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RSS2010 Vol. 22, No. 11
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2010,
22.
Abstract:
In order to study the laser interference effects of multi-spectral cameras, interference saturation experiments were conducted on a three-channel CCD camera using red, green, and blue lasers. The saturation threshold at different wavelengths was measured for each channel. The difference among saturation thresholds of different channels was analyzed from the operating principle of the camera, and the saturation interference of single-wavelength and multi-wavelength coupling was comparatively studied under the same power. It is found that the coupled multi-wavelength laser has better interference effect than the single-wavelength one.
In order to study the laser interference effects of multi-spectral cameras, interference saturation experiments were conducted on a three-channel CCD camera using red, green, and blue lasers. The saturation threshold at different wavelengths was measured for each channel. The difference among saturation thresholds of different channels was analyzed from the operating principle of the camera, and the saturation interference of single-wavelength and multi-wavelength coupling was comparatively studied under the same power. It is found that the coupled multi-wavelength laser has better interference effect than the single-wavelength one.
2010,
22.
Abstract:
The laser diode array (LDA) pumped Yb:YAG thin disc laser has been analysed and optimized. The Yb:YAG disc with 10 mm diameter and 340 μm thickness was employed. The Yb3+ atom fraction is 10%. It was mounted onto the micro-channel copper heat sink by Cr/Au/In. The four-pass optical coupling system was well designed with two spherical imaging mirrors which have a diameter of 30 mm and radius of curvature of 50 mm. The pump-beam radius was calculated by LightTools Software. Considering mode matching, the output mirror which has radius of curvature 200 mm was employed. When the incident power was 18.73 W, a CW output power of 4.81 W at 1 030 nm was obtained. The optical conversion efficiency was 25.7%.
The laser diode array (LDA) pumped Yb:YAG thin disc laser has been analysed and optimized. The Yb:YAG disc with 10 mm diameter and 340 μm thickness was employed. The Yb3+ atom fraction is 10%. It was mounted onto the micro-channel copper heat sink by Cr/Au/In. The four-pass optical coupling system was well designed with two spherical imaging mirrors which have a diameter of 30 mm and radius of curvature of 50 mm. The pump-beam radius was calculated by LightTools Software. Considering mode matching, the output mirror which has radius of curvature 200 mm was employed. When the incident power was 18.73 W, a CW output power of 4.81 W at 1 030 nm was obtained. The optical conversion efficiency was 25.7%.
2010,
22.
Abstract:
In order to increase out power of DL, the copper micro-channel cooler’s property was tested, and its ability to dissipate heat was analyzed. An indium alloy solder was developed, which can dispel crystal beard. The CW 100 W high power laser diode was packaged directly on the cooler with new technique and tested. The results of measurement show that the CW 100 W laser diode output power more than 100 W at drive current of 105 A, the central wavelengh is 808.5 nm and the FWHM is 2.15 nm. The smile effect of the packaged diode bars is usually less than 2 μm, for some samples, it is even less than 0.5 μm.
In order to increase out power of DL, the copper micro-channel cooler’s property was tested, and its ability to dissipate heat was analyzed. An indium alloy solder was developed, which can dispel crystal beard. The CW 100 W high power laser diode was packaged directly on the cooler with new technique and tested. The results of measurement show that the CW 100 W laser diode output power more than 100 W at drive current of 105 A, the central wavelengh is 808.5 nm and the FWHM is 2.15 nm. The smile effect of the packaged diode bars is usually less than 2 μm, for some samples, it is even less than 0.5 μm.
2010,
22.
Abstract:
The adaptive optical system with close-loop control can modulate the wavefront of femtosecond pulses, which can effectively improve the reduced efficiency caused by the phase distortion and optical deviation in the interaction between laser and materials. Using a programmable pure-phase liquid crystal spatial light modulator, the adaptive optimal system based on simulated annealing algorithm can automatically compensate the efficiency decline caused by the phase distortion and optical deviation during the second harmonic generation process of femtosecond pulses in a BBO crystal.
The adaptive optical system with close-loop control can modulate the wavefront of femtosecond pulses, which can effectively improve the reduced efficiency caused by the phase distortion and optical deviation in the interaction between laser and materials. Using a programmable pure-phase liquid crystal spatial light modulator, the adaptive optimal system based on simulated annealing algorithm can automatically compensate the efficiency decline caused by the phase distortion and optical deviation during the second harmonic generation process of femtosecond pulses in a BBO crystal.
2010,
22.
Abstract:
A finite element transmission matrix model is founded for the eigenmode of multi-element optical resonator. A novel conception of mode calculation relative error(MCRE) and its mathematical expression are introduced. The conception can well reflect the effect of finite element amount on the mode calculation precision of resonators with different Fresnel number, because it is mainly independent of Fresnel number. Another new conception of finite element fineness (FEF) is proposed to characterize the division precision of finite elements. FEF is defined as the ratio of the finite element amount of cavity mirror to Fresnel number, where Fresnel number is used as the relative requirement of the division number. The relationship between MCRE and FEF is analyzed, and an empirical expression betwe
A finite element transmission matrix model is founded for the eigenmode of multi-element optical resonator. A novel conception of mode calculation relative error(MCRE) and its mathematical expression are introduced. The conception can well reflect the effect of finite element amount on the mode calculation precision of resonators with different Fresnel number, because it is mainly independent of Fresnel number. Another new conception of finite element fineness (FEF) is proposed to characterize the division precision of finite elements. FEF is defined as the ratio of the finite element amount of cavity mirror to Fresnel number, where Fresnel number is used as the relative requirement of the division number. The relationship between MCRE and FEF is analyzed, and an empirical expression betwe
2010,
22.
Abstract:
The correction of low order Zernike aberrations by a 37-element curvature adaptive optics system is simulated. The results indicate that the system can effectively correct the low order Zernike aberrations. Correction results of Zernike aberrations with zero curvature and with non-zero curvature are analyzed comparatively. It is found that the Zernike aberrations with zero curvature can be corrected, and the correction is more accurate than that for the non-zero curvature aberrations.
The correction of low order Zernike aberrations by a 37-element curvature adaptive optics system is simulated. The results indicate that the system can effectively correct the low order Zernike aberrations. Correction results of Zernike aberrations with zero curvature and with non-zero curvature are analyzed comparatively. It is found that the Zernike aberrations with zero curvature can be corrected, and the correction is more accurate than that for the non-zero curvature aberrations.
2010,
22.
Abstract:
A one-dimensional bulk absorption model to simulate the accelerating process of laser-driven flyer plate is presented, in which the laser energy deposition, the laser absorption in plasma and acceleration of flyer plates are included. In the laser intensity range of GW/cm2, the gasdynamical behavior of the ablated foil plasma is described with a modified one-dimensional Lagrangian hydrodynamic code. The histories of the flyer velocity and the density profiles are given by this model. The calculated results of the ablated thickness of films in the launch of laser-driven flyer plates are in good agreement with the experimental results.
A one-dimensional bulk absorption model to simulate the accelerating process of laser-driven flyer plate is presented, in which the laser energy deposition, the laser absorption in plasma and acceleration of flyer plates are included. In the laser intensity range of GW/cm2, the gasdynamical behavior of the ablated foil plasma is described with a modified one-dimensional Lagrangian hydrodynamic code. The histories of the flyer velocity and the density profiles are given by this model. The calculated results of the ablated thickness of films in the launch of laser-driven flyer plates are in good agreement with the experimental results.
2010,
22.
Abstract:
This paper studied the model about heat release from the oxidation when the high-energy laser irradiated the iron plate, and a numerical simulation code was developed by using the finite-element method. The temporal and spatial distributions of temperature in the iron plate were simulated under the conditions of airflow, nitrogen flow, or no flow. The quantity of heat in the course of oxidation was analyzed. Numerical results indicated that the difference of temperature rising was very small under the conditions of nitrogen flow and no flow, and the quantity of heat release in oxidation was approximately 35% of the total energy deposited in the iron plate for the air flow condition. The numerical results agreed well with the experimental results reported in the open literature.
This paper studied the model about heat release from the oxidation when the high-energy laser irradiated the iron plate, and a numerical simulation code was developed by using the finite-element method. The temporal and spatial distributions of temperature in the iron plate were simulated under the conditions of airflow, nitrogen flow, or no flow. The quantity of heat in the course of oxidation was analyzed. Numerical results indicated that the difference of temperature rising was very small under the conditions of nitrogen flow and no flow, and the quantity of heat release in oxidation was approximately 35% of the total energy deposited in the iron plate for the air flow condition. The numerical results agreed well with the experimental results reported in the open literature.
2010,
22.
