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RSS2011 Vol. 23, No. 06
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2011,
23.
Abstract:
Based on our achievements and that of peers of home and abroad, several aspects of nodular defect are summarized and reviewed. The size, shape and surface properties of nodule seed determinate the size, boundaries continuity and topography of nodule. The seed sources are mainly the residue during the processing and cleaning of substrate, contamination from the coating chamber and particulate from the evaporation source material. The corresponding methods to eliminate the seed source are given. The electronic field enhancement is another main reason for the damage susceptibility of nodule. Laser conditioning and mitigation method can improve the capacity of laser damage resistance.
Based on our achievements and that of peers of home and abroad, several aspects of nodular defect are summarized and reviewed. The size, shape and surface properties of nodule seed determinate the size, boundaries continuity and topography of nodule. The seed sources are mainly the residue during the processing and cleaning of substrate, contamination from the coating chamber and particulate from the evaporation source material. The corresponding methods to eliminate the seed source are given. The electronic field enhancement is another main reason for the damage susceptibility of nodule. Laser conditioning and mitigation method can improve the capacity of laser damage resistance.
2011,
23.
Abstract:
This paper introduces main modules of 0.14 THz super high speed wireless communication experimental system and experimental results. The THz research group of Institute of Electronic Engineering of China Academy of Engineering Physics, from the view point of THz electronics, based on the THz semiconductor devices and wide band digital modulation and demodulation technologies, utilizing the technologies of “low frequency band hyper-speed vector modulation + sub-harmonic mixer + amplifier”， successfully achieves 0.14 THz 0.5 km 10 Gb/s high speed transmission afterwards by means of soft demodulation, realizes 4 channel high-definition video signal real-time transmission and demodulation for the first time in China.
This paper introduces main modules of 0.14 THz super high speed wireless communication experimental system and experimental results. The THz research group of Institute of Electronic Engineering of China Academy of Engineering Physics, from the view point of THz electronics, based on the THz semiconductor devices and wide band digital modulation and demodulation technologies, utilizing the technologies of “low frequency band hyper-speed vector modulation + sub-harmonic mixer + amplifier”， successfully achieves 0.14 THz 0.5 km 10 Gb/s high speed transmission afterwards by means of soft demodulation, realizes 4 channel high-definition video signal real-time transmission and demodulation for the first time in China.
2011,
23.
Abstract:
Using the pixellated CdZnTe detector, the radiation imaging experiment for the Rh target X-ray source was accomplished. The experimental results indicate that the response signals of the anode pixels, which distribute over the center irradiated area, are completely shut-off when the tube voltage is 45 kV and the tube current increases to 20 μA. Moreover, the non-response pixel area expands with the increase of the tube current, and the total event count of the CdZnTe detector reduces obviously. Furthermore, the inner electric potential and electric field distributions of the pixellated CdZnTe detector were simulated based on the Poisson equation. The simulation results reveal that the accumulation of the hole carriers, which results from the extremely low drift ability of the hole carrier
Using the pixellated CdZnTe detector, the radiation imaging experiment for the Rh target X-ray source was accomplished. The experimental results indicate that the response signals of the anode pixels, which distribute over the center irradiated area, are completely shut-off when the tube voltage is 45 kV and the tube current increases to 20 μA. Moreover, the non-response pixel area expands with the increase of the tube current, and the total event count of the CdZnTe detector reduces obviously. Furthermore, the inner electric potential and electric field distributions of the pixellated CdZnTe detector were simulated based on the Poisson equation. The simulation results reveal that the accumulation of the hole carriers, which results from the extremely low drift ability of the hole carrier
2011,
23.
Abstract:
Correction of gain nonuniformity is researched by using taper microstrip. The physical correction model is founded. The taper microstrip compensates the magnitude attenuation by compensating the impedance of microstrip. The taper microstrip is designed. The correction results of curve taper microstrip and straight taper microstrip are compared with each other. The voltage nonuniformity decreases from 15.0% to 1.6% and the gain nonuniformity decreases from 70% to 8% with curve taper microstrip compensation while the frequency of pulse is between 0 and 4 GHz. The taper microstrip with width from 6.00 mm to 4 mm has a good effect of correcting the gain nonuniformity for current framing camera.
Correction of gain nonuniformity is researched by using taper microstrip. The physical correction model is founded. The taper microstrip compensates the magnitude attenuation by compensating the impedance of microstrip. The taper microstrip is designed. The correction results of curve taper microstrip and straight taper microstrip are compared with each other. The voltage nonuniformity decreases from 15.0% to 1.6% and the gain nonuniformity decreases from 70% to 8% with curve taper microstrip compensation while the frequency of pulse is between 0 and 4 GHz. The taper microstrip with width from 6.00 mm to 4 mm has a good effect of correcting the gain nonuniformity for current framing camera.
2011,
23.
Abstract:
An all-fiber configuration master oscillator power amplification (MOPA) structured high power laser with China-made components is constructed. The fiber laser is composed of a 10 W seed laser and a high power fiber amplifier. A maximum output of 245 W centered at 1 080 nm is achieved at the launched pump power of 356 W. The optical to optical conversion efficiency is 69%. The power fluctuation is less than 1% within half an hour. The experimental results have demonstrated the potential for higher output power with more powerful pump source.
An all-fiber configuration master oscillator power amplification (MOPA) structured high power laser with China-made components is constructed. The fiber laser is composed of a 10 W seed laser and a high power fiber amplifier. A maximum output of 245 W centered at 1 080 nm is achieved at the launched pump power of 356 W. The optical to optical conversion efficiency is 69%. The power fluctuation is less than 1% within half an hour. The experimental results have demonstrated the potential for higher output power with more powerful pump source.
2011,
23.
Abstract:
Pump coupling is the hard-core of the high-power diode array pumped solid-state laser, which directly determines system cost, gain capacity, gain uniformity, pump-induced wave front distortion, pump-induced beam drift and so on. Based on the three-dimensional ray tracing method, this paper established the theoretical model of the high-power diode array end-pumped solid-state laser. Then a new type of pump coupling was optimized, which adopted a diode array arranged to be spherical and a hollow silver duct, and experiments on pump coupling efficiency and uniformity and transmission of the pump field were conducted. With the optimization, a uniform flat-topped pump-coupled output field was derived within 5 mm range from the duct exit, with 72% coupling efficiency and 80% transmission efficie
Pump coupling is the hard-core of the high-power diode array pumped solid-state laser, which directly determines system cost, gain capacity, gain uniformity, pump-induced wave front distortion, pump-induced beam drift and so on. Based on the three-dimensional ray tracing method, this paper established the theoretical model of the high-power diode array end-pumped solid-state laser. Then a new type of pump coupling was optimized, which adopted a diode array arranged to be spherical and a hollow silver duct, and experiments on pump coupling efficiency and uniformity and transmission of the pump field were conducted. With the optimization, a uniform flat-topped pump-coupled output field was derived within 5 mm range from the duct exit, with 72% coupling efficiency and 80% transmission efficie
2011,
23.
Abstract:
An all-fiber pulsed Yb-doped fiber laser with master oscillator power amplifier (MOPA) structure is reported. The seed laser is an acousto-optic (AO) Q-switched fiber laser. The effect of repetition rate, pump wavelength on laser output power and pulse width are experimentally investigated. Finally, output laser with pulse width of 25 ns and pulse energy of 45 μJ is achieved at 10 kHz repetition rate. At repetition rate of 50 kHz, a seed laser with a 0.6 W output power is amplified in a two stage Yb-doped all-fiber amplifier system to a output power of 102.5 W.
An all-fiber pulsed Yb-doped fiber laser with master oscillator power amplifier (MOPA) structure is reported. The seed laser is an acousto-optic (AO) Q-switched fiber laser. The effect of repetition rate, pump wavelength on laser output power and pulse width are experimentally investigated. Finally, output laser with pulse width of 25 ns and pulse energy of 45 μJ is achieved at 10 kHz repetition rate. At repetition rate of 50 kHz, a seed laser with a 0.6 W output power is amplified in a two stage Yb-doped all-fiber amplifier system to a output power of 102.5 W.
2011,
23.
Abstract:
In order to analyze the effect of aberration of amplitude and phase of laser beam on second-order moment radius of focal spot, based on the Fraunhofer formula for light wave scalar diffraction theory and the definition of second-order moment radius, the general expression for focal spot second-order moment radius depending on the complex amplitude of near field is derived. The second-order moment radius of the focal spot depending on intensity distribution and phase distribution of near field is derived, and its clear physical meaning is described. The second-order moment radius and the divergence angle of focal spot may be easily calculated with the second-order moment radius expression of focal spot. At last, the divergence angles of focal spots of several kinds of Gaussian laser beams a
In order to analyze the effect of aberration of amplitude and phase of laser beam on second-order moment radius of focal spot, based on the Fraunhofer formula for light wave scalar diffraction theory and the definition of second-order moment radius, the general expression for focal spot second-order moment radius depending on the complex amplitude of near field is derived. The second-order moment radius of the focal spot depending on intensity distribution and phase distribution of near field is derived, and its clear physical meaning is described. The second-order moment radius and the divergence angle of focal spot may be easily calculated with the second-order moment radius expression of focal spot. At last, the divergence angles of focal spots of several kinds of Gaussian laser beams a
2011,
23.
