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RSS2005 Vol. 17, No. 08
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2005,
17.
Abstract:
Spatial harmonic coefficients are theoretically calculated for transverse magnetic TM01 mode in slow wave structure (SWS) of relativistic backward-wave oscillators(RBWO). It is proved that there are four means to construct resonant SWS cavities whose electromagnetic properties are the same as those of infinite SWS cavities. According to the field distribution in SWS and computer simulation results, it is suggested that the SWS generally begin with the deepest location of corrugation in order to increase the conversion efficiency.
Spatial harmonic coefficients are theoretically calculated for transverse magnetic TM01 mode in slow wave structure (SWS) of relativistic backward-wave oscillators(RBWO). It is proved that there are four means to construct resonant SWS cavities whose electromagnetic properties are the same as those of infinite SWS cavities. According to the field distribution in SWS and computer simulation results, it is suggested that the SWS generally begin with the deepest location of corrugation in order to increase the conversion efficiency.
2005,
17.
Abstract:
In this paper, the three-dimensional simulation code MAFIA and its quasi-periodic boundary conditions and the postprocessor are used to determine the coupled cavity slow wave structure cold-test characteristics. Some simulation methods of dispersion and on-axis interaction impedance of Hughes coupled cavity slow wave structure have been studied. Two different defintions of the whole impedance and the Pierce impedance are discussed. The electrons interact with the negative once resonance of microwave and the interaction impedance is the mean value on the beam. There is a factor difference between the whole interaction impedance and the Pierce interaction impedance. The simulation result is consistent with the actual measurement result.
In this paper, the three-dimensional simulation code MAFIA and its quasi-periodic boundary conditions and the postprocessor are used to determine the coupled cavity slow wave structure cold-test characteristics. Some simulation methods of dispersion and on-axis interaction impedance of Hughes coupled cavity slow wave structure have been studied. Two different defintions of the whole impedance and the Pierce impedance are discussed. The electrons interact with the negative once resonance of microwave and the interaction impedance is the mean value on the beam. There is a factor difference between the whole interaction impedance and the Pierce interaction impedance. The simulation result is consistent with the actual measurement result.
2005,
17.
Abstract:
A high power traveling wave tube (TWT) using a ferroelectric cathode as the electron source is reported. The Ferroelectric electron gun (FEG) consists of PLZT ceramic and field enhancing grids, which allows an electron beam to be extracted from the FEG with relatively high beam quality. With the peak current exceeding 100 A, the electron beam is compressed downstream, before it enters into the slow wave structure of the TWT. Both the theoretical analysis and the experimental results show that the mechanism of electron emission is rather complicated. Nevertheless, the radio frequency experiment suggests that the TWT be capable of producing a microwave output at X-band (9.15 GHz), with a band-width of 580 MHz. The measured maximum output power is 5.8 MW, corresponding to 25.2 dB gain. This p
A high power traveling wave tube (TWT) using a ferroelectric cathode as the electron source is reported. The Ferroelectric electron gun (FEG) consists of PLZT ceramic and field enhancing grids, which allows an electron beam to be extracted from the FEG with relatively high beam quality. With the peak current exceeding 100 A, the electron beam is compressed downstream, before it enters into the slow wave structure of the TWT. Both the theoretical analysis and the experimental results show that the mechanism of electron emission is rather complicated. Nevertheless, the radio frequency experiment suggests that the TWT be capable of producing a microwave output at X-band (9.15 GHz), with a band-width of 580 MHz. The measured maximum output power is 5.8 MW, corresponding to 25.2 dB gain. This p
2005,
17.
Abstract:
The high-power millimeter device with large diameter, short period and two SWSs is put forward. The device is analysed using our universal linear theory and PIC method. The output power and frequency of the device are measured. The experimental results are in accordance with the theoretical and simulation results, which support our theoretical and PIC simulation methods.
The high-power millimeter device with large diameter, short period and two SWSs is put forward. The device is analysed using our universal linear theory and PIC method. The output power and frequency of the device are measured. The experimental results are in accordance with the theoretical and simulation results, which support our theoretical and PIC simulation methods.
2005,
17.
Abstract:
An experiment on an axial feedback vircator was performed on the intense electron beam accelerator SPARK-04. The far-field measurement method was employed to obtain the main mode and the power of the microwave generated by this device. The experimental results showed that the main mode of the radiation was the TM01 mode, and the microwave power exceeded 500 MW, with an power efficiency of above 3%, a radiation frequency of about 3.6 GHz, and a pulse width of over 20 ns. In the experiment, the directed propagation was achieved for the microwave generated by the vircator through the use of a Vlasov antenna with a microwave reflector.
An experiment on an axial feedback vircator was performed on the intense electron beam accelerator SPARK-04. The far-field measurement method was employed to obtain the main mode and the power of the microwave generated by this device. The experimental results showed that the main mode of the radiation was the TM01 mode, and the microwave power exceeded 500 MW, with an power efficiency of above 3%, a radiation frequency of about 3.6 GHz, and a pulse width of over 20 ns. In the experiment, the directed propagation was achieved for the microwave generated by the vircator through the use of a Vlasov antenna with a microwave reflector.
