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RSS2003 Vol. 15, No. 11
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2003,
15.
Abstract:
In this paper, the radiation characteristics of constant impedance TEM horn of various geometrical structures are calculated. In each calculation, peaktopeak value of axial electric field obtained from an equivalent ideal aperture is used to normalize electric fields along axial of practical antennas. The specific value is defined as feeding coefficients and then applied to determine how the radiation properties of the horns can be affected if the horn structure is adjusted. These results provide a basis to design and fabricate practical ultrawideband antenna.
In this paper, the radiation characteristics of constant impedance TEM horn of various geometrical structures are calculated. In each calculation, peaktopeak value of axial electric field obtained from an equivalent ideal aperture is used to normalize electric fields along axial of practical antennas. The specific value is defined as feeding coefficients and then applied to determine how the radiation properties of the horns can be affected if the horn structure is adjusted. These results provide a basis to design and fabricate practical ultrawideband antenna.
2003,
15.
Abstract:
A new structure of the coaxial vircator is proposed and studied numerically in this paper. Using the coaxial extraction structure, the beam-wave interaction and energy extraction are carried out separately. The left wall of the extraction cavity will reflect the microwave, thus provide a feedback for the beam-wave interaction; And it can also absorb the used electrons drifting in the outer space of the interaction region. When a pulse with peak voltage of 500kV is fed into the vircator, a peak instant power greater than 2.5GW is achieved by simulation at 2.175GHz; the peak period-averaged power reaches 1.2GW with an rms efficiency of 11%. The output power has high mode purity and narrow bandwidth as in a conventional coaxial viractor.
A new structure of the coaxial vircator is proposed and studied numerically in this paper. Using the coaxial extraction structure, the beam-wave interaction and energy extraction are carried out separately. The left wall of the extraction cavity will reflect the microwave, thus provide a feedback for the beam-wave interaction; And it can also absorb the used electrons drifting in the outer space of the interaction region. When a pulse with peak voltage of 500kV is fed into the vircator, a peak instant power greater than 2.5GW is achieved by simulation at 2.175GHz; the peak period-averaged power reaches 1.2GW with an rms efficiency of 11%. The output power has high mode purity and narrow bandwidth as in a conventional coaxial viractor.
2003,
15.
Abstract:
In this paper, coupling of electromagnetic fields generated by electrostatic discharge (ESD) spark in near area into a metallic cavity with an aperture is studied by using Finite-Difference Time-Domain (FDTD) method and a numerical coupling model is established, which is based on the revised electric dipole model of electrostatic discharge spark and the discharge current analytic expression obtained by pulse function. The analysis of the calculated results shows that there is strong electrostatic induction field at the vicinity of the aperture in the cavity and the transient field coupled in the cavity can resonate the cavity with the TE-101 mode as the leading mode, but the amplitude of the resonance is very low.
In this paper, coupling of electromagnetic fields generated by electrostatic discharge (ESD) spark in near area into a metallic cavity with an aperture is studied by using Finite-Difference Time-Domain (FDTD) method and a numerical coupling model is established, which is based on the revised electric dipole model of electrostatic discharge spark and the discharge current analytic expression obtained by pulse function. The analysis of the calculated results shows that there is strong electrostatic induction field at the vicinity of the aperture in the cavity and the transient field coupled in the cavity can resonate the cavity with the TE-101 mode as the leading mode, but the amplitude of the resonance is very low.
2003,
15.
Abstract:
In this paper, by using rigorous field analysis, a coupled-cavity（ＣＣ） chain filled with plasma has been analyzed. How the hybrid wave between the cavity mode and plasma mode is formed has been studied. The periodical CC chain filled with plasma demonstrates periodical TG modes with a cutoff frequency of zero. When the plasma density increase to a large scale, the cavity mode of the CC chain overlaps the TG mode, these two modes couple with each other and form the hybrid modes. In the case of hybrid modes, the "cold " bandwidth and the "warm" bandwidth expand, and the coupled impedance increases about 5 times larger than that of the vacuum. As a whole, the slow wave characteristics are improved substantially due to the formation of the hybrid mode.