Abstract:
This paper established optical propagation tracing mathematical model based on geometrical optics and parabolic approximation method, extracting maximum inter-vision ranges (MIVR) to denote the absolute detection range limit imposed by refraction for a given sensor and target height, determining the appearance mechanism of mirage. When wind speed is constant, MIVR decreases with the increase of air-sea difference in temperature (ASTD); but MIVR decreases with the increase of wind speed under the constant ASTD; the MIVR decreases with ASTD increasing, the corresponding relationships of MIVR and the height position is a standard straight line, and MIVR reduces with the height parameter decreasing; the accuracy of MIVR is better.
This paper established optical propagation tracing mathematical model based on geometrical optics and parabolic approximation method, extracting maximum inter-vision ranges (MIVR) to denote the absolute detection range limit imposed by refraction for a given sensor and target height, determining the appearance mechanism of mirage. When wind speed is constant, MIVR decreases with the increase of air-sea difference in temperature (ASTD); but MIVR decreases with the increase of wind speed under the constant ASTD; the MIVR decreases with ASTD increasing, the corresponding relationships of MIVR and the height position is a standard straight line, and MIVR reduces with the height parameter decreasing; the accuracy of MIVR is better.
2011,
23.
Abstract:
Through theoretic analysis and numerical simulation, the focal shift of a focused flat beam propagating in turbulent atmosphere is studied. When a focused flat beam propagates in turbulent atmosphere, the effect of turbulence will induce the focal spot to move toward the transmitter. The turbulence is stronger and the diameter of transmitter is smaller, the measure of focal shift is larger. When adjusting the focus of transmitter and letting the focal spot of beam locate on detector, the laser intensity received by detector is not the strongest. The laser intensity will be the strongest if the focus of transmitter equals to the distance from transmitter to detector.
Through theoretic analysis and numerical simulation, the focal shift of a focused flat beam propagating in turbulent atmosphere is studied. When a focused flat beam propagates in turbulent atmosphere, the effect of turbulence will induce the focal spot to move toward the transmitter. The turbulence is stronger and the diameter of transmitter is smaller, the measure of focal shift is larger. When adjusting the focus of transmitter and letting the focal spot of beam locate on detector, the laser intensity received by detector is not the strongest. The laser intensity will be the strongest if the focus of transmitter equals to the distance from transmitter to detector.
2011,
23.
Abstract:
The fuzzy C-means (FCM) algorithm has many disadvantages such as number of clusters must be determined before FCM clustering is implemented and the algorithm needs an amount of calculation. In order to solve these problems, a novel method of fast FCM clustering is proposed. Seed pixels can be obtained by neighborhood searching of edge information firstly; Number of clusters and the value of cluster centers can be achieved by region growing method. Image is separated into cluster regions and undetermined cluster regions. The value of cluster centers and FCM are adopted to determine the undetermined cluster regions. Experiences show that the new method greatly improved the efficiency of image segmentation. Since the relationship of neighbored pixels are taken into account, the results of ima
The fuzzy C-means (FCM) algorithm has many disadvantages such as number of clusters must be determined before FCM clustering is implemented and the algorithm needs an amount of calculation. In order to solve these problems, a novel method of fast FCM clustering is proposed. Seed pixels can be obtained by neighborhood searching of edge information firstly; Number of clusters and the value of cluster centers can be achieved by region growing method. Image is separated into cluster regions and undetermined cluster regions. The value of cluster centers and FCM are adopted to determine the undetermined cluster regions. Experiences show that the new method greatly improved the efficiency of image segmentation. Since the relationship of neighbored pixels are taken into account, the results of ima
2011,
23.
Abstract:
Deposition errors of nonnormal incident optical coatings have a serious degradation impact on their spectral characteristics according to practical preparation experiences. A novel active multilayer optical coating design method based on sensitivity control concept is put forward to minimize the impact. The distribution law of deposited layer parameters errors is thoroughly analyzed under available production environment. Precise calculation model of multilayer optical coating’s sensitivity is analytically established by use of the derivatives calculation model of multilayer system’s spectral coefficients with respect to layer parameters. Numerical design experiments in a non-polarization antireflection coating with 45° light incidence are operated to explore and verify the feasibility,
Deposition errors of nonnormal incident optical coatings have a serious degradation impact on their spectral characteristics according to practical preparation experiences. A novel active multilayer optical coating design method based on sensitivity control concept is put forward to minimize the impact. The distribution law of deposited layer parameters errors is thoroughly analyzed under available production environment. Precise calculation model of multilayer optical coating’s sensitivity is analytically established by use of the derivatives calculation model of multilayer system’s spectral coefficients with respect to layer parameters. Numerical design experiments in a non-polarization antireflection coating with 45° light incidence are operated to explore and verify the feasibility,
2011,
23.
Abstract:
The structure and beam propagation property of helical axicon is analyzed. Based on diffraction integral theory, propagation process behind helical axiocn incident by diverging spherical wave and Laguerre-Gauss beam is studied. The result shows that Bessel beam is generated by helical axicon after diverging spherical wave incident, its beam order is equal to topological charge, but central spot (hollow spot) radius increases with propagation distance; Bessel beam is also generated by helical axicon after Laguerre-Gauss beam incident, but its beam order is equal to the sum of topological charge of Laguerre-Gauss beam and helical axicon, and the topological charge of the outgoing beam is equal to beam order itself.
The structure and beam propagation property of helical axicon is analyzed. Based on diffraction integral theory, propagation process behind helical axiocn incident by diverging spherical wave and Laguerre-Gauss beam is studied. The result shows that Bessel beam is generated by helical axicon after diverging spherical wave incident, its beam order is equal to topological charge, but central spot (hollow spot) radius increases with propagation distance; Bessel beam is also generated by helical axicon after Laguerre-Gauss beam incident, but its beam order is equal to the sum of topological charge of Laguerre-Gauss beam and helical axicon, and the topological charge of the outgoing beam is equal to beam order itself.
2011,
23.
Abstract:
For the convenient application of continuous-wave cavity ring-down spectroscopy (CW-CRDS), a compact measure system based on the DSP technique is presented. The DSP system is capable of signal adjustment, high-speed signal acquisition, and data processing. It is used to replace a test system composed of high-speed A/D card and computer in the traditional CW-CRDS measure system, to obtain and fit the ring-down signal. The fastest acquisition speed of the DSP system can reach 80 MHz with the A/D resolution of 16 bits, thus it can obtain the ring-down signal and determine the ring-down time accurately. Experiments show that the DSP system can achieve the noise-equivalent (RMS) absorption coefficient of about 1.0×10-8 cm-1 in an optical feedback CW-CRDS system, and its repeatability at a sing
For the convenient application of continuous-wave cavity ring-down spectroscopy (CW-CRDS), a compact measure system based on the DSP technique is presented. The DSP system is capable of signal adjustment, high-speed signal acquisition, and data processing. It is used to replace a test system composed of high-speed A/D card and computer in the traditional CW-CRDS measure system, to obtain and fit the ring-down signal. The fastest acquisition speed of the DSP system can reach 80 MHz with the A/D resolution of 16 bits, thus it can obtain the ring-down signal and determine the ring-down time accurately. Experiments show that the DSP system can achieve the noise-equivalent (RMS) absorption coefficient of about 1.0×10-8 cm-1 in an optical feedback CW-CRDS system, and its repeatability at a sing
2011,
23.
Abstract:
This article proposes a simple method using a false crystal (316L steel) to estimate the surface heat transfer coefficient of solid-state laser. First we set a low cooling water temperature, measure the temperature evolution of outlet water and the false crystal with two thermal couples, and then we calculate temporal evolution of temperature with arbitrary heat transfer coefficient using finite element analysis. By searching the lowest least square difference between measurement and simulation, heat transfer coefficient is estimated finally. The impact of heat transfer coefficient in rep-rated and high-energy laser design is also presented.
This article proposes a simple method using a false crystal (316L steel) to estimate the surface heat transfer coefficient of solid-state laser. First we set a low cooling water temperature, measure the temperature evolution of outlet water and the false crystal with two thermal couples, and then we calculate temporal evolution of temperature with arbitrary heat transfer coefficient using finite element analysis. By searching the lowest least square difference between measurement and simulation, heat transfer coefficient is estimated finally. The impact of heat transfer coefficient in rep-rated and high-energy laser design is also presented.
2011,
23.
Abstract:
The thermometry of tunable diode laser absorption spectroscopy(TDLAS) wavelength modulation spectroscopy (WMS) technique was briefly introduced. Two adjacent water lines at 1 397.75 nm and at 1 397.87 nm were selected, and the on-line measurement system of WMS technique for CH4/air premix flame temperature was established. A 250 Hz real-time readout rate was achieved by using a multifunctional data acquisition card for signal processing and diode laser control. The measurements were performed on the calibration burner, and the A type standard uncertainty of temperature was less than 53 K base on the analysis of the measurement results.
