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RSS2008 Vol. 20, No. 10
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2008,
20.
Abstract:
A single-module two-stage ejector test facility was established to investigate the supersonic ejector performance, and hot gases with various were used as parameters first-stage and second-stage driving fluids. The investigation indicates that there is a lower limit of flux when second-stage ejector start alone, and the parameter matching range is relatively wide for the system itself, but the parameter matching range will reduce greatly for the system with load. Pressure matching is a all-important question for multi-stage ejector.
A single-module two-stage ejector test facility was established to investigate the supersonic ejector performance, and hot gases with various were used as parameters first-stage and second-stage driving fluids. The investigation indicates that there is a lower limit of flux when second-stage ejector start alone, and the parameter matching range is relatively wide for the system itself, but the parameter matching range will reduce greatly for the system with load. Pressure matching is a all-important question for multi-stage ejector.
2008,
20.
Abstract:
There are strong interactions or couples among multi-fields in the mixing nozzle of the COIL, such as gas-dynamics, chemical reaction kinetics and optics. Three-dimensional CFD technology was applied on the RADICL model by solving the laminar Navier-Stokes equations and transportation equations to study the small signal gain distributions. A simulation was done in the condition of different flow rate ratio of primary to secondary flow. Results show that the appropriate flow rate ratio plays an important role on the spatial distribution of the small signal gain. Both too high and too low concentration of iodine goes against the proper gain.
There are strong interactions or couples among multi-fields in the mixing nozzle of the COIL, such as gas-dynamics, chemical reaction kinetics and optics. Three-dimensional CFD technology was applied on the RADICL model by solving the laminar Navier-Stokes equations and transportation equations to study the small signal gain distributions. A simulation was done in the condition of different flow rate ratio of primary to secondary flow. Results show that the appropriate flow rate ratio plays an important role on the spatial distribution of the small signal gain. Both too high and too low concentration of iodine goes against the proper gain.
2008,
20.
Abstract:
The response surface model of Hypersonic Low Temperature(HYLTE) nozzle was built, and the design matrix of sample data points, used in this model, was derived by orthogonal design of experiment(DOE) procedure. The sample data were obtained by the nozzle and cavity flowfield calculation using computational fluid dynamics(CFD) method based on 3-dimensional viscous Navier-Stokes equation. Using the nozzle response surface model, multi-objective optimization of nozzle configuration was implemented. An integrated performance parameter was defined to evaluate the nozzle efficiently. Results indicate that the mixing of the optimized nozzle is enhanced remarkably and the integrated performance improves. So the optimization strategy based on response surface can satisfy the requirement for precisio
The response surface model of Hypersonic Low Temperature(HYLTE) nozzle was built, and the design matrix of sample data points, used in this model, was derived by orthogonal design of experiment(DOE) procedure. The sample data were obtained by the nozzle and cavity flowfield calculation using computational fluid dynamics(CFD) method based on 3-dimensional viscous Navier-Stokes equation. Using the nozzle response surface model, multi-objective optimization of nozzle configuration was implemented. An integrated performance parameter was defined to evaluate the nozzle efficiently. Results indicate that the mixing of the optimized nozzle is enhanced remarkably and the integrated performance improves. So the optimization strategy based on response surface can satisfy the requirement for precisio
2008,
20.
Abstract:
A new atmospheric remote sensing detection system, White-light Lidar, was designed and a detection method based on radar mode of long-path differential absorption spectra was developed. The main structure of the White-light Lidar and time-resolved spectrum detecting technology were introduced. The feature of the femtosecond laser pulses propagating for filament formation in atmosphere and white-light supercontinuum were expounded. Using the White-light Lidar system, the long-path differential absorption spectra of oxygen molecules in the range of 685~694 nm and 759~769 nm were detected. The measured results are in good agreement with the fitted spectra of Hitran database, which indicates the correctness of the remote sensing detection system of White-light Lidar and the feasibility of the
A new atmospheric remote sensing detection system, White-light Lidar, was designed and a detection method based on radar mode of long-path differential absorption spectra was developed. The main structure of the White-light Lidar and time-resolved spectrum detecting technology were introduced. The feature of the femtosecond laser pulses propagating for filament formation in atmosphere and white-light supercontinuum were expounded. Using the White-light Lidar system, the long-path differential absorption spectra of oxygen molecules in the range of 685~694 nm and 759~769 nm were detected. The measured results are in good agreement with the fitted spectra of Hitran database, which indicates the correctness of the remote sensing detection system of White-light Lidar and the feasibility of the
2008,
20.
Abstract:
From the formation mechanism of the wind profiler radar’s echoes, this paper studied a retrieval method of the turbulent kinetic energy dissipation rate from spectral width measured by a wind profiler. Two key steps of the method are extracting spectral width contributed by turbulence and calculating turbulent dissipation rate based on the relation between turbulent dissipation rate and turbulent spectral width. The paper also analyzed the data of spectral width measured by wind profiler in Hefei and the result is that the turbulent kinetic energy dissipation rate over Hefei at the height of 300 m distributes between 10-4 and 10-1 m2/s3. The result accords with theory, so the retrieval method is viable.
From the formation mechanism of the wind profiler radar’s echoes, this paper studied a retrieval method of the turbulent kinetic energy dissipation rate from spectral width measured by a wind profiler. Two key steps of the method are extracting spectral width contributed by turbulence and calculating turbulent dissipation rate based on the relation between turbulent dissipation rate and turbulent spectral width. The paper also analyzed the data of spectral width measured by wind profiler in Hefei and the result is that the turbulent kinetic energy dissipation rate over Hefei at the height of 300 m distributes between 10-4 and 10-1 m2/s3. The result accords with theory, so the retrieval method is viable.
2008,
20.