2005,
17.
Abstract:
An 8 mm fundamental wave gyro traveling wave tube is studied. By the analysis of stability, the parameters are determined. Employing a PIC code, the interaction between electron beam and wave is simulated and discussed in detail, and the primary design is presented. The results indicate that an over 450 kW output power and 50 dB gain are obtained from amplifier under the optimum condition. The efficiency exceeds 22.5% and the 3 dB bandwidth is about 5%.
An 8 mm fundamental wave gyro traveling wave tube is studied. By the analysis of stability, the parameters are determined. Employing a PIC code, the interaction between electron beam and wave is simulated and discussed in detail, and the primary design is presented. The results indicate that an over 450 kW output power and 50 dB gain are obtained from amplifier under the optimum condition. The efficiency exceeds 22.5% and the 3 dB bandwidth is about 5%.
2005,
17.
Abstract:
This paper focuses on two factors of 0-harmonic component and modes interval in frequency-agile relativistic magnetron under thermal cavity condition by way of example of 10 cavites rising-sun magnetron. Based on the analysis of these factors, it suggests to optimize the tunable bandwidth by balancing the effective impedance, adjusting the cavity and opening the anode port face,and reduce 0-harmonic component. The simulation result shows that the frequency-agile range increases from 380 MHz to 900 MHz after using the above mentioned methods．
This paper focuses on two factors of 0-harmonic component and modes interval in frequency-agile relativistic magnetron under thermal cavity condition by way of example of 10 cavites rising-sun magnetron. Based on the analysis of these factors, it suggests to optimize the tunable bandwidth by balancing the effective impedance, adjusting the cavity and opening the anode port face,and reduce 0-harmonic component. The simulation result shows that the frequency-agile range increases from 380 MHz to 900 MHz after using the above mentioned methods．
2005,
17.
Abstract:
The three-dimensional analysis PIC code KARAT-3D was used to assess the multiple beam klystron(MBK). A power output of about 128 kW was obtained at 1.25 GHz when input voltage was 14 kV and input current was 20.8 A. Specially, the beam transimission coefficient and the current modulated coefficient were calculated.It was concluded that the current modulated coefficients were increased by the cavity number and that the energy of the electron decreased very fast when the electron passed the output cavity because some of the electron energy was transformed to microwave energy.
The three-dimensional analysis PIC code KARAT-3D was used to assess the multiple beam klystron(MBK). A power output of about 128 kW was obtained at 1.25 GHz when input voltage was 14 kV and input current was 20.8 A. Specially, the beam transimission coefficient and the current modulated coefficient were calculated.It was concluded that the current modulated coefficients were increased by the cavity number and that the energy of the electron decreased very fast when the electron passed the output cavity because some of the electron energy was transformed to microwave energy.
2005,
17.
Abstract:
According to the Maxwell equations, an analytic solution related with coaxial diode current, applied voltage and geometry parameters is obtained by introducing certain approximation. The relation among the coaxial diode impedance, the potential distribution in diode gap and the external voltage are also derived, and the relative error is analyzed comparing with the precision numerical evaluation of the 1D analytic model. Meanwhile, PIC simulations are carried out to test the accuracy of the analytic equations under practical parameters, which yield consistent results. The diode impedance obtained by the analytic solution is very close to the experimental data under relativistic voltage range of 300~700 kV.
According to the Maxwell equations, an analytic solution related with coaxial diode current, applied voltage and geometry parameters is obtained by introducing certain approximation. The relation among the coaxial diode impedance, the potential distribution in diode gap and the external voltage are also derived, and the relative error is analyzed comparing with the precision numerical evaluation of the 1D analytic model. Meanwhile, PIC simulations are carried out to test the accuracy of the analytic equations under practical parameters, which yield consistent results. The diode impedance obtained by the analytic solution is very close to the experimental data under relativistic voltage range of 300~700 kV.
2005,
17.
Abstract:
A C-band magnetically insulated transmission line oscillator (MILO) has been designed, manufactured and tested. The C-band MILO typically operates in single-shot mode with 437~464 kV, 36~39 kA beam pulses, generating 1.60~1.68 GW high power microwave pulses at 3.60~3.66 GHz. The output powers radiate through the extractor coax, where they propagate in the TEM mode. The power conversion efficiency is greater than 9% in experiments. The experimental results agree well with the simulations.
A C-band magnetically insulated transmission line oscillator (MILO) has been designed, manufactured and tested. The C-band MILO typically operates in single-shot mode with 437~464 kV, 36~39 kA beam pulses, generating 1.60~1.68 GW high power microwave pulses at 3.60~3.66 GHz. The output powers radiate through the extractor coax, where they propagate in the TEM mode. The power conversion efficiency is greater than 9% in experiments. The experimental results agree well with the simulations.
2005,
17.
Abstract:
The ghigh peak power klystron works as a high power microwave source and is receiving much recognition. The single beam high power klystron has experienced many drawbacks that are unable to overcome, such as the high operating voltage, the low output efficiency, and the bulky system volume etc. In this paper, the high peak power Multi-Beam Klystron(MBK) was preliminarily researched and the electron optics system and RF interaction system of an S-band 50 MW MBK were studied. The results show that the MBK has many advantages compared with the single beam klystron. Under the same power level, the MBK reduces the operating voltage and improves the efficiency greatly.
