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RSS2012 Vol. 24, No. 09
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2012,
24: 2017-2021.
doi: 10.3788/HPLPB20122409.2017
Abstract:
A forced vibration measurement method by laser combining the laser signal and high frequency CCD in optical systems is introduced. The method solves the conversion problem between the vibration signal and laser signal in optical systems, which can not only measure the impact of vibration on the beam stability, but also acquire the frequency characteristics of vibration signals. Forced vibration in an optical system is measured when the frequencies of vibration signals are 150 Hz and 200 Hz by using the method and the attributes of the vibration signals obtained fits those of the input signals. Test and analysis results demonstrate that the method has a time amplitude uncertainty of 6.25 m and frequency resolution of 2 Hz. The handy and efficient method, whose measurement is precise, has been applied to the beam pointing stability study of the multiplexing excimer MOPA laser targeting test platform accordingly.
A forced vibration measurement method by laser combining the laser signal and high frequency CCD in optical systems is introduced. The method solves the conversion problem between the vibration signal and laser signal in optical systems, which can not only measure the impact of vibration on the beam stability, but also acquire the frequency characteristics of vibration signals. Forced vibration in an optical system is measured when the frequencies of vibration signals are 150 Hz and 200 Hz by using the method and the attributes of the vibration signals obtained fits those of the input signals. Test and analysis results demonstrate that the method has a time amplitude uncertainty of 6.25 m and frequency resolution of 2 Hz. The handy and efficient method, whose measurement is precise, has been applied to the beam pointing stability study of the multiplexing excimer MOPA laser targeting test platform accordingly.
2012,
24: 2022-2026.
doi: 10.3788/HPLPB20122409.2022
Abstract:
Based on two theoretical models of refractive index structure parameters, the influence on atmosphere turbulence optical parameters exerted by atmosphere turbulence in different heights are discussed, including coherence length, isoplanatic angle, tilt isoplanatic angle, Greenwood frequency, Tyler frequency, and log-amplitude variance. Coherence length and log-amplitude variance are mainly controlled by the lower atmosphere turbulence, but isoplanatic angle, tilt isoplanatic angle, Greenwood frequency, and Tyler frequency are controlled by the upper troposphere turbulence strongly. Considering the importance of isoplanatic angle, the contribution rates of three parts of atmosphere turbulence are studied. The contributions of the lower atmosphere turbulence are all less than 3%, and those of theupper troposphere turbulence are all greater than 25%.
Based on two theoretical models of refractive index structure parameters, the influence on atmosphere turbulence optical parameters exerted by atmosphere turbulence in different heights are discussed, including coherence length, isoplanatic angle, tilt isoplanatic angle, Greenwood frequency, Tyler frequency, and log-amplitude variance. Coherence length and log-amplitude variance are mainly controlled by the lower atmosphere turbulence, but isoplanatic angle, tilt isoplanatic angle, Greenwood frequency, and Tyler frequency are controlled by the upper troposphere turbulence strongly. Considering the importance of isoplanatic angle, the contribution rates of three parts of atmosphere turbulence are studied. The contributions of the lower atmosphere turbulence are all less than 3%, and those of theupper troposphere turbulence are all greater than 25%.
2012,
24: 2027-2030.
doi: 10.3788/HPLPB20122409.2027
Abstract:
The development of the fiber laser-pumped optical parametric oscillator and its application in the directional infrared countermeasures technology was described. Some basic theories of laser infrared countermeasures were discussed. Based on the self-developed fiber laser-pumped continuous-wave optical parametric oscillator, 3.41, 3.63 and 3.82 m infrared lasers in the watt-level output were achieved by way of periodic tuning. The infrared jamming experiment was carried out by using all the three wavelengths of the laser and a mid-wave infrared thermography. Through comparison of the experimental results for the 3.82 m output laser in the transmission 750 m distance, it is obtained that the gray level of the infrared thermography saturated and unsaturated zone results changes greatly when the radiation density before the HgCdTe detectors is greater than 10 W/cm2. It can achieve the purpose of covering useful signal, and can make the guidance system failure.
The development of the fiber laser-pumped optical parametric oscillator and its application in the directional infrared countermeasures technology was described. Some basic theories of laser infrared countermeasures were discussed. Based on the self-developed fiber laser-pumped continuous-wave optical parametric oscillator, 3.41, 3.63 and 3.82 m infrared lasers in the watt-level output were achieved by way of periodic tuning. The infrared jamming experiment was carried out by using all the three wavelengths of the laser and a mid-wave infrared thermography. Through comparison of the experimental results for the 3.82 m output laser in the transmission 750 m distance, it is obtained that the gray level of the infrared thermography saturated and unsaturated zone results changes greatly when the radiation density before the HgCdTe detectors is greater than 10 W/cm2. It can achieve the purpose of covering useful signal, and can make the guidance system failure.
2012,
24: 2031-2036.
doi: 10.3788/HPLPB20122409.2031
Abstract:
The mid-infrared supercontinuum generation in telluride photonic crystal fiber with 2 m wavelength region pulsed laser pumping is numerically investigated. The material Raman response function is indirectly obtained from the Raman gain spectrum. The effective refractive index of the fundamental mode in telluride photonic crystal fiber is obtained using the material refractive index and waveguide structure through COMSOL software. Then the calculated dispersion and confinement loss of telluride photonic crystal fiber are plotted using the effective refractive index of the fundamental mode. The supercontinuum generation process in telluride photonic crystal fiber is studied by the adaptive split-step Fourier method. Assuming a 50 fs pulsed laser launched into telluride photonic crystal fiber with 1.96 m central wavelength and 20 kW peak power, a mid-infrared supercontinuum with a bandwidth from 1 m to 4.5 m is obtained when the fiber length is 6 cm.
The mid-infrared supercontinuum generation in telluride photonic crystal fiber with 2 m wavelength region pulsed laser pumping is numerically investigated. The material Raman response function is indirectly obtained from the Raman gain spectrum. The effective refractive index of the fundamental mode in telluride photonic crystal fiber is obtained using the material refractive index and waveguide structure through COMSOL software. Then the calculated dispersion and confinement loss of telluride photonic crystal fiber are plotted using the effective refractive index of the fundamental mode. The supercontinuum generation process in telluride photonic crystal fiber is studied by the adaptive split-step Fourier method. Assuming a 50 fs pulsed laser launched into telluride photonic crystal fiber with 1.96 m central wavelength and 20 kW peak power, a mid-infrared supercontinuum with a bandwidth from 1 m to 4.5 m is obtained when the fiber length is 6 cm.
2012,
24: 2037-2042.
doi: 10.3788/HPLPB20122409.2037
Abstract:
The wind profiles measured by a Rayleigh Doppler wind lidar are in good agreement with the pilot balloon wind profiles. The maximum discrepancy of the wind profiles of both the lidar and the pilot balloon is 3 m/s below 10 km and 4.5 m/s below 20 km. The maximum standard deviation of wind direction is 32 except for the inflexion at about 20 km altitude. The sequential detection results made by the lidar show the clear intense westerly jet with a local maximum speed of 70 m/s at about 10-12 km altitude, and a local minimum speed no less than 30 m/s. The minimum wind speed is less than 1 m/s at about 20 km altitude and wind speed increases with the altitude increasing above the inflexion. The wind direction is west wind of about 270 below the inflexion and east wind of about 90 above the inflexion. The capability of Rayleigh Doppler wind lidar, tracking the variation law of large scale season climate characteristics while giving prominence to the forming and evolving procedure of small scale transient climate characteristics, has been demonstrate.
The wind profiles measured by a Rayleigh Doppler wind lidar are in good agreement with the pilot balloon wind profiles. The maximum discrepancy of the wind profiles of both the lidar and the pilot balloon is 3 m/s below 10 km and 4.5 m/s below 20 km. The maximum standard deviation of wind direction is 32 except for the inflexion at about 20 km altitude. The sequential detection results made by the lidar show the clear intense westerly jet with a local maximum speed of 70 m/s at about 10-12 km altitude, and a local minimum speed no less than 30 m/s. The minimum wind speed is less than 1 m/s at about 20 km altitude and wind speed increases with the altitude increasing above the inflexion. The wind direction is west wind of about 270 below the inflexion and east wind of about 90 above the inflexion. The capability of Rayleigh Doppler wind lidar, tracking the variation law of large scale season climate characteristics while giving prominence to the forming and evolving procedure of small scale transient climate characteristics, has been demonstrate.
2012,
24: 2043-2046.
doi: 10.3788/HPLPB20122409.2043
Abstract:
Based on the thermal elastic model with thermal-mechanical uncoupling approximation and commonly-used assumptions, the scaling law in thermal deformation of high reflecting mirror under laser irradiation is obtained by equation analysis. For the same model, displacement, temperature rise, stress and strain change linearly with laser power density. The numerical results are consistent with the theory. The conclusions lay the foundation for using scaled small model to investigate the thermal deformation of large-size mirror under laser irradiation, and provide specific guidelines for the model designing and transforming experiment results to the prototype.
Based on the thermal elastic model with thermal-mechanical uncoupling approximation and commonly-used assumptions, the scaling law in thermal deformation of high reflecting mirror under laser irradiation is obtained by equation analysis. For the same model, displacement, temperature rise, stress and strain change linearly with laser power density. The numerical results are consistent with the theory. The conclusions lay the foundation for using scaled small model to investigate the thermal deformation of large-size mirror under laser irradiation, and provide specific guidelines for the model designing and transforming experiment results to the prototype.