Abstract:
PV-type HgCdTe infrared detector is irradiated by 10.6 μm CW laser which is out of the detector’s response waveband. A series of detector output under various laser intensities are obtained. Responses of the detector to the irradiation of 10.6 μm laser are positive to that of in-band laser. The voltage output of the detector first increases and then decreases as the laser power density is increasing. Analysis shows that temperature rise and temperature grads are the main causes. Thermovoltage is generated when heat excited free electrons and vacancies diffuse under temperature grads, then separated by the electric field of PN junction. Thermovoltage is the main part of output when PV-type detector is irradiated by out-of-band laser.
PV-type HgCdTe infrared detector is irradiated by 10.6 μm CW laser which is out of the detector’s response waveband. A series of detector output under various laser intensities are obtained. Responses of the detector to the irradiation of 10.6 μm laser are positive to that of in-band laser. The voltage output of the detector first increases and then decreases as the laser power density is increasing. Analysis shows that temperature rise and temperature grads are the main causes. Thermovoltage is generated when heat excited free electrons and vacancies diffuse under temperature grads, then separated by the electric field of PN junction. Thermovoltage is the main part of output when PV-type detector is irradiated by out-of-band laser.
2010,
22.
Abstract:
This paper studies the spectral narrowing technology for the optical pumping XeF(C-A) bule-green laser with surface discharge. Two types of resonators, spectral overlapping resonator and grating resonator are used to compress the laser spectrum. A pectral linewidth of about 7 nm can be obtained when the spectral overlappting resonator is used, and the laser output energy is about 750 mJ. Narrow-linewidth tunable laser output is realized by grating resonator, with a spectral width of about 1 nm and a tunable range from 470 to 495 nm.
This paper studies the spectral narrowing technology for the optical pumping XeF(C-A) bule-green laser with surface discharge. Two types of resonators, spectral overlapping resonator and grating resonator are used to compress the laser spectrum. A pectral linewidth of about 7 nm can be obtained when the spectral overlappting resonator is used, and the laser output energy is about 750 mJ. Narrow-linewidth tunable laser output is realized by grating resonator, with a spectral width of about 1 nm and a tunable range from 470 to 495 nm.
2010,
22.
Abstract:
To filter out salt and pepper noise and Gaussian noise, this paper presents a waveletbased adaptive filtering algorithm for mixed noise. The median filter is firstly applied to remove salt and pepper noise and the edge detection is used to distinguish between the nonedge region and the edge region. Then an improved average filter is adopted on the nonedge region, initially weakening the Gaussian noise, without blurring the edge. Finally, an improved wavelet threshold filtering algorithm is utilized on the entire image, using different threshold functions on different subbands. The parameters of these threshold functions are gained in a linear regression process. The experimental results show that the proposed adaptive mixednoise filtering algorithm can effectively remove salt and
To filter out salt and pepper noise and Gaussian noise, this paper presents a waveletbased adaptive filtering algorithm for mixed noise. The median filter is firstly applied to remove salt and pepper noise and the edge detection is used to distinguish between the nonedge region and the edge region. Then an improved average filter is adopted on the nonedge region, initially weakening the Gaussian noise, without blurring the edge. Finally, an improved wavelet threshold filtering algorithm is utilized on the entire image, using different threshold functions on different subbands. The parameters of these threshold functions are gained in a linear regression process. The experimental results show that the proposed adaptive mixednoise filtering algorithm can effectively remove salt and
2010,
22.
Abstract:
Effects of temperature gradient and uniform temperature on reflectors in periscopic laser communication terminals were studied. Zernike polynomials on elliptical aperture were used to fit wave-front aberration of the elliptical reflectors due to temperature distribution. RMS value, pointing error and peak intensity degradation at the receiver caused by thermal deformation were studied in inter-satellite laser communication system. The results show that the effect of temperature gradient cause drift of peak intensity and a little degradation. The pointing error reaches 2.1 μrad when temperature gradient is 14 ℃/m. The uniform temperature will cause variation of intensity distribution at the receiver and result in larger pointing error and degradation of intensity. The pointing error is le
Effects of temperature gradient and uniform temperature on reflectors in periscopic laser communication terminals were studied. Zernike polynomials on elliptical aperture were used to fit wave-front aberration of the elliptical reflectors due to temperature distribution. RMS value, pointing error and peak intensity degradation at the receiver caused by thermal deformation were studied in inter-satellite laser communication system. The results show that the effect of temperature gradient cause drift of peak intensity and a little degradation. The pointing error reaches 2.1 μrad when temperature gradient is 14 ℃/m. The uniform temperature will cause variation of intensity distribution at the receiver and result in larger pointing error and degradation of intensity. The pointing error is le
2010,
22.
Abstract:
System performances of two four-aperture coherent length monitors, whose optical source is tungsten-halogen lamp at horizontal direction, were explored by synchro contrast experiments. Experimental results show that, dimensions and temporal varying tendencies of atmospheric coherent length, measured by these two systems, are almost the same, and the correlation coefficients are all larger than 0.94. Influence of Dome effect on system performances was also researched. The main influence of this effect was embodied by the decreased of atmospheric coherent length, and the influence intensity was determined by the distance of the shifting system along the optical path. When the distance was smaller than 15 cm, there was no remarkable Dome effect. As the distance increased from 15 cm to 55 cm,
System performances of two four-aperture coherent length monitors, whose optical source is tungsten-halogen lamp at horizontal direction, were explored by synchro contrast experiments. Experimental results show that, dimensions and temporal varying tendencies of atmospheric coherent length, measured by these two systems, are almost the same, and the correlation coefficients are all larger than 0.94. Influence of Dome effect on system performances was also researched. The main influence of this effect was embodied by the decreased of atmospheric coherent length, and the influence intensity was determined by the distance of the shifting system along the optical path. When the distance was smaller than 15 cm, there was no remarkable Dome effect. As the distance increased from 15 cm to 55 cm,
2010,
22.
Abstract:
Shock wave merging happens when the waves have damped, for repetitively pulsed laser irradiation induced waves. The influence of laser duration on the wave evolution becomes important as the laser pulse interval is small. Thus the evolution of the shock waves was numerically studied with laser incident process being taken into account. Results show that the shock wave front is ellipsoidal at the beginning, and then becomes spherical gradually. The distance from the sphere center to the breakdown point decreases gradually to a constant value. Based on the application of laser shock wave merging, shock waveradius, shock wave length, and overpressure as functions of time and shock wave front radius were derived at the Mach number from 1 to 2．
Shock wave merging happens when the waves have damped, for repetitively pulsed laser irradiation induced waves. The influence of laser duration on the wave evolution becomes important as the laser pulse interval is small. Thus the evolution of the shock waves was numerically studied with laser incident process being taken into account. Results show that the shock wave front is ellipsoidal at the beginning, and then becomes spherical gradually. The distance from the sphere center to the breakdown point decreases gradually to a constant value. Based on the application of laser shock wave merging, shock waveradius, shock wave length, and overpressure as functions of time and shock wave front radius were derived at the Mach number from 1 to 2．
2010,
22.
Abstract:
An automatic design method of gas laser electrode has been developed based on the standard ACIS model format file. In the method, Ernst profiles are approximated by utilizing Inventor VBA program language and B-spline curve, and the 3D Ernst electrode entity model is obtained with the linear extension method. The object file can be exported to Ansys for 3D finite element analysis. The errors of the Ernst curves approximated with points of different density were compared, and the reason for the errors was elucidated. Denser sampling was adopted in the part of higher curvature to balance the curve precision and computing speed. The designed object was analyzed in Ansys program.
An automatic design method of gas laser electrode has been developed based on the standard ACIS model format file. In the method, Ernst profiles are approximated by utilizing Inventor VBA program language and B-spline curve, and the 3D Ernst electrode entity model is obtained with the linear extension method. The object file can be exported to Ansys for 3D finite element analysis. The errors of the Ernst curves approximated with points of different density were compared, and the reason for the errors was elucidated. Denser sampling was adopted in the part of higher curvature to balance the curve precision and computing speed. The designed object was analyzed in Ansys program.
2010,
22.
Abstract:
An image sequence-based method is proposed for target detection within a large-field bright background from a long distance. Optimal estimation of image background is obtained using adaptive prediction of local background. For the image with background subtracted, energy accumulation and median filter are used to further remove clutter and to improve signal-to-noise ratio (SNR). Then the targets are located by double window filtering with buffer window which further segments the targets from background. With improved high order correlation, the true dim target is eventually detected with a small amount of calculations. The proposed method is implemented in field experiments. Using three order correlation, its detection probability achieves 98% when the local SNR is higher than 0.3.
An image sequence-based method is proposed for target detection within a large-field bright background from a long distance. Optimal estimation of image background is obtained using adaptive prediction of local background. For the image with background subtracted, energy accumulation and median filter are used to further remove clutter and to improve signal-to-noise ratio (SNR). Then the targets are located by double window filtering with buffer window which further segments the targets from background. With improved high order correlation, the true dim target is eventually detected with a small amount of calculations. The proposed method is implemented in field experiments. Using three order correlation, its detection probability achieves 98% when the local SNR is higher than 0.3.
