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RSS2017 Vol. 29, No. 09
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2017,
29: 091001.
doi: 10.11884/HPLPB201729.170105
Abstract:
This paper reports a 100 fs Yb-doped mode-locked fiber laser based on pre-chirp managed nonlinear amplification. The system was first constructed with the mode-locked seed laser by using the nonlinear polarization rotation technology, which could deliver near-linear chirped stable pulse sequence at a repetition rate of 82.3 MHz. After a pre-amplifier and the pre-chirp managed nonlinear amplifier, the average power of the laser output was boosted over 12 W while the pulse width was reduced to less than 100 fs, effectively improved as a comparison to the 180 fs FWHM of the compressed seed pulse.
This paper reports a 100 fs Yb-doped mode-locked fiber laser based on pre-chirp managed nonlinear amplification. The system was first constructed with the mode-locked seed laser by using the nonlinear polarization rotation technology, which could deliver near-linear chirped stable pulse sequence at a repetition rate of 82.3 MHz. After a pre-amplifier and the pre-chirp managed nonlinear amplifier, the average power of the laser output was boosted over 12 W while the pulse width was reduced to less than 100 fs, effectively improved as a comparison to the 180 fs FWHM of the compressed seed pulse.
2017,
29: 091002.
doi: 10.11884/HPLPB201729.170053
Abstract:
A coupling system with a high contraction coefficient, up to 86∶1, has been designed and manufactured. The output from the spherically arranged 80 kW LD arrays is delivered by orthogonal cylindrical lenses and a hollow duct. Experimentally measured coupling efficiency of the system is 84.2%. Intensity modulation values of the pump-field at the exit are 1.30 of LD fast axis and 1.18 of LD slow axis. The pump light can transport a distance of 8.5 mm at least with its shape preserved. The coupling system can meet the requirements of end-pumped slab amplifiers for high pump power and pump power density.
A coupling system with a high contraction coefficient, up to 86∶1, has been designed and manufactured. The output from the spherically arranged 80 kW LD arrays is delivered by orthogonal cylindrical lenses and a hollow duct. Experimentally measured coupling efficiency of the system is 84.2%. Intensity modulation values of the pump-field at the exit are 1.30 of LD fast axis and 1.18 of LD slow axis. The pump light can transport a distance of 8.5 mm at least with its shape preserved. The coupling system can meet the requirements of end-pumped slab amplifiers for high pump power and pump power density.
2017,
29: 091003.
doi: 10.11884/HPLPB201729.170066
Abstract:
It is difficult to distinguish the laser damage from local surroundings by computer in the laser damage image which includes images with background noise, ghost reflections, different illumination and other sources of variation. Based on difference of Gaussian filter, we developed a new local area Signal-to-Noise ratio algorithm for extracting the seed of multi-scale laser damage in final optical images from a large laser system. This algorithm was used to extract the seed of flaws in the image where the field of view of a pixel is approximately 125 m, and captured the seed of flaws with diameter more than 50 m at 100% extraction rate.
It is difficult to distinguish the laser damage from local surroundings by computer in the laser damage image which includes images with background noise, ghost reflections, different illumination and other sources of variation. Based on difference of Gaussian filter, we developed a new local area Signal-to-Noise ratio algorithm for extracting the seed of multi-scale laser damage in final optical images from a large laser system. This algorithm was used to extract the seed of flaws in the image where the field of view of a pixel is approximately 125 m, and captured the seed of flaws with diameter more than 50 m at 100% extraction rate.
2017,
29: 091004.
doi: 10.11884/HPLPB201729.170076
Abstract:
We designed a novel zone plate by employing the trapezoidal transmission function. Numerical simulations based on Fresnel-Kirchhoff diffraction theory have demonstrated the quasi-single-order focusing characteristic and different performance of this plate from Fresnel zone plate. The comparison with a binary Gabor zone plate shows that the first-order diffraction efficiency of this plate is about 11.3% higher. Besides, all foci with orders of 2q and 3q(q=1,2,3,) are eliminated for this plate, and the diffraction efficiency of the fifth order is only 1/625 of the first order theoretically. More importantly, due to its symmetric structure and duplicable sectors that have equal width in a half-wave zone, this plate is much easier for nanofabrication.
We designed a novel zone plate by employing the trapezoidal transmission function. Numerical simulations based on Fresnel-Kirchhoff diffraction theory have demonstrated the quasi-single-order focusing characteristic and different performance of this plate from Fresnel zone plate. The comparison with a binary Gabor zone plate shows that the first-order diffraction efficiency of this plate is about 11.3% higher. Besides, all foci with orders of 2q and 3q(q=1,2,3,) are eliminated for this plate, and the diffraction efficiency of the fifth order is only 1/625 of the first order theoretically. More importantly, due to its symmetric structure and duplicable sectors that have equal width in a half-wave zone, this plate is much easier for nanofabrication.
2017,
29: 091005.
doi: 10.11884/HPLPB201729.170085
Abstract:
Our theoretical simulation calculation is expected to provide an approach for realizing narrow line width for a spectral beam combined diode laser bar. The conventional spectral beam combining structure was improved by adding a pair of anamorphic prisms. The anamorphic prisms reduces the output spot of the semiconductor laser line array, thereby theoretically reducing the incident angle to the grating and reducing the whole spectral line width .With the help of anamorphic prisms the whole wavelength of a spectral combined laser bar can be narrowed down to 3.2 nm from more than 10 nm. Compared with the method to reduce the spectral line width by increasing the focal length of cylindrical lens, the advantage of this approach is to ensure the overall structure of the whole spectral beam combining within 500 mm, which provides sufficient amount of feedback and guarantees the beam quality and efficiency of beam combining.
