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RSS2006 Vol. 18, No. 06
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2006,
18.
Abstract:
Considering some necessary factors in the design of SSHCL, material properties of Nd doped glass, YAG and GGG were compared. Transient temperature fields and thermal stress in these slab mediums during one working cycle were simulated. Numerical analysis results showed that the internal-external temperature difference in a neodymium doped glass slab was 75 K and the peak temperature value was 400 K when pumping time arrived 5 s. The maximum stress came to 50% of glass fracture limit. During subsequent water cooling period, the initial state was recovered after 120 s. On the same boundary conditions, Nd: YAG and Nd: GGG slabs could maintain relatively smooth temperature profile while the temperature rising and equivalent thermal stress were lower compared to glass. In later cooling phase, b
Considering some necessary factors in the design of SSHCL, material properties of Nd doped glass, YAG and GGG were compared. Transient temperature fields and thermal stress in these slab mediums during one working cycle were simulated. Numerical analysis results showed that the internal-external temperature difference in a neodymium doped glass slab was 75 K and the peak temperature value was 400 K when pumping time arrived 5 s. The maximum stress came to 50% of glass fracture limit. During subsequent water cooling period, the initial state was recovered after 120 s. On the same boundary conditions, Nd: YAG and Nd: GGG slabs could maintain relatively smooth temperature profile while the temperature rising and equivalent thermal stress were lower compared to glass. In later cooling phase, b
2006,
18.
Abstract:
The optimum fiber length of the single mode Yb-doped fiber amplifier is simulated. Experiments of the single-mode Yb-doped fiber amplifier and gratings compressor are discussed. The seed pulses come from a mode-locking Yb-doped fiber ring laser. The maximum output average power of the fiber laser is 7 mW at 25.4 MHz repetition rate with a pulse width of 56 ps. The seed pulses are amplified by using three different length single mode Yb-doped fibers respectively which are pumped by a 976 nm semiconductor laser with a maximum output power about 250 mW. The amplified pulses are compressed by using the traditional gratings compressor. When the length of the single mode Yb-doped fiber is 1.2 m, the fiber amplifier generates a maximum power of 140 mW corresponding to a gain about 13 dB. The ampl
The optimum fiber length of the single mode Yb-doped fiber amplifier is simulated. Experiments of the single-mode Yb-doped fiber amplifier and gratings compressor are discussed. The seed pulses come from a mode-locking Yb-doped fiber ring laser. The maximum output average power of the fiber laser is 7 mW at 25.4 MHz repetition rate with a pulse width of 56 ps. The seed pulses are amplified by using three different length single mode Yb-doped fibers respectively which are pumped by a 976 nm semiconductor laser with a maximum output power about 250 mW. The amplified pulses are compressed by using the traditional gratings compressor. When the length of the single mode Yb-doped fiber is 1.2 m, the fiber amplifier generates a maximum power of 140 mW corresponding to a gain about 13 dB. The ampl
2006,
18.
Abstract:
The Rytov approximation theory is applied to the angle-of-arrival fluctuation and the analytical expressions are developed for variance and power spectrum associated with the angle-of-arrival fluctuation of unbounded plane waves and spherical waves in strong turbulence regime. The derived expressions are then compared with the previous weak fluctuation theory, and effects of the scattering disk scale on power spectrum are analyzed. Results show that the derived displacement variances extending into weak turbulence regime are in good agreement with those of the traditional weak-fluctuation theory and are valid in all turbulence regimes; The angle-of-arrival fluctuation tends to saturate with increasing Rytov variance; The high-frequency power spectra drops at a much faster rate along with t
The Rytov approximation theory is applied to the angle-of-arrival fluctuation and the analytical expressions are developed for variance and power spectrum associated with the angle-of-arrival fluctuation of unbounded plane waves and spherical waves in strong turbulence regime. The derived expressions are then compared with the previous weak fluctuation theory, and effects of the scattering disk scale on power spectrum are analyzed. Results show that the derived displacement variances extending into weak turbulence regime are in good agreement with those of the traditional weak-fluctuation theory and are valid in all turbulence regimes; The angle-of-arrival fluctuation tends to saturate with increasing Rytov variance; The high-frequency power spectra drops at a much faster rate along with t
2006,
18.
Abstract:
A 3D physical optics model of a loaded cavity with phase disturbance is built. With a foldaway unstable resonator in a COIL, the effects of shock waves with different intensities at different physical locations on the phase and the output power of the optical field are simulated. It is shown that the location and intensity of shock waves can bring different degrees of optical beam degeneration. Stronger disturbance such as central shock waves ought to be avoided. The photographs of ablation from experiment are reproduced by the numerical simulations with the phase disturbance by shock waves in the optical cavity.
A 3D physical optics model of a loaded cavity with phase disturbance is built. With a foldaway unstable resonator in a COIL, the effects of shock waves with different intensities at different physical locations on the phase and the output power of the optical field are simulated. It is shown that the location and intensity of shock waves can bring different degrees of optical beam degeneration. Stronger disturbance such as central shock waves ought to be avoided. The photographs of ablation from experiment are reproduced by the numerical simulations with the phase disturbance by shock waves in the optical cavity.
2006,
18.
Abstract:
Using the model of dual-hyperbolic two temperature, taking the gold film as example, the temperature effects on heat capacity, thermal conductivity and relaxation time have been studied with an accuracy and stability forward-difference scheme, to which one kind of artificial viscosities and adaptive time steps method is introduced. The primary researches in this paper are on the thermal response of 50 nm gold film irradiated by 0.1 ps laser pulse. The numerical results indicate that after having been heated for 0.27 ps the maximum electron temperature at the front surface occurs, after about 1.6 ps the temperature equilibration time of all electrons is achieved, while that of the whole film is got after about 60 ps. Hot-electron blast force damage could be a dominant mechanism in ultra-sho
Using the model of dual-hyperbolic two temperature, taking the gold film as example, the temperature effects on heat capacity, thermal conductivity and relaxation time have been studied with an accuracy and stability forward-difference scheme, to which one kind of artificial viscosities and adaptive time steps method is introduced. The primary researches in this paper are on the thermal response of 50 nm gold film irradiated by 0.1 ps laser pulse. The numerical results indicate that after having been heated for 0.27 ps the maximum electron temperature at the front surface occurs, after about 1.6 ps the temperature equilibration time of all electrons is achieved, while that of the whole film is got after about 60 ps. Hot-electron blast force damage could be a dominant mechanism in ultra-sho
2006,
18.
