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RSS2011 Vol. 23, No. 10
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2011,
23.
Abstract:
The effects of neutron irradiation and electron irradiation on Si NPN-BJT (bipolar junction transistor) were investigated. After neutron irradiation and electron irradiation, the diffusion capacitance of transistor degraded, and even the negative capacitance(NC) phenomenon occurred. After electron irradiation, the barrier capacitance of transistor degraded, but it did not after neutron irradiation. A detailed analysis was made on the degradation mechanism of the junction capacitance after neutron irradiation and electron irradiation. The results indicate that, the defect is the cause of degradation. The defect clusters in transistor induced by both irradiations show as recombination centers, which greatly reduce the concentration and lifetime of minority carriers, giving rise to a serious
The effects of neutron irradiation and electron irradiation on Si NPN-BJT (bipolar junction transistor) were investigated. After neutron irradiation and electron irradiation, the diffusion capacitance of transistor degraded, and even the negative capacitance(NC) phenomenon occurred. After electron irradiation, the barrier capacitance of transistor degraded, but it did not after neutron irradiation. A detailed analysis was made on the degradation mechanism of the junction capacitance after neutron irradiation and electron irradiation. The results indicate that, the defect is the cause of degradation. The defect clusters in transistor induced by both irradiations show as recombination centers, which greatly reduce the concentration and lifetime of minority carriers, giving rise to a serious
2011,
23.
Abstract:
The proton beam window(PBW) is a boundary wall between the high vacuum area in the proton beam line and the helium atmosphere in the helium vessel at a high beam power target. The thermal and mechanical problems of PBW have been studied in foreign spallation neutron sources; however, the scattering effect in PBW is seldom reported which poses serious problems to the target design if not well treated. This paper will report the simulation studies of the scattering effect in PBW. Different materials and different structures of PBW are discussed. Taking China Spallation Neutron Source(CSNS) as an example, a thin single-layered aluminum alloy PBW with edge cooling has been chosen for CSNS-Ⅰ and CSNS-Ⅱ, and a sandwiched aluminum alloy PBW has been chosen for CSNS-Ⅲ. The simulations results o
The proton beam window(PBW) is a boundary wall between the high vacuum area in the proton beam line and the helium atmosphere in the helium vessel at a high beam power target. The thermal and mechanical problems of PBW have been studied in foreign spallation neutron sources; however, the scattering effect in PBW is seldom reported which poses serious problems to the target design if not well treated. This paper will report the simulation studies of the scattering effect in PBW. Different materials and different structures of PBW are discussed. Taking China Spallation Neutron Source(CSNS) as an example, a thin single-layered aluminum alloy PBW with edge cooling has been chosen for CSNS-Ⅰ and CSNS-Ⅱ, and a sandwiched aluminum alloy PBW has been chosen for CSNS-Ⅲ. The simulations results o
2011,
23.
Abstract:
The paper analyzes the influence of γ-rays on coincidence measurement system performance according to the principle of coincidence measurement in verification technology of nuclear arms control, and proposes the refusing window method to remove γ-peak. Experiments show that this method can significantly reduce the γ-peak, and the removal rate of γ-rays reaches 99%. Thus the refusing window method improves the precision of coincidence measurement system.
The paper analyzes the influence of γ-rays on coincidence measurement system performance according to the principle of coincidence measurement in verification technology of nuclear arms control, and proposes the refusing window method to remove γ-peak. Experiments show that this method can significantly reduce the γ-peak, and the removal rate of γ-rays reaches 99%. Thus the refusing window method improves the precision of coincidence measurement system.
2011,
23.
Abstract:
The scale-fusion wavelet edge detection algorithm is brought forward in dealing with streak camera images of planar wire array Z-pinch on “Qiangguang-Ⅰ facility”, and parameters of the algorithm that may influence the edge detection effect are analyzed. The proposed algorithm has the advantages of multi-scale edge detection methods with both small and big scale parameters, and the edges derived are smoother than those obtained from median values of grayscales, and are less sensitive to noise.
The scale-fusion wavelet edge detection algorithm is brought forward in dealing with streak camera images of planar wire array Z-pinch on “Qiangguang-Ⅰ facility”, and parameters of the algorithm that may influence the edge detection effect are analyzed. The proposed algorithm has the advantages of multi-scale edge detection methods with both small and big scale parameters, and the edges derived are smoother than those obtained from median values of grayscales, and are less sensitive to noise.
2011,
23.
Abstract:
The design of readout electronics based on multi-channel charge-sensitive pre-amplifier application specific integrated circuit(ASIC) are introduced，which is to be applied in the two-dimensional position-sensitive thermal neutron detector based on thick gas electron multiplier(THGEM). The ASIC is VA64TA2, a bare chip with 64 channels of charge sensitive preamplifier-shaper circuits and every channel with the function of trigger. These chips are packaged with the ceramic pin grid array package CPGA257, with 257 pints. The readout electronics is controlled by FPGA. The results of single-channel linear performance test and electronics noise performance test are given. The results show that the readout system has good linearity with the dynamic range of 16 fC, and low electronics noise of 1.2
The design of readout electronics based on multi-channel charge-sensitive pre-amplifier application specific integrated circuit(ASIC) are introduced，which is to be applied in the two-dimensional position-sensitive thermal neutron detector based on thick gas electron multiplier(THGEM). The ASIC is VA64TA2, a bare chip with 64 channels of charge sensitive preamplifier-shaper circuits and every channel with the function of trigger. These chips are packaged with the ceramic pin grid array package CPGA257, with 257 pints. The readout electronics is controlled by FPGA. The results of single-channel linear performance test and electronics noise performance test are given. The results show that the readout system has good linearity with the dynamic range of 16 fC, and low electronics noise of 1.2
2011,
23.
Abstract:
The structure of 1×2 type photonic crystal power splitter with ring resonators is designed in a two-dimensional square-lattice dielectric-rod photonic-crystal structure, and it consists of one input and two outputs. Its electromagnetic wave transmission performance is investigated by using finite-difference time-domain method. The results show that the structure has a high transmission efficiency in the third communication window (wavelength 1 550 nm), and can split pass band electromagnetic waves equally. It is compact with low loss and design flexibility in propagation direction of electromagnetic waves.
The structure of 1×2 type photonic crystal power splitter with ring resonators is designed in a two-dimensional square-lattice dielectric-rod photonic-crystal structure, and it consists of one input and two outputs. Its electromagnetic wave transmission performance is investigated by using finite-difference time-domain method. The results show that the structure has a high transmission efficiency in the third communication window (wavelength 1 550 nm), and can split pass band electromagnetic waves equally. It is compact with low loss and design flexibility in propagation direction of electromagnetic waves.
2011,
23.
Abstract:
In order to investigate the influence of polarization conditions on azo-dye molecular orientation in films, azo-dye polymer films of guest-host system were prepared by spin-coating method. The average alignment factor of azo-dye molecules in films were investigated by UV-Vis spectra measured before and after corona poling, as well as second harmonic generation at different corona poling conditions. The experimental results show that the average alignment factor of azo-dye films becomes bigger, and second harmonic intensity first increases and then decreases with the increasing of poling temperature. The closer the poling temperature is to the polymer’s glass transition temperature, the more likely the molecules are orientated. However, PMMA will fall into a state of viscosity at too high
In order to investigate the influence of polarization conditions on azo-dye molecular orientation in films, azo-dye polymer films of guest-host system were prepared by spin-coating method. The average alignment factor of azo-dye molecules in films were investigated by UV-Vis spectra measured before and after corona poling, as well as second harmonic generation at different corona poling conditions. The experimental results show that the average alignment factor of azo-dye films becomes bigger, and second harmonic intensity first increases and then decreases with the increasing of poling temperature. The closer the poling temperature is to the polymer’s glass transition temperature, the more likely the molecules are orientated. However, PMMA will fall into a state of viscosity at too high
2011,
23.
Abstract:
To calculate the lifetime of a Hall thruster, a two-dimensional model of magnetic and electric fields was established for the discharge channel of the thruster, and the assumed propellant is the xenon. The movement of particles in the magnetic and electric fields was tracked using PIC method. The Laplace equation was used to calculate the magnetic field, and the Poisson equation to calculate the electric field. Electrons were injected from the cathode and then ions were generated from the atom-electron ionization collision. In the process of tracking, we recorded the number, angle and energy of ions hitting against the inner and outer walls. Then we calculated the erosion rate at the threshold energy of 10, 20, 30, 40 and 50 eV, respectively. The maximal erosion rate at the outlet is 1.7×
To calculate the lifetime of a Hall thruster, a two-dimensional model of magnetic and electric fields was established for the discharge channel of the thruster, and the assumed propellant is the xenon. The movement of particles in the magnetic and electric fields was tracked using PIC method. The Laplace equation was used to calculate the magnetic field, and the Poisson equation to calculate the electric field. Electrons were injected from the cathode and then ions were generated from the atom-electron ionization collision. In the process of tracking, we recorded the number, angle and energy of ions hitting against the inner and outer walls. Then we calculated the erosion rate at the threshold energy of 10, 20, 30, 40 and 50 eV, respectively. The maximal erosion rate at the outlet is 1.7×
2011,
23.