2010,
22.
Abstract:
Three-dimensional whole digital simulation is an important research tool for laser tracking and pointing system. In view of the whole laser tracking and pointing simulation system, problems such as projection transform of target’s imaging, relation of imaging and tracking, control process’s simulation of the existing methods are studied for improving accuracy. A tracking and pointing simulation technology based on a kind of imaging series is discussed, and the kind of imaging series has big viewports and considers the effect of atmosphere transfer. Characteristics of accuracy analysis in simulation system are also illustrated. In a simulation scene, two methods are designed, which are named vertex-of-head tracking and pointing method and two-point-acquiring tracking and pointing method.
Three-dimensional whole digital simulation is an important research tool for laser tracking and pointing system. In view of the whole laser tracking and pointing simulation system, problems such as projection transform of target’s imaging, relation of imaging and tracking, control process’s simulation of the existing methods are studied for improving accuracy. A tracking and pointing simulation technology based on a kind of imaging series is discussed, and the kind of imaging series has big viewports and considers the effect of atmosphere transfer. Characteristics of accuracy analysis in simulation system are also illustrated. In a simulation scene, two methods are designed, which are named vertex-of-head tracking and pointing method and two-point-acquiring tracking and pointing method.
2010,
22.
Abstract:
Basic principles of reference-beam laser Doppler velocimeter (LDV) is expounded. The influences of error factors on LDV measurements are theoretically analyzed, such as principle formula approximation, Gauss-beam interference, laser linewidth, detector aperture, finite transition time, signal processing algorithm, change of air refractive index and angle measurement. The theoretical formula of measurement error caused by each error factor is presented, and the influence of optical parameters on each error is discussed. Theoretical analyses and experiments show that, narrow-band laser and small-aperture photoelectric detector are required to reduce measurement errors in experiments. When one chooses beam facular aperture and the angle of between light central beam and particle motion direct
Basic principles of reference-beam laser Doppler velocimeter (LDV) is expounded. The influences of error factors on LDV measurements are theoretically analyzed, such as principle formula approximation, Gauss-beam interference, laser linewidth, detector aperture, finite transition time, signal processing algorithm, change of air refractive index and angle measurement. The theoretical formula of measurement error caused by each error factor is presented, and the influence of optical parameters on each error is discussed. Theoretical analyses and experiments show that, narrow-band laser and small-aperture photoelectric detector are required to reduce measurement errors in experiments. When one chooses beam facular aperture and the angle of between light central beam and particle motion direct
2010,
22.
Abstract:
A bilamellar image converter tube was introduced, which adopts plate poles and electric quadrupole lenses. Based on the bilamellar tube model, the structure, operation mode and imaging characteristics, etc. of the tube were analyzed. The results show that the bilamellar structure can effectively control the space-charge effect and thus increase the temporal/spatial resolution of imaging.
A bilamellar image converter tube was introduced, which adopts plate poles and electric quadrupole lenses. Based on the bilamellar tube model, the structure, operation mode and imaging characteristics, etc. of the tube were analyzed. The results show that the bilamellar structure can effectively control the space-charge effect and thus increase the temporal/spatial resolution of imaging.
2010,
22.
Abstract:
The absorption of thin films is an important factor that reduces their laser induced damage threshold. The absorption at 1 064 nm and the laser-induced damage threshold at different wavelengths (1 064, 532, 355 nm) of single-layer HfO2 films were measured and analyzed. The results show that laser induced damage threshold is determined by the average value and uniformity of the film’s absorption, which depend on the type and quantity, and the distribution of defects in the film, respectively. The laser damage resistance of the single-layer HfO2 film irradiated at the three wavelengths (1 064, 532, 355 nm) can be deduced qualitatively by the measured absorption at 1 064 nm.
The absorption of thin films is an important factor that reduces their laser induced damage threshold. The absorption at 1 064 nm and the laser-induced damage threshold at different wavelengths (1 064, 532, 355 nm) of single-layer HfO2 films were measured and analyzed. The results show that laser induced damage threshold is determined by the average value and uniformity of the film’s absorption, which depend on the type and quantity, and the distribution of defects in the film, respectively. The laser damage resistance of the single-layer HfO2 film irradiated at the three wavelengths (1 064, 532, 355 nm) can be deduced qualitatively by the measured absorption at 1 064 nm.
2010,
22.
Abstract:
The measurement methods of M2 factor using hyperbolic fit and Hartmann-Shack sensor are studied experimentally. The results and experimental errors are compared and analyzed. It is shown that the measured M2 factor is approximately consistent using the two methods when the Hartmann-Shack wavefront sensor contains enough lenslet array, the reconstruction error is small and the orders of the Zernike polynomial is suitably chosen. Compared with the method using hyperbolic fit, the methods using Hartmann-Shack sensor has small scope of application. However, the method using Hartmann-Shack sensor is more simple when it contents the working condition.
The measurement methods of M2 factor using hyperbolic fit and Hartmann-Shack sensor are studied experimentally. The results and experimental errors are compared and analyzed. It is shown that the measured M2 factor is approximately consistent using the two methods when the Hartmann-Shack wavefront sensor contains enough lenslet array, the reconstruction error is small and the orders of the Zernike polynomial is suitably chosen. Compared with the method using hyperbolic fit, the methods using Hartmann-Shack sensor has small scope of application. However, the method using Hartmann-Shack sensor is more simple when it contents the working condition.
2010,
22.
Abstract:
Magnetic Ni-Co-Fe-P alloy plating was deposited on surface of ICF glass targets by electroless plating technology. Composition, morphology and magnetic property of the plated Ni-Co-Fe-P alloy plating were characterized by scanning electron microscopy, atomic force microscopy, energy diffraction spectrum and vibrating sample magnetometer. The results showed that the Ni-Co-Fe-P plating on surface of ICF glass targets was composed of small grains, the average diameters of which were 50 nm or so. The Ni-Co-Fe-P plated ICF glass targets had better surface smoothness and magnetic parameters than the Ni-P plated ones, and could be used in experimental research of magnetic suspension.
Magnetic Ni-Co-Fe-P alloy plating was deposited on surface of ICF glass targets by electroless plating technology. Composition, morphology and magnetic property of the plated Ni-Co-Fe-P alloy plating were characterized by scanning electron microscopy, atomic force microscopy, energy diffraction spectrum and vibrating sample magnetometer. The results showed that the Ni-Co-Fe-P plating on surface of ICF glass targets was composed of small grains, the average diameters of which were 50 nm or so. The Ni-Co-Fe-P plated ICF glass targets had better surface smoothness and magnetic parameters than the Ni-P plated ones, and could be used in experimental research of magnetic suspension.
2010,
22.
Abstract:
Full aperture backscatter system and experimental measurement of hohlraum with 351 nm wavelength laser on Shenguang Ⅱ laser facility is reported. FABS optical path has been analyzed and the backscattering light completely entried FABS collecting optical path. FABS existed the background light when the eight beams symmetrically acted on hohlraum. The background light is composed of 526.5 nm and 1 053 nm wavelength remains while the 1 053 nm wavelength changes into 351 nm wavelength, according to records of laser sensitive paper and optical filter. The background light accounts for 15% of FABS energy from experimental measurement result.
Full aperture backscatter system and experimental measurement of hohlraum with 351 nm wavelength laser on Shenguang Ⅱ laser facility is reported. FABS optical path has been analyzed and the backscattering light completely entried FABS collecting optical path. FABS existed the background light when the eight beams symmetrically acted on hohlraum. The background light is composed of 526.5 nm and 1 053 nm wavelength remains while the 1 053 nm wavelength changes into 351 nm wavelength, according to records of laser sensitive paper and optical filter. The background light accounts for 15% of FABS energy from experimental measurement result.
2010,
22.
Abstract:
The morphology, composition and causes of defects are analyzed to reduce defects on the gold layer prepared by electrochemical deposition from sulfite solution, and to improve the surface quality of sub-millimeter cylindrical gold targets, by means of SEM and EDS. The effects of current density, metallic impurity, organic pollution, pre-deposition parameters and mandrel quality on the quality of the gold plating are discussed, along with their mechanisms. The result indicates that the current density must be controlled strictly. The optimal current density ranges from 2.4 to 3.2 mA/cm2 when the concentration of gold ranges from 13 to 22 g/L, and from 2.0 to 2.6 mA/cm2 when the concentration of gold ranges from 5 to 13 g/L. The parameters of predeposition must be optim
The morphology, composition and causes of defects are analyzed to reduce defects on the gold layer prepared by electrochemical deposition from sulfite solution, and to improve the surface quality of sub-millimeter cylindrical gold targets, by means of SEM and EDS. The effects of current density, metallic impurity, organic pollution, pre-deposition parameters and mandrel quality on the quality of the gold plating are discussed, along with their mechanisms. The result indicates that the current density must be controlled strictly. The optimal current density ranges from 2.4 to 3.2 mA/cm2 when the concentration of gold ranges from 13 to 22 g/L, and from 2.0 to 2.6 mA/cm2 when the concentration of gold ranges from 5 to 13 g/L. The parameters of predeposition must be optim
2010,
22.