In this paper, by using rigorous field analysis, a coupled-cavity（ＣＣ） chain filled with plasma has been analyzed. How the hybrid wave between the cavity mode and plasma mode is formed has been studied. The periodical CC chain filled with plasma demonstrates periodical TG modes with a cutoff frequency of zero. When the plasma density increase to a large scale, the cavity mode of the CC chain overlaps the TG mode, these two modes couple with each other and form the hybrid modes. In the case of hybrid modes, the "cold " bandwidth and the "warm" bandwidth expand, and the coupled impedance increases about 5 times larger than that of the vacuum. As a whole, the slow wave characteristics are improved substantially due to the formation of the hybrid mode.
2003,
15.
Abstract:
A single anode magnetron injection electron gun is designed and calculated according to the requirements of gyrotrons with a presented method, which combines synthesis with analysis. A set of computer program has been developed. The electrode shapes, electron trajectory and electron beam parameters are also given with the computer aided design. The electron gun has the characteristics such as small velocity spread, good laminar flow and small volume etc. This gun was applied in the experiment, which shows a gun designed with the method has obtained 127kＷ peak power with over 10% efficiency.
A single anode magnetron injection electron gun is designed and calculated according to the requirements of gyrotrons with a presented method, which combines synthesis with analysis. A set of computer program has been developed. The electrode shapes, electron trajectory and electron beam parameters are also given with the computer aided design. The electron gun has the characteristics such as small velocity spread, good laminar flow and small volume etc. This gun was applied in the experiment, which shows a gun designed with the method has obtained 127kＷ peak power with over 10% efficiency.
2003,
15.
Abstract:
A repeatedly operating splitcavity oscillator with conducting foils with hole on fool for focusing the electronic beam is presented. An equilibrium equation for foilfocused electron beam is deyived, and the collector of electron beam is designed, Which can generate 50MW to 900MW of output power without change parameters of system.
A repeatedly operating splitcavity oscillator with conducting foils with hole on fool for focusing the electronic beam is presented. An equilibrium equation for foilfocused electron beam is deyived, and the collector of electron beam is designed, Which can generate 50MW to 900MW of output power without change parameters of system.
2003,
15.
Abstract:
The radiating characteristics of apertures excited by step and Gaussian pulses are presented in this paper. The relationships of the incoming pulse width, the size of the aperture, and the location of the observer are analyzed. The radiating characteristics of apertures excited by Gaussian pulse are thoroughly investigated. Along the radiating axis, several regions, each bearing somehow unique radiating properties, can be divided as radiating farfield region, transit region, and nearfield region in order to describe the behavior of an ultrawideband (UWB) aperture antenna.
The radiating characteristics of apertures excited by step and Gaussian pulses are presented in this paper. The relationships of the incoming pulse width, the size of the aperture, and the location of the observer are analyzed. The radiating characteristics of apertures excited by Gaussian pulse are thoroughly investigated. Along the radiating axis, several regions, each bearing somehow unique radiating properties, can be divided as radiating farfield region, transit region, and nearfield region in order to describe the behavior of an ultrawideband (UWB) aperture antenna.
2003,
15.
Abstract:
In a lot of singleshot applications and experiments at remote locations where magnetocumulative generator provide the most practical pulse power, it is impracticable to use a capacitor bank as the initial energy source. Ｖ．Ｖ．Gdovnina et al has used a permanent magnet ring as the initial energy source to drive a magnetocumulative generator, but the energy density stored in a single permanent magnet ring is very low. In this paper，the possibility of using periodic structure permanent magnetic rings as initial energy source of magnetocumulative generator is analyzed theoretically. It is concluded that 1kJ initial energy can be provided to magnetocumulative generator by the periodic structure permanent magnetic ring whose mass is less than 30kg and the outside radius less than 60
In a lot of singleshot applications and experiments at remote locations where magnetocumulative generator provide the most practical pulse power, it is impracticable to use a capacitor bank as the initial energy source. Ｖ．Ｖ．Gdovnina et al has used a permanent magnet ring as the initial energy source to drive a magnetocumulative generator, but the energy density stored in a single permanent magnet ring is very low. In this paper，the possibility of using periodic structure permanent magnetic rings as initial energy source of magnetocumulative generator is analyzed theoretically. It is concluded that 1kJ initial energy can be provided to magnetocumulative generator by the periodic structure permanent magnetic ring whose mass is less than 30kg and the outside radius less than 60
2003,
15.