The thermometry of tunable diode laser absorption spectroscopy(TDLAS) wavelength modulation spectroscopy (WMS) technique was briefly introduced. Two adjacent water lines at 1 397.75 nm and at 1 397.87 nm were selected, and the on-line measurement system of WMS technique for CH4/air premix flame temperature was established. A 250 Hz real-time readout rate was achieved by using a multifunctional data acquisition card for signal processing and diode laser control. The measurements were performed on the calibration burner, and the A type standard uncertainty of temperature was less than 53 K base on the analysis of the measurement results.
2011,
23.
Abstract:
A 6.2 W 589 nm yellow laser at a repetition rate of 800 Hz was reported. Double rod and symmetry plane-plane cavity was adopted. The gain medium was Nd:YAG, 11.1 W 1 064 nm and 12.6 W 1 319 nm was obtained by acousto-optic (AO) Q-switched. The sum-frequency medium was a 4 mm×4 mm×30 mm lithium triborate (LBO) crystal with type Ⅰ critical phase match. Two beams were combinated with beam splitter and focused into the LBO crystal. A maximum power 6.2 W of the 589 nm laser was obtained, laser pulse width was 50 ns. The sum-frequency efficiency was 26.2%. The beam quality factor was 3.20 and 3.61 respectively in parallel and perpendicular direction．
A 6.2 W 589 nm yellow laser at a repetition rate of 800 Hz was reported. Double rod and symmetry plane-plane cavity was adopted. The gain medium was Nd:YAG, 11.1 W 1 064 nm and 12.6 W 1 319 nm was obtained by acousto-optic (AO) Q-switched. The sum-frequency medium was a 4 mm×4 mm×30 mm lithium triborate (LBO) crystal with type Ⅰ critical phase match. Two beams were combinated with beam splitter and focused into the LBO crystal. A maximum power 6.2 W of the 589 nm laser was obtained, laser pulse width was 50 ns. The sum-frequency efficiency was 26.2%. The beam quality factor was 3.20 and 3.61 respectively in parallel and perpendicular direction．
2011,
23.
Abstract:
Phase diversity wave-front sensing(PDWFS) is a method for estimating wave-front aberrations from two (or more) images whose pupil phases differ from one another with a known diversity phase. It can be used to estimate wave-front for point source as well as extended source. The accuracy of the estimate is relied on the diversity phase and is always given quantitatively in Cramér-Rao theorem. With defocus is used as the diversity mode, the effect of the object and the aberration on the optimum defocus is studied using Cramér-Rao theorem in this paper when the photons is enough. The results show that the optimum defocus does not depend on the peak-to-valley value or the spatial frequency of the aberration observably in the case of point source. For extended source, although the optimum defo
Phase diversity wave-front sensing(PDWFS) is a method for estimating wave-front aberrations from two (or more) images whose pupil phases differ from one another with a known diversity phase. It can be used to estimate wave-front for point source as well as extended source. The accuracy of the estimate is relied on the diversity phase and is always given quantitatively in Cramér-Rao theorem. With defocus is used as the diversity mode, the effect of the object and the aberration on the optimum defocus is studied using Cramér-Rao theorem in this paper when the photons is enough. The results show that the optimum defocus does not depend on the peak-to-valley value or the spatial frequency of the aberration observably in the case of point source. For extended source, although the optimum defo
2011,
23.
Abstract:
Coupling coefficients of TE01 rectangular waveguide mode to TE02, TE03 mode have been derived theoretically. Based on mode coupling theory, two kinds of transmission lines were reported. Firstly, a TE01 to TE02 mode converter at 9.5 GHz was designed. The conversion efficiency is 99.9% at center frequency. In the frequency range of 8.60～10.48 GHz, the conversion efficiency exceeds 90%. Secondly, dual- or tri-bend rectangular waveguide transmission line was designed to realize the transmission of TE01 mode, without stimulating higher order modes. The bandwidth and power capability can meet our requirements, which have been applied in high power microwave experiments.
Coupling coefficients of TE01 rectangular waveguide mode to TE02, TE03 mode have been derived theoretically. Based on mode coupling theory, two kinds of transmission lines were reported. Firstly, a TE01 to TE02 mode converter at 9.5 GHz was designed. The conversion efficiency is 99.9% at center frequency. In the frequency range of 8.60～10.48 GHz, the conversion efficiency exceeds 90%. Secondly, dual- or tri-bend rectangular waveguide transmission line was designed to realize the transmission of TE01 mode, without stimulating higher order modes. The bandwidth and power capability can meet our requirements, which have been applied in high power microwave experiments.
2011,
23.
Abstract:
The initial experimental results of relativistic klystron amplifier (RKA) driven by linear transformer driver (LTD) pulse power supply are introduced. Hollow electron beam of 600 kV, 6 kA, and 150 ns is generated by foilless graphite cathode. Modulated current of 5 kA, 110 ns is obtained through an input cavity and two idler cavities. The modulated current generates peak microwave power of 820 MW, pulse width of 110 ns, and its efficiency is 28%, its gain is 36 dB. The phase and repetition operation characteristics of RKA are investigated in the experiments. The radiated microwave arrives 800 MW/100 ns, the phase shaking is less than ±20° at 10 Hz.
The initial experimental results of relativistic klystron amplifier (RKA) driven by linear transformer driver (LTD) pulse power supply are introduced. Hollow electron beam of 600 kV, 6 kA, and 150 ns is generated by foilless graphite cathode. Modulated current of 5 kA, 110 ns is obtained through an input cavity and two idler cavities. The modulated current generates peak microwave power of 820 MW, pulse width of 110 ns, and its efficiency is 28%, its gain is 36 dB. The phase and repetition operation characteristics of RKA are investigated in the experiments. The radiated microwave arrives 800 MW/100 ns, the phase shaking is less than ±20° at 10 Hz.
2011,
23.
Abstract:
A 220 GHz folded waveguide slow-wave structure is designed and its dispersion relation, interaction impedance and circuit attenuation are analyzed. The simulation results show good agreement with the theoretical formula analysis. The folded waveguide slow-wave structure has broad cold bandwidth about 119 GHz, flat dispersion relation, fairly high interaction impedance about 3 Ω and low circuit attenuation for a 220 GHz central frequency. The large signal performance of 27 mm (50 periods) folded waveguide circuit is predicted. Simulations show that the nonlinear gain is 14.5 dB at 220 GHz where beam voltage and current are 20 kV and 10 mA, respectively. A saturated 3 dB bandwidth is 16.3 GHz (211.9 GHz to 228.2 GHz).
A 220 GHz folded waveguide slow-wave structure is designed and its dispersion relation, interaction impedance and circuit attenuation are analyzed. The simulation results show good agreement with the theoretical formula analysis. The folded waveguide slow-wave structure has broad cold bandwidth about 119 GHz, flat dispersion relation, fairly high interaction impedance about 3 Ω and low circuit attenuation for a 220 GHz central frequency. The large signal performance of 27 mm (50 periods) folded waveguide circuit is predicted. Simulations show that the nonlinear gain is 14.5 dB at 220 GHz where beam voltage and current are 20 kV and 10 mA, respectively. A saturated 3 dB bandwidth is 16.3 GHz (211.9 GHz to 228.2 GHz).
2011,
23.
Abstract:
A novel short helicone antenna is proposed in this paper which can be used as a cell of HPM array antenna. Mutual coupling of two short helicone antennas at different distances is simulated using the numerical simulation software. By comparing with mutual coupling of two short helical antennas in the same situation, restriction to be followed is that: when the cell distance is equal to 0.9λ, mutual coupling of the short helicone antenna corresponded to the short helical antenna; when the cell distance is smaller than 0.9λ, mutual coupling of the short helicone antenna is bigger than the short helical antenna; when the cell distance is larger than 0.9λ, mutual coupling of the short helicone antenna is smaller than the short helical antenna. Based on the restriction condition, a short hel
A novel short helicone antenna is proposed in this paper which can be used as a cell of HPM array antenna. Mutual coupling of two short helicone antennas at different distances is simulated using the numerical simulation software. By comparing with mutual coupling of two short helical antennas in the same situation, restriction to be followed is that: when the cell distance is equal to 0.9λ, mutual coupling of the short helicone antenna corresponded to the short helical antenna; when the cell distance is smaller than 0.9λ, mutual coupling of the short helicone antenna is bigger than the short helical antenna; when the cell distance is larger than 0.9λ, mutual coupling of the short helicone antenna is smaller than the short helical antenna. Based on the restriction condition, a short hel
2011,
23.