Abstract:
Multi-walled carbon nanotubes water-surfactant suspensions were prepared by ultrasonication, and the optical limiting curves were measured for 1 064 nm, 10 ns Nd:YAG Q-switched puled laser. The experimental results indicated that the output energy varied linearly with input fluences at a lower level, when the incident fluences increase to about 160 mJ/cm2, the output was clamped and tended to the value 16 mJ finally, and the transmittance of the sample decreased from 71% to 15%. In addition, the optical limiting mechanisms were investigated through performing Z-scan, pump-probe and 45° scattering experiments. The results show that the nonlinear scattering dominates the transmittance losses and the nonlinear refraction is secondary.
Multi-walled carbon nanotubes water-surfactant suspensions were prepared by ultrasonication, and the optical limiting curves were measured for 1 064 nm, 10 ns Nd:YAG Q-switched puled laser. The experimental results indicated that the output energy varied linearly with input fluences at a lower level, when the incident fluences increase to about 160 mJ/cm2, the output was clamped and tended to the value 16 mJ finally, and the transmittance of the sample decreased from 71% to 15%. In addition, the optical limiting mechanisms were investigated through performing Z-scan, pump-probe and 45° scattering experiments. The results show that the nonlinear scattering dominates the transmittance losses and the nonlinear refraction is secondary.
2006,
18.
Abstract:
Based on laser induced plasma switch technology, the output pulse width of 4.4 ns of the solid-state Nd:YAG laser is obtained. The influences of the focal length of the lens and the laser beam energy on the shortened laser pulse width are presented. The shorter the focal length is, the narrower the shortened pulse durationis, the greater the laser energy loss is. A hyperbola relationship between the pulse duration and the laser pulse energy is obtained. The laser pulse width is shortened to 6.4 ns by the plasma switch generated by the laser discharge in atmosphere. Placing a Cu pinhole on the focus of the lens to prevent the plasma from diffusing, a short output pulse with a width of 4.4 ns is obtained.
Based on laser induced plasma switch technology, the output pulse width of 4.4 ns of the solid-state Nd:YAG laser is obtained. The influences of the focal length of the lens and the laser beam energy on the shortened laser pulse width are presented. The shorter the focal length is, the narrower the shortened pulse durationis, the greater the laser energy loss is. A hyperbola relationship between the pulse duration and the laser pulse energy is obtained. The laser pulse width is shortened to 6.4 ns by the plasma switch generated by the laser discharge in atmosphere. Placing a Cu pinhole on the focus of the lens to prevent the plasma from diffusing, a short output pulse with a width of 4.4 ns is obtained.
2006,
18.
Abstract:
Experimental research on X-ray guiding capillaries is the foundation of X-ray lens design. The experimental results of measuring transmission efficiency within the energy range of 50 eV~1.5 keV for a variety type of capillaries are presented, including different materials, different inner radius and different bent radius. It is shown that the transmission efficiency of curved capillary increases with the decrease of the X-ray energy, the inner diameter of capillary, and the bend radius of curved capillary. As a result, the capillary manufactured of glass DM308 with an inner diameter of 0.45 mm and an outer diameter of 0.60 mm is the best choice for the soft X-ray lens.
Experimental research on X-ray guiding capillaries is the foundation of X-ray lens design. The experimental results of measuring transmission efficiency within the energy range of 50 eV~1.5 keV for a variety type of capillaries are presented, including different materials, different inner radius and different bent radius. It is shown that the transmission efficiency of curved capillary increases with the decrease of the X-ray energy, the inner diameter of capillary, and the bend radius of curved capillary. As a result, the capillary manufactured of glass DM308 with an inner diameter of 0.45 mm and an outer diameter of 0.60 mm is the best choice for the soft X-ray lens.
2006,
18.
Abstract:
Theoretical research on soft-damage in photovoltaic semiconductor detectors under medium power density laser irradiation (between the saturation threshold and the damage threshold of detector) was carried out and a new mechanism was proposed. When laser irradiation density exceeds the saturation threshold of a detector, the transitions of the carriers between bands saturated, hot carriers are produced in the semiconductor and the hot carrier temperature is higher than the crystal lattice temperature. Therefore the output of the photovoltaic detector decreases with the increase of laser power density till zero-voltage output appears. The output of a photovoltaic HgCdTe detector under laser irradiation is calculated. The calculating results are identical with experimental results.
Theoretical research on soft-damage in photovoltaic semiconductor detectors under medium power density laser irradiation (between the saturation threshold and the damage threshold of detector) was carried out and a new mechanism was proposed. When laser irradiation density exceeds the saturation threshold of a detector, the transitions of the carriers between bands saturated, hot carriers are produced in the semiconductor and the hot carrier temperature is higher than the crystal lattice temperature. Therefore the output of the photovoltaic detector decreases with the increase of laser power density till zero-voltage output appears. The output of a photovoltaic HgCdTe detector under laser irradiation is calculated. The calculating results are identical with experimental results.
2006,
18.
Abstract:
The beam wander of focused laser beam in atmospheric boundary layer was studied experimentally over 1 000 m path at five meters above sea level using a position sensitive photomultiplier tube (PSPMT). A new experimental setup was designed to directly measure two dimensional position variations in the active area of 80 mm diameter. The high spatial resolution of the new setup reaching 1 mm is better than that of the quadrant detector and the detector array system markedly. This system is better than the ordinary imaging systems for its high sampling frequency of 80 kHz and wide dynamic range. The statistic results show that the beam wander is strongly anisotropic. The beam wander in horizontal direction is between 5.61 mm and 14.83 mm and in vertical direction always varies from 3.54 mm to
The beam wander of focused laser beam in atmospheric boundary layer was studied experimentally over 1 000 m path at five meters above sea level using a position sensitive photomultiplier tube (PSPMT). A new experimental setup was designed to directly measure two dimensional position variations in the active area of 80 mm diameter. The high spatial resolution of the new setup reaching 1 mm is better than that of the quadrant detector and the detector array system markedly. This system is better than the ordinary imaging systems for its high sampling frequency of 80 kHz and wide dynamic range. The statistic results show that the beam wander is strongly anisotropic. The beam wander in horizontal direction is between 5.61 mm and 14.83 mm and in vertical direction always varies from 3.54 mm to
2006,
18.