Our theoretical simulation calculation is expected to provide an approach for realizing narrow line width for a spectral beam combined diode laser bar. The conventional spectral beam combining structure was improved by adding a pair of anamorphic prisms. The anamorphic prisms reduces the output spot of the semiconductor laser line array, thereby theoretically reducing the incident angle to the grating and reducing the whole spectral line width .With the help of anamorphic prisms the whole wavelength of a spectral combined laser bar can be narrowed down to 3.2 nm from more than 10 nm. Compared with the method to reduce the spectral line width by increasing the focal length of cylindrical lens, the advantage of this approach is to ensure the overall structure of the whole spectral beam combining within 500 mm, which provides sufficient amount of feedback and guarantees the beam quality and efficiency of beam combining.
2017,
29: 091006.
doi: 10.11884/HPLPB201729.160500
Abstract:
Obtaining spatially high-resolution optical information effectively through overcoming the restriction of the diffraction limit in the optical field system has become an important research topic in the area of nanophotonics. We applied finite difference time domain (FDTD) method to study the characteristics of the focused spot nanometer jet formed by a core shell structure with various core refractive index and core radius. Results show that under the circumstance of the core radius unchanged, while the core had low refractive index, the incident energy was concentrated in the boundary region of the core and the shell layer, at the same time, large amount of energy injects into the side lobe; when the refractive index of the core was larger than that of the outer shell, double enhanced points at the end of the core shell structure could be formed; as the cores relative refractive index was unchanged, active control of internal and external core focus point location by changing the core radius was achieved.
Obtaining spatially high-resolution optical information effectively through overcoming the restriction of the diffraction limit in the optical field system has become an important research topic in the area of nanophotonics. We applied finite difference time domain (FDTD) method to study the characteristics of the focused spot nanometer jet formed by a core shell structure with various core refractive index and core radius. Results show that under the circumstance of the core radius unchanged, while the core had low refractive index, the incident energy was concentrated in the boundary region of the core and the shell layer, at the same time, large amount of energy injects into the side lobe; when the refractive index of the core was larger than that of the outer shell, double enhanced points at the end of the core shell structure could be formed; as the cores relative refractive index was unchanged, active control of internal and external core focus point location by changing the core radius was achieved.
2017,
29: 091007.
doi: 10.11884/HPLPB201729.170162
Abstract:
Based on metal electron gas model, the studies and analysis on the effect of temperature and pressure on gold reflectance characteristics changes were done. The experiments of pressure effect on gold reflectivity characteristics under 488 nm wavelength laser by DAC setup and those of temperature effect under high energy laser which supplies dynamic temperature rise were also done, the reflectance characteristics changes were obtained in 11 GPa pressure range and room temperature to 350 ℃ temperature range. The results show that the pressure effect comparing with temperature effect on reflectivity is negligible, the reflectivity is monotonely increasing and up to 10% increase, there is a one-to-one correspondence between reflectivity and temperature. Through the requirement analysis of temperature measurement in dynamic high pressure condition, the measurement method of material transient temperature can be established by gold reflectivity change under 488 nm wavelength laser in lower temperature (1000 K) section of dynamic high pressure loading.
Based on metal electron gas model, the studies and analysis on the effect of temperature and pressure on gold reflectance characteristics changes were done. The experiments of pressure effect on gold reflectivity characteristics under 488 nm wavelength laser by DAC setup and those of temperature effect under high energy laser which supplies dynamic temperature rise were also done, the reflectance characteristics changes were obtained in 11 GPa pressure range and room temperature to 350 ℃ temperature range. The results show that the pressure effect comparing with temperature effect on reflectivity is negligible, the reflectivity is monotonely increasing and up to 10% increase, there is a one-to-one correspondence between reflectivity and temperature. Through the requirement analysis of temperature measurement in dynamic high pressure condition, the measurement method of material transient temperature can be established by gold reflectivity change under 488 nm wavelength laser in lower temperature (1000 K) section of dynamic high pressure loading.
2017,
29: 091008.
doi: 10.11884/HPLPB201729.170052
Abstract:
The paper uses Gaussian distribution to describe the non-uniformity of the power spectrums power law along the propagation path. It presents the simulation of the non-Kolmogorov turbulence phase screens based on equivalent structure constant by power spectrum inversion method, and the simulation of the transmissions of laser beam through isotropous and non-Kolmogorov turbulence. By analyzing the light intensity uniformity, drift and scintillation indices of the beam propagating through single phase screen and multiple screens respectively, the influences can be found. When beam propagates through single phase screen, the maximum and uniformity of light intensity increase first and then decrease with power law. And beam drift is affected randomly in single screen and regularly in average data. When beam propagates through multiple phase screens, the scintillation indices of beams are affected by the number of phase screens. When the number is large, the scintillation indices through the isotropous turbulence is much larger than that in non-Kolmogorov turbulence, and the relative errors of beam drift in two models is close to 0. It is necessary to verify the influence by experiments and divide the scope of Kolmogorov turbulence and non-Kolmogorov turbulence.