2012,
24: 2047-2052.
doi: 10.3788/HPLPB20122409.2047
Abstract:
The far-field of the linearly polarized Gaussian beams diffracted at a circular aperture can be expressed as a sum of two orthogonal transversal electric (TE) and transversal magnetic (TM) terms. According to the far-field energy flux distributions of the TE and TM terms, the analytical expressions of the power of the TE and TM terms for the Gaussian diffracted beam are derived, which allow one to examine the ratios of the power of the TE and TM terms to the whole beam power. Based on the definition of the second-order moment of the far-field energy flux distributions, the analytical formulae of the far-field divergence angles of the Gaussian diffracted beam and its TE and TM terms are obtained, as well as the relationship among those far-field divergence angles. The influences of the f-parameter and the truncation parameter on the far-field divergence angles are analyzed. With the increase of the f-parameter, the far-field divergence angles first increase and finally tend to their respective saturated values. The influence of the truncation parameter on the far-field divergence angles is related to the f-parameter. When the f-parameter is relatively large, the effect of the truncation parameter on the far-field divergence angles is not distinct. When the f-parameter is moderate, the far-field divergence angles first decrease and finally tend to their respective minimum values with increasing the truncation parameter. When the f-parameter is relatively small, the far-field divergence angles of the Gaussian diffracted beam and its TM term fluctuate in a certain degree with varying the truncation parameter.
The far-field of the linearly polarized Gaussian beams diffracted at a circular aperture can be expressed as a sum of two orthogonal transversal electric (TE) and transversal magnetic (TM) terms. According to the far-field energy flux distributions of the TE and TM terms, the analytical expressions of the power of the TE and TM terms for the Gaussian diffracted beam are derived, which allow one to examine the ratios of the power of the TE and TM terms to the whole beam power. Based on the definition of the second-order moment of the far-field energy flux distributions, the analytical formulae of the far-field divergence angles of the Gaussian diffracted beam and its TE and TM terms are obtained, as well as the relationship among those far-field divergence angles. The influences of the f-parameter and the truncation parameter on the far-field divergence angles are analyzed. With the increase of the f-parameter, the far-field divergence angles first increase and finally tend to their respective saturated values. The influence of the truncation parameter on the far-field divergence angles is related to the f-parameter. When the f-parameter is relatively large, the effect of the truncation parameter on the far-field divergence angles is not distinct. When the f-parameter is moderate, the far-field divergence angles first decrease and finally tend to their respective minimum values with increasing the truncation parameter. When the f-parameter is relatively small, the far-field divergence angles of the Gaussian diffracted beam and its TM term fluctuate in a certain degree with varying the truncation parameter.
2012,
24: 2053-2058.
doi: 10.3788/HPLPB20122409.2053
Abstract:
With water as the working fluid, experiments on the heat transfer characteristics of spray cooling of micro-structured surfaces were performed in a closed loop system. Experimental data were analyzed in the view of the ratio between convective heat transfer and phase change heat transfer. The results indicate that heat transfer is obviously enhanced for micro-channel surfaces relative to the flat surface because of higher phase change heat transfer. For the geometries tested at lower surface temperature, the straight finned surface has the largest heat flux; while at higher surface temperature, the cubic pin finned surface has the largest heat flux. Heat fluxes of all the surfaces grow with increasing flow rates, except for the straight finned surface under lower surface temperature. The ratio of phase change to total heat transfer is bigger than 20% for the flat surface, and higher than 50% for micro-structured surfaces. Critical heat fluxes of 159.1, 120.2, and 109.8 W/cm2 are attained for cubic pin finned, straight finned and flat surfaces respectively when the flow rate is 15.9 mL/min, and the corresponding evaporation efficiencies are 96.0%, 72.5%, 67.1%.
With water as the working fluid, experiments on the heat transfer characteristics of spray cooling of micro-structured surfaces were performed in a closed loop system. Experimental data were analyzed in the view of the ratio between convective heat transfer and phase change heat transfer. The results indicate that heat transfer is obviously enhanced for micro-channel surfaces relative to the flat surface because of higher phase change heat transfer. For the geometries tested at lower surface temperature, the straight finned surface has the largest heat flux; while at higher surface temperature, the cubic pin finned surface has the largest heat flux. Heat fluxes of all the surfaces grow with increasing flow rates, except for the straight finned surface under lower surface temperature. The ratio of phase change to total heat transfer is bigger than 20% for the flat surface, and higher than 50% for micro-structured surfaces. Critical heat fluxes of 159.1, 120.2, and 109.8 W/cm2 are attained for cubic pin finned, straight finned and flat surfaces respectively when the flow rate is 15.9 mL/min, and the corresponding evaporation efficiencies are 96.0%, 72.5%, 67.1%.
2012,
24: 2059-2062.
doi: 10.3788/HPLPB20122409.2059
Abstract:
In grading-eliminated no-nonsense observation of ultrafast incident laser light e-fields(GRENOUILLE) measurements of femtosecond laser pulse, a nonuniform spatial beam profile can largely distort the trace, which results in an inaccurate temporal measurement. The spatial beam profile effects on the GRENOUILLE trace are demonstrated both theoretically and numerically. Results from the numerical simulation show that due to the presence of feedback regarding the validity of the measurement data, the GRENOUILLE phase-retrieval algorithm is insensitive to trace distortion; hence a nonuniform spatial beam profile can hardly introduce any noticeable inaccuracy. Special attention should be paid to the situation where incident beam is too narrow to generate adequate delay between two replicas of the pulse, which leads to a clipped trace followed by a misleading temporal result.
In grading-eliminated no-nonsense observation of ultrafast incident laser light e-fields(GRENOUILLE) measurements of femtosecond laser pulse, a nonuniform spatial beam profile can largely distort the trace, which results in an inaccurate temporal measurement. The spatial beam profile effects on the GRENOUILLE trace are demonstrated both theoretically and numerically. Results from the numerical simulation show that due to the presence of feedback regarding the validity of the measurement data, the GRENOUILLE phase-retrieval algorithm is insensitive to trace distortion; hence a nonuniform spatial beam profile can hardly introduce any noticeable inaccuracy. Special attention should be paid to the situation where incident beam is too narrow to generate adequate delay between two replicas of the pulse, which leads to a clipped trace followed by a misleading temporal result.
2012,
24: 2063-2067.
doi: 10.3788/HPLPB20122409.2063
Abstract:
This paper investigates a problem of universal approximation and modeling, which is used for the Takagi-Sugeno fuzzy model of hyperchaotic laser systems with parameters perturbation. Firstly, hyperchaos dynamics in laser system with parameters perturbation is analyzed. Then, based on the typical modeling principle of Takagi-Sugeno (T-S) fuzzy systems, the universal approximation of laser hyperchaos Takagi-Sugeno fuzzy systems is studied. To achieve a T-S fuzzy model of hyperchaotic laser system, the key variables of nonlinearity, fuzzy membership function and fuzzy rules are identified according to the dynamics of hyperchaotic systems. Finally, the simulation results show that the proposed model can effectively approximate the hyperchaotic laser system with parameters perturbation.
This paper investigates a problem of universal approximation and modeling, which is used for the Takagi-Sugeno fuzzy model of hyperchaotic laser systems with parameters perturbation. Firstly, hyperchaos dynamics in laser system with parameters perturbation is analyzed. Then, based on the typical modeling principle of Takagi-Sugeno (T-S) fuzzy systems, the universal approximation of laser hyperchaos Takagi-Sugeno fuzzy systems is studied. To achieve a T-S fuzzy model of hyperchaotic laser system, the key variables of nonlinearity, fuzzy membership function and fuzzy rules are identified according to the dynamics of hyperchaotic systems. Finally, the simulation results show that the proposed model can effectively approximate the hyperchaotic laser system with parameters perturbation.
2012,
24: 2068-2072.
doi: 10.3788/HPLPB20122409.2068
Abstract:
To solve the superposition problem of stress birefringence in measuring stress birefringence of optical glass, using optical equivalence principle, the superposition model was replaced by a system containing a birefringent plate and a rotator. The superposition of stress birefringence analyzed and calculated. Curves of phase retardation, azimuth of the principal axis of birefringent model, and rotation angle of the rotator changing with the angle between two azimuths of principal axis of the birefringent model were obtained. Results indicate that the superposition of stress birefringence is not a simple sum of it, it is related to the magnitude of birefringence and the angle of stress of each superposition model. The stress birefringence measurement value matches the theoretical value. The superposition of stress birefringence influences optical glass measurement adversely, reducing the measurement precision, especially when transparent support or refractive liquid containers exist, the influence of superposition of stress birefringence cannot be ignored.
To solve the superposition problem of stress birefringence in measuring stress birefringence of optical glass, using optical equivalence principle, the superposition model was replaced by a system containing a birefringent plate and a rotator. The superposition of stress birefringence analyzed and calculated. Curves of phase retardation, azimuth of the principal axis of birefringent model, and rotation angle of the rotator changing with the angle between two azimuths of principal axis of the birefringent model were obtained. Results indicate that the superposition of stress birefringence is not a simple sum of it, it is related to the magnitude of birefringence and the angle of stress of each superposition model. The stress birefringence measurement value matches the theoretical value. The superposition of stress birefringence influences optical glass measurement adversely, reducing the measurement precision, especially when transparent support or refractive liquid containers exist, the influence of superposition of stress birefringence cannot be ignored.