Abstract:
Based on the magnetic charge model, the numerical algorithm of three-dimensional permanent magnets was derived by the finite difference method. Then combining the full three-dimensional particle-in-cell/Monte Carlo algorithm (PIC/MCC), two multi-peak magnetic field configurations, external magnetic filter and tent-shaped filter, were analyzed respectively, and their influences on electron energy distribution were compared. The simulation results show that both configurations can confine the diffusion of particles and can extract negative hydrogen ions; their electron energy distributions are basically similar, presenting double energy state, which are consistent with the basic mechanism of plasma discharge. The former configuration is stronger in confining and can produce more particles,
Based on the magnetic charge model, the numerical algorithm of three-dimensional permanent magnets was derived by the finite difference method. Then combining the full three-dimensional particle-in-cell/Monte Carlo algorithm (PIC/MCC), two multi-peak magnetic field configurations, external magnetic filter and tent-shaped filter, were analyzed respectively, and their influences on electron energy distribution were compared. The simulation results show that both configurations can confine the diffusion of particles and can extract negative hydrogen ions; their electron energy distributions are basically similar, presenting double energy state, which are consistent with the basic mechanism of plasma discharge. The former configuration is stronger in confining and can produce more particles,
2011,
23.
Abstract:
This paper summarizes the structural design and experimental study of UV pre-ionizing for multi-gap gas switch. The structures of needle UV pre-ionizing and hole UV pre-ionizing are designed. Static properties of switches with three trigger structures are obtained. There is no evident change of static field in switches and the change of self-breakdown voltage is under 3% with UV pre-ionizing. The jitter of UV pre-ionizing switches is about 20% less than that of the switch without UV pre-ionizing. The needle UV pre-ionizing method can lower the trigger voltage by 10 kV, and the hole UV one by 5 kV. For needle UV pre-ionizing, the UV intensity with different trigger voltages, gas pressures and distance of UV gap are measured. The optimum distance of UV gap is experimentally determined as 1.5
This paper summarizes the structural design and experimental study of UV pre-ionizing for multi-gap gas switch. The structures of needle UV pre-ionizing and hole UV pre-ionizing are designed. Static properties of switches with three trigger structures are obtained. There is no evident change of static field in switches and the change of self-breakdown voltage is under 3% with UV pre-ionizing. The jitter of UV pre-ionizing switches is about 20% less than that of the switch without UV pre-ionizing. The needle UV pre-ionizing method can lower the trigger voltage by 10 kV, and the hole UV one by 5 kV. For needle UV pre-ionizing, the UV intensity with different trigger voltages, gas pressures and distance of UV gap are measured. The optimum distance of UV gap is experimentally determined as 1.5
2011,
23.
Abstract:
This paper presents a composite intercepting projectile, which is designed for continuous firing, enhancing intercepting effect and reinforcing driving coil. The 3-D electromagnetic fields in the non-ferromagnet area, ferromagnet area and air area are described by magnetic vector potential and magnetic scalar potential based on Maxwell’s equation. The electromagnetic field distribution in the intercepting projectile is then simulated by the MAXWELL3D module of finite element analysis software Ansoft. The simulation results show that, the field distribution of the intercepting projectile with ferromagnet possesses some special characteristics: there exists a repulsion force between induction layer and driving coil, and there exists an attraction force between shielding layer and driving c
This paper presents a composite intercepting projectile, which is designed for continuous firing, enhancing intercepting effect and reinforcing driving coil. The 3-D electromagnetic fields in the non-ferromagnet area, ferromagnet area and air area are described by magnetic vector potential and magnetic scalar potential based on Maxwell’s equation. The electromagnetic field distribution in the intercepting projectile is then simulated by the MAXWELL3D module of finite element analysis software Ansoft. The simulation results show that, the field distribution of the intercepting projectile with ferromagnet possesses some special characteristics: there exists a repulsion force between induction layer and driving coil, and there exists an attraction force between shielding layer and driving c
2011,
23.
Abstract:
Temperature rise and hot spot formation in photoconductive semiconductor switch(PCSS) chip caused by joule heating restrain the PCSS’s power, repetition rate and lifetime, thus active cooling technology is necessary. In the paper, a high efficiency silicon rectangular micro-channel cooler is designed and experimentally tested. The cooler has two sections, principal frame and cover, joined by Si-Si bonding. The former section has an array of micro-channels between the distributary groove and the conflux groove, and the latter is punched by semiconductor etching technology. With water as coolant, the heat flux, temperature uniformity and fluid pressure drop at different coolant volumetric flow rate and inlet temperature are tested. The experimental results indicate that the cooler has a hig
Temperature rise and hot spot formation in photoconductive semiconductor switch(PCSS) chip caused by joule heating restrain the PCSS’s power, repetition rate and lifetime, thus active cooling technology is necessary. In the paper, a high efficiency silicon rectangular micro-channel cooler is designed and experimentally tested. The cooler has two sections, principal frame and cover, joined by Si-Si bonding. The former section has an array of micro-channels between the distributary groove and the conflux groove, and the latter is punched by semiconductor etching technology. With water as coolant, the heat flux, temperature uniformity and fluid pressure drop at different coolant volumetric flow rate and inlet temperature are tested. The experimental results indicate that the cooler has a hig
2011,
23.
Abstract:
A technical solution for high power pulse generator which is based on both induction voltage adder (IVA) and rolled strip line is introduced. The induction cell is designed for a 10-stage IVA, its equivalent circuit is obtained and corresponding simulation research is carried out. To study the response characteristics of the induction cell, a rolled strip pulse forming line with an impedance of 3 Ω and pulse duration of 230 ns is fabricated as the voltage drive source. Experimental investigations on both the single induction cell and 4-stage IVA are carried out. The results show that the cell has good response characteristics. The current efficiency of the 4-stage IVA can reach about 80%, and the output voltage is about 4 times the magnitude of the input. In the repetitive condition, the
A technical solution for high power pulse generator which is based on both induction voltage adder (IVA) and rolled strip line is introduced. The induction cell is designed for a 10-stage IVA, its equivalent circuit is obtained and corresponding simulation research is carried out. To study the response characteristics of the induction cell, a rolled strip pulse forming line with an impedance of 3 Ω and pulse duration of 230 ns is fabricated as the voltage drive source. Experimental investigations on both the single induction cell and 4-stage IVA are carried out. The results show that the cell has good response characteristics. The current efficiency of the 4-stage IVA can reach about 80%, and the output voltage is about 4 times the magnitude of the input. In the repetitive condition, the
2011,
23.
Abstract:
A numerical compensation method is proposed to reduce nanosecond signal distortion caused by tens meters of cable. The method calibrates the target cable with a relatively short cable, performs Fourier transform on the output signals of the two cables, and then gets the original function of the long cable sensitivity and phase with frequency, by using the frequency characteristics of the signals. For this original function is full of noise, it needs to be the fitted with system model. And then the cable’s output signal can be compensated after the experiment signal being measured in frequency domain. The experiment shows that this method can improve the bandwidth of cable significantly. The 100 m-long SYV-50-7-2 cable whose bandwidth is just 40 MHz is improved to 1 GHz by compensation.
A numerical compensation method is proposed to reduce nanosecond signal distortion caused by tens meters of cable. The method calibrates the target cable with a relatively short cable, performs Fourier transform on the output signals of the two cables, and then gets the original function of the long cable sensitivity and phase with frequency, by using the frequency characteristics of the signals. For this original function is full of noise, it needs to be the fitted with system model. And then the cable’s output signal can be compensated after the experiment signal being measured in frequency domain. The experiment shows that this method can improve the bandwidth of cable significantly. The 100 m-long SYV-50-7-2 cable whose bandwidth is just 40 MHz is improved to 1 GHz by compensation.
2011,
23.
Abstract:
A preliminary understanding of electromagnetic pulse generated by nuclear explosions in space has been developed with case signal model. For observers in large distances, a net dipole can be resulted from the average movements of space charges. Based on the law of electron movements, the electric dipole moment of the whole system has been analytically described. The radiation fields are closely related to the derivatives of the dipole moment with time. The peak value of radiation signal in far field increases linearly with the initial kinetic energies of electrons, and quadratically with the radius of bomb and with the rise time constant. The peak is irrelevant to explosion yield, while the peak time will be postponed as the yield decreases.
