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RSS2014 Vol. 26, No. 12
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2014,
26: 120101.
doi: 10.11884/HPLPB201426.120101
Abstract:
Using independently developed all-fiber passive mode-locked laser and high power mode field adaptor to couple 145 W picosecond pulse into photonic crystal fiber, we obtain a 67.9 W high power all-fiber white-light supercontinuum laser source. Its spectrum ranges from 500 nm to 1700 nm and 10 dB spectral width is over 1000 nm (expect pump wavelength). The optical-optical conversion efficiency (from the power of semiconductor laser pump source to the power of supercontinuum laser) of the entire laser system reached 33.8%.
Using independently developed all-fiber passive mode-locked laser and high power mode field adaptor to couple 145 W picosecond pulse into photonic crystal fiber, we obtain a 67.9 W high power all-fiber white-light supercontinuum laser source. Its spectrum ranges from 500 nm to 1700 nm and 10 dB spectral width is over 1000 nm (expect pump wavelength). The optical-optical conversion efficiency (from the power of semiconductor laser pump source to the power of supercontinuum laser) of the entire laser system reached 33.8%.
2014,
26: 120102.
doi: 10.11884/HPLPB201426.120102
Abstract:
A compact 650 kV, 2 ns high voltage pulse generator is developed. The specialties in principle and structure are described. It can generate narrow pulse by using a triple resonance pulse transformer and a pulse forming line. A compact conical double winding silicon- steel magnetic core transformer is developed. The circuit of the triple resonance pulse transformer is made up of the transformer, LC tuning circuit and the 27 pF, 30 pulse forming line. The narrow pulse generator is compact and portable. The experimental results show that the compact design is feasible and can deliver more than 650 kV onto a 80 load with 2 ns pulse width when the oil switch is closed.
A compact 650 kV, 2 ns high voltage pulse generator is developed. The specialties in principle and structure are described. It can generate narrow pulse by using a triple resonance pulse transformer and a pulse forming line. A compact conical double winding silicon- steel magnetic core transformer is developed. The circuit of the triple resonance pulse transformer is made up of the transformer, LC tuning circuit and the 27 pF, 30 pulse forming line. The narrow pulse generator is compact and portable. The experimental results show that the compact design is feasible and can deliver more than 650 kV onto a 80 load with 2 ns pulse width when the oil switch is closed.
Calibration methods and calibration systems of water-absorption-type high energy laser energy meters
2014,
26: 120201.
doi: 10.11884/HPLPB201426.120201
Abstract:
Water-absorption-type high energy laser energy meters are widely applied to the energy measurement of high energy lasers for their high efficiency in the heat exchange. However, its calibration is a considerable difficulty for the absence of high power standard lasers. A calibration method for the high energy laser energy meter with the electric heating wires was introduced, and water was led into a heating container at the entrance of the absorption cavity. Then it is heated before flowing into the absorption cavity. The energy absorbed by the water flow was estimated and compared with the one measured by the energy meter to calibrate the energy meter. The conclusion can be drawn that the heat exchange modal of the calibration system is just the same with the one in the absorption cavity. They include two stages, in the first stage energy is stored and in the second stage the power reaches equivalent. The scattering of the flow and the gas has few effects on the measurement results, and the effects can be ignored after the results are calibrated. It can be concluded that the remaining energy and the flow rate have great effects on the measurement results and the effects caused by remaining energy on the measurement uncertainty can be efficiently decreased by increasing the volume of the reservoir. The measurement uncertainty was estimated at 4.8％(k=2) after it was calibrated, and the calibrated high energy laser energy meter was compared with the other measurement systems, yielding a calibration coefficient of 1.006 and a standard deviation of 1.4% (k=2).
Water-absorption-type high energy laser energy meters are widely applied to the energy measurement of high energy lasers for their high efficiency in the heat exchange. However, its calibration is a considerable difficulty for the absence of high power standard lasers. A calibration method for the high energy laser energy meter with the electric heating wires was introduced, and water was led into a heating container at the entrance of the absorption cavity. Then it is heated before flowing into the absorption cavity. The energy absorbed by the water flow was estimated and compared with the one measured by the energy meter to calibrate the energy meter. The conclusion can be drawn that the heat exchange modal of the calibration system is just the same with the one in the absorption cavity. They include two stages, in the first stage energy is stored and in the second stage the power reaches equivalent. The scattering of the flow and the gas has few effects on the measurement results, and the effects can be ignored after the results are calibrated. It can be concluded that the remaining energy and the flow rate have great effects on the measurement results and the effects caused by remaining energy on the measurement uncertainty can be efficiently decreased by increasing the volume of the reservoir. The measurement uncertainty was estimated at 4.8％(k=2) after it was calibrated, and the calibrated high energy laser energy meter was compared with the other measurement systems, yielding a calibration coefficient of 1.006 and a standard deviation of 1.4% (k=2).
2014,
26: 121001.
doi: 10.11884/HPLPB201426.121001
Abstract:
A theoretical model is established, and the effect of core dislocation on laser power and beam quality is analyzed theoretically. It is indicated that each mode in the core will lose a part of power when core dislocation occurred in the fiber, and the basic mode will couple to a higher order mode, which will reduce the beam quality. A high-power all fiber laser oscillation system was built using a 20/400 m double-clad ytterbium-doped fiber. The effects of core dislocation on laser performance were researched experimentally while the core dislocation occurred in cavity, out of cavity or both. It is found that the laser performance will be reducing when the core dislocation occurred either in cavity or out of cavity. The core dislocation occurred in cavity will lead to a big decrease of the laser power while the core dislocation occurred both in cavity and out of cavity will lead to a great decrease of the beam quality.
A theoretical model is established, and the effect of core dislocation on laser power and beam quality is analyzed theoretically. It is indicated that each mode in the core will lose a part of power when core dislocation occurred in the fiber, and the basic mode will couple to a higher order mode, which will reduce the beam quality. A high-power all fiber laser oscillation system was built using a 20/400 m double-clad ytterbium-doped fiber. The effects of core dislocation on laser performance were researched experimentally while the core dislocation occurred in cavity, out of cavity or both. It is found that the laser performance will be reducing when the core dislocation occurred either in cavity or out of cavity. The core dislocation occurred in cavity will lead to a big decrease of the laser power while the core dislocation occurred both in cavity and out of cavity will lead to a great decrease of the beam quality.
2014,
26: 121002.
doi: 10.11884/HPLPB201426.121002
Abstract:
The thermal damages of the frequently-used infrared optical materials ZnS and SiO2 induced by infrared short pulse laser were studied. The thermal effect of ZnS and SiO2 irradiated by the same laser were analyzed. The thermal effects of ZnS and SiO2 irradiated by different laser were respectively analyzed. The following conclusions were drawn. The temperature on the surface of SiO2 rose faster than that of ZnS irradiated by the infrared laser. The temperature under the surface of SiO2 rose slower than that of ZnS. Peak temperature of SiO2 was higher than the latter. The depth of the region where its temperature was above normal in the SiO2 was shallower than that in the ZnS. Temperature of materials in the case of picosecond pulse laser rose faster and higher than that in the case of nanosecond pulse laser for the energy of picosecond pulse laser was more concentrated. As the pulse width diminished, the single pulse energy of laser nonlinear decreased and the rate of change grew, which made the peak temperature achieve melting point.
The thermal damages of the frequently-used infrared optical materials ZnS and SiO2 induced by infrared short pulse laser were studied. The thermal effect of ZnS and SiO2 irradiated by the same laser were analyzed. The thermal effects of ZnS and SiO2 irradiated by different laser were respectively analyzed. The following conclusions were drawn. The temperature on the surface of SiO2 rose faster than that of ZnS irradiated by the infrared laser. The temperature under the surface of SiO2 rose slower than that of ZnS. Peak temperature of SiO2 was higher than the latter. The depth of the region where its temperature was above normal in the SiO2 was shallower than that in the ZnS. Temperature of materials in the case of picosecond pulse laser rose faster and higher than that in the case of nanosecond pulse laser for the energy of picosecond pulse laser was more concentrated. As the pulse width diminished, the single pulse energy of laser nonlinear decreased and the rate of change grew, which made the peak temperature achieve melting point.
2014,
26: 121003.
doi: 10.11884/HPLPB201426.121003
Abstract:
A high spectral resolution lidar(HSRL) for measurement of low-stratosphere temperature by scanning Fabry-Perot interferometer (FPI) is proposed and demonstrated. The transmission of Rayleigh backscatter through the FPI is obtained by scanning the cavity spacing of the FPI, and then fitted to Gaussian function using the nonlinear fitting algorithm. Temperature is calculated from the fitted bandwidth of the measured transmission. To reduce systematic error due to frequency instability of the laser, another solid FPI is incorporated into the optical receiver to monitor the frequency drift, which compensates in the data processing. The statistical error is calculated based on a maximum likelihood estimator, which is less than 1.9 K/9.8 K below 30 km/50 km. In the comparison experiment, the max temperature deviation between the high spectral resolution lidar (HSRL) and radiosonde is 4.7 K from 18 km to 36 km, and it is 2.7 K between the HSRL and Rayleigh integration lidar (RIL) from 27 km to 34 km. The temperature profile from Rayleigh integration lidar deviates from the results from HSRL and radiosonde obviously from 15 km to 27 km, with a max deviation of 22.8 K, which may due to the aerosol contamination.
