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RSS2008 Vol. 20, No. 11
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2008,
20.
Abstract:
Based on the requirement and the influence of environmental factor on weapon system, two typical high energy fiber laser systems, coherent- and incoherent-combining types, were analyzed and compared. Beam propagation factor(BPF) was introduced as the beam quality factor for the combined beam. The influence of array element beam quality, atmospheric propagation, tracking jitter, phase control on the combined beam quality was numerically evaluated. The development trends of high energy fiber laser system were briefly discussed.
Based on the requirement and the influence of environmental factor on weapon system, two typical high energy fiber laser systems, coherent- and incoherent-combining types, were analyzed and compared. Beam propagation factor(BPF) was introduced as the beam quality factor for the combined beam. The influence of array element beam quality, atmospheric propagation, tracking jitter, phase control on the combined beam quality was numerically evaluated. The development trends of high energy fiber laser system were briefly discussed.
2008,
20.
Abstract:
The article introduces the progress in research on the ICF target materials and target fabrication technology in China Academy of Engineering Physics. It involves mainly the following aspects: the target materials, capsule fabrication technology, ICF film-targets, precise micro technology, and target parameter measurement. In the aspect of target materials, the perdeuterated polystyrene (D-PS) organic materials, the micro target doped materials and the metal nano-material and nanoclusters for the laser absorption and conversion of X-ray have been prepared. We have studied exploringly the new organic aerogel hydrogen storage, the theory of metal small clusters and nano intermetallic compound materials. For the fabrication technology of target, we have fulfilled the fabrication of PS monolay
The article introduces the progress in research on the ICF target materials and target fabrication technology in China Academy of Engineering Physics. It involves mainly the following aspects: the target materials, capsule fabrication technology, ICF film-targets, precise micro technology, and target parameter measurement. In the aspect of target materials, the perdeuterated polystyrene (D-PS) organic materials, the micro target doped materials and the metal nano-material and nanoclusters for the laser absorption and conversion of X-ray have been prepared. We have studied exploringly the new organic aerogel hydrogen storage, the theory of metal small clusters and nano intermetallic compound materials. For the fabrication technology of target, we have fulfilled the fabrication of PS monolay
2008,
20.
Abstract:
HIRFL-CSR is a new heavy ion cooler-storage-ring synchrotron system in Lanzhou. It consists of a main ring (CSRm) and an experimental ring (CSRe) with multi-usages and multi-functions. The two existing cyclotrons SFC (K=69) and SSC (K=450) of the Heavy Ion Research Facility in Lanzhou (HIRFL) are used as its injector system. The heavy ion beams from HIRFL with the energy of 7~25 MeV/u will be first injected into CSRm, accompanying with the accumulation, e-cooling and acceleration, and finally extracted slowly with the energy of 500～1 000 MeV/u for many external-target experiments, or extracted fast with the energy of 200～700 MeV/u to produce radioactive ion beams (RIBs) or high Z beams at the primary target of the beam line. The secondary beams will be accepted and stored in CSRe for man
HIRFL-CSR is a new heavy ion cooler-storage-ring synchrotron system in Lanzhou. It consists of a main ring (CSRm) and an experimental ring (CSRe) with multi-usages and multi-functions. The two existing cyclotrons SFC (K=69) and SSC (K=450) of the Heavy Ion Research Facility in Lanzhou (HIRFL) are used as its injector system. The heavy ion beams from HIRFL with the energy of 7~25 MeV/u will be first injected into CSRm, accompanying with the accumulation, e-cooling and acceleration, and finally extracted slowly with the energy of 500～1 000 MeV/u for many external-target experiments, or extracted fast with the energy of 200～700 MeV/u to produce radioactive ion beams (RIBs) or high Z beams at the primary target of the beam line. The secondary beams will be accepted and stored in CSRe for man
2008,
20.
Abstract:
Experimental research on plasma radiation characteristics and plasma implosion of Kr gas-puff, W wire array, Ne gas-puff and Al wire array Z pinches performed on Qiangguang-Ⅰ pulsed power generator of 1.4~ 2.1 MA current with 80~100 ns rise time is reported. In the experiments, the voltage divider and two Rogowskii coils were used to measure the voltage and the current of diode respectively, a filter-XRD and a scintillator-photodiode detector with even energy respond in the energy region from 100 eV to 1 400 eV were used to measure X-ray waveforms, the Ni-film bolometer was developed for measuring the total soft X-ray energy, the time-resolved X-ray image diagnostic system was developed for recording the imploding process of Z pinches, and an elliptically-curved crystal spectrometer with
Experimental research on plasma radiation characteristics and plasma implosion of Kr gas-puff, W wire array, Ne gas-puff and Al wire array Z pinches performed on Qiangguang-Ⅰ pulsed power generator of 1.4~ 2.1 MA current with 80~100 ns rise time is reported. In the experiments, the voltage divider and two Rogowskii coils were used to measure the voltage and the current of diode respectively, a filter-XRD and a scintillator-photodiode detector with even energy respond in the energy region from 100 eV to 1 400 eV were used to measure X-ray waveforms, the Ni-film bolometer was developed for measuring the total soft X-ray energy, the time-resolved X-ray image diagnostic system was developed for recording the imploding process of Z pinches, and an elliptically-curved crystal spectrometer with
2008,
20.
