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RSS2009 Vol. 21, No. 12
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2009,
21.
Abstract:
Based on the unified theory of coherence and polarization of electromagnetic beams, the expression for the cross-spectral density of partially polarized, partially coherent vectorial cosh-Gaussian(ChG) beams propagating through a bifocal lens is derived. The propagation of partially polarized, partially coherent vectorial Gaussian Schell-model(GSM) beams propagating through a bifocal lens and the propagation of partially polarized, partially coherent vectorial ChG beams propagating through a conventional lens can be treated as two special cases of our results. It is shown that the intensity, degree of polarization, spectral degree of coherence and focal shifts of focused vectrial ChG beams depend on the decentered parameter, correlation length, waist width and focal length.
Based on the unified theory of coherence and polarization of electromagnetic beams, the expression for the cross-spectral density of partially polarized, partially coherent vectorial cosh-Gaussian(ChG) beams propagating through a bifocal lens is derived. The propagation of partially polarized, partially coherent vectorial Gaussian Schell-model(GSM) beams propagating through a bifocal lens and the propagation of partially polarized, partially coherent vectorial ChG beams propagating through a conventional lens can be treated as two special cases of our results. It is shown that the intensity, degree of polarization, spectral degree of coherence and focal shifts of focused vectrial ChG beams depend on the decentered parameter, correlation length, waist width and focal length.
2009,
21.
Abstract:
Using water as coolant, TG0.3 full-cone nozzles supplied by Spraying Systems Co. are applied to study heat transfer performance of micro-channel surface in non-boiling regime of spray cooling when volumetric flux ranges from 0.044 m3/(m2·s to 0.053 m3/(m2·s. The results indicate that heat transfer is obviously enhanced for micro-channel surfaces relative to the flat surface. It is found that when the wall temperature is 52 ℃ and the volumetric flux is 0.044 m3/(m2·s, the heat flux dissipated on micro-channel surface, whose fin height is 0.2 mm, could reach 260 W/cm2; when the volumetric flux increases to 0.053 m3/(m2·s, the heat flux could reach 376 W/cm2 at the same surface temperature. For the sm
Using water as coolant, TG0.3 full-cone nozzles supplied by Spraying Systems Co. are applied to study heat transfer performance of micro-channel surface in non-boiling regime of spray cooling when volumetric flux ranges from 0.044 m3/(m2·s to 0.053 m3/(m2·s. The results indicate that heat transfer is obviously enhanced for micro-channel surfaces relative to the flat surface. It is found that when the wall temperature is 52 ℃ and the volumetric flux is 0.044 m3/(m2·s, the heat flux dissipated on micro-channel surface, whose fin height is 0.2 mm, could reach 260 W/cm2; when the volumetric flux increases to 0.053 m3/(m2·s, the heat flux could reach 376 W/cm2 at the same surface temperature. For the sm
2009,
21.
Abstract:
Combined with radiation transport equation, with energy source terms including laser energy absorbed by air and loss energy irradiated by high-temperature gas added to the energy equation of fluid dynamics equations set, the physical/mechanical model and computational method of laser energy deposition process in air-breathing laser propulsion are established. The phenomenon of air absorbing laser energy, the effect of plasma shielding laser and the propagation law of laser supported detonation wave can be simulated correctly by the radiation fluid dynamics computational code. The results indicate that the laser energy deposition efficiency is about 57%, and the velocity of laser supported detonation wave agrees well with the results of theory and experiment under similar conditions.
Combined with radiation transport equation, with energy source terms including laser energy absorbed by air and loss energy irradiated by high-temperature gas added to the energy equation of fluid dynamics equations set, the physical/mechanical model and computational method of laser energy deposition process in air-breathing laser propulsion are established. The phenomenon of air absorbing laser energy, the effect of plasma shielding laser and the propagation law of laser supported detonation wave can be simulated correctly by the radiation fluid dynamics computational code. The results indicate that the laser energy deposition efficiency is about 57%, and the velocity of laser supported detonation wave agrees well with the results of theory and experiment under similar conditions.
2009,
21.
Abstract:
Phase locking of a high-power DLA in-phase mode output with a volume Bragg grating as an external cavity mirror was achieved experimentally. The linear array consisted of 49 wide-aperture diodes with a diode width of 100 μm and a spacing period of 200 μm was phase locked. Improved output beam quality in the far-field and suppressed bandwidth were demonstrated. The DLA’s single lobe output was 3.67 W for a free running paser of 15 W, the far-field divergence of the phase-locked beam was 1.47 mrad, and the spectral full width at half maximum of the output beam was suppressed from 1.7 nm to 0.17 nm.
