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RSS2009 Vol. 21, No. 03
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2009,
21.
Abstract:
The deflection-scan subsystem of the femtosecond electron diffraction system was theoretically studied and an exact solution of the deflection distance was got. The numerical calculations under relativistic correction and non-relativistic correction show that the difference of the deflection distances is about 61.4 mm, and the difference of the electron pulse widths is about 65 fs. The result can be useful for the design of the subsystem and the test of the time resolution of the ultra-fast electron diffraction system, especially for the synchronization process of the test.
The deflection-scan subsystem of the femtosecond electron diffraction system was theoretically studied and an exact solution of the deflection distance was got. The numerical calculations under relativistic correction and non-relativistic correction show that the difference of the deflection distances is about 61.4 mm, and the difference of the electron pulse widths is about 65 fs. The result can be useful for the design of the subsystem and the test of the time resolution of the ultra-fast electron diffraction system, especially for the synchronization process of the test.
2009,
21.
Abstract:
The “defects” on optics is the main limiting factor in enhancing the power of a high power solid-state laser system. This paper established a “defects” model about amplitude modulation based on statistics. Aimed at the booster of SG-Ⅲ prototype, the relationship between characteristic parameters of the model and the near-field quality of the beam was studied. The results show that, both the increase of total density of “defects” and the decrease of power exponent can cause the degradation of beam quality; for median-high frequency, different total densities of “defects” have approximately equal effects, while the effects of different power exponents vary; the larger “defects” can lead to more serious degradation of beam quality; for the booster, it is necessary to control the to
The “defects” on optics is the main limiting factor in enhancing the power of a high power solid-state laser system. This paper established a “defects” model about amplitude modulation based on statistics. Aimed at the booster of SG-Ⅲ prototype, the relationship between characteristic parameters of the model and the near-field quality of the beam was studied. The results show that, both the increase of total density of “defects” and the decrease of power exponent can cause the degradation of beam quality; for median-high frequency, different total densities of “defects” have approximately equal effects, while the effects of different power exponents vary; the larger “defects” can lead to more serious degradation of beam quality; for the booster, it is necessary to control the to
2009,
21.
Abstract:
To study the effect of diffuser throat length on the starting characteristic of the directly drained CW DF/HF chemical laser(DDCL), a double-nozzle small-scale model of the DDCL gas channel was built up. A series of experiments without a secondary flow was conducted with diffusers whose throat lengths were different, and the starting and operating pressures were acquired and considered to be the criterion for judging the length of the diffuser throat. The experimental result indicates that the optimal length of the diffuser throat in the given experimental model is 17 times that of the equivalent diameter.
To study the effect of diffuser throat length on the starting characteristic of the directly drained CW DF/HF chemical laser(DDCL), a double-nozzle small-scale model of the DDCL gas channel was built up. A series of experiments without a secondary flow was conducted with diffusers whose throat lengths were different, and the starting and operating pressures were acquired and considered to be the criterion for judging the length of the diffuser throat. The experimental result indicates that the optimal length of the diffuser throat in the given experimental model is 17 times that of the equivalent diameter.
2009,
21.
Abstract:
Considering material dispersion and tunneling ray, the D.Gloge’s theory formula of time response of multimode step-index fiber is modified. The modified formula is used to calculate the function of time response of 50 m long, 0.2 mm core diameter step-index fiber with scintillator illumination. Results show that it is near a Gaussian distribution with FWHM 3.0 ns, the pulse risetime is more than the falling time and the falling time has a trailing.Time response of scintillator-fiber system is modeled by numerical method, the results of modeling accords with experimental results.
Considering material dispersion and tunneling ray, the D.Gloge’s theory formula of time response of multimode step-index fiber is modified. The modified formula is used to calculate the function of time response of 50 m long, 0.2 mm core diameter step-index fiber with scintillator illumination. Results show that it is near a Gaussian distribution with FWHM 3.0 ns, the pulse risetime is more than the falling time and the falling time has a trailing.Time response of scintillator-fiber system is modeled by numerical method, the results of modeling accords with experimental results.
2009,
21.
Abstract:
For a laser resonator cavitiy using an unstable resonator configuration, experiments have proved that the intracavity perturbation is an important influencing factor for degrading the output energy and the beam quality. The influence on eigenmode properties for passive unstable resonators has been analyzed. The effect of the intracavity astigmatism-tilted perturbation on the mode properties for positive-branch confocal unstable resonators has been calculated numerically by using an iterative method. The phase structure of the output beam is analyzed by adopting the Zernike mode-reconstruction theory; and Zernike aberration coefficients of the first 35 order, integrated relative far-field intensity, and point spread function(PSF) are all obtained. These numerical results illustrate that sma
For a laser resonator cavitiy using an unstable resonator configuration, experiments have proved that the intracavity perturbation is an important influencing factor for degrading the output energy and the beam quality. The influence on eigenmode properties for passive unstable resonators has been analyzed. The effect of the intracavity astigmatism-tilted perturbation on the mode properties for positive-branch confocal unstable resonators has been calculated numerically by using an iterative method. The phase structure of the output beam is analyzed by adopting the Zernike mode-reconstruction theory; and Zernike aberration coefficients of the first 35 order, integrated relative far-field intensity, and point spread function(PSF) are all obtained. These numerical results illustrate that sma
2009,
21.