Abstract:
In this paper, we studied on the principle and technical difficulties of beam coherent combination with three self-imaging cavity, which were Talbot cavity, Self-Fourier cavity and self-imaging cavity of Fourier transform. Finally, we implemented 1×2 fiber lasers coherent combination and 2×2 fiber lasers coherent combination with Self-Fourier cavity, and the coherent output powers reached 122 W and 26 W, respectively.
In this paper, we studied on the principle and technical difficulties of beam coherent combination with three self-imaging cavity, which were Talbot cavity, Self-Fourier cavity and self-imaging cavity of Fourier transform. Finally, we implemented 1×2 fiber lasers coherent combination and 2×2 fiber lasers coherent combination with Self-Fourier cavity, and the coherent output powers reached 122 W and 26 W, respectively.
2008,
20.
Abstract:
It is proposed that a chirped pulse can be better amplified using a chirped electron beam at an free-electron laser (FEL), and the reasons of which and the effects of the slippage between the optical and electron beams are analyzed. The processes of the FEL amplifier with energy-chirped beam amplifying chirped pulses with different chirped parameters are studied through numerical simulations using our 1D time-dependent code GOFEL-P. The peak power and width of the final compressed pulse with different chirped parameters have been computed. The results show that, comparing with a normal electron beam, the energy-chirped beam can amplify chirped pulse with larger chirped parameter, and the peak power of the final compressed pulse can even reach near 10 times larger and the width of the pulse
It is proposed that a chirped pulse can be better amplified using a chirped electron beam at an free-electron laser (FEL), and the reasons of which and the effects of the slippage between the optical and electron beams are analyzed. The processes of the FEL amplifier with energy-chirped beam amplifying chirped pulses with different chirped parameters are studied through numerical simulations using our 1D time-dependent code GOFEL-P. The peak power and width of the final compressed pulse with different chirped parameters have been computed. The results show that, comparing with a normal electron beam, the energy-chirped beam can amplify chirped pulse with larger chirped parameter, and the peak power of the final compressed pulse can even reach near 10 times larger and the width of the pulse
2008,
20.
Abstract:
Simulation experiments of adaptive optics compensation to thermal blooming phase distortion induced by high energy laser propagation in the atmosphere were carried out. The results of spot pattern, centroid excursion, second moment radius and the Strehl ratio in the focal plane were obtained when the adaptive optics system was in the open or closed loop shape. The effect of adaptive optics compensation was prominent when the Bradley-Hermann distortion number was less than 300, and the Strehl ratio was more than 0.4 on the whole. Phase compensation instability appeared when the distortion number ND became greater than 300, in this case, the compensated beam Strehl ratio went down rapidly. The experimental Strehl ratio without adaptive optics compensation agreeed well with that of the thin l
Simulation experiments of adaptive optics compensation to thermal blooming phase distortion induced by high energy laser propagation in the atmosphere were carried out. The results of spot pattern, centroid excursion, second moment radius and the Strehl ratio in the focal plane were obtained when the adaptive optics system was in the open or closed loop shape. The effect of adaptive optics compensation was prominent when the Bradley-Hermann distortion number was less than 300, and the Strehl ratio was more than 0.4 on the whole. Phase compensation instability appeared when the distortion number ND became greater than 300, in this case, the compensated beam Strehl ratio went down rapidly. The experimental Strehl ratio without adaptive optics compensation agreeed well with that of the thin l
2008,
20.
