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RSS2022 Vol. 34, No. 4
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2022,
34: 1-2.
2022,
34: 041001.
doi: 10.11884/HPLPB202234.220058
Abstract:
Applying the home made chirped fiber Bragg grating (CFBG) writing system, CFBGs are successfully fabricated and applied in fiber mode-locked oscillator and chirped pulse amplification (CPA) systems. The oscillator can output 19.4 nm bandwidth, 18 mW average power laser, and can be compressed to 143 fs. With pulse stretching, power amplification and compression, 264 fs pulse width can be obtained. The experimental results initially demonstrate the feasibility of the domestic CFBG in femtosecond laser systems.
2022,
34: 041002.
doi: 10.11884/HPLPB202234.210504
Abstract:
Narrow linewidth fiber lasers (NLFLs) are widely employed in application of beam combining. However, the power scaling of the NLFL are severely limited by the transverse mode instability (TMI) effect. In this work, we have verified that the TMI threshold of narrow linewidth fiber amplifier can be enhanced by employing a 981 nm pump scheme. By constructing a 981 nm counter-pumped fiber amplifier, the output power of single mode NLFL is scaled to over 4 kW. In the experiment, the narrow linewidth seed laser is white noise signal phase modulated single frequency laser, and the main amplifier has two types of laser diodes at wavelengths of 976 nm and 981 nm as counter-pump. When the 976 nm laser diodes are employed, the NLFL is scaled to a maximum of 3.4 kW, which is limited by the occurrence of TMI effect. When the 981nm laser diodes are employed, the NLFL is scaled to 4.05 kW without any sign of TMI. The M2 factor of the output laser is 1.3. Further power scaling of the fiber amplifier is only limited by the available pump power. By optimizing the fiber laser design and employing bidirectional-pump, NLFL with higher power is achievable.
2022,
34: 041003.
doi: 10.11884/HPLPB202234.210414
Abstract:
High power Yb-doped fiber lasers have gained increasing application in space environment. However, the space radiation will bring color centers in Yb-doped fiber materials, thus increasing the inherent loss of the fiber. As a result, the optical properties of typical fiber-based components and the fiber lasers will be deteriorated, which makes it difficult for high power fiber lasers to achieve long-term stable operation in space environment. In this paper, a detailed introduction from three main aspects is given. Firstly, the influence of space radiation on typical optical components, thermal loading and nonlinear effects in high power fiber laser are introduced. Next, the typical suppressing methods of space radiation and their feasibility in high power fiber laser system are discussed. In the end, the representative research progress on the influence of space radiation on high power Yb-doped fiber lasers and effective suppressing methods at home and abroad are introduced.
2022,
34: 041004.
doi: 10.11884/HPLPB202234.210238
Abstract:
Based on the nonlinear Schrödinger equation, the step FFT is used to simulate the propagation of the square super-Gaussian beam in Kerr medium, and the evolution characteristics of the axial center and diagonal intensity of the square super-Gaussian beam are analyzed. At the same time, the self-focusing characteristics, the variation of peak intensity and B-integral in Kerr medium are also analyzed. The research results show that after the square super-Gaussian beam passes through the Kerr medium, there are different degrees of intensity enhancement and depression at different distances from the center of the beam, the intensity enhancement and depression are weak near the beam center, strong at the edge and four corners of the beam, and they are stronger in the diagonal direction than in the axial center direction. Reducing the order can slow down the edge intensity enhancement of the beam and the growth of the B-integral. Reducing the thickness of the Kerr medium can reduce the intensity enhancement of the beam edge and the size of the B-integral. It is proposed that the main reason for the fluctuation of the edge intensity of the beam probably be the coherent superposition of the beam.
Based on the nonlinear Schrödinger equation, the step FFT is used to simulate the propagation of the square super-Gaussian beam in Kerr medium, and the evolution characteristics of the axial center and diagonal intensity of the square super-Gaussian beam are analyzed. At the same time, the self-focusing characteristics, the variation of peak intensity and B-integral in Kerr medium are also analyzed. The research results show that after the square super-Gaussian beam passes through the Kerr medium, there are different degrees of intensity enhancement and depression at different distances from the center of the beam, the intensity enhancement and depression are weak near the beam center, strong at the edge and four corners of the beam, and they are stronger in the diagonal direction than in the axial center direction. Reducing the order can slow down the edge intensity enhancement of the beam and the growth of the B-integral. Reducing the thickness of the Kerr medium can reduce the intensity enhancement of the beam edge and the size of the B-integral. It is proposed that the main reason for the fluctuation of the edge intensity of the beam probably be the coherent superposition of the beam.