A high spectral resolution lidar(HSRL) for measurement of low-stratosphere temperature by scanning Fabry-Perot interferometer (FPI) is proposed and demonstrated. The transmission of Rayleigh backscatter through the FPI is obtained by scanning the cavity spacing of the FPI, and then fitted to Gaussian function using the nonlinear fitting algorithm. Temperature is calculated from the fitted bandwidth of the measured transmission. To reduce systematic error due to frequency instability of the laser, another solid FPI is incorporated into the optical receiver to monitor the frequency drift, which compensates in the data processing. The statistical error is calculated based on a maximum likelihood estimator, which is less than 1.9 K/9.8 K below 30 km/50 km. In the comparison experiment, the max temperature deviation between the high spectral resolution lidar (HSRL) and radiosonde is 4.7 K from 18 km to 36 km, and it is 2.7 K between the HSRL and Rayleigh integration lidar (RIL) from 27 km to 34 km. The temperature profile from Rayleigh integration lidar deviates from the results from HSRL and radiosonde obviously from 15 km to 27 km, with a max deviation of 22.8 K, which may due to the aerosol contamination.
2014,
26: 121004.
doi: 10.11884/HPLPB201426.121004
Abstract:
Based on nonlocal nonlinear Schrodinger equations of double beams, the evolutional rules of parameters and critical powers of transmission of orthogonal polarization center-coincidence double Hermite-Gaussian beams are calculated with variational approximation method in strongly nonlocal medium by expanding the response function in Taylors series to the second order. The evolutional rules of the beam width and phase shift are numerically simulated with split-step Fourier algorithm. The orthogonal polarization center-coincidence double Hermite-Gaussian spatial optical solitons and their large phase shifts evolutional rules are obtained when the two beams are incident with critical powers. The beams can form breathers, but the breathers become unstable with the increasing of the order when the two beams are incident with the total critical power but two incident powers are different. For breathers of each order, the beam width with high power periodically compacted oscillates; the beam width with low power periodically extended oscillates. Moreover, the phase shift of higher power breather increases faster with the increasing of transmission distance. When the order of Hermite-Gaussian is under the fifth order, the variational approximate solution agrees well with the numerical solution.
Based on nonlocal nonlinear Schrodinger equations of double beams, the evolutional rules of parameters and critical powers of transmission of orthogonal polarization center-coincidence double Hermite-Gaussian beams are calculated with variational approximation method in strongly nonlocal medium by expanding the response function in Taylors series to the second order. The evolutional rules of the beam width and phase shift are numerically simulated with split-step Fourier algorithm. The orthogonal polarization center-coincidence double Hermite-Gaussian spatial optical solitons and their large phase shifts evolutional rules are obtained when the two beams are incident with critical powers. The beams can form breathers, but the breathers become unstable with the increasing of the order when the two beams are incident with the total critical power but two incident powers are different. For breathers of each order, the beam width with high power periodically compacted oscillates; the beam width with low power periodically extended oscillates. Moreover, the phase shift of higher power breather increases faster with the increasing of transmission distance. When the order of Hermite-Gaussian is under the fifth order, the variational approximate solution agrees well with the numerical solution.
2014,
26: 121005.
doi: 10.11884/HPLPB201426.121005
Abstract:
A detecting system is set up based on image processing used for EUV source. The tin target motion and stability are displayed by image capturing and processing in real time. The system is tested when tin droplet is generated by the tin generator at 34 kHz. The result reveals that tin droplet size is close to 137 m, and the distance between every two drops is about 375 m. The lateral droplet stability is analyzed which contributes to laser produced plasma EUV source.
A detecting system is set up based on image processing used for EUV source. The tin target motion and stability are displayed by image capturing and processing in real time. The system is tested when tin droplet is generated by the tin generator at 34 kHz. The result reveals that tin droplet size is close to 137 m, and the distance between every two drops is about 375 m. The lateral droplet stability is analyzed which contributes to laser produced plasma EUV source.
2014,
26: 121006.
doi: 10.11884/HPLPB201426.121006
Abstract:
The output power of dual-frequency laser source is usually low that it cannot meet the requirements of measurement of long distance. The amplification of 125-165 MHz sweep beat frequency signal using an all-fiber master oscillator power-amplifier (MOPA) system is demonstrated. A non-planar ring oscillator laser (NPRO) with central wavelength of 1064 nm is designed as the single frequency laser seed. An acoustic modulator with central frequency of 150 MHz is used to produce 50 mW dual frequency signal with combination of master and diffraction beam by 1064 nm frequency shifting. The power of dual frequency laser is boosted up to 10 W. The beat signal can sweep from 125 MHz to 165 MHz. The relative magnitude of the two single-frequency signals is maintained in the amplification process and the maximal output power of beat signal can be realized by polarization controlling. The signal noise rate and bandwidth of beat signal are also experimented and analyzed.
The output power of dual-frequency laser source is usually low that it cannot meet the requirements of measurement of long distance. The amplification of 125-165 MHz sweep beat frequency signal using an all-fiber master oscillator power-amplifier (MOPA) system is demonstrated. A non-planar ring oscillator laser (NPRO) with central wavelength of 1064 nm is designed as the single frequency laser seed. An acoustic modulator with central frequency of 150 MHz is used to produce 50 mW dual frequency signal with combination of master and diffraction beam by 1064 nm frequency shifting. The power of dual frequency laser is boosted up to 10 W. The beat signal can sweep from 125 MHz to 165 MHz. The relative magnitude of the two single-frequency signals is maintained in the amplification process and the maximal output power of beat signal can be realized by polarization controlling. The signal noise rate and bandwidth of beat signal are also experimented and analyzed.
2014,
26: 121007.
doi: 10.11884/HPLPB201426.121007
Abstract:
InGaZnO ceramic target was obtained by solid-state reactions in atmospheric pressure. Pulsed laser deposition method was applied to growing amorphous InGaZnO films on the quartz glass at room temperature under 1Pa oxygen pressure. The film properties were carefully examined using X-ray diffraction (XRD), transmission spectra, Raman spectra and Hall effect measurement. InGaZnO thin films were amorphous structure and with high quality. The transmitted spectrum shows that thin films exhibit perfect light transmission and narrow band gap. The InGaZnO film contains amorphous structure, perfect light transmission and high carrier mobility at low deposition temperature with inch-indium content. These amorphous IGZO thin films with high mobility and transparency are highly desirable for device fabrication on flexible substrates.
InGaZnO ceramic target was obtained by solid-state reactions in atmospheric pressure. Pulsed laser deposition method was applied to growing amorphous InGaZnO films on the quartz glass at room temperature under 1Pa oxygen pressure. The film properties were carefully examined using X-ray diffraction (XRD), transmission spectra, Raman spectra and Hall effect measurement. InGaZnO thin films were amorphous structure and with high quality. The transmitted spectrum shows that thin films exhibit perfect light transmission and narrow band gap. The InGaZnO film contains amorphous structure, perfect light transmission and high carrier mobility at low deposition temperature with inch-indium content. These amorphous IGZO thin films with high mobility and transparency are highly desirable for device fabrication on flexible substrates.
2014,
26: 121008.
doi: 10.11884/HPLPB201426.121008
Abstract:
A systematic model was developed by combining the procedures of laser kinetics and heat transfer together to explore the radial population density and temperature distribution in the transverse section of a rubidium vapor cell. The relationships between the pump power and the laser output, the optical-optical conversion efficiency and the other relevant physical parameters were obtained. The procedures to improve the pump absorption efficiency were discussed. The influences of the relaxation rate between the two fine-levels 2P3/2 and 2P1/2 on the physical characteristics of a DPAL were also revealed. The results show that: when different uses of diode-pumped alkali metal vapor lasers are designed, it is necessary to consider various factors in order to determine the corresponding optimal structural parameters.
A systematic model was developed by combining the procedures of laser kinetics and heat transfer together to explore the radial population density and temperature distribution in the transverse section of a rubidium vapor cell. The relationships between the pump power and the laser output, the optical-optical conversion efficiency and the other relevant physical parameters were obtained. The procedures to improve the pump absorption efficiency were discussed. The influences of the relaxation rate between the two fine-levels 2P3/2 and 2P1/2 on the physical characteristics of a DPAL were also revealed. The results show that: when different uses of diode-pumped alkali metal vapor lasers are designed, it is necessary to consider various factors in order to determine the corresponding optimal structural parameters.
2014,
26: 121009.
doi: 10.11884/HPLPB201426.121009
Abstract:
In order to research the influence factors of laser coherent noise in high speed photography, and reduce the impact brought by speckle noise on the quality of high-speed photography imaging, the relationship between the roughness of the surface irradiated by the laser and the statistical properties of the laser speckle was studied. Based on the principle of Fresnel-Kirchhoff diffraction theory, the laser speckle patterns by reflection on random surface by Gaussian beam incident was analyzed, and the relationship between the SNR and autocorrelation and probability density function and the roughness of the incident surface was obtained through the statistics of a large amount of data of laser speckles. The results show that bigger roughness lead to smaller SNR of speckle field, degree of coherence and probability density, that is to say, the noise of the speckle increases with the increase of the roughness of the surface.
In order to research the influence factors of laser coherent noise in high speed photography, and reduce the impact brought by speckle noise on the quality of high-speed photography imaging, the relationship between the roughness of the surface irradiated by the laser and the statistical properties of the laser speckle was studied. Based on the principle of Fresnel-Kirchhoff diffraction theory, the laser speckle patterns by reflection on random surface by Gaussian beam incident was analyzed, and the relationship between the SNR and autocorrelation and probability density function and the roughness of the incident surface was obtained through the statistics of a large amount of data of laser speckles. The results show that bigger roughness lead to smaller SNR of speckle field, degree of coherence and probability density, that is to say, the noise of the speckle increases with the increase of the roughness of the surface.
2014,
26: 121010.
doi: 10.11884/HPLPB201426.121010
Abstract:
The transfer matrix method is used to calculate the transmissivity of the defect mode of the photonic crystal with defects, and the influence of the absorption effect of material on the characteristics of photonic crystal temperature sensing is mainly discussed. The research object is the defect mode at the wavelength 800 nm. Simulated with the mathematical software MATLAB, it is found that: firstly, the transmissivity of the defect mode decreases with the increase of temperature, the photonic crystal is sensitive to the change of temperature; secondly, the absorption effect of material can slow down the speed of change of transmission peak with the change of temperature, and make the sensitivity of the photonic crystal changes less with temperature; finally, the greater the extinction coefficient of the material, the smaller the sensitivity of defect mode of the photonic crystal to the change of temperature.