Abstract:
The temperature distributions and thermal distortions of Si mirror nonuniformly heated by high energy laser beam are calculated with finite element methods, and the distorted mirror surface is fitted with 65 orders Zernike polynomials for the convenience of ray tracing. The wavefront changes over time with different times of reflection by 45° mirrors are presented, and the corresponding wavefront characteristics such as PV, Strehl ratio and aberration coefficients are tabled. The results show that, distortion occurred on Si mirror nonuniformly heated by the rectangular laser beam with rectangular port, and wavefront aberrations are introduced after multi-reflection. In the aberrations, the y astigmatism and defocus are main contributors. The high order aberration coefficients will gro
The temperature distributions and thermal distortions of Si mirror nonuniformly heated by high energy laser beam are calculated with finite element methods, and the distorted mirror surface is fitted with 65 orders Zernike polynomials for the convenience of ray tracing. The wavefront changes over time with different times of reflection by 45° mirrors are presented, and the corresponding wavefront characteristics such as PV, Strehl ratio and aberration coefficients are tabled. The results show that, distortion occurred on Si mirror nonuniformly heated by the rectangular laser beam with rectangular port, and wavefront aberrations are introduced after multi-reflection. In the aberrations, the y astigmatism and defocus are main contributors. The high order aberration coefficients will gro
2008,
20.
Abstract:
In order to validate the cat eye effect and its application feasibility of ordinary optical lens, an experiment was operated by 532 nm laser irradiating on an ordinary optical zoom lens whose focus ranged from 12 mm to 72 mm. The absolute reflectivity of cat eye effect was tested, and variable rules of the reflectivity were obtained when the focus, F number and incident angle were adjusted. When the reflected light returned from the original way and disturbed the incident ray, the reflectivity could not be tested easily and it was solved by using the method of double-ray testing. The results reveal that the maximal absolute reflectivity can be as high as 35.87%, and the reflectivity is in direct proportion to focus, inverse proportion to F number and incident angle; the geometrical diverge
In order to validate the cat eye effect and its application feasibility of ordinary optical lens, an experiment was operated by 532 nm laser irradiating on an ordinary optical zoom lens whose focus ranged from 12 mm to 72 mm. The absolute reflectivity of cat eye effect was tested, and variable rules of the reflectivity were obtained when the focus, F number and incident angle were adjusted. When the reflected light returned from the original way and disturbed the incident ray, the reflectivity could not be tested easily and it was solved by using the method of double-ray testing. The results reveal that the maximal absolute reflectivity can be as high as 35.87%, and the reflectivity is in direct proportion to focus, inverse proportion to F number and incident angle; the geometrical diverge
2008,
20.
Abstract:
A DL-pumped Nd:YAG all-solid-state sum-frequency laser is presented. Efficient sum-frequency mixing 1 064 nm and 1 319 nm in a 6 mm×6 mm×12 mm KTP crystal is obtained by extra-cavity sum-frequency. Type Ⅱ critical phase-match(CPM) is realized by controlling the temperature of the KTP crystal. By injecting 3.05 W and 2.46 W of 1 064 nm and 1 319 nm Q-switched radiation, respectively, into the KTP crystal, 1.3 W of sum-frequency maximum output is generated with a pulse repetition rate of 400 Hz and pulse duration of about 35 ns, narrowband less than 3 GHz,efficiency up to 23.5%.The beam quality factor of 589 nm laser was 1.84,1.93 in parellel and perpendicular direction, respectively. Experimental results show that the extra-cavity sum-frequency mixing is an effective method for obtaining
A DL-pumped Nd:YAG all-solid-state sum-frequency laser is presented. Efficient sum-frequency mixing 1 064 nm and 1 319 nm in a 6 mm×6 mm×12 mm KTP crystal is obtained by extra-cavity sum-frequency. Type Ⅱ critical phase-match(CPM) is realized by controlling the temperature of the KTP crystal. By injecting 3.05 W and 2.46 W of 1 064 nm and 1 319 nm Q-switched radiation, respectively, into the KTP crystal, 1.3 W of sum-frequency maximum output is generated with a pulse repetition rate of 400 Hz and pulse duration of about 35 ns, narrowband less than 3 GHz,efficiency up to 23.5%.The beam quality factor of 589 nm laser was 1.84,1.93 in parellel and perpendicular direction, respectively. Experimental results show that the extra-cavity sum-frequency mixing is an effective method for obtaining
2008,
20.
Abstract:
A novel approach to the design of the polarizing beam splitters based on the subwavelength dielectric grating is presented. Using rigorous coupled-wave theory and matrix LU decomposition, the Rayleigh anomaly and the effects of the grave depth, the duty cycle, the incident angle and the incident wavelength on the diffraction efficiency were investigated. The results show that at the incident wave length of 1 550 nm, the grating period of l0/2, the Rayleigh incident angle of 30°, the grave depth of 0.9l0 and the duty cycle of 0.5, using Rayleigh anomaly the TE polarization and TM polarization diffraction efficiency of 0-order reached nearly 100% at the same time.
A novel approach to the design of the polarizing beam splitters based on the subwavelength dielectric grating is presented. Using rigorous coupled-wave theory and matrix LU decomposition, the Rayleigh anomaly and the effects of the grave depth, the duty cycle, the incident angle and the incident wavelength on the diffraction efficiency were investigated. The results show that at the incident wave length of 1 550 nm, the grating period of l0/2, the Rayleigh incident angle of 30°, the grave depth of 0.9l0 and the duty cycle of 0.5, using Rayleigh anomaly the TE polarization and TM polarization diffraction efficiency of 0-order reached nearly 100% at the same time.
2008,
20.
Abstract:
Nonlinearity of the sweep circuit of streak camera distorts the time and intensity information of the streak image. In order to make the streak image closer to the actual object and to improve the measuring precision, this paper presents a correction algorithm based on image processing. It fits the sweep time curve based on the nominal sweep time to obtain the sweep time of each channel, and chooses the mean value of the sweep time as a criterion. According to the numerical relation between the criterion and the sweep time of each channel, the position and intensity of each pixel are corrected. The result indicates that this algorithm can reduce the nonlinearity to less than 2% from the original 8%.
