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RSS2007 Vol. 19, No. 01
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2007,
19.
Abstract:
Taking the second-order-moment and power of the bucket as the beam width definition, changes of the beam parameters such as the beam width and farfield divergence angle of Gaussian beams after passing through an astigmatic lens are studied both analytically and numerically. It is found that the relative errors of the beam width and far-field divergence angle introduced by the astigmatism depend on the astigmatic coefficient, the Rayleigh range and the focal length of the lens. For the beam width, the errors also depend on the propagation distance. At the geometrical focal plane the relative errors in the x and y directions are equal. The results are of practical interest for the design of laser optics systems.
Taking the second-order-moment and power of the bucket as the beam width definition, changes of the beam parameters such as the beam width and farfield divergence angle of Gaussian beams after passing through an astigmatic lens are studied both analytically and numerically. It is found that the relative errors of the beam width and far-field divergence angle introduced by the astigmatism depend on the astigmatic coefficient, the Rayleigh range and the focal length of the lens. For the beam width, the errors also depend on the propagation distance. At the geometrical focal plane the relative errors in the x and y directions are equal. The results are of practical interest for the design of laser optics systems.
2007,
19.
Abstract:
In order to investigate the thermal effect of moving quartz glass heated by CO2 laser, a mathematical model was established as the influence of irradiation and convection was considered. The temperature distribution was obtained using the software ANSYS. The relationships between temperature and velocity and laser parameters (power and radius) were obtained by comparing the temperature distribution for different velocity and laser parameters. The results show that the surface temperature of quartz glass increases when the laser power increases, the laser focus decreases and the speed of the quartz glass decreases.
In order to investigate the thermal effect of moving quartz glass heated by CO2 laser, a mathematical model was established as the influence of irradiation and convection was considered. The temperature distribution was obtained using the software ANSYS. The relationships between temperature and velocity and laser parameters (power and radius) were obtained by comparing the temperature distribution for different velocity and laser parameters. The results show that the surface temperature of quartz glass increases when the laser power increases, the laser focus decreases and the speed of the quartz glass decreases.
2007,
19.
Abstract:
In the experiment of 100 TW laser interacting with 5 μm thick Cu target, CR39 and Thomson spectrum are used to detect the energy spectra of proton and radiochromic HD810 is used to detect the distribution of protons at the normal direction of the target’s back. The results show that the protons are emitted from the normal direction of target-back and have 570 keV cut-off energy and the jet angle is about 10°. The results of the experiment verify that target normal sheath acceleration of proton in the ultra-short and ultra-intense laser interacts with plasmas.
In the experiment of 100 TW laser interacting with 5 μm thick Cu target, CR39 and Thomson spectrum are used to detect the energy spectra of proton and radiochromic HD810 is used to detect the distribution of protons at the normal direction of the target’s back. The results show that the protons are emitted from the normal direction of target-back and have 570 keV cut-off energy and the jet angle is about 10°. The results of the experiment verify that target normal sheath acceleration of proton in the ultra-short and ultra-intense laser interacts with plasmas.
2007,
19.
Abstract:
Using 1.06 μm single pulse laser to irradiate optical element model of photoelectricity system in different energy density, physical model of multilayer films is found and temperature field of facula center, radial direction and axes direction is calculated with ANSYS software. At the same time thermal stresses in radial direction, axes direction and round direction in different energy density are calculated. Change of temperature field and thermal stress are analysed.
Using 1.06 μm single pulse laser to irradiate optical element model of photoelectricity system in different energy density, physical model of multilayer films is found and temperature field of facula center, radial direction and axes direction is calculated with ANSYS software. At the same time thermal stresses in radial direction, axes direction and round direction in different energy density are calculated. Change of temperature field and thermal stress are analysed.
2007,
19.
Abstract:
The matching angle, the efficient nonlinear coefficient and the temporal and spatial walk-off length of collinear and non-collinear phase-matching for ultra-short mid-infrared laser optical parametric amplification in MgO:LiNbO3 crystal are analyzed. Based on this analysis, the group velocity matching, the efficient nonlinear coefficient’s increase and the larger signal’s walk-off length for non-collinear phase-matching optical parametric amplification are obtained. The enhanced spatial walk-off effect for the idler is also obtained, but it can be ignored. In a word, non-collinear phase-matching is beneficial to parametric conversion efficiency’s increase.
The matching angle, the efficient nonlinear coefficient and the temporal and spatial walk-off length of collinear and non-collinear phase-matching for ultra-short mid-infrared laser optical parametric amplification in MgO:LiNbO3 crystal are analyzed. Based on this analysis, the group velocity matching, the efficient nonlinear coefficient’s increase and the larger signal’s walk-off length for non-collinear phase-matching optical parametric amplification are obtained. The enhanced spatial walk-off effect for the idler is also obtained, but it can be ignored. In a word, non-collinear phase-matching is beneficial to parametric conversion efficiency’s increase.
2007,
19.
Abstract:
Phase locking of a diode laser array by an external cavity consisting of a mode selecting mirror or a phase grid was studied theoretically, on the basis of Fresnel diffraction and coupled mode theory. The relative complex amplitude distribution of the emitters operating in different super modes was computed for both cases. The compared results with sinusoid curves demonstrate that the mode selecting mirror is effective for in-phase mode selection and fluctuation elimination of amplitude resulted from edge effect, and the phase grid is also effective for in-phase mode selection.
Phase locking of a diode laser array by an external cavity consisting of a mode selecting mirror or a phase grid was studied theoretically, on the basis of Fresnel diffraction and coupled mode theory. The relative complex amplitude distribution of the emitters operating in different super modes was computed for both cases. The compared results with sinusoid curves demonstrate that the mode selecting mirror is effective for in-phase mode selection and fluctuation elimination of amplitude resulted from edge effect, and the phase grid is also effective for in-phase mode selection.
2007,
19.