The paper uses Gaussian distribution to describe the non-uniformity of the power spectrums power law along the propagation path. It presents the simulation of the non-Kolmogorov turbulence phase screens based on equivalent structure constant by power spectrum inversion method, and the simulation of the transmissions of laser beam through isotropous and non-Kolmogorov turbulence. By analyzing the light intensity uniformity, drift and scintillation indices of the beam propagating through single phase screen and multiple screens respectively, the influences can be found. When beam propagates through single phase screen, the maximum and uniformity of light intensity increase first and then decrease with power law. And beam drift is affected randomly in single screen and regularly in average data. When beam propagates through multiple phase screens, the scintillation indices of beams are affected by the number of phase screens. When the number is large, the scintillation indices through the isotropous turbulence is much larger than that in non-Kolmogorov turbulence, and the relative errors of beam drift in two models is close to 0. It is necessary to verify the influence by experiments and divide the scope of Kolmogorov turbulence and non-Kolmogorov turbulence.
2017,
29: 091009.
doi: 10.11884/HPLPB201729.170063
Abstract:
In order to realize real-time three-dimensional (3D) reconstruction, this paper proposes a novel dual-frequency method for measuring the 3D surface geometry of objects. First, a group of unit-frequency sinusoidal wave patterns and a group of high-frequency sinusoidal wave patterns are combines. Then the generated patterns are projected onto the object surface and the reflected patterns distorted by the object are captured by a camera simultaneously. Second, the unit-frequency phase and high-frequency phase can be derived through the captured unit-frequency patterns and high-frequency patterns respectively. The unwrapped phase can be obtained by unwrapping the high-frequency phase by means of the unit-frequency phase which represents the correspondences between the projector and the camera, i.e., the high-frequency patterns guarantee high-quality phase and the unit-frequency patterns help to conveniently unwrap the wrapped phase generated from the high-frequency patterns. Finally, the high-quality 3D point clouds of the object can be computed using the unwrapped phase through triangulation. To confirm the validity of the proposed method, a statue is scanned and the results indicate that the variance of the phase error is 5.559 110-6 rad2 and the sweep time is 0.156 3 s. Compared with the data of the traditional methods, the proposed method reduces the number of projected patterns and keeps the accuracy of reconstructed results.
In order to realize real-time three-dimensional (3D) reconstruction, this paper proposes a novel dual-frequency method for measuring the 3D surface geometry of objects. First, a group of unit-frequency sinusoidal wave patterns and a group of high-frequency sinusoidal wave patterns are combines. Then the generated patterns are projected onto the object surface and the reflected patterns distorted by the object are captured by a camera simultaneously. Second, the unit-frequency phase and high-frequency phase can be derived through the captured unit-frequency patterns and high-frequency patterns respectively. The unwrapped phase can be obtained by unwrapping the high-frequency phase by means of the unit-frequency phase which represents the correspondences between the projector and the camera, i.e., the high-frequency patterns guarantee high-quality phase and the unit-frequency patterns help to conveniently unwrap the wrapped phase generated from the high-frequency patterns. Finally, the high-quality 3D point clouds of the object can be computed using the unwrapped phase through triangulation. To confirm the validity of the proposed method, a statue is scanned and the results indicate that the variance of the phase error is 5.559 110-6 rad2 and the sweep time is 0.156 3 s. Compared with the data of the traditional methods, the proposed method reduces the number of projected patterns and keeps the accuracy of reconstructed results.
2017,
29: 092001.
doi: 10.11884/HPLPB201729.170126
Abstract:
A preliminary experimental study of the indirect-driven implosion by means of proton radiography has been carried out on the SGⅡ-U laser facility. In the experiment, the probing protons were generated by a picosecond laser irradiating on a thin Au target via the target normal sheath acceleration scheme. Maximum proton energy up to 18 MeV was achieved as a result of optimizing the laser and target parameters. In the static imaging of objects, the spatial resolution of proton radiography was demonstrated to be better than 20 m. In the time-resolved imaging of the implosion, the proton radiographs of the capsule at various stages of compression were obtained. It is found that the probing protons were expelled from the center region, which, covered an area much larger than the size of the compressed capsule. The detailed analysis reveals that the protons are expelled by the surrounding electric-magnetic fields as well as by the compressed capsule itself. It is also found that the energy of probing protons decreased when the nanosecond laser was present in the experiment. This is because the X-ray, generated from the nanosecond laser irradiation on targets, would partially destroy the rear side of proton target, thus leading to the less efficient proton acceleration. To improve the proton energy, the shielding design of proton target should be further considered in the next experiments.
A preliminary experimental study of the indirect-driven implosion by means of proton radiography has been carried out on the SGⅡ-U laser facility. In the experiment, the probing protons were generated by a picosecond laser irradiating on a thin Au target via the target normal sheath acceleration scheme. Maximum proton energy up to 18 MeV was achieved as a result of optimizing the laser and target parameters. In the static imaging of objects, the spatial resolution of proton radiography was demonstrated to be better than 20 m. In the time-resolved imaging of the implosion, the proton radiographs of the capsule at various stages of compression were obtained. It is found that the probing protons were expelled from the center region, which, covered an area much larger than the size of the compressed capsule. The detailed analysis reveals that the protons are expelled by the surrounding electric-magnetic fields as well as by the compressed capsule itself. It is also found that the energy of probing protons decreased when the nanosecond laser was present in the experiment. This is because the X-ray, generated from the nanosecond laser irradiation on targets, would partially destroy the rear side of proton target, thus leading to the less efficient proton acceleration. To improve the proton energy, the shielding design of proton target should be further considered in the next experiments.
