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RSS2005 Vol. 17, No. 03
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2005,
17.
Abstract:
Scattering of the atmosphere particles such as fogs is one of the important factors which limit the precision of laser control and guide. Based on Mie's theory,the scattering efficiency factor of a spherical particle is analyzed, the scattering coefficient of spherical particles 1~6 μm in radius is presented. According to Bouguer's theory the expression of the scattering intensity of particles is obtained. Then in the field of view of the receiver, the distribution of scattering intensity is simulated. The simulation results show that, in the orientation of propagation, the scattering intensity exhibits undulation, and approaching the axial orientation, the scattering intensity tends to decrease．
Scattering of the atmosphere particles such as fogs is one of the important factors which limit the precision of laser control and guide. Based on Mie's theory,the scattering efficiency factor of a spherical particle is analyzed, the scattering coefficient of spherical particles 1~6 μm in radius is presented. According to Bouguer's theory the expression of the scattering intensity of particles is obtained. Then in the field of view of the receiver, the distribution of scattering intensity is simulated. The simulation results show that, in the orientation of propagation, the scattering intensity exhibits undulation, and approaching the axial orientation, the scattering intensity tends to decrease．
2005,
17.
Abstract:
Numerical simulation was used to quantitatively analyze the statistical properties of short-exposure images with strong turbulent effects. Moreover, we compared the numerical results with the experimental results. The analytic results show that the short-exposure images break into some small spots with strong turbulent effects.For example, the coherence length of atmosphere is equal to 4.7 cm. In addition, the equivalent scale of these broken spots is comparable with the Airy spot. Moreover, when the receive aperture is equal to the dimension of Airy spot, the received average intensity on the axis is the largest.
Numerical simulation was used to quantitatively analyze the statistical properties of short-exposure images with strong turbulent effects. Moreover, we compared the numerical results with the experimental results. The analytic results show that the short-exposure images break into some small spots with strong turbulent effects.For example, the coherence length of atmosphere is equal to 4.7 cm. In addition, the equivalent scale of these broken spots is comparable with the Airy spot. Moreover, when the receive aperture is equal to the dimension of Airy spot, the received average intensity on the axis is the largest.
2005,
17.
Abstract:
X-ray to light convertor in a real time radiography image formation system plays an important role. A new type Tb3＋ doped silicate luminescent glass has been developed recently. There is no visible light dispersion in the glass and it can take the place of traditional rare earth fluorescent screen in high energy radiography applications. For its spatial resolution will not be greatly reduced when its thickness increases in a certain range, a thicker glass can be used to reach a higher DQE. The luminescent glass can be used in a radiography image formation system which adopts a high energy X-ray source up to 30 MeV. The spatial resolution is about the same as 301 type luminescent glass excitated by 100 keV X-ray and the spatial resolution may not be less than 1.5 lp/mm when excitated by 12
X-ray to light convertor in a real time radiography image formation system plays an important role. A new type Tb3＋ doped silicate luminescent glass has been developed recently. There is no visible light dispersion in the glass and it can take the place of traditional rare earth fluorescent screen in high energy radiography applications. For its spatial resolution will not be greatly reduced when its thickness increases in a certain range, a thicker glass can be used to reach a higher DQE. The luminescent glass can be used in a radiography image formation system which adopts a high energy X-ray source up to 30 MeV. The spatial resolution is about the same as 301 type luminescent glass excitated by 100 keV X-ray and the spatial resolution may not be less than 1.5 lp/mm when excitated by 12
2005,
17.
