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2023, 21(10):1204-1210.
DOI: 10.11805/TKYDA2023199
Abstract:
As a novel developing vacuum electronic device, sheet beam traveling wave tube has a wide range of application prospects in the field of radar and communications. Compared to cylindrical beam devices, there are still fewer beam-wave interaction models for sheet beam traveling wave tubes. Based on the electric circuit principles, a hybrid circuit model consisting of distributed transmission line components and lumped elements for a commonly used sheet beam slow wave structure(SWS)—staggered double vane is developed, and the feasibility of applying the model to high frequency SWS is validated.The problem of mapping from the geometrical parameters of SWS to the physical parameters of hybrid circuit is focused on. The hybrid circuit model of staggered double-vane is developed, and its dispersion relation is analyzed. Besides, a model-based Simulated Annealing(SA) algorithm procedure, capable of achieving high precision parameter fitting is coded. The results show that the proposed hybrid circuit model can accurately reproduce the dispersion characteristics of the staggered double-vane. It is significant for the subsequent development of a large signal sheet beam-wave interaction procedure based on the hybrid circuit model.
As a novel developing vacuum electronic device, sheet beam traveling wave tube has a wide range of application prospects in the field of radar and communications. Compared to cylindrical beam devices, there are still fewer beam-wave interaction models for sheet beam traveling wave tubes. Based on the electric circuit principles, a hybrid circuit model consisting of distributed transmission line components and lumped elements for a commonly used sheet beam slow wave structure(SWS)—staggered double vane is developed, and the feasibility of applying the model to high frequency SWS is validated.The problem of mapping from the geometrical parameters of SWS to the physical parameters of hybrid circuit is focused on. The hybrid circuit model of staggered double-vane is developed, and its dispersion relation is analyzed. Besides, a model-based Simulated Annealing(SA) algorithm procedure, capable of achieving high precision parameter fitting is coded. The results show that the proposed hybrid circuit model can accurately reproduce the dispersion characteristics of the staggered double-vane. It is significant for the subsequent development of a large signal sheet beam-wave interaction procedure based on the hybrid circuit model.
2 Research on hydrogen annealing in UV-LIGA microfabrication of folded waveguide slow wave structures
2023, 21(10):1198-1203.
DOI: 10.11805/TKYDA2023206
Abstract:
The effect of hydrogen annealing in each stage of the production of all-copper structure folded waveguide by Ultraviolet-Lithographie Galvanoformung Abformung(UV-LIGA) is studied in detail. The hydrogen annealing step is in two stages, the first stage is the hydrogen treatment of the copper substrate(early stage), and the second stage is the treatment of the substrate and the electroformed layer after realizing the metal structure(later stage). Experiments show that in addition to cleaning the substrate and reducing the internal stress, hydrogen annealing in the early stage also migrates grain boundaries, so that the grain growth tends to be stable at high temperatures, which is conducive to the growth of the electroformed layer with better combination. However, this treatment needs to be advanced before the substrate is polished, otherwise the flatness will deteriorate. In addition to testing whether the all-copper structure can withstand high-temperature welding, hydrogen annealing in the later stage also helps to further remove the photoresist and promotes grain growth of substrate and electroformed layer as a whole at high temperature.
The effect of hydrogen annealing in each stage of the production of all-copper structure folded waveguide by Ultraviolet-Lithographie Galvanoformung Abformung(UV-LIGA) is studied in detail. The hydrogen annealing step is in two stages, the first stage is the hydrogen treatment of the copper substrate(early stage), and the second stage is the treatment of the substrate and the electroformed layer after realizing the metal structure(later stage). Experiments show that in addition to cleaning the substrate and reducing the internal stress, hydrogen annealing in the early stage also migrates grain boundaries, so that the grain growth tends to be stable at high temperatures, which is conducive to the growth of the electroformed layer with better combination. However, this treatment needs to be advanced before the substrate is polished, otherwise the flatness will deteriorate. In addition to testing whether the all-copper structure can withstand high-temperature welding, hydrogen annealing in the later stage also helps to further remove the photoresist and promotes grain growth of substrate and electroformed layer as a whole at high temperature.
2023, 21(10):1194-1197.