2017,
29: 092002.
doi: 10.11884/HPLPB201729.170103
Abstract:
The discrete model of reinforced concrete structure considers the actual distribution of rebars, and with high accuracy, but the modeling process is complex. A kind of simplified modeling method is adopted to establish the finite element reinforced concrete model of opto-mechanical structure of ICF. This method is a kind of integrated modeling method with the equivalent modal feature of discrete model, by which concrete and rebar are considered as a kind of equivalent material. For typical combined structure, equivalent component models are obtained, and these equivalent models are assembled as a general structure. The numerical simulation results indicate that, under the same excitation, the response of discrete model and equivalent model is rather close, and the size of equivalent model is rather smaller than that of discrete model, and the effectiveness of equivalent modeling method is validated. At last, this equivalent modeling method is applied in opto-mechanical structure of the ICF facility SG Ⅲ, the random response of target ball is calculated under tested base excitation, and the simulation result and test data match well. The equivalent modeling method could be used in further stability analysis of giant opto-mechanical structures.
The discrete model of reinforced concrete structure considers the actual distribution of rebars, and with high accuracy, but the modeling process is complex. A kind of simplified modeling method is adopted to establish the finite element reinforced concrete model of opto-mechanical structure of ICF. This method is a kind of integrated modeling method with the equivalent modal feature of discrete model, by which concrete and rebar are considered as a kind of equivalent material. For typical combined structure, equivalent component models are obtained, and these equivalent models are assembled as a general structure. The numerical simulation results indicate that, under the same excitation, the response of discrete model and equivalent model is rather close, and the size of equivalent model is rather smaller than that of discrete model, and the effectiveness of equivalent modeling method is validated. At last, this equivalent modeling method is applied in opto-mechanical structure of the ICF facility SG Ⅲ, the random response of target ball is calculated under tested base excitation, and the simulation result and test data match well. The equivalent modeling method could be used in further stability analysis of giant opto-mechanical structures.
2017,
29: 093001.
doi: 10.11884/HPLPB201729.170075
Abstract:
A coaxial collinear (COCO) array antenna is one of the key components in wind profile radars, which requires simple structure, low sidelobe and high gain. This paper presents a novel COCO array antenna with an adjustable radiation sectors. By employing these adjustable sectors, the modified Taylor distribution of the arrays surface amplitude can be achieved. Using numerical analysis, the proposed COCO array antenna is optimized, the sidelobe level at working frequency on E and H planes are -23 dB and -22.3 dB, respectively, and the gain reaches 25.7 dB. Furthermore, the experiments show that the COCO array antenna can meet all of the design goals.
A coaxial collinear (COCO) array antenna is one of the key components in wind profile radars, which requires simple structure, low sidelobe and high gain. This paper presents a novel COCO array antenna with an adjustable radiation sectors. By employing these adjustable sectors, the modified Taylor distribution of the arrays surface amplitude can be achieved. Using numerical analysis, the proposed COCO array antenna is optimized, the sidelobe level at working frequency on E and H planes are -23 dB and -22.3 dB, respectively, and the gain reaches 25.7 dB. Furthermore, the experiments show that the COCO array antenna can meet all of the design goals.
2017,
29: 093002.
doi: 10.11884/HPLPB201729.170087
Abstract:
Based on the device physics simulation, we studied the microwave pulse thermal process of the PIN limiter diode, and the devices 2D multi-physical field model was established with software Sentaurus-TCAD. The peak temperature change of different thickness of Ⅰ layer was analyzed under injections of 5.3,7.5 and 9.4 GHz microwave signals. Simulation results show that the influence of Ⅰ layer thickness on thermal process of PIN diode divides into two stages, before the turning point, the peak temperature changes with the increasing of Ⅰ layer thickness, after the point the peak temperature decreases with the increasing of Ⅰ layer thickness. The influence of microwave pulse frequency on the turning point is not obvious.
Based on the device physics simulation, we studied the microwave pulse thermal process of the PIN limiter diode, and the devices 2D multi-physical field model was established with software Sentaurus-TCAD. The peak temperature change of different thickness of Ⅰ layer was analyzed under injections of 5.3,7.5 and 9.4 GHz microwave signals. Simulation results show that the influence of Ⅰ layer thickness on thermal process of PIN diode divides into two stages, before the turning point, the peak temperature changes with the increasing of Ⅰ layer thickness, after the point the peak temperature decreases with the increasing of Ⅰ layer thickness. The influence of microwave pulse frequency on the turning point is not obvious.
2017,
29: 093003.
doi: 10.11884/HPLPB201729.170090
Abstract:
To achieve miniaturized beam steering system for phased array antenna, a Controller Area Network (CAN) controller IP core based on Avalon bus was designed. Function structure of the IP core was given based on CAN2.0B protocol specification, and designs of controller interface logic, bit stream processor, bit timing logic and so on were completed using Verilog HDL language, and its hardware driver and communication software were developed. The reusability of the IP core was demonstrated with the designed SoPC system which integrated the CAN controller IP core, Nios II microprocessor, phase controller IP core and so on. The experimental results show that the system can realize data communication in the actual network reliably and stably. The built-up system based on this module has many of advantages, such as easy expansion, high portability and broad applicability. The IP core can also be used in high-density and compact industrial control equipments.
To achieve miniaturized beam steering system for phased array antenna, a Controller Area Network (CAN) controller IP core based on Avalon bus was designed. Function structure of the IP core was given based on CAN2.0B protocol specification, and designs of controller interface logic, bit stream processor, bit timing logic and so on were completed using Verilog HDL language, and its hardware driver and communication software were developed. The reusability of the IP core was demonstrated with the designed SoPC system which integrated the CAN controller IP core, Nios II microprocessor, phase controller IP core and so on. The experimental results show that the system can realize data communication in the actual network reliably and stably. The built-up system based on this module has many of advantages, such as easy expansion, high portability and broad applicability. The IP core can also be used in high-density and compact industrial control equipments.