Abstract:
The surfaces of HgCdTe plates irradiated by one pulse of TEA-CO2 laser with 37.5 J and energy density of 937.5 J/cm2 are examined by an optical microscope. After laser irradiation, there are large numbers of cracks and much trace of melting in the surface of the plate, and the cracks extending in (111) are the densest in laser irradiation zone. With the increase of the action number of laser pulses at repetition rate of 1 Hz, the melting is more serious, and the numbers, depth and breadth of cracks are all increased. Analyses show the destruction of HgCdTe plates is related with laser energy, action number of laser pulses at repetition rate of 1 Hz, laser field intensity, thermal stress, laser supported combustion wave and evaporation wave.
The surfaces of HgCdTe plates irradiated by one pulse of TEA-CO2 laser with 37.5 J and energy density of 937.5 J/cm2 are examined by an optical microscope. After laser irradiation, there are large numbers of cracks and much trace of melting in the surface of the plate, and the cracks extending in (111) are the densest in laser irradiation zone. With the increase of the action number of laser pulses at repetition rate of 1 Hz, the melting is more serious, and the numbers, depth and breadth of cracks are all increased. Analyses show the destruction of HgCdTe plates is related with laser energy, action number of laser pulses at repetition rate of 1 Hz, laser field intensity, thermal stress, laser supported combustion wave and evaporation wave.
2006,
18.
Abstract:
The window function of circular hard-edge apertures is simulated and optimized by the Laguerre-Gauss truncated series, and applied to study the diffraction of Gaussian beams and 0-order Bessel-Gaussian beams by the hard-edge aperture. The results of the axial and transversal intensity distributions of Gaussian beams and 0-order Bessel-Gaussian beams show that the results by the optimized Laguerre-Gaussian truncated series are in good agreement with those by the Fresnel diffraction integral method if the integration plane is not close to the aperture.
The window function of circular hard-edge apertures is simulated and optimized by the Laguerre-Gauss truncated series, and applied to study the diffraction of Gaussian beams and 0-order Bessel-Gaussian beams by the hard-edge aperture. The results of the axial and transversal intensity distributions of Gaussian beams and 0-order Bessel-Gaussian beams show that the results by the optimized Laguerre-Gaussian truncated series are in good agreement with those by the Fresnel diffraction integral method if the integration plane is not close to the aperture.
2006,
18.
Abstract:
In the study of the uniform droplet singlet oxygen generator, the breakup of a round jet into the droplet stream is a vital technology. The disturbance applied threw by the piezoelectric transducer to the stream grow on the surface of the stream. The growth of the disturbance continues exponentially until a fluid parcel, is pinched off of the capillary. Analysis shows that several parameters affect the growth rate of the disturbance. The increase in the surface tension of the stream fluid and the decrease in the orifice diameter enhance the growth rate of the disturbance. The other parameters have less effect on the growth rate of the disturbance. The relatively broad bandwidth of the curve in the paper reveals that there are many potential growth rates on the surface that can theoreticall
In the study of the uniform droplet singlet oxygen generator, the breakup of a round jet into the droplet stream is a vital technology. The disturbance applied threw by the piezoelectric transducer to the stream grow on the surface of the stream. The growth of the disturbance continues exponentially until a fluid parcel, is pinched off of the capillary. Analysis shows that several parameters affect the growth rate of the disturbance. The increase in the surface tension of the stream fluid and the decrease in the orifice diameter enhance the growth rate of the disturbance. The other parameters have less effect on the growth rate of the disturbance. The relatively broad bandwidth of the curve in the paper reveals that there are many potential growth rates on the surface that can theoreticall
2006,
18.
Abstract:
Optical transmission is a key issue of the Thomson scattering system due to the weak scattered signal. In this paper, the methods of reducing the stray light and increasing the optical transmittance of the system is discussed. Simulation shows that the transmission of the polychromator is nearly proportional to the electron temperature and it reaches 10% when electron temperature is 1 keV. Scattered signal is very small and there are only hundreds of photons in each channel when electron density is 1×1019/m3. When the electron temperature is more than 300 eV, the measuring uncertainty of the system from photon fluctuation is less than 3%.
Optical transmission is a key issue of the Thomson scattering system due to the weak scattered signal. In this paper, the methods of reducing the stray light and increasing the optical transmittance of the system is discussed. Simulation shows that the transmission of the polychromator is nearly proportional to the electron temperature and it reaches 10% when electron temperature is 1 keV. Scattered signal is very small and there are only hundreds of photons in each channel when electron density is 1×1019/m3. When the electron temperature is more than 300 eV, the measuring uncertainty of the system from photon fluctuation is less than 3%.
2006,
18.
Abstract:
200 μg/cm2 free-standing Zr filters of 20 mm in diameter were made by DC magnetron sputtering. Soft X-ray spectral transmittance of the filters was measured in the National Synchrotron Radiation Laboratory, and the light blocking performance was tested by spectrophotometer. The elements in Zr filters were analyzed using Auger Electron Spectroscopy. The results indicate that Zr filters have good transmittance(19%) at 13.9 nm and perfect visible light blocking properties(43 dB), N，O arisen from background pressure, oxidation and surface contamination are the major species that affect the transmittance of Zr films in the soft X-ray．
200 μg/cm2 free-standing Zr filters of 20 mm in diameter were made by DC magnetron sputtering. Soft X-ray spectral transmittance of the filters was measured in the National Synchrotron Radiation Laboratory, and the light blocking performance was tested by spectrophotometer. The elements in Zr filters were analyzed using Auger Electron Spectroscopy. The results indicate that Zr filters have good transmittance(19%) at 13.9 nm and perfect visible light blocking properties(43 dB), N，O arisen from background pressure, oxidation and surface contamination are the major species that affect the transmittance of Zr films in the soft X-ray．
2006,
18.