DOI: 10.11805/TKYDA2023185
Abstract:
According to the satellite communication application requirements for high-frequency space Traveling Wave Tube(TWT), the experimental results of an E-band continuous wave space TWT are introduced. The parameters of the Folded Waveguide(FWG) slow wave structure are further optimized and the phase velocity taper scheme is adjusted to reform the gain fluctuation, improve the overall efficiency. A prototype tube is fabricated and tested with beam voltage of 14.7 kV and beam current of 74 mA, the experimental measurement results show this prototype is capable of producing an output power up to 85 W and a gain above 40 dB, with the total efficiency over 37% from 71 to 76 GHz. In addition, the TWT has achieved a beam transmission over 98% at the continuous wave operation.
According to the satellite communication application requirements for high-frequency space Traveling Wave Tube(TWT), the experimental results of an E-band continuous wave space TWT are introduced. The parameters of the Folded Waveguide(FWG) slow wave structure are further optimized and the phase velocity taper scheme is adjusted to reform the gain fluctuation, improve the overall efficiency. A prototype tube is fabricated and tested with beam voltage of 14.7 kV and beam current of 74 mA, the experimental measurement results show this prototype is capable of producing an output power up to 85 W and a gain above 40 dB, with the total efficiency over 37% from 71 to 76 GHz. In addition, the TWT has achieved a beam transmission over 98% at the continuous wave operation.
2023, 21(10):1189-1193.
DOI: 10.11805/TKYDA2023200
Abstract:
With the fast development of folded waveguide Traveling Wave Tube(TWT), there is an urgent need for attenuation materials with high thermal conductivity and good mechanical properties. In this study, boron-doped diamond film is prepared and the dielectric property of the film is analyzed. Meanwhile, the boron-doped diamond attenuator is fabricated and the thermal stability of the attenuator is investigated. The results show that the dielectric constant and dielectric loss tangent are 7.18 and 0.30 in W-band for the diamond film with boron concentration of 1.81×1019 cm-3. Moreover, the return loss and insertion loss of boron-doped diamond attenuator are 19.67 dB and 44.03 dB, respectively. With the temperature increased from room temperature to 90 ℃, the return loss and insertion loss of attenuator are increased to 20.94 dB and 45.63 dB, which demonstrates high thermal stability of the boron-doped diamond attenuator.
With the fast development of folded waveguide Traveling Wave Tube(TWT), there is an urgent need for attenuation materials with high thermal conductivity and good mechanical properties. In this study, boron-doped diamond film is prepared and the dielectric property of the film is analyzed. Meanwhile, the boron-doped diamond attenuator is fabricated and the thermal stability of the attenuator is investigated. The results show that the dielectric constant and dielectric loss tangent are 7.18 and 0.30 in W-band for the diamond film with boron concentration of 1.81×1019 cm-3. Moreover, the return loss and insertion loss of boron-doped diamond attenuator are 19.67 dB and 44.03 dB, respectively. With the temperature increased from room temperature to 90 ℃, the return loss and insertion loss of attenuator are increased to 20.94 dB and 45.63 dB, which demonstrates high thermal stability of the boron-doped diamond attenuator.
2023, 21(10):1211-1216.
DOI: 10.11805/TKYDA2023207
Abstract:
To analyze the power and spectrum performance of the Folded Waveguide(FWG) Traveling Wave Tube(TWT) sever region, a W-band TWT with four-port structure is proposed and developed. The S-parameter of interaction circuit, power and spectrum characteristic at the sever region are obtained and analyzed. The analysis shows that the power amplitude of port 2(sever of the input segment) mainly depends on the input power of the TWT at the saturated state, which is not proportional to the gain of the input segment.The power of port 3(sever of output segment) mainly depends on the matching performance of the ports, and the calculated power is in an excellent agreement with the measured data. The study in this paper provide a practical method for designing sever region of the millimeter wave and terahertz TWTs.
To analyze the power and spectrum performance of the Folded Waveguide(FWG) Traveling Wave Tube(TWT) sever region, a W-band TWT with four-port structure is proposed and developed. The S-parameter of interaction circuit, power and spectrum characteristic at the sever region are obtained and analyzed. The analysis shows that the power amplitude of port 2(sever of the input segment) mainly depends on the input power of the TWT at the saturated state, which is not proportional to the gain of the input segment.The power of port 3(sever of output segment) mainly depends on the matching performance of the ports, and the calculated power is in an excellent agreement with the measured data. The study in this paper provide a practical method for designing sever region of the millimeter wave and terahertz TWTs.
2024, 22(1):6-10.