Abstract:
Using the amplification transfer function of type ⅠBBO crystal, the theoretical study of spatial properties of the optical parametric fluorescence generated by homochromatic signal and polychromatic signal in optical parametric amplification is investigated. The numerical simulation results demonstrate that when the homochromatic signal is injected into optical parametric amplifier, the fluorescence signal is first emitted in a cone and then in a ring while centering on the pump wave direction. For the amplification of the polychromatic signal pulse, the spectrum of the fluorescence is over a wide wavelength range under a special phase matching angle. The result provides a theoretical reference for controlling the generation of the optical parametric fluorescence and quantum entanglement
Using the amplification transfer function of type ⅠBBO crystal, the theoretical study of spatial properties of the optical parametric fluorescence generated by homochromatic signal and polychromatic signal in optical parametric amplification is investigated. The numerical simulation results demonstrate that when the homochromatic signal is injected into optical parametric amplifier, the fluorescence signal is first emitted in a cone and then in a ring while centering on the pump wave direction. For the amplification of the polychromatic signal pulse, the spectrum of the fluorescence is over a wide wavelength range under a special phase matching angle. The result provides a theoretical reference for controlling the generation of the optical parametric fluorescence and quantum entanglement
2008,
20.
Abstract:
The paper demonstrated that by using the nonlinear polarization rotation as the mode-locking mechanism, the laser could operate stably in either CW fundamental wave mode-locked or high-order harmonically mode-locked regimes by changing the pump power and adjusting the polarization controller. Under the pump power of 10 mW, fundamental wave mode-locked pulses with repetition rate of 15.89 MHz, output spectrum width of 9.9 nm, central wavelength of 1.557 nm was obtained. Under a different pump power of 75 mW, we obtained second harmonically mode-locked pulses with repetition rate of 31.79 MHz and third harmonically mode-locked pulses with repetition rate of 46.68 MHz. The paper also presented some preliminary theoretical analyses.
The paper demonstrated that by using the nonlinear polarization rotation as the mode-locking mechanism, the laser could operate stably in either CW fundamental wave mode-locked or high-order harmonically mode-locked regimes by changing the pump power and adjusting the polarization controller. Under the pump power of 10 mW, fundamental wave mode-locked pulses with repetition rate of 15.89 MHz, output spectrum width of 9.9 nm, central wavelength of 1.557 nm was obtained. Under a different pump power of 75 mW, we obtained second harmonically mode-locked pulses with repetition rate of 31.79 MHz and third harmonically mode-locked pulses with repetition rate of 46.68 MHz. The paper also presented some preliminary theoretical analyses.
2008,
20.
Abstract:
Laser-induced plasma can be generated by focusing pulses from a Q-switch Nd:YAG laser on the surface of a paint sample. The plasma emission was collected with a set of lens onto the entrance slit of a monochromator and finally detected by a photomultiplier tube. A rapid qualitative analysis of heavy metals in paints can be achieved by analysis of spectral emission of the plasma. The contents of heavy metals(Pb,Cu,Cr,Mn) in several commercial paints have been analyzed experimentally. It is demonstrated that, the spectral intensity of one element is proportional to its concentration for the same type of paint and under the same analytical condition. Thus a rapid quantitative analysis of heavy metals in paints with laser-induced breakdown spectroscopy is practical．
Laser-induced plasma can be generated by focusing pulses from a Q-switch Nd:YAG laser on the surface of a paint sample. The plasma emission was collected with a set of lens onto the entrance slit of a monochromator and finally detected by a photomultiplier tube. A rapid qualitative analysis of heavy metals in paints can be achieved by analysis of spectral emission of the plasma. The contents of heavy metals(Pb,Cu,Cr,Mn) in several commercial paints have been analyzed experimentally. It is demonstrated that, the spectral intensity of one element is proportional to its concentration for the same type of paint and under the same analytical condition. Thus a rapid quantitative analysis of heavy metals in paints with laser-induced breakdown spectroscopy is practical．
2008,
20.
Abstract:
Since there’s no standard high energy laser(HEL) calorimeter or standard laser beam, conventional methods can’t be used to calibrate HEL calorimeter. A method using existing small calorimeter for calibration with uncertainty transfer in measurements was introduced, and a way utilizing energy equivalence theory to calibrate HEL calorimeter was suggested. Uncertainty transfer method is convenient, but it has many courses, which result in great uncertainty of the HEL calorimeter. Equivalence method includes electricity-calibration and light-calibration. Electricity-calibration requires preciser design but easier data processing. Light-calibration needs no specific design, but the remainder caloric of lamps and the caloric loss must be measured before calibration. The three conditions of equ
Since there’s no standard high energy laser(HEL) calorimeter or standard laser beam, conventional methods can’t be used to calibrate HEL calorimeter. A method using existing small calorimeter for calibration with uncertainty transfer in measurements was introduced, and a way utilizing energy equivalence theory to calibrate HEL calorimeter was suggested. Uncertainty transfer method is convenient, but it has many courses, which result in great uncertainty of the HEL calorimeter. Equivalence method includes electricity-calibration and light-calibration. Electricity-calibration requires preciser design but easier data processing. Light-calibration needs no specific design, but the remainder caloric of lamps and the caloric loss must be measured before calibration. The three conditions of equ
2008,
20.