Abstract:
An optical device with simple structure and low price is developed, which can adjust the laser beam parallel with the telescope axis conveniently and rapidly. The device is mainly composed of two optical wedge planes. The direction of the outgoing laser beam from this device can be changed arbitrarily by turning the two planes through two motors within a certain range, which depends on the wedge angle and the refractive index of the plane material. By using refraction law, the relationship between the rotation angles of two wedge planes and the direction of outgoing laser beam is deduced strictly. A lidar system adjustment is proposed with the device inserted into the transmitting optical path and spiral, circular and radial scans of the out beam, and the criterion and the process for alig
An optical device with simple structure and low price is developed, which can adjust the laser beam parallel with the telescope axis conveniently and rapidly. The device is mainly composed of two optical wedge planes. The direction of the outgoing laser beam from this device can be changed arbitrarily by turning the two planes through two motors within a certain range, which depends on the wedge angle and the refractive index of the plane material. By using refraction law, the relationship between the rotation angles of two wedge planes and the direction of outgoing laser beam is deduced strictly. A lidar system adjustment is proposed with the device inserted into the transmitting optical path and spiral, circular and radial scans of the out beam, and the criterion and the process for alig
2009,
21.
Abstract:
α-C∶H thin films were deposited by low-pressure plasma chemical vapor deposition(LPPCVD) with H2 (99.999 9%) and Trans-2-butene as source gases. The chemical bonds and electronic structure are analyzed by using FTIR and XPS. The ratio of sp3/sp2 and the percentage of sp3 C are also analyzed by using the fitting of Gaussian peak fitting. The results show that the chemical structure and composition of the films change with the pressure, and this films mainly contain sp3C—H bond, which have low pressure and possess less C=C bonds. When the pressure increases, the sp3/sp2 hybrid ratios and the percentage of sp3 bonds increase. The optical properties of a-C∶H films are investigated by UV-VIS spectrum in the range of 400~1 100 nm. The transmission ratios can reach 98% in the visible light
α-C∶H thin films were deposited by low-pressure plasma chemical vapor deposition(LPPCVD) with H2 (99.999 9%) and Trans-2-butene as source gases. The chemical bonds and electronic structure are analyzed by using FTIR and XPS. The ratio of sp3/sp2 and the percentage of sp3 C are also analyzed by using the fitting of Gaussian peak fitting. The results show that the chemical structure and composition of the films change with the pressure, and this films mainly contain sp3C—H bond, which have low pressure and possess less C=C bonds. When the pressure increases, the sp3/sp2 hybrid ratios and the percentage of sp3 bonds increase. The optical properties of a-C∶H films are investigated by UV-VIS spectrum in the range of 400~1 100 nm. The transmission ratios can reach 98% in the visible light
2009,
21.
Abstract:
The effect of the filling gas natural convection in the French Laser Mega Joule(LMJ) hohlraum on the target temperature distribution has been studied with a CFD code (Fluent). In order to reduce the temperature nonuniformity around the target, the division of the hohlraum with polymer membranes has been simulated to obtain the optimum division mode. In combination with the correct temperatures of the two cooling rings with a temperature difference of ±0.5 mK between them, the seven gas-division mode can meet the uniformity requirement of cryogenic target in the inertial confinement fusion.
The effect of the filling gas natural convection in the French Laser Mega Joule(LMJ) hohlraum on the target temperature distribution has been studied with a CFD code (Fluent). In order to reduce the temperature nonuniformity around the target, the division of the hohlraum with polymer membranes has been simulated to obtain the optimum division mode. In combination with the correct temperatures of the two cooling rings with a temperature difference of ±0.5 mK between them, the seven gas-division mode can meet the uniformity requirement of cryogenic target in the inertial confinement fusion.
2009,
21.
Abstract:
The measurement of plasma electron temperature and density in the HL-2A Tokamak using a YAG laser multipoint Thomson scattering system is described. In this system, a standard lamp-monochromator combination is utilized for the calibration of spectral responses. The experimental results of the 6-point electron temperatures and densities around the plasma center are presented during different discharges of plasma with a time resolution of 100 ms and a spatial resolution of 2.2 cm. The total measurement uncertainty of electron temperature are estimated to be ±12%. And the system spatial range of electron temperature measurement is -35 ~ -3 cm.
The measurement of plasma electron temperature and density in the HL-2A Tokamak using a YAG laser multipoint Thomson scattering system is described. In this system, a standard lamp-monochromator combination is utilized for the calibration of spectral responses. The experimental results of the 6-point electron temperatures and densities around the plasma center are presented during different discharges of plasma with a time resolution of 100 ms and a spatial resolution of 2.2 cm. The total measurement uncertainty of electron temperature are estimated to be ±12%. And the system spatial range of electron temperature measurement is -35 ~ -3 cm.
2009,
21.
Abstract:
The image converter tube is a core component in the streak cameras. Its operation was introduced and the model for its internal electronic optical system was built. Numerical simulations were done by ANSYS based on the finite element method, in which the functional is solved by Hamilton principle. The distribution of the electrostatic field was calculated in an operation voltage and the tracks of electrons were calculated in different operation voltages. The results agree well with that of the symmetric electrostatic field theoretical analysis. They also indicate that the size and shape of electrode has a slight influence on imaging, and the proper voltages(containing accelerating, focusing and anode voltages) has more.
