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RSS2007 Vol. 19, No. 09
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2007,
19.
Abstract:
A novel power scaling solution based on helical-core fiber for high-power fiber lasers is introduced. The operation principle of this helical-core fiber laser and its latest theoretical and experimental development are specified. The power scaling ability of helical-core fiber laser is explored and an idea of coherently combining fiber lasers based on multi-helical-core fiber for further power scaling is presented.
A novel power scaling solution based on helical-core fiber for high-power fiber lasers is introduced. The operation principle of this helical-core fiber laser and its latest theoretical and experimental development are specified. The power scaling ability of helical-core fiber laser is explored and an idea of coherently combining fiber lasers based on multi-helical-core fiber for further power scaling is presented.
2007,
19.
Abstract:
By using an external cavity, a commercially available broad-stripe semiconductor diode laser array(DLA) has been phase locked. Measurements show that the spectral width of the phase-locked DLA is reduced to 0.16 nm compared to 1.9 nm of the free-running DLA, and the peak wavelength is shifted from 803.8 nm to 805.5 nm. An angular spacing between the lobes of the far field pattern of 1.6 mrad, coincident with the ratio of the wavelength to emitter distance, indicates that the DLA is operated in the fundamental(or highest) super mode. The modulation depth of the peak-valley pattern is measured to be larger than 0.8. It has also been verified that phase locking can be achieved for external cavity length between 1/10 to 1/16 of the Talbot distance zT. Based on experimental facts, it is believe
By using an external cavity, a commercially available broad-stripe semiconductor diode laser array(DLA) has been phase locked. Measurements show that the spectral width of the phase-locked DLA is reduced to 0.16 nm compared to 1.9 nm of the free-running DLA, and the peak wavelength is shifted from 803.8 nm to 805.5 nm. An angular spacing between the lobes of the far field pattern of 1.6 mrad, coincident with the ratio of the wavelength to emitter distance, indicates that the DLA is operated in the fundamental(or highest) super mode. The modulation depth of the peak-valley pattern is measured to be larger than 0.8. It has also been verified that phase locking can be achieved for external cavity length between 1/10 to 1/16 of the Talbot distance zT. Based on experimental facts, it is believe
2007,
19.
Abstract:
The calculating procedure that ethanol (C2H6O) reacting with Hydrogen peroxide (H2O2) was deduced based on chemical theory and characters of C2H6O and H2O2. An experimental gas generator installation was established and applied to research the self-ignition behavior of ethanol while it was injected into hot oxidizing gas mixture produced by decomposing of H2O2 with high concentration. The impacts of different spray nozzle types and injecting pressures on temperature uniformity of the exhausted flow field of the gas generator were studied experimentally. Test results suggested that the autogenous combustion can be realized and the calculation method can be used to predict the performance of a gas generator adequately.
The calculating procedure that ethanol (C2H6O) reacting with Hydrogen peroxide (H2O2) was deduced based on chemical theory and characters of C2H6O and H2O2. An experimental gas generator installation was established and applied to research the self-ignition behavior of ethanol while it was injected into hot oxidizing gas mixture produced by decomposing of H2O2 with high concentration. The impacts of different spray nozzle types and injecting pressures on temperature uniformity of the exhausted flow field of the gas generator were studied experimentally. Test results suggested that the autogenous combustion can be realized and the calculation method can be used to predict the performance of a gas generator adequately.
2007,
19.
Abstract:
Using Fourier model method, the near-field distribution of a total interual reflection(TIR) grating with high efficiency was analyzed under the irradiation of different polarized lights. The dependence of electric field enhancement in the TIR grating on constructive parameters and incident angle was also discussed. It is shown that electric field in the grating is sensitive to the polarization state, and peak electric field can be reduced greatly with short period and also decreases linearly with the increasing of incident angle. For the application of TIR grating to the high-energy laser system, reduction of the internal field enhancement can avoid the danger of damage effectively.
Using Fourier model method, the near-field distribution of a total interual reflection(TIR) grating with high efficiency was analyzed under the irradiation of different polarized lights. The dependence of electric field enhancement in the TIR grating on constructive parameters and incident angle was also discussed. It is shown that electric field in the grating is sensitive to the polarization state, and peak electric field can be reduced greatly with short period and also decreases linearly with the increasing of incident angle. For the application of TIR grating to the high-energy laser system, reduction of the internal field enhancement can avoid the danger of damage effectively.
2007,
19.
Abstract:
The influences of the thermal deformation of resonator mirrors induced by absorption of laser energy on geometric structure parameters of unstable resonators and intensity distributions of the far field were theoretically analyzed using finite difference methods. The far-field intensity distribution of virtual confocal unstable resonator under different thermal distortions was simulated. The results show that the resonator parameters changed significantly due to thermal deformation of the mirrors, and the central intensities of the far fields reduced obviously with thermal deformation increase.
The influences of the thermal deformation of resonator mirrors induced by absorption of laser energy on geometric structure parameters of unstable resonators and intensity distributions of the far field were theoretically analyzed using finite difference methods. The far-field intensity distribution of virtual confocal unstable resonator under different thermal distortions was simulated. The results show that the resonator parameters changed significantly due to thermal deformation of the mirrors, and the central intensities of the far fields reduced obviously with thermal deformation increase.
2007,
19.