Abstract:
In this paper, the electron temperature, electron density and areal density of imploded fuel pellet driven by SGⅡ laser were diagnosed through X-ray method. The electron temperature deduced from intensity ratio of Ly-beta line and He-beta line of Ar tracer doped in DD fuel was determined to be(950±100) eV. The electron density which was deduced from Stark broadening of He-beta line was determined to be (0.9±0.2)×1024cm-3. And the fuel areal density, which was deduced from X-ray monochromatic imaging of compressed fuel, was determined to be (3.2±0.5) mg/cm2.
In this paper, the electron temperature, electron density and areal density of imploded fuel pellet driven by SGⅡ laser were diagnosed through X-ray method. The electron temperature deduced from intensity ratio of Ly-beta line and He-beta line of Ar tracer doped in DD fuel was determined to be(950±100) eV. The electron density which was deduced from Stark broadening of He-beta line was determined to be (0.9±0.2)×1024cm-3. And the fuel areal density, which was deduced from X-ray monochromatic imaging of compressed fuel, was determined to be (3.2±0.5) mg/cm2.
2006,
18.
Abstract:
Phloroglucinol-formaldehyde(PF) aerogels and carbonized PF (CPF) aerogels were prepared from Phloroglucinol(P) and Formaldehyde(F) by sol-gel, solvent exchanging, supercritical drying and carbonization processes. The aerogel has a large specific surface area, continuous nano-network and porous structure. The density and mean porosity radius will enlarge after being carbonizied, while the specific surface area will be influenced little. The micro-structure and density of aerogel are controlled by concentration of total reactants and catalyzer, respectively. Aerogels with different micro-structure and different density fit for ICF targets can be prepared by optimizing synthesis conditions.
Phloroglucinol-formaldehyde(PF) aerogels and carbonized PF (CPF) aerogels were prepared from Phloroglucinol(P) and Formaldehyde(F) by sol-gel, solvent exchanging, supercritical drying and carbonization processes. The aerogel has a large specific surface area, continuous nano-network and porous structure. The density and mean porosity radius will enlarge after being carbonizied, while the specific surface area will be influenced little. The micro-structure and density of aerogel are controlled by concentration of total reactants and catalyzer, respectively. Aerogels with different micro-structure and different density fit for ICF targets can be prepared by optimizing synthesis conditions.
2006,
18.
Abstract:
Pure Ti films were fabricated by DC magnetron sputtering. The deposition rate, surface roughness, crystal structure and stress of Ti films at different sputtering power were studied. The deposition rate in-creases with the increase of the sputtering power. The AFM images show that the films are compact and smooth, and the minimum RMS is 0.9 nm when the sputtering power is 20 W. The X-ray diffraction results indicate that the Ti films are hexagonal structure. The stress in the Ti films increases firstly and reaches a maximum stress of 945.1 MPa when the sputtering power is 60 W, then decreases with higher sputtering power.
Pure Ti films were fabricated by DC magnetron sputtering. The deposition rate, surface roughness, crystal structure and stress of Ti films at different sputtering power were studied. The deposition rate in-creases with the increase of the sputtering power. The AFM images show that the films are compact and smooth, and the minimum RMS is 0.9 nm when the sputtering power is 20 W. The X-ray diffraction results indicate that the Ti films are hexagonal structure. The stress in the Ti films increases firstly and reaches a maximum stress of 945.1 MPa when the sputtering power is 60 W, then decreases with higher sputtering power.
2006,
18.
Abstract:
The influence of the wall thickness and filling gas procedure on the permeability of the hollow glass microspheres (HGM) were discussed. The primary experiments show that the deuterium permeation coefficient was 5.0×10-22 mol·m-1·s-1·Pa-1 with the wall thickness more than 2 mm at room temperature, while it was 1.56×10-20 mol·m-1·s-1·Pa-1 with the wall thickness less than 1 mm. The permeation coefficient of thin wall HGM increased 30 times more than that of thick one. The main reason for the effect of the wall thickness on the HGM permeability was microcrack on the HGM surface. The permeation coefficient increases about 50% if HGM experienced one cycle of filling and deflating gas, and doubles after two cycles owing to the voids and flaws on the HGM surface caused by high temperatur
The influence of the wall thickness and filling gas procedure on the permeability of the hollow glass microspheres (HGM) were discussed. The primary experiments show that the deuterium permeation coefficient was 5.0×10-22 mol·m-1·s-1·Pa-1 with the wall thickness more than 2 mm at room temperature, while it was 1.56×10-20 mol·m-1·s-1·Pa-1 with the wall thickness less than 1 mm. The permeation coefficient of thin wall HGM increased 30 times more than that of thick one. The main reason for the effect of the wall thickness on the HGM permeability was microcrack on the HGM surface. The permeation coefficient increases about 50% if HGM experienced one cycle of filling and deflating gas, and doubles after two cycles owing to the voids and flaws on the HGM surface caused by high temperatur
2006,
18.
Abstract:
Adopting zircon pump as inspiration pump, a static state simulation equipment was designed for vacuum holding. The feasibility simulation experiment about keeping vacuum was performed, and the simulation results indicated that the pressure of this equipment was 1.4×10-3 Pa after vacuum holding for ten days. Based on the success of the simulation experiment, a hardtube apparatus was designed for microwave experiment by adopting MVE technology and a vacuum experiment was carried out. The experimental result showed that the pressure was 2×10-2 Pa after fifteen days. When the peak voltage was 330 kV, the power of output microwave was 650 MW, the width of microwave pulse was 40 ns, and the major frequency was 3.68 GHz. Compared with the experimental result of common apparatus, the output powe
Adopting zircon pump as inspiration pump, a static state simulation equipment was designed for vacuum holding. The feasibility simulation experiment about keeping vacuum was performed, and the simulation results indicated that the pressure of this equipment was 1.4×10-3 Pa after vacuum holding for ten days. Based on the success of the simulation experiment, a hardtube apparatus was designed for microwave experiment by adopting MVE technology and a vacuum experiment was carried out. The experimental result showed that the pressure was 2×10-2 Pa after fifteen days. When the peak voltage was 330 kV, the power of output microwave was 650 MW, the width of microwave pulse was 40 ns, and the major frequency was 3.68 GHz. Compared with the experimental result of common apparatus, the output powe
2006,
18.