The ghigh peak power klystron works as a high power microwave source and is receiving much recognition. The single beam high power klystron has experienced many drawbacks that are unable to overcome, such as the high operating voltage, the low output efficiency, and the bulky system volume etc. In this paper, the high peak power Multi-Beam Klystron(MBK) was preliminarily researched and the electron optics system and RF interaction system of an S-band 50 MW MBK were studied. The results show that the MBK has many advantages compared with the single beam klystron. Under the same power level, the MBK reduces the operating voltage and improves the efficiency greatly.
2005,
17.
Abstract:
An S-band MILO was designed by 2D particle-in-cell(PIC) electromagnetic code, based on the L-band hard-tube MILO of the Philips laboratory. The working frequency of the S-band MILO was 2.3 GHz. The design was further improved to increase the output power and efficiency. The emission increase from the cross section resulted in better magnetic insulation. A metal film was used to replace the conductor so that the load current, which had only supplied magnetic insulation, could be used to participate in the wave-beam energy transformation. The average output power in a period was 2 GW when the input voltage was 450 kV and the input current was about 45 kA. The efficiency was up to 10%.
An S-band MILO was designed by 2D particle-in-cell(PIC) electromagnetic code, based on the L-band hard-tube MILO of the Philips laboratory. The working frequency of the S-band MILO was 2.3 GHz. The design was further improved to increase the output power and efficiency. The emission increase from the cross section resulted in better magnetic insulation. A metal film was used to replace the conductor so that the load current, which had only supplied magnetic insulation, could be used to participate in the wave-beam energy transformation. The average output power in a period was 2 GW when the input voltage was 450 kV and the input current was about 45 kA. The efficiency was up to 10%.
2005,
17.
Abstract:
A high power UWB pulse radiation source was developed, which was composed of a repetition rate high power pulse source, a wideband pulse producing setup and a wideband pulse emission antenna. The parameters of the high power UWB pulse radiation source were that the output voltage of the pulse source was 600 kV, the repetition rate 100 Hz, the pulse output peak power 10 GW, the pulse duration 1.2 ns, the radiation peak electric-field of the IRA 16.1 kV/m, and the equivalent power 0.42×1012 W at the distance of 220 m on the principal axis of the IRA. The half-power width of E-side of the radiation was at 8° and that of H-side was at 9°.
A high power UWB pulse radiation source was developed, which was composed of a repetition rate high power pulse source, a wideband pulse producing setup and a wideband pulse emission antenna. The parameters of the high power UWB pulse radiation source were that the output voltage of the pulse source was 600 kV, the repetition rate 100 Hz, the pulse output peak power 10 GW, the pulse duration 1.2 ns, the radiation peak electric-field of the IRA 16.1 kV/m, and the equivalent power 0.42×1012 W at the distance of 220 m on the principal axis of the IRA. The half-power width of E-side of the radiation was at 8° and that of H-side was at 9°.
2005,
17.
Abstract:
A coaxial vircator with a new kind of quasi- optical resonator was presented. The 3- mirror cavity's field distribution shows that the maximum field in the resonator is located in the cavity's center, which can greatly enhance the beam- wave interaction efficiency. PIC simulation of this vircator was made using the MAGIC code. When the input voltage was 600 kV, the current of the diode was 50 kA and a microwave pulse output power with a dominant frequency of 7.0 GHz, a peak power of 6 GW was obtained. The average power was 2.5 GW and its officiency was about 8.3%.
A coaxial vircator with a new kind of quasi- optical resonator was presented. The 3- mirror cavity's field distribution shows that the maximum field in the resonator is located in the cavity's center, which can greatly enhance the beam- wave interaction efficiency. PIC simulation of this vircator was made using the MAGIC code. When the input voltage was 600 kV, the current of the diode was 50 kA and a microwave pulse output power with a dominant frequency of 7.0 GHz, a peak power of 6 GW was obtained. The average power was 2.5 GW and its officiency was about 8.3%.
2005,
17.
Abstract:
In order to analyze the rectangular waveguide grating which is a typical slow wave structure, the dispersion relation was obtained by the field-matching method. The coupling impedance was subsequently obtained from the relevant equations. The higher orders were retained as an infinite sum of standing eigen-waves to deal with the fields inside the grooves. Computations and analysis were done for two typical structures of the rectangular waveguide grating, the shallow grating and the deep grating, and reasonable results were obtained. The results show that the deeper the groove is, the stronger the dispersion is and the narrower the pass-band is. The coupling impedance increases significantly. The operating point moves toward the forward wave zone, it is fit for the slow wave structure of an
In order to analyze the rectangular waveguide grating which is a typical slow wave structure, the dispersion relation was obtained by the field-matching method. The coupling impedance was subsequently obtained from the relevant equations. The higher orders were retained as an infinite sum of standing eigen-waves to deal with the fields inside the grooves. Computations and analysis were done for two typical structures of the rectangular waveguide grating, the shallow grating and the deep grating, and reasonable results were obtained. The results show that the deeper the groove is, the stronger the dispersion is and the narrower the pass-band is. The coupling impedance increases significantly. The operating point moves toward the forward wave zone, it is fit for the slow wave structure of an
2005,
17.
