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RSS2006 Vol. 18, No. 11
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2006,
18.
Abstract:
Considering the factors such as the left or right turning directions of wave, the wave being forward or backward, all the possible modes in helical wave guide are given by using the coupling wave equations of helical wave guide. The relationships among all the possible modes are analyzed according to the characteristics of coupling wave equations and Blagg conditions, the mode coupling characteristics of traveling wave tube and backward wave tube with the helical corrugation are given correspondingly. The corresponding coupling relationships and the rules of mode coupling are obtained. Combined with the dispersion equations of helical wave guide, the effects of the helical corrugation period and corrugation fluctuation degree on mode coupling are discussed that with the period increase of
Considering the factors such as the left or right turning directions of wave, the wave being forward or backward, all the possible modes in helical wave guide are given by using the coupling wave equations of helical wave guide. The relationships among all the possible modes are analyzed according to the characteristics of coupling wave equations and Blagg conditions, the mode coupling characteristics of traveling wave tube and backward wave tube with the helical corrugation are given correspondingly. The corresponding coupling relationships and the rules of mode coupling are obtained. Combined with the dispersion equations of helical wave guide, the effects of the helical corrugation period and corrugation fluctuation degree on mode coupling are discussed that with the period increase of
2006,
18.
Abstract:
This paper focuses on an intense relativistic annular electron beam in an equi-potential resonant cavity nonlinear self-modulation oscillation. By using the small signal theory, the start oscillation condition is analyzed and the perturbation frequency of the electron start oscillation is given. Based on this mechanism, a new type of high power microwave source is suggested with no additional magnetic field which is mainly made up of a cylinder cavity and a coaxial output cavity. PIC simulation of the nonlinear progress and the effect of input voltage and current on the output microwave power is carried out by using the 2.5-dimensional MAGIC code. The simulation results show that nonlinear instability truly exists in this configuration, the frequency of the self-modulation perturbation dep
This paper focuses on an intense relativistic annular electron beam in an equi-potential resonant cavity nonlinear self-modulation oscillation. By using the small signal theory, the start oscillation condition is analyzed and the perturbation frequency of the electron start oscillation is given. Based on this mechanism, a new type of high power microwave source is suggested with no additional magnetic field which is mainly made up of a cylinder cavity and a coaxial output cavity. PIC simulation of the nonlinear progress and the effect of input voltage and current on the output microwave power is carried out by using the 2.5-dimensional MAGIC code. The simulation results show that nonlinear instability truly exists in this configuration, the frequency of the self-modulation perturbation dep
2006,
18.
Abstract:
To investigate the effects of low and high dose UWB microwave irradiations on peripheral blood cells in rats, wistar rats were exposed to 90 kV/m and 180 kV/m UWB microwave irradiation for 10 min.Venous blood samples were collected at 0, 3, 12, 24 and 188 h post exposure and differential counting of blood cells were performed. Immediate increase in WBC was observed after exposure to low dose UWB microwave and thereafter it maintained at the significant higher level. High dose exposure resulted in the elevation of WBC only at 0 h and WBC decreased at 12 h, 24 h post exposure. On day 7, it elevated significantly higher than control. RBC, HGB, HCT and RDW-CV slightly increased within 12 h, markedly elevated at 24 h post exposure and returned to the control levels on day 7. MCV and MCH showed
To investigate the effects of low and high dose UWB microwave irradiations on peripheral blood cells in rats, wistar rats were exposed to 90 kV/m and 180 kV/m UWB microwave irradiation for 10 min.Venous blood samples were collected at 0, 3, 12, 24 and 188 h post exposure and differential counting of blood cells were performed. Immediate increase in WBC was observed after exposure to low dose UWB microwave and thereafter it maintained at the significant higher level. High dose exposure resulted in the elevation of WBC only at 0 h and WBC decreased at 12 h, 24 h post exposure. On day 7, it elevated significantly higher than control. RBC, HGB, HCT and RDW-CV slightly increased within 12 h, markedly elevated at 24 h post exposure and returned to the control levels on day 7. MCV and MCH showed
2006,
18.
Abstract:
A serpentine TM01-TE11 mode converter with input and output ports aligned on the same axis was designed by adopting phase rematch technique. The converter is formed with three constant-curvature bent waveguides and two straight waveguides. Numerical investigations on this mode converter were presented with a general optimizing code employing coupled mode theory. A mode converter of this kind centered at 7.0 GHz was designed. The efficiency of the conversion from TM01-TE11 exceeds 99% at 7.0 GHz and 90% over the frequency range of 6.5 to 7.5 GHz. Simulations with FDTD and FEM methods verified the theoretical designing results respectively.
A serpentine TM01-TE11 mode converter with input and output ports aligned on the same axis was designed by adopting phase rematch technique. The converter is formed with three constant-curvature bent waveguides and two straight waveguides. Numerical investigations on this mode converter were presented with a general optimizing code employing coupled mode theory. A mode converter of this kind centered at 7.0 GHz was designed. The efficiency of the conversion from TM01-TE11 exceeds 99% at 7.0 GHz and 90% over the frequency range of 6.5 to 7.5 GHz. Simulations with FDTD and FEM methods verified the theoretical designing results respectively.
2006,
18.
