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RSS2008 Vol. 20, No. 05
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2008,
20.
Abstract:
The interaction between the temperature field and the laser field plays a crucial role in solid-state lasers. In this paper, the optic-thermal coupling in the diode pumped solid-state lasers(DPSSL) is investigated. From the point of view of microcosmic physics, the thermal transition of particles at upper laser level makes heat generation of the laser crystals depend on the shape of the laser beam, while the laser field is influenced by the temperature in terms of thermal partition of doped particles. These effects, together with the usual thermal-optic effect of a fluctuation of the refraction index induce by uneven temperature distribution, lead to a complicated coupling between the laser field and the temperature field. It is shown that the optic-thermal coupling plays an important role
The interaction between the temperature field and the laser field plays a crucial role in solid-state lasers. In this paper, the optic-thermal coupling in the diode pumped solid-state lasers(DPSSL) is investigated. From the point of view of microcosmic physics, the thermal transition of particles at upper laser level makes heat generation of the laser crystals depend on the shape of the laser beam, while the laser field is influenced by the temperature in terms of thermal partition of doped particles. These effects, together with the usual thermal-optic effect of a fluctuation of the refraction index induce by uneven temperature distribution, lead to a complicated coupling between the laser field and the temperature field. It is shown that the optic-thermal coupling plays an important role
2008,
20.
Abstract:
Mirror surface reflecting high power laser would be deformed by the pressure of the coolant in a liquid cooling mirror system. In order to eliminate the impact of pressure and vibration of cooling water of micro channel mirror on the stability of the output beam and the space limitation of micro channel to flow of water, an outside cooling mirror with heatpipe was designed. In the same conditions, solid mirror, micro channel water cooled mirror and heatpipe outside cooling mirror are simulated by ANSYS program. The time-varying thermal deformation of the mirrors under heat absorption of 12 W/cm2 and continuous work of 60 s is obtained. The results indicate that the maximal mirror surface deformation of z-axis between peak and valley of solid mirror, micro channel water cooled mirror and h
Mirror surface reflecting high power laser would be deformed by the pressure of the coolant in a liquid cooling mirror system. In order to eliminate the impact of pressure and vibration of cooling water of micro channel mirror on the stability of the output beam and the space limitation of micro channel to flow of water, an outside cooling mirror with heatpipe was designed. In the same conditions, solid mirror, micro channel water cooled mirror and heatpipe outside cooling mirror are simulated by ANSYS program. The time-varying thermal deformation of the mirrors under heat absorption of 12 W/cm2 and continuous work of 60 s is obtained. The results indicate that the maximal mirror surface deformation of z-axis between peak and valley of solid mirror, micro channel water cooled mirror and h
2008,
20.
Abstract:
The relation between ratio of parallel and perpendicular polarization components of the airborne lidar’s polarized backscatted signals and crystal thickness are analyzed quantitatively using plane parallel plate pattern and crystal membranous theory when the polarized lights permeate 1/2 retardation sheet. Optimal processing thickness and appropriate processing thickness ranges of 1/2 quartz retardation sheet and 1/2 calcite retardation sheet for measurement of airborne lidar polarization gain ratio values are analyzed quantitatively and discussed. At the same time, unfitted processing thickness ranges are pointed out. There are some differences between gain ratios measured respectively when the polarized direction of return signal is parallel or perpendicular with the optical axis of
The relation between ratio of parallel and perpendicular polarization components of the airborne lidar’s polarized backscatted signals and crystal thickness are analyzed quantitatively using plane parallel plate pattern and crystal membranous theory when the polarized lights permeate 1/2 retardation sheet. Optimal processing thickness and appropriate processing thickness ranges of 1/2 quartz retardation sheet and 1/2 calcite retardation sheet for measurement of airborne lidar polarization gain ratio values are analyzed quantitatively and discussed. At the same time, unfitted processing thickness ranges are pointed out. There are some differences between gain ratios measured respectively when the polarized direction of return signal is parallel or perpendicular with the optical axis of
2008,
20.
Abstract:
The physical models of spectral beam combining for two beams and three beams by one and two reflective volume Bragg gratings(VBG) are founded in this article. The physical models consider the absorbability of VBG and suppose that the incident beam has a Gaussian shape. Two and three spectral beams combinings are numerically analyzed. When the spectral width is 0.1 nm, the spectral beam combining efficiencies are 98.76% and 97.69%, and when the spectral width is 0.3 nm, the spectral beam combining efficiencies are 97.34% and 95.78%, respectively. The increscent spectral width decreases the spectral beam combining efficiency. The results show that the high spectral beam combining efficiency for more beams can be obtained by this method, which provides a doable way for high power laser.
The physical models of spectral beam combining for two beams and three beams by one and two reflective volume Bragg gratings(VBG) are founded in this article. The physical models consider the absorbability of VBG and suppose that the incident beam has a Gaussian shape. Two and three spectral beams combinings are numerically analyzed. When the spectral width is 0.1 nm, the spectral beam combining efficiencies are 98.76% and 97.69%, and when the spectral width is 0.3 nm, the spectral beam combining efficiencies are 97.34% and 95.78%, respectively. The increscent spectral width decreases the spectral beam combining efficiency. The results show that the high spectral beam combining efficiency for more beams can be obtained by this method, which provides a doable way for high power laser.
2008,
20.
