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RSS2006 Vol. 18, No. 04
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2006,
18.
Abstract:
The tapered coaxial slow-wave-structure is the most important part of a MILO. According to the Maxwell equations and Floquet’s theorem, the dispersion function of TM modes in the tapered MILO is derived in this paper. Through numerical calculation, the influences of several structure parameters on the dispersion characteristics are summarized, which provide some theoretical fundamental to the design of the tapered MILO.
The tapered coaxial slow-wave-structure is the most important part of a MILO. According to the Maxwell equations and Floquet’s theorem, the dispersion function of TM modes in the tapered MILO is derived in this paper. Through numerical calculation, the influences of several structure parameters on the dispersion characteristics are summarized, which provide some theoretical fundamental to the design of the tapered MILO.
2006,
18.
Abstract:
Negative refractive index materials are artificial materials with permittivity and permeability both negative within certain microwave frequency band. FDTD method is used to simulate the distribution of electromagnetic field inside and around the negative refractive index materials by the treated Maxwell’s equations for TE mode. Unstable situation during calculation is avoided. Numerical experiment results of the distribution of electromagnetic fields in the area are given.
Negative refractive index materials are artificial materials with permittivity and permeability both negative within certain microwave frequency band. FDTD method is used to simulate the distribution of electromagnetic field inside and around the negative refractive index materials by the treated Maxwell’s equations for TE mode. Unstable situation during calculation is avoided. Numerical experiment results of the distribution of electromagnetic fields in the area are given.
2006,
18.
Abstract:
Dispersion and interaction impedance of two kinds of vane-loaded helical SWS were measured in 2～18 GHz with Agilent8510C Vector Network Analyzer. The measurement system was represented by proper microwave network and a formula to modify phase shift of SWS was derived that took reflection effects of transmission ports into account. Thus the fluctuation of experiment values were damped effectively. Dispersion and interaction impedance of them were also simulated by HFSS with space-harmonics effects included and ignored respectively. The experimental and theoretical values of dispersion and interaction impedance are found to be close in the band of 2～18 GHz.
Dispersion and interaction impedance of two kinds of vane-loaded helical SWS were measured in 2～18 GHz with Agilent8510C Vector Network Analyzer. The measurement system was represented by proper microwave network and a formula to modify phase shift of SWS was derived that took reflection effects of transmission ports into account. Thus the fluctuation of experiment values were damped effectively. Dispersion and interaction impedance of them were also simulated by HFSS with space-harmonics effects included and ignored respectively. The experimental and theoretical values of dispersion and interaction impedance are found to be close in the band of 2～18 GHz.
2006,
18.
Abstract:
The tapered coaxial slow-wave-structure is the most important part of a MILO. According to the Maxwell equations and Floquet’s theorem, the dispersion function of TM modes in the tapered MILO is derived in this paper. Through numerical calculation, the influences of several structure parameters on the dispersion characteristics are summarized, which provide some theoretical fundamental to the design of the tapered MILO.
The tapered coaxial slow-wave-structure is the most important part of a MILO. According to the Maxwell equations and Floquet’s theorem, the dispersion function of TM modes in the tapered MILO is derived in this paper. Through numerical calculation, the influences of several structure parameters on the dispersion characteristics are summarized, which provide some theoretical fundamental to the design of the tapered MILO.
2006,
18.
Abstract:
Certain gyro-type devices, including moderately high power, high harmonic gyrotrons, gyro-TWT and peniotrons, require an axis encircling electron beam. To develop practical and efficient devices of this type, it is necessary to first develop a gun that generates a high quality beam with low velocity spread and ripple. This paper analyzes the large orbit gyrotron cusp electron beam, builds up the physical models of the cusp electron beam, and discusses the effect on the factor in designing the large orbit gyrotron cusp electron gun based on theoretic analysis. The cusp gun designed can generate an axis encircling beam with low-velocity spread and small beam ripple for high-harmonic high-power (52 kV, 2.7 A) operation in gyrotrons.
Certain gyro-type devices, including moderately high power, high harmonic gyrotrons, gyro-TWT and peniotrons, require an axis encircling electron beam. To develop practical and efficient devices of this type, it is necessary to first develop a gun that generates a high quality beam with low velocity spread and ripple. This paper analyzes the large orbit gyrotron cusp electron beam, builds up the physical models of the cusp electron beam, and discusses the effect on the factor in designing the large orbit gyrotron cusp electron gun based on theoretic analysis. The cusp gun designed can generate an axis encircling beam with low-velocity spread and small beam ripple for high-harmonic high-power (52 kV, 2.7 A) operation in gyrotrons.
2006,
18.
Abstract:
Based on the MAFIA simulation platform, the effects of helix pitch on dispersion, interaction impedance and attenuation characteristics are analyzed for an ultra-wide band(4~18 GHz) helical slow-wave structure. The rules of the cold-test characteristics changing with helix pitch are also studied and it turns out that, with increasing helix pitch, the phase velocity increases linearly, the interaction impedance changes nonlinearly and the attenuation constant decreases nonlinearly. At the same time, with the limitation of the synchronism between the electron beam and the electromagnetic wave, the change of pitch is small and therefore an approximate linear relation can be introduced. Based on these effects and rules, the linear interposition method is suggested to get the cold-test characte
Based on the MAFIA simulation platform, the effects of helix pitch on dispersion, interaction impedance and attenuation characteristics are analyzed for an ultra-wide band(4~18 GHz) helical slow-wave structure. The rules of the cold-test characteristics changing with helix pitch are also studied and it turns out that, with increasing helix pitch, the phase velocity increases linearly, the interaction impedance changes nonlinearly and the attenuation constant decreases nonlinearly. At the same time, with the limitation of the synchronism between the electron beam and the electromagnetic wave, the change of pitch is small and therefore an approximate linear relation can be introduced. Based on these effects and rules, the linear interposition method is suggested to get the cold-test characte
2006,
18.
