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RSS2005 Vol. 17, No. 05
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Fabrication of collimating module and measurement of far field divergence of laser beam of 1 550 nm
2005,
17.
Abstract:
Theory analysis of the collimation about Gaussian light beam is described and the designed collimating lens have achieved the technique target in wavefront aberration by intervention measurement. The experimental data are measured by the designed experimental installation system and are processed by Gaussian power distributing curve, the spot size corresponding to half of the maximum light power is measured by the light power meter, which is used to determine the far field divergence angle of laser beam. In the experiment, average of the measured maximal light power is 27.89 nW and average of the spot size difference is 6.33 mm. Therefore, minimal far-field divergence angle of the laser beam is 0.315 mrad. The collimation system of the experiment is validated and it can reduce far field di
Theory analysis of the collimation about Gaussian light beam is described and the designed collimating lens have achieved the technique target in wavefront aberration by intervention measurement. The experimental data are measured by the designed experimental installation system and are processed by Gaussian power distributing curve, the spot size corresponding to half of the maximum light power is measured by the light power meter, which is used to determine the far field divergence angle of laser beam. In the experiment, average of the measured maximal light power is 27.89 nW and average of the spot size difference is 6.33 mm. Therefore, minimal far-field divergence angle of the laser beam is 0.315 mrad. The collimation system of the experiment is validated and it can reduce far field di
2005,
17.
Abstract:
Laser propagating through resonance media taking into account of spatial effect was discussed by simultaneously solving the Maxwell-Bloch equations with definite differential method. Results indicate that the propagation of a 2π pulse form would no longer be a soliton, its profile would expand, and the degree of distortion depends on the interaction intensity of laser and material: stronger interaction causes more distortion till the profile split. The interaction intensity was decided by such elements as the laser frequency, laser intensity, the dipole of material, detuning and the concentration of resonance particles．
Laser propagating through resonance media taking into account of spatial effect was discussed by simultaneously solving the Maxwell-Bloch equations with definite differential method. Results indicate that the propagation of a 2π pulse form would no longer be a soliton, its profile would expand, and the degree of distortion depends on the interaction intensity of laser and material: stronger interaction causes more distortion till the profile split. The interaction intensity was decided by such elements as the laser frequency, laser intensity, the dipole of material, detuning and the concentration of resonance particles．
2005,
17.
Abstract:
Nd:YAG laser is used as a spontaneous vibrational Raman scattering (SVRS) source in combustion diagnostics. Multiple species data are acquired from both mathane-air combustion and solid fuel combustion. Spatially resolved Raman scattering spectra are used to measure concentrations of all major species (N2, O2, H2O, CH4) in methane-air flames with different ratio of CH4 and air. Temperature of the flame is calculated by measuring the concentrations of all major species in flames, also by measuring the ratio of Stokes spectrum intensity and anti-Stokes spectrum intensity. Uncertainty of concentrations and temperature data is analyzed, too. Moreover, the technique is used to diagnose solid fuel combustion with single-pulse. The Raman spectra of major species（N2, H2CO, CH4, H2O）at different
Nd:YAG laser is used as a spontaneous vibrational Raman scattering (SVRS) source in combustion diagnostics. Multiple species data are acquired from both mathane-air combustion and solid fuel combustion. Spatially resolved Raman scattering spectra are used to measure concentrations of all major species (N2, O2, H2O, CH4) in methane-air flames with different ratio of CH4 and air. Temperature of the flame is calculated by measuring the concentrations of all major species in flames, also by measuring the ratio of Stokes spectrum intensity and anti-Stokes spectrum intensity. Uncertainty of concentrations and temperature data is analyzed, too. Moreover, the technique is used to diagnose solid fuel combustion with single-pulse. The Raman spectra of major species（N2, H2CO, CH4, H2O）at different
2005,
17.
Abstract:
In this paper, sol-gel single-layer SiO2 anti-reflective coatings modified with PEG were deposited on K9 glass by sol-gel dipping-coating method. The coatings were irradiated by a Q-switched Nd:YAG high power laser whose wavelength was 1 064 nm and pulse width was 3 ns. The microstructure of sol was observed by TEM and the surface morphologies of the coatings were observed by AFM before they were irradiated. The morphologies of the damaged coatings were observed by microscope. Damage mechanics of the laser were studied. The results show that PEG can modify the microstructure of SiO2 coating and thus the induced damage threshold of coating was distinctly improved.
In this paper, sol-gel single-layer SiO2 anti-reflective coatings modified with PEG were deposited on K9 glass by sol-gel dipping-coating method. The coatings were irradiated by a Q-switched Nd:YAG high power laser whose wavelength was 1 064 nm and pulse width was 3 ns. The microstructure of sol was observed by TEM and the surface morphologies of the coatings were observed by AFM before they were irradiated. The morphologies of the damaged coatings were observed by microscope. Damage mechanics of the laser were studied. The results show that PEG can modify the microstructure of SiO2 coating and thus the induced damage threshold of coating was distinctly improved.
2005,
17.