Abstract:
The diffraction equations for continuous subwavelength dielectric polarization gratings are derived using Jones matrix approach. The polarization characteristics and diffraction efficiencies are also discussed. The results show that, by setting up the parameters such as the incident light polarization state and grating phase delay, only three diffraction orders with an arbitrary diffraction efficiencies distribution exist in continuous subwavelength dielectric polarization grating, and the total efficiency of the diffraction orders is always 100%. Moreover, the polarization state of zeroorder wave is identical to the incident wave. Ｔhe polarization state of +１order is a rightcircularly polarized wave and the polarization state of －１order is a leftcircularly polarized wave, bo
The diffraction equations for continuous subwavelength dielectric polarization gratings are derived using Jones matrix approach. The polarization characteristics and diffraction efficiencies are also discussed. The results show that, by setting up the parameters such as the incident light polarization state and grating phase delay, only three diffraction orders with an arbitrary diffraction efficiencies distribution exist in continuous subwavelength dielectric polarization grating, and the total efficiency of the diffraction orders is always 100%. Moreover, the polarization state of zeroorder wave is identical to the incident wave. Ｔhe polarization state of +１order is a rightcircularly polarized wave and the polarization state of －１order is a leftcircularly polarized wave, bo
2008,
20.
Abstract:
Time-resolved photos of the discharge of TEA(transversely excited atmospheric pressure) CO2 laser taken by ICCD camera were analyzed. Quantitative data on the spatial distribution and the temporal development of the discharge were given. Second glow originated from the selfsustained discharge was found in the case of usual capacitor discharge circuit (long pulse discharge circuit). The light emission of the preionization with a short pulse discharge circuit using a magnetic compress switch formed later, but the interval between preionization and main discharge was shorter. For both long pulse discharge circuit and short pulse discharge circuit, the formation of cathode sheath occurred in the late stage of discharge. Short pulse discharge circuit has advantages to obtain shorter pulse dur
Time-resolved photos of the discharge of TEA(transversely excited atmospheric pressure) CO2 laser taken by ICCD camera were analyzed. Quantitative data on the spatial distribution and the temporal development of the discharge were given. Second glow originated from the selfsustained discharge was found in the case of usual capacitor discharge circuit (long pulse discharge circuit). The light emission of the preionization with a short pulse discharge circuit using a magnetic compress switch formed later, but the interval between preionization and main discharge was shorter. For both long pulse discharge circuit and short pulse discharge circuit, the formation of cathode sheath occurred in the late stage of discharge. Short pulse discharge circuit has advantages to obtain shorter pulse dur
2008,
20.
Abstract:
The motional characteristics, spreading way and obscuration effect of infrared smoke screen particle are analyzed in this paper. Feasibility of infrared smoke screen used in exoatmospheric space is evaluated. Ultra-micro powder crystalline flake graphite with diameter of 1～10 μm is chosen as smoke screen material in consideration of its infrared attenuation effect. Initial velocity of smoke screen particle affects diffusivity of smoke screen. Obscuration for exoatmospheric target during about 10 minutes could be achieved with less smoke screen material by control the spreading velocity of smoke screen generator.
The motional characteristics, spreading way and obscuration effect of infrared smoke screen particle are analyzed in this paper. Feasibility of infrared smoke screen used in exoatmospheric space is evaluated. Ultra-micro powder crystalline flake graphite with diameter of 1～10 μm is chosen as smoke screen material in consideration of its infrared attenuation effect. Initial velocity of smoke screen particle affects diffusivity of smoke screen. Obscuration for exoatmospheric target during about 10 minutes could be achieved with less smoke screen material by control the spreading velocity of smoke screen generator.
2008,
20.
Abstract:
Considering the beam divergence ,the angle dispersion and the fabrication errors of groove angle of the grating and using ray tracing method, the calculation model for the phase change of the laser beam obliquely incident on the grating has been built up. Then, making use of the diffraction integral method and the principle of incoherent superposition of laser beams, the analytical expression for the output intensity distribution of each emitter after passing through the spectral beam combining system has been derived. Finally, according to the intensity second-order moments method, the M2-factor of the combined beam has been calculated and the efffects of the angle dispersion and the fabrication errors of grating groove angle on the beam characterristics of the spectral combining system h
Considering the beam divergence ,the angle dispersion and the fabrication errors of groove angle of the grating and using ray tracing method, the calculation model for the phase change of the laser beam obliquely incident on the grating has been built up. Then, making use of the diffraction integral method and the principle of incoherent superposition of laser beams, the analytical expression for the output intensity distribution of each emitter after passing through the spectral beam combining system has been derived. Finally, according to the intensity second-order moments method, the M2-factor of the combined beam has been calculated and the efffects of the angle dispersion and the fabrication errors of grating groove angle on the beam characterristics of the spectral combining system h
2008,
20.
Abstract:
Collimator is one of the key tools to assemble, correct, adjust and test optical instrument, and it is an important part of the measuring instrument. In order to improve the measure accuracy, based on the particular aberration property of the diffraction optical element, the hybrid refractive- diffractive aberration correction method is put forward. The diameter of the collimator is 80 mm, the focal length is 500 mm. The overall length is less than 550 mm. The resolution is less than 4.3″. Having been optimized, the maximum spot is 5.2 mm, and the modulation transfer function(MTF) at 50 lp/mm is over 0.8, better than the conventional method.
Collimator is one of the key tools to assemble, correct, adjust and test optical instrument, and it is an important part of the measuring instrument. In order to improve the measure accuracy, based on the particular aberration property of the diffraction optical element, the hybrid refractive- diffractive aberration correction method is put forward. The diameter of the collimator is 80 mm, the focal length is 500 mm. The overall length is less than 550 mm. The resolution is less than 4.3″. Having been optimized, the maximum spot is 5.2 mm, and the modulation transfer function(MTF) at 50 lp/mm is over 0.8, better than the conventional method.