Abstract:
The application of high-speed shadowgraph technology to flow field evolvement diagnosis of laser propulsion is presented. Shadow technology and a high-speed camera are combined to investigate the flow field evolvement. The zero point of the time sequence is provided by the high-speed camera, the delay time of laser and strobo is setted in advance, and all the equipment could be synchronized. The time sequence is designed and the time interval between high-speed camera, strobo and laser is controlled. In the experiment, clear flow field evolvement pictures were obtained.
The application of high-speed shadowgraph technology to flow field evolvement diagnosis of laser propulsion is presented. Shadow technology and a high-speed camera are combined to investigate the flow field evolvement. The zero point of the time sequence is provided by the high-speed camera, the delay time of laser and strobo is setted in advance, and all the equipment could be synchronized. The time sequence is designed and the time interval between high-speed camera, strobo and laser is controlled. In the experiment, clear flow field evolvement pictures were obtained.
2007,
19.
Abstract:
The limitation of classical adaptive optics and the basic principle of multi-conjugate adaptive optics are briefly introduced. The conjugate heights of single-conjugate and dual-conjugate systems are numerically simulated, and the gains of isoplanatic angle are demonstrated combined level-propagation and upright-propagation. The simulated results indicate that when the propagation distance is 20 km, the conjugation height has notable effect on the gain of the isoplanatic angle. For a single-conjugate system, the gain of isoplanatic angle is good in level propagation, but bad in upright, and the range of enlargement is limited during 3.6 km. For a dual-conjugate system, the deformable mirror for the first conjugate height mostly corrects the atmospheric turbulence near the pupil plane, and
The limitation of classical adaptive optics and the basic principle of multi-conjugate adaptive optics are briefly introduced. The conjugate heights of single-conjugate and dual-conjugate systems are numerically simulated, and the gains of isoplanatic angle are demonstrated combined level-propagation and upright-propagation. The simulated results indicate that when the propagation distance is 20 km, the conjugation height has notable effect on the gain of the isoplanatic angle. For a single-conjugate system, the gain of isoplanatic angle is good in level propagation, but bad in upright, and the range of enlargement is limited during 3.6 km. For a dual-conjugate system, the deformable mirror for the first conjugate height mostly corrects the atmospheric turbulence near the pupil plane, and
2007,
19.
Abstract:
Silicon atom was obtained by pyrolysis of silane and then reacted with N2O to produce the metastable state storage medium-SiO (b3П). An improved experiment device was set up and the optimal experiment parameters were achieved through plenty of experiments. Based on the present experiment device, when the ratio of the flow of N2O and SiH4 is 8～10，the SiH4 is diluted to 0.3% and the temperature of the oven is in the range of 1 160~1 170 ℃, the intensity of the spectrum measured in the experiment is the strongest.
Silicon atom was obtained by pyrolysis of silane and then reacted with N2O to produce the metastable state storage medium-SiO (b3П). An improved experiment device was set up and the optimal experiment parameters were achieved through plenty of experiments. Based on the present experiment device, when the ratio of the flow of N2O and SiH4 is 8～10，the SiH4 is diluted to 0.3% and the temperature of the oven is in the range of 1 160~1 170 ℃, the intensity of the spectrum measured in the experiment is the strongest.
2007,
19.
Abstract:
An ejector test facility was established to investigate the performance of a multi-nozzle supersonic ejector with a secondary flow. Using the hot rocket exhaust gases as primary and simulated secondary driving fluids, wall static pressure distributions on the ejector were obtained. Emphases were laid on the reliability of the multi-nozzle ejector and the influence of the primary flow total pressure and nozzle assembling configurations on the performance of the ejector. Experimental results show that the pumping requirement of the simulated secondary flow can be satisfied by using the multi-nozzle supersonic ejector. With the secondary flow joined, the pressure losses can be reduced greatly, which almost corresponds to 15 percents of the primary flow total energy. The lower primary flow tot
An ejector test facility was established to investigate the performance of a multi-nozzle supersonic ejector with a secondary flow. Using the hot rocket exhaust gases as primary and simulated secondary driving fluids, wall static pressure distributions on the ejector were obtained. Emphases were laid on the reliability of the multi-nozzle ejector and the influence of the primary flow total pressure and nozzle assembling configurations on the performance of the ejector. Experimental results show that the pumping requirement of the simulated secondary flow can be satisfied by using the multi-nozzle supersonic ejector. With the secondary flow joined, the pressure losses can be reduced greatly, which almost corresponds to 15 percents of the primary flow total energy. The lower primary flow tot
2007,
19.
Abstract:
The oscillator utilized a linear(F-P) cavity in which the halfwave plates and polarization splitters were placed to introduce polarization rotation. Combining the self-starting of semiconductor saturable absorber mirror, the passive mode-locked operation was achieved. The grating pair, providing negative group velocity dispersion, compensated the positive dispersion of fiber to compress the pulse. The stable mode-locked was operated with a pump power of 300 mW and the distance between the grating pair was 10 cm. The mode-locked output power was 28 mW while the pulse repetition was 20 MHz and the output spectrum width was 15 nm. The pulse width was less than 100 fs calculated by the formula that time bandwidth product equal to 0.315.
The oscillator utilized a linear(F-P) cavity in which the halfwave plates and polarization splitters were placed to introduce polarization rotation. Combining the self-starting of semiconductor saturable absorber mirror, the passive mode-locked operation was achieved. The grating pair, providing negative group velocity dispersion, compensated the positive dispersion of fiber to compress the pulse. The stable mode-locked was operated with a pump power of 300 mW and the distance between the grating pair was 10 cm. The mode-locked output power was 28 mW while the pulse repetition was 20 MHz and the output spectrum width was 15 nm. The pulse width was less than 100 fs calculated by the formula that time bandwidth product equal to 0.315.
