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RSS2004 Vol. 16, No. 08
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2004,
16.
Abstract:
When a laser beam irradiates a cylinder shell, the irradiated area becomes softer and will destroy cylinder shell. On the basis of early work, 3-D solid element is adopted to simulate the stress of internally pressured cylinder shell irradiated by laser. The properties of material varying with temperature are also taken into account in the computation. It is analyzed by numerical simulation that the ratio of circumferential stress and strength of outer shell along axis is affected by irradiation time, laser beam spot radius and power . With the computations, it concludes that the crack will initiate from the beam spot edge at the conditions of short heating time and large inner pressure, the smaller beam spot will easily crack at the condition of the same laser power, and that the ratio of
When a laser beam irradiates a cylinder shell, the irradiated area becomes softer and will destroy cylinder shell. On the basis of early work, 3-D solid element is adopted to simulate the stress of internally pressured cylinder shell irradiated by laser. The properties of material varying with temperature are also taken into account in the computation. It is analyzed by numerical simulation that the ratio of circumferential stress and strength of outer shell along axis is affected by irradiation time, laser beam spot radius and power . With the computations, it concludes that the crack will initiate from the beam spot edge at the conditions of short heating time and large inner pressure, the smaller beam spot will easily crack at the condition of the same laser power, and that the ratio of
2004,
16.
Abstract:
According to experimental parameters, a theory model is made up to simulate measurement of reflectivity for length misadjustment of ring-down cavity. According to propagation equation of Gaussian beam, the influence of length misadjustment of ringdown cavity on its mode coupling is investigated, and the equation is given for relation between length misadjustment and output power, then the relation between ring-down signal and reflectivity is deduced from output characteristic of optical cavity. Applying this model, it is simulated that ringdown signal changes with length misadjustment of -10~10mm. The relation between metrical precision and length misadjustment is also numerically simulated. The analysis shows that the metrical precision drops rapidly with length misadjustment. To achiev
According to experimental parameters, a theory model is made up to simulate measurement of reflectivity for length misadjustment of ring-down cavity. According to propagation equation of Gaussian beam, the influence of length misadjustment of ringdown cavity on its mode coupling is investigated, and the equation is given for relation between length misadjustment and output power, then the relation between ring-down signal and reflectivity is deduced from output characteristic of optical cavity. Applying this model, it is simulated that ringdown signal changes with length misadjustment of -10~10mm. The relation between metrical precision and length misadjustment is also numerically simulated. The analysis shows that the metrical precision drops rapidly with length misadjustment. To achiev
2004,
16.
Abstract:
The static performance models are important links in thermal imaging technologies. In this paper, the equations of operating range are set up for the extended source object by minimum resolved temperature difference (MRTD) based on different static performance models such as NVL75, FLIR92 and CFLIR. At last, the visual range prediction simulation results with different models were compared. And the results show that for the infrared staring system, the MRTD value based on the CFLIR model is close to measurement value in the laboratory and the CFLIR model is superior to the FLIR92 model in the visual range prediction. On the other hand, judging by MRTD, the visual range prediction of the staring system is superior to that of the scan system when the parameters are equal．
The static performance models are important links in thermal imaging technologies. In this paper, the equations of operating range are set up for the extended source object by minimum resolved temperature difference (MRTD) based on different static performance models such as NVL75, FLIR92 and CFLIR. At last, the visual range prediction simulation results with different models were compared. And the results show that for the infrared staring system, the MRTD value based on the CFLIR model is close to measurement value in the laboratory and the CFLIR model is superior to the FLIR92 model in the visual range prediction. On the other hand, judging by MRTD, the visual range prediction of the staring system is superior to that of the scan system when the parameters are equal．
2004,
16.
Abstract:
Based on the Whispering Gallery Mode, a kind of laser with intrinsic high quality factor and low threshold can be obtained, which is called microsphere laser. It is widely applied in many fields such as microcavity quantum electric dynamics, optical fiber communication, sensors, nonlinear optics, low threshold laser equipment and quantum optics due to its sensitivity to pressure and temperature.In this paper, the principle and the method to produce the microsphere laser and its characters, applications and newly development are reviewed.
Based on the Whispering Gallery Mode, a kind of laser with intrinsic high quality factor and low threshold can be obtained, which is called microsphere laser. It is widely applied in many fields such as microcavity quantum electric dynamics, optical fiber communication, sensors, nonlinear optics, low threshold laser equipment and quantum optics due to its sensitivity to pressure and temperature.In this paper, the principle and the method to produce the microsphere laser and its characters, applications and newly development are reviewed.