Abstract:
The experiments were carried out on a verti-COIL, with the chlorine flowrate of 155 mmol/s, which was designed for N2. The effect on the output power was studied, with different import positions, different dilution ratios and different buffer gases, N2, Ar, and CO2. The buffer gas introduced from singlet oxygen generator(SOG) was positive to the output power and it increased with the dilution ratio within a certain range(0~1.0). The output power differed from each other when different buffer gases were used. The calculation indicated that Ar gas showed better performance in improving the small signal gain coefficient and lowering the temperature of gas.
The experiments were carried out on a verti-COIL, with the chlorine flowrate of 155 mmol/s, which was designed for N2. The effect on the output power was studied, with different import positions, different dilution ratios and different buffer gases, N2, Ar, and CO2. The buffer gas introduced from singlet oxygen generator(SOG) was positive to the output power and it increased with the dilution ratio within a certain range(0~1.0). The output power differed from each other when different buffer gases were used. The calculation indicated that Ar gas showed better performance in improving the small signal gain coefficient and lowering the temperature of gas.
2008,
20.
Abstract:
Ejector-type pressure recovery system plays an important part in the application of chemical lasers. For improving ejector efficiency and reducing system size, an important method is to reduce the temperature of gas mixture out from laser cavity. The feasibility of implementing this method using heat exchanger through numerical simulation is investigated. The thermophysical properties of gas mixture are calculated first, and then modeling methods and numerical simulation conditions are given here. Based on the comparison of heat exchanger performances in different simulation conditions, it is found that the heat transfer efficiency and pressure drop are much smaller than that in common industrial heat exchanger. That's because the density of gas mixture is too low. To enlarge tube size and
Ejector-type pressure recovery system plays an important part in the application of chemical lasers. For improving ejector efficiency and reducing system size, an important method is to reduce the temperature of gas mixture out from laser cavity. The feasibility of implementing this method using heat exchanger through numerical simulation is investigated. The thermophysical properties of gas mixture are calculated first, and then modeling methods and numerical simulation conditions are given here. Based on the comparison of heat exchanger performances in different simulation conditions, it is found that the heat transfer efficiency and pressure drop are much smaller than that in common industrial heat exchanger. That's because the density of gas mixture is too low. To enlarge tube size and
2008,
20.
Abstract:
Design ideas of supersonic transverse free-vortex aerodynamic window(ADW) were discussed, and the reason of a single-stage ADW not easily reaching high sealing pressure ratio was analyzed. Based on the pneumatic parameter distribution at the ADW diffuser inlet, an active diffuser with wall boost was designed and validated by tests, whose sealing pressure ratio reached 85 in the test.The results show that the air blowing in diffuser inlet is an efficient method for improving sealing pressure ratio; the blowing in the diffuser’s inner wall has more impact on sealing pressure ratio than that in the outer wall.
Design ideas of supersonic transverse free-vortex aerodynamic window(ADW) were discussed, and the reason of a single-stage ADW not easily reaching high sealing pressure ratio was analyzed. Based on the pneumatic parameter distribution at the ADW diffuser inlet, an active diffuser with wall boost was designed and validated by tests, whose sealing pressure ratio reached 85 in the test.The results show that the air blowing in diffuser inlet is an efficient method for improving sealing pressure ratio; the blowing in the diffuser’s inner wall has more impact on sealing pressure ratio than that in the outer wall.
2008,
20.
Abstract:
The effect of linewidth of the transmitted laser on measurement sensitivity and error of double-edge noncoherent wind lidar is presented. The quantitative relationship between linewidth of the transmitted laser and the FWHM(full width at half maximum) of the backscattered spectrum was simulated by using the Monte-Carlo method since it cannot be expressed by an analytic formula. The relationship was fitted by using quadratic fit and was used to calculate the measurement sensitivity and error furthermore. The FWHM of the backscattered spectrum increases from 3.853 GHz to 5.371 GHz while the linewidth of the transmitted laser increases from monochromatic to 2 GHz. The measurement greatly suffered from the broadening of the linewidth of the transmitted laser. The measurement sensitivity reduce
The effect of linewidth of the transmitted laser on measurement sensitivity and error of double-edge noncoherent wind lidar is presented. The quantitative relationship between linewidth of the transmitted laser and the FWHM(full width at half maximum) of the backscattered spectrum was simulated by using the Monte-Carlo method since it cannot be expressed by an analytic formula. The relationship was fitted by using quadratic fit and was used to calculate the measurement sensitivity and error furthermore. The FWHM of the backscattered spectrum increases from 3.853 GHz to 5.371 GHz while the linewidth of the transmitted laser increases from monochromatic to 2 GHz. The measurement greatly suffered from the broadening of the linewidth of the transmitted laser. The measurement sensitivity reduce
2008,
20.
