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RSS2006 Vol. 18, No. 07
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2006,
18.
Abstract:
Based on compound pendulum model, a new way is put forward to measure impulse coupling coefficient using high speed photography. The system parameters of the compound pendulum are demarcated by an encoder when impulse is loaded slowly, and after the pulsed laser impacting the pendulum, the maximum angle is measured by CCD camera when impulse is loaded instantaneously, which efficiently solves the problem that the encoder can not distinguish angles due to vibration in the experiment. The result shows that the relative error of demarcating system parameter is below 2%. The results of impulse coupling coefficient have good repeatability with the range of (32.3～32.9)×10-5 N·s·J-1, which is consistent with the data reported by foreign authors for similar laser thruster.
Based on compound pendulum model, a new way is put forward to measure impulse coupling coefficient using high speed photography. The system parameters of the compound pendulum are demarcated by an encoder when impulse is loaded slowly, and after the pulsed laser impacting the pendulum, the maximum angle is measured by CCD camera when impulse is loaded instantaneously, which efficiently solves the problem that the encoder can not distinguish angles due to vibration in the experiment. The result shows that the relative error of demarcating system parameter is below 2%. The results of impulse coupling coefficient have good repeatability with the range of (32.3～32.9)×10-5 N·s·J-1, which is consistent with the data reported by foreign authors for similar laser thruster.
2006,
18.
Abstract:
Based on the vectorial Rayleigh-Sommerfeld diffraction integrals, the two expressions for the intensity of nonparaxial vectorial beams, i.e., the conventional intensity expression and the z component of the time-averaged Poynting vector, are studied without using any approximation. A detailed numerical comparison for nonparaxial vectorial Gaussian beams shows that the discrepancy between the two expressions, namely, the relative error, depends on the ratio of the waist width to the propagation distance and that of the wavelength to the propagation distance, respectively, and the error decreases with the increase of the two ratios. For nonparaxial vectorial Gaussian beams, if the ratio of the wavelength to the propagation distance is 10, and the ratio of the waist width to the propagation i
Based on the vectorial Rayleigh-Sommerfeld diffraction integrals, the two expressions for the intensity of nonparaxial vectorial beams, i.e., the conventional intensity expression and the z component of the time-averaged Poynting vector, are studied without using any approximation. A detailed numerical comparison for nonparaxial vectorial Gaussian beams shows that the discrepancy between the two expressions, namely, the relative error, depends on the ratio of the waist width to the propagation distance and that of the wavelength to the propagation distance, respectively, and the error decreases with the increase of the two ratios. For nonparaxial vectorial Gaussian beams, if the ratio of the wavelength to the propagation distance is 10, and the ratio of the waist width to the propagation i
2006,
18.
Abstract:
The temporal and spatial variation of branch points was computed by four-dimension code of laser propagating in atmosphere. The branch points originating and annihilating were emulated. The evolvement of branch points in some propagating range with time was emulated, too. The computational results indicate that branch points are moving along with the movement of a light wave in the space, and they originate and annihilate in pairs. The position of branch points of distorted optical field varies with time when the propagating range is fixed. When the condition of laser beam propagating in atmosphere is fixed, the ensemble average of branch points of distorted optical field can be definite at the fixed propagating range.
The temporal and spatial variation of branch points was computed by four-dimension code of laser propagating in atmosphere. The branch points originating and annihilating were emulated. The evolvement of branch points in some propagating range with time was emulated, too. The computational results indicate that branch points are moving along with the movement of a light wave in the space, and they originate and annihilate in pairs. The position of branch points of distorted optical field varies with time when the propagating range is fixed. When the condition of laser beam propagating in atmosphere is fixed, the ensemble average of branch points of distorted optical field can be definite at the fixed propagating range.
2006,
18.
Abstract:
It is important to evaluate the anisotropic thermal characteristics of nonlinear KTP crystal for improving the harmonic generation effect to reduce thermal stress produced by laser beam and the 3w setup is developed. The thermal conductivity of SiO2 film on Si substrate is measured and the result shows that the system is valid. The thermal conductivities of KTP crystal in the harmonic generation and radial direction are determined using the 3w technique. The results show a strong anisotropy of thermal conduction in the KTP crystal.
It is important to evaluate the anisotropic thermal characteristics of nonlinear KTP crystal for improving the harmonic generation effect to reduce thermal stress produced by laser beam and the 3w setup is developed. The thermal conductivity of SiO2 film on Si substrate is measured and the result shows that the system is valid. The thermal conductivities of KTP crystal in the harmonic generation and radial direction are determined using the 3w technique. The results show a strong anisotropy of thermal conduction in the KTP crystal.
2006,
18.
Abstract:
A design of an optical pumping source with multichannel surface discharge is introduced. The effects of the trigger voltage and risetime, and the thickness of dielectric substrate on trigger characteristic are analyzed theoretically. The electric field at two electrodes of each channel is intensely deformed, and it is nearly zero at the middle of channels by the action of trigger voltage. Two methods including taking pictures of discharging channels with high-speed multi-frame camera and measuring discharge current with Rogowski coils have been used experimentally to study the discharge synchronism and uniformity of the pumping source. The jitter of about 20 ns of 10 channel uniform discharge is obtained on the conditions of the charging voltage -20 kV, the trigger voltage of 30 kV with th
A design of an optical pumping source with multichannel surface discharge is introduced. The effects of the trigger voltage and risetime, and the thickness of dielectric substrate on trigger characteristic are analyzed theoretically. The electric field at two electrodes of each channel is intensely deformed, and it is nearly zero at the middle of channels by the action of trigger voltage. Two methods including taking pictures of discharging channels with high-speed multi-frame camera and measuring discharge current with Rogowski coils have been used experimentally to study the discharge synchronism and uniformity of the pumping source. The jitter of about 20 ns of 10 channel uniform discharge is obtained on the conditions of the charging voltage -20 kV, the trigger voltage of 30 kV with th
2006,
18.