2017,
29: 093004.
doi: 10.11884/HPLPB201729.170125
Abstract:
During the experiment research of the Relative Klystron Amplifier(RKA) we found that there were huge differences between currents and the forms of every electron beam. We made a research on this problem with PIC simulation software to investigate the effect of geometric size on the emitted electron beam distribution, which indicates that difference of geometric size between multi-beam cathodes, especially the radial difference, is the main factor causing the multi-beam asymmetry. Besides, the cross section of electron beams has a certain relation with the radius of the cathodes.
During the experiment research of the Relative Klystron Amplifier(RKA) we found that there were huge differences between currents and the forms of every electron beam. We made a research on this problem with PIC simulation software to investigate the effect of geometric size on the emitted electron beam distribution, which indicates that difference of geometric size between multi-beam cathodes, especially the radial difference, is the main factor causing the multi-beam asymmetry. Besides, the cross section of electron beams has a certain relation with the radius of the cathodes.
2017,
29: 093005.
doi: 10.11884/HPLPB201729.170131
Abstract:
The phase characteristic of multiple beams relativistic klystron amplifier is an important parameter, which limits the amplifiers applications. In order to reduce the phase jitter and improve the stability of the device, the phase characteristics of intense relativistic klystron amplifier is studied by one dimension non-linear theory. The theoretical results indicate that multiple frequency in the cavity and velocity gradient of electron beams caused by the characteristics of intense pulse voltage are the main reasons leading to phase fluctuation. Then numerical analysis of phase jitter caused by intense pulse power are developed based on an X-band multiple beam relativistic klystron amplifier with 18 electron beams. The theoretical and simulation results show together that front edge and fluctuation of pulse voltage both can lead to frequency shift and phase jitter. And the shift of operation frequency and fluctuation of phase will be greater while the rise time of pulse voltage is shorter. Besides, the shift of operation frequency is only determined by the fluctuation gradient of pulse voltage and the fluctuation of phase is determined by the fluctuation amplifier and gradient of pulse voltage.
The phase characteristic of multiple beams relativistic klystron amplifier is an important parameter, which limits the amplifiers applications. In order to reduce the phase jitter and improve the stability of the device, the phase characteristics of intense relativistic klystron amplifier is studied by one dimension non-linear theory. The theoretical results indicate that multiple frequency in the cavity and velocity gradient of electron beams caused by the characteristics of intense pulse voltage are the main reasons leading to phase fluctuation. Then numerical analysis of phase jitter caused by intense pulse power are developed based on an X-band multiple beam relativistic klystron amplifier with 18 electron beams. The theoretical and simulation results show together that front edge and fluctuation of pulse voltage both can lead to frequency shift and phase jitter. And the shift of operation frequency and fluctuation of phase will be greater while the rise time of pulse voltage is shorter. Besides, the shift of operation frequency is only determined by the fluctuation gradient of pulse voltage and the fluctuation of phase is determined by the fluctuation amplifier and gradient of pulse voltage.
2017,
29: 093201.
doi: 10.11884/HPLPB201729.170058
Abstract:
Field coupling to transmission line is an important subject for electromagnetic compatibility analysis and electromagnetic effect evaluation. The classical models of field-to-transmission line coupling are limited by the quasi-TEM wave approximation, which leads to unacceptable model errors at higher frequencies. The transmission line super theory (TLST) has established the model of high frequency field-to-transmission line coupling and solved the difficulty of the classical models. Based on TLST the model of high frequency field coupling to the non-uniform multi-conductor transmission line is introduced in this paper. The boundary conditions in three cases of different terminal loads are also proposed. Finally, the results of some numerical examples of high frequency model are compared with the results of the classical models and the full wave analysis, which shows the universal applicability of the high frequency model, the validity of the boundary conditions setting and the correctness of the numerical implementation.
Field coupling to transmission line is an important subject for electromagnetic compatibility analysis and electromagnetic effect evaluation. The classical models of field-to-transmission line coupling are limited by the quasi-TEM wave approximation, which leads to unacceptable model errors at higher frequencies. The transmission line super theory (TLST) has established the model of high frequency field-to-transmission line coupling and solved the difficulty of the classical models. Based on TLST the model of high frequency field coupling to the non-uniform multi-conductor transmission line is introduced in this paper. The boundary conditions in three cases of different terminal loads are also proposed. Finally, the results of some numerical examples of high frequency model are compared with the results of the classical models and the full wave analysis, which shows the universal applicability of the high frequency model, the validity of the boundary conditions setting and the correctness of the numerical implementation.
2017,
29: 093202.
doi: 10.11884/HPLPB201729.170065
Abstract:
When the electromagnetic wave transports through apertures into the multi-port microwave chaotic cavities, random coupling mode for apertures is derived to predict the statistical characteristics of coupling voltage. A complex calculation method, aperture random topology model(ARTM), which combines random coupling model and electromagnetic topology theory, is proposed to determine the statistical characteristics of coupling voltage and transmission coefficient for interconnected cavities. This method is proved accurate through comparing results of ARTM and that of network cascaded theory. The results are beneficial for the analysis of the aperture coupling on complex irregular chaotic cavities as well as the research of reverberation chambers.
When the electromagnetic wave transports through apertures into the multi-port microwave chaotic cavities, random coupling mode for apertures is derived to predict the statistical characteristics of coupling voltage. A complex calculation method, aperture random topology model(ARTM), which combines random coupling model and electromagnetic topology theory, is proposed to determine the statistical characteristics of coupling voltage and transmission coefficient for interconnected cavities. This method is proved accurate through comparing results of ARTM and that of network cascaded theory. The results are beneficial for the analysis of the aperture coupling on complex irregular chaotic cavities as well as the research of reverberation chambers.