2004,
16.
Abstract:
Based on the thermal conduction equations and thermalelastic equations, while the laser speckle radius on the reflectors are much larger than or almost approximate to the thermal diffusion lengths of the substrate materials, and while the reflectors boundaries are constrained or unconstrained, the maximum temperature rise, thermal distortion and thermal stress of silicon or silicabased multilayered infrared CW laser reflectors are calculated by a finite element analysis method. And the dependences of these parameters on the laser speckle radius is discussed. The results indicate that the ultimate axial displacements on the surfaces of the reflectors are approximately linear with the incidence beams radius while the reflectors have unconstrained boundarties, but the ultimate thermal
Based on the thermal conduction equations and thermalelastic equations, while the laser speckle radius on the reflectors are much larger than or almost approximate to the thermal diffusion lengths of the substrate materials, and while the reflectors boundaries are constrained or unconstrained, the maximum temperature rise, thermal distortion and thermal stress of silicon or silicabased multilayered infrared CW laser reflectors are calculated by a finite element analysis method. And the dependences of these parameters on the laser speckle radius is discussed. The results indicate that the ultimate axial displacements on the surfaces of the reflectors are approximately linear with the incidence beams radius while the reflectors have unconstrained boundarties, but the ultimate thermal
2004,
16.
Abstract:
A transverse jet singlet oxygen generator (TJSOG) with BHP liquid driven by a pump circulation was demonstrated. This TJSOG represents the trend for its engineering scalability. In the initial experimental stage, a singlet oxygen yield of 58% was obtained for a chlorine flowrate of 530mmol/s, corresponding to a chlorine utilization of above 80% and a relative water vapor concentration no more than 0.5. The O2 (1Δ) and the water vapor content in the gas were determined from the emission of the 1 270nm and 762nm wavelength, respectively, according to the PistonSource method. Chlorine untilization was measured by detecting the absorption of 340nm light by residual chlorine. The TJSOG can work steadily when the total gas flow rate reaches the maximum．
A transverse jet singlet oxygen generator (TJSOG) with BHP liquid driven by a pump circulation was demonstrated. This TJSOG represents the trend for its engineering scalability. In the initial experimental stage, a singlet oxygen yield of 58% was obtained for a chlorine flowrate of 530mmol/s, corresponding to a chlorine utilization of above 80% and a relative water vapor concentration no more than 0.5. The O2 (1Δ) and the water vapor content in the gas were determined from the emission of the 1 270nm and 762nm wavelength, respectively, according to the PistonSource method. Chlorine untilization was measured by detecting the absorption of 340nm light by residual chlorine. The TJSOG can work steadily when the total gas flow rate reaches the maximum．
2004,
16.
Abstract:
Two dimensional laminar flow N-S equations are solved to simulate the large scale vortical structures in heated jet flow field, and the optics path lengths at different streamwise positions were computed. The results indicated that the features of the vortical structure induced different optical aberration. Because of the existence of the large scale vortical structures the optical inhomogeneity of turbulent flowfield was educed.
Two dimensional laminar flow N-S equations are solved to simulate the large scale vortical structures in heated jet flow field, and the optics path lengths at different streamwise positions were computed. The results indicated that the features of the vortical structure induced different optical aberration. Because of the existence of the large scale vortical structures the optical inhomogeneity of turbulent flowfield was educed.
2004,
16.
Abstract:
In this paper, the deformation and failure of a cylinder with inner pressure, which is irradiated by high power continuous wave laser beam, are investigated using the similarity analysis theory and FEM. At first, several dimensionless parameters are presented as the similarity criterion based on the dimensional analysis and equations analysis methods. In order to verify the above criterion, numerical simulations on mechanical responses of different size cylinder, but with the same similarity parameters, are accomplished with the commercial FEM code ANSYS. FEM results demonstrate that main dimensionless physical parameters are invariable at the same dimensionless position and time in different scale models, and prove that the similarity criterion presented in this paper is valid.
In this paper, the deformation and failure of a cylinder with inner pressure, which is irradiated by high power continuous wave laser beam, are investigated using the similarity analysis theory and FEM. At first, several dimensionless parameters are presented as the similarity criterion based on the dimensional analysis and equations analysis methods. In order to verify the above criterion, numerical simulations on mechanical responses of different size cylinder, but with the same similarity parameters, are accomplished with the commercial FEM code ANSYS. FEM results demonstrate that main dimensionless physical parameters are invariable at the same dimensionless position and time in different scale models, and prove that the similarity criterion presented in this paper is valid.
2004,
16.