Abstract:
The formula for calculating the threshold of average transmitting power of cylindrical TE-11 mode window is revised by accurate deduction．Ａ practical method for calculating the temperature increment of the dielectric disk in cylindrical box type window is given. Meanwhile, a typical cylindrical box type window is calculated and used as an example to discuss the power capacity, the special harmfulness and elimination of ghost mode resonance when the window is used to transmit high power CW.It is showed that, in L band, general cylindrical box type windows may be used to transmit 120~150kW CW and the possible relative bandwidth is 14% or so, in the case of elimination of the ghost mode.
The formula for calculating the threshold of average transmitting power of cylindrical TE-11 mode window is revised by accurate deduction．Ａ practical method for calculating the temperature increment of the dielectric disk in cylindrical box type window is given. Meanwhile, a typical cylindrical box type window is calculated and used as an example to discuss the power capacity, the special harmfulness and elimination of ghost mode resonance when the window is used to transmit high power CW.It is showed that, in L band, general cylindrical box type windows may be used to transmit 120~150kW CW and the possible relative bandwidth is 14% or so, in the case of elimination of the ghost mode.
2003,
15.
Abstract:
By employing hydrodynamic theory, the interaction between the electron beam and the highfrequency field in the radial gap of the radial transittime oscillator is studied. By using numerical method, curves are given to illustrate the relation between the beamfield power exchange and the gap's transit angle. It shows that the cruuent density and the energy exchange will be oscillating with the transit angle increasing. The number density of beam is bigger, the energy exchange between the beam and the field is stronger. The results obtained from hydrodynamic theory are of more generality compared with those from single electron theory.
By employing hydrodynamic theory, the interaction between the electron beam and the highfrequency field in the radial gap of the radial transittime oscillator is studied. By using numerical method, curves are given to illustrate the relation between the beamfield power exchange and the gap's transit angle. It shows that the cruuent density and the energy exchange will be oscillating with the transit angle increasing. The number density of beam is bigger, the energy exchange between the beam and the field is stronger. The results obtained from hydrodynamic theory are of more generality compared with those from single electron theory.
2003,
15.
Abstract:
In this paper，the research methods for linear coupling of microwave pulses into a cavity through slots are discussed. The physical basis for the linear coupling is provided. The coupling function is defined, and the formulation of coupling function for the different polarization directions of the incident electric field is derived. To numerically solve the linear coupling problems, the finitedifference timedomain method and its modified algorithm are simply described. To measure the coupling function, this paper suggests the experimental setup which mainly consists of the vector network analyzer HP8510C. By investigating the coupling function, the phenomena of resonant and enhancement effects are observed, and the universal equation for microwave coupling into differentshaped slots
In this paper，the research methods for linear coupling of microwave pulses into a cavity through slots are discussed. The physical basis for the linear coupling is provided. The coupling function is defined, and the formulation of coupling function for the different polarization directions of the incident electric field is derived. To numerically solve the linear coupling problems, the finitedifference timedomain method and its modified algorithm are simply described. To measure the coupling function, this paper suggests the experimental setup which mainly consists of the vector network analyzer HP8510C. By investigating the coupling function, the phenomena of resonant and enhancement effects are observed, and the universal equation for microwave coupling into differentshaped slots
2003,
15.
Abstract:
The disturance experiment of array CCD detectors is represented in this paper. In the experiment the visible-light array CCD detector are irradiated by 1.319μm CW YAG laser. The disturbance saturation reason of CCD detector is analyzed and the saturation threshold is measured. It can be concluded that visible-light array CCD detector could be effectively disturbed by 1.319μm CW YAG laser from the experiment. When the laser intensity on imaging plane reachs the level of 10２W/cm２ and 10３Ｗ／cm２, the CCD camera appears line saturation and full screen saturation.
The disturance experiment of array CCD detectors is represented in this paper. In the experiment the visible-light array CCD detector are irradiated by 1.319μm CW YAG laser. The disturbance saturation reason of CCD detector is analyzed and the saturation threshold is measured. It can be concluded that visible-light array CCD detector could be effectively disturbed by 1.319μm CW YAG laser from the experiment. When the laser intensity on imaging plane reachs the level of 10２W/cm２ and 10３Ｗ／cm２, the CCD camera appears line saturation and full screen saturation.
