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RSS2016 Vol. 28, No. 02
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2016,
28: 021001.
doi: 10.11884/HPLPB201628.021001
Abstract:
Assessing the importance of every particle is the key factor to ensure the accuracy of the dim target tracking based on particle filter. A small dim target tracking algorithm based on particle sparse discriminative representation is proposed in this paper to cope with the issue of the uncertainty of moving target tracking. An adaptive discriminative over-complete dictionary is trained and constructed according to infrared image, wherein the target dictionary describes the target signals character and the background dictionary embeds the background clutter. It is helpful to highlight the difference between the target particle and the background particle in the adaptive discriminative over-complete dictionary. The importance of every particle is constructed based on the significant residual difference between target particle and background particle, and then the observation model of particle filter is estimated to track target state. Meanwhile, the subspace of the over-complete dictionary is updated online by the stochastic estimation algorithm. Some experiments were carried out and the experimental results show this proposed approach could not only enhance the target state estimation ability of particle, but also improve the adaptive ability and target recognition accuracy of small dim moving target.
Assessing the importance of every particle is the key factor to ensure the accuracy of the dim target tracking based on particle filter. A small dim target tracking algorithm based on particle sparse discriminative representation is proposed in this paper to cope with the issue of the uncertainty of moving target tracking. An adaptive discriminative over-complete dictionary is trained and constructed according to infrared image, wherein the target dictionary describes the target signals character and the background dictionary embeds the background clutter. It is helpful to highlight the difference between the target particle and the background particle in the adaptive discriminative over-complete dictionary. The importance of every particle is constructed based on the significant residual difference between target particle and background particle, and then the observation model of particle filter is estimated to track target state. Meanwhile, the subspace of the over-complete dictionary is updated online by the stochastic estimation algorithm. Some experiments were carried out and the experimental results show this proposed approach could not only enhance the target state estimation ability of particle, but also improve the adaptive ability and target recognition accuracy of small dim moving target.
2016,
28: 021002.
doi: 10.11884/HPLPB201628.021002
Abstract:
Computational fluid dynamics simulation was conducted in studying characteristics of fluid flow and heat transfer of microchannel cooler installed in a solid-state laser. Two-dimensional and three-dimensional physical models were developed, respectively, based on the cooler structure. Fluid flow within the microchannel was first investigated with the two models, then effects of Reynolds number and heat generation rate of crystal slice on fluid flow and heat transfer in the cooler were numerically examined. Results showed that the two-dimensional model was sufficient to describe the fluid flow and heat transfer behaviors in the laminar flow region in the rectangular microchannel between two parallel planes, and the three-dimensional model was more suitable for the transition region. When the Reynolds number was increased to the transition point, the effect of heat transfer from fluid flow was significantly enhanced. With the Reynolds number rising, the effect of the heat on minimum pressure required within the channel was gradually reduced. The change in the heat had an important influence on fluid flow, but little influence on Nusselt number and total pressure drop of the channel.
Computational fluid dynamics simulation was conducted in studying characteristics of fluid flow and heat transfer of microchannel cooler installed in a solid-state laser. Two-dimensional and three-dimensional physical models were developed, respectively, based on the cooler structure. Fluid flow within the microchannel was first investigated with the two models, then effects of Reynolds number and heat generation rate of crystal slice on fluid flow and heat transfer in the cooler were numerically examined. Results showed that the two-dimensional model was sufficient to describe the fluid flow and heat transfer behaviors in the laminar flow region in the rectangular microchannel between two parallel planes, and the three-dimensional model was more suitable for the transition region. When the Reynolds number was increased to the transition point, the effect of heat transfer from fluid flow was significantly enhanced. With the Reynolds number rising, the effect of the heat on minimum pressure required within the channel was gradually reduced. The change in the heat had an important influence on fluid flow, but little influence on Nusselt number and total pressure drop of the channel.
Statistical characteristics of vertical profile of refractive index structure parameter in gobi area
2016,
28: 021003.
doi: 10.11884/HPLPB201628.021003
Abstract:
Using the platforms of captive balloon and sounding balloon equipped with micro-temperature sensors, atmospheric refractive index structure parameter(C2n) had been measured in arid area for a long time. A statistical analysis based on experimental data of atmospheric refractive index structure parameter was carried out about the average C2n in daytime and nighttime, distribution of standard deviation on height, skewness and kurtosis, as well as the strength characteristics of seasonal variation. The obtained results show that there is a great difference on the ratio of arithmetic mean and logarithmic mean between day and night, the logarithmic mean value and standard deviation coefficient of C2n in daytime and nighttime generally decrease with height while they fluctuate at the same height, especially in nighttime; the difference of the right skewed and leptokurtic characteristics between day and night were indicated for different heights; seasonal changes have significant impact on the strength of turbulence distribution, as for the median turbulence and weak turbulence distribution change interactively at different height.
Using the platforms of captive balloon and sounding balloon equipped with micro-temperature sensors, atmospheric refractive index structure parameter(C2n) had been measured in arid area for a long time. A statistical analysis based on experimental data of atmospheric refractive index structure parameter was carried out about the average C2n in daytime and nighttime, distribution of standard deviation on height, skewness and kurtosis, as well as the strength characteristics of seasonal variation. The obtained results show that there is a great difference on the ratio of arithmetic mean and logarithmic mean between day and night, the logarithmic mean value and standard deviation coefficient of C2n in daytime and nighttime generally decrease with height while they fluctuate at the same height, especially in nighttime; the difference of the right skewed and leptokurtic characteristics between day and night were indicated for different heights; seasonal changes have significant impact on the strength of turbulence distribution, as for the median turbulence and weak turbulence distribution change interactively at different height.
2016,
28: 021004.
doi: 10.11884/HPLPB201628.021004
Abstract:
Acoustic field directivity patterns of longitudinal wave are theoretically and experimentally analyzed, when the oblique laser supported combustion wave exists. Based on laser ultrasonic generation mechanism, the normal displacement of particle in the far field is deduced under the condition that splash materially vertically impacts on the surface of workpiece. The directivity function is obtained, and the relevant factors are analyzed. A measurement system for directivity patterns is established to verify the function. Longitudinal wave is received by piezoelectric transducer whose peak frequency is 5 MHz in a state of laser supported combustion. The experimental data and theoretical data agree well with each other. For the longitudinal wave under the same size of spot, the directivity patterns become narrower with the increase of the inclined angle, which means that the energy of the longitudinal wave field is also more concentrated, but the angle of the acoustic beam axis remains unchanged.
Acoustic field directivity patterns of longitudinal wave are theoretically and experimentally analyzed, when the oblique laser supported combustion wave exists. Based on laser ultrasonic generation mechanism, the normal displacement of particle in the far field is deduced under the condition that splash materially vertically impacts on the surface of workpiece. The directivity function is obtained, and the relevant factors are analyzed. A measurement system for directivity patterns is established to verify the function. Longitudinal wave is received by piezoelectric transducer whose peak frequency is 5 MHz in a state of laser supported combustion. The experimental data and theoretical data agree well with each other. For the longitudinal wave under the same size of spot, the directivity patterns become narrower with the increase of the inclined angle, which means that the energy of the longitudinal wave field is also more concentrated, but the angle of the acoustic beam axis remains unchanged.