A preliminary understanding of electromagnetic pulse generated by nuclear explosions in space has been developed with case signal model. For observers in large distances, a net dipole can be resulted from the average movements of space charges. Based on the law of electron movements, the electric dipole moment of the whole system has been analytically described. The radiation fields are closely related to the derivatives of the dipole moment with time. The peak value of radiation signal in far field increases linearly with the initial kinetic energies of electrons, and quadratically with the radius of bomb and with the rise time constant. The peak is irrelevant to explosion yield, while the peak time will be postponed as the yield decreases.
2011,
23.
Abstract:
A repetitive trigger generator with low jitter and fast rise time is introduced and the principles of designing and choosing the units in the trigger generator are given. The trigger generator is composed with control unit, charging unit and pulse forming unit. The pulse forming unit is a capacitor-fast-discharging trigger with hydrogen thyratron. The repetitive rate of trigger can reach 100 pps (pulses per second), the delay time is about 225 ns, the jitter is about 1 ns, the rise time is about 26 ns and the FWHM (full-width at half-magnitude) is about 70 ns. The amplitude of electrical pulse on the load with high impedance is about -40 kV at 100 pps, -51 kV at 50 pps, -60 kV at single shot, respectively. The micro-closing of hydrogen thyratron is discussed. As the anode voltage increases
A repetitive trigger generator with low jitter and fast rise time is introduced and the principles of designing and choosing the units in the trigger generator are given. The trigger generator is composed with control unit, charging unit and pulse forming unit. The pulse forming unit is a capacitor-fast-discharging trigger with hydrogen thyratron. The repetitive rate of trigger can reach 100 pps (pulses per second), the delay time is about 225 ns, the jitter is about 1 ns, the rise time is about 26 ns and the FWHM (full-width at half-magnitude) is about 70 ns. The amplitude of electrical pulse on the load with high impedance is about -40 kV at 100 pps, -51 kV at 50 pps, -60 kV at single shot, respectively. The micro-closing of hydrogen thyratron is discussed. As the anode voltage increases
Simulation design and power distribution calculations of linac collinear load based on Kanthal alloy
2011,
23.
Abstract:
In order to miniaturize irradiation accelerators, the collinear load is proposed to substitute for the waveguide load. The key technique is to dissipate the remnant power in load cavities which are coated with efficient microwave-absorbing materials on their inner walls. Taking advantage of a 2π/3 mode resonance structure, the S-band collinear load based on Kanthal(Fe-Cr-Al) which is a kind of surface-attenuating metal is studied in CST. The influences of the coating position and area on the operation frequency and cavity quality factor are analyzed. The compensation of cavity dimensions for tuning at 2 856 MHz is determined. A two-period collinear load composed of six cavities is designed, with one-way attenuation of -18.63 dB. The power density calculations of the coatings and copper wa
In order to miniaturize irradiation accelerators, the collinear load is proposed to substitute for the waveguide load. The key technique is to dissipate the remnant power in load cavities which are coated with efficient microwave-absorbing materials on their inner walls. Taking advantage of a 2π/3 mode resonance structure, the S-band collinear load based on Kanthal(Fe-Cr-Al) which is a kind of surface-attenuating metal is studied in CST. The influences of the coating position and area on the operation frequency and cavity quality factor are analyzed. The compensation of cavity dimensions for tuning at 2 856 MHz is determined. A two-period collinear load composed of six cavities is designed, with one-way attenuation of -18.63 dB. The power density calculations of the coatings and copper wa
2011,
23.
Abstract:
The paper reports the experimental study of back-streaming ion effect in the target region of Dragon-I linear induction accelerator(LIA). The double-foil technique was used in the experiments. A thin target foil was used to generate backstreaming ions via interaction with electron beam, and a set of beam profile measurement system based on optical transition radiation (OTR) was used to record the time-resolved beam profiles. The study has proved the existence of backstreaming ions in the target region of Dragon-I LIA. The influences of backstreaming ions on high-current relativistic electron beam were observed by using different foils. The beam will partially focus and partially defocus with a metallic foil (Mo), while dramatic transverse motion will occur with a polymer foil (Kapton).
The paper reports the experimental study of back-streaming ion effect in the target region of Dragon-I linear induction accelerator(LIA). The double-foil technique was used in the experiments. A thin target foil was used to generate backstreaming ions via interaction with electron beam, and a set of beam profile measurement system based on optical transition radiation (OTR) was used to record the time-resolved beam profiles. The study has proved the existence of backstreaming ions in the target region of Dragon-I LIA. The influences of backstreaming ions on high-current relativistic electron beam were observed by using different foils. The beam will partially focus and partially defocus with a metallic foil (Mo), while dramatic transverse motion will occur with a polymer foil (Kapton).
2011,
23.
Abstract:
This paper describes the control system for HIRFL-CSRe internal target facility based on VAC800, VAC600 and TC hardware platform which integrates temperature control, vacuum and valve control and molecular pump control. It is able to realize remote monitor and control on temperature and vacuum and meets the requirements of physical experiments in the internal target facility. In the help of this system, Xe54+-N2 collisions experiments have been finished successfully. The whole system has been working for six months stably and safely.
This paper describes the control system for HIRFL-CSRe internal target facility based on VAC800, VAC600 and TC hardware platform which integrates temperature control, vacuum and valve control and molecular pump control. It is able to realize remote monitor and control on temperature and vacuum and meets the requirements of physical experiments in the internal target facility. In the help of this system, Xe54+-N2 collisions experiments have been finished successfully. The whole system has been working for six months stably and safely.
2011,
23.
Abstract:
A design scheme of microwave gun with two independent microwave power feed-in ports is proposed. Numerical simulation results show that the electron back-bombardment of the thermionic-cathode microwave gun can be greatly decreased, and high quality electron beams can be obtained by adjusting the phase displacement between the two microwave ports. Cold test results of the resonance frequency of the cavities and the field distribution of the RF gun are given. Preliminary hot test results show that, the beam current intensity and spot size at the gun output port are over 500 mA and around 3 mm, respectively, and the normalized emittance is 13.5π·mm·mrad, which is obtained with dual-screen measurement. The measured parameters agree well with the theoretical design.
A design scheme of microwave gun with two independent microwave power feed-in ports is proposed. Numerical simulation results show that the electron back-bombardment of the thermionic-cathode microwave gun can be greatly decreased, and high quality electron beams can be obtained by adjusting the phase displacement between the two microwave ports. Cold test results of the resonance frequency of the cavities and the field distribution of the RF gun are given. Preliminary hot test results show that, the beam current intensity and spot size at the gun output port are over 500 mA and around 3 mm, respectively, and the normalized emittance is 13.5π·mm·mrad, which is obtained with dual-screen measurement. The measured parameters agree well with the theoretical design.
2011,
23.
Abstract:
The Robinson instability of storage ring is discussed. A new beam stability condition that the equivalent detuning angle should be over zero is presented. The relationship between the beam instability and the detuning of RF cavity is measured during 200 MeV injection at Hefei Light Source storage ring. The results indicate that when the beam stability condition is not satisfied, the beam will be lost if the detuning is large; the beam tends to be lost partially when the detuning is small; in the case of negative detuning, the beam current is limited within a low level.
The Robinson instability of storage ring is discussed. A new beam stability condition that the equivalent detuning angle should be over zero is presented. The relationship between the beam instability and the detuning of RF cavity is measured during 200 MeV injection at Hefei Light Source storage ring. The results indicate that when the beam stability condition is not satisfied, the beam will be lost if the detuning is large; the beam tends to be lost partially when the detuning is small; in the case of negative detuning, the beam current is limited within a low level.
2011,
23.
Abstract:
The Marx solid-state modulator, designed for international linear collider(ILC), is a Marx-type modulator which uses integrated gate bipolar transistors (IGBTs) as switch. This article introduces the design and test of Marx cell, which includes charge and discharge circles, real-time monitor for voltage and current, control system and protective interlocks. It also introduces voltage balance of IGBTs and takes some simulations for that. Components were laid out on the unit bracket of Marx solid-state modulator according to electrical standard. Four Marx cells have passed the multi-cell HV test and output a superimposed voltage of 24 kV. All the components worked well in HV test.
The Marx solid-state modulator, designed for international linear collider(ILC), is a Marx-type modulator which uses integrated gate bipolar transistors (IGBTs) as switch. This article introduces the design and test of Marx cell, which includes charge and discharge circles, real-time monitor for voltage and current, control system and protective interlocks. It also introduces voltage balance of IGBTs and takes some simulations for that. Components were laid out on the unit bracket of Marx solid-state modulator according to electrical standard. Four Marx cells have passed the multi-cell HV test and output a superimposed voltage of 24 kV. All the components worked well in HV test.
2011,
23.