Nonlinearity of the sweep circuit of streak camera distorts the time and intensity information of the streak image. In order to make the streak image closer to the actual object and to improve the measuring precision, this paper presents a correction algorithm based on image processing. It fits the sweep time curve based on the nominal sweep time to obtain the sweep time of each channel, and chooses the mean value of the sweep time as a criterion. According to the numerical relation between the criterion and the sweep time of each channel, the position and intensity of each pixel are corrected. The result indicates that this algorithm can reduce the nonlinearity to less than 2% from the original 8%.
2008,
20.
Abstract:
To study the starting characteristic of directly drained CW DF/HF chemical laser(DDCL), a double-nozzle small-scale device of DDCL gas channel was set up, and a series of experiments were conducted with different stagnation pressure of secondary flow. The effect of stagnation pressure in secondary flow on the starting characteristic was studied, and the experimental results show that greater stagnation pressure of secondary flow results in lower starting pressure of experimental device, the starting pressure without secondary flow is obviously higher than that with secondary flow, thus it is helpful to start DDCL with combustor flow. An theoretical model from the entrance of nozzles to the exit of diffuser is constructed by using one-dimension method. The change law of the starting pressur
To study the starting characteristic of directly drained CW DF/HF chemical laser(DDCL), a double-nozzle small-scale device of DDCL gas channel was set up, and a series of experiments were conducted with different stagnation pressure of secondary flow. The effect of stagnation pressure in secondary flow on the starting characteristic was studied, and the experimental results show that greater stagnation pressure of secondary flow results in lower starting pressure of experimental device, the starting pressure without secondary flow is obviously higher than that with secondary flow, thus it is helpful to start DDCL with combustor flow. An theoretical model from the entrance of nozzles to the exit of diffuser is constructed by using one-dimension method. The change law of the starting pressur
2008,
20.
Abstract:
The character and alignment demand of laser optical path were analyzed, and a method of fast adjustment and alignment of optical path by using visible light source and glass grid was given. The adjustment process and the problem in operating wereexampled by Pre-amplifier diagnostic module of prototype facility, and the adjustment and alignment error was calculated and checked by using a collimeter. Result shows the lens axle alignment error is less than 0.07 mm in radius and less than 25″ in direction.
The character and alignment demand of laser optical path were analyzed, and a method of fast adjustment and alignment of optical path by using visible light source and glass grid was given. The adjustment process and the problem in operating wereexampled by Pre-amplifier diagnostic module of prototype facility, and the adjustment and alignment error was calculated and checked by using a collimeter. Result shows the lens axle alignment error is less than 0.07 mm in radius and less than 25″ in direction.
2008,
20.
Abstract:
Ta2O5-TiO2 composite aerogels were successfully prepared from titanium n-butoxide and tantalum ethylate dissolved in ethanol by sol-gel process and supercritical drying technique and the structural properties and ingredient of the aerogel samples were characterized by means of BET，SEM，TEM and EDS.The results indicate that the final aerogels (density of about 90 mg/cm3 and specific surface area of 492.9 m2/g) consist of hydroxyl oxide colloidal particles in nanometer and the pore size distribution is mostly in the range of 5~15 nm.
Ta2O5-TiO2 composite aerogels were successfully prepared from titanium n-butoxide and tantalum ethylate dissolved in ethanol by sol-gel process and supercritical drying technique and the structural properties and ingredient of the aerogel samples were characterized by means of BET，SEM，TEM and EDS.The results indicate that the final aerogels (density of about 90 mg/cm3 and specific surface area of 492.9 m2/g) consist of hydroxyl oxide colloidal particles in nanometer and the pore size distribution is mostly in the range of 5~15 nm.
2008,
20.
Abstract:
Proton generation and angular distribution produced by supershort laser pulse irradiating thin solid Au target were investigated. The experiment was performed on the SILEX-Ⅰ laser facility. CR39 was mounted 3.3 cm behind the target to record the protons from the target. How the laser intensity and laser contrast ratio influenced the mechanism of proton acceleration was studied by analysing the proton angular distributions. The primary acceleration mechanism of proton is sensitive to the prepulse. When the prepulse is weak, the primary proton acceleration is target normal sheath acceleration. When the prepulse is strong, most protons is primarily accelerated in the front of target.
Proton generation and angular distribution produced by supershort laser pulse irradiating thin solid Au target were investigated. The experiment was performed on the SILEX-Ⅰ laser facility. CR39 was mounted 3.3 cm behind the target to record the protons from the target. How the laser intensity and laser contrast ratio influenced the mechanism of proton acceleration was studied by analysing the proton angular distributions. The primary acceleration mechanism of proton is sensitive to the prepulse. When the prepulse is weak, the primary proton acceleration is target normal sheath acceleration. When the prepulse is strong, most protons is primarily accelerated in the front of target.
2008,
20.
Abstract:
S∶1, 1∶1 and R∶1 laser damage tests for fused silica were performed under different gas atmosphere (air, O2, N2) and pressures (10-3~105 Pa) with 351 nm Nd:YLF laser. The results show that laser-induced damage threshold(LIDT) via 1∶1 and S∶1 tests are almost the same in different gas atmosphere and pressures. The LIDT via R∶1 tests are more liable to pressure than gas atmosphere. The R∶1 threshold of fused silica under pressures lower than 103 Pa decrease by 28%~41% compared with that at 105 Pa. Under equal pressure but different gas atmosphere the R∶1 threshold has less than 10% deviation, which is within the measurement error. The multi-pulse irradiation resistant property for different gas atmosphere and pressures were also studied under irradiation of half of the damage thresho
S∶1, 1∶1 and R∶1 laser damage tests for fused silica were performed under different gas atmosphere (air, O2, N2) and pressures (10-3~105 Pa) with 351 nm Nd:YLF laser. The results show that laser-induced damage threshold(LIDT) via 1∶1 and S∶1 tests are almost the same in different gas atmosphere and pressures. The LIDT via R∶1 tests are more liable to pressure than gas atmosphere. The R∶1 threshold of fused silica under pressures lower than 103 Pa decrease by 28%~41% compared with that at 105 Pa. Under equal pressure but different gas atmosphere the R∶1 threshold has less than 10% deviation, which is within the measurement error. The multi-pulse irradiation resistant property for different gas atmosphere and pressures were also studied under irradiation of half of the damage thresho
2008,
20.