2012,
24: 2073-2078.
doi: 10.3788/HPLPB20122409.2073
Abstract:
The reconstruction of water temperature in combustion is realized by the tunable diode laser absorption spectroscopy technique. The model for H2O temperature distribution is assumed as a Gaussian function, ranging from 300 K to 1300 K. Radon transform is used to simulate the experimental results. The reconstruction of temperature distribution is achieved by reconstruction of two temperature-dependent line strengths based on the filtered back-projection method. The temperature reconstruction result agrees well with the original model. Moreover, the influences of the number of projections and random errors in projections on reconstruction are also studied. The simulation results indicate that the decrease in projection number or the increase in noise increases the mean square error of the reconstructed temperature, deteriorating the reconstructed image. The temperature reconstruction can not reveal the original temperature distribution when the projection number reduces to four.
The reconstruction of water temperature in combustion is realized by the tunable diode laser absorption spectroscopy technique. The model for H2O temperature distribution is assumed as a Gaussian function, ranging from 300 K to 1300 K. Radon transform is used to simulate the experimental results. The reconstruction of temperature distribution is achieved by reconstruction of two temperature-dependent line strengths based on the filtered back-projection method. The temperature reconstruction result agrees well with the original model. Moreover, the influences of the number of projections and random errors in projections on reconstruction are also studied. The simulation results indicate that the decrease in projection number or the increase in noise increases the mean square error of the reconstructed temperature, deteriorating the reconstructed image. The temperature reconstruction can not reveal the original temperature distribution when the projection number reduces to four.
2012,
24: 2079-2084.
doi: 10.3788/HPLPB20122409.2079
Abstract:
In frequency conversion systems of inertial confinement fusion, surface quality of KDP crystals with large dimension and low thickness is one of the key factors influencing the frequency conversion efficiency. For the third harmonic generation KDP crystals with 400 mm400 mm dimensions and with 45 departure angle from the horizontal plane, finite element models have been built up to analyze the effect of the fabrication errors on the additional surface variations of KDP crystals under different clamping modes, and the P-V and RMS values of the surface variations under different clamping modes and fabrication errors are given. The results show that the clamping modes and the fabrication errors are responsible for the additional surface variations, and the additional surface variation can be controlled by the clamping bars on the front even if the fabrication errors of KDP crystals and clamps exist.
In frequency conversion systems of inertial confinement fusion, surface quality of KDP crystals with large dimension and low thickness is one of the key factors influencing the frequency conversion efficiency. For the third harmonic generation KDP crystals with 400 mm400 mm dimensions and with 45 departure angle from the horizontal plane, finite element models have been built up to analyze the effect of the fabrication errors on the additional surface variations of KDP crystals under different clamping modes, and the P-V and RMS values of the surface variations under different clamping modes and fabrication errors are given. The results show that the clamping modes and the fabrication errors are responsible for the additional surface variations, and the additional surface variation can be controlled by the clamping bars on the front even if the fabrication errors of KDP crystals and clamps exist.
Adjustable delay analysis using frequency shift characteristics of electro-optic intensity modulator
2012,
24: 2085-2088.
doi: 10.3788/HPLPB20122409.2085
Abstract:
To meet the requirements of the adjustable delay of the pulse in the data synchronization processing of optical communication systems, a structural design scheme of adjusting the delay has been proposed. The light frequency shift characteristics of electro-optic intensity modulator (EOIM) have been analyzed, and based on the modulation of EOIM to the sideband and the light intensity, the delay adjusting could be achieved by regulating the pump light of the stimulated Brillouin scattering slow light. The mathematical model of the pulse delay has been established, and the modulation depth and the DC bias voltage varying with the pulse delay have been stimulated respectively at a fixed microwave frequency. From the experimental results, it is shown that the pulse delay gradually decreases with the increasing of modulation depth when the size of the DC bias voltage is half of the half-wave voltage, and the pulse delay gradually increases with the increasing of the DC bias voltage when the modulation depth is 1.39. The maximum delay can attain to 1.106 times the delay without modulation, which means adjustable delay is achieved effectively.
To meet the requirements of the adjustable delay of the pulse in the data synchronization processing of optical communication systems, a structural design scheme of adjusting the delay has been proposed. The light frequency shift characteristics of electro-optic intensity modulator (EOIM) have been analyzed, and based on the modulation of EOIM to the sideband and the light intensity, the delay adjusting could be achieved by regulating the pump light of the stimulated Brillouin scattering slow light. The mathematical model of the pulse delay has been established, and the modulation depth and the DC bias voltage varying with the pulse delay have been stimulated respectively at a fixed microwave frequency. From the experimental results, it is shown that the pulse delay gradually decreases with the increasing of modulation depth when the size of the DC bias voltage is half of the half-wave voltage, and the pulse delay gradually increases with the increasing of the DC bias voltage when the modulation depth is 1.39. The maximum delay can attain to 1.106 times the delay without modulation, which means adjustable delay is achieved effectively.
2012,
24: 2089-2093.
doi: 10.3788/HPLPB20122409.2089
Abstract:
For the packaging demand of high power diode laser, the method of magnetron sputtering was used to fabricate the Au80Sn20 alloy solder. A scanning electron microscope (SEM) was adopted to observe its microstructure and surface topography, an energy dispersive X-ray detector(EDX) to test its composition, and the differential thermal analysis (DTA) to test its melting temperature. The weldability of the Au80Sn20 alloy solder was analyzed by reflow soldering process. In conclusion, using magnetron sputtering can successfully manufacture the Au80Sn20 alloy solder. The prepared Au80Sn20 alloy solder features compact surface structure, easy wetting, small void content, and large bonding strength. Its composition and melting point are close to the theoretical situation.
For the packaging demand of high power diode laser, the method of magnetron sputtering was used to fabricate the Au80Sn20 alloy solder. A scanning electron microscope (SEM) was adopted to observe its microstructure and surface topography, an energy dispersive X-ray detector(EDX) to test its composition, and the differential thermal analysis (DTA) to test its melting temperature. The weldability of the Au80Sn20 alloy solder was analyzed by reflow soldering process. In conclusion, using magnetron sputtering can successfully manufacture the Au80Sn20 alloy solder. The prepared Au80Sn20 alloy solder features compact surface structure, easy wetting, small void content, and large bonding strength. Its composition and melting point are close to the theoretical situation.
2012,
24: 2094-2098.
doi: 10.3788/HPLPB20122409.2094
Abstract:
A Cu-1.5%Be alloy ribbon was prepared by single-roller rapid solidification method, and rapid solidification cooling rate was estimated according to the heat transport equilibrium equation. The microstructure and phase choice of the ribbon were characterized by powder X-ray diffraction and scanning electron microscopy. The results indicate that when the line speed of the roll surface is between 29.93 m/s and 39.19 m/s, the cooling rate can get to 9.80105-1.63106 K/s . With the increase of roller speed and the decrease of eject pressure, the thickness and grain size of the ribbon gradually decrease. With increasing cooling rate, the effect of solute trapping is enhanced, the phase structure changes from multiphase to single phase. As the line speed reaches to 34.54 m/s, the single phase -Cu solid solution is formed in Cu-1.5%Be alloy, and the microstrcture of the ribbon becomes fine so that nanocrystalline could be formed. The cross-section microstructure of the alloy ribbon along the direction vertical to the wheel surface is characterized by fine equiaxed, columnar and coarse equiaxed gain.
A Cu-1.5%Be alloy ribbon was prepared by single-roller rapid solidification method, and rapid solidification cooling rate was estimated according to the heat transport equilibrium equation. The microstructure and phase choice of the ribbon were characterized by powder X-ray diffraction and scanning electron microscopy. The results indicate that when the line speed of the roll surface is between 29.93 m/s and 39.19 m/s, the cooling rate can get to 9.80105-1.63106 K/s . With the increase of roller speed and the decrease of eject pressure, the thickness and grain size of the ribbon gradually decrease. With increasing cooling rate, the effect of solute trapping is enhanced, the phase structure changes from multiphase to single phase. As the line speed reaches to 34.54 m/s, the single phase -Cu solid solution is formed in Cu-1.5%Be alloy, and the microstrcture of the ribbon becomes fine so that nanocrystalline could be formed. The cross-section microstructure of the alloy ribbon along the direction vertical to the wheel surface is characterized by fine equiaxed, columnar and coarse equiaxed gain.
2012,
24: 2099-2102.
doi: 10.3788/HPLPB20122409.2099
Abstract:
Polypropylene(PP) and polyethylene(PE) are treated with radio frequency(RF) glow discharge plasma and dielectric barrier discharge(DBD) plasma. Then the shear strength of the mixing adhesion of PP and PE using polyurethane as adhesive is tested. Results show that the shear strength highly increases when the DBD plasma is applied with 200 W power. The maxium shear strength after DBD plasma processing is 1.58 MPa(20 s) which is 14.36 times that of untreated samples. However, the PP and PE are burned in 10 s when the power is 300 W, and there is no change when the power is 100 W. The effect of air RF discharge with maximum shear strength of 1.60 MPa(100 W, 3 min) is nearly the same as that of N2 RF discharge with maximum shear strength of 1.57 MPa (200 W, 3 min). Through scanning electron microscope analysis, the surfaces of samples treated with plasma are rough as a result of appearance of bubbles on the surfaces whereas the surfaces of untreated samples are smooth. Therefore, the shear strength of the mixing adhesion of PP and PE increases greatly aftertreatment with DBD plasma and RF glow discharge plasma.