2008,
20.
Abstract:
SiO2 nanoparticles were prepared by sol-gel method with tetraethyl-ortho-silicate(TEOS) as silica source, cetyltrimethylanmmonium bromide(CTAB) as template, and polyethylene glycol(PEG) as disperser agent. The samples were characterized by TEM, SEM, XRD, IR and EDX. The results indicated that the products were rod-like nanoparticles with periodically regular mesopores, and their aspect ratio decreased when lowering the concentration of the silica source, template and disperser agent. If ethanol existed in the reacting system, the shape of the nanoparticles changed from rod to spheroid, further into irregular agglomerate with increase of the volume ratio of ethanol to water. The SiO2 nanorods were silanized and adsorbed Au seeds with average diameter of 3.7 nm on their surface. Then a multi
SiO2 nanoparticles were prepared by sol-gel method with tetraethyl-ortho-silicate(TEOS) as silica source, cetyltrimethylanmmonium bromide(CTAB) as template, and polyethylene glycol(PEG) as disperser agent. The samples were characterized by TEM, SEM, XRD, IR and EDX. The results indicated that the products were rod-like nanoparticles with periodically regular mesopores, and their aspect ratio decreased when lowering the concentration of the silica source, template and disperser agent. If ethanol existed in the reacting system, the shape of the nanoparticles changed from rod to spheroid, further into irregular agglomerate with increase of the volume ratio of ethanol to water. The SiO2 nanorods were silanized and adsorbed Au seeds with average diameter of 3.7 nm on their surface. Then a multi
2008,
20.
Abstract:
Runaway electron detection system composed of CdTe, BGO and NaI was used to measure the hard X-ray (HXR) emission in the energy range 0.3～15 MeV when the runaways hit the first wall. With electron cyclotron emission and neutron detect systems,the runaway electrons on HT-7 Tokamak with low hybrid current drive (LHCD) were investigated. It was found that in LHCD discharges with high loop voltage as well as the termination of high low hybrid power can accelerate the fast electrons into runaways. The results also indicate that the reduction of the electric field accomplished by LHCD produces a suppression of the existing runaway population.
Runaway electron detection system composed of CdTe, BGO and NaI was used to measure the hard X-ray (HXR) emission in the energy range 0.3～15 MeV when the runaways hit the first wall. With electron cyclotron emission and neutron detect systems,the runaway electrons on HT-7 Tokamak with low hybrid current drive (LHCD) were investigated. It was found that in LHCD discharges with high loop voltage as well as the termination of high low hybrid power can accelerate the fast electrons into runaways. The results also indicate that the reduction of the electric field accomplished by LHCD produces a suppression of the existing runaway population.
2008,
20.
Abstract:
The plasma dynamics was used in degenerated electron-positron plasma, and the transverse dispersion law in ultra-relativistic regime was investigated. The analytical solutions show that the dispersion curves are discontinuous with separate long wave and short wave solutions. Then the dispersion equation was numerically simulated. The numerical dispersion curve connects the long wave part with the short wave part, thus a full dispersion curve was obtained.
The plasma dynamics was used in degenerated electron-positron plasma, and the transverse dispersion law in ultra-relativistic regime was investigated. The analytical solutions show that the dispersion curves are discontinuous with separate long wave and short wave solutions. Then the dispersion equation was numerically simulated. The numerical dispersion curve connects the long wave part with the short wave part, thus a full dispersion curve was obtained.
2008,
20.
Abstract:
In this paper, DKDP crystals were grown from 85%-deuterated solution of different materials by traditional temperature-reduction method. Then some of the crystals were chosen to test laser damage threshold by the third harmonic generation of 1 064 nm. It was found that the solution stability of DKDP crystal growth dropped slightly, but obviously, and the laser damage threshold increased for purer raw material as the metallic ionic impurity varied in the materials.
In this paper, DKDP crystals were grown from 85%-deuterated solution of different materials by traditional temperature-reduction method. Then some of the crystals were chosen to test laser damage threshold by the third harmonic generation of 1 064 nm. It was found that the solution stability of DKDP crystal growth dropped slightly, but obviously, and the laser damage threshold increased for purer raw material as the metallic ionic impurity varied in the materials.
2008,
20.
Abstract:
The effects of chemical etching with a buffered HF solution on fused silica surface were studied by measuring the etched depth, via interferometer and step meter, and etched material mass under different etching time. The depth etching rate and material removal rate became constant after about 8 min etching. The redeposition layer of optical polished surface was about 16 nm, while the subsurface defect layer was deeper than 106 nm. The laser-induced damage threshold and surface roughness before and after chemical etching were also measured. The results showed that, firstly, the damage threshold increased with the removal of the redeposition layer. Then, it decreased with the exposure of the subsurface defects followed by an increase with the increase of etching time. Finally, it was almost
The effects of chemical etching with a buffered HF solution on fused silica surface were studied by measuring the etched depth, via interferometer and step meter, and etched material mass under different etching time. The depth etching rate and material removal rate became constant after about 8 min etching. The redeposition layer of optical polished surface was about 16 nm, while the subsurface defect layer was deeper than 106 nm. The laser-induced damage threshold and surface roughness before and after chemical etching were also measured. The results showed that, firstly, the damage threshold increased with the removal of the redeposition layer. Then, it decreased with the exposure of the subsurface defects followed by an increase with the increase of etching time. Finally, it was almost
2008,
20.