Abstract:
The paper describes the experiment on shocking aluminum plates of different shapes with shortlypulsed high power laser beams under confinement structure and the effect of confinement and black paint .It is found that the induced pressure is much more huge than that produced in nonconfining case,though it's inferior to it's forecasted value.Within the research range,black coating plays the surface-protecting role more effectively than enhances the absorption of laser,while superfluous coating will decrease the induced pressure significantly.Convex Al plates were also shocked with the confinement of plane glass,and the plane glass's confinement is still effective as long as the plate's circumflexion radius is greater than 400mm.
The paper describes the experiment on shocking aluminum plates of different shapes with shortlypulsed high power laser beams under confinement structure and the effect of confinement and black paint .It is found that the induced pressure is much more huge than that produced in nonconfining case,though it's inferior to it's forecasted value.Within the research range,black coating plays the surface-protecting role more effectively than enhances the absorption of laser,while superfluous coating will decrease the induced pressure significantly.Convex Al plates were also shocked with the confinement of plane glass,and the plane glass's confinement is still effective as long as the plate's circumflexion radius is greater than 400mm.
2004,
16.
Abstract:
The characteristics and optical path difference of beam reflected by cubecorner prism(CCP) with dihedral angle errors were researched; the CCP with errors acts as a phase screen comprised 6 optical wedges. The positions at cavity mirror of ray which propagates back and forth in the CCP laser resonator are analyzed, it shows that the CCP resonator with three equal dihedral angle errors (three dihedral angle errors are not 0) is an unstable resonator. The CCP laser resonator mode is simulated with FoxLi numeric method. The result shows that the CCP resonator oscillates typically in TEM03 mode of LaguerreGaussian beam. The beam pattern consists of 6 pieces and looks like an asterisk. The pieces of the pattern are not symmetric and equal when the 3 dihedral angle errors are different. In
The characteristics and optical path difference of beam reflected by cubecorner prism(CCP) with dihedral angle errors were researched; the CCP with errors acts as a phase screen comprised 6 optical wedges. The positions at cavity mirror of ray which propagates back and forth in the CCP laser resonator are analyzed, it shows that the CCP resonator with three equal dihedral angle errors (three dihedral angle errors are not 0) is an unstable resonator. The CCP laser resonator mode is simulated with FoxLi numeric method. The result shows that the CCP resonator oscillates typically in TEM03 mode of LaguerreGaussian beam. The beam pattern consists of 6 pieces and looks like an asterisk. The pieces of the pattern are not symmetric and equal when the 3 dihedral angle errors are different. In
2004,
16.
Abstract:
Two LCTV are combined by a relay lens.One of the LCTVs is used to simulate a distorted wavefront and the other is used to control and correct this distortion. And the results of simulation and crrection of the distorted wavefront are tested by our CRSI(cyclic radial shearing interferometer), respectively. The results of our testing show that phase-mostly LCTV can be used to control the smallscale wavefront distortion of a laser beam．
Two LCTV are combined by a relay lens.One of the LCTVs is used to simulate a distorted wavefront and the other is used to control and correct this distortion. And the results of simulation and crrection of the distorted wavefront are tested by our CRSI(cyclic radial shearing interferometer), respectively. The results of our testing show that phase-mostly LCTV can be used to control the smallscale wavefront distortion of a laser beam．
2004,
16.
Abstract:
The acrylates organic-inorganic hybrid sol was applied to modify the UV-curable acrylates adhesives. By this way, we prepared a novel kind of UV-curable adhesives, which has good shearing strength and solvent resistance. It's good properties show a promising future in fabrication of ICF targets. The results of the properties tests show that the adhesive has stronger adhering force when the reactive diluent has more hydroxy and carboxyl groups. The content of hybrid sol affects the shear strength and solvent resistance of adhesive, too. When the mass of solid content of hybrid sol reached 60% of UV-cured resin, the shear strength was up to 12MPa, and the adhesive showed perfect solvent resistance.
The acrylates organic-inorganic hybrid sol was applied to modify the UV-curable acrylates adhesives. By this way, we prepared a novel kind of UV-curable adhesives, which has good shearing strength and solvent resistance. It's good properties show a promising future in fabrication of ICF targets. The results of the properties tests show that the adhesive has stronger adhering force when the reactive diluent has more hydroxy and carboxyl groups. The content of hybrid sol affects the shear strength and solvent resistance of adhesive, too. When the mass of solid content of hybrid sol reached 60% of UV-cured resin, the shear strength was up to 12MPa, and the adhesive showed perfect solvent resistance.
2004,
16.