Abstract:
The beam propagation in nonlocal Kerr media is modeled by the nonlocal nonlinear Schrodinger equation. This problem can be re-interpreted with the variational approach. In the case of strong nonlocality, the response function can be expanded in Taylor's series, so that the variational problem can be found in a closed form. The evolution of the beam width can be obtained qualitatively by analysing the potential function. By means of a Reyleigh-Ritz optimization procedure, the closed form solutions for the evolution of beams in both defocusing and self-focusing cases can be obtained. When the beam propagates in a self-focusing material and its input power reaches a critical value, its width becomes fixed. The comparison with analytical solutions obtained by other approaches shows that the va
The beam propagation in nonlocal Kerr media is modeled by the nonlocal nonlinear Schrodinger equation. This problem can be re-interpreted with the variational approach. In the case of strong nonlocality, the response function can be expanded in Taylor's series, so that the variational problem can be found in a closed form. The evolution of the beam width can be obtained qualitatively by analysing the potential function. By means of a Reyleigh-Ritz optimization procedure, the closed form solutions for the evolution of beams in both defocusing and self-focusing cases can be obtained. When the beam propagates in a self-focusing material and its input power reaches a critical value, its width becomes fixed. The comparison with analytical solutions obtained by other approaches shows that the va
2005,
17.
Abstract:
The double clad fiber made in China was fabricated by the modified chemical-vapor deposition (MCVD) technique. The geometric, fluorescence, and laser characters of the fiber were measured. The fiber has a 16 ?m diameter Yb-doped core with a numerical aperture (NA) of 0.18,and the inner cladding has a 400/450 ?m diameter for the longer/shorter axis with a NA of 0.36. The fluorescence spectrum ranged from 1 000~1 140 nm, and the spectrum width at 1 030 nm is greater than 50 nm．When one end of the fiber was pumped by a high-power laser diode with the launched power of 61 W, 32 W laser output was obtained with the slope efficiency of 64%. There is no evidence of saturation at high pump powers, so the output power can be further improved by optimizing the parameters.
The double clad fiber made in China was fabricated by the modified chemical-vapor deposition (MCVD) technique. The geometric, fluorescence, and laser characters of the fiber were measured. The fiber has a 16 ?m diameter Yb-doped core with a numerical aperture (NA) of 0.18,and the inner cladding has a 400/450 ?m diameter for the longer/shorter axis with a NA of 0.36. The fluorescence spectrum ranged from 1 000~1 140 nm, and the spectrum width at 1 030 nm is greater than 50 nm．When one end of the fiber was pumped by a high-power laser diode with the launched power of 61 W, 32 W laser output was obtained with the slope efficiency of 64%. There is no evidence of saturation at high pump powers, so the output power can be further improved by optimizing the parameters.
2005,
17.
Abstract:
In order to evaluate the different design schemes of high- power laser facility and choose the best configuration, a relatively complete system of evaluation indices for laser design was presented. And then, mathematical model of the evaluation system was established using multi- objective decision- making theory and weighted method. Finally, comprehensive evaluation results, including performance and cost, of 4 structures of high- power laser facility were achieved using the above model. The results showed that the model is reasonable.
In order to evaluate the different design schemes of high- power laser facility and choose the best configuration, a relatively complete system of evaluation indices for laser design was presented. And then, mathematical model of the evaluation system was established using multi- objective decision- making theory and weighted method. Finally, comprehensive evaluation results, including performance and cost, of 4 structures of high- power laser facility were achieved using the above model. The results showed that the model is reasonable.
2005,
17.
Abstract:
A numerical model is presented to simulate the temperature distribution on the rotational cylindrical shell under laser irradiation. Thermal property parameters varying with temperature and the rotating frequency of the cylindrical shell are included and the effect of the variation of the temperature distribution is studied in this paper. Results show that temperature rise induced by laser decreases largely when cylindrical shell rotates; the temperature of exterior surface rises periodically according to the rotating frequency but the temperature of inner surface only has such property with low frequency because of heat conduction.
A numerical model is presented to simulate the temperature distribution on the rotational cylindrical shell under laser irradiation. Thermal property parameters varying with temperature and the rotating frequency of the cylindrical shell are included and the effect of the variation of the temperature distribution is studied in this paper. Results show that temperature rise induced by laser decreases largely when cylindrical shell rotates; the temperature of exterior surface rises periodically according to the rotating frequency but the temperature of inner surface only has such property with low frequency because of heat conduction.
2005,
17.
Abstract:
The 3-dimensional transient temperature distribution in a tube YAG laser pumped by repeat pulses was studied by experiment and simulation. The result shows that the transient temperature in the tube increases with the number of pump pulses like a saw-toothed curve at the beginning of pumping, and the position of the maximum transient temperature shifts from the inner surface to the inside of the tube. After about 490 pulses, the transient temperature in the tube changes repeatedly with the same frequency of the pump pulse, and the position of the maximum transient temperature occurs at a fixed point. At this time, the temperature inside the tube is higher than that at the inner-or outer-surface of the tube, and the temperature at the inner surface is higher than that at the outer surface.?
The 3-dimensional transient temperature distribution in a tube YAG laser pumped by repeat pulses was studied by experiment and simulation. The result shows that the transient temperature in the tube increases with the number of pump pulses like a saw-toothed curve at the beginning of pumping, and the position of the maximum transient temperature shifts from the inner surface to the inside of the tube. After about 490 pulses, the transient temperature in the tube changes repeatedly with the same frequency of the pump pulse, and the position of the maximum transient temperature occurs at a fixed point. At this time, the temperature inside the tube is higher than that at the inner-or outer-surface of the tube, and the temperature at the inner surface is higher than that at the outer surface.?