2016,
28: 021005.
doi: 10.11884/HPLPB201628.021005
Abstract:
Transverse stimulated Raman scattering (TSRS) gain coefficient in a large aperture 65% deuterated potassium dihydrogen phosphate (DKDP) is measured at 351 nm. The measurement involves the use of an optical fiber sensor system to detect Raman scattering light in the DKDP crystal. A Raman scattering gain coefficient of 0.109 cm/GW is obtained and will be used to set upper limit of the DKDP crystals in our laser facility to avoid the TSRS induced energy loss and laser damage. The effect of bulk damage on growth behavior of TSRS is also examined and it is found that bulk damage has little impact on the TSRS growth. Thus the influence of bulk damage on the measurement of TSRS gain coefficient can be ignored.
Transverse stimulated Raman scattering (TSRS) gain coefficient in a large aperture 65% deuterated potassium dihydrogen phosphate (DKDP) is measured at 351 nm. The measurement involves the use of an optical fiber sensor system to detect Raman scattering light in the DKDP crystal. A Raman scattering gain coefficient of 0.109 cm/GW is obtained and will be used to set upper limit of the DKDP crystals in our laser facility to avoid the TSRS induced energy loss and laser damage. The effect of bulk damage on growth behavior of TSRS is also examined and it is found that bulk damage has little impact on the TSRS growth. Thus the influence of bulk damage on the measurement of TSRS gain coefficient can be ignored.
2016,
28: 022001.
doi: 10.11884/HPLPB201628.022001
Abstract:
The imaging plate is an important tool in high power laser-matter interactions. The slit method is employed to measure the modulation transfer function of Fuji BAS-SR IP. Meanwhile, periodic streaks are used to verify the result. The cut-off space frequency of SR IP up to 17 lp/mm is demonstrated. The spatial dispersion of IP is simulated by the MC code FLUKA when it exposed to the 17.5 keV X-ray. Compared to the spatial dispersion of image scanned by scanner, much less spatial dispersion is engendered by IP. The results are helpful for the quantitative measure of IP, and improving the spatial resolution of IP in the experiments.
The imaging plate is an important tool in high power laser-matter interactions. The slit method is employed to measure the modulation transfer function of Fuji BAS-SR IP. Meanwhile, periodic streaks are used to verify the result. The cut-off space frequency of SR IP up to 17 lp/mm is demonstrated. The spatial dispersion of IP is simulated by the MC code FLUKA when it exposed to the 17.5 keV X-ray. Compared to the spatial dispersion of image scanned by scanner, much less spatial dispersion is engendered by IP. The results are helpful for the quantitative measure of IP, and improving the spatial resolution of IP in the experiments.
2016,
28: 022002.
doi: 10.11884/HPLPB201628.022002
Abstract:
AlMg alloy films with a thickness less than 5 m could be used as raw materials of precision cutting for ribbon array load in Z-pinch physics tests. In this paper, the thermal evaporation was used to prepare such ultrathin AlMg alloy films. By controlling the deposition rate of the thermal evaporation craft, AlMg alloy films with a thickness less than 5 m were coated on super-smooth NaCl substrate and after subsequent process of NaCl substrate solution, unbraced AlMg alloy films were achieved. Thickness uniformity, surface roughness, diffraction peak site, crystal grain size and elements component with different distances to surface were measured. It was found that in such a thermal evaporation way, the thickness uniformity of AlMg alloy films was better than 8%, the surface roughness (Ra) of both sides of samples less than 180 nm, the crystal grain size less than 20 nm. It was showed that diffraction peak site of samples with different thickness hardly displaced in the common meaning of few internal stress. It was also showed that the content of Mg element under different depths was stable, the impurity content of film surface was higher than that in the center place, and an anticipative component could be achieved under 6 nm depth stably. Prepared by thermal evaporation, unbraced AlMg alloy films with the characteristics of controllable and uniform thickness, stable component and few internal stress were applicable for ribbon array load of Z-pinch.
AlMg alloy films with a thickness less than 5 m could be used as raw materials of precision cutting for ribbon array load in Z-pinch physics tests. In this paper, the thermal evaporation was used to prepare such ultrathin AlMg alloy films. By controlling the deposition rate of the thermal evaporation craft, AlMg alloy films with a thickness less than 5 m were coated on super-smooth NaCl substrate and after subsequent process of NaCl substrate solution, unbraced AlMg alloy films were achieved. Thickness uniformity, surface roughness, diffraction peak site, crystal grain size and elements component with different distances to surface were measured. It was found that in such a thermal evaporation way, the thickness uniformity of AlMg alloy films was better than 8%, the surface roughness (Ra) of both sides of samples less than 180 nm, the crystal grain size less than 20 nm. It was showed that diffraction peak site of samples with different thickness hardly displaced in the common meaning of few internal stress. It was also showed that the content of Mg element under different depths was stable, the impurity content of film surface was higher than that in the center place, and an anticipative component could be achieved under 6 nm depth stably. Prepared by thermal evaporation, unbraced AlMg alloy films with the characteristics of controllable and uniform thickness, stable component and few internal stress were applicable for ribbon array load of Z-pinch.
2016,
28: 022003.
doi: 10.11884/HPLPB201628.022003
Abstract:
With increasing of deposition machines dimension, the growth process of thin film material will show new phenomena. In order to get homogenous large caliber optical thin film, different single SiO2 layers were fabricated using ion-assisted electric gun evaporation under different ion source energy, deposition pressure, substrate temperature and different rotation speed. Spectroscopic ellipsometry and spectrometer were used to measure SiO2 samples ellipsometric parameters and transmission spectra, respectively. Refractive index and its distribution were got by fitting the corresponding measurement results. It is shown that rotation speed is the main cause for the inhomogeneity of large caliber SiO2 thin film. Ion source energy, deposition pressure and substrate temperature can modulate the inhomogeneity by affecting SiO2 thin films growing process. When the rotation speed is limited for large dimension optical elements, homogenous optical thin film can also be got by optimizing other deposition parameters.
With increasing of deposition machines dimension, the growth process of thin film material will show new phenomena. In order to get homogenous large caliber optical thin film, different single SiO2 layers were fabricated using ion-assisted electric gun evaporation under different ion source energy, deposition pressure, substrate temperature and different rotation speed. Spectroscopic ellipsometry and spectrometer were used to measure SiO2 samples ellipsometric parameters and transmission spectra, respectively. Refractive index and its distribution were got by fitting the corresponding measurement results. It is shown that rotation speed is the main cause for the inhomogeneity of large caliber SiO2 thin film. Ion source energy, deposition pressure and substrate temperature can modulate the inhomogeneity by affecting SiO2 thin films growing process. When the rotation speed is limited for large dimension optical elements, homogenous optical thin film can also be got by optimizing other deposition parameters.