Abstract:
The PV, H2Pc, CuPc monolayer or PV/H２Pc, PV/CuPc bilayer films were prepared by vacuum deposition. The films were characterized by AFM, FTIR, UV/Vis and FL. Results showed that the surface of these films was very smooth, they presented strong adsorption in 450~750 nm. Though monolayer film displayed fluorescence, the bilayer film showed strong fluorescence quench. These phenomena agreed with the request of the uniform laser ablation of target in highly compressed implosion．
The PV, H2Pc, CuPc monolayer or PV/H２Pc, PV/CuPc bilayer films were prepared by vacuum deposition. The films were characterized by AFM, FTIR, UV/Vis and FL. Results showed that the surface of these films was very smooth, they presented strong adsorption in 450~750 nm. Though monolayer film displayed fluorescence, the bilayer film showed strong fluorescence quench. These phenomena agreed with the request of the uniform laser ablation of target in highly compressed implosion．
2008,
20.
Abstract:
Smooth diamond-like carbon films are fabricated by pulsed laser deposition at different substrate temperature. DLC films grown at room temperature exhibit excellent mechanical properties, their hardness and elastic modulus are 45 GPa and 290 GPa, and their friction coefficient and wear rate, at the condition of 80% RH, are 0.045 and 5.74×10-10 mm3·N-1·m-1 respectively. However, the hardness and modulus of films decrease with increasing the substrate temperature, at the same time, the friction coefficient and wear rate increase with the deposition temperature. Raman spectrum indicates that the carbon film grow at low temperature is typical tetrahedral diamond-like carbon film with high sp3 content (about 76.8%), and the sp3 content of the film reduces with temperature and the mechanical
Smooth diamond-like carbon films are fabricated by pulsed laser deposition at different substrate temperature. DLC films grown at room temperature exhibit excellent mechanical properties, their hardness and elastic modulus are 45 GPa and 290 GPa, and their friction coefficient and wear rate, at the condition of 80% RH, are 0.045 and 5.74×10-10 mm3·N-1·m-1 respectively. However, the hardness and modulus of films decrease with increasing the substrate temperature, at the same time, the friction coefficient and wear rate increase with the deposition temperature. Raman spectrum indicates that the carbon film grow at low temperature is typical tetrahedral diamond-like carbon film with high sp3 content (about 76.8%), and the sp3 content of the film reduces with temperature and the mechanical
2008,
20.
Abstract:
Switchyard is an important part of the beam propagation system, the stability of which has a direct effect on the beam’s propagation. A model of the switchyard mirror mount is built by the finite element analysis software, a digital seismograph is adopted to measure the micro vibration of the mirror mounts' install base, the processed velocity power spectra are used as the loads and the beam direction of each optical elements is studied. The rotations of four optical elements of the switchyard are 0.338 mrad, 0.327 mrad, 0.289 mrad and 0.241 mrad, all less than the required stability index of 0.460 mrad. The error between analysis result and measurement one is 0.6%, which indicates that the analysis result is reasonable.
Switchyard is an important part of the beam propagation system, the stability of which has a direct effect on the beam’s propagation. A model of the switchyard mirror mount is built by the finite element analysis software, a digital seismograph is adopted to measure the micro vibration of the mirror mounts' install base, the processed velocity power spectra are used as the loads and the beam direction of each optical elements is studied. The rotations of four optical elements of the switchyard are 0.338 mrad, 0.327 mrad, 0.289 mrad and 0.241 mrad, all less than the required stability index of 0.460 mrad. The error between analysis result and measurement one is 0.6%, which indicates that the analysis result is reasonable.
2008,
20.
Abstract:
The monodispersed silicon dioxide spherical particles were synthesized by improved Sol-gel methods, tetraethoxysilane as silicon material, ammonia as catalyst and ethanol as solvent. The sedimentation and organization of silica spheres with mean diameter of about 250nm, 280nm and 320nm in different mediums of distilled water, ethanol, acetone and water-ethanol mixture were investigated. Images by SEM show the gravity sedimentation of monodispersed silica particles in ethanol or acetone can form three-dimension closed packing structural opal, and ethanol is superior to acetone in opal fabrication. Silica spheres sedimentation experiment indicated that the velocity of isometric silica microspheres sedimentation in water, ethanol and acetone has little difference. The influence of sedimentat
The monodispersed silicon dioxide spherical particles were synthesized by improved Sol-gel methods, tetraethoxysilane as silicon material, ammonia as catalyst and ethanol as solvent. The sedimentation and organization of silica spheres with mean diameter of about 250nm, 280nm and 320nm in different mediums of distilled water, ethanol, acetone and water-ethanol mixture were investigated. Images by SEM show the gravity sedimentation of monodispersed silica particles in ethanol or acetone can form three-dimension closed packing structural opal, and ethanol is superior to acetone in opal fabrication. Silica spheres sedimentation experiment indicated that the velocity of isometric silica microspheres sedimentation in water, ethanol and acetone has little difference. The influence of sedimentat
2008,
20.
Abstract:
To resolve the transferring problem of neutron activated Cu sample on prototype, a “rabbit” system has been researched and designed. The problem of smoothly transfer, locating of the “rabbit”, lubricating and air-tight sealing between the pipe and “rabbit” are resolved. The experimental result shows that the “rabbit”has been successfully transferred 14.3 m within 1.12 s, and the average velocity of the “rabbit” is 12.8 m/s. In the same condition, the theoretical curve and the experimental curve of the “rabbit” movement characteristic fit very well, which means the design of the “rabbit”syst em is successful．
To resolve the transferring problem of neutron activated Cu sample on prototype, a “rabbit” system has been researched and designed. The problem of smoothly transfer, locating of the “rabbit”, lubricating and air-tight sealing between the pipe and “rabbit” are resolved. The experimental result shows that the “rabbit”has been successfully transferred 14.3 m within 1.12 s, and the average velocity of the “rabbit” is 12.8 m/s. In the same condition, the theoretical curve and the experimental curve of the “rabbit” movement characteristic fit very well, which means the design of the “rabbit”syst em is successful．
2008,
20.