Abstract:
A parallelized finite-difference time-domain(FDTD) algorithm based on MPI platform, combined with antenna theory, is presented for analysis of the radiation characteristics of the large biconical-cylindrical cage antenna fed through the coaxial transmission line and excited by a double-exponential pulse, which can not be done on a personal computer due to long time and limited computation resources. The number of total cells for parallelized FDTD computing is about 2 billion. Numerical results show that cage antenna radius do not have a significant effect on the rise time and the peak value of the radiated electric field when the cage antenna radius is more than 3.5 m. In addition, the reflection and the loss from the ground have a great effect on the peak value and pulse width of the radi
A parallelized finite-difference time-domain(FDTD) algorithm based on MPI platform, combined with antenna theory, is presented for analysis of the radiation characteristics of the large biconical-cylindrical cage antenna fed through the coaxial transmission line and excited by a double-exponential pulse, which can not be done on a personal computer due to long time and limited computation resources. The number of total cells for parallelized FDTD computing is about 2 billion. Numerical results show that cage antenna radius do not have a significant effect on the rise time and the peak value of the radiated electric field when the cage antenna radius is more than 3.5 m. In addition, the reflection and the loss from the ground have a great effect on the peak value and pulse width of the radi
2011,
23.
Abstract:
Based on adiabatic compression theory and electro-optical theory, a double-anode magnetron injection gun for 170 GHz gyrotron was designed. By theoretical analysis and calculations, using simulation software to simulate and optimize the electron gun, and got the result that the velocity ratio of electron beam was 1.31, the transverse velocity spread was 3.5% and the axial velocity spread was 7.1%,the beam current was 51 A. The effects of the cathode magnetic field, the control voltage and the second anode voltage on the properties of electron beam were discussed and found that electron beam were very sensitive with these factors. When cathode magnetic field increased, the velocity ratio of electron beam decreased, the axial velocity spread increased first and then decreased, the transvers
Based on adiabatic compression theory and electro-optical theory, a double-anode magnetron injection gun for 170 GHz gyrotron was designed. By theoretical analysis and calculations, using simulation software to simulate and optimize the electron gun, and got the result that the velocity ratio of electron beam was 1.31, the transverse velocity spread was 3.5% and the axial velocity spread was 7.1%,the beam current was 51 A. The effects of the cathode magnetic field, the control voltage and the second anode voltage on the properties of electron beam were discussed and found that electron beam were very sensitive with these factors. When cathode magnetic field increased, the velocity ratio of electron beam decreased, the axial velocity spread increased first and then decreased, the transvers
2011,
23.
Abstract:
A massively parallel code named NEPTUNE for 3D fully electromagnetic and particle-in-cell (PIC) simulations is introduced, which can run on the Linux system with hundreds or even thousands of CPUs. NEPTUNE is capable of three-dimensional simulation of various typical high power microwave (HPM) devices. In NEPTUNE code, electromagnetic fields are updated by using finite-difference time-domain (FDTD) method to solve Maxwell equations and particles are moved by using Buneman-Boris method to solve the relativistic Newton-Lorentz equation. The electromagnetic fields and particles are coupled by using linear weighing interpolation PIC method, and the electric field components are corrected by using Boris method to solve the Poisson equation in order to ensure charge-conservation. NEPTUNE code ca
A massively parallel code named NEPTUNE for 3D fully electromagnetic and particle-in-cell (PIC) simulations is introduced, which can run on the Linux system with hundreds or even thousands of CPUs. NEPTUNE is capable of three-dimensional simulation of various typical high power microwave (HPM) devices. In NEPTUNE code, electromagnetic fields are updated by using finite-difference time-domain (FDTD) method to solve Maxwell equations and particles are moved by using Buneman-Boris method to solve the relativistic Newton-Lorentz equation. The electromagnetic fields and particles are coupled by using linear weighing interpolation PIC method, and the electric field components are corrected by using Boris method to solve the Poisson equation in order to ensure charge-conservation. NEPTUNE code ca
2011,
23.
Abstract:
By theoretical analysis of potential and electric field distribution of a gyrotron electron beam, the formula of velocity ratio measurements is presented. The electron beam is equivalent to transmission-line inner conductor. A ceramic capacitance divider is proposed for velocity ratio measurements. The design and processing technique of the measurement system, the calibration method and result interpretation of the ceramic capacitance divider are presented. At last, the result of primary experiment is introduced. Capacitance divider was selected for the velocity ratio measurement because it does not perturb the electron beam and normal operation of the gyrotron is preserved as a result. This technology can be used to guide the design of magnetron injection gun and the gyrotron experiments.
By theoretical analysis of potential and electric field distribution of a gyrotron electron beam, the formula of velocity ratio measurements is presented. The electron beam is equivalent to transmission-line inner conductor. A ceramic capacitance divider is proposed for velocity ratio measurements. The design and processing technique of the measurement system, the calibration method and result interpretation of the ceramic capacitance divider are presented. At last, the result of primary experiment is introduced. Capacitance divider was selected for the velocity ratio measurement because it does not perturb the electron beam and normal operation of the gyrotron is preserved as a result. This technology can be used to guide the design of magnetron injection gun and the gyrotron experiments.
2011,
23.
Abstract:
The dispersion characteristics of metal periodic slow-wave structure in rectangular cross-section Cerenkov maser have been analyzed. The effects of the geometrical parameters on the dispersion curves were investigated. In order to avoid the reflect oscillation induced by the changes at two ends of the slow-wave structure, the taper for matching the smooth waveguide and the slow-wave structure was analyzed by use of equivalent circuit method. Through comparing the linear, the two-piece linear and the exponential tapers, we know that the exponential taper gives the lowest total power reflection coefficient at the end, and the total change is mild. So the exponential taper can be used as an optimal solution for transition between slow and fast modes. The effects of frequency and fabrication e
The dispersion characteristics of metal periodic slow-wave structure in rectangular cross-section Cerenkov maser have been analyzed. The effects of the geometrical parameters on the dispersion curves were investigated. In order to avoid the reflect oscillation induced by the changes at two ends of the slow-wave structure, the taper for matching the smooth waveguide and the slow-wave structure was analyzed by use of equivalent circuit method. Through comparing the linear, the two-piece linear and the exponential tapers, we know that the exponential taper gives the lowest total power reflection coefficient at the end, and the total change is mild. So the exponential taper can be used as an optimal solution for transition between slow and fast modes. The effects of frequency and fabrication e
2011,
23.
Abstract:
In order to acquire Kilo-Ampere level emission current, a 100 mm diameter scandate cathode was manufactured. A 2 MV injector test stand was established with a large area thermionic cathode. A 1 038 A emission current was produced with a diode voltage 1.95 MV, pulse width 120 ns(FWHM), cathode temperature 1 120 ℃.The emission current density was 13 A/cm2. The results indicate that the ability of cathode emission relies on diode vacuum and cathode activation temperature.
In order to acquire Kilo-Ampere level emission current, a 100 mm diameter scandate cathode was manufactured. A 2 MV injector test stand was established with a large area thermionic cathode. A 1 038 A emission current was produced with a diode voltage 1.95 MV, pulse width 120 ns(FWHM), cathode temperature 1 120 ℃.The emission current density was 13 A/cm2. The results indicate that the ability of cathode emission relies on diode vacuum and cathode activation temperature.
2011,
23.
Abstract:
High frequency characteristics analysis and three-dimension fully electromagnetic particle-in-cell(PIC) simulation about the electron beam collector influence on the wide gap klystron(WKA) output power efficiency was presented. The electron beam collector will change the high frequency characteristics of the WKA output cavity. However, the collector nearby the output cavity gap will short out the radial electric field and reduce the space-charge potential depression, which as a result increase the WKA output power efficiency. By using a three-dimension fully electromagnetic PIC code, the output cavity power extraction effect was simulated. At beam voltage of 700 kV, cathode current of 6 kA and current modulation depth of 94%, the WKA with an optimized beam collector outputs microwave power
High frequency characteristics analysis and three-dimension fully electromagnetic particle-in-cell(PIC) simulation about the electron beam collector influence on the wide gap klystron(WKA) output power efficiency was presented. The electron beam collector will change the high frequency characteristics of the WKA output cavity. However, the collector nearby the output cavity gap will short out the radial electric field and reduce the space-charge potential depression, which as a result increase the WKA output power efficiency. By using a three-dimension fully electromagnetic PIC code, the output cavity power extraction effect was simulated. At beam voltage of 700 kV, cathode current of 6 kA and current modulation depth of 94%, the WKA with an optimized beam collector outputs microwave power
2011,
23.
Abstract:
The paper introduces the principle and some feasible structures of dielectric wall accelerator (DWA). By the study of electromagnetic scattering of multilayer dielectric cylinders, the relation of scattering width, parameters of materials and structure of beam pipe of DWA is investigated with FORTRAN program, for designing the accelerating beam pipe of DWA with high accelerating gradient and high energy coupling efficiency. The results confirm that，with permittivities of dielectric cylinders fixed, the scattering width becomes larger when the radiuses get larger. With radiuses of dielectric cylinders fixed, the scattering width shows no obvious change when the permittivities become larger, but the minimal scattering width becomes smaller. When the radiuses and permittivities of the first
The paper introduces the principle and some feasible structures of dielectric wall accelerator (DWA). By the study of electromagnetic scattering of multilayer dielectric cylinders, the relation of scattering width, parameters of materials and structure of beam pipe of DWA is investigated with FORTRAN program, for designing the accelerating beam pipe of DWA with high accelerating gradient and high energy coupling efficiency. The results confirm that，with permittivities of dielectric cylinders fixed, the scattering width becomes larger when the radiuses get larger. With radiuses of dielectric cylinders fixed, the scattering width shows no obvious change when the permittivities become larger, but the minimal scattering width becomes smaller. When the radiuses and permittivities of the first
2011,
23.