Abstract:
The edge effects would happen when a workpiece extends beyond a polishing tool, which could lead to low polishing efficiency. So a new skin model, representing the nonlinear pressure distribution, was proposed to avoid the negative pressure and to calculate the amount of removed materials for the case of a circular tool that polishes a circular workpiece. A material removal amount model was established considering workpiece radius, workpiece-tool center distance and speed ratio. Its simulations show that good surface figures could be achieved by choosing proper values for the latter two parameters based on that model.
The edge effects would happen when a workpiece extends beyond a polishing tool, which could lead to low polishing efficiency. So a new skin model, representing the nonlinear pressure distribution, was proposed to avoid the negative pressure and to calculate the amount of removed materials for the case of a circular tool that polishes a circular workpiece. A material removal amount model was established considering workpiece radius, workpiece-tool center distance and speed ratio. Its simulations show that good surface figures could be achieved by choosing proper values for the latter two parameters based on that model.
2008,
20.
Abstract:
In order to meet the requirement of symmetry tuning and measurement in implosion experiment, a image processing method has been adopted. This method is based on Legendre fitting, with the theory of radiation drive symmetry，which help the analysis of compressed core image. Through a series of data analysis, a detailed comparison of two methods has been processed. The results show the error of the new method is smaller than that of the current applied image processing method, and the new methodcan get more high modes details (neglected in the past).
In order to meet the requirement of symmetry tuning and measurement in implosion experiment, a image processing method has been adopted. This method is based on Legendre fitting, with the theory of radiation drive symmetry，which help the analysis of compressed core image. Through a series of data analysis, a detailed comparison of two methods has been processed. The results show the error of the new method is smaller than that of the current applied image processing method, and the new methodcan get more high modes details (neglected in the past).
2008,
20.
Abstract:
The stimulated backward Raman scattering generated by femosecond laser interaction with gas target was measured. In the condition of experiment, the stimulated Raman backscatter(SRS) is in the strongly coupled mode, and several nonlinear Stokes satellite peaks appeare in the scattering spectrum. The frequency space of Stokes peaks is smaller than the plasma wave frequency. The plasma density range of laser interaction with gas target deduced from backward SRS is 5×1018 cm-3. These results are consistent with the prediction of a strongly coupled Raman theory．
The stimulated backward Raman scattering generated by femosecond laser interaction with gas target was measured. In the condition of experiment, the stimulated Raman backscatter(SRS) is in the strongly coupled mode, and several nonlinear Stokes satellite peaks appeare in the scattering spectrum. The frequency space of Stokes peaks is smaller than the plasma wave frequency. The plasma density range of laser interaction with gas target deduced from backward SRS is 5×1018 cm-3. These results are consistent with the prediction of a strongly coupled Raman theory．
2008,
20.
Abstract:
Based on the nonlinear dispersion relation of electromagnetic wave in relativistic plasma, the nonlinear controlling equation for linearly polarized mode is obtained using Karpman’s method. The modulation instability of intense laser pulse propagating through relativistic plasma is analyzed and the modulation instability growth rate as a function of perturbation wave number for laser beam propagating through relativistic plasma is given.
Based on the nonlinear dispersion relation of electromagnetic wave in relativistic plasma, the nonlinear controlling equation for linearly polarized mode is obtained using Karpman’s method. The modulation instability of intense laser pulse propagating through relativistic plasma is analyzed and the modulation instability growth rate as a function of perturbation wave number for laser beam propagating through relativistic plasma is given.
2008,
20.
Abstract:
HEM11 mode in a transverse deflecting structure was simulated, analyzed and compared with TM01 mode. A prototype of this deflecting structure has been made, whose transverse field distribution is simulated with Ansoft HFSS. Perturbation method is used to measure the transverse field distribution with six cavities. The test results accord with the simulated ones. Dispersion curve is also simulated with Ansoft HFSS and it is consistent with the measured one. The equivalent circuit model of the deflector is given. The intercell coupling factors are calculated and the measured results accord with the simulated ones.
HEM11 mode in a transverse deflecting structure was simulated, analyzed and compared with TM01 mode. A prototype of this deflecting structure has been made, whose transverse field distribution is simulated with Ansoft HFSS. Perturbation method is used to measure the transverse field distribution with six cavities. The test results accord with the simulated ones. Dispersion curve is also simulated with Ansoft HFSS and it is consistent with the measured one. The equivalent circuit model of the deflector is given. The intercell coupling factors are calculated and the measured results accord with the simulated ones.
2008,
20.
Abstract:
Using external longitudinal magnetic-field to guide dual-beam out of the dual-shift tubes is a key step for the practicality of synchronizing dual-beam produced by a single accelerator. On the basis of the simulation of the confining magnetic-field for the solid dual-beam, the experiment of magnetic-field guiding annular dual-beam was presented. When the diode voltage was 380 kV, dual-beam currents of 5.10 kA and 4.92 kA were obtained. The experimental results indicate that the designed magnetic-field system could confine the annular dual-beam effectively, and the critical confining magnetic-field is about 0.5 T．
Using external longitudinal magnetic-field to guide dual-beam out of the dual-shift tubes is a key step for the practicality of synchronizing dual-beam produced by a single accelerator. On the basis of the simulation of the confining magnetic-field for the solid dual-beam, the experiment of magnetic-field guiding annular dual-beam was presented. When the diode voltage was 380 kV, dual-beam currents of 5.10 kA and 4.92 kA were obtained. The experimental results indicate that the designed magnetic-field system could confine the annular dual-beam effectively, and the critical confining magnetic-field is about 0.5 T．
2008,
20.