Abstract:
Quantitative analysis of the large-signal beam-wave interaction of coupled-cavity traveling-wave tube (TWT) is performed using three-dimensional PIC code. With an integrated model, an S-band CW coupled-cavity TWT is designed. The design parameters of this tube are：operating frequency from 2.0 GHz to 2.3 GHz，output power 4.3 kW，gain fluctuation ±0.7 dB. In order to reduce the computing error of interaction impedance, a method using perturbation dielectric rod with big dielectric constant is proposed. Cold cavity characteristic of coupled-cavity TWT is also studied and the simulation results of dispersion and interaction impedance are given.
Quantitative analysis of the large-signal beam-wave interaction of coupled-cavity traveling-wave tube (TWT) is performed using three-dimensional PIC code. With an integrated model, an S-band CW coupled-cavity TWT is designed. The design parameters of this tube are：operating frequency from 2.0 GHz to 2.3 GHz，output power 4.3 kW，gain fluctuation ±0.7 dB. In order to reduce the computing error of interaction impedance, a method using perturbation dielectric rod with big dielectric constant is proposed. Cold cavity characteristic of coupled-cavity TWT is also studied and the simulation results of dispersion and interaction impedance are given.
2006,
18.
Abstract:
A simple measurement system for the shielding effectiveness is developed, and a method for measuring pulse electric field shielding effectiveness of shielding body is presented. The system is made up of pulse electric field radiation device and its receiver. The rising time of the pulse electric field radiated by the device is less than 3.3 ns, the falling time more than 5 μs, and the peak value more than 7.5 kV/m at 60 cm in front of the antenna. Optic fiber device is used in the system for electronic field measurement, and the powerful EMI is restrained. The measurement program is written in Matlab language for automation and signal processing. The system has 97 dB dynamic range and is portable. Experimental results show that the attenuation of the maximum electric field value can refle
A simple measurement system for the shielding effectiveness is developed, and a method for measuring pulse electric field shielding effectiveness of shielding body is presented. The system is made up of pulse electric field radiation device and its receiver. The rising time of the pulse electric field radiated by the device is less than 3.3 ns, the falling time more than 5 μs, and the peak value more than 7.5 kV/m at 60 cm in front of the antenna. Optic fiber device is used in the system for electronic field measurement, and the powerful EMI is restrained. The measurement program is written in Matlab language for automation and signal processing. The system has 97 dB dynamic range and is portable. Experimental results show that the attenuation of the maximum electric field value can refle
2006,
18.
Abstract:
Electric field waveform in the simulator working region was calculated using the moment method and fast multipole method. The relationship between transitional section structure and EMP waveform was studied. And the optimum cone angles of transitional section of EMP simulator were designed. The results indicate that the front and back transitional sections will both evoke the electric field along the transmitting direction. The front transitional section puts influence mainly on the rising time of field waveform in working region. When the front cone angle becomes smaller, the rising time of waveform first decreases and then increases slowly. While the back transitional section puts influence mainly on the decline portion of waveform, it makes decline portion of waveform produce much more
Electric field waveform in the simulator working region was calculated using the moment method and fast multipole method. The relationship between transitional section structure and EMP waveform was studied. And the optimum cone angles of transitional section of EMP simulator were designed. The results indicate that the front and back transitional sections will both evoke the electric field along the transmitting direction. The front transitional section puts influence mainly on the rising time of field waveform in working region. When the front cone angle becomes smaller, the rising time of waveform first decreases and then increases slowly. While the back transitional section puts influence mainly on the decline portion of waveform, it makes decline portion of waveform produce much more
2006,
18.
Abstract:
For purpose of getting the radial electric current density in the medium of the cable due to X-rays illumination, Monte Carlo method and Finite-Difference Time-Domain (FDTD) method are used. Using the radial electric current density as the source of Maxwell functions, center conductor response current is calculated under the condition of matching load of cable ends. Distributed charges in center conductor, medium and shielding are considered in this method. The results show that the center conductor response current is proportional to the length of the illumination, and it is in the opposite direction of the source. In source zone, there is static field. The distributed charge of the center conductor is calculated using electric field, and it is about 20% less than the solution of Monte Ca
For purpose of getting the radial electric current density in the medium of the cable due to X-rays illumination, Monte Carlo method and Finite-Difference Time-Domain (FDTD) method are used. Using the radial electric current density as the source of Maxwell functions, center conductor response current is calculated under the condition of matching load of cable ends. Distributed charges in center conductor, medium and shielding are considered in this method. The results show that the center conductor response current is proportional to the length of the illumination, and it is in the opposite direction of the source. In source zone, there is static field. The distributed charge of the center conductor is calculated using electric field, and it is about 20% less than the solution of Monte Ca
2006,
18.
Abstract:
According to the general coupled-wave equations of wave-guide with helical corrugation, selecting the import-mode TE11, the coupled mode TE21 is gained. Based on the rules of mode coupling in helical wave-guide the determinate formula for coupling equation is obtained and analyzed. Using the iterative method can simplify the coupling equation. At the same time, analyzing the result can give the impact of transmission characteristics by the periods of helical wave-guide. The analytic formula of simplied coupling equation is employed to operate the rate of amplications in the work mode of helical wave-guide. The result indicates that the hybrid mode can be given within work frequencies, in which the main mode is TE21. The value of group velocity of hybrid mode is a constant number. And the b
According to the general coupled-wave equations of wave-guide with helical corrugation, selecting the import-mode TE11, the coupled mode TE21 is gained. Based on the rules of mode coupling in helical wave-guide the determinate formula for coupling equation is obtained and analyzed. Using the iterative method can simplify the coupling equation. At the same time, analyzing the result can give the impact of transmission characteristics by the periods of helical wave-guide. The analytic formula of simplied coupling equation is employed to operate the rate of amplications in the work mode of helical wave-guide. The result indicates that the hybrid mode can be given within work frequencies, in which the main mode is TE21. The value of group velocity of hybrid mode is a constant number. And the b
2006,
18.