The transfer matrix method is used to calculate the transmissivity of the defect mode of the photonic crystal with defects, and the influence of the absorption effect of material on the characteristics of photonic crystal temperature sensing is mainly discussed. The research object is the defect mode at the wavelength 800 nm. Simulated with the mathematical software MATLAB, it is found that: firstly, the transmissivity of the defect mode decreases with the increase of temperature, the photonic crystal is sensitive to the change of temperature; secondly, the absorption effect of material can slow down the speed of change of transmission peak with the change of temperature, and make the sensitivity of the photonic crystal changes less with temperature; finally, the greater the extinction coefficient of the material, the smaller the sensitivity of defect mode of the photonic crystal to the change of temperature.
2014,
26: 121011.
doi: 10.11884/HPLPB201426.121011
Abstract:
Regarding to the reconstruction problem of an infrared image in compressed sensing, we proposed a modified block compressed sensing method. First, the original infrared image is divided into small blocks, each of which is sampled with a Gaussian random matrix to generate a small amount of measurement data. Second, Spectral Graph Wavelet transform with excellent sparse features is applied into reconstruction process of projected Landweber algorithm, and the hybrid median filter is used for enhancing image smoothness and reducing block artifacts. Finally, the high-quality infrared image satisfied termination conditions is obtained. Experimental results on various types of infrared images show that the proposed method attains much better performance in CS recovery than the conventional ones and can obtain higher quality infrared images.
Regarding to the reconstruction problem of an infrared image in compressed sensing, we proposed a modified block compressed sensing method. First, the original infrared image is divided into small blocks, each of which is sampled with a Gaussian random matrix to generate a small amount of measurement data. Second, Spectral Graph Wavelet transform with excellent sparse features is applied into reconstruction process of projected Landweber algorithm, and the hybrid median filter is used for enhancing image smoothness and reducing block artifacts. Finally, the high-quality infrared image satisfied termination conditions is obtained. Experimental results on various types of infrared images show that the proposed method attains much better performance in CS recovery than the conventional ones and can obtain higher quality infrared images.
2014,
26: 121012.
doi: 10.11884/HPLPB201426.121012
Abstract:
The process of oxygen-iodine mixing is one of the most important steps in chemical oxygen-iodine laser (COIL). The quality of oxygen-iodine mixing is directly related to the COILs operating efficiency and beam quality. Employing chemical fluorescence method (CFM)，the effects of trip tabs on the process of supersonic mixing of parallel oxygen-iodine flows in COIL was studied. The experimental results indicated that the mixing process with 1# trip tabs was improved obviously. Comparing with the mixing without trips, when using 1# trip tabs, the streamwise distance required by the fluorescence to reach the centerline of the primary flow was shortened largely and the area ratio of fluorescence in the region of iodine dissociation region was enlarged by 4.2 times. When using 2# trip tabs, the streamuise distance decreased further by 40%-60%, and the area ratio value increased by 20%-40% again. Using 2# trip tabs, the mixing processes with and without the primary buffer gas were compared, and the results showed that the latter was better.
The process of oxygen-iodine mixing is one of the most important steps in chemical oxygen-iodine laser (COIL). The quality of oxygen-iodine mixing is directly related to the COILs operating efficiency and beam quality. Employing chemical fluorescence method (CFM)，the effects of trip tabs on the process of supersonic mixing of parallel oxygen-iodine flows in COIL was studied. The experimental results indicated that the mixing process with 1# trip tabs was improved obviously. Comparing with the mixing without trips, when using 1# trip tabs, the streamwise distance required by the fluorescence to reach the centerline of the primary flow was shortened largely and the area ratio of fluorescence in the region of iodine dissociation region was enlarged by 4.2 times. When using 2# trip tabs, the streamuise distance decreased further by 40%-60%, and the area ratio value increased by 20%-40% again. Using 2# trip tabs, the mixing processes with and without the primary buffer gas were compared, and the results showed that the latter was better.
2014,
26: 121013.
doi: 10.11884/HPLPB201426.121013
Abstract:
In phase measuring profilometry(PMP), the intensity values exceed the maximum quantization range of camera because of the larger surface reflectivity of object, that is intensity saturation. This paper analyzes phase error caused by intensity saturation, and proposes a phase fusion algorithm. Using this algorithm, we find the largest normalized modulation intensity of each pixel, and extract the corresponding phase and fuse them. The proposed method can effectively restrain the saturation error in the ideal situation and in the situation where exists gamma distortion in the camera-projector pair. The corrected phase error decrease 558.86% in experiment.
In phase measuring profilometry(PMP), the intensity values exceed the maximum quantization range of camera because of the larger surface reflectivity of object, that is intensity saturation. This paper analyzes phase error caused by intensity saturation, and proposes a phase fusion algorithm. Using this algorithm, we find the largest normalized modulation intensity of each pixel, and extract the corresponding phase and fuse them. The proposed method can effectively restrain the saturation error in the ideal situation and in the situation where exists gamma distortion in the camera-projector pair. The corrected phase error decrease 558.86% in experiment.
2014,
26: 121014.
doi: 10.11884/HPLPB201426.121014
Abstract:
Solar pumped lasers directly convert sunlight into laser radiation. In this paper, we improve the configuration and structure of the hybrid pumping cavity adding a water-cooling system in the copper cavity. Output laser power is up to 23.7 W, using an Nd:YAG crystal rod with a diameter of 8 mm and a length of 115 mm as laser media, and a 7.87% slope efficiency is achieved. A Fresnel lens with a surface of 1.03 m2 is used as the primary solar light concentrator. It is shown through comparison experiments that the design of the new pumping cavity is an effective solution with a 55.92% increase in output power. We analyze the absorption loss and coupling efficiency of side-pumping light in the new cavity, and confirm that the new structure can improve the side-pumping efficiency. At the end of the article another design of composite cavity with ceramic material is put forward.
Solar pumped lasers directly convert sunlight into laser radiation. In this paper, we improve the configuration and structure of the hybrid pumping cavity adding a water-cooling system in the copper cavity. Output laser power is up to 23.7 W, using an Nd:YAG crystal rod with a diameter of 8 mm and a length of 115 mm as laser media, and a 7.87% slope efficiency is achieved. A Fresnel lens with a surface of 1.03 m2 is used as the primary solar light concentrator. It is shown through comparison experiments that the design of the new pumping cavity is an effective solution with a 55.92% increase in output power. We analyze the absorption loss and coupling efficiency of side-pumping light in the new cavity, and confirm that the new structure can improve the side-pumping efficiency. At the end of the article another design of composite cavity with ceramic material is put forward.
2014,
26: 121015.
doi: 10.11884/HPLPB201426.121015
Abstract:
The super-Gaussian vortex beams generated from spiral phase plates (SPP) with different topological charges are discussed, also the properties of the light intensity distribution like max light intensity, radius of light beams and its encircled energy varying with propagation distance and with topological charges are studied and compared, which shows that the radius of light intensity or of encircled energy presents rough linear relationships to the propagation distance and topological charges. Moreover, the energy of Gaussian vortex beams is always more dispersed than that of super-Gaussian vortex beams, while the radius of light intensity of Gaussian vortex beams is smaller than that super-Gaussian vortex beams when referring to higher topological charges. The generalized M2 factor varying with propagation distance and topological charges is also discussed to feature the quality of beams, which shows that the super-Gaussian beam at a relatively far distance with lower topological charges could have better quality.
The super-Gaussian vortex beams generated from spiral phase plates (SPP) with different topological charges are discussed, also the properties of the light intensity distribution like max light intensity, radius of light beams and its encircled energy varying with propagation distance and with topological charges are studied and compared, which shows that the radius of light intensity or of encircled energy presents rough linear relationships to the propagation distance and topological charges. Moreover, the energy of Gaussian vortex beams is always more dispersed than that of super-Gaussian vortex beams, while the radius of light intensity of Gaussian vortex beams is smaller than that super-Gaussian vortex beams when referring to higher topological charges. The generalized M2 factor varying with propagation distance and topological charges is also discussed to feature the quality of beams, which shows that the super-Gaussian beam at a relatively far distance with lower topological charges could have better quality.
Quasimonoenergetic proton beam acceleration from intense laser interaction with a double cone target
2014,
26: 122001.
doi: 10.11884/HPLPB201426.122001
Abstract:
A new double cone target for accelerating quasimonoenergetic proton beam is proposed in this paper. Using two-dimensional PIC (particle-in-cell) simulation, the physical process of accelerating protons and the quality of proton beam from interaction of intense laser with the double cone target are investigated. In the case of same laser parameters, the peak energy and divergence angle of proton beams accelerated by the double cone target are superior to those by the single cone or planar target. Especially, compared to the planar target, the peak proton energy in the double cone target is increased by more than five times and quasimonoenergy can be well maintained. The critical density of the inner cone of the double cone target can increase the laser absorption efficiency. Moreover, the larger quasistatic magnetic field inside the double cone target can confine and guide more fast electrons to transport through the cone tip, which may enhance the sheath field for proton acceleration.
A new double cone target for accelerating quasimonoenergetic proton beam is proposed in this paper. Using two-dimensional PIC (particle-in-cell) simulation, the physical process of accelerating protons and the quality of proton beam from interaction of intense laser with the double cone target are investigated. In the case of same laser parameters, the peak energy and divergence angle of proton beams accelerated by the double cone target are superior to those by the single cone or planar target. Especially, compared to the planar target, the peak proton energy in the double cone target is increased by more than five times and quasimonoenergy can be well maintained. The critical density of the inner cone of the double cone target can increase the laser absorption efficiency. Moreover, the larger quasistatic magnetic field inside the double cone target can confine and guide more fast electrons to transport through the cone tip, which may enhance the sheath field for proton acceleration.