DOI: 10.11805/TKYDA2023191
Abstract:
Millimeter-wave Traveling Wave Tubes(TWTs) have the characteristics of high power, broad band and high gain, and are widely used in modern military electronic equipment, such as radar, high-speed communication and electronic countermeasures, etc. In order to improve the coupling impedance of the Folded Waveguide(FWG) and the engineering applicability, a novel type of ear-FWG is proposed, which increases the coupling impedance in the working frequency band by more than 30% and reduces the loss by 10% compared with the conventional rectangular waveguide. When the ear-FWG W-band TWT operates at 21.9 kV and 210 mA, and the duty cycle is 5%, the output power in the 10.8 GHz bandwidth is higher than 192 W, the peak power reaches 278 W, the electron efficiency and gain reach 6.3% and 44.6 dB, respectively, and the TWT works stably.
Millimeter-wave Traveling Wave Tubes(TWTs) have the characteristics of high power, broad band and high gain, and are widely used in modern military electronic equipment, such as radar, high-speed communication and electronic countermeasures, etc. In order to improve the coupling impedance of the Folded Waveguide(FWG) and the engineering applicability, a novel type of ear-FWG is proposed, which increases the coupling impedance in the working frequency band by more than 30% and reduces the loss by 10% compared with the conventional rectangular waveguide. When the ear-FWG W-band TWT operates at 21.9 kV and 210 mA, and the duty cycle is 5%, the output power in the 10.8 GHz bandwidth is higher than 192 W, the peak power reaches 278 W, the electron efficiency and gain reach 6.3% and 44.6 dB, respectively, and the TWT works stably.
2024, 22(1):35-38.
DOI: 10.11805/TKYDA2023283
Abstract:
As an important vacuum electron device, the gyrotron has the capability to generate high peak and average powers in the millimeter-wave and terahertz frequency ranges, holding broad prospects of application in fields such as spectroscopy, radar, communication, and biomedical science. However, conventional gyrotrons inevitably face intense mode competition issues, and the introduction of quasi-optical cavity is expected to significantly alleviate the severity of mode competition. In this study, based on the theory of electron gyrotron oscillation, the innovative combination of quasi-optical cavity and sheet electron beam is proposed with the aim of achieving higher output power and efficiency. Simulation results indicate that under conditions of 40 kV electron voltage and an 8.4 T background magnetic field, the designed quasi-optical gyrotron can generate 6.1 kW of output power at a frequency of 220 GHz, with an electron efficiency of 6.1% and stable operation over a certain duration. The proposed structure in this study may provide a novel solution for gyrotron design operating in high-frequency and even higher harmonic regimes, thus furthering its applications in fields such as radar and controlled nuclear fusion.
As an important vacuum electron device, the gyrotron has the capability to generate high peak and average powers in the millimeter-wave and terahertz frequency ranges, holding broad prospects of application in fields such as spectroscopy, radar, communication, and biomedical science. However, conventional gyrotrons inevitably face intense mode competition issues, and the introduction of quasi-optical cavity is expected to significantly alleviate the severity of mode competition. In this study, based on the theory of electron gyrotron oscillation, the innovative combination of quasi-optical cavity and sheet electron beam is proposed with the aim of achieving higher output power and efficiency. Simulation results indicate that under conditions of 40 kV electron voltage and an 8.4 T background magnetic field, the designed quasi-optical gyrotron can generate 6.1 kW of output power at a frequency of 220 GHz, with an electron efficiency of 6.1% and stable operation over a certain duration. The proposed structure in this study may provide a novel solution for gyrotron design operating in high-frequency and even higher harmonic regimes, thus furthering its applications in fields such as radar and controlled nuclear fusion.
2024, 22(1):1-5.
DOI: 10.11805/TKYDA2023288
Abstract:
A four-channel electron beam planar focusing system is designed to meet the application requirements of the planar integrated traveling wave tube for one-dimensional electron beam array focusing. The calculated results of the axial and transverse components of the magnetic field along the axis are compared with the measured results, which confirms the accuracy of Opera software in calculating the magnetic field distribution. In order to compare with the magnetic field distribution in the electron beam channel of the axisymmetric Periodic Permanent Magnet(PPM) focusing system, a model of the PPM focusing system is established, and the tested results are in good agreement with the calculated results. By comparing the longitudinal and transverse distribution characteristics of the magnetic field in the electron beam channel of the planar focusing system and the axisymmetric PPM focusing system, it is shown that the two focusing systems share the same magnetic field distribution characteristics in the electron beam channel, the ratios of transverse magnetic field component to the axial component are both about 0.11 on the circumference at the same off-axis position, and it is expected that the planar focusing system can achieve good focusing of the one-dimensional array electron beam.