Polypropylene(PP) and polyethylene(PE) are treated with radio frequency(RF) glow discharge plasma and dielectric barrier discharge(DBD) plasma. Then the shear strength of the mixing adhesion of PP and PE using polyurethane as adhesive is tested. Results show that the shear strength highly increases when the DBD plasma is applied with 200 W power. The maxium shear strength after DBD plasma processing is 1.58 MPa(20 s) which is 14.36 times that of untreated samples. However, the PP and PE are burned in 10 s when the power is 300 W, and there is no change when the power is 100 W. The effect of air RF discharge with maximum shear strength of 1.60 MPa(100 W, 3 min) is nearly the same as that of N2 RF discharge with maximum shear strength of 1.57 MPa (200 W, 3 min). Through scanning electron microscope analysis, the surfaces of samples treated with plasma are rough as a result of appearance of bubbles on the surfaces whereas the surfaces of untreated samples are smooth. Therefore, the shear strength of the mixing adhesion of PP and PE increases greatly aftertreatment with DBD plasma and RF glow discharge plasma.
2012,
24: 2103-2108.
doi: 10.3788/HPLPB20122409.2103
Abstract:
Mission-availability of inertial confinement fusion (ICF) laser facilities is considered as an important factor of facility construction. Based on basic models for mission-availability, processes of the facility performing tasks are analyzed with their types and a model diagram of mission-time for indicating time-limits of a mission and its repair presented, and then a mission-availability evaluation model for a single mission is given. Utilizing curve-fitting and goodness-of-fit test methods, and considering different impact on next missions and its probability, a mission-availability evaluation model for multiple tasks of the facilities is constructed. And then, the facility mission-availability evaluation methods and its steps are definitely given to provide a general model and method for systematic research of ICF laser facility mission-availability evaluation. Failure data of SG-Ⅲ prototype facility during operation are processed and analyzed by the use of the evaluation approach, to verify that the approach and the model are correct and economical. The results will be directly used for reliability engineering construction of SG-Ⅲ laser facility.
Mission-availability of inertial confinement fusion (ICF) laser facilities is considered as an important factor of facility construction. Based on basic models for mission-availability, processes of the facility performing tasks are analyzed with their types and a model diagram of mission-time for indicating time-limits of a mission and its repair presented, and then a mission-availability evaluation model for a single mission is given. Utilizing curve-fitting and goodness-of-fit test methods, and considering different impact on next missions and its probability, a mission-availability evaluation model for multiple tasks of the facilities is constructed. And then, the facility mission-availability evaluation methods and its steps are definitely given to provide a general model and method for systematic research of ICF laser facility mission-availability evaluation. Failure data of SG-Ⅲ prototype facility during operation are processed and analyzed by the use of the evaluation approach, to verify that the approach and the model are correct and economical. The results will be directly used for reliability engineering construction of SG-Ⅲ laser facility.
2012,
24: 2109-2112.
doi: 10.3788/HPLPB20122409.2109
Abstract:
The double-peak fusion rate of capsules for high yield implosion experiments on Shenguang Ⅲ prototype laser is studied by numerical simulation. The competition of energy gain and loss in the fusion region causes the double-peak phenomenon in fusion rate. During the time of fusion, the ions in fusion region obtain energy mainly due to compression, and lose energy mainly by the Coulomb collision with electrons. The shock wave moves back and forth in the DT fuel because of the reflections in the center and at the inner surface of glass, which causes the fluctuation in compression power. The competition between the compression work and Coulomb collision fluctuates the internal energy of ions, resulting in the double-peak fusion rate. The simulations of bangtime are in good agreement with experiments.
The double-peak fusion rate of capsules for high yield implosion experiments on Shenguang Ⅲ prototype laser is studied by numerical simulation. The competition of energy gain and loss in the fusion region causes the double-peak phenomenon in fusion rate. During the time of fusion, the ions in fusion region obtain energy mainly due to compression, and lose energy mainly by the Coulomb collision with electrons. The shock wave moves back and forth in the DT fuel because of the reflections in the center and at the inner surface of glass, which causes the fluctuation in compression power. The competition between the compression work and Coulomb collision fluctuates the internal energy of ions, resulting in the double-peak fusion rate. The simulations of bangtime are in good agreement with experiments.
2012,
24: 2113-2116.
doi: 10.3788/HPLPB20122409.2113
Abstract:
Soft X-ray mirror used in inertial confinement fusion (ICF) experiments have been preformed at the 4B7B beam-line of Beijing Synchrotron Radiation Facility (BSRF). The main factors influencing the mirror reflectance were investigated and confirmed to be the contamination and the installation angle of mirrors. Simulation of the reflectance of contamination mirrors confirms the contamination is the carbon and oxygen from oil in ICF experiments. The contamination can be effectively removed by a radio-frequency glow discharge treatment for mirrors. The reflectance of mirrors which is improved after cleaning process is found to be in good agreement with the calculation results.
Soft X-ray mirror used in inertial confinement fusion (ICF) experiments have been preformed at the 4B7B beam-line of Beijing Synchrotron Radiation Facility (BSRF). The main factors influencing the mirror reflectance were investigated and confirmed to be the contamination and the installation angle of mirrors. Simulation of the reflectance of contamination mirrors confirms the contamination is the carbon and oxygen from oil in ICF experiments. The contamination can be effectively removed by a radio-frequency glow discharge treatment for mirrors. The reflectance of mirrors which is improved after cleaning process is found to be in good agreement with the calculation results.
2012,
24: 2117-2120.
doi: 10.3788/HPLPB20122409.2117
Abstract:
A series of plasma characteristic spectral lines of red copper were obtained under nanosecond laser shock with a pulsed Nd:YAG laser (1064 nm， maximum energy 500 mJ). It can be inferred from the experimental result that the copper atomic spectrum is incomplete, only five distinct excitation spectral lines (CuⅠ 406.33 nm, CuⅠ 458.69 nm, CuⅠ 521.8 nm, CuⅠ 529.25 nm, CuⅠ 578.2 nm) are found in our experimental condition. The line shapes of broadening of CuⅠ 521.8 nm and CuⅠ 578.2 nm atomic spectral lines are different, and belong to Lorenz and Gauss line shapes, respectively. The analysis of corresponding equations of line shapes shows that different bands in the same atomic spectrum correspond to different spectral broadening mechanisms.
A series of plasma characteristic spectral lines of red copper were obtained under nanosecond laser shock with a pulsed Nd:YAG laser (1064 nm， maximum energy 500 mJ). It can be inferred from the experimental result that the copper atomic spectrum is incomplete, only five distinct excitation spectral lines (CuⅠ 406.33 nm, CuⅠ 458.69 nm, CuⅠ 521.8 nm, CuⅠ 529.25 nm, CuⅠ 578.2 nm) are found in our experimental condition. The line shapes of broadening of CuⅠ 521.8 nm and CuⅠ 578.2 nm atomic spectral lines are different, and belong to Lorenz and Gauss line shapes, respectively. The analysis of corresponding equations of line shapes shows that different bands in the same atomic spectrum correspond to different spectral broadening mechanisms.
2012,
24: 2121-2124.
doi: 10.3788/HPLPB20122409.2121
Abstract:
Based on SG-Ⅲ prototype laser facility, an experimental method to examine the accuracy of shock speed measurement by imaging velocity interferometer system for any reflector(VISAR) was developed. The conventional double-sensitivity method leads to multiple results. Whereas, with samples of known thickness, the accurate curve of shock wave velocity and accuracy of shock speed measurement were achieved by the proposed method. Also a theoretical calculation of this system was carried out. The theoretical and experimental results agree with each other perfectly. This method can also help to acquire the number of lost fringes on single-sensitivity VISAR. With only one streak camera, the accurate curve of shock wave velocity can be achieved.
Based on SG-Ⅲ prototype laser facility, an experimental method to examine the accuracy of shock speed measurement by imaging velocity interferometer system for any reflector(VISAR) was developed. The conventional double-sensitivity method leads to multiple results. Whereas, with samples of known thickness, the accurate curve of shock wave velocity and accuracy of shock speed measurement were achieved by the proposed method. Also a theoretical calculation of this system was carried out. The theoretical and experimental results agree with each other perfectly. This method can also help to acquire the number of lost fringes on single-sensitivity VISAR. With only one streak camera, the accurate curve of shock wave velocity can be achieved.
2012,
24: 2125-2129.
doi: 10.3788/HPLPB20122409.2125
Abstract:
Silica colloidal crystals and multilayer heterostructures were fabricated by using monodisperse silica microspheres. Non-closely-packed colloidal crystals, whose volume ratio of voids was larger than 26% in face-centered closely-packed structure, were obtained after calcining and etching silica colloidal crystals sequentially. The volume ratio of voids increases as the etching time is prolonged. It was found that the smaller the spheres forming colloidal crystals were, the bigger the ratio of voids was, after colloidal crystals were etched under the same condition. Graded silica colloidal films were obtained by calcining and etching silica multilayer heterostructures, which were used as templates to prepare polystyrene porous films with graded density. The different layers in porous films displayed a smooth transition where there were no obvious interlayer defects. Moreover, there were no large channels between pores that existed in conventional three-dimensionally ordered porous structures.
Silica colloidal crystals and multilayer heterostructures were fabricated by using monodisperse silica microspheres. Non-closely-packed colloidal crystals, whose volume ratio of voids was larger than 26% in face-centered closely-packed structure, were obtained after calcining and etching silica colloidal crystals sequentially. The volume ratio of voids increases as the etching time is prolonged. It was found that the smaller the spheres forming colloidal crystals were, the bigger the ratio of voids was, after colloidal crystals were etched under the same condition. Graded silica colloidal films were obtained by calcining and etching silica multilayer heterostructures, which were used as templates to prepare polystyrene porous films with graded density. The different layers in porous films displayed a smooth transition where there were no obvious interlayer defects. Moreover, there were no large channels between pores that existed in conventional three-dimensionally ordered porous structures.