Phase locking of a high-power DLA in-phase mode output with a volume Bragg grating as an external cavity mirror was achieved experimentally. The linear array consisted of 49 wide-aperture diodes with a diode width of 100 μm and a spacing period of 200 μm was phase locked. Improved output beam quality in the far-field and suppressed bandwidth were demonstrated. The DLA’s single lobe output was 3.67 W for a free running paser of 15 W, the far-field divergence of the phase-locked beam was 1.47 mrad, and the spectral full width at half maximum of the output beam was suppressed from 1.7 nm to 0.17 nm.
2009,
21.
Abstract:
Based on the characteristic analysis of the laser single-pulse energy, force analysis of the lightcraft is done. For the minimum single-pulse energy, the minimum mean thrust, and the minimum impulse, the design methods are proposed. The equation of motion of the lightcraft is deduced during the vertical movement, and the velocity and displacement are calculated. The effects of air drag, friction drag and lightcraft mass on flight velocity and the mean thrust are discussed. The quantitative results indicate that flight velocity is independent of air drag; when the friction drag becomes larger, the flight velocity becomes smaller; the minimum single pulse energy needed for flight mission would increase as the lightcraft mass increases.
Based on the characteristic analysis of the laser single-pulse energy, force analysis of the lightcraft is done. For the minimum single-pulse energy, the minimum mean thrust, and the minimum impulse, the design methods are proposed. The equation of motion of the lightcraft is deduced during the vertical movement, and the velocity and displacement are calculated. The effects of air drag, friction drag and lightcraft mass on flight velocity and the mean thrust are discussed. The quantitative results indicate that flight velocity is independent of air drag; when the friction drag becomes larger, the flight velocity becomes smaller; the minimum single pulse energy needed for flight mission would increase as the lightcraft mass increases.
2009,
21.
Abstract:
The nonlinear Schrdinger equation is solved by slit-step Fourier numerical method. The variation of B integral in several propagation media in the ultra-short pulse laser system is numerically simulated and briefly analyzed. The results show that B integral increases with input intensity and gain coefficient increasing. The shape of the input pulse has some effect on B integral, and the B integral of picosecond chirp pulse is smaller than that of femtosecond Gaussian pulse. It is also found that proper group-velocity and high-order dispersions can reduce B integral for the selected calculation model. The approach can be reference resources to the design of the ultra-short pulse laser system.
The nonlinear Schrdinger equation is solved by slit-step Fourier numerical method. The variation of B integral in several propagation media in the ultra-short pulse laser system is numerically simulated and briefly analyzed. The results show that B integral increases with input intensity and gain coefficient increasing. The shape of the input pulse has some effect on B integral, and the B integral of picosecond chirp pulse is smaller than that of femtosecond Gaussian pulse. It is also found that proper group-velocity and high-order dispersions can reduce B integral for the selected calculation model. The approach can be reference resources to the design of the ultra-short pulse laser system.
2009,
21.
Abstract:
According to image characteristics of laser active imaging, a new image denoising method is presented combining wavelet transform and median filter. After wavelet transform, high frequency sub-band images at horizontal, vertical and angular directions are denoised by three different filter templates. In order to protect edge information, edge detection is used to separate edge information from noises. Denoised-image was gained by composing the three high frequency detail images with mean filtering and low frequency approximation image. Experimental results show that this method can remove the noise of image effectively. Meanwhile, the detail of the image is kept well and the de-noising effect is better.
According to image characteristics of laser active imaging, a new image denoising method is presented combining wavelet transform and median filter. After wavelet transform, high frequency sub-band images at horizontal, vertical and angular directions are denoised by three different filter templates. In order to protect edge information, edge detection is used to separate edge information from noises. Denoised-image was gained by composing the three high frequency detail images with mean filtering and low frequency approximation image. Experimental results show that this method can remove the noise of image effectively. Meanwhile, the detail of the image is kept well and the de-noising effect is better.
2009,
21.
Abstract:
The principle of a lidar system for measuring atmospheric turbulence vertical profiles has been introduced. The profile retrieval technique is based on the measurement of coherent lengths of different atmospheric layers, and uses plane wave approximation algorithm in profile inversion. The data of atmospheric turbulence vertical profiles were got by the experiment lidar system, and compared with the data from microthermal meter at the same altitude. This comparative experiment has validated the feasibility of the approximation iterative algorithms of the integrat. Experiment errors was discussed at last.
The principle of a lidar system for measuring atmospheric turbulence vertical profiles has been introduced. The profile retrieval technique is based on the measurement of coherent lengths of different atmospheric layers, and uses plane wave approximation algorithm in profile inversion. The data of atmospheric turbulence vertical profiles were got by the experiment lidar system, and compared with the data from microthermal meter at the same altitude. This comparative experiment has validated the feasibility of the approximation iterative algorithms of the integrat. Experiment errors was discussed at last.