2016,
28: 022004.
doi: 10.11884/HPLPB201628.022004
Abstract:
Emittance is one of the most important parameters for electron beams. Based on the emittance and transfer martrix, beam envelope and angular divergence can be precisely calculated. Considering the limitation of traditional emittance measurement methods, we employed the multi-slit method to measure the emittance of the laser wakefield accelerated electron beams. In our simulation, the slit width was set as 20 m, the emittance was 0.05 mmmrad. We have achieved a good consistence with 5% relative error between the measured emittance and the given emittance. We also observed the effect of different parameters on the precisions of measured emittance. It is concluded that the slit width is the most important parameter, the emittance measurement is more accurate with the narrower slit width.
Emittance is one of the most important parameters for electron beams. Based on the emittance and transfer martrix, beam envelope and angular divergence can be precisely calculated. Considering the limitation of traditional emittance measurement methods, we employed the multi-slit method to measure the emittance of the laser wakefield accelerated electron beams. In our simulation, the slit width was set as 20 m, the emittance was 0.05 mmmrad. We have achieved a good consistence with 5% relative error between the measured emittance and the given emittance. We also observed the effect of different parameters on the precisions of measured emittance. It is concluded that the slit width is the most important parameter, the emittance measurement is more accurate with the narrower slit width.
2016,
28: 022005.
doi: 10.11884/HPLPB201628.022005
Abstract:
In order to mitigate the effect of the strong electromagnetic pulse, which produces laser-plasma interactions, we designed a new streaked X-ray spectrometer (SXS) enclosed within a well-sealed, electromagnetic interference-free cavity. The SXS can cover a wide selection of spectral windows using interchangeable Bragg crystals and by appropriate adjustment of the Bragg angle. The SXS has been used to observe time-resolved X-ray spectrum in the 2.5 keV to 3.5 keV photon-energy range, resulting in a demonstrated spectral resolution of about 13 at 2960 eV with a time resolution of 10 ps. The observed time and spectral resolutions demonstrate the applicability of the SXS for studies of laser-produced plasmas.
In order to mitigate the effect of the strong electromagnetic pulse, which produces laser-plasma interactions, we designed a new streaked X-ray spectrometer (SXS) enclosed within a well-sealed, electromagnetic interference-free cavity. The SXS can cover a wide selection of spectral windows using interchangeable Bragg crystals and by appropriate adjustment of the Bragg angle. The SXS has been used to observe time-resolved X-ray spectrum in the 2.5 keV to 3.5 keV photon-energy range, resulting in a demonstrated spectral resolution of about 13 at 2960 eV with a time resolution of 10 ps. The observed time and spectral resolutions demonstrate the applicability of the SXS for studies of laser-produced plasmas.
2016,
28: 022006.
doi: 10.11884/HPLPB201628.022006
Abstract:
In order to inspect the surface topography of spherical target accurately, efficiently and exhaustively, which is the core component in inertial confinement fusion experiment, a shape detection system is founded based on the technologies of sub-aperture stitching and diffraction interferometry. The basic testing principle and the calculation method of lateral resolution in once single measurement are provided. The configuration of sub-aperture is planned for the rotation scanning of the target. In order to solve the problem that the matching algorithm shows a slow convergence rate or even misconvergence caused by the overlarge lateral distance between cloud data points, a method of data points transverse compression is proposed, which replaces the actual radius of curvature by a virtual tiny radius. This method can improve the matching rate and the accuracy of the algorithm with the topography feature remaining unchanged. At last, a gold coated target with a diameter of 1mm is measured actually, and the PV value and RMS value of the relative topography errors after stitched are 1.332 and 0.479 respectively. The macroscopic fluctuation characteristics and the partial topography detail can be obtained, and the refactored target surface has a good visual quality.
In order to inspect the surface topography of spherical target accurately, efficiently and exhaustively, which is the core component in inertial confinement fusion experiment, a shape detection system is founded based on the technologies of sub-aperture stitching and diffraction interferometry. The basic testing principle and the calculation method of lateral resolution in once single measurement are provided. The configuration of sub-aperture is planned for the rotation scanning of the target. In order to solve the problem that the matching algorithm shows a slow convergence rate or even misconvergence caused by the overlarge lateral distance between cloud data points, a method of data points transverse compression is proposed, which replaces the actual radius of curvature by a virtual tiny radius. This method can improve the matching rate and the accuracy of the algorithm with the topography feature remaining unchanged. At last, a gold coated target with a diameter of 1mm is measured actually, and the PV value and RMS value of the relative topography errors after stitched are 1.332 and 0.479 respectively. The macroscopic fluctuation characteristics and the partial topography detail can be obtained, and the refactored target surface has a good visual quality.
2016,
28: 023001.
doi: 10.11884/HPLPB201628.023001
Abstract:
An algorithm for precisely calculating the inductance of a three-section solenoid is presented, which is based on summing the layer self-inductances and the mutual inductances. A theoretical model with explicit expressions is firstly developed to calculate the self-inductance of a single layer, and then numerical calculation of the mutual inductance between two layers is introduced. Using the presented computation method, the inductance of a solenoid designed in the experiment is successfully calculated (4.30 mH), which has a difference of less than 1% from the experimental data.
An algorithm for precisely calculating the inductance of a three-section solenoid is presented, which is based on summing the layer self-inductances and the mutual inductances. A theoretical model with explicit expressions is firstly developed to calculate the self-inductance of a single layer, and then numerical calculation of the mutual inductance between two layers is introduced. Using the presented computation method, the inductance of a solenoid designed in the experiment is successfully calculated (4.30 mH), which has a difference of less than 1% from the experimental data.
2016,
28: 023002.
doi: 10.11884/HPLPB201628.023002
Abstract:
This paper studied the dispersion of the gyro-TWT with a helical waveguide, and the dispersion equations were obtained by theoretic analysis. The dispersion curves were studied through numerical computation. The paper mainly analyzed how the change of the structure parameters would affect the dispersion characteristics. Reasonable structure parameters were given. By using the electromagnetic simulation software CST, the operating eigenwave of helical waveguide with given parameters was calculated and compared with theoretical data.
This paper studied the dispersion of the gyro-TWT with a helical waveguide, and the dispersion equations were obtained by theoretic analysis. The dispersion curves were studied through numerical computation. The paper mainly analyzed how the change of the structure parameters would affect the dispersion characteristics. Reasonable structure parameters were given. By using the electromagnetic simulation software CST, the operating eigenwave of helical waveguide with given parameters was calculated and compared with theoretical data.
2016,
28: 023003.
doi: 10.11884/HPLPB201628.023003
Abstract:
With the electromagnetic code, the buncher and output section of an S-band broadband relativistic klystron amplifier (RKA) are designed and calculated. Three stagger-tuned bunching cavities are used to modulate the electron beam to achieve a bandwidth of 11% when the depth of the fundamental harmonic current is not less than 80%. In order to enhance the bandwidth of the output circuit for RKA, the overlapped mode double-gap output cavity is modeled and simulated. The two modes are overlapped when the structure parameters of the output cavity are appropriate. And the output circuit bandwidth reaches 15% at 80% depth of the fundamental harmonic current. A maximum output power of 1.58 GW and a 10% working bandwidth of 3 dB are obtained by adjusting the frequency and the power of the driven microwave in the particle-in-cell simulation with the designed structure of the whole broadband relativistic klystron amplifier, and the power in the bandwidth is not less than 1 GW.
