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RSS2006 Vol. 18, No. 09
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2006,
18.
Abstract:
A high-power linearly polarized CW diode-side-pumped Nd:YAlO3(Nd:YAP) laser oscillating at 1 341.4 nm was reported. By analyzing the level structure and characteristics of transition in Nd:YAP crystal, the advantages of Nd:YAP crystal as a kind of working matter medium of 1.3 μm laser were displayed. Different output couplers for the laser were studied by experiment. Finally, a c-axis polarized laser with an output power as high as 121 W at 1 341.4 nm was obtained with a coupler transmittance of 6.5% at the maximum pumping power of 555 W. The beam quality factor was 34, the optical-optical efficiency was 21.8% and the optical slope efficiency was 41%. The a-axis polarized laser at 1 339.2 nm was also successfully obtained at the c-axis polarized laser being instable.
A high-power linearly polarized CW diode-side-pumped Nd:YAlO3(Nd:YAP) laser oscillating at 1 341.4 nm was reported. By analyzing the level structure and characteristics of transition in Nd:YAP crystal, the advantages of Nd:YAP crystal as a kind of working matter medium of 1.3 μm laser were displayed. Different output couplers for the laser were studied by experiment. Finally, a c-axis polarized laser with an output power as high as 121 W at 1 341.4 nm was obtained with a coupler transmittance of 6.5% at the maximum pumping power of 555 W. The beam quality factor was 34, the optical-optical efficiency was 21.8% and the optical slope efficiency was 41%. The a-axis polarized laser at 1 339.2 nm was also successfully obtained at the c-axis polarized laser being instable.
2006,
18.
Abstract:
The influence of the excitation spot area and the scatter concentration on the laser threshold were investigated in the TiO2/Rhodamine B gain media. Frequency-doubled output of a mode-locked Nd:YAG laser(20 Hz repetition rate, 6 ns pulse width) was used as the pump laser. Monte Carlo method with ring laser was used to calculate the threshold gain required for modeling the input-output characteristics in scattering gain media. The model is based on the transient two-level laser equations and includes the detailed spectral properties of the dye gain system. Monte Carlo simulation of random walks is performed in the geometry. The calculated results show that the laser threshold is related to the length of photons in gain media and the possibility of photons reflected from boundary. With the i
The influence of the excitation spot area and the scatter concentration on the laser threshold were investigated in the TiO2/Rhodamine B gain media. Frequency-doubled output of a mode-locked Nd:YAG laser(20 Hz repetition rate, 6 ns pulse width) was used as the pump laser. Monte Carlo method with ring laser was used to calculate the threshold gain required for modeling the input-output characteristics in scattering gain media. The model is based on the transient two-level laser equations and includes the detailed spectral properties of the dye gain system. Monte Carlo simulation of random walks is performed in the geometry. The calculated results show that the laser threshold is related to the length of photons in gain media and the possibility of photons reflected from boundary. With the i
2006,
18.
Abstract:
The time independent rate equations for fiber amplifier were solved by average inversion ratio iteration method. In this paper, a novel arithmetic based on genetic algorithm was proposed to optimize the distributed pump powers and the lengths of fiber segments in kilowatt YDDC fiber amplifier. The standard deviation of maximum temperatures in fiber segments was incorporated into evaluation function. This ensured that the maximum temperature in each fiber segment was identical. Based on the genetic algorithm method, the maximum temperature and standard deviation of maximum temperatures in seven-segment scheme were 126.34 ℃ and 1.95 ℃，compared to 147.12 ℃ and 21.37 ℃ without the optimization process. To eight-segment scheme, the optimized results were 119.76 ℃ and 2.12 ℃. The calculat
The time independent rate equations for fiber amplifier were solved by average inversion ratio iteration method. In this paper, a novel arithmetic based on genetic algorithm was proposed to optimize the distributed pump powers and the lengths of fiber segments in kilowatt YDDC fiber amplifier. The standard deviation of maximum temperatures in fiber segments was incorporated into evaluation function. This ensured that the maximum temperature in each fiber segment was identical. Based on the genetic algorithm method, the maximum temperature and standard deviation of maximum temperatures in seven-segment scheme were 126.34 ℃ and 1.95 ℃，compared to 147.12 ℃ and 21.37 ℃ without the optimization process. To eight-segment scheme, the optimized results were 119.76 ℃ and 2.12 ℃. The calculat
2006,
18.
Abstract:
Considering inhomogeneous heat generation and real heat-transfer conditions, the transient temperature and thermal stress distribution in disk of heat capacity laser pumped by high power LDA are simulated and analyzed by use of finite element methods. Optical distortions and birefringence are computed subsequently. The results indicate that the magnitude of the thermal effect in heat capacity disk laser are seriously underestimated in the condition of the medium not being full-aperturedly pumped. Simulation results also indicate that for the same pump intensity, the temperature and thermal stress distribution are not only related with the medium geometry and the special distribution of pump intensity but also related with filling factor of pump area versus hard aperture of disk. When the f
Considering inhomogeneous heat generation and real heat-transfer conditions, the transient temperature and thermal stress distribution in disk of heat capacity laser pumped by high power LDA are simulated and analyzed by use of finite element methods. Optical distortions and birefringence are computed subsequently. The results indicate that the magnitude of the thermal effect in heat capacity disk laser are seriously underestimated in the condition of the medium not being full-aperturedly pumped. Simulation results also indicate that for the same pump intensity, the temperature and thermal stress distribution are not only related with the medium geometry and the special distribution of pump intensity but also related with filling factor of pump area versus hard aperture of disk. When the f
2006,
18.