Abstract:
Surface wave bandgap of mushroom-like electromagnetic bandgap(EBG) structure with finite units was analyzed by direct transmission method. Compared with surface wave dispersion diagram, surface wave bandgap is fast determined and analysis time obviously shortened. The effect of different waveguide heights and periods of EBG structure on surface wave bandgap was analyzed by simulating the transmission coefficient of waveguide in which the EBG units were placed. The EBG structure dielectric board was fabricated and the surface wave bandgap was measured. Experimental results show that surface wave bandgap determined by this method is consistent with the measured one.
Surface wave bandgap of mushroom-like electromagnetic bandgap(EBG) structure with finite units was analyzed by direct transmission method. Compared with surface wave dispersion diagram, surface wave bandgap is fast determined and analysis time obviously shortened. The effect of different waveguide heights and periods of EBG structure on surface wave bandgap was analyzed by simulating the transmission coefficient of waveguide in which the EBG units were placed. The EBG structure dielectric board was fabricated and the surface wave bandgap was measured. Experimental results show that surface wave bandgap determined by this method is consistent with the measured one.
2008,
20.
Abstract:
A high-efficiency L-MILO is designed based on advantageous mechanisms of both hard-tube MILO and tapered MILO by 2D particle-in-cell(PIC) electromagnetic code . The high-efficiency L-MILO has high efficiency and is easy to work up. The design is optimized under rectangular voltages and pulse voltages with long rising time respectively. Each optimal model outputs microwave signal with power averaged in a period above 5 GW and efficiency above 20% in L-band when the peak of input voltage is between 500~600 kV. Possible problem in the future experiment and the corresponding resolution are discussed.
A high-efficiency L-MILO is designed based on advantageous mechanisms of both hard-tube MILO and tapered MILO by 2D particle-in-cell(PIC) electromagnetic code . The high-efficiency L-MILO has high efficiency and is easy to work up. The design is optimized under rectangular voltages and pulse voltages with long rising time respectively. Each optimal model outputs microwave signal with power averaged in a period above 5 GW and efficiency above 20% in L-band when the peak of input voltage is between 500~600 kV. Possible problem in the future experiment and the corresponding resolution are discussed.
2008,
20.
Abstract:
The frequency, quality factor and gap impedance of outloaded resonant cavity have been calculated analytically by the equivalent circuit model, and the results agree well with those of electromagnetic simulation software. The analytical and simulated results show that the main cavity’s quality factor can be depressed through the outload technology and the bandwidth can be extended with the mode overlapping. In addition, with the equivalent circuit model, the influences of the main and absorbing cavities’quality factors, the frequency deviation between the main and absorbing cavities, and the coupling parameters on the quality factors as well as gap impedance of the outloaded resonant cavity have been considered．
The frequency, quality factor and gap impedance of outloaded resonant cavity have been calculated analytically by the equivalent circuit model, and the results agree well with those of electromagnetic simulation software. The analytical and simulated results show that the main cavity’s quality factor can be depressed through the outload technology and the bandwidth can be extended with the mode overlapping. In addition, with the equivalent circuit model, the influences of the main and absorbing cavities’quality factors, the frequency deviation between the main and absorbing cavities, and the coupling parameters on the quality factors as well as gap impedance of the outloaded resonant cavity have been considered．
2008,
20.
Abstract:
Based on the tangential boundary conditions, the propagation characteristics of the electromagnetic wave incident from a linear conventional medium(RHM) into a nonlinear left-handed medium(LHM) are derived in detail. The nonlinear Goos-Hnchen shift of total reflection at the interface of nonlinear left-handed medium is obtained using the phase-change approach. The dependence of the lateral shift on the incident angle and incident field intensity is analyzed. It is found that the incident field intensity plays an important role in the propagation of the electromagnetic wave. If the incident field intensity is lower than critical field intensity, the lateral shift can be regulated through the change of the incident field intensity, else if the incident field intensity is larger than cr
Based on the tangential boundary conditions, the propagation characteristics of the electromagnetic wave incident from a linear conventional medium(RHM) into a nonlinear left-handed medium(LHM) are derived in detail. The nonlinear Goos-Hnchen shift of total reflection at the interface of nonlinear left-handed medium is obtained using the phase-change approach. The dependence of the lateral shift on the incident angle and incident field intensity is analyzed. It is found that the incident field intensity plays an important role in the propagation of the electromagnetic wave. If the incident field intensity is lower than critical field intensity, the lateral shift can be regulated through the change of the incident field intensity, else if the incident field intensity is larger than cr
2008,
20.
Abstract:
The constitution, primary technique target and the transmission line structure of the subnanosecond EMP simulator are introduced in this paper. The transmission and spatial distribution of the electric-field were simulated numerically by Finite Difference-Time Domain method. and the real electric-field distribution was measured, Some conclusions drawn from the data are that the rise time of different position is invariable, the rise time is about 800ps, the work zone of the simulator is 1 m×1 m×1 m, and the electric-field of the work zone is well-proportional. The actual spatial distribution of the electric-field agrees well with the numerically results.