The image converter tube is a core component in the streak cameras. Its operation was introduced and the model for its internal electronic optical system was built. Numerical simulations were done by ANSYS based on the finite element method, in which the functional is solved by Hamilton principle. The distribution of the electrostatic field was calculated in an operation voltage and the tracks of electrons were calculated in different operation voltages. The results agree well with that of the symmetric electrostatic field theoretical analysis. They also indicate that the size and shape of electrode has a slight influence on imaging, and the proper voltages(containing accelerating, focusing and anode voltages) has more.
2009,
21.
Abstract:
A KBA X-ray microscope is a non-coaxial grazing incident X-ray imaging system, whose solid angle is small and image quality requirement is high. It requires strict installation of four reflective mirrors. The conventional position or angle measurements, under the space confinement of the ICF target chamber, can not attain enough precision. In order to ensure the image quality, we use a 4″ precision goniometer to control the error of the angle between the bimirror less than 20″. The grazing incident angle has much effect on the imaging quality, therefore, in order to ensure a precision smaller than 10″, we have used our own optical path system. The principal mirror aperture angle of the KBA X-ray microscope is 4×10－6 sr, which can not achieve sharp focusing, thus an auxiliar
A KBA X-ray microscope is a non-coaxial grazing incident X-ray imaging system, whose solid angle is small and image quality requirement is high. It requires strict installation of four reflective mirrors. The conventional position or angle measurements, under the space confinement of the ICF target chamber, can not attain enough precision. In order to ensure the image quality, we use a 4″ precision goniometer to control the error of the angle between the bimirror less than 20″. The grazing incident angle has much effect on the imaging quality, therefore, in order to ensure a precision smaller than 10″, we have used our own optical path system. The principal mirror aperture angle of the KBA X-ray microscope is 4×10－6 sr, which can not achieve sharp focusing, thus an auxiliar
2009,
21.
Abstract:
The deposition capability of nickel on the surface of poly-α-methylstyrene microspheres was improved by combined treatment of ozone aeration and UV irradiation in aqueous ammonia. Surface properties of the treated film were investigated by X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared(FT-TR) measurements. The samples were characterized by SEM. The results indicate that after ultraviolet joint ozone treatment, the surfaces of microspheres were oxidized, and the amine and amide groups are introduced on their surface. The images of SEM show the adhesion between microspheres and nickel-phosphorus films was improved after surface modification. This was attributed to amide which could chemisorb palladium ions to catalyze electroless nickel plating on the pretreated surfac
The deposition capability of nickel on the surface of poly-α-methylstyrene microspheres was improved by combined treatment of ozone aeration and UV irradiation in aqueous ammonia. Surface properties of the treated film were investigated by X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared(FT-TR) measurements. The samples were characterized by SEM. The results indicate that after ultraviolet joint ozone treatment, the surfaces of microspheres were oxidized, and the amine and amide groups are introduced on their surface. The images of SEM show the adhesion between microspheres and nickel-phosphorus films was improved after surface modification. This was attributed to amide which could chemisorb palladium ions to catalyze electroless nickel plating on the pretreated surfac
2009,
21.
Abstract:
Molybdenum thin films were fabricated on Si(100) substrates by pulsed laser deposition technique. The effect of substrate temperature on structure and surface morphology of the molybdenum films was investigated at 10－6 Pa with laser pulses of 2 Hz repetition rate and 5.2 J/cm2 power density. Results of atomic force microscopy(AFM) and X-ray diffraction (XRD) show that root mean square of the film surface roughness is below 2 nm, and indicate that the surface morphology and microstructures of the molybdenum films depend greatly on substrate temperature during growth. Structural quality and surface morphology of the molybdenum films are improved with the temperature increasing from 373 K to 573 K．
Molybdenum thin films were fabricated on Si(100) substrates by pulsed laser deposition technique. The effect of substrate temperature on structure and surface morphology of the molybdenum films was investigated at 10－6 Pa with laser pulses of 2 Hz repetition rate and 5.2 J/cm2 power density. Results of atomic force microscopy(AFM) and X-ray diffraction (XRD) show that root mean square of the film surface roughness is below 2 nm, and indicate that the surface morphology and microstructures of the molybdenum films depend greatly on substrate temperature during growth. Structural quality and surface morphology of the molybdenum films are improved with the temperature increasing from 373 K to 573 K．
2009,
21.
Abstract:
The Kelvin-Helmholtz instability in the inviscid fluid was simulated by applying high-order weighted essentially non-oscillatory(WENO) scheme to solve the two-dimensional conservative Euler equations. The simulation adopted the periodic boundary condition for the velocity shear direction and the fringe method as the outflow boundary condition for the disturbance growth direction, where an unstable wavelength contained 64 grids. The linear growth rate of the disturbance amplitude derived from this numerical simulation agrees well with that from the linear stability analysis, which proves the validity and accuracy of the simulation method. The method can provide clear density contours, showing a good capturing ability of interface deformation.
The Kelvin-Helmholtz instability in the inviscid fluid was simulated by applying high-order weighted essentially non-oscillatory(WENO) scheme to solve the two-dimensional conservative Euler equations. The simulation adopted the periodic boundary condition for the velocity shear direction and the fringe method as the outflow boundary condition for the disturbance growth direction, where an unstable wavelength contained 64 grids. The linear growth rate of the disturbance amplitude derived from this numerical simulation agrees well with that from the linear stability analysis, which proves the validity and accuracy of the simulation method. The method can provide clear density contours, showing a good capturing ability of interface deformation.