2014,
26: 122002.
doi: 10.11884/HPLPB201426.122002
Abstract:
A method to directly measure the DD-produced proton spectra is proposed and applied to an ICF implosion experiment. This method is based on the CR39 responding curve. It is designed to get higher counts, and it is suitable for low proton yield cases. Before the experiment, CR39 is calibrated and the background is measured to increase the accuracy. After the experiment，the CR39 responding curve is used to clarify the primary proton energy, and the Geant4 is used to modified the membrane effect. The implosion areal density which is propitious to further analyze implosion experiment results is obtained by measuring the proton spectrum peak shift.
A method to directly measure the DD-produced proton spectra is proposed and applied to an ICF implosion experiment. This method is based on the CR39 responding curve. It is designed to get higher counts, and it is suitable for low proton yield cases. Before the experiment, CR39 is calibrated and the background is measured to increase the accuracy. After the experiment，the CR39 responding curve is used to clarify the primary proton energy, and the Geant4 is used to modified the membrane effect. The implosion areal density which is propitious to further analyze implosion experiment results is obtained by measuring the proton spectrum peak shift.
2014,
26: 123003.
doi: 10.11884/HPLPB201426.123003
Abstract:
The initial design of magnetron injection gun was analyzed based on the theory of the adiabatic compression and conservation of angular momentum. A series of initial parameters of 55 GHz double anode magnetron injection gun were obtained by Matlab programming. Independent research and development of three-dimensional particle simulation software CHIPIC was used to carry out numerical simulation. The obtained simulation data were analyzed and optimized. High-performance electron beam was obtained with a ratio of transverse velocity to axial velocity of 1.44 and a maximum velocity spread of 5.8%. The beam could meet the requirements of 55 GHz gyrotron oscillator tube.
The initial design of magnetron injection gun was analyzed based on the theory of the adiabatic compression and conservation of angular momentum. A series of initial parameters of 55 GHz double anode magnetron injection gun were obtained by Matlab programming. Independent research and development of three-dimensional particle simulation software CHIPIC was used to carry out numerical simulation. The obtained simulation data were analyzed and optimized. High-performance electron beam was obtained with a ratio of transverse velocity to axial velocity of 1.44 and a maximum velocity spread of 5.8%. The beam could meet the requirements of 55 GHz gyrotron oscillator tube.
2014,
26: 123004.
doi: 10.11884/HPLPB201426.123004
Abstract:
A novel 8-way Ka band radial waveguide spatial power divider/combiner is analyzed and designed through the combination of theoretical research and high frequency electromagnetic field simulation. Compared with traditional coaxial structure, this new design uses a standard rectangular waveguide as the input and output structure. This all metal structure is much simpler, compacter and easier to manufacture. Simulation results show that the relative bandwidth of this device is 34% (the absolute bandwidth is 12 GHz), which nearly covers the whole Ka band, and S11 in the whole working bandwidth is below -20 dB; and that the phase difference of each way is under 5. Using the new Chebyshev transition in the coaxial transition decreases the size of the device, and keeps a good S-parameter in bandwidth. This novel eight-way Ka band radial waveguide spatial power divider/combiner can to be applied to pre-stage solid state power amplifiers and promote the gyro-TWT development.
A novel 8-way Ka band radial waveguide spatial power divider/combiner is analyzed and designed through the combination of theoretical research and high frequency electromagnetic field simulation. Compared with traditional coaxial structure, this new design uses a standard rectangular waveguide as the input and output structure. This all metal structure is much simpler, compacter and easier to manufacture. Simulation results show that the relative bandwidth of this device is 34% (the absolute bandwidth is 12 GHz), which nearly covers the whole Ka band, and S11 in the whole working bandwidth is below -20 dB; and that the phase difference of each way is under 5. Using the new Chebyshev transition in the coaxial transition decreases the size of the device, and keeps a good S-parameter in bandwidth. This novel eight-way Ka band radial waveguide spatial power divider/combiner can to be applied to pre-stage solid state power amplifiers and promote the gyro-TWT development.
2014,
26: 123005.
doi: 10.11884/HPLPB201426.123005
Abstract:
The theory of field-matching to build scattering matrix method was established to analyse optimization calculation for the multiple-disk output window. Through a lot of numerical calculation program design, the structure parameters of Q-band gyro-TWT double disk output window were given. Then by high frequency software HFSS simulation verification, the wide-band output windows of Q-band with band width about 4 GHz when S11 parameter is less than -20 dB were attained. Finally, on the basis of the further research, using a new method of collaborative simulation, thermal analysis of software ANSYS and HFSS was carried out on the double-disk output window to research the thermal property and power capacity of the new type output window with wind cooling. The research shows that the temperature difference of the new type output window compared with traditional output windows dropped significantly and the power capacity increased by 21.8 kW to 90 kW saturation power capacity.
The theory of field-matching to build scattering matrix method was established to analyse optimization calculation for the multiple-disk output window. Through a lot of numerical calculation program design, the structure parameters of Q-band gyro-TWT double disk output window were given. Then by high frequency software HFSS simulation verification, the wide-band output windows of Q-band with band width about 4 GHz when S11 parameter is less than -20 dB were attained. Finally, on the basis of the further research, using a new method of collaborative simulation, thermal analysis of software ANSYS and HFSS was carried out on the double-disk output window to research the thermal property and power capacity of the new type output window with wind cooling. The research shows that the temperature difference of the new type output window compared with traditional output windows dropped significantly and the power capacity increased by 21.8 kW to 90 kW saturation power capacity.
2014,
26: 123006.
doi: 10.11884/HPLPB201426.123006
Abstract:
W-Re, W-Sc, W-Zr, W-Y metal alloy cathodes were prepared, with Re, Sc, Zr and Y in metal alloy cathodes having the same mass fraction of 5%. Secondary electron emission coefficient testing results show that Re doped metal alloy cathodes can enhance the coefficient of pure W cathode sintered with W powder in the same preparation environment remarkably. 20%, 10%，6%, 5%, 4% and 3% mass fraction Re doped metal alloy cathodes were researched. 5% Re doped W-Re metal alloy cathode has the biggest maximum secondary electron emission coefficient of 1.8, 80% higher than that of pure W cathode. With the mass fraction of Re reducing, the coefficient of metal alloy cathodes were rising. When the mass fraction of Re dropped to 5%, metal alloy cathode had the biggest coefficient. However, for the mass fraction 4% of Re, the maximum coefficient of the metal alloy cathode dropped to 1.41. For the mass fraction 3% of Re, the maximum coefficient of metal alloy cathodes was only 1.1.
W-Re, W-Sc, W-Zr, W-Y metal alloy cathodes were prepared, with Re, Sc, Zr and Y in metal alloy cathodes having the same mass fraction of 5%. Secondary electron emission coefficient testing results show that Re doped metal alloy cathodes can enhance the coefficient of pure W cathode sintered with W powder in the same preparation environment remarkably. 20%, 10%，6%, 5%, 4% and 3% mass fraction Re doped metal alloy cathodes were researched. 5% Re doped W-Re metal alloy cathode has the biggest maximum secondary electron emission coefficient of 1.8, 80% higher than that of pure W cathode. With the mass fraction of Re reducing, the coefficient of metal alloy cathodes were rising. When the mass fraction of Re dropped to 5%, metal alloy cathode had the biggest coefficient. However, for the mass fraction 4% of Re, the maximum coefficient of the metal alloy cathode dropped to 1.41. For the mass fraction 3% of Re, the maximum coefficient of metal alloy cathodes was only 1.1.
2014,
26: 123007.
doi: 10.11884/HPLPB201426.123007
Abstract:
C band magnetron with high stabilization is the focus of magnetron research at present. 5.8 GHz magnetron is studied in both simulation and experiment. mode frequency of the magnetron is 5.863 GHz in the cold cavity simulation. The frequency separation of the magnetron is 44% between the operating frequency and the adjacent frequency when anode vanes are connected with straps alternative anode vanes at both ends. A magnetrons output frequency of 5.856 GHz and an output power of 1.2 kW are obtained in simulation. The experiment of the injection locked magnetron is studied in this paper, and the results show that the saturated output power is 1.047 kW and the efficiency is 58%. The frequency and phase difference of magnetron are stabilized when the frequency and the phase are locked.
C band magnetron with high stabilization is the focus of magnetron research at present. 5.8 GHz magnetron is studied in both simulation and experiment. mode frequency of the magnetron is 5.863 GHz in the cold cavity simulation. The frequency separation of the magnetron is 44% between the operating frequency and the adjacent frequency when anode vanes are connected with straps alternative anode vanes at both ends. A magnetrons output frequency of 5.856 GHz and an output power of 1.2 kW are obtained in simulation. The experiment of the injection locked magnetron is studied in this paper, and the results show that the saturated output power is 1.047 kW and the efficiency is 58%. The frequency and phase difference of magnetron are stabilized when the frequency and the phase are locked.
2014,
26: 123101.
doi: 10.11884/HPLPB201426.123101
Abstract:
The folded waveguide, the electron optical system, input and output windows of the 0.14 THz folded waveguide traveling-wave tubes were designed and simulated with the help of HFSS and CST. The beam wave interaction was also simulated. Research on development of 0.14 THz TWTs was done, including fabrication and welding of the folded waveguide slow wave structure and hot test experiment. In the condition of voltage 15.4 kV, the maximum saturated output power was 8.3 W and the output frequency was 140.8 GHz. The maximum gain was 28 dB and maximum power bandwidth was 2.9 GHz.