Abstract:
By use of such theories as lossy transmission line, microwave equivalent circuits, network matrix of electromagnetism and so on, this paper analyses the process of energy storage and energy dumping of the cavity of the excessive modes cylindrical cavity pulse compress system, and gains the theoretic calculating formula of power gain, which is consistent with experiment result. Consequently the formula is proved to be reliable and feasible perfect direct the effect on the design, manufacture, and debugging of the compress system. Moreover, it is beneficial to develop deeper research.
By use of such theories as lossy transmission line, microwave equivalent circuits, network matrix of electromagnetism and so on, this paper analyses the process of energy storage and energy dumping of the cavity of the excessive modes cylindrical cavity pulse compress system, and gains the theoretic calculating formula of power gain, which is consistent with experiment result. Consequently the formula is proved to be reliable and feasible perfect direct the effect on the design, manufacture, and debugging of the compress system. Moreover, it is beneficial to develop deeper research.
2006,
18.
Abstract:
An improved three-wave-coupling model of optical parametric chirped pulse amplification（OPCPA） including the effects of phase mismatching, pulse temporal profile and synchronization-time jitter was presented in this paper. With the model, we investigated and compared the effect of synchronization-time jitter on the gain stability of OPCPA in small signal amplification regime and in saturation regime respectively. The results show that in the case of one nanosecond synchronization-time jitter, the jitter shifts the amplified signal gain spectrum obviously, leads to pulse profile asymmetry and decreases the gain overall. The broader signal spectrum will aggravate the influence of jitter on parametric gain. However, when the parametric amplification is saturated, the impact of jitter upon o
An improved three-wave-coupling model of optical parametric chirped pulse amplification（OPCPA） including the effects of phase mismatching, pulse temporal profile and synchronization-time jitter was presented in this paper. With the model, we investigated and compared the effect of synchronization-time jitter on the gain stability of OPCPA in small signal amplification regime and in saturation regime respectively. The results show that in the case of one nanosecond synchronization-time jitter, the jitter shifts the amplified signal gain spectrum obviously, leads to pulse profile asymmetry and decreases the gain overall. The broader signal spectrum will aggravate the influence of jitter on parametric gain. However, when the parametric amplification is saturated, the impact of jitter upon o
2006,
18.
Abstract:
In this paper, a new method is proposed to effectively lower the high temperature, smooth the thermal stress and reduce the thermal deformation of mirrors in high power laser systems utilizing functionally graded materials (FGMs). Two kinds of laser source are discussed at the same time. One is the doughnut-shaped laser, and the other is the Gaussian-distributed laser. Numerical results from finite element analysis show that the thermal deformation of silicon and copper mirrors can be much reduced in magnitude, and the temperature rise is also lowered obviously by this means. The effects of slope regulation of the functions for representation of thermophysical and mechanical properties on thermal deformation of mirrors are discussed to meet the requirement of optimum design and manufacture
In this paper, a new method is proposed to effectively lower the high temperature, smooth the thermal stress and reduce the thermal deformation of mirrors in high power laser systems utilizing functionally graded materials (FGMs). Two kinds of laser source are discussed at the same time. One is the doughnut-shaped laser, and the other is the Gaussian-distributed laser. Numerical results from finite element analysis show that the thermal deformation of silicon and copper mirrors can be much reduced in magnitude, and the temperature rise is also lowered obviously by this means. The effects of slope regulation of the functions for representation of thermophysical and mechanical properties on thermal deformation of mirrors are discussed to meet the requirement of optimum design and manufacture
2006,
18.
Abstract:
The possibility of phase locking high-order lateral modes of broad-stripe laser diode array (LDA) with a short external cavity is analyzed theoretically. The far field pattern of multi-lateral modes, which comprises a main lobe and side lobes, is observed for a LDA positioned in a short external cavity. From the experimental records, structures composed of peaks and valleys, symbolizing phase locking, can be observed within the side lobes. Moreover, the modulation depth of this structure is considerably larger than that in the main lobe. From these results, it can be concluded that the phase-locking between high-order lateral modes of emitters of the LDA is realized when the external cavity is short enough.
The possibility of phase locking high-order lateral modes of broad-stripe laser diode array (LDA) with a short external cavity is analyzed theoretically. The far field pattern of multi-lateral modes, which comprises a main lobe and side lobes, is observed for a LDA positioned in a short external cavity. From the experimental records, structures composed of peaks and valleys, symbolizing phase locking, can be observed within the side lobes. Moreover, the modulation depth of this structure is considerably larger than that in the main lobe. From these results, it can be concluded that the phase-locking between high-order lateral modes of emitters of the LDA is realized when the external cavity is short enough.
2006,
18.
Abstract:
The transmission characteristics of the hollow dielectric film-coated waveguide for THz radiation are theoretically analyzed, and the eigenequation and the mode distribution of the waveguide are obtained. The relationship between attenuation coefficient and the bore diameter of the hollow waveguide is described based on the ray-optics principle. The attenuation coefficient of the dominant mode is less than 1 dB/m when the dielectric material is polyimide and the depth is 0.05 mm, which is far less than that of the same bore diameter metal circle waveguide for THz radiation. The transmission characteristics of the film-coated waveguide is simulated when the frequncy of the electromagnetic wave ranges from 0 to 1 THz, and the attenuation coefficient is less than 0.5 dB/m in the passband of 0
The transmission characteristics of the hollow dielectric film-coated waveguide for THz radiation are theoretically analyzed, and the eigenequation and the mode distribution of the waveguide are obtained. The relationship between attenuation coefficient and the bore diameter of the hollow waveguide is described based on the ray-optics principle. The attenuation coefficient of the dominant mode is less than 1 dB/m when the dielectric material is polyimide and the depth is 0.05 mm, which is far less than that of the same bore diameter metal circle waveguide for THz radiation. The transmission characteristics of the film-coated waveguide is simulated when the frequncy of the electromagnetic wave ranges from 0 to 1 THz, and the attenuation coefficient is less than 0.5 dB/m in the passband of 0
2006,
18.