Abstract:
The theory of non-Kolmogorov turbulence and the method to measure the scaling exponent of power spectrum are introduced. The experimental investigations of temperature fluctuation near the ground have been conducted in many places. The results show that most of the power spectrum exponents in real atmosphere are unequal to -5/3, and they always vary during the range of -2 and -1. The relativity of power spectrum exponent and the turbulence strength are analyzed. Meanwhile, distributions of power with scale at different turbulence strengths are also analyzed by the method of wavelet transform. As a result, the absolute value of temperature's power spectrum exponent to some extent has the tendency of increasing with the increment of turbulence strength.
The theory of non-Kolmogorov turbulence and the method to measure the scaling exponent of power spectrum are introduced. The experimental investigations of temperature fluctuation near the ground have been conducted in many places. The results show that most of the power spectrum exponents in real atmosphere are unequal to -5/3, and they always vary during the range of -2 and -1. The relativity of power spectrum exponent and the turbulence strength are analyzed. Meanwhile, distributions of power with scale at different turbulence strengths are also analyzed by the method of wavelet transform. As a result, the absolute value of temperature's power spectrum exponent to some extent has the tendency of increasing with the increment of turbulence strength.
2006,
18.
Abstract:
A new way to control the active lap by CMAC (cerebellar model articulation controller) neural network is put forward, based on the controlling system features of nonlinear and muti-variables. Using parameters of lap surface as input variables, pulse voltages of servo control unit as output variables, the function between input and output variables could be fitted by CMAC neural network. To testify this intelligent controlling idea, an experimental platform is constructed, which is composed of an active lap and lap testing system. The lap is controlled by 3 actuate motors with its available changing caliber f420 mm, and the change of lap surface could be measured by 60 micro displacement sensor matrix. The active lap is actuated by a single motor, two motors and three motors respectively, a
A new way to control the active lap by CMAC (cerebellar model articulation controller) neural network is put forward, based on the controlling system features of nonlinear and muti-variables. Using parameters of lap surface as input variables, pulse voltages of servo control unit as output variables, the function between input and output variables could be fitted by CMAC neural network. To testify this intelligent controlling idea, an experimental platform is constructed, which is composed of an active lap and lap testing system. The lap is controlled by 3 actuate motors with its available changing caliber f420 mm, and the change of lap surface could be measured by 60 micro displacement sensor matrix. The active lap is actuated by a single motor, two motors and three motors respectively, a
2006,
18.
Abstract:
Stimulated Raman scattering(SRS) and thermal effect can limit the power scaling of fiber laser. According to rate equations and heat conduction equations, SRS and thermal effect in high power Yb3+ doped double clad fiber laser are studied for two-end pumping and distributed pumping. The power distribution of pump, laser and Stokes in the fiber, the output characteristic of fiber laser, and temperature distribution in the fiber are obtained. The results show that the slope efficiency and maximum output power for distributed pumping are slightly less than the ones for two-end pumping, but the temperature distribution is decreased effectively for distributed pumping. The results are very useful for designing high power fiber lasers.
Stimulated Raman scattering(SRS) and thermal effect can limit the power scaling of fiber laser. According to rate equations and heat conduction equations, SRS and thermal effect in high power Yb3+ doped double clad fiber laser are studied for two-end pumping and distributed pumping. The power distribution of pump, laser and Stokes in the fiber, the output characteristic of fiber laser, and temperature distribution in the fiber are obtained. The results show that the slope efficiency and maximum output power for distributed pumping are slightly less than the ones for two-end pumping, but the temperature distribution is decreased effectively for distributed pumping. The results are very useful for designing high power fiber lasers.
2006,
18.
Abstract:
The quality of pulsed Nd:YAG laser cladding depends on the voltage, electric current, pulse length, pulse frequency, scanning speed, and beam diameter of the Nd:YAG laser. In order to fully conside the effect of these processing parameters and simplify the processes, spot overlap definition is referred. With the help of theoretic analysis, the relationship between spot overlap and three parameters (the pulse frequency, the scanning speed and the beam diameter of the Nd:YAG laser) is formulated. The experiment, which is based on lower carbon steel, is carried out with precoated layer by laser cladding Ni-base alloy. The perfect processing parameters are available,with single pulsed energy and spot overlap separately 6.7 J and 97.4% or 21 J and 69.4%.
The quality of pulsed Nd:YAG laser cladding depends on the voltage, electric current, pulse length, pulse frequency, scanning speed, and beam diameter of the Nd:YAG laser. In order to fully conside the effect of these processing parameters and simplify the processes, spot overlap definition is referred. With the help of theoretic analysis, the relationship between spot overlap and three parameters (the pulse frequency, the scanning speed and the beam diameter of the Nd:YAG laser) is formulated. The experiment, which is based on lower carbon steel, is carried out with precoated layer by laser cladding Ni-base alloy. The perfect processing parameters are available,with single pulsed energy and spot overlap separately 6.7 J and 97.4% or 21 J and 69.4%.
2006,
18.
Abstract:
Based on the nonlinear optics, the theoretical basis of 589 nm laser frequency-summed by 1 064 nm and 1 319 nm laser was analyzed. Phase-matching factor and optimum length of lithium triborate (LBO) crystal were numerically simulated and the corresponding effective sum-frequency coefficient was figured out on this analytic solution. The calculated effective sum-frequency coefficient is 0.952×10-12 m/V at phase matching angles of 90° and 3.39°. A simple and high-effective experimental scheme was designed and Nd:YAG laser pumped by diode output 1 064 nm and 1 319 nm laser, which were summed by pulse synchronization adjustment to generate 589 nm quasi-continuous yellow laser with an average power of 500 mW, the beam quality factor M2 is about 2.1 and the frequency-summed efficiency is 18%.
Based on the nonlinear optics, the theoretical basis of 589 nm laser frequency-summed by 1 064 nm and 1 319 nm laser was analyzed. Phase-matching factor and optimum length of lithium triborate (LBO) crystal were numerically simulated and the corresponding effective sum-frequency coefficient was figured out on this analytic solution. The calculated effective sum-frequency coefficient is 0.952×10-12 m/V at phase matching angles of 90° and 3.39°. A simple and high-effective experimental scheme was designed and Nd:YAG laser pumped by diode output 1 064 nm and 1 319 nm laser, which were summed by pulse synchronization adjustment to generate 589 nm quasi-continuous yellow laser with an average power of 500 mW, the beam quality factor M2 is about 2.1 and the frequency-summed efficiency is 18%.