Abstract:
The micro-structure surface and fluorescence of silicon slice fabricated by femtosecond laser under the assistant of low consistency sulfuric acid liquor are reported. A 10 mm×10 mm square region was fabricated from 0.5 mm thick and 26 mm in diameter silicon slice. The absorbency is increased due to the change of the surface microstructure of the silicon. Photoluminescence spectra display a high fluorescence emission at the wavelength from 700 nm to 750 nm, thus show a new and simple method to increase the fluorescence property of silicon.
The micro-structure surface and fluorescence of silicon slice fabricated by femtosecond laser under the assistant of low consistency sulfuric acid liquor are reported. A 10 mm×10 mm square region was fabricated from 0.5 mm thick and 26 mm in diameter silicon slice. The absorbency is increased due to the change of the surface microstructure of the silicon. Photoluminescence spectra display a high fluorescence emission at the wavelength from 700 nm to 750 nm, thus show a new and simple method to increase the fluorescence property of silicon.
2006,
18.
Abstract:
A kind of image processing method is introduced, which is based on the classical method about edge detection. Gray restrain is brought in，and the relations between the grid and its eight neighbours are considered in calculating the gradient. There are several optics which are laid with Browster angle and the image collected by CCD includes many noises, so the components of the image are quite complex and the quality is bad. The advanced method has been proved that it is possible to get over the problem and get information about the size of damage accurately. In addition, systemic analysis and calculation of optic damages are presented. The result shows that the damage size calculated in advance accords with the real size, and the error is in the scope of permission. The image processing m
A kind of image processing method is introduced, which is based on the classical method about edge detection. Gray restrain is brought in，and the relations between the grid and its eight neighbours are considered in calculating the gradient. There are several optics which are laid with Browster angle and the image collected by CCD includes many noises, so the components of the image are quite complex and the quality is bad. The advanced method has been proved that it is possible to get over the problem and get information about the size of damage accurately. In addition, systemic analysis and calculation of optic damages are presented. The result shows that the damage size calculated in advance accords with the real size, and the error is in the scope of permission. The image processing m
2006,
18.
Abstract:
Using a laser created plasma switch, a 1.58 ns short output pulse from a UV-preionized XeCl excimer laser is obtained. The influence of the beam energy intensity focused on the film surface for the generated plasma density is analyzed. The pulse shorting effects of different plasma density and hold time are discussed, and the experimental results are presented with the resonant cavity operating in stable cavity and unstable cavity modes separately. Working in stable cavity mode, the pulse width can be narrowed to 2.87 ns. While in an unstable cavity mode, by reducing the focused beam area to improve the energy intensity, a 1.58 ns short output pulse is obtained. This technique can applied to any other excimer laser.
Using a laser created plasma switch, a 1.58 ns short output pulse from a UV-preionized XeCl excimer laser is obtained. The influence of the beam energy intensity focused on the film surface for the generated plasma density is analyzed. The pulse shorting effects of different plasma density and hold time are discussed, and the experimental results are presented with the resonant cavity operating in stable cavity and unstable cavity modes separately. Working in stable cavity mode, the pulse width can be narrowed to 2.87 ns. While in an unstable cavity mode, by reducing the focused beam area to improve the energy intensity, a 1.58 ns short output pulse is obtained. This technique can applied to any other excimer laser.
2006,
18.
Abstract:
Design and fabrication of the X-ray supermirror used as reflective optical element in Kirkpatrick-Baez (KB) microscope were proposed. W/B4C was selected as coating materials pair. Design method and optimization of X-ray supermirrors were discussed. The designed multilayer structure was deposited on the Si wafer substrate using magnetron-sputtering system. The reflectivities of W/B4C supermirrors were measured by X-ray diffraction instrument (8 keV). The reflectivities of supermirrors are 20% at 1.052° and 1.143° designed grazing incident angles. The bandwidth of reflective plateau reaches 0.3°, which can fulfill the requirements of KB microscope.
Design and fabrication of the X-ray supermirror used as reflective optical element in Kirkpatrick-Baez (KB) microscope were proposed. W/B4C was selected as coating materials pair. Design method and optimization of X-ray supermirrors were discussed. The designed multilayer structure was deposited on the Si wafer substrate using magnetron-sputtering system. The reflectivities of W/B4C supermirrors were measured by X-ray diffraction instrument (8 keV). The reflectivities of supermirrors are 20% at 1.052° and 1.143° designed grazing incident angles. The bandwidth of reflective plateau reaches 0.3°, which can fulfill the requirements of KB microscope.
2006,
18.