Abstract:
High precision wavefront reconstruction is very important for effective compensation, control and quality improvement of high power laser beam. The low and the middle and high frequency components of the distorted wavefront in the high power laser system can be described by use of RMS gradient and uniform random distribution respectively. First the intensity distributions on the input plane and other three faraway diffraction planes are used to iteratively reconstruct the low frequency component of the distorted wavefront in the high power laser system, and then the intensity distributions on the input plane and two near by diffraction planes are applied to iteratively reconstruct the middle and high frequency component. This algorithm shows good convergence when the reconstructed amplitud
High precision wavefront reconstruction is very important for effective compensation, control and quality improvement of high power laser beam. The low and the middle and high frequency components of the distorted wavefront in the high power laser system can be described by use of RMS gradient and uniform random distribution respectively. First the intensity distributions on the input plane and other three faraway diffraction planes are used to iteratively reconstruct the low frequency component of the distorted wavefront in the high power laser system, and then the intensity distributions on the input plane and two near by diffraction planes are applied to iteratively reconstruct the middle and high frequency component. This algorithm shows good convergence when the reconstructed amplitud
2007,
19.
Abstract:
The spraying auto-decomposition of NCl3 was preliminarily investigated in a cylindrical gas flow tube. The red flame of NCl3 auto-decomposition by spraying was observed and its spectrum was measured. The spectrum was attributed to Cl2(B→X) transition. The decomposition mechanism of NCl3 molecule was discussed. It was believed that the preliminary decomposition of NCl3 was induced by shockwave and then Cl and NCl2 radicals produced reacted with NCl3 to give sustained flame. The experimental results show that NCl3 auto-decomposition can produce a large amount of radicals to replace discharge or combustor as the source of chlorine atom.
The spraying auto-decomposition of NCl3 was preliminarily investigated in a cylindrical gas flow tube. The red flame of NCl3 auto-decomposition by spraying was observed and its spectrum was measured. The spectrum was attributed to Cl2(B→X) transition. The decomposition mechanism of NCl3 molecule was discussed. It was believed that the preliminary decomposition of NCl3 was induced by shockwave and then Cl and NCl2 radicals produced reacted with NCl3 to give sustained flame. The experimental results show that NCl3 auto-decomposition can produce a large amount of radicals to replace discharge or combustor as the source of chlorine atom.
2007,
19.
Abstract:
The master oscillator, power amplifier arrangement was experimentally investigated. The master laser was divided into 2 paths by a fiber beam splitter, and the two amplified beams were combined by a fiber coupler. A sample of the combined beam was relayed to a PC based on phase detection system which comprised photodiodes, preamplifiers and an A/D card. Phase corrections were calculated using Labview and the feedback voltages were applied to the phase shifters directly from analogue output channels. Coherent combining of two fiber lasers array was realized. After the control loop was turned on, optical path difference of two fiber amplifiers was modulo 2π, the output intensity was kept at the status of stable high brightness.
The master oscillator, power amplifier arrangement was experimentally investigated. The master laser was divided into 2 paths by a fiber beam splitter, and the two amplified beams were combined by a fiber coupler. A sample of the combined beam was relayed to a PC based on phase detection system which comprised photodiodes, preamplifiers and an A/D card. Phase corrections were calculated using Labview and the feedback voltages were applied to the phase shifters directly from analogue output channels. Coherent combining of two fiber lasers array was realized. After the control loop was turned on, optical path difference of two fiber amplifiers was modulo 2π, the output intensity was kept at the status of stable high brightness.
2007,
19.
Abstract:
For a pulsed kJ-level high energy Nd: glass solid-state laser, temperature distributions have been numerically studied under two thermal management methods, a traditional method with a fixed cooling water temperature, and a novel method with a prompt water temperature rise after each pump pulse. The results have shown that the temperature gradient in the laser rod can be limited to a low level to ensure the high energy output laser with a high beam quality, by employing the novel thermal management method. And the optimized values of the heated water temperature rise, near the average temperature rise value caused by one pump pulse, have been calculated for different pulse intervals and different input energies. For an interval time of 15 s, the heated water temperature rise after one pump
For a pulsed kJ-level high energy Nd: glass solid-state laser, temperature distributions have been numerically studied under two thermal management methods, a traditional method with a fixed cooling water temperature, and a novel method with a prompt water temperature rise after each pump pulse. The results have shown that the temperature gradient in the laser rod can be limited to a low level to ensure the high energy output laser with a high beam quality, by employing the novel thermal management method. And the optimized values of the heated water temperature rise, near the average temperature rise value caused by one pump pulse, have been calculated for different pulse intervals and different input energies. For an interval time of 15 s, the heated water temperature rise after one pump
2007,
19.
Abstract:
The laser angle detection system using different optical transformation characters of the beam expander in forward and converse dirction, and the angle sensitive multiply optical system of bi-directional transmission in a common aperture is combined with photoelectric precise position sensitive detector(PSD) in this system. The basic principle of high sensitive optics angle detection is analyzed, and the relation between detected angle and the signal of the position sensitive detector is given. In order to eliminate the influence of the photoelectric noise on detection resolution, the correlation detection mode is adopted in signal processing. By compressing effective band width of the system noise signal, the disturbed signal is filtered from frequency domain, and the high-resolution angl
The laser angle detection system using different optical transformation characters of the beam expander in forward and converse dirction, and the angle sensitive multiply optical system of bi-directional transmission in a common aperture is combined with photoelectric precise position sensitive detector(PSD) in this system. The basic principle of high sensitive optics angle detection is analyzed, and the relation between detected angle and the signal of the position sensitive detector is given. In order to eliminate the influence of the photoelectric noise on detection resolution, the correlation detection mode is adopted in signal processing. By compressing effective band width of the system noise signal, the disturbed signal is filtered from frequency domain, and the high-resolution angl
2007,
19.