2005,
17.
Abstract:
A theoretical model of one point side-pumped Yb3+ doped double clad fiber laser was built up. By numerical analysis, the distribution of pump power and laser power along the fiber, and the relation between pump position and output power were obtained for forward pump, backward pump and bidirectional pump. The results show that pump position has little effects on laser power distribution and output power for bidirectional pump. This method can become a good choice for side-pumped double clad fiber laser.
A theoretical model of one point side-pumped Yb3+ doped double clad fiber laser was built up. By numerical analysis, the distribution of pump power and laser power along the fiber, and the relation between pump position and output power were obtained for forward pump, backward pump and bidirectional pump. The results show that pump position has little effects on laser power distribution and output power for bidirectional pump. This method can become a good choice for side-pumped double clad fiber laser.
2005,
17.
Abstract:
A mobile dual-wavelength Mie lidar(DWL) is introduced. The DWL can be used to measure the aerosol extinction coefficient profiles at 1 064 nm and 532 nm wavelength. The DWL system is composed of a transmission unit, a signal receiving unit, a signal acquiring unit and a processing control unit. Some main specifications of the DWL system are presented, which include laser with 1 064 & 532 nm wavelengths and 400 & 300 mJ pulse energy, 20 Hz repetition rate and less 0.5 mrad divergence, telescope with 1~3 mrad FOV, two different PMT R3236 & H7680 and two different amplifier VT120 & Phillips777 for 1 064& 532 nm signal detecting, filters with 1 064 & 532 nm center wavelength they have 1 nm bandwidth, even different data acquiring cards and so on. The fundamental principles and key techniques o
A mobile dual-wavelength Mie lidar(DWL) is introduced. The DWL can be used to measure the aerosol extinction coefficient profiles at 1 064 nm and 532 nm wavelength. The DWL system is composed of a transmission unit, a signal receiving unit, a signal acquiring unit and a processing control unit. Some main specifications of the DWL system are presented, which include laser with 1 064 & 532 nm wavelengths and 400 & 300 mJ pulse energy, 20 Hz repetition rate and less 0.5 mrad divergence, telescope with 1~3 mrad FOV, two different PMT R3236 & H7680 and two different amplifier VT120 & Phillips777 for 1 064& 532 nm signal detecting, filters with 1 064 & 532 nm center wavelength they have 1 nm bandwidth, even different data acquiring cards and so on. The fundamental principles and key techniques o
2005,
17.
Abstract:
In this paper we have studied the excitation of plasma wake field by an ultrashort laser pulse in the near-resonant regime through one-dimensional particle-in-cell (PIC) simulations. Preliminary results are given of the amplitude of the plasma wake field versus laser pulse duration from resonant to near resonant regime. It is found that the wake field excitation is enhanced at near-resonant regime. The wake field is also obtained by numerically solving a nonlinear equation, which have been used to study wake field excitation under quasi-static approximation. By comparing the results from the two methods, the appropriate region of using the nonlinear equation is established that the laser pulse duration has to be 4 times less than the plasma wave wavelength. For longer laser pulses, the non
In this paper we have studied the excitation of plasma wake field by an ultrashort laser pulse in the near-resonant regime through one-dimensional particle-in-cell (PIC) simulations. Preliminary results are given of the amplitude of the plasma wake field versus laser pulse duration from resonant to near resonant regime. It is found that the wake field excitation is enhanced at near-resonant regime. The wake field is also obtained by numerically solving a nonlinear equation, which have been used to study wake field excitation under quasi-static approximation. By comparing the results from the two methods, the appropriate region of using the nonlinear equation is established that the laser pulse duration has to be 4 times less than the plasma wave wavelength. For longer laser pulses, the non
2005,
17.
Abstract:
The studies of the wavelet structures of the molecular excitations with the high intense laser are very active in the strong laser field physics. The one-dimensional time-dependent Schr-dinger equation was numerically solved with the symmetric splitting of the short-time exponential propagator and the fast Fourier transformation, and influence of intensity and pulse with on ionization of linear multi-atom molecular ion in two-color laser fields was researched. The theory results show that the dependence of ionization probability on the atomic distance can be altered obviously with the fundamental wave-field-intensity of 1.2×1013~12×1015 W/cm2, but unchanged with respect to different intensity ratios. In addition, the continuous interaction of laser pulse can enhance molecular ionization,
The studies of the wavelet structures of the molecular excitations with the high intense laser are very active in the strong laser field physics. The one-dimensional time-dependent Schr-dinger equation was numerically solved with the symmetric splitting of the short-time exponential propagator and the fast Fourier transformation, and influence of intensity and pulse with on ionization of linear multi-atom molecular ion in two-color laser fields was researched. The theory results show that the dependence of ionization probability on the atomic distance can be altered obviously with the fundamental wave-field-intensity of 1.2×1013~12×1015 W/cm2, but unchanged with respect to different intensity ratios. In addition, the continuous interaction of laser pulse can enhance molecular ionization,
2005,
17.