Abstract:
The coupled Maxwell's equations, heat transport equation and carrier equations are solved to simulate the change of temperature and scatering parameters of the GaAs MESFET which is under the irradiation of high power electromagnetic pulses. The transient temperature response curves are also calculated. The effects of electromagnetic pulse sequences with different magnitude and pulses with different rise time are studied and compared. The global modeling method and the heat transport equation are coupled for the first time. This method is based on physical modeling, taking into account the electromagnetic coupling, radiation effects and electron-wave interaction. The results show that the temperature between the gate and the source rises rapidly and the scattering parameters deteriorate dra
The coupled Maxwell's equations, heat transport equation and carrier equations are solved to simulate the change of temperature and scatering parameters of the GaAs MESFET which is under the irradiation of high power electromagnetic pulses. The transient temperature response curves are also calculated. The effects of electromagnetic pulse sequences with different magnitude and pulses with different rise time are studied and compared. The global modeling method and the heat transport equation are coupled for the first time. This method is based on physical modeling, taking into account the electromagnetic coupling, radiation effects and electron-wave interaction. The results show that the temperature between the gate and the source rises rapidly and the scattering parameters deteriorate dra
2006,
18.
Abstract:
In this paper, a compact L-band coaxial relativistic backward wave oscillator is investigated using the 2.5 D particle simulation code. Detail physical interaction pictures of the oscillator are presented. Simulation results show that the radius of the L-band slow-wave structure can be much smaller in the coaxial BWO case than that in the non-coaxial BWO case, because the TM01 mode of the coaxial BWO has no cut-off frequency, which is similar to the TEM mode in the conventional coaxial wave-guide. It is mentioned that the longitudinal component of electric field of the coaxial TM01 mode can be strong, differing from the TEM mode in the conventional coaxial waveguide. Therefore, the coaxial TM01 mode could have strong interaction with the electron beam. For an electron beam of 240 keV and 1
In this paper, a compact L-band coaxial relativistic backward wave oscillator is investigated using the 2.5 D particle simulation code. Detail physical interaction pictures of the oscillator are presented. Simulation results show that the radius of the L-band slow-wave structure can be much smaller in the coaxial BWO case than that in the non-coaxial BWO case, because the TM01 mode of the coaxial BWO has no cut-off frequency, which is similar to the TEM mode in the conventional coaxial wave-guide. It is mentioned that the longitudinal component of electric field of the coaxial TM01 mode can be strong, differing from the TEM mode in the conventional coaxial waveguide. Therefore, the coaxial TM01 mode could have strong interaction with the electron beam. For an electron beam of 240 keV and 1
2006,
18.
Abstract:
Research method to achieve large bandwidth pulses for detecting neural weak signal is given. Much larger survey depth, better resolution ratio, more powerful image capability and recognition capability can be achieved by using UWB electromagnetic pulse as survey signal than using harmonic wave. However, transmit power of search-and-rescue radar, whose transmit signal is UWB electromagnetic pulse, is much restricted. In this paper, it is discussed in detail that pseudo-random code can be used to modulate UWB short pulse. Encoded signal can keep the bandwidth of the sub pulse signal and have high energy. So that the search-and-rescue radar can transmit noise-like long seriary pulses signal at a low power and improve the survey distance. Based on the fundamental research and computer simulati
Research method to achieve large bandwidth pulses for detecting neural weak signal is given. Much larger survey depth, better resolution ratio, more powerful image capability and recognition capability can be achieved by using UWB electromagnetic pulse as survey signal than using harmonic wave. However, transmit power of search-and-rescue radar, whose transmit signal is UWB electromagnetic pulse, is much restricted. In this paper, it is discussed in detail that pseudo-random code can be used to modulate UWB short pulse. Encoded signal can keep the bandwidth of the sub pulse signal and have high energy. So that the search-and-rescue radar can transmit noise-like long seriary pulses signal at a low power and improve the survey distance. Based on the fundamental research and computer simulati
2006,
18.
Abstract:
A new radial klystron oscillator driven by intense relativistic electron beam is studied in this paper. A radial intense relativistic electron beam goes through foldaway coaxial cavity , and sel-excites the cavity. The space charge limited current of the radial gap with moderate RF voltage is investigated theoretically and simulatedly. In the radial modulating gap, electron bunches may be generated instantaneously when the radial current is close to or exceeds the limiting current. The new radial klystron oscillator driven by intense relativistic electron beam with foldaway coaxial cavity is designed and simulated by Magic PIC. An output power of 6 GW is generated with 500 kV voltage, 30 kA beam current and the frequency is 1.3 GHz.
A new radial klystron oscillator driven by intense relativistic electron beam is studied in this paper. A radial intense relativistic electron beam goes through foldaway coaxial cavity , and sel-excites the cavity. The space charge limited current of the radial gap with moderate RF voltage is investigated theoretically and simulatedly. In the radial modulating gap, electron bunches may be generated instantaneously when the radial current is close to or exceeds the limiting current. The new radial klystron oscillator driven by intense relativistic electron beam with foldaway coaxial cavity is designed and simulated by Magic PIC. An output power of 6 GW is generated with 500 kV voltage, 30 kA beam current and the frequency is 1.3 GHz.
2006,
18.
Abstract:
This paper presents how to design cavities for 8 mm second-harmonic gyroklystron amplifier based on the theory of gyroklystron amplifier. A lot of factors, such as the radius, length of cavity, modes competing, beam-wave coupling coefficient and the character of coated medium which can restrain the unwanted modes are discussed. Two high frequency structures composed of five designed cavities are tested, one has obtained an output power of about 251 kW with an efficiency of 23.9%, a gain of 27.2 dB and the 3 dB bandwidth is over 0.4%. The other has obtained an output power of about 246 kW and the other parameters are to be tested.
This paper presents how to design cavities for 8 mm second-harmonic gyroklystron amplifier based on the theory of gyroklystron amplifier. A lot of factors, such as the radius, length of cavity, modes competing, beam-wave coupling coefficient and the character of coated medium which can restrain the unwanted modes are discussed. Two high frequency structures composed of five designed cavities are tested, one has obtained an output power of about 251 kW with an efficiency of 23.9%, a gain of 27.2 dB and the 3 dB bandwidth is over 0.4%. The other has obtained an output power of about 246 kW and the other parameters are to be tested.