Abstract:
The function between voltage and displacement of actuator and the linear superposing of the actuators for micromachined membrane deformable mirror are analyzed by means of the measured influence function of actuators. The voltage decoupling model for micromachined membrane deformable mirror is established through theoretical and experimental analysis of the fitting aberration of a continuous-surface deformable mirror. The fitting of the former 10-order Zernike mode is carried out. Analyzing the residual fitting error and correction capacity to the former 36-order Zernike mode, the conclusion is that micromachined membrane deformable mirror can be applied to correct the low order aberrations (especially for the former 10-order Zernike mode, with which it has a larger correcting capacity and
The function between voltage and displacement of actuator and the linear superposing of the actuators for micromachined membrane deformable mirror are analyzed by means of the measured influence function of actuators. The voltage decoupling model for micromachined membrane deformable mirror is established through theoretical and experimental analysis of the fitting aberration of a continuous-surface deformable mirror. The fitting of the former 10-order Zernike mode is carried out. Analyzing the residual fitting error and correction capacity to the former 36-order Zernike mode, the conclusion is that micromachined membrane deformable mirror can be applied to correct the low order aberrations (especially for the former 10-order Zernike mode, with which it has a larger correcting capacity and
2006,
18.
Abstract:
The thermodynamics of electro-optic switches with such materials as KDP, DKDP, LiNbO3 and BBO is analyzed by use of finite element methods with different laser intensity distributions such as the Gaussian, super-Gaussian under two mechanical boundaries, the free boundary and the fixed boundary independently. The results indicate that the ultimate axial displacements on the surfaces of the crystal increase with the increase of the order of Gaussian beams while the crystal has free boundaries, and the ultimate thermal stress in the crystal increases with the increase of the order of Gaussian beams while the crystal has fixed boundaries. The influences of the tackling states on these two parameters increase while the order of Gaussian beams increases. Irradiated by the same laser source and u
The thermodynamics of electro-optic switches with such materials as KDP, DKDP, LiNbO3 and BBO is analyzed by use of finite element methods with different laser intensity distributions such as the Gaussian, super-Gaussian under two mechanical boundaries, the free boundary and the fixed boundary independently. The results indicate that the ultimate axial displacements on the surfaces of the crystal increase with the increase of the order of Gaussian beams while the crystal has free boundaries, and the ultimate thermal stress in the crystal increases with the increase of the order of Gaussian beams while the crystal has fixed boundaries. The influences of the tackling states on these two parameters increase while the order of Gaussian beams increases. Irradiated by the same laser source and u
2006,
18.
Abstract:
Spin coating can be controlled by a few parameters such as the rotating speed and solid density to yield a well-defined film, which can often be used to create highly uniform coatings. Solid pyromellitic dianhydride and 4,4-oxydianiline were added to N,N-dimethyl acetamide to form polypyromellitamic acid solution and films were cast from the solution.The paper focuses on fabrication of high quality polyimide on the basis of experiments especially for uniformity film thickness and good film properties. It implicates that the rotating speed and fluid density have strong effects on the film thickness. Under suitable experiment condition polyimide film can be fabricated with suitable thickness. The film thickness fluctuation is no more than 5％, and the film surface finish 0.3～0.4 nm. The ten
Spin coating can be controlled by a few parameters such as the rotating speed and solid density to yield a well-defined film, which can often be used to create highly uniform coatings. Solid pyromellitic dianhydride and 4,4-oxydianiline were added to N,N-dimethyl acetamide to form polypyromellitamic acid solution and films were cast from the solution.The paper focuses on fabrication of high quality polyimide on the basis of experiments especially for uniformity film thickness and good film properties. It implicates that the rotating speed and fluid density have strong effects on the film thickness. Under suitable experiment condition polyimide film can be fabricated with suitable thickness. The film thickness fluctuation is no more than 5％, and the film surface finish 0.3～0.4 nm. The ten
2006,
18.
Abstract:
An experiment of laser-plasma interaction in hohlraum plasmas produced by laser beams with 351 nm wavelength, 2 ns pulse duration at SGII laser facility was reported in this paper. The time-resolved spectra and energy of scattered light by stimulated Raman scattering (SRS) were measured. When 2 ns laser entered into a small hohlraum(700 mm×1 250 mm), the energy of scattered light from a slot hohlraum was 1.3 times that from a hohlraum. With different hohlraum size, the energy of scattered light from a small hohlraum was 1.6 times higher than that from a standard hohlraum(800 mm×1 350 mm). Compared with 1 ns laser, when 2 ns laser interacted with hohlraum, the energy of SRS light was lower because of the decline of laser power, while the duration time was longer. The exper
An experiment of laser-plasma interaction in hohlraum plasmas produced by laser beams with 351 nm wavelength, 2 ns pulse duration at SGII laser facility was reported in this paper. The time-resolved spectra and energy of scattered light by stimulated Raman scattering (SRS) were measured. When 2 ns laser entered into a small hohlraum(700 mm×1 250 mm), the energy of scattered light from a slot hohlraum was 1.3 times that from a hohlraum. With different hohlraum size, the energy of scattered light from a small hohlraum was 1.6 times higher than that from a standard hohlraum(800 mm×1 350 mm). Compared with 1 ns laser, when 2 ns laser interacted with hohlraum, the energy of SRS light was lower because of the decline of laser power, while the duration time was longer. The exper
2006,
18.
Abstract:
Inner doped polystyrene capsules are required to meet the demand of the characterization of implosion interface, the elemental content, especially the doped elemental content is the key point to the performance. In this paper, the outer and inner surface structures of the polystyrene capsule doped with sulfur were analyzed by SAXPS technique, the analyzed area was 150 mm in diameter. The results show that sulfur exists in the inner surface of the polystyrene capsule, which is consistent with the capsule producing techniques.
Inner doped polystyrene capsules are required to meet the demand of the characterization of implosion interface, the elemental content, especially the doped elemental content is the key point to the performance. In this paper, the outer and inner surface structures of the polystyrene capsule doped with sulfur were analyzed by SAXPS technique, the analyzed area was 150 mm in diameter. The results show that sulfur exists in the inner surface of the polystyrene capsule, which is consistent with the capsule producing techniques.