Abstract:
Time-resolved spectra of highly ionized Cr and Ti tracers， which are buried in the inner wall of golden hohlraum， are measured by the streaked crystal spectrometer on the Shenguang Ⅱ laser facility. The collisional radiative model is adopted for non-LTE (local thermodynamic equilibrium) population calculations, and configuration-averaged rate coefficients are obtained based on the first-order perturbation theory. Hartree-Fock Slater self-consistent field method is used to calculate electron wavefunctions. The isoelectronic line-ratio of He-α for Cr and Ti tracers is derived in the electron density range of 1019～1022 cm-3. The evolution of time-resolved electron temperature in hohlraum in the process of laser-plasma interaction is deduced by isoelectronic X-ray spectroscopy
Time-resolved spectra of highly ionized Cr and Ti tracers， which are buried in the inner wall of golden hohlraum， are measured by the streaked crystal spectrometer on the Shenguang Ⅱ laser facility. The collisional radiative model is adopted for non-LTE (local thermodynamic equilibrium) population calculations, and configuration-averaged rate coefficients are obtained based on the first-order perturbation theory. Hartree-Fock Slater self-consistent field method is used to calculate electron wavefunctions. The isoelectronic line-ratio of He-α for Cr and Ti tracers is derived in the electron density range of 1019～1022 cm-3. The evolution of time-resolved electron temperature in hohlraum in the process of laser-plasma interaction is deduced by isoelectronic X-ray spectroscopy
2010,
22.
Abstract:
Multi-channel soft X-ray spectrometers are used to detect the time history of radiation flux in ICF experiments. The responses of the spectrometer channels are linearly combined to get a equivalent flat response in order to calculate the radiation flux without unfolding. To deal with errors caused by the shapes of the spectra and local oscillations of the equivalent flat response, a method with weighting has been introduced. Flux recovery ratios of different methods for different spectrum shapes were compared. The improved method has been used to analyze ICF experiment data, and a modified time history of equivalent temperature was obtained.
Multi-channel soft X-ray spectrometers are used to detect the time history of radiation flux in ICF experiments. The responses of the spectrometer channels are linearly combined to get a equivalent flat response in order to calculate the radiation flux without unfolding. To deal with errors caused by the shapes of the spectra and local oscillations of the equivalent flat response, a method with weighting has been introduced. Flux recovery ratios of different methods for different spectrum shapes were compared. The improved method has been used to analyze ICF experiment data, and a modified time history of equivalent temperature was obtained.
2010,
22.
Abstract:
In order to characterize and specify small-scale local wavefront deformation of optical component, a method based on Wigner distribution function has been proposed, which can describe wavefront deformation in spatial and spatial frequency domain. The relationship between Wigner distribution function and power spectral density is analyzed and thus the specification of small-scale local wavefront deformation is obtained by Wigner distribution function. Simulation and experiment demonstrate the effectiveness of the proposed method. The proposed method can not only identify whether the optical component meets the requirement of inertial confinement fusion(ICF), but also determine the location where small-scale wavefront deformation is unqualified. Thus it provides an effective guide to the rev
In order to characterize and specify small-scale local wavefront deformation of optical component, a method based on Wigner distribution function has been proposed, which can describe wavefront deformation in spatial and spatial frequency domain. The relationship between Wigner distribution function and power spectral density is analyzed and thus the specification of small-scale local wavefront deformation is obtained by Wigner distribution function. Simulation and experiment demonstrate the effectiveness of the proposed method. The proposed method can not only identify whether the optical component meets the requirement of inertial confinement fusion(ICF), but also determine the location where small-scale wavefront deformation is unqualified. Thus it provides an effective guide to the rev
2010,
22.
Abstract:
In order to meet the ignition pulse power requirements for fast ignition, fast ignition drivers being constructed and planned mainly adopt similar technology of segmented primary mirrors as the astronomical telescopes, realizing large-aperture multi-channel laser coherent focusing. Using the geometrical optics tracing and Fourier method to solve the model of tiling focusing, the effect of tiling scale of parabolic mirrors and control precision on focal-spot peak power is studied by theory and numerical simulation. Under certain control precision, the Strehl ratio of far-field focal spot is simulated on 2×2， 3×3 and 4×4 tiling scales of off-axis parabolic mirrors, and the effect of precision error on focal-spot Strehl ratio is statistically analyzed by Monte-Carlo method of normal distr
In order to meet the ignition pulse power requirements for fast ignition, fast ignition drivers being constructed and planned mainly adopt similar technology of segmented primary mirrors as the astronomical telescopes, realizing large-aperture multi-channel laser coherent focusing. Using the geometrical optics tracing and Fourier method to solve the model of tiling focusing, the effect of tiling scale of parabolic mirrors and control precision on focal-spot peak power is studied by theory and numerical simulation. Under certain control precision, the Strehl ratio of far-field focal spot is simulated on 2×2， 3×3 and 4×4 tiling scales of off-axis parabolic mirrors, and the effect of precision error on focal-spot Strehl ratio is statistically analyzed by Monte-Carlo method of normal distr
2010,
22.
Abstract:
The spectrum characteristics of initial phase and unwrapped phase have been analyzed respectively. The differences between the spectrum characteristics show that some high frequency modulation would be led into the unwrapped phase in the iterative process. According to the analysis and comparison, the cut-off frequency of phase filter should be equal to the cut-off frequency of initial phase in frequency-domain. Using this method, a continuous phase plate has been simulated, and the mean square error, energy utilization rate and top non-uniformity which corresponded to the far field spot are 0.267 2, 96.32% and 0.101 2.
The spectrum characteristics of initial phase and unwrapped phase have been analyzed respectively. The differences between the spectrum characteristics show that some high frequency modulation would be led into the unwrapped phase in the iterative process. According to the analysis and comparison, the cut-off frequency of phase filter should be equal to the cut-off frequency of initial phase in frequency-domain. Using this method, a continuous phase plate has been simulated, and the mean square error, energy utilization rate and top non-uniformity which corresponded to the far field spot are 0.267 2, 96.32% and 0.101 2.
2010,
22.
Abstract:
The difficulties in producing long pulse high-power microwave (HPM) with relativistic backward wave oscillators (RBWOs) are analyzed theoretically. The field distributions of a single-mode slow-wave structure (SWS) and an overmoded SWS with the overmode ration of about 3 are calculated and compared, which indicates that the latter can effectively reduce the RF-field on SWS surface under the same energy storage, but the reduction is not as notable as the increase of the overmode ration due to the change of field distribution. An X-band long pulse HPM source using an SWS with the overmode ration of 3 is designed and investigated experimentally. The devices generates 2 GW microwave power with pulse duration of 80 ns at single shot mode, and 1.2 GW microwave power with pulse duration of 100 ns
The difficulties in producing long pulse high-power microwave (HPM) with relativistic backward wave oscillators (RBWOs) are analyzed theoretically. The field distributions of a single-mode slow-wave structure (SWS) and an overmoded SWS with the overmode ration of about 3 are calculated and compared, which indicates that the latter can effectively reduce the RF-field on SWS surface under the same energy storage, but the reduction is not as notable as the increase of the overmode ration due to the change of field distribution. An X-band long pulse HPM source using an SWS with the overmode ration of 3 is designed and investigated experimentally. The devices generates 2 GW microwave power with pulse duration of 80 ns at single shot mode, and 1.2 GW microwave power with pulse duration of 100 ns
2010,
22.
Abstract:
This paper explores the generation and distribution, the influences on electron motion and interactions of the self-magnetic field in the relativistic magnetron. It is found that the electron beams located close to the accelerator are more obviously influenced by the self magnetic field, leading to the speeding in the angular motion of electron beams, and the mode competition intensifies. Meanwhile, if the cathode lays closer to the accelerator, especially in the region adjacent to the 1/4 length of anode, the mode competition will be further intensified.
This paper explores the generation and distribution, the influences on electron motion and interactions of the self-magnetic field in the relativistic magnetron. It is found that the electron beams located close to the accelerator are more obviously influenced by the self magnetic field, leading to the speeding in the angular motion of electron beams, and the mode competition intensifies. Meanwhile, if the cathode lays closer to the accelerator, especially in the region adjacent to the 1/4 length of anode, the mode competition will be further intensified.
2010,
22.