2006,
18.
Abstract:
A new gas-solid reaction system for singlet oxygen generation in which sodium peroxide reacted with gaseous chlorine(Na2O2/Cl2) in a fixed-bed reactor was reported. The singlet oxygen emission spectra from Na2O2/Cl2 reaction system were recorded by a near-IR sensitive Optical Multichannel Analyzer(OMA-V) and a visible sensitive CCD Optical Spectroscopy Analyzer(OPA). The 1 270 nm optical signal and the temperature of reaction zone and detection zone of the Na2O2/Cl2 reaction systems were monitored by a Ge-detector and a data-collection system, respectively. The experimental results showed that singlet oxygen was produced in the Na2O2/Cl2 reaction system, but the process was accompanied with a drastically strong heat release.
A new gas-solid reaction system for singlet oxygen generation in which sodium peroxide reacted with gaseous chlorine(Na2O2/Cl2) in a fixed-bed reactor was reported. The singlet oxygen emission spectra from Na2O2/Cl2 reaction system were recorded by a near-IR sensitive Optical Multichannel Analyzer(OMA-V) and a visible sensitive CCD Optical Spectroscopy Analyzer(OPA). The 1 270 nm optical signal and the temperature of reaction zone and detection zone of the Na2O2/Cl2 reaction systems were monitored by a Ge-detector and a data-collection system, respectively. The experimental results showed that singlet oxygen was produced in the Na2O2/Cl2 reaction system, but the process was accompanied with a drastically strong heat release.
2006,
18.
Abstract:
The pressure recovery system is an important part of Chemical Oxygen-Iodine Laser(COIL). Adopting cryosorption vacuum system as the pressure recovery system of COIL, the pressure recovery capability of cryosorption vacuum system is determined directly by the performance of adsorption bed. In this paper, the heat transfer efficiency of the adsorption bed with different structure was studied with theoretic and experimental approaches. It is found that the flow state and pattern of liquid nitrogen in pipe have great influences on the heat transfer. After structure improvement, the heat transfer coefficient between adsorption bed and liquid nitrogen has been increased by 2.2 times. It is proved that the improvement in the adsorption bed structure has enhanced the heat transfer effect of adsorp
The pressure recovery system is an important part of Chemical Oxygen-Iodine Laser(COIL). Adopting cryosorption vacuum system as the pressure recovery system of COIL, the pressure recovery capability of cryosorption vacuum system is determined directly by the performance of adsorption bed. In this paper, the heat transfer efficiency of the adsorption bed with different structure was studied with theoretic and experimental approaches. It is found that the flow state and pattern of liquid nitrogen in pipe have great influences on the heat transfer. After structure improvement, the heat transfer coefficient between adsorption bed and liquid nitrogen has been increased by 2.2 times. It is proved that the improvement in the adsorption bed structure has enhanced the heat transfer effect of adsorp
2006,
18.
Abstract:
A method for measuring atmospheric turbulence by lidar is reported with its principle, technology and the primary measurement results. Time variations of atmospheric coherence length measured in different altitude range, average atmospheric coherence length and the deviation of atmospheric coherence length are obtained. The integration of the measured atmospheric structure parameter is compared with that of model atmospheric structure parameter, and the roughly coincident result is obtained. The realization of this method provides a new means for the measurement of atmospheric turbulence in different direction and different altitude, and also a technical base of the laser guide star for adaptive optics.
A method for measuring atmospheric turbulence by lidar is reported with its principle, technology and the primary measurement results. Time variations of atmospheric coherence length measured in different altitude range, average atmospheric coherence length and the deviation of atmospheric coherence length are obtained. The integration of the measured atmospheric structure parameter is compared with that of model atmospheric structure parameter, and the roughly coincident result is obtained. The realization of this method provides a new means for the measurement of atmospheric turbulence in different direction and different altitude, and also a technical base of the laser guide star for adaptive optics.
2006,
18.
Abstract:
Based on double-edge technique, the optimization of the operation parameters of Fabry-Perot interferometers in the direct detection Doppler wind lidar is presented. The effects of the laser spectral width, mirror surface defects, parallelism errors, beam divergence of illumination on the transmittance of the etalon are considered. By convolution method, the Fabry-Perot interferometer transmittance function with different spectral broadening defect is given. The free spectrum range is chosen to subtract the Rayleigh signal from the atmospheric back-scattering correctly. The transmittance of aerosol back-scatter signal through the interferometer is expressed as a function of the reflectance finesse, which is the unique system parameter. By considering the ratio of the measurement uncertainty
Based on double-edge technique, the optimization of the operation parameters of Fabry-Perot interferometers in the direct detection Doppler wind lidar is presented. The effects of the laser spectral width, mirror surface defects, parallelism errors, beam divergence of illumination on the transmittance of the etalon are considered. By convolution method, the Fabry-Perot interferometer transmittance function with different spectral broadening defect is given. The free spectrum range is chosen to subtract the Rayleigh signal from the atmospheric back-scattering correctly. The transmittance of aerosol back-scatter signal through the interferometer is expressed as a function of the reflectance finesse, which is the unique system parameter. By considering the ratio of the measurement uncertainty
2006,
18.