2007,
19.
Abstract:
DISORT method was employed to study radiative properties of cirrus clouds in the shortwave infrared spectral region. The properties were shown, as well as their dependence on wavelength, visible optical thickness of cirrus clouds, cloud altitude, the particle shapes and effective size of cirrus clouds, and so on. The influences of cirrus clouds on atmospheric infrared background radiation were analysed. The main result is that at 2.7 μm atmospheric absorption region, the atmosphere background radiance is very weak, but when cirrus clouds appear in the sky, they reflect solar energy, thus the atmosphere background radiance is greatly enhanced.
DISORT method was employed to study radiative properties of cirrus clouds in the shortwave infrared spectral region. The properties were shown, as well as their dependence on wavelength, visible optical thickness of cirrus clouds, cloud altitude, the particle shapes and effective size of cirrus clouds, and so on. The influences of cirrus clouds on atmospheric infrared background radiation were analysed. The main result is that at 2.7 μm atmospheric absorption region, the atmosphere background radiance is very weak, but when cirrus clouds appear in the sky, they reflect solar energy, thus the atmosphere background radiance is greatly enhanced.
2007,
19.
Abstract:
Rate equations of passively Q-switched lasers were numerically calculated. The optimization of thermally bonded passively Q-switched lasers was discussed. The effect of key parameters of passively Q-switched lasers such as the initial transmission of the saturable absorber, the reflection of the output mirror, the pump power was got by numerical simulation. Output mirror transmission can be optimized to get the maximized output power and pulse energy. Decreasing initial transmission of the saturable absorber can cause pulse energy increase, pulse duration decrease and the threshold pump power increase respectively. The repeat rate and output power increase with pump power approximately linearly, and can shorten the pulse duration while increase the pump power. Theoretic calculation results
Rate equations of passively Q-switched lasers were numerically calculated. The optimization of thermally bonded passively Q-switched lasers was discussed. The effect of key parameters of passively Q-switched lasers such as the initial transmission of the saturable absorber, the reflection of the output mirror, the pump power was got by numerical simulation. Output mirror transmission can be optimized to get the maximized output power and pulse energy. Decreasing initial transmission of the saturable absorber can cause pulse energy increase, pulse duration decrease and the threshold pump power increase respectively. The repeat rate and output power increase with pump power approximately linearly, and can shorten the pulse duration while increase the pump power. Theoretic calculation results
2007,
19.
Abstract:
The thermodynamic quantities (such as the enthalpies of reaction, ΔHr, the Gibbs free energies of reaction, ΔGr and the constant of chemical reaction equilibrium, K) of the gas-solid reaction systems for singlet oxygen generation were calculated through the Gaussian 03 program in the level of RHF/Lanl2dz. The gas-solid reaction systems were made up of four possible solid reactants (alkali metal or alkaline earth metal peroxides or superoxides) with three possible gas reactants (the possible halogen gas or hydrogen (deuterium) halide gas). The effects of different solid reactants and gas reactants on the thermodynamic quantities of the gas-solid reaction system for singlet oxygen generation were compared and analyzed. The calculations showed that most of the gas-solid reaction systems hav
The thermodynamic quantities (such as the enthalpies of reaction, ΔHr, the Gibbs free energies of reaction, ΔGr and the constant of chemical reaction equilibrium, K) of the gas-solid reaction systems for singlet oxygen generation were calculated through the Gaussian 03 program in the level of RHF/Lanl2dz. The gas-solid reaction systems were made up of four possible solid reactants (alkali metal or alkaline earth metal peroxides or superoxides) with three possible gas reactants (the possible halogen gas or hydrogen (deuterium) halide gas). The effects of different solid reactants and gas reactants on the thermodynamic quantities of the gas-solid reaction system for singlet oxygen generation were compared and analyzed. The calculations showed that most of the gas-solid reaction systems hav
2007,
19.
Abstract:
Thermal focal length of an LD side-pumped Nd:YAG laser rod is measured and discussed. The edge-cooled solid-state laser rod pumped uniformly likes a lens. When the parallel beam goes through the rod, its wavefront will be changed and equal to the focal length. With the wavefront curvature sensor, the wavefront of the beam can be measured exactly. Any equipment should not move and change during the measurement, so that few errors may appear. In this way, the thermal focal length of the pumped laser rod can be measured easily. The experimental result shows that the thermal focal length of high power solidstate laser rod is short, and the theoretical and practical result is close．
Thermal focal length of an LD side-pumped Nd:YAG laser rod is measured and discussed. The edge-cooled solid-state laser rod pumped uniformly likes a lens. When the parallel beam goes through the rod, its wavefront will be changed and equal to the focal length. With the wavefront curvature sensor, the wavefront of the beam can be measured exactly. Any equipment should not move and change during the measurement, so that few errors may appear. In this way, the thermal focal length of the pumped laser rod can be measured easily. The experimental result shows that the thermal focal length of high power solidstate laser rod is short, and the theoretical and practical result is close．
2007,
19.
Abstract:
In order to double the injection rate of positron beam from the linac to the storage ring of BEPCⅡ, a two-pulse generation and acceleration scheme has been proposed. The two-pulse simulation by programs including LIAR, PARMELA, EGUN and TRANSPORT is described first and the method is applied in the beam dynamics studies of BEPCⅡ linac. The experiment of two-pulse acceleration was performed in BEPCⅡ linac and some preliminary results are obtained, which provides a good reference for further upgrading of BEPCⅡ injector linac.