The constitution, primary technique target and the transmission line structure of the subnanosecond EMP simulator are introduced in this paper. The transmission and spatial distribution of the electric-field were simulated numerically by Finite Difference-Time Domain method. and the real electric-field distribution was measured, Some conclusions drawn from the data are that the rise time of different position is invariable, the rise time is about 800ps, the work zone of the simulator is 1 m×1 m×1 m, and the electric-field of the work zone is well-proportional. The actual spatial distribution of the electric-field agrees well with the numerically results.
2008,
20.
Abstract:
The modulation mechanism and RF extraction of an S-band relativistic klystron oscillator were studied via experiment. It is found that intense relativistic electron beams(IREBs) can generate intense current modulation when the IREBs drift through three pillboxes with high coupling. After bunching in the downstream the modulated IREBs can excite high power microwave in the triaxial cavity. The RKO has properties of short oscillating time, compact geometry and high beam-wave conversion efficiency. Using a 1 MV/13 kA/40 ns electron beam and leading magnetic field of 0.9 T, 3.5 GW radiated power was extracted in 20 ns FWHM pulses at 2.86 GHz. The beam-wave transition efficiency is 29%, and the instantaneous bandwidth is 2%. The radiated power is 3.4 GW with the efficiency of 26% when repetitiv
The modulation mechanism and RF extraction of an S-band relativistic klystron oscillator were studied via experiment. It is found that intense relativistic electron beams(IREBs) can generate intense current modulation when the IREBs drift through three pillboxes with high coupling. After bunching in the downstream the modulated IREBs can excite high power microwave in the triaxial cavity. The RKO has properties of short oscillating time, compact geometry and high beam-wave conversion efficiency. Using a 1 MV/13 kA/40 ns electron beam and leading magnetic field of 0.9 T, 3.5 GW radiated power was extracted in 20 ns FWHM pulses at 2.86 GHz. The beam-wave transition efficiency is 29%, and the instantaneous bandwidth is 2%. The radiated power is 3.4 GW with the efficiency of 26% when repetitiv
2008,
20.
Abstract:
Based on the nodal admittance method which is convenient to analyze the responses at terminals of multiconductor transmission lines excited by EM field, Mento Carlo method for the characterization of wiring-harness susceptibility to external interference was applied. Field-coupling onto two-conductor transmission line and multiconductor transmission line loaded by terminal resistances were considered. The external field was modeled by a plane wave with random parameters as polarization angle, incident angle and azimuth angle generated by computer. The response formulas of two-conductor and multiconductor line were applied, and the peak value of voltages or currents was computed for every set of random values. For incident parameter range of ［0, p/2］, the probability distributions of term
Based on the nodal admittance method which is convenient to analyze the responses at terminals of multiconductor transmission lines excited by EM field, Mento Carlo method for the characterization of wiring-harness susceptibility to external interference was applied. Field-coupling onto two-conductor transmission line and multiconductor transmission line loaded by terminal resistances were considered. The external field was modeled by a plane wave with random parameters as polarization angle, incident angle and azimuth angle generated by computer. The response formulas of two-conductor and multiconductor line were applied, and the peak value of voltages or currents was computed for every set of random values. For incident parameter range of ［0, p/2］, the probability distributions of term
2008,
20.
Abstract:
The ill-posedness of the inverse problem on determination of mode content in a multimode cylindrical waveguide using far field measurements is investigated in this paper. The radiation patterns of different mode radiated from a conical horn antenna fed by a multi-mode waveguide are calculated. Then the ill-posedness of the inverse problem is investigated by comparing the radiation pattern generated by different hybrid modes. Results show that the inverse problem is severely ill-posed, because the far field at certain positions is not sensitive to the variation of the mode contents. It is difficult to determine the mode content accurately according to the measurements at those positions. After analyzing the change of far-field with the variation of mode content, the positions where measurem
The ill-posedness of the inverse problem on determination of mode content in a multimode cylindrical waveguide using far field measurements is investigated in this paper. The radiation patterns of different mode radiated from a conical horn antenna fed by a multi-mode waveguide are calculated. Then the ill-posedness of the inverse problem is investigated by comparing the radiation pattern generated by different hybrid modes. Results show that the inverse problem is severely ill-posed, because the far field at certain positions is not sensitive to the variation of the mode contents. It is difficult to determine the mode content accurately according to the measurements at those positions. After analyzing the change of far-field with the variation of mode content, the positions where measurem
2008,
20.
Abstract:
In the development of a new L band klystron, in order to reduce the size, weight and power waste of magnetic focusing system, the size of output waveguide should be reduced. To solve this problem, a ridge waveguide was used in the output circuit. To validate this method, a ridge waveguide output circuit was designed and tested. The circuit’s voltage standing wave ratio is under 1.2 within 10% band width and theoretical power capacity is 490 MW.The output circuit with a ridge waveguide is compact and easy to make and test,and it has been used in the L band klystron．
In the development of a new L band klystron, in order to reduce the size, weight and power waste of magnetic focusing system, the size of output waveguide should be reduced. To solve this problem, a ridge waveguide was used in the output circuit. To validate this method, a ridge waveguide output circuit was designed and tested. The circuit’s voltage standing wave ratio is under 1.2 within 10% band width and theoretical power capacity is 490 MW.The output circuit with a ridge waveguide is compact and easy to make and test,and it has been used in the L band klystron．
2008,
20.