Abstract:
Ｔhe power spectral density(PSD) has been employed as the specifying parameter of the optical components with large aperture in the testing process. According to the different wavefront modulation with different depth or frequency, the PSD curves present different variation rule. The change of the modulation frequency will change the corresponding frequency value of the protuberant part on the PSD curve, and at the same time the peak value of the protuberant part is changed. Ｔhe modulation depth is focused on the intensity change of the protuberant part of the PSD curves．Ｉt cannot influence the frequency value of the protuberant part.
Ｔhe power spectral density(PSD) has been employed as the specifying parameter of the optical components with large aperture in the testing process. According to the different wavefront modulation with different depth or frequency, the PSD curves present different variation rule. The change of the modulation frequency will change the corresponding frequency value of the protuberant part on the PSD curve, and at the same time the peak value of the protuberant part is changed. Ｔhe modulation depth is focused on the intensity change of the protuberant part of the PSD curves．Ｉt cannot influence the frequency value of the protuberant part.
2004,
16.
Abstract:
This paper mainly discusses the application of microwave plasma technology in the field of the inertial confinement fusion(ICF) target fabrication, including films preparation, reactive ion beam etching(RIBE) and focused ion beam(FIB) etching, as well as the nano-metal particles synthesis and its surface polymer-coated modification. This technology is very useful to solve the problem occurred in ICF target fabrication and improve the quality of the ICF target produced.
This paper mainly discusses the application of microwave plasma technology in the field of the inertial confinement fusion(ICF) target fabrication, including films preparation, reactive ion beam etching(RIBE) and focused ion beam(FIB) etching, as well as the nano-metal particles synthesis and its surface polymer-coated modification. This technology is very useful to solve the problem occurred in ICF target fabrication and improve the quality of the ICF target produced.
2004,
16.
Abstract:
The high energy density selfhealing metallized film pulse capacitor has been applied to all kinds of laser facilities for their power conditioning systems, whose reliability and expense are straightforwardly affected by the reliability level of the capacitors. Based on the related research in literature, this paper analyses the degradation mechanism of the capacitor, and presents a new degradation failure model-the Gauss-Poisson model．The Guass-Poisson model divides degradation of capacitor into naturalness degradation and outburst one.Compared with traditional weibull failure model, the new model is more precise in evaluating the lifetime of the capacitor, and the life tests for this model are simple in design, and lower in the cost of time or expense．The GaussPoisson model will be
The high energy density selfhealing metallized film pulse capacitor has been applied to all kinds of laser facilities for their power conditioning systems, whose reliability and expense are straightforwardly affected by the reliability level of the capacitors. Based on the related research in literature, this paper analyses the degradation mechanism of the capacitor, and presents a new degradation failure model-the Gauss-Poisson model．The Guass-Poisson model divides degradation of capacitor into naturalness degradation and outburst one.Compared with traditional weibull failure model, the new model is more precise in evaluating the lifetime of the capacitor, and the life tests for this model are simple in design, and lower in the cost of time or expense．The GaussPoisson model will be
2004,
16.
Abstract:
In Z-pinch physical experiments carried out on accelerators with horizontal cathode and anode, the distance between the electrodes will shorten by a scale of 2 ～3 mm while the chamber is pumped to vacuum. Due to this change, wires of the cylindric array loaded between the electrodes will loosen to a degree beyond the physical experiments. To solve this problem and to make sure that the wire-array can be fabricated, stored, transported and loaded to the electrodes, we make use of the spring's flexibilities and have developed a set of techniques to fabricate singlewalled cylindric wirearray. Due to the pressed spring, the fabricated wirearray will themselves fit the distance changes of the electrodes. And the loads can keep their designed initial states required by physical experiment
In Z-pinch physical experiments carried out on accelerators with horizontal cathode and anode, the distance between the electrodes will shorten by a scale of 2 ～3 mm while the chamber is pumped to vacuum. Due to this change, wires of the cylindric array loaded between the electrodes will loosen to a degree beyond the physical experiments. To solve this problem and to make sure that the wire-array can be fabricated, stored, transported and loaded to the electrodes, we make use of the spring's flexibilities and have developed a set of techniques to fabricate singlewalled cylindric wirearray. Due to the pressed spring, the fabricated wirearray will themselves fit the distance changes of the electrodes. And the loads can keep their designed initial states required by physical experiment
2004,
16.