With the electromagnetic code, the buncher and output section of an S-band broadband relativistic klystron amplifier (RKA) are designed and calculated. Three stagger-tuned bunching cavities are used to modulate the electron beam to achieve a bandwidth of 11% when the depth of the fundamental harmonic current is not less than 80%. In order to enhance the bandwidth of the output circuit for RKA, the overlapped mode double-gap output cavity is modeled and simulated. The two modes are overlapped when the structure parameters of the output cavity are appropriate. And the output circuit bandwidth reaches 15% at 80% depth of the fundamental harmonic current. A maximum output power of 1.58 GW and a 10% working bandwidth of 3 dB are obtained by adjusting the frequency and the power of the driven microwave in the particle-in-cell simulation with the designed structure of the whole broadband relativistic klystron amplifier, and the power in the bandwidth is not less than 1 GW.
2016,
28: 023004.
doi: 10.11884/HPLPB201628.023004
Abstract:
Based on the S-band classical pill-box window, Monte Carlo (MC) numerical simulation was performed to study the multipactor regime. The behavior of the multipactor under multi-mode (TE11 mode and TM11 mode) electric field in the S-band classical pill-box window loaded with 2 distinct window disks was investigated. The characteristics of one-sided multipactor and two-sided multipactor in the pill-box window were analyzed. It was proved that the two-sided multipactor would be excited between the copper wall and the window disk under the effect of TM11 mode in the surface of un-coated window disk when low power was transmitting. In addition, the one-sided multipactor would be apparent in the center of window disk when high power was transmitting.
Based on the S-band classical pill-box window, Monte Carlo (MC) numerical simulation was performed to study the multipactor regime. The behavior of the multipactor under multi-mode (TE11 mode and TM11 mode) electric field in the S-band classical pill-box window loaded with 2 distinct window disks was investigated. The characteristics of one-sided multipactor and two-sided multipactor in the pill-box window were analyzed. It was proved that the two-sided multipactor would be excited between the copper wall and the window disk under the effect of TM11 mode in the surface of un-coated window disk when low power was transmitting. In addition, the one-sided multipactor would be apparent in the center of window disk when high power was transmitting.
2016,
28: 023101.
doi: 10.11884/HPLPB201628.023101
Abstract:
Using CST Microwave Studio，the dispersion characteristics of a staggered double rectangular grating slow wave structure(SDRG SWS) is calculated, and the structure parameters of SDRG SWS for a 0.22 THz（D band） traveling wave tube(TWT) are determined based on the dispersion data. Then phase velocity re-synchronization techniques are applied in D band TWT based on SDRG SWS, and four D band TWTs which have different period configurations are simulated by CST PIC solver. The results demonstrate that the phase velocity re-synchronization techniques have raised output power level from 10-13 W to 19-28 W, as well as electron efficiency from 1.4%-2.2% to 2.6%-3.9% within 218-232 GHz in those TWTs which has a concentrated attenuator, and have raised output power level from 8-16.8 W to 32-41 W, as well as electron efficiency from 1.5%-2.8% to 4.4%-5.7% within 218-232 GHz in those TWTs which has not a concentrated attenuator. Besides, whether a TWT has a concentrated attenuator or not, phase velocity re-synchronization techniques have obviously improved its gain flatness.
Using CST Microwave Studio，the dispersion characteristics of a staggered double rectangular grating slow wave structure(SDRG SWS) is calculated, and the structure parameters of SDRG SWS for a 0.22 THz（D band） traveling wave tube(TWT) are determined based on the dispersion data. Then phase velocity re-synchronization techniques are applied in D band TWT based on SDRG SWS, and four D band TWTs which have different period configurations are simulated by CST PIC solver. The results demonstrate that the phase velocity re-synchronization techniques have raised output power level from 10-13 W to 19-28 W, as well as electron efficiency from 1.4%-2.2% to 2.6%-3.9% within 218-232 GHz in those TWTs which has a concentrated attenuator, and have raised output power level from 8-16.8 W to 32-41 W, as well as electron efficiency from 1.5%-2.8% to 4.4%-5.7% within 218-232 GHz in those TWTs which has not a concentrated attenuator. Besides, whether a TWT has a concentrated attenuator or not, phase velocity re-synchronization techniques have obviously improved its gain flatness.
2016,
28: 023102.
doi: 10.11884/HPLPB201628.023102
Abstract:
This paper presents D-band SiGe power amplifier(PA) developed by using the 0.13 m SiGe BiCMOS technology. Building blocks of a 4-way amplifier are implemented using three-stage cascode power amplifier units, and T-junction networks are used for power combining and splitting. The PA chip works in 125-150 GHz, and achieves a small-signal biggest gain of 21 dB at 131 GHz, with a small-signal lowest gain of 17 dB at 150 GHz. The PA module exhibits a saturated output power of 13.6 dBm and an output 1 dB gain compression power of 12.9 dBm at 139 GHz.
This paper presents D-band SiGe power amplifier(PA) developed by using the 0.13 m SiGe BiCMOS technology. Building blocks of a 4-way amplifier are implemented using three-stage cascode power amplifier units, and T-junction networks are used for power combining and splitting. The PA chip works in 125-150 GHz, and achieves a small-signal biggest gain of 21 dB at 131 GHz, with a small-signal lowest gain of 17 dB at 150 GHz. The PA module exhibits a saturated output power of 13.6 dBm and an output 1 dB gain compression power of 12.9 dBm at 139 GHz.
2016,
28: 023103.
doi: 10.11884/HPLPB201628.023103
Abstract:
Schottky diode detector is one of the key devices of THz wireless communication system. In order to make further research on the nonlinear characteristic of a Schottky diode detector (SBD), a model was established based on Ritz-Galerkin method. Meanwhile, the model has been used to predict the output and the sensitivity of the detector, which indicates this model can precisely predict the performance of the detector. Finally, the influences of the power levels, load resistance and temperature on nonlinearity behavior of the SBD in 0.34 THz were investigated by this model, which indicates that the diode detectors exhibit true square-law to a linear law with an increase of power level is correct only under restrictive conditions, and that slopes corresponding to higher-order effect can be easily encountered in practical situations.
Schottky diode detector is one of the key devices of THz wireless communication system. In order to make further research on the nonlinear characteristic of a Schottky diode detector (SBD), a model was established based on Ritz-Galerkin method. Meanwhile, the model has been used to predict the output and the sensitivity of the detector, which indicates this model can precisely predict the performance of the detector. Finally, the influences of the power levels, load resistance and temperature on nonlinearity behavior of the SBD in 0.34 THz were investigated by this model, which indicates that the diode detectors exhibit true square-law to a linear law with an increase of power level is correct only under restrictive conditions, and that slopes corresponding to higher-order effect can be easily encountered in practical situations.