Abstract:
The spectral and temporal properties of two-dimensional spatially and spectrally partially coherent Gaussian Schell-model pulsed(GSMP) beams propagating in free space are studied and analyzed numerically. It is shown that the spectral shift takes place, which depends on the position of the field point, spatial correlation length and the temporal coherence length, as GSMP beams propagate in free space. The on-axis spectrum is blue-shifted, and the relative spectral shift increases with increasing propagation distance, and decreases as the spatial correlation length and temporal coherence length increase, and then approaches an asymptotic value. The off-axis spectrum is blue-shifted or red-shifted, depending on the spatial correlation length and temporal coherence length. The temporal intens
The spectral and temporal properties of two-dimensional spatially and spectrally partially coherent Gaussian Schell-model pulsed(GSMP) beams propagating in free space are studied and analyzed numerically. It is shown that the spectral shift takes place, which depends on the position of the field point, spatial correlation length and the temporal coherence length, as GSMP beams propagate in free space. The on-axis spectrum is blue-shifted, and the relative spectral shift increases with increasing propagation distance, and decreases as the spatial correlation length and temporal coherence length increase, and then approaches an asymptotic value. The off-axis spectrum is blue-shifted or red-shifted, depending on the spatial correlation length and temporal coherence length. The temporal intens
2008,
20.
Abstract:
Dispersive formulas were deduced adding a phase correction term to the optical path difference, and the formulas were validated through ray tracing method. From both the ray tracing method and formulas, the stretcher model with Offner triplet stretcher were studied. The influences of the incident angle and the distance between the grating and the concave mirror were discussed. The residual dispersions of Offner triplet stretchers and a conjugate compressor systems of some grating-concave-mirror distances and incident angles were analyzed comparatively. The influences of unmatched gratings on dispersions were also presented.
Dispersive formulas were deduced adding a phase correction term to the optical path difference, and the formulas were validated through ray tracing method. From both the ray tracing method and formulas, the stretcher model with Offner triplet stretcher were studied. The influences of the incident angle and the distance between the grating and the concave mirror were discussed. The residual dispersions of Offner triplet stretchers and a conjugate compressor systems of some grating-concave-mirror distances and incident angles were analyzed comparatively. The influences of unmatched gratings on dispersions were also presented.
2008,
20.
Abstract:
Experimental study of 1.54 THz laser imaging and transmission property were studied by using a CW THz waveguide discharge-pumped high-power DCN laser system operating on 1.54 THz. A real-time, continuous-wave terahertz imaging is demonstrated with the 1.54 THz laser and a simple two-dimension scanning system. The position and shape of a plastic sign card and a metal coin hidden in an envelop are easily identified through just measuring the transmission intensity of the THz laser. Absorption coefficients of a few samples were also measured with the 1.54 THz laser system. The 1.54 THz laser transmission property of these samples was reported in detail.
Experimental study of 1.54 THz laser imaging and transmission property were studied by using a CW THz waveguide discharge-pumped high-power DCN laser system operating on 1.54 THz. A real-time, continuous-wave terahertz imaging is demonstrated with the 1.54 THz laser and a simple two-dimension scanning system. The position and shape of a plastic sign card and a metal coin hidden in an envelop are easily identified through just measuring the transmission intensity of the THz laser. Absorption coefficients of a few samples were also measured with the 1.54 THz laser system. The 1.54 THz laser transmission property of these samples was reported in detail.
2008,
20.
Abstract:
Based on the typical structure of inertial confinement fusion facility and the principles of propagation, amplify and frequency conversion of wave, a beam propagation code for ICF device with adaptive optics system was set up. By comparing the results of light propagating in linear and nonlinear media with those reported in papers at home or abroad, the reliability of this code is validated. One of the examples about the intensity distribution of infrared light and ultraviolet light before and after the correction of adaptive optics was presented to show the effect of adaptive optics in the improvement of output wave from ICF device. The code will help to optimize the design of adaptive optics in ICF device.
Based on the typical structure of inertial confinement fusion facility and the principles of propagation, amplify and frequency conversion of wave, a beam propagation code for ICF device with adaptive optics system was set up. By comparing the results of light propagating in linear and nonlinear media with those reported in papers at home or abroad, the reliability of this code is validated. One of the examples about the intensity distribution of infrared light and ultraviolet light before and after the correction of adaptive optics was presented to show the effect of adaptive optics in the improvement of output wave from ICF device. The code will help to optimize the design of adaptive optics in ICF device.