2009,
21.
Abstract:
With the high-power semiconductor laser diode array and its applications becoming widespread, spectral purity research of high-power semiconductor laser as the pump source in related fields has become one of the hotspots. The spectrum envelope is reasonably approximated Gaussian. The laser diode array spectrum synthesis simulation software is compiled taking the Gaussian algorithm as the foundation, which achieves a synthesis of the wavelength of the laser array, as well as the full wave at half maximum of the analog spectrum graphics and simulation. Simulation results shows that there is a difference between the simulated and the actually tested wavelength values. The difference is analysed for verification and then used to modify.
With the high-power semiconductor laser diode array and its applications becoming widespread, spectral purity research of high-power semiconductor laser as the pump source in related fields has become one of the hotspots. The spectrum envelope is reasonably approximated Gaussian. The laser diode array spectrum synthesis simulation software is compiled taking the Gaussian algorithm as the foundation, which achieves a synthesis of the wavelength of the laser array, as well as the full wave at half maximum of the analog spectrum graphics and simulation. Simulation results shows that there is a difference between the simulated and the actually tested wavelength values. The difference is analysed for verification and then used to modify.
2009,
21.
Abstract:
Phenolic-doped melamine-formaldehyde(MF) aerogels were investigated by adding resorcin to MF sol before the formation of crosslink. The solvents in wet gel were then exchanged with ethanol. After CO2 supercritical drying process, the doped MF areogels were prepared with the lowest density of about 50 kg·-3. The samples were also characterized by HRTEM，FESEM, IR absorption spectroscopy and thermogravimetric analyses. The results indicates that the structures of the aerogels are different by changing the mole ratio of melamine to resorcin, and the thermal stability is improved under the temperature of 300 ℃.
Phenolic-doped melamine-formaldehyde(MF) aerogels were investigated by adding resorcin to MF sol before the formation of crosslink. The solvents in wet gel were then exchanged with ethanol. After CO2 supercritical drying process, the doped MF areogels were prepared with the lowest density of about 50 kg·-3. The samples were also characterized by HRTEM，FESEM, IR absorption spectroscopy and thermogravimetric analyses. The results indicates that the structures of the aerogels are different by changing the mole ratio of melamine to resorcin, and the thermal stability is improved under the temperature of 300 ℃.
2009,
21.
Abstract:
Using sintered α-FeFe2O3 as target, FeFe3O4 thin films were grown on MgO (100) substrates by laser molecular beam epitaxy. The quality of the films was checked in situ by monitoring reflection high energy electron diffraction patterns during deposition. The results showed that the surface of the films is smooth. Raman spectroscopy and X-ray photoelectron spectroscopy(XPS) analysis confirms the presence of single-phase FeFe3O4 in the surface of the films, and no other iron oxides exist. The magnetic and electrical properties of the FeFe3O4 thin films were investigated. The results showed that the resistivity of the Fe3O4 thin films increases sharply about 100 K, and the temperature range of Verwey trans
Using sintered α-FeFe2O3 as target, FeFe3O4 thin films were grown on MgO (100) substrates by laser molecular beam epitaxy. The quality of the films was checked in situ by monitoring reflection high energy electron diffraction patterns during deposition. The results showed that the surface of the films is smooth. Raman spectroscopy and X-ray photoelectron spectroscopy(XPS) analysis confirms the presence of single-phase FeFe3O4 in the surface of the films, and no other iron oxides exist. The magnetic and electrical properties of the FeFe3O4 thin films were investigated. The results showed that the resistivity of the Fe3O4 thin films increases sharply about 100 K, and the temperature range of Verwey trans
2009,
21.
Abstract:
Second-harmonic generation(SHG) of high-intensity laser with an SHG crystal for typeⅠangle phase matching has been studied by the use of a split-step algorithm based on the fast Fourier transform and a fourth-order Runge-Kutta(R-K) integrator. The transverse walk-off effect, diffraction, the second-order and the third-order nonlinear effects have been taken into consideration. Influences of a temperature rise distribution of the SHG crystal on the refractive indices of ordinary wave and extraordinary wave have been discussed. The rules of phase mismatching quantity, intensity distribution of output beam and frequency conversion efficiency varying with the temperature rise distribution of the SHG crystal have been analyzed quantitatively. The calculated results indicate that in a high powe
Second-harmonic generation(SHG) of high-intensity laser with an SHG crystal for typeⅠangle phase matching has been studied by the use of a split-step algorithm based on the fast Fourier transform and a fourth-order Runge-Kutta(R-K) integrator. The transverse walk-off effect, diffraction, the second-order and the third-order nonlinear effects have been taken into consideration. Influences of a temperature rise distribution of the SHG crystal on the refractive indices of ordinary wave and extraordinary wave have been discussed. The rules of phase mismatching quantity, intensity distribution of output beam and frequency conversion efficiency varying with the temperature rise distribution of the SHG crystal have been analyzed quantitatively. The calculated results indicate that in a high powe
2009,
21.