2017,
29: 093203.
doi: 10.11884/HPLPB201729.170088
Abstract:
In order to study the protective performance of energy selective surface(ESS), this paper uses the PIN diode Spice model to obtain the transient response waveform of ESS by field-circuit co-simulation in time domain. The parameters that affect insertion loss and protective performance are studied, and structural parameters are optimized to reduce spikes. The results show that the double ESS can effectively protect the reverse pulse, and increasing the length of the metal strip can reduce the pulse spike. In this paper, the transmission of small signals and shielding of high power electromagnetic pulse are verified by high power electromagnetic pulse irradiation experiment, which provides a reliable method for HPM protection.
In order to study the protective performance of energy selective surface(ESS), this paper uses the PIN diode Spice model to obtain the transient response waveform of ESS by field-circuit co-simulation in time domain. The parameters that affect insertion loss and protective performance are studied, and structural parameters are optimized to reduce spikes. The results show that the double ESS can effectively protect the reverse pulse, and increasing the length of the metal strip can reduce the pulse spike. In this paper, the transmission of small signals and shielding of high power electromagnetic pulse are verified by high power electromagnetic pulse irradiation experiment, which provides a reliable method for HPM protection.
2017,
29: 095001.
doi: 10.11884/HPLPB201729.170077
Abstract:
Yingguang-1 is a multi-bank program-discharged pulsed power device for investigating the formation, confinement and instability of the high temperature and high density field reversed configuration (FRC) plasma injector in magnetized target fusion (MTF), which has been constructed at the Institute of Fluid Physics (IFP) in 2014. In this paper we will present the composition and the parameters of the Yingguang-1 device, and briefly describe the progress on the experiments of the FRC formation. In construction of the Yingguang-1 device, the rail gap switch with the peak current of 400 kA and the corresponding trigger system with the voltage greater than 200 kV and rise time less than 20 ns were firstly developed. Utilizing the mixture of 25% sulfur hexafluoride (SF6) and 75% nitrogen (N2) as the insulation gas, the switch could operate from 50 kV to 150 kV and the maximum offset of the start-up time would be less than 50 ns during repetitive test. By the high speed frame camera more than 5 discharged channels were observed in the switch. Experimental results of the pulsed power system show that the peak current/magnetic fields were 110 kA/0.3 T, 10 kA/1.2 T and 1.7 MA/3.4 T in the bias, mirror and -pinch circuit with the quarter cycle of 80 s, 700 s and 3.8 s when the charging voltage were set to 7 kV, 7 kV and 60 kV respectively. After the construction of Yingguang-1 device the preliminary experiments of the FRC target formation was conducted. With the H2 gas of 8.5 Pa, the plasma target of density 3.51016 cm-3, separatrix radius 4 cm, length 17 cm, average total temperature 200 eV and life time 3 s approximately equals to the half pulse width of the reversed field were obtained through the -pinch method when the bias, mirror, ionization and -pinch bank were charged to 5 kV, 5 kV, 55 kV and 45 kV respectively. The images from the end-on frame camera demonstrate the formation of FRC and agree with the results from the two dimension magneto hydrodynamics code (2D-MHD).
Yingguang-1 is a multi-bank program-discharged pulsed power device for investigating the formation, confinement and instability of the high temperature and high density field reversed configuration (FRC) plasma injector in magnetized target fusion (MTF), which has been constructed at the Institute of Fluid Physics (IFP) in 2014. In this paper we will present the composition and the parameters of the Yingguang-1 device, and briefly describe the progress on the experiments of the FRC formation. In construction of the Yingguang-1 device, the rail gap switch with the peak current of 400 kA and the corresponding trigger system with the voltage greater than 200 kV and rise time less than 20 ns were firstly developed. Utilizing the mixture of 25% sulfur hexafluoride (SF6) and 75% nitrogen (N2) as the insulation gas, the switch could operate from 50 kV to 150 kV and the maximum offset of the start-up time would be less than 50 ns during repetitive test. By the high speed frame camera more than 5 discharged channels were observed in the switch. Experimental results of the pulsed power system show that the peak current/magnetic fields were 110 kA/0.3 T, 10 kA/1.2 T and 1.7 MA/3.4 T in the bias, mirror and -pinch circuit with the quarter cycle of 80 s, 700 s and 3.8 s when the charging voltage were set to 7 kV, 7 kV and 60 kV respectively. After the construction of Yingguang-1 device the preliminary experiments of the FRC target formation was conducted. With the H2 gas of 8.5 Pa, the plasma target of density 3.51016 cm-3, separatrix radius 4 cm, length 17 cm, average total temperature 200 eV and life time 3 s approximately equals to the half pulse width of the reversed field were obtained through the -pinch method when the bias, mirror, ionization and -pinch bank were charged to 5 kV, 5 kV, 55 kV and 45 kV respectively. The images from the end-on frame camera demonstrate the formation of FRC and agree with the results from the two dimension magneto hydrodynamics code (2D-MHD).
