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RSS2009 Vol. 21, No. 09
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2009,
21.
Abstract:
There are strong interactions or couplings among multi-fields in the mixing nozzle of the chemical oxygen-iodine laser(COIL), such as gas-dynamics, chemical reaction kinetics and optics. In this paper, three-dimensional computational flow dynamic technology was applied on the research assessment device improvement chemical laser model by solving the laminar Navier-Stokes equations and transportation equations to study iodine molecule dissociation rate, iodine atom pumping rate, singlet oxygen yield rate and small signal gain distributions. The simulation was done in the condition of that the secondary flow jet would take place in the supersonic section of the nozzle. The detailed flow field and distribution of yield, dissociation and pumping rates were investigated. The distribution charac
There are strong interactions or couplings among multi-fields in the mixing nozzle of the chemical oxygen-iodine laser(COIL), such as gas-dynamics, chemical reaction kinetics and optics. In this paper, three-dimensional computational flow dynamic technology was applied on the research assessment device improvement chemical laser model by solving the laminar Navier-Stokes equations and transportation equations to study iodine molecule dissociation rate, iodine atom pumping rate, singlet oxygen yield rate and small signal gain distributions. The simulation was done in the condition of that the secondary flow jet would take place in the supersonic section of the nozzle. The detailed flow field and distribution of yield, dissociation and pumping rates were investigated. The distribution charac
2009,
21.
Abstract:
The differences of electric field distribution produced by the variation of parameters in an asymmetric multielectrode system for high power gas lasers are studied. With the highprecision finite element method, the model of such complicated electrodes system is presented, and its electric field is calculated numerically. For a typical TEA CO2 laser with asymmetric electrodes and printed circuit board preionization structure, this method is applied to analyze electric field uniformity and uniform field range. The results suggest that a better distribution of electric field can be obtained by optimizing of structure parameters based on simulation, and lower cost for the electrodes configuration can be achieved at the same time. Stable operation at 200 Hz with an average output of 7 J per
The differences of electric field distribution produced by the variation of parameters in an asymmetric multielectrode system for high power gas lasers are studied. With the highprecision finite element method, the model of such complicated electrodes system is presented, and its electric field is calculated numerically. For a typical TEA CO2 laser with asymmetric electrodes and printed circuit board preionization structure, this method is applied to analyze electric field uniformity and uniform field range. The results suggest that a better distribution of electric field can be obtained by optimizing of structure parameters based on simulation, and lower cost for the electrodes configuration can be achieved at the same time. Stable operation at 200 Hz with an average output of 7 J per
2009,
21.
Abstract:
An initial baseline approach of fabricating the full ring HYLTE nozzle blade from 4-1/4 ring segments is selected. A novel 1/4 ring HYLTE nozzle structure including three gas supply pipelines is obtained by further simplifing existing ring nozzle structures. The section centers of the pipelines are all on the symmetric plane of the nozzle blade. These changements will not influence the performance of the nozzle. In addition, two fabricating methods of ring HYLTE nozzle blades are presented, one is vacuum brazing method, the other is embed-casting method. Samples are made using the first method. The corresponding testing results demonstrate that the welds of the ring nozzle blade have the characteristics of resistance to leaking, well mechanical properties and working properly in high tempe
An initial baseline approach of fabricating the full ring HYLTE nozzle blade from 4-1/4 ring segments is selected. A novel 1/4 ring HYLTE nozzle structure including three gas supply pipelines is obtained by further simplifing existing ring nozzle structures. The section centers of the pipelines are all on the symmetric plane of the nozzle blade. These changements will not influence the performance of the nozzle. In addition, two fabricating methods of ring HYLTE nozzle blades are presented, one is vacuum brazing method, the other is embed-casting method. Samples are made using the first method. The corresponding testing results demonstrate that the welds of the ring nozzle blade have the characteristics of resistance to leaking, well mechanical properties and working properly in high tempe
2009,
21.
Abstract:
The air breakdown in the coupling area of 15 MW laser pulse and 600 μm silica optical fiber is investigated. The air breakdown of the focal area is theoretically and experimentally researched. The air breakdown threshold is measured as 0.79×109 W/cm2。. The laser induced damage threshold of the solid medium is measured as 2.12×109 W/cm2。, which is consistent with the theory analyze. A sevenfiber coupler is presented to solve the air breakdown problem. The coupling efficiency of the seven fiber bundle tested is 67.21%. It is concluded that the sevenfiber coupler could couple 15 MW laser pulse into 600 μm silica optical fiber．
The air breakdown in the coupling area of 15 MW laser pulse and 600 μm silica optical fiber is investigated. The air breakdown of the focal area is theoretically and experimentally researched. The air breakdown threshold is measured as 0.79×109 W/cm2。. The laser induced damage threshold of the solid medium is measured as 2.12×109 W/cm2。, which is consistent with the theory analyze. A sevenfiber coupler is presented to solve the air breakdown problem. The coupling efficiency of the seven fiber bundle tested is 67.21%. It is concluded that the sevenfiber coupler could couple 15 MW laser pulse into 600 μm silica optical fiber．
2009,
21.