Abstract:
Optics aberrations are studied for the case when the aero-noise pulse is propagating through the optical beam. The flow is governed by the Favre-averaged N-S equations. To split the viscosity flux and the convective flux of the N-S equations, the second-order central scheme and the AUSMPW+ scheme, based on the third-order MUSCL one, are adopted respectively. With the four-step Runge-Kutta scheme in fourth-order, the code is advanced in time. The J-B turbulence model, with the Sarkar's compressive modification, is used for turbulence simulations. Aero-optical effects are analyzed with the physics optics by introducing the mean flow OTF(Optical Transfer Function) and turbulence OTF. The results indicate that the moving vorticity pulse can bring the maximal boresight error up to 1.7 μrad, an
Optics aberrations are studied for the case when the aero-noise pulse is propagating through the optical beam. The flow is governed by the Favre-averaged N-S equations. To split the viscosity flux and the convective flux of the N-S equations, the second-order central scheme and the AUSMPW+ scheme, based on the third-order MUSCL one, are adopted respectively. With the four-step Runge-Kutta scheme in fourth-order, the code is advanced in time. The J-B turbulence model, with the Sarkar's compressive modification, is used for turbulence simulations. Aero-optical effects are analyzed with the physics optics by introducing the mean flow OTF(Optical Transfer Function) and turbulence OTF. The results indicate that the moving vorticity pulse can bring the maximal boresight error up to 1.7 μrad, an
2006,
18.
Abstract:
In the field of fiber laser coherent combining, phase controlling of ytterbium fiber amplifiers is the most difficult technology in the Master Oscillator-Power Amplifier scheme. Two methods to realize phase controlling of ytterbium fiber amplifiers are studied. One is “climbing hill”, which can optimize the control voltage automatically and the other is “heterodyne detection”, which can realize real-time detection and correction of the phase change. In the experiments, the wavelength of the master oscillator is 1 083 nm and the output power is between 0~100 mW. Phase noises are controlled by LiNO3 phase modulator. The output power of ytterbium fiber amplifiers is between 0~1 W. The fibers are polarizedly maintained. The “climbing hill” control system works at 100 kHz and the control
In the field of fiber laser coherent combining, phase controlling of ytterbium fiber amplifiers is the most difficult technology in the Master Oscillator-Power Amplifier scheme. Two methods to realize phase controlling of ytterbium fiber amplifiers are studied. One is “climbing hill”, which can optimize the control voltage automatically and the other is “heterodyne detection”, which can realize real-time detection and correction of the phase change. In the experiments, the wavelength of the master oscillator is 1 083 nm and the output power is between 0~100 mW. Phase noises are controlled by LiNO3 phase modulator. The output power of ytterbium fiber amplifiers is between 0~1 W. The fibers are polarizedly maintained. The “climbing hill” control system works at 100 kHz and the control
2006,
18.
Abstract:
To accurately profile transparent element with parallel surface, this article presents a new simple and useful method by using a Fourier analysis technique with single three-beam interfere pattern. The test surface’s frequency spectrum from the frequency spectrum of three-beam interfere pattern is extracted by a spatial filter according to the amplitude in the spatial carrier frequency. The test wavefront is obtained by using inverse Fourier transform method. Simulated results demonstrate the validity of the method and the accuracy which is better than l/1 000. In the experiment, by testing the parallel surface element by FFT with single three-beam interfere pattern, Fourier analysis combined with wavelength tuning and traditional phase shifting interferometry with index matching lacquers
To accurately profile transparent element with parallel surface, this article presents a new simple and useful method by using a Fourier analysis technique with single three-beam interfere pattern. The test surface’s frequency spectrum from the frequency spectrum of three-beam interfere pattern is extracted by a spatial filter according to the amplitude in the spatial carrier frequency. The test wavefront is obtained by using inverse Fourier transform method. Simulated results demonstrate the validity of the method and the accuracy which is better than l/1 000. In the experiment, by testing the parallel surface element by FFT with single three-beam interfere pattern, Fourier analysis combined with wavelength tuning and traditional phase shifting interferometry with index matching lacquers
2006,
18.
Abstract:
With fringe fields the experiments were carried out to improve the image resolution. The illuminating field is composed of cosine fringes, then the higher frequency component beyond the cutoff of the optical system can be passed. A higher resolution image can be obtained by processing the images from fringes with the same frequency but different phases. In the experiment, a laser is used to form ten cosine fringe fields which have 1/10 period displacement, every adjacent fringe, and the captured images are integrated to get higher-resolution image. The experiment result shows the method is feasible.
With fringe fields the experiments were carried out to improve the image resolution. The illuminating field is composed of cosine fringes, then the higher frequency component beyond the cutoff of the optical system can be passed. A higher resolution image can be obtained by processing the images from fringes with the same frequency but different phases. In the experiment, a laser is used to form ten cosine fringe fields which have 1/10 period displacement, every adjacent fringe, and the captured images are integrated to get higher-resolution image. The experiment result shows the method is feasible.
2006,
18.
Abstract:
The experimental results of the stable high-order harmonically mode-locked pulses generation, amplification and compression in Yb3+-doped fiber laser system were reported. Using nonlinear polarization rotation(NPR) effect, the artifical saturable absorber was generated and the stable high-order harmonically mode-locked pulses were generated from Yb3+-doped fiber ring laser. The characteristics of Yb3+-doped mode-locked fiber laser were analyzed theoretically. Three different ways were found, with which high-order harmonically mode-locked pulses were generated from Yb3+-doped mode-locked fiber laser. The stable 4th harmonically mode-locked (107.2 MHz repetition rate) pulses were amplified to an average power of 100 mW and pulse width of 22.8 ps through an amplifier with 1 m high concentrati
The experimental results of the stable high-order harmonically mode-locked pulses generation, amplification and compression in Yb3+-doped fiber laser system were reported. Using nonlinear polarization rotation(NPR) effect, the artifical saturable absorber was generated and the stable high-order harmonically mode-locked pulses were generated from Yb3+-doped fiber ring laser. The characteristics of Yb3+-doped mode-locked fiber laser were analyzed theoretically. Three different ways were found, with which high-order harmonically mode-locked pulses were generated from Yb3+-doped mode-locked fiber laser. The stable 4th harmonically mode-locked (107.2 MHz repetition rate) pulses were amplified to an average power of 100 mW and pulse width of 22.8 ps through an amplifier with 1 m high concentrati
2006,
18.