Abstract:
Based on the technology of the collinear phase-matching about three-wave interactions in uniaxial crystal, the phase-match angle, walk-off angle, acceptance angle and effective nonlinear coefficient of the terahertz wave based on difference-frequency generation are calculated under oeo type and oee type phase-matching conditions in AgGaSe2 crystal pumped by CO2 laser. The results show that terahertz wave tunable range is very wide with two types of phase-matching conditions, and the walk-off angles are less than 1°, the acceptance angles are large enough. In the vast majority of terahertz wave region, effective nonlinear coefficient of oee type is much larger than that of oeo type, thus oee type is more suitable to be used in experiments.
Based on the technology of the collinear phase-matching about three-wave interactions in uniaxial crystal, the phase-match angle, walk-off angle, acceptance angle and effective nonlinear coefficient of the terahertz wave based on difference-frequency generation are calculated under oeo type and oee type phase-matching conditions in AgGaSe2 crystal pumped by CO2 laser. The results show that terahertz wave tunable range is very wide with two types of phase-matching conditions, and the walk-off angles are less than 1°, the acceptance angles are large enough. In the vast majority of terahertz wave region, effective nonlinear coefficient of oee type is much larger than that of oeo type, thus oee type is more suitable to be used in experiments.
2010,
22.
Abstract:
The main reasons of causing pulse-shortening in high power microwave devices are qualitatively analyzed. Some important rules for designing a long-pulse relativistic backwardwave oscillator(RBWO) are given. According to the above rules and the basic theory of resonant RBWO, an S-band long-pulse RBWO is designed and investigated both numerically and experimentally. Experimental results show that a 2 GW microwave with pulse duration of 90 ns at single shot mode and 1 GW microwaves with pulse duration of 100 ns at 10 Hz repetition rate mode are obtained. The microwave frequency is 3.6 GHz with dominant mode of TM01, and power conversion efficiency is about 20%. The explosive electron emission in intense RF field between the cut-off neck and the first slow-wave structure (SWS) is one of the
The main reasons of causing pulse-shortening in high power microwave devices are qualitatively analyzed. Some important rules for designing a long-pulse relativistic backwardwave oscillator(RBWO) are given. According to the above rules and the basic theory of resonant RBWO, an S-band long-pulse RBWO is designed and investigated both numerically and experimentally. Experimental results show that a 2 GW microwave with pulse duration of 90 ns at single shot mode and 1 GW microwaves with pulse duration of 100 ns at 10 Hz repetition rate mode are obtained. The microwave frequency is 3.6 GHz with dominant mode of TM01, and power conversion efficiency is about 20%. The explosive electron emission in intense RF field between the cut-off neck and the first slow-wave structure (SWS) is one of the
2010,
22.
Abstract:
A GW level high power combiner is investigated with theoretical analysis, numerical calculation and full wave simulation. The power combiner operates at X band, and is fed by two X-band microwave sources. To meet the requirements of power handling capacity, the overmoding ratio of the operating waveguide in the high microwave sources for combining is 12.7, which gives difficulties for the design of the combiner. This paper focuses on how to design the X band high power combiner based on overmoded waveguides, i.e., the methods for enhancing the transmission efficiency and power handling capacity, while suppressing the higher order modes. The designed power combiner has a power handing capacity higher than 5.6 GW, and its one-way transmission efficiency is above 99.0%. The power handling cap
A GW level high power combiner is investigated with theoretical analysis, numerical calculation and full wave simulation. The power combiner operates at X band, and is fed by two X-band microwave sources. To meet the requirements of power handling capacity, the overmoding ratio of the operating waveguide in the high microwave sources for combining is 12.7, which gives difficulties for the design of the combiner. This paper focuses on how to design the X band high power combiner based on overmoded waveguides, i.e., the methods for enhancing the transmission efficiency and power handling capacity, while suppressing the higher order modes. The designed power combiner has a power handing capacity higher than 5.6 GW, and its one-way transmission efficiency is above 99.0%. The power handling cap
2010,
22.
Abstract:
The test method of the pulse power capacity of microwave attenuators is proposed, which can be summarized to use directional couplers to test and compare. The pending microwave attenuators are placed between two directional couplers which are used to detect the waveforms. With increasing the input microwave power, the waveforms of pulses will change, which is a criterion to estimate the working state of attenuators. The measurement system contains a microwave source, directional couplers, attenuators, detectors, and oscillographs. Primary measurement results show that, at X band, with single pulse of μs duration, the power capacity of ferrite BJ-100 rectangular waveguide attenuator is 50 kW; the power capability of thick film resistance coaxial attenuator exceeds 10 kW.
The test method of the pulse power capacity of microwave attenuators is proposed, which can be summarized to use directional couplers to test and compare. The pending microwave attenuators are placed between two directional couplers which are used to detect the waveforms. With increasing the input microwave power, the waveforms of pulses will change, which is a criterion to estimate the working state of attenuators. The measurement system contains a microwave source, directional couplers, attenuators, detectors, and oscillographs. Primary measurement results show that, at X band, with single pulse of μs duration, the power capacity of ferrite BJ-100 rectangular waveguide attenuator is 50 kW; the power capability of thick film resistance coaxial attenuator exceeds 10 kW.
2010,
22.
Abstract:
The moving coordinate frame finite-difference time-domain (FDTD) method is developed to simulate the propagation of electromagnetic pulses over long distances. The discretized form of moving coordinate frame FDTD scheme in three dimensions is given, and is applied to calculate the propagation of different pulses in rectangular waveguides. The widths of pulses in propagation direction increase when the pulses propagate in the waveguide. Dispersion phenomena appear, and slow parts of the pulses move to the pulse tail. Result comparison between conventional FDTD method and moving coordinate frame FDTD method shows the relative error of less than 0.1%. The proposed method is shown to be accurate with a considerable reduction in time and memory consumption.
The moving coordinate frame finite-difference time-domain (FDTD) method is developed to simulate the propagation of electromagnetic pulses over long distances. The discretized form of moving coordinate frame FDTD scheme in three dimensions is given, and is applied to calculate the propagation of different pulses in rectangular waveguides. The widths of pulses in propagation direction increase when the pulses propagate in the waveguide. Dispersion phenomena appear, and slow parts of the pulses move to the pulse tail. Result comparison between conventional FDTD method and moving coordinate frame FDTD method shows the relative error of less than 0.1%. The proposed method is shown to be accurate with a considerable reduction in time and memory consumption.
2010,
22.
Abstract:
Stable sheet electron beam transport or focusing is critical for the sheet electron beam vacuum electronic device (VED) which is a kind of promising high power device in millimeter and sub-millimeter wave band. This paper proposes a periodic elliptical solenoid structure for the transport of high-elliptical sheet electron beams. The magnetic field of the elliptical solenoid is analyzed, and the conditions for the stable transport of sheet beams in the structure are derived. Particle-in-cell simulations are conducted and verify the conditions.
Stable sheet electron beam transport or focusing is critical for the sheet electron beam vacuum electronic device (VED) which is a kind of promising high power device in millimeter and sub-millimeter wave band. This paper proposes a periodic elliptical solenoid structure for the transport of high-elliptical sheet electron beams. The magnetic field of the elliptical solenoid is analyzed, and the conditions for the stable transport of sheet beams in the structure are derived. Particle-in-cell simulations are conducted and verify the conditions.
2010,
22.
Abstract:
The coupling effect of the low-frequency nonnuclear electromagnetic pulse (EMP) on the electrically large complex object is analyzed. A method of modeling and analysis for the coupling effect is presented based on finite-difference time-domain (FDTD) method. A simulation experiment of low-frequency EMP excitation is carried out on a model with a scale of 1∶1, the coupling characteristic data are analyzed, and a protective method is proposed. The results show the engineering applicability of the modeling and analysis method and the shielding efficiency of the transparent conductive material to coupling effect.
The coupling effect of the low-frequency nonnuclear electromagnetic pulse (EMP) on the electrically large complex object is analyzed. A method of modeling and analysis for the coupling effect is presented based on finite-difference time-domain (FDTD) method. A simulation experiment of low-frequency EMP excitation is carried out on a model with a scale of 1∶1, the coupling characteristic data are analyzed, and a protective method is proposed. The results show the engineering applicability of the modeling and analysis method and the shielding efficiency of the transparent conductive material to coupling effect.
2010,
22.
Abstract:
Behavior and process of oxidization of ultra-fine tungsten wire prepared by electrochemical corrosion technology were studied using SEM photography, energy spectrum, XRD and mechanical property test. It was shown that black-brown oxidized products in the air were complex oxidates where oxygen quantivalence was between +4 and +6. Mass percent of oxygen in the surface of ultra-fine tungsten wire after electrochemical corrosion had already exceeded 1%. While the tungsten wire was oxidating in air, oxygen content in the surface of tungsten wire first increased and then decreased. Regular strips formed on the surface of W wire after electrochemical corrosion, while 10 months after oxidation, irregular striation appeared, and 85 months after fluctuation of both regular strips and irregular stria
Behavior and process of oxidization of ultra-fine tungsten wire prepared by electrochemical corrosion technology were studied using SEM photography, energy spectrum, XRD and mechanical property test. It was shown that black-brown oxidized products in the air were complex oxidates where oxygen quantivalence was between +4 and +6. Mass percent of oxygen in the surface of ultra-fine tungsten wire after electrochemical corrosion had already exceeded 1%. While the tungsten wire was oxidating in air, oxygen content in the surface of tungsten wire first increased and then decreased. Regular strips formed on the surface of W wire after electrochemical corrosion, while 10 months after oxidation, irregular striation appeared, and 85 months after fluctuation of both regular strips and irregular stria
2010,
22.