Abstract:
The optimized simulation result of a C-band 16-element single-layered radial line helical square array antenna is presented and the experiment researches are developed for an antenna fabricated according to simulated structure. During experiment research, an impedance converter is designed to connect standard port with antenna port, and the method of comparing with standard linearly polarized antenna is used to measure antenna circularly polarized gain. The experiment result shows that, in the range of 3.8 GHz to 4.2 GHz, antenna gain is over 17 dB, aperture efficiency is over 74%, axial ratio is below 1.3 dB and antenna VSWR is below 1.2. It shows a good agreement with simulation result．
The optimized simulation result of a C-band 16-element single-layered radial line helical square array antenna is presented and the experiment researches are developed for an antenna fabricated according to simulated structure. During experiment research, an impedance converter is designed to connect standard port with antenna port, and the method of comparing with standard linearly polarized antenna is used to measure antenna circularly polarized gain. The experiment result shows that, in the range of 3.8 GHz to 4.2 GHz, antenna gain is over 17 dB, aperture efficiency is over 74%, axial ratio is below 1.3 dB and antenna VSWR is below 1.2. It shows a good agreement with simulation result．
2008,
20.
Abstract:
The transmission line method(TLM) is extended to include higher-order transverse electric(TE) cavity modes which are introduced by aperture coupling and the extended TLM is used to analyze the shielding effectiveness(SE) of double layer rectangular enclosure with apertures to the wide band electromagnetic pulse. The electric SE of single layer with an aperture is compared with that of double layer with apertures. The simulation results show that SE can be improved greatly with double layer shielding and it is worse on the resonance frequency of cavity modes. On the condition of aperture-cavity resonance, SE drops significantly in the center of the inner cavity. From 0.1 GHz to 4.5 GHz, SE has a declining trend as a whole.
The transmission line method(TLM) is extended to include higher-order transverse electric(TE) cavity modes which are introduced by aperture coupling and the extended TLM is used to analyze the shielding effectiveness(SE) of double layer rectangular enclosure with apertures to the wide band electromagnetic pulse. The electric SE of single layer with an aperture is compared with that of double layer with apertures. The simulation results show that SE can be improved greatly with double layer shielding and it is worse on the resonance frequency of cavity modes. On the condition of aperture-cavity resonance, SE drops significantly in the center of the inner cavity. From 0.1 GHz to 4.5 GHz, SE has a declining trend as a whole.
2008,
20.
Abstract:
The quasi-optical mode converter consists of a ripple-wall waveguide launcher, a quasi-elliptical mirror and two toroidal mirrors.The wave beam in the launcher can be described by geometric optics. the coupled-mode theory has been used to analyze the operation of the prebunching waveguide launcher. 170 GHz TE22,6 mode was transform into 8 sattlite modes by the ripple-wall waveguide, and a quasi-Gaussian field was obtained by superposition of the main mode and satelite modes. Then the radiation was launched from the prebunching section by cutting the waveguide wall around a gaussian bundle.The launcher length is less than 150 mm, and the quasi-Gaussian bundle can be used directly.
The quasi-optical mode converter consists of a ripple-wall waveguide launcher, a quasi-elliptical mirror and two toroidal mirrors.The wave beam in the launcher can be described by geometric optics. the coupled-mode theory has been used to analyze the operation of the prebunching waveguide launcher. 170 GHz TE22,6 mode was transform into 8 sattlite modes by the ripple-wall waveguide, and a quasi-Gaussian field was obtained by superposition of the main mode and satelite modes. Then the radiation was launched from the prebunching section by cutting the waveguide wall around a gaussian bundle.The launcher length is less than 150 mm, and the quasi-Gaussian bundle can be used directly.
2008,
20.
Abstract:
The eigenfrequency and the characteristic impedance of π-TM high order mode of rectangular double-gap cavity with a coupling slot in the center are calculated by analytic method. The influence of sizes and the position of the coupling slot on the frequency and the characteristic impedance of π-TM mode are discussed. The results of the analytic calculation are compared with ISFEL3D simulation results, and it is shown that the analytic results are consistent with the simulation results on the whole, especially for the TM310 mode. Our research shows that the width of the coupling wall in double gap cavity has little influence, while the position and the sizes of the coupling slot have strong influence on the frequency and the characteristic impedance of π-TM modes. Meanwhile, it is found
The eigenfrequency and the characteristic impedance of π-TM high order mode of rectangular double-gap cavity with a coupling slot in the center are calculated by analytic method. The influence of sizes and the position of the coupling slot on the frequency and the characteristic impedance of π-TM mode are discussed. The results of the analytic calculation are compared with ISFEL3D simulation results, and it is shown that the analytic results are consistent with the simulation results on the whole, especially for the TM310 mode. Our research shows that the width of the coupling wall in double gap cavity has little influence, while the position and the sizes of the coupling slot have strong influence on the frequency and the characteristic impedance of π-TM modes. Meanwhile, it is found
2008,
20.
Abstract:
The analytic expression of high order mode electronic conductance model in double gap coupling multi-beam klystron(MBK) cavity is presented. The oscillations of high order modes were studied by the model and field structures have been simulated with electromagnetic field software ISFEL3D. It is shown that there are self-excitation modes 2.9 GHz and 3.89 GHz in the double gap coupling MBK cavity, which is verified by the three-dimensional PIC simulation. In addition, the corresponding self-excitation modes’ frequencies are also given with the temperature increase of the absorbing cavity and coupling ring by the analysis of experimental results.
