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RSS2018 Vol. 30, No. 10
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2018,
30: 100101.
doi: 10.11884/HPLPB201830.180220
Abstract:
Supercontinuum spectrum has wide applications in many fields, and it was one of the hottest research directions the past twenty years. However, limited by the mismatch of mode area between pig-tail of amplifier and the photonic crystal fiber and the balance of peak power and output power of the amplifier, the power of white-light supercontinuum is about 200 W. Based on frequency repetition and pulse duration of the amplifier and the high-efficient match of mode area, 563 W high power all-fiber white-light supercontinuum source was generated.
Supercontinuum spectrum has wide applications in many fields, and it was one of the hottest research directions the past twenty years. However, limited by the mismatch of mode area between pig-tail of amplifier and the photonic crystal fiber and the balance of peak power and output power of the amplifier, the power of white-light supercontinuum is about 200 W. Based on frequency repetition and pulse duration of the amplifier and the high-efficient match of mode area, 563 W high power all-fiber white-light supercontinuum source was generated.
2018,
30: 101001.
doi: 10.11884/HPLPB201830.180096
Abstract:
This paper presents an experimental method to realize the best high-order harmonic generation(HHG) phase matching in the interaction of strong optical field and gas target. By studying the effects of the relative location between gas target source and Gaussian-type driving field focus on the harmonic phase matching, conclusions are obtained that the optimum position of gas target for phase matching is always 3-5 mm behind the focal point of the driving field, with much lower HHG yield before the focus caused by serious harmonic phase mismatch. At the same time, in the optimum relative position, the driving field and the high-order harmonic field have similar spatial distribution characteristics, providing the experimental basis for the commonly used assumptions of Gaussian beam for high-order harmonic field.
This paper presents an experimental method to realize the best high-order harmonic generation(HHG) phase matching in the interaction of strong optical field and gas target. By studying the effects of the relative location between gas target source and Gaussian-type driving field focus on the harmonic phase matching, conclusions are obtained that the optimum position of gas target for phase matching is always 3-5 mm behind the focal point of the driving field, with much lower HHG yield before the focus caused by serious harmonic phase mismatch. At the same time, in the optimum relative position, the driving field and the high-order harmonic field have similar spatial distribution characteristics, providing the experimental basis for the commonly used assumptions of Gaussian beam for high-order harmonic field.
2018,
30: 101002.
doi: 10.11884/HPLPB201830.180113
Abstract:
The model of diffuser used on chemical laser's pressure recovery system is built, the fluid field is simulated. The results show that when the supersonic part of the diffuser is 1310 mm long, the background pressure that the chemical laser can lase normally is 7.18 kPa. When the supersonoic length is 1810 mm, the diffuser's recovery pressure rises to 8.25 kPa; when there are 2 vanes in the supersonic flow channel, the diffuser's recovery pressure rises to 8.52 kPa. The lengthening of the diffuser can raise the pressure, but the losing of the total energy will induce the difficulty of the diffuser's start-up. The use of vanes can raise the diffuser's recovery pressure successfully, and the scale of the recovery system could be reduced at the same time.
The model of diffuser used on chemical laser's pressure recovery system is built, the fluid field is simulated. The results show that when the supersonic part of the diffuser is 1310 mm long, the background pressure that the chemical laser can lase normally is 7.18 kPa. When the supersonoic length is 1810 mm, the diffuser's recovery pressure rises to 8.25 kPa; when there are 2 vanes in the supersonic flow channel, the diffuser's recovery pressure rises to 8.52 kPa. The lengthening of the diffuser can raise the pressure, but the losing of the total energy will induce the difficulty of the diffuser's start-up. The use of vanes can raise the diffuser's recovery pressure successfully, and the scale of the recovery system could be reduced at the same time.
2018,
30: 102001.
doi: 10.11884/HPLPB201830.180150
Abstract:
Fatigue effect is one of the factors leading to the damage of chemical film on optical components in high power laser system. However, few attentions are given on this issue. In this work, two irradiation types, single fluences with multi-shots and multi-gradient fluence with multi-shots, are utilized to investigate the characteristics and effect of laser fatigue damage on antireflection film at 1064 nm. The results indicate that fatigue damage is easy to occur on film under multi-shot laser irradiation. While the damage threshold and the resistance of fatigue effect can be effectively improved at the multi-gradient fluence with multi-shots. The results can provide references on methods and technique to improve the resistance ability and resist the fatigue damage of film.
Fatigue effect is one of the factors leading to the damage of chemical film on optical components in high power laser system. However, few attentions are given on this issue. In this work, two irradiation types, single fluences with multi-shots and multi-gradient fluence with multi-shots, are utilized to investigate the characteristics and effect of laser fatigue damage on antireflection film at 1064 nm. The results indicate that fatigue damage is easy to occur on film under multi-shot laser irradiation. While the damage threshold and the resistance of fatigue effect can be effectively improved at the multi-gradient fluence with multi-shots. The results can provide references on methods and technique to improve the resistance ability and resist the fatigue damage of film.
2018,
30: 103001.
doi: 10.11884/HPLPB201830.180157
Abstract:
As a novel, safe and high efficient spectrum utilization technology, orbital angular momentum(OAM) has attracted a great deal of attention in scientific community. In this paper, a broadband and multimode OAM antenna which works in X-band is designed based on uniform circular array(UCA). The antenna is composed of rotatingly arranged triangular element uniform antenna array. Its characteristic is that the number of positive and negative modes is related to the feed mode and the rotation mode of the array elements in the uniform circular array. Simulation experiments show that the antenna works at X band (9.33-10.37 GHz) and bandwidth is 1.04 GHz, relative bandwidth is 52%, and the modes of this antenna is more than the rectangular patch antenna with same number of elements. The antenna has the advantages of simple feeding network, wide bandwidth and easy control of the number of modes.