Abstract:
By means of coaxial apparatus, a high electrical voltage breakdown experiment for pressurized glycol/water mixture with microsecond charging is carried out. The experimental results are presented and analyzed. The conclusions are shown as follows: the breakdown strength increases with the hydrostatic pressure to the one eighth power; the coefficient in Martin formula increases with increasing glycol concentration; the highest breakdown stress of 235.5 kV/cm observed in the glycol/water mixture of glycol concentration of 80% at a hydrostatic pressure of 12×105 Pa is 112.2% higher than that in pure water at constant pressure; it is accumulative for the pressurization and glycol addition for the capability to improve electrical breakdown strength of water dielectric, and the pressurization i
By means of coaxial apparatus, a high electrical voltage breakdown experiment for pressurized glycol/water mixture with microsecond charging is carried out. The experimental results are presented and analyzed. The conclusions are shown as follows: the breakdown strength increases with the hydrostatic pressure to the one eighth power; the coefficient in Martin formula increases with increasing glycol concentration; the highest breakdown stress of 235.5 kV/cm observed in the glycol/water mixture of glycol concentration of 80% at a hydrostatic pressure of 12×105 Pa is 112.2% higher than that in pure water at constant pressure; it is accumulative for the pressurization and glycol addition for the capability to improve electrical breakdown strength of water dielectric, and the pressurization i
2005,
17.
Abstract:
An experimental system of foilless diode operating in low guiding magnetic field was designed on the pulsed power generator S-5N. In the experiment, a trapezium-shape wavefrom was obtained with a rise time of about 9 ns and a flat top of about 26 ns when magnetic field strength was 0.5 T. The diode voltage was 420 kV and the current was 2.7 kA. The average radius of the beam spot was 16 mm. There was a good agreement between the design and experimental results. It was observed that the diode impedance increases following the guiding magnetic field until it reaches a turning point.
An experimental system of foilless diode operating in low guiding magnetic field was designed on the pulsed power generator S-5N. In the experiment, a trapezium-shape wavefrom was obtained with a rise time of about 9 ns and a flat top of about 26 ns when magnetic field strength was 0.5 T. The diode voltage was 420 kV and the current was 2.7 kA. The average radius of the beam spot was 16 mm. There was a good agreement between the design and experimental results. It was observed that the diode impedance increases following the guiding magnetic field until it reaches a turning point.
2005,
17.
Abstract:
The principle and parameters of a low impedance pulsed electron accelerator MC55 are described. The experimental waveforms of the electron beam produced by MC55 are also presented. MC55 consists a 24-stages Marx generator, a 10 Ω water coaxial pulse forming line and outputting line, a main gas switch and a vacuum diode. An intense pulsed electron beam with diode voltage of 500 kV, current of 50 kA, and pulsewidth of 50 ns can be produced by this accelerator. The experimental research of coaxial virtual cathode oscillator driven by MC55 is carried out.
The principle and parameters of a low impedance pulsed electron accelerator MC55 are described. The experimental waveforms of the electron beam produced by MC55 are also presented. MC55 consists a 24-stages Marx generator, a 10 Ω water coaxial pulse forming line and outputting line, a main gas switch and a vacuum diode. An intense pulsed electron beam with diode voltage of 500 kV, current of 50 kA, and pulsewidth of 50 ns can be produced by this accelerator. The experimental research of coaxial virtual cathode oscillator driven by MC55 is carried out.
2005,
17.
Abstract:
Models of electron emission mechanism are established concerning metal and carbon fiber cathodes. Correctness of the electron emission mechanism was proved according to micro-photos and electron scanning photos of cathodes respectively. The experimental results and analysis show that the surface flashover induces the electron emission of carbon fiber cathode and there are electron emission phenomena from the top of the carbon and also from its side surface. In addition, compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fiber cathode is slower and the pulse duration of output microwave can be widened by using the carbon fiber cathode.
Models of electron emission mechanism are established concerning metal and carbon fiber cathodes. Correctness of the electron emission mechanism was proved according to micro-photos and electron scanning photos of cathodes respectively. The experimental results and analysis show that the surface flashover induces the electron emission of carbon fiber cathode and there are electron emission phenomena from the top of the carbon and also from its side surface. In addition, compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fiber cathode is slower and the pulse duration of output microwave can be widened by using the carbon fiber cathode.
2005,
17.