2003,
15.
Abstract:
Transient Stimulated Brillouin Scattering (SBS) coupled equations are solved for onedimension approximation. Through numerical study, dependence of influence induced by SBS procession on parameters of laser and medium is investigated respectively. The ralationship between pulse duration, interaction length and the damage threshold is discussed in terms of the stress and reflectivity built in SBS procession. Find out a better configuration of parameters to restrain the damage induced by SBS procession. We can get the conclusion that temporal variation of stree field in the SBS medium with different size follows the same rule when interaction length is less than some value; a greatest interaction length which SBS medium is easy to be damaged is existent; and we also find that we can obtain
Transient Stimulated Brillouin Scattering (SBS) coupled equations are solved for onedimension approximation. Through numerical study, dependence of influence induced by SBS procession on parameters of laser and medium is investigated respectively. The ralationship between pulse duration, interaction length and the damage threshold is discussed in terms of the stress and reflectivity built in SBS procession. Find out a better configuration of parameters to restrain the damage induced by SBS procession. We can get the conclusion that temporal variation of stree field in the SBS medium with different size follows the same rule when interaction length is less than some value; a greatest interaction length which SBS medium is easy to be damaged is existent; and we also find that we can obtain
2003,
15.
Abstract:
A realtime data acquisition system is designed to investigate the supersonic diffuser in COIL. The hardware is based on EVOC PCI data acquiring board and the software is developed under VB6.0. By this system, high precision of data acquisition can be achieved for the measurement of flow pressure in the supersonic diffuser. It will benefit the optimum design of the supersonic diffuser and the miniaturization and practicality of COIL.
A realtime data acquisition system is designed to investigate the supersonic diffuser in COIL. The hardware is based on EVOC PCI data acquiring board and the software is developed under VB6.0. By this system, high precision of data acquisition can be achieved for the measurement of flow pressure in the supersonic diffuser. It will benefit the optimum design of the supersonic diffuser and the miniaturization and practicality of COIL.
2003,
15.
Abstract:
In this paper, the Nd:YAG laser with wavelength 1 064nm is used to study the improvement effect of damage threshold of HfO2/SiO2 coating samples. The experiment of laser conditioning effect was taken by use of N-on-1 mode, namely the irradiation energy density started from about 70% of the damage threshold, and increased 5J/cm2 energy pulse by pulse until serious damage appeared. The experiment results show that 1064nm laser irradiation can improve the damage threshold of HfO2/SiO2 coating up to 3 times. The mechanisms of laser conditioning on HfO2/SiO2 mirror are found in two forms: laser annealing and laser cleaning of coating. Laser annealing can increase the damage threshold of non-defective coating up to 3 times on the average. Laser cleaning means that coating defects such as nodul
In this paper, the Nd:YAG laser with wavelength 1 064nm is used to study the improvement effect of damage threshold of HfO2/SiO2 coating samples. The experiment of laser conditioning effect was taken by use of N-on-1 mode, namely the irradiation energy density started from about 70% of the damage threshold, and increased 5J/cm2 energy pulse by pulse until serious damage appeared. The experiment results show that 1064nm laser irradiation can improve the damage threshold of HfO2/SiO2 coating up to 3 times. The mechanisms of laser conditioning on HfO2/SiO2 mirror are found in two forms: laser annealing and laser cleaning of coating. Laser annealing can increase the damage threshold of non-defective coating up to 3 times on the average. Laser cleaning means that coating defects such as nodul
2003,
15.
Abstract:
The principle of cube corner array's approximate phase conjugation was analyzed. The cube corner array's restraining effect from wave-front aberration of low spatial frequency was validated, and the optimization of array's cell number was researched, and the localization and effectual application field was pointed out. The result of simulation indicates that the focus energy concentricity of aberration beam was improved effectively by using cube corner array, and this new method could be used in restraining wave front aberration of low spatial frequency.
The principle of cube corner array's approximate phase conjugation was analyzed. The cube corner array's restraining effect from wave-front aberration of low spatial frequency was validated, and the optimization of array's cell number was researched, and the localization and effectual application field was pointed out. The result of simulation indicates that the focus energy concentricity of aberration beam was improved effectively by using cube corner array, and this new method could be used in restraining wave front aberration of low spatial frequency.