2006,
18.
Abstract:
Using the model of transient stimulated rotational Raman scattering (SRRS) and phase perturbation, SRRS effects on high power ultraviolet laser beams with phase noise through long air paths were studied. The effects of both low and high frequency phase perturbation on the threshold of the SRRS effects, the conversion efficiency of Stokes field and the phase of the residual pump field and the Stokes field were discussed in detail. The results show that the influence of the phase noise of the initial pump field on the Stokes field is more obvious than on the residual pump field. The variation of the conversion efficiency with the high frequency phase perturbation is larger than that with the low one. The SRRS threshold decreases with the increasing of the RMS value of low-frequency phase per
Using the model of transient stimulated rotational Raman scattering (SRRS) and phase perturbation, SRRS effects on high power ultraviolet laser beams with phase noise through long air paths were studied. The effects of both low and high frequency phase perturbation on the threshold of the SRRS effects, the conversion efficiency of Stokes field and the phase of the residual pump field and the Stokes field were discussed in detail. The results show that the influence of the phase noise of the initial pump field on the Stokes field is more obvious than on the residual pump field. The variation of the conversion efficiency with the high frequency phase perturbation is larger than that with the low one. The SRRS threshold decreases with the increasing of the RMS value of low-frequency phase per
2006,
18.
Abstract:
High power divider with ultra-wide-band was designed based on coaxial structure. The divider input impedance was first translated to the desired impedance for matching and then the offset was made to ease the mechanical processing. High frequency simulation software was used to simulate the divider and the practical divider was fabricated. High voltage experiment shows that the divider can resist high power up to millions watt. The measurement of voltage standing wave ratio(VSWR) is less than 1.5 from 0.18 GHz to 0.85 GHz and the average value is about 1.2. The transmission parameters indicate the output ports have well amplitude consistency. The measurements show that the divider is applicable to high power antenna array.
High power divider with ultra-wide-band was designed based on coaxial structure. The divider input impedance was first translated to the desired impedance for matching and then the offset was made to ease the mechanical processing. High frequency simulation software was used to simulate the divider and the practical divider was fabricated. High voltage experiment shows that the divider can resist high power up to millions watt. The measurement of voltage standing wave ratio(VSWR) is less than 1.5 from 0.18 GHz to 0.85 GHz and the average value is about 1.2. The transmission parameters indicate the output ports have well amplitude consistency. The measurements show that the divider is applicable to high power antenna array.
2006,
18.
Abstract:
An S-band cylindrical cavity works on TM610 higher-order mode was designed on the basis of electromagnetic theory. Electromagnetic field distribution, frequency and mode spacing of TM610 mode and its adjacent modes were calculated by using HFSS, ISFELD3D, MAFIA and CST-MS. Simulation results indicate that the electromagnetic field of TM610 mode distributes in the section around drift tube, and there is no electromagnetic field in the center of the cavity. A ferrite RF absorber was set in the center of the cavity to suppress the non-work modes based on the characteristic of TM610 mode. Simulation results of HFSS show that most non-work modes are eliminated by RF absorber except the TM510 mode. An absorption cavity coupled to the main cavity was used to suppress the TM510 mode. Simulation re
An S-band cylindrical cavity works on TM610 higher-order mode was designed on the basis of electromagnetic theory. Electromagnetic field distribution, frequency and mode spacing of TM610 mode and its adjacent modes were calculated by using HFSS, ISFELD3D, MAFIA and CST-MS. Simulation results indicate that the electromagnetic field of TM610 mode distributes in the section around drift tube, and there is no electromagnetic field in the center of the cavity. A ferrite RF absorber was set in the center of the cavity to suppress the non-work modes based on the characteristic of TM610 mode. Simulation results of HFSS show that most non-work modes are eliminated by RF absorber except the TM510 mode. An absorption cavity coupled to the main cavity was used to suppress the TM510 mode. Simulation re
2006,
18.
Abstract:
The hydrodynamic model (HDM) is presented for the transient simulation of GaAs metal-semiconductor-field-effect-transistor(MESFET) which works at high electric fields and frequencies. The finite volume discretization scheme and operator split method used for solving the HDM equations are discussed. A two-dimensional MESFET device is numerically simulated by using the HDM. Some typical numerical results are presented, such as the I-V curves, distribution of electron density and temperature of the device, etc. The results show that while the gate biases are more negative, the Schottky depletion layer is thicker and the source-drain current flow is lower. In the region of high electric field, the electron temperature is much higher than the lattice temperature, and the so-called hot electrons
The hydrodynamic model (HDM) is presented for the transient simulation of GaAs metal-semiconductor-field-effect-transistor(MESFET) which works at high electric fields and frequencies. The finite volume discretization scheme and operator split method used for solving the HDM equations are discussed. A two-dimensional MESFET device is numerically simulated by using the HDM. Some typical numerical results are presented, such as the I-V curves, distribution of electron density and temperature of the device, etc. The results show that while the gate biases are more negative, the Schottky depletion layer is thicker and the source-drain current flow is lower. In the region of high electric field, the electron temperature is much higher than the lattice temperature, and the so-called hot electrons
2006,
18.