2008,
20.
Abstract:
Based on influences of geometric aberration, diffraction, figure error and surface roughness, a root-mean-square spatial resolution model of Kirkpatrick-Baez(KB) microscope with single-layer film is proposed. An 8 keV X-ray imaging experiment by KB microscope with single Ir layer is performed, and the resolution is about 2 mm in central field and better than 5 mm in ±50 mm. The calculated results from the model is in good agreement with the experiment results, and using this model, the spatial resolution related to visual field can be estimated during the systems-design phase.
Based on influences of geometric aberration, diffraction, figure error and surface roughness, a root-mean-square spatial resolution model of Kirkpatrick-Baez(KB) microscope with single-layer film is proposed. An 8 keV X-ray imaging experiment by KB microscope with single Ir layer is performed, and the resolution is about 2 mm in central field and better than 5 mm in ±50 mm. The calculated results from the model is in good agreement with the experiment results, and using this model, the spatial resolution related to visual field can be estimated during the systems-design phase.
2008,
20.
Abstract:
By the ultra-cavity single-pass configuration, stimulated Raman scattering(SRS) of LiIO3 crystal was realized. When the pump source was a 532 nm picosecond laser, three Stokes lines (556.07, 582.30, 611.76 nm) and one anti-Stokes line (509.57 nm) were observed, and the frequency shifting was calculated to be 820 cm-1. The SRS thresholds and Raman gain coefficients for different scattering lines were measured, and the total conversion efficiency reached 56%. Picosecond, external resonator Raman laser was realized based on LiIO3 crystal, the total conversion efficiency for dual-wavelength output was 27%, and the largest output energy was 1.4 mJ.
By the ultra-cavity single-pass configuration, stimulated Raman scattering(SRS) of LiIO3 crystal was realized. When the pump source was a 532 nm picosecond laser, three Stokes lines (556.07, 582.30, 611.76 nm) and one anti-Stokes line (509.57 nm) were observed, and the frequency shifting was calculated to be 820 cm-1. The SRS thresholds and Raman gain coefficients for different scattering lines were measured, and the total conversion efficiency reached 56%. Picosecond, external resonator Raman laser was realized based on LiIO3 crystal, the total conversion efficiency for dual-wavelength output was 27%, and the largest output energy was 1.4 mJ.
2008,
20.
Abstract:
A general waveguide pill-box window could provide maxim relative bandwidth no more than 30% because of the ghost mode effects. A new full band waveguide high power asymmetric pill-box window without ghost mode simulation and optimized approach is presented. This type pill-box window has broad band, no ghost mode and excellent voltage standing wave ratio(VSWR) characters and specially suits for high power helix TWT with kW level output. An L-band pill-box window 3-D simulation prototype connected with impedance match waveguide is obtained according to this method, which has a relative bandwidth up to 41.4% without ghost mode and the VSWR is lower than 1.1．
A general waveguide pill-box window could provide maxim relative bandwidth no more than 30% because of the ghost mode effects. A new full band waveguide high power asymmetric pill-box window without ghost mode simulation and optimized approach is presented. This type pill-box window has broad band, no ghost mode and excellent voltage standing wave ratio(VSWR) characters and specially suits for high power helix TWT with kW level output. An L-band pill-box window 3-D simulation prototype connected with impedance match waveguide is obtained according to this method, which has a relative bandwidth up to 41.4% without ghost mode and the VSWR is lower than 1.1．
2008,
20.
Abstract:
A hybrid method for shielding efficiency or coupling efficiency estimation of slot in double-layer shielding cavity is presented. The coupling efficiency of outer slot is calculated by the transmission line model and the coupling efficiency of inner slot is based on the coupling theory of small holes and its equivalent model of magnetic dipole, which is excited by magnetic current. The distribution of electric field and the rule of shielding efficiency in inner cavity is obtained by the hybrid method. The validity is given by the well matched of trasmission line model, magnetic dipole, Micro-Stripes software simulated data and measured data. The result of the hybrid method exhibit the relationship between the slot position, slot number and the shielding efficiency of different watching poi
A hybrid method for shielding efficiency or coupling efficiency estimation of slot in double-layer shielding cavity is presented. The coupling efficiency of outer slot is calculated by the transmission line model and the coupling efficiency of inner slot is based on the coupling theory of small holes and its equivalent model of magnetic dipole, which is excited by magnetic current. The distribution of electric field and the rule of shielding efficiency in inner cavity is obtained by the hybrid method. The validity is given by the well matched of trasmission line model, magnetic dipole, Micro-Stripes software simulated data and measured data. The result of the hybrid method exhibit the relationship between the slot position, slot number and the shielding efficiency of different watching poi
2008,
20.