2003,
15.
Abstract:
Using a new cleaning technology, K9 glass substrates were cleaned, and some singlelayer films were prepared with various oxide materials on the surface of the substrates using the electron beam evaporation technique. The laser induced damage thresholds of the film were got by using Ron1 test and the experiment repeatability is good. The experiment results show that the placement duration of the substrate after cleaning should influence the homogeneity of the damage threshold of the films, but do not influence the damage thresholds itself. To improve the homogeneity of the film thresholds, films are, as soon as possible, deposited after cleaning. Threshold uniformity is also influenced by laser parameters.
Using a new cleaning technology, K9 glass substrates were cleaned, and some singlelayer films were prepared with various oxide materials on the surface of the substrates using the electron beam evaporation technique. The laser induced damage thresholds of the film were got by using Ron1 test and the experiment repeatability is good. The experiment results show that the placement duration of the substrate after cleaning should influence the homogeneity of the damage threshold of the films, but do not influence the damage thresholds itself. To improve the homogeneity of the film thresholds, films are, as soon as possible, deposited after cleaning. Threshold uniformity is also influenced by laser parameters.
2003,
15.
Abstract:
The absorption characteristics of the composite reinforced by polyaryl amide fibers irradiated by laser beam with a wavelength of 1.06μm were investigated using two integrated spheres and photodiode system. The intensity of laser beam, surface and volumetric reflectivity, volumetric absorption coefficient, transmissivity were obtained from the experiments. Experiments results show that volumetric reflectivity increases with both material thickness and laser intensity, volumetric absorption coefficient increases with material thickness, but decreases with laser intensity. A reasonable explanation is suggested based on the results and the material properties.
The absorption characteristics of the composite reinforced by polyaryl amide fibers irradiated by laser beam with a wavelength of 1.06μm were investigated using two integrated spheres and photodiode system. The intensity of laser beam, surface and volumetric reflectivity, volumetric absorption coefficient, transmissivity were obtained from the experiments. Experiments results show that volumetric reflectivity increases with both material thickness and laser intensity, volumetric absorption coefficient increases with material thickness, but decreases with laser intensity. A reasonable explanation is suggested based on the results and the material properties.
2003,
15.
Abstract:
In this paper, an integrated diagnostic system built and used at Shenguang II and Xingguang II laser facility for inertial confinement fusion experiment has been reviewed. The progress of diagnostic technique for Xray optical band, fusion products has been emphasized. The many diagnostic instruments, such as three chromatic spectrometer (TCS) that consists of Xray streaked camera and was applied in many experiments, have been developed. The Xray's temporalspatial behaviors of three kinds of wavelength could be investigated in the meantime using TCS. The application on investigation of hohlraum target physics, implosion dynamic and opacity have been introduced.
In this paper, an integrated diagnostic system built and used at Shenguang II and Xingguang II laser facility for inertial confinement fusion experiment has been reviewed. The progress of diagnostic technique for Xray optical band, fusion products has been emphasized. The many diagnostic instruments, such as three chromatic spectrometer (TCS) that consists of Xray streaked camera and was applied in many experiments, have been developed. The Xray's temporalspatial behaviors of three kinds of wavelength could be investigated in the meantime using TCS. The application on investigation of hohlraum target physics, implosion dynamic and opacity have been introduced.
2003,
15.
Abstract:
Particleincell algorithms for computing current density and explosion electron emitting from cathode are briefly introduced. The current density algorithm which satisfies charge and current continuity equation, can avoid complex Poisson adjustment and can be used in simulation of physics problem with complex boundarys. Based on the algorithms of computing current density, a new model for explosion electron emission from conducting boundary surfaces is described. The new model is proved out by results of particle simulations of vacuum diode.
Particleincell algorithms for computing current density and explosion electron emitting from cathode are briefly introduced. The current density algorithm which satisfies charge and current continuity equation, can avoid complex Poisson adjustment and can be used in simulation of physics problem with complex boundarys. Based on the algorithms of computing current density, a new model for explosion electron emission from conducting boundary surfaces is described. The new model is proved out by results of particle simulations of vacuum diode.
2003,
15.