Abstract:
Inertial confinement fusion(ICF) experiments need the incorporation of dopant atoms into the low density foam. Through a phase-separation process, the Bromine (Br) doped foams with a typical density of 50 mg/cm3 were synthesized contaning 58.91% Br atom. A lamellar structure was observed in the scanning electron microscope (SEM) image of the PMP foam. The monomer hexabromobenzene acted as the “crystalloid” in the sol-gel process. As the dopant level increased, there were more “crystalloids”, which would make the lamellar become smaller. Taking the measurement error into account, the dopant was dispread uniformly in the foam sample. The thermo gravimetric analysis used in different dopant level indicates the solvent was removed completely from the whole foam system.
Inertial confinement fusion(ICF) experiments need the incorporation of dopant atoms into the low density foam. Through a phase-separation process, the Bromine (Br) doped foams with a typical density of 50 mg/cm3 were synthesized contaning 58.91% Br atom. A lamellar structure was observed in the scanning electron microscope (SEM) image of the PMP foam. The monomer hexabromobenzene acted as the “crystalloid” in the sol-gel process. As the dopant level increased, there were more “crystalloids”, which would make the lamellar become smaller. Taking the measurement error into account, the dopant was dispread uniformly in the foam sample. The thermo gravimetric analysis used in different dopant level indicates the solvent was removed completely from the whole foam system.
2005,
17.
Abstract:
The K-shell emission lines of laser-produced aluminum plasma were measured by the space-resolved spectrometer, which was constructed by a flat crystal spectrometer with a 20 μm-wide slit. The electron density profile beyond the critical density is obtained by fitting the Stark-broadened line wings of hydrogenic ions, then the diagnostics on high electron density has been developed tentatively.
The K-shell emission lines of laser-produced aluminum plasma were measured by the space-resolved spectrometer, which was constructed by a flat crystal spectrometer with a 20 μm-wide slit. The electron density profile beyond the critical density is obtained by fitting the Stark-broadened line wings of hydrogenic ions, then the diagnostics on high electron density has been developed tentatively.
Experimental studies of the interaction of microwaves with mixture burning plasmas in the atmosphere
2005,
17.
Abstract:
A kind of chemical mixture is designed and prepared. With the method of thermodynamics, the average electron density of the plasma generated by burning the mixture is calculated. The reflection and attenuation of the microwaves, in the band of 2~15 GHz, by the plasma are measured. The results of measurements indicate that the plasma can absorb the energies of the microwaves in a broad band. The average absorption is above 25 dB, but the reflection is too weak to be distinguished from the background noise. Moreover, theoretical discussion indicates that the electron-neutral particle collision is the major factor that results in the absorption in the wide band.
A kind of chemical mixture is designed and prepared. With the method of thermodynamics, the average electron density of the plasma generated by burning the mixture is calculated. The reflection and attenuation of the microwaves, in the band of 2~15 GHz, by the plasma are measured. The results of measurements indicate that the plasma can absorb the energies of the microwaves in a broad band. The average absorption is above 25 dB, but the reflection is too weak to be distinguished from the background noise. Moreover, theoretical discussion indicates that the electron-neutral particle collision is the major factor that results in the absorption in the wide band.
2005,
17.
Abstract:
The structure of quadrupole mass spectrometers (QMS) and the quantitative analysis principle of gas analysis mass spectrometers (GAM) are described. The GAM system is very sensitive and can be used to quantitatively analyze the gas mixture in fusion targets. It can work in a normal resolution mode or in a high resolution mode. In the high resolution mode, it can selectively detect deuterium (with a mass number of 4.028 2) and helium (with a mass number of 4.002 6). This system can offer reference data of filled microsphere targets for inertial confinement fusion (ICF) experiments.
The structure of quadrupole mass spectrometers (QMS) and the quantitative analysis principle of gas analysis mass spectrometers (GAM) are described. The GAM system is very sensitive and can be used to quantitatively analyze the gas mixture in fusion targets. It can work in a normal resolution mode or in a high resolution mode. In the high resolution mode, it can selectively detect deuterium (with a mass number of 4.028 2) and helium (with a mass number of 4.002 6). This system can offer reference data of filled microsphere targets for inertial confinement fusion (ICF) experiments.
2005,
17.
Abstract:
To explore heat transfer process between the hollow glass microspheres and furnace atmosphere in fabricating hollow glass microspheres by the sol-gel technology, the effect of component percentage, temperature and total pressure of Ar/He gas mixture on the overall thermal resistance between microsphere and furnace atmosphere was studied. The influence of the diameter and the wall thickness of a microsphere on the overall thermal resistance was also investigated. The results show that, in the range of component percentage, temperature and pressure of Ar/He gas mixture commonly used in fabricating hollow glass microspheres by the sol-gel technology, an increase in the volume fraction of helium in the furnace atmosphere can significantly reduce the overall thermal resistance, but increasing t
To explore heat transfer process between the hollow glass microspheres and furnace atmosphere in fabricating hollow glass microspheres by the sol-gel technology, the effect of component percentage, temperature and total pressure of Ar/He gas mixture on the overall thermal resistance between microsphere and furnace atmosphere was studied. The influence of the diameter and the wall thickness of a microsphere on the overall thermal resistance was also investigated. The results show that, in the range of component percentage, temperature and pressure of Ar/He gas mixture commonly used in fabricating hollow glass microspheres by the sol-gel technology, an increase in the volume fraction of helium in the furnace atmosphere can significantly reduce the overall thermal resistance, but increasing t
2005,
17.