Abstract:
The concept of repetitively-pumped times of atomic iodine in COIL was introduced. According to the law of energy-conservation, an equivalent lasing model was built. The non-extractable residual energy while lasing, the relaxation period for upper energy-level of atomic iodine and the energy-transfer period of collision between singlet oxygen and atomic iodine were calculated. The calculation formula for COIL output power agrees better with the experimental results than the original one does. Both theoretical and experimental results indicate that: if the iodine flow rate is too low, the laser gain is less than the loss, and the laser cannot start operating. If the iodine flow rate is increased gradually, the laser output power increases accordingly, and the repetitively-pumped times of the
The concept of repetitively-pumped times of atomic iodine in COIL was introduced. According to the law of energy-conservation, an equivalent lasing model was built. The non-extractable residual energy while lasing, the relaxation period for upper energy-level of atomic iodine and the energy-transfer period of collision between singlet oxygen and atomic iodine were calculated. The calculation formula for COIL output power agrees better with the experimental results than the original one does. Both theoretical and experimental results indicate that: if the iodine flow rate is too low, the laser gain is less than the loss, and the laser cannot start operating. If the iodine flow rate is increased gradually, the laser output power increases accordingly, and the repetitively-pumped times of the
2007,
19.
Abstract:
Influences on the mode of positive-branch confocal unstable resonator are analyzed, which is caused by deformation of resonator mirrors. The coupling relations between deformation of resonator mirrors and laser modes are solved by using methods of time discrete, fast Fourier transform(FFT) and finite element analysis(FEA). With the increasing working time of laser discreteness, the results of calculation show that temperature increment and deformation of resonator mirrors become serious, which causes decline of laser modes and beam quality. The uniformity of phase and dispersing appearance are discussed. The correlative experiments show that laser output beam quality becomes worse when the laser works longer.
Influences on the mode of positive-branch confocal unstable resonator are analyzed, which is caused by deformation of resonator mirrors. The coupling relations between deformation of resonator mirrors and laser modes are solved by using methods of time discrete, fast Fourier transform(FFT) and finite element analysis(FEA). With the increasing working time of laser discreteness, the results of calculation show that temperature increment and deformation of resonator mirrors become serious, which causes decline of laser modes and beam quality. The uniformity of phase and dispersing appearance are discussed. The correlative experiments show that laser output beam quality becomes worse when the laser works longer.
2007,
19.
Abstract:
Because of the reflection on the surface of the gratings, the transmittance of the components can not meet the requirement of the inertial confinement fusion(ICF) system. To resolve the problem, this paper introduces a kind of scheme adopting coating to reduce the reflection of the gratings' surface. The characteristics of beam sampling grating(BSG) with anti-reflection sol-gel coating are analyzed using the rigorous coupled-wave theory. The anti-reflection characteristics of the BSG with conformal anti-reflective(AR) coating and planar AR coating are discussed in detail. The results show that the planar AR coating eliminates the reflection of the gratings' surface drastically. The validity of the anti-reflection technology is distinct in the application in the high power laser propagation
Because of the reflection on the surface of the gratings, the transmittance of the components can not meet the requirement of the inertial confinement fusion(ICF) system. To resolve the problem, this paper introduces a kind of scheme adopting coating to reduce the reflection of the gratings' surface. The characteristics of beam sampling grating(BSG) with anti-reflection sol-gel coating are analyzed using the rigorous coupled-wave theory. The anti-reflection characteristics of the BSG with conformal anti-reflective(AR) coating and planar AR coating are discussed in detail. The results show that the planar AR coating eliminates the reflection of the gratings' surface drastically. The validity of the anti-reflection technology is distinct in the application in the high power laser propagation
2007,
19.
Abstract:
The high intensity pulse source of soft X-ray for calibration was formed with multilayer mirror as dispersive elements and laser plasma interaction as X-ray source. The monochromator system with 4 channels was set up and its performance was studied on SGⅡ high power laser facility experiment. The experiments included measurement of source intensity and stability, consistency of related channels and so on. Photon energy of source is 253 eV with 1.8×1019 photon/(s·cm2) source intensity and 820 eV with 3.2×1019 photon/(s·cm2) source intensity. The results show that the source can be used to calibrate XRD, mirror, multilayer, transmission grating and filter.
The high intensity pulse source of soft X-ray for calibration was formed with multilayer mirror as dispersive elements and laser plasma interaction as X-ray source. The monochromator system with 4 channels was set up and its performance was studied on SGⅡ high power laser facility experiment. The experiments included measurement of source intensity and stability, consistency of related channels and so on. Photon energy of source is 253 eV with 1.8×1019 photon/(s·cm2) source intensity and 820 eV with 3.2×1019 photon/(s·cm2) source intensity. The results show that the source can be used to calibrate XRD, mirror, multilayer, transmission grating and filter.
2007,
19.
Abstract:
The gradient bromating amorphous hydrogenated carbon films were prepared by low-pressure plasma chemical vapor deposition (LPPCVD) method using the mixture of bromoethane and hydrogen as source gas. The relationships of the film deposition rate and the hydrogen, and that of the bromine content and the bromioethane flowrate were described. The influences of the etching time and bromine flowrate on the main bounding state of the film CH C-Csp2 and C-Csp3 were analyzed. The results show that the deposition speed of the thin film decreases linearly with the increment of the hydrogen flowrate. Bromine content increases at first and then reduces with inreasment of the bromoethane flowrate. The longer the etch time and the lower the bromoethane flowrate are, the harder the prapared thin film is.
The gradient bromating amorphous hydrogenated carbon films were prepared by low-pressure plasma chemical vapor deposition (LPPCVD) method using the mixture of bromoethane and hydrogen as source gas. The relationships of the film deposition rate and the hydrogen, and that of the bromine content and the bromioethane flowrate were described. The influences of the etching time and bromine flowrate on the main bounding state of the film CH C-Csp2 and C-Csp3 were analyzed. The results show that the deposition speed of the thin film decreases linearly with the increment of the hydrogen flowrate. Bromine content increases at first and then reduces with inreasment of the bromoethane flowrate. The longer the etch time and the lower the bromoethane flowrate are, the harder the prapared thin film is.