The analytic expression of high order mode electronic conductance model in double gap coupling multi-beam klystron(MBK) cavity is presented. The oscillations of high order modes were studied by the model and field structures have been simulated with electromagnetic field software ISFEL3D. It is shown that there are self-excitation modes 2.9 GHz and 3.89 GHz in the double gap coupling MBK cavity, which is verified by the three-dimensional PIC simulation. In addition, the corresponding self-excitation modes’ frequencies are also given with the temperature increase of the absorbing cavity and coupling ring by the analysis of experimental results.
2008,
20.
Abstract:
It was found that the pressure-current curves were linear in electron ring, while non-linear in positron ring, especially in arc sections of positron ring. It might be since that the synchrotron photoelectrons transversely kicked by the positron beam bunches hit the vacuum chamber surface and the hit produces secondary electrons, which cause beam-induced multipacting(BIM) and large outgassing under some conditions. To find these conditions, bunch filling patterns of positron beams were changed to derive the corresponding non-linear pressure-current curves. The result is consistent with that from KEK-B low energy ring, which shows the non-linearity exhibits a threshold behavior. The non-linearity will take place only when the single bunch current and the quantity of the successive bunch in
It was found that the pressure-current curves were linear in electron ring, while non-linear in positron ring, especially in arc sections of positron ring. It might be since that the synchrotron photoelectrons transversely kicked by the positron beam bunches hit the vacuum chamber surface and the hit produces secondary electrons, which cause beam-induced multipacting(BIM) and large outgassing under some conditions. To find these conditions, bunch filling patterns of positron beams were changed to derive the corresponding non-linear pressure-current curves. The result is consistent with that from KEK-B low energy ring, which shows the non-linearity exhibits a threshold behavior. The non-linearity will take place only when the single bunch current and the quantity of the successive bunch in
2008,
20.
Abstract:
As a new RF generator, the direct digital synthesizer(DDS) has been widely used. In order to reduce the high cost of the signal generator comprising a high performance DDS device, the method of picking-up a desired aliased signal DDS output is adopted in the design. A device of AD9850 is used to generate RF signal in the system, and the amplitude modulation of the system is achieved by using a voltage variable attenuator.The amplifier based on tetrode is selected to get an output power of 10kW at (96±1) MHz. Amplifier operates in a grounded cathode configuration. A short-circuited coaxial transmission line is adopted in both input circuit and output circuit. The PID-control strategy has been used in control system ,and the relay method has been used for measurement. The controller has a b
As a new RF generator, the direct digital synthesizer(DDS) has been widely used. In order to reduce the high cost of the signal generator comprising a high performance DDS device, the method of picking-up a desired aliased signal DDS output is adopted in the design. A device of AD9850 is used to generate RF signal in the system, and the amplitude modulation of the system is achieved by using a voltage variable attenuator.The amplifier based on tetrode is selected to get an output power of 10kW at (96±1) MHz. Amplifier operates in a grounded cathode configuration. A short-circuited coaxial transmission line is adopted in both input circuit and output circuit. The PID-control strategy has been used in control system ,and the relay method has been used for measurement. The controller has a b
2008,
20.
Abstract:
Magnetic-field power-supply controlling system needs to update wave-data in time for the Heavy lon Research Facility at Lanzhou Cooler Storage Ring. So a software for the system with data-driven pattern was designed and optimized adopting the TMS320C6713 chip as the central processor, based on FPGA logic programming and double-FIFO data cache technique. The Aifken algorithm is used to process the updated wave-data and reduce the primitive wave-data’s size to 1/1024, which improves the data transmission and storage efficiency. Practice shows that the system works stably and reliably and can meet the power supply control’s request.
Magnetic-field power-supply controlling system needs to update wave-data in time for the Heavy lon Research Facility at Lanzhou Cooler Storage Ring. So a software for the system with data-driven pattern was designed and optimized adopting the TMS320C6713 chip as the central processor, based on FPGA logic programming and double-FIFO data cache technique. The Aifken algorithm is used to process the updated wave-data and reduce the primitive wave-data’s size to 1/1024, which improves the data transmission and storage efficiency. Practice shows that the system works stably and reliably and can meet the power supply control’s request.
2008,
20.
Abstract:
A scanning motion control system was developed for the high-energy X-ray industrial computerized tomography (CT). The system consists of an industrial control computer, a counter card, a control card, servo drivers, servo motors, working platforms, gratings and control software. Based on windows driver model(WDM) mode, the composition of the driver program for the system was studied. Took the motor control card as an example, the method to develop the driver program was researched, and the intercourse process between the device driver program and the user-program was analyzed. The real-time control of the system was implemented using the WDM driver. The real-time performance and reliability of the system can satisfy the requirement of high-energy X-ray industrial CT．
A scanning motion control system was developed for the high-energy X-ray industrial computerized tomography (CT). The system consists of an industrial control computer, a counter card, a control card, servo drivers, servo motors, working platforms, gratings and control software. Based on windows driver model(WDM) mode, the composition of the driver program for the system was studied. Took the motor control card as an example, the method to develop the driver program was researched, and the intercourse process between the device driver program and the user-program was analyzed. The real-time control of the system was implemented using the WDM driver. The real-time performance and reliability of the system can satisfy the requirement of high-energy X-ray industrial CT．
2008,
20.
Abstract:
The general property of space charge dominated beam behavior is that a beam with an initial non-linear profile tends to become more uniform and this process is associated with strong emittance and the appearance of beam halo which are the potential sources of beam loss in high intensity accelerators. To simulate the beam behavior, a general particle tracking code including space charge effect was implemented using C++ language. Based on the classical PIC method, this code employs the boundary element method as the Poisson solver to compute space charge force with non-equidistant multi-grid. The comparison of simulative and analytical results of the beam distribution in free space shows good consistency. Finally, the simulative result of an injection beam line is presented. The computation
The general property of space charge dominated beam behavior is that a beam with an initial non-linear profile tends to become more uniform and this process is associated with strong emittance and the appearance of beam halo which are the potential sources of beam loss in high intensity accelerators. To simulate the beam behavior, a general particle tracking code including space charge effect was implemented using C++ language. Based on the classical PIC method, this code employs the boundary element method as the Poisson solver to compute space charge force with non-equidistant multi-grid. The comparison of simulative and analytical results of the beam distribution in free space shows good consistency. Finally, the simulative result of an injection beam line is presented. The computation
2008,
20.