Abstract:
This paper presents the progress on design and adjustment of cavities, experiments of beam-current modulation and microwave extraction for an S-band long-pulse-intense-current relativistic klystron amplifier. Modulation of long-pulse intense relativistic electron beams and self-exciting oscillation of output microwave are described in detail. The cause of self-exciting oscillation and its results is also introduced. The self-exciting oscillation was suppressed to a certain extent by taking relevant adjustments. In experiments, a hollow electron beam of 550 kV, 4 kA and 210 ns generates an electron beam with modulated current of 3.2 kA and pulse width of 150 ns after optimization and adjustment of the parameters of cavities. More than 580 MW RF power with a duration of 140 ns is obtained. T
This paper presents the progress on design and adjustment of cavities, experiments of beam-current modulation and microwave extraction for an S-band long-pulse-intense-current relativistic klystron amplifier. Modulation of long-pulse intense relativistic electron beams and self-exciting oscillation of output microwave are described in detail. The cause of self-exciting oscillation and its results is also introduced. The self-exciting oscillation was suppressed to a certain extent by taking relevant adjustments. In experiments, a hollow electron beam of 550 kV, 4 kA and 210 ns generates an electron beam with modulated current of 3.2 kA and pulse width of 150 ns after optimization and adjustment of the parameters of cavities. More than 580 MW RF power with a duration of 140 ns is obtained. T
2006,
18.
Abstract:
The interaction of two electron beams in a cylindrical waveguide filled with plasma is studied in this paper. The linear theory is established based on a fluid model. The numerical results show the two-stream instability of two electron beams can produce Cherenkov radiation through the interaction between the fast space charge wave and the slow space charge wave, and the frequency of radiation can be above the plasma frequency. When the plasma frequency exceeds the frequency scope of the interaction, the interactions of beam-plasma and beam-beam can be improved and enhanced greatly.
The interaction of two electron beams in a cylindrical waveguide filled with plasma is studied in this paper. The linear theory is established based on a fluid model. The numerical results show the two-stream instability of two electron beams can produce Cherenkov radiation through the interaction between the fast space charge wave and the slow space charge wave, and the frequency of radiation can be above the plasma frequency. When the plasma frequency exceeds the frequency scope of the interaction, the interactions of beam-plasma and beam-beam can be improved and enhanced greatly.
2006,
18.
Abstract:
A high-voltage high-repetition-rate multi-channel gas switch was designed and the principle of the swith was described in the paper. Primary experiment was carried out on the accelerator SINUS-700. The primary experiment shows that the switch can operate steadily at voltage up to 1.15MV, peak current up to about 14.4kA, and repetition rate up to 100Hz, and multi channel charging can be realized.
A high-voltage high-repetition-rate multi-channel gas switch was designed and the principle of the swith was described in the paper. Primary experiment was carried out on the accelerator SINUS-700. The primary experiment shows that the switch can operate steadily at voltage up to 1.15MV, peak current up to about 14.4kA, and repetition rate up to 100Hz, and multi channel charging can be realized.
2006,
18.
Abstract:
Digital signal processing (DSP) is widely used in the field of beam diagnostics. Especially, DSP achieves very good performance in beam position signal analysis and betatron tune measurement. In Hefei light source, when beam was excited by narrowband Gaussian white noise, Libera, a digital beam position processor, was used to process the signals from beam position monitor (BPM), which contained betatron oscillation. Fast Fourier transform (FFT) was applied to finding out betatron resonance frequency, from which the decimal part of betatron oscillation tune was calculated．By this means, the measure of horizontal tune was 3.535 2 and the measure of vertical tune is 2.629 9.
Digital signal processing (DSP) is widely used in the field of beam diagnostics. Especially, DSP achieves very good performance in beam position signal analysis and betatron tune measurement. In Hefei light source, when beam was excited by narrowband Gaussian white noise, Libera, a digital beam position processor, was used to process the signals from beam position monitor (BPM), which contained betatron oscillation. Fast Fourier transform (FFT) was applied to finding out betatron resonance frequency, from which the decimal part of betatron oscillation tune was calculated．By this means, the measure of horizontal tune was 3.535 2 and the measure of vertical tune is 2.629 9.
2006,
18.
Abstract:
Effects of the geometry parameters of drawing electrode， oscillator plate voltage and extraction voltage on the focusing degree of ion source are measured and the experimental results are analyzed to ensure the quality extraction of the RF ion source. On the condition that the other parameters keep unchanged, the ratio of the outer diameter D to its inner diameter d of the drawing electrode has an optimum value. The increase of D/d is beneficial to the re-focusing of over-focusing ion beam. The length of the drawing electrode is L and the quartz pipe is l longer than the drawing electrode. The increase of l/D leads to the increase of focusing degree and the decrease of extraction beam intensity. Focusing degree rises with the decrease of L/d and the rising tendency slows down when L/d is
Effects of the geometry parameters of drawing electrode， oscillator plate voltage and extraction voltage on the focusing degree of ion source are measured and the experimental results are analyzed to ensure the quality extraction of the RF ion source. On the condition that the other parameters keep unchanged, the ratio of the outer diameter D to its inner diameter d of the drawing electrode has an optimum value. The increase of D/d is beneficial to the re-focusing of over-focusing ion beam. The length of the drawing electrode is L and the quartz pipe is l longer than the drawing electrode. The increase of l/D leads to the increase of focusing degree and the decrease of extraction beam intensity. Focusing degree rises with the decrease of L/d and the rising tendency slows down when L/d is
2006,
18.
Abstract:
A new RFKO（RF Knock Out） system for partial filling operation is in commission at the Hefei liglit source storage ring. This system is composed of a frequency divider, waveform generator, vector signal source and wideband amplifier. The in-phase signal of beam bunch is obtained by dividing the reference signal from the storage ring's RF system. Triggered by the in-phase signal, the waveform generator outputs a pulse burst. Modulated by the pulse, the waveform generator produces the RFKO signal, and the RFKO signal is applied to the strip line after amplification. The single bunch operation is achieved in this way and the current has reached 18 mA at present. Some bunch-train patterns such as 3-train with 6-bunch and non-uniform bunch train are also tested.