As a novel, safe and high efficient spectrum utilization technology, orbital angular momentum(OAM) has attracted a great deal of attention in scientific community. In this paper, a broadband and multimode OAM antenna which works in X-band is designed based on uniform circular array(UCA). The antenna is composed of rotatingly arranged triangular element uniform antenna array. Its characteristic is that the number of positive and negative modes is related to the feed mode and the rotation mode of the array elements in the uniform circular array. Simulation experiments show that the antenna works at X band (9.33-10.37 GHz) and bandwidth is 1.04 GHz, relative bandwidth is 52%, and the modes of this antenna is more than the rectangular patch antenna with same number of elements. The antenna has the advantages of simple feeding network, wide bandwidth and easy control of the number of modes.
2018,
30: 103002.
doi: 10.11884/HPLPB201830.180143
Abstract:
A composite guide magnetic field system for axial foilless diode was designed, which included a solenoid, a permanent magnet and a soft magnet. The cathode emission region was put outside the solenoid magnet, to get smaller inner radius of solenoid and lower electric field on cathode rod surface. The permanent magnet and the soft magnet compensate magnetic density of the cathode emission region, to meet the requirement for stable transmission. Weight and power of the guide magnetic field system were both reduced more than 40% as compared with the system using a classical solenoid magnet. PIC simulation on transmission characteristic of electron beams in the composite guide magnetic field system was studied, which proved that axial electron beams could be stably transmitted in the system.
A composite guide magnetic field system for axial foilless diode was designed, which included a solenoid, a permanent magnet and a soft magnet. The cathode emission region was put outside the solenoid magnet, to get smaller inner radius of solenoid and lower electric field on cathode rod surface. The permanent magnet and the soft magnet compensate magnetic density of the cathode emission region, to meet the requirement for stable transmission. Weight and power of the guide magnetic field system were both reduced more than 40% as compared with the system using a classical solenoid magnet. PIC simulation on transmission characteristic of electron beams in the composite guide magnetic field system was studied, which proved that axial electron beams could be stably transmitted in the system.
2018,
30: 103101.
doi: 10.11884/HPLPB201830.180153
Abstract:
In this paper, the eigen equation is utilized to study the high-order mode coaxial resonant cavity operating in the terahertz (THz) band, the cavity's resonant frequencies of TMm, 1, 0 mode, TMm, 2, 0 mode and TMm, 1, 1 mode associating with the geometric parameters are discussed, and the evidence for selecting the operating mode is presented. On this foundation, a new type of 0.3 THz TM10, 1, 0 mode coaxial coupled cavity chain is proposed, analyzed by equivalent circuit and simulated by CST-MWS simulation software. Its properties of cold cavity such as dispersion characteristic, characteristic impedance and electric field pattern are presented. In addition, the effect of the geometric parameters on the dispersion characteristic and the characteristic impedance is analyzed and summarized emphatically. The results of the study indicate that, TM10, 1, 0 mode is a reasonable operating mode for the THz high-order mode coaxial coupled cavity chain. The 0.3 THz TM10, 1, 0 mode coaxial coupled cavity chain operating in the 2π cavity mode has a large characteristic impedance, but the frequency spacing between the modes is small, so it can be applied to a narrow-band terahertz extended interaction device. Increasing the angle of the coupling slot is the best way to increase the mode spacing.
In this paper, the eigen equation is utilized to study the high-order mode coaxial resonant cavity operating in the terahertz (THz) band, the cavity's resonant frequencies of TMm, 1, 0 mode, TMm, 2, 0 mode and TMm, 1, 1 mode associating with the geometric parameters are discussed, and the evidence for selecting the operating mode is presented. On this foundation, a new type of 0.3 THz TM10, 1, 0 mode coaxial coupled cavity chain is proposed, analyzed by equivalent circuit and simulated by CST-MWS simulation software. Its properties of cold cavity such as dispersion characteristic, characteristic impedance and electric field pattern are presented. In addition, the effect of the geometric parameters on the dispersion characteristic and the characteristic impedance is analyzed and summarized emphatically. The results of the study indicate that, TM10, 1, 0 mode is a reasonable operating mode for the THz high-order mode coaxial coupled cavity chain. The 0.3 THz TM10, 1, 0 mode coaxial coupled cavity chain operating in the 2π cavity mode has a large characteristic impedance, but the frequency spacing between the modes is small, so it can be applied to a narrow-band terahertz extended interaction device. Increasing the angle of the coupling slot is the best way to increase the mode spacing.
2018,
30: 103201.
doi: 10.11884/HPLPB201830.180127
Abstract:
In order to explore the damage threshold of the fast electromagnetic pulse (FRTEMP) to the transceiver of UAV, a UAV transceiver is taken as the equipment under test(EUT), and a type of pulse source along the GTEM chamber is used to generate the fast electromagnetic pulse to irradiate the transceiver. The transceiver's failure to work is taken as the criteria of electromagnetic pulse damage, and after then, the inner circuit of the transceiver is detected to determine the damaged device. The experimental results show that the electromagnetic pulse can cause damage to the transceiver of UAV, and the electromagnetic field threshold of the electromagnetic pulse is obtained. The damaged UAV transceiver mechanism analysis and testing results show that the local oscillator circuit damage makes the transceiver unable to output signals, and phase-locked loop (PLL) damage is the key reason why the oscillator is unable to work. Determination of the specific damaged device can provide a basis for the protection of vulnerable devices.