2009,
21.
Abstract:
The stabilization effect on Rayleigh-Taylor instability of density gradient was studied, with the variational and finite element approach to solve the Chandrasekhar equation. The growth rates under different density profiles were gained for ideal incompressible fluids and compared with those derived by the modified Lindl formula. The largest difference between of the results the numerical simulation and the formula happens when the perturbation wave length equals to the density scale length, and the peak value of the perturbation lies at the points where the scale length function meets its extreme. The two results agree well when the pertubation wave number appoaches infinity or infinitesimal. The pertubation velocities were also got in the simulation.
The stabilization effect on Rayleigh-Taylor instability of density gradient was studied, with the variational and finite element approach to solve the Chandrasekhar equation. The growth rates under different density profiles were gained for ideal incompressible fluids and compared with those derived by the modified Lindl formula. The largest difference between of the results the numerical simulation and the formula happens when the perturbation wave length equals to the density scale length, and the peak value of the perturbation lies at the points where the scale length function meets its extreme. The two results agree well when the pertubation wave number appoaches infinity or infinitesimal. The pertubation velocities were also got in the simulation.
2009,
21.
Abstract:
According to the requirement of 220 GHz gyrotron designed by University of Science and Technology of China, a pulsed magnet system and electron gun have been designed. The pulsed magnet system is dumbbell-shaped with the advantages of long uniform district, little resistance and inductance. It can obtain a high peak pulsed magnetic field with small inductor and capacitor. A double-anode magnetron injection gun has been designed and optimized by EGUN for the gyrotron. The electron beam velocity ratio is 1.53, and the velocity spread is 3.1%. The experimental results show that, the peak magnet field of the pulsed magnet system was 8 T, the electron beam current reached 2 A, the electrons were transported to the target, and few electrons were not sent to the control anode and anode, which mea
According to the requirement of 220 GHz gyrotron designed by University of Science and Technology of China, a pulsed magnet system and electron gun have been designed. The pulsed magnet system is dumbbell-shaped with the advantages of long uniform district, little resistance and inductance. It can obtain a high peak pulsed magnetic field with small inductor and capacitor. A double-anode magnetron injection gun has been designed and optimized by EGUN for the gyrotron. The electron beam velocity ratio is 1.53, and the velocity spread is 3.1%. The experimental results show that, the peak magnet field of the pulsed magnet system was 8 T, the electron beam current reached 2 A, the electrons were transported to the target, and few electrons were not sent to the control anode and anode, which mea
2009,
21.
Abstract:
The nonlinear theory of the Ka-band second harmonic gyrotron traveling wave amplifier with two-stage loss waveguide was studied. The two-stage loss waveguide consisted of a loss waveguide and a copper waveguide. The operating parameters of the 35 GHz TE02 mode second harmonic gyro-TWT were determined by stability analysis, and the radius of the waveguide is 1.02 cm, the working voltage of electron beam is 90 kV, the working current is 25 A, the magnetic field is 0.642 6 T, and the transverse-longitudinal velocity ratio is 1.2. The effect of several factors on the amplifier performance, including operating current, waveguide loss and velocity spread, were analyzed through simulation. The results show that the loss waveguide can effectively restrain the unwanted modes in this structure, thus
The nonlinear theory of the Ka-band second harmonic gyrotron traveling wave amplifier with two-stage loss waveguide was studied. The two-stage loss waveguide consisted of a loss waveguide and a copper waveguide. The operating parameters of the 35 GHz TE02 mode second harmonic gyro-TWT were determined by stability analysis, and the radius of the waveguide is 1.02 cm, the working voltage of electron beam is 90 kV, the working current is 25 A, the magnetic field is 0.642 6 T, and the transverse-longitudinal velocity ratio is 1.2. The effect of several factors on the amplifier performance, including operating current, waveguide loss and velocity spread, were analyzed through simulation. The results show that the loss waveguide can effectively restrain the unwanted modes in this structure, thus
2009,
21.
Abstract:
The thermal performance of a Ku-band space traveling wave tube collector was simulated using the finite element method, attaining the temperature distribution of the collector. The influences of contact resistance and heat radiation on the thermal performance were analyzed and compared. The results show that the contact resistance obviously hinders the heat dissipation so that the temperature of the whole collector raises and the highest temperature increases about 13 ℃; the heat radiation reduces the temperature at the same time and the highest temperature falls about 5.2 ℃, leading to a more uniform temperature distribution. The heat-stress coupled analysis was done using an indirect method, gaining the displacement distribution contour map of the collector. It is shown that the struct
The thermal performance of a Ku-band space traveling wave tube collector was simulated using the finite element method, attaining the temperature distribution of the collector. The influences of contact resistance and heat radiation on the thermal performance were analyzed and compared. The results show that the contact resistance obviously hinders the heat dissipation so that the temperature of the whole collector raises and the highest temperature increases about 13 ℃; the heat radiation reduces the temperature at the same time and the highest temperature falls about 5.2 ℃, leading to a more uniform temperature distribution. The heat-stress coupled analysis was done using an indirect method, gaining the displacement distribution contour map of the collector. It is shown that the struct
2009,
21.