2007,
19.
Abstract:
The feasibility of gradient optical films taking the place of classical layered structure high-reflectivity films in the field of high power laser is theoretically studied. To study the wavelength matching and electric field distribution, an example that the laser of 1 064 nm wavelength transmits in gradient optical films which is prepared with linear co-evaporation method is given. A numerical method which is applied to the gradient film with 14 perioded structure is proposed to obtain the matching thickness. Based on the Maxwell equation, the distribution of electric field is calculated. The result indicates that the distribution is similar to the classical layered high-reflectivity film but gradient film is likely to get damaged in surface. The design object of gradient film is to make
The feasibility of gradient optical films taking the place of classical layered structure high-reflectivity films in the field of high power laser is theoretically studied. To study the wavelength matching and electric field distribution, an example that the laser of 1 064 nm wavelength transmits in gradient optical films which is prepared with linear co-evaporation method is given. A numerical method which is applied to the gradient film with 14 perioded structure is proposed to obtain the matching thickness. Based on the Maxwell equation, the distribution of electric field is calculated. The result indicates that the distribution is similar to the classical layered high-reflectivity film but gradient film is likely to get damaged in surface. The design object of gradient film is to make
2007,
19.
Abstract:
High density resorcinol-formaldehyde carbonized aerogel(CRF) ICF target was prepared from resorcinol and formaldehyde by improving synthesis conditions, and the cracking problem of high density CRF aerogels was solved. The elements and phase of CRF carbonized aerogels were analyzed. N2 and H2 adsorption properties of the aerogels were analyzed with Autosorb-1. The results show that the CRF carbonized aerogels is a kind of non-crystalline graphite-like solids mainly composed of carbon, the aerogels has homogeneous structure and excellent processable characteristic. The specific surface area and the average pore diameter of the aerogels are 676 m2·g-1 and 7.16 nm, respectively. The aerogel has a favorable hydrogen adsorption with a mass percent of 2.28% and a volumetric density of 17.83 kg?
High density resorcinol-formaldehyde carbonized aerogel(CRF) ICF target was prepared from resorcinol and formaldehyde by improving synthesis conditions, and the cracking problem of high density CRF aerogels was solved. The elements and phase of CRF carbonized aerogels were analyzed. N2 and H2 adsorption properties of the aerogels were analyzed with Autosorb-1. The results show that the CRF carbonized aerogels is a kind of non-crystalline graphite-like solids mainly composed of carbon, the aerogels has homogeneous structure and excellent processable characteristic. The specific surface area and the average pore diameter of the aerogels are 676 m2·g-1 and 7.16 nm, respectively. The aerogel has a favorable hydrogen adsorption with a mass percent of 2.28% and a volumetric density of 17.83 kg?
2007,
19.
Abstract:
Mo/Si multilayers were prepared by magnetron sputtering. With different sputtering power of Mo target, surface morphology and crystal phases of Mo/Si multilayers were studied by AFM and XRD. Soft X-ray reflectivity of Mo/Si multilayers were measured. As sputtering power of Mo target was increasing, surface roughness of Mo/Si film was increasing, characteristic diffraction peak of Mo species became stronger and stronger, furthermore, soft X-ray peak reflectivity of Mo/Si multilayers first increased and then reduced.
Mo/Si multilayers were prepared by magnetron sputtering. With different sputtering power of Mo target, surface morphology and crystal phases of Mo/Si multilayers were studied by AFM and XRD. Soft X-ray reflectivity of Mo/Si multilayers were measured. As sputtering power of Mo target was increasing, surface roughness of Mo/Si film was increasing, characteristic diffraction peak of Mo species became stronger and stronger, furthermore, soft X-ray peak reflectivity of Mo/Si multilayers first increased and then reduced.
2007,
19.
Abstract:
Organic polymer foams have many uses in inertial confinement fusion targets and Z-pinch loads. However, many low density foams are not uniform in some extent, which has bad effects on their performance. Two techniques, the beta radiation technology and X-ray computed tomography(CT) are used for density uniformity characterizing. The data show that the trimethylolpropane trimethacrylate(TMPTA) polymer foams have small density variations: the density is greater at the outer edges than that of the interior of foam. The experiment shows that the measurement of the density distribution in foams can meet the requirement of experiment fundamentally at present, while the spatial resolution and the density resolution need improvement.
Organic polymer foams have many uses in inertial confinement fusion targets and Z-pinch loads. However, many low density foams are not uniform in some extent, which has bad effects on their performance. Two techniques, the beta radiation technology and X-ray computed tomography(CT) are used for density uniformity characterizing. The data show that the trimethylolpropane trimethacrylate(TMPTA) polymer foams have small density variations: the density is greater at the outer edges than that of the interior of foam. The experiment shows that the measurement of the density distribution in foams can meet the requirement of experiment fundamentally at present, while the spatial resolution and the density resolution need improvement.
2007,
19.
Abstract:
A model of a compact wide-band TM01-TE11 mode converter with power capacity more than 1 GW and the maximum dimension of φ20.5 cm×55.2 cm is designed, in which the coaxial TEM and rectangular TE10 modes are used as the intermediate modes. When the frequency is 1.63~2.22 GHz, the conversion efficiency of the converter is over 90% with bandwidth over 30%, and the reflectance is less than -11 dB. The highest conversion efficiency is 99.8% and lowest reflectance is -26.3 dB when the frequency is 1.72 GHz. The input and output ports of the converter are exactly aligned on the same axis, which is helpful for designing the compact microwave launching systems.