Abstract:
The polarization diversity of laser scattering field is studied in this paper.According to the vector small perturbation solution of extinction theorem,the scattering field from rough surfaces is classified as the zero order or higher order solution. When the light incident is linearly polarized, the polarization degree of reflected light is 1, the scattering light is partial polarized and changes of polarization degree have relation to the observational plane. Stokes-Muller system is used to measure the depolarization matrices of different surfaces. The results show that the slick plane can keep polarizability of incident linearly polarized light and rough plane will result in polarization loss. Long distance imaging experiments show polarization diversity active imaging can increase dete
The polarization diversity of laser scattering field is studied in this paper.According to the vector small perturbation solution of extinction theorem,the scattering field from rough surfaces is classified as the zero order or higher order solution. When the light incident is linearly polarized, the polarization degree of reflected light is 1, the scattering light is partial polarized and changes of polarization degree have relation to the observational plane. Stokes-Muller system is used to measure the depolarization matrices of different surfaces. The results show that the slick plane can keep polarizability of incident linearly polarized light and rough plane will result in polarization loss. Long distance imaging experiments show polarization diversity active imaging can increase dete
2005,
17.
Abstract:
Starting from the Fresnel-Kirchhoff and Rayleigh-Sommerfeld diffraction integral formulas, respectively, and in consideration of the inclination factor, the general diffraction integral expressions for convergent spherical waves diffracted at a circular aperture are derived, which are not only used to compute focal shifts of the diffraction field, but also valid for both weak and strong focusing cases, and thus have the generally applicable advantage. The results are compared with those got using the Li-Wolf formula, and the Li-Wolf formula can be regarded as an approximation of the general expressions under certain condition. The results are useful for the study of the beam precise focusing.
Starting from the Fresnel-Kirchhoff and Rayleigh-Sommerfeld diffraction integral formulas, respectively, and in consideration of the inclination factor, the general diffraction integral expressions for convergent spherical waves diffracted at a circular aperture are derived, which are not only used to compute focal shifts of the diffraction field, but also valid for both weak and strong focusing cases, and thus have the generally applicable advantage. The results are compared with those got using the Li-Wolf formula, and the Li-Wolf formula can be regarded as an approximation of the general expressions under certain condition. The results are useful for the study of the beam precise focusing.
2005,
17.
Abstract:
The on-axis intensity distribution was investigated in the focal region of partially coherent light focused by an annular lens. The results show that, when the partially coherent light is focused by an annular lens, the best focusing point is not located at the geometrical focus. This means that the phenomenon of focal shifts occurs. Moreover, the amount of the focal shifts depends on the Fresnel number of the focusing lens, the spatial coherence of the partially coherent light and the central obstruction ratio of the annular lens etc. It is shown that the smaller the Fresnel number, the larger the focal shift; the lower the spatial coherence, the larger the focal shift;for a fixed Fresnel number, the larger the central obstruction ratio is, the larger the focal shift is. However, when the
The on-axis intensity distribution was investigated in the focal region of partially coherent light focused by an annular lens. The results show that, when the partially coherent light is focused by an annular lens, the best focusing point is not located at the geometrical focus. This means that the phenomenon of focal shifts occurs. Moreover, the amount of the focal shifts depends on the Fresnel number of the focusing lens, the spatial coherence of the partially coherent light and the central obstruction ratio of the annular lens etc. It is shown that the smaller the Fresnel number, the larger the focal shift; the lower the spatial coherence, the larger the focal shift;for a fixed Fresnel number, the larger the central obstruction ratio is, the larger the focal shift is. However, when the
2005,
17.
Abstract:
The focal switch effect of Bessel-Gaussian beams focused by a thin lens without aperture is studied in detail. The third-order algebraic equation determining the position of the axial maximum intensity and the formula of the relative transition height are derived. Numerical calculation results are presented to illustrate the theoretical predictions. It is shown that, if the beam parameter is bigger than 2, the focal switch of Bessel-Gaussian beams can appear. The relative transition height increases with increasing the beam parameter. The normalized axial minimum intensity decreases with increasing the beam parameter, and the normalized axial minimum intensity is zero, as the beam parameter is bigger than 3.9.
The focal switch effect of Bessel-Gaussian beams focused by a thin lens without aperture is studied in detail. The third-order algebraic equation determining the position of the axial maximum intensity and the formula of the relative transition height are derived. Numerical calculation results are presented to illustrate the theoretical predictions. It is shown that, if the beam parameter is bigger than 2, the focal switch of Bessel-Gaussian beams can appear. The relative transition height increases with increasing the beam parameter. The normalized axial minimum intensity decreases with increasing the beam parameter, and the normalized axial minimum intensity is zero, as the beam parameter is bigger than 3.9.