Abstract:
The effects of the misalignment between the inner-rod axis and the outer-wall axis in an open coaxial resonator are simulated by using the software CST microwave studio. The calculated results show that either the parallel misalignment or the oblique misalignment between the inner-rod axis and the outer-wall axis causes substantial decrease of the resonant frequency, the Q-factor, and the field amplitude of the open coaxial resonator; and generally, an oblique misalignment has more adverse influence than a parallel misalignment.
The effects of the misalignment between the inner-rod axis and the outer-wall axis in an open coaxial resonator are simulated by using the software CST microwave studio. The calculated results show that either the parallel misalignment or the oblique misalignment between the inner-rod axis and the outer-wall axis causes substantial decrease of the resonant frequency, the Q-factor, and the field amplitude of the open coaxial resonator; and generally, an oblique misalignment has more adverse influence than a parallel misalignment.
2008,
20.
Abstract:
Base on the breakdown theory of vacuum gaps, experiments have been done to find out the breakdown electric field intensities in high voltage single-and triple-pulse for 26 vacuum gaps with different shapes. The experimental results match up to the theory and confirm the effect of the pulse-number increase on the breakdown electric field intensity. The key point to decide the macroscopical breakdown electric field intensity of a vacuum gap has been pointed out with some advises about the design of a multi-pulse linear inductive accelerator’s accelerate gap.
Base on the breakdown theory of vacuum gaps, experiments have been done to find out the breakdown electric field intensities in high voltage single-and triple-pulse for 26 vacuum gaps with different shapes. The experimental results match up to the theory and confirm the effect of the pulse-number increase on the breakdown electric field intensity. The key point to decide the macroscopical breakdown electric field intensity of a vacuum gap has been pointed out with some advises about the design of a multi-pulse linear inductive accelerator’s accelerate gap.
2008,
20.
Abstract:
Beam loss control is a key point in the design of high power facilities like the Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS). The patterns of the RF acceleration voltage, frequency and phase are the main factors to determine the longitudinal motion of beam and the beam loss level. Therefore, the low-level RF system (LLRF) control system of CSNS/RCS must be stable and precise. In this paper, the design of the LLRF control system of CSNS/RCS was presented, especially the voltage control loop. In the loop, the difference between the deteeted voltage and a pattern is fed to a PI compensation function, and the PI output controls the amplitude of the RF signal. Through the modeling and analysis of each part of the control loop, a proper PI controller design was
Beam loss control is a key point in the design of high power facilities like the Rapid Cycling Synchrotron (RCS) of the China Spallation Neutron Source (CSNS). The patterns of the RF acceleration voltage, frequency and phase are the main factors to determine the longitudinal motion of beam and the beam loss level. Therefore, the low-level RF system (LLRF) control system of CSNS/RCS must be stable and precise. In this paper, the design of the LLRF control system of CSNS/RCS was presented, especially the voltage control loop. In the loop, the difference between the deteeted voltage and a pattern is fed to a PI compensation function, and the PI output controls the amplitude of the RF signal. Through the modeling and analysis of each part of the control loop, a proper PI controller design was
2008,
20.
Abstract:
Based on the BFEL improvement goals, this paper discusses the main physical and technical problems of dual-band operation of BFEL facility in IR and X-ray ranges by Compton scattering. The preliminary design shows that the wavelength can change from 4.9 to 16.8 μm. with macropulse energy of 50mJ. In addition, the photon energy of back-scattering X-ray source by intra-cavity Compton back-scattering can be 0.475~ 3.49 keV, the macropulse spectral brightness can reach 3.0×1020 photons/(s·mm2·mrad2·0.1%BW), thus broaden the application areas of the BFEL facility into X-ray range.
Based on the BFEL improvement goals, this paper discusses the main physical and technical problems of dual-band operation of BFEL facility in IR and X-ray ranges by Compton scattering. The preliminary design shows that the wavelength can change from 4.9 to 16.8 μm. with macropulse energy of 50mJ. In addition, the photon energy of back-scattering X-ray source by intra-cavity Compton back-scattering can be 0.475~ 3.49 keV, the macropulse spectral brightness can reach 3.0×1020 photons/(s·mm2·mrad2·0.1%BW), thus broaden the application areas of the BFEL facility into X-ray range.
2008,
20.