Abstract:
The dispersion characteristics of corrugated waveguide with an inner coaxial structure are studied and the influences on dispersion characteristics of the corrugation period, amplitude and the radius of the inner coaxial conductor are discussed. It is shown that the cutoff frequency of system increases with the introduction of inner coaxial conductor, the size of system can be greater than conventional corrugated waveguide BWO, large radius hollow electron beam could be used and device could operate with a low guiding magnetic field. A PIC simulation is carried out using MAGIC software, which shows that the field distribution of coaxial waveguide is beneficial to the beamwave interaction. A nonuniform coaxial BWO with high interaction efficiency of 60% and low guiding magnetic field l
The dispersion characteristics of corrugated waveguide with an inner coaxial structure are studied and the influences on dispersion characteristics of the corrugation period, amplitude and the radius of the inner coaxial conductor are discussed. It is shown that the cutoff frequency of system increases with the introduction of inner coaxial conductor, the size of system can be greater than conventional corrugated waveguide BWO, large radius hollow electron beam could be used and device could operate with a low guiding magnetic field. A PIC simulation is carried out using MAGIC software, which shows that the field distribution of coaxial waveguide is beneficial to the beamwave interaction. A nonuniform coaxial BWO with high interaction efficiency of 60% and low guiding magnetic field l
2006,
18.
Abstract:
The antenna arrays which are composed of the combined-oscillator antennas are studied. The finite-difference time-domain method is used to simulate the radiation properties of the antenna arrays. The efficiency of feeding from the coaxial line to the antenna is calculated. The numerical results of the radiated fields and energy patterns for the single antenna, two- and four-element arrays are presented in this paper. The energy patterns for different configurations are compared. The numerical simulation results demonstrate that this kind of antenna array has the broad band characteristic and high feeding efficiency, and it can be used to radiate the ultrawide band electromagnetic pulse.
The antenna arrays which are composed of the combined-oscillator antennas are studied. The finite-difference time-domain method is used to simulate the radiation properties of the antenna arrays. The efficiency of feeding from the coaxial line to the antenna is calculated. The numerical results of the radiated fields and energy patterns for the single antenna, two- and four-element arrays are presented in this paper. The energy patterns for different configurations are compared. The numerical simulation results demonstrate that this kind of antenna array has the broad band characteristic and high feeding efficiency, and it can be used to radiate the ultrawide band electromagnetic pulse.
2006,
18.
Abstract:
The scattering characteristics of an airplane model and the radar absorbing material covered on the model are simulated by the finite-difference time-domain (FDTD) method, and the time-domain echoes and frequency-domain radar cross section echoes of the model from nose-angle, side-angle and back-angle stimulated by an ns pulse are obtained. The results of the simulation and outdoor experiment show that the echo amplitude of the nose-angle is the lowest and that of the side-angle is the highest. The pulse-width of the nose-angle echo is the widest and that of the side-angle is the narrowest. The shape-stealth and material-stealth are not effective for ns or sub-ns pulse signals.
The scattering characteristics of an airplane model and the radar absorbing material covered on the model are simulated by the finite-difference time-domain (FDTD) method, and the time-domain echoes and frequency-domain radar cross section echoes of the model from nose-angle, side-angle and back-angle stimulated by an ns pulse are obtained. The results of the simulation and outdoor experiment show that the echo amplitude of the nose-angle is the lowest and that of the side-angle is the highest. The pulse-width of the nose-angle echo is the widest and that of the side-angle is the narrowest. The shape-stealth and material-stealth are not effective for ns or sub-ns pulse signals.
2006,
18.
Abstract:
The software MWS (microwave studio) which is provided by the CST company in German was introduced to simulate and calculate dispersion relation and coupling impedance. The high frequency characteristics of the inner slotted rectangular waveguide grating was simulated. The results indicate that the slotted rectangular waveguide grating has lower phase-velocity than the un-slotted one. When it is used as the slow-wave structure of the traveling wave tube, the operating voltage decreases, and the coupling impedance also decreases but it lies above 45 Ω, which satisfies the need of millimeter wave traveling wave tube (TWT). Meanwhile, keeping the inner slotted width constant, it is very useful to increase the groove-depth, grating-spacmg and grating-period for improving the phase velocity of
The software MWS (microwave studio) which is provided by the CST company in German was introduced to simulate and calculate dispersion relation and coupling impedance. The high frequency characteristics of the inner slotted rectangular waveguide grating was simulated. The results indicate that the slotted rectangular waveguide grating has lower phase-velocity than the un-slotted one. When it is used as the slow-wave structure of the traveling wave tube, the operating voltage decreases, and the coupling impedance also decreases but it lies above 45 Ω, which satisfies the need of millimeter wave traveling wave tube (TWT). Meanwhile, keeping the inner slotted width constant, it is very useful to increase the groove-depth, grating-spacmg and grating-period for improving the phase velocity of
2006,
18.
Abstract:
The analysis of the EMP coupling to buried cables is important in EMP protection. Based on the Agrawal model of transmission line and the 1-D FDTD method, this coupling problem is studied. A linear fitting method is proposed to avoid the complicated convolution between ground impedance and transmission line voltage/current. The basic theory and calculation result of the method are introduced. A simple approach is provided to analyze the transmission line model in time-domain considering ground impedance. Comparison of the time domain and frequency domain calculation results shows the proposed method is effective and can solve the coupling problem in non-uniform environment where the frequency domain method does not work.
The analysis of the EMP coupling to buried cables is important in EMP protection. Based on the Agrawal model of transmission line and the 1-D FDTD method, this coupling problem is studied. A linear fitting method is proposed to avoid the complicated convolution between ground impedance and transmission line voltage/current. The basic theory and calculation result of the method are introduced. A simple approach is provided to analyze the transmission line model in time-domain considering ground impedance. Comparison of the time domain and frequency domain calculation results shows the proposed method is effective and can solve the coupling problem in non-uniform environment where the frequency domain method does not work.