Abstract:
The thermal-mechanical effects on rotating internally pressured cylindrical shell irradiated by the laser beam have been calculated by using finite element method, and the physical parameters are obtained, such as temperature, stress, strain, and displacement of the shell wall. The double time step method, which includes one main time step and many sub time steps, is presented. This method can overcome the difficulty in the numerical calculation of the moving heat-flux loads. Some examples indicate that the double time step method can improve the calculation precision and efficiency. The numerical results show that the damage-threshold time of rotating internally pressured cylindrical shell depends closely on the rotating frequency and the power density of the laser beam, and the cracked p
The thermal-mechanical effects on rotating internally pressured cylindrical shell irradiated by the laser beam have been calculated by using finite element method, and the physical parameters are obtained, such as temperature, stress, strain, and displacement of the shell wall. The double time step method, which includes one main time step and many sub time steps, is presented. This method can overcome the difficulty in the numerical calculation of the moving heat-flux loads. Some examples indicate that the double time step method can improve the calculation precision and efficiency. The numerical results show that the damage-threshold time of rotating internally pressured cylindrical shell depends closely on the rotating frequency and the power density of the laser beam, and the cracked p
2006,
18.
Abstract:
Field experiments were performed upon the laser beam propagation using a three-wavelength scintillometer in the maritime atmospheric boundary layer. The results show that the high-frequency spectrum behavior has something to do with the wavelength. The slope of the scaling region (or the scaling exponent) is anti-correlated with the wavelength, that is to say, the longer the wavelength is, the less the scaling exponent is, and vice versa.
Field experiments were performed upon the laser beam propagation using a three-wavelength scintillometer in the maritime atmospheric boundary layer. The results show that the high-frequency spectrum behavior has something to do with the wavelength. The slope of the scaling region (or the scaling exponent) is anti-correlated with the wavelength, that is to say, the longer the wavelength is, the less the scaling exponent is, and vice versa.
2006,
18.
Abstract:
The temperature fields and stress fields of solid-state heat-capacity laser(SSHCL) and solid steady state laser were analyzed by finite-element analysis. The distance between LD arrays and laser crystal is 3.5 mm, LD array power 4 200 W×2, LD bars interval is 0.4 mm, While luminescence area 1 μm×5 mm, frequency 100 Hz, pulse width 100 μs, temperature of crystal and cooling water 20 ℃. The calculation reveals that the temperature on SSHCL surface is even higher than that in its interior, but the inverse phenomenon is found in solid steady state laser. The extremum temperature difference in solid steady state laser is 3.1 times than that in SSHCL, with there values being 19.8 ℃ and 6.4 ℃ respectively. The extremum temperature grads in solid steady state laser is 4.8 times than that in
The temperature fields and stress fields of solid-state heat-capacity laser(SSHCL) and solid steady state laser were analyzed by finite-element analysis. The distance between LD arrays and laser crystal is 3.5 mm, LD array power 4 200 W×2, LD bars interval is 0.4 mm, While luminescence area 1 μm×5 mm, frequency 100 Hz, pulse width 100 μs, temperature of crystal and cooling water 20 ℃. The calculation reveals that the temperature on SSHCL surface is even higher than that in its interior, but the inverse phenomenon is found in solid steady state laser. The extremum temperature difference in solid steady state laser is 3.1 times than that in SSHCL, with there values being 19.8 ℃ and 6.4 ℃ respectively. The extremum temperature grads in solid steady state laser is 4.8 times than that in
2006,
18.
Abstract:
Laser focuses onto a target, producing an ablation back-jet, which provides a micro-impulse. The torsion pendulum micro-impulse measure method was studied. The equations of oscillation were put forward under the thrust of ablation back-jet. And the integral equation of impulse was presented under the action of single pulse laser. Based on the discrete integral equation of impulse, the calculation method of single pulse impulse was proposed. Furthermore the error of calculation was analyzed. This method could be used in engineering measure and calculation for single pulse impulse with torsion pendulum.
Laser focuses onto a target, producing an ablation back-jet, which provides a micro-impulse. The torsion pendulum micro-impulse measure method was studied. The equations of oscillation were put forward under the thrust of ablation back-jet. And the integral equation of impulse was presented under the action of single pulse laser. Based on the discrete integral equation of impulse, the calculation method of single pulse impulse was proposed. Furthermore the error of calculation was analyzed. This method could be used in engineering measure and calculation for single pulse impulse with torsion pendulum.
2006,
18.
Abstract:
Phase modulation was always used to prevent stimulated Brillouin scattering(SBS) which could damage the optics such as lenses in high power laser systems. Band pass filters such as fiber Bragg gratings were usually used in the optical fiber amplifiers to restrain the amplified spontaneous emission(ASE). When the phase modulated laser passes the filter, unbalanced sidebands will be caused by the wavelength mismatch between the laser and filter. The result is fast amplitude modulation on the top of the waveform. The problem is discussed and simulated with a simulation software developed by ourselves in this paper. It is obtained that the fast amplitude modulation is worsened with narrower bandwidth and larger wavelength mismatch. With 0.05 nm mismatch for 0.2 nm bandwidth filter, the modulat
Phase modulation was always used to prevent stimulated Brillouin scattering(SBS) which could damage the optics such as lenses in high power laser systems. Band pass filters such as fiber Bragg gratings were usually used in the optical fiber amplifiers to restrain the amplified spontaneous emission(ASE). When the phase modulated laser passes the filter, unbalanced sidebands will be caused by the wavelength mismatch between the laser and filter. The result is fast amplitude modulation on the top of the waveform. The problem is discussed and simulated with a simulation software developed by ourselves in this paper. It is obtained that the fast amplitude modulation is worsened with narrower bandwidth and larger wavelength mismatch. With 0.05 nm mismatch for 0.2 nm bandwidth filter, the modulat
2006,
18.