Abstract:
A polarization Mie lidar has been developed for measuring profiles of depolarization ratio of cirrus clouds and dust aerosols. The fundamental principle of the polarization lidar was briefly introduced. Overall structure and specifications of the polarization lidar were described as well as measurement and data processing methods. The typical observational results of depolarization ratio and structure of the cirrus over western suburb of Hefei were presented and discussed. The optical properties of the cirrus were also described. The primary observational results showed that the depolarization ratio for cirrus clouds varies from 0.2 to 0.5 within the altitude range of 6～10 km, and the lidar has the ability to measure the optical properties of cirrus clouds and their temporal and spatial v
A polarization Mie lidar has been developed for measuring profiles of depolarization ratio of cirrus clouds and dust aerosols. The fundamental principle of the polarization lidar was briefly introduced. Overall structure and specifications of the polarization lidar were described as well as measurement and data processing methods. The typical observational results of depolarization ratio and structure of the cirrus over western suburb of Hefei were presented and discussed. The optical properties of the cirrus were also described. The primary observational results showed that the depolarization ratio for cirrus clouds varies from 0.2 to 0.5 within the altitude range of 6～10 km, and the lidar has the ability to measure the optical properties of cirrus clouds and their temporal and spatial v
2009,
21.
Abstract:
The optical true time delay scheme based on magneto-optic(MO) switch was analyzed, and optical and electrical features of MO switch were discussed. The advantages and disadvantages of different topologies were analyzed, i.e. bypass structure and differential structure. A method for measuring optical delay with high precision and high efficiency was put forward. A 5 bit optical delay line system based on MO switch and fiber was set up, and the maximal delay error was less than 3 ps. The test of optical delay units shows that the insertion loss of 32 delay states ranges from 0.12 dB to 0.88 dB at a temperature of 0 to 40 ℃.
The optical true time delay scheme based on magneto-optic(MO) switch was analyzed, and optical and electrical features of MO switch were discussed. The advantages and disadvantages of different topologies were analyzed, i.e. bypass structure and differential structure. A method for measuring optical delay with high precision and high efficiency was put forward. A 5 bit optical delay line system based on MO switch and fiber was set up, and the maximal delay error was less than 3 ps. The test of optical delay units shows that the insertion loss of 32 delay states ranges from 0.12 dB to 0.88 dB at a temperature of 0 to 40 ℃.
2009,
21.
Abstract:
A miniature high-temperature supersonic flow simulation device has been introduced. The velocity distribution of the flow produced by the device was diagnosed using hydroxyl tagging velocimetry(HTV). Through changing the spatial position of the 193 nm laser relative to the flow, some HTV experimental images were acquired at different areas of the flow. And axial velocity distributions of the flow were calculated from the images. The measurement results indicated that the velocity of the flow in the compression area is much slower than that in the expansion area. In the initial part of the compression area the velocity at the flow center is higher than that at both sides, while in the second expansion area the velocity at the center is slower.
A miniature high-temperature supersonic flow simulation device has been introduced. The velocity distribution of the flow produced by the device was diagnosed using hydroxyl tagging velocimetry(HTV). Through changing the spatial position of the 193 nm laser relative to the flow, some HTV experimental images were acquired at different areas of the flow. And axial velocity distributions of the flow were calculated from the images. The measurement results indicated that the velocity of the flow in the compression area is much slower than that in the expansion area. In the initial part of the compression area the velocity at the flow center is higher than that at both sides, while in the second expansion area the velocity at the center is slower.
2009,
21.
Abstract:
As for the numerical solution of cascaded Raman fiber laser(CRFL) optical power coupling equations, the problem is that the conventional shooting algorithm is a waste of time and easily undershoots. In the new algorithm the equations is simply transformed to obtain the fitness function which can be solved by the optimization algorithm. According to the actual situation of fitness function, the improved particle swarm optimization(PSO) can enhance the optimization capability of complex functions compared with the basic PSO. The algorithm is also tested by the fitness functions derived from the theoretical model of different structures of CRFLs, and the calculating time is no more than 15 s when the accuracy of the fitness function is 10-5. The algorithm used in conjunction with the Newton-R
As for the numerical solution of cascaded Raman fiber laser(CRFL) optical power coupling equations, the problem is that the conventional shooting algorithm is a waste of time and easily undershoots. In the new algorithm the equations is simply transformed to obtain the fitness function which can be solved by the optimization algorithm. According to the actual situation of fitness function, the improved particle swarm optimization(PSO) can enhance the optimization capability of complex functions compared with the basic PSO. The algorithm is also tested by the fitness functions derived from the theoretical model of different structures of CRFLs, and the calculating time is no more than 15 s when the accuracy of the fitness function is 10-5. The algorithm used in conjunction with the Newton-R
2009,
21.