Abstract:
A complicated nonlinear dynamical system——cross-injection locking diode lasers system is proposed. Equations are derived for the simplest system which is composed of two lasers only, and the locked steady-state analytical solutions are obtained for the simplest case in which the two lasers have the same free-running frequency without locking. The results show that with an equal coupling，locking bandwidth of cross-injection is approximately twice than that of master-slave injection and even in such special system a frequency shift may happen after the constituent lasers are locked.
A complicated nonlinear dynamical system——cross-injection locking diode lasers system is proposed. Equations are derived for the simplest system which is composed of two lasers only, and the locked steady-state analytical solutions are obtained for the simplest case in which the two lasers have the same free-running frequency without locking. The results show that with an equal coupling，locking bandwidth of cross-injection is approximately twice than that of master-slave injection and even in such special system a frequency shift may happen after the constituent lasers are locked.
2006,
18.
Abstract:
From the theory of uniform-field electrodes, profiles of electrodes, theoretical and practical distributions of electric field on the surface of near Rogowski electrode, Chang electrode (including compact Chang electrode) and Ernst electrode were calculated and discussed. Using these electrodes in our laboratory, pulsed discharge experiments were carried out on TEA CO2 laser, so discharge performance and output characteristics were obtained, and the results of the experiments on these electrodes were compared and analyzed. The calculation results show that Ernst electrode has the most compact profile and optimal uniform electric-field distribution if electrodes have the same fundamental parameters. The experiment results indicate that TEA CO2 laser gains the biggest glow discharge area and
From the theory of uniform-field electrodes, profiles of electrodes, theoretical and practical distributions of electric field on the surface of near Rogowski electrode, Chang electrode (including compact Chang electrode) and Ernst electrode were calculated and discussed. Using these electrodes in our laboratory, pulsed discharge experiments were carried out on TEA CO2 laser, so discharge performance and output characteristics were obtained, and the results of the experiments on these electrodes were compared and analyzed. The calculation results show that Ernst electrode has the most compact profile and optimal uniform electric-field distribution if electrodes have the same fundamental parameters. The experiment results indicate that TEA CO2 laser gains the biggest glow discharge area and
2006,
18.
Abstract:
The temperature-related laser performances of the Yb3+:YAG slab laser have been investigated based on quasi-three level rate equation model, which include the energy storage and extraction efficiency. The results show that the extractable energy storage efficiency decreases significantly from 43% to 26% with the increase of the temperature in the lasing slab from 300 to 400 K. We also have demonstrated the feasibility of double-face cooling of lasing slab with a diamond window whose thermal conductivity is so high that a very thin plate suffices to efficiently remove the heat generated in the lasing slab. Simulation results show that with a pump intensity of 15 kW/cm2 and repetition rate of 10 Hz, to keep the maximum temperature of the lasing slab below a reasonable value, e.g., less than
The temperature-related laser performances of the Yb3+:YAG slab laser have been investigated based on quasi-three level rate equation model, which include the energy storage and extraction efficiency. The results show that the extractable energy storage efficiency decreases significantly from 43% to 26% with the increase of the temperature in the lasing slab from 300 to 400 K. We also have demonstrated the feasibility of double-face cooling of lasing slab with a diamond window whose thermal conductivity is so high that a very thin plate suffices to efficiently remove the heat generated in the lasing slab. Simulation results show that with a pump intensity of 15 kW/cm2 and repetition rate of 10 Hz, to keep the maximum temperature of the lasing slab below a reasonable value, e.g., less than
2006,
18.
Abstract:
The Trigonometric-function operator is put forward as a novoel image segmentation arithmetic. It is deduced by the principle of optical interference and applied in fast image segmentation. The hardware of Trigonometric-function operator is analyzed. The pseud phase of input image is important for the operator and need to be translated from the intensity distribution by appropriate conversion rule. Various conversion manners are defined, including linearity, logarithm function, tangent function and arc tangent function. Numerical simulation results show that image segmentation effects of trigonometric-function operator vary with the manners of intensity-pseud phase translation and their parameters. When logarithm sigmoid tranfer function is used as intensity-phase conversion manner, the tri
The Trigonometric-function operator is put forward as a novoel image segmentation arithmetic. It is deduced by the principle of optical interference and applied in fast image segmentation. The hardware of Trigonometric-function operator is analyzed. The pseud phase of input image is important for the operator and need to be translated from the intensity distribution by appropriate conversion rule. Various conversion manners are defined, including linearity, logarithm function, tangent function and arc tangent function. Numerical simulation results show that image segmentation effects of trigonometric-function operator vary with the manners of intensity-pseud phase translation and their parameters. When logarithm sigmoid tranfer function is used as intensity-phase conversion manner, the tri
2006,
18.
Abstract:
This paper expatiates on the theory of a distributed infrared optical fiber Raman temperature sensor on the infrared double wavelength with a Er doped waveguide amplifier. For restraining the amplifier ASE increase and the temperature excursion accumulation and the anti-Stokes back-scattering intermingling with the Rayleigh back scattering, it thinks over what to demodulate on the basis of the newly acquired temperature curves and two pending standard temperature curves. It advances the temperature precision to ±0.1 ℃ and system stability, it reduces the cost and has the consistency of theory and test.
This paper expatiates on the theory of a distributed infrared optical fiber Raman temperature sensor on the infrared double wavelength with a Er doped waveguide amplifier. For restraining the amplifier ASE increase and the temperature excursion accumulation and the anti-Stokes back-scattering intermingling with the Rayleigh back scattering, it thinks over what to demodulate on the basis of the newly acquired temperature curves and two pending standard temperature curves. It advances the temperature precision to ±0.1 ℃ and system stability, it reduces the cost and has the consistency of theory and test.
2006,
18.
Abstract:
Influence of doping on transmission properties of two-dimensional photonic crystals is analyzed numerically in the paper. The crystals’ transmission spectra are obtained by numerical calculation with plane wave expansion method. The results show that the width and position of photonic band gaps as well as transmittivities relate to the dielectric constants and the difference between radii of dielectric cylinders. In addition, the width of photonic band gap can be adjusted by changing air cylinder geometry.