Abstract:
Due to the real-time monitoring requirement of field devices in EAST-NBI ion source test stand, this paper introduces a programmable logic controller(PLC) system based on Profibus protocol. The hardware configuration of PLC system can be determined according to the requirement of test stand, a Profibus-DP network with single-master workstation make a distributed I/O system. The PLC system can monitor the field devices’ status in real time, exchange data with NBI control system and instruct field devices work stably. In addition, full graphical user interface can realize the visualization of system operation, data storage and display in real-time, which will provide a basis for experimental analysis for physical operator. The whole PLC system is reliable, reproducible, well compatible and
Due to the real-time monitoring requirement of field devices in EAST-NBI ion source test stand, this paper introduces a programmable logic controller(PLC) system based on Profibus protocol. The hardware configuration of PLC system can be determined according to the requirement of test stand, a Profibus-DP network with single-master workstation make a distributed I/O system. The PLC system can monitor the field devices’ status in real time, exchange data with NBI control system and instruct field devices work stably. In addition, full graphical user interface can realize the visualization of system operation, data storage and display in real-time, which will provide a basis for experimental analysis for physical operator. The whole PLC system is reliable, reproducible, well compatible and
2011,
23.
Abstract:
With the particle-in-cell (PIC) method adopted, a three-dimensional numerical model was developed to study the motion behaviors of beam ions and charge exchange (CEX) ions in the ion thruster optics. Based on the geometric and physical parameters designated, the electric potential in calculation domain, the trajectories and velocities phase space distributions of the beam and CEX ions, and the grid currents were obtained with simulation. The CEX ions produced at the downstream of the acceleration grid will be accelerated by electric field and then impinge on the downstream surface of the acceleration grid, which would be the main reason for acceleration grid erosion. On the other hand, the CEX ions produced between the screen grid and the acceleration grid would impinge on the inner wall o
With the particle-in-cell (PIC) method adopted, a three-dimensional numerical model was developed to study the motion behaviors of beam ions and charge exchange (CEX) ions in the ion thruster optics. Based on the geometric and physical parameters designated, the electric potential in calculation domain, the trajectories and velocities phase space distributions of the beam and CEX ions, and the grid currents were obtained with simulation. The CEX ions produced at the downstream of the acceleration grid will be accelerated by electric field and then impinge on the downstream surface of the acceleration grid, which would be the main reason for acceleration grid erosion. On the other hand, the CEX ions produced between the screen grid and the acceleration grid would impinge on the inner wall o
2011,
23.
Abstract:
High-energy deuterons can be produced by ultraintense and ultrashort laser pulse interacting with CD4 cluster, and induce deuterium-deuterium (DD) fusion. This cluster fusion neutron source has extensive application. DD nuclear fusion has been performed on SILEX-I Ti:Sapphire laser system using 200 TW/30 fs laser pulses focused on CD4 cluster with f/2.7 optics. Neutron yield of DD fusion is measured by high sensitivity neutron detector. With this experimental condition, only 103 neutrons are observed．
High-energy deuterons can be produced by ultraintense and ultrashort laser pulse interacting with CD4 cluster, and induce deuterium-deuterium (DD) fusion. This cluster fusion neutron source has extensive application. DD nuclear fusion has been performed on SILEX-I Ti:Sapphire laser system using 200 TW/30 fs laser pulses focused on CD4 cluster with f/2.7 optics. Neutron yield of DD fusion is measured by high sensitivity neutron detector. With this experimental condition, only 103 neutrons are observed．
2011,
23.
Abstract:
The equation of state, melting line and metallization of helium have been studied by using quantum and classical molecular dynamics simulations. The melting line has been obtained by analyzing the radial distribution function and the diffusion parameter which is close to the experimental values. Equations of state when the temperature is less than 4.5 eV and the density is between 0.3 g/cm3 and 5.0 g/cm3 are also studied. Finally, it is found that the temperature can reduce the metallization density and metallization pressure of helium.
The equation of state, melting line and metallization of helium have been studied by using quantum and classical molecular dynamics simulations. The melting line has been obtained by analyzing the radial distribution function and the diffusion parameter which is close to the experimental values. Equations of state when the temperature is less than 4.5 eV and the density is between 0.3 g/cm3 and 5.0 g/cm3 are also studied. Finally, it is found that the temperature can reduce the metallization density and metallization pressure of helium.
2011,
23.
Abstract:
It is very difficult to rapidly and directly manufacture functional metal part with complex structure and full density (FMPCD) . In this study, the method of rapid manufacturing FMPCD by selective laser melting (SLM) was discussed, and the problem of ensuring synchronously part density and precision during SLM process was analyzed in detail combined with some SLM experiments. The results show that in order to rapidly manufacture FMPCD by SLM, it is necessary to reduce the effects of balling, spattering and air holes on part density and precision; Balling and air holes can be avoided by maintaining enough re-melting amount of upper solidified layer which can be got through use of enough thin powder layer thickness and careful adjustment of other processing parameters under good antioxidant
It is very difficult to rapidly and directly manufacture functional metal part with complex structure and full density (FMPCD) . In this study, the method of rapid manufacturing FMPCD by selective laser melting (SLM) was discussed, and the problem of ensuring synchronously part density and precision during SLM process was analyzed in detail combined with some SLM experiments. The results show that in order to rapidly manufacture FMPCD by SLM, it is necessary to reduce the effects of balling, spattering and air holes on part density and precision; Balling and air holes can be avoided by maintaining enough re-melting amount of upper solidified layer which can be got through use of enough thin powder layer thickness and careful adjustment of other processing parameters under good antioxidant
2011,
23.
Abstract:
A series of W, WSi2, Si thin films and W/Si, WSi2/Si periodic multilayers were fabricated by using DC magnetron sputtering technology. Surface profiles before and after deposition were measured with a stylus profiler and the stresses were calculated. The results indicate that W thin films show relatively large compressive stress, while W/Si multilayers show tensile stress. Both WSi2 thin films and WSi2/Si periodic multilayers show compressive stress. WSi2/Si periodic multilayers have the most stable stress state with no sharp change, and is a good material combination for X-ray multilayer optics with a large number of bilayers.
A series of W, WSi2, Si thin films and W/Si, WSi2/Si periodic multilayers were fabricated by using DC magnetron sputtering technology. Surface profiles before and after deposition were measured with a stylus profiler and the stresses were calculated. The results indicate that W thin films show relatively large compressive stress, while W/Si multilayers show tensile stress. Both WSi2 thin films and WSi2/Si periodic multilayers show compressive stress. WSi2/Si periodic multilayers have the most stable stress state with no sharp change, and is a good material combination for X-ray multilayer optics with a large number of bilayers.
2011,
23.
Abstract:
Based on main physical processes of secondary electron emission, the probability of secondary electron reaching the surface and emitting into vacuum at emission angles θ was deduced; the angular distribution of secondary electron released per primary electron entering polycrystalline obliquely was deduced, and the angular distribution of secondary electron released per backscattered electron was deduced. The angular distribution of secondary electron emitted from polycrystalline surfaces is formulated as cosinoidal function and independent of the incidence angle of the primary electron at high electron energy. It is concluded that the angular distribution of the secondary electron follow of the simple cosine distribution as the number of secondary electrons excited by primary electron and
Based on main physical processes of secondary electron emission, the probability of secondary electron reaching the surface and emitting into vacuum at emission angles θ was deduced; the angular distribution of secondary electron released per primary electron entering polycrystalline obliquely was deduced, and the angular distribution of secondary electron released per backscattered electron was deduced. The angular distribution of secondary electron emitted from polycrystalline surfaces is formulated as cosinoidal function and independent of the incidence angle of the primary electron at high electron energy. It is concluded that the angular distribution of the secondary electron follow of the simple cosine distribution as the number of secondary electrons excited by primary electron and
Calculation of temperature and population distribution in DF laser cavity based on emission spectrum
2011,
23.
Abstract:
The relational expressions between gain coefficient, intensity of spectral lines and the temperature, population distribution in optical cavity were established, and the emission spectrum of a combustion-driven DF chemical laser was measured, calculation based on spectral data showed that the temperature in optical cavity was 381.4 K, the ratio of population in ν=1 vibration level to ν=0 level, population in ν=2 level to ν=1 level, and population in ν=3 level to ν=2 level were 0.60～0.62, 0.676 4, 0.71～0.74, respectively.