Abstract:
X-ray calorimeters are ready to measure the total soft X-ray energy emitted from the plasma produced by laser because of their bodily absorption, linear response, insensitivity to the electromagnetic disturbance, and so on. The calorimeters mainly include absorbers, thermocouples, bases and shrouds. When X-rays are deposited in the absorders, photon energy absorbed is quickly converted into intrinsic energy which simultaneously dissipates by thermal conduction and radiation. The X-ray calorimeters were absolutely on-line calibrated in Shenguang-Ⅱ laser facility with the X-ray diode array spectrometer which has been absolutely calibrated on Beijing Synchrotron Radiation Facility. 20 shots' experimental results show that the X-ray calorimeters are stable, the sensitivity of calorimeter is (
X-ray calorimeters are ready to measure the total soft X-ray energy emitted from the plasma produced by laser because of their bodily absorption, linear response, insensitivity to the electromagnetic disturbance, and so on. The calorimeters mainly include absorbers, thermocouples, bases and shrouds. When X-rays are deposited in the absorders, photon energy absorbed is quickly converted into intrinsic energy which simultaneously dissipates by thermal conduction and radiation. The X-ray calorimeters were absolutely on-line calibrated in Shenguang-Ⅱ laser facility with the X-ray diode array spectrometer which has been absolutely calibrated on Beijing Synchrotron Radiation Facility. 20 shots' experimental results show that the X-ray calorimeters are stable, the sensitivity of calorimeter is (
2005,
17.
Abstract:
Far-field measurement is carried out for the radiation patterns from the opening of the vircator and the opening of the TM01-TE11 converter connected with the vircator, with the distance being 1.00 m between the openings of the receiving horn and that of the microwave radiation. The results show that the main modes of the radiation are the TM01 and TE11, respectively. This confirms the theoretical expectation of the TM01 main mode for the microwave generated by an axial feedback vircator with experimentally cylindrical symmetry. Modes analysis shows that the radiated microwave has its main mode of the TM01 with its mode-purity of about 90%, and that the radiation power exceeds 300 MW, with the power of the TE11 mode being approximately 5% of that of the TM01 mode, and the total power of th
Far-field measurement is carried out for the radiation patterns from the opening of the vircator and the opening of the TM01-TE11 converter connected with the vircator, with the distance being 1.00 m between the openings of the receiving horn and that of the microwave radiation. The results show that the main modes of the radiation are the TM01 and TE11, respectively. This confirms the theoretical expectation of the TM01 main mode for the microwave generated by an axial feedback vircator with experimentally cylindrical symmetry. Modes analysis shows that the radiated microwave has its main mode of the TM01 with its mode-purity of about 90%, and that the radiation power exceeds 300 MW, with the power of the TE11 mode being approximately 5% of that of the TM01 mode, and the total power of th
2005,
17.
Abstract:
The theoretical analysis about electron beam and waves interaction is presented. Based on the analysis and calculations of RF system and magnetron injection gun, a four-cavity gyro klystron amplifier is designed and optimized. 230 kW peak output power, 45% efficiency, 33 dB saturated gain with 200 MHz bandwidth centered at 34 GHz for a 65 kV, 8 A electron beam with 1.5 the ratio of the transverse velocity to the longitudinal velocity are achieved by simulation. The influences of electron beam and RF system parameters, magnetic field on output power, efficiency, bandwidth and gain are discussed. The numerical simulation results are used to develop a Ka band high power gyro klystron amplifier. It is necessary to increase the peak output power and average power, enhance the band-width, get hi
The theoretical analysis about electron beam and waves interaction is presented. Based on the analysis and calculations of RF system and magnetron injection gun, a four-cavity gyro klystron amplifier is designed and optimized. 230 kW peak output power, 45% efficiency, 33 dB saturated gain with 200 MHz bandwidth centered at 34 GHz for a 65 kV, 8 A electron beam with 1.5 the ratio of the transverse velocity to the longitudinal velocity are achieved by simulation. The influences of electron beam and RF system parameters, magnetic field on output power, efficiency, bandwidth and gain are discussed. The numerical simulation results are used to develop a Ka band high power gyro klystron amplifier. It is necessary to increase the peak output power and average power, enhance the band-width, get hi
2005,
17.
Abstract:
A cascaded helical explosively-driven magnetic flux compression generator (HMFCG) has more than one stage and the follow stage captures the magnetic flux of the preceding one and further amplifies the energy. In this paper, the inductance and resistance computation uses the image current model and the magnetic flux coupling between the two stages takes the capture model. At the same time the equivalent magnetic flux loss resistance is supposed to be directly proportional to the equivalent direct current resistance. The computed results of dynamic-cascaded HMFCG fit the experiment data to some extend. This equivalent circuit model is simple and practical, which can be used to optimize the HMFCG parameters and applications. Additionally, the capture model has some reference values to computi
A cascaded helical explosively-driven magnetic flux compression generator (HMFCG) has more than one stage and the follow stage captures the magnetic flux of the preceding one and further amplifies the energy. In this paper, the inductance and resistance computation uses the image current model and the magnetic flux coupling between the two stages takes the capture model. At the same time the equivalent magnetic flux loss resistance is supposed to be directly proportional to the equivalent direct current resistance. The computed results of dynamic-cascaded HMFCG fit the experiment data to some extend. This equivalent circuit model is simple and practical, which can be used to optimize the HMFCG parameters and applications. Additionally, the capture model has some reference values to computi
2005,
17.