Abstract:
According to the relationship between the autocorrelation function of neutron pulse signal and the mass of fissile material (252U), this paper proposes an identification method for the mass of fissile material by means of artificial neural network and stationary wavelet transform. In order to suppress the “noise effect” of autocorrelation function due to statistical fluctuation of neutron signal, the wavelet approximation subband of the 2nd level is extracted after the autocorrelation function is decomposed, and the subband coefficients of different mass are reused as the input variables of distributed Elman neural network for training and recognizing. The impact of the number of subnetworks is also studied. The experimental results show that, under an ideal condition (4 kinds of mass a
According to the relationship between the autocorrelation function of neutron pulse signal and the mass of fissile material (252U), this paper proposes an identification method for the mass of fissile material by means of artificial neural network and stationary wavelet transform. In order to suppress the “noise effect” of autocorrelation function due to statistical fluctuation of neutron signal, the wavelet approximation subband of the 2nd level is extracted after the autocorrelation function is decomposed, and the subband coefficients of different mass are reused as the input variables of distributed Elman neural network for training and recognizing. The impact of the number of subnetworks is also studied. The experimental results show that, under an ideal condition (4 kinds of mass a
2011,
23.
Abstract:
This paper reviews the development of high power neodymium laser glasses and their main properties. The emphasis is on the research progress of pot melting, continuous melting and cladding techniques for large aperture N31 neodymium phosphate laser glass developed by Shanghai Institute of Optics and Fine Mechanics. The main properties of N31 glasses, prepared by pot melting and continuous melting, are compared. The attenuation at laser wavelength, fluorescent lifetime and small signal gain coefficient of N31 glasses at different Nd2O3 doping level are also reported. One thousand times testing on the cladding of 400 mm aperture N31 glass had been finished, in which the pumping density of Xenon lamps was almost the same as that in Shenguang Ⅲ facility.
This paper reviews the development of high power neodymium laser glasses and their main properties. The emphasis is on the research progress of pot melting, continuous melting and cladding techniques for large aperture N31 neodymium phosphate laser glass developed by Shanghai Institute of Optics and Fine Mechanics. The main properties of N31 glasses, prepared by pot melting and continuous melting, are compared. The attenuation at laser wavelength, fluorescent lifetime and small signal gain coefficient of N31 glasses at different Nd2O3 doping level are also reported. One thousand times testing on the cladding of 400 mm aperture N31 glass had been finished, in which the pumping density of Xenon lamps was almost the same as that in Shenguang Ⅲ facility.
2011,
23.
Abstract:
An optically pumped pulsed terahertz laser is presented. The pump laser is a line-tunable TEA CO2 laser. The terahertz cavity consists of a 2 m-long quartz glass tube, a GaAs input coupler and a SiO2 output coupler, and is filled with ammonia gas as terahertz active medium. Intense terahertz radiation is emitted at different wavelengths from the terahertz laser. The terahertz wavelengths are measured by a Fabry-Perot interferometer which is composed of two metal grids. As high as 204 mJ pulse energy is obtained at 151.5 μm wavelength when the cavity is pumped by a 32 J CO2 laser. The terahertz laser is applied in transmission imaging, and some preliminary imaging results are presented.
An optically pumped pulsed terahertz laser is presented. The pump laser is a line-tunable TEA CO2 laser. The terahertz cavity consists of a 2 m-long quartz glass tube, a GaAs input coupler and a SiO2 output coupler, and is filled with ammonia gas as terahertz active medium. Intense terahertz radiation is emitted at different wavelengths from the terahertz laser. The terahertz wavelengths are measured by a Fabry-Perot interferometer which is composed of two metal grids. As high as 204 mJ pulse energy is obtained at 151.5 μm wavelength when the cavity is pumped by a 32 J CO2 laser. The terahertz laser is applied in transmission imaging, and some preliminary imaging results are presented.
2011,
23.
Abstract:
Cryogenic adsorption technique may replace machinery pump and exhaust processing system, hence nitrogen dilution is used in discharge-driven continuous wave(CW) HF/DF chemical laser, which can greatly reduce the size and weight of laser system. The gain distribution of supersonic discharge-driven CW HF chemical laser is measured by small signal gain measurement system. Gain distribution curves of P1(4), P1(6), P2(4), P2(5), P2(6) are obtained at four different laser power, and the highest gain spectral line is P2(4) with the highest gain of 0.1 cm-1. The position of the highest gain is just the best position of optical axis. Under supersonic air stream, the gain zone extends to 2.5 cm.
Cryogenic adsorption technique may replace machinery pump and exhaust processing system, hence nitrogen dilution is used in discharge-driven continuous wave(CW) HF/DF chemical laser, which can greatly reduce the size and weight of laser system. The gain distribution of supersonic discharge-driven CW HF chemical laser is measured by small signal gain measurement system. Gain distribution curves of P1(4), P1(6), P2(4), P2(5), P2(6) are obtained at four different laser power, and the highest gain spectral line is P2(4) with the highest gain of 0.1 cm-1. The position of the highest gain is just the best position of optical axis. Under supersonic air stream, the gain zone extends to 2.5 cm.
2011,
23.
Abstract:
An algorithm is proposed to reconstruct wavefront using the whole spatial distribution of curvature signals mea-suredby curvature sensor with grating. The curvature signal’s spatial distributions of curvature deformable mirror’s response functions are used to fit the measured curvature signal, the control voltages are obtained by the least square method, and then the distorted wavefront is corrected. A 41-element curvature adaptive optic system is simulated to correct the distorted wavefront by the whole signal algorithm. The results show that the 4th to 28th order Zernike aberrations can be corrected, and Zernike aberrations with zero curvature can be reconstructed more accurately than the ones with non-zero curvature. Compared with the signal-divided algorithm, the whole signal algor
An algorithm is proposed to reconstruct wavefront using the whole spatial distribution of curvature signals mea-suredby curvature sensor with grating. The curvature signal’s spatial distributions of curvature deformable mirror’s response functions are used to fit the measured curvature signal, the control voltages are obtained by the least square method, and then the distorted wavefront is corrected. A 41-element curvature adaptive optic system is simulated to correct the distorted wavefront by the whole signal algorithm. The results show that the 4th to 28th order Zernike aberrations can be corrected, and Zernike aberrations with zero curvature can be reconstructed more accurately than the ones with non-zero curvature. Compared with the signal-divided algorithm, the whole signal algor
2011,
23.
Abstract:
Based on all-vector finite element method, general features of the loss spectrum of large-pitch kagome lattice hollow-core photonic crystal fiber(HC-PCF) are exhibited by investigating the effects of the core size, core shape and core-cladding boundary width on the guidance properties of the fiber. The numerical simulations show that the operational bandwidth of the fiber is drastically affected by improper core design parameters which cause the interaction among the fundamental core modes, surface modes and cladding modes. Therefore, the design of large-pitch kagome lattice HC-PCF with low loss and broad bandwidth should satisfy these conditions: the core size maintains the complete micro-structures of the cladding, the core shape matches the micro-structure of the cladding cells, and the
Based on all-vector finite element method, general features of the loss spectrum of large-pitch kagome lattice hollow-core photonic crystal fiber(HC-PCF) are exhibited by investigating the effects of the core size, core shape and core-cladding boundary width on the guidance properties of the fiber. The numerical simulations show that the operational bandwidth of the fiber is drastically affected by improper core design parameters which cause the interaction among the fundamental core modes, surface modes and cladding modes. Therefore, the design of large-pitch kagome lattice HC-PCF with low loss and broad bandwidth should satisfy these conditions: the core size maintains the complete micro-structures of the cladding, the core shape matches the micro-structure of the cladding cells, and the
2011,
23.
Abstract:
The main amplifier configuration verification platform of Shenguang-Ⅲ(SG-Ⅲ) laser facility is constructed by multi-path amplifier connection of SG-Ⅲ prototype facility. Based on this platform, the isolation ability of small switch, and the static transmission rate, isolation ratio and energy output capability of main amplifier system are tested. The result shows that, the beam average fluence of 1ω output meets the designed level of SG-Ⅲ laser facility and the effectiveness of SG-Ⅲ main amplifier configuration is verified.
The main amplifier configuration verification platform of Shenguang-Ⅲ(SG-Ⅲ) laser facility is constructed by multi-path amplifier connection of SG-Ⅲ prototype facility. Based on this platform, the isolation ability of small switch, and the static transmission rate, isolation ratio and energy output capability of main amplifier system are tested. The result shows that, the beam average fluence of 1ω output meets the designed level of SG-Ⅲ laser facility and the effectiveness of SG-Ⅲ main amplifier configuration is verified.
2011,
23.