2006,
18.
Abstract:
A method to determine the atmospheric aerosol model from the spectral relationships of aerosol optical thickness was presented in this paper. The atmospheric aerosol optical thickness were computed by 6S atmospheric radiative transfer model at multiple spectral bands for continental, maritime, urban aerosol model and Junge power-law model. The values computed were compared with the observed values. Then the most suitable atmospheric aerosol model among the several aerosol models was determined by minimizing the standard deviation between the observed values and those of computed values. This method was applied to the data from the sun-photometer measueements in the outskirt of Beijing in 2004. The results show that the actual atmospheric aerosol model was close to urban aerosol model. The
A method to determine the atmospheric aerosol model from the spectral relationships of aerosol optical thickness was presented in this paper. The atmospheric aerosol optical thickness were computed by 6S atmospheric radiative transfer model at multiple spectral bands for continental, maritime, urban aerosol model and Junge power-law model. The values computed were compared with the observed values. Then the most suitable atmospheric aerosol model among the several aerosol models was determined by minimizing the standard deviation between the observed values and those of computed values. This method was applied to the data from the sun-photometer measueements in the outskirt of Beijing in 2004. The results show that the actual atmospheric aerosol model was close to urban aerosol model. The
2006,
18.
Abstract:
Based on the temporal covariance of logarithmic amplitude, analytical expression was obtained for power spectrum of atmospheric scintillation with aperture receiving in the weak fluctuation regime. The effect of the receiving aperture on the power spectrum of atmospheric scintillation was analyzed, the experiment of laser propagation through atmosphere was accomplished and the real power spectrum of atmospheric scintillation was obtained. The theoretical analysis accords well with experiment results. These results show that the power spectrum of atmospheric scintillation with aperture receiving includes low-frequency spectrum and high-frequency components. The amplitude of the low-frequency spectrum is constant. The high-frequency spectrum obeys the power law with an exponent of -11/3. Whe
Based on the temporal covariance of logarithmic amplitude, analytical expression was obtained for power spectrum of atmospheric scintillation with aperture receiving in the weak fluctuation regime. The effect of the receiving aperture on the power spectrum of atmospheric scintillation was analyzed, the experiment of laser propagation through atmosphere was accomplished and the real power spectrum of atmospheric scintillation was obtained. The theoretical analysis accords well with experiment results. These results show that the power spectrum of atmospheric scintillation with aperture receiving includes low-frequency spectrum and high-frequency components. The amplitude of the low-frequency spectrum is constant. The high-frequency spectrum obeys the power law with an exponent of -11/3. Whe
2006,
18.
Abstract:
By simulating amplitude and phase fluctuations induced by atmospheric turbulence, signal fading for coupling space light into single mode fiber is studied in wavefront tip-tilt corrected system. Tracking algorithm of CCD image is studied. Simulation results show that when the ratio of the receiving aperture to the Fried’s parameter is large, the performance of tip-tilt corrected system using centroid tracking algorithm is very poor and the signal fading depth is very large. A gaussian template matching tracking algorithm is proposed and by using this algorithm, the signal fading depth can be reduced greatly when the ratio of the receiving aperture to the Fried’s parameter is large, and that the disadvantage of the performance of large aperture may be inferior to that of small aperture ca
By simulating amplitude and phase fluctuations induced by atmospheric turbulence, signal fading for coupling space light into single mode fiber is studied in wavefront tip-tilt corrected system. Tracking algorithm of CCD image is studied. Simulation results show that when the ratio of the receiving aperture to the Fried’s parameter is large, the performance of tip-tilt corrected system using centroid tracking algorithm is very poor and the signal fading depth is very large. A gaussian template matching tracking algorithm is proposed and by using this algorithm, the signal fading depth can be reduced greatly when the ratio of the receiving aperture to the Fried’s parameter is large, and that the disadvantage of the performance of large aperture may be inferior to that of small aperture ca
2006,
18.
Abstract:
Phase conjugation technology with liquid CH3COCH3 as medium to improve beam quality in double-pass amplifier laser system is experimentally investigated. The results operating at 400 Hz repetition rate show that the thermal effects of the liquid medium can be effectively reduced when the beam scanning system is adopted. A maximum SBS reflectivity of 65% by using liquid CH3COCH3 is achieved at 400 Hz. In addition, the pulse width of laser has been compressed to 5 ns, and the beam quality has been improved.
Phase conjugation technology with liquid CH3COCH3 as medium to improve beam quality in double-pass amplifier laser system is experimentally investigated. The results operating at 400 Hz repetition rate show that the thermal effects of the liquid medium can be effectively reduced when the beam scanning system is adopted. A maximum SBS reflectivity of 65% by using liquid CH3COCH3 is achieved at 400 Hz. In addition, the pulse width of laser has been compressed to 5 ns, and the beam quality has been improved.
2006,
18.
Abstract:
When Hartmann-Shack sensor was assembled with lens array and CCD, the assembly error was produced inevitably. It would greatly reduce the precision of the wavefront measurement. Two types of assembly error of Hartmann-Shack sensor were analyzed and emendation matrix was obtained in this paper. The assembly error would be eliminated with corresponding matrix. The relationship of the relative reconstruction error to the assemble error was obtained by using Monte-Carlo relative reconstruction error simulation technology which provides theoretical basis and specification for assembling of Hartmann-Shack sensor.