Abstract:
A Rayleigh-Raman-Mie lidar(RRML) was constructed to detect atmosphere temperature, aerosols and cirrus. The simulated signal was calculated using aerosol model and lidar system parameters, and the design method of the signal detection unit and optical receiver unit was based on the characteristic of the simulated signal. By using the extremely sensitive R4632 photomultiplier tube and the photon counting system, the lidar system achieved higher signal to noise ratios of Raman and Rayleigh signals. By using the PMT gating control unit and the optical signal attenuating mirror, the system could detect signals backscattered by aerosols and cirrus linearly. Finally, the signal detected by the RRML system was given, which proves the rationality of the RRML design method.
A Rayleigh-Raman-Mie lidar(RRML) was constructed to detect atmosphere temperature, aerosols and cirrus. The simulated signal was calculated using aerosol model and lidar system parameters, and the design method of the signal detection unit and optical receiver unit was based on the characteristic of the simulated signal. By using the extremely sensitive R4632 photomultiplier tube and the photon counting system, the lidar system achieved higher signal to noise ratios of Raman and Rayleigh signals. By using the PMT gating control unit and the optical signal attenuating mirror, the system could detect signals backscattered by aerosols and cirrus linearly. Finally, the signal detected by the RRML system was given, which proves the rationality of the RRML design method.
2009,
21.
Abstract:
Plasma was produced by laser-induced breakdown in air using the 10.6 μm beam from an pulsed CO2 laser. The plasma spectra were collected by the spectrometer and ICCD. The plasma temperasure was calculated by using the model of local thermodynamic equilibrium. When the laser pulse energy was 35 J, according to the relative intensities of two atom spectral lines NⅡ399.5 nm and NⅡ500.5 nm, the temperature of the plasmas at different time delays was evaluated. It is demonatrated that, the temporal evolution of plasma temperature is ascent-saturation-descent by sampling at the different positions of the plasma, and the temperature at the front edge of the plasma is sooner to become saturated than the temperature near the target.
Plasma was produced by laser-induced breakdown in air using the 10.6 μm beam from an pulsed CO2 laser. The plasma spectra were collected by the spectrometer and ICCD. The plasma temperasure was calculated by using the model of local thermodynamic equilibrium. When the laser pulse energy was 35 J, according to the relative intensities of two atom spectral lines NⅡ399.5 nm and NⅡ500.5 nm, the temperature of the plasmas at different time delays was evaluated. It is demonatrated that, the temporal evolution of plasma temperature is ascent-saturation-descent by sampling at the different positions of the plasma, and the temperature at the front edge of the plasma is sooner to become saturated than the temperature near the target.
2009,
21.
Abstract:
The signal intensity was estimated for on-line measurement X-ray pinhole camera with CCD as measurement equipment. The X-ray signal intensity counts after the attenuation of thickness-varied Be filters and different material flat mirrors respectively were estimated using the energy spectrum of certain laser prototyper and the quantum efficiency curve of PI-SX1300 CCD camera. The calculated results indicate that Be filters no thicker than 200 μm can only reduce signal intensity by one order of magnitude, and so can Au flat mirror with 3° incident angle,Ni, C and Si flat mirrors with 5° incident angle, but the signal intensity counts for both attenuation methods are beyond the saturation counts of the CCD camera. We also calculated the attenuation of signal intensity for different thickne
The signal intensity was estimated for on-line measurement X-ray pinhole camera with CCD as measurement equipment. The X-ray signal intensity counts after the attenuation of thickness-varied Be filters and different material flat mirrors respectively were estimated using the energy spectrum of certain laser prototyper and the quantum efficiency curve of PI-SX1300 CCD camera. The calculated results indicate that Be filters no thicker than 200 μm can only reduce signal intensity by one order of magnitude, and so can Au flat mirror with 3° incident angle,Ni, C and Si flat mirrors with 5° incident angle, but the signal intensity counts for both attenuation methods are beyond the saturation counts of the CCD camera. We also calculated the attenuation of signal intensity for different thickne
2009,
21.
Abstract:
The influence of plasma density on plasma discharge has been introduced. In order to obtain the long pulse discharge, the Langmuir probe was employed to measure the plasma density and to control the plasma discharge with feedback. The hardware and software of the control parts were designed and the plasma density feedback control system was established based on the Langmuir probe measurement. Besides, the system was applied to the ion source plasma discharge experiment successfully. The long pulse discharge of 4.5 s was got and it provides the fundamental for the steadystate operation of neutral beam injection in the future．
The influence of plasma density on plasma discharge has been introduced. In order to obtain the long pulse discharge, the Langmuir probe was employed to measure the plasma density and to control the plasma discharge with feedback. The hardware and software of the control parts were designed and the plasma density feedback control system was established based on the Langmuir probe measurement. Besides, the system was applied to the ion source plasma discharge experiment successfully. The long pulse discharge of 4.5 s was got and it provides the fundamental for the steadystate operation of neutral beam injection in the future．
2009,
21.