Abstract:
Temperature induced phase transition model was brought forward in this paper. ZrO2 and YSZ thin films were prepared by electron-beam evaporation method and their laser induced damage thresholds(LIDT) were measured; Moreover, structure of ZrO2 and YSZ coating materials and thin films was tested by X-ray diffraction. These results indicate that ZrO2 coating material and thin films are monoclinic phase and YSZ coating material and thin films are cubic phase; LIDT of 7% and 13% mole fraction YSZ thin film are 18.7 J/cm2 and 19.4 J/cm2 respectively which is higher than that of ZrO2 thin film 12.2 J/cm2. The reason is that ZrO2 material is prone to lace phase transition and defects, during the course of evaporation while YSZ material is not. The defects would become absorptive centers and initia
Temperature induced phase transition model was brought forward in this paper. ZrO2 and YSZ thin films were prepared by electron-beam evaporation method and their laser induced damage thresholds(LIDT) were measured; Moreover, structure of ZrO2 and YSZ coating materials and thin films was tested by X-ray diffraction. These results indicate that ZrO2 coating material and thin films are monoclinic phase and YSZ coating material and thin films are cubic phase; LIDT of 7% and 13% mole fraction YSZ thin film are 18.7 J/cm2 and 19.4 J/cm2 respectively which is higher than that of ZrO2 thin film 12.2 J/cm2. The reason is that ZrO2 material is prone to lace phase transition and defects, during the course of evaporation while YSZ material is not. The defects would become absorptive centers and initia
2008,
20.
Abstract:
The influence of nonlinear refraction in a medium on the in-line holographic imaging of the particle was investigated theoretically and experimentally. According to the in-line Fraunhofer holographic imaging of the particle and nonlinear paraxial wave equation, the complex amplitude and intensity of the diffracted field in the holographic plate were derived. The hologram transferred from the linear and nonlinear medium were also studied numerically and experimentally. The results indicate that the hologram transferred from the nonlinear medium was different to that from the linear medium. As the medium is disrupted easily by high-power pulsed laser,this phenomenon is a reference to the application of the high-power pulsed laser.
The influence of nonlinear refraction in a medium on the in-line holographic imaging of the particle was investigated theoretically and experimentally. According to the in-line Fraunhofer holographic imaging of the particle and nonlinear paraxial wave equation, the complex amplitude and intensity of the diffracted field in the holographic plate were derived. The hologram transferred from the linear and nonlinear medium were also studied numerically and experimentally. The results indicate that the hologram transferred from the nonlinear medium was different to that from the linear medium. As the medium is disrupted easily by high-power pulsed laser,this phenomenon is a reference to the application of the high-power pulsed laser.
2008,
20.
Abstract:
The wavelengths and weighted oscillator strengths for S8+-S13+ ions were systematically studied by using the relativistic Hartree-Fock method with configuration interaction. Comparison of the available experiment and theoretical calculations were carried out. It is found that the purities of S8+-S11+ states are very high in LS coupling scheme. As the ion charge increases, the levels of the S12+-S13+ atomic states begin to mix, and the effect of configuration interaction (CI) becomes important. Thirty-two spectral lines from 16.8 nm to 45.0 nm are identified, most of which arise from the transitions among the levels of the 2s22pk, 2s2pk+1 and 2pk+2(k=0,1,2,3,4) of S8+-S13+ ions by analyzing the results of the experiment. Most of the absolute error between the calculated results and the expe
The wavelengths and weighted oscillator strengths for S8+-S13+ ions were systematically studied by using the relativistic Hartree-Fock method with configuration interaction. Comparison of the available experiment and theoretical calculations were carried out. It is found that the purities of S8+-S11+ states are very high in LS coupling scheme. As the ion charge increases, the levels of the S12+-S13+ atomic states begin to mix, and the effect of configuration interaction (CI) becomes important. Thirty-two spectral lines from 16.8 nm to 45.0 nm are identified, most of which arise from the transitions among the levels of the 2s22pk, 2s2pk+1 and 2pk+2(k=0,1,2,3,4) of S8+-S13+ ions by analyzing the results of the experiment. Most of the absolute error between the calculated results and the expe
2008,
20.
Abstract:
Electron with an appropriate initial velocity injected into an oncoming, ultra-intense circularly polarized laser pulse will execute circular relativistic motion at the peak of laser pulse. The circulating electron then radiates in the same manner as that in the storage ring of a conventional synchrotron source. Owing to the extremely small orbit radius, the laser-field synchrotron radiation thus generated is an attosecond or zeptosecond X-ray pulse. The pulse width of the scattered radiation decreases and the power of the scattered radiation increases with increasing the intensity of the laser pulse and the electron’s initial energy. The unique feature makes the laser-field synchrotron radiation a promising synchrotron radiation source with short wavelength and short duration.
Electron with an appropriate initial velocity injected into an oncoming, ultra-intense circularly polarized laser pulse will execute circular relativistic motion at the peak of laser pulse. The circulating electron then radiates in the same manner as that in the storage ring of a conventional synchrotron source. Owing to the extremely small orbit radius, the laser-field synchrotron radiation thus generated is an attosecond or zeptosecond X-ray pulse. The pulse width of the scattered radiation decreases and the power of the scattered radiation increases with increasing the intensity of the laser pulse and the electron’s initial energy. The unique feature makes the laser-field synchrotron radiation a promising synchrotron radiation source with short wavelength and short duration.