2017,
29: 095002.
doi: 10.11884/HPLPB201729.170082
Abstract:
A novel monocycle pulse generator for road detection ground penetrating radar is designed and demonstrated in this paper. It contains a pulse drive circuit, an step recovery diode(SRD) pulse generating circuit and a pulse forming circuit. The pulse drive circuit can make the TTL signal a sharper and stronger trigger pulse, the SRD pulse generating circuit uses a low transit time diode to produce a negative polarity Gaussian pulse. At last, the pulse forming circuit utilizes micro-strip short circuit line, Schottky diode and capacitor parallel structure to generate monocycle pulse and eliminate the signal ringing. Measurement results show the output of the generator is monocycle pulse with peak values of 23 V at 1 MHz pulse repetition frequency(PRF) and 1.3 ns in full width at half maximum with 1.25% ringing. When the PRF increase to 5 MHz, the amplitude and bandwidth of the pulse generator are almost the same as before. These characteristics show that the pulse generator is pretty stable under high pulse repetition frequency, and will have a very good performance high resolution detection application.
A novel monocycle pulse generator for road detection ground penetrating radar is designed and demonstrated in this paper. It contains a pulse drive circuit, an step recovery diode(SRD) pulse generating circuit and a pulse forming circuit. The pulse drive circuit can make the TTL signal a sharper and stronger trigger pulse, the SRD pulse generating circuit uses a low transit time diode to produce a negative polarity Gaussian pulse. At last, the pulse forming circuit utilizes micro-strip short circuit line, Schottky diode and capacitor parallel structure to generate monocycle pulse and eliminate the signal ringing. Measurement results show the output of the generator is monocycle pulse with peak values of 23 V at 1 MHz pulse repetition frequency(PRF) and 1.3 ns in full width at half maximum with 1.25% ringing. When the PRF increase to 5 MHz, the amplitude and bandwidth of the pulse generator are almost the same as before. These characteristics show that the pulse generator is pretty stable under high pulse repetition frequency, and will have a very good performance high resolution detection application.
2017,
29: 095101.
doi: 10.11884/HPLPB201729.170023
Abstract:
In order to realize the phase locking of the digital beam position monitor (BPM) clock system, a clock synchronization system with low jitter and low phase noise is designed based on the principle of PLL synchronization. According to the working principle of the PLL circuit, the hardware and firmware are designed for the digital BPM clock synchronization system, the phase locking of the external input clock signal and the systems internal main work clock signal is realized, the output frequency and phase of the clock signal can be adjusted to meet the ADC sampling requirements in the back-end. The test results show that the design can meet the phase locking for the external clock signal which changes in a certain frequency range and the output clock signal jitter satisfies the requirement of beam experiments. Meanwhile, this study provides a basis for the subsequent research of digital BPM.
In order to realize the phase locking of the digital beam position monitor (BPM) clock system, a clock synchronization system with low jitter and low phase noise is designed based on the principle of PLL synchronization. According to the working principle of the PLL circuit, the hardware and firmware are designed for the digital BPM clock synchronization system, the phase locking of the external input clock signal and the systems internal main work clock signal is realized, the output frequency and phase of the clock signal can be adjusted to meet the ADC sampling requirements in the back-end. The test results show that the design can meet the phase locking for the external clock signal which changes in a certain frequency range and the output clock signal jitter satisfies the requirement of beam experiments. Meanwhile, this study provides a basis for the subsequent research of digital BPM.
2017,
29: 096001.
doi: 10.11884/HPLPB201729.170165
Abstract:
A gamma spectrometry method used to determine burnup based on the equilibrium concentration of short half-life nuclides is proposed. Spent fuel is irradiated under constant neutron flux for a period time to make the short half-life indicator isotopes reach the equilibrium concentration, burnup value can be obtained based on the relationship between the equilibrium concentration and residual 235U content. The theoretical simulation results and fuel irradiation experiment on the LR-0 research reactor show that the characteristic peaks of short half-life nuclides 88Kr and 92Sr can be significantly distinguished when fuel is irradiated for a short period of time, thus confirming the feasibility of using 88Kr and 92Sr as indicator isotopes for burnup measurement. This paper simulates the burnup of 20% enriched spent fuel under different experimental conditions, the experimental result shows that the characteristic peaks of indicator isotopes 88Kr, 92S and the corresponding interfering isotopes 132I, 88Rb can be distinguished in the corresponding energy range, and the gamma spectrum measurement should be carried out within 11 hours after discharge. Finally, the calculated burnup values consistent with the theoretical values can be obtained via 88Kr and 92Sr. Compared with other methods, this burnup measurement method is not affected by the irradiation history, fuel enrichment and cooling time before re-irradiation.
A gamma spectrometry method used to determine burnup based on the equilibrium concentration of short half-life nuclides is proposed. Spent fuel is irradiated under constant neutron flux for a period time to make the short half-life indicator isotopes reach the equilibrium concentration, burnup value can be obtained based on the relationship between the equilibrium concentration and residual 235U content. The theoretical simulation results and fuel irradiation experiment on the LR-0 research reactor show that the characteristic peaks of short half-life nuclides 88Kr and 92Sr can be significantly distinguished when fuel is irradiated for a short period of time, thus confirming the feasibility of using 88Kr and 92Sr as indicator isotopes for burnup measurement. This paper simulates the burnup of 20% enriched spent fuel under different experimental conditions, the experimental result shows that the characteristic peaks of indicator isotopes 88Kr, 92S and the corresponding interfering isotopes 132I, 88Rb can be distinguished in the corresponding energy range, and the gamma spectrum measurement should be carried out within 11 hours after discharge. Finally, the calculated burnup values consistent with the theoretical values can be obtained via 88Kr and 92Sr. Compared with other methods, this burnup measurement method is not affected by the irradiation history, fuel enrichment and cooling time before re-irradiation.