When Hartmann-Shack sensor was assembled with lens array and CCD, the assembly error was produced inevitably. It would greatly reduce the precision of the wavefront measurement. Two types of assembly error of Hartmann-Shack sensor were analyzed and emendation matrix was obtained in this paper. The assembly error would be eliminated with corresponding matrix. The relationship of the relative reconstruction error to the assemble error was obtained by using Monte-Carlo relative reconstruction error simulation technology which provides theoretical basis and specification for assembling of Hartmann-Shack sensor.
2006,
18.
Abstract:
This paper theoretically and experimentally investigated the physical process of fast Z-pinch implosion and radiation, carried through 1 D, 2 D radiation magneto-hydrodynamics codes. A series of experimental studies were expanded on facilities of S-300, Angara-5-1 in Russia and “Yang”, Qiangguang-1 in China. Several diagnostic systems were developed for observing radiation Z-pinch plasma. Loads tungsten wire-array of one-layer, two-layer and with deuterium-polymer in core were studied. Emphasizing physical law energy conjugation and implosion, some new experimental results and picture of implosion dynamics were obtained.
This paper theoretically and experimentally investigated the physical process of fast Z-pinch implosion and radiation, carried through 1 D, 2 D radiation magneto-hydrodynamics codes. A series of experimental studies were expanded on facilities of S-300, Angara-5-1 in Russia and “Yang”, Qiangguang-1 in China. Several diagnostic systems were developed for observing radiation Z-pinch plasma. Loads tungsten wire-array of one-layer, two-layer and with deuterium-polymer in core were studied. Emphasizing physical law energy conjugation and implosion, some new experimental results and picture of implosion dynamics were obtained.
2006,
18.
Abstract:
WO3 / polystyrene nanocomposite has been prepared by on-line sonochemical irradiation of an N, N-dimethyll-formamide solution of polystyrene and W(CO)5. WO3 particle sizes are from 20 nm to 50 nm and WO3 particles are distributed evenly throughout polystyrene. The nanocomposite materials are characterized by analytical method such as XPS, TEM, TG and FTIR. On the basis of the obtained data, a possible mechanism of the formation of nanocomposite materials is proposed.
WO3 / polystyrene nanocomposite has been prepared by on-line sonochemical irradiation of an N, N-dimethyll-formamide solution of polystyrene and W(CO)5. WO3 particle sizes are from 20 nm to 50 nm and WO3 particles are distributed evenly throughout polystyrene. The nanocomposite materials are characterized by analytical method such as XPS, TEM, TG and FTIR. On the basis of the obtained data, a possible mechanism of the formation of nanocomposite materials is proposed.
2006,
18.
Abstract:
The stimulated Brillouin scattering (SBS) medium hexachlorobuta-1,3-diene (C4Cl6) with little absorption coefficient is studied in terms of the absorption theory of medium to the light. Through basic physical parameters, the SBS parameters of C4Cl6 with the incident beam wavelength of 1 064 nm are determined. The absorption coefficient is 0.003 cm-1, the phonon lifetime is 0.25 ns and the gain coefficient is 4.9 cm·GW-1. Whereas the Brillouin frequency is inversely proportional to the incident beam wavelength and the phonon is proportional to its square, the gain coefficient is wavelength-independent. In the single-cell SBS system pumped by Nd:YAG Q-switched laser, the SBS performances of C4Cl6 are studied. The results show that the saturation energy reflectivity of C4Cl6 is above 55%, we
The stimulated Brillouin scattering (SBS) medium hexachlorobuta-1,3-diene (C4Cl6) with little absorption coefficient is studied in terms of the absorption theory of medium to the light. Through basic physical parameters, the SBS parameters of C4Cl6 with the incident beam wavelength of 1 064 nm are determined. The absorption coefficient is 0.003 cm-1, the phonon lifetime is 0.25 ns and the gain coefficient is 4.9 cm·GW-1. Whereas the Brillouin frequency is inversely proportional to the incident beam wavelength and the phonon is proportional to its square, the gain coefficient is wavelength-independent. In the single-cell SBS system pumped by Nd:YAG Q-switched laser, the SBS performances of C4Cl6 are studied. The results show that the saturation energy reflectivity of C4Cl6 is above 55%, we
2006,
18.
Abstract:
ZrO2 sol was obtained by using hydrothermal synthesis. Thin ZrO2 films and ZrO2-PVP composite films were prepared with spin coating method. Both the ZrO2 films and ZrO2-PVP composite films were characterized by ellipsometer, FTIR, AFM respectively. The crystallization behavior of ZrO2 xerogels was examined by X-ray diffraction. And 1-on-1 laser-induced damage threshold tests on ZrO2 films and ZrO2-PVP composite films were carried out with a Q-switched Nd:YAG high power laser at 1 064 nm with a pulse width of 10 ns. The measured laser-induced damage threshold of ZrO2 films with heat treatment at 300 ℃ for 60 min was 24.5 J/cm2, and 37.5 J/cm2 for that of ZrO2-PVP composite films. The experimental results show that the incorporating organic binder PVP (polyvinyl pyrrolidone), without obviou
ZrO2 sol was obtained by using hydrothermal synthesis. Thin ZrO2 films and ZrO2-PVP composite films were prepared with spin coating method. Both the ZrO2 films and ZrO2-PVP composite films were characterized by ellipsometer, FTIR, AFM respectively. The crystallization behavior of ZrO2 xerogels was examined by X-ray diffraction. And 1-on-1 laser-induced damage threshold tests on ZrO2 films and ZrO2-PVP composite films were carried out with a Q-switched Nd:YAG high power laser at 1 064 nm with a pulse width of 10 ns. The measured laser-induced damage threshold of ZrO2 films with heat treatment at 300 ℃ for 60 min was 24.5 J/cm2, and 37.5 J/cm2 for that of ZrO2-PVP composite films. The experimental results show that the incorporating organic binder PVP (polyvinyl pyrrolidone), without obviou
2006,
18.