2006,
18.
Abstract:
In the paper the linear gain of coaxial-cavity cyclotron autoresonance maser amplifier is researched by the gyrokinetics. The outer-contructor radius, the electron beam radius and beam voltage's change on the linear gain is great, but the influence of the inner-rod radius's change on the linear gain is small. It is shown by optimizing the parameters that the linear gain of the simulation might be raised up to 294.96 dB/m that the outer-contructor radius is 3.805 cm, the inner-rod radius is 1.039 cm, the electron beam radius is 1.309 cm, beam voltage is 54.9 kV.
In the paper the linear gain of coaxial-cavity cyclotron autoresonance maser amplifier is researched by the gyrokinetics. The outer-contructor radius, the electron beam radius and beam voltage's change on the linear gain is great, but the influence of the inner-rod radius's change on the linear gain is small. It is shown by optimizing the parameters that the linear gain of the simulation might be raised up to 294.96 dB/m that the outer-contructor radius is 3.805 cm, the inner-rod radius is 1.039 cm, the electron beam radius is 1.309 cm, beam voltage is 54.9 kV.
2006,
18.
Abstract:
The energy conversion probability from the primary X-ray to the first scattered ray in object material is analytically obtained in consideration of three interaction types, including photoelectric effect, Compton scatter and pair production. The approximative formulae for the scattering exposure and the minimal direct-scatter ratio on the imaging plane in radiography are given. The estimated minimal direct-scatter ratio for FTO is in agreement with the of National Insitute of Heath experiment result.
The energy conversion probability from the primary X-ray to the first scattered ray in object material is analytically obtained in consideration of three interaction types, including photoelectric effect, Compton scatter and pair production. The approximative formulae for the scattering exposure and the minimal direct-scatter ratio on the imaging plane in radiography are given. The estimated minimal direct-scatter ratio for FTO is in agreement with the of National Insitute of Heath experiment result.
2006,
18.
Abstract:
In fast neutron radiography, scintillator plates are often employed as converters of fast neutron radiation. In this paper, the simulation of interaction between BC400 scintillator plates and vertical-incidence D-T neutrons is presented, and the point spread function of scintillator plates is calculated, which exhibits a stable profile during the thickness increasing of plates from 2 mm to 100 mm. The calculation also indicates that, for a certain spatial resolution, there is not an improvement in the contrast of neutron images when the thickness of plates increases.
In fast neutron radiography, scintillator plates are often employed as converters of fast neutron radiation. In this paper, the simulation of interaction between BC400 scintillator plates and vertical-incidence D-T neutrons is presented, and the point spread function of scintillator plates is calculated, which exhibits a stable profile during the thickness increasing of plates from 2 mm to 100 mm. The calculation also indicates that, for a certain spatial resolution, there is not an improvement in the contrast of neutron images when the thickness of plates increases.
2006,
18.
Abstract:
The dynamics of a one-dimensional hydrogen molecule ion (H2+) in two-color intense laser field was studied. The classical trajectories were obtained by solving numerically the classical Hamiltonian equations. Based on the classical theory and symplectic algorithm, the probabilities of survival, ionization, dissociation and Coulomb explosion were implemented, meanwhile the influence of the intensity of the laser field on this diatomic ion model was evaluated. The classical dynamics caused by the phase-difference, the laser intensity-difference, and the frequency-difference between the two laser pulses were illustrated and some physical explanations were given.
The dynamics of a one-dimensional hydrogen molecule ion (H2+) in two-color intense laser field was studied. The classical trajectories were obtained by solving numerically the classical Hamiltonian equations. Based on the classical theory and symplectic algorithm, the probabilities of survival, ionization, dissociation and Coulomb explosion were implemented, meanwhile the influence of the intensity of the laser field on this diatomic ion model was evaluated. The classical dynamics caused by the phase-difference, the laser intensity-difference, and the frequency-difference between the two laser pulses were illustrated and some physical explanations were given.
2006,
18.
Abstract:
At present the PIC method is often adopted in the numerical simulation of ion thruster optical system. In the PIC method, the movement of the single particles needs to be traced, so the information of particles must be saved. In the traditional particle simulation program array is used to save the information of particles, in which the disadvantage is that the array can not adapt to the variation of the particle quantity. In this paper, a particle simulation program based on linked list storage structure is developed, in which the single linked list is used as the save method. Based on this method, the plasma particle simulation of ion thruster optics is carried out by PIC method, so that the feasibility of applying the linked list method to the particle simulation is validated. The simula
At present the PIC method is often adopted in the numerical simulation of ion thruster optical system. In the PIC method, the movement of the single particles needs to be traced, so the information of particles must be saved. In the traditional particle simulation program array is used to save the information of particles, in which the disadvantage is that the array can not adapt to the variation of the particle quantity. In this paper, a particle simulation program based on linked list storage structure is developed, in which the single linked list is used as the save method. Based on this method, the plasma particle simulation of ion thruster optics is carried out by PIC method, so that the feasibility of applying the linked list method to the particle simulation is validated. The simula
2006,
18.
Abstract:
The principle of the neutron penumbra imaging was introduced, and the effect factors of the resolution of the imaging system were analyzed. The neutron penumbra imaging process was simulated with MCNP software. The coded image of one point source on the imaging principal axis and that of two point souces off the principal axis with and without noise and background were reconstructed by the improved inverse filter and Wiener filter method respectively. The simulation results indicated that the Wiener filter method could restrain noise better.