The folded waveguide, the electron optical system, input and output windows of the 0.14 THz folded waveguide traveling-wave tubes were designed and simulated with the help of HFSS and CST. The beam wave interaction was also simulated. Research on development of 0.14 THz TWTs was done, including fabrication and welding of the folded waveguide slow wave structure and hot test experiment. In the condition of voltage 15.4 kV, the maximum saturated output power was 8.3 W and the output frequency was 140.8 GHz. The maximum gain was 28 dB and maximum power bandwidth was 2.9 GHz.
2014,
26: 123201.
doi: 10.11884/HPLPB201426.123201
Abstract:
At present weighted support vector regression(WSVR) algorithms almost select a function of an important eigen quantity to calculate the weights, which leads to high errors in doing regression in high dimension eigen space. Aiming at this problem, a method of determining weights by the Euclidean distance in high dimension eigen space is presented, therefore an improved weighted support vector regression algorithm is built up and applied to the vulnerability assessment of electronic devices illuminated or injected by high power microwave(HPM). The simulation results show that our method is more accurate than the algorithms using fuzzy neural network(FNN), standard support vector regression and common weighted support vector regression. Because of the additional process of calculating weights, the presented methods efficiency is as high as that of the common WSVR algorithm but a little lower than that of the standard support vector regression algorithm and the FNN algorithm.
At present weighted support vector regression(WSVR) algorithms almost select a function of an important eigen quantity to calculate the weights, which leads to high errors in doing regression in high dimension eigen space. Aiming at this problem, a method of determining weights by the Euclidean distance in high dimension eigen space is presented, therefore an improved weighted support vector regression algorithm is built up and applied to the vulnerability assessment of electronic devices illuminated or injected by high power microwave(HPM). The simulation results show that our method is more accurate than the algorithms using fuzzy neural network(FNN), standard support vector regression and common weighted support vector regression. Because of the additional process of calculating weights, the presented methods efficiency is as high as that of the common WSVR algorithm but a little lower than that of the standard support vector regression algorithm and the FNN algorithm.
2014,
26: 124001.
doi: 10.11884/HPLPB201426.124001
Abstract:
In this paper, a novel preprocessing technique is proposed for the correction of ring artifact in X-ray CT image. By fitting each projection in sinogram image with piecewise polynomial, a set of candidate correction factors for mis-calibrated detector is created and then the factor with maximum probability occurrence is picked out to rectify the projection data. Principle and procedure of the method is illustrated. Tests under different condition show that, sparse or continuous ring artifact in the CT image can both be well rectified effectively, while spatial resolution of the image preserved. CT images for multi-material object can also be corrected by the method.
In this paper, a novel preprocessing technique is proposed for the correction of ring artifact in X-ray CT image. By fitting each projection in sinogram image with piecewise polynomial, a set of candidate correction factors for mis-calibrated detector is created and then the factor with maximum probability occurrence is picked out to rectify the projection data. Principle and procedure of the method is illustrated. Tests under different condition show that, sparse or continuous ring artifact in the CT image can both be well rectified effectively, while spatial resolution of the image preserved. CT images for multi-material object can also be corrected by the method.
2014,
26: 124002.
doi: 10.11884/HPLPB201426.124002
Abstract:
To provide energy loss loading conditions for the thermal analysis of Hall thruster, a thermal model of Hall thruster is developed. Based on the plasma theory, the mechanism of various energy losses in discharge chamber is analyzed, and related functions are established between these energy losses and operation, performance parameters and structural parameters. At last the complete thermal model of Hall thruster is obtained. The thermal model for LHT100 thruster is calculated. The following results under the steady operation are obtained: the beam energy loss is about 889 W, the energy loss at wall is about 300 W, the anode energy loss is about 44 W, the ionization energy loss is 43 W, and the radiation energy loss is 34 W, respectively. Taking these energy losses as loading conditions to perform finite element thermal analysis and using thermal balance to validate experimentally, the results indicate that the calculated values agree well with the experimental ones, the maximum error is no more than 5%.
To provide energy loss loading conditions for the thermal analysis of Hall thruster, a thermal model of Hall thruster is developed. Based on the plasma theory, the mechanism of various energy losses in discharge chamber is analyzed, and related functions are established between these energy losses and operation, performance parameters and structural parameters. At last the complete thermal model of Hall thruster is obtained. The thermal model for LHT100 thruster is calculated. The following results under the steady operation are obtained: the beam energy loss is about 889 W, the energy loss at wall is about 300 W, the anode energy loss is about 44 W, the ionization energy loss is 43 W, and the radiation energy loss is 34 W, respectively. Taking these energy losses as loading conditions to perform finite element thermal analysis and using thermal balance to validate experimentally, the results indicate that the calculated values agree well with the experimental ones, the maximum error is no more than 5%.
2014,
26: 124003.
doi: 10.11884/HPLPB201426.124003
Abstract:
The 252Cf-Source-Driven neutron pulse series have special sparse structure of 0, 1. There is no doubt that it satisfies the general condition of compressive sensing(CS). Unlike conventional compressive sensing approaches, we model the compressive sensing process with bipartite graph, combining with minimal covering of bipartite graph and adding some suitable conditions to the bipartite graph to construct a sparse and uniform measurement matrix. The results show that this new CS reconstruction algorithm is feasible for the 252Cf-source-driven neutron pulse series, and has a better performance than l1 method. Furthermore, this research provides a new approach or method for the signal processing of 252Cf-source-driven neutron pulse series.
The 252Cf-Source-Driven neutron pulse series have special sparse structure of 0, 1. There is no doubt that it satisfies the general condition of compressive sensing(CS). Unlike conventional compressive sensing approaches, we model the compressive sensing process with bipartite graph, combining with minimal covering of bipartite graph and adding some suitable conditions to the bipartite graph to construct a sparse and uniform measurement matrix. The results show that this new CS reconstruction algorithm is feasible for the 252Cf-source-driven neutron pulse series, and has a better performance than l1 method. Furthermore, this research provides a new approach or method for the signal processing of 252Cf-source-driven neutron pulse series.
2014,
26: 124004.
doi: 10.11884/HPLPB201426.124004
Abstract:
This paper described the design of a portable spectrometer, which could accomplish the mission of dose-rate and energy spectra analysis. The spectrometer system achieved a man-machine conversation platform for energy spectra data recording and processing using wireless WIFI communication technology and Android operating system. Emphases were focused on the scheme, including measuring principles, hardware design and software design. The principles, functions and cruces of every unit were explained in detail. Finally, according to measuring result of energy spectrum detection and contrast experiment, the capability of the instrument was analyzed. This system had 64k channels. The resolution was 3.81%.
This paper described the design of a portable spectrometer, which could accomplish the mission of dose-rate and energy spectra analysis. The spectrometer system achieved a man-machine conversation platform for energy spectra data recording and processing using wireless WIFI communication technology and Android operating system. Emphases were focused on the scheme, including measuring principles, hardware design and software design. The principles, functions and cruces of every unit were explained in detail. Finally, according to measuring result of energy spectrum detection and contrast experiment, the capability of the instrument was analyzed. This system had 64k channels. The resolution was 3.81%.
2014,
26: 124005.
doi: 10.11884/HPLPB201426.124005
Abstract:
The collective electric excitations in layered two-dimensional electron gases supported by an insulating substrate induced by a moving charged particle are investigated using linearized quantum hydrodynamic (LQHD) theory. General expressions of the induced potential, the stopping and image forces acting on the incident particle are derived by selecting appropriate boundary conditions. The influence of dielectric constant on induced potential, the stopping and image forces is discussed. Numerical results indicate that the substrate property has little influence on the induced electric field at smaller incident particle speed due to the weaker polarized electric field but the influence is remarkable at higher speed due to the stronger polarized electric field; the smaller the distance between the incident charged particle and the electron gas plane connected to the substrate, the more the influence of dielectric constant on relevant physics properties.
The collective electric excitations in layered two-dimensional electron gases supported by an insulating substrate induced by a moving charged particle are investigated using linearized quantum hydrodynamic (LQHD) theory. General expressions of the induced potential, the stopping and image forces acting on the incident particle are derived by selecting appropriate boundary conditions. The influence of dielectric constant on induced potential, the stopping and image forces is discussed. Numerical results indicate that the substrate property has little influence on the induced electric field at smaller incident particle speed due to the weaker polarized electric field but the influence is remarkable at higher speed due to the stronger polarized electric field; the smaller the distance between the incident charged particle and the electron gas plane connected to the substrate, the more the influence of dielectric constant on relevant physics properties.
2014,
26: 124101.
doi: 10.11884/HPLPB201426.124101
Abstract:
Capacitive RF MEMS switch will latch at high power RF signal handling situations. Due to the roughly contact between the switch membrane and the dielectric layer, the down-state capacitance of the switch degrades. The high-fidelity analytical computation model of the latching failure threshold power for a capacitive RF MEMS switch is very hard to establish. The comparative modelling method between a 3D electromagnetic simulation and an equivalent circuit simulation is proposed. First of all, the 3D electromagnetic simulation model is established. The simulation curve of the switch isolation (S21) is got at different surface roughness. And then the equivalent circuit model of the same switch is established. The simulation curve of the S21 of the switch equivalent circuit and the simulation result of the 3D electromagnetic are matched by tuning the down-state capacitance in the equivalent circuit. The set of function relationship between the surface roughness of dielectric layer and the down-state capacitance is identified. And the function relationships between the surface roughness of dielectric layer and the degradation of down-state capacitance are identified by changing the surface roughness level of dielectric layer and repeating the above steps. The rationality of the method is verified by comparing the calculated values of the down-state capacitance with the measured values in related literature. The analytical formula of latching failure threshold power of the switch with smooth dielectric layer is revised using the function relationships between the surface roughness of dielectric layer and the degradation of down-state capacitance to predict the power handling capacity of the switch with rough dielectric layer.