Abstract:
The inner electric field of EMP simulator with fast rise-time is studied using FEKO which is based on Method of moments(MOM). The simulation result is analyzed and the distribution law of vertical electric field is deduced. The result shows that: (1) the changing trend from center to edge of different level differs in three part, concussion very near the upper transmission line, increasing at first and then decreasing near upper and lower lines, and monotone decreasing other part; (2) the ±10% uniform field area of inner simulator is formed of two parts: one is the area with height of 20% to 85% and width of 80% from the center, the other is the area with height below 20% and width of 30% from the center.
The inner electric field of EMP simulator with fast rise-time is studied using FEKO which is based on Method of moments(MOM). The simulation result is analyzed and the distribution law of vertical electric field is deduced. The result shows that: (1) the changing trend from center to edge of different level differs in three part, concussion very near the upper transmission line, increasing at first and then decreasing near upper and lower lines, and monotone decreasing other part; (2) the ±10% uniform field area of inner simulator is formed of two parts: one is the area with height of 20% to 85% and width of 80% from the center, the other is the area with height below 20% and width of 30% from the center.
2009,
21.
Abstract:
By studying the cavity structure of a second-harmonic complex cavity gyrotron with abrupt transition, the modes competition and the interaction between the electron beam and wave, the characteristics of the RF structure, suppression of parasite oscillations and optimization of the work parameters are discussed. The simulation results of the low-loss TE02/TE03 low-voltage gyrotron are given. Using a gradient magnetic field in calculation, the interaction efficiency is significantly improved. PIC simulation results show that the gyrotron can generate 37 kW at 94 GHz with 37% efficiency with a 25 kV, 4 A and velocity ratio 1.6 beam.
By studying the cavity structure of a second-harmonic complex cavity gyrotron with abrupt transition, the modes competition and the interaction between the electron beam and wave, the characteristics of the RF structure, suppression of parasite oscillations and optimization of the work parameters are discussed. The simulation results of the low-loss TE02/TE03 low-voltage gyrotron are given. Using a gradient magnetic field in calculation, the interaction efficiency is significantly improved. PIC simulation results show that the gyrotron can generate 37 kW at 94 GHz with 37% efficiency with a 25 kV, 4 A and velocity ratio 1.6 beam.
2009,
21.
Abstract:
A novel compact circularly-polarized(CP) mode converter that converts a TM01 (or TEM) mode into a CP TE11 mode was developed. It is composed of two turnstile junctions. The first turnstile junction transforms the input TM01 circular waveguide mode into TE10 modes in four rectangular waveguides with non-uniform lengths; the second then converts those four TE10 modes with different phase delays into CP TE11 circular waveguide mode. A mode converter at 1.75 GHz was designed. The conversion efficiency of TM01 to TE11 is 99% at center frequency with an axial ratio of 0.03 dB. Over the frequency range of 1.575~1.900 GHz, the conversion efficiency exceeds 90%, and the axial ratio is less than 2.5 dB with the corresponding bandwidth of 18.6%.
A novel compact circularly-polarized(CP) mode converter that converts a TM01 (or TEM) mode into a CP TE11 mode was developed. It is composed of two turnstile junctions. The first turnstile junction transforms the input TM01 circular waveguide mode into TE10 modes in four rectangular waveguides with non-uniform lengths; the second then converts those four TE10 modes with different phase delays into CP TE11 circular waveguide mode. A mode converter at 1.75 GHz was designed. The conversion efficiency of TM01 to TE11 is 99% at center frequency with an axial ratio of 0.03 dB. Over the frequency range of 1.575~1.900 GHz, the conversion efficiency exceeds 90%, and the axial ratio is less than 2.5 dB with the corresponding bandwidth of 18.6%.
2009,
21.
Abstract:
A linearly polarized array antenna with radial waveguide for L-band was put forward, which can realize rotundity array antenna based on triangle grid. The multilayer radial waveguide and a horizontal ring antenna was researched, then the L-band linearly polarized array antenna with the array element space of less than one wavelength. The results indicate that this structure is feasible to realize the linearly polarized radial waveguide array antenna; the antenna gain is 19.97 dBi, the axial ratio is -52.06 dB and the reflection coefficient is 0.105 2 at 1.57 GHz; In the range of 1.37 GHz to 1.77 GHz , the gain is over 18.64 dBi and the axial ratio is below -46.45 dB.
A linearly polarized array antenna with radial waveguide for L-band was put forward, which can realize rotundity array antenna based on triangle grid. The multilayer radial waveguide and a horizontal ring antenna was researched, then the L-band linearly polarized array antenna with the array element space of less than one wavelength. The results indicate that this structure is feasible to realize the linearly polarized radial waveguide array antenna; the antenna gain is 19.97 dBi, the axial ratio is -52.06 dB and the reflection coefficient is 0.105 2 at 1.57 GHz; In the range of 1.37 GHz to 1.77 GHz , the gain is over 18.64 dBi and the axial ratio is below -46.45 dB.
2009,
21.
Abstract:
A new configuration of an axially-extracted vircator with several resonant cavities was put forward. Electromagnetic feature analysis shows this structure can get higher extraction efficiency. Particle simulation indicates this device can produce of 4.0 GHz microwave with an averaged power of over 1.7 GW a quasi-single TM01 mode under the diode voltage of 700 kV and the beam current of 23 kA. The power conversion efficiency is more than 10%. In the following experiment, the 410 GHz microwave with an output power of over 700 MW.