Abstract:
This paper summarizes recent results of the study and development of high-power repetitive nanosecond generators employing a semiconductor opening switch(SOS). The SOS-based pulsed power generator(SPG200, SPG700) has been developed and tested in Northwest Institute of Nuclear Technology. Some applications are carried out on the SOS-based generator, such as the high-frequency diode, research of long lifetime cathode, insulating research of breakdown. An experimental system of foilless diode with low guiding magnetic field is designed on the generator S-5N. The SPG200 delivers pulses with FWHM of 35 ns and amplitude up to 200 kV at 2 kHz repetition rate into a load in burst mode. The average output power is 13 kW. The generator can work at 300 Hz continuously. The SPG700 is designed by the s
This paper summarizes recent results of the study and development of high-power repetitive nanosecond generators employing a semiconductor opening switch(SOS). The SOS-based pulsed power generator(SPG200, SPG700) has been developed and tested in Northwest Institute of Nuclear Technology. Some applications are carried out on the SOS-based generator, such as the high-frequency diode, research of long lifetime cathode, insulating research of breakdown. An experimental system of foilless diode with low guiding magnetic field is designed on the generator S-5N. The SPG200 delivers pulses with FWHM of 35 ns and amplitude up to 200 kV at 2 kHz repetition rate into a load in burst mode. The average output power is 13 kW. The generator can work at 300 Hz continuously. The SPG700 is designed by the s
2005,
17.
Abstract:
The lifetime of conventional trigatron is limited by the erosion of the trigger electrode. An extended lifetime trigatron was designed with three new types of trigger electrode based on the analysis of trigger mechanism. The experimental results indicate that the performances of the new trigatron are as high as the conventional trigatron. The minimum delay time of the new trigatron is 77 ns and the jitter is 2.5 ns.
The lifetime of conventional trigatron is limited by the erosion of the trigger electrode. An extended lifetime trigatron was designed with three new types of trigger electrode based on the analysis of trigger mechanism. The experimental results indicate that the performances of the new trigatron are as high as the conventional trigatron. The minimum delay time of the new trigatron is 77 ns and the jitter is 2.5 ns.
2005,
17.
Abstract:
The spiral line was analyzed through a simple theory, the code simulation and the experimental test. The pulse width of spiral forming line was widened comparing with that of non-spiral forming line, which could be determined by a simple formula and be testified by the results of the code simulation. According to the theory and the code simulation, a water-dielectric Blumlein type of PFL with spiral line was built up and the insulated underlay of spiral line was designed carefully to improve the charging voltage. The experiments were carried out using diode load. As a typical result, a pulse output with a diode voltage of 500 kV and a diode current of 28 kA with an FWHM (full width of half maximum) of 128 ns was obtained when the charging voltage of PFL was up to 550 kV.
The spiral line was analyzed through a simple theory, the code simulation and the experimental test. The pulse width of spiral forming line was widened comparing with that of non-spiral forming line, which could be determined by a simple formula and be testified by the results of the code simulation. According to the theory and the code simulation, a water-dielectric Blumlein type of PFL with spiral line was built up and the insulated underlay of spiral line was designed carefully to improve the charging voltage. The experiments were carried out using diode load. As a typical result, a pulse output with a diode voltage of 500 kV and a diode current of 28 kA with an FWHM (full width of half maximum) of 128 ns was obtained when the charging voltage of PFL was up to 550 kV.
2005,
17.
Abstract:
The experimental studies of 400 kW PSM high voltage power supply are summarized in this paper. Firstly, the rapid protective method to shut down high voltage in 10 μs under over-current situation is described. The arc-deposited energy in the process of klystron breakdown is studied. The body-current waveforms of the klystron in different grounding modes are compared. The experimental results show that this type of all-solid state high voltage power supply has many advantages, such as the high anti-jamming capability, high efficiency and maintainability. It provides a highly beneficial path for high power vacuum microwave devices test.
The experimental studies of 400 kW PSM high voltage power supply are summarized in this paper. Firstly, the rapid protective method to shut down high voltage in 10 μs under over-current situation is described. The arc-deposited energy in the process of klystron breakdown is studied. The body-current waveforms of the klystron in different grounding modes are compared. The experimental results show that this type of all-solid state high voltage power supply has many advantages, such as the high anti-jamming capability, high efficiency and maintainability. It provides a highly beneficial path for high power vacuum microwave devices test.
2005,
17.
Abstract:
Using the finite element method, a numerical study of the electric field enhancement factor of a metallic microprotrusion on the cathode surface of an infinite planar diode was presented. According to the numeral results, the relationship between the electric enhancement factors and the dimensions of microprotrusions with typical geometry was obtained, which was useful in the analysis of explosive electron emission.
Using the finite element method, a numerical study of the electric field enhancement factor of a metallic microprotrusion on the cathode surface of an infinite planar diode was presented. According to the numeral results, the relationship between the electric enhancement factors and the dimensions of microprotrusions with typical geometry was obtained, which was useful in the analysis of explosive electron emission.
2005,
17.
Abstract:
The high electric field of high power microwave propagating in atmosphere makes air breakdown possible, which confines the maximun transmitting power of microwave antenna because of its intense power density. It is in the near field that the air breakdown often occurs. The power density distributions of rectangle and circular aperture antennae were analyzed and the normalized power density of different aperture distribution was obtained. Based on the air breakdown power density threshold, the maximum transmitting power of circular antenna was given.