Abstract:
The coded source can increase the neutron flux while keep good beam collimation in neutron imaging. A computer simulation method for modified uniformly redundant arrays coded neutron source imaging was established and the optical experiments were carried out subsequently. The results indicate that the image can be reconstructed well by the correlation algorithm in coded source imaging. The dimension and resolution of the reconstructed objects are similar with those acquired by single pinhole, and the exposure time is shortened greatly. The impact of non-ideal conditions on image quality was also explored. If the object is placed in a position with magnifying and rotating deviations from ideal conditions, the projection can not match the CCD pixels of the detector and the decoding array, wh
The coded source can increase the neutron flux while keep good beam collimation in neutron imaging. A computer simulation method for modified uniformly redundant arrays coded neutron source imaging was established and the optical experiments were carried out subsequently. The results indicate that the image can be reconstructed well by the correlation algorithm in coded source imaging. The dimension and resolution of the reconstructed objects are similar with those acquired by single pinhole, and the exposure time is shortened greatly. The impact of non-ideal conditions on image quality was also explored. If the object is placed in a position with magnifying and rotating deviations from ideal conditions, the projection can not match the CCD pixels of the detector and the decoding array, wh
2010,
22.
Abstract:
The injection system for the China spallation neutron source (CSNS) rapid cycling synchrotron (RCS) needs two pulsed power supplies bump horizontal power supply (BHPS) and bump vertical power supply (BVPS) to eight painting bump magnets, both of which are programmable pulsed high power supplies. The prototype of the power supplies has been developed. It adopted the insulated gate bipolar transistor (IGBT) H-bridge configuration in a series and parallel topology and phase shifted operating mode in the main circuit, and could output a high power of about 60 MW (3.319 kV, 18 kA) with the equivalent frequency of IGBT topology of 1.843 2 MHz. The problem of average voltage and current in the IGBT has been solved. The prototype adopted an optimized feedback control strategy to achieve high speed
The injection system for the China spallation neutron source (CSNS) rapid cycling synchrotron (RCS) needs two pulsed power supplies bump horizontal power supply (BHPS) and bump vertical power supply (BVPS) to eight painting bump magnets, both of which are programmable pulsed high power supplies. The prototype of the power supplies has been developed. It adopted the insulated gate bipolar transistor (IGBT) H-bridge configuration in a series and parallel topology and phase shifted operating mode in the main circuit, and could output a high power of about 60 MW (3.319 kV, 18 kA) with the equivalent frequency of IGBT topology of 1.843 2 MHz. The problem of average voltage and current in the IGBT has been solved. The prototype adopted an optimized feedback control strategy to achieve high speed
2010,
22.
Abstract:
On EAST, effective ionic charge was routinely computed from line integrated measurements of visible bremsstrahlung. Comparison between the value of effective ionic charge before and after boronization shows that the amount of impurities decreases a lot after boronization. Analysis on a large database of EAST experimental campaign 2009 shows strong linear relationship between effective ionic charge and line radiation of carbon, and the fitting factor varies from 3.4 to 5.8, depending on both plasma current and auxiliary power. The amount of main impurities were compared with each other through UV-VIS spectrum, and the result shows that carbon contributes the most to effective ionic charge than any other light impurities.
On EAST, effective ionic charge was routinely computed from line integrated measurements of visible bremsstrahlung. Comparison between the value of effective ionic charge before and after boronization shows that the amount of impurities decreases a lot after boronization. Analysis on a large database of EAST experimental campaign 2009 shows strong linear relationship between effective ionic charge and line radiation of carbon, and the fitting factor varies from 3.4 to 5.8, depending on both plasma current and auxiliary power. The amount of main impurities were compared with each other through UV-VIS spectrum, and the result shows that carbon contributes the most to effective ionic charge than any other light impurities.
2010,
22.
Abstract:
In order to get an RF electric field which has stable amplitude, phase and frequency, the radio frequency low level control system for HIRFL-CSRe has been constructed at Institute of Modern Physics. To ensure the control of stability, reliability and real-time, analogous modules are mainly used. At the same time, digital module is used to coordinate the modules and compensate for non-linear error of some function modules. The system is consisted of three subsystems-phase stabilizing system amplitude control system and frequency tuning system, and mainly uses the technology as PID, RF phase detect, DSP, FPGA and so on. Low-level control system of HIRFL-CSRe has been tested through a long-term stability experiments and high-power experiments, the control accuracy meeting the amplitude accura
In order to get an RF electric field which has stable amplitude, phase and frequency, the radio frequency low level control system for HIRFL-CSRe has been constructed at Institute of Modern Physics. To ensure the control of stability, reliability and real-time, analogous modules are mainly used. At the same time, digital module is used to coordinate the modules and compensate for non-linear error of some function modules. The system is consisted of three subsystems-phase stabilizing system amplitude control system and frequency tuning system, and mainly uses the technology as PID, RF phase detect, DSP, FPGA and so on. Low-level control system of HIRFL-CSRe has been tested through a long-term stability experiments and high-power experiments, the control accuracy meeting the amplitude accura
2010,
22.
Abstract:
The echo-enabled harmonic generation free electron laser (EEHG FEL) was proposed for producing short wavelength FEL radiation recently. The parameter sensitivity of EEHG FEL is studied through numerical simulation as the main method and analytical calculation. The simulation results are in excellent agreement with the analytical calculation results. The energy spread growth and emittance growth due to the coherent synchrotron radiation (CSR) in dispersing section are estimated and simulation is also done. The results show that the energy spread growth and emittance growth are small and can be ignored.
The echo-enabled harmonic generation free electron laser (EEHG FEL) was proposed for producing short wavelength FEL radiation recently. The parameter sensitivity of EEHG FEL is studied through numerical simulation as the main method and analytical calculation. The simulation results are in excellent agreement with the analytical calculation results. The energy spread growth and emittance growth due to the coherent synchrotron radiation (CSR) in dispersing section are estimated and simulation is also done. The results show that the energy spread growth and emittance growth are small and can be ignored.
2010,
22.
Abstract:
The point spread function (PSF) has been calculated by Monte Carlo method for neutron penumbral imaging in inertial confinement fusion experiments, and the impact of scattered neutrons in the aperture, the chamber and the pipe, and the high density target was analyzed. The neutron penumbral imaging for a planar neutron source was simulated and the image was reconstructed by Wiener method. According to the results, the scattered neutrons in the penumbral-aperture, the chamber and the pipe will only raise the background but not distort the PSF, thus their influence on diagnosis can be ignored. The scattered neutrons in the high density target can smooth the PSF, however, the effect on diagnosis is quite limited.
The point spread function (PSF) has been calculated by Monte Carlo method for neutron penumbral imaging in inertial confinement fusion experiments, and the impact of scattered neutrons in the aperture, the chamber and the pipe, and the high density target was analyzed. The neutron penumbral imaging for a planar neutron source was simulated and the image was reconstructed by Wiener method. According to the results, the scattered neutrons in the penumbral-aperture, the chamber and the pipe will only raise the background but not distort the PSF, thus their influence on diagnosis can be ignored. The scattered neutrons in the high density target can smooth the PSF, however, the effect on diagnosis is quite limited.
2010,
22.
Abstract:
The formation of copper excited state4d′4F9/2 and its transition in the copper plasma induced by laser are studied by the time-resolved spectra technology. The experimental results indicate that the formation of excited state4d′4F9/2 follows different mechanisms, such as recombination of electrons and ions, collision between the elemental species and self-absorption of atomic lines, during the evolution of plasma. When the collision between particles is severe, the excited state4d′4F9/2 transits to low energy states4p′4Do7/2 and4p′4Fo9/2 with the same probability. After 500 ns of plasma radiation, the collision becomes weak, and the excited state4d′4F9/2 mainly transits to4p′4Do7/2 with emitting the characteristic line Cu Ⅰ 359.91 nm.
The formation of copper excited state4d′4F9/2 and its transition in the copper plasma induced by laser are studied by the time-resolved spectra technology. The experimental results indicate that the formation of excited state4d′4F9/2 follows different mechanisms, such as recombination of electrons and ions, collision between the elemental species and self-absorption of atomic lines, during the evolution of plasma. When the collision between particles is severe, the excited state4d′4F9/2 transits to low energy states4p′4Do7/2 and4p′4Fo9/2 with the same probability. After 500 ns of plasma radiation, the collision becomes weak, and the excited state4d′4F9/2 mainly transits to4p′4Do7/2 with emitting the characteristic line Cu Ⅰ 359.91 nm.