A new configuration of an axially-extracted vircator with several resonant cavities was put forward. Electromagnetic feature analysis shows this structure can get higher extraction efficiency. Particle simulation indicates this device can produce of 4.0 GHz microwave with an averaged power of over 1.7 GW a quasi-single TM01 mode under the diode voltage of 700 kV and the beam current of 23 kA. The power conversion efficiency is more than 10%. In the following experiment, the 410 GHz microwave with an output power of over 700 MW.
2009,
21.
Abstract:
The ensemble of the cavity scattering matrix and the corresponding radiation scattering matrix were computed, which were converted into normalized scattering matrix and normalized impedance matrix. Eigenvalues of the normalized scattering matrix were statistically analyzed by Dyson’s circular ensemble. The statistical independence of the magnitude and phase of the normalized eigenvalues were verified, and the phase is approximate to a uniform distribution, proving the existence of wavechaotic scattering in the cavity. There is a good agreement between the numerically determined marginal PDFs and those generated from random matrix theory．
The ensemble of the cavity scattering matrix and the corresponding radiation scattering matrix were computed, which were converted into normalized scattering matrix and normalized impedance matrix. Eigenvalues of the normalized scattering matrix were statistically analyzed by Dyson’s circular ensemble. The statistical independence of the magnitude and phase of the normalized eigenvalues were verified, and the phase is approximate to a uniform distribution, proving the existence of wavechaotic scattering in the cavity. There is a good agreement between the numerically determined marginal PDFs and those generated from random matrix theory．
2009,
21.
Abstract:
A new idea of azimuthal partition to generate bifrequency high power microwave (HPM) is put forward in this paper. According to the operation mechanism of a conventional magnetically insulated transmission line oscillator (MILO), the interaction between electron flow and microwave is in the axial and radial direction, but not in the azimuthal direction. Therefore, establishing the azimuthal partition of cavitydepth in a conventional MILO, an L-band bifrequency MILO (BFMILO) is designed. The BFMILO is simulated and optimized by electromagnetic simulation. The particle simulation shows that when the electron beam voltage is 530 kV and the beam current is about 45.5 kA, a BFMILO can generates about 2.65 GW of HPM with two stable and separate frequencies-1.28 GHz and 1.50 GHz. The power effici
A new idea of azimuthal partition to generate bifrequency high power microwave (HPM) is put forward in this paper. According to the operation mechanism of a conventional magnetically insulated transmission line oscillator (MILO), the interaction between electron flow and microwave is in the axial and radial direction, but not in the azimuthal direction. Therefore, establishing the azimuthal partition of cavitydepth in a conventional MILO, an L-band bifrequency MILO (BFMILO) is designed. The BFMILO is simulated and optimized by electromagnetic simulation. The particle simulation shows that when the electron beam voltage is 530 kV and the beam current is about 45.5 kA, a BFMILO can generates about 2.65 GW of HPM with two stable and separate frequencies-1.28 GHz and 1.50 GHz. The power effici
2009,
21.
Abstract:
An exact dispersion has been obtained and components of the electromagnetic fields have been evaluated by expanding the surface currents on a thin tape of a traveling wave tube(TWT) in a series of Chebyshev polynomials. And based on the axial components of the fields the interaction impedance and magnetic admittance are calculated. These are foundation of 3-D nonlinear theory to design TWT. An example is given and axial components of the electromagnetic fields are computed. It is found that the result of interaction impedance according to the fields and the one obtained by Chernin agree to good accuracy, which validates the expressions of the fields. The interaction admittance calculation is a part of the 3-D TWT CAD．
An exact dispersion has been obtained and components of the electromagnetic fields have been evaluated by expanding the surface currents on a thin tape of a traveling wave tube(TWT) in a series of Chebyshev polynomials. And based on the axial components of the fields the interaction impedance and magnetic admittance are calculated. These are foundation of 3-D nonlinear theory to design TWT. An example is given and axial components of the electromagnetic fields are computed. It is found that the result of interaction impedance according to the fields and the one obtained by Chernin agree to good accuracy, which validates the expressions of the fields. The interaction admittance calculation is a part of the 3-D TWT CAD．
2009,
21.
Abstract:
The situation of titanium foil of high power electron accelerator (1.2 MW)extraction window was studied, because the operating temperature of titanium foil should be controlled within 150 ℃, forced aircooling is the only way to disperse the heat (under such temperature, the effects of heat dispersion of heat radiation and conduction can be neglected). With the fluid analog software (Fluent), the relationships among cooling efficiency of titanium foil, initial air velocity and distance, existence of refluent zone and its affects were analysed, also the structure of extraction window was primarily optimized. Additionally, simulation analysis was made on the closed space formed by additional protective window. Non-homogenous-distribution scanning has been proved that the output capacity of
The situation of titanium foil of high power electron accelerator (1.2 MW)extraction window was studied, because the operating temperature of titanium foil should be controlled within 150 ℃, forced aircooling is the only way to disperse the heat (under such temperature, the effects of heat dispersion of heat radiation and conduction can be neglected). With the fluid analog software (Fluent), the relationships among cooling efficiency of titanium foil, initial air velocity and distance, existence of refluent zone and its affects were analysed, also the structure of extraction window was primarily optimized. Additionally, simulation analysis was made on the closed space formed by additional protective window. Non-homogenous-distribution scanning has been proved that the output capacity of
2009,
21.