2016,
28: 023104.
doi: 10.11884/HPLPB201628.023104
Abstract:
For the applications of vanadium dioxide (VO2) thin film in terahertz tunable functional devices, the vanadium dioxide VO2 thin film was prepared by magnetron sputtering technique on K9 glass substrate, and the crystal structure was characterized by X-ray diffraction (XRD). Spectral characteristics and their variations of terahertz (THz) reflection and transmission signal passing through the sample at different temperatures were studied by the THz time domain spectroscopy system (THz-TDS) equipped with heating device. The experimental results indicated that the semiconductor-metal transition of VO2 thin film occurred with the increase of the heating temperature and showed excellent modulation to the broadband THz wave. The modulation depth was dependent on the THz frequency. The THz wave amplitude modulation depth of reflection power and transmission showed remarkable fluctuation in the band of 0.3-0.5 THz. The transmittance of THz wave was larger in the low frequency band than that in the high frequency band, and the modulation depth varied in the range of 35%-65%. The thin film was prepared simply and had high quality, which can be applied to THz modulator functions such as devices and switches.
For the applications of vanadium dioxide (VO2) thin film in terahertz tunable functional devices, the vanadium dioxide VO2 thin film was prepared by magnetron sputtering technique on K9 glass substrate, and the crystal structure was characterized by X-ray diffraction (XRD). Spectral characteristics and their variations of terahertz (THz) reflection and transmission signal passing through the sample at different temperatures were studied by the THz time domain spectroscopy system (THz-TDS) equipped with heating device. The experimental results indicated that the semiconductor-metal transition of VO2 thin film occurred with the increase of the heating temperature and showed excellent modulation to the broadband THz wave. The modulation depth was dependent on the THz frequency. The THz wave amplitude modulation depth of reflection power and transmission showed remarkable fluctuation in the band of 0.3-0.5 THz. The transmittance of THz wave was larger in the low frequency band than that in the high frequency band, and the modulation depth varied in the range of 35%-65%. The thin film was prepared simply and had high quality, which can be applied to THz modulator functions such as devices and switches.
2016,
28: 023201.
doi: 10.11884/HPLPB201628.023201
Abstract:
The susceptibility of field coupling to transmission line inside a rectangular metallic enclosure is investigated. Dyadic Green function is used to calculate the electromagnetic field distribution inside the enclosure, and Agrawal-model is used to obtain the current induced on a single wire due to field coupling. Then, influences on the induced current resulted from the perturbations of the enclosure dimensions, the position of the electromagnetic interference source and the position of the single wire are discussed. The results show that the slight variation of both enclosure dimension size and interference source position may greatly influence the disturbance on terminal loads. Moreover, the disturbance on the load is susceptible to the change of the endpoints position of the wire, while it is insensitive to the slight variation of height above the metallic wall.
The susceptibility of field coupling to transmission line inside a rectangular metallic enclosure is investigated. Dyadic Green function is used to calculate the electromagnetic field distribution inside the enclosure, and Agrawal-model is used to obtain the current induced on a single wire due to field coupling. Then, influences on the induced current resulted from the perturbations of the enclosure dimensions, the position of the electromagnetic interference source and the position of the single wire are discussed. The results show that the slight variation of both enclosure dimension size and interference source position may greatly influence the disturbance on terminal loads. Moreover, the disturbance on the load is susceptible to the change of the endpoints position of the wire, while it is insensitive to the slight variation of height above the metallic wall.
2016,
28: 024001.
doi: 10.11884/HPLPB201628.024001
Abstract:
In order to improve the triangular mesh quality of the mesh models reconstructed by industrial CT slice images, the mesh regularization algorithm combining the vertex adjustment and feature factors was presented. Introducing the improvement degree of the local mesh quality and the model feature factors as the control condition of the mesh adjustment, the local detail features of the original model were retained. The way of self-adaptive control mesh adjustment was adopted according to the normal vector threshold increasing regularity, different curvature features were identified automatically. Compared with the existing methods, experimental results show that the presented method can better regulate the triangular mesh while preserving the details features of the original model.
In order to improve the triangular mesh quality of the mesh models reconstructed by industrial CT slice images, the mesh regularization algorithm combining the vertex adjustment and feature factors was presented. Introducing the improvement degree of the local mesh quality and the model feature factors as the control condition of the mesh adjustment, the local detail features of the original model were retained. The way of self-adaptive control mesh adjustment was adopted according to the normal vector threshold increasing regularity, different curvature features were identified automatically. Compared with the existing methods, experimental results show that the presented method can better regulate the triangular mesh while preserving the details features of the original model.
2016,
28: 024002.
doi: 10.11884/HPLPB201628.024002
Abstract:
LiF(Mg, Ti)-M thermoluminescence dosimestries(TLDs) are studied and their uniformity, repeatability and linearity of the response to rays are compared. The mean and standard deviation of their readout values are measured. The variable coefficients of their sensitivities under different absorbed doses are analyzed and the influence of the irradiation of high dose beyond linearity upper limit on linearity is obtained. The results indicate that the LiF(Mg, Ti)-M TLD produced by Beijing Research Institute of Chemical Defence exhibits the best performance. For the samples of this type of TLD whose absorbed dose is 6 Gy(Si), the variable coefficient of their readout values is 3.11% and the repeatability indicator is within 5%. The linearity upper limit of this type of TLD is within 50~100 Gy(Si). The drifting of the sensitivity of this type of TLD after exposure to 150 Gy(Si) and annealing is about 11%.
LiF(Mg, Ti)-M thermoluminescence dosimestries(TLDs) are studied and their uniformity, repeatability and linearity of the response to rays are compared. The mean and standard deviation of their readout values are measured. The variable coefficients of their sensitivities under different absorbed doses are analyzed and the influence of the irradiation of high dose beyond linearity upper limit on linearity is obtained. The results indicate that the LiF(Mg, Ti)-M TLD produced by Beijing Research Institute of Chemical Defence exhibits the best performance. For the samples of this type of TLD whose absorbed dose is 6 Gy(Si), the variable coefficient of their readout values is 3.11% and the repeatability indicator is within 5%. The linearity upper limit of this type of TLD is within 50~100 Gy(Si). The drifting of the sensitivity of this type of TLD after exposure to 150 Gy(Si) and annealing is about 11%.
2016,
28: 024003.
doi: 10.11884/HPLPB201628.024003
Abstract:
Based on the radiographic physics, the imaging formula with various physical quantities is presented for the basic layout of flash radiography with the anti-scatter grid camera. Before reducing the formula, the role of the anti-scatter grid camera is discussed through numerical simulation and theoretical analysis in limiting X-ray scatter and noise and blur, and the radiographic method with the anti-scatter grid camera is explored. It is shown that the anti-scatter grid camera is provided with high sensitive, little scatter and high resolution. Therefore, the formula of the transmission image with only the point spread function of X-ray source can be obtained through twice radiographing with/without the graded collimator and object.