2010,
22.
Abstract:
The Tb3+-doped silicate glasses with and without Li+ ions were synthesized by high-temperature melting method. The effects of Li+ ions on the luminescent properties of Tb3+-doped silicate glasses were studied with ultraviolet-visible transmission, emission and decay time spectra. The results show that the Li+ ion co-dopant can increase the emission intensity of Tb3+-doped silicate glasses. Additionally, the optimal Tb3+ dopant concentration can be raised from 12.8% to 15.3% in the silicate glasses with 2.0% Li+ ion co-dopant compared to those without Li+ ions. The reason is tentatively ascribed to nonbridge oxygen. The nonbridge oxygen is propitious to uniform distribution of Tb3+ ions, thereby its increase reduces the energy loss due to nonradiative transition within Tb3+ ions and increas
The Tb3+-doped silicate glasses with and without Li+ ions were synthesized by high-temperature melting method. The effects of Li+ ions on the luminescent properties of Tb3+-doped silicate glasses were studied with ultraviolet-visible transmission, emission and decay time spectra. The results show that the Li+ ion co-dopant can increase the emission intensity of Tb3+-doped silicate glasses. Additionally, the optimal Tb3+ dopant concentration can be raised from 12.8% to 15.3% in the silicate glasses with 2.0% Li+ ion co-dopant compared to those without Li+ ions. The reason is tentatively ascribed to nonbridge oxygen. The nonbridge oxygen is propitious to uniform distribution of Tb3+ ions, thereby its increase reduces the energy loss due to nonradiative transition within Tb3+ ions and increas
2010,
22.
Abstract:
The total-dose irradiation damage effects and post-irradiation annealing behavior of Altera SRAM-based FPGA were investigated in order to assess the anti-radiation level of FPGA devices used in space. Different modules were used to achieve the function of frequency division, and output waveforms of distinct modules changed following the total dose and annealing time. As various programs have different modules, by comparing power currents varying with the total dose and annealing time of different programs, different modules accumulated dose and annealing time were discussed. At the same time, the cause and difference of power current restoration under various annealing temperature were analysed. In the end, high and low level voltages at the output terminal were measured, and their relatio
The total-dose irradiation damage effects and post-irradiation annealing behavior of Altera SRAM-based FPGA were investigated in order to assess the anti-radiation level of FPGA devices used in space. Different modules were used to achieve the function of frequency division, and output waveforms of distinct modules changed following the total dose and annealing time. As various programs have different modules, by comparing power currents varying with the total dose and annealing time of different programs, different modules accumulated dose and annealing time were discussed. At the same time, the cause and difference of power current restoration under various annealing temperature were analysed. In the end, high and low level voltages at the output terminal were measured, and their relatio
2010,
22.
Abstract:
To study the filtering properties of the cylindrical one-dimensional doped photonic crystal, expressions of light wave modes propagating in the crystal are obtained considering the crystal’s radial restriction. Variations of defect mode in TE and TM waves with mode quantum number and impurity optical thickness are calculated. The frequency of defect mode for both waves increases with the mode quantum number increasing, and for both waves of the same pattern it decreases with the impurity optical thickness increasing. The features can be used to realize multi-channel filtering and tunable filtering, respectively.
To study the filtering properties of the cylindrical one-dimensional doped photonic crystal, expressions of light wave modes propagating in the crystal are obtained considering the crystal’s radial restriction. Variations of defect mode in TE and TM waves with mode quantum number and impurity optical thickness are calculated. The frequency of defect mode for both waves increases with the mode quantum number increasing, and for both waves of the same pattern it decreases with the impurity optical thickness increasing. The features can be used to realize multi-channel filtering and tunable filtering, respectively.
2010,
22.
Abstract:
To integrate industrial computed tomography (CT) technology with rapid prototyping (RP) directly, a new method creating an RP slice file directly from industrial CT slicing images is presented. Firstly, through edge extraction and contour de-noising, connecting, thinning and tracing, the basic contour point data of the interior and exterior structure of a sample piece are obtained. Subsequently, matching point pairs between adjacent layers are established, interlayer contours are got by linear interpolation, and then all contours are fitted by cubic B-spline curves. Finally, a CLI file is created after contour point sampling and interior and exterior contour recognizing. The CLI file is then input into an RP system and a product is manufactured. Applications of the method prove that it is
To integrate industrial computed tomography (CT) technology with rapid prototyping (RP) directly, a new method creating an RP slice file directly from industrial CT slicing images is presented. Firstly, through edge extraction and contour de-noising, connecting, thinning and tracing, the basic contour point data of the interior and exterior structure of a sample piece are obtained. Subsequently, matching point pairs between adjacent layers are established, interlayer contours are got by linear interpolation, and then all contours are fitted by cubic B-spline curves. Finally, a CLI file is created after contour point sampling and interior and exterior contour recognizing. The CLI file is then input into an RP system and a product is manufactured. Applications of the method prove that it is
2010,
22.
Abstract:
In order to meet the demand of mini fiber optical gyro for pint-sized devices, the structure of a mini LiNbO3 multi-function integrated optical device (MIOD) is analyzed and optimized. The loss induced by the curvature of S-bend waveguide and the refractive index difference between waveguide and substrate are simulated by beam propagation method software. The bend loss of Sbend waveguide is decreased by adjusting the parameters of annealed proton exchange. Compared with conventional design, longer bend transition section occupying smaller area is realized by replacing the straight output waveguide with S-bend waveguide directly. The chip length is decreased from 20.0 to 12.5 mm, and the package length is 20.0 mm, which is 2/3 of conventional devices. The typical insertion loss of the min
In order to meet the demand of mini fiber optical gyro for pint-sized devices, the structure of a mini LiNbO3 multi-function integrated optical device (MIOD) is analyzed and optimized. The loss induced by the curvature of S-bend waveguide and the refractive index difference between waveguide and substrate are simulated by beam propagation method software. The bend loss of Sbend waveguide is decreased by adjusting the parameters of annealed proton exchange. Compared with conventional design, longer bend transition section occupying smaller area is realized by replacing the straight output waveguide with S-bend waveguide directly. The chip length is decreased from 20.0 to 12.5 mm, and the package length is 20.0 mm, which is 2/3 of conventional devices. The typical insertion loss of the min
2010,
22.
Abstract:
The surface effect in the spectrum measurement of radioactive sources bombarding targets was studied. The existence of surface effect was validated by comparative experiments of Mg bombarded-targets using mixed electron and X-ray source and X-ray source. And the effect not only has a relationship to the electrons but also shows some characteristics of the target surface. It is inferred that there is a stopping layer on the Mg bombarded-target surface through the experiment about the variation of spectra with target storage time, and the stopping layer can stop new-state hydrogen atoms diffusing from the target surface. The spectra of radioactive sources bombarding Re target and burnished and unburnished Mg targets indicate that, the stopping layer may be a new-state hydrogen atom enrichmen
The surface effect in the spectrum measurement of radioactive sources bombarding targets was studied. The existence of surface effect was validated by comparative experiments of Mg bombarded-targets using mixed electron and X-ray source and X-ray source. And the effect not only has a relationship to the electrons but also shows some characteristics of the target surface. It is inferred that there is a stopping layer on the Mg bombarded-target surface through the experiment about the variation of spectra with target storage time, and the stopping layer can stop new-state hydrogen atoms diffusing from the target surface. The spectra of radioactive sources bombarding Re target and burnished and unburnished Mg targets indicate that, the stopping layer may be a new-state hydrogen atom enrichmen
2010,
22.
Abstract:
The single crystal silicon wafers are irradiated by the cumulative Ti: sapphire femtosecond laser pulses in SF6, air or vacuum atmosphere. The evolution of silicon surface microstructures formed in SF6 is investigated. The one-dimensional ripple structures induced by laser pulses are formed on silicon on early stages of irradiation. With increasing number of pulses, the structures gradually evolve into two-dimensional concave-convex structures. The quasi-ordered arrays of spikes with high aspect ratio are formed on silicon after six hundred laser shots irradiation. Compared with the reported results, the spikes show the characteristics of relatively low height and nonobvious ball on their tips. It is believed that gas pressure is primarily responsible for the results. The number density
The single crystal silicon wafers are irradiated by the cumulative Ti: sapphire femtosecond laser pulses in SF6, air or vacuum atmosphere. The evolution of silicon surface microstructures formed in SF6 is investigated. The one-dimensional ripple structures induced by laser pulses are formed on silicon on early stages of irradiation. With increasing number of pulses, the structures gradually evolve into two-dimensional concave-convex structures. The quasi-ordered arrays of spikes with high aspect ratio are formed on silicon after six hundred laser shots irradiation. Compared with the reported results, the spikes show the characteristics of relatively low height and nonobvious ball on their tips. It is believed that gas pressure is primarily responsible for the results. The number density
2010,
22.