Influence of doping on transmission properties of two-dimensional photonic crystals is analyzed numerically in the paper. The crystals’ transmission spectra are obtained by numerical calculation with plane wave expansion method. The results show that the width and position of photonic band gaps as well as transmittivities relate to the dielectric constants and the difference between radii of dielectric cylinders. In addition, the width of photonic band gap can be adjusted by changing air cylinder geometry.
2006,
18.
Abstract:
Beam quality measurement is very important for high power laser facility. It ensures the facility work in a safe state and offers parameters to beam control system at the same time .Using radial shearing interferometer (RSI) based on spatial phase modulation combined diagnostic phase, near field and far field in experiment. It is found that this method can get high spatial resolution phase information, and that the power in bucket (PIB) curve of far field measured by RSI agrees very well with that by CCD. The only problem is that high resolution near field can't be obtained with RSI now.
Beam quality measurement is very important for high power laser facility. It ensures the facility work in a safe state and offers parameters to beam control system at the same time .Using radial shearing interferometer (RSI) based on spatial phase modulation combined diagnostic phase, near field and far field in experiment. It is found that this method can get high spatial resolution phase information, and that the power in bucket (PIB) curve of far field measured by RSI agrees very well with that by CCD. The only problem is that high resolution near field can't be obtained with RSI now.
2006,
18.
Abstract:
Bubbles caused by laser irradiation can be observed usually via microscope during the experiments of laser induced damage of films, each bubble looks large and very symmetry. From the point of gasification of impurity, we have analyzed the formation mechanism of bubbles in the surface of films using model of a spherical shell which endures high inner pressure. The results reveal that films are more easily damaged when the size of the inclusion is large or the embedment is shallow. At the first time of damage occurred, the bubble is larger when the size of inclusion or the embedded depth is larger. The coupling model of thermal-elastic makes up the present theory and adapts to higher temperature.
Bubbles caused by laser irradiation can be observed usually via microscope during the experiments of laser induced damage of films, each bubble looks large and very symmetry. From the point of gasification of impurity, we have analyzed the formation mechanism of bubbles in the surface of films using model of a spherical shell which endures high inner pressure. The results reveal that films are more easily damaged when the size of the inclusion is large or the embedment is shallow. At the first time of damage occurred, the bubble is larger when the size of inclusion or the embedded depth is larger. The coupling model of thermal-elastic makes up the present theory and adapts to higher temperature.
2006,
18.
Abstract:
Third harmonic beam splitter at 355 nm was deposited on silica substrates by electron beam evaporation and photoelectric maximum control method. Part of the samples were annealed in air at 250 ℃ for 3 hours. The optical transmittance of samples was measured by spectrometer LAMBDA900, the weak absorption of coatings was characterized with surface thermal lensing technique (STL), and the laser induced damage threshold (LIDT) of coatings assessed using 355 nm Q-switch pulsed laser at a pulse length of 7 ns. It was found that the samples had good spectrum performance before and after annealing. After annealing the LIDT of the samples at 1 064 nm increased remarkably from 14.6 J/cm2 to 18.8 J/cm2 with the decreasing of absorption from 1.07×10-4 to 6.2×10-5, but the LIDT at 355 nm decreased o
Third harmonic beam splitter at 355 nm was deposited on silica substrates by electron beam evaporation and photoelectric maximum control method. Part of the samples were annealed in air at 250 ℃ for 3 hours. The optical transmittance of samples was measured by spectrometer LAMBDA900, the weak absorption of coatings was characterized with surface thermal lensing technique (STL), and the laser induced damage threshold (LIDT) of coatings assessed using 355 nm Q-switch pulsed laser at a pulse length of 7 ns. It was found that the samples had good spectrum performance before and after annealing. After annealing the LIDT of the samples at 1 064 nm increased remarkably from 14.6 J/cm2 to 18.8 J/cm2 with the decreasing of absorption from 1.07×10-4 to 6.2×10-5, but the LIDT at 355 nm decreased o
2006,
18.
Abstract:
This paper presents the ab initio calculations results of K vacancy in KDP crystals. The electronic structures and formation energy as well as the relaxing configuration of K vacancy were detailedly studied. The properties of density of states and band structure on KDP with K vacancy were discussed. The formation energy of K vacancy was calculated to be about 6.5 eV and much lower than that of K interstitial (13.07 eV). The cell parameters increase due to K vacancy and the volume enlargement of cavum surrounded by the neighboring eight O atoms is nearly 3.2%, which is in favor of the transference for K atoms and is benefit for the impurity atoms to fill the cavum in KDP. The increasing of mobility ratio of K induces the increasing of ionic conductivity, therefore laser-induced damage thres
This paper presents the ab initio calculations results of K vacancy in KDP crystals. The electronic structures and formation energy as well as the relaxing configuration of K vacancy were detailedly studied. The properties of density of states and band structure on KDP with K vacancy were discussed. The formation energy of K vacancy was calculated to be about 6.5 eV and much lower than that of K interstitial (13.07 eV). The cell parameters increase due to K vacancy and the volume enlargement of cavum surrounded by the neighboring eight O atoms is nearly 3.2%, which is in favor of the transference for K atoms and is benefit for the impurity atoms to fill the cavum in KDP. The increasing of mobility ratio of K induces the increasing of ionic conductivity, therefore laser-induced damage thres
2006,
18.
Abstract:
Laser-induced damage of a single 500 nm HfO2 film and a single 500 nm ZrO2 film were studied with single- and multi-pulse femtosecond laser. The laser-induced damage thresholds (LIDT) of both samples by the 1-on-1 method and the 1 000-on -1 method were reported. It was discovered that the LIDT of the HfO2 single film was higher than that of the ZrO2 single film by both test methods, which was explained by simple Keldysh' s multiphoton ionization theory. The LIDT of multi-pulse was lower than that of single-pulse for both samples as a result of accumulative effect.