In order to double the injection rate of positron beam from the linac to the storage ring of BEPCⅡ, a two-pulse generation and acceleration scheme has been proposed. The two-pulse simulation by programs including LIAR, PARMELA, EGUN and TRANSPORT is described first and the method is applied in the beam dynamics studies of BEPCⅡ linac. The experiment of two-pulse acceleration was performed in BEPCⅡ linac and some preliminary results are obtained, which provides a good reference for further upgrading of BEPCⅡ injector linac.
2007,
19.
Abstract:
A 750 keV, 201.25 MHz radio frequency quadrupole accelerator was designed as the injector of the Beijing proton linac. The beam dynamics study of this accelerator is described. The main parameters and results of two designs are presented. The influences of non-ideal conditions of parameters such as energy dispersion, emittance, Twiss parameters, input current and energy on beam transmission efficiency are analyzed. The similarities and differences of the two designs are shown. The results of the beam dynamics simulation show that the two designs both satisfy the physics requirement.
A 750 keV, 201.25 MHz radio frequency quadrupole accelerator was designed as the injector of the Beijing proton linac. The beam dynamics study of this accelerator is described. The main parameters and results of two designs are presented. The influences of non-ideal conditions of parameters such as energy dispersion, emittance, Twiss parameters, input current and energy on beam transmission efficiency are analyzed. The similarities and differences of the two designs are shown. The results of the beam dynamics simulation show that the two designs both satisfy the physics requirement.
2007,
19.
Abstract:
The formation of hot image in a broadband laser system is numerically studied. It is found that in a broadband system the hot image is, though the same in location, well restrained by the bandwidth and has a peak intensity much smaller when compared to that in a narrowband system. In addition, the quantitative description for the influences of bandwidth on the hot image and on the uniformity of the beam is presented by modifying the chirp and temporal width of pulse. The results show that the intensity of the hot image and the corresponding contrast are inversely proportional to the chirp and proportional to the temporal width of the incident pulse, indicating that a bandwidth can suppress the formation of a hot image and improve the uniformity. The physical reasons for such a suppressing
The formation of hot image in a broadband laser system is numerically studied. It is found that in a broadband system the hot image is, though the same in location, well restrained by the bandwidth and has a peak intensity much smaller when compared to that in a narrowband system. In addition, the quantitative description for the influences of bandwidth on the hot image and on the uniformity of the beam is presented by modifying the chirp and temporal width of pulse. The results show that the intensity of the hot image and the corresponding contrast are inversely proportional to the chirp and proportional to the temporal width of the incident pulse, indicating that a bandwidth can suppress the formation of a hot image and improve the uniformity. The physical reasons for such a suppressing
2007,
19.
Abstract:
The influence of electrolyte component on the surface roughness and topography of Ti film has been analyzed. It is found that, the solution of sulfuric acid and methanol is an ideal electrolyte system compared with the other electrolyte systems mentioned in this paper. The Ti films with surface mean roughness value less than 30 nm were obtained under appropriate electropolishing process conditions such as polishing potential, temperature, time, flow rate etc.The relation between anodic potential and removal rate of the metal was investigated in the solution of sulfuric acid and methanol.The removal rate increases with the polishing potential increasing at the initiative stage of polishing. When the potential reaches 28～42 V,the rate keeps almost constant. The rate increases swift again w
The influence of electrolyte component on the surface roughness and topography of Ti film has been analyzed. It is found that, the solution of sulfuric acid and methanol is an ideal electrolyte system compared with the other electrolyte systems mentioned in this paper. The Ti films with surface mean roughness value less than 30 nm were obtained under appropriate electropolishing process conditions such as polishing potential, temperature, time, flow rate etc.The relation between anodic potential and removal rate of the metal was investigated in the solution of sulfuric acid and methanol.The removal rate increases with the polishing potential increasing at the initiative stage of polishing. When the potential reaches 28～42 V,the rate keeps almost constant. The rate increases swift again w
2007,
19.
Abstract:
The Ka absorption spectrum is one of the important methods to determine the temperature of radiation-produced plasmas. The CH-sandwiched aluminum foil, deposited on the back surface of the gold foil, was heated by the X-ray radiation from the laser-irradiated gold foil on the Xingguang Ⅱ laser facility. The Ka absorption spectra for various thickness aluminum samples were measured with the PET crystal spectrometer. Obvious Ka absorption lines from He-like to F-like Al ions were observed. As comparison, the aluminum Ka absorption spectra at different temperatures and densities were also calculated using the detailed term accounting(DTA) model. The simulated spectra are in good agreement with the experimental ones, which can be applied to determine the sample temperature in opacity experime
The Ka absorption spectrum is one of the important methods to determine the temperature of radiation-produced plasmas. The CH-sandwiched aluminum foil, deposited on the back surface of the gold foil, was heated by the X-ray radiation from the laser-irradiated gold foil on the Xingguang Ⅱ laser facility. The Ka absorption spectra for various thickness aluminum samples were measured with the PET crystal spectrometer. Obvious Ka absorption lines from He-like to F-like Al ions were observed. As comparison, the aluminum Ka absorption spectra at different temperatures and densities were also calculated using the detailed term accounting(DTA) model. The simulated spectra are in good agreement with the experimental ones, which can be applied to determine the sample temperature in opacity experime
2007,
19.