In order to explore the damage threshold of the fast electromagnetic pulse (FRTEMP) to the transceiver of UAV, a UAV transceiver is taken as the equipment under test(EUT), and a type of pulse source along the GTEM chamber is used to generate the fast electromagnetic pulse to irradiate the transceiver. The transceiver's failure to work is taken as the criteria of electromagnetic pulse damage, and after then, the inner circuit of the transceiver is detected to determine the damaged device. The experimental results show that the electromagnetic pulse can cause damage to the transceiver of UAV, and the electromagnetic field threshold of the electromagnetic pulse is obtained. The damaged UAV transceiver mechanism analysis and testing results show that the local oscillator circuit damage makes the transceiver unable to output signals, and phase-locked loop (PLL) damage is the key reason why the oscillator is unable to work. Determination of the specific damaged device can provide a basis for the protection of vulnerable devices.
2018,
30: 103202.
doi: 10.11884/HPLPB201830.180130
Abstract:
A test system capable of simultaneously measuring the induced currents in the cable shield and inner conductor was developed to study the coupling problem of the cable on the ground under the natural lightning condition. The results show that: Waveforms of cable induced currents in the cable shield at different positions are basically the same, but the amplitudes are different which shows that the spatial distribution of the induced currents is not uniform. The time-domain waveforms and frequency spectrums of the induced currents measured in the inner conductor and cable shield are alike and the energy is concentrated between 1 kHz and 1 MHz. The induced voltage waveforms in the inner conductor of the positive and negative cloud-to-ground lightning are all single-pulse waveforms with a duration of 10-49 μs. The amplitude and their mean value of the cable induced voltages of the positive cloud-to-ground lightning are greater than the corresponding results for negative cloud-to-ground lightning, indicating that the cable coupling effect of positive cloud-to-ground lightning is greater than that of the negative cloud-to-ground lightning. The cable induced voltage amplitude and magnetic flux density of different lightning processes have small correlation and the same lightning process is basically linear. The cable induced voltage waveform duration time, the half-peak width, the range of the 10%-90% rise time and their average value of the positive cloud-to-ground lightning are all greater than those of the negative cloud-to-ground lightning.
A test system capable of simultaneously measuring the induced currents in the cable shield and inner conductor was developed to study the coupling problem of the cable on the ground under the natural lightning condition. The results show that: Waveforms of cable induced currents in the cable shield at different positions are basically the same, but the amplitudes are different which shows that the spatial distribution of the induced currents is not uniform. The time-domain waveforms and frequency spectrums of the induced currents measured in the inner conductor and cable shield are alike and the energy is concentrated between 1 kHz and 1 MHz. The induced voltage waveforms in the inner conductor of the positive and negative cloud-to-ground lightning are all single-pulse waveforms with a duration of 10-49 μs. The amplitude and their mean value of the cable induced voltages of the positive cloud-to-ground lightning are greater than the corresponding results for negative cloud-to-ground lightning, indicating that the cable coupling effect of positive cloud-to-ground lightning is greater than that of the negative cloud-to-ground lightning. The cable induced voltage amplitude and magnetic flux density of different lightning processes have small correlation and the same lightning process is basically linear. The cable induced voltage waveform duration time, the half-peak width, the range of the 10%-90% rise time and their average value of the positive cloud-to-ground lightning are all greater than those of the negative cloud-to-ground lightning.
2018,
30: 103203.
doi: 10.11884/HPLPB201830.180115
Abstract:
High-altitude electromagnetic pulse (HEMP) can couple into electronic equipment through channels, such as cables and apertures, causing temporary or permanent damage to various electronic systems. Considering the extremely high level of safety protection of nuclear power plants, it is necessary to study the sensibility, vulnerability and protective measures of the electronic systems in nuclear power plants under the radiation of electromagnetic pulses. In this paper, firstly, a minimum safety system of nuclear power plant was determined and built, including electrical, instrumentation, and clock synchronization systems. Then the radiation experimental platform of HEMP was built, and the electrical field waveform of HEMP simulator meets the requirements of GJB 8848-2016 standard. Finally, the electromagnetic pulse radiation experiment was performed on the minimum safety system. Based on the experimental data and effects, a preliminary analysis was performed for the electromagnetic pulse coupling to the minimum safety system of the nuclear power plant, and it is found that HEMP has a certain degree of threat to the minimum safety system of the nuclear power plant, but doesn't affect its core functions. By summarizing the effect phenomena, analyzing sensitive parts and thresholds, this study provides a basis for the following vulnerability assessment and protection strategy formulation.
High-altitude electromagnetic pulse (HEMP) can couple into electronic equipment through channels, such as cables and apertures, causing temporary or permanent damage to various electronic systems. Considering the extremely high level of safety protection of nuclear power plants, it is necessary to study the sensibility, vulnerability and protective measures of the electronic systems in nuclear power plants under the radiation of electromagnetic pulses. In this paper, firstly, a minimum safety system of nuclear power plant was determined and built, including electrical, instrumentation, and clock synchronization systems. Then the radiation experimental platform of HEMP was built, and the electrical field waveform of HEMP simulator meets the requirements of GJB 8848-2016 standard. Finally, the electromagnetic pulse radiation experiment was performed on the minimum safety system. Based on the experimental data and effects, a preliminary analysis was performed for the electromagnetic pulse coupling to the minimum safety system of the nuclear power plant, and it is found that HEMP has a certain degree of threat to the minimum safety system of the nuclear power plant, but doesn't affect its core functions. By summarizing the effect phenomena, analyzing sensitive parts and thresholds, this study provides a basis for the following vulnerability assessment and protection strategy formulation.