Abstract:
The energy loss of charged particles moving in magnetized two-component plasmas has been studied based on the linearized Vlasov-Poisson equations, in which special attention is paid to the effects of the magnetic filed and dynamic polarization on the energy loss. The numerical results show that there are two peaks in the energy loss. One is located in the low-velocity region and corresponds to the ion’s polarizations, and the other is located in the high-velocity region and corresponds to the electron’s polarizations. In the case of the strong magnetic filed, the energy loss of the low-velocity particles is mainly caused by the ion’s polarizations; while in the case of weak magnetic filed, the energy loss of the high-velocity particles is mainly caused by the electron’s polarization．
The energy loss of charged particles moving in magnetized two-component plasmas has been studied based on the linearized Vlasov-Poisson equations, in which special attention is paid to the effects of the magnetic filed and dynamic polarization on the energy loss. The numerical results show that there are two peaks in the energy loss. One is located in the low-velocity region and corresponds to the ion’s polarizations, and the other is located in the high-velocity region and corresponds to the electron’s polarizations. In the case of the strong magnetic filed, the energy loss of the low-velocity particles is mainly caused by the ion’s polarizations; while in the case of weak magnetic filed, the energy loss of the high-velocity particles is mainly caused by the electron’s polarization．
2008,
20.
Abstract:
A triple resonance pulse transformer, based on an air-cored transformer, is described. By analyzing the triple resonance pulse transformer lossless circuit, the analytical expression for the output voltage and the relation of the circuit parameters are presented when the normal-mode frequencies are in the ratios of 1∶2∶3. In this case, the ratio of the peak high voltage winding’s voltage to the peak output voltage is 0.36. According to the results of theoretic analysis, the circuit parameters of a triple resonance pulse transformer such as coupling coefficient, tuning inductor, tuning capacitor, primary capacitor, load capacitor are simulated. The simulation results show that the output voltage and the energy efficiency have few variations when the tuning inductor and the tuning capacit
A triple resonance pulse transformer, based on an air-cored transformer, is described. By analyzing the triple resonance pulse transformer lossless circuit, the analytical expression for the output voltage and the relation of the circuit parameters are presented when the normal-mode frequencies are in the ratios of 1∶2∶3. In this case, the ratio of the peak high voltage winding’s voltage to the peak output voltage is 0.36. According to the results of theoretic analysis, the circuit parameters of a triple resonance pulse transformer such as coupling coefficient, tuning inductor, tuning capacitor, primary capacitor, load capacitor are simulated. The simulation results show that the output voltage and the energy efficiency have few variations when the tuning inductor and the tuning capacit
2008,
20.
Abstract:
Both Townsend theory and the traditional streamer model are the basis for study on gas discharge, however, they both have drawbacks dealing with nanosecond pulse gas breakdown. Based on the traditional mechanisms, the paper summarizes nanosecond pulse breakdown mechanisms in gases, presents some analyses on the validity of streamer criterion in the range of nanosecond pulse, describes the phenomenon of electron runaway and the theory of fast ionization wave breakdown, and gives some simulation calculations about runaway process of high-energy fast electrons. The results show that the runaway breakdown model induced by high-energy fast electrons is promising as accounting for the nanosecond pulse discharge in gases.
Both Townsend theory and the traditional streamer model are the basis for study on gas discharge, however, they both have drawbacks dealing with nanosecond pulse gas breakdown. Based on the traditional mechanisms, the paper summarizes nanosecond pulse breakdown mechanisms in gases, presents some analyses on the validity of streamer criterion in the range of nanosecond pulse, describes the phenomenon of electron runaway and the theory of fast ionization wave breakdown, and gives some simulation calculations about runaway process of high-energy fast electrons. The results show that the runaway breakdown model induced by high-energy fast electrons is promising as accounting for the nanosecond pulse discharge in gases.
2008,
20.
Abstract:
An electrical insulation optimum design and electric-field numerical simulation of a 1MV compact repetitive Marx generator filled with sulfur hexafluoride gas was performed. Two critical insulating regions in Marx generator, modular switch cavity and outer shell were well-designed with compact dimension base on the analysis of sulfur hexafluoride insulating property in static and pulse high-voltage environment, 3D electric-field numerical simulation results of the interested regions indicate that the current design meets the insulating requests of Sulfur hexafluoride at 0.3 MPa.
An electrical insulation optimum design and electric-field numerical simulation of a 1MV compact repetitive Marx generator filled with sulfur hexafluoride gas was performed. Two critical insulating regions in Marx generator, modular switch cavity and outer shell were well-designed with compact dimension base on the analysis of sulfur hexafluoride insulating property in static and pulse high-voltage environment, 3D electric-field numerical simulation results of the interested regions indicate that the current design meets the insulating requests of Sulfur hexafluoride at 0.3 MPa.