2022,
34: 041005.
doi: 10.11884/HPLPB202234.210341
Abstract:
The effects of the laser pulse duration and the number of pulses on the ablation threshold of Ni-based superalloy were experimentally investigated. In this experiment, Ni-based superalloy samples were irradiated by 1, 10, 50, 100, 300, 500 and 1000 laser pulses with different pulse duration, respectively, and pulse duration 290 fs, 1 ps and 7 ps were explored. The diameter of ablation holes expands with the increase of laser pulse and the effect of pulse number on the diameter of ablation holes increases with the pulse duration from the experiments. By analyzing the relationship between the diameter of ablation holes and laser pulse energy, multi-pulse ablation threshold of Ni-based superalloy irradiated by ultrafast laser with different pulse duration can be obtained. No matter what the pulse duration of the laser was, the incubation effects of multi-pulse irradiation on the surface of the superalloy were significant. And the incubation coefficient for the thresholds calculated by diameter respectively in 290 fs, 1 ps, and 7 ps is fitted to be 0.88, 0.86 and 0.78.
The effects of the laser pulse duration and the number of pulses on the ablation threshold of Ni-based superalloy were experimentally investigated. In this experiment, Ni-based superalloy samples were irradiated by 1, 10, 50, 100, 300, 500 and 1000 laser pulses with different pulse duration, respectively, and pulse duration 290 fs, 1 ps and 7 ps were explored. The diameter of ablation holes expands with the increase of laser pulse and the effect of pulse number on the diameter of ablation holes increases with the pulse duration from the experiments. By analyzing the relationship between the diameter of ablation holes and laser pulse energy, multi-pulse ablation threshold of Ni-based superalloy irradiated by ultrafast laser with different pulse duration can be obtained. No matter what the pulse duration of the laser was, the incubation effects of multi-pulse irradiation on the surface of the superalloy were significant. And the incubation coefficient for the thresholds calculated by diameter respectively in 290 fs, 1 ps, and 7 ps is fitted to be 0.88, 0.86 and 0.78.
2022,
34: 041006.
doi: 10.11884/HPLPB202234.220035
Abstract:
A computer tomography scheme based on single-element interferometer is proposed to measure the three-dimensional refractive index distribution of optical fiber. Based on the principle of microscopic imaging, the single-element interferometer improves the lateral resolution of the system. The phase is extracted by fast Fourier transform, and the refractive index distribution of the fiber is reconstructed by filtered back projection algorithm. Based on the proposed scheme, an experimental measurement device is built to actually measure the refractive index distribution of single-mode and multimode optical fibers. The results show that the measurement can simply and quickly obtain the full optical field data, has the advantages of being lossless and non-contact, and the optical path structure is compact and stable, which provides a new idea for the miniaturization of computed tomography equipment.
A computer tomography scheme based on single-element interferometer is proposed to measure the three-dimensional refractive index distribution of optical fiber. Based on the principle of microscopic imaging, the single-element interferometer improves the lateral resolution of the system. The phase is extracted by fast Fourier transform, and the refractive index distribution of the fiber is reconstructed by filtered back projection algorithm. Based on the proposed scheme, an experimental measurement device is built to actually measure the refractive index distribution of single-mode and multimode optical fibers. The results show that the measurement can simply and quickly obtain the full optical field data, has the advantages of being lossless and non-contact, and the optical path structure is compact and stable, which provides a new idea for the miniaturization of computed tomography equipment.
2022,
34: 043001.
doi: 10.11884/HPLPB202234.210162
Abstract:
To achieve beam scanning of mechanical phased array antenna, the miniature brushless DC motor is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. A new micro brushless DC motor position control system is designed. A proportional sliding mode surface super twisting algorithm controller is constructed for velocity control, the position PID controller combined with velocity profile strategy is used to realize the intermediate process control of the rotation. Establishing the control system simulation model in Simulink, the feasibility of this scheme is verified, and the control system is constructed on an FPGA hardware experiment platform. According to the results of simulation and experiment, it’s indicated the micro brushless DC motor can drive the antenna to follow the preset velocity profile curve accurately, and the rotation angle reaches 180° within a 50 ms control period. Both the position tracking deviation in the intermediate process and the residual error at the balance position are less than ±3°.
To achieve beam scanning of mechanical phased array antenna, the miniature brushless DC motor is adopted to drive a helical antenna element to rotate to a predetermined radiation phase. A new micro brushless DC motor position control system is designed. A proportional sliding mode surface super twisting algorithm controller is constructed for velocity control, the position PID controller combined with velocity profile strategy is used to realize the intermediate process control of the rotation. Establishing the control system simulation model in Simulink, the feasibility of this scheme is verified, and the control system is constructed on an FPGA hardware experiment platform. According to the results of simulation and experiment, it’s indicated the micro brushless DC motor can drive the antenna to follow the preset velocity profile curve accurately, and the rotation angle reaches 180° within a 50 ms control period. Both the position tracking deviation in the intermediate process and the residual error at the balance position are less than ±3°.