Abstract:
The ion temperature in Tokamak plamsa is an important parameter. A vibration mirror instrument for measurement of plasma ion temperature was established, and this system consists of a 0.5m Czerny-Turner spectrometer and a vibration quartz mirror in front of the exit slit of the spectrometer. The CV (227.1nm) line shape was measured by vibrating the mirror, which was controlled by a scan controller, the time dispersion of the system is less than 10ms and the error is less than 20eV.The ion temperature in HT-6M Tokamak was derived from the Doppler broaden of CV line during OMH and ICRH. The result shows that the ion temperature rises from 200eV to 300eV during ICRH. The equipment can be widely applied to small and medium sized Tokamak.
The ion temperature in Tokamak plamsa is an important parameter. A vibration mirror instrument for measurement of plasma ion temperature was established, and this system consists of a 0.5m Czerny-Turner spectrometer and a vibration quartz mirror in front of the exit slit of the spectrometer. The CV (227.1nm) line shape was measured by vibrating the mirror, which was controlled by a scan controller, the time dispersion of the system is less than 10ms and the error is less than 20eV.The ion temperature in HT-6M Tokamak was derived from the Doppler broaden of CV line during OMH and ICRH. The result shows that the ion temperature rises from 200eV to 300eV during ICRH. The equipment can be widely applied to small and medium sized Tokamak.
2004,
16.
Abstract:
Inner-Si-doped polystyrene capsules are required to meet the demand of characterization of implosion interface. With dimethyldiethoxysilane (DMDES) as silicon donor, an encapsulation method is used to fabricate the inner-Si-doped polystyrene capsules. Noncontact X-radiography and X-spectrum analysis indicate that the resultant capsules appear with Si content at inner surface much higher about 2~3 order than that at outer surface and thickness of Sidoped layer less than 0.3μm．
Inner-Si-doped polystyrene capsules are required to meet the demand of characterization of implosion interface. With dimethyldiethoxysilane (DMDES) as silicon donor, an encapsulation method is used to fabricate the inner-Si-doped polystyrene capsules. Noncontact X-radiography and X-spectrum analysis indicate that the resultant capsules appear with Si content at inner surface much higher about 2~3 order than that at outer surface and thickness of Sidoped layer less than 0.3μm．
2004,
16.
Abstract:
The dependences of the delay and jitter of the laser triggered multistage multi-channel switch on the energy of laser pulse, voltage, gas species and pressure were reported in this paper. The experimental phenomena was illustrated by a 0-demension model in which the delay of the laser triggered gap was calculated by a “2-2”model and the delay of the self-breakdown gaps was calculated by T.H.Martin formulas adjusted by Levinson’s data. The laser ionization mechanism in gas indicated by “2-2”model as 2-photon excitation metastable state of gas particles was followed by 2-photon ionization of the excited gas particles. The delay and jitter decreased as the energy of laser pulse, voltage, pressure increased, and increased as the percentage of SF6 in SF6-N2, SF6-Ar mixtures increased. The
The dependences of the delay and jitter of the laser triggered multistage multi-channel switch on the energy of laser pulse, voltage, gas species and pressure were reported in this paper. The experimental phenomena was illustrated by a 0-demension model in which the delay of the laser triggered gap was calculated by a “2-2”model and the delay of the self-breakdown gaps was calculated by T.H.Martin formulas adjusted by Levinson’s data. The laser ionization mechanism in gas indicated by “2-2”model as 2-photon excitation metastable state of gas particles was followed by 2-photon ionization of the excited gas particles. The delay and jitter decreased as the energy of laser pulse, voltage, pressure increased, and increased as the percentage of SF6 in SF6-N2, SF6-Ar mixtures increased. The
2004,
16.
Abstract:
It is pointed out that the key problem is multi-capacitive loading resistances matching for increasing microstrip-tapped sampling speed. According to distributed parameter theory and microwave transmission line theory, the partial matched model is proposed and the computing formulas for resistance matching are deduced. The results of numerical analysis and circuit simulation show that ps pulse transmission line of different operating frequency and multi-tapped capacitances can be well compensated by the partial matched method, so the distortion to every sampling waveforms of transmission line is very small, the effect of compensation is obvious and microstrip-tapped sampling speed is increased.
It is pointed out that the key problem is multi-capacitive loading resistances matching for increasing microstrip-tapped sampling speed. According to distributed parameter theory and microwave transmission line theory, the partial matched model is proposed and the computing formulas for resistance matching are deduced. The results of numerical analysis and circuit simulation show that ps pulse transmission line of different operating frequency and multi-tapped capacitances can be well compensated by the partial matched method, so the distortion to every sampling waveforms of transmission line is very small, the effect of compensation is obvious and microstrip-tapped sampling speed is increased.
2004,
16.