2018,
30: 103204.
doi: 10.11884/HPLPB201830.180052
Abstract:
This paper presents two kinds of absorbing boundaries for the two-dimensional (2-D) Leapfrog Alternating Direction Implicit Finite-Difference Time-Domain (Leapfrog ADI-FDTD) method—Mur boundary and CPML absorbing boundary condition. Leapfrog ADI-FDTD had unconditional stability and all the iterative equations were implicit. However, the electric and magnetic field components for the 2-D leapfrog ADI-FDTD method were updated implicitly as well as explicitly, absorbing boundary condition for difference components might keep diversity. Updating equations of CPML are presented in the paper according to its derived theory and compared with first-order Mur absorbing boundary condition. What's more, the reflection error of free space was used to represent absorbing ability of absorbing boundary condition.
This paper presents two kinds of absorbing boundaries for the two-dimensional (2-D) Leapfrog Alternating Direction Implicit Finite-Difference Time-Domain (Leapfrog ADI-FDTD) method—Mur boundary and CPML absorbing boundary condition. Leapfrog ADI-FDTD had unconditional stability and all the iterative equations were implicit. However, the electric and magnetic field components for the 2-D leapfrog ADI-FDTD method were updated implicitly as well as explicitly, absorbing boundary condition for difference components might keep diversity. Updating equations of CPML are presented in the paper according to its derived theory and compared with first-order Mur absorbing boundary condition. What's more, the reflection error of free space was used to represent absorbing ability of absorbing boundary condition.
2018,
30: 103205.
doi: 10.11884/HPLPB201830.180146
Abstract:
Tropospheric refraction error is one of the main factors that affect the accuracy of radar measurement and positioning system. In view of the poor real-time and low resolution of the Vienna Mapping Function 1 (VMF1) in refraction error correction, this paper introduces the GPT2w model that can provide some relevant parameters with a resolution of 1°×1°, and build a new model that named as SG-VMF1 by combining with the Saastamoinen model. Based on the new model and the calculation principle of the mapping function method, the tropospheric refraction error values of 4 International GNSS Service (IGS) stations at different elevation angles are estimated. The results demonstrate that when taking the results calculated by ray-tracing method based on IGS meteorological data as a reference, the RMS with the result of SG-VMF1 model and relevant calculation theory can reach 0.4 m when the elevation angle is 6°, and the RMS can reach 0.1 m when the elevation angle is greater than 30°. The new calculation method is feasible and effective, and with real-time and higher resolution.
Tropospheric refraction error is one of the main factors that affect the accuracy of radar measurement and positioning system. In view of the poor real-time and low resolution of the Vienna Mapping Function 1 (VMF1) in refraction error correction, this paper introduces the GPT2w model that can provide some relevant parameters with a resolution of 1°×1°, and build a new model that named as SG-VMF1 by combining with the Saastamoinen model. Based on the new model and the calculation principle of the mapping function method, the tropospheric refraction error values of 4 International GNSS Service (IGS) stations at different elevation angles are estimated. The results demonstrate that when taking the results calculated by ray-tracing method based on IGS meteorological data as a reference, the RMS with the result of SG-VMF1 model and relevant calculation theory can reach 0.4 m when the elevation angle is 6°, and the RMS can reach 0.1 m when the elevation angle is greater than 30°. The new calculation method is feasible and effective, and with real-time and higher resolution.
2018,
30: 103206.
doi: 10.11884/HPLPB201830.180088
Abstract:
A beam scanning metamaterial planar reflective array antenna is designed by combining square and octagonal rings. Compared with the traditional array antenna design, this array antenna adopts a new phase compensation method thus by combining the phase curve obtained by the reflective array unit when the material of the dielectric substrate is different, the phase compensation from 0-360° is realized, so that the phase curve of the array unit need not to completely cover 0-360°, and Hermite interpolation way is used to make up for the poor linearity of the phase characteristics. The advantage of this method is its universality, which reduces the design requirements for the array unit. Using this method, several single-layer plane reflectarray antennas were designed. The simulation results show that the direction of the reflected beam is consistent with the expected setting, and the side lobe and the main lobe are at least 15 dB apart. By adjusting the range of the solid-state plasma excitation region of the metamaterial to change the resonance structure of the array unit, beam scanning in different spatial frequencies is achieved, which provides a new method for the design of the planar reflectarray antenna.
A beam scanning metamaterial planar reflective array antenna is designed by combining square and octagonal rings. Compared with the traditional array antenna design, this array antenna adopts a new phase compensation method thus by combining the phase curve obtained by the reflective array unit when the material of the dielectric substrate is different, the phase compensation from 0-360° is realized, so that the phase curve of the array unit need not to completely cover 0-360°, and Hermite interpolation way is used to make up for the poor linearity of the phase characteristics. The advantage of this method is its universality, which reduces the design requirements for the array unit. Using this method, several single-layer plane reflectarray antennas were designed. The simulation results show that the direction of the reflected beam is consistent with the expected setting, and the side lobe and the main lobe are at least 15 dB apart. By adjusting the range of the solid-state plasma excitation region of the metamaterial to change the resonance structure of the array unit, beam scanning in different spatial frequencies is achieved, which provides a new method for the design of the planar reflectarray antenna.