2022,
34: 043002.
doi: 10.11884/HPLPB202234.210289
Abstract:
This paper presents a miniaturized L-band microstrip line directional coupler loaded with double branches. Power cancellation technology is used to increase the isolation of the directional coupler, and two loading branches with different lengths are used to reflect signals at two similar frequency points respectively, so as to realize the bandwidth expansion of the coupler; at the same time, the slow wave characteristics of the defective ground structure are used to reduce the physical size of the directional coupler, and the notch generated by the defective ground structure is used to combine the two notch waves generated by the reflection of the two branches to further improve the bandwidth and isolation of the directional coupler. The coupler works in the L-band, the coupling is about 10 dB, the isolation in the entire L-band is better than −20 dB, and the maximum is about −52.81 dB, and the fractional bandwidth is 60%. Finally, the designed directional coupler is processed and tested, and the test and simulation results are in good agreement, which proves the feasibility of the circuit.
This paper presents a miniaturized L-band microstrip line directional coupler loaded with double branches. Power cancellation technology is used to increase the isolation of the directional coupler, and two loading branches with different lengths are used to reflect signals at two similar frequency points respectively, so as to realize the bandwidth expansion of the coupler; at the same time, the slow wave characteristics of the defective ground structure are used to reduce the physical size of the directional coupler, and the notch generated by the defective ground structure is used to combine the two notch waves generated by the reflection of the two branches to further improve the bandwidth and isolation of the directional coupler. The coupler works in the L-band, the coupling is about 10 dB, the isolation in the entire L-band is better than −20 dB, and the maximum is about −52.81 dB, and the fractional bandwidth is 60%. Finally, the designed directional coupler is processed and tested, and the test and simulation results are in good agreement, which proves the feasibility of the circuit.
2022,
34: 043003.
doi: 10.11884/HPLPB202234.210337
Abstract:
Magnetic field measurement in a strong electric field environment such as a lightning strike is one of the difficulties in electromagnetic pulse measurement technology. The traditional shielded small-loop antenna introduces radial asymmetry due to the output end structure, and it is difficult to avoid electric field interference. In response to this, this paper has developed a pulsed magnetic field sensor based on a dual-loop differential structure, which is composed of a dual-loop antenna and an optical transmission system. According to the distribution electromagnetic characteristics of the near-field, the dual-loop antenna chooses to be placed in parallel mirror symmetry, so that the terminal voltage can be divided into the magnetic field response component and the electric field response component, and then the electric field response component is removed by the differential circuit to obtain the pure magnetic field response component. Experiments have shown that in the nearby lightning strike electromagnetic field environment simulator, the dual-loop sensor has stronger anti-interference capability than the single-loop sensor, and can achieve accurate magnetic field measurement.
Magnetic field measurement in a strong electric field environment such as a lightning strike is one of the difficulties in electromagnetic pulse measurement technology. The traditional shielded small-loop antenna introduces radial asymmetry due to the output end structure, and it is difficult to avoid electric field interference. In response to this, this paper has developed a pulsed magnetic field sensor based on a dual-loop differential structure, which is composed of a dual-loop antenna and an optical transmission system. According to the distribution electromagnetic characteristics of the near-field, the dual-loop antenna chooses to be placed in parallel mirror symmetry, so that the terminal voltage can be divided into the magnetic field response component and the electric field response component, and then the electric field response component is removed by the differential circuit to obtain the pure magnetic field response component. Experiments have shown that in the nearby lightning strike electromagnetic field environment simulator, the dual-loop sensor has stronger anti-interference capability than the single-loop sensor, and can achieve accurate magnetic field measurement.
2022,
34: 043004.
doi: 10.11884/HPLPB202234.210340
Abstract:
A scalable all metal reflective element is proposed in this paper, and an all-metal reflective array antenna for high power microwave application is also designed. By sliding the connecting rod up and down, the transmission path of the incident wave to each element can be changed to achieve the corresponding phase modulation. Thus, the beam scanning can be achieved. Simulation result shows that the unit can realize linear phase adjustment of 360° within 10−13 GHz and has a power handling capacity of 3 MW, which means the array can achieve 5 GW/m2 power handling capacity level after the formation (under vacuum condition). Under the standard of 3 dB gain variation, the antenna can realize a two-dimensional spatial beam scanning within the range of 90° revolving cone angle.
A scalable all metal reflective element is proposed in this paper, and an all-metal reflective array antenna for high power microwave application is also designed. By sliding the connecting rod up and down, the transmission path of the incident wave to each element can be changed to achieve the corresponding phase modulation. Thus, the beam scanning can be achieved. Simulation result shows that the unit can realize linear phase adjustment of 360° within 10−13 GHz and has a power handling capacity of 3 MW, which means the array can achieve 5 GW/m2 power handling capacity level after the formation (under vacuum condition). Under the standard of 3 dB gain variation, the antenna can realize a two-dimensional spatial beam scanning within the range of 90° revolving cone angle.
2022,
34: 043005.
doi: 10.11884/HPLPB202234.210501
Abstract:
In the high-power millimeter wave systems of hundreds of kW or MW, the output millimeter wave power is generally measured by calorimetry. According to the needs of power measurement of hundreds of kW long pulse high-power millimeter wave systems, a power measurement system based on calorimetry is designed in this paper. In the proposed design, the incident millimeter wave energy is converted into heat by absorbing load. By monitoring the temperature and flow at the inlet and outlet, the power measurement of high-power millimeter wave is realized, and repeated experiments are carried out. To trace the quantity value and improve the accuracy of the measurement system, the energy standard device is designed, and the system energy measurement error is deduced to calibrate the measurement systems.