Abstract:
It is an effective way to obtain high convergent compression of fuel with a shaped pulse driven implosion. The hydrodynamic process of the gas capsule compression with a single radiative pulse drive is divided into four phases: shock compression, nearly isentropic compression, compression and expansion with temperature reduction. High density will be achieved mainly through the adiabatic process. By variating the end time of first step pulse, the appropriate two-step shaped pulse drive is found, which will obtain higher density than the single-pulse drive. The simulation shows that the shock produced by the first step pulse compresses the gas fuel many times, meanwhile the pressure in the fuel improves. Hence the second shock into the fuel is so weak that scarcely any entropy increases，an
It is an effective way to obtain high convergent compression of fuel with a shaped pulse driven implosion. The hydrodynamic process of the gas capsule compression with a single radiative pulse drive is divided into four phases: shock compression, nearly isentropic compression, compression and expansion with temperature reduction. High density will be achieved mainly through the adiabatic process. By variating the end time of first step pulse, the appropriate two-step shaped pulse drive is found, which will obtain higher density than the single-pulse drive. The simulation shows that the shock produced by the first step pulse compresses the gas fuel many times, meanwhile the pressure in the fuel improves. Hence the second shock into the fuel is so weak that scarcely any entropy increases，an
2009,
21.
Abstract:
The use of a large number of wires in annular Z-pinch implosions has enabled the generation of strong X rays, which is significantly affected by the structure of the wire-array and the assembly precision of the wires.In order to obtain more symmetrical and straight wire-arrays, we studied the Z-pinch wire-array micro assembly station, and developed an experimental facility which was based on machine vision,micro force sensor and precision motion system.The station successfully accomplished the assembly of a nested wire-array with 5 μm tungsten filaments and the tension precision reached 0.002 N.
The use of a large number of wires in annular Z-pinch implosions has enabled the generation of strong X rays, which is significantly affected by the structure of the wire-array and the assembly precision of the wires.In order to obtain more symmetrical and straight wire-arrays, we studied the Z-pinch wire-array micro assembly station, and developed an experimental facility which was based on machine vision,micro force sensor and precision motion system.The station successfully accomplished the assembly of a nested wire-array with 5 μm tungsten filaments and the tension precision reached 0.002 N.
2009,
21.
Abstract:
Based on the optical configuration of laser facility prototype, a precise energy control program of preamplifier system using half-plate and polarizer was fixed. The flow of the program was designed and applied to the system successfully. The program’s reliability was tested by experiments. The results show that the static energy and the shot energy can be precisely controlled with the program, the static energy deviation can be reduced to 3% in 30 s, the shot energy deviation can be reduced to 5% in 1~2 shots and it can be also stable in a long time.
Based on the optical configuration of laser facility prototype, a precise energy control program of preamplifier system using half-plate and polarizer was fixed. The flow of the program was designed and applied to the system successfully. The program’s reliability was tested by experiments. The results show that the static energy and the shot energy can be precisely controlled with the program, the static energy deviation can be reduced to 3% in 30 s, the shot energy deviation can be reduced to 5% in 1~2 shots and it can be also stable in a long time.
2009,
21.
Abstract:
1 064 nm, 532 nm frequency-doubled antireflection coatings with no buffer layer or with different buffer layers were fabricated on LBO crystal using electron beam evaporation technique. The optical property, adhesion and laser-induced damage threshold(LIDT) were investigated. The results showed that the reflectance of all samples was below 0.1% and 0.2% at wavelength of 1 064 nm and 532 nm, respectively. Compared with the sample with no buffer layer, the critical adhesion of the sample with Al2O3 buffer layer of was increased by 43.1% and that of the coating with SiO2 buffer layer of was improved significantly, and the critical adhesion of the coating with MgF2 buffer layer of was decreased. The mechanism of adhesion strengthening of the coating was analyzed by full plastic indentation and
1 064 nm, 532 nm frequency-doubled antireflection coatings with no buffer layer or with different buffer layers were fabricated on LBO crystal using electron beam evaporation technique. The optical property, adhesion and laser-induced damage threshold(LIDT) were investigated. The results showed that the reflectance of all samples was below 0.1% and 0.2% at wavelength of 1 064 nm and 532 nm, respectively. Compared with the sample with no buffer layer, the critical adhesion of the sample with Al2O3 buffer layer of was increased by 43.1% and that of the coating with SiO2 buffer layer of was improved significantly, and the critical adhesion of the coating with MgF2 buffer layer of was decreased. The mechanism of adhesion strengthening of the coating was analyzed by full plastic indentation and
2009,
21.
Abstract:
Hollow silver microspheres have been prepared using modified polystyrene microspheres as hard template. The process of preparation is as follows:polystyrene microspheres with a layer of silver coated on their surface by the chemical planting method were dissolved in tetrahydrofuran, then the hollow silver microspheres were prepared. The properties of silver microspheres were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The optical properties of silver microspheres were studied using UV-Vis spectrophotometer. The inside diameter of silver hollow microspheres is 250 nm, the shell thickness is 15 nm, and the absorption peak of nanoparticles can redshift from 600 nm to 900 nm at the range of UV-Vis spectra. These routes realize a faci
Hollow silver microspheres have been prepared using modified polystyrene microspheres as hard template. The process of preparation is as follows:polystyrene microspheres with a layer of silver coated on their surface by the chemical planting method were dissolved in tetrahydrofuran, then the hollow silver microspheres were prepared. The properties of silver microspheres were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The optical properties of silver microspheres were studied using UV-Vis spectrophotometer. The inside diameter of silver hollow microspheres is 250 nm, the shell thickness is 15 nm, and the absorption peak of nanoparticles can redshift from 600 nm to 900 nm at the range of UV-Vis spectra. These routes realize a faci
2009,
21.