Abstract:
The calculation of the voltage distribution of pulse transformer’s taper winding with more than 4 000 turns is difficult, for the workload of calculating induction coefficient matrix is very heavy. In order to reduce the workload, the characteristics of the induction coefficient matrix were studied. The reults show that the self-induction coefficient of the middle turns of the taper winding increase linearly except for the end turns and the mutual induction coefficient decrease rapidly with the inturn-distance increasing. A simplified method for the simulation of multi-turns tape winding is brought forward, which can reduce the calculation steps from n(n+1)/2 to 2n+25, where n is the turns of the winding.
The calculation of the voltage distribution of pulse transformer’s taper winding with more than 4 000 turns is difficult, for the workload of calculating induction coefficient matrix is very heavy. In order to reduce the workload, the characteristics of the induction coefficient matrix were studied. The reults show that the self-induction coefficient of the middle turns of the taper winding increase linearly except for the end turns and the mutual induction coefficient decrease rapidly with the inturn-distance increasing. A simplified method for the simulation of multi-turns tape winding is brought forward, which can reduce the calculation steps from n(n+1)/2 to 2n+25, where n is the turns of the winding.
2008,
20.
Abstract:
Primary test stand(PTS) is an underway highcurrent accelerator for Z-pinch experiment in CAEP. In the paper a circuit model have been developed, in which all the PTS's transmission line sections from water transmission lines, to vacuum insulator stack, to both outer and inner MITL, and eventually to a wire array load, have been treated as a total of 273 transmission line elements with different transit time and impedance, among which are 195 MITL elements. With the aid of a circuit model the performance of all these sections were predicted and discussed, including conducting current, interface voltage, loss current, flow impedance and grounded resistor of each MITL element, as well as the dynamic characteristics of the wire array load. The reliability and accuracy of all thes predicted r
Primary test stand(PTS) is an underway highcurrent accelerator for Z-pinch experiment in CAEP. In the paper a circuit model have been developed, in which all the PTS's transmission line sections from water transmission lines, to vacuum insulator stack, to both outer and inner MITL, and eventually to a wire array load, have been treated as a total of 273 transmission line elements with different transit time and impedance, among which are 195 MITL elements. With the aid of a circuit model the performance of all these sections were predicted and discussed, including conducting current, interface voltage, loss current, flow impedance and grounded resistor of each MITL element, as well as the dynamic characteristics of the wire array load. The reliability and accuracy of all thes predicted r
2008,
20.
Abstract:
In this paper, a numerical model is proposed based on the investigation of the operational mechanism of reversely biased 4H-SiC Schottky diode as γ-ray detector. The detector characteristics of dark current, current response and sensitivity at different bias voltages and irradiation doses are simulated. The sensitivity increases linearly with the square root of the total voltage across the Schottky diode. When the doping concentration in the epitarial layor is 2.2×1015 cm-3, the sensitivity is 13.9×10-9 C/Gy at zero bias, 24.5×10-9 C/Gy at bais of 100 V. The results from simulation agree very well with the experimental data.
In this paper, a numerical model is proposed based on the investigation of the operational mechanism of reversely biased 4H-SiC Schottky diode as γ-ray detector. The detector characteristics of dark current, current response and sensitivity at different bias voltages and irradiation doses are simulated. The sensitivity increases linearly with the square root of the total voltage across the Schottky diode. When the doping concentration in the epitarial layor is 2.2×1015 cm-3, the sensitivity is 13.9×10-9 C/Gy at zero bias, 24.5×10-9 C/Gy at bais of 100 V. The results from simulation agree very well with the experimental data.
2008,
20.
Abstract:
The basic physical properties, the methods about the detection of character parameters, and the signal disposal of back streaming ions are analyzed. A program about laser interferometry is designed. The strongpoint and disadvantage of the program are introduced briefly. Based on the concrete experimental test, approaches for high quality images are summarized. Dynamic interferometry image would be obtained through adding a cutdown lens between the output of laser interferometry list and the framing camera. The signal-to-noise of measured images would be improved through shielding the framing camera using plumbum and some other heavy metal materials. Within 6μs, the state information of back streaming ions can be obtained by changing delay and time space. Through analysis and disposal of
The basic physical properties, the methods about the detection of character parameters, and the signal disposal of back streaming ions are analyzed. A program about laser interferometry is designed. The strongpoint and disadvantage of the program are introduced briefly. Based on the concrete experimental test, approaches for high quality images are summarized. Dynamic interferometry image would be obtained through adding a cutdown lens between the output of laser interferometry list and the framing camera. The signal-to-noise of measured images would be improved through shielding the framing camera using plumbum and some other heavy metal materials. Within 6μs, the state information of back streaming ions can be obtained by changing delay and time space. Through analysis and disposal of
2008,
20.
Abstract:
The structure of neutral beam injector on EAST is introduced. Neutral beam usually contains three kinds of high-energy ions, which do not lost charge in the neutralizer. Taking a deuterium beam with energy of 80 keV as a reference beam, the paper calculates radius of ions with different energy and explains the section extension. As a result, three dimension relation of window in bending system is given. Then, principle of the cause of divergence angle is described. Effect of divergence angle on design of window in bending system is analyzed. The result and analysis illustrate that dimension of entrance window and return window have the same numerical value as that of beam. When relative position and dimension between entrance window and return window is reasonable, energy deposition at inj
The structure of neutral beam injector on EAST is introduced. Neutral beam usually contains three kinds of high-energy ions, which do not lost charge in the neutralizer. Taking a deuterium beam with energy of 80 keV as a reference beam, the paper calculates radius of ions with different energy and explains the section extension. As a result, three dimension relation of window in bending system is given. Then, principle of the cause of divergence angle is described. Effect of divergence angle on design of window in bending system is analyzed. The result and analysis illustrate that dimension of entrance window and return window have the same numerical value as that of beam. When relative position and dimension between entrance window and return window is reasonable, energy deposition at inj
2008,
20.