Abstract:
In order to suppress complex background, an improved detection algorithm based on complex filter bank is presented for dim-small target under infrared background clutter. First, the spectrum characteristics of both the complex background image and the target image are analyzed, and the idea of sub-band processing is presented. Then after the comparison filters, the complex filter bank is adopted to decompose the infrared image with dim-small target into sections of different frequency bands. Next, the Robinson filter algorithm is used to process the decomposed sub-band images for extracting target. And finally these images are integrated with the method of weighting. The targets in the final processed image are enhanced notably and the backgrounds are suppressed effectively. The experiment
In order to suppress complex background, an improved detection algorithm based on complex filter bank is presented for dim-small target under infrared background clutter. First, the spectrum characteristics of both the complex background image and the target image are analyzed, and the idea of sub-band processing is presented. Then after the comparison filters, the complex filter bank is adopted to decompose the infrared image with dim-small target into sections of different frequency bands. Next, the Robinson filter algorithm is used to process the decomposed sub-band images for extracting target. And finally these images are integrated with the method of weighting. The targets in the final processed image are enhanced notably and the backgrounds are suppressed effectively. The experiment
2011,
23.
Abstract:
Laser-conditioning on multilayer dielectric gratings(MDGs) is investigated with the standard N-on-1 test method. It is found that the laser induced damage threshold(LIDT) of MDGs is increased up to 2.0 times the value without laser-conditioning. The possible physical mechanism can be explained by the reduction of contamination and surface roughness in the grating region under the irradiation of laser with low energy. In addition to the existing methods such as grating structure optimization and acid-cleaning, laser-conditioning could be an alternative way to improve the LIDT of MDGs.
Laser-conditioning on multilayer dielectric gratings(MDGs) is investigated with the standard N-on-1 test method. It is found that the laser induced damage threshold(LIDT) of MDGs is increased up to 2.0 times the value without laser-conditioning. The possible physical mechanism can be explained by the reduction of contamination and surface roughness in the grating region under the irradiation of laser with low energy. In addition to the existing methods such as grating structure optimization and acid-cleaning, laser-conditioning could be an alternative way to improve the LIDT of MDGs.
2011,
23.
Abstract:
The measurement of beam size is important for optimizing system parameters and ensuring stable operation of synchrotron radiation light sources. An interferometric method was adopted to measure the vertical size of beam section at Hefei Light Source. Based on the theory of Cittert-Zernike, the size of beam section can be calculated according to the double-slit interferogram contrast. The interferometric system consists of interference imaging system and image processing system. The results of the five experiments conducted agree well with the theoretical value, verifying the effectiveness of the interferometric method.
The measurement of beam size is important for optimizing system parameters and ensuring stable operation of synchrotron radiation light sources. An interferometric method was adopted to measure the vertical size of beam section at Hefei Light Source. Based on the theory of Cittert-Zernike, the size of beam section can be calculated according to the double-slit interferogram contrast. The interferometric system consists of interference imaging system and image processing system. The results of the five experiments conducted agree well with the theoretical value, verifying the effectiveness of the interferometric method.
2011,
23.
Abstract:
Direct laser welding was used to study the lead-free packaging of network filter through three different methods. The methods for direct laser welding of enameled copper wire with a diameter of 0.10 mm in network filter are obtained without removing the insulating paint of enameled wire. The results show that, as the laser irradiates the enameled wire of network filter, the insulating paint is wiped off; the copper core, which has a high melting temperature and good fluidity, is melted; the liquid copper whose temperature is higher than the melting temperature of aluminum flows down and coats the aluminum pin; the aluminum pin, which has many disadvantages such as poor fluidity, difficult to weld, easy oxidization, is coated by liquid copper and melts partly; mutual solution and diffusion
Direct laser welding was used to study the lead-free packaging of network filter through three different methods. The methods for direct laser welding of enameled copper wire with a diameter of 0.10 mm in network filter are obtained without removing the insulating paint of enameled wire. The results show that, as the laser irradiates the enameled wire of network filter, the insulating paint is wiped off; the copper core, which has a high melting temperature and good fluidity, is melted; the liquid copper whose temperature is higher than the melting temperature of aluminum flows down and coats the aluminum pin; the aluminum pin, which has many disadvantages such as poor fluidity, difficult to weld, easy oxidization, is coated by liquid copper and melts partly; mutual solution and diffusion
2011,
23.
Abstract:
Telecentric optical path and computer vision detection system were used to detect the space azimuth of a specific board. The number of feature points was studied about its influence on the detection, and further more about its determination to increase the detection reliability. The pictures of a specific board were captured by charge-coupled device(CCD), and the space azimuth of the specific board was obtained by image processing. A large number of experiments show that the detection accuracy has a certain relationship with the number of feature points. If the distance between specific board and CCD is from 2 m to 5 m, the calculated space azimuth is more accurate when the number of effective feature points on the specific board is greater than 28.
Telecentric optical path and computer vision detection system were used to detect the space azimuth of a specific board. The number of feature points was studied about its influence on the detection, and further more about its determination to increase the detection reliability. The pictures of a specific board were captured by charge-coupled device(CCD), and the space azimuth of the specific board was obtained by image processing. A large number of experiments show that the detection accuracy has a certain relationship with the number of feature points. If the distance between specific board and CCD is from 2 m to 5 m, the calculated space azimuth is more accurate when the number of effective feature points on the specific board is greater than 28.
2011,
23.
Abstract:
Based on the Mie scattering theory and the low density approximation, the Anderson localization parameters of photonic crystal constituted by GaAs were calculated theoretically, and the factors which influenced the localization phenomenon were analyzed. The results show that strict Anderson localization phenomena appear in far infrared region (50~65 μm) under the conditions of volumetric percentage of 10% and relative refractive index greater than 3.8. With the increase of the scatterer radius, the localization area shifts to longer wavelength, and the localization parameter firstly increases and then decreases.
Based on the Mie scattering theory and the low density approximation, the Anderson localization parameters of photonic crystal constituted by GaAs were calculated theoretically, and the factors which influenced the localization phenomenon were analyzed. The results show that strict Anderson localization phenomena appear in far infrared region (50~65 μm) under the conditions of volumetric percentage of 10% and relative refractive index greater than 3.8. With the increase of the scatterer radius, the localization area shifts to longer wavelength, and the localization parameter firstly increases and then decreases.
2011,
23.
Abstract:
Graphitemodified epoxy resin was prepared, the mechanisms of energy coupling between the modified epoxy resin and laser were discussed, and the laser resistance capability of the resin was studied. Damage morphologies of the resin irradiated by laser of different parameters were analyzed, and the ablation threshold and damage forms were confirmed. The results indicate that irradiated by continuous wave laser, the resin has a ablation threshold higher than 2 kW/cm2. The energy coupling coefficient is only about 10%, the thermal-ablation rate is as low as several μg/J, and the longitudinal adiabatic capability is excellent, with the thermal conductance lower than 10 W·K-1·m-1. At lower power density, the ablation of the resin is caused by slight oxidation, while it is caused by vaporizati
Graphitemodified epoxy resin was prepared, the mechanisms of energy coupling between the modified epoxy resin and laser were discussed, and the laser resistance capability of the resin was studied. Damage morphologies of the resin irradiated by laser of different parameters were analyzed, and the ablation threshold and damage forms were confirmed. The results indicate that irradiated by continuous wave laser, the resin has a ablation threshold higher than 2 kW/cm2. The energy coupling coefficient is only about 10%, the thermal-ablation rate is as low as several μg/J, and the longitudinal adiabatic capability is excellent, with the thermal conductance lower than 10 W·K-1·m-1. At lower power density, the ablation of the resin is caused by slight oxidation, while it is caused by vaporizati
2011,
23.
Abstract:
The paper introduces the mechanism of liquid-crystal-on-silicon(LCOS) display. tendue value is used to illustrate luminous flux and optical efficiency, and the relation between optical efficiency and étendue value is analyzed. Zemax and Tracepro are used in the design simulation. Experimental results show that the optical engine has advantages such as small size, low étendue, high light uniformity of more than 92% and high energy efficiency of 56%, and can meet the needs of projection display.
The paper introduces the mechanism of liquid-crystal-on-silicon(LCOS) display. tendue value is used to illustrate luminous flux and optical efficiency, and the relation between optical efficiency and étendue value is analyzed. Zemax and Tracepro are used in the design simulation. Experimental results show that the optical engine has advantages such as small size, low étendue, high light uniformity of more than 92% and high energy efficiency of 56%, and can meet the needs of projection display.
2011,
23.
Abstract:
The lightning optical signals were measured by a silicon photodiode detector(PDD) at Conghua city Guangdong province and Changping district Beijing city in summer, 2008. Totally, 12 observed data were analyzed statistically. The maximum optical peak magnitude is ［10.97(5.55)±12.46］ mW/cm2, the 10%-90% pulse rise time is 1.14(0.44)±2.02 ms, the 50%-50% pulse-width is ［1.44(0.49)±2.07］ ms and the single lightning optical peak count is 3.78(3.00)±2.30. The radiance peak is one to two orders of magnitude more and the pulse-width is broader, compared with the FORTE’s PDD data. These results are reasonable according to the lightning radiance mechanism and physical evolution process.