Laser-induced damage of a single 500 nm HfO2 film and a single 500 nm ZrO2 film were studied with single- and multi-pulse femtosecond laser. The laser-induced damage thresholds (LIDT) of both samples by the 1-on-1 method and the 1 000-on -1 method were reported. It was discovered that the LIDT of the HfO2 single film was higher than that of the ZrO2 single film by both test methods, which was explained by simple Keldysh' s multiphoton ionization theory. The LIDT of multi-pulse was lower than that of single-pulse for both samples as a result of accumulative effect.
2006,
18.
Abstract:
An optical system was designed. It can be applied in monitoring the real-time bouncing status of ICF target micro-sphere with 0.2~1.0 mm in diameter. A ring Light Emitting Diode (LED) for specific illumination was designed, and through the Petzval objective system, the micro-sphere was imaged onto the CCD with details resolution. Video detection system by personal computer captured and disposed every video image. Monitoring the real-time status of micro-sphere was realized and the coating efficiency improved greatly. The optical system had very good image quality, with the maximum spot diameter on-axis and off-axis of 12.6 μm and 15.8 μm, respectively. The fields were uniform and had high resolution. Particularly, the field curvature less than 15 μm and the distortion less than 0.012% f
An optical system was designed. It can be applied in monitoring the real-time bouncing status of ICF target micro-sphere with 0.2~1.0 mm in diameter. A ring Light Emitting Diode (LED) for specific illumination was designed, and through the Petzval objective system, the micro-sphere was imaged onto the CCD with details resolution. Video detection system by personal computer captured and disposed every video image. Monitoring the real-time status of micro-sphere was realized and the coating efficiency improved greatly. The optical system had very good image quality, with the maximum spot diameter on-axis and off-axis of 12.6 μm and 15.8 μm, respectively. The fields were uniform and had high resolution. Particularly, the field curvature less than 15 μm and the distortion less than 0.012% f
2006,
18.
Abstract:
The Ag coating Cu bimetallic nano-powders were synthesized by substitution reaction with AgNO3.The synthesis process was discussed and the bimetallic powders were characterized by TEM, EDXS and XRD. The experimental results indicate that the bimetallic powders have a Ag coating Cu nano-powder structure and disperse well, the average grain size is 70 nm and the Ag molar content on the surfaces of the bimetallic powders reaches 74.28%. The oxidation of Cu nano-powders in the lavation process was avoided effective by adding of protective reagent.
The Ag coating Cu bimetallic nano-powders were synthesized by substitution reaction with AgNO3.The synthesis process was discussed and the bimetallic powders were characterized by TEM, EDXS and XRD. The experimental results indicate that the bimetallic powders have a Ag coating Cu nano-powder structure and disperse well, the average grain size is 70 nm and the Ag molar content on the surfaces of the bimetallic powders reaches 74.28%. The oxidation of Cu nano-powders in the lavation process was avoided effective by adding of protective reagent.
2006,
18.
Abstract:
Gas-barrier material-polyvinyl alcohol (PVA) of multilayer laser microsphere was cross linked by glutaraldehyde (GA) in order to improve the gas-barrier properties of microsphere. Different content of GA, from 300 μL to 1 700 μL were added into the identical blended solutions of 10 mL, 3% PVA and 20 μL hydrochloric acid. Gas-barrier properties of polyvinyl glutaral (PVG) membranes was measured after cross linking reaction and permeability coefficient of PVG membranes was worked out. It was found that PVG′s permeability coefficient first decreases, and then increases, then keeps stead, at last increases with the increase of GA content in PVG membranes . Moreover, when GA content is 800 μL, the permeability coefficient of PVG film is the minimum with the best gas-barrier properties.
Gas-barrier material-polyvinyl alcohol (PVA) of multilayer laser microsphere was cross linked by glutaraldehyde (GA) in order to improve the gas-barrier properties of microsphere. Different content of GA, from 300 μL to 1 700 μL were added into the identical blended solutions of 10 mL, 3% PVA and 20 μL hydrochloric acid. Gas-barrier properties of polyvinyl glutaral (PVG) membranes was measured after cross linking reaction and permeability coefficient of PVG membranes was worked out. It was found that PVG′s permeability coefficient first decreases, and then increases, then keeps stead, at last increases with the increase of GA content in PVG membranes . Moreover, when GA content is 800 μL, the permeability coefficient of PVG film is the minimum with the best gas-barrier properties.
2006,
18.
Abstract:
This paper describes a new data acquisition system for middle speed and low speed signal in ICF experiments, i.e., the FF detector. It is made up of two parts : the standard modular hardware based on VXI bus and the flexible software application developed under LabWindows/CVI. This structure takes full advantage of mature industry standard and versatile integrated development environment. It satisfies the request of measuring superthermal electrons in ICF experiments and improves the stability and precision of the old nonstandard acquisition system. In addition, the delay of system under different trigger conditions is carefully measured.
This paper describes a new data acquisition system for middle speed and low speed signal in ICF experiments, i.e., the FF detector. It is made up of two parts : the standard modular hardware based on VXI bus and the flexible software application developed under LabWindows/CVI. This structure takes full advantage of mature industry standard and versatile integrated development environment. It satisfies the request of measuring superthermal electrons in ICF experiments and improves the stability and precision of the old nonstandard acquisition system. In addition, the delay of system under different trigger conditions is carefully measured.
2006,
18.
Abstract:
A new experimental method to measure the surface scattering and volume scattering of the K9 glass substrate by the total integrated scattering(TIS) was presented. Ag film with a few ten nanometers thickness was deposited by magnetron sputtering, which differentiated the surface and volume of the substrate. Root mean square roughness of the front and back surface of the K9 substrate was measured by TIS, according to which the total scattering and the surface scattering of the substrate were obtained and the volume scattering was calculated. The total scatterings of 3 samples were 6.06×10-4，5.84×10-4 and 6.48×10-4, respectively. Surface scatterings were in the range of 1.25×10-4~1.56×10-4. TIS and atomic force microscopy(AFM) were used to measure root mean square roughness of Ag films,
A new experimental method to measure the surface scattering and volume scattering of the K9 glass substrate by the total integrated scattering(TIS) was presented. Ag film with a few ten nanometers thickness was deposited by magnetron sputtering, which differentiated the surface and volume of the substrate. Root mean square roughness of the front and back surface of the K9 substrate was measured by TIS, according to which the total scattering and the surface scattering of the substrate were obtained and the volume scattering was calculated. The total scatterings of 3 samples were 6.06×10-4，5.84×10-4 and 6.48×10-4, respectively. Surface scatterings were in the range of 1.25×10-4~1.56×10-4. TIS and atomic force microscopy(AFM) were used to measure root mean square roughness of Ag films,
2006,
18.