The high electric field of high power microwave propagating in atmosphere makes air breakdown possible, which confines the maximun transmitting power of microwave antenna because of its intense power density. It is in the near field that the air breakdown often occurs. The power density distributions of rectangle and circular aperture antennae were analyzed and the normalized power density of different aperture distribution was obtained. Based on the air breakdown power density threshold, the maximum transmitting power of circular antenna was given.
2005,
17.
Abstract:
In an HPM radiation system, the horn feeds which have high power capacity and favorable radiation performance are required. The multimode and smooth-wall horn can fulfill the requirement. Based on the single step mode-matching technololgy, the method to get the scatter matrix of the smooth-profile horn was presented. By the method, the process of modes coupling which happened when TE11 mode was incident to horn feed was analyzed. The relationship of mode coupling and the change of radiation performance was investigated. Through simulation and selection, the primary design model, which had high power capacity above 1.5 GW and favorable radiation performance, was obtained and measured. Excellent correspondence between the experimental result and theory was demonstrated.
In an HPM radiation system, the horn feeds which have high power capacity and favorable radiation performance are required. The multimode and smooth-wall horn can fulfill the requirement. Based on the single step mode-matching technololgy, the method to get the scatter matrix of the smooth-profile horn was presented. By the method, the process of modes coupling which happened when TE11 mode was incident to horn feed was analyzed. The relationship of mode coupling and the change of radiation performance was investigated. Through simulation and selection, the primary design model, which had high power capacity above 1.5 GW and favorable radiation performance, was obtained and measured. Excellent correspondence between the experimental result and theory was demonstrated.
2005,
17.
Abstract:
Mode coupling coefficients are the bases of coupled-wave theory (CWT). The mode coupling coefficients in coaxial waveguide with radii changes were deduced. It is revealed that the mode coupling coefficients in circular waveguide are just the special cases of those in coaxial waveguide. The coaxial waveguide modes and their eigenvalues were analyzed. The eigenvalues calculating method was obtained by constructing the corresponding relation between coaxial waveguide modes and rectangular waveguide modes. The mode coupling coefficients formulae were validated by the finite-element method (FEM). The calculation results of CWT agree well with that of FEM.
Mode coupling coefficients are the bases of coupled-wave theory (CWT). The mode coupling coefficients in coaxial waveguide with radii changes were deduced. It is revealed that the mode coupling coefficients in circular waveguide are just the special cases of those in coaxial waveguide. The coaxial waveguide modes and their eigenvalues were analyzed. The eigenvalues calculating method was obtained by constructing the corresponding relation between coaxial waveguide modes and rectangular waveguide modes. The mode coupling coefficients formulae were validated by the finite-element method (FEM). The calculation results of CWT agree well with that of FEM.
2005,
17.
Abstract:
The low-frequency-compensation principle for TEM-horn antenna was verified by experiment. The low frequency transmission and radiation characters were improved by the low-frequency-compensation. When the magnitudes and directions of the electric and magnetic dipoles were matched, the radiation in backward and sideward direction was obviously restrained. When the magnetic dipole moment made by low-frequency-compensation loop was large enough, the magnitude of radiation in forward direction would be enhanced and the low frequency component would be increased.
The low-frequency-compensation principle for TEM-horn antenna was verified by experiment. The low frequency transmission and radiation characters were improved by the low-frequency-compensation. When the magnitudes and directions of the electric and magnetic dipoles were matched, the radiation in backward and sideward direction was obviously restrained. When the magnetic dipole moment made by low-frequency-compensation loop was large enough, the magnitude of radiation in forward direction would be enhanced and the low frequency component would be increased.
2005,
17.
Abstract:
An improved COBRA lens antenna in X-band for TM01 mode is designed. The dielectric lens consisting of three or four sectors is located on the aperture plane of a conical horn. The antenna can radiate circular polarzied patterns, with a boresight peak and a high gain. The results of simulation demonstrate that at the operating frequency, the gain, the aperture efficiency and the radial efficiency are 19 dB, 25%, and more than 90% respectively. The axial ratio is less than 2 dB and the relative band-width of 3 dB is more than 30%, which covers almost the whole X-band.
An improved COBRA lens antenna in X-band for TM01 mode is designed. The dielectric lens consisting of three or four sectors is located on the aperture plane of a conical horn. The antenna can radiate circular polarzied patterns, with a boresight peak and a high gain. The results of simulation demonstrate that at the operating frequency, the gain, the aperture efficiency and the radial efficiency are 19 dB, 25%, and more than 90% respectively. The axial ratio is less than 2 dB and the relative band-width of 3 dB is more than 30%, which covers almost the whole X-band.
2005,
17.
Abstract:
In this paper，the finite-difference time-domain (FDTD) and the discrete fast Fourier transform (DFFT) methods are adopted to calculate the transfer function and the sensitivity of TEM horn of various length and flare angle. The max relative error and the relative average deviation are used to analyze the ultra-wideband receiving characteristics. The results provide a basis to design a ultra-wideband receiving TEM horn.
In this paper，the finite-difference time-domain (FDTD) and the discrete fast Fourier transform (DFFT) methods are adopted to calculate the transfer function and the sensitivity of TEM horn of various length and flare angle. The max relative error and the relative average deviation are used to analyze the ultra-wideband receiving characteristics. The results provide a basis to design a ultra-wideband receiving TEM horn.