Abstract:
A high power slow-wave source operated at low magnetic field is designed. A Cerenkov oscillator is connected to a tapered amplifier by a resonant cavity in the new device. The electron beam current is effectively used to yield microwave with high efficiency. The results of the primary experimental study of the new high power microwave source are reported. At the beam parameters of 450 kV, 2.3 kA, and peak magnetic field of 0.6 T, an output microwave power of 230 MW and efficiency of 23% are achieved, and the mode is a typical TM01 with the main frequency of 10.33 GHz. The measured microwave power and mode are in accordance with those simulated under the same condition.
A high power slow-wave source operated at low magnetic field is designed. A Cerenkov oscillator is connected to a tapered amplifier by a resonant cavity in the new device. The electron beam current is effectively used to yield microwave with high efficiency. The results of the primary experimental study of the new high power microwave source are reported. At the beam parameters of 450 kV, 2.3 kA, and peak magnetic field of 0.6 T, an output microwave power of 230 MW and efficiency of 23% are achieved, and the mode is a typical TM01 with the main frequency of 10.33 GHz. The measured microwave power and mode are in accordance with those simulated under the same condition.
2005,
17.
Abstract:
The reflection of tapered transmission line impedance is analyzed in theory and the VSWR curve of coaxial to plane converter is drawn. Using the FDTD method, the transmission of coaxial to plane converter is simulated. And the loss of transmission is analyzed. A TEM horn antenna with coaxial to plane converter which can endure high power is made for experiment. The reflection of the converter and pattern in E-plane of the antenna are measured. The experiments verify that there is no aberrance when UWB pulse transmits through the converter, and the efficiency of transmission reaches 85% when the length of converter is long enough. The results of experiment accord with that of simulation and theory analysis.
The reflection of tapered transmission line impedance is analyzed in theory and the VSWR curve of coaxial to plane converter is drawn. Using the FDTD method, the transmission of coaxial to plane converter is simulated. And the loss of transmission is analyzed. A TEM horn antenna with coaxial to plane converter which can endure high power is made for experiment. The reflection of the converter and pattern in E-plane of the antenna are measured. The experiments verify that there is no aberrance when UWB pulse transmits through the converter, and the efficiency of transmission reaches 85% when the length of converter is long enough. The results of experiment accord with that of simulation and theory analysis.
2005,
17.
Abstract:
A circuit model for magnetically insulated transmission line (MITL) based on TLCODE was established .In the model the MITL is divided into lots of lossy transmission lines, each of which comprises of a segment a lossless transmission line and a grounded resistor .According to the insulation theories, the states of these lossy segments can be identified and the related variables can be calculated. The interface voltage at the end of the MITL，which is necessary for TLCODE, is deduced from a wire array load. The solution process of the model is described. The comparison of the calculated results of Yang accelerator's MITL by the model with the experimental results indicates that the model is validated and is suitable for design and analysis of MITL.
A circuit model for magnetically insulated transmission line (MITL) based on TLCODE was established .In the model the MITL is divided into lots of lossy transmission lines, each of which comprises of a segment a lossless transmission line and a grounded resistor .According to the insulation theories, the states of these lossy segments can be identified and the related variables can be calculated. The interface voltage at the end of the MITL，which is necessary for TLCODE, is deduced from a wire array load. The solution process of the model is described. The comparison of the calculated results of Yang accelerator's MITL by the model with the experimental results indicates that the model is validated and is suitable for design and analysis of MITL.
2005,
17.
Abstract:
By means of a coaxial apparatus, a high electrical breakdown experiment for pressurized water dielectric with microsecond charging was carried out. The experimental results were presented and analyzed. The conclusions are as follows: (1) breakdown for water dielectric initiates at the positive electrode; (2) observed breakdown stress at constant pressure is in good agreement with Martin formula; (3) primary mechanism to improve electrical breakdown strength for pressurized water dielectric is that, bubbles on the surface of electrodes is compressed by pressurization and the number of the bubbles is reduced.
By means of a coaxial apparatus, a high electrical breakdown experiment for pressurized water dielectric with microsecond charging was carried out. The experimental results were presented and analyzed. The conclusions are as follows: (1) breakdown for water dielectric initiates at the positive electrode; (2) observed breakdown stress at constant pressure is in good agreement with Martin formula; (3) primary mechanism to improve electrical breakdown strength for pressurized water dielectric is that, bubbles on the surface of electrodes is compressed by pressurization and the number of the bubbles is reduced.
2005,
17.
Abstract:
The components, main characters and operation principles of the repetitive pulsed and intense current electron- beam accelerator which is based on pulsed transformer are introduced in this paper, on this equipment, the experiment study of long- time and stable operation of electron- beam source are carried out, and the results reach or partially exceed the designed parameters. While the repetition rate is 100 Hz, the pulsed transformer can deliver high voltage pulse of 1.15 MV, the intense current electron- beam diode can operate steadily as long as 5 s, its output beam voltage exceeds 800 kV, beam current exceeds 7 kA, pulse width is 45 ns, and the emission density of cathode is near 10 kA/cm2. A quasi- periodic slow wave structure device is studied using this electron- beam source, the r
The components, main characters and operation principles of the repetitive pulsed and intense current electron- beam accelerator which is based on pulsed transformer are introduced in this paper, on this equipment, the experiment study of long- time and stable operation of electron- beam source are carried out, and the results reach or partially exceed the designed parameters. While the repetition rate is 100 Hz, the pulsed transformer can deliver high voltage pulse of 1.15 MV, the intense current electron- beam diode can operate steadily as long as 5 s, its output beam voltage exceeds 800 kV, beam current exceeds 7 kA, pulse width is 45 ns, and the emission density of cathode is near 10 kA/cm2. A quasi- periodic slow wave structure device is studied using this electron- beam source, the r
2005,
17.