The lightning optical signals were measured by a silicon photodiode detector(PDD) at Conghua city Guangdong province and Changping district Beijing city in summer, 2008. Totally, 12 observed data were analyzed statistically. The maximum optical peak magnitude is ［10.97(5.55)±12.46］ mW/cm2, the 10%-90% pulse rise time is 1.14(0.44)±2.02 ms, the 50%-50% pulse-width is ［1.44(0.49)±2.07］ ms and the single lightning optical peak count is 3.78(3.00)±2.30. The radiance peak is one to two orders of magnitude more and the pulse-width is broader, compared with the FORTE’s PDD data. These results are reasonable according to the lightning radiance mechanism and physical evolution process.
2011,
23.
Abstract:
By using the method of generalized Huygens-Fresnel diffraction integral, the transmission analytical expression of flattened Gaussian beams in gradient-index media is deduced. The influence on the propagation properties of the medium gradient refractive index coefficient and the beam order is discussed. The results show that when flattened Gaussian beams propagate in gradient-index media, the intensity distribution on the axis varies periodically. Its change period is decided by the gradient-index coefficient, and has nothing to do with the beam order. The transverse intensity distribution of the peak on the axis is affected largely by the gradient-index coefficient and the beam order. The maximum on the plane with transversal intensity increases with the increase of the gradient-index coe
By using the method of generalized Huygens-Fresnel diffraction integral, the transmission analytical expression of flattened Gaussian beams in gradient-index media is deduced. The influence on the propagation properties of the medium gradient refractive index coefficient and the beam order is discussed. The results show that when flattened Gaussian beams propagate in gradient-index media, the intensity distribution on the axis varies periodically. Its change period is decided by the gradient-index coefficient, and has nothing to do with the beam order. The transverse intensity distribution of the peak on the axis is affected largely by the gradient-index coefficient and the beam order. The maximum on the plane with transversal intensity increases with the increase of the gradient-index coe
2011,
23.
Abstract:
In order to measure the actual elongation of piezoelectric transducer(PZT) driven by fast alternative electric field, a method based on frequency-modulation(FM) laser heterodyne signal demodulation technique is proposed. The method shifts the frequency spectrum of signal by using FM laser heterodyne technique so that the signal will not be disturbed by low-frequency noises. In that case, the Fourier spectrum of end plane velocity of PZT is measured accurately, with which the velocity variation can be deduced. Then, the elongation of PZT can be obtained by performing integration on the velocity. The results show that, this method simple, can acquire high quality signal easily, and has high sensitivity high accuracy.
In order to measure the actual elongation of piezoelectric transducer(PZT) driven by fast alternative electric field, a method based on frequency-modulation(FM) laser heterodyne signal demodulation technique is proposed. The method shifts the frequency spectrum of signal by using FM laser heterodyne technique so that the signal will not be disturbed by low-frequency noises. In that case, the Fourier spectrum of end plane velocity of PZT is measured accurately, with which the velocity variation can be deduced. Then, the elongation of PZT can be obtained by performing integration on the velocity. The results show that, this method simple, can acquire high quality signal easily, and has high sensitivity high accuracy.
2011,
23.
Abstract:
Copper-based aerogels were prepared by sol-gel method using inorganic salt as precursor and propylene oxide as gelation agent. The morphology of the copper-based aerogels was characterized by field-emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM), which suggests that the aerogels have a structure of 3-D networks and the skeleton is composed of CuO particles. The X-ray diffraction(XRD) results indicate that, the calcination of the aerogels at higher temperatures induces a phase change which results in the formation of copper oxide aerogels. The N2 adsorption/desorption result shows that the copper-based aerogels have a high specific surface area of about 386 m2/g.
Copper-based aerogels were prepared by sol-gel method using inorganic salt as precursor and propylene oxide as gelation agent. The morphology of the copper-based aerogels was characterized by field-emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM), which suggests that the aerogels have a structure of 3-D networks and the skeleton is composed of CuO particles. The X-ray diffraction(XRD) results indicate that, the calcination of the aerogels at higher temperatures induces a phase change which results in the formation of copper oxide aerogels. The N2 adsorption/desorption result shows that the copper-based aerogels have a high specific surface area of about 386 m2/g.
2011,
23.
Abstract:
The research on pinhole-assisted point-projection backlighting has been performed on Shanghai Shenguang-Ⅱ laser facility. The point-like X-ray source at 4.75 keV was produced from 200 J/200 ps/351 nm backlighting laser interaction with 10 μm thick Ti target. And the clear gridding image with a spatial resolution of 7 μm was obtained. Key issues in improving signal-to-noise ratio and preventing blasting debris were analyzed. The pinhole-assisted point-projection backlighting shows advantages over traditional backlighting techniques, such as high spatial resolution, large view field.
The research on pinhole-assisted point-projection backlighting has been performed on Shanghai Shenguang-Ⅱ laser facility. The point-like X-ray source at 4.75 keV was produced from 200 J/200 ps/351 nm backlighting laser interaction with 10 μm thick Ti target. And the clear gridding image with a spatial resolution of 7 μm was obtained. Key issues in improving signal-to-noise ratio and preventing blasting debris were analyzed. The pinhole-assisted point-projection backlighting shows advantages over traditional backlighting techniques, such as high spatial resolution, large view field.
2011,
23.
Abstract:
Intermittent characteristics of turbulence induced by coherent structures (Blob) are manifested clearly on the Langmuir probe signal of HT-7 tokamak. With conditional analysis, asymmetric characteristics of the intermittent bursts are demonstrated. The parameter of plasma inside the Blob is larger than the background plasma parameter. Due to the radial propagation of the coherent structures, the particle density and temperature profiles in the scrape-off layer (SOL) are non-exponential and flat away from the last closed flux surface(LCFS). Around the LCFS, large burst fluctuations are responsible for about 50% of the total transport. These experimental finds may imply that the coherent structures are distorted by the developed shear flow in the shear layer. In SOL region, the coherent stru
Intermittent characteristics of turbulence induced by coherent structures (Blob) are manifested clearly on the Langmuir probe signal of HT-7 tokamak. With conditional analysis, asymmetric characteristics of the intermittent bursts are demonstrated. The parameter of plasma inside the Blob is larger than the background plasma parameter. Due to the radial propagation of the coherent structures, the particle density and temperature profiles in the scrape-off layer (SOL) are non-exponential and flat away from the last closed flux surface(LCFS). Around the LCFS, large burst fluctuations are responsible for about 50% of the total transport. These experimental finds may imply that the coherent structures are distorted by the developed shear flow in the shear layer. In SOL region, the coherent stru
2011,
23.
Abstract:
The nonlinear coupling equations of low-frequency potential, high-frequency modulation field and density disturbance in strong turbulent plasmas were numerically calculated in the static limit case. The evolutions of double layers and density cavitons were obtained. The results show that the double layer in downward current region of aurora is formed by localized drop in density owing to collapsed high frequency field. The structure is a double-double layer and a nonlinear entity: caviton. The ramp potential of the double layer is in range of 14 to 40 V, and the thickness of the structure is between 100 and 200 m, roughly tens of Debye lengths; the maximum density perturbation rate is up to more than 80%, which are all in harmony with the measurements by the Fast Auroral Snapshot satellite
The nonlinear coupling equations of low-frequency potential, high-frequency modulation field and density disturbance in strong turbulent plasmas were numerically calculated in the static limit case. The evolutions of double layers and density cavitons were obtained. The results show that the double layer in downward current region of aurora is formed by localized drop in density owing to collapsed high frequency field. The structure is a double-double layer and a nonlinear entity: caviton. The ramp potential of the double layer is in range of 14 to 40 V, and the thickness of the structure is between 100 and 200 m, roughly tens of Debye lengths; the maximum density perturbation rate is up to more than 80%, which are all in harmony with the measurements by the Fast Auroral Snapshot satellite
2011,
23.
Abstract:
A focusing spectrometer with toroidally bent crystal is designed for X-ray monochromatic imaging. The focusing properties of toroidally bent crystal and spherically bent crystal in Bragg geometry are discussed, and the conditions for optimized two-dimensional(2D) imaging of X-ray source are proposed. X-ray backlight imaging experiments have been carried out in Research Center of Laser Fusion. A toroidally bent crystal of mica was used as the imaging element with curvature radii of 290 mm and 190 mm in meridional and sagittal planes, respectively. With the high collection efficiency of the bent crystal spectrometer, high quality visible 2D X-ray backlighting images were obtained by the imaging plate. It is demonstrated that, the toroidally bent mica crystal can be used for X-ray monochromat
A focusing spectrometer with toroidally bent crystal is designed for X-ray monochromatic imaging. The focusing properties of toroidally bent crystal and spherically bent crystal in Bragg geometry are discussed, and the conditions for optimized two-dimensional(2D) imaging of X-ray source are proposed. X-ray backlight imaging experiments have been carried out in Research Center of Laser Fusion. A toroidally bent crystal of mica was used as the imaging element with curvature radii of 290 mm and 190 mm in meridional and sagittal planes, respectively. With the high collection efficiency of the bent crystal spectrometer, high quality visible 2D X-ray backlighting images were obtained by the imaging plate. It is demonstrated that, the toroidally bent mica crystal can be used for X-ray monochromat
2011,
23.