Capacitive RF MEMS switch will latch at high power RF signal handling situations. Due to the roughly contact between the switch membrane and the dielectric layer, the down-state capacitance of the switch degrades. The high-fidelity analytical computation model of the latching failure threshold power for a capacitive RF MEMS switch is very hard to establish. The comparative modelling method between a 3D electromagnetic simulation and an equivalent circuit simulation is proposed. First of all, the 3D electromagnetic simulation model is established. The simulation curve of the switch isolation (S21) is got at different surface roughness. And then the equivalent circuit model of the same switch is established. The simulation curve of the S21 of the switch equivalent circuit and the simulation result of the 3D electromagnetic are matched by tuning the down-state capacitance in the equivalent circuit. The set of function relationship between the surface roughness of dielectric layer and the down-state capacitance is identified. And the function relationships between the surface roughness of dielectric layer and the degradation of down-state capacitance are identified by changing the surface roughness level of dielectric layer and repeating the above steps. The rationality of the method is verified by comparing the calculated values of the down-state capacitance with the measured values in related literature. The analytical formula of latching failure threshold power of the switch with smooth dielectric layer is revised using the function relationships between the surface roughness of dielectric layer and the degradation of down-state capacitance to predict the power handling capacity of the switch with rough dielectric layer.
2014,
26: 124102.
doi: 10.11884/HPLPB201426.124102
Abstract:
To improve the machining accuracy of the hole on the polystyrene microspheres for laser fusion, a fundamental understanding of the mechanisms of femtosecond laser ablation is required. We establish a molecular dynamics model of femtosecond laser ablation of polymers by optimally selecting the molecule representation model and related force field. Subsequent molecular dynamics simulations of femtosecond laser ablation of polyethylene and polystyrene show that the laser ablation-induced polymer material removal is caused by single chain ejection-accompanied surface evaporation and single chain motion-accompanied thermal expansion within the bulk. Furthermore, the microscopic deformation mechanisms of the single chain include inter-chain sliding and intra-chain change. It is found that the discrepancy in the molecule architecture has strong influence on the femtosecond laser ablation of polyethylene and polystyrene.
To improve the machining accuracy of the hole on the polystyrene microspheres for laser fusion, a fundamental understanding of the mechanisms of femtosecond laser ablation is required. We establish a molecular dynamics model of femtosecond laser ablation of polymers by optimally selecting the molecule representation model and related force field. Subsequent molecular dynamics simulations of femtosecond laser ablation of polyethylene and polystyrene show that the laser ablation-induced polymer material removal is caused by single chain ejection-accompanied surface evaporation and single chain motion-accompanied thermal expansion within the bulk. Furthermore, the microscopic deformation mechanisms of the single chain include inter-chain sliding and intra-chain change. It is found that the discrepancy in the molecule architecture has strong influence on the femtosecond laser ablation of polyethylene and polystyrene.
2014,
26: 124103.
doi: 10.11884/HPLPB201426.124103
Abstract:
Carbon nanotube is an ideal cold cathode material because of its good field emission characteristics. In order to develop field-emission carbon nanotube cold cathode devices, the characteristics of three kinds of mesh grid structures on carbon nanotube cold cathodes are simulated by using three-dimensional PIC simulation software. The properties of hexagon mesh, triangle mesh, and square mesh are investigated by calculating the electric-field distribution on the surface of cold cathode and field emission beam current pass rate. Simulation results show that the hexagon mesh characteristics is the best. The optimal mesh size of hexagon mesh is obtained and the maximum current pass rate is 75%.
Carbon nanotube is an ideal cold cathode material because of its good field emission characteristics. In order to develop field-emission carbon nanotube cold cathode devices, the characteristics of three kinds of mesh grid structures on carbon nanotube cold cathodes are simulated by using three-dimensional PIC simulation software. The properties of hexagon mesh, triangle mesh, and square mesh are investigated by calculating the electric-field distribution on the surface of cold cathode and field emission beam current pass rate. Simulation results show that the hexagon mesh characteristics is the best. The optimal mesh size of hexagon mesh is obtained and the maximum current pass rate is 75%.
2014,
26: 124104.
doi: 10.11884/HPLPB201426.124104
Abstract:
Mo coatings on microspheres surface were fabricated by magnetron sputtering with different conditions. Using white light interference instrument and scanning electron microscope, the cross section and surface morphology of the samples were studied. The effects of working pressure and sputtering time on the morphology of Mo coatings were investigated. The result shows that Mo coatings with a thickness from 3.5 m to 14.1 m can be fabricated on microspheres surface, all of the coating thicknesses are uniform. The coatings show highly packed microstructures, with coating thickness increased, the interspaces between different grains increase.
Mo coatings on microspheres surface were fabricated by magnetron sputtering with different conditions. Using white light interference instrument and scanning electron microscope, the cross section and surface morphology of the samples were studied. The effects of working pressure and sputtering time on the morphology of Mo coatings were investigated. The result shows that Mo coatings with a thickness from 3.5 m to 14.1 m can be fabricated on microspheres surface, all of the coating thicknesses are uniform. The coatings show highly packed microstructures, with coating thickness increased, the interspaces between different grains increase.
2014,
26: 125001.
doi: 10.11884/HPLPB201426.125001
Abstract:
A compact high-power(GW level) nanosecond pulse generator is developed. The pulse generator includes a 40 coaxial pulse forming line charged by a built-in Tesla transformer with open circuit magnetic core, primary circuit and high-voltage gas switch with gas circulating between the electrodes. The generator has characteristics of high transformer ratio, compact structure, high energy transfer efficiency, and convenient for high repetition rate operation. The operation principles, design methods and simulated calculations of pulse forming line, Tesla transformer and main switch are described. The experimental results show that the output voltage of the pulse generator is more than 200 kV with a width of about 8 ns, and it can operate steadily under the condition of repetition rate of 100 Hz and average output power of 1 GW, the experimental results are in good agreement with that from theoretical design.
A compact high-power(GW level) nanosecond pulse generator is developed. The pulse generator includes a 40 coaxial pulse forming line charged by a built-in Tesla transformer with open circuit magnetic core, primary circuit and high-voltage gas switch with gas circulating between the electrodes. The generator has characteristics of high transformer ratio, compact structure, high energy transfer efficiency, and convenient for high repetition rate operation. The operation principles, design methods and simulated calculations of pulse forming line, Tesla transformer and main switch are described. The experimental results show that the output voltage of the pulse generator is more than 200 kV with a width of about 8 ns, and it can operate steadily under the condition of repetition rate of 100 Hz and average output power of 1 GW, the experimental results are in good agreement with that from theoretical design.
2014,
26: 125002.
doi: 10.11884/HPLPB201426.125002
Abstract:
In order to test the capacitors lifetime at different voltage under short circuit, a lifetime test platform is designed based on resonant charge and pulsed transformer and discharge switch. The platform has met the following design specifications on the 2.5 nF capacitor: more than 100 kV output voltage, about 7 kA discharge current, 50 Hz repetition frequency and up to 5 min runtime. The platform is controlled by a PC and can record runtime automatically.
In order to test the capacitors lifetime at different voltage under short circuit, a lifetime test platform is designed based on resonant charge and pulsed transformer and discharge switch. The platform has met the following design specifications on the 2.5 nF capacitor: more than 100 kV output voltage, about 7 kA discharge current, 50 Hz repetition frequency and up to 5 min runtime. The platform is controlled by a PC and can record runtime automatically.
2014,
26: 125101.
doi: 10.11884/HPLPB201426.125101
Abstract:
For the proper operation of Dalian Coherent Light Source (DCLS) linac, measurement and control of the electron bunch is essential. In order to test control algorithms and high level physical applications, a virtual accelerator environment is constructed based on ELEGANT code and SDDS Toolkit. The required beam parameter measurement and orbit control tools are tested under this virtual environment and will greatly speed up the development of machine commissioning tools. The design concept and current development status are presented.
For the proper operation of Dalian Coherent Light Source (DCLS) linac, measurement and control of the electron bunch is essential. In order to test control algorithms and high level physical applications, a virtual accelerator environment is constructed based on ELEGANT code and SDDS Toolkit. The required beam parameter measurement and orbit control tools are tested under this virtual environment and will greatly speed up the development of machine commissioning tools. The design concept and current development status are presented.
2014,
26: 125102.
doi: 10.11884/HPLPB201426.125102
Abstract:
The beam orbit interlock system is one of the most important components of the machine protection system (MPS) of Shanghai Synchrotron Radiation Facility(SSRF). The daily research asks for recording the interlock signal coming from different Libera BPM in the beam position measurement system, and lathing turn by turn data in Post Mortem buffer in Libera electronics when interlock occurs. This will be helpful to distinguish mistaken interlock signal and improve the stability of the accelerator. In our system, we use NI PXI-7813R DAQ equipment based on FPGA to achieve these functions. This system will be integrated to EPICS control system. The laboratory test results show that the system is able to distinguish the simulated interlock signal in the range of tens of nanoseconds, and output specific trigger signal to the corresponding Libera electronics, which prove that the system meets the designed requirements.
The beam orbit interlock system is one of the most important components of the machine protection system (MPS) of Shanghai Synchrotron Radiation Facility(SSRF). The daily research asks for recording the interlock signal coming from different Libera BPM in the beam position measurement system, and lathing turn by turn data in Post Mortem buffer in Libera electronics when interlock occurs. This will be helpful to distinguish mistaken interlock signal and improve the stability of the accelerator. In our system, we use NI PXI-7813R DAQ equipment based on FPGA to achieve these functions. This system will be integrated to EPICS control system. The laboratory test results show that the system is able to distinguish the simulated interlock signal in the range of tens of nanoseconds, and output specific trigger signal to the corresponding Libera electronics, which prove that the system meets the designed requirements.
2014,
26: 125103.
doi: 10.11884/HPLPB201426.125103
Abstract:
This article studies the relationship between the copper layer thickness of the outer conductor of superconducting cavity input coupler and the heat leak.We compared copper coatings of 10，20，30 m respectively of 325 MHz coupler through high power test and aimed to find the optimum thickness of the copper plating layer in order to decrease the cryogenic heat load . The experimental results show that 20 m layer has lower dynamic heat leak. Considering both static heat leak and dynamic heat leak, the 20 m thickness of copper layer is the optimum one.