Abstract:
The preheating effect on planer-window materials in direct driven experiments was studied with imaging velocity interferometer system for any reflector(VISAR). The transmitting process of shock wave in the transparent material has been analyzed. It is found that the first and second shocks transform in adhesive, and the third shock transforms in fused silica. From the experiment data, no disconnected stripe induced by the first and second shocks is observed due to the ionization caused by X-ray radiation. Because the transparent adhesive is bleached by the second laser pulse and the first half of the third, the recorded stripe is disconnected. The acceleration and deceleration processes of shock wave in fused silica has been observed. After we explained the shocktiming data, some con
The preheating effect on planer-window materials in direct driven experiments was studied with imaging velocity interferometer system for any reflector(VISAR). The transmitting process of shock wave in the transparent material has been analyzed. It is found that the first and second shocks transform in adhesive, and the third shock transforms in fused silica. From the experiment data, no disconnected stripe induced by the first and second shocks is observed due to the ionization caused by X-ray radiation. Because the transparent adhesive is bleached by the second laser pulse and the first half of the third, the recorded stripe is disconnected. The acceleration and deceleration processes of shock wave in fused silica has been observed. After we explained the shocktiming data, some con
2009,
21.
Abstract:
Beam sampling gratings are used to sample the high-power transmitted light with an efficiency of 5% which is sent into an energy meter for energy diagnostics in the final optical focusing system of ICF. This paper proposes the structure of grating pair instead of single one. The designed grating is aberration-free by choosing system parameters properly, including the distance between two gratings，inclination angle, etc. and can be used for energy diagnostics as well as pulse response and far-field image quality measurements. The calculated results show that the optical path difference decreases from 8.3 cm in the case of single grating to 8.7 mm, and the root mean square radius of image point is 0.777 μm, which reaches the diffraction limit and can meet application requirements.
Beam sampling gratings are used to sample the high-power transmitted light with an efficiency of 5% which is sent into an energy meter for energy diagnostics in the final optical focusing system of ICF. This paper proposes the structure of grating pair instead of single one. The designed grating is aberration-free by choosing system parameters properly, including the distance between two gratings，inclination angle, etc. and can be used for energy diagnostics as well as pulse response and far-field image quality measurements. The calculated results show that the optical path difference decreases from 8.3 cm in the case of single grating to 8.7 mm, and the root mean square radius of image point is 0.777 μm, which reaches the diffraction limit and can meet application requirements.
2009,
21.
Abstract:
A new type of double negative medium(DNG) is proposed, which is made of two split ring resonators and has a simple structure. The numerical simulation of the new DNG is studied by using FDTD method and CST software, the physical mechanism of this structure is analyzed and its double negative effect is illuminated. Finally, the inversion scheme, which is the extension of commonly used Nicolson-Ross-Weir method, is deduced to obtain the constitutive parameters of the double negative medium in a waveguide. The extraction of its constitutive parameters shows that the real parts of the effective permittivity and permeability of this new type of DNG are both negative at frequency 10.3 GHz and its vicinity,which confirms its double negative effect．
A new type of double negative medium(DNG) is proposed, which is made of two split ring resonators and has a simple structure. The numerical simulation of the new DNG is studied by using FDTD method and CST software, the physical mechanism of this structure is analyzed and its double negative effect is illuminated. Finally, the inversion scheme, which is the extension of commonly used Nicolson-Ross-Weir method, is deduced to obtain the constitutive parameters of the double negative medium in a waveguide. The extraction of its constitutive parameters shows that the real parts of the effective permittivity and permeability of this new type of DNG are both negative at frequency 10.3 GHz and its vicinity,which confirms its double negative effect．
2009,
21.
Abstract:
The equivalent circuit of the three-gap coupled cavity type output section is given, with which resonant frequency of resonant modes and gap impedance matrix are calculated. Based on gap impedance, mode-overlapping theory of double-gap coupled cavity is discussed, and is used to expand the bandwidth of a Ka-band three-gap coupled cavity type output section. Resonator interaction impedance of three-gap coupled cavity is obtained from energy conservation law. The circuit’s 3 dB-bandwith has reached 4.48% by adjusting circuit parameters.
The equivalent circuit of the three-gap coupled cavity type output section is given, with which resonant frequency of resonant modes and gap impedance matrix are calculated. Based on gap impedance, mode-overlapping theory of double-gap coupled cavity is discussed, and is used to expand the bandwidth of a Ka-band three-gap coupled cavity type output section. Resonator interaction impedance of three-gap coupled cavity is obtained from energy conservation law. The circuit’s 3 dB-bandwith has reached 4.48% by adjusting circuit parameters.
2009,
21.