Abstract:
Armature and aluminized explosives detonation products were compared based on the conductor working condition of flux compression generators. Detonation conductivity of some mixed explosives was summed up, whose magnetic Reynolds numbers were calculated, and the possibility of using detonation products of high conductivity instead of armature to compress magnetic flux was analyzed. A modified design of helical flux compression generator utilizing detonation products to compress flux was proposed, whose running process and equivalent circuit were acquired. Simulation results indicate that the modified design has a better output performance than the traditional one of the same volume. Furthermore, the modified design is simpler, and some problems such as turn-skipping and flux losses of arma
Armature and aluminized explosives detonation products were compared based on the conductor working condition of flux compression generators. Detonation conductivity of some mixed explosives was summed up, whose magnetic Reynolds numbers were calculated, and the possibility of using detonation products of high conductivity instead of armature to compress magnetic flux was analyzed. A modified design of helical flux compression generator utilizing detonation products to compress flux was proposed, whose running process and equivalent circuit were acquired. Simulation results indicate that the modified design has a better output performance than the traditional one of the same volume. Furthermore, the modified design is simpler, and some problems such as turn-skipping and flux losses of arma
2010,
22.
Abstract:
In order to correct the effect of the atrociousness parameter of monitor on waveform, we made Fourier transform of the signals of source and monitor and got the function of monitor sensitivity and phase with frequency using the signal spectrum of source dividing the signal spectrum of monitor. In measurement, we made Fourier transform of the signal of monitor, multiplied by the function of monitor sensitivity and phase with frequency, then reconstructed the waveform with Fourier reverse transform. The method transforms the time domain signals into frequency domain signals, and then reconstructs the signal with a coefficient determined from calibration. Theoretically, the method can improve the monitor’s spectrum as the standard monitor. It is proved with experiment that this method can re
In order to correct the effect of the atrociousness parameter of monitor on waveform, we made Fourier transform of the signals of source and monitor and got the function of monitor sensitivity and phase with frequency using the signal spectrum of source dividing the signal spectrum of monitor. In measurement, we made Fourier transform of the signal of monitor, multiplied by the function of monitor sensitivity and phase with frequency, then reconstructed the waveform with Fourier reverse transform. The method transforms the time domain signals into frequency domain signals, and then reconstructs the signal with a coefficient determined from calibration. Theoretically, the method can improve the monitor’s spectrum as the standard monitor. It is proved with experiment that this method can re
2010,
22.
Abstract:
The paper introduces the differential and original waveform measurement principles for pulsed E-field, and develops an pulsed E-field sensor based on original waveform measurement along with its theoretical correction model. The sensor consists of antenna, integrator, amplifier and driver, optic-electric/electric-iptic conversion module and transmission module. The time-domain calibration in TEM cell indicates that, its risetime response is shorter than 1.0 ns, and the output pulse width at 90% of the maximum amplitude is wider than 10.0 μs. The output amplitude of the sensor is linear to the electric field intensity in a dynamic range of 20 dB. The measurement capability can be extended to 10 V/m or 50 kV/m by changing the system’s antenna and other relative modules．
The paper introduces the differential and original waveform measurement principles for pulsed E-field, and develops an pulsed E-field sensor based on original waveform measurement along with its theoretical correction model. The sensor consists of antenna, integrator, amplifier and driver, optic-electric/electric-iptic conversion module and transmission module. The time-domain calibration in TEM cell indicates that, its risetime response is shorter than 1.0 ns, and the output pulse width at 90% of the maximum amplitude is wider than 10.0 μs. The output amplitude of the sensor is linear to the electric field intensity in a dynamic range of 20 dB. The measurement capability can be extended to 10 V/m or 50 kV/m by changing the system’s antenna and other relative modules．
2010,
22.
Abstract:
Feed modes affect the parameters of and wave propagation in the linear transformer, while a water dielectric pulse forming line is used to feed the primary coil of the transformer to develop a pulsed driver. With the help of Maxwell software, simulation research on different feed modes was done from a standpoint of field uniformity. Simulation results show that, the current density in the primary coil of a unilateral fed linear transformer distributes non-uniformly, the magnetizing inductance is much larger than ideal values calculated by equivalent formulas, and their ratio, namely, current density magnification coefficient has little influence on the coupling coefficient of the transformer. Tetrahedral feed produces more uniform field but with high cost and complexity. Thus bilateral fee
Feed modes affect the parameters of and wave propagation in the linear transformer, while a water dielectric pulse forming line is used to feed the primary coil of the transformer to develop a pulsed driver. With the help of Maxwell software, simulation research on different feed modes was done from a standpoint of field uniformity. Simulation results show that, the current density in the primary coil of a unilateral fed linear transformer distributes non-uniformly, the magnetizing inductance is much larger than ideal values calculated by equivalent formulas, and their ratio, namely, current density magnification coefficient has little influence on the coupling coefficient of the transformer. Tetrahedral feed produces more uniform field but with high cost and complexity. Thus bilateral fee
2010,
22.
Abstract:
The measurement of short pulse X-ray of high energy produced by Qiangguang Ⅰ accelerator for radiation effect study includes X-ray dose and pulse duration measuring. The thermoluminescence dosemeter (TLD) is used to measure X-ray dose, and the PIN semiconductor detector is employed for recording waveforms of X-ray. The dose rate is calculated out by the results of X-ray dose and pulse duration. By the mathematic model of uncertainty, factors with important effect on X-ray measuring are analyzed. For the measurement uncertainty of X-ray pulse duration is 3.7%, the measuring of X-ray dose with relative standard uncertainty of 25.1% plays a crucial role in determining X-ray dose rate, and the expanded uncertainty of dose rate is about 50.8% with confidence probability of 95%．
The measurement of short pulse X-ray of high energy produced by Qiangguang Ⅰ accelerator for radiation effect study includes X-ray dose and pulse duration measuring. The thermoluminescence dosemeter (TLD) is used to measure X-ray dose, and the PIN semiconductor detector is employed for recording waveforms of X-ray. The dose rate is calculated out by the results of X-ray dose and pulse duration. By the mathematic model of uncertainty, factors with important effect on X-ray measuring are analyzed. For the measurement uncertainty of X-ray pulse duration is 3.7%, the measuring of X-ray dose with relative standard uncertainty of 25.1% plays a crucial role in determining X-ray dose rate, and the expanded uncertainty of dose rate is about 50.8% with confidence probability of 95%．
2010,
22.
Abstract:
The heat dissipation process of GaAs photoconductive semiconductor switch (PCSS) in nonlinear mode has been simulated based on finite difference time domain method (FDTD). Factors affecting the critical frequency, such as location, radius, number of current filament, dimensions of PCSS chip and environment temperature were discussed. The results are as follows: the critical frequency exponentially increases as radius and the number of current filament increases, it decreases exponentially as distance between location of current filament and surface of chip increases and thickness of chip increases. The critical frequency decreases linearly as environment temperature rises in a special range.
The heat dissipation process of GaAs photoconductive semiconductor switch (PCSS) in nonlinear mode has been simulated based on finite difference time domain method (FDTD). Factors affecting the critical frequency, such as location, radius, number of current filament, dimensions of PCSS chip and environment temperature were discussed. The results are as follows: the critical frequency exponentially increases as radius and the number of current filament increases, it decreases exponentially as distance between location of current filament and surface of chip increases and thickness of chip increases. The critical frequency decreases linearly as environment temperature rises in a special range.
2010,
22.
Abstract:
From the T-model’s equivalent circuit, the analytical expressions of charging pulse forming line (PFL) with capacitor through transformer are obtained, based on the assumption that the voltage on magnetization inductance in the equivalent circuit varying a little during the charging process of the PFL from the start to the first charging voltage peak. The loop resistance and the loop inductance are considered in the expressions. The simulation shows that the results of the analytical expressions are in good accordance with those of the simulation from the start of charging to the first charging voltage peak. The expressions are valid as the coupling coefficient of transformer is varied from no more than 0.7 to nearly 1, in the case that the primary capacitance and the equivalent capacita
From the T-model’s equivalent circuit, the analytical expressions of charging pulse forming line (PFL) with capacitor through transformer are obtained, based on the assumption that the voltage on magnetization inductance in the equivalent circuit varying a little during the charging process of the PFL from the start to the first charging voltage peak. The loop resistance and the loop inductance are considered in the expressions. The simulation shows that the results of the analytical expressions are in good accordance with those of the simulation from the start of charging to the first charging voltage peak. The expressions are valid as the coupling coefficient of transformer is varied from no more than 0.7 to nearly 1, in the case that the primary capacitance and the equivalent capacita