Abstract:
2D and 3D fractal methods are used to analyze the KDP crystal surfaces machined by SPDT(single point diamond tools) method. The difference between 3D fractal dimension and roughness parameter is analyzed. And 3D fractal dimension has the inverse ratio with 3D roughness. Through 2D profile fractal analyses, it is found that the KDP crystal surfaces machined by SPDT method are strongly anisotropic and microscale wavenesses form to impact the optical performance of KDP components. The microscale waveness is incorrelate with roughness in certain range but has a direct relationship with the profile fractal dimension distribution of machined surface. Hence the microscale waveness can be reduced by adopting reasonable cutting parameters when the same roughness is maintained. In addition the profi
2D and 3D fractal methods are used to analyze the KDP crystal surfaces machined by SPDT(single point diamond tools) method. The difference between 3D fractal dimension and roughness parameter is analyzed. And 3D fractal dimension has the inverse ratio with 3D roughness. Through 2D profile fractal analyses, it is found that the KDP crystal surfaces machined by SPDT method are strongly anisotropic and microscale wavenesses form to impact the optical performance of KDP components. The microscale waveness is incorrelate with roughness in certain range but has a direct relationship with the profile fractal dimension distribution of machined surface. Hence the microscale waveness can be reduced by adopting reasonable cutting parameters when the same roughness is maintained. In addition the profi
2007,
19.
Abstract:
Using statistical methods and numerical simulation, the far-field description methods for high power ultra-short pulse laser were established. The results show that the percentage of energy in FWHM of the ideal super-Gaussion beam is no more than 70%, and it reduces with the order of the super-Gaussian beam increasing. The FWHM of focus will keep a constant when beam quality was good, and the power density in FWHM has no relationship with FWHM, whereas, it has a linear relationship with Strehl ratio and percentage of energy in FWHM. Therefore, the paper points out that FWHM of focus or severalfold diffraction limits cannot be simply used in giving the peak power density. Strehl ratio or the encircled energy within FWHM is more appropriate.
Using statistical methods and numerical simulation, the far-field description methods for high power ultra-short pulse laser were established. The results show that the percentage of energy in FWHM of the ideal super-Gaussion beam is no more than 70%, and it reduces with the order of the super-Gaussian beam increasing. The FWHM of focus will keep a constant when beam quality was good, and the power density in FWHM has no relationship with FWHM, whereas, it has a linear relationship with Strehl ratio and percentage of energy in FWHM. Therefore, the paper points out that FWHM of focus or severalfold diffraction limits cannot be simply used in giving the peak power density. Strehl ratio or the encircled energy within FWHM is more appropriate.
2007,
19.
Abstract:
The single-layer SiO2, single-layer ZrO2,two-layer ZrO2/SiO2 and two-layer SiO2/ZrO2 thin films were deposited on K9 glass by Sol-Gel spin-coating method. The colloidal suspension of ZrO2 was prepared using Zr(OPr)4 and colloidal suspension of SiO2 was prepared using TEOS as precursor. The surface morphologies of SiO2 and ZrO2 thin films were observed by AFM. Ellipsometry was used to measure the thickness and refractive index of the films. UV-VIS spectrophotometer was used to measure the transmittance of the films. The results showed that the infiltration of the two-layer SiO2/ZrO2 film was much serious than that of the two-layer ZrO2/SiO2 film, which is very trifling. With the TFCalc thin film design software, the transmittance of the films was simulated with the theoretical three-layer m
The single-layer SiO2, single-layer ZrO2,two-layer ZrO2/SiO2 and two-layer SiO2/ZrO2 thin films were deposited on K9 glass by Sol-Gel spin-coating method. The colloidal suspension of ZrO2 was prepared using Zr(OPr)4 and colloidal suspension of SiO2 was prepared using TEOS as precursor. The surface morphologies of SiO2 and ZrO2 thin films were observed by AFM. Ellipsometry was used to measure the thickness and refractive index of the films. UV-VIS spectrophotometer was used to measure the transmittance of the films. The results showed that the infiltration of the two-layer SiO2/ZrO2 film was much serious than that of the two-layer ZrO2/SiO2 film, which is very trifling. With the TFCalc thin film design software, the transmittance of the films was simulated with the theoretical three-layer m
2007,
19.
Abstract:
Some scientists used waveguide as the cavity to produce a plasma jet, while large volume microwave plasma was relatively hard to get in atmospheric pressure. However, a few research institutes have already developed devices to generate large volume of atmospheric pressure microwave plasma, such as CYRANNUS and SLAN series, which can be widely applied. In this paper, present a microwave plasma system with ring waveguide to excite large volume of atmospheric pressure microwave plasma, plot curves on theoretical disruption electric field of some working gases, emulate the cavity through software, measure the power density to validate and show the appearance of microwave plasma. At present, large volume of argon and helium plasma have already been generated steadily by atmospheric pressure mic
Some scientists used waveguide as the cavity to produce a plasma jet, while large volume microwave plasma was relatively hard to get in atmospheric pressure. However, a few research institutes have already developed devices to generate large volume of atmospheric pressure microwave plasma, such as CYRANNUS and SLAN series, which can be widely applied. In this paper, present a microwave plasma system with ring waveguide to excite large volume of atmospheric pressure microwave plasma, plot curves on theoretical disruption electric field of some working gases, emulate the cavity through software, measure the power density to validate and show the appearance of microwave plasma. At present, large volume of argon and helium plasma have already been generated steadily by atmospheric pressure mic
2007,
19.