2005,
17.
Abstract:
This paper presents a high power feed system for 7.3 m Cassegrain antenna. In order to make E and H patterns of the feed equal in the illuminated area, the dual-mode conical horn is chosen as the feed form. Since the high power signal is transmitted from the BJ-32 waveguide, a mode convertor from rectangular TE10 mode to circular TE11 mode in the feed system should be provided. The feed system, including a dual-mode conical horn and a mode convertor, was designed, manufactured, and measured. The measured results indicate that the feed system achieves the design goal, and the measured results agree well with the theoretical results.
This paper presents a high power feed system for 7.3 m Cassegrain antenna. In order to make E and H patterns of the feed equal in the illuminated area, the dual-mode conical horn is chosen as the feed form. Since the high power signal is transmitted from the BJ-32 waveguide, a mode convertor from rectangular TE10 mode to circular TE11 mode in the feed system should be provided. The feed system, including a dual-mode conical horn and a mode convertor, was designed, manufactured, and measured. The measured results indicate that the feed system achieves the design goal, and the measured results agree well with the theoretical results.
2005,
17.
Abstract:
The axis length and the beat-wave wavelength in double-bent circular waveguide TM01-TE11 mode converter are analyzed, keeping the axis of the output port parallel to that of the input port and keeping the two curvature radii equal. It is proved that the axis length is directly proportional to the beat wave wavelength and the ratio of the axis length to the beat-wave wavelength is 2/2. The lower limit of the pass band is obtained by theory and simulation when the simulated power conversion efficiency exceeds 98%, which is 1.07 times of that of the TM01 mode cut-off frequency.
The axis length and the beat-wave wavelength in double-bent circular waveguide TM01-TE11 mode converter are analyzed, keeping the axis of the output port parallel to that of the input port and keeping the two curvature radii equal. It is proved that the axis length is directly proportional to the beat wave wavelength and the ratio of the axis length to the beat-wave wavelength is 2/2. The lower limit of the pass band is obtained by theory and simulation when the simulated power conversion efficiency exceeds 98%, which is 1.07 times of that of the TM01 mode cut-off frequency.
2005,
17.
Abstract:
Severe attenuation happens when the high-power microwave propagates through a certain altitude. At this altitude, the microwave pulse will ionize the surrounding air and create a plasma, so the severe nonlinear attenuation will be caused, even the breakdown will happen. At the lower ionosphere, the density of the natural ionized free electrons is very intensive. The characteristic of the attenuation when high-power microwave propagates through the lower ionosphere is analyzed in this paper. Calculations indicate that the maximal nonlinear absorption attenuation occurs at the altitude of 50 km. This altitude is very possible to be breakdown. At the same electric-field intensity, the narrower the pulse duration is, the smaller the attenuation coefficient is. At the lower ionosphere, the atte
Severe attenuation happens when the high-power microwave propagates through a certain altitude. At this altitude, the microwave pulse will ionize the surrounding air and create a plasma, so the severe nonlinear attenuation will be caused, even the breakdown will happen. At the lower ionosphere, the density of the natural ionized free electrons is very intensive. The characteristic of the attenuation when high-power microwave propagates through the lower ionosphere is analyzed in this paper. Calculations indicate that the maximal nonlinear absorption attenuation occurs at the altitude of 50 km. This altitude is very possible to be breakdown. At the same electric-field intensity, the narrower the pulse duration is, the smaller the attenuation coefficient is. At the lower ionosphere, the atte
2005,
17.
Abstract:
Based on physic-optics and geometric-optics, a design method of high power microwave feed vacuum output window was discussed. For an X band, 1.5 GW pulse power handling ability gaussian feed, a dishing type of Teflon vacuum output window was fabricated, with a diameter of 548 mm, a height of 83.4 mm and a thickness of 33.4 mm. The test results are in good agreement with theoretics. The voltage standing wave ratio(VSWR) at the central frequency 9.3 GHz was 1.07. The band with VWSR less than 1.24 was 9%. The direction pattern of the feed with the dielectric window was the same as that without the dielectric window. The temperature distribution was analysed by one dimension stable heat transmission theory.
Based on physic-optics and geometric-optics, a design method of high power microwave feed vacuum output window was discussed. For an X band, 1.5 GW pulse power handling ability gaussian feed, a dishing type of Teflon vacuum output window was fabricated, with a diameter of 548 mm, a height of 83.4 mm and a thickness of 33.4 mm. The test results are in good agreement with theoretics. The voltage standing wave ratio(VSWR) at the central frequency 9.3 GHz was 1.07. The band with VWSR less than 1.24 was 9%. The direction pattern of the feed with the dielectric window was the same as that without the dielectric window. The temperature distribution was analysed by one dimension stable heat transmission theory.
2005,
17.