The relational expressions between gain coefficient, intensity of spectral lines and the temperature, population distribution in optical cavity were established, and the emission spectrum of a combustion-driven DF chemical laser was measured, calculation based on spectral data showed that the temperature in optical cavity was 381.4 K, the ratio of population in ν=1 vibration level to ν=0 level, population in ν=2 level to ν=1 level, and population in ν=3 level to ν=2 level were 0.60～0.62, 0.676 4, 0.71～0.74, respectively.
2011,
23.
Abstract:
The effect on monocrystalline silicon cells after being irradiated of CO2 CW laser was researched, the damage mechanism of which was analyzed. When the power density is relatively low that can’t cause physical damage to the cells, the performance of cells reduces temporarily because of the temperature increase between the irradiation; when the laser power density is high enough to cause physical damage to the cells, the performance of cells will fall permanently. The voltage-current characteristic curves and output power curves before and after irradiation were compared, damage morphology in the facular area was observed, it is concluded that the performance of monocrystalline silicon cells declines a lot after being irradiated by laser with enough power density, the primary reason is the
The effect on monocrystalline silicon cells after being irradiated of CO2 CW laser was researched, the damage mechanism of which was analyzed. When the power density is relatively low that can’t cause physical damage to the cells, the performance of cells reduces temporarily because of the temperature increase between the irradiation; when the laser power density is high enough to cause physical damage to the cells, the performance of cells will fall permanently. The voltage-current characteristic curves and output power curves before and after irradiation were compared, damage morphology in the facular area was observed, it is concluded that the performance of monocrystalline silicon cells declines a lot after being irradiated by laser with enough power density, the primary reason is the
2011,
23.
Abstract:
A novel bifrequency-magnetically insulated transmission line oscillator(MILO) with axial partition is put forward. The interaction field between beam and microwave of this kind of MILO is separated into 2 pieces of slow wave structure (SWS) which have different period and cavity depth. Bifrequency microwave is gained because of interaction between beam and microwave in SWS pieces with different frequency character. A 2.5-D full electro-magnetic numerical simulation is conducted by using PIC software at diode voltage of 450 kV and beams current of 40 kA. A microwave pulse TEM mode with power of 1.4 GW and an efficiency of 7% is obtained. Output frequencies are 1.25 GHz and 1.65 GHz respectively with an amplitude difference of 1.5 dB.
A novel bifrequency-magnetically insulated transmission line oscillator(MILO) with axial partition is put forward. The interaction field between beam and microwave of this kind of MILO is separated into 2 pieces of slow wave structure (SWS) which have different period and cavity depth. Bifrequency microwave is gained because of interaction between beam and microwave in SWS pieces with different frequency character. A 2.5-D full electro-magnetic numerical simulation is conducted by using PIC software at diode voltage of 450 kV and beams current of 40 kA. A microwave pulse TEM mode with power of 1.4 GW and an efficiency of 7% is obtained. Output frequencies are 1.25 GHz and 1.65 GHz respectively with an amplitude difference of 1.5 dB.
2011,
23.
Abstract:
The technique and system integration of imaging system to diagnose annular electron beam were introduced. The system is constructed basing on the principle and technology of digital flash X-ray intensifying screen. The principle is that the X-rays are emitted when the target material is bombarded by the high energy annular electron beam, the scintillator is irradiated by the X-ray outputs visible light. which is recorded by digital imaging system. In order to achieve necessary system sensitivity and spatial resolution, the target material and the maximum target thickness were ascertained by theoretic computing. The measure ment systems for field test fielded were designed, and its performance is well suited to testing application. The annular electron beam image was acquired, which shows
The technique and system integration of imaging system to diagnose annular electron beam were introduced. The system is constructed basing on the principle and technology of digital flash X-ray intensifying screen. The principle is that the X-rays are emitted when the target material is bombarded by the high energy annular electron beam, the scintillator is irradiated by the X-ray outputs visible light. which is recorded by digital imaging system. In order to achieve necessary system sensitivity and spatial resolution, the target material and the maximum target thickness were ascertained by theoretic computing. The measure ment systems for field test fielded were designed, and its performance is well suited to testing application. The annular electron beam image was acquired, which shows
2011,
23.
Abstract:
The advantages of the atmospheric pressure microwave plasma jet(MPJ) over the previous and conventional methods make it a potential system for certain industrial material processes. This paper presents the design of this MPJ, the theoretical consideration of microwave ignition, the optimization of the nozzle and the simulation results, including the distributions of the electric field inside the TE103 rectangular cavity as well as the tip of the nozzle. The results show that when the nozzle length passed through the hole on the cavity wall is 1 mm and the power is 500 W, the electric field strength at the position of tip nozzle is above 1.2×106 V·m-1 which is higher than the breakdown field strength of the working gases. Both simulation result and the observations of the MPJ are in good
The advantages of the atmospheric pressure microwave plasma jet(MPJ) over the previous and conventional methods make it a potential system for certain industrial material processes. This paper presents the design of this MPJ, the theoretical consideration of microwave ignition, the optimization of the nozzle and the simulation results, including the distributions of the electric field inside the TE103 rectangular cavity as well as the tip of the nozzle. The results show that when the nozzle length passed through the hole on the cavity wall is 1 mm and the power is 500 W, the electric field strength at the position of tip nozzle is above 1.2×106 V·m-1 which is higher than the breakdown field strength of the working gases. Both simulation result and the observations of the MPJ are in good
2011,
23.
Abstract:
The sintered permanent magnets of Nd33Fe65.95B1.05 were prepared via smelting, powdering, forming, sintering and tempering process. The mode and microstructure of the fracture surface were researched by SEM and metallographic microscope. It was showed that the fracture surfaces of the ingot are intergranuler fracture for its big brittleness and there are many Nd-rich phases at fracture surface but Nd2Fe14B phases are relatively integrated. The fracture mode of sintered NdFeB magnets is intergranuler fracture and transgranular fracture because there are lots of defects in magnets, however, their fracture mode is primarily intergranuler fracture. There are two factors accounting to the facture of sintered NdFeB magnets. The extrinsic factor is that there are a good deal of defects, such as h
The sintered permanent magnets of Nd33Fe65.95B1.05 were prepared via smelting, powdering, forming, sintering and tempering process. The mode and microstructure of the fracture surface were researched by SEM and metallographic microscope. It was showed that the fracture surfaces of the ingot are intergranuler fracture for its big brittleness and there are many Nd-rich phases at fracture surface but Nd2Fe14B phases are relatively integrated. The fracture mode of sintered NdFeB magnets is intergranuler fracture and transgranular fracture because there are lots of defects in magnets, however, their fracture mode is primarily intergranuler fracture. There are two factors accounting to the facture of sintered NdFeB magnets. The extrinsic factor is that there are a good deal of defects, such as h
2011,
23.
Abstract:
The macroscopical long aligned carbon nanotube arrays(ACNTs) with a thickness of 2.7 mm were prepared by the pyrolysis of organometallic mixtures in 100 min using ferrocene and xylene as catalyzer and carbon source. Using a chemical vapor deposited with no template, the grow rate reached 27 μm·min-1. This process was carried out in a single-furnace system. The products were characterized by scanning electron microscopy (SEM) , transmission electron microscopy(TEM) and Raman spectroscopy. The results indicate that ACNTs have good alignment and fine graphite form. Both the optimized process parameters and the formation mechanism of fast growing macroscopical long ACNTs were summarized. A formation mechanism which the catalyst remains stable and the open ends was adopted, the rapid growth
The macroscopical long aligned carbon nanotube arrays(ACNTs) with a thickness of 2.7 mm were prepared by the pyrolysis of organometallic mixtures in 100 min using ferrocene and xylene as catalyzer and carbon source. Using a chemical vapor deposited with no template, the grow rate reached 27 μm·min-1. This process was carried out in a single-furnace system. The products were characterized by scanning electron microscopy (SEM) , transmission electron microscopy(TEM) and Raman spectroscopy. The results indicate that ACNTs have good alignment and fine graphite form. Both the optimized process parameters and the formation mechanism of fast growing macroscopical long ACNTs were summarized. A formation mechanism which the catalyst remains stable and the open ends was adopted, the rapid growth
2011,
23.
Abstract:
Carbon aerogels were prepared from resorcinol and formaldehyde via sol-gel process, high temperature carbonization and atmospheric pressure drying technology with solvent replacement. By changing the resorcinol-sodium carbonate molar ratio and the mass fraction of the reactants, resorcinol and formaldehyde, the pore structure of carbon aerogels can be controlled and the palladium-doped carbon aerogels were prepared. By transmission electron microscopy (TEM), X-ray diffraction (XRD) spectra, it is confirmed that the Pd exists in the skeleton structure of carbon aerogels as a form of nano simple substance pellet. The specific surface area is successfully raised by 2 times , and palladium-doped carbon aerogels with a specific surface area of 1 273 m2/g have been obtained by carrying out the a
Carbon aerogels were prepared from resorcinol and formaldehyde via sol-gel process, high temperature carbonization and atmospheric pressure drying technology with solvent replacement. By changing the resorcinol-sodium carbonate molar ratio and the mass fraction of the reactants, resorcinol and formaldehyde, the pore structure of carbon aerogels can be controlled and the palladium-doped carbon aerogels were prepared. By transmission electron microscopy (TEM), X-ray diffraction (XRD) spectra, it is confirmed that the Pd exists in the skeleton structure of carbon aerogels as a form of nano simple substance pellet. The specific surface area is successfully raised by 2 times , and palladium-doped carbon aerogels with a specific surface area of 1 273 m2/g have been obtained by carrying out the a
2011,
23.