A four-channel electron beam planar focusing system is designed to meet the application requirements of the planar integrated traveling wave tube for one-dimensional electron beam array focusing. The calculated results of the axial and transverse components of the magnetic field along the axis are compared with the measured results, which confirms the accuracy of Opera software in calculating the magnetic field distribution. In order to compare with the magnetic field distribution in the electron beam channel of the axisymmetric Periodic Permanent Magnet(PPM) focusing system, a model of the PPM focusing system is established, and the tested results are in good agreement with the calculated results. By comparing the longitudinal and transverse distribution characteristics of the magnetic field in the electron beam channel of the planar focusing system and the axisymmetric PPM focusing system, it is shown that the two focusing systems share the same magnetic field distribution characteristics in the electron beam channel, the ratios of transverse magnetic field component to the axial component are both about 0.11 on the circumference at the same off-axis position, and it is expected that the planar focusing system can achieve good focusing of the one-dimensional array electron beam.
2024, 22(1):17-21.
DOI: 10.11805/TKYDA2023289
Abstract:
In order to meet the demand of THz vacuum devices for miniature electron beam with high current density, a kind of miniature cathode has been prepared by depositing Ta/Zr coating on impregnated scandate cathode surface via dual Ion-Beam-Assisted Deposition (Dual IBAD) and etching an emission zone with a diameter of 100 m via Focus Ion Beam(FIB). Based on the previous study, this paper focuses on the characteristics of anti-emission coating. It is shown in the experimental results that Ta/Zr coating prepared by dual Ion Beam Assisted Deposition(Dual IBAD) can suppress electron emission more effectively and has a longer life time than that prepared by magnetron sputtering. The reasons for the sound anti-emission performance are that composition with high work function is formed in the process of Barium diffusion into the Ta/Zr coating, and that Barium diffusion is effectively suppressed by the high dense Ta/Zr coating.
In order to meet the demand of THz vacuum devices for miniature electron beam with high current density, a kind of miniature cathode has been prepared by depositing Ta/Zr coating on impregnated scandate cathode surface via dual Ion-Beam-Assisted Deposition (Dual IBAD) and etching an emission zone with a diameter of 100 m via Focus Ion Beam(FIB). Based on the previous study, this paper focuses on the characteristics of anti-emission coating. It is shown in the experimental results that Ta/Zr coating prepared by dual Ion Beam Assisted Deposition(Dual IBAD) can suppress electron emission more effectively and has a longer life time than that prepared by magnetron sputtering. The reasons for the sound anti-emission performance are that composition with high work function is formed in the process of Barium diffusion into the Ta/Zr coating, and that Barium diffusion is effectively suppressed by the high dense Ta/Zr coating.
2024, 22(1):11-16.
DOI: 10.11805/TKYDA2023290
Abstract:
With the rapid development of terahertz technology, people are increasingly interested in its various applications in communications, spectroscopy, and sensing. The basis for the development and application of terahertz technology is high-performance terahertz sources. Traditional terahertz sources are large in size and require high-power power supply to drive and are difficult to adapt to the development of integrated terahertz technology. Therefore, there is an urgent need to develop micro-terahertz sources with new mechanisms. This paper studies a new type of miniaturized free electron terahertz radiator, which realizes the excitation of terahertz waves based on the interaction of free electrons and the terahertz waves excited in the grating dielectric waveguide structure. This research provides new options for developing efficient on-chip terahertz radiation sources and expanding advanced terahertz applications.
With the rapid development of terahertz technology, people are increasingly interested in its various applications in communications, spectroscopy, and sensing. The basis for the development and application of terahertz technology is high-performance terahertz sources. Traditional terahertz sources are large in size and require high-power power supply to drive and are difficult to adapt to the development of integrated terahertz technology. Therefore, there is an urgent need to develop micro-terahertz sources with new mechanisms. This paper studies a new type of miniaturized free electron terahertz radiator, which realizes the excitation of terahertz waves based on the interaction of free electrons and the terahertz waves excited in the grating dielectric waveguide structure. This research provides new options for developing efficient on-chip terahertz radiation sources and expanding advanced terahertz applications.