2012,
24: 2130-2134.
doi: 10.3788/HPLPB20122409.2130
Abstract:
An exponential impedance matching method is used to optimize the structure of constant impedance TEM horn used in ultra-wide spectrum radiation system. Both the constant impedance TEM horn and the ridged TEM horn have been fabricated and tested under Gaussian pulses of about 1 ns duration. The simulation and experiment results indicate that the radiation factor on the principal axis has been improved by the introduction of ridge. When the reflector impulse radiation antenna (IRA) is fed by a ridged TEM horn, the distribution of the electric fields peak intensity on the reflector is intensified, and the symmetry of electric field on the reflector and the radiation factor of the reflector IRA are improved.
An exponential impedance matching method is used to optimize the structure of constant impedance TEM horn used in ultra-wide spectrum radiation system. Both the constant impedance TEM horn and the ridged TEM horn have been fabricated and tested under Gaussian pulses of about 1 ns duration. The simulation and experiment results indicate that the radiation factor on the principal axis has been improved by the introduction of ridge. When the reflector impulse radiation antenna (IRA) is fed by a ridged TEM horn, the distribution of the electric fields peak intensity on the reflector is intensified, and the symmetry of electric field on the reflector and the radiation factor of the reflector IRA are improved.
2012,
24: 2135-2140.
doi: 10.3788/HPLPB20122409.2135
Abstract:
This paper presents the optimum design and simulation results of 0.22 THz folded waveguide TWT(traveling wave tube) components. Precision machining and assembly welding technologies are investigated for these components. Finally, the components with high precision, satisfying the design requirements, are obtained.
This paper presents the optimum design and simulation results of 0.22 THz folded waveguide TWT(traveling wave tube) components. Precision machining and assembly welding technologies are investigated for these components. Finally, the components with high precision, satisfying the design requirements, are obtained.
2012,
24: 2141-2144.
doi: 10.3788/HPLPB20122409.2141
Abstract:
Large orbit axis-encircling electron beams can provide improved coupling and mode selectivity in a high harmonic terahertz gyrotron. For developing a 0.6 THz 3rd-harmonic large orbit gyrotron, a cusp gun with a beam voltage of 55 kV and a beam current of 1 A has been designed based on a comparatively simple Pierce-type electron gun and cusp magnetic field. The optimized result shows thatthe velocity ratio, axial velocity spread and transverse velocity spread are 1.53, 7.10% and 3.39%, respectively.
Large orbit axis-encircling electron beams can provide improved coupling and mode selectivity in a high harmonic terahertz gyrotron. For developing a 0.6 THz 3rd-harmonic large orbit gyrotron, a cusp gun with a beam voltage of 55 kV and a beam current of 1 A has been designed based on a comparatively simple Pierce-type electron gun and cusp magnetic field. The optimized result shows thatthe velocity ratio, axial velocity spread and transverse velocity spread are 1.53, 7.10% and 3.39%, respectively.
2012,
24: 2145-2150.
doi: 10.3788/HPLPB20122409.2145
Abstract:
Aiming at the problems that the existing methods based on the probability statistical theory and the fuzzy neural network method must be built on the foundation of large quantities of statistical data, and the failure thresholds of electronic devices estimated by the fuzzy information diffusion could be higher than the actual ones, a new method is presented that the raw experimental data are processed by the fuzzy information processing technology to obtain the training samples, on the basis of which the damage probabilities of electronic devices illuminated or injected by the high power microwave are predicted by support vector regression. The simulation results show that the fuzzy neural network and the new method both achieve good prediction results. But the results of the latter are more accurate and it overcomes the defect that errors could occur in the results predicted by the fuzzy neural network under the condition of small samples.
Aiming at the problems that the existing methods based on the probability statistical theory and the fuzzy neural network method must be built on the foundation of large quantities of statistical data, and the failure thresholds of electronic devices estimated by the fuzzy information diffusion could be higher than the actual ones, a new method is presented that the raw experimental data are processed by the fuzzy information processing technology to obtain the training samples, on the basis of which the damage probabilities of electronic devices illuminated or injected by the high power microwave are predicted by support vector regression. The simulation results show that the fuzzy neural network and the new method both achieve good prediction results. But the results of the latter are more accurate and it overcomes the defect that errors could occur in the results predicted by the fuzzy neural network under the condition of small samples.
2012,
24: 2151-2154.
doi: 10.3788/HPLPB20122409.2151
Abstract:
The introduction of bunching cavities can significantly increase the gain of relativistic klystron amplifier, and correspondingly the power of the seeding microwave can be reduced to a very low level. Though higher gain can be obtained with more bunching cavities, the self-exciting problem will seriously disturb the working mode in the device. A special structure is introduced to deal with such problem. Based on the engineering requirement, a S-band of 3 GW relativistic klystron amplifier is designed with the seeding power 20 kW. In the simulation, the fundamental current modulation depth is 80% and the output microwave power reaches 3.3 GW with the seeding power of kilowatts.
The introduction of bunching cavities can significantly increase the gain of relativistic klystron amplifier, and correspondingly the power of the seeding microwave can be reduced to a very low level. Though higher gain can be obtained with more bunching cavities, the self-exciting problem will seriously disturb the working mode in the device. A special structure is introduced to deal with such problem. Based on the engineering requirement, a S-band of 3 GW relativistic klystron amplifier is designed with the seeding power 20 kW. In the simulation, the fundamental current modulation depth is 80% and the output microwave power reaches 3.3 GW with the seeding power of kilowatts.
2012,
24: 2155-2158.
doi: 10.3788/HPLPB20122409.2155
Abstract:
For the shortcomings of large size and narrow band width, a variable-period serpentine circular waveguide mode converter is proposed to realize high efficiency conversion of TE01 to TE11. According to the coupled wave equation, the optimal configurations of a variable-period converter and a traditional one (their radii are all 16 mm) are respectively obtained to realize the optimal mode conversion at 30.5 GHz. Calculation results show that the variable-period converter with a optimal length of 1 056.97 mm, realizes a TE11 conversion efficiency of 98.1% with its TE11 conversion bandwidth over 90% being 3.3%. However, the traditional converter with a optimal length of 769.53 mm, realizes a TE11 conversion efficiency of 99.3% with its TE11 conversion bandwidth over 90% being 5.9%. The variable-period converter assumes evident advantages in size and bandwidth over the traditional one. Test results indicate that the variable-period converter acts very well in conversion of TE01 to TE11 mode.
For the shortcomings of large size and narrow band width, a variable-period serpentine circular waveguide mode converter is proposed to realize high efficiency conversion of TE01 to TE11. According to the coupled wave equation, the optimal configurations of a variable-period converter and a traditional one (their radii are all 16 mm) are respectively obtained to realize the optimal mode conversion at 30.5 GHz. Calculation results show that the variable-period converter with a optimal length of 1 056.97 mm, realizes a TE11 conversion efficiency of 98.1% with its TE11 conversion bandwidth over 90% being 3.3%. However, the traditional converter with a optimal length of 769.53 mm, realizes a TE11 conversion efficiency of 99.3% with its TE11 conversion bandwidth over 90% being 5.9%. The variable-period converter assumes evident advantages in size and bandwidth over the traditional one. Test results indicate that the variable-period converter acts very well in conversion of TE01 to TE11 mode.
2012,
24: 2159-2163.
doi: 10.3788/HPLPB20122409.2159
Abstract:
The diode spurious oscillation in wide-gap klystron amplifiers was studied by using a three-dimensional high frequency program and particle-in-cell softwave. Due to the cut-off of the high-order mode TM31 in the diode region at 6.18 GHz, the diodes together formed a resonant cavity and a strong electric field was generated in the anode-cathode gap, which resulted in intense electron beam modulation. According to simulation results, some improvements were brought forward to optimize the diode structure. The diode spurious oscillation was eliminated ultimately.
The diode spurious oscillation in wide-gap klystron amplifiers was studied by using a three-dimensional high frequency program and particle-in-cell softwave. Due to the cut-off of the high-order mode TM31 in the diode region at 6.18 GHz, the diodes together formed a resonant cavity and a strong electric field was generated in the anode-cathode gap, which resulted in intense electron beam modulation. According to simulation results, some improvements were brought forward to optimize the diode structure. The diode spurious oscillation was eliminated ultimately.
2012,
24: 2164-2168.
doi: 10.3788/HPLPB20122409.2164
Abstract:
The staggered double vane was employed as the slow wave circuit and a transition structure and an output coupler were proposed to design a W-band backward wave oscillator (BWO) operating with sheet electron beam. The transition structure and the output coupler can effectively reduce the attenuation and reflection of such type of straight-waveguide device. Compared to conventional pencil beam device, the oscillator can provide much higher output power. The dynamic process between the electron beam and the electromagnetic wave was simulated by three dimensional particle-in-cell (PIC) code. The simulation results demonstrate that the BWO can provide a stable output power in the order of a few watts in the frequency range from 92 GHz to 98 GHz by adjusting the operation voltage, assuming a constant operation current of 12 mA. The output signal shows good monochromaticity, with the central frequency quite close to the design.
The staggered double vane was employed as the slow wave circuit and a transition structure and an output coupler were proposed to design a W-band backward wave oscillator (BWO) operating with sheet electron beam. The transition structure and the output coupler can effectively reduce the attenuation and reflection of such type of straight-waveguide device. Compared to conventional pencil beam device, the oscillator can provide much higher output power. The dynamic process between the electron beam and the electromagnetic wave was simulated by three dimensional particle-in-cell (PIC) code. The simulation results demonstrate that the BWO can provide a stable output power in the order of a few watts in the frequency range from 92 GHz to 98 GHz by adjusting the operation voltage, assuming a constant operation current of 12 mA. The output signal shows good monochromaticity, with the central frequency quite close to the design.