Abstract:
Polystyrene(PS), polyethylene(PE) and their deuterated polymers are important fuel container materials of Z-pinch driven ICF experiment. To meet the shape demand of physical experiment, filaments with the diameter of 30～100 μm were prepared by melt spinning via high pressure capillary rheometer and its accessory section HAUL-OFF system. According to the study on mechanical relaxation properties of PS, PE and deuterated polystyrene(DPS) filaments, the creep deformation of PS filament is obviously less than that of PE filament. PS filament shows better dimensional stability. When the fixed percentage of elongation is 1%, the stress relaxation rate of PS filament is also significantly less than PE filament’s. The creep deformation and stress relaxation behaviors of DPS filament and PS fila
Polystyrene(PS), polyethylene(PE) and their deuterated polymers are important fuel container materials of Z-pinch driven ICF experiment. To meet the shape demand of physical experiment, filaments with the diameter of 30～100 μm were prepared by melt spinning via high pressure capillary rheometer and its accessory section HAUL-OFF system. According to the study on mechanical relaxation properties of PS, PE and deuterated polystyrene(DPS) filaments, the creep deformation of PS filament is obviously less than that of PE filament. PS filament shows better dimensional stability. When the fixed percentage of elongation is 1%, the stress relaxation rate of PS filament is also significantly less than PE filament’s. The creep deformation and stress relaxation behaviors of DPS filament and PS fila
2009,
21.
Abstract:
The vacuum laser damage experimental facility was established. The samples of Hf22/SiO2 high reflective coatings were prepared by electron beam evaporation and ion assisted technology. The laser induced damage thresholds(LIDT) of samples were determined.The damage behaviors of the samples in vacuum and air environment were different. The results showe that the 1∶1 and R∶1 LIDTs of coatings in vacuum decreased about 30% compared with those inair, which might be caused by different thermal diffusion processes.
The vacuum laser damage experimental facility was established. The samples of Hf22/SiO2 high reflective coatings were prepared by electron beam evaporation and ion assisted technology. The laser induced damage thresholds(LIDT) of samples were determined.The damage behaviors of the samples in vacuum and air environment were different. The results showe that the 1∶1 and R∶1 LIDTs of coatings in vacuum decreased about 30% compared with those inair, which might be caused by different thermal diffusion processes.
2009,
21.
Abstract:
An anisotropic magnetized plasma channel antenna(AMPCA) for radiating high power microwave is presented. The concrete realization method of AMPCA is simply described. The operating principle of AMPCA is given, and the electromagnetic model of AMPCA is created. The wave equations for the longitudinal electromagnetic fields are deduced, and the relations between the transverse electromagnetic fields and the longitudinal ones of anisotropic magnetic plasma in generalized cylindrical coordinate are given. The characteristic equation of modes for AMPCA is deduced by applying the boundary conditions of electromagnetic fields. In the limit cases, the results of this paper are consistent with that given in literature’s. The dispersive curves of modes for AMPCA are calculated.
An anisotropic magnetized plasma channel antenna(AMPCA) for radiating high power microwave is presented. The concrete realization method of AMPCA is simply described. The operating principle of AMPCA is given, and the electromagnetic model of AMPCA is created. The wave equations for the longitudinal electromagnetic fields are deduced, and the relations between the transverse electromagnetic fields and the longitudinal ones of anisotropic magnetic plasma in generalized cylindrical coordinate are given. The characteristic equation of modes for AMPCA is deduced by applying the boundary conditions of electromagnetic fields. In the limit cases, the results of this paper are consistent with that given in literature’s. The dispersive curves of modes for AMPCA are calculated.
2009,
21.
