasma torch and the powder feeder. In addition, it was shown that high spheroidization rate of the alumina powders can be achieved with the laminar plasma torch working at low power. The main phases of the raw and treated alumina are η and α, respectively, characterized by the XRD based on PDF card matching method.