Abstract:
The experimental results of focal spot measured with schlieren method were reported in this paper. The far field focal spot was enlarged by an imaging lens and collected by a scientific-grade CCD camera with 12 bit. Schlieren data were taken by shading the central lobe of focal spot with a certain size spherule and controlling the receiving attenuation. When the schlieren data were added to the central lobe data, the relative intensity profile of focal spot was achieved. The schlieren method can provide larger effective dynamic measurement range and improve the measurement precision of focal spot.
The experimental results of focal spot measured with schlieren method were reported in this paper. The far field focal spot was enlarged by an imaging lens and collected by a scientific-grade CCD camera with 12 bit. Schlieren data were taken by shading the central lobe of focal spot with a certain size spherule and controlling the receiving attenuation. When the schlieren data were added to the central lobe data, the relative intensity profile of focal spot was achieved. The schlieren method can provide larger effective dynamic measurement range and improve the measurement precision of focal spot.
2006,
18.
Abstract:
Atom hologram lithography employs binary computer generated hologram to handle atoms for making microstructure. The conventional binary hologram is inconvenient because it often has more than one reconstructed images. A new method of amplitude-only encoding is investigated. A hologram is formed by adding together a series of elementary functions, and then it is encoded with Lohmann Ⅲ like encoding to obtain a binary computer generated hologram. A simulation result shows that the mask made with the new method could produce a unique microstructure according to the original pattern.
Atom hologram lithography employs binary computer generated hologram to handle atoms for making microstructure. The conventional binary hologram is inconvenient because it often has more than one reconstructed images. A new method of amplitude-only encoding is investigated. A hologram is formed by adding together a series of elementary functions, and then it is encoded with Lohmann Ⅲ like encoding to obtain a binary computer generated hologram. A simulation result shows that the mask made with the new method could produce a unique microstructure according to the original pattern.
2006,
18.
Abstract:
By comparing the kinematical equation of a shock wave in free air, the study of transmission characteristics of the laser plasma shock wave in Compton scattering is presented. The results show that the attenuation course of the kinematics of he laser plasma shock wave is related not only with the explosion fountainhead and the characteristics of the explosion course, total energy release, air elastic, but also with multi-photon nonlinear Compton scattering. Because of the scattering the initial radius of the shock wave increases, the attenuation course shortens, the energy metastasis efficiency rises. The results of the numerical analysis and the actual values of the shock waves in air by a way intense explosion are very tallying.
By comparing the kinematical equation of a shock wave in free air, the study of transmission characteristics of the laser plasma shock wave in Compton scattering is presented. The results show that the attenuation course of the kinematics of he laser plasma shock wave is related not only with the explosion fountainhead and the characteristics of the explosion course, total energy release, air elastic, but also with multi-photon nonlinear Compton scattering. Because of the scattering the initial radius of the shock wave increases, the attenuation course shortens, the energy metastasis efficiency rises. The results of the numerical analysis and the actual values of the shock waves in air by a way intense explosion are very tallying.
2006,
18.
Abstract:
Based on the performance requirement of the ignitor, raw materials such as B4C and BN were chosen to produce a new type of ignitor with no poison, high igniting and good performance with powder metallurgy technology. The microcosmic structure of the ignitor was analysed by using XRD and SEM method. The performance factors such as ingredient,surfacial idensity,cold resistance and hot resistance were discussed. The results indicate that B4C can enhance electric performance of the ignitor and BN can increase hot transmittability and tune up the resistance of the ignitor and make the ignitor work stably in high temperature. Surface appearance influences the ignition performance seriously. The cold resistance and the hot resistance of the ignitor can only offer judgement for the contact bet
Based on the performance requirement of the ignitor, raw materials such as B4C and BN were chosen to produce a new type of ignitor with no poison, high igniting and good performance with powder metallurgy technology. The microcosmic structure of the ignitor was analysed by using XRD and SEM method. The performance factors such as ingredient,surfacial idensity,cold resistance and hot resistance were discussed. The results indicate that B4C can enhance electric performance of the ignitor and BN can increase hot transmittability and tune up the resistance of the ignitor and make the ignitor work stably in high temperature. Surface appearance influences the ignition performance seriously. The cold resistance and the hot resistance of the ignitor can only offer judgement for the contact bet
2006,
18.
Abstract:
The spectacular progress made during the last few years in rod-pinch diode(RPD) research opens new perspectives of flash X-ray radiography, especially in the small-scale hydrodynamic experiments. This survey covers essentially all aspects of RPD with various configurations (i.e. vacuum RPD and plasma-filled RPD): basic principle, scaling laws, significance and applications. The parameters and experimental results of the Cygnus underground facility are introduced. The development of RPD in the near future is also stated and discussed.
The spectacular progress made during the last few years in rod-pinch diode(RPD) research opens new perspectives of flash X-ray radiography, especially in the small-scale hydrodynamic experiments. This survey covers essentially all aspects of RPD with various configurations (i.e. vacuum RPD and plasma-filled RPD): basic principle, scaling laws, significance and applications. The parameters and experimental results of the Cygnus underground facility are introduced. The development of RPD in the near future is also stated and discussed.
2006,
18.