Abstract:
The structure of the sub-nanosecond gas switch with adjustable gap used on the UWB-1 system are optimized. During commissioning, the optimized rotary knob can adjust the gaps easily and measure gap size accurately. The static electric-field distributions at insulators and electrodes of the switch are simulated. The maximal static electric-field strength at the optimized insulator is 126.6 kV/mm, which is under theory breakdown field strength and satisfies insulation requirement. High voltage experiments are conducted on the switch. The results show that no breakdown happens at the insulators, and the switch can work steadily and output shorter pulses with steeper rise and fall edges. When the system works at 5 Hz repetition rate, rise time, fall time and pulse width of the output pulse dec
The structure of the sub-nanosecond gas switch with adjustable gap used on the UWB-1 system are optimized. During commissioning, the optimized rotary knob can adjust the gaps easily and measure gap size accurately. The static electric-field distributions at insulators and electrodes of the switch are simulated. The maximal static electric-field strength at the optimized insulator is 126.6 kV/mm, which is under theory breakdown field strength and satisfies insulation requirement. High voltage experiments are conducted on the switch. The results show that no breakdown happens at the insulators, and the switch can work steadily and output shorter pulses with steeper rise and fall edges. When the system works at 5 Hz repetition rate, rise time, fall time and pulse width of the output pulse dec
2009,
21.
Abstract:
The dual-wire method is a widely used transverse impedance measurement method. When the transverse impedance of the device under test is very small, large lateral distance between the two wires and large diameter of the wires are prefered to get large signal and thus the measurement results are reliable and reproducible. However, large lateral distance and diameter would lead to large systematic error. A numerical research using HFSS were carried out on the systematic error due to the dual-wire distance and diameter. Its result shows that, for moderately small dual-wire distance and wire diameter, the measured transverse impedance is smaller than the theoretical value calculated by ABCI and HFSS,and larger dual-wire distance and diameter lead to larger systematic error. In the case of a ca
The dual-wire method is a widely used transverse impedance measurement method. When the transverse impedance of the device under test is very small, large lateral distance between the two wires and large diameter of the wires are prefered to get large signal and thus the measurement results are reliable and reproducible. However, large lateral distance and diameter would lead to large systematic error. A numerical research using HFSS were carried out on the systematic error due to the dual-wire distance and diameter. Its result shows that, for moderately small dual-wire distance and wire diameter, the measured transverse impedance is smaller than the theoretical value calculated by ABCI and HFSS,and larger dual-wire distance and diameter lead to larger systematic error. In the case of a ca
2009,
21.
Abstract:
Azimuthal arrays of B-dot loops are often used to measure the time-resolved beam centroid position of a pulsed, intense electron beam propagating in a metallic tube. This paper describes the designing principle, parameters and calibration of the B-dot monitors. According to the beam current pulse rise time, fall time and the pulse width,the B-dot is designed to work as a differential loop, the loop inductance is about 60 nH. The B-dot monitor’s sensitivity and the displacement curve are calibrated in the test stand. The sensitivity of the B-dots and the passive RC integrator is averagely 4 147 A/V, integrate constant is about 1 μs. The B-dot monitors are used to measure the Dragon-Ⅰ electron beam and the experimental results show that the B-dot monitors can measure the beam current and
Azimuthal arrays of B-dot loops are often used to measure the time-resolved beam centroid position of a pulsed, intense electron beam propagating in a metallic tube. This paper describes the designing principle, parameters and calibration of the B-dot monitors. According to the beam current pulse rise time, fall time and the pulse width,the B-dot is designed to work as a differential loop, the loop inductance is about 60 nH. The B-dot monitor’s sensitivity and the displacement curve are calibrated in the test stand. The sensitivity of the B-dots and the passive RC integrator is averagely 4 147 A/V, integrate constant is about 1 μs. The B-dot monitors are used to measure the Dragon-Ⅰ electron beam and the experimental results show that the B-dot monitors can measure the beam current and
2009,
21.
Abstract:
This paper briefly introduces the detecting demand for the characteristic parameters of backstreaming ions, and analyses features of several detecting methods. The integration experiment scheme of ion detection is designed. Three experiment methods and the analysis process of the test result are introduced. The methods adopt laser interferometer plus framing camera, Faraday cup and solid tracking detector, respectively. The original test data of the methods are analysed. Based on the information fusion technology, the analysis results are fused and the all-around analysis conclusion is obtained about the variety, motion velocity, density, etc. of backstreaming ions.
This paper briefly introduces the detecting demand for the characteristic parameters of backstreaming ions, and analyses features of several detecting methods. The integration experiment scheme of ion detection is designed. Three experiment methods and the analysis process of the test result are introduced. The methods adopt laser interferometer plus framing camera, Faraday cup and solid tracking detector, respectively. The original test data of the methods are analysed. Based on the information fusion technology, the analysis results are fused and the all-around analysis conclusion is obtained about the variety, motion velocity, density, etc. of backstreaming ions.
2009,
21.