Abstract:
RF system of HIRFL-CSRe(cooling storage experimental ring) was designed by ourselves and manufactured domestically, which operates in the frequency range of 0.5~2.0 MHz at first and second harmonic modes. Based on detailed engineering calculation, the design of RF generator was completed. It will work not only in CW mode but also in the mode of ramping pulse modulation, and the maximum power is up to 70 kW. It satisfies the requirement of 10 kV maximum deceleration voltage to capture the irradiative beam and decelerate the beam from 400 MeV/u to 30 MeV/u.
RF system of HIRFL-CSRe(cooling storage experimental ring) was designed by ourselves and manufactured domestically, which operates in the frequency range of 0.5~2.0 MHz at first and second harmonic modes. Based on detailed engineering calculation, the design of RF generator was completed. It will work not only in CW mode but also in the mode of ramping pulse modulation, and the maximum power is up to 70 kW. It satisfies the requirement of 10 kV maximum deceleration voltage to capture the irradiative beam and decelerate the beam from 400 MeV/u to 30 MeV/u.
2009,
21.
Abstract:
In order to eliminate the effect of scattered radiation in image reconstruction with the iterative method, it is necessary to design the layout and configuration of the high-energy flash X-ray radiography system with uniform scattering distribution. The definition of scattering uniformity is given and the optical path error produced by eliminating the effect of scattered radiation with average scattering exposure is analyzed. Various factors affecting the scattering uniformity are studied using Monte-Carlo method, including system magnification, radiographic distance and the distance between back protection cone and imaging plane. It is shown that a main factor affecting the scattering uniformity is the distance, which determines the shape of scattering distribution and scattering exposure
In order to eliminate the effect of scattered radiation in image reconstruction with the iterative method, it is necessary to design the layout and configuration of the high-energy flash X-ray radiography system with uniform scattering distribution. The definition of scattering uniformity is given and the optical path error produced by eliminating the effect of scattered radiation with average scattering exposure is analyzed. Various factors affecting the scattering uniformity are studied using Monte-Carlo method, including system magnification, radiographic distance and the distance between back protection cone and imaging plane. It is shown that a main factor affecting the scattering uniformity is the distance, which determines the shape of scattering distribution and scattering exposure
2009,
21.
Abstract:
The beam optical transfer is important for neutron generator research, therefore the research of the beam transfer system was conducted and the system optical character and composition were expatiated.As a typical case, the composition and optical characteristics of the transfer system of ns-200 neutron generator were detailedly analyzed. The data input card of this system was derived according to LEADS software requirement. The simulation calculation produces the beam transfer envelope using relevant optical calculation modules of LEADS based on the card. The envelope agrees well with the designed one．
The beam optical transfer is important for neutron generator research, therefore the research of the beam transfer system was conducted and the system optical character and composition were expatiated.As a typical case, the composition and optical characteristics of the transfer system of ns-200 neutron generator were detailedly analyzed. The data input card of this system was derived according to LEADS software requirement. The simulation calculation produces the beam transfer envelope using relevant optical calculation modules of LEADS based on the card. The envelope agrees well with the designed one．
2009,
21.
Abstract:
In order to achieve the best expanding effeciency of the diffuser and to use most protons to radiate the French Test Object, the material is chosed from three aspects. They are MCS (multiple Coulomb scattering) angle, energy loss and penetration rate for proton per unit areal mass. The analyzed results of these aspects show that the bigger the atomic number is, the higher the efficiency is. The material is determined to be tungsten considering cost and applicability. The thickness of the diffuser is designed according to the demands of uniform proton flux distribution and small noise. As a result, the diffuser thicknesses are 3.1 cm without collimator and 2.4 cm with 3.0 mrad collimator.
In order to achieve the best expanding effeciency of the diffuser and to use most protons to radiate the French Test Object, the material is chosed from three aspects. They are MCS (multiple Coulomb scattering) angle, energy loss and penetration rate for proton per unit areal mass. The analyzed results of these aspects show that the bigger the atomic number is, the higher the efficiency is. The material is determined to be tungsten considering cost and applicability. The thickness of the diffuser is designed according to the demands of uniform proton flux distribution and small noise. As a result, the diffuser thicknesses are 3.1 cm without collimator and 2.4 cm with 3.0 mrad collimator.
2009,
21.
Abstract:
Two D-dot voltage monitors and a B-dot current monitor have been designed for laser-triggered switch of PTS prototype. The D-dot monitor consists of a capacitive divider where the capacitance to ground in the probe is relatively small and does not affect the calibration. One has been installed in the switch entrance and the other in the export. The waveform of the D-dot in export is different from the calculated waveform because the capacitance to the high-voltage electrode of export is small and almost equal to the capacitance to the electrode of entrance, so the monitor influences the voltage in the export and that in the entrance. The coupling coefficient from the monitor to the high-voltage electrode of entrance can be obtained by test, then the modified waveform is calculated. The B-d
Two D-dot voltage monitors and a B-dot current monitor have been designed for laser-triggered switch of PTS prototype. The D-dot monitor consists of a capacitive divider where the capacitance to ground in the probe is relatively small and does not affect the calibration. One has been installed in the switch entrance and the other in the export. The waveform of the D-dot in export is different from the calculated waveform because the capacitance to the high-voltage electrode of export is small and almost equal to the capacitance to the electrode of entrance, so the monitor influences the voltage in the export and that in the entrance. The coupling coefficient from the monitor to the high-voltage electrode of entrance can be obtained by test, then the modified waveform is calculated. The B-d
2009,
21.