Abstract:
A pair of superconducting quadrupole(SCQ) magnets are applied for Beijing Electron-Positron Collider Upgrade (BEPC Ⅱ). The magnet can be destroyed by the excess mechanical stress caused by thermal gradients during the cool-down and warm-up processes. This paper presents the cool-down and warm-up processes in terms of magnet safe operation. A mathematical model and an analytical method are developed and the time of cool-down and warm-up is calculated, which is respectively 120 minutes and 150 minutes. The transient changes of the operation parameters are obtained, including the inlet and outlet temperature and pressure of helium to cooling loop of the magnet, the highest and lowest temperature of the magnet, and the maximum temperature difference along the magnet. The peak maximum temperat
A pair of superconducting quadrupole(SCQ) magnets are applied for Beijing Electron-Positron Collider Upgrade (BEPC Ⅱ). The magnet can be destroyed by the excess mechanical stress caused by thermal gradients during the cool-down and warm-up processes. This paper presents the cool-down and warm-up processes in terms of magnet safe operation. A mathematical model and an analytical method are developed and the time of cool-down and warm-up is calculated, which is respectively 120 minutes and 150 minutes. The transient changes of the operation parameters are obtained, including the inlet and outlet temperature and pressure of helium to cooling loop of the magnet, the highest and lowest temperature of the magnet, and the maximum temperature difference along the magnet. The peak maximum temperat
2006,
18.
Abstract:
Based on the results of the DC-SC photocathode injector experiments at Peking University, an improved design of the injector is proposed. The new injector can provide both high average power electron beams with bunch charge of 100 pC, repetition rate of 81.25 MHz, transversal emittance lower than 2 mm·mrad, bunch length of 4 ps, and high peak current electron beams with bunch charge of 300 pC, transversal emittance lower than 3 mm·mrad and bunch length of about 9 ps. The detailed design of the injector, influence of bunch shape to the beam emittance and analysis of solenoid compensation technology are presented in this paper.
Based on the results of the DC-SC photocathode injector experiments at Peking University, an improved design of the injector is proposed. The new injector can provide both high average power electron beams with bunch charge of 100 pC, repetition rate of 81.25 MHz, transversal emittance lower than 2 mm·mrad, bunch length of 4 ps, and high peak current electron beams with bunch charge of 300 pC, transversal emittance lower than 3 mm·mrad and bunch length of about 9 ps. The detailed design of the injector, influence of bunch shape to the beam emittance and analysis of solenoid compensation technology are presented in this paper.
2006,
18.
Abstract:
A 0-dimension model of laser triggered SF6 gap switch is established and the numerical results compared with a series of experimental data presented by Woodworth and Li hong-tao in the paper. The calculated delay is in agreement with the experimental one. When gas pressure is constant, delay decreases with the increase of laser energy and percent of self-breakdown voltage(SBV). The slope of the curve of delay vs percent of SBV for different laser energy also decreases with the increase of laser energy and percent of SBV. When laser energy is constant, delay decreases with the decrease of pressure and the increase of voltage, and the curve slope of delay vs voltage for different pressure decreases with the increase of voltage. The delay decreases as pressure increases for constant V/p.
A 0-dimension model of laser triggered SF6 gap switch is established and the numerical results compared with a series of experimental data presented by Woodworth and Li hong-tao in the paper. The calculated delay is in agreement with the experimental one. When gas pressure is constant, delay decreases with the increase of laser energy and percent of self-breakdown voltage(SBV). The slope of the curve of delay vs percent of SBV for different laser energy also decreases with the increase of laser energy and percent of SBV. When laser energy is constant, delay decreases with the decrease of pressure and the increase of voltage, and the curve slope of delay vs voltage for different pressure decreases with the increase of voltage. The delay decreases as pressure increases for constant V/p.
2006,
18.
Abstract:
This paper describes a Multiwire Proportional Chamber (MWPC) for the Test Beam on BEPC(Beijing Electron Positron Colider). The distance between the anode surface and the cathode surface of the MWPC is 6 mm. Both surfaces are made of gold-plated tungsten wires, the anode wires are 20 μm in diameter and 2 mm apart, and the cathode wires are 50 μm indiameter and 0.7 mm apart. Six adjacent wires are connected together to form a 4.2 mm wide cathode strip. The MWPC can localize the particles of e, π by cathode-induced charge centre-of-gravity read-out. For 5.9 keV γ photon, the positional resolution is less than 0.3 mm (FWHM) and for 1.1 GeV beam electron, 0.224 mm (FWHM) positional resolution is attained.
This paper describes a Multiwire Proportional Chamber (MWPC) for the Test Beam on BEPC(Beijing Electron Positron Colider). The distance between the anode surface and the cathode surface of the MWPC is 6 mm. Both surfaces are made of gold-plated tungsten wires, the anode wires are 20 μm in diameter and 2 mm apart, and the cathode wires are 50 μm indiameter and 0.7 mm apart. Six adjacent wires are connected together to form a 4.2 mm wide cathode strip. The MWPC can localize the particles of e, π by cathode-induced charge centre-of-gravity read-out. For 5.9 keV γ photon, the positional resolution is less than 0.3 mm (FWHM) and for 1.1 GeV beam electron, 0.224 mm (FWHM) positional resolution is attained.
2006,
18.
Abstract:
In order to find out the invalidation of submicrometer semiconductor devices under different microwave pulses, the author developed a simulation program based on the hydrodynamic method (HDM). Coupled Newton method was used in the program to solve nonlinear equations that describe device properties. The paper has shown the transient simulation results on a one dimensional ballistic diode done by the program, including the electron temperature, electric field, electron and hole densities, etc. When a relatively high voltage (10 V) is applied to the device, the results show great difference from low ones. The author has tried the second breakdown theory on the phenomenon. Further work should be done to get more accurate simulation results and reasonable physical analysis.
In order to find out the invalidation of submicrometer semiconductor devices under different microwave pulses, the author developed a simulation program based on the hydrodynamic method (HDM). Coupled Newton method was used in the program to solve nonlinear equations that describe device properties. The paper has shown the transient simulation results on a one dimensional ballistic diode done by the program, including the electron temperature, electric field, electron and hole densities, etc. When a relatively high voltage (10 V) is applied to the device, the results show great difference from low ones. The author has tried the second breakdown theory on the phenomenon. Further work should be done to get more accurate simulation results and reasonable physical analysis.
Experiment research of solid-state pulsed power generator for pulsed plasma induced chemical process
2006,
18.