Abstract:
Using photon sieves as the spectral components, this paper designs a new soft X-ray spectrograph, and analyses its principles, structure and design. The theoretical measurement range of the spectrograph is 100 eV to 2 keV with a spectral resolution of 0.35 nm. The X-ray emission spectrum from femtosecond laser-Cu target interaction has been obtained with the spectrograph on SILEX-Ⅰ. It proves that the spectrograph can meet the design requirements, suitable for researches on soft X-rays produced by laser-plasma interaction.
Using photon sieves as the spectral components, this paper designs a new soft X-ray spectrograph, and analyses its principles, structure and design. The theoretical measurement range of the spectrograph is 100 eV to 2 keV with a spectral resolution of 0.35 nm. The X-ray emission spectrum from femtosecond laser-Cu target interaction has been obtained with the spectrograph on SILEX-Ⅰ. It proves that the spectrograph can meet the design requirements, suitable for researches on soft X-rays produced by laser-plasma interaction.
2011,
23.
Abstract:
In this paper, a study on the oriented thermal vapor deposition device which is used for coating microspheres with polyamic acid (PAA) is developed. Influences of the processing of monomer material and the adjusting of heating process on the deposition rate are discussed. Two different monomers are poured into two evaporators and evaporated independently, the deposition rate and film thickness are measured via two film thickness measuring probes with the crystal vibration. Space position and symmetry of sample pan, two probes and the oriented tube tip are adjusted so that two monomers’ deposition ratio approximates to stoichiometric ratio. High quality coating of PAA on poly-aipha-methylstyrene microsphere is acquired by intermittent piezoelectricity vibration or striking which accompanie
In this paper, a study on the oriented thermal vapor deposition device which is used for coating microspheres with polyamic acid (PAA) is developed. Influences of the processing of monomer material and the adjusting of heating process on the deposition rate are discussed. Two different monomers are poured into two evaporators and evaporated independently, the deposition rate and film thickness are measured via two film thickness measuring probes with the crystal vibration. Space position and symmetry of sample pan, two probes and the oriented tube tip are adjusted so that two monomers’ deposition ratio approximates to stoichiometric ratio. High quality coating of PAA on poly-aipha-methylstyrene microsphere is acquired by intermittent piezoelectricity vibration or striking which accompanie
2011,
23.
Abstract:
The neutron emission time diagnostic was researched, and a bang time detector was made with ultra fast scintillator and microchannel-plate photomutiplier tube. The neutron emission time diagnostic was implemented in the implosion experiments at certain large-scale laser facility prototype, and the time interval between the beginning of the laser pulse and bang time was acquired. The experiment showed that DD and DT neutron can both be detetcted by the detector, and this detector can work in implosion experiments in which neutron yield is greater than 107, its timing precision is less than 20 ps. We found that the neutron emission time is relative to the thickness of CH layers clothed outside the targets in several shots.
The neutron emission time diagnostic was researched, and a bang time detector was made with ultra fast scintillator and microchannel-plate photomutiplier tube. The neutron emission time diagnostic was implemented in the implosion experiments at certain large-scale laser facility prototype, and the time interval between the beginning of the laser pulse and bang time was acquired. The experiment showed that DD and DT neutron can both be detetcted by the detector, and this detector can work in implosion experiments in which neutron yield is greater than 107, its timing precision is less than 20 ps. We found that the neutron emission time is relative to the thickness of CH layers clothed outside the targets in several shots.
2011,
23.
Abstract:
Considering the deformations of surface profiles of the KDP crystals with large dimension and low thickness under different clamps and departure angles from the horizontal plane in inertial confined fusion(ICF) systems, which influenced by clamps and departure angles, a finite element analysis model for the KDP crystals with large dimension and low thickness under different clamps and departure angles has been built and the boundary condition determination has been presented. For the case of departure angles from the horizontal plane of 30°and 90°, respectively, the deformations of the surface profiles under different clamps, such as full periphery simple supported and point force on the front, full periphery clamped and compliant strip on the front, full periphery simple supported and p
Considering the deformations of surface profiles of the KDP crystals with large dimension and low thickness under different clamps and departure angles from the horizontal plane in inertial confined fusion(ICF) systems, which influenced by clamps and departure angles, a finite element analysis model for the KDP crystals with large dimension and low thickness under different clamps and departure angles has been built and the boundary condition determination has been presented. For the case of departure angles from the horizontal plane of 30°and 90°, respectively, the deformations of the surface profiles under different clamps, such as full periphery simple supported and point force on the front, full periphery clamped and compliant strip on the front, full periphery simple supported and p
2011,
23.
Abstract:
A theoretical model for calculating the near field caused by continuous phase plates (CPP) applied in high-power laser system is built up for decreasing the laser induced damage probability of the elements behind CPP. The distribution of near field caused by CPP is calculated and analysed using this model, and the effect on the uniformity of the near field caused by the intensity modulation of input beam, interference and diffraction from CPP is analysed. The simulative and analytical results show that the interference ,the diffraction and the input beam quality affect the uniformity of the near field, and the input beam affect the beam quality of CPP more severely than the interference and diffraction when the beam quality is bad, but the interference and diffraction will decrease the uni
A theoretical model for calculating the near field caused by continuous phase plates (CPP) applied in high-power laser system is built up for decreasing the laser induced damage probability of the elements behind CPP. The distribution of near field caused by CPP is calculated and analysed using this model, and the effect on the uniformity of the near field caused by the intensity modulation of input beam, interference and diffraction from CPP is analysed. The simulative and analytical results show that the interference ,the diffraction and the input beam quality affect the uniformity of the near field, and the input beam affect the beam quality of CPP more severely than the interference and diffraction when the beam quality is bad, but the interference and diffraction will decrease the uni
2011,
23.
Abstract:
The hafnium dioxide thin films were prepared by using ion beam in substrate clean, deposition and posttreatment of films. The optical performance, surface characteristics and laser damage of the films were tested and analyzed. Experiment results show that the application of ion beam deposition in clean of substrates can wipe off polishing powder particle, enhance surface adsorption and increase stacking density. The application of ion beam deposition in deposition of thin films can improve thin films structure, decrease absorption of moisture, and increase damage threshold. The application of ion beam deposition in post-treatment can reduce surface roughness and improve damage threshold．
The hafnium dioxide thin films were prepared by using ion beam in substrate clean, deposition and posttreatment of films. The optical performance, surface characteristics and laser damage of the films were tested and analyzed. Experiment results show that the application of ion beam deposition in clean of substrates can wipe off polishing powder particle, enhance surface adsorption and increase stacking density. The application of ion beam deposition in deposition of thin films can improve thin films structure, decrease absorption of moisture, and increase damage threshold. The application of ion beam deposition in post-treatment can reduce surface roughness and improve damage threshold．
2011,
23.
Abstract:
Theoretical modeling has been used to discuss advantages and disadvantages among the squash fixed mode, the silica fixed mode and the complete periphery clamping mode in this paper. Besides, numerical calculation has been used to analyze the influence on KDP surface and conversion efficiency. The results show that the conversion efficiency reduction of Gaussian beam is less than that of plane wave caused by surface deformation. when the intensity of fundamental frequency laser is up to 6 GW·cm-2, the conversion efficiencies reduce 7.5%, 9.0% and 7.2% to plane wave, respectively; and the conversion efficiencies reduce 1.3%, 1.0% and 1.5% to Gaussian beam, respectively.
Theoretical modeling has been used to discuss advantages and disadvantages among the squash fixed mode, the silica fixed mode and the complete periphery clamping mode in this paper. Besides, numerical calculation has been used to analyze the influence on KDP surface and conversion efficiency. The results show that the conversion efficiency reduction of Gaussian beam is less than that of plane wave caused by surface deformation. when the intensity of fundamental frequency laser is up to 6 GW·cm-2, the conversion efficiencies reduce 7.5%, 9.0% and 7.2% to plane wave, respectively; and the conversion efficiencies reduce 1.3%, 1.0% and 1.5% to Gaussian beam, respectively.
2011,
23.