Abstract:
An X-ray charge coupled device(CCD) was calibrated on the beamline 4B7B at Beijing Synchrotron Radiation Facility after the optimization of suppressing methods for high-order harmonics. In the process of data analysis, equivalent exposure time was introduced to correct the exposure time. Then the sensitivities of the CCD in the energy range between 100 and 1 500 eV were obtained. The calibration experiment fills the data gap of the sensitivity of the CCD in the energy range between 300 and 600 eV and validates the modeling in this energy range.
An X-ray charge coupled device(CCD) was calibrated on the beamline 4B7B at Beijing Synchrotron Radiation Facility after the optimization of suppressing methods for high-order harmonics. In the process of data analysis, equivalent exposure time was introduced to correct the exposure time. Then the sensitivities of the CCD in the energy range between 100 and 1 500 eV were obtained. The calibration experiment fills the data gap of the sensitivity of the CCD in the energy range between 300 and 600 eV and validates the modeling in this energy range.
2011,
23.
Abstract:
The spatial resolution model of KBA X-ray microscope is built, taking into account geometrical aberration, diffraction effect, etc. Through ray-tracing, the edge response function(ERF) of different fields of view is got, and the geometrical aberration resolution based on the criterion of the ERF between 20% and 80% of its peak-valley value is determined. According to our model, the ideal resolution is obtained. In all the field of view, the geometrical aberration resolution, ideal resolution and experimental resolution are in good agreement. Using the X-ray image from the single film KBA microscope, the resolution is calculated to be about 4 μm in central field and better than 6 μm in ±100 μm range. The experiment result shows that, geometrical aberration is the key factor that determi
The spatial resolution model of KBA X-ray microscope is built, taking into account geometrical aberration, diffraction effect, etc. Through ray-tracing, the edge response function(ERF) of different fields of view is got, and the geometrical aberration resolution based on the criterion of the ERF between 20% and 80% of its peak-valley value is determined. According to our model, the ideal resolution is obtained. In all the field of view, the geometrical aberration resolution, ideal resolution and experimental resolution are in good agreement. Using the X-ray image from the single film KBA microscope, the resolution is calculated to be about 4 μm in central field and better than 6 μm in ±100 μm range. The experiment result shows that, geometrical aberration is the key factor that determi
2011,
23.
Abstract:
Glycidylamine-type polyurethane(GAPU) was prepared through the reaction of SKE-1 and self-made polyurethane prepolymer. The structure of GAPU was characterized by Fourier transform infrared(FT-IR) spectroscopy and phase separation was confirmed by differential scanning calorimetry(DSC). The curing process of GAPU cured by m-XDA was monitoring with on-line FT-IR spectroscopy and the thermodynamic stability was analyzed by thermal gravity(TG) analysis. The morphology of the fractured surface of tensile shear strength test specimen was investigated by scanning electron microscopy(SEM). Effects of different contents and different curing agents on mechanical properties of the cured GAPU were studied. The results show that GAPU is fully cured by m-XDA in two hours at 60 ℃, gives good thermal s
Glycidylamine-type polyurethane(GAPU) was prepared through the reaction of SKE-1 and self-made polyurethane prepolymer. The structure of GAPU was characterized by Fourier transform infrared(FT-IR) spectroscopy and phase separation was confirmed by differential scanning calorimetry(DSC). The curing process of GAPU cured by m-XDA was monitoring with on-line FT-IR spectroscopy and the thermodynamic stability was analyzed by thermal gravity(TG) analysis. The morphology of the fractured surface of tensile shear strength test specimen was investigated by scanning electron microscopy(SEM). Effects of different contents and different curing agents on mechanical properties of the cured GAPU were studied. The results show that GAPU is fully cured by m-XDA in two hours at 60 ℃, gives good thermal s
Multi-parameter measurement method of image intensifier based on Fourier transform phase measurement
2011,
23.
Abstract:
An imaging quality measuring method of image intensifier is presented, which can obtain many characters simultaneously by Fourier transform phase measurement. When a sinusoidal pattern is the input, a deformed fringe pattern will be the output if there is any imaging quality problem in the image intensifier. Obtaining the phase changes of the deformed fringe pattern by Fourier transform phase measurement can extract the information of magnification， magnification inhomogeneity, pillow-shaped distortion, barrel-shaped distortion, snake-shaped distortion, and shearing distortion. And after the calibration of the measurement system, the above parameters can be derived simultaneously. The experimental results show that, the measured central magnification has a difference of the magnitude of
An imaging quality measuring method of image intensifier is presented, which can obtain many characters simultaneously by Fourier transform phase measurement. When a sinusoidal pattern is the input, a deformed fringe pattern will be the output if there is any imaging quality problem in the image intensifier. Obtaining the phase changes of the deformed fringe pattern by Fourier transform phase measurement can extract the information of magnification， magnification inhomogeneity, pillow-shaped distortion, barrel-shaped distortion, snake-shaped distortion, and shearing distortion. And after the calibration of the measurement system, the above parameters can be derived simultaneously. The experimental results show that, the measured central magnification has a difference of the magnitude of
2011,
23.
Abstract:
The research of inertial confinement fusion demands a streak image tube with femtosecond temporal resolution and large dynamic range. In order to obtain a setup in the practical application, a novel soft X-ray streak image tube was proposed and designed. A planar symmetric electrostatic cylindrical lens with five electrodes was introduced into the image tube model, which has a strong ability to focus the electron beam, and has no cross-over effects as in the axial-symmetrical system. The cylindrical lens can shorten the length of image tube, reduce the transit time dispersion, and restrain space charge effects, thus enlarging the dynamic range and improving the temporal resolution. The simulation results show that if the photoelectron’s initial energy spread is 1.6 eV, and the slit area i
The research of inertial confinement fusion demands a streak image tube with femtosecond temporal resolution and large dynamic range. In order to obtain a setup in the practical application, a novel soft X-ray streak image tube was proposed and designed. A planar symmetric electrostatic cylindrical lens with five electrodes was introduced into the image tube model, which has a strong ability to focus the electron beam, and has no cross-over effects as in the axial-symmetrical system. The cylindrical lens can shorten the length of image tube, reduce the transit time dispersion, and restrain space charge effects, thus enlarging the dynamic range and improving the temporal resolution. The simulation results show that if the photoelectron’s initial energy spread is 1.6 eV, and the slit area i
2011,
23.
Abstract:
Numerical simulations and analyses are done on two types of gas targets by using a computational fluid-dynamics software. For a gas-filling capillary, a stable laminar flow can be formed. It can produce a uniform density distribution and the nonuniformity between the two inlets is only 1%. The capillary parameters such as the capillary’s inlet locations and the inlet width have evident influence on the density profiles around the capillary’s ends, but negligible on the density-profile distributions inside the capillary. For a conical gas jet, it can make the end-density profile steeper than that of the capillary. But the supersonic flow of the gas jet may cause turbulence, which may cause the gas flow unstable and the gas-density profile less uniform.
Numerical simulations and analyses are done on two types of gas targets by using a computational fluid-dynamics software. For a gas-filling capillary, a stable laminar flow can be formed. It can produce a uniform density distribution and the nonuniformity between the two inlets is only 1%. The capillary parameters such as the capillary’s inlet locations and the inlet width have evident influence on the density profiles around the capillary’s ends, but negligible on the density-profile distributions inside the capillary. For a conical gas jet, it can make the end-density profile steeper than that of the capillary. But the supersonic flow of the gas jet may cause turbulence, which may cause the gas flow unstable and the gas-density profile less uniform.
2011,
23.
Abstract:
The paper presents a method to get high power microwave gas breakdown by changing the effective aperture of horn antenna. Changing the effective aperture can adjust the electric field near the inner dielectric window, lending to air breakdown. The principle of this method is introduced. In addition, the verification experiment has been carried out for L band microwave with pulse duration being 30 ns, and the experimental waveforms are analyzed. The breakdown threshold of 0.40×105 Pa air was measured to be 33.9 kV/cm. The experimental results agree well with the design, and the method is proved to be effective to study high power microwave gas breakdown.