This article studies the relationship between the copper layer thickness of the outer conductor of superconducting cavity input coupler and the heat leak.We compared copper coatings of 10，20，30 m respectively of 325 MHz coupler through high power test and aimed to find the optimum thickness of the copper plating layer in order to decrease the cryogenic heat load . The experimental results show that 20 m layer has lower dynamic heat leak. Considering both static heat leak and dynamic heat leak, the 20 m thickness of copper layer is the optimum one.
2014,
26: 129001.
doi: 10.11884/HPLPB201426.129001
Abstract:
To obtain the coating with excellent properties, FeSiCrCoMo high entropy alloy (HEA) coatings on Q235 steel were prepared by laser cladding. The effect of adding WC on microstructure and properties of the HEA coatings were investigated. By means of OM, XRD, SEM, microhardness test and hardmeter abrasion tester, the microstructure, phase structure, hardness and wear resistance of the coatings adding WC and without adding WC were studied. The experimental results indicate that the microstructure of the FeSiCrCoMo HEAs coating is dendrite, the coating is mainly composed of body centered cubic (BCC) with intermetallics. The microstructure of the coating with WC is grain cellular crystal, at the same time, the BCC phase increase and intermetallics decrease. The mechanical properties of the coating are also enhanced by adding WC. With WC added, the average hardness of the coating increases by 23%, the average hardness of coating reaches 687HV0.2; on the other hand, the wear rate decreases and wear resistance increases, hence the wear-resisting performance improves.
To obtain the coating with excellent properties, FeSiCrCoMo high entropy alloy (HEA) coatings on Q235 steel were prepared by laser cladding. The effect of adding WC on microstructure and properties of the HEA coatings were investigated. By means of OM, XRD, SEM, microhardness test and hardmeter abrasion tester, the microstructure, phase structure, hardness and wear resistance of the coatings adding WC and without adding WC were studied. The experimental results indicate that the microstructure of the FeSiCrCoMo HEAs coating is dendrite, the coating is mainly composed of body centered cubic (BCC) with intermetallics. The microstructure of the coating with WC is grain cellular crystal, at the same time, the BCC phase increase and intermetallics decrease. The mechanical properties of the coating are also enhanced by adding WC. With WC added, the average hardness of the coating increases by 23%, the average hardness of coating reaches 687HV0.2; on the other hand, the wear rate decreases and wear resistance increases, hence the wear-resisting performance improves.
2014,
26: 129002.
doi: 10.11884/HPLPB201426.129002
Abstract:
The performance parameters of a hypersonic inlet (the designed mach number is 6) are computed using finite volume method with three dimensional unsteady compressible N-S equations, and the performance is found descending clearly. In order to improve the inlet performance, laser energy whose power is 15 kW is injected into the flow field in front of the solid cowl of inlet, and then the virtual cowl is formed. The inflow mass capture ratio increases by 34%, 20.6% and 15.6% when the inflow mach number is 4.5, 5 and 5.5 respectively. Pressure contours of the inlet at peak value of inflow mass capture ratio under different mach numbers are illustrated. Characteristics and forming mechanism of the virtual cowl are explained. The results indicate that the smaller the inflow mach number is, the lower the inflow mass capture ratio is, but relative to that without laser energy being injected, the inflow mass capture advancing level is more obvious. Under different inflow mach numbers, the optimum can be achieved through changing the configuration and position of laser induced shock wave. The optimum is the state that transmission wave formed by laser induced shock intersecting with the oblique shock in the leading edge of inflow injects on the inlet shoulder.
The performance parameters of a hypersonic inlet (the designed mach number is 6) are computed using finite volume method with three dimensional unsteady compressible N-S equations, and the performance is found descending clearly. In order to improve the inlet performance, laser energy whose power is 15 kW is injected into the flow field in front of the solid cowl of inlet, and then the virtual cowl is formed. The inflow mass capture ratio increases by 34%, 20.6% and 15.6% when the inflow mach number is 4.5, 5 and 5.5 respectively. Pressure contours of the inlet at peak value of inflow mass capture ratio under different mach numbers are illustrated. Characteristics and forming mechanism of the virtual cowl are explained. The results indicate that the smaller the inflow mach number is, the lower the inflow mass capture ratio is, but relative to that without laser energy being injected, the inflow mass capture advancing level is more obvious. Under different inflow mach numbers, the optimum can be achieved through changing the configuration and position of laser induced shock wave. The optimum is the state that transmission wave formed by laser induced shock intersecting with the oblique shock in the leading edge of inflow injects on the inlet shoulder.
2014,
26: 129003.
doi: 10.11884/HPLPB201426.129003
Abstract:
Regularization algorithm is a common method to recover the particle size distributions (PSDs) from dynamic light scattering (DLS) data. The initial regularization model has important influence on the inversion results. In this paper, the narrow and wide simulation distributions of 90 nm and 250 nm particles were inversed by the smallest, the flattest and the smoothest initial model respectively. The inversion results show that the initial model has almost no influence on the inversion results under the noise level of 0. With the increase of noise level, although the errors of peak and PSD value inversed by the three initial models are all increased, the increases by using flattest model and smoothest model are obviously less than that using the smallest model. When the noise level is greater than 0.01, the better particle size distribution results can be obtained by using the flattest model than the smallest and the smoothest models, and more accurate particle peak values can be got by using the smoothest model than the flattest and the smallest models. For obtaining the optimal PSDs inversed by regularization from noisy DLS data, the flattest model is recommended, and for getting the optimal peak value, the smoothest model is the best choice.
Regularization algorithm is a common method to recover the particle size distributions (PSDs) from dynamic light scattering (DLS) data. The initial regularization model has important influence on the inversion results. In this paper, the narrow and wide simulation distributions of 90 nm and 250 nm particles were inversed by the smallest, the flattest and the smoothest initial model respectively. The inversion results show that the initial model has almost no influence on the inversion results under the noise level of 0. With the increase of noise level, although the errors of peak and PSD value inversed by the three initial models are all increased, the increases by using flattest model and smoothest model are obviously less than that using the smallest model. When the noise level is greater than 0.01, the better particle size distribution results can be obtained by using the flattest model than the smallest and the smoothest models, and more accurate particle peak values can be got by using the smoothest model than the flattest and the smallest models. For obtaining the optimal PSDs inversed by regularization from noisy DLS data, the flattest model is recommended, and for getting the optimal peak value, the smoothest model is the best choice.
2014,
26: 129004.
doi: 10.11884/HPLPB201426.129004
Abstract:
In order to investigate the properties of electron beam plasma in high velocity flow, a multi-stage numerical model including the Monte Carlo model, multi-fluid plasma model and CFD model is established. In the near-sound-speed flow, the characteristics of electron beam air plasma are studied in detail. The results indicate that the energy deposition of the electron beam is nonuniform in space and the flow fields are distinct in subsonic and supersonic flow. In the subsonic flow, the density of boundary layer in the downstream decreases; but in the supersonic flow, a weak shockwave is induced by the injected beam. The plasma density decreases and the significant plasma transportation is observed in the high velocity flow, thus the plasma is transported to the downstream. The effect of the velocity magnitude on the plasma distribution is small in the near-sound-speed flow. However, the injection angle of beam influences the plasma density and distribution significantly.
In order to investigate the properties of electron beam plasma in high velocity flow, a multi-stage numerical model including the Monte Carlo model, multi-fluid plasma model and CFD model is established. In the near-sound-speed flow, the characteristics of electron beam air plasma are studied in detail. The results indicate that the energy deposition of the electron beam is nonuniform in space and the flow fields are distinct in subsonic and supersonic flow. In the subsonic flow, the density of boundary layer in the downstream decreases; but in the supersonic flow, a weak shockwave is induced by the injected beam. The plasma density decreases and the significant plasma transportation is observed in the high velocity flow, thus the plasma is transported to the downstream. The effect of the velocity magnitude on the plasma distribution is small in the near-sound-speed flow. However, the injection angle of beam influences the plasma density and distribution significantly.
2014,
26: 122003.
doi: 10.11884/HPLPB201426.122003
Abstract:
The CMOS detector systems have been introduced for diagnosing on-line soft X-ray imaging signals by coupling fiber optic plate covered scintillator and CMOS image sensor. The thickness of CsI scintillator was confirmed to be 30 m according to XOP program calculation in 1-10 keV energy range. Based on the micro-point X-ray source, the spatial resolution of the systems was found to be 60 m using Typ 18-d standard resolution test target. The CMOS detector systems were applied in hydromechanical instability and mixture research on shenguang-Ⅲ prototype facility to diagnose Ti spectra of backlit source. The H-like and He-like spectra were recorded clearly. The data analysis showed the experimental spectral resolution (/) that was about 442 nearly accorded with that of the theoretical model. The CMOS detector systems are suitable for universities and scientific academies in on-line soft X-ray diagnosis since they have obvious advantages such as small volume, high performance and low price.
The CMOS detector systems have been introduced for diagnosing on-line soft X-ray imaging signals by coupling fiber optic plate covered scintillator and CMOS image sensor. The thickness of CsI scintillator was confirmed to be 30 m according to XOP program calculation in 1-10 keV energy range. Based on the micro-point X-ray source, the spatial resolution of the systems was found to be 60 m using Typ 18-d standard resolution test target. The CMOS detector systems were applied in hydromechanical instability and mixture research on shenguang-Ⅲ prototype facility to diagnose Ti spectra of backlit source. The H-like and He-like spectra were recorded clearly. The data analysis showed the experimental spectral resolution (/) that was about 442 nearly accorded with that of the theoretical model. The CMOS detector systems are suitable for universities and scientific academies in on-line soft X-ray diagnosis since they have obvious advantages such as small volume, high performance and low price.