2012,
24: 2169-2173.
doi: 10.3788/HPLPB20122409.2169
Abstract:
A compact TEM-TE11 mode converter suitable for narrow band high power microwave system was developed. The coaxial waveguide is divided into several sectorial waveguides with different phase propagation constants, and the waveguides with relatively large phase propagation constants are transversely folded to shorten their axial lengths. When the microwaves in different sectorial waveguides have a phase shift of 180 degree at the end of the mode converter, they compose a coaxial TE11 mode. A mode converter is designed for L-band 1.31 GHz magnetically insulated transmission line oscillator (MILO) system. The conversion efficiency of TEM-TE11 mode at center frequency is 95%. In the frequency range of 1.23-1.40 GHz, the conversion efficiency exceeds 90%, with a corresponding bandwidth of 13%. The directional radiation performance of the mode converter connected to L band MILO tube is tested. The experimental result reveals that the mode converter works well.
A compact TEM-TE11 mode converter suitable for narrow band high power microwave system was developed. The coaxial waveguide is divided into several sectorial waveguides with different phase propagation constants, and the waveguides with relatively large phase propagation constants are transversely folded to shorten their axial lengths. When the microwaves in different sectorial waveguides have a phase shift of 180 degree at the end of the mode converter, they compose a coaxial TE11 mode. A mode converter is designed for L-band 1.31 GHz magnetically insulated transmission line oscillator (MILO) system. The conversion efficiency of TEM-TE11 mode at center frequency is 95%. In the frequency range of 1.23-1.40 GHz, the conversion efficiency exceeds 90%, with a corresponding bandwidth of 13%. The directional radiation performance of the mode converter connected to L band MILO tube is tested. The experimental result reveals that the mode converter works well.
2012,
24: 2174-2178.
doi: 10.3788/HPLPB20122409.2174
Abstract:
The output circuit of high-order TM310 mode in single- and double-gap cylindrical coaxial cavities of klystron is designed. The gap impedances at the drift tube centers and corresponding output bandwidths are calculated, simulated and compared according to the equivalent circuit theory when the cavities are loaded with TE10 mode in empty rectangular waveguide. It is found that, double gap cavities have larger gap impedances and bandwidths than those of single gap cavities. By means of setting copper short circuit line in the inner side of output holes, the external quality factor is reduced and the mode uniformity in cavities is increased. This output circuit is suitable for high frequency, high power and narrowband klystrons. The research results are significant to output circuit design of high-order TM mode coaxial cavities of klystrons.
The output circuit of high-order TM310 mode in single- and double-gap cylindrical coaxial cavities of klystron is designed. The gap impedances at the drift tube centers and corresponding output bandwidths are calculated, simulated and compared according to the equivalent circuit theory when the cavities are loaded with TE10 mode in empty rectangular waveguide. It is found that, double gap cavities have larger gap impedances and bandwidths than those of single gap cavities. By means of setting copper short circuit line in the inner side of output holes, the external quality factor is reduced and the mode uniformity in cavities is increased. This output circuit is suitable for high frequency, high power and narrowband klystrons. The research results are significant to output circuit design of high-order TM mode coaxial cavities of klystrons.
2012,
24: 2179-2182.
doi: 10.3788/HPLPB20122409.2179
Abstract:
A wall current monitor(WCM) was designed and built for measuring the bunch longitudinal length and beam intensity of the radio frequency quadrupole accelerator supported by 973 Program. The design method will be used for the WCM of Rapid Cycling Synchrotron of China Spallation Neutron Source. A high frequency electromagnetic field simulation software was used to simulate the performance of WCM with ferrite rings and shielding cavity and corresponding improvements by using a microwave absorber to restrain cavity resonance. Test was done and the original result was affected by the test system. Finally the expected result was obtained by improving the impedance of the unmatched part of the test bench.
A wall current monitor(WCM) was designed and built for measuring the bunch longitudinal length and beam intensity of the radio frequency quadrupole accelerator supported by 973 Program. The design method will be used for the WCM of Rapid Cycling Synchrotron of China Spallation Neutron Source. A high frequency electromagnetic field simulation software was used to simulate the performance of WCM with ferrite rings and shielding cavity and corresponding improvements by using a microwave absorber to restrain cavity resonance. Test was done and the original result was affected by the test system. Finally the expected result was obtained by improving the impedance of the unmatched part of the test bench.
2012,
24: 2183-2168.
doi: 10.3788/HPLPB20122409.2183
Abstract:
The SXFEL has stringent restrictions on beam emittance growth, and the traditional optical alignment can no longer meet its requirements, but the beam-based alignment(BBA) method allows more precise alignment, further reducing the linac errors to meet SXFEL requirements. In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position, but also the errors of undulator magnet. In order to achieve alignment accuracy over long distance, the quadrupole magnet errors and beam position monitor (BPM) offset are obtained by measuring. BPM data under different conditions and using SVD algorithm for calculation and analysis,With the method above, software based on Matlab has been designed and comparedwith other software simulation results demonstrate that the orbit offset could be reduced by one order.
The SXFEL has stringent restrictions on beam emittance growth, and the traditional optical alignment can no longer meet its requirements, but the beam-based alignment(BBA) method allows more precise alignment, further reducing the linac errors to meet SXFEL requirements. In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position, but also the errors of undulator magnet. In order to achieve alignment accuracy over long distance, the quadrupole magnet errors and beam position monitor (BPM) offset are obtained by measuring. BPM data under different conditions and using SVD algorithm for calculation and analysis,With the method above, software based on Matlab has been designed and comparedwith other software simulation results demonstrate that the orbit offset could be reduced by one order.
2012,
24: 2187-2192.
doi: 10.3788/HPLPB20122409.2187
Abstract:
The development technology of Sm2Co17 magnets in China has been improved and sample magnets of three forming-sintering designs have been tested. The test results show that the magnetic properties of Sm2Co17 magnets are improved, and their magnetic moment consistence and stability are fine. The regular magnetic field distribution data and optimized design of Chinas Sm2Co17 magnets for in-vacuum undulators(IVUs) were obtained and analyzed. Domestic Sm2Co17 magnets will be first installed in the IVUs for the Shanghai protein line station of Shanghai Synchrotron Radiation Facility.
The development technology of Sm2Co17 magnets in China has been improved and sample magnets of three forming-sintering designs have been tested. The test results show that the magnetic properties of Sm2Co17 magnets are improved, and their magnetic moment consistence and stability are fine. The regular magnetic field distribution data and optimized design of Chinas Sm2Co17 magnets for in-vacuum undulators(IVUs) were obtained and analyzed. Domestic Sm2Co17 magnets will be first installed in the IVUs for the Shanghai protein line station of Shanghai Synchrotron Radiation Facility.
2012,
24: 2193-2197.
doi: 10.3788/HPLPB20122409.2193
Abstract:
An 11 MeV H－ compact cyclotron used for medical radioactive isotope production is under construction in Institute of Fluid Physics, CAEP. The cyclotron magnet adopts the design of small valley gaps and coulee structure which can provide high average magnetic field and strong focus ability. To achieve 510-4 measuring accuracy, a magnetic field mapping system has been developed. After iterative correction using field measurement data, the total phase excursion of the cyclotron is within 9 and the first harmonic is less than 10-3 T, which are all acceptable. Furthermore, the beam testing declares the successful construction of the cyclotron magnet. Besides, some magnetic field influence factors were discussed, including the magnetic field distortion and measurement error.
An 11 MeV H－ compact cyclotron used for medical radioactive isotope production is under construction in Institute of Fluid Physics, CAEP. The cyclotron magnet adopts the design of small valley gaps and coulee structure which can provide high average magnetic field and strong focus ability. To achieve 510-4 measuring accuracy, a magnetic field mapping system has been developed. After iterative correction using field measurement data, the total phase excursion of the cyclotron is within 9 and the first harmonic is less than 10-3 T, which are all acceptable. Furthermore, the beam testing declares the successful construction of the cyclotron magnet. Besides, some magnetic field influence factors were discussed, including the magnetic field distortion and measurement error.
2012,
24: 2198-2202.
doi: 10.3788/HPLPB20122409.2198
Abstract:
The producing mechanism of secondary electrons from target surfaces under ion beam bombardment is discussed. Several methods to suppress the secondary electrons in special vacuum devices and their advantages and disadvantages are introduced. The ways of using self-bias and curved surface targets are proposed and verified in the experiment. The results show that the secondary electrons can be effectively suppressed when the self-bias is larger than 80 V. The secondary electron yield decreases by using curved surface target instead of flat target. The secondary electron yield calculated from the experimental data is about 0.67, which is slightly larger than the value (0.58) from the literature due to the impurities of the ion beam and target surface. The effect of suppressing the electron countercurrent by the self-bias method is analyzed. The result shows that the self-bias method can suppress not only the secondary electrons from target surface under ion beams bombardment, but also the electron countercurrent resulting from the instability of the pulsed power source.
The producing mechanism of secondary electrons from target surfaces under ion beam bombardment is discussed. Several methods to suppress the secondary electrons in special vacuum devices and their advantages and disadvantages are introduced. The ways of using self-bias and curved surface targets are proposed and verified in the experiment. The results show that the secondary electrons can be effectively suppressed when the self-bias is larger than 80 V. The secondary electron yield decreases by using curved surface target instead of flat target. The secondary electron yield calculated from the experimental data is about 0.67, which is slightly larger than the value (0.58) from the literature due to the impurities of the ion beam and target surface. The effect of suppressing the electron countercurrent by the self-bias method is analyzed. The result shows that the self-bias method can suppress not only the secondary electrons from target surface under ion beams bombardment, but also the electron countercurrent resulting from the instability of the pulsed power source.