Abstract:
In practice, the working properties of the 120 gas switches which play very an important role in the operation of LTD on Qiangguang I accelerator vary with the number of discharges. With the accumulated shots of accelerator, the gas switches in LTD roughly pass through three different phases: initial phase, middle and post phase and erratic phase. The static characteristics acquired by experiments show that the switch in erratic phase with over 300 shots has discharging jitter about 20 to 33 percent. For the switch in middle and post phase with more than 100 shots, by analyzing the constant voltage data of static discharging of the switch of 0.08 MPa, the self-discharging probability is respectively presented with Gauss and Weibull distribution model; Further more, for 42 kV operation volt
In practice, the working properties of the 120 gas switches which play very an important role in the operation of LTD on Qiangguang I accelerator vary with the number of discharges. With the accumulated shots of accelerator, the gas switches in LTD roughly pass through three different phases: initial phase, middle and post phase and erratic phase. The static characteristics acquired by experiments show that the switch in erratic phase with over 300 shots has discharging jitter about 20 to 33 percent. For the switch in middle and post phase with more than 100 shots, by analyzing the constant voltage data of static discharging of the switch of 0.08 MPa, the self-discharging probability is respectively presented with Gauss and Weibull distribution model; Further more, for 42 kV operation volt
2005,
17.
Abstract:
The ionization irradiation effects were researched on very large scale integrated circuits(VLSI) made with CMOS technique under the neutron and γ-ray synthetical irradiation environment of a reactor. Through the experiments of the synthetical irradiation effects on different 80C196KC20 and PSD501B1 SCM( single chip microprocessor) system chips, it was found that the static current did not increase apparently. The conclusion is that under the neutron and γ-ray synthetical irradiation environment of a reactor, ionization effects of neutron on the VLSI made with CMOS technology are weak, and that the displacement effects of neutron induces the decreases of mobility ratio and density of charge carrier, which causes the decrease of the total static current, so it compensates the increase of
The ionization irradiation effects were researched on very large scale integrated circuits(VLSI) made with CMOS technique under the neutron and γ-ray synthetical irradiation environment of a reactor. Through the experiments of the synthetical irradiation effects on different 80C196KC20 and PSD501B1 SCM( single chip microprocessor) system chips, it was found that the static current did not increase apparently. The conclusion is that under the neutron and γ-ray synthetical irradiation environment of a reactor, ionization effects of neutron on the VLSI made with CMOS technology are weak, and that the displacement effects of neutron induces the decreases of mobility ratio and density of charge carrier, which causes the decrease of the total static current, so it compensates the increase of
2005,
17.
Abstract:
A simple measurement of beta-function is to detect the shift in the betatron tune as the strength of an individual quadrupole magnet is varied. The beta-function value obtained is a mean value respect to the length of the quadrupole. The beta-function values at 30 quadrupoles in the HLS storage ring were measured by this means. The measurement results using different calculation formulas are compared with the ideal values. Error analysis is also given. Methods to improve the precision of the measurement are put forward for the advanced measurement.
A simple measurement of beta-function is to detect the shift in the betatron tune as the strength of an individual quadrupole magnet is varied. The beta-function value obtained is a mean value respect to the length of the quadrupole. The beta-function values at 30 quadrupoles in the HLS storage ring were measured by this means. The measurement results using different calculation formulas are compared with the ideal values. Error analysis is also given. Methods to improve the precision of the measurement are put forward for the advanced measurement.
2005,
17.
Abstract:
Based on the comparison of several commonly used wavelets in the engineering, biorthogonal wavelet is considered to be the most suitable mother wavelet for the nanosecond pulse analysis. A time variant soft threshold is proposed in the signal denoising on the basis of the characteristic of the noise. A Doppler wave in Matlab and a square pulse generated by square wave generator are chosen to validate the effect of the method. The results prove that the time-variant soft threshold method proposed in this paper is better than the traditionally used threshold-fixed method.
Based on the comparison of several commonly used wavelets in the engineering, biorthogonal wavelet is considered to be the most suitable mother wavelet for the nanosecond pulse analysis. A time variant soft threshold is proposed in the signal denoising on the basis of the characteristic of the noise. A Doppler wave in Matlab and a square pulse generated by square wave generator are chosen to validate the effect of the method. The results prove that the time-variant soft threshold method proposed in this paper is better than the traditionally used threshold-fixed method.
2005,
17.
Abstract:
This paper summarizes a novel method for high-power high repetition rate square pulse generator. By using high voltage rectifier diodes, three single square pulses are combined to form an MHz level repetition rate square tripl-pulse. Suitable connection design in parallel and in series lets the rectifier diodes stand high reverse voltage in high frequency and elevates rectified pulse current to kA level. The square triple-pulses generator has an output voltage up to 250 kV, a pulsed current of 10 kA, pulse power of 2.5 GW, a repetition rate of 1 MHz, a pulse risetime of 40 ns, and a pulse flat top of 50 ns.