2018,
30: 103207.
doi: 10.11884/HPLPB201830.180112
Abstract:
In order to study the blocking effect of digital communication stations with the change of the electromagnetic pulse train repetition rate, an electromagnetic pulse injection test was performed on a digital communication station. The bit error rate (BER) of the radio stations follow the change of amplitude and repetition rate of the electromagnetic pulse train was studied. The results show that the BER of the radio station increases with the the pulse amplitude when the repetition rate is below 50 Hz. The BER no longer changes after reaching the sensitive BER. There is a linear relationship between the repetition rate of the electromagnetic pulse and the sensitive BER of the radio station. The higher the repetition rate, the higher the BER. The pulse amplitude is basically the same within the allowable experimental error when the BER reaches the sensitive BER. It can be inferred from the analysis that the blocking effect of the radio station is the accumulation of single-pulse blocking effects when the pulse repetition rate is below 414 Hz. The pulse effect time will overlap only at repetition rate over 414 Hz. And the sensitive voltage will decrease with the increases of repetition rate.
In order to study the blocking effect of digital communication stations with the change of the electromagnetic pulse train repetition rate, an electromagnetic pulse injection test was performed on a digital communication station. The bit error rate (BER) of the radio stations follow the change of amplitude and repetition rate of the electromagnetic pulse train was studied. The results show that the BER of the radio station increases with the the pulse amplitude when the repetition rate is below 50 Hz. The BER no longer changes after reaching the sensitive BER. There is a linear relationship between the repetition rate of the electromagnetic pulse and the sensitive BER of the radio station. The higher the repetition rate, the higher the BER. The pulse amplitude is basically the same within the allowable experimental error when the BER reaches the sensitive BER. It can be inferred from the analysis that the blocking effect of the radio station is the accumulation of single-pulse blocking effects when the pulse repetition rate is below 414 Hz. The pulse effect time will overlap only at repetition rate over 414 Hz. And the sensitive voltage will decrease with the increases of repetition rate.
2018,
30: 105001.
doi: 10.11884/HPLPB201830.180147
Abstract:
The magnetic switch is used widely in the field of pulsed power technology due to its special saturation conduction mechanism, and it can be used as a pry off switch to steepen the falling edge. A high-voltage pulse quasi square wave with a certain flat top can be obtained on load based on the voltage clamping effect of metal-oxide varistor, which enables the adjustment of the pulse width by changing the volt-second integration of the magnetic switch. This paper presents a high voltage pulse generator with adjustable pulse width. With the use of varistor to generate high-voltage pulse quasi-square wave, and the magnetic switch as a pry off switch to steep the falling edge, by changing the magnetic switch reset current to control the reset depth of magnetic switch, it achieves adjustable pulse width. This paper presents theoretical analysis as well as simulation research and the preliminary experimental research based on the simulation result. In the preliminary experiment, the falling edge of the voltage waveform obtained on load is less than 30 ns and the pulse width modulation range is about 30%.
The magnetic switch is used widely in the field of pulsed power technology due to its special saturation conduction mechanism, and it can be used as a pry off switch to steepen the falling edge. A high-voltage pulse quasi square wave with a certain flat top can be obtained on load based on the voltage clamping effect of metal-oxide varistor, which enables the adjustment of the pulse width by changing the volt-second integration of the magnetic switch. This paper presents a high voltage pulse generator with adjustable pulse width. With the use of varistor to generate high-voltage pulse quasi-square wave, and the magnetic switch as a pry off switch to steep the falling edge, by changing the magnetic switch reset current to control the reset depth of magnetic switch, it achieves adjustable pulse width. This paper presents theoretical analysis as well as simulation research and the preliminary experimental research based on the simulation result. In the preliminary experiment, the falling edge of the voltage waveform obtained on load is less than 30 ns and the pulse width modulation range is about 30%.
2018,
30: 105002.
doi: 10.11884/HPLPB201830.170420
Abstract:
We investigated the discharge channel optical images of surface flashover on insulator under pulsed voltage in air. The CCD camera was used to diagnose the flashover characteristics of PMMA with finger electrodes in air. The experiments show that discharges occurred in both cathode region and anode region in channel forming and expansion stage. The velocity of channel forming was fast in 15 ns. The channel region kept on expanding with high luminous intensity and the whole discharge lasted more than 1 μs. Next, we would analyse the flashover physical process in air based on the discharge channel optical images.
We investigated the discharge channel optical images of surface flashover on insulator under pulsed voltage in air. The CCD camera was used to diagnose the flashover characteristics of PMMA with finger electrodes in air. The experiments show that discharges occurred in both cathode region and anode region in channel forming and expansion stage. The velocity of channel forming was fast in 15 ns. The channel region kept on expanding with high luminous intensity and the whole discharge lasted more than 1 μs. Next, we would analyse the flashover physical process in air based on the discharge channel optical images.
2018,
30: 105003.
doi: 10.11884/HPLPB201830.180069
Abstract:
This paper presents the design of a repetitive frequency gas spark switch. The switch adopts a three-electrode field-distortion structure, which has the advantages of small size and compactness, and it can work at voltage 100 kV, current 10 kA. Experimental study of the trigger characteristics of this field distortion spark gap switch were carried out with the changes in frequency, gas composition, working pressure and work coefficient. The breakdown time delay and jitter of the switch are calculated, and the main factors influencing the breakdown characteristics of the switch are analyzed. The experimental results show that the time jitter of the switch increases with the repetitive frequency. The switch has better performance when filled with gas mixture of SF6 and N2 of volumetric ratio of 1 ∶1, the working coefficient mainly affects the time jitter of the second discharge spark gap (gap 2).
This paper presents the design of a repetitive frequency gas spark switch. The switch adopts a three-electrode field-distortion structure, which has the advantages of small size and compactness, and it can work at voltage 100 kV, current 10 kA. Experimental study of the trigger characteristics of this field distortion spark gap switch were carried out with the changes in frequency, gas composition, working pressure and work coefficient. The breakdown time delay and jitter of the switch are calculated, and the main factors influencing the breakdown characteristics of the switch are analyzed. The experimental results show that the time jitter of the switch increases with the repetitive frequency. The switch has better performance when filled with gas mixture of SF6 and N2 of volumetric ratio of 1 ∶1, the working coefficient mainly affects the time jitter of the second discharge spark gap (gap 2).