2012,
24: 2203-2206.
doi: 10.3788/HPLPB20122409.2203
Abstract:
The impact velocity between space debris and spacecraft is normally in excess of 10 km/s. The impact process at such velocity features high temperature, high pressure and high strain rate, along with phase transitions. The vapor occur at the same time. Based on AUTODYN/SPH secondary development, Sesame EOS library and phase diagram of Al are embedded in the AUTODYN/SPH. The simulated hole diameters of bumpers are 9.02 and 9.34 mm at the impact velocities of 5.0 and 5.6 km/s. The simulation results are consistent well with the experimental results, which shows that the physical modeling and the selection of parameters are reasonable and the method of numerical simulation is correct and valid. The phase distributions of debris cloud generated by hypervelocity impact are computed, and the distribution of gas state, liquid state and solid state in debris cloud is also derived.
The impact velocity between space debris and spacecraft is normally in excess of 10 km/s. The impact process at such velocity features high temperature, high pressure and high strain rate, along with phase transitions. The vapor occur at the same time. Based on AUTODYN/SPH secondary development, Sesame EOS library and phase diagram of Al are embedded in the AUTODYN/SPH. The simulated hole diameters of bumpers are 9.02 and 9.34 mm at the impact velocities of 5.0 and 5.6 km/s. The simulation results are consistent well with the experimental results, which shows that the physical modeling and the selection of parameters are reasonable and the method of numerical simulation is correct and valid. The phase distributions of debris cloud generated by hypervelocity impact are computed, and the distribution of gas state, liquid state and solid state in debris cloud is also derived.
2012,
24: 2207-2211.
doi: 10.3788/HPLPB20122409.2207
Abstract:
To improve accuracy and efficiency of contour processing of industrial computed tomography (CT) images for reverse engineering, an industrial CT slicing image contour extraction and optimization system is developed in this paper. The system includes five parts, which are modules of image processing, contour recognition and extraction, contour fitting and optimization, image processing algorithm library, and contour data format transform. The processing results of the system can be organized as 3-D point clouds or contour line used standard format, which can be used to reconstruct 3D CAD model directly in professional softwares of reverse engineering. Further more, a fitting model based on global constraints is constructed to find the optimal contour curves, and a method combining directed graph decomposition and numerical algebra is proposed to improve the accuracy and efficiency of fitting contours. Finally, the effectiveness and feasibility of this system is proved with an experiment.
To improve accuracy and efficiency of contour processing of industrial computed tomography (CT) images for reverse engineering, an industrial CT slicing image contour extraction and optimization system is developed in this paper. The system includes five parts, which are modules of image processing, contour recognition and extraction, contour fitting and optimization, image processing algorithm library, and contour data format transform. The processing results of the system can be organized as 3-D point clouds or contour line used standard format, which can be used to reconstruct 3D CAD model directly in professional softwares of reverse engineering. Further more, a fitting model based on global constraints is constructed to find the optimal contour curves, and a method combining directed graph decomposition and numerical algebra is proposed to improve the accuracy and efficiency of fitting contours. Finally, the effectiveness and feasibility of this system is proved with an experiment.
2012,
24: 2212-2214.
doi: 10.3788/HPLPB20122409.2212
Abstract:
In order to diagnose electromagnetic radiation generated by hypervelocity impact, the experimental and microwave diagnostic system for the electromagnetic radiation was established. Experimental diagnostics of electromagnetic radiation generated by impacting LY12 aluminum target were finished by using the microwave diagnostic system under loading velocities of 4.60 and 4.66 km/s separately. The relationship between electromagnetic radiation and target thickness was analyzed in the experiments. Experimental results show that, the microwave radiation intensity is large, when target thickness is small; the power of microwave radiation was proportional to the microcrack number generated by hypervelocity impact. Meanwhile, the physical mechanism of electromagnetic radiation generated by hypervelocity impact can be explained as thermal excitation produced electron and existence of crack created by impact.
In order to diagnose electromagnetic radiation generated by hypervelocity impact, the experimental and microwave diagnostic system for the electromagnetic radiation was established. Experimental diagnostics of electromagnetic radiation generated by impacting LY12 aluminum target were finished by using the microwave diagnostic system under loading velocities of 4.60 and 4.66 km/s separately. The relationship between electromagnetic radiation and target thickness was analyzed in the experiments. Experimental results show that, the microwave radiation intensity is large, when target thickness is small; the power of microwave radiation was proportional to the microcrack number generated by hypervelocity impact. Meanwhile, the physical mechanism of electromagnetic radiation generated by hypervelocity impact can be explained as thermal excitation produced electron and existence of crack created by impact.
2012,
24: 2215-2219.
doi: 10.3788/HPLPB20122409.2215
Abstract:
A BP neural network based image restoration algorithm is proposed against the blur of flash radiographic images with low signal-to-noise ratios. Firstly the degraded image and the sample image are both divided into the edge part and the smooth part. Secondly the nonlinear mapping relationship between the degraded image and its original image is established by training the BP neural network which has the ability of learning, remembrance and generalizing with the edge part of the sample image. Finally the edge part of the degraded image could be restored by the trained neural network. Numerical results show that this method could restore the image information near edges when the systematic point-spread function is unknown, and the restored image is greatly improved in the signal-to-noise ratio and in the visual.
A BP neural network based image restoration algorithm is proposed against the blur of flash radiographic images with low signal-to-noise ratios. Firstly the degraded image and the sample image are both divided into the edge part and the smooth part. Secondly the nonlinear mapping relationship between the degraded image and its original image is established by training the BP neural network which has the ability of learning, remembrance and generalizing with the edge part of the sample image. Finally the edge part of the degraded image could be restored by the trained neural network. Numerical results show that this method could restore the image information near edges when the systematic point-spread function is unknown, and the restored image is greatly improved in the signal-to-noise ratio and in the visual.
2012,
24: 2220-2224.
doi: 10.3788/HPLPB20122409.2220
Abstract:
Based on Fresnel-Kirchhoff diffraction theory, the propagation behavior of the Gaussian beam passing through the nonlinear optical medium is theoretically analyzed under strong absorption or without absorption. A unified equation is derived, which can describe the open-aperture Z-scan curve and the closed-aperture Z-scan curve. The numerical simulation of Z-scan curve under different conditions shows that the transmission Z-scan curve with peak and valley has some new features. As the incident laser peak intensity increases, the transmittance peak is suppressed and the valley is strengthened; increasing of nonlinear phase shift can heighten the peak and deepen the valley; the larger the laser beam waist radiusis, the more obvious the features of peak-valley configuration are.
Based on Fresnel-Kirchhoff diffraction theory, the propagation behavior of the Gaussian beam passing through the nonlinear optical medium is theoretically analyzed under strong absorption or without absorption. A unified equation is derived, which can describe the open-aperture Z-scan curve and the closed-aperture Z-scan curve. The numerical simulation of Z-scan curve under different conditions shows that the transmission Z-scan curve with peak and valley has some new features. As the incident laser peak intensity increases, the transmittance peak is suppressed and the valley is strengthened; increasing of nonlinear phase shift can heighten the peak and deepen the valley; the larger the laser beam waist radiusis, the more obvious the features of peak-valley configuration are.
2012,
24: 2225-2229.
doi: 10.3788/HPLPB20122409.2225
Abstract:
For better computing efficiency in high-performance clusters, a three-dimensional electromagnetic PIC parallel code was developed in Linux system based on the CHIPIC software code. By testing a magnetically insulated transmission line oscillator, gyrotron and relativistic klystron, speedups of 3.70, 6.72, 6.00 are obtained for them respectively. Results show that the high-performance clusters have much higher speedups and computing efficiency than the PC clusters with the same processes, so high-performance clusters could make better use of computing resources.
For better computing efficiency in high-performance clusters, a three-dimensional electromagnetic PIC parallel code was developed in Linux system based on the CHIPIC software code. By testing a magnetically insulated transmission line oscillator, gyrotron and relativistic klystron, speedups of 3.70, 6.72, 6.00 are obtained for them respectively. Results show that the high-performance clusters have much higher speedups and computing efficiency than the PC clusters with the same processes, so high-performance clusters could make better use of computing resources.
2012,
24: 2230-2234.
doi: 10.3788/HPLPB20122409.2230
Abstract:
Basic principles and physical mechanism of image measurement by using imaging plates(IPs) are studied in this paper, and fundamental problems about applications of the IPs in gamma-ray image measurement are also analyzed. Monte Carlo models of imaging plates in common use are built, involving three types of IPs, i.e. MS, SR, TR. And the energy deposition of gamma rays of different energies in the IPs are calculated through the MCNPX code and the NPE code based on a Geant4 platform. As a result, the energy deposition of SR-type and MS-type IPs is 3-5 times larger than that of TR-type IPs in the low energy part, and 7-9 times larger in the high energy part. The theoretical and experimental results of the relation between gamma-ray sensitivity of MS-type IPs and copper foil thickness agree well with each other. The spatial resolution of IPs in gamma-ray imaging is better than 50 m.