Abstract:
A plasma erosion opening switch (PEOS) which works in long-conduction-time (about 1μs) has been developed. The influence of plasma source parameters including the time delay bwtween plasma gun and Marx generator, the working voltage and the number of plasma guns on the performances of PEOS has been investigated in experiments. As a result, the conduction time and the PEOS voltage increase with increasing Marx-plasma gun time delay, the working voltage and the number of plasma guns. Nevertheless, when the conduction time is close to the quarter period of the main electrical circuit, the PEOS voltage drops abruptly. With Marx voltage of 120kV and four plasma guns, the maximal voltage multiplication factor is about 1.8.
A plasma erosion opening switch (PEOS) which works in long-conduction-time (about 1μs) has been developed. The influence of plasma source parameters including the time delay bwtween plasma gun and Marx generator, the working voltage and the number of plasma guns on the performances of PEOS has been investigated in experiments. As a result, the conduction time and the PEOS voltage increase with increasing Marx-plasma gun time delay, the working voltage and the number of plasma guns. Nevertheless, when the conduction time is close to the quarter period of the main electrical circuit, the PEOS voltage drops abruptly. With Marx voltage of 120kV and four plasma guns, the maximal voltage multiplication factor is about 1.8.
2004,
16.
Abstract:
Linac with mm diameter beam spot strikes the bremsstrahlung converter target to generate Ｘ-ray and the backstreaming ions.As ions move through the electron beam,the beam will be pinched which results in a moving focus before the target.Two sets of Faraday cup are combined designed to collect backstreaming ions produced at bremsstrahlung converter target of 12MeV linac. Analyses and comparison of numerical simulation and experiment results show that no backstreaming ions, close to targets between 6０° and 70°, are observed．
Linac with mm diameter beam spot strikes the bremsstrahlung converter target to generate Ｘ-ray and the backstreaming ions.As ions move through the electron beam,the beam will be pinched which results in a moving focus before the target.Two sets of Faraday cup are combined designed to collect backstreaming ions produced at bremsstrahlung converter target of 12MeV linac. Analyses and comparison of numerical simulation and experiment results show that no backstreaming ions, close to targets between 6０° and 70°, are observed．
2004,
16.
Abstract:
At first, this paper gave the definition of real efficient secondary electron emission coefficient and discussed its relation the incident energy of high energy primary electron in metal in theory. When high energy primary electron of different incident energy collided with the same metal emitter. The product of their veal efficient secondary electron emission coefficent and the incident energy of primary electron is approximately constant. Then the theory was proved to be true by experimental date and we also discussed the reasons that the product of real efficient secondary electron emission and the incident energy of primary electron had same discrepancy because of different incident energy of primary electron.
At first, this paper gave the definition of real efficient secondary electron emission coefficient and discussed its relation the incident energy of high energy primary electron in metal in theory. When high energy primary electron of different incident energy collided with the same metal emitter. The product of their veal efficient secondary electron emission coefficent and the incident energy of primary electron is approximately constant. Then the theory was proved to be true by experimental date and we also discussed the reasons that the product of real efficient secondary electron emission and the incident energy of primary electron had same discrepancy because of different incident energy of primary electron.
2004,
16.
Abstract:
Primary factors affecting determination of the optical path in radiography are investigated. For two different detect ways, the direct and the converting screen methods, these factors are the same, including the scattering effect, the angle distribution effect of the exposure, and the inverse effect of the exposure to the square of radiographic distance. In the high-energy radiography, the scatter is very serious and it is the most important factor. The scatter effect makes the measured value of optical path 20%~40% lower than its actual value. Before CT reconstruct of the radiographic image, it is necessary to reduce scatter effect from the measured optical path.
Primary factors affecting determination of the optical path in radiography are investigated. For two different detect ways, the direct and the converting screen methods, these factors are the same, including the scattering effect, the angle distribution effect of the exposure, and the inverse effect of the exposure to the square of radiographic distance. In the high-energy radiography, the scatter is very serious and it is the most important factor. The scatter effect makes the measured value of optical path 20%~40% lower than its actual value. Before CT reconstruct of the radiographic image, it is necessary to reduce scatter effect from the measured optical path.
2004,
16.
Abstract:
The cavity around magnetic cores in linear induction cell act as a non-linear winding when the pulses come. This paper explains how to create PSpice model by its normal parts to simulate a non-linear winding with magnetic core, with a flux switch, the model take into account factors such as saturation, hysteresis and the power losses caused by frequency. By change some pellucid parameters, this model can work in different frequency. This paper also gives some practive examples.