Based on the radiographic physics, the imaging formula with various physical quantities is presented for the basic layout of flash radiography with the anti-scatter grid camera. Before reducing the formula, the role of the anti-scatter grid camera is discussed through numerical simulation and theoretical analysis in limiting X-ray scatter and noise and blur, and the radiographic method with the anti-scatter grid camera is explored. It is shown that the anti-scatter grid camera is provided with high sensitive, little scatter and high resolution. Therefore, the formula of the transmission image with only the point spread function of X-ray source can be obtained through twice radiographing with/without the graded collimator and object.
2016,
28: 024101.
doi: 10.11884/HPLPB201628.024101
Abstract:
The MEMS bionic vector hydrophone is a new type of underwater acoustic sensor, whose working performance is determined by the geometrical, material and environmental parameters of the internal MEMS acoustic-electric transduction microstructure. In order to have an insight of this kind of hydrophone and improve its working performance, the single degree of a freedom equivalent mechanical model of the microstructure is established through reasonable simplification. On this basis, the first order natural frequency of the micro structure of the hydrophone currently used is calculated, and an experimental platform is built to verify the calculated result. The results show that the error between the theoretical value and the experimental value is less than 5%, which verifies the validity of the mechanical model. This mechanical model provides a theoretical basis and reference for the design and optimization of the hydrophone and it is also a foundation for the performance analysis of sensors with similar structure.
The MEMS bionic vector hydrophone is a new type of underwater acoustic sensor, whose working performance is determined by the geometrical, material and environmental parameters of the internal MEMS acoustic-electric transduction microstructure. In order to have an insight of this kind of hydrophone and improve its working performance, the single degree of a freedom equivalent mechanical model of the microstructure is established through reasonable simplification. On this basis, the first order natural frequency of the micro structure of the hydrophone currently used is calculated, and an experimental platform is built to verify the calculated result. The results show that the error between the theoretical value and the experimental value is less than 5%, which verifies the validity of the mechanical model. This mechanical model provides a theoretical basis and reference for the design and optimization of the hydrophone and it is also a foundation for the performance analysis of sensors with similar structure.
2016,
28: 025001.
doi: 10.11884/HPLPB201628.025001
Abstract:
The impedance of an azimuthal transmission line should be accurately evaluated when we design and model the induction cavity of an induction voltage adder generator. Because of the complexity of the azimuthal transmission line, the impedance cannot be derived analytically. One method to calculate the impedance of a complex structure transmission line is introduced in this paper. This method is based on the telegraph equation and the transient EM simulation. The impedances of the azimuthal transmission lines with constant width and variable width are evaluated by using this method. The results show that the impedance of the azimuthal transmission line can be estimated by micro-strip transmission line formula, which is more accurate than the triplate transmission line formula.
The impedance of an azimuthal transmission line should be accurately evaluated when we design and model the induction cavity of an induction voltage adder generator. Because of the complexity of the azimuthal transmission line, the impedance cannot be derived analytically. One method to calculate the impedance of a complex structure transmission line is introduced in this paper. This method is based on the telegraph equation and the transient EM simulation. The impedances of the azimuthal transmission lines with constant width and variable width are evaluated by using this method. The results show that the impedance of the azimuthal transmission line can be estimated by micro-strip transmission line formula, which is more accurate than the triplate transmission line formula.
2016,
28: 025002.
doi: 10.11884/HPLPB201628.025002
Abstract:
The electromagnetic environment generated by radiating-wave simulators could simulate the free fields of the high altitude electromagnetic pulse (HEMP) approximately. However, the electromagnetic fields imposed on the devices under the real threat environments were the synthesized fields from the incident waves and the reflected waves. The total fields synthesized by the incident and reflected waves of the free electromagnetic fields on different situations above the lossy earth were calculated. Through comparing the field strengths and waveforms of the total fields with the initial incident waves, the features of the synthesized fields nearby the ground were analyzed. An equivalent calculating method from the simulated environment to the real environment was suggested, and the correction factor of the simulated environment was calculated using this method for the 45 polarized incident wave. Based on the results, we proposed that the devices should be tested for at least three mutually orthogonal orientations and electromagnetic pulse widths should be reduced appropriately for the experiments of radiating-wave simulators.
The electromagnetic environment generated by radiating-wave simulators could simulate the free fields of the high altitude electromagnetic pulse (HEMP) approximately. However, the electromagnetic fields imposed on the devices under the real threat environments were the synthesized fields from the incident waves and the reflected waves. The total fields synthesized by the incident and reflected waves of the free electromagnetic fields on different situations above the lossy earth were calculated. Through comparing the field strengths and waveforms of the total fields with the initial incident waves, the features of the synthesized fields nearby the ground were analyzed. An equivalent calculating method from the simulated environment to the real environment was suggested, and the correction factor of the simulated environment was calculated using this method for the 45 polarized incident wave. Based on the results, we proposed that the devices should be tested for at least three mutually orthogonal orientations and electromagnetic pulse widths should be reduced appropriately for the experiments of radiating-wave simulators.
2016,
28: 025003.
doi: 10.11884/HPLPB201628.025003
Abstract:
In this paper, a switch is used as a crowbar to suppress the muzzle arc. The switch has low resistance when it is triggered. The results are compared between two experiments in which the crowbar switch is or not triggered just before the muzzle timing. When the crowbar switch is triggered, the muzzle voltage reduces obviously, almost all current flows through the crowbar switch, images obtained from high-speed photography show that the light intensity of muzzle arc is decreased visibly. It is also found that the conduction of the crowbar switch is delayed compared to the triggered signal. The delay affect the performance of the arc suppressing.
In this paper, a switch is used as a crowbar to suppress the muzzle arc. The switch has low resistance when it is triggered. The results are compared between two experiments in which the crowbar switch is or not triggered just before the muzzle timing. When the crowbar switch is triggered, the muzzle voltage reduces obviously, almost all current flows through the crowbar switch, images obtained from high-speed photography show that the light intensity of muzzle arc is decreased visibly. It is also found that the conduction of the crowbar switch is delayed compared to the triggered signal. The delay affect the performance of the arc suppressing.
2016,
28: 025004.
doi: 10.11884/HPLPB201628.025004
Abstract:
A solid state high power long pulse generator has been designed and constructed based on the key technologies of magnetic switch, low impedance pulse forming line, and inductive voltage adder, which was verified by single mode operation for peak power of 2 GW. For repetitive operation, a repetitive primary power supply of moderate voltage level was developed, the two stage magnetic pulse compressor was improved from aspects of reset and insulation, the pulsed charging was optimized where the inductive voltage adder was utilized for pulsed voltage step-up as well as for pulse charging and on-line direct current (DC) reset was achieved by reasonable design of reset current path. At present, the experimental results achieved on a dummy load are output pulsed power of 2.1 GW, pulse width of 170 ns, repetitive rate of 20 Hz, operation time of 1 s and good for repeatability. For further improvement, the pseudospark switch would be replaced by serial connected thyristors to accomplish all solid-state design.