2008,
20.
Abstract:
Al-Cu-Fe thin films were successfully deposited by magnetron co-sputtering. The substrates were pure Al, pure Cu in polished state and the stainless steel with different surface roughness. The surface morphologies of the films were observed by Atomic Force Microscopy(AFM). The element compositions of the films were analyzed by Energy Dispersive Spectrum(EDS), and the bond strength and friction coefficient of the films were determined by nanoindentation (MTS systems). The results showed that the bond strength of the film for the stainless steel substrate was the biggest. The friction coefficient of the film with pure Cu substrate was 0.17, while the other films were not more than 0.03. The surface morphology of films was related with the initial surface morphology of the substrates. The sm
Al-Cu-Fe thin films were successfully deposited by magnetron co-sputtering. The substrates were pure Al, pure Cu in polished state and the stainless steel with different surface roughness. The surface morphologies of the films were observed by Atomic Force Microscopy(AFM). The element compositions of the films were analyzed by Energy Dispersive Spectrum(EDS), and the bond strength and friction coefficient of the films were determined by nanoindentation (MTS systems). The results showed that the bond strength of the film for the stainless steel substrate was the biggest. The friction coefficient of the film with pure Cu substrate was 0.17, while the other films were not more than 0.03. The surface morphology of films was related with the initial surface morphology of the substrates. The sm
2008,
20.
Abstract:
The preparation,characterization and application of nanocrystalline diamond films have become a new “hot point” in the development of diamond films prepared by chemical vapor deposition. The preparation process of nanocrystalline diamond films with MPCVD method was introduced, as well as the result of surfaces analysis.Then an experiment device is designed to measure the Secondary electron emission coefficient(ＳＥＥＣ) in reflection mode.An expectable aim(ＳＥＥＣ is 15) has been achieved．
The preparation,characterization and application of nanocrystalline diamond films have become a new “hot point” in the development of diamond films prepared by chemical vapor deposition. The preparation process of nanocrystalline diamond films with MPCVD method was introduced, as well as the result of surfaces analysis.Then an experiment device is designed to measure the Secondary electron emission coefficient(ＳＥＥＣ) in reflection mode.An expectable aim(ＳＥＥＣ is 15) has been achieved．
2008,
20.
Abstract:
Numerical analysis was carried out based on the intrinsic breakdown model and the electro-mechanical breakdown model. The self-breakdown voltage characteristic of the polyester foil was measured in a plane-plane electrode arrangement with DC voltage. The thickness of the polyester foil varied among 9, 12, 15 and 18 μm. Experimental results show the average strength of the polyester foil. The comparison between the theoretical analysis and the experimental results was presented. The results show that the critical breakdown strength of the polyester foil in the intrinsic breakdown model is far lower than the experimental results, and the critical breakdown strength of the polyester foil in the electro-mechanical breakdown model is higher than the experimental data of the polyester foil.
Numerical analysis was carried out based on the intrinsic breakdown model and the electro-mechanical breakdown model. The self-breakdown voltage characteristic of the polyester foil was measured in a plane-plane electrode arrangement with DC voltage. The thickness of the polyester foil varied among 9, 12, 15 and 18 μm. Experimental results show the average strength of the polyester foil. The comparison between the theoretical analysis and the experimental results was presented. The results show that the critical breakdown strength of the polyester foil in the intrinsic breakdown model is far lower than the experimental results, and the critical breakdown strength of the polyester foil in the electro-mechanical breakdown model is higher than the experimental data of the polyester foil.
2008,
20.
Abstract:
For the need of intense current electron accelerator, a high voltage, long-life gas spark switch was designed. Anti-pollution design is used in the switch, the outer housing of the switch is made of Cu and a metal baffle is used to prevent the top plate from pollution. These measures can prevent arc form approaching the insulated bracket as far as possible and increase the life of the switch. And the electrode structure is optimized with electromagnetic simulation software. The experimental results indicate that the operating voltage is 32~42 kV and charge transfer is about 0.38~0.48 C per pulse at 0.1~0.2 MPa pressure, and the switch works stably and reliably.
For the need of intense current electron accelerator, a high voltage, long-life gas spark switch was designed. Anti-pollution design is used in the switch, the outer housing of the switch is made of Cu and a metal baffle is used to prevent the top plate from pollution. These measures can prevent arc form approaching the insulated bracket as far as possible and increase the life of the switch. And the electrode structure is optimized with electromagnetic simulation software. The experimental results indicate that the operating voltage is 32~42 kV and charge transfer is about 0.38~0.48 C per pulse at 0.1~0.2 MPa pressure, and the switch works stably and reliably.
2008,
20.
Abstract:
This paper introduces the design and experimental study of the primary energy source of an accelerator which can produce high power pulses (up to GW level) of duration about 6 ns, and repetition rate controllable from 1 to 300 Hz. The primary energy source is powered by a commercial three-phase AC power supply, rectified by semiconductor devices, and resonantly charges the Tesla transformer controlled by solid switches and relays. The experimental results indicate that this system can produce repetitive high voltage pulses (up to 300 kV) at a 120 Ω load through the Tesla transformer and operates stably. Meanwhile, this source takes the advantage of self-shutoff of the thyristors to realize energy recovery.
This paper introduces the design and experimental study of the primary energy source of an accelerator which can produce high power pulses (up to GW level) of duration about 6 ns, and repetition rate controllable from 1 to 300 Hz. The primary energy source is powered by a commercial three-phase AC power supply, rectified by semiconductor devices, and resonantly charges the Tesla transformer controlled by solid switches and relays. The experimental results indicate that this system can produce repetitive high voltage pulses (up to 300 kV) at a 120 Ω load through the Tesla transformer and operates stably. Meanwhile, this source takes the advantage of self-shutoff of the thyristors to realize energy recovery.