Abstract:
The method for calculating the expression of the trapezoidal corrugation slow-wave structure (SWS) is studied in detail, which uses Fourier series expandedness. The dispersion curves of the two lowest symmetry TM0n waves are obtained with numerical calculation. Moreover, longitudinal resonance properties of the finite-length coaxial SWS are investigated with the S-parameter method. It is proposed that the introduction of a well designed coaxial extractor to slow-wave devices can reduce the period-number of the SWS, which not only can make the devices more compact, but also can avoid destructive competition between various longitudinal modes. Based on the theoretical study, a compact L-band coaxial relativistic backward wave oscillator is designed using the 2.5 D particle simulation code. S
The method for calculating the expression of the trapezoidal corrugation slow-wave structure (SWS) is studied in detail, which uses Fourier series expandedness. The dispersion curves of the two lowest symmetry TM0n waves are obtained with numerical calculation. Moreover, longitudinal resonance properties of the finite-length coaxial SWS are investigated with the S-parameter method. It is proposed that the introduction of a well designed coaxial extractor to slow-wave devices can reduce the period-number of the SWS, which not only can make the devices more compact, but also can avoid destructive competition between various longitudinal modes. Based on the theoretical study, a compact L-band coaxial relativistic backward wave oscillator is designed using the 2.5 D particle simulation code. S
2009,
21.
Abstract:
Characteristics of a two-layer patch microstrip antenna(MSA) for high power wide-band microwave radiation was studied. A new conical feeder was introduced to reduce lead inductance of conventional probe feeder. It increases antenna’s power capacity to hundred megawatt level and plays as a convertor between coaxial waveguide and dielectric resonator, which means less reflection at the port. The effect of dielectric substrate thickness and patch size on MSA’s bandwidth was analyzed based on electromagnetic simulation. Percentage bandwidth of 34.9% (voltage standing-wave ratio less than 3) was obtained after dimension optimization, the gain is above 6.5 dB over the whole band with the maximum of 8.3 dB at 310 MHz, and the ratio of far-zone radiation factor to input impulse voltage is 1.3 i
Characteristics of a two-layer patch microstrip antenna(MSA) for high power wide-band microwave radiation was studied. A new conical feeder was introduced to reduce lead inductance of conventional probe feeder. It increases antenna’s power capacity to hundred megawatt level and plays as a convertor between coaxial waveguide and dielectric resonator, which means less reflection at the port. The effect of dielectric substrate thickness and patch size on MSA’s bandwidth was analyzed based on electromagnetic simulation. Percentage bandwidth of 34.9% (voltage standing-wave ratio less than 3) was obtained after dimension optimization, the gain is above 6.5 dB over the whole band with the maximum of 8.3 dB at 310 MHz, and the ratio of far-zone radiation factor to input impulse voltage is 1.3 i
2009,
21.
Abstract:
Using optic injectors driven by laser as the electron source is advantageous in the research of free electron laser. To get the driving laser meeting certain requirement, a laser system has been designed. In the laser system, a mode-locked Nd:YVO4 laser offers the seed pulse sequence and an laser diode array pumped Nd:YAG amplification system amplifies the seed sequence. In the amplification process, the shape of the sequence envelope is aberrated due to gain saturation effect. 24 mJ fundemental wave(1 064 nm), 5.7 mJ second harmonic and 0.6 mJ fourth harmonic have been obtained respectively in the system. The aberration and the way to compensate are also studied experimentally. As a result, the ultraviolet sequence with flat-topped envelope was obtained after fourth harmonic conversion of
Using optic injectors driven by laser as the electron source is advantageous in the research of free electron laser. To get the driving laser meeting certain requirement, a laser system has been designed. In the laser system, a mode-locked Nd:YVO4 laser offers the seed pulse sequence and an laser diode array pumped Nd:YAG amplification system amplifies the seed sequence. In the amplification process, the shape of the sequence envelope is aberrated due to gain saturation effect. 24 mJ fundemental wave(1 064 nm), 5.7 mJ second harmonic and 0.6 mJ fourth harmonic have been obtained respectively in the system. The aberration and the way to compensate are also studied experimentally. As a result, the ultraviolet sequence with flat-topped envelope was obtained after fourth harmonic conversion of
2009,
21.
Abstract:
A new side-appending radial three-cavity transit time oscillator is proposed based on the 3D single particle theory of transit time effects. For enhancing the transverse swing of the beam in the cavity, some annuluses’ ends are widened, and so the transverse fields can be strengthened. The 3D theory demonstrates that, the oscillator can obtain an efficiency higher than 50%. Numerical simulation indicates that, it can produce an average power of 1.6 GW at 6.1 GHz with the beam-wave interaction efficiency of 52.3%, when excited by a 170 kV, 18 kA radial electron beam.
A new side-appending radial three-cavity transit time oscillator is proposed based on the 3D single particle theory of transit time effects. For enhancing the transverse swing of the beam in the cavity, some annuluses’ ends are widened, and so the transverse fields can be strengthened. The 3D theory demonstrates that, the oscillator can obtain an efficiency higher than 50%. Numerical simulation indicates that, it can produce an average power of 1.6 GW at 6.1 GHz with the beam-wave interaction efficiency of 52.3%, when excited by a 170 kV, 18 kA radial electron beam.