In the high-power millimeter wave systems of hundreds of kW or MW, the output millimeter wave power is generally measured by calorimetry. According to the needs of power measurement of hundreds of kW long pulse high-power millimeter wave systems, a power measurement system based on calorimetry is designed in this paper. In the proposed design, the incident millimeter wave energy is converted into heat by absorbing load. By monitoring the temperature and flow at the inlet and outlet, the power measurement of high-power millimeter wave is realized, and repeated experiments are carried out. To trace the quantity value and improve the accuracy of the measurement system, the energy standard device is designed, and the system energy measurement error is deduced to calibrate the measurement systems.
2022,
34: 043006.
doi: 10.11884/HPLPB202234.210393
Abstract:
To analyze the effect of the uncertainty of cable structure parameters on terminal voltage under the coupling of multi-conductor transmission lines, a method of Chebyshev polynomial approximation based on interval analysis is introduced. Firstly, the telegraph equation of transmission line is transformed into an ordinary differential equation. Secondly, the extension function of the telegraph equation is obtained by Chebyshev polynomial, and then the fluctuation range of terminal voltage is obtained. Compared with the mixed polynomial method and MC (Monte Carlo) method, this method only needs to input the range of fluctuation of random parameters. The multi-conductor wire beam with random variation of height and spacing under electromagnetic pulse irradiation was simulated. The simulation results show that the distance has little effect on terminal voltage, and the terminal voltage is more sensitive to height. Under the condition that the calculated results are in agreement with each other, the computation time of Chebyshev polynomial approximation method is much less than that of MC method.
To analyze the effect of the uncertainty of cable structure parameters on terminal voltage under the coupling of multi-conductor transmission lines, a method of Chebyshev polynomial approximation based on interval analysis is introduced. Firstly, the telegraph equation of transmission line is transformed into an ordinary differential equation. Secondly, the extension function of the telegraph equation is obtained by Chebyshev polynomial, and then the fluctuation range of terminal voltage is obtained. Compared with the mixed polynomial method and MC (Monte Carlo) method, this method only needs to input the range of fluctuation of random parameters. The multi-conductor wire beam with random variation of height and spacing under electromagnetic pulse irradiation was simulated. The simulation results show that the distance has little effect on terminal voltage, and the terminal voltage is more sensitive to height. Under the condition that the calculated results are in agreement with each other, the computation time of Chebyshev polynomial approximation method is much less than that of MC method.
2022,
34: 043007.
doi: 10.11884/HPLPB202234.210451
Abstract:
In the research project of high performance free electron laser, it is necessary to absorb the residual power at the end of its acceleration structure. At the operating frequency of 11.424 GHz, the RF load with the VSWR (voltage standing wave ratio) of less than 1.1 and high power absorption capacity needs to be developed. The software CST (Computer Simulation Technology) is used to design the loads. For the cylindrical water chamber water load, the design VSWRs are 1.0325 and 1.0533; At 50 MW peak power, the peak field intensities are 21.16 MV/m and 17.57 MV/m; the test VSWRs are 1.0582 and 1.0763. The effect of dielectric properties of ceramic and water on VSWR is also investigated. For the cylinder-shaped water load, the simulation results show that it has a high power tolerance level. For the dry load, the length of the load and the structure of the absorbing tooth are optimized to make it more convenient for machining. The results of thermal stress analysis calculated by ANSYS show that the maximum temperature and stress are 83.478 ℃ and 63.917 MPa respectively, and the maximum deformation is 0.072 971 mm.
In the research project of high performance free electron laser, it is necessary to absorb the residual power at the end of its acceleration structure. At the operating frequency of 11.424 GHz, the RF load with the VSWR (voltage standing wave ratio) of less than 1.1 and high power absorption capacity needs to be developed. The software CST (Computer Simulation Technology) is used to design the loads. For the cylindrical water chamber water load, the design VSWRs are 1.0325 and 1.0533; At 50 MW peak power, the peak field intensities are 21.16 MV/m and 17.57 MV/m; the test VSWRs are 1.0582 and 1.0763. The effect of dielectric properties of ceramic and water on VSWR is also investigated. For the cylinder-shaped water load, the simulation results show that it has a high power tolerance level. For the dry load, the length of the load and the structure of the absorbing tooth are optimized to make it more convenient for machining. The results of thermal stress analysis calculated by ANSYS show that the maximum temperature and stress are 83.478 ℃ and 63.917 MPa respectively, and the maximum deformation is 0.072 971 mm.