The principle of the neutron penumbra imaging was introduced, and the effect factors of the resolution of the imaging system were analyzed. The neutron penumbra imaging process was simulated with MCNP software. The coded image of one point source on the imaging principal axis and that of two point souces off the principal axis with and without noise and background were reconstructed by the improved inverse filter and Wiener filter method respectively. The simulation results indicated that the Wiener filter method could restrain noise better.
2006,
18.
Abstract:
Penumbral imaging has high sensitivity, which will be the main technical method of neutron imaging in inertial confinement fusion (ICF) experiments. Based on the requirement of neutron penumbral imaging, two-dimensional image of neutrons transport in the coded aperture is simulated by Monte Carlo method, with the biased sampling skill and surface-flux replaced by volume-flux skill. The source image is obtained by reconstruction program. According to the simulation result, the 5 cm thick W bulk is selected as the shileding material and the optimized aperture outer radius is 1 cm.
Penumbral imaging has high sensitivity, which will be the main technical method of neutron imaging in inertial confinement fusion (ICF) experiments. Based on the requirement of neutron penumbral imaging, two-dimensional image of neutrons transport in the coded aperture is simulated by Monte Carlo method, with the biased sampling skill and surface-flux replaced by volume-flux skill. The source image is obtained by reconstruction program. According to the simulation result, the 5 cm thick W bulk is selected as the shileding material and the optimized aperture outer radius is 1 cm.
2006,
18.
Abstract:
Ion-implantation-enhanced hardening and microstructure change of a Ti-2Al-2.5Zr alloy by 75 keV helium ion implantation with the dose of 5×1016 cm-2 or 1×1017 cm-2 is investigated. The maximum temperature during the implantation was monitored to be less than 200 ℃. The base pressure in the vacuum chamber was 6×10-4 Pa, and the working pressure was 1.6×10-3 Pa. The morphology and the structure of the implant samples have been characterized by TEM using a JEOL 2010FEG at 200 keV. The surface characterization of samples was studied by Vickers hardness tests. The He-induced hardening was observed. The He-induced hardening decreases with annealing at 350 ℃ and 550 ℃. The results of TEM analysis show that helium bubbles and dislocation loops are formed in the near surface region. He-ion-i
Ion-implantation-enhanced hardening and microstructure change of a Ti-2Al-2.5Zr alloy by 75 keV helium ion implantation with the dose of 5×1016 cm-2 or 1×1017 cm-2 is investigated. The maximum temperature during the implantation was monitored to be less than 200 ℃. The base pressure in the vacuum chamber was 6×10-4 Pa, and the working pressure was 1.6×10-3 Pa. The morphology and the structure of the implant samples have been characterized by TEM using a JEOL 2010FEG at 200 keV. The surface characterization of samples was studied by Vickers hardness tests. The He-induced hardening was observed. The He-induced hardening decreases with annealing at 350 ℃ and 550 ℃. The results of TEM analysis show that helium bubbles and dislocation loops are formed in the near surface region. He-ion-i
2006,
18.
Abstract:
The biggest challenge of survey and alignment is the soft groundwork and the tight positioning requirement for Shanghai Synchrotron Radiation Facility. Control network, fiducialization, pre-alignment and installation on site and smoothing are five crucial steps for the installation and alignment process. By utilizing the laser tracker and hydrostatic levelling system, the error budget should be within 0.08 mm for control network and 0.05 mm for the other steps. The expected error budget is 0.12 mm for elements between girders, which is a little smaller than the requirement of 0.15 mm. Besides the target of error control, reliability, efficiency, cost and real-time monitoring are factors considered in the design.
The biggest challenge of survey and alignment is the soft groundwork and the tight positioning requirement for Shanghai Synchrotron Radiation Facility. Control network, fiducialization, pre-alignment and installation on site and smoothing are five crucial steps for the installation and alignment process. By utilizing the laser tracker and hydrostatic levelling system, the error budget should be within 0.08 mm for control network and 0.05 mm for the other steps. The expected error budget is 0.12 mm for elements between girders, which is a little smaller than the requirement of 0.15 mm. Besides the target of error control, reliability, efficiency, cost and real-time monitoring are factors considered in the design.
2006,
18.
Abstract:
The restoration of magnetic cores is very important to multiple-pulses linear induced accelerator(LIA). This paper describes how to restore LIA's cores between two pulses with interval less than 1 μs by the method of overlap restoration. The restore circuit is simple and effective; by covering the exciting pulses over a long inverted voltage pulse can form an inverted pulse between every two exciting pulses to restore the cores. The results show that the overlap restoration can effectively improve the efficiency of the magnetic cores worked multiple-pulses mode with pulse width less than 100 ns and interval more than 500 ns. In addition, the restoration has no dramatic effect on the accelerate pulses, which proves it is possible to reconstruct the single pulse cavity to the multi-pulse ca
The restoration of magnetic cores is very important to multiple-pulses linear induced accelerator(LIA). This paper describes how to restore LIA's cores between two pulses with interval less than 1 μs by the method of overlap restoration. The restore circuit is simple and effective; by covering the exciting pulses over a long inverted voltage pulse can form an inverted pulse between every two exciting pulses to restore the cores. The results show that the overlap restoration can effectively improve the efficiency of the magnetic cores worked multiple-pulses mode with pulse width less than 100 ns and interval more than 500 ns. In addition, the restoration has no dramatic effect on the accelerate pulses, which proves it is possible to reconstruct the single pulse cavity to the multi-pulse ca
2006,
18.