Abstract:
DZ4 substrates were coated with NiCoCrAlY by plasma spray and subsequently treated by high current pulsed electron beams(HCPEB) of different parameters. The surface microstructure, phase structure and high temperature oxidation resistance were studied. It has been shown that as a result of the HCPEB treatment the loose and rough structure remelted and the surface became smooth. Smooth microregion, craters and cracks appeared on the surface. The γ′ phase manifolded and there was no visible thermal stress. The oxidation test at 900 ℃ for 100 h showed that a more compact and successive α-Al2O3 scale was formed on the surface of the samples after HCPEB irradiation, which improved the oxidation resistance of the NiCoCrAlY coatings obviously.
DZ4 substrates were coated with NiCoCrAlY by plasma spray and subsequently treated by high current pulsed electron beams(HCPEB) of different parameters. The surface microstructure, phase structure and high temperature oxidation resistance were studied. It has been shown that as a result of the HCPEB treatment the loose and rough structure remelted and the surface became smooth. Smooth microregion, craters and cracks appeared on the surface. The γ′ phase manifolded and there was no visible thermal stress. The oxidation test at 900 ℃ for 100 h showed that a more compact and successive α-Al2O3 scale was formed on the surface of the samples after HCPEB irradiation, which improved the oxidation resistance of the NiCoCrAlY coatings obviously.
2009,
21.
Abstract:
The effects of 5 MeV and 2 MeV proton irradiations on multi-quantum-well laser diodes with Fabry-Perot cavity and distributed feedback are investigated. It is found that the threshold current and total current at low voltage range of current-voltage characteristics curves increase gradually at the fluence level from 5×1012 cm-2 to 5×1013 cm-2. The damage mechanism is attributed to the displacement effect of protons with the help of 60Coγ total dose experiment. Trim program simulation shows that the number of vacancies induced by 2 MeV protons is more than that induced by 5 MeV protons and so does the threshold current. Due to forward-bias-induced annealing effects, the laser diode biased during irradiation is less degraded than that short-circuited, and annealing curves can b
The effects of 5 MeV and 2 MeV proton irradiations on multi-quantum-well laser diodes with Fabry-Perot cavity and distributed feedback are investigated. It is found that the threshold current and total current at low voltage range of current-voltage characteristics curves increase gradually at the fluence level from 5×1012 cm-2 to 5×1013 cm-2. The damage mechanism is attributed to the displacement effect of protons with the help of 60Coγ total dose experiment. Trim program simulation shows that the number of vacancies induced by 2 MeV protons is more than that induced by 5 MeV protons and so does the threshold current. Due to forward-bias-induced annealing effects, the laser diode biased during irradiation is less degraded than that short-circuited, and annealing curves can b
2009,
21.
Abstract:
Obliquely-incident X-ray photons interacting with metal through Compton scattering can produce a large current density along the metal surface in the incident direction. In this paper, angular distributions of scattered electron momentum and differential cross section were calculated. The results show that for photon energy of 1 MeV and X-ray intensity up to 1021 W·m-2, the Compton current density on the metal surface is as large as 107 A·m-2. The electromagnetic pulse caused by this current was calculated using a one-dimensional electrodynamic model. It is found that radiated magnetic field per unit length of metal is derived with the magnitude of 106A·m-1 and the duration of picoseconds. The emitted electromagnetic radiation is well-directed, propagating mainly in the specular directi
Obliquely-incident X-ray photons interacting with metal through Compton scattering can produce a large current density along the metal surface in the incident direction. In this paper, angular distributions of scattered electron momentum and differential cross section were calculated. The results show that for photon energy of 1 MeV and X-ray intensity up to 1021 W·m-2, the Compton current density on the metal surface is as large as 107 A·m-2. The electromagnetic pulse caused by this current was calculated using a one-dimensional electrodynamic model. It is found that radiated magnetic field per unit length of metal is derived with the magnitude of 106A·m-1 and the duration of picoseconds. The emitted electromagnetic radiation is well-directed, propagating mainly in the specular directi
2009,
21.
Abstract:
The model of the non-collision plasma sheath is developed in the presence of secondary electron emission(SEE) and negative ions. The effect is discussed of the secondary electron emission and negative ions on the sheath of a one-dimensional stationary plasma. The interaction between secondary electrons and negative ions is also analyzed. It is found that the increase of SEE coefficient and negative ion content in the plasma will reduce the width of plasma sheath. If the SEE coefficient is larger than the critical emission coefficient, the sheath would not only formed by ions. In the sheath of a multicomponent plasma, the density of negative ions increases when the SEE coefficient enhances, and the critical SEE coefficient will be bigger with the enhancement of negative ions. In addition,
The model of the non-collision plasma sheath is developed in the presence of secondary electron emission(SEE) and negative ions. The effect is discussed of the secondary electron emission and negative ions on the sheath of a one-dimensional stationary plasma. The interaction between secondary electrons and negative ions is also analyzed. It is found that the increase of SEE coefficient and negative ion content in the plasma will reduce the width of plasma sheath. If the SEE coefficient is larger than the critical emission coefficient, the sheath would not only formed by ions. In the sheath of a multicomponent plasma, the density of negative ions increases when the SEE coefficient enhances, and the critical SEE coefficient will be bigger with the enhancement of negative ions. In addition,
2009,
21.