A new RFKO（RF Knock Out） system for partial filling operation is in commission at the Hefei liglit source storage ring. This system is composed of a frequency divider, waveform generator, vector signal source and wideband amplifier. The in-phase signal of beam bunch is obtained by dividing the reference signal from the storage ring's RF system. Triggered by the in-phase signal, the waveform generator outputs a pulse burst. Modulated by the pulse, the waveform generator produces the RFKO signal, and the RFKO signal is applied to the strip line after amplification. The single bunch operation is achieved in this way and the current has reached 18 mA at present. Some bunch-train patterns such as 3-train with 6-bunch and non-uniform bunch train are also tested.
2006,
18.
Abstract:
Scattering is a most important factor in determining the object information in high energy X-ray radiography. The characteristics and tally methods of FXRMC and MCNP are given. Several high energy X-ray radiography systems are simulated with FXRMC and MCNP using the same X-ray source parameters. It is shown that the relative difference of the scatterings simulated by FXRMC and MCNP is within 5%. The FXRMC and MCNP scattering exposure distributions agree well with the experimental result for the aluminum cone radiography. Therefore, both FXRMC and MCNP can be used to simulate the scattering of high energy X-ray radiography. Suggests are also given to verify the results of Monte Carlo simulation.
Scattering is a most important factor in determining the object information in high energy X-ray radiography. The characteristics and tally methods of FXRMC and MCNP are given. Several high energy X-ray radiography systems are simulated with FXRMC and MCNP using the same X-ray source parameters. It is shown that the relative difference of the scatterings simulated by FXRMC and MCNP is within 5%. The FXRMC and MCNP scattering exposure distributions agree well with the experimental result for the aluminum cone radiography. Therefore, both FXRMC and MCNP can be used to simulate the scattering of high energy X-ray radiography. Suggests are also given to verify the results of Monte Carlo simulation.
2006,
18.
Abstract:
A metallic capillary atom beam source of simple and compact design is described. As the first test, thulium is evaporated and the cations which are mainly due to the thermal ionization are measured. The strongpoint of small power and high temperature of atom source is proved by temperature approaching 2 300 K corresponding to only 180 W power. The stability of thulium atom beam for two hours is better than 5 %. An atom beam density of about 8×1012cm－3 in the region at a distance 35 mm beyond the source exit is easily attained and can be sustained for about 8 hours. The test has testified that the metallic capillary atom beam source is suitable for crossed beam study of collision processes involving electrons, ions or photons where the collision products may be studied by methods based on
A metallic capillary atom beam source of simple and compact design is described. As the first test, thulium is evaporated and the cations which are mainly due to the thermal ionization are measured. The strongpoint of small power and high temperature of atom source is proved by temperature approaching 2 300 K corresponding to only 180 W power. The stability of thulium atom beam for two hours is better than 5 %. An atom beam density of about 8×1012cm－3 in the region at a distance 35 mm beyond the source exit is easily attained and can be sustained for about 8 hours. The test has testified that the metallic capillary atom beam source is suitable for crossed beam study of collision processes involving electrons, ions or photons where the collision products may be studied by methods based on
2006,
18.
Abstract:
Gold nanoparticles have been prepared by magnetron sputtering technique, and their morphologies, granularities, structures, optical absorption properties and chemical components have been characterized by using TEM, XRD, UV-Vis and XPS. The results indicate that the gold nanoparticles prepared are approximately spherical, their average size is estimated to be about 10nm, and they are pure and unpolluted. The structure of the gold nanoparticles is face center cubic (FCC). The surface plasma resonant absorption appears at 519 nm.The binding energy of 4f7/2 and 4f5/2 electrons of elemental gold atoms are 83.3 eV and 86.9 eV, respectively. And there is no asymmetry in the peak, which indicates that no Au atoms are oxidated.
Gold nanoparticles have been prepared by magnetron sputtering technique, and their morphologies, granularities, structures, optical absorption properties and chemical components have been characterized by using TEM, XRD, UV-Vis and XPS. The results indicate that the gold nanoparticles prepared are approximately spherical, their average size is estimated to be about 10nm, and they are pure and unpolluted. The structure of the gold nanoparticles is face center cubic (FCC). The surface plasma resonant absorption appears at 519 nm.The binding energy of 4f7/2 and 4f5/2 electrons of elemental gold atoms are 83.3 eV and 86.9 eV, respectively. And there is no asymmetry in the peak, which indicates that no Au atoms are oxidated.
2006,
18.
Abstract:
Organic powder and carbon aerogel powder were prepared by sol-gel method with the help of ultrasonic emulsification technology using resorcinol and formaldehyde. Different experimental conditions were investigated to reveal the formation mechanism of aerogel powder. The particle-diameter distributions were measured with Zetasizer, and the aerogel powder was checked with TEM. The influences of supersonic field, the mass percentage, temperature, time and the volume ratio of dispersant to reactive liquid were investigated to optimize the experimental conditions.
Organic powder and carbon aerogel powder were prepared by sol-gel method with the help of ultrasonic emulsification technology using resorcinol and formaldehyde. Different experimental conditions were investigated to reveal the formation mechanism of aerogel powder. The particle-diameter distributions were measured with Zetasizer, and the aerogel powder was checked with TEM. The influences of supersonic field, the mass percentage, temperature, time and the volume ratio of dispersant to reactive liquid were investigated to optimize the experimental conditions.
2006,
18.
Abstract:
Breakdown experiments of point-plane gas gaps were investigated with repetitive burst conditions under variant repetition rates (10, 100, 500 and 1 000 Hz), diverse gap distances (0.5 cm and 1.0 cm) and different gas pressures (0.1~0.4 MPa) respectively. Relations among breakdown delay time, repetitively stressing time, number of applied pulses, and repetition rates were presented. The results indicate that breakdown time lag increases with the decrease of the division between applied electric-field and gas pressure, but repetitively stressing time and applied pulse number change hardly with the division between applied electric-field and gas pressure in the experimental condition. Breakdown time lag and repetitively stressing time decrease with the increase of repetition rate, but applied
Breakdown experiments of point-plane gas gaps were investigated with repetitive burst conditions under variant repetition rates (10, 100, 500 and 1 000 Hz), diverse gap distances (0.5 cm and 1.0 cm) and different gas pressures (0.1~0.4 MPa) respectively. Relations among breakdown delay time, repetitively stressing time, number of applied pulses, and repetition rates were presented. The results indicate that breakdown time lag increases with the decrease of the division between applied electric-field and gas pressure, but repetitively stressing time and applied pulse number change hardly with the division between applied electric-field and gas pressure in the experimental condition. Breakdown time lag and repetitively stressing time decrease with the increase of repetition rate, but applied
2006,
18.