A model of a compact wide-band TM01-TE11 mode converter with power capacity more than 1 GW and the maximum dimension of φ20.5 cm×55.2 cm is designed, in which the coaxial TEM and rectangular TE10 modes are used as the intermediate modes. When the frequency is 1.63~2.22 GHz, the conversion efficiency of the converter is over 90% with bandwidth over 30%, and the reflectance is less than -11 dB. The highest conversion efficiency is 99.8% and lowest reflectance is -26.3 dB when the frequency is 1.72 GHz. The input and output ports of the converter are exactly aligned on the same axis, which is helpful for designing the compact microwave launching systems.
2007,
19.
Abstract:
A new radial three-cavity structure of the coaxial virtual cathode oscillator is proposed and studied numerically in this paper. Using the radial three-cavity structure, the beam-wave conversion efficiency is enhanced by modulating the E-field in the beam-wave interaction area, whereas the resonator composed of the radial three-cavity configuration and the mesh anode helps restrain mode competition efficiently. Also, the output microwave power is improved by the coaxial extraction structure in respect that it benefits the energy extraction and it absorbs the used electrons entering the drifting tube. With an electron beam of 400 kV and 50 kA, a peak instantaneous power about 6 GW is achieved by simulation at 4.14 GHz. The peak period-averaged power reaches 2.45 GW and the beam-wave convers
A new radial three-cavity structure of the coaxial virtual cathode oscillator is proposed and studied numerically in this paper. Using the radial three-cavity structure, the beam-wave conversion efficiency is enhanced by modulating the E-field in the beam-wave interaction area, whereas the resonator composed of the radial three-cavity configuration and the mesh anode helps restrain mode competition efficiently. Also, the output microwave power is improved by the coaxial extraction structure in respect that it benefits the energy extraction and it absorbs the used electrons entering the drifting tube. With an electron beam of 400 kV and 50 kA, a peak instantaneous power about 6 GW is achieved by simulation at 4.14 GHz. The peak period-averaged power reaches 2.45 GW and the beam-wave convers
2007,
19.
Abstract:
This paper introduces the 2 kW continuous wave power combining technique based on TWTs. It mainly proceeds the analysis of the combining efficiency and the factors influencing the conformation of magnitude and phase. A 2 kW power amplifier is designed based on the analysis. The magnitude equalizing, phase equalizing and combiner protecting are also discussed. The experiments indicate that the combining efficiency can be greater than 95% with magnitude and phase equalizing technique.
This paper introduces the 2 kW continuous wave power combining technique based on TWTs. It mainly proceeds the analysis of the combining efficiency and the factors influencing the conformation of magnitude and phase. A 2 kW power amplifier is designed based on the analysis. The magnitude equalizing, phase equalizing and combiner protecting are also discussed. The experiments indicate that the combining efficiency can be greater than 95% with magnitude and phase equalizing technique.
2007,
19.
Abstract:
During the experiments on electromagnetic pulse (EMP) action utility of micro-electronic components, aimed at three kinds of micro-wave low-noise silicon dynatron transistors, positive EMP (including ESD and square-wave EMP) stresses were injected into all the combinations (CB, BC, CE, EC, EB and BE). Through recording and comparing the damaged voltage of each injected combination, it can be found that the most sensitive port to EMP of micro-wave low-noise transistors is not EB (emitter-base) but CB (collector-base). By analyzing the device fabric and the process of discharge, the failure mechanism of CB and EB is separately determined. So it makes clear that CB is more sensitive to EMP than EB.
During the experiments on electromagnetic pulse (EMP) action utility of micro-electronic components, aimed at three kinds of micro-wave low-noise silicon dynatron transistors, positive EMP (including ESD and square-wave EMP) stresses were injected into all the combinations (CB, BC, CE, EC, EB and BE). Through recording and comparing the damaged voltage of each injected combination, it can be found that the most sensitive port to EMP of micro-wave low-noise transistors is not EB (emitter-base) but CB (collector-base). By analyzing the device fabric and the process of discharge, the failure mechanism of CB and EB is separately determined. So it makes clear that CB is more sensitive to EMP than EB.
2007,
19.
Abstract:
Applying CST electromagnetic software, using Guass pulse and PML6 boundary condition, the relation between physical structural parameters and performance of the electric-magnetic vibrator combined ultrawideband (UWB) antenna was investigated. The results indicate the conductor screen and current loop of antenna improve port parameter of different frequency. When the total lergth of current loop with 105 cm is about twice as antenna size with 50 cm, the reflected energy of antenna is less and the port parameter is flatted. Radiation bandwidth of antenna is decided by its physicl size, and the bigger the antenna size is, the better the radiated performance of low frequency is.
Applying CST electromagnetic software, using Guass pulse and PML6 boundary condition, the relation between physical structural parameters and performance of the electric-magnetic vibrator combined ultrawideband (UWB) antenna was investigated. The results indicate the conductor screen and current loop of antenna improve port parameter of different frequency. When the total lergth of current loop with 105 cm is about twice as antenna size with 50 cm, the reflected energy of antenna is less and the port parameter is flatted. Radiation bandwidth of antenna is decided by its physicl size, and the bigger the antenna size is, the better the radiated performance of low frequency is.
2007,
19.
Abstract:
The Cusp electron gun for second harmonic Gyro-TWT is simulated by the three dimensional PIC software and Ukrainion electronic optical software TAU, and the electronic 3D velocity value is extracted to calculate the velocity ratio of the transverse velocity and longitudinal velocity. With the anode voltage and the cathode current changing, the variational process of the electron velocity ratio and spread is simulated, and the results of the average velocity ratio 1.1 and spread 9.5% are obtained. Based on the mean radius of the electron beam and the relationship between the radius and the transverse, longitudinal relocity, an experimental method of measuring the electron velocity ratio is put forward. When the electron holding some energy shock at a fluorescence glass, the light spot induc
The Cusp electron gun for second harmonic Gyro-TWT is simulated by the three dimensional PIC software and Ukrainion electronic optical software TAU, and the electronic 3D velocity value is extracted to calculate the velocity ratio of the transverse velocity and longitudinal velocity. With the anode voltage and the cathode current changing, the variational process of the electron velocity ratio and spread is simulated, and the results of the average velocity ratio 1.1 and spread 9.5% are obtained. Based on the mean radius of the electron beam and the relationship between the radius and the transverse, longitudinal relocity, an experimental method of measuring the electron velocity ratio is put forward. When the electron holding some energy shock at a fluorescence glass, the light spot induc
2007,
19.