This paper summarizes a novel method for high-power high repetition rate square pulse generator. By using high voltage rectifier diodes, three single square pulses are combined to form an MHz level repetition rate square tripl-pulse. Suitable connection design in parallel and in series lets the rectifier diodes stand high reverse voltage in high frequency and elevates rectified pulse current to kA level. The square triple-pulses generator has an output voltage up to 250 kV, a pulsed current of 10 kA, pulse power of 2.5 GW, a repetition rate of 1 MHz, a pulse risetime of 40 ns, and a pulse flat top of 50 ns.
2005,
17.
Abstract:
To study the interference effect of the electromagnetic pulse (EMP) on the PIN diode, the one- dimensional numerical modeling is carried out, which solves the semiconductor equations based on the drift- diffusion model. By observing the variation of the distribution of current density and charge density in the PIN diode during the pulse, the occurrence of an overshoot current under a positive or negative voltage is analyzed. The results show that the overshoot current is due to the capacitive performance of PIN diode under high frequency. Whether the pulse voltage is positive or negative, the magnitude of the overshoot current is increasing with less rise time or higher initial positive bias voltage.
To study the interference effect of the electromagnetic pulse (EMP) on the PIN diode, the one- dimensional numerical modeling is carried out, which solves the semiconductor equations based on the drift- diffusion model. By observing the variation of the distribution of current density and charge density in the PIN diode during the pulse, the occurrence of an overshoot current under a positive or negative voltage is analyzed. The results show that the overshoot current is due to the capacitive performance of PIN diode under high frequency. Whether the pulse voltage is positive or negative, the magnitude of the overshoot current is increasing with less rise time or higher initial positive bias voltage.
2005,
17.
Abstract:
A Monte-Carlo method is used to simulate the transport process of X-ray photons in a model which is made by a 3 m radiographic system for FTO. The scatter distribution of system and the contribution of each cell to the scatter are obtained. It is shown that the back-protected-cone (BPC) is the main source of the scatter in the system. For any pixel, the scattered exposure from the BPC is more than 75% of the total exposure. The outer materials and the edge of FTO produce the main scatter of the object. In order to reduce the scatter of the edge of FTO and BPC, a graded collimator is used in the radiographic system. The graded collimator can reduce the scatter exposure effectively and effectively improve the image quality.
A Monte-Carlo method is used to simulate the transport process of X-ray photons in a model which is made by a 3 m radiographic system for FTO. The scatter distribution of system and the contribution of each cell to the scatter are obtained. It is shown that the back-protected-cone (BPC) is the main source of the scatter in the system. For any pixel, the scattered exposure from the BPC is more than 75% of the total exposure. The outer materials and the edge of FTO produce the main scatter of the object. In order to reduce the scatter of the edge of FTO and BPC, a graded collimator is used in the radiographic system. The graded collimator can reduce the scatter exposure effectively and effectively improve the image quality.
2005,
17.
Abstract:
The study of three parallel tungsten wire loads and five parallel tungsten wire loads implosion experiment on accelerator “Yang” are reported. Tungsten wires (17 μm) with separation of 1 mm were used. The pinch was driven by a 350 kA peak current, 80 ns 10%~90% rise time. By means of pinhole camera and X-ray diagnostics technology, a non-uniform plasma column is formed among the wires and soft X-ray pulse are observed. The change of load current are analyzed, the development of sausage instability and kink instability, “hot spot” effect and dispersion spot for plasma column are also discussed.
The study of three parallel tungsten wire loads and five parallel tungsten wire loads implosion experiment on accelerator “Yang” are reported. Tungsten wires (17 μm) with separation of 1 mm were used. The pinch was driven by a 350 kA peak current, 80 ns 10%~90% rise time. By means of pinhole camera and X-ray diagnostics technology, a non-uniform plasma column is formed among the wires and soft X-ray pulse are observed. The change of load current are analyzed, the development of sausage instability and kink instability, “hot spot” effect and dispersion spot for plasma column are also discussed.
2005,
17.
Abstract:
We have installed and aligned all magnets of CSRm( the main ring of cooler storage ring) by laser tracker and its fitting software Insight. Firstly, we set up a global Frame to determine the theoretical position of origin of each subsystem for whole HIRFL-CSR. A local Frame which based on theoretical origin was set up for each subsystem, by which we aligned all devices in it. A part frame was used for every device. Secondly, 8 benchmarks were welded on each magnet, and were surveyed to decide the positions of benchmarks in the part frame before magnet installation. Thirdly, control network's points of CSRm were surveyed to resume local frame of main ring. Finally, according to the device's theoretical coordinates in the local frame, we have calculated relational translating parameters and
We have installed and aligned all magnets of CSRm( the main ring of cooler storage ring) by laser tracker and its fitting software Insight. Firstly, we set up a global Frame to determine the theoretical position of origin of each subsystem for whole HIRFL-CSR. A local Frame which based on theoretical origin was set up for each subsystem, by which we aligned all devices in it. A part frame was used for every device. Secondly, 8 benchmarks were welded on each magnet, and were surveyed to decide the positions of benchmarks in the part frame before magnet installation. Thirdly, control network's points of CSRm were surveyed to resume local frame of main ring. Finally, according to the device's theoretical coordinates in the local frame, we have calculated relational translating parameters and