2018,
30: 105004.
doi: 10.11884/HPLPB201830.180183
Abstract:
A 7-channel hard X-ray spectrometer was designed for measuring the photon energy distribution of the hard X-ray emitting from the loads used in Z-pinch experiments on PTS. In this paper, we present the measuring principle, configuration, measuring parameter and the unfolding method of the spectrometer. We tested our spectrometer on PTS machine, detected the hard X-rays produced during Z-pinch and acquired the signal curves of high signal-to-noise ratio. The maximum entropy method was employed in unfolding these curves and the spectrum of the X-ray radiation was obtained. The result of unfolding indicates that the hard X-ray radiation distributed mainly in 200-500 keV, rarely over 1 MeV.
A 7-channel hard X-ray spectrometer was designed for measuring the photon energy distribution of the hard X-ray emitting from the loads used in Z-pinch experiments on PTS. In this paper, we present the measuring principle, configuration, measuring parameter and the unfolding method of the spectrometer. We tested our spectrometer on PTS machine, detected the hard X-rays produced during Z-pinch and acquired the signal curves of high signal-to-noise ratio. The maximum entropy method was employed in unfolding these curves and the spectrum of the X-ray radiation was obtained. The result of unfolding indicates that the hard X-ray radiation distributed mainly in 200-500 keV, rarely over 1 MeV.
2018,
30: 105101.
doi: 10.11884/HPLPB201830.180186
Abstract:
The China Spallation Neutron Source (CSNS) accelerator mainly consists of a linear accelerator, a 1.6 GeV rapid cycling synchrotron (RCS), a low energy transport line and a high energy transport line. A rotating coil measurement system was developed for the DC magnets of the CSNS accelerator. This system solves the compatibility problems of different center heights, masses, effective lengths, and magnetic field strengths among CSNS bulk magnets. After testing, the repeatability error of the integral field measurement is less than ±0.02%, the repeatability error of harmonics is less than 0.005%, the repeatability error of the magnetic center measurement is less than ±0.03mm. It has successfully completed the task of detecting 150 magnets of the China Spallation Neutron Source. In this paper, the development plan, function, accuracy, types of measured magnets and some measurement results are introduced.
The China Spallation Neutron Source (CSNS) accelerator mainly consists of a linear accelerator, a 1.6 GeV rapid cycling synchrotron (RCS), a low energy transport line and a high energy transport line. A rotating coil measurement system was developed for the DC magnets of the CSNS accelerator. This system solves the compatibility problems of different center heights, masses, effective lengths, and magnetic field strengths among CSNS bulk magnets. After testing, the repeatability error of the integral field measurement is less than ±0.02%, the repeatability error of harmonics is less than 0.005%, the repeatability error of the magnetic center measurement is less than ±0.03mm. It has successfully completed the task of detecting 150 magnets of the China Spallation Neutron Source. In this paper, the development plan, function, accuracy, types of measured magnets and some measurement results are introduced.
Heavy ion medical machine synchrotron RF signal source design based on Field-Programmable Gate Array
2018,
30: 105102.
doi: 10.11884/HPLPB201830.180116
Abstract:
To meet the needs of different beam energy waveforms output of heavy ion medical machine (HIMM) synchrotron RF system, a synchronous signal source that can output different cavity voltage and bias current waveforms has been designed and realized. The ARTERA's FPGA is used as the core processing element to receive and process multiple sets of cavity voltage and bias current waveform files. And DAC is used to output waveforms after receiving synchronous optical trigger signal. The system enables seamless switching of different beam energy. The results show that the signal source is stable and can realize seamless switching and synchronized output waveforms. Its performance fully meets the requirements of the HIMM system for accelerating and capturing carbon ions. Compared with commercial arbitrary waveform generator, this system is cheaper and the modular design is easy to integrate. It can also be widely used in other occasions which need arbitrary waveform signals.
To meet the needs of different beam energy waveforms output of heavy ion medical machine (HIMM) synchrotron RF system, a synchronous signal source that can output different cavity voltage and bias current waveforms has been designed and realized. The ARTERA's FPGA is used as the core processing element to receive and process multiple sets of cavity voltage and bias current waveform files. And DAC is used to output waveforms after receiving synchronous optical trigger signal. The system enables seamless switching of different beam energy. The results show that the signal source is stable and can realize seamless switching and synchronized output waveforms. Its performance fully meets the requirements of the HIMM system for accelerating and capturing carbon ions. Compared with commercial arbitrary waveform generator, this system is cheaper and the modular design is easy to integrate. It can also be widely used in other occasions which need arbitrary waveform signals.
2018,
30: 105103.
doi: 10.11884/HPLPB201830.170523
Abstract:
The signal processing algorithm is one of the keys for digital beam position monitor(BPM) system. In order to optimize the digital BPM algorithm effectively, it is important and significant to research the BPM algorithm offline by using MATLAB. In this paper, the principle and framework of digital BPM algorithm are introduced firstly, the raw ADC data is subsequently obtained from BEPC Ⅱ based on the digital BPM hardware platform, which is domestically made by Institute of High Energy Physics, Chinese Academy of Sciences. Then NCO module, CIC filter, FIR filter and TBT position data calculation modules are designed with MATLAB, and the specific design parameters of each module are provided. Finally, each algorithm module is tested using raw ADC data and signal spectrograms are given. The turn-by-turn position resolution in horizontal and vertical directions under the actual beam are 4.55 μm and 4.28 μm. The offline research provides a reliable theoretical basis for the implementation and optimization of FPGA algorithm.