Abstract:
Because the general mixed metal matrix cathode can’t meet emission performance needs, the research focus on the W-Ir mixed metal-based cathode made with Sol-Gel method. The composition, microgram and granularity of the power and the surface and inner of the mixed metal-based cathode are studied by XRD and SEM. The emission performance of the mixed metal-based cathode has been measured. And the influence of activation temperature and time on the emission performance has been studied. The results show that the surface and inner structure and the emission performance of the mixed metal-based cathode made with Sol-Gel method are all better than the general mixed metal matrix cathode made with solid-liquid doping．
Because the general mixed metal matrix cathode can’t meet emission performance needs, the research focus on the W-Ir mixed metal-based cathode made with Sol-Gel method. The composition, microgram and granularity of the power and the surface and inner of the mixed metal-based cathode are studied by XRD and SEM. The emission performance of the mixed metal-based cathode has been measured. And the influence of activation temperature and time on the emission performance has been studied. The results show that the surface and inner structure and the emission performance of the mixed metal-based cathode made with Sol-Gel method are all better than the general mixed metal matrix cathode made with solid-liquid doping．
2011,
23.
Abstract:
To account for output power balancing capability of large laser facilities, a synthetic method with beam to beam root-mean-square is presented. Firstly, a conversion process for the facilities from original data of beam powers to regular data is given. The regular data contribute to the normal distribution approximately, and then a corresponding simple method of root-mean-square for beam to beam power balancing capability is given. Secondly, based on theory of total control charts and cause-selecting control charts, control charts with root-mean-square are established which show short-term variety of power balancing capability of the facilities. Mean rate of failure occurrence is also defined and used to describe long-term trend of global balancing capabilities of the facilities. Finally,
To account for output power balancing capability of large laser facilities, a synthetic method with beam to beam root-mean-square is presented. Firstly, a conversion process for the facilities from original data of beam powers to regular data is given. The regular data contribute to the normal distribution approximately, and then a corresponding simple method of root-mean-square for beam to beam power balancing capability is given. Secondly, based on theory of total control charts and cause-selecting control charts, control charts with root-mean-square are established which show short-term variety of power balancing capability of the facilities. Mean rate of failure occurrence is also defined and used to describe long-term trend of global balancing capabilities of the facilities. Finally,
2011,
23.
Abstract:
In order to study the influence of flexible foundation on the stability of ICF facility due to ambient vibration, two models are established for the “rigid” foundation and the flexible foundation, respectively. The soil-structure interaction (SSI) is considered by setting the springs and dampers on the dummy boundary, and uncertain soil properties are simulated by setting some stochastic parameters for stiffness of the springs and damping factors of the dampers. The influences of SSI and uncertain soil properties on the response of ICF facility are revealed by comparing simulation results of the two models. The ratios of the major displacement response and the rotation response in the flexible foundation model to those in the “rigid” foundation model are 1.24 and 1.49, respectively.
In order to study the influence of flexible foundation on the stability of ICF facility due to ambient vibration, two models are established for the “rigid” foundation and the flexible foundation, respectively. The soil-structure interaction (SSI) is considered by setting the springs and dampers on the dummy boundary, and uncertain soil properties are simulated by setting some stochastic parameters for stiffness of the springs and damping factors of the dampers. The influences of SSI and uncertain soil properties on the response of ICF facility are revealed by comparing simulation results of the two models. The ratios of the major displacement response and the rotation response in the flexible foundation model to those in the “rigid” foundation model are 1.24 and 1.49, respectively.
2011,
23.
Abstract:
A lowimpedance experimental platform based on strip pulse forming line(PFL) is introduced. Two different types of matching loads for the platform are designed and tested. The results show that the rail water load has very low inductance and is qualified to be the matching load for the low-impedance PFL. Load loop inductance is the decisive factor that affects the output waveform quality of the low-impedance PFL, when the inductance of the switch is constant. When the load loop inductance is less than 30 nH, the output voltage waveform is a quasi-square wave for the impedance of strip PFL being 0.5 Ω. Moreover, the influence of load loop inductance on the output waveform of PFLs with different impedances is analyzed by numerical simulation. The influence is found to decrease with the in
A lowimpedance experimental platform based on strip pulse forming line(PFL) is introduced. Two different types of matching loads for the platform are designed and tested. The results show that the rail water load has very low inductance and is qualified to be the matching load for the low-impedance PFL. Load loop inductance is the decisive factor that affects the output waveform quality of the low-impedance PFL, when the inductance of the switch is constant. When the load loop inductance is less than 30 nH, the output voltage waveform is a quasi-square wave for the impedance of strip PFL being 0.5 Ω. Moreover, the influence of load loop inductance on the output waveform of PFLs with different impedances is analyzed by numerical simulation. The influence is found to decrease with the in
2011,
23.
Abstract:
The design method for measuring current and voltage of compact X-pinch pulsed power device according to the coaxial cylindrical structure of pulse transmission line (PTL) on X-pinch compact pulsed power source, a stainless steel film connecting the outer tube and load was designed as pulsed current monitor. A capacitive voltage divider was designed in the end of the PTL as pulsed voltage monitor. A circuit simulation software was used to simulate the process. The capacitive load voltage probe and the load current probe were calibrated online. The experimental results show that the probes are stable, corresponding to fast, which are ideal tools for measuring load current and voltage.
The design method for measuring current and voltage of compact X-pinch pulsed power device according to the coaxial cylindrical structure of pulse transmission line (PTL) on X-pinch compact pulsed power source, a stainless steel film connecting the outer tube and load was designed as pulsed current monitor. A capacitive voltage divider was designed in the end of the PTL as pulsed voltage monitor. A circuit simulation software was used to simulate the process. The capacitive load voltage probe and the load current probe were calibrated online. The experimental results show that the probes are stable, corresponding to fast, which are ideal tools for measuring load current and voltage.
2011,
23.
Abstract:
The performance degradation of spacecraft thermal control coatings irradiated by protons is generally investigated by using protons with the same energy in ground testing while the energy of protons is in succession in space. The irradiation equivalence of the two kinds of protons is still not well understood. In this paper, a method of producing protons with continuous energy by plasma sheath acceleration using pulse voltage with discrete steps is proposed for better analysis of irradiation equivalence. The dose-energy distribution on the sample is numerically investigated by particle-in-cell(PIC) method. The characteristics of dose-energy distribution and the formation mechanism of protons with continuous energy are then discussed. The results show that protons with continuous energy can
The performance degradation of spacecraft thermal control coatings irradiated by protons is generally investigated by using protons with the same energy in ground testing while the energy of protons is in succession in space. The irradiation equivalence of the two kinds of protons is still not well understood. In this paper, a method of producing protons with continuous energy by plasma sheath acceleration using pulse voltage with discrete steps is proposed for better analysis of irradiation equivalence. The dose-energy distribution on the sample is numerically investigated by particle-in-cell(PIC) method. The characteristics of dose-energy distribution and the formation mechanism of protons with continuous energy are then discussed. The results show that protons with continuous energy can
2011,
23.
Abstract:
3D model of pulse forming network with 2.5 Ω impedance, 200 ns pulse width was established. Through the finite element analysis and simulation, the induction of the switch part and the load part was simulated and studied. The simulated results show that the induction was decreased with increasing frequency. The inner inductance of lead can be ignored when the frequency equal to 2.5 MHz. The inductance of lead is 10nH less in frequency 2.5 MHz than that in frequency zero. The simulated results also show that the mutual inductance can not be ignored when the switches work in parallel. In order to reduce the induction of lead, the configuration which isolates the switches was designed. The pulse rising time can be reduced 2 ns under the configuration. The experimental results indicate that t
3D model of pulse forming network with 2.5 Ω impedance, 200 ns pulse width was established. Through the finite element analysis and simulation, the induction of the switch part and the load part was simulated and studied. The simulated results show that the induction was decreased with increasing frequency. The inner inductance of lead can be ignored when the frequency equal to 2.5 MHz. The inductance of lead is 10nH less in frequency 2.5 MHz than that in frequency zero. The simulated results also show that the mutual inductance can not be ignored when the switches work in parallel. In order to reduce the induction of lead, the configuration which isolates the switches was designed. The pulse rising time can be reduced 2 ns under the configuration. The experimental results indicate that t
2011,
23.
Abstract:
The high energy density selfhealing metallized film pulse capacitor has been applied to all kinds of laser facilities for their power conditioning systems, whose reliability is straightforward affected by the reliability level of capacitors. Reliability analysis of highly reliable devices, such as metallized film capacitors, is a challenge due to cost and time restriction. Accelerated degradation test provides a way to predict its life cost and time effectively. A model and analyses for accelerated degradation data of metallized film capacitors are described. Also described is a method for estimating the distribution of failure time. The estimation values of the unknown parameters in this model are 9.066 9×10-8 and 0.022 1. Both the failure probability density function (PDF) and the cum
The high energy density selfhealing metallized film pulse capacitor has been applied to all kinds of laser facilities for their power conditioning systems, whose reliability is straightforward affected by the reliability level of capacitors. Reliability analysis of highly reliable devices, such as metallized film capacitors, is a challenge due to cost and time restriction. Accelerated degradation test provides a way to predict its life cost and time effectively. A model and analyses for accelerated degradation data of metallized film capacitors are described. Also described is a method for estimating the distribution of failure time. The estimation values of the unknown parameters in this model are 9.066 9×10-8 and 0.022 1. Both the failure probability density function (PDF) and the cum