Abstract:
The 30° Au conical target and Au foil target were irradiated by 20 TW ps P-polarized laser plasma, the characteristics of the forward produced hot electrons were studied. The hot electron number of the cone target was larger than that of the foil target, especially within the range of 2.0~2.5 MeV. The divergence of the forward hot electrons of the cone target was larger than that of the plane one, which was caused by different electron density of the pre-plasma with dissimilar target geometry produced by the driving laser.
The 30° Au conical target and Au foil target were irradiated by 20 TW ps P-polarized laser plasma, the characteristics of the forward produced hot electrons were studied. The hot electron number of the cone target was larger than that of the foil target, especially within the range of 2.0~2.5 MeV. The divergence of the forward hot electrons of the cone target was larger than that of the plane one, which was caused by different electron density of the pre-plasma with dissimilar target geometry produced by the driving laser.
2006,
18.
Abstract:
A mathematic model is established that formulated the relationship between the working temperature and thermal gradient in producing a uniform liquid layer of binary fuel mixture inside a cryogenic spherical shell inertial confinement fusion target. When the external linear thermal gradient was imposed on the target, the model showed the gradient of face tension induced by thermal gradient acted on the far field pull the liquid inside the ICF forward. This motion overcame the effect of gravitation to produce a uniform liquid layer inside ICF. And a finite element analysis of the heat transfer in hollow micro-sphere filled with the ICF fuel was made, the results compared with the experimental finding by K.Kim and the tendency of the thermal gradient was shown to be similar.
A mathematic model is established that formulated the relationship between the working temperature and thermal gradient in producing a uniform liquid layer of binary fuel mixture inside a cryogenic spherical shell inertial confinement fusion target. When the external linear thermal gradient was imposed on the target, the model showed the gradient of face tension induced by thermal gradient acted on the far field pull the liquid inside the ICF forward. This motion overcame the effect of gravitation to produce a uniform liquid layer inside ICF. And a finite element analysis of the heat transfer in hollow micro-sphere filled with the ICF fuel was made, the results compared with the experimental finding by K.Kim and the tendency of the thermal gradient was shown to be similar.
2006,
18.
Abstract:
Surface damage of optical components is the main cause of lowering the laser-induced damage threshold. Surface scratches are observed exactly, and are divided into three kinds, namely, one scratch, two scratches and multi-scratches. By the method of Finite Difference Time Domain(FDTD), the intensity distribution around the surface scratches was numerically simulated on the basis of a common semicircle scratch with a half wavelength diameter. The graph of the maximal value of light intensity versus distance between scratches is got. It is concluded that optical damage is easily induced by scratches on the rear surface than those on the front surface. It also shows that in the case of multi-scratches, the maximum light intensity varies periodically with the increase of the distance between s
Surface damage of optical components is the main cause of lowering the laser-induced damage threshold. Surface scratches are observed exactly, and are divided into three kinds, namely, one scratch, two scratches and multi-scratches. By the method of Finite Difference Time Domain(FDTD), the intensity distribution around the surface scratches was numerically simulated on the basis of a common semicircle scratch with a half wavelength diameter. The graph of the maximal value of light intensity versus distance between scratches is got. It is concluded that optical damage is easily induced by scratches on the rear surface than those on the front surface. It also shows that in the case of multi-scratches, the maximum light intensity varies periodically with the increase of the distance between s
2006,
18.
Abstract:
Polyvinyl alcohol(PVA) capsule layer, as a gas barrier, were developed for the inertial confinement fusion(ICF) program. This paper presented the simulation study on fabrication of PVA coating using drop-tower technique. Based on the heat, mass and momentum transfer of the transformation process, a physical model was established and the related mathematic model was developed. The influence of processing parameters on the transformation was simulated. The key processing parameters that greatly affected the gel-to-shell transformation and the resulting PVA properties had been found to be initial PVA concentration, PS diameter, furnace temperature profile and thermal conductivity of the furnace gas.
Polyvinyl alcohol(PVA) capsule layer, as a gas barrier, were developed for the inertial confinement fusion(ICF) program. This paper presented the simulation study on fabrication of PVA coating using drop-tower technique. Based on the heat, mass and momentum transfer of the transformation process, a physical model was established and the related mathematic model was developed. The influence of processing parameters on the transformation was simulated. The key processing parameters that greatly affected the gel-to-shell transformation and the resulting PVA properties had been found to be initial PVA concentration, PS diameter, furnace temperature profile and thermal conductivity of the furnace gas.
2006,
18.
Abstract:
MF aerogels were prepared from Melamine(P) and Formaldehyde(F) by sol-gel and supercritical drying process. The structure and function of the MF aerogels were characterized by means of SEM, TEM, BET and XRD, and the results indicate that the MF aerogels are an amorphous material with large specific surface area (1 015.98 m2/g) and small pore diameter（5~30 nm）, have continuous nano-network and porous structure and it is hopeful for application in ICF experiments.
MF aerogels were prepared from Melamine(P) and Formaldehyde(F) by sol-gel and supercritical drying process. The structure and function of the MF aerogels were characterized by means of SEM, TEM, BET and XRD, and the results indicate that the MF aerogels are an amorphous material with large specific surface area (1 015.98 m2/g) and small pore diameter（5~30 nm）, have continuous nano-network and porous structure and it is hopeful for application in ICF experiments.