2017,
29: 096002.
doi: 10.11884/HPLPB201729.170056
Abstract:
A wide range pulsed neutron detection technology based on BF3 proportional counters is introduced. In this technology, multi-channel and modular BF3 tube array neutron detectors are adopted to achieve a wide range of pulsed neutron test applications, and the lower limit of measurement is also taken into account. Based on this technology, a set of BF3 array neutron detection system was developed and applied to the testing of pulsed neutron source. The experimental results show that the pulsed neutron measurement range of the system can reach the range of 56 to 8106, the lower limit of measurement is low and the output signal is clear, indicating the feasibility and effectiveness of the technology.
A wide range pulsed neutron detection technology based on BF3 proportional counters is introduced. In this technology, multi-channel and modular BF3 tube array neutron detectors are adopted to achieve a wide range of pulsed neutron test applications, and the lower limit of measurement is also taken into account. Based on this technology, a set of BF3 array neutron detection system was developed and applied to the testing of pulsed neutron source. The experimental results show that the pulsed neutron measurement range of the system can reach the range of 56 to 8106, the lower limit of measurement is low and the output signal is clear, indicating the feasibility and effectiveness of the technology.
2017,
29: 096003.
doi: 10.11884/HPLPB201729.170031
Abstract:
The reactivity feedback effect of metal burst reactors is driven by the thermal expansion of fuel. The inertia effect on metal burst reactors is caused by delay of reactivity feedback when the material expansion cannot respond to rapid heating changes in time from power excursions. We simulated vibrations by ANSYS under sudden thermal loading, and we calculated quench coefficient on metal burst reactors by stochastic neutron transport program at the same time. After introducing the reactivity feedback behaviors with vibration into the equations of point reactor kinetics, we obtained waveforms of fission pulses in consideration of inertia effect by numerical calculations, and the waveforms are in agreement with experiment results of Godiva. There is a quantitative relationship between the reactor periods and the inertia effect through numerical calculations, and the inertia effect is obvious when reactor periods are narrow.
The reactivity feedback effect of metal burst reactors is driven by the thermal expansion of fuel. The inertia effect on metal burst reactors is caused by delay of reactivity feedback when the material expansion cannot respond to rapid heating changes in time from power excursions. We simulated vibrations by ANSYS under sudden thermal loading, and we calculated quench coefficient on metal burst reactors by stochastic neutron transport program at the same time. After introducing the reactivity feedback behaviors with vibration into the equations of point reactor kinetics, we obtained waveforms of fission pulses in consideration of inertia effect by numerical calculations, and the waveforms are in agreement with experiment results of Godiva. There is a quantitative relationship between the reactor periods and the inertia effect through numerical calculations, and the inertia effect is obvious when reactor periods are narrow.
2017,
29: 096004.
doi: 10.11884/HPLPB201729.160269
Abstract:
To accelerate neutron transport calculation using discrete ordinates method, this paper presents a parallel partial current rebalance(PCR) algorithm based on domain decomposition, which is coupled with algebraic multigrid solver. The parallel PCR algorithm has been integrated in JSNT software and its correctness and effectiveness have been verified by typical critical and extraneous source calculation. In the pressure vessel shielding calculation of the pressurized water reactor in China, the iteration number and total computing time are decreased by more than 3 and 2 times respectively, the parallel efficiency on 1024 cores is 42.8%.
To accelerate neutron transport calculation using discrete ordinates method, this paper presents a parallel partial current rebalance(PCR) algorithm based on domain decomposition, which is coupled with algebraic multigrid solver. The parallel PCR algorithm has been integrated in JSNT software and its correctness and effectiveness have been verified by typical critical and extraneous source calculation. In the pressure vessel shielding calculation of the pressurized water reactor in China, the iteration number and total computing time are decreased by more than 3 and 2 times respectively, the parallel efficiency on 1024 cores is 42.8%.
2017,
29: 099001.
doi: 10.11884/HPLPB201729.170104
Abstract:
In order to eliminate the influence of strong Bremsstrahlung emission existed in laser-induced plasma on photomultiplier tube (PMT) and preamplifier and to improve signal detection sensitivity of laser-induced breakdown spectroscopy (LIBS), an end-on gated PMT was designed based on CR110 PMT and was used in weak signal detection of LIBS. The influence of strong Bremsstrahlung emission of the plasma could be successfully eliminated and the weak atomic emission signal could be further amplified after using this gated PMT combined with a preamplifier in signal detection, thus the spectral analysis sensitivity could be improved significantly. In analysis of chromium in aluminum alloy samples by LIBS, the limit of detection of chromium reached 5.55 ppm using this gated PMT as the signal detector, the detectability was improved nearly 6 folds in comparison with that using normal PMT. It was demonstrated that application of this gated photomultiplier tube in time-resolved signal detections could give good measurement results.
In order to eliminate the influence of strong Bremsstrahlung emission existed in laser-induced plasma on photomultiplier tube (PMT) and preamplifier and to improve signal detection sensitivity of laser-induced breakdown spectroscopy (LIBS), an end-on gated PMT was designed based on CR110 PMT and was used in weak signal detection of LIBS. The influence of strong Bremsstrahlung emission of the plasma could be successfully eliminated and the weak atomic emission signal could be further amplified after using this gated PMT combined with a preamplifier in signal detection, thus the spectral analysis sensitivity could be improved significantly. In analysis of chromium in aluminum alloy samples by LIBS, the limit of detection of chromium reached 5.55 ppm using this gated PMT as the signal detector, the detectability was improved nearly 6 folds in comparison with that using normal PMT. It was demonstrated that application of this gated photomultiplier tube in time-resolved signal detections could give good measurement results.