The cavity around magnetic cores in linear induction cell act as a non-linear winding when the pulses come. This paper explains how to create PSpice model by its normal parts to simulate a non-linear winding with magnetic core, with a flux switch, the model take into account factors such as saturation, hysteresis and the power losses caused by frequency. By change some pellucid parameters, this model can work in different frequency. This paper also gives some practive examples.
2004,
16.
Abstract:
A two-electron-group model for capacitively coupled radio-frequency (CCRF) glow discharge used to excite ion laser is developed. The model assumes electrons in the discharge zone are classified into two groups, i.e. bulk or plasma electrons and fast or secondary emission electrons. These two groups of electrons are responsible for α and γ processes respectively. Results from the model reveal that plasma parameters change largely at the transition regions between two operating modes. The ionization rates distribution at the high current mode of a narrow electrode gap RF discharge which is analog to a hollow cathode discharge demonstrates the pendulum effect exists in the CCRF discharge.
A two-electron-group model for capacitively coupled radio-frequency (CCRF) glow discharge used to excite ion laser is developed. The model assumes electrons in the discharge zone are classified into two groups, i.e. bulk or plasma electrons and fast or secondary emission electrons. These two groups of electrons are responsible for α and γ processes respectively. Results from the model reveal that plasma parameters change largely at the transition regions between two operating modes. The ionization rates distribution at the high current mode of a narrow electrode gap RF discharge which is analog to a hollow cathode discharge demonstrates the pendulum effect exists in the CCRF discharge.
2004,
16.
Abstract:
The hybrid undulator, is optimized in beam direction based on transverse optimization developed in ESRF. The thickness of the magnet and the pole is optimized at the ratio of 16∶9 for the maximized peak field. The analytical equations for designing the hybrid undulator are listed and discussed. One prototype hybrid undulator with 25mm period length is being constructed with NdFeB magnets and vanadium permendur poles by the optimized results. The magnet gap of the hybrid undulator can be tunable in 10~300mm. At 10mm magnetic gap, the undulator peak field can reach 0.648T with only the main magnet. It can be enhanced to 0.722T and 0.773T by further adding the side magnet and top magnet. The field resolution is better than 10-4T with 1μm gap tuning system driven by servomotor. All optim
The hybrid undulator, is optimized in beam direction based on transverse optimization developed in ESRF. The thickness of the magnet and the pole is optimized at the ratio of 16∶9 for the maximized peak field. The analytical equations for designing the hybrid undulator are listed and discussed. One prototype hybrid undulator with 25mm period length is being constructed with NdFeB magnets and vanadium permendur poles by the optimized results. The magnet gap of the hybrid undulator can be tunable in 10~300mm. At 10mm magnetic gap, the undulator peak field can reach 0.648T with only the main magnet. It can be enhanced to 0.722T and 0.773T by further adding the side magnet and top magnet. The field resolution is better than 10-4T with 1μm gap tuning system driven by servomotor. All optim
2004,
16.
Abstract:
By using two-dimensional numerical computation model for exploding foil, the computation is carried out for the inductive energy storage pulsed-power conditioning system with an exploding foil opening switch. On the basis of computation, a low inductance exploding foil opening switch is designed and tested. When energized by a capacitor bank (4μF/75kV), an output pulse voltage of 250 kV with over 400ns duration is obtained on a 13Ω load.
By using two-dimensional numerical computation model for exploding foil, the computation is carried out for the inductive energy storage pulsed-power conditioning system with an exploding foil opening switch. On the basis of computation, a low inductance exploding foil opening switch is designed and tested. When energized by a capacitor bank (4μF/75kV), an output pulse voltage of 250 kV with over 400ns duration is obtained on a 13Ω load.
2004,
16.
Abstract:
HLS (Hefei Light Source) is a second generation synchrotron radiation light source. After injected into the storage ring at energy of 200MeV, beam will be ramped to 800MeV. At first, the accelerator physics analysis about the ramping process is described. After the structure diagram of HLS storage ring's main P.S. control system is shown, the ramping table calculation and the ramping process control are described in detail. Operation of HLS shows that the method of beam soft ramping is flexible and effective, and can satisfy the demands of HLS machine operation.
HLS (Hefei Light Source) is a second generation synchrotron radiation light source. After injected into the storage ring at energy of 200MeV, beam will be ramped to 800MeV. At first, the accelerator physics analysis about the ramping process is described. After the structure diagram of HLS storage ring's main P.S. control system is shown, the ramping table calculation and the ramping process control are described in detail. Operation of HLS shows that the method of beam soft ramping is flexible and effective, and can satisfy the demands of HLS machine operation.
2004,
16.