Abstract:
The sand and dust attenuation has a great effect on the microwave propagation in the air. The calculation model of the sand and dust attenuation was got, combining the formula of the complex dielectric constant of dry sand with the dielectric constant of water. The model analysed the attenuation of sand and dust produced by explosion, vehicle and nature, and simulated attenuation rate of sand with different content of water. The result of numerical calculation shows that natural sand and vehicular sand have little effect on microwave when the frequency is not very high, but the attenuation of explosive sand could not be ignored. It also shows the attenuation of explosive sand rises quickly along with the increase of water content. This effect reaches saturated state when the humidity range
The sand and dust attenuation has a great effect on the microwave propagation in the air. The calculation model of the sand and dust attenuation was got, combining the formula of the complex dielectric constant of dry sand with the dielectric constant of water. The model analysed the attenuation of sand and dust produced by explosion, vehicle and nature, and simulated attenuation rate of sand with different content of water. The result of numerical calculation shows that natural sand and vehicular sand have little effect on microwave when the frequency is not very high, but the attenuation of explosive sand could not be ignored. It also shows the attenuation of explosive sand rises quickly along with the increase of water content. This effect reaches saturated state when the humidity range
2005,
17.
Abstract:
The effect of HPM on the intracellular calcium of sperm cells was determined using laser scanning confocal microscopy. The abnormality，micronucleus frequency，livability, numbers and the acrosin reaction of the sperm cells were studied at the same time.The experiments indicate that there are no visible damaging effects on the abnormality and micronucleus frequency of the sperm cells after HPM irradiation,but the acrosin reaction of the rat sperm cells was restrained significantly after 4×105 pulses irradiation. The function of the sperm cells was probably induced by changing the intracytoplasmic calcium concentration of the rat sperm cells.
The effect of HPM on the intracellular calcium of sperm cells was determined using laser scanning confocal microscopy. The abnormality，micronucleus frequency，livability, numbers and the acrosin reaction of the sperm cells were studied at the same time.The experiments indicate that there are no visible damaging effects on the abnormality and micronucleus frequency of the sperm cells after HPM irradiation,but the acrosin reaction of the rat sperm cells was restrained significantly after 4×105 pulses irradiation. The function of the sperm cells was probably induced by changing the intracytoplasmic calcium concentration of the rat sperm cells.
2005,
17.
Abstract:
The characteristics of microwave pulses from different sources penetrating various kind of walls were studied. The walls used in the experiment included common brick-mix wall, common reinforced concrete wall and reinforcing steel bar-net concrete wall. The microwave sources used were narrow band microwave source, 100 V UWB radiation source and single periodic UWB pulse radiation source. The attenuation and the change of spectrum for different electromagnetic pulse after penetrating various walls were provided and analyzed. For the narrow band pulse penetrating common brick-mix wall and common reinforced concrete wall, the attenuation was 0.342～0.699 dB/cm. For the UWB pulse penetrating common brick-mix wall and common reinforced concrete wall, the attenuation was 0.134～0.183 dB/cm. For r
The characteristics of microwave pulses from different sources penetrating various kind of walls were studied. The walls used in the experiment included common brick-mix wall, common reinforced concrete wall and reinforcing steel bar-net concrete wall. The microwave sources used were narrow band microwave source, 100 V UWB radiation source and single periodic UWB pulse radiation source. The attenuation and the change of spectrum for different electromagnetic pulse after penetrating various walls were provided and analyzed. For the narrow band pulse penetrating common brick-mix wall and common reinforced concrete wall, the attenuation was 0.342～0.699 dB/cm. For the UWB pulse penetrating common brick-mix wall and common reinforced concrete wall, the attenuation was 0.134～0.183 dB/cm. For r
2005,
17.
Abstract:
The electromagnetic interaction with electric devices caused by high power microwave(HPM) is now much concerned. The BLT equation can solve some problems of electromagnetic interaction. This paper firstly introduces the formulations of the BLT equation and the parameters of the equations. Secondly it extends the conventional BLT equation through studying a simple HPM interaction model. Finally it provides a numerical example to analyze the interaction responses arising from HPM. The results show that the extended BLT equation can evaluate the propagation of the electromagnetic energy along the conductors and the electromagnetic field propagation in the space.
The electromagnetic interaction with electric devices caused by high power microwave(HPM) is now much concerned. The BLT equation can solve some problems of electromagnetic interaction. This paper firstly introduces the formulations of the BLT equation and the parameters of the equations. Secondly it extends the conventional BLT equation through studying a simple HPM interaction model. Finally it provides a numerical example to analyze the interaction responses arising from HPM. The results show that the extended BLT equation can evaluate the propagation of the electromagnetic energy along the conductors and the electromagnetic field propagation in the space.
2005,
17.
Abstract:
The retinal histopathological effects and electro-retinograms (ERG) were recorded before and after exposure to determine ocular structural and functional and retinal ultra-structural changes in chinchilla rabbits. It is shown that HPM exposure may bring about early retinal injure and strongly decrease the vision electro-physiological function in chinchilla rabbits. These effects show the dose- and time-dependent features.
The retinal histopathological effects and electro-retinograms (ERG) were recorded before and after exposure to determine ocular structural and functional and retinal ultra-structural changes in chinchilla rabbits. It is shown that HPM exposure may bring about early retinal injure and strongly decrease the vision electro-physiological function in chinchilla rabbits. These effects show the dose- and time-dependent features.