Abstract:
LaF3 single-layer coatings were prepared by thermal boat evaporation at the deposition temperatures of 189, 255, 277 and 321 ℃ respectively. The crystal structures of the coatings were characterized by X-ray diffraction(XRD). A spectrophotometer was employed to measure its transmittance. Moreover, refractive index, extinction coefficient and cut-off wavelength were obtained from the measured transmittance spectral curve. The residual stress was evaluated by the Stoney’s equation and optical interferometer. Laser induce damage threshold(LIDT) was performed by a tripled Nd: YAG laser system. The results show that the crystallization status becomes better with the deposition temperature increasing. Correspondingly, the grain size also gets larger. Meanwhile, the coatings become more compact
LaF3 single-layer coatings were prepared by thermal boat evaporation at the deposition temperatures of 189, 255, 277 and 321 ℃ respectively. The crystal structures of the coatings were characterized by X-ray diffraction(XRD). A spectrophotometer was employed to measure its transmittance. Moreover, refractive index, extinction coefficient and cut-off wavelength were obtained from the measured transmittance spectral curve. The residual stress was evaluated by the Stoney’s equation and optical interferometer. Laser induce damage threshold(LIDT) was performed by a tripled Nd: YAG laser system. The results show that the crystallization status becomes better with the deposition temperature increasing. Correspondingly, the grain size also gets larger. Meanwhile, the coatings become more compact
2007,
19.
Abstract:
Planar beams can generate high-power radiation in device like sheet-beam klystrons at high-frequency range. Electron optics system is the key part of the sheet beam klystron. Two-plane Wiggler focusing principle is illustrated in this paper. Elliptical sheet beams with uniform current density are generated by the new-style electron gun geometry which comprises of an elliptically cylindrical cathode and an elliptical focusing electrode. The fill factor of 75% and the beam transmission of 100% are obtained through the center notched Wiggler focusing system with total length and period length of 108 mm and 8 mm respectively. The trajectories are uniformly distributed in the new diamond-shaped collector.
Planar beams can generate high-power radiation in device like sheet-beam klystrons at high-frequency range. Electron optics system is the key part of the sheet beam klystron. Two-plane Wiggler focusing principle is illustrated in this paper. Elliptical sheet beams with uniform current density are generated by the new-style electron gun geometry which comprises of an elliptically cylindrical cathode and an elliptical focusing electrode. The fill factor of 75% and the beam transmission of 100% are obtained through the center notched Wiggler focusing system with total length and period length of 108 mm and 8 mm respectively. The trajectories are uniformly distributed in the new diamond-shaped collector.
2007,
19.
Abstract:
The optical and electrical signals of lightning discharges were measured simultaneously by using the wide-band electric field instrument and the optical ripple detector at Conghua city Guangdong province in summer, 2006. The observation data were analyzed statistically in this paper. The results show that the lightning optical signal is always delayed from the electric signal on onset and peak time, and the optical pulse rises more slowly to the peak and its pulse-width is broader. Using the back propagation artificial neural networks methods, the pattern recognition in lighting flashes chassification was further investigated by optical and electric time series. The results are up to the standard except in-cloud flash ones.
The optical and electrical signals of lightning discharges were measured simultaneously by using the wide-band electric field instrument and the optical ripple detector at Conghua city Guangdong province in summer, 2006. The observation data were analyzed statistically in this paper. The results show that the lightning optical signal is always delayed from the electric signal on onset and peak time, and the optical pulse rises more slowly to the peak and its pulse-width is broader. Using the back propagation artificial neural networks methods, the pattern recognition in lighting flashes chassification was further investigated by optical and electric time series. The results are up to the standard except in-cloud flash ones.
2007,
19.
Abstract:
Based on the transmission line approximation, three different equivalent coupling formulations (by Taylor et al., by Agrawal et al. and by Rachidi, resoectively) are been proposed for evaluating the interaction between an external electromagnetic field and a transmission line. An analytic method is used to discuss the load voltage and current response with the Taylor and Agrawal coupling models for a planewave excitation. The analytic solutions of the load response are obtained for the two models. It is proved that these solutions are equal indeed. In other words, the two coupling formulations are different expressions of the same equations, cast in terms of different combinations of various electromagnetic field components. By analytical frequency-domain solution and the Fourier trans
Based on the transmission line approximation, three different equivalent coupling formulations (by Taylor et al., by Agrawal et al. and by Rachidi, resoectively) are been proposed for evaluating the interaction between an external electromagnetic field and a transmission line. An analytic method is used to discuss the load voltage and current response with the Taylor and Agrawal coupling models for a planewave excitation. The analytic solutions of the load response are obtained for the two models. It is proved that these solutions are equal indeed. In other words, the two coupling formulations are different expressions of the same equations, cast in terms of different combinations of various electromagnetic field components. By analytical frequency-domain solution and the Fourier trans
2007,
19.
Abstract:
This article puts forward a numerical method which could compute dispersion curves in an arbitrary axial-symmetric tapered quasi-periodic slow-wave structure, based on field-matching method and Fourier series theory. Using this numerical method, the dispersion curves of a tapered sinusoidal ripple waveguide and a tapered disk-loaded waveguide were computed by programming Matlab codes. The dispersion characteristics of these two typical tapered quasi-periodic slow-wave structures were analyzed and discussed. Numerical results were compared with the simulated results of multidimensional full electromagnetic software, and the reliability of this numerical method was validated. The numerical method has a strong universality and expansibility in designing slow-wave structures, it could also com
This article puts forward a numerical method which could compute dispersion curves in an arbitrary axial-symmetric tapered quasi-periodic slow-wave structure, based on field-matching method and Fourier series theory. Using this numerical method, the dispersion curves of a tapered sinusoidal ripple waveguide and a tapered disk-loaded waveguide were computed by programming Matlab codes. The dispersion characteristics of these two typical tapered quasi-periodic slow-wave structures were analyzed and discussed. Numerical results were compared with the simulated results of multidimensional full electromagnetic software, and the reliability of this numerical method was validated. The numerical method has a strong universality and expansibility in designing slow-wave structures, it could also com
2007,
19.