Abstract:
The high energy density self-healing metallized film pulse capacitor has been applied to all kinds of laser facilities for their power conditioning systems, whose reliability and expense are straightforwardly affected by the reliability level of capacitors. Reliability analysis of highly reliable devices, such as metallized film capacitors, is a challenge due to cost and time restriction. Accelerated degradation testing provides a way to predict its life cost and time effectively. A model and analysis based on accelerated degradation data of metallized film capacitors are described. Also described is a method for estimating the distribution of time to failure. The estimation values of the unknown parameters in this model are 9.066 9×10-8 and 0.022 1, respectively. Both the failure probabi
The high energy density self-healing metallized film pulse capacitor has been applied to all kinds of laser facilities for their power conditioning systems, whose reliability and expense are straightforwardly affected by the reliability level of capacitors. Reliability analysis of highly reliable devices, such as metallized film capacitors, is a challenge due to cost and time restriction. Accelerated degradation testing provides a way to predict its life cost and time effectively. A model and analysis based on accelerated degradation data of metallized film capacitors are described. Also described is a method for estimating the distribution of time to failure. The estimation values of the unknown parameters in this model are 9.066 9×10-8 and 0.022 1, respectively. Both the failure probabi
2006,
18.
Abstract:
Based on the classical electromagnetic radiation theory, the spectral characteristics of 90° linear Thomson scattering with linearly polarized few-cycle laser pulses were obtained. The research results showed that the fewer the cycle number of the few-cycle pulse was, the wider the scattering spectrum and the weaker the center intensity of the spectrum were, and the spectral width was proportional to the square of the electronic relativity factor, as well as the incidence pulse frequency. The spectral intensity was proportional to the square of the product of normalized light field intensity and electronic relativity factor. The carrier-envelope function could widen radiation spectrum further and make the spectrum symmetry better and eliminate the oscillation of spectrum. The spectral int
Based on the classical electromagnetic radiation theory, the spectral characteristics of 90° linear Thomson scattering with linearly polarized few-cycle laser pulses were obtained. The research results showed that the fewer the cycle number of the few-cycle pulse was, the wider the scattering spectrum and the weaker the center intensity of the spectrum were, and the spectral width was proportional to the square of the electronic relativity factor, as well as the incidence pulse frequency. The spectral intensity was proportional to the square of the product of normalized light field intensity and electronic relativity factor. The carrier-envelope function could widen radiation spectrum further and make the spectrum symmetry better and eliminate the oscillation of spectrum. The spectral int
2006,
18.
Abstract:
For uniform irradiation in ICF, a non-contact target is the key technology. A magnetic suspension system is one of the best ways. In this paper a magnetic suspension system is primarily designed and a phase-lead controller operating in the inner loop is utilized to stabilize the magnetic suspension system. In simulation, the ball vibrates slightly in the first 10 ms, then stabilizes gradually and eventually reaches the set position. The result shows that the system can work stably and the magnetic suspension for ICF target is feasible.
For uniform irradiation in ICF, a non-contact target is the key technology. A magnetic suspension system is one of the best ways. In this paper a magnetic suspension system is primarily designed and a phase-lead controller operating in the inner loop is utilized to stabilize the magnetic suspension system. In simulation, the ball vibrates slightly in the first 10 ms, then stabilizes gradually and eventually reaches the set position. The result shows that the system can work stably and the magnetic suspension for ICF target is feasible.
2006,
18.
Abstract:
In fast ignition mode by exploding push, the fuel is first compressed by a conventional inertial confinement fusion driver, producing a low density hotspot surrounded by a relatively cold and dense main fuel region, and then a short (about 10 ps) pulse, high-power laser is injected, the suprathermal electrons heat the cold region, and the cold shell explodes, compressing and heating the hot-spot. The analysis in this paper shows that the compressing rate of hot-spot is 64, neutron yield is about two orders of magnitude greater than before, and the energy gain is 3 times increased. But the ion temperature is increased slightly, for the mass of cold region is too large. If the mass of cold region is decreased or the energy of relativistic electrons is increased above 10 kJ, the rise of ion t
In fast ignition mode by exploding push, the fuel is first compressed by a conventional inertial confinement fusion driver, producing a low density hotspot surrounded by a relatively cold and dense main fuel region, and then a short (about 10 ps) pulse, high-power laser is injected, the suprathermal electrons heat the cold region, and the cold shell explodes, compressing and heating the hot-spot. The analysis in this paper shows that the compressing rate of hot-spot is 64, neutron yield is about two orders of magnitude greater than before, and the energy gain is 3 times increased. But the ion temperature is increased slightly, for the mass of cold region is too large. If the mass of cold region is decreased or the energy of relativistic electrons is increased above 10 kJ, the rise of ion t
2006,
18.
Abstract:
This paper introduces fabrication of polystyrene and aluminum surface perturbation targets used for flank illumination Rayleigh-Taylor instability experiment. By figure transfer, incising targets, controlling constructional technique and measuring targets' parameters, we obtained surface perturbation targets with sinusoidal surface perturbation figures with thickness of several tens micrometer, the wavelength about 50 micrometer and amplitude from several to several tens micrometer. The width of two kinds of eargets is about 200 micrometer and the profile is clear.
This paper introduces fabrication of polystyrene and aluminum surface perturbation targets used for flank illumination Rayleigh-Taylor instability experiment. By figure transfer, incising targets, controlling constructional technique and measuring targets' parameters, we obtained surface perturbation targets with sinusoidal surface perturbation figures with thickness of several tens micrometer, the wavelength about 50 micrometer and amplitude from several to several tens micrometer. The width of two kinds of eargets is about 200 micrometer and the profile is clear.
2006,
18.