The signal processing algorithm is one of the keys for digital beam position monitor(BPM) system. In order to optimize the digital BPM algorithm effectively, it is important and significant to research the BPM algorithm offline by using MATLAB. In this paper, the principle and framework of digital BPM algorithm are introduced firstly, the raw ADC data is subsequently obtained from BEPC Ⅱ based on the digital BPM hardware platform, which is domestically made by Institute of High Energy Physics, Chinese Academy of Sciences. Then NCO module, CIC filter, FIR filter and TBT position data calculation modules are designed with MATLAB, and the specific design parameters of each module are provided. Finally, each algorithm module is tested using raw ADC data and signal spectrograms are given. The turn-by-turn position resolution in horizontal and vertical directions under the actual beam are 4.55 μm and 4.28 μm. The offline research provides a reliable theoretical basis for the implementation and optimization of FPGA algorithm.
2018,
30: 105104.
doi: 10.11884/HPLPB201830.180056
Abstract:
The HIAF (High Intensity heavy ion Accelerator Facility) project, proposed by the Institute of Modern Physics (IMP) of Chinese Academy of Sciences, has entered the preliminary design stage. As the key accelerator of the HIAF complex, the Booster Ring (BRing) can accumulate 238U35+ beam up to 1.0×1011 particles per pulse using two plane painting injection scheme, and accelerate it from injection energy of 17 MeV/u to high extraction energy range of 200-835 MeV/u. To provide quasi-continuous beam in several seconds for irradiation and some special nuclear physics experiments, slow extraction system has been designed. The third order resonance and RF-knockout extraction scheme will be adopted for the slow extraction system. Two kinds of sextupoles in the synchrotron, for correcting chromaticity and driving resonance, are considered to be orthogonal. This paper discusses the simulation results for the large and the small stable acceptance in the BRing and presents the optical parameters at the electrostatic septum ESe1 for different extraction energies of the 238U35+ beam. It can provide important theoretical base for slowly extracted heavy ion beams from the BRing, and for the entrance lattice design of HIAF FRagment Separator (HFRS).
The HIAF (High Intensity heavy ion Accelerator Facility) project, proposed by the Institute of Modern Physics (IMP) of Chinese Academy of Sciences, has entered the preliminary design stage. As the key accelerator of the HIAF complex, the Booster Ring (BRing) can accumulate 238U35+ beam up to 1.0×1011 particles per pulse using two plane painting injection scheme, and accelerate it from injection energy of 17 MeV/u to high extraction energy range of 200-835 MeV/u. To provide quasi-continuous beam in several seconds for irradiation and some special nuclear physics experiments, slow extraction system has been designed. The third order resonance and RF-knockout extraction scheme will be adopted for the slow extraction system. Two kinds of sextupoles in the synchrotron, for correcting chromaticity and driving resonance, are considered to be orthogonal. This paper discusses the simulation results for the large and the small stable acceptance in the BRing and presents the optical parameters at the electrostatic septum ESe1 for different extraction energies of the 238U35+ beam. It can provide important theoretical base for slowly extracted heavy ion beams from the BRing, and for the entrance lattice design of HIAF FRagment Separator (HFRS).
2018,
30: 105105.
doi: 10.11884/HPLPB201830.180057
Abstract:
Dump beam window is an important part of the dump. The Gaussian distribution of energy was decided by the beam size and power. The energy deposition was calculated by the Monte Carlo method. The thermal steady-state analysis of ANSYS was applied to decide the material, section shape and thickness of the dump beam window. The temperature, stress and deformation with different materials, section shapes and thickness were analyzed and compared to get the suitable material, section shape and thickness for the dump beam window. The final structure of the dump beam window was decided accordingly and the temperature of the window was simulated by the transient analysis of ANSYS.
Dump beam window is an important part of the dump. The Gaussian distribution of energy was decided by the beam size and power. The energy deposition was calculated by the Monte Carlo method. The thermal steady-state analysis of ANSYS was applied to decide the material, section shape and thickness of the dump beam window. The temperature, stress and deformation with different materials, section shapes and thickness were analyzed and compared to get the suitable material, section shape and thickness for the dump beam window. The final structure of the dump beam window was decided accordingly and the temperature of the window was simulated by the transient analysis of ANSYS.
2018,
30: 106001.
doi: 10.11884/HPLPB201830.180051
Abstract:
In order to carry out the physical experiment of magnetic confinement core combustion plasma, the HL-2M device under construction is intended to construct three 5 MW neutral beam injection heating lines. This paper briefly outlines the overall planning of the neutral beam injection (NBI) heating system of the HL-2M device, the design of the first 5MW-NBI heating beam line, the ion source commissioning experiment, the installation and test results of the injector core components. Through debugging, for single ion source the extraction beam current reaches 36 A, the acceleration voltage is 75 kV, the ion beam power reaches 2.4 MW, and the pulse width is 3 s. It is found by testing that the convergence angle error of 4 ion beam from the injector is less than +0.1°, the deviation between the test values and simulation values of magnetic field with deflecting magnet for deflecting residual ions is less than ±5%, and the static vacuum value of the injector reached 1.0×10-3 Pa. The injector has adopted a large non-standard cryogenic pump with a pumping speed of 2.4×106 L·s-1. The trial assembly and test results of the first 5MW-NBI heating beam show that the beam line can meet the technical requirements of NBI heating on HL-2M device.