Abstract:
Bunch-by-bunch beam current detection system is an important facility in the multibunch storage ring. In this paper, the established bunch-by-bunch beam current detection systems for the accelerator such as Cornell, SLAC and KEKB were compared and studied. The design of the bunch-by-bunch beam current detection system for HLS, which was based on the bunch-by-bunch tracing measurement system in HLS was given. Both demodulation by sine wave and square were applied in this paper, the deviation of the detect system was determined by the longitudinal oscillation. Compared the data acquired form ADC with the data from DCCT, the ADC data was scaled by the bunch current. The standard deviations of linear fit were about 1%, and the standard deviations of polynomial fit were less than 0.5% in both s
Bunch-by-bunch beam current detection system is an important facility in the multibunch storage ring. In this paper, the established bunch-by-bunch beam current detection systems for the accelerator such as Cornell, SLAC and KEKB were compared and studied. The design of the bunch-by-bunch beam current detection system for HLS, which was based on the bunch-by-bunch tracing measurement system in HLS was given. Both demodulation by sine wave and square were applied in this paper, the deviation of the detect system was determined by the longitudinal oscillation. Compared the data acquired form ADC with the data from DCCT, the ADC data was scaled by the bunch current. The standard deviations of linear fit were about 1%, and the standard deviations of polynomial fit were less than 0.5% in both s
2006,
18.
Abstract:
The basic principle of soft X-ray power meter is introduced in the paper and the experimental process and the result of thin plastic scintillator linear luminescence under intense soft X-ray irradiation are described. A range of flux density of energy for thin plastic scintillator linear luminescence under intense soft X-ray irradiation is included. The upper limit of the flux density is 1.47×105 W/cm2.
The basic principle of soft X-ray power meter is introduced in the paper and the experimental process and the result of thin plastic scintillator linear luminescence under intense soft X-ray irradiation are described. A range of flux density of energy for thin plastic scintillator linear luminescence under intense soft X-ray irradiation is included. The upper limit of the flux density is 1.47×105 W/cm2.
2006,
18.
Abstract:
The plasma opening switch(POS) is a critical element in inductive energy storage systems. In this paper the erosion model is introduced to analyze the foundational principle of the POS and diode system on Qiangguang I generator. The simulation waveforms of the total generator current and the diode beam current are obtained by using the erosion model and compared with experimental waveforms. The calculation results show that the POS is not completely magnetic insulated while about 60% of the total current still flow through the POS. However, about 4.5 MV diode voltage is obtained because of the rapid change rate of current.
The plasma opening switch(POS) is a critical element in inductive energy storage systems. In this paper the erosion model is introduced to analyze the foundational principle of the POS and diode system on Qiangguang I generator. The simulation waveforms of the total generator current and the diode beam current are obtained by using the erosion model and compared with experimental waveforms. The calculation results show that the POS is not completely magnetic insulated while about 60% of the total current still flow through the POS. However, about 4.5 MV diode voltage is obtained because of the rapid change rate of current.
2006,
18.
Abstract:
The structure of spiral Blumlein line consisting of spiral inner cylinder, spiral center cylinder and conductive outer cylinder was discussed in this paper. The formulas approximating characteristic parameters of spiral Blumlein line were obtained by thin current layer model supposing that the exterior line transmits high voltage pulse independently. The principle verifying experiment to generate long pulse on a spiral Blumlein line was proceeded preliminarily. Theoretic amplitude and width of output pulse voltage were 543 V and 24 ns respectively, while the experimental ones measured from current divider were 471 V and 30 ns respectively. The difference between theoretical and experimental values was due to the hypothesis condition that the exterior line independently transmit high voltag
The structure of spiral Blumlein line consisting of spiral inner cylinder, spiral center cylinder and conductive outer cylinder was discussed in this paper. The formulas approximating characteristic parameters of spiral Blumlein line were obtained by thin current layer model supposing that the exterior line transmits high voltage pulse independently. The principle verifying experiment to generate long pulse on a spiral Blumlein line was proceeded preliminarily. Theoretic amplitude and width of output pulse voltage were 543 V and 24 ns respectively, while the experimental ones measured from current divider were 471 V and 30 ns respectively. The difference between theoretical and experimental values was due to the hypothesis condition that the exterior line independently transmit high voltag
2006,
18.
Abstract:
It is executed to study flashover properties of polymethyl methacrylate and nylon 1010 in transformer oil in coaxial electric field by means of high voltage pulsed power supply SPG200 based on SOS switch. Flashover voltage of both solid dielectrics almost increases according to exponent following the linear growing inner electrode diameter, so do flashover voltage as well as flashover time lag versus flashover length almost linearly. polymethyl methacrylate doesn’t take on higher flashover voltage than nylon 1010 in the experimental condition. Radial stress in coaxial electrodes focuses in the vicinity of inner electrode surface, as a result, flashover voltage under coaxial electric field depends on the electric intensity on the inner electrode surface and uniformity degree of radial elec
It is executed to study flashover properties of polymethyl methacrylate and nylon 1010 in transformer oil in coaxial electric field by means of high voltage pulsed power supply SPG200 based on SOS switch. Flashover voltage of both solid dielectrics almost increases according to exponent following the linear growing inner electrode diameter, so do flashover voltage as well as flashover time lag versus flashover length almost linearly. polymethyl methacrylate doesn’t take on higher flashover voltage than nylon 1010 in the experimental condition. Radial stress in coaxial electrodes focuses in the vicinity of inner electrode surface, as a result, flashover voltage under coaxial electric field depends on the electric intensity on the inner electrode surface and uniformity degree of radial elec