2022,
34: 043008.
doi: 10.11884/HPLPB202234.210453
Abstract:
In this paper, a shared-aperture planar phased array antenna operated at C and Ku band with wide-angle scan and high-power capacity is designed. The proposed phased array contains a printed dipole element-based 4×4 C-band array and a Ku-band array composed of 9×8 hybrid zeroth-order resonance patch elements. The wide-angle scanning performance of the designed phased array attributes the success to the wide-beam radiation of the dual-band elements. The bottom zeroth-order resonance patch element can not only be used as the Ku-band wide-beam radiation element, but also supplies the zero-phased reflection for the C-band printed dipoles which generate the wide-beam patterns based on the image theory. Furthermore, the antenna is designed with all metals buried by substrates to avoid air breakdown, and thus to improve the power capacity of the phased array. Full-wave simulation results show that the designed array can obtain a ±45° beam scan with its gain fluctuation less than 3 dB in both C and Ku bands, and the power capacity of the array reaches 18.9 MW when the total input power is 1 W.
In this paper, a shared-aperture planar phased array antenna operated at C and Ku band with wide-angle scan and high-power capacity is designed. The proposed phased array contains a printed dipole element-based 4×4 C-band array and a Ku-band array composed of 9×8 hybrid zeroth-order resonance patch elements. The wide-angle scanning performance of the designed phased array attributes the success to the wide-beam radiation of the dual-band elements. The bottom zeroth-order resonance patch element can not only be used as the Ku-band wide-beam radiation element, but also supplies the zero-phased reflection for the C-band printed dipoles which generate the wide-beam patterns based on the image theory. Furthermore, the antenna is designed with all metals buried by substrates to avoid air breakdown, and thus to improve the power capacity of the phased array. Full-wave simulation results show that the designed array can obtain a ±45° beam scan with its gain fluctuation less than 3 dB in both C and Ku bands, and the power capacity of the array reaches 18.9 MW when the total input power is 1 W.
2022,
34: 044001.
doi: 10.11884/HPLPB202234.210260
Abstract:
The fitting of the local control network is realized based on the method of Taylor expansion, and the chi-square test is used to judge whether there is a deformation point in the local control network. If there are deformation points, find all the deformation points in the local control network in the process of weight selection iteration, repeat the above process until the chi-square test passes. The two-phase observation results of the Harbin Institute of Technology Space Environment Simulation and Research Infrastructure (SESRI) No.2 terminal control network are analyzed. The experiments show that after adding the chi-square test and the weight selection iteration method to the control network fitting, the deformation points in the local control network can be well detected. After finding all the deformation points, more accurate local control network fitting parameters can be obtained.
The fitting of the local control network is realized based on the method of Taylor expansion, and the chi-square test is used to judge whether there is a deformation point in the local control network. If there are deformation points, find all the deformation points in the local control network in the process of weight selection iteration, repeat the above process until the chi-square test passes. The two-phase observation results of the Harbin Institute of Technology Space Environment Simulation and Research Infrastructure (SESRI) No.2 terminal control network are analyzed. The experiments show that after adding the chi-square test and the weight selection iteration method to the control network fitting, the deformation points in the local control network can be well detected. After finding all the deformation points, more accurate local control network fitting parameters can be obtained.
2022,
34: 044002.
doi: 10.11884/HPLPB202234.210261
Abstract:
The single-cavity bunch length monitor uses two eigenmodes in the resonant cavity to measure the bunch length in the order of picoseconds. The key is how to couple and extract two modes of different frequencies without interfering with each other. To solve this problem, based on the theory of low-pass and band-pass filters, a coaxial filter coupling structure and a diaphragm-loaded waveguide filter structure are proposed. The filters are modeled and simulated in CST Microwave Studio to obtain S parameters. In order to test the effect of the coupler, a bunch length monitor with the coupling structure is designed. According to the beam characteristics of the National Synchrotron Radiation Laboratory based on the tunable infrared laser energy chemistry research large-scale experimental device (FELiChEM), a beam simulation is performed on the designed monitor in CST. The simulation results show that the coupler can realize the coupling of specific modes and effectively reduce the interference of other modes. The resonant cavity monitor adopting the coaxial filter and the diaphragm-loaded waveguide filter can achieve high-precision measurement of the bunch length of the FELiChEM, and the measurement error is less than 2%.
The single-cavity bunch length monitor uses two eigenmodes in the resonant cavity to measure the bunch length in the order of picoseconds. The key is how to couple and extract two modes of different frequencies without interfering with each other. To solve this problem, based on the theory of low-pass and band-pass filters, a coaxial filter coupling structure and a diaphragm-loaded waveguide filter structure are proposed. The filters are modeled and simulated in CST Microwave Studio to obtain S parameters. In order to test the effect of the coupler, a bunch length monitor with the coupling structure is designed. According to the beam characteristics of the National Synchrotron Radiation Laboratory based on the tunable infrared laser energy chemistry research large-scale experimental device (FELiChEM), a beam simulation is performed on the designed monitor in CST. The simulation results show that the coupler can realize the coupling of specific modes and effectively reduce the interference of other modes. The resonant cavity monitor adopting the coaxial filter and the diaphragm-loaded waveguide filter can achieve high-precision measurement of the bunch length of the FELiChEM, and the measurement error is less than 2%.