In order to carry out the physical experiment of magnetic confinement core combustion plasma, the HL-2M device under construction is intended to construct three 5 MW neutral beam injection heating lines. This paper briefly outlines the overall planning of the neutral beam injection (NBI) heating system of the HL-2M device, the design of the first 5MW-NBI heating beam line, the ion source commissioning experiment, the installation and test results of the injector core components. Through debugging, for single ion source the extraction beam current reaches 36 A, the acceleration voltage is 75 kV, the ion beam power reaches 2.4 MW, and the pulse width is 3 s. It is found by testing that the convergence angle error of 4 ion beam from the injector is less than +0.1°, the deviation between the test values and simulation values of magnetic field with deflecting magnet for deflecting residual ions is less than ±5%, and the static vacuum value of the injector reached 1.0×10-3 Pa. The injector has adopted a large non-standard cryogenic pump with a pumping speed of 2.4×106 L·s-1. The trial assembly and test results of the first 5MW-NBI heating beam show that the beam line can meet the technical requirements of NBI heating on HL-2M device.
2018,
30: 106002.
doi: 10.11884/HPLPB201830.180012
Abstract:
A coupling interface between Monte Carlo neutron transport code JMCT2.2 and commercial CFD code FLUENT was developed by C++ language. The one-by-one mapping strategy that one cell in the MCNP model logically corresponded to the computational domain in the FLUENT model was used in this coupling method to realize simple partition of the physical model and refinement of partition of CFD mesh. The calculated results of a PWR single cell model and a PWR 3×3 fuel model were compared between this program and the MCNP-FLUENT program to validate its accuracy. The results demonstrate that this coupling method between JMCT code and FLUENT code is reasonable and it can accurately calculate the feedback parameters.
A coupling interface between Monte Carlo neutron transport code JMCT2.2 and commercial CFD code FLUENT was developed by C++ language. The one-by-one mapping strategy that one cell in the MCNP model logically corresponded to the computational domain in the FLUENT model was used in this coupling method to realize simple partition of the physical model and refinement of partition of CFD mesh. The calculated results of a PWR single cell model and a PWR 3×3 fuel model were compared between this program and the MCNP-FLUENT program to validate its accuracy. The results demonstrate that this coupling method between JMCT code and FLUENT code is reasonable and it can accurately calculate the feedback parameters.
2018,
30: 106003.
doi: 10.11884/HPLPB201830.180102
Abstract:
In this paper, a relative entropy based method is proposed to identify the gamma-ray spectra of radioactive sources. Firstly, Principal Component Analysis (PCA) algorithm is used to compress data and construct an eigenspace of the gamma-ray spectrum. Then, Randomization Technique (RT) is adopted to normalize the eigenvalue of the gamma-ray spectrum in eigenspace. Hence, the eigenspaces of gamma-ray spectra can be regarded as probability spaces. Finally, the relative entropy of two probability spaces is defined to measure the difference between two contrasted gamma-ray spectra. It was experimentally demonstrated that the proposed method could perform better judgment about the identity of two gamma-ray spectra over most existing methods. The proposed method has the characteristics of less calculation and higher robustness for impact factors of statistic fluctuations, peaks drift and background.
In this paper, a relative entropy based method is proposed to identify the gamma-ray spectra of radioactive sources. Firstly, Principal Component Analysis (PCA) algorithm is used to compress data and construct an eigenspace of the gamma-ray spectrum. Then, Randomization Technique (RT) is adopted to normalize the eigenvalue of the gamma-ray spectrum in eigenspace. Hence, the eigenspaces of gamma-ray spectra can be regarded as probability spaces. Finally, the relative entropy of two probability spaces is defined to measure the difference between two contrasted gamma-ray spectra. It was experimentally demonstrated that the proposed method could perform better judgment about the identity of two gamma-ray spectra over most existing methods. The proposed method has the characteristics of less calculation and higher robustness for impact factors of statistic fluctuations, peaks drift and background.
2018,
30: 109001.
doi: 10.11884/HPLPB201830.180092
Abstract:
During the quality inspection of BGA solder balls based on X-ray images, existing image processing algorithm can not effectively deal with the images of unexpectedly inclined PCB. A method which could automatically judge the inclination of X-ray images of BGA solder balls and correct them was proposed. The feature of BGA solder balls array was used in the method to rebuild the structural information firstly. Then the transformation matrix between ideal front view image and real inclined image would be calculated by Moore-Penrose generalized inverse matrix. Finally, the inverse matrix of transformation matrix was used to get the ideal front view image. At the same time, the angle of PCB could be estimated by using the transformation matrix. When used in the inclined X-ray images of BGA solder balls, the method could judge the inclination effectively and correct it to get the front view image. The method can be used as an image quality evaluation algorithm to judge whether the image is a desired image in industrial detection, as well as be used as an automatic image correction algorithm to improve the adaptability of the automatic detection system based on X-ray.
During the quality inspection of BGA solder balls based on X-ray images, existing image processing algorithm can not effectively deal with the images of unexpectedly inclined PCB. A method which could automatically judge the inclination of X-ray images of BGA solder balls and correct them was proposed. The feature of BGA solder balls array was used in the method to rebuild the structural information firstly. Then the transformation matrix between ideal front view image and real inclined image would be calculated by Moore-Penrose generalized inverse matrix. Finally, the inverse matrix of transformation matrix was used to get the ideal front view image. At the same time, the angle of PCB could be estimated by using the transformation matrix. When used in the inclined X-ray images of BGA solder balls, the method could judge the inclination effectively and correct it to get the front view image. The method can be used as an image quality evaluation algorithm to judge whether the image is a desired image in industrial detection, as well as be used as an automatic image correction algorithm to improve the adaptability of the automatic detection system based on X-ray.
2018,
30: 1-2.