Abstract:
In order to suppress the back bombardment of electrons in RF thermionic guns, a new kind of on axis coupled structure type RF gun was developed. It is composed of two half cells and a full cell. The first half cell is shortened and a half cell is inserted between the first half cell and the main accelerating cell to defocus the particles moving backwards with highest energy, thus the cathode back bombardment power is strongly reduced. For the field stability the π/2 mode is chosen. The electromagnetic field analytical codes SUPERFISH and PAMELA are mainly used to do the calculation and simulation. The average back bombardment power is about 3.6W, assuming the pulse width of 6μs and a repetition rate of 25Hz.
In order to suppress the back bombardment of electrons in RF thermionic guns, a new kind of on axis coupled structure type RF gun was developed. It is composed of two half cells and a full cell. The first half cell is shortened and a half cell is inserted between the first half cell and the main accelerating cell to defocus the particles moving backwards with highest energy, thus the cathode back bombardment power is strongly reduced. For the field stability the π/2 mode is chosen. The electromagnetic field analytical codes SUPERFISH and PAMELA are mainly used to do the calculation and simulation. The average back bombardment power is about 3.6W, assuming the pulse width of 6μs and a repetition rate of 25Hz.
2004,
16.
Abstract:
In this paper, the system generated electromagnetic pulse (SGEMP) phenomena caused by photoelectrons emission in cylinder cavity was simulated with FDTD and PIC methods. The characters of electric field waveforms and space distributions were analyzed and summarized in the monoenergetic photoelectron circumstance. Then, with the methods of particle sample and particle emission at a proper interval, the results were obtained when the photoelectrons emit with specific spectrum. At the same time, the results attained from two different particle simulations show that the above methods can decrease the particle numbers involved efficiently except a little bit noise increasing. Therefore, it can be used in the 3D particle simulation. The results also reveal that the length of strong electric
In this paper, the system generated electromagnetic pulse (SGEMP) phenomena caused by photoelectrons emission in cylinder cavity was simulated with FDTD and PIC methods. The characters of electric field waveforms and space distributions were analyzed and summarized in the monoenergetic photoelectron circumstance. Then, with the methods of particle sample and particle emission at a proper interval, the results were obtained when the photoelectrons emit with specific spectrum. At the same time, the results attained from two different particle simulations show that the above methods can decrease the particle numbers involved efficiently except a little bit noise increasing. Therefore, it can be used in the 3D particle simulation. The results also reveal that the length of strong electric
2004,
16.
Abstract:
When a high power microwave pulse propagates through the atmosphere, the ionization is expected to occur and produces plasma, and dielectric constant and refractive index of air will change. This paper introduces the dielectric constant of isotropy plasma in primary theory. It presents the influence of collision frequency between electron and gas molecule on the dielectric constant of air based on Maxwell's distribution of velocity. The air dielectric constant in high power microwave propagation in atmosphere and its correction coefficient are introduced by the method of dynamics.The correction of coefficient relate to the frequency and collision frequency. When the ratio of them is very big, the correction of coefficient approximate 1, when the ration of them is small, it approximate
When a high power microwave pulse propagates through the atmosphere, the ionization is expected to occur and produces plasma, and dielectric constant and refractive index of air will change. This paper introduces the dielectric constant of isotropy plasma in primary theory. It presents the influence of collision frequency between electron and gas molecule on the dielectric constant of air based on Maxwell's distribution of velocity. The air dielectric constant in high power microwave propagation in atmosphere and its correction coefficient are introduced by the method of dynamics.The correction of coefficient relate to the frequency and collision frequency. When the ratio of them is very big, the correction of coefficient approximate 1, when the ration of them is small, it approximate
2004,
16.
Abstract:
This paper presents the physical characteristics of the electric-magnetic vibrator combined antenna. By calculating numerically and measuring the input/output character of the antenna in frequency-domain and time-domain, it proves that working-frequency of the miniature antenna is widen, and the radiation-efficiency is promoted by the complement of electronic vibrator and magnetic vibrator in the combined antenna. The frequency bandwidth of the antenna is about 10 octave (110MHz~super 1.1GHz) if volt standing-wave ratio is below 3.
This paper presents the physical characteristics of the electric-magnetic vibrator combined antenna. By calculating numerically and measuring the input/output character of the antenna in frequency-domain and time-domain, it proves that working-frequency of the miniature antenna is widen, and the radiation-efficiency is promoted by the complement of electronic vibrator and magnetic vibrator in the combined antenna. The frequency bandwidth of the antenna is about 10 octave (110MHz~super 1.1GHz) if volt standing-wave ratio is below 3.