2006,
18.
Abstract:
Large ICF experiments require their physical diagnosis systems to be equipped with a sophisticated central control system, which makes sure the whole experiment would be safe and efficient. An integrated central control system framework for physical diagnosis system serving for domestic ICF large laser device, which is being built, is brought forward. Two subsystems in the central control system are designed with field programmable gate array(FPGA) technology, implementing a high performance embedded system on chip(SoC) platform for instruction synchronous system in FPGA and integrating the synchronous trigger system into a PXI system for central control by FPGA.
Large ICF experiments require their physical diagnosis systems to be equipped with a sophisticated central control system, which makes sure the whole experiment would be safe and efficient. An integrated central control system framework for physical diagnosis system serving for domestic ICF large laser device, which is being built, is brought forward. Two subsystems in the central control system are designed with field programmable gate array(FPGA) technology, implementing a high performance embedded system on chip(SoC) platform for instruction synchronous system in FPGA and integrating the synchronous trigger system into a PXI system for central control by FPGA.
2006,
18.
Abstract:
A theory model which describes the localized wavefront deformation of the optics elements is set up. The propagation regularity of the high-power plane-wave in the optics elements with localized wavefront deformation is investigated by linearization method of the ripple propagation. A continuous laser medium as an example is simulated with the model, and the spectral distribution clue to the localized wavefront deformation with different scales, the nonlinear gain of the amplitude clue to wave-front ripple with differen frequency, the relationship between the nonlinear gain and the beam transmission distance in the case of different B integral, the transmission distance where there exists the largest nonlinear gain of the output beam amplitude, and the amplitude distribution by the localiz
A theory model which describes the localized wavefront deformation of the optics elements is set up. The propagation regularity of the high-power plane-wave in the optics elements with localized wavefront deformation is investigated by linearization method of the ripple propagation. A continuous laser medium as an example is simulated with the model, and the spectral distribution clue to the localized wavefront deformation with different scales, the nonlinear gain of the amplitude clue to wave-front ripple with differen frequency, the relationship between the nonlinear gain and the beam transmission distance in the case of different B integral, the transmission distance where there exists the largest nonlinear gain of the output beam amplitude, and the amplitude distribution by the localiz
2006,
18.
Abstract:
High current linear induction accelerator(LIA) is a complicated experimental physics device. It is difficult to evaluate and predict its performance. This paper presents a method which combines wavelet packet transform and radial basis function(RBF) neural network to build fault diagnosis and performance evaluation in order to improve reliability of high current LIA. The signal characteristics vectors which are extracted based on energy parameters of wavelet packet transform can well present the temporal and steady features of pulsed power signal, and reduce data dimensions effectively. The fault diagnosis system for accelerating cell and the trend classification system for the beam current based on RBF networks can perform fault diagnosis and evaluation, and provide predictive information
High current linear induction accelerator(LIA) is a complicated experimental physics device. It is difficult to evaluate and predict its performance. This paper presents a method which combines wavelet packet transform and radial basis function(RBF) neural network to build fault diagnosis and performance evaluation in order to improve reliability of high current LIA. The signal characteristics vectors which are extracted based on energy parameters of wavelet packet transform can well present the temporal and steady features of pulsed power signal, and reduce data dimensions effectively. The fault diagnosis system for accelerating cell and the trend classification system for the beam current based on RBF networks can perform fault diagnosis and evaluation, and provide predictive information
2006,
18.
Abstract:
A photon beam position monitor signal processing system with logarithmic ratio method was designed for two-wire monitor in the machine diagnostic beamline(MDBL) at Hefei Light Source(HLS). A current-voltage converter was designed which is capable of measuring current value from 0.1 nA to 3.5 mA using LOG112 chip. The resolution of the photon beam position monitor is about 1 μm in MDBL, and the linearity range is more than ±3 mm. The system has a good performance price ratio.
A photon beam position monitor signal processing system with logarithmic ratio method was designed for two-wire monitor in the machine diagnostic beamline(MDBL) at Hefei Light Source(HLS). A current-voltage converter was designed which is capable of measuring current value from 0.1 nA to 3.5 mA using LOG112 chip. The resolution of the photon beam position monitor is about 1 μm in MDBL, and the linearity range is more than ±3 mm. The system has a good performance price ratio.
2006,
18.
Abstract:
Using molecular dynamics methods combined with two-step radiation heating model, a complete microscopic description of the dynamic progresses involved in laser induced back-surface spallation in metallic film in stress confinement regime is provided. Different from the front-surface ejection with strongly affected mechanical stability of the front-surface by laser heating, the back-surface spallation is a disintegration of cold material. The mechanism of spallation is analyzed as a result of the interaction of the unloading wave and reflected stress wave. The propagation of laser-induced stress wave is also further investigated, and the influences of film thickness on spall thickness as well as the time when spallation begins are predicted.
Using molecular dynamics methods combined with two-step radiation heating model, a complete microscopic description of the dynamic progresses involved in laser induced back-surface spallation in metallic film in stress confinement regime is provided. Different from the front-surface ejection with strongly affected mechanical stability of the front-surface by laser heating, the back-surface spallation is a disintegration of cold material. The mechanism of spallation is analyzed as a result of the interaction of the unloading wave and reflected stress wave. The propagation of laser-induced stress wave is also further investigated, and the influences of film thickness on spall thickness as well as the time when spallation begins are predicted.
2006,
18.