2009,
21.
Abstract:
Linear coupling processes of microwave pulses into rectangular and cylindrical cavities with narrow rectangular slots are investigated by finite-difference time-domain (FDTD) method. Phenomena of field enhancement, cavity modulation, and pulse width stretch are observed, especially the spectrum separation effect. When the electrical field of microwave pulses is parallel to slot short-side, the distribution of coupling microwave electrical fields inside the two cavities are calculated. The coupling electrical field in the plane, which is perpendicular to slot short-side, decreases rapidly near the inner wall of the cavity. In addition, in the cross-sections of the cavities, coupling electrical fields oscillate in a quasi-periodic manner, and the field amplitude is relatively uniform for the
Linear coupling processes of microwave pulses into rectangular and cylindrical cavities with narrow rectangular slots are investigated by finite-difference time-domain (FDTD) method. Phenomena of field enhancement, cavity modulation, and pulse width stretch are observed, especially the spectrum separation effect. When the electrical field of microwave pulses is parallel to slot short-side, the distribution of coupling microwave electrical fields inside the two cavities are calculated. The coupling electrical field in the plane, which is perpendicular to slot short-side, decreases rapidly near the inner wall of the cavity. In addition, in the cross-sections of the cavities, coupling electrical fields oscillate in a quasi-periodic manner, and the field amplitude is relatively uniform for the
2009,
21.
Abstract:
Improved particle-in-cell(PIC) algorithms were proposed, including volume weighting cloud-in-cell model, geo-metry profile considered explosive electron emission model and divergence error diffused perfectly matched layer boundary, which increased the precision of the algorithm and decreased the numerical noise. Based on the improved models, an user-friendly, 2.5-dimensional PIC code UNIPIC has been developed, which could be used to simulate high power microwave source devices and used for their geometry optimization in x-y, z-r and r-φcoordinate systems. The simulation results of relativistic magnetron, magnetically insulated line oscillator, virtual cathode oscillator showed good physics image and beam-wave interaction characteristics.
Improved particle-in-cell(PIC) algorithms were proposed, including volume weighting cloud-in-cell model, geo-metry profile considered explosive electron emission model and divergence error diffused perfectly matched layer boundary, which increased the precision of the algorithm and decreased the numerical noise. Based on the improved models, an user-friendly, 2.5-dimensional PIC code UNIPIC has been developed, which could be used to simulate high power microwave source devices and used for their geometry optimization in x-y, z-r and r-φcoordinate systems. The simulation results of relativistic magnetron, magnetically insulated line oscillator, virtual cathode oscillator showed good physics image and beam-wave interaction characteristics.
2009,
21.
Abstract:
The ripple of static trajectories focusing by the uniform solenoidal magnetic field and periodic permanent magnetic(PPM) field has been studied. the period and the amplitude of the ripple by the two kinds of field has been concluded. The effect of the magnetic field strength has been discussed. The small wavelet by PPM field has been reasoned out, whose period is a half of the PPM field period. The ripple of static trajectories by PPM field is nearly equivalent to the one by solenoidal magnetic field superposing the small wavelet. The ripple has been proved by 3D beam-wave interaction simulator(BWIS) module of microwave tube simulator suite(MTSS),which was developed by University of Electronic Science and Technology of China.
The ripple of static trajectories focusing by the uniform solenoidal magnetic field and periodic permanent magnetic(PPM) field has been studied. the period and the amplitude of the ripple by the two kinds of field has been concluded. The effect of the magnetic field strength has been discussed. The small wavelet by PPM field has been reasoned out, whose period is a half of the PPM field period. The ripple of static trajectories by PPM field is nearly equivalent to the one by solenoidal magnetic field superposing the small wavelet. The ripple has been proved by 3D beam-wave interaction simulator(BWIS) module of microwave tube simulator suite(MTSS),which was developed by University of Electronic Science and Technology of China.
2009,
21.
Abstract:
Articulated arm is widely used in Shanghai Synchrotron Radiation Facility(SSRF) for components’fiducialization with its portability and high accuracy. The design, actual technical method and quality assurance measures of fiducialization are addressed, while how to operate articulated arm correctly is stressed. When utilizing the arm, working efficiency is highly improved using its software’s study function. And measurement results with high accuracy are achieved through controlling tempera ture variation within 2℃ and comparing results between different apparatuses to monitor and amend systematic error.
Articulated arm is widely used in Shanghai Synchrotron Radiation Facility(SSRF) for components’fiducialization with its portability and high accuracy. The design, actual technical method and quality assurance measures of fiducialization are addressed, while how to operate articulated arm correctly is stressed. When utilizing the arm, working efficiency is highly improved using its software’s study function. And measurement results with high accuracy are achieved through controlling tempera ture variation within 2℃ and comparing results between different apparatuses to monitor and amend systematic error.