A solid state high power long pulse generator has been designed and constructed based on the key technologies of magnetic switch, low impedance pulse forming line, and inductive voltage adder, which was verified by single mode operation for peak power of 2 GW. For repetitive operation, a repetitive primary power supply of moderate voltage level was developed, the two stage magnetic pulse compressor was improved from aspects of reset and insulation, the pulsed charging was optimized where the inductive voltage adder was utilized for pulsed voltage step-up as well as for pulse charging and on-line direct current (DC) reset was achieved by reasonable design of reset current path. At present, the experimental results achieved on a dummy load are output pulsed power of 2.1 GW, pulse width of 170 ns, repetitive rate of 20 Hz, operation time of 1 s and good for repeatability. For further improvement, the pseudospark switch would be replaced by serial connected thyristors to accomplish all solid-state design.
2016,
28: 025005.
doi: 10.11884/HPLPB201628.025005
Abstract:
The tri-electrode gas switch and two-electrode rail-gap switch were designed. Experiments for breakdown-voltage and repetitive operation of these switches were done in different gas pressure and gap conditions. The results show the relation between breakdown-voltage and gas pressure is linear. Breakdown-voltage of two-electrode rail-gap switch with 8 mm gap can be adjusted from 90 to 125 kV at gas pressure 0.1 to 0.2 MPa. Operating voltage of trigger switch with 7 mm gap can be adjusted from 40 to 95 kV. Repetitive operation rate of these switches was up to 20 Hz with 20 kA current. Based on these switches, an 8-stage compact Marx generator was setup. Multi-pulse output with 5 or 10 Hz repetitive rate was gained in experiments. The output peak power was about 7 GW for 5 Hz, and 3.5 GW for 10 Hz with pulse width (FWHM) of 150 ns.
The tri-electrode gas switch and two-electrode rail-gap switch were designed. Experiments for breakdown-voltage and repetitive operation of these switches were done in different gas pressure and gap conditions. The results show the relation between breakdown-voltage and gas pressure is linear. Breakdown-voltage of two-electrode rail-gap switch with 8 mm gap can be adjusted from 90 to 125 kV at gas pressure 0.1 to 0.2 MPa. Operating voltage of trigger switch with 7 mm gap can be adjusted from 40 to 95 kV. Repetitive operation rate of these switches was up to 20 Hz with 20 kA current. Based on these switches, an 8-stage compact Marx generator was setup. Multi-pulse output with 5 or 10 Hz repetitive rate was gained in experiments. The output peak power was about 7 GW for 5 Hz, and 3.5 GW for 10 Hz with pulse width (FWHM) of 150 ns.
2016,
28: 025006.
doi: 10.11884/HPLPB201628.025006
Abstract:
This paper addresses parameters and setup of diagnostics for Z-pinch study on PTS. Experimental results of single and nested wire array Z-pinch implosion dynamics and radiation characteristics are presented, with wire number in a range from 132 to 300, wire diameter in a range from 5 to 10 m, wire array diameter in a range from 13 to 30 mm. Experimental results reveal that, stagnation time of W wire array Z-pinch agree with 0-D thin shell calculation, however implosion trajectories diverges. Acceleration inferred by trajectory starts at about 67% of implosion time, thus indicates an ablation dominated pinch. With increasing of load linear mass and initial radius, load current increases, implosion time increases correspondingly. Meanwhile, X-ray pulse width increases and peak power decreases. Comparing implosion images of single and nested array, better uniformity and simultaneity are produced with nested array implosion, with an enhancement of peak radiation power. Total radiation energies produced by single array and nested array are comparable, with an energy conversion ratio of 15%。Preliminary results of dynamic hohlraum study and a comparison to wire array Z-pinch experiment are presented.
This paper addresses parameters and setup of diagnostics for Z-pinch study on PTS. Experimental results of single and nested wire array Z-pinch implosion dynamics and radiation characteristics are presented, with wire number in a range from 132 to 300, wire diameter in a range from 5 to 10 m, wire array diameter in a range from 13 to 30 mm. Experimental results reveal that, stagnation time of W wire array Z-pinch agree with 0-D thin shell calculation, however implosion trajectories diverges. Acceleration inferred by trajectory starts at about 67% of implosion time, thus indicates an ablation dominated pinch. With increasing of load linear mass and initial radius, load current increases, implosion time increases correspondingly. Meanwhile, X-ray pulse width increases and peak power decreases. Comparing implosion images of single and nested array, better uniformity and simultaneity are produced with nested array implosion, with an enhancement of peak radiation power. Total radiation energies produced by single array and nested array are comparable, with an energy conversion ratio of 15%。Preliminary results of dynamic hohlraum study and a comparison to wire array Z-pinch experiment are presented.
2016,
28: 025007.
doi: 10.11884/HPLPB201628.025007
Abstract:
The flash X-ray generator with an industrial X-ray diode would be widely applied in research and industrial detection, which is capable of generating intense x-ray under high repetitive frame. An industrial X-ray diode was driven by the pulsed power supply under 100 Hz to 1 kHz, whose copper cathode was heated to analyze how the surface adsorption affects the electrons emission process. Plasma diffuse processes were investigated simply based on voltage duration and impedance model. The study shows that explosive emission electrons come from gas desorption on copper cathode surface, and the key factor affecting repetitive rate is not diode recovery. Gas absorption velocity between shots is under no more than 1 kHz, so it is a groundwork to develop a novel cathode capable of supplying enough electron beam with high repetitive rate.
The flash X-ray generator with an industrial X-ray diode would be widely applied in research and industrial detection, which is capable of generating intense x-ray under high repetitive frame. An industrial X-ray diode was driven by the pulsed power supply under 100 Hz to 1 kHz, whose copper cathode was heated to analyze how the surface adsorption affects the electrons emission process. Plasma diffuse processes were investigated simply based on voltage duration and impedance model. The study shows that explosive emission electrons come from gas desorption on copper cathode surface, and the key factor affecting repetitive rate is not diode recovery. Gas absorption velocity between shots is under no more than 1 kHz, so it is a groundwork to develop a novel cathode capable of supplying enough electron beam with high repetitive rate.
2016,
28: 025008.
doi: 10.11884/HPLPB201628.025008
Abstract:
In order to analysis the electromagnetic railgun in-bore magnetic field distribution characteristic at zero speed, a two-dimensional railgun computational model is built. Based on the magnetic diffusion equation and Amperes law, the current density in each part of the rail and armature is obtained. Through the Biot and Savarts law, the magnetic flux density of the investigated point which locates in front of the armature is calculated, Based on the electromagnetic induction method, the magnetic field measurement experiments are carried out. The experimental values are in agreement with the calculation values. The results show that the magnitude of the magnetic field is determined by the current flowing through the armature and rails. To the investigated points in the central axis in front of the armature, the magnetic flux density decreases with the increase of the distance from the investigated point to armature, but the decay rate is gradually smaller. The results are helpful for the in-bore magnetic field shielding and intelligent ammunition design.