Abstract:
High current and high-charge transfer spark gap switches are required for a range of capacitor bank applications such as electromagnetic rail, power conditioning system that power the flashlamps for laser fusion drivers. A compact long-lived spark gap and a matched series-injection trigger generator have been developed. The switch has two electrodes made of alloy Cu-W and a spark gap located in the centre of metal chamber. This kind of structure can prevent arc form approaching the insulated bracket. Elimination of the trigger electrode, used in many other switches, combined with an integral, coaxial current-return housing, allows the switch to handle very high current and charge transfer. Recently, the peak current of the switch is near 150 kA with a transfer-charge of 50 C. The two-elect
High current and high-charge transfer spark gap switches are required for a range of capacitor bank applications such as electromagnetic rail, power conditioning system that power the flashlamps for laser fusion drivers. A compact long-lived spark gap and a matched series-injection trigger generator have been developed. The switch has two electrodes made of alloy Cu-W and a spark gap located in the centre of metal chamber. This kind of structure can prevent arc form approaching the insulated bracket. Elimination of the trigger electrode, used in many other switches, combined with an integral, coaxial current-return housing, allows the switch to handle very high current and charge transfer. Recently, the peak current of the switch is near 150 kA with a transfer-charge of 50 C. The two-elect
2006,
18.
Abstract:
The stability of a cell pulse source is a key index in multi-source’s synchronization. The stability index of pulse source is defined in this article. Potential advantage of full-solid nanosecond pulse sources for synchronizing is remarked, because of its high stability. Mechanisms of pulser’s time drift and wave flutter are analyzed, and the key technology routes are given, including over triggering and deficit charging, to improve the cell pulser’s stability. And the stability indexes reach as follows: the short time jitter less than 20 ps per times, the long time drift less than 100 ps/min, the pulse width jitter less than 1%, and the peak voltage jitter less than 1%. Finally, integrating both circuit and space synchronizations, synchronizations of 16×16 elements are realized, and a
The stability of a cell pulse source is a key index in multi-source’s synchronization. The stability index of pulse source is defined in this article. Potential advantage of full-solid nanosecond pulse sources for synchronizing is remarked, because of its high stability. Mechanisms of pulser’s time drift and wave flutter are analyzed, and the key technology routes are given, including over triggering and deficit charging, to improve the cell pulser’s stability. And the stability indexes reach as follows: the short time jitter less than 20 ps per times, the long time drift less than 100 ps/min, the pulse width jitter less than 1%, and the peak voltage jitter less than 1%. Finally, integrating both circuit and space synchronizations, synchronizations of 16×16 elements are realized, and a
2006,
18.
Abstract:
This paper presents a kind of helical pulse forming line which is designed for a long pulse accelerator. The calculating formulae and the experimental result are both presented. The forming line is charged by a pulse source with a maximum output voltage of 300 kV. The length of helical line is 2.7 m,immersed in the castor oil. The pulse width about 200 ns is obtained. And the characteristic resistance is about 100 ohm. The effects of the switch inductance, charge time and spirality structure on the forming line output pulse are analysed that the helical structure can extend the pulse width efficaciously is proved by experiment.
This paper presents a kind of helical pulse forming line which is designed for a long pulse accelerator. The calculating formulae and the experimental result are both presented. The forming line is charged by a pulse source with a maximum output voltage of 300 kV. The length of helical line is 2.7 m,immersed in the castor oil. The pulse width about 200 ns is obtained. And the characteristic resistance is about 100 ohm. The effects of the switch inductance, charge time and spirality structure on the forming line output pulse are analysed that the helical structure can extend the pulse width efficaciously is proved by experiment.
2006,
18.
Abstract:
The high sensitive laser interferometer of checking minuteness phase shift 0.2° was built using the way of heterodyne and phase track. The line mass-density of gas puff Z-pinch load was measured. The interruption of machine vibration to interference-signal was eliminated by putting the interferometer into the vacuum chamber and setting the laser and vacuum chamber and optic elements on the full gas optical platform. The curve of average line mass-density of Ar gas load varying with time was obtained. It can be used to optimize the Lavale nozzle design. The forming time of gas fluid stationary state is helpful for adjusting the synchronization between the opening time of electromagnetic valve and the drive current from pulse power facilities in Z-pinch experiment.
The high sensitive laser interferometer of checking minuteness phase shift 0.2° was built using the way of heterodyne and phase track. The line mass-density of gas puff Z-pinch load was measured. The interruption of machine vibration to interference-signal was eliminated by putting the interferometer into the vacuum chamber and setting the laser and vacuum chamber and optic elements on the full gas optical platform. The curve of average line mass-density of Ar gas load varying with time was obtained. It can be used to optimize the Lavale nozzle design. The forming time of gas fluid stationary state is helpful for adjusting the synchronization between the opening time of electromagnetic valve and the drive current from pulse power facilities in Z-pinch experiment.
2006,
18.
Abstract:
The breakdown test apparatus with the measurement system of voltage and current signals in liquid dielectrics is designed; The relations of repetitive frequency, electrode shape and gap to some breakdown characteristics of liquid dielectrics such as breakdown field, breakdown voltage, breakdown time, and so on, are theoretically analyzed. And the insulating capabilities of three typical liquid dielectrics (transformer oil, dodecylbenzene, and castor oil) are compared, which indicates that a ranking of the withstand voltage rate for three materials , from smallest to largest, is dodecylbenzene, transformer oil and castor oil.
The breakdown test apparatus with the measurement system of voltage and current signals in liquid dielectrics is designed; The relations of repetitive frequency, electrode shape and gap to some breakdown characteristics of liquid dielectrics such as breakdown field, breakdown voltage, breakdown time, and so on, are theoretically analyzed. And the insulating capabilities of three typical liquid dielectrics (transformer oil, dodecylbenzene, and castor oil) are compared, which indicates that a ranking of the withstand voltage rate for three materials , from smallest to largest, is dodecylbenzene, transformer oil and castor oil.