2009,
21.
Abstract:
Insulated gate biploar transistors(IGBTs) operating in series and parallel, which endure high voltage and heavy load currents, bring the problems of static and dynamic voltage and current balancing, which can be minimized by using passive balancing methods. This paper analyzes the main factors causing unbalance in theory and describes the passive snubber circuit used to equalize the voltage sharing and current balancing for serial and parallel IGBTs in both switching transients and steady state. The passive snubber circuit for voltage sharing consists of an RCD snubber and a balancing resistor. The current balancing technique consists of derating the parallel devices and impedance balancing by using a current balancing transformer. The snubber circuit was optimized by modeling the behavior
Insulated gate biploar transistors(IGBTs) operating in series and parallel, which endure high voltage and heavy load currents, bring the problems of static and dynamic voltage and current balancing, which can be minimized by using passive balancing methods. This paper analyzes the main factors causing unbalance in theory and describes the passive snubber circuit used to equalize the voltage sharing and current balancing for serial and parallel IGBTs in both switching transients and steady state. The passive snubber circuit for voltage sharing consists of an RCD snubber and a balancing resistor. The current balancing technique consists of derating the parallel devices and impedance balancing by using a current balancing transformer. The snubber circuit was optimized by modeling the behavior
2009,
21.
Abstract:
The electromagnetic pulse(EMP) damage mechanism and failure modes are obtained for the input port and output port of solid state relays by current injection method. The results show that the output port would misoperate when the EMP signal is injected at input port, and the input port may lose its control function when the base-emitter junction of the transistor in input circuit is burned out by the signal, that is, the output port would not be switched into conduction when control sygnals are applied to the input. The output port can be shorted when the drain and source are damaged by injected EMP signals at output port.
The electromagnetic pulse(EMP) damage mechanism and failure modes are obtained for the input port and output port of solid state relays by current injection method. The results show that the output port would misoperate when the EMP signal is injected at input port, and the input port may lose its control function when the base-emitter junction of the transistor in input circuit is burned out by the signal, that is, the output port would not be switched into conduction when control sygnals are applied to the input. The output port can be shorted when the drain and source are damaged by injected EMP signals at output port.
2009,
21.
Abstract:
The data exchange system of the cooler-storage-ring(CSR) control system for heavy ion radiotherapy has been introduced for the heavy ion CSR at Lanzhou(HIRFL-CSR). Using etchniques of Java, component object model(COM), Oracle, DSP and FPGA, this system can achieve real-time control of magnet power supplies simultanceously, and control beams and their switching in 256 energy levels. It has been used in the commissioning of slow extraction for the main CSR(CSRm), showing stable and reliable performance.
The data exchange system of the cooler-storage-ring(CSR) control system for heavy ion radiotherapy has been introduced for the heavy ion CSR at Lanzhou(HIRFL-CSR). Using etchniques of Java, component object model(COM), Oracle, DSP and FPGA, this system can achieve real-time control of magnet power supplies simultanceously, and control beams and their switching in 256 energy levels. It has been used in the commissioning of slow extraction for the main CSR(CSRm), showing stable and reliable performance.
2009,
21.
Abstract:
This paper introduces a new type Irradiation accelerator-petal-shaped radiation accelerator NB100（10 MeV/100 kW）.The RF characteristic parameters of the accelerating cavity of NB100 was simulated with Microwave Studio. The relationships between the RF characteristic parameters and the geometrical parameters were studied. The paper optimizes the 100 MHz accelerating structure considering the transit-time of electron beam. The results show that the new type accelerating cavity has relatively high effective shunt impedance and quality factor.
This paper introduces a new type Irradiation accelerator-petal-shaped radiation accelerator NB100（10 MeV/100 kW）.The RF characteristic parameters of the accelerating cavity of NB100 was simulated with Microwave Studio. The relationships between the RF characteristic parameters and the geometrical parameters were studied. The paper optimizes the 100 MHz accelerating structure considering the transit-time of electron beam. The results show that the new type accelerating cavity has relatively high effective shunt impedance and quality factor.
2009,
21.
Abstract:
Linear optics from closed orbits (LOCO) has been used during the commissioning of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The LOCO compares a model response matrix to the real machine response matrix. Using the measured response matrix of the SSRF storage ring, the gradients in all 200 quadrupole magnets were determined, and the calibration factors of steering magnets and beam position monitors (BPMs) were obtained at the same time. After adjusting the currents of quadrupole-magnet power supplies by the maximum of 1.5%, the optics parameters were restored very close to the designed values. The horizontal and vertical differences of beta function from the design values are around 10% before correction and 1% after correction.