Abstract:
A synthesis technique for the preliminary design of convergent Pierce electron guns is introduced briefly which has a series of advantages over the traditional methods. A thermal cathode electron gun used in the accelerator for radiation sterilization with the synthesis method is redesigned, and the validity of this method is proved. Based on the preliminary design parameters given by the synthesis method, a simulating calculation program, EGUN, was used in the numerical figure design of the focusing electrode and the anode. The final results can meet the engineering requirement as the current being 1A, the normalized emittance being less than 4 mm·mrad, and the final current density showing uniformity.
A synthesis technique for the preliminary design of convergent Pierce electron guns is introduced briefly which has a series of advantages over the traditional methods. A thermal cathode electron gun used in the accelerator for radiation sterilization with the synthesis method is redesigned, and the validity of this method is proved. Based on the preliminary design parameters given by the synthesis method, a simulating calculation program, EGUN, was used in the numerical figure design of the focusing electrode and the anode. The final results can meet the engineering requirement as the current being 1A, the normalized emittance being less than 4 mm·mrad, and the final current density showing uniformity.
2003,
15.
Abstract:
One of the important building blocks on Qiangguang I accelerator is longpulse highimpedance intense electron beam diode, which is mainly used to convert electrical pulse from long pulse power generator into electron beam and intense bremsstrahlung. In this paper, the long pulse power system on Qiangguang I accelerator is introduced. The insulation characteristics of insulator and MITL of longpulse highimpedance intense electron beam diode were analyzed in detail. The design approach for diode operating parameters including the diode impedance, cathode and anode are described. The experimental results are：the diode voltage is 0.75~2.6MV，the beam current is 65~85kA，the impedance corresponding to the amplitude of diode voltage is 14~44Ω，the pulse duration of bremsstrahlung is
One of the important building blocks on Qiangguang I accelerator is longpulse highimpedance intense electron beam diode, which is mainly used to convert electrical pulse from long pulse power generator into electron beam and intense bremsstrahlung. In this paper, the long pulse power system on Qiangguang I accelerator is introduced. The insulation characteristics of insulator and MITL of longpulse highimpedance intense electron beam diode were analyzed in detail. The design approach for diode operating parameters including the diode impedance, cathode and anode are described. The experimental results are：the diode voltage is 0.75~2.6MV，the beam current is 65~85kA，the impedance corresponding to the amplitude of diode voltage is 14~44Ω，the pulse duration of bremsstrahlung is
2003,
15.
Abstract:
The prepulse phenomena in the discharge process of accelerator are analyzed in this paper. The prepulse will result in forming plasma, and further affect the diode performance. To remove or reduce this effect, a crowbar tube with cold cathode was adopted in the accelerator. The results show that prepulse voltage decreased from about 150kV to 50kV after adopting crowbar tube. The output power of relativistic backwardwave oscillator increased from 50MW to 250MW under the same condition. The frequency of relativistic magnetron tended to be reasonable obviously too.
The prepulse phenomena in the discharge process of accelerator are analyzed in this paper. The prepulse will result in forming plasma, and further affect the diode performance. To remove or reduce this effect, a crowbar tube with cold cathode was adopted in the accelerator. The results show that prepulse voltage decreased from about 150kV to 50kV after adopting crowbar tube. The output power of relativistic backwardwave oscillator increased from 50MW to 250MW under the same condition. The frequency of relativistic magnetron tended to be reasonable obviously too.
2003,
15.
Abstract:
There are abnormally accelerated particles with very high energy during pseudospark discharge, and it has been verified by using analyses magnet field. The authors consider that it has the common reason of vortex dynamics with other abnormal acceleration at all the levels in the nature, such as quasar spiral structure and cosmic ray with extremely high energy etc., and the theory of torsion field originated from spin and angular moment is proposed to be used to reveal the mechanisms of those unexplained phenomena. The theories of collective field and weak field are insufficient for interpreting these anomalous phenomena.
There are abnormally accelerated particles with very high energy during pseudospark discharge, and it has been verified by using analyses magnet field. The authors consider that it has the common reason of vortex dynamics with other abnormal acceleration at all the levels in the nature, such as quasar spiral structure and cosmic ray with extremely high energy etc., and the theory of torsion field originated from spin and angular moment is proposed to be used to reveal the mechanisms of those unexplained phenomena. The theories of collective field and weak field are insufficient for interpreting these anomalous phenomena.