2014,
26: 122004.
doi: 10.11884/HPLPB201426.122004
Abstract:
Polycarbosilane (PCS) was irradiated by electron beam (EB) with inert gas protection. The as-prepared specimens were characterized using IR, Gel content measurements and TG-GC-MS. The chemical structures, the pyrolysis properties and the effects of irradiation dose were investigated. The result shows that three-dimensional netlike gel products composed as SiCSi crosslinking bonds were formed in the irradiated products, and that SiH bonds and CH bonds were partly broken down in the process of irradiation. The gel content of PCS increased evidently with the irradiation dose, especially when the absorbed dose was above 3 MGy. Furthermore, the thermo-stability and ceramic yield could be improved by EB radiation and the ceramic yield of PCS irradiated under 20 MGy could be up to 87%. In addition, the gel content, the pyrolysis temperature and the ceramic yield of pre-heatment at 400 ℃ could be higher than the PCS raw material at the same absorbed dose.
Polycarbosilane (PCS) was irradiated by electron beam (EB) with inert gas protection. The as-prepared specimens were characterized using IR, Gel content measurements and TG-GC-MS. The chemical structures, the pyrolysis properties and the effects of irradiation dose were investigated. The result shows that three-dimensional netlike gel products composed as SiCSi crosslinking bonds were formed in the irradiated products, and that SiH bonds and CH bonds were partly broken down in the process of irradiation. The gel content of PCS increased evidently with the irradiation dose, especially when the absorbed dose was above 3 MGy. Furthermore, the thermo-stability and ceramic yield could be improved by EB radiation and the ceramic yield of PCS irradiated under 20 MGy could be up to 87%. In addition, the gel content, the pyrolysis temperature and the ceramic yield of pre-heatment at 400 ℃ could be higher than the PCS raw material at the same absorbed dose.
2014,
26: 122007.
doi: 10.11884/HPLPB201426.122007
Abstract:
Carbon-deuterium polymer films were fabricated at different powers by the discharge polymerization technology. The difference of chemical structures was characterized by FT-IR. The content of deuterium of films was characterized by element analysis and the hardness and modulus of films were measured by nanoindentation. It was found that with the RF power increasing, the D contents in the films firstly increased, then decreased, and reached to the biggest at 10 W. The CD bands content increased, while the CD2 bands content decreased. The hardness and modulus of films decreased when the RF power increased.
Carbon-deuterium polymer films were fabricated at different powers by the discharge polymerization technology. The difference of chemical structures was characterized by FT-IR. The content of deuterium of films was characterized by element analysis and the hardness and modulus of films were measured by nanoindentation. It was found that with the RF power increasing, the D contents in the films firstly increased, then decreased, and reached to the biggest at 10 W. The CD bands content increased, while the CD2 bands content decreased. The hardness and modulus of films decreased when the RF power increased.
2014,
26: 122008.
doi: 10.11884/HPLPB201426.122008
Abstract:
Subsurface damage will be generated in grinding, lapping and polishing process, the subsurface defects such as micro cracks, scratches and residual stress will decrease the anti-laser-induced damage ability of fused silica optics. How to quickly and accurately detect subsurface damage becomes a vital problem in the field of optics manufacturing. In this paper, subsurface damage morphology and depths of fused silica optics were detected and analyzed by HF acid etching, taper polishing and MRF slope polishing methods. The results show that there are some differences in the test results of subsurface damage depth by different detection methods, the subsurface damage depths obtained by HF acid etching method are larger than those obtained by taper polishing and MRF slope polishing methods. The larger the abrasive particles are, the more serious the phenomenon of brittle fracture in surface and subsurface will be, and the greater the depth of subsurface defects will be.
Subsurface damage will be generated in grinding, lapping and polishing process, the subsurface defects such as micro cracks, scratches and residual stress will decrease the anti-laser-induced damage ability of fused silica optics. How to quickly and accurately detect subsurface damage becomes a vital problem in the field of optics manufacturing. In this paper, subsurface damage morphology and depths of fused silica optics were detected and analyzed by HF acid etching, taper polishing and MRF slope polishing methods. The results show that there are some differences in the test results of subsurface damage depth by different detection methods, the subsurface damage depths obtained by HF acid etching method are larger than those obtained by taper polishing and MRF slope polishing methods. The larger the abrasive particles are, the more serious the phenomenon of brittle fracture in surface and subsurface will be, and the greater the depth of subsurface defects will be.
2014,
26: 123001.
doi: 10.11884/HPLPB201426.123001
Abstract:
Based on the working principle of the backward wave oscillator (BWO) with a low magnetic field, a frequency-agile relativistic backward wave oscillator (RBWO), whose frequency can be counterchanged between X band and C band by changing the strength of the guiding magnetic field, is designed. To actualize frequencys agile counterchange, two sections of slow wave structure (SWS), whose appeals on parameters of electron beams are accordant, are linked. When the energy of the electron is 670 keV while the beam current is 8 kA, the simulated result of 1.0 GW output microwave power with 6.28 GHz frequency is obtained on conduction of 0.5 T guiding magnetic field, while 0.75 GW output microwave power with 9.26 GHz frequency is obtained on conduction of 0.8 T guiding magnetic field.
Based on the working principle of the backward wave oscillator (BWO) with a low magnetic field, a frequency-agile relativistic backward wave oscillator (RBWO), whose frequency can be counterchanged between X band and C band by changing the strength of the guiding magnetic field, is designed. To actualize frequencys agile counterchange, two sections of slow wave structure (SWS), whose appeals on parameters of electron beams are accordant, are linked. When the energy of the electron is 670 keV while the beam current is 8 kA, the simulated result of 1.0 GW output microwave power with 6.28 GHz frequency is obtained on conduction of 0.5 T guiding magnetic field, while 0.75 GW output microwave power with 9.26 GHz frequency is obtained on conduction of 0.8 T guiding magnetic field.
2014,
26: 123002.
doi: 10.11884/HPLPB201426.123002
Abstract:
The de-embedding technology is implemented through the idea that views the measurement circuit as an equivalent network cascade in radio frequency. Usually, the working frequency is below 6 GHz. For it can realize the accurate measurement of the device under test (DUT), it has been the focus for many tests. But when it refers to the de-embedding technology in microwave measurement, the present study is not enough. In order to get the actual value of the DUT, based on the principle of error model parameters correction, this article takes the Gyro-TWT output window as an example to verify the principle and finally gets the actual results of the DUT after de-embedding whose working frequency is on Q band. This principle gets rid of the resonance problem, and shows that the de-embedding principle has a high accuracy in microwave measurement. This article introduces the de-embedding principles and concretes the implementation methods, which have important significance on microwave de-embedding.
The de-embedding technology is implemented through the idea that views the measurement circuit as an equivalent network cascade in radio frequency. Usually, the working frequency is below 6 GHz. For it can realize the accurate measurement of the device under test (DUT), it has been the focus for many tests. But when it refers to the de-embedding technology in microwave measurement, the present study is not enough. In order to get the actual value of the DUT, based on the principle of error model parameters correction, this article takes the Gyro-TWT output window as an example to verify the principle and finally gets the actual results of the DUT after de-embedding whose working frequency is on Q band. This principle gets rid of the resonance problem, and shows that the de-embedding principle has a high accuracy in microwave measurement. This article introduces the de-embedding principles and concretes the implementation methods, which have important significance on microwave de-embedding.
2014,
26: 122005.
doi: 10.11884/HPLPB201426.122005
Abstract:
Beam deflection of a monospeckle laser beam propagating in a plasma with parameters relevant to Inertial Confinement Fusion is investigated using three dimensional Euler laser plasma interaction code LAP3D. Effects of the beam intensity and the speed of the transverse flow on the beam deflection are analyzed. Simulation results suggest that the beam deflection is caused by laser self-focusing and plasma transverse flow. It is found that the beam deflection is evident only when the speed of plasma transverse flow is closer to that of ion acoustic wave and the angle of the beam deflection is in proportion to the laser intensity. When the speed of plasma transverse flow becomes lower than that of ion acoustic wave, the beam deflection is suppressed. When the speed of plasma transverse flow becomes larger than that of ion acoustic wave, refraction effect becomes dominant.
Beam deflection of a monospeckle laser beam propagating in a plasma with parameters relevant to Inertial Confinement Fusion is investigated using three dimensional Euler laser plasma interaction code LAP3D. Effects of the beam intensity and the speed of the transverse flow on the beam deflection are analyzed. Simulation results suggest that the beam deflection is caused by laser self-focusing and plasma transverse flow. It is found that the beam deflection is evident only when the speed of plasma transverse flow is closer to that of ion acoustic wave and the angle of the beam deflection is in proportion to the laser intensity. When the speed of plasma transverse flow becomes lower than that of ion acoustic wave, the beam deflection is suppressed. When the speed of plasma transverse flow becomes larger than that of ion acoustic wave, refraction effect becomes dominant.
2014,
26: 122006.
doi: 10.11884/HPLPB201426.122006
Abstract:
The flat on the side of hohlraum mandrel was machined by electrical discharge machining technology. The surface roughness and contour were characterized by Veeco NT 1100 white light interferometer. The results indicate surface average roughness of flat less than 0.5 m and maximum peak to valley height less than 15 m. The flat size was characterized by OLYMPUS STM6 measuring microscope. The results indicate axial dimension precision of flat less than 10 m and dimension uniformity less than 2 m.
The flat on the side of hohlraum mandrel was machined by electrical discharge machining technology. The surface roughness and contour were characterized by Veeco NT 1100 white light interferometer. The results indicate surface average roughness of flat less than 0.5 m and maximum peak to valley height less than 15 m. The flat size was characterized by OLYMPUS STM6 measuring microscope. The results indicate axial dimension precision of flat less than 10 m and dimension uniformity less than 2 m.