Abstract:
When Rogowski coils are used to measure the time-domain waveforms of lightning currents flowing down tall column towers, the coils must have large inside radius and high current capability, then the low-frequency distortion caused in the measurement can be corrected. However, the most commonly used Rogowski coil cannot fulfill all of these. Therefore, this paper presents a large Rogowski coil with a flexible belt-like nonmagnetic core. Large inductance is obtained by increasing the turns of the coil, which makes the coil have self-integrating capability and reduces the difficulty of additional integration. At the mean time, the coil would not work in nonlinear and saturation ranges as the core is nonmagnetic.The calibration results show that this coil has a good self-integrating performanc
When Rogowski coils are used to measure the time-domain waveforms of lightning currents flowing down tall column towers, the coils must have large inside radius and high current capability, then the low-frequency distortion caused in the measurement can be corrected. However, the most commonly used Rogowski coil cannot fulfill all of these. Therefore, this paper presents a large Rogowski coil with a flexible belt-like nonmagnetic core. Large inductance is obtained by increasing the turns of the coil, which makes the coil have self-integrating capability and reduces the difficulty of additional integration. At the mean time, the coil would not work in nonlinear and saturation ranges as the core is nonmagnetic.The calibration results show that this coil has a good self-integrating performanc
2009,
21.
Abstract:
The pulse current generated by pulsed power supply could be several hundred thousand amperes, which could produce great interference to the electronic apparatus and other modules of the power supply. Thereby, the measurement of spatial and temporal distributions of radiated electromagnetic fields could be useful. Two supplies with spark gap(SG) switches and silicon controlled rectifier(SCR) switches are focused, and both use capacitors to store energy. Several B-dot probes, D-dot probes and a digital oscilloscope, with enough sampling rate and memory depth, are used to measure the magnetic and electric fields. The result shows that the spectrum of magnetic fields around SG switches can reach 10 MHz, while that around SCR switches is less than 1 MHz. The latter would be better for the syste
The pulse current generated by pulsed power supply could be several hundred thousand amperes, which could produce great interference to the electronic apparatus and other modules of the power supply. Thereby, the measurement of spatial and temporal distributions of radiated electromagnetic fields could be useful. Two supplies with spark gap(SG) switches and silicon controlled rectifier(SCR) switches are focused, and both use capacitors to store energy. Several B-dot probes, D-dot probes and a digital oscilloscope, with enough sampling rate and memory depth, are used to measure the magnetic and electric fields. The result shows that the spectrum of magnetic fields around SG switches can reach 10 MHz, while that around SCR switches is less than 1 MHz. The latter would be better for the syste
2009,
21.
Abstract:
Using a referral method, a multistage transmission line pulse transformer(TLT) was simplified, and a simple circuit of the TLT frequency response was also established. On this basis, a frequency response equation of the TLT was deduced from a two-port network model of the transmission line. According to the equation, TLT frequency response curves were calculated. Numerical simulations of the frequency response were conducted in terms of the simplified circuit, and the result of the numerical analysis agreed with that of theoretical calculations well. Both of these two results indicated that the TLT has an outstanding performance in frequency response if the secondary line inductance and stray capacitance are suitable. Particularly, the range of frequency response can be 30 kHz~1 GHz when t
Using a referral method, a multistage transmission line pulse transformer(TLT) was simplified, and a simple circuit of the TLT frequency response was also established. On this basis, a frequency response equation of the TLT was deduced from a two-port network model of the transmission line. According to the equation, TLT frequency response curves were calculated. Numerical simulations of the frequency response were conducted in terms of the simplified circuit, and the result of the numerical analysis agreed with that of theoretical calculations well. Both of these two results indicated that the TLT has an outstanding performance in frequency response if the secondary line inductance and stray capacitance are suitable. Particularly, the range of frequency response can be 30 kHz~1 GHz when t
2009,
21.
Abstract:
A compact long pulse generator was presented, whose spiral Blumlein line possessed inner magnetic conductor cylinder, central spiral cylinder and outer magnetic conductor cylinder. The spiral Blumlein line was charged by means of a built-in high coupling Tesla transformer, whose primary coil was adjacent to outer conductor cylinder and secondary coil was located between central spiral cylinder and outer conductor cylinder. Theoretic calculation of characteristic parameters, such as slow wave coefficient, switch closing current, variable factors describing wave transmission behavior on the interface of closed switch, was given by physical analysis of wave transmission on spiral Blumlein line. Numerical simulation of part of wave transmission courses on spiral Blumlein line was proceeded by
A compact long pulse generator was presented, whose spiral Blumlein line possessed inner magnetic conductor cylinder, central spiral cylinder and outer magnetic conductor cylinder. The spiral Blumlein line was charged by means of a built-in high coupling Tesla transformer, whose primary coil was adjacent to outer conductor cylinder and secondary coil was located between central spiral cylinder and outer conductor cylinder. Theoretic calculation of characteristic parameters, such as slow wave coefficient, switch closing current, variable factors describing wave transmission behavior on the interface of closed switch, was given by physical analysis of wave transmission on spiral Blumlein line. Numerical simulation of part of wave transmission courses on spiral Blumlein line was proceeded by