Abstract:
HfO2 films have been deposited by dual-ion beam sputtering technology with starting material Hf. Optical, residual stress, structural properties and laser-induced damage threshold of the HfO2 films have been studied. It is found that the HfO2 shows uniform structural properties, film compact and structure and higher laser-induced damage threshold. The relation between structural and damage threshold of HfO2 films has also been studied.
HfO2 films have been deposited by dual-ion beam sputtering technology with starting material Hf. Optical, residual stress, structural properties and laser-induced damage threshold of the HfO2 films have been studied. It is found that the HfO2 shows uniform structural properties, film compact and structure and higher laser-induced damage threshold. The relation between structural and damage threshold of HfO2 films has also been studied.
2007,
19.
Abstract:
The micro sub-surface cracks of fused silica are observed by AFM and optical microscope. Due to the morphology characters, the cracks are sorted into three types: Boussinesq-point-force crack(BPFC), Hertzian-conical scratch(HCS) and plastic indent(PI). The laser induced damage thresholds of the cracks are measured. The damage mechanism is also discussed. The results show that the damage threshold of sharp tip BPFC is less than 2.0 J/cm2, that of HCS get to 2.6 J/cm2, and that of PI with large shape change is 2.8 J/cm2. The laser induced damage threshold of PI with small change is parallel with that of perfect surface. It is obvious that BPFC and HCS with depth more than 1 μm are the main factors to decrease the laser induced damage threshold of fused silica.
The micro sub-surface cracks of fused silica are observed by AFM and optical microscope. Due to the morphology characters, the cracks are sorted into three types: Boussinesq-point-force crack(BPFC), Hertzian-conical scratch(HCS) and plastic indent(PI). The laser induced damage thresholds of the cracks are measured. The damage mechanism is also discussed. The results show that the damage threshold of sharp tip BPFC is less than 2.0 J/cm2, that of HCS get to 2.6 J/cm2, and that of PI with large shape change is 2.8 J/cm2. The laser induced damage threshold of PI with small change is parallel with that of perfect surface. It is obvious that BPFC and HCS with depth more than 1 μm are the main factors to decrease the laser induced damage threshold of fused silica.
2007,
19.
Abstract:
A relativistic distorted-wave approximation is used to calculate the autoionization rates and dielectronic capture strengths for Cu-like Pb ion. The calculated results show that autoionization rates varies regularly with the effect of spectator electron. Autoionization rates and dielectronic capture strengths of two other high-Z elements Au and Ta for comparison are also calculated. The comparison shows good agreement between the present calculation and the theoretical results of the relative parameter potential method, the quasi-relativistic Hartree-Fock- Relativistic method and the spin-orbit-split array modle method.
A relativistic distorted-wave approximation is used to calculate the autoionization rates and dielectronic capture strengths for Cu-like Pb ion. The calculated results show that autoionization rates varies regularly with the effect of spectator electron. Autoionization rates and dielectronic capture strengths of two other high-Z elements Au and Ta for comparison are also calculated. The comparison shows good agreement between the present calculation and the theoretical results of the relative parameter potential method, the quasi-relativistic Hartree-Fock- Relativistic method and the spin-orbit-split array modle method.
2007,
19.
Abstract:
With ZrO2 and AlCl2Pc/SiO2 as high and low refractive index materials respectively, the high reflective film of 21 layers was deposited on well-cleaned polycarbonate substrate via sol-gel process. The film was designed as l0/6-l0/3 typed periodic symmetric coating stacks. Reflection to 1 064 nm and 532 nm lasers was realized. At the same time, absorption to 680 nm laser was obtained. The transmissivity at 1 064 nm, 532 nm, and 680 nm were 1.67%, 18.24% and 2.4% respectively. With this method, anti-laser protection was easily acquired at these three laser wavelengths.
With ZrO2 and AlCl2Pc/SiO2 as high and low refractive index materials respectively, the high reflective film of 21 layers was deposited on well-cleaned polycarbonate substrate via sol-gel process. The film was designed as l0/6-l0/3 typed periodic symmetric coating stacks. Reflection to 1 064 nm and 532 nm lasers was realized. At the same time, absorption to 680 nm laser was obtained. The transmissivity at 1 064 nm, 532 nm, and 680 nm were 1.67%, 18.24% and 2.4% respectively. With this method, anti-laser protection was easily acquired at these three laser wavelengths.
2007,
19.