Abstract:
The monolayer water soluble thiol pretected cluster is doped in the agar-gelatin complex foam target materials. The TEM photographes indicate that, after doping, the density along axial direction of the complex foam is uniform and the microstructure of the complex foam is not affected evidently by Au MPC. When the density of the doped foam is as low as 5.8 mg/cm3 and the mass percent of the dopant is as high as 30%, Au MPC does not assemble or sedimentate in the agar-gelatin foam. The preparation procedure of Au MPC doped agar-gelatin complex foam is studied, and the doped foams with the density less than 10 mg/cm3, cell sizes less than 100 mm are prepared with water as the solvent.
The monolayer water soluble thiol pretected cluster is doped in the agar-gelatin complex foam target materials. The TEM photographes indicate that, after doping, the density along axial direction of the complex foam is uniform and the microstructure of the complex foam is not affected evidently by Au MPC. When the density of the doped foam is as low as 5.8 mg/cm3 and the mass percent of the dopant is as high as 30%, Au MPC does not assemble or sedimentate in the agar-gelatin foam. The preparation procedure of Au MPC doped agar-gelatin complex foam is studied, and the doped foams with the density less than 10 mg/cm3, cell sizes less than 100 mm are prepared with water as the solvent.
2006,
18.
Abstract:
Problems in the electro-optical system in high peak power multi-beam klystrons are analyzed. The electro-optical system of an S-band 50 MW klystron is designed by using an indirect method. Respective shield barrels are used to generate side-symmetrical magnetic field in the cathode-anode area. With the combination of 2D electron-optical code EGUN, 3D electromagnetic code MAFIA and 3D PIC (particle-in-cell) code, the electro-optical system is modeled in detail. The result shows that the shield barrels could generate side-symmetrical magnetic field, and that the track of electrons is perfect.
Problems in the electro-optical system in high peak power multi-beam klystrons are analyzed. The electro-optical system of an S-band 50 MW klystron is designed by using an indirect method. Respective shield barrels are used to generate side-symmetrical magnetic field in the cathode-anode area. With the combination of 2D electron-optical code EGUN, 3D electromagnetic code MAFIA and 3D PIC (particle-in-cell) code, the electro-optical system is modeled in detail. The result shows that the shield barrels could generate side-symmetrical magnetic field, and that the track of electrons is perfect.
2006,
18.
Abstract:
An electromagnetic topological model used to analyze the interaction of the different electrical components is presented. Combining this model with the algorithm which may find the kth shortest path, an algorithm that can find the paths whose shielding electromagnetic values from source node to destination node are less than prescribed value under different frequency range is obtained. The electromagnetic coupling paths needed to be improved can be got with this algorithm.
An electromagnetic topological model used to analyze the interaction of the different electrical components is presented. Combining this model with the algorithm which may find the kth shortest path, an algorithm that can find the paths whose shielding electromagnetic values from source node to destination node are less than prescribed value under different frequency range is obtained. The electromagnetic coupling paths needed to be improved can be got with this algorithm.
2006,
18.
Abstract:
The receiving electric fields of the slot antenna array with different element number and different adjcent element spacing were measured using self-built time domain measurement system. The time domain waveform, normalized energy pattern and normalized peak-amplitude pattern were presented. The analysis results show that the amplitude of the received waveform becomes smaller with the increase of the observation angle off boresight. The antenna array characteristics in some plane are concerned with the elements number and adjacent element spacing of this plane. The more the integrated elements are and the larger the adjcent elements spacing is, the narrower the directional pattern beamwidth is.
The receiving electric fields of the slot antenna array with different element number and different adjcent element spacing were measured using self-built time domain measurement system. The time domain waveform, normalized energy pattern and normalized peak-amplitude pattern were presented. The analysis results show that the amplitude of the received waveform becomes smaller with the increase of the observation angle off boresight. The antenna array characteristics in some plane are concerned with the elements number and adjacent element spacing of this plane. The more the integrated elements are and the larger the adjcent elements spacing is, the narrower the directional pattern beamwidth is.
2006,
18.
Abstract:
This paper presents the results from simulative and experimental studies of backward wave oscillator(BWO) with resonant reflector operating at low magnetic field. The influence of drift tube length between the resonant reflector and the slow wave structure on the efficiency of the BWO is studied. Simulation and experimental results indicate that because of the pre-modulation effect of resonant reflector, there are several efficiency spikes at optimum drift lengths. When the applied magnetic field was 0.7 T and the drift length was 4.9 cm in the experiment, the microwave power of 700 MW with 8.7 GHz frequency and 20 ns pulse width was obtained.
This paper presents the results from simulative and experimental studies of backward wave oscillator(BWO) with resonant reflector operating at low magnetic field. The influence of drift tube length between the resonant reflector and the slow wave structure on the efficiency of the BWO is studied. Simulation and experimental results indicate that because of the pre-modulation effect of resonant reflector, there are several efficiency spikes at optimum drift lengths. When the applied magnetic field was 0.7 T and the drift length was 4.9 cm in the experiment, the microwave power of 700 MW with 8.7 GHz frequency and 20 ns pulse width was obtained.
2006,
18.
Abstract:
Studying the high frequency properties of serpentine circular groove guide slow wave structure (SWS), the dispersion curves and interaction impedance are obtained by theoretic analysis and numerical computation. It is analyzed that the change of the structure parameter affects dispersion properties and interaction impedance. It shows that, dispersion property weakens and interaction impedance increases as the pitch L decreases. Though dispersion property weakens as the length of straight guide H increases, the interaction impedance still decreases. Therefore, short period is in favor of improving the high frequency properties of serpentine circular groove guide slow wave circuit, whereas the low interaction impedance of the circuit, interaction impedance can be improved by decreasing H pro
Studying the high frequency properties of serpentine circular groove guide slow wave structure (SWS), the dispersion curves and interaction impedance are obtained by theoretic analysis and numerical computation. It is analyzed that the change of the structure parameter affects dispersion properties and interaction impedance. It shows that, dispersion property weakens and interaction impedance increases as the pitch L decreases. Though dispersion property weakens as the length of straight guide H increases, the interaction impedance still decreases. Therefore, short period is in favor of improving the high frequency properties of serpentine circular groove guide slow wave circuit, whereas the low interaction impedance of the circuit, interaction impedance can be improved by decreasing H pro
2006,
18.