The paper presents a method to get high power microwave gas breakdown by changing the effective aperture of horn antenna. Changing the effective aperture can adjust the electric field near the inner dielectric window, lending to air breakdown. The principle of this method is introduced. In addition, the verification experiment has been carried out for L band microwave with pulse duration being 30 ns, and the experimental waveforms are analyzed. The breakdown threshold of 0.40×105 Pa air was measured to be 33.9 kV/cm. The experimental results agree well with the design, and the method is proved to be effective to study high power microwave gas breakdown.
2011,
23.
Abstract:
The passive harmonically mode-locked fiber ring laser with a small segment of Er3+/Yb3+ codoped double-clad fiber as gain medium, which is pumped by 976 nm LD laser and mode-locked exploiting the nonlinear polarization rotation technique, was successfully demonstrated for the generation of self-starting mode-locked pulses. When the laser was pumped at 2.4 W, stable mode-locked pulses were obtained at the repetition rate of 8.829 MHz through modulating the fiber polarization controllers. The average output power of the fiber laser was 52.5 mW, and the threshold power of the self-starting mode-locked pumping is 0.6 W. The high-order mode-locked, Q-switched and Q-switched-mode-locked pulses were also observed experimentally.
The passive harmonically mode-locked fiber ring laser with a small segment of Er3+/Yb3+ codoped double-clad fiber as gain medium, which is pumped by 976 nm LD laser and mode-locked exploiting the nonlinear polarization rotation technique, was successfully demonstrated for the generation of self-starting mode-locked pulses. When the laser was pumped at 2.4 W, stable mode-locked pulses were obtained at the repetition rate of 8.829 MHz through modulating the fiber polarization controllers. The average output power of the fiber laser was 52.5 mW, and the threshold power of the self-starting mode-locked pumping is 0.6 W. The high-order mode-locked, Q-switched and Q-switched-mode-locked pulses were also observed experimentally.
2011,
23.
Abstract:
A radial line mode converter is developed, which can convert TEM (or TM01) mode to TE11 mode by changing the azimuthal symmetry of field distribution in wavequide. The principle of the mode converter is as follows: the coaxial TEM mode is converted to 4-way 90°-sector-waveguide TE11 mode by setting fins into the coaxial waveguide; the output phase differences among the sector waveguides are realized by transforming the sector waveguide to two-layered radial line. A mode converter centered at 1.6 GHz based on this principle is designed and optimized. The calculated results show that it has high power handling capacity, with about 10% bandwidth (1.52 to 1.68 GHz) where the conversion efficiency exceeds 90% and the conversion efficiency and reflection are 99% and 0.05 respectively at the cen
A radial line mode converter is developed, which can convert TEM (or TM01) mode to TE11 mode by changing the azimuthal symmetry of field distribution in wavequide. The principle of the mode converter is as follows: the coaxial TEM mode is converted to 4-way 90°-sector-waveguide TE11 mode by setting fins into the coaxial waveguide; the output phase differences among the sector waveguides are realized by transforming the sector waveguide to two-layered radial line. A mode converter centered at 1.6 GHz based on this principle is designed and optimized. The calculated results show that it has high power handling capacity, with about 10% bandwidth (1.52 to 1.68 GHz) where the conversion efficiency exceeds 90% and the conversion efficiency and reflection are 99% and 0.05 respectively at the cen
2011,
23.
Abstract:
This paper studies a W-band high-order harmonic peniotron with magnetron resonant system, which has the merits of high efficiency, low external magnetic field and low operation voltage. By solving the dispersion relation of the resonant system, the relation between the resonant system and the selection of harmonics has been pointed out. The primary design of an 11-vane high-order harmonic peniotron working in 2π mode has been completed. Three-dimensional PIC simulation and optimization results show that this device can produce an average output power of 8.6 kW with 28.7% efficiency at 99.1 GHz, under the external magnetic field of 0.379 T, velocity ratio of 2, and operation voltage and current of 30 kV and 1 A, respectively.
This paper studies a W-band high-order harmonic peniotron with magnetron resonant system, which has the merits of high efficiency, low external magnetic field and low operation voltage. By solving the dispersion relation of the resonant system, the relation between the resonant system and the selection of harmonics has been pointed out. The primary design of an 11-vane high-order harmonic peniotron working in 2π mode has been completed. Three-dimensional PIC simulation and optimization results show that this device can produce an average output power of 8.6 kW with 28.7% efficiency at 99.1 GHz, under the external magnetic field of 0.379 T, velocity ratio of 2, and operation voltage and current of 30 kV and 1 A, respectively.
2011,
23.
Abstract:
An electron beam collection method in relativistic klystron amplifier(RKA) controlled by magnetic field is proposed. The influence of collection position on beam-wave conversion efficiency and stability of RKA is also analyzed. When the electron beam is collected at a proper position, the interaction between beam and microwave can be enhanced, and the space charge potential of electron beam and the number of reflected electrons can be reduced. An RKA has been improved with electron beam collection at the frequency of 2.85 GHz. When the electron beam voltage and current are 510 keV, 8.1 kA, the input power is 500 kW, and the guiding magnetic field is 1.5 T, an output power of 1.4 GW is obtained, and the corresponding efficiency and gain are 33.7% and 33.8 dB, respectively. When the beam col
An electron beam collection method in relativistic klystron amplifier(RKA) controlled by magnetic field is proposed. The influence of collection position on beam-wave conversion efficiency and stability of RKA is also analyzed. When the electron beam is collected at a proper position, the interaction between beam and microwave can be enhanced, and the space charge potential of electron beam and the number of reflected electrons can be reduced. An RKA has been improved with electron beam collection at the frequency of 2.85 GHz. When the electron beam voltage and current are 510 keV, 8.1 kA, the input power is 500 kW, and the guiding magnetic field is 1.5 T, an output power of 1.4 GW is obtained, and the corresponding efficiency and gain are 33.7% and 33.8 dB, respectively. When the beam col
2011,
23.
Abstract:
An atmospheric pressure microwave plasma torch(MPT) operating at 2.45 GHz was designed. Corresponding simulation based on HFSS code was performed and the influences of structure parameters on the E-field distribution in the device were analyzed. The results indicate that the use of coupling probe will have a distinct impact on the field distribution in the device. A MPT with strong electric field amplitude and high Q-factor about 20 000 was achieved in simulation by adjusting the structure parameters, which could produce microwave plasma at atmospheric pressure.
An atmospheric pressure microwave plasma torch(MPT) operating at 2.45 GHz was designed. Corresponding simulation based on HFSS code was performed and the influences of structure parameters on the E-field distribution in the device were analyzed. The results indicate that the use of coupling probe will have a distinct impact on the field distribution in the device. A MPT with strong electric field amplitude and high Q-factor about 20 000 was achieved in simulation by adjusting the structure parameters, which could produce microwave plasma at atmospheric pressure.
2011,
23.
Abstract:
This paper proposes an improved design method of slotted waveguide antennas. Since Elliott’s design method for slotted waveguide antennas applies only to the case with real voltage distribution it is incapable of designing slotted waveguide antennas with arbitrary radiation pattern. The improved design method presented and is extends its applications to case of the complex voltage distribution including the effects of mutual coupling. The comparison of results derived by the improved method and the commercial software Ansoft HFSS shows that, the method is accurate and effective.
This paper proposes an improved design method of slotted waveguide antennas. Since Elliott’s design method for slotted waveguide antennas applies only to the case with real voltage distribution it is incapable of designing slotted waveguide antennas with arbitrary radiation pattern. The improved design method presented and is extends its applications to case of the complex voltage distribution including the effects of mutual coupling. The comparison of results derived by the improved method and the commercial software Ansoft HFSS shows that, the method is accurate and effective.
2011,
23.
Abstract:
This article mainly studies the influence of source stirring on the field characteristics, especially the field uniformity, in the reverberation chamber under short pulse excitation. Firstly, the factors that may affect the field distribution are summarized. Then the focus is on the effects of moving the sources consecutively on the electromagnetic field distributions, including the maximum and the standard deviation of electric field strength. The results show that the maximum of electric field strength can reach as high as 6.7 kV/m and the standard deviation of the field distribution falls below 3 dB after stirring the sources. Therefore, the method of source stirring can improve the field uniformity effectively and it is useful in the construction of homogenous electromagnetic field env
This article mainly studies the influence of source stirring on the field characteristics, especially the field uniformity, in the reverberation chamber under short pulse excitation. Firstly, the factors that may affect the field distribution are summarized. Then the focus is on the effects of moving the sources consecutively on the electromagnetic field distributions, including the maximum and the standard deviation of electric field strength. The results show that the maximum of electric field strength can reach as high as 6.7 kV/m and the standard deviation of the field distribution falls below 3 dB after stirring the sources. Therefore, the method of source stirring can improve the field uniformity effectively and it is useful in the construction of homogenous electromagnetic field env