Abstract:
In order to detect the new spectral series of hydrogen gas discharge source bombarding target more integrated, the experiment of bombarding targets with known particles or beams, such as electron and X-ray was carried out. Under the condition of 45° diffractive angle and 45° measure angle, six new spectral lines were detected, they were （2.25±0.07） keV and （2.56±0.08） keV; （3.25±0.10） keV and （3.62±0.11） keV; （4.42±0.13） keV and （4.79±0.15） keV. The spectral lines showed the energy level of new atom state of hydrogen. The fact of these new spectral lines being detected indicated that new hydrogen atoms with new atom state were produced in hydrogen gas discharge.
In order to detect the new spectral series of hydrogen gas discharge source bombarding target more integrated, the experiment of bombarding targets with known particles or beams, such as electron and X-ray was carried out. Under the condition of 45° diffractive angle and 45° measure angle, six new spectral lines were detected, they were （2.25±0.07） keV and （2.56±0.08） keV; （3.25±0.10） keV and （3.62±0.11） keV; （4.42±0.13） keV and （4.79±0.15） keV. The spectral lines showed the energy level of new atom state of hydrogen. The fact of these new spectral lines being detected indicated that new hydrogen atoms with new atom state were produced in hydrogen gas discharge.
2006,
18.
Abstract:
In this paper, two kinds of photonic crystals are designed. One is the super narrow band optical filter, the other is the comb-shaped multi-channel optical filter. Based on the transfer matrix method, after inserting one layer of heterogeneous medium into two different homogeneous mediums, a super narrow pass band with a 100% transmitivity can be obtained near 1 550 nm by adopting a dissymmetric structure and adjusting parameters in this crystal. In the complex-period optical crystal integrated by mediums with two alternatively distributed high and low refractive indexes whose complex period is combined by two separate cell periods, by following the law that the channel number is calculated by subtracting one from the complex-period number, a comb-shaped 8-channel and a comb-shaped 16-chan
In this paper, two kinds of photonic crystals are designed. One is the super narrow band optical filter, the other is the comb-shaped multi-channel optical filter. Based on the transfer matrix method, after inserting one layer of heterogeneous medium into two different homogeneous mediums, a super narrow pass band with a 100% transmitivity can be obtained near 1 550 nm by adopting a dissymmetric structure and adjusting parameters in this crystal. In the complex-period optical crystal integrated by mediums with two alternatively distributed high and low refractive indexes whose complex period is combined by two separate cell periods, by following the law that the channel number is calculated by subtracting one from the complex-period number, a comb-shaped 8-channel and a comb-shaped 16-chan
2006,
18.
Abstract:
A numerical model of laser triggered SF6-N2 mixture switch is established on gas discharge physics. The photoionizations of SF6 and N2 are described by the double photon ionization model. The photoionization of hydrocarbon can be modeled as a three energy level system simplified from the model of Bischel W K. The mixture is heated by eletric field, and the heating ionizations of mixtures are considered.The calculated switch time delay is compared with that of experiment in the paper. The calculated values of laser triggered delay are in agreement with the experimental results. The delay of laser triggered SF6-N2 mixture switch increases as the percentage of SF6 in the mixture increases, and decreases as the energy of laser pulse, or the pressure increases.
A numerical model of laser triggered SF6-N2 mixture switch is established on gas discharge physics. The photoionizations of SF6 and N2 are described by the double photon ionization model. The photoionization of hydrocarbon can be modeled as a three energy level system simplified from the model of Bischel W K. The mixture is heated by eletric field, and the heating ionizations of mixtures are considered.The calculated switch time delay is compared with that of experiment in the paper. The calculated values of laser triggered delay are in agreement with the experimental results. The delay of laser triggered SF6-N2 mixture switch increases as the percentage of SF6 in the mixture increases, and decreases as the energy of laser pulse, or the pressure increases.
2006,
18.
Abstract:
A high power multi-pulse modulator was presented which could generate three pulses with adjustable interval on the field-emission diode. In the system, a pulse transformer was employed to upgrade the discharging voltage of three groups of capacitors and charge the Blumlein pulse forming line. When the main gap being closed at interval of a certain time, three pulses were obtained on the field-emission diode, the peak power of each pulse was over 20 GW, pulse duration about 80 ns, and pulse interval about 15 ms. The simulation results agreed well with the experimental results. The experimental results showed that the recovery time of the main gap was an important effect factor on the pulse interval of the modulator.
A high power multi-pulse modulator was presented which could generate three pulses with adjustable interval on the field-emission diode. In the system, a pulse transformer was employed to upgrade the discharging voltage of three groups of capacitors and charge the Blumlein pulse forming line. When the main gap being closed at interval of a certain time, three pulses were obtained on the field-emission diode, the peak power of each pulse was over 20 GW, pulse duration about 80 ns, and pulse interval about 15 ms. The simulation results agreed well with the experimental results. The experimental results showed that the recovery time of the main gap was an important effect factor on the pulse interval of the modulator.
2006,
18.
Abstract:
In order to study the physical nature of Explosive Magnetic Flux Compression Generator (EMFCG) of cylinder-taper configuration, a code MFCG(Ⅴ) was developed. A series of models have been calculated and analyzed by using this code. The computational results of the cylinder-taper configuration were compared with that of cylinder-cylinder. Under the same conditions of output current, the operation time was shortened, and the output power was correspondingly increased. Practicable computer code of the test design was given for numerical simulation of the cylinder with taper.
In order to study the physical nature of Explosive Magnetic Flux Compression Generator (EMFCG) of cylinder-taper configuration, a code MFCG(Ⅴ) was developed. A series of models have been calculated and analyzed by using this code. The computational results of the cylinder-taper configuration were compared with that of cylinder-cylinder. Under the same conditions of output current, the operation time was shortened, and the output power was correspondingly increased. Practicable computer code of the test design was given for numerical simulation of the cylinder with taper.