Abstract:
A pulse constant-current source based on capacitor discharge was developed for LIA accelerator. Theoretic analysis and simulation for this source was proceeded. Numerical simulation has consistent result with experiment. The experiment result shows that this kind of source can work in pulse and its input power has reduced greatly. When the output current is 500 A and current duration is 0.3 s, this source has an output current of 0.2%, input power of 400 W and output power of 25 kW. This kind of source is very suitable for LIA.
A pulse constant-current source based on capacitor discharge was developed for LIA accelerator. Theoretic analysis and simulation for this source was proceeded. Numerical simulation has consistent result with experiment. The experiment result shows that this kind of source can work in pulse and its input power has reduced greatly. When the output current is 500 A and current duration is 0.3 s, this source has an output current of 0.2%, input power of 400 W and output power of 25 kW. This kind of source is very suitable for LIA.
2007,
19.
Abstract:
A high speed circuit is designed for obtaining the BEPCⅡ bunch fiducial signal based on tunnel diode circuit, monostable multivibrator and ECL logic technology. The bunch train with a gap in storage ring is described. The waveforms of the induced signal of the pickup electrode after long cable transmission decay are analyzed. A monostable multivibrator using tunnel diode is described, with which a positive pulse of 0.3 ns is stretched to a 4 ns ECL signal. The ways to find out gap in standard and non-standard injection mode are presented. The test result shows that the circuit works well in standard and non-standard bunch injection modes and the measured timing jitter of 80.49 ps(RMS) fits for the design.
A high speed circuit is designed for obtaining the BEPCⅡ bunch fiducial signal based on tunnel diode circuit, monostable multivibrator and ECL logic technology. The bunch train with a gap in storage ring is described. The waveforms of the induced signal of the pickup electrode after long cable transmission decay are analyzed. A monostable multivibrator using tunnel diode is described, with which a positive pulse of 0.3 ns is stretched to a 4 ns ECL signal. The ways to find out gap in standard and non-standard injection mode are presented. The test result shows that the circuit works well in standard and non-standard bunch injection modes and the measured timing jitter of 80.49 ps(RMS) fits for the design.
2007,
19.
Abstract:
Based on the merger design theory, the transportation of the merger in PKU-ERL is designed,and the optimized parameters is given which can satisfy the demands of PKU-ERL. The increasements of the emittance and energy spread caused by space charge and coherent synchrotron radiation(CSR) in the merger part are studied. Simulation results show that space charge influences the beam envelope obviously but has little influences on the emittance. CSR has little influence on the emittance, the energy spread and the envelope.
Based on the merger design theory, the transportation of the merger in PKU-ERL is designed,and the optimized parameters is given which can satisfy the demands of PKU-ERL. The increasements of the emittance and energy spread caused by space charge and coherent synchrotron radiation(CSR) in the merger part are studied. Simulation results show that space charge influences the beam envelope obviously but has little influences on the emittance. CSR has little influence on the emittance, the energy spread and the envelope.
2007,
19.
Abstract:
From the basic define of the inductance, a new formula to calculate dynamic inductance is deduced, which can figure out the nonlinear inductance of winding with magnetic cores easily by numerical calculation. The dynamic inductances of a pure winding in 50 Hz alternating current, a 5 rounds winding with a ferrite core in 50 Hz alternating current and a coaxial cavity with 17 ferrite cores in double pulses exciting current are calculated to prove the accuracy of the formula. The magnetic core’s permeability can be figure out from the inductance, which make it easily to confirm the applicability of the magnetic core.
From the basic define of the inductance, a new formula to calculate dynamic inductance is deduced, which can figure out the nonlinear inductance of winding with magnetic cores easily by numerical calculation. The dynamic inductances of a pure winding in 50 Hz alternating current, a 5 rounds winding with a ferrite core in 50 Hz alternating current and a coaxial cavity with 17 ferrite cores in double pulses exciting current are calculated to prove the accuracy of the formula. The magnetic core’s permeability can be figure out from the inductance, which make it easily to confirm the applicability of the magnetic core.
2007,
19.
Abstract:
DPF-300 pulsed X-ray source is a mather-type dense plasma focus device and the synchronous triggering of 40 switches is the key of the device. This paper introduces the structural model, principle and performance of the the synchronous trigger system. The system triggers by three steps in series. Firstly, the initial pulsed generator triggers a hydrogenous thyratron. Secondly, the thyratron triggers the multi-output switch. Thirdly, the multi-output switch triggers the main discharge switch. The system can synchronously trigger 40 coaxial field distortion switches. The triggering voltage scope of activities is 20~40 kV, rise time of the triggering pulse is about 40 ns, pulsed width is about 60 ns, and the rise gradient of the triggering voltage is about 0.67 kV/ns. The triggering pulse's j
DPF-300 pulsed X-ray source is a mather-type dense plasma focus device and the synchronous triggering of 40 switches is the key of the device. This paper introduces the structural model, principle and performance of the the synchronous trigger system. The system triggers by three steps in series. Firstly, the initial pulsed generator triggers a hydrogenous thyratron. Secondly, the thyratron triggers the multi-output switch. Thirdly, the multi-output switch triggers the main discharge switch. The system can synchronously trigger 40 coaxial field distortion switches. The triggering voltage scope of activities is 20~40 kV, rise time of the triggering pulse is about 40 ns, pulsed width is about 60 ns, and the rise gradient of the triggering voltage is about 0.67 kV/ns. The triggering pulse's j
2007,
19.