Basic principles and physical mechanism of image measurement by using imaging plates(IPs) are studied in this paper, and fundamental problems about applications of the IPs in gamma-ray image measurement are also analyzed. Monte Carlo models of imaging plates in common use are built, involving three types of IPs, i.e. MS, SR, TR. And the energy deposition of gamma rays of different energies in the IPs are calculated through the MCNPX code and the NPE code based on a Geant4 platform. As a result, the energy deposition of SR-type and MS-type IPs is 3-5 times larger than that of TR-type IPs in the low energy part, and 7-9 times larger in the high energy part. The theoretical and experimental results of the relation between gamma-ray sensitivity of MS-type IPs and copper foil thickness agree well with each other. The spatial resolution of IPs in gamma-ray imaging is better than 50 m.
2012,
24: 2235-2238.
doi: 10.3788/HPLPB20122409.2235
Abstract:
In order to solve the problem of scattering artifacts in the computed tomography images, a modified Poisson distribution function is presented and used as the scatter model. A set of scatter basis images are obtained from scatter estimations with different parameter values in the model. Then the corrected image is obtained by adding the basis images to the original image. The coefficients for the linear combination are determined by minimizing the total variation of the combined images. The method requires low computational effort and allows flexible application to different scanned objects. Experiment results indicate that cupping and dark bands artifacts due to scattering are effectively depressed by the proposed method， and the image contrast is enhanced.
In order to solve the problem of scattering artifacts in the computed tomography images, a modified Poisson distribution function is presented and used as the scatter model. A set of scatter basis images are obtained from scatter estimations with different parameter values in the model. Then the corrected image is obtained by adding the basis images to the original image. The coefficients for the linear combination are determined by minimizing the total variation of the combined images. The method requires low computational effort and allows flexible application to different scanned objects. Experiment results indicate that cupping and dark bands artifacts due to scattering are effectively depressed by the proposed method， and the image contrast is enhanced.
2012,
24: 2239-2244.
doi: 10.3788/HPLPB20122409.2239
Abstract:
Factors affecting the triggering breakdown characteristics of a multi-gap gas switch have been investigated in this paper. Experiments were carried out to study the relationship between the trigger jitter and various switch parameters, e.g. the trigger voltage, the switch pressure and the ultraviolet (UV) pre-ionizing duration. Results indicate that the trigger jitter decreases evidently with the trigger voltage changing from 50 kV to 80 kV, and the statistical delay jitter decreases more evidently than the formative delay jitter. Both the statistical delay jitter and the formative delay jitter increase with the gas pressure changing from 0.16 MPa to 0.28 MPa. The trigger jitter and the formative delay jitter also decrease when the duration of the UV pre-ionizing is prolonged. The optimized duration of UV pre-ionizing is 80-140 ns and the trigger jitter decreases by about 39%. The UV pre-ionizion could effectively reduce the statistical delay jitter, but has little effect on the formation of delay.
Factors affecting the triggering breakdown characteristics of a multi-gap gas switch have been investigated in this paper. Experiments were carried out to study the relationship between the trigger jitter and various switch parameters, e.g. the trigger voltage, the switch pressure and the ultraviolet (UV) pre-ionizing duration. Results indicate that the trigger jitter decreases evidently with the trigger voltage changing from 50 kV to 80 kV, and the statistical delay jitter decreases more evidently than the formative delay jitter. Both the statistical delay jitter and the formative delay jitter increase with the gas pressure changing from 0.16 MPa to 0.28 MPa. The trigger jitter and the formative delay jitter also decrease when the duration of the UV pre-ionizing is prolonged. The optimized duration of UV pre-ionizing is 80-140 ns and the trigger jitter decreases by about 39%. The UV pre-ionizion could effectively reduce the statistical delay jitter, but has little effect on the formation of delay.
2012,
24: 2245-2249.
doi: 10.3788/HPLPB20122409.2245
Abstract:
In this paper, a strip air-core pulse transformer is designed to convert the current. And, how it works and the process of making iselaborated in detail. The transformer contains leads, insulator, copper strip and supporting core. Under the conditions of the charging voltage 2500 V, 5.52 kA and 1.48 kA peak current of primary and secondary windings are obtained, and correspondingly, the current rising rate is 37 A/s and 138 A/s. It is supported by analysis and experiment that the transformer can reduce the requirement of the rising rate of the switching current effectively. So, the thyristor can be used in the pulse current system which has a high current rising rate and improve its performance on repetition and stability.
In this paper, a strip air-core pulse transformer is designed to convert the current. And, how it works and the process of making iselaborated in detail. The transformer contains leads, insulator, copper strip and supporting core. Under the conditions of the charging voltage 2500 V, 5.52 kA and 1.48 kA peak current of primary and secondary windings are obtained, and correspondingly, the current rising rate is 37 A/s and 138 A/s. It is supported by analysis and experiment that the transformer can reduce the requirement of the rising rate of the switching current effectively. So, the thyristor can be used in the pulse current system which has a high current rising rate and improve its performance on repetition and stability.
2012,
24: 2250-2254.
doi: 10.3788/HPLPB20122409.2250
Abstract:
A resistive-voltage-dividing high-power load used for experiments of magnetically insulated transmission lines (MITLs) has been designed, and the resistance of this load can be changed from 2.0 to 14.0 . By using the system identification tool of MATLAB and the electromagnetism module of ANSYS, the frequency response and the surface electrical security of the load were studied, respectively. Also, the influences of the temperature and skin effect were particularly considered. The resistive load has been used for one-meter long MITL experiments on Qiangguang-Ⅰ accelerator. With the load resistance of 2.1 , the peak load voltage can reach about 1.2 MV, and the peak current can reach about 494.4 kA with a risetime of about 125 ns. The results of the measurement accord closely with those of the TLCODE calculations.
A resistive-voltage-dividing high-power load used for experiments of magnetically insulated transmission lines (MITLs) has been designed, and the resistance of this load can be changed from 2.0 to 14.0 . By using the system identification tool of MATLAB and the electromagnetism module of ANSYS, the frequency response and the surface electrical security of the load were studied, respectively. Also, the influences of the temperature and skin effect were particularly considered. The resistive load has been used for one-meter long MITL experiments on Qiangguang-Ⅰ accelerator. With the load resistance of 2.1 , the peak load voltage can reach about 1.2 MV, and the peak current can reach about 494.4 kA with a risetime of about 125 ns. The results of the measurement accord closely with those of the TLCODE calculations.
2012,
24: 2255-2258.
doi: 10.3788/HPLPB20122409.2255
Abstract:
This paper investigates the effects of the impedance, and transmission voltage and current of magnetically insulated transmission lines(MITLs) on the current of the generated space electron flow and the thickness of the cathode electron sheath. The three-dimensional approximate model of the four-layer disc cone MITLs is established and simulated by CHIPIC software. The comparison of the theoretical calculation, the three-dimensional simulation values and the two-dimensional simulation results of some relevant literatures verifies the correctness of the three-dimensional simulation. Finally, the effects of the distance changes between anode and cathode on transmission efficiency of the disc cone MITLs are studied.
This paper investigates the effects of the impedance, and transmission voltage and current of magnetically insulated transmission lines(MITLs) on the current of the generated space electron flow and the thickness of the cathode electron sheath. The three-dimensional approximate model of the four-layer disc cone MITLs is established and simulated by CHIPIC software. The comparison of the theoretical calculation, the three-dimensional simulation values and the two-dimensional simulation results of some relevant literatures verifies the correctness of the three-dimensional simulation. Finally, the effects of the distance changes between anode and cathode on transmission efficiency of the disc cone MITLs are studied.
2012,
24: 2259-2263.
doi: 10.3788/HPLPB20122409.2259
Abstract:
The paper investigates an NEMP(nuclear electromagnetic pulse) detection technique in the absence of nuclear testing. After threshold demodulation, DC elimination, filtering, interpolation and normalization, the method uses wavelet analysis to extract the forth segment of wavelet pack energy spectrum, the first and forth segments of wavelet coefficient box-counting dimension as eigenvalues, establishes their respective membership functions according to statistical analysis, and then uses the fuzzy identification theory to identify NEMP signals. The method has been used to process measured NEMP signals and LEMP(lightning electromagnetic pulse) signals, which are the main source of interference. The identification rate is 99.41%.
The paper investigates an NEMP(nuclear electromagnetic pulse) detection technique in the absence of nuclear testing. After threshold demodulation, DC elimination, filtering, interpolation and normalization, the method uses wavelet analysis to extract the forth segment of wavelet pack energy spectrum, the first and forth segments of wavelet coefficient box-counting dimension as eigenvalues, establishes their respective membership functions according to statistical analysis, and then uses the fuzzy identification theory to identify NEMP signals. The method has been used to process measured NEMP signals and LEMP(lightning electromagnetic pulse) signals, which are the main source of interference. The identification rate is 99.41%.
2012,
24: 2264-2268.
doi: 10.3788/HPLPB20122409.2264
Abstract:
On the basis of the nonlinear equations, the characteristic of nonlinear chaotic dynamics was investigated in a traveling-wave tube amplifier. The phase space of the electron orbits, the time-space distribution and the output power of the radiation field were studied numerically. The result shows the radiation field and the electron beam is a dissipative system. When the parameters such as current or detuning changes and are above a certain threshold, chaotic characteristic is appeared in the whole time and space of the system. The output power is characterized by the irregularly oscillation with the wide continuous spectrum.
On the basis of the nonlinear equations, the characteristic of nonlinear chaotic dynamics was investigated in a traveling-wave tube amplifier. The phase space of the electron orbits, the time-space distribution and the output power of the radiation field were studied numerically. The result shows the radiation field and the electron beam is a dissipative system. When the parameters such as current or detuning changes and are above a certain threshold, chaotic characteristic is appeared in the whole time and space of the system. The output power is characterized by the irregularly oscillation with the wide continuous spectrum.