Abstract:
A novel photonic-band-gap(PBG) Vlasov antenna is designed. The antenna is surrounded by a metallic PBG structure which is formed by square arrays of metal posts. The lowest global band gap of the two-dimensional PBG structure is determined numerically, and the gap is used to reflect and focus the antenna radiation. By numerical computation and experimental measurement, the radiation patterns of the PBG Vlasov antenna have been presented. Moreover, the numerical and experimental results both show that the maximum gain of the PBG antenna has a 2~3 dB addition.
A novel photonic-band-gap(PBG) Vlasov antenna is designed. The antenna is surrounded by a metallic PBG structure which is formed by square arrays of metal posts. The lowest global band gap of the two-dimensional PBG structure is determined numerically, and the gap is used to reflect and focus the antenna radiation. By numerical computation and experimental measurement, the radiation patterns of the PBG Vlasov antenna have been presented. Moreover, the numerical and experimental results both show that the maximum gain of the PBG antenna has a 2~3 dB addition.
2006,
18.
Abstract:
The iterative formulas in Vaughan’s iterative method are discussed and more logical ones are proposed. This improved iterative synthesis method will never be limited to the convergent Pierce electron guns with low convergence or the initial value of the convergence half angle. And 13 practical cases numerically show that, even if its initial value of convergence half angle arbitrarily varies in the range of 0°~70°, the proposed method would get reasonable results in the case of low, normal or high-convergence. The proposed method’s results of guns with normal and high-convergence agree well with that of Vaughan’s method, and the results of guns with extremely low convergence are well consistent with the corresponding actual values.
The iterative formulas in Vaughan’s iterative method are discussed and more logical ones are proposed. This improved iterative synthesis method will never be limited to the convergent Pierce electron guns with low convergence or the initial value of the convergence half angle. And 13 practical cases numerically show that, even if its initial value of convergence half angle arbitrarily varies in the range of 0°~70°, the proposed method would get reasonable results in the case of low, normal or high-convergence. The proposed method’s results of guns with normal and high-convergence agree well with that of Vaughan’s method, and the results of guns with extremely low convergence are well consistent with the corresponding actual values.
2006,
18.
Abstract:
The microwave radiation effects on a personal computer are investigated experimentally in the frequency range from 1.2 to 2.0 GHz. The microwave power threshold for the computer to be crashed is studied under various microwave carrier frequencies, modulation types and modulation degrees. The microwave power thresholds are obtained under 4 computer operating states, the full CPU load, the disk operating, the memory reading and writing and the system idle. The microwave radiation effect on the computer during system booting is also studied. The experimental results show that when the microwave carrier frequency is 1.47 GHz, the computer is interfered most easily. At low modulation frequency, the instantaneous microwave power is the key effect factor of the microwave radiation on the personal
The microwave radiation effects on a personal computer are investigated experimentally in the frequency range from 1.2 to 2.0 GHz. The microwave power threshold for the computer to be crashed is studied under various microwave carrier frequencies, modulation types and modulation degrees. The microwave power thresholds are obtained under 4 computer operating states, the full CPU load, the disk operating, the memory reading and writing and the system idle. The microwave radiation effect on the computer during system booting is also studied. The experimental results show that when the microwave carrier frequency is 1.47 GHz, the computer is interfered most easily. At low modulation frequency, the instantaneous microwave power is the key effect factor of the microwave radiation on the personal
2006,
18.
Abstract:
A new method to calculate the equivalent relative dielectric constant of the dielectric loaded ring-plane slow-wave structure is proposed. Expressions of dispersion equation and interaction impedance are derived for dielectric loaded ring-plane slow-wave structure by variational method. The results manifest that the dielectric-loading can lower the operating voltage of the ring-plane slow-wave structure. Good accordance was obtained between results by this method and that of CST-MWS.
A new method to calculate the equivalent relative dielectric constant of the dielectric loaded ring-plane slow-wave structure is proposed. Expressions of dispersion equation and interaction impedance are derived for dielectric loaded ring-plane slow-wave structure by variational method. The results manifest that the dielectric-loading can lower the operating voltage of the ring-plane slow-wave structure. Good accordance was obtained between results by this method and that of CST-MWS.
2006,
18.
Abstract:
The relativistic backward-wave oscillator (RBWO) with inner coaxial disk-loaded slow-wave structure (SWS) is studied. The dispersion relation of the SWS is deduced by using the Borgnis’s potential function method according to Maxwell’s equation and Floquet theory. Numerical analysis is carried out and the dispersion curves are gotten. The beam-wave interaction of the device is simulated and optimized by PIC method. The effect of the longitudinal magnetic field, the distance r1 between beam and SWS, the depth r2 of loaded-disk and the distance of two next disks are discussed in detail. The results show that increasing the periodic length can decrease the cut-off frequency and the operating frequency of the same mode and that the variation of the inner conductor radius almost has no effect
The relativistic backward-wave oscillator (RBWO) with inner coaxial disk-loaded slow-wave structure (SWS) is studied. The dispersion relation of the SWS is deduced by using the Borgnis’s potential function method according to Maxwell’s equation and Floquet theory. Numerical analysis is carried out and the dispersion curves are gotten. The beam-wave interaction of the device is simulated and optimized by PIC method. The effect of the longitudinal magnetic field, the distance r1 between beam and SWS, the depth r2 of loaded-disk and the distance of two next disks are discussed in detail. The results show that increasing the periodic length can decrease the cut-off frequency and the operating frequency of the same mode and that the variation of the inner conductor radius almost has no effect
2006,
18.