Abstract:
The paper presents a solid-state pulsed power generator, which is based on the integrated technology of semiconductor switch, magnetic switch and saturable pulse transformer. This pulsed power generator is used for pulsed plasma induced chemical process(PPCP) . Based on the theory analysis, the trial model is set up. The results of the experiment testify the feasibility of the generator. The experiment solves the static and dynamic voltage-equilibrium problem and the conduction synchronization of 8 thyristors in series. The working properties of saturable pulse transformer and magnetic switch are analyzed and calculated. The main parameters of the generator are as follows: peak voltage 37.5 kV with resistance load, pulse rise time 101 ns, pulse width 1 μs, repetition frequency 300 Hz, and
The paper presents a solid-state pulsed power generator, which is based on the integrated technology of semiconductor switch, magnetic switch and saturable pulse transformer. This pulsed power generator is used for pulsed plasma induced chemical process(PPCP) . Based on the theory analysis, the trial model is set up. The results of the experiment testify the feasibility of the generator. The experiment solves the static and dynamic voltage-equilibrium problem and the conduction synchronization of 8 thyristors in series. The working properties of saturable pulse transformer and magnetic switch are analyzed and calculated. The main parameters of the generator are as follows: peak voltage 37.5 kV with resistance load, pulse rise time 101 ns, pulse width 1 μs, repetition frequency 300 Hz, and
2006,
18.
Abstract:
Gas temperature decay is the primary factor which restricts the repetitive operation of spark switch. The gas temperature decay in gas spark switch after operation is simulated based on fluent equation, thermal conductivity equation and general gas law. The simulated results indicate some rules of the gas temperature decay in spark gap switch:(1) the heat loss of the gas is mainly caused by thermal conduction;(2) the hot gas an hardly cooldown in several tens of milliseconds;(3) the influence of convection are notable after a few tens of milliseconds; (4) the influence of the viscosity coefficient of gas on the temperature decay could be ignored. Finally the methods for accelerating gas decay are discussed and presented.
Gas temperature decay is the primary factor which restricts the repetitive operation of spark switch. The gas temperature decay in gas spark switch after operation is simulated based on fluent equation, thermal conductivity equation and general gas law. The simulated results indicate some rules of the gas temperature decay in spark gap switch:(1) the heat loss of the gas is mainly caused by thermal conduction;(2) the hot gas an hardly cooldown in several tens of milliseconds;(3) the influence of convection are notable after a few tens of milliseconds; (4) the influence of the viscosity coefficient of gas on the temperature decay could be ignored. Finally the methods for accelerating gas decay are discussed and presented.
2006,
18.
Abstract:
By the two-dimensional finite-difference time-domain simulation, the damage of bipolar junction transistor(BJT) under high power electromagnetic pulses was studied, considering the different response of BJT under the electro-magnetic pulse injected from different electrode. The possibility of burnout was analyzed according to the temperature concentration. The simulation results show that the emitter injection is easier to burnout the BJT than the collector injection, and the base injection is relatively difficult. The energy needed for burnout decreases with the magnitude of the pulse in the case of emitter injection, while it becomes independent of the magnitude that is higher than about 30 V. The energy needed for burnout increases with the magnitude of the pulse in the case of collecto
By the two-dimensional finite-difference time-domain simulation, the damage of bipolar junction transistor(BJT) under high power electromagnetic pulses was studied, considering the different response of BJT under the electro-magnetic pulse injected from different electrode. The possibility of burnout was analyzed according to the temperature concentration. The simulation results show that the emitter injection is easier to burnout the BJT than the collector injection, and the base injection is relatively difficult. The energy needed for burnout decreases with the magnitude of the pulse in the case of emitter injection, while it becomes independent of the magnitude that is higher than about 30 V. The energy needed for burnout increases with the magnitude of the pulse in the case of collecto
2006,
18.
Abstract:
The bubble breakdown theories of liquid that summarizes of the experimental data of the Siberian Research Institute of Energetic in Russia is presented in this paper. The breakdown experiments of the water switch have been done under the two short pulsed voltages of 1 μs and 300 ns.Some valuable experimental data about the relations of the breakdown electric field intensity and the hold-off time of pressurized deionized water breakdown have been acquired. The experimental results indicate that the breakdown electric field and the hold-off time of pressurized deionized water is enhanced under the two short pulsed voltages, when the pressure of water between the electrodes increases. However, the effects of water pressure is different under the short pulsed voltages of 1us and 300 ns; Short
The bubble breakdown theories of liquid that summarizes of the experimental data of the Siberian Research Institute of Energetic in Russia is presented in this paper. The breakdown experiments of the water switch have been done under the two short pulsed voltages of 1 μs and 300 ns.Some valuable experimental data about the relations of the breakdown electric field intensity and the hold-off time of pressurized deionized water breakdown have been acquired. The experimental results indicate that the breakdown electric field and the hold-off time of pressurized deionized water is enhanced under the two short pulsed voltages, when the pressure of water between the electrodes increases. However, the effects of water pressure is different under the short pulsed voltages of 1us and 300 ns; Short
2006,
18.
Abstract:
The transportation experiments of high power ion beams(HPIB) on the FLASH Ⅱ accelerator are presented. The transportation of HPIB in different transporting conditions and distances was studied. The influence of neutralization on the radius of beam and the uniformity of the current distribution was analyzed and numerically simulated. The results of the simulation are consistent with the experimental data. Being neutralized, the HPIB can be effectively transported to a distance farther than 80 cm. During the transportation, the distribution of current is uniformed; the defocus of HPIB is reduced.
The transportation experiments of high power ion beams(HPIB) on the FLASH Ⅱ accelerator are presented. The transportation of HPIB in different transporting conditions and distances was studied. The influence of neutralization on the radius of beam and the uniformity of the current distribution was analyzed and numerically simulated. The results of the simulation are consistent with the experimental data. Being neutralized, the HPIB can be effectively transported to a distance farther than 80 cm. During the transportation, the distribution of current is uniformed; the defocus of HPIB is reduced.