In order to analysis the electromagnetic railgun in-bore magnetic field distribution characteristic at zero speed, a two-dimensional railgun computational model is built. Based on the magnetic diffusion equation and Amperes law, the current density in each part of the rail and armature is obtained. Through the Biot and Savarts law, the magnetic flux density of the investigated point which locates in front of the armature is calculated, Based on the electromagnetic induction method, the magnetic field measurement experiments are carried out. The experimental values are in agreement with the calculation values. The results show that the magnitude of the magnetic field is determined by the current flowing through the armature and rails. To the investigated points in the central axis in front of the armature, the magnetic flux density decreases with the increase of the distance from the investigated point to armature, but the decay rate is gradually smaller. The results are helpful for the in-bore magnetic field shielding and intelligent ammunition design.
2016,
28: 025009.
doi: 10.11884/HPLPB201628.025009
Abstract:
This paper presents a novel design of a current pulse generator using an inductor as energy-storage component based on solid-state Marx adder, in which the structure of the basic unit in solid-state Marx adders was changed. The design principles are described and the control method is also given. The feasibility of the design was validated by experimenting. The designed current pulse generator is able to produce short current pulse with a good flat, a fast-rising edge and a fast-falling edge, regardless of the impact that the resistive load changes in a certain range. The generator also has the characteristics of simple control, reliability and so on.
This paper presents a novel design of a current pulse generator using an inductor as energy-storage component based on solid-state Marx adder, in which the structure of the basic unit in solid-state Marx adders was changed. The design principles are described and the control method is also given. The feasibility of the design was validated by experimenting. The designed current pulse generator is able to produce short current pulse with a good flat, a fast-rising edge and a fast-falling edge, regardless of the impact that the resistive load changes in a certain range. The generator also has the characteristics of simple control, reliability and so on.
2016,
28: 026001.
doi: 10.11884/HPLPB201628.026001
Abstract:
This paper proposes a new method to calculate the single particle displacement damage currents in ultra-low leakage current diode. The spatial distribution of primary knock-on atoms in the diode is simulated with SRIM. Based on the SRIM results, the SPDD current steps in the diode irradiated by 252Cf are calculated with Shockley-Read-Hall theory. The theoretical calculations of single particle displacement damage currents conduce to good agreements with experimental data. A stratified constant-gradient method is proposed to approximately describe the non-uniform distribution of electric field in the depletion region, therefore, the contributions of defects created in different positions in the depletion region to the increased leakage current can be calculated independently. The results show that the carriers emission is most significantly enhanced by electric field near the PN junction. Compared to the calculated results without considering the field-enhanced emission effect, the contribution of single defect near the PN junction to the increase of leakage current is two orders of magnitude higher when the electric field-enhanced emission effect is taken into consideration. Besides, the SPDD currents induced by 80 MeV Nd ions are generally higher than that by 106 MeV Cd ions. The SPDD currents induced by these ions are mainly between 1 fA to 1 pA.
This paper proposes a new method to calculate the single particle displacement damage currents in ultra-low leakage current diode. The spatial distribution of primary knock-on atoms in the diode is simulated with SRIM. Based on the SRIM results, the SPDD current steps in the diode irradiated by 252Cf are calculated with Shockley-Read-Hall theory. The theoretical calculations of single particle displacement damage currents conduce to good agreements with experimental data. A stratified constant-gradient method is proposed to approximately describe the non-uniform distribution of electric field in the depletion region, therefore, the contributions of defects created in different positions in the depletion region to the increased leakage current can be calculated independently. The results show that the carriers emission is most significantly enhanced by electric field near the PN junction. Compared to the calculated results without considering the field-enhanced emission effect, the contribution of single defect near the PN junction to the increase of leakage current is two orders of magnitude higher when the electric field-enhanced emission effect is taken into consideration. Besides, the SPDD currents induced by 80 MeV Nd ions are generally higher than that by 106 MeV Cd ions. The SPDD currents induced by these ions are mainly between 1 fA to 1 pA.
2016,
28: 029001.
doi: 10.11884/HPLPB201628.029001
Abstract:
In order to obtain excellent coating materials, FeCrNiMnMoB0.5 high entropy alloy coatings were prepared on Q235 steel by laser cladding. The effect of Mo on microstructure and properties of high entropy alloy coatings have been investigated emphatically. By means of optical microscope, X-ray diffraction, scanning electron microscope, hardness tester and electrochemical workstation, the microstructure, phase structure, hardness and corrosion resistance were studied. Results show that the microstructure of FeCrNiMnMoB0.5 high entropy alloy coatings is dendrites and the coating is mainly composed of fcc phase and a small amount of intermetallic compounds. After adding a small amount of Mo, the average hardness is very low, about 290 HV. With the increase of Mo, lattice distortion is enhanced and metal compounds appear. The hardness of the coating reaches a maximum of 658 HV. Polarization curves indicate that FeCrNiMnMo0.4B0.5 shows good corrosion resistance in the saturated salt mud solution.
In order to obtain excellent coating materials, FeCrNiMnMoB0.5 high entropy alloy coatings were prepared on Q235 steel by laser cladding. The effect of Mo on microstructure and properties of high entropy alloy coatings have been investigated emphatically. By means of optical microscope, X-ray diffraction, scanning electron microscope, hardness tester and electrochemical workstation, the microstructure, phase structure, hardness and corrosion resistance were studied. Results show that the microstructure of FeCrNiMnMoB0.5 high entropy alloy coatings is dendrites and the coating is mainly composed of fcc phase and a small amount of intermetallic compounds. After adding a small amount of Mo, the average hardness is very low, about 290 HV. With the increase of Mo, lattice distortion is enhanced and metal compounds appear. The hardness of the coating reaches a maximum of 658 HV. Polarization curves indicate that FeCrNiMnMo0.4B0.5 shows good corrosion resistance in the saturated salt mud solution.
2016,
28: 029002.
doi: 10.11884/HPLPB201628.029002
Abstract:
In order to improve the wear resistance of copper, laser shock peening is put forward. The wear performances of copper with and without laser shock peening are measured by the ball milling experiment. The phase structure and grain distribution of the surface layer with and without annealing are tested and analyzed by X-ray diffraction (XRD) and electron back scatter diffraction (EBSD). The mechanism of wear resistance improvement is discussed. The results indicate that after LSP, the specific wearability of copper has reduced by 19.5 percent compared with the sample untreated. Simultaneously, the initial friction coefficient of copper increases with the surface roughness increasing, but with the friction cycle increasing, the coefficient of friction declines obviously. Because of the grains refining, twin and sub-structure which block dislocation motion and increase the deformation resistance, the wear resistance of copper treated by LSP is improved.
In order to improve the wear resistance of copper, laser shock peening is put forward. The wear performances of copper with and without laser shock peening are measured by the ball milling experiment. The phase structure and grain distribution of the surface layer with and without annealing are tested and analyzed by X-ray diffraction (XRD) and electron back scatter diffraction (EBSD). The mechanism of wear resistance improvement is discussed. The results indicate that after LSP, the specific wearability of copper has reduced by 19.5 percent compared with the sample untreated. Simultaneously, the initial friction coefficient of copper increases with the surface roughness increasing, but with the friction cycle increasing, the coefficient of friction declines obviously. Because of the grains refining, twin and sub-structure which block dislocation motion and increase the deformation resistance, the wear resistance of copper treated by LSP is improved.