2022,
34: 044003.
doi: 10.11884/HPLPB202234.210328
Abstract:
Loop heat pipe can be used on the photon absorber to improve its heat exchange efficiency and reduce its structural size, and for vibration-free operation, so it is an important technical reserve for the future design of photon absorbers in high-performance accelerators. The heat transfer performance is analyzed when the loop heat pipe is applied to the photon absorber, the results show that the current heat transfer capacity of the loop heat pipe fully suffice the requirements of the photon absorber, but the structure of the heat sink, especially the heat transfer distance, needs to be strictly optimized. Then, using the type “C18” loop heat pipe made by China Academy of Space Technology, a prototype of the photon absorber heat extracted by loop heat pipe was designed and optimized, the temperature distribution is simulated numerically, and the heat transfer capacity was tested experimentally.
Loop heat pipe can be used on the photon absorber to improve its heat exchange efficiency and reduce its structural size, and for vibration-free operation, so it is an important technical reserve for the future design of photon absorbers in high-performance accelerators. The heat transfer performance is analyzed when the loop heat pipe is applied to the photon absorber, the results show that the current heat transfer capacity of the loop heat pipe fully suffice the requirements of the photon absorber, but the structure of the heat sink, especially the heat transfer distance, needs to be strictly optimized. Then, using the type “C18” loop heat pipe made by China Academy of Space Technology, a prototype of the photon absorber heat extracted by loop heat pipe was designed and optimized, the temperature distribution is simulated numerically, and the heat transfer capacity was tested experimentally.
2022,
34: 044004.
doi: 10.11884/HPLPB202234.210390
Abstract:
As a key component, CCD has been widely used in space-based CCD cameras. However, it is vulnerable to the impact of high-energy electron radiation in space environment, resulting in performance degradation and abnormal operation. For this problem, a domestic N-channel three-phase polysilicon CCD with an overlapping gate and frame-transfer structure is selected to study the effect of electron irradiation. The models were established by FLUKA for Si and SiO2 irradiated with electrons, which are the composition material of CCD. We simulated the physical process of electrons and material interaction and calculated the total mass stopping power and range of different energy electron beams in Si and SiO2, then compared them with the theoretical results, and the correctness of the simulation method is verfied. A three-dimensional model of CCD pixel array was established. The effects of electron irradiation with different energy on the energy deposition process of electrons in CCD and the effect of between pixels on DPA (Displacement Per Atom) of electrons in CCD pixels were simulated and calculated. The mechanism of radiation damage difference is analyzed respectively.
As a key component, CCD has been widely used in space-based CCD cameras. However, it is vulnerable to the impact of high-energy electron radiation in space environment, resulting in performance degradation and abnormal operation. For this problem, a domestic N-channel three-phase polysilicon CCD with an overlapping gate and frame-transfer structure is selected to study the effect of electron irradiation. The models were established by FLUKA for Si and SiO2 irradiated with electrons, which are the composition material of CCD. We simulated the physical process of electrons and material interaction and calculated the total mass stopping power and range of different energy electron beams in Si and SiO2, then compared them with the theoretical results, and the correctness of the simulation method is verfied. A three-dimensional model of CCD pixel array was established. The effects of electron irradiation with different energy on the energy deposition process of electrons in CCD and the effect of between pixels on DPA (Displacement Per Atom) of electrons in CCD pixels were simulated and calculated. The mechanism of radiation damage difference is analyzed respectively.
2022,
34: 044005.
doi: 10.11884/HPLPB202234.210419
Abstract:
To improve the anti-mechanical performance of the 20 cm diameter ion thruster, the mechanical analysis and experimental verification of its existing structure were carried out. After the grids were handled equivalently, the modal analysis and impact response spectrum analysis of ion thruster were carried out based on finite element analysis. The modal analysis results were validated by the fundamental frequency sweep test. Finally, the impact response of the thruster after adopting the damping structure was simulated and verified by experiments. The obtained results indicate that after the grids assembly being handled equivalently, the analysis results’ difference are about 8.3%−11.9%. The modal analysis result shows that the base frequencies of the thruster in the x, y and z directions are 246, 248 and 336 Hz respectively. The grids and middle magnet pole are the weak links in the mechanics of the ion thruster and affect the overall structural stability. The 1600g response spectrum analysis results indicate that 1600g, the surface stress of the grids concentrates on the rim of the aperture region, furthermore the deformation largely occurs in this region. When the vibration damping effect with the stiffness of 1000 kN/m is taken, the overall deformation of the grids is reduced by 60%−82%. Mechanical test results show that, during the low-frequency scanning process of 10−1200 Hz, the base frequencies of the thruster x, y and z directions are 256, 258 and 348 Hz respectively, basically consistent with the simulation results. Secondly, the 20 cm diameter ion thruster with damping measures passed the 1600 g impact test.