Abstract:
The wave process and principle of the transmission line charging in impedance matched and mismatched condition are analyzed. The results show that the impedance mismatched charging technology can realize the power gain but lower the energy efficiency, while the impedance matched charging technology can obtain an energy transmission efficiency of 100%, but can’t realize the power gain. The radiation fields of the 5 W charged transmission line with length of 30, 45, 60 mm are studied experimentally, using 27 W charging transmission line, which is 540 mm long. A output pulse with risetime about 210 ps and peak voltage about 150 kV is obtained on the 5 Ω charged line, which is 45 mm long. The radiation electric field increases a little as the length of the charged transmission line increases
The wave process and principle of the transmission line charging in impedance matched and mismatched condition are analyzed. The results show that the impedance mismatched charging technology can realize the power gain but lower the energy efficiency, while the impedance matched charging technology can obtain an energy transmission efficiency of 100%, but can’t realize the power gain. The radiation fields of the 5 W charged transmission line with length of 30, 45, 60 mm are studied experimentally, using 27 W charging transmission line, which is 540 mm long. A output pulse with risetime about 210 ps and peak voltage about 150 kV is obtained on the 5 Ω charged line, which is 45 mm long. The radiation electric field increases a little as the length of the charged transmission line increases
2007,
19.
Abstract:
Working principle of magnetic core in linear transformer driver(LTD) was introduced. The influence of the magnetic core’s volt-second product on the output of LTD was deduced by means of simulation. A series of experiments were designed to evaluate the saturation of the magnetic core. These experiments were carried out under such conditions as different volt-second product of the core, different reset state of the core and different load resistance. Conclusions as the criteria of magnetic core saturation and reset effects of reverse current to magnetic core were drawn from the experiment results. The experiment results validate the simulation results. Application of the saturation effect of magnetic core to specific fields were suggested.
Working principle of magnetic core in linear transformer driver(LTD) was introduced. The influence of the magnetic core’s volt-second product on the output of LTD was deduced by means of simulation. A series of experiments were designed to evaluate the saturation of the magnetic core. These experiments were carried out under such conditions as different volt-second product of the core, different reset state of the core and different load resistance. Conclusions as the criteria of magnetic core saturation and reset effects of reverse current to magnetic core were drawn from the experiment results. The experiment results validate the simulation results. Application of the saturation effect of magnetic core to specific fields were suggested.
2007,
19.
Abstract:
To investigate the problem of breakdown between the adjacent turns of the helix pulse forming line (PFL), the influences on the axial electric field of the helix PFL were analyzed numerically. Numerical results indicated that it was easier to breakdown between the adjacent turns if the helix angle was bigger, the rise time of the switch or the load value was smaller. To study the problem of the upshot and hollow on the output pulse, the influences on the waveform caused by the impedance mismatched sections in helix PFL accelerator were analyzed numerically and experimentally. An approximate square high voltage pulse was obtained by making the impedances of the joint section (between the helix line and switch) and the transition section (between switch and load) close to that of the helix l
To investigate the problem of breakdown between the adjacent turns of the helix pulse forming line (PFL), the influences on the axial electric field of the helix PFL were analyzed numerically. Numerical results indicated that it was easier to breakdown between the adjacent turns if the helix angle was bigger, the rise time of the switch or the load value was smaller. To study the problem of the upshot and hollow on the output pulse, the influences on the waveform caused by the impedance mismatched sections in helix PFL accelerator were analyzed numerically and experimentally. An approximate square high voltage pulse was obtained by making the impedances of the joint section (between the helix line and switch) and the transition section (between switch and load) close to that of the helix l
2007,
19.
Abstract:
In order to study the impulse voltage distribution in the pulse transformer’s taper windings, experiment was carried out with 3 kinds of single impulse voltage input whose pulse width was 1 μs, 500 ns and 100 ns respectively. Under experimental conditions, turn-to-ground voltage and interturn voltage in the structural windings with air-core and iron-core were compared. The result indicates that the impulse voltage distribution in the coils is nonlinear and oscillates obvious at high frequency, which increases voltage gradients in the head of windings obviously. Distortion also appears as the pulse width decreases. The interturn voltage fluctuates due to the voltage wave transmission. The extremal interturn voltage always appear in either head or end of the windings. To some extent, the i
In order to study the impulse voltage distribution in the pulse transformer’s taper windings, experiment was carried out with 3 kinds of single impulse voltage input whose pulse width was 1 μs, 500 ns and 100 ns respectively. Under experimental conditions, turn-to-ground voltage and interturn voltage in the structural windings with air-core and iron-core were compared. The result indicates that the impulse voltage distribution in the coils is nonlinear and oscillates obvious at high frequency, which increases voltage gradients in the head of windings obviously. Distortion also appears as the pulse width decreases. The interturn voltage fluctuates due to the voltage wave transmission. The extremal interturn voltage always appear in either head or end of the windings. To some extent, the i
2007,
19.
Abstract:
The design of strip Blumlein line was presented with the polymer-composite as energy storage dielectric and GaAs-PCSS as circuit switch.The experment results show that relative permittivity of the polymer-composite reaches 80~250, the permittivity and susceptibility of the dielectric do not change under different voltages.The risetime of voltage pulse of the strip Blumlein line is less than 5 ns, the flat top is about 22 ns with ripples of flattop about ±1%. The designed Blumlein line can satisfy the needs of application.
The design of strip Blumlein line was presented with the polymer-composite as energy storage dielectric and GaAs-PCSS as circuit switch.The experment results show that relative permittivity of the polymer-composite reaches 80~250, the permittivity and susceptibility of the dielectric do not change under different voltages.The risetime of voltage pulse of the strip Blumlein line is less than 5 ns, the flat top is about 22 ns with ripples of flattop about ±1%. The designed Blumlein line can satisfy the needs of application.
2007,
19.