Abstract:
The a/2〈111〉{110} edge dislocation in bcc Fe was created using periodic array of dislocations methods. Molecular dynamic calculations were performed to study the stability of He-vacancy clusters in the dislocation core in bcc Fe, and the results were compared with simulations performed in perfect bcc Fe. The comparison show that the He-vacancy clusters are unstable for the effects of the dislocation field. The binding energies of an interstitial He atom, a vacancy and a self-interstitial Fe atom to the He-vacancy clusters depend mainly on the He-to-vacancy ratios of the clusters. In the dislocation core, for the ratio larger than 3 and less than 6, the binding energies are almost unchanging.
The a/2〈111〉{110} edge dislocation in bcc Fe was created using periodic array of dislocations methods. Molecular dynamic calculations were performed to study the stability of He-vacancy clusters in the dislocation core in bcc Fe, and the results were compared with simulations performed in perfect bcc Fe. The comparison show that the He-vacancy clusters are unstable for the effects of the dislocation field. The binding energies of an interstitial He atom, a vacancy and a self-interstitial Fe atom to the He-vacancy clusters depend mainly on the He-to-vacancy ratios of the clusters. In the dislocation core, for the ratio larger than 3 and less than 6, the binding energies are almost unchanging.
2008,
20.
Abstract:
Based on the study of explosive emission, the dielectric enhancement electric-field emission model is brought forward, and the metal-dielectric complex cathode material is manufactured. Based on the investigation of surface-flash explosive emission, the graphite-carbon fiber complex cathode is manufactured. Then the experiments are developed respectively, and the result shows the electron emission density of these two complex cathode materials is more than 17 kA/cm2, and their lifetime is more than 105 pulses．
Based on the study of explosive emission, the dielectric enhancement electric-field emission model is brought forward, and the metal-dielectric complex cathode material is manufactured. Based on the investigation of surface-flash explosive emission, the graphite-carbon fiber complex cathode is manufactured. Then the experiments are developed respectively, and the result shows the electron emission density of these two complex cathode materials is more than 17 kA/cm2, and their lifetime is more than 105 pulses．
2008,
20.
Abstract:
The basic principle and characteristic parameter of water dielectric coaxial pulse delay-line are introduced, and the main reasons of pulse losses and pulse distortion in the process of pulse transmission are analyzed. A test equipment of water dielectric coaxial pulse delay-line has been built, and its characteristic impedance is 12 Ω. The elementary test results indicate a pulse loss rate of 9.6% and a delay time of 476 ns.
The basic principle and characteristic parameter of water dielectric coaxial pulse delay-line are introduced, and the main reasons of pulse losses and pulse distortion in the process of pulse transmission are analyzed. A test equipment of water dielectric coaxial pulse delay-line has been built, and its characteristic impedance is 12 Ω. The elementary test results indicate a pulse loss rate of 9.6% and a delay time of 476 ns.
2008,
20.
Abstract:
In order to characterize the undulators at Shanghai Synchroton Radiation Facility(SSRF), a flipping coil magnetic field integral measurement system for the measurement of both first and second magnetic field integral distributions and integrated multipole errors in undulators has been developed recently.The system can automatically finish motion control, data acquisition and data analysis. The main features of this system are their high speed of measurement, high precision. Initial results demonstrated that the system achieves a system measurement precision of 1×10-6 T·m in a field integral measurement of 3.4×10-4 T·m.The system is efficient enough to finish the measurements of magnetic field integral in undulators.
In order to characterize the undulators at Shanghai Synchroton Radiation Facility(SSRF), a flipping coil magnetic field integral measurement system for the measurement of both first and second magnetic field integral distributions and integrated multipole errors in undulators has been developed recently.The system can automatically finish motion control, data acquisition and data analysis. The main features of this system are their high speed of measurement, high precision. Initial results demonstrated that the system achieves a system measurement precision of 1×10-6 T·m in a field integral measurement of 3.4×10-4 T·m.The system is efficient enough to finish the measurements of magnetic field integral in undulators.
2008,
20.
Abstract:
For keeping up with the international development of pulsed power technology，some new techniques such as the water coaxial line parallel connection, the multi-gap multi-channel gas output switch and synchronized trigger system have been studied on “Flash-Ⅱ”accelerator. 2 Ω pulse forming line(PFL) formed by three small 6 Ω PFLs with parallel connection after simulating electric field distribution on the three-dimensional and the insulation designing. The 3 MV multi-gap multi-channel gas output switches have been developed and three switches have been synchronously operated with parallel connection. Synchronized trigger system that operation delay is only 446 ns has been applied in synchronous operation between Marx generator and main switches. The water treatment technique in which wh
For keeping up with the international development of pulsed power technology，some new techniques such as the water coaxial line parallel connection, the multi-gap multi-channel gas output switch and synchronized trigger system have been studied on “Flash-Ⅱ”accelerator. 2 Ω pulse forming line(PFL) formed by three small 6 Ω PFLs with parallel connection after simulating electric field distribution on the three-dimensional and the insulation designing. The 3 MV multi-gap multi-channel gas output switches have been developed and three switches have been synchronously operated with parallel connection. Synchronized trigger system that operation delay is only 446 ns has been applied in synchronous operation between Marx generator and main switches. The water treatment technique in which wh