2024, 22(1):22-27.
DOI: 10.11805/TKYDA2023277
Abstract:
A design of the electro-optical system for D-band Travelling Wave Tubes (TWTs), including an electron gun and a Periodic Permanent Magnet(PPM) focusing system, is presented and verified. The electron gun utilizes the classical Pierce electron gun structure, the outer layer of the cathode emission surface is set with a cathode sleeve to suppress stray emission at the edge of the cathode, and a cylindrical control electrode is used instead of a conical control electrode, and a negative bias is added to the focusing electrode to adjust the compression state of the electron injection. The electron gun can provide a beam current 57 mA with the beam waist radius of 0.068 mm and the shooting distance of 14.9 mm at the beam voltage of 1.9 kV. A sleeve tube is attached on the cathode to block the electron emission from the edge of the cathode. A cylindrical focusing electrode is used in the electron gun for adjusting the beam focusing state. To stably focus and transmit the electron beam in the beam tunnel of 0.15 mm radius, a PPM focusing system is employed. The peak magnetic field is 2.9 times the Brillouin magnetic field to increase the rigidity of electron injection. The simulated result shows the fluctuation radius of the electron beam is less than 0.1 mm. In order to validate the effectiveness of the D-band TWT electro-optical system, the electron gun and the PPM focusing system have been machined and assembled. The experimental results show the beam current is 49.83 mA, and the collector current is 49.6 mA. The beam transmission rate of 99.5% are obtained by carefully adjusting the PPM system, which achieves the design goal.
A design of the electro-optical system for D-band Travelling Wave Tubes (TWTs), including an electron gun and a Periodic Permanent Magnet(PPM) focusing system, is presented and verified. The electron gun utilizes the classical Pierce electron gun structure, the outer layer of the cathode emission surface is set with a cathode sleeve to suppress stray emission at the edge of the cathode, and a cylindrical control electrode is used instead of a conical control electrode, and a negative bias is added to the focusing electrode to adjust the compression state of the electron injection. The electron gun can provide a beam current 57 mA with the beam waist radius of 0.068 mm and the shooting distance of 14.9 mm at the beam voltage of 1.9 kV. A sleeve tube is attached on the cathode to block the electron emission from the edge of the cathode. A cylindrical focusing electrode is used in the electron gun for adjusting the beam focusing state. To stably focus and transmit the electron beam in the beam tunnel of 0.15 mm radius, a PPM focusing system is employed. The peak magnetic field is 2.9 times the Brillouin magnetic field to increase the rigidity of electron injection. The simulated result shows the fluctuation radius of the electron beam is less than 0.1 mm. In order to validate the effectiveness of the D-band TWT electro-optical system, the electron gun and the PPM focusing system have been machined and assembled. The experimental results show the beam current is 49.83 mA, and the collector current is 49.6 mA. The beam transmission rate of 99.5% are obtained by carefully adjusting the PPM system, which achieves the design goal.
2024, 22(1):28-34.
DOI: 10.11805/TKYDA2023280
Abstract:
To satisfy the application requirements of sapphire output window for the 170 GHz megawatt-class gyrotron short-pulsed experiment, by calculating the characteristic of reflection and absorbing of Gaussian beam transmitted through sapphire window, a sapphire window unit is designed with low reflection and low loss power. The low reflectance is verified by vector network analyzer that the Voltage Standing Wave Ratio(VSWR)<1.1. The maximum output average power threshold of the sapphire window has been calculated approximately to be 590 W by analyzing the damage mechanism. The 170 GHz gyrotron employing sapphire window is fabricated, and the power threshold calculated theoretically is verified, providing a reliable theoretical basis for the application of sapphire output window used in high power gyrotron.
To satisfy the application requirements of sapphire output window for the 170 GHz megawatt-class gyrotron short-pulsed experiment, by calculating the characteristic of reflection and absorbing of Gaussian beam transmitted through sapphire window, a sapphire window unit is designed with low reflection and low loss power. The low reflectance is verified by vector network analyzer that the Voltage Standing Wave Ratio(VSWR)<1.1. The maximum output average power threshold of the sapphire window has been calculated approximately to be 590 W by analyzing the damage mechanism. The 170 GHz gyrotron employing sapphire window is fabricated, and the power threshold calculated theoretically is verified, providing a reliable theoretical basis for the application of sapphire output window used in high power gyrotron.