To improve the anti-mechanical performance of the 20 cm diameter ion thruster, the mechanical analysis and experimental verification of its existing structure were carried out. After the grids were handled equivalently, the modal analysis and impact response spectrum analysis of ion thruster were carried out based on finite element analysis. The modal analysis results were validated by the fundamental frequency sweep test. Finally, the impact response of the thruster after adopting the damping structure was simulated and verified by experiments. The obtained results indicate that after the grids assembly being handled equivalently, the analysis results’ difference are about 8.3%−11.9%. The modal analysis result shows that the base frequencies of the thruster in the x, y and z directions are 246, 248 and 336 Hz respectively. The grids and middle magnet pole are the weak links in the mechanics of the ion thruster and affect the overall structural stability. The 1600g response spectrum analysis results indicate that 1600g, the surface stress of the grids concentrates on the rim of the aperture region, furthermore the deformation largely occurs in this region. When the vibration damping effect with the stiffness of 1000 kN/m is taken, the overall deformation of the grids is reduced by 60%−82%. Mechanical test results show that, during the low-frequency scanning process of 10−1200 Hz, the base frequencies of the thruster x, y and z directions are 256, 258 and 348 Hz respectively, basically consistent with the simulation results. Secondly, the 20 cm diameter ion thruster with damping measures passed the 1600 g impact test.
2022,
34: 044006.
doi: 10.11884/HPLPB202234.210430
Abstract:
As a fundamental component of a linac-based beam injector, the rectangular-waveguide coupler is a conventional device for feeding high power, but it will induce field asymmetry and resonant-frequency shifting. Furthermore, it is also difficult to adjust the coupling factor for adjustable beam injectors. In this paper, an equivalent circuit model is established for the coupler with a tuning rod. Based on theoretical analysis, the optimal position for the rod is given. Besides, the frequency shifting is corrected by using another rod inserted to the cavity in the opposite direction. Sizes and adjustment ranges of both rods are given by three-dimensional electromagnetic simulation using CST MICROWAVE STUDIO. Jointly adjusted simulation results show that, critical-coupled states are achieved for different beam intensity while the resonant frequency remains stable, thus the risk of reflected power caused by coupler mismatching can be avoided, and the field asymmetry due to a small coupling hole can be reduced.
2022,
34: 045001.
doi: 10.11884/HPLPB202234.210344
Abstract:
To study the adaptability of the modularized Marx generator in mechanical environment, simulation and vibration experiment of the generator are conducted based on the random vibration theory and finite element analysis method. Firstly, the finite element simulation model of an 8-stage Marx generator is established, and the stress concentration positions are identified. Secondly, the finite element model is corrected according to the initial results of shaking table test. Then an optimization scheme is proposed to modify the Marx generator. As a result, the first-order frequency of the Marx generator is increased from 15.4 Hz to 19.7 Hz. It is helpful to reduce the dynamic response in vertical direction and enhance the mechanical environment adaptability. Results show that more attention should be paid to the reliability in vertical direction when a Marx generator is being designed. The connection of the generator is stable in the vibration experiment, and the stresses mainly concentrate on the corner pieces between the generator and the U-shape support plates, the connections between U-shape support plates and side support plates, and the switch junctions, which are the weak points in design.
To study the adaptability of the modularized Marx generator in mechanical environment, simulation and vibration experiment of the generator are conducted based on the random vibration theory and finite element analysis method. Firstly, the finite element simulation model of an 8-stage Marx generator is established, and the stress concentration positions are identified. Secondly, the finite element model is corrected according to the initial results of shaking table test. Then an optimization scheme is proposed to modify the Marx generator. As a result, the first-order frequency of the Marx generator is increased from 15.4 Hz to 19.7 Hz. It is helpful to reduce the dynamic response in vertical direction and enhance the mechanical environment adaptability. Results show that more attention should be paid to the reliability in vertical direction when a Marx generator is being designed. The connection of the generator is stable in the vibration experiment, and the stresses mainly concentrate on the corner pieces between the generator and the U-shape support plates, the connections between U-shape support plates and side support plates, and the switch junctions, which are the weak points in design.
2022,
34: 045002.
doi: 10.11884/HPLPB202234.210333
Abstract:
Low temperature plasma excited by dielectric barrier discharges (DBDs) is widely used in medical health, air purification and other fields, and DBDs are commonly driven by high voltage pulse generators. In this paper, a high voltage pulse generator based on the combination of resonant circuit and pulsed transformer is proposed. The circuit uses the resonant effect of capacitor and inductor, combined with boost effect of pulsed transformer, and only one semiconductor switch to output high voltage pulses. The structure is simple, the cost is low, and zero voltage switching (ZVS) can be realized. In this paper, the operation mode of the circuit is analyzed theoretically, and the prototype is built for experiment. Under the condition of capacitive load, high voltage pulses with adjustable frequency of 1−15 kHz and amplitude of 0−10 kV are generated , and the influence of freewheeling branch and freewheeling resistance on the output high-voltage pulse waveform is analyzed. The DBD discharge experiment was carried out by using the pulse generator, and the DBD reactor was successfully driven, which further verified the feasibility of the circuit.