Abstract:
In order to study the physics of fast Z-pinches and the key issues of pulse power technology, a 10 MA/6 MV Z-pinch Primary Test Stand(PTS) composed of 24 modules will be built in Institute of Fluid Physics. The prototype module adopting capacitive storage scheme has been built and tested. It is composed of a 6 MV/300 kJ Marx generator(MG), intermediate storage capacitor(IC), laser-triggered switch(LTS), pulse forming line(PFL), water self-breakdown switch(WS), and a tri plate pulse transmission line(PTL). The measured output current of the prototype is approximately 450 kA, and the output voltage is approximately 2.2 MV. The unique multi-stage LTS based on uniform field distribution design and multi-pin unsymmetrical WS makes the prototype modules have low systemic delay jitter which is ne
In order to study the physics of fast Z-pinches and the key issues of pulse power technology, a 10 MA/6 MV Z-pinch Primary Test Stand(PTS) composed of 24 modules will be built in Institute of Fluid Physics. The prototype module adopting capacitive storage scheme has been built and tested. It is composed of a 6 MV/300 kJ Marx generator(MG), intermediate storage capacitor(IC), laser-triggered switch(LTS), pulse forming line(PFL), water self-breakdown switch(WS), and a tri plate pulse transmission line(PTL). The measured output current of the prototype is approximately 450 kA, and the output voltage is approximately 2.2 MV. The unique multi-stage LTS based on uniform field distribution design and multi-pin unsymmetrical WS makes the prototype modules have low systemic delay jitter which is ne
2009,
21.
Abstract:
Circuit models of transmission line transformers are analyzed. A method to restrain the impact of the secondary line is adopted, which is enhancing the impedance of the secondary line. Two typical topologies of transmission line transformers are analyzed and discussed, and the expressions of output waveforms are derived. Optimization of each secondary line inductance is given. The optimal value of the n-stage inductance is n-1 times the magnitude of that of the second stage for the structure without coupling between stages, and the inductance of each induced by the same magnetic core is equal for the structure with coupling between stages. At last, comparing the outputs of several structures, the results indicate the topology of the structure with mutually coupling between stages needs the
Circuit models of transmission line transformers are analyzed. A method to restrain the impact of the secondary line is adopted, which is enhancing the impedance of the secondary line. Two typical topologies of transmission line transformers are analyzed and discussed, and the expressions of output waveforms are derived. Optimization of each secondary line inductance is given. The optimal value of the n-stage inductance is n-1 times the magnitude of that of the second stage for the structure without coupling between stages, and the inductance of each induced by the same magnetic core is equal for the structure with coupling between stages. At last, comparing the outputs of several structures, the results indicate the topology of the structure with mutually coupling between stages needs the
2009,
21.
Abstract:
Transmission lines are widely used in the fast signal transmission at short distances due to its low cost. But its bandwidth should be compensated for its narrowband. A compensation method based on filter is provided and the compensators of small size are designed and used in QG-Ⅰ accelerator. Experimental results show that the transmission bandwidth could reach 200 MHz and the amplitude of signal could be 1/3 of the original one after compensation. The comparison of original, uncompensated and compensated signals shows that signals’ aberrations can be well compensated with this method, which meets the demand of the high speed signal transmission in the QG-I accelerator. A software for compensator design has been developed for the automation of Pole-Zeros finding and element parameter
Transmission lines are widely used in the fast signal transmission at short distances due to its low cost. But its bandwidth should be compensated for its narrowband. A compensation method based on filter is provided and the compensators of small size are designed and used in QG-Ⅰ accelerator. Experimental results show that the transmission bandwidth could reach 200 MHz and the amplitude of signal could be 1/3 of the original one after compensation. The comparison of original, uncompensated and compensated signals shows that signals’ aberrations can be well compensated with this method, which meets the demand of the high speed signal transmission in the QG-I accelerator. A software for compensator design has been developed for the automation of Pole-Zeros finding and element parameter
2009,
21.
Abstract:
The rising edge of the output voltage generated by a linear transformer driver(LTD) was analyzed, and circuit parameters corresponding to the aberration forms of the output voltages were investigated. An LTD was designed based on these analysis, and then simulated with designed parameters. The result is an output pulse with 30 ns rising time, 130 ns pulse width and 125 kV amplitude. A single LTD stage was experimented and generated an output pulse with 35 ns rising time, 130 ns pulse width and 125 kV amplitude, basically consistent with the simulated one. Although the falling edge is not too well with oscillations for several factors like imperfect load match. However, it could still meet the design requirement．
The rising edge of the output voltage generated by a linear transformer driver(LTD) was analyzed, and circuit parameters corresponding to the aberration forms of the output voltages were investigated. An LTD was designed based on these analysis, and then simulated with designed parameters. The result is an output pulse with 30 ns rising time, 130 ns pulse width and 125 kV amplitude. A single LTD stage was experimented and generated an output pulse with 35 ns rising time, 130 ns pulse width and 125 kV amplitude, basically consistent with the simulated one. Although the falling edge is not too well with oscillations for several factors like imperfect load match. However, it could still meet the design requirement．