Abstract:
This paper presents the research on transmission and reflection characterization of left-handed materials. It introduces correlative sample patterns and the measuring system. Using high frequency structure simulator(HFSS) method, based on former broad-band measurement which got a high uniform between simulation and measurement of S parameters. Simulation of insertion loss demonstrates that losses in measurements mainly attribute to finite conductivity of copper wire, and optimal-lossless frequency region must be higher than resonance frequency of split ring resonators in theory.
This paper presents the research on transmission and reflection characterization of left-handed materials. It introduces correlative sample patterns and the measuring system. Using high frequency structure simulator(HFSS) method, based on former broad-band measurement which got a high uniform between simulation and measurement of S parameters. Simulation of insertion loss demonstrates that losses in measurements mainly attribute to finite conductivity of copper wire, and optimal-lossless frequency region must be higher than resonance frequency of split ring resonators in theory.
2007,
19.
Abstract:
An improved 2D finite difference time domain (FDTD) method for TM mode based on the lossy Drude dispersive models is presented. The characteristics of a Gaussian beam propagation through a double negative media(DNG) slab are studied by using the dispersive FDTD method. Meanwhile, the electric field intensity distributions inside and outside the DNG slab are presented. The results show that the DNG slab can focus the normal incident Gaussian beam, and that as to the oblique incident one, the refracted beam and the incident beam are on the same side of the normal, which suggests that the Gaussian beam undergoes a negative refraction in the interface of DNG slab and air. The results validate the dispersive FDTD method in this paper.
An improved 2D finite difference time domain (FDTD) method for TM mode based on the lossy Drude dispersive models is presented. The characteristics of a Gaussian beam propagation through a double negative media(DNG) slab are studied by using the dispersive FDTD method. Meanwhile, the electric field intensity distributions inside and outside the DNG slab are presented. The results show that the DNG slab can focus the normal incident Gaussian beam, and that as to the oblique incident one, the refracted beam and the incident beam are on the same side of the normal, which suggests that the Gaussian beam undergoes a negative refraction in the interface of DNG slab and air. The results validate the dispersive FDTD method in this paper.
2007,
19.
Abstract:
A device for measuring secondary electron emission yield of insulator was set up successfully, which was made up of electron gun system, vacuum system and electrical system, the energy band of primary current produced by the device was 0.8~60 keV. By the single-pulse electron gun method, the secondary electron emission yield of polycrystal MgO yield was measured when the primary electron energy band was 0.8~45 keV. In the experimental measurement, the distance from material surface to secondary electron collector was 35 mm, the bias voltage was 45 V. The maximum measured yield of MgO produced by the method of magnetron sputtering was 2.83, which was in the range of 2 to 26, and the corresponding primary electron energy was 980 eV. These results proved that the secondary electron emission y
A device for measuring secondary electron emission yield of insulator was set up successfully, which was made up of electron gun system, vacuum system and electrical system, the energy band of primary current produced by the device was 0.8~60 keV. By the single-pulse electron gun method, the secondary electron emission yield of polycrystal MgO yield was measured when the primary electron energy band was 0.8~45 keV. In the experimental measurement, the distance from material surface to secondary electron collector was 35 mm, the bias voltage was 45 V. The maximum measured yield of MgO produced by the method of magnetron sputtering was 2.83, which was in the range of 2 to 26, and the corresponding primary electron energy was 980 eV. These results proved that the secondary electron emission y
2007,
19.
Abstract:
Considering recoil of electron, a new theory to explain axial channelling radiation is presented based on Compton scattering of virtual photon with relativistic electron. In the reference system of the electron at rest, the crystal field is taken as virtual photon. By Compton scattering of virtual photon with relativistic electron, the virtual photon can be transformed into real photon to radiate out. According to this theory, the precise wavelength formula of axial channelling radiation is obtained. The wavelength formula of classical theory is the approximate formula of the precise wavelength formula of axial channelling radiation. The precise power formula of axial channelling radiation is obtained. The results are consistent with classical scattering theory.
Considering recoil of electron, a new theory to explain axial channelling radiation is presented based on Compton scattering of virtual photon with relativistic electron. In the reference system of the electron at rest, the crystal field is taken as virtual photon. By Compton scattering of virtual photon with relativistic electron, the virtual photon can be transformed into real photon to radiate out. According to this theory, the precise wavelength formula of axial channelling radiation is obtained. The wavelength formula of classical theory is the approximate formula of the precise wavelength formula of axial channelling radiation. The precise power formula of axial channelling radiation is obtained. The results are consistent with classical scattering theory.
2007,
19.
Abstract:
ZnO:Al thin films doped with different aluminum concentration are deposited on(0001) sapphire substrates by the sol-gel technique. Thermal annealing of ZnO thin films is carried out in argon atmosphere from 600 to 950 ℃. The effects of annealing temperature and dopant concentration on the optical properties of ZnO:Al thin films are investigated. Results show that the UV peak intensity is enhanced as increasing annealing temperature and dopant concentration while green emission related with deep level defects is decreased. The optical band gap increases from 3.21 eV to 3.25 eV as increasing dopant concentration from 0.01% up to 1%. The optical absorption in the visible region increases with increasing annealing temperature while decreases in the ultraviolet region. The optical transmittanc
ZnO:Al thin films doped with different aluminum concentration are deposited on(0001) sapphire substrates by the sol-gel technique. Thermal annealing of ZnO thin films is carried out in argon atmosphere from 600 to 950 ℃. The effects of annealing temperature and dopant concentration on the optical properties of ZnO:Al thin films are investigated. Results show that the UV peak intensity is enhanced as increasing annealing temperature and dopant concentration while green emission related with deep level defects is decreased. The optical band gap increases from 3.21 eV to 3.25 eV as increasing dopant concentration from 0.01% up to 1%. The optical absorption in the visible region increases with increasing annealing temperature while decreases in the ultraviolet region. The optical transmittanc