Low temperature plasma excited by dielectric barrier discharges (DBDs) is widely used in medical health, air purification and other fields, and DBDs are commonly driven by high voltage pulse generators. In this paper, a high voltage pulse generator based on the combination of resonant circuit and pulsed transformer is proposed. The circuit uses the resonant effect of capacitor and inductor, combined with boost effect of pulsed transformer, and only one semiconductor switch to output high voltage pulses. The structure is simple, the cost is low, and zero voltage switching (ZVS) can be realized. In this paper, the operation mode of the circuit is analyzed theoretically, and the prototype is built for experiment. Under the condition of capacitive load, high voltage pulses with adjustable frequency of 1−15 kHz and amplitude of 0−10 kV are generated , and the influence of freewheeling branch and freewheeling resistance on the output high-voltage pulse waveform is analyzed. The DBD discharge experiment was carried out by using the pulse generator, and the DBD reactor was successfully driven, which further verified the feasibility of the circuit.
2022,
34: 049001.
doi: 10.11884/HPLPB202234.210277
Abstract:
Two atmospheric pressure microwave plasma jet (MW-APPJ) devices with different nozzle structures are designed which are based on the coaxial transmission line structure. The frequency is 2.45 GHz and working gas is argon. What's more, the effects of two different nozzle structures on the characteristics of plasma discharge have been studied. Based on the electromagnetic field simulation results, the MW-APPJ generates a high-intensity electric field at the nozzle. After optimizing the structure, the field strength at the nozzle have reached the breakdown field strength required for argon ionization under the frequency of 2.45 GHz. Meanwhile, the simulation of the argon flow distribution was carried out under steady-state using multi-physics coupling simulation software. In addition, the basic characteristics of the atmospheric pressure argon plasma jet under the two nozzle structures were compared and analyzed through experiments. The experimental results show that different nozzle structures can affect the variation of reflection parameter with input power, but do not affect the variation of plasma jet length with input power and the variation of reflected power with inlet flow; at the same time, under atmospheric pressure, the steady-state microwave plasma jet exhibits metal-like property and the electrons in the plasma can only absorb microwave energy in a very thin area, which causes large reflected power of the microwave.
Two atmospheric pressure microwave plasma jet (MW-APPJ) devices with different nozzle structures are designed which are based on the coaxial transmission line structure. The frequency is 2.45 GHz and working gas is argon. What's more, the effects of two different nozzle structures on the characteristics of plasma discharge have been studied. Based on the electromagnetic field simulation results, the MW-APPJ generates a high-intensity electric field at the nozzle. After optimizing the structure, the field strength at the nozzle have reached the breakdown field strength required for argon ionization under the frequency of 2.45 GHz. Meanwhile, the simulation of the argon flow distribution was carried out under steady-state using multi-physics coupling simulation software. In addition, the basic characteristics of the atmospheric pressure argon plasma jet under the two nozzle structures were compared and analyzed through experiments. The experimental results show that different nozzle structures can affect the variation of reflection parameter with input power, but do not affect the variation of plasma jet length with input power and the variation of reflected power with inlet flow; at the same time, under atmospheric pressure, the steady-state microwave plasma jet exhibits metal-like property and the electrons in the plasma can only absorb microwave energy in a very thin area, which causes large reflected power of the microwave.
2022,
34: 049002.
doi: 10.11884/HPLPB202234.210425
Abstract:
We present a formula to directly obtain the final relative energy spread of a trailing beam at the maximal acceleration distance. The formula works for electron beams in a two-bunch plasma wakefield acceleration stage in the so-called nonlinear bubble regime. It only requires the longitudinal profile of the trailing beam and the longitudinal wakefield within the trailing beam at the beginning of an acceleration. This formula not only works well for drive beams and trailing beams with the same initial energies, but is also available for those beams with different initial energies. We find that the relative energy spread of the trailing beam obtained from the formula is determined by the ratio of the trailing beam’s initial energy to the drive beam’s initial energy rather than the specific value of their initial energies. We perform several computational simulations using the quasi-static particle-in-cell code QuickPIC, and the results agree well with that calculated from the formula.
We present a formula to directly obtain the final relative energy spread of a trailing beam at the maximal acceleration distance. The formula works for electron beams in a two-bunch plasma wakefield acceleration stage in the so-called nonlinear bubble regime. It only requires the longitudinal profile of the trailing beam and the longitudinal wakefield within the trailing beam at the beginning of an acceleration. This formula not only works well for drive beams and trailing beams with the same initial energies, but is also available for those beams with different initial energies. We find that the relative energy spread of the trailing beam obtained from the formula is determined by the ratio of the trailing beam’s initial energy to the drive beam’s initial energy rather than the specific value of their initial energies. We perform several computational simulations using the quasi-static particle-in-cell code QuickPIC, and the results agree well with that calculated from the formula.