Abstract:
In the early stage of UV excimer laser ablation of semiconductor, plasma induced by laser ablation was assumed at local thermodynamic equilibrium. One-dimension hydrodynamic model is presented for the laser ablation of Ge in a background gas (He) at 133.32 Pa and the characteristics of plasma induced by Gaussian-shaped KrF laser pulse with wavelength of 248 nm, pulse width of 17 ns, and peak power of 4×108 W/cm2. The results show that the ablated depth arrives 55 nm after laser pulse irradiation. The background gas He is gradually pushed away by the Ge vapor, forming a compression shock wave. And the maximum temperature always locates at the front of the shock wave. Spatial distribution of ionization degrees at different time shows that the first-order ionization degree of Ge always domin
In the early stage of UV excimer laser ablation of semiconductor, plasma induced by laser ablation was assumed at local thermodynamic equilibrium. One-dimension hydrodynamic model is presented for the laser ablation of Ge in a background gas (He) at 133.32 Pa and the characteristics of plasma induced by Gaussian-shaped KrF laser pulse with wavelength of 248 nm, pulse width of 17 ns, and peak power of 4×108 W/cm2. The results show that the ablated depth arrives 55 nm after laser pulse irradiation. The background gas He is gradually pushed away by the Ge vapor, forming a compression shock wave. And the maximum temperature always locates at the front of the shock wave. Spatial distribution of ionization degrees at different time shows that the first-order ionization degree of Ge always domin
2007,
19.
Abstract:
Principle and method to simulate pulse forming net(PFN) were expatiated from the viewpoint of wave process. The method can simulate PFN with temporal circuit parameters as well as pulsed power system with MITL, switch, implosion plasma. The high fidelity, quick convergence, straightforward procedure, rapid operation and the easy extension are characterized with wave process based method by comparison with Pspice simulation.
Principle and method to simulate pulse forming net(PFN) were expatiated from the viewpoint of wave process. The method can simulate PFN with temporal circuit parameters as well as pulsed power system with MITL, switch, implosion plasma. The high fidelity, quick convergence, straightforward procedure, rapid operation and the easy extension are characterized with wave process based method by comparison with Pspice simulation.
2007,
19.
Abstract:
The configuration, pulse forming line section and experimental results of a pulse power machine were introduced. The insulative inspection of pulse forming line, the jitter of lasertriggered switch, the jitter of output switch and the jitter of the pulse forming line section were investigated. The experimental results indicate that the nylon clapboards of the pulse forming line have no flashover along the surfaces at 3.6 MV. The jitter of the laser-triggered switch is smaller than 1.6 ns while the jitter of the output switch less than 3.1 ns and that of the pulse forming line section less than 3.0 ns. All the experimental results meet the requirements of the design．
The configuration, pulse forming line section and experimental results of a pulse power machine were introduced. The insulative inspection of pulse forming line, the jitter of lasertriggered switch, the jitter of output switch and the jitter of the pulse forming line section were investigated. The experimental results indicate that the nylon clapboards of the pulse forming line have no flashover along the surfaces at 3.6 MV. The jitter of the laser-triggered switch is smaller than 1.6 ns while the jitter of the output switch less than 3.1 ns and that of the pulse forming line section less than 3.0 ns. All the experimental results meet the requirements of the design．
2007,
19.
Abstract:
A 40 kV/6 kA pulsed power supply was designed for the rapid cycling synchrotron(RCS) extraction Kicker magnet of Chinese Spallation Neutron Source. The calculation of the pulsed power supply’s parameters, the design of power supply’s system, the optimization of pulse forming network(PFN) are introduced. A new type of low impedance PFN is also presented. The magnet current pulse waveform was simulated by PSPICE program in the situation of 36.5 kV charging voltage, and the amplitude of the pulse was 5.8 kA. The simulation results show that, with the same PFN section capacitor and inductor, the pulse length of the current is prolonged when more section number of PFN is chosen, while the rise time and flatness of the pulse has no significant changes, choosing the suitable length of transmiss
A 40 kV/6 kA pulsed power supply was designed for the rapid cycling synchrotron(RCS) extraction Kicker magnet of Chinese Spallation Neutron Source. The calculation of the pulsed power supply’s parameters, the design of power supply’s system, the optimization of pulse forming network(PFN) are introduced. A new type of low impedance PFN is also presented. The magnet current pulse waveform was simulated by PSPICE program in the situation of 36.5 kV charging voltage, and the amplitude of the pulse was 5.8 kA. The simulation results show that, with the same PFN section capacitor and inductor, the pulse length of the current is prolonged when more section number of PFN is chosen, while the rise time and flatness of the pulse has no significant changes, choosing the suitable length of transmiss
2007,
19.
Abstract:
The radiation effects of L band microwave pulses with a carrier frequency at 1.3 GHz on a personal computer motherboard are studied in this paper. Microwave pulse power thresholds are achieved in experiments with different pulse parameters, such as pulse width, pulse repetition frequency and pulse number. Microwave radiation beyond power thresholds will lead to personal computer system crashes. Moreover, the cumulative effects of microwave pulse radiation are discussed briefly as well. The power thresholds decrease, when either the pulse width is longer, or the pulse repetition frequency is higher, or the pulse number at a fixed repetition frequency increases. The power thresholds of pulsed microwave are always less than that of continuous microwave. On the other hand, when either the inte
The radiation effects of L band microwave pulses with a carrier frequency at 1.3 GHz on a personal computer motherboard are studied in this paper. Microwave pulse power thresholds are achieved in experiments with different pulse parameters, such as pulse width, pulse repetition frequency and pulse number. Microwave radiation beyond power thresholds will lead to personal computer system crashes. Moreover, the cumulative effects of microwave pulse radiation are discussed briefly as well. The power thresholds decrease, when either the pulse width is longer, or the pulse repetition frequency is higher, or the pulse number at a fixed repetition frequency increases. The power thresholds of pulsed microwave are always less than that of continuous microwave. On the other hand, when either the inte