Abstract:
A cavity beam position monitor (BPM) is designed for the injector of PKU-FEL Facility. The designed frequency of the dipole mode TM110 is 1.3 GHz, which is equal to the frequency of the main accelerator in PKU-FEL Facility. The cross-talk problem is solved by introducing two rectangular recesses into the cavity. The position resolution of the cavity BPM is about 10 mm, the dynamic range is more than 30 mm and the time response is bunch to bunch, which are sufficient for the PKU-FEL injector. Compared with the bunch power, the power dissipation of the main resonant modes excited by e-bunches can be neglected.
A cavity beam position monitor (BPM) is designed for the injector of PKU-FEL Facility. The designed frequency of the dipole mode TM110 is 1.3 GHz, which is equal to the frequency of the main accelerator in PKU-FEL Facility. The cross-talk problem is solved by introducing two rectangular recesses into the cavity. The position resolution of the cavity BPM is about 10 mm, the dynamic range is more than 30 mm and the time response is bunch to bunch, which are sufficient for the PKU-FEL injector. Compared with the bunch power, the power dissipation of the main resonant modes excited by e-bunches can be neglected.
2006,
18.
Abstract:
The design of the trigger based on complex programmable logic device(CPLD), the driver circuit and the residual current device(RCD) circuit of MOSFET pulse modulator were introduced, and the parallel-switch and inductive-adder MOSFET modulators were experimentally studied. The push-pull output circuit made up of a pair of MOSFETs was used in the driver circuit. The Pspice simulation results indicated that the peak inverse voltage on MOSFET switch could be clamped by RCD. A pulse current with an amplitude of 13 A, a rise time of 20 ns and a flat top time of 80 ns was obtained on the load of 30 Ω when 3 parallel MOSFET modulator was adopted as the switch and the charge voltage was 450 V, while the amplitude of the obtained pulse was 40 A, the rise time 25 ns and flat top time 70 ns on the l
The design of the trigger based on complex programmable logic device(CPLD), the driver circuit and the residual current device(RCD) circuit of MOSFET pulse modulator were introduced, and the parallel-switch and inductive-adder MOSFET modulators were experimentally studied. The push-pull output circuit made up of a pair of MOSFETs was used in the driver circuit. The Pspice simulation results indicated that the peak inverse voltage on MOSFET switch could be clamped by RCD. A pulse current with an amplitude of 13 A, a rise time of 20 ns and a flat top time of 80 ns was obtained on the load of 30 Ω when 3 parallel MOSFET modulator was adopted as the switch and the charge voltage was 450 V, while the amplitude of the obtained pulse was 40 A, the rise time 25 ns and flat top time 70 ns on the l
2006,
18.
Abstract:
The effects due to the stray field from Lambertson septum magnet are important, including beam high order resonance and unstable effect, etc, The 3D numerical simulations with OPERA3D/TOSCA code and the optimizing processes of design of Lambertson septum magnet were described in this paper. The simulations were performed for different models so that we could decrease the ratio of integrated stray field to integrated main field. After optimization of design, including increasing the thickness of septum to 15 mm and adding a shielding hat with radius of 200 mm and thickness of 10 mm, the ratios of transverse stray field to main field were 0.8‰(in y direction) and 0.36‰(in x direction). The results were satisfactory to the requirement of RCS beam dynamics.
The effects due to the stray field from Lambertson septum magnet are important, including beam high order resonance and unstable effect, etc, The 3D numerical simulations with OPERA3D/TOSCA code and the optimizing processes of design of Lambertson septum magnet were described in this paper. The simulations were performed for different models so that we could decrease the ratio of integrated stray field to integrated main field. After optimization of design, including increasing the thickness of septum to 15 mm and adding a shielding hat with radius of 200 mm and thickness of 10 mm, the ratios of transverse stray field to main field were 0.8‰(in y direction) and 0.36‰(in x direction). The results were satisfactory to the requirement of RCS beam dynamics.
2006,
18.
Abstract:
The distortion of closed orbit usually causes much side effect which is harmful to synchrotron radiation source such as HLS, so it is necessary to correct the distortion of closed orbit. In this paper, the correction principle, development procedure and test of MATLAB based on beam orbit correction system of HLS storage ring are described. The correction system is consisted of the beam orbit measure system, corrector magnet system and the control system, and the beam orbit correction code based on MATLAB is working on the operation interface. The data of the beam orbit are analyzed and calculated firstly, and then the orbit is corrected by changing corrector strength via control system. The test shows that the distortion of closed orbit is from max 4.468 mm before correction to max 0.299 m
The distortion of closed orbit usually causes much side effect which is harmful to synchrotron radiation source such as HLS, so it is necessary to correct the distortion of closed orbit. In this paper, the correction principle, development procedure and test of MATLAB based on beam orbit correction system of HLS storage ring are described. The correction system is consisted of the beam orbit measure system, corrector magnet system and the control system, and the beam orbit correction code based on MATLAB is working on the operation interface. The data of the beam orbit are analyzed and calculated firstly, and then the orbit is corrected by changing corrector strength via control system. The test shows that the distortion of closed orbit is from max 4.468 mm before correction to max 0.299 m
2006,
18.
Abstract:
To improve the acceleration properties of the niobium cavities and niobium-sputtered copper cavities, studies are carried out. For niobium-sputtered copper cavities, by adding a layer of NbN between the copper and niobium, the transition temperature of the superconducting film can be increased so that the superconducting properties can be improved. Analysis shows that the accelerating gradient can be improved by preparing SIS multilayers on the surface of the superconducting cavities.
To improve the acceleration properties of the niobium cavities and niobium-sputtered copper cavities, studies are carried out. For niobium-sputtered copper cavities, by adding a layer of NbN between the copper and niobium, the transition temperature of the superconducting film can be increased so that the superconducting properties can be improved. Analysis shows that the accelerating gradient can be improved by preparing SIS multilayers on the surface of the superconducting cavities.