Linear optics from closed orbits (LOCO) has been used during the commissioning of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The LOCO compares a model response matrix to the real machine response matrix. Using the measured response matrix of the SSRF storage ring, the gradients in all 200 quadrupole magnets were determined, and the calibration factors of steering magnets and beam position monitors (BPMs) were obtained at the same time. After adjusting the currents of quadrupole-magnet power supplies by the maximum of 1.5%, the optics parameters were restored very close to the designed values. The horizontal and vertical differences of beta function from the design values are around 10% before correction and 1% after correction.
2009,
21.
Abstract:
The principle of random nuclear signal power spectrum density analysis is introduced. Using Matlab, block-averaging method is adopted to process the random nuclear signals from the three measurement channels in the nuclear information system of the 252Cf fission neutron source. Then correlation calculation is done for every block, and the derived correlation functions are summed up and then transformed into power spectrum with Fourier transform. Finally, power spectrum density estimates are obtained after averaging the spectrum. With these results, improtant parameters are got, such as correlation functions multiplicity, coherence and power spectrum density ratio.
The principle of random nuclear signal power spectrum density analysis is introduced. Using Matlab, block-averaging method is adopted to process the random nuclear signals from the three measurement channels in the nuclear information system of the 252Cf fission neutron source. Then correlation calculation is done for every block, and the derived correlation functions are summed up and then transformed into power spectrum with Fourier transform. Finally, power spectrum density estimates are obtained after averaging the spectrum. With these results, improtant parameters are got, such as correlation functions multiplicity, coherence and power spectrum density ratio.
2009,
21.
Abstract:
According to the characteristics of flash radiographic image with low signal-to-noise ratio, a generalized variation(GV) regularization based image reconstruction algorithm is proposed. In the new algorithm, p-norm is used as regularized term instead of total variation(TV) norm in widely-used TV-based image denoising methods. Then a smoothing functional is constructed for image reconstruction. Thus, the problem of image reconstruction is transformed to a problem of functional minimization. A nonlinear partial differential equation(PDE) is deduced from the new image reconstruction model. To solve the nonlinear PDE, fixed point iteration(FPI) scheme is introduced to linearize the PDE, ensuring the stability and convergence of regularized solution. Numerical results show that, compared with T
According to the characteristics of flash radiographic image with low signal-to-noise ratio, a generalized variation(GV) regularization based image reconstruction algorithm is proposed. In the new algorithm, p-norm is used as regularized term instead of total variation(TV) norm in widely-used TV-based image denoising methods. Then a smoothing functional is constructed for image reconstruction. Thus, the problem of image reconstruction is transformed to a problem of functional minimization. A nonlinear partial differential equation(PDE) is deduced from the new image reconstruction model. To solve the nonlinear PDE, fixed point iteration(FPI) scheme is introduced to linearize the PDE, ensuring the stability and convergence of regularized solution. Numerical results show that, compared with T
2009,
21.
Abstract:
The structures of PdCO2, PdCO, and PdH are optimized by the relativistic effective core potential (RECP) and the density functional theory B3P86 method. The results show that the stable geometry of Pd-CO2 molecule is plane structure. The ground state of PdCO2 is (X1A′) of Cs group. The structure parameters of RPdC, RCO, RC O′ and∠OCO′ are 0.203 0 nm, 0.118 3 nm, 0.121 0 nm and 154.215°,respectively. For PdCO molecule, the ground state is 1∑+, and the structure parameters of R(PdC), R(CO), and ∠PdCO are 0.183 4 nm, 0.114 0 nm, and 180°, respectively. The ground state of PdH is 2∑, and the bond length is 0.152 6 nm. Furthermore, the thermodynamic functions of PdCO2, PdCO, and PdH are also calculated according to electronic-vibration approximation. An
The structures of PdCO2, PdCO, and PdH are optimized by the relativistic effective core potential (RECP) and the density functional theory B3P86 method. The results show that the stable geometry of Pd-CO2 molecule is plane structure. The ground state of PdCO2 is (X1A′) of Cs group. The structure parameters of RPdC, RCO, RC O′ and∠OCO′ are 0.203 0 nm, 0.118 3 nm, 0.121 0 nm and 154.215°,respectively. For PdCO molecule, the ground state is 1∑+, and the structure parameters of R(PdC), R(CO), and ∠PdCO are 0.183 4 nm, 0.114 0 nm, and 180°, respectively. The ground state of PdH is 2∑, and the bond length is 0.152 6 nm. Furthermore, the thermodynamic functions of PdCO2, PdCO, and PdH are also calculated according to electronic-vibration approximation. An