2005,
17.
Abstract:
The article analyses and simulates the variation of beam energy error,spot centroid error and spot distribution with the detector sensitivity dynamic range, sensitivity difference and space between detectors in laser spot measurement by uniform square detector array. Simulation results show that if detector sensitivity dynamic range is more than 30dB, sensitivity difference is less than 10% and space between contiguous detectors is less than 20% of beam diameter, beam energy error is less than 6%, spot centroid error is less than 2% of beam diameter and the spot distribution imitated is comparatively ideal．
The article analyses and simulates the variation of beam energy error,spot centroid error and spot distribution with the detector sensitivity dynamic range, sensitivity difference and space between detectors in laser spot measurement by uniform square detector array. Simulation results show that if detector sensitivity dynamic range is more than 30dB, sensitivity difference is less than 10% and space between contiguous detectors is less than 20% of beam diameter, beam energy error is less than 6%, spot centroid error is less than 2% of beam diameter and the spot distribution imitated is comparatively ideal．
2005,
17.
Abstract:
This paper presents the experimental method to measure the high reflectivity of optical mirror by cavity ring-down spectroscopy. The experimental system uses a straight cavity composed of a pair of cavity mirrors with same reflectivity or a folded cavity which is formed from the straight cavity to be folded at 22.5° angle, a reflector is laid at folded point.The reflectivity of the cavity mirrors is measured to be（99.925±0.001）% and the reflector to be (99.992±0.003)％．The metrical precision achieves 10－5.The low loss and high reflectivity mirrors can be measured accurately by this setup．
This paper presents the experimental method to measure the high reflectivity of optical mirror by cavity ring-down spectroscopy. The experimental system uses a straight cavity composed of a pair of cavity mirrors with same reflectivity or a folded cavity which is formed from the straight cavity to be folded at 22.5° angle, a reflector is laid at folded point.The reflectivity of the cavity mirrors is measured to be（99.925±0.001）% and the reflector to be (99.992±0.003)％．The metrical precision achieves 10－5.The low loss and high reflectivity mirrors can be measured accurately by this setup．
2005,
17.
Abstract:
Output characteristics were tested under two diluent injecting methods on a single tube discharge excited infrared multi-band chemical laser by taking DF as a typical case. Experiment results of laser power output, mode characteristics, and spectra distributions indicated that injecting He from the end of discharge tube in addition to regular He injecting can increase the power of output, lengthen flow direction's gain length and strengthen the transitions between higher vibration levels, the reason was attributed to reduction of combination less of F atoms on wall, increase of active zone's flow rate and mitigation of deactivation effect.
Output characteristics were tested under two diluent injecting methods on a single tube discharge excited infrared multi-band chemical laser by taking DF as a typical case. Experiment results of laser power output, mode characteristics, and spectra distributions indicated that injecting He from the end of discharge tube in addition to regular He injecting can increase the power of output, lengthen flow direction's gain length and strengthen the transitions between higher vibration levels, the reason was attributed to reduction of combination less of F atoms on wall, increase of active zone's flow rate and mitigation of deactivation effect.
2005,
17.
Abstract:
Laser propulsion technology is one of the advanced propulsion technologies that has been paid a great deal of attention to. Of all the laser propulsion technologies, laser thruster technology is an important technology, and it is also a vital one. Based on a thoroughly research on the home and foreign literatures, the status and development trend of concept studies on laser propulsion thrusters is summarized. The advantages and disadvantages of the thrusters are pointed out．
Laser propulsion technology is one of the advanced propulsion technologies that has been paid a great deal of attention to. Of all the laser propulsion technologies, laser thruster technology is an important technology, and it is also a vital one. Based on a thoroughly research on the home and foreign literatures, the status and development trend of concept studies on laser propulsion thrusters is summarized. The advantages and disadvantages of the thrusters are pointed out．
2005,
17.
Abstract:
When a low-orbit satellite moves under thermal condition, the normal line of the antenna mirror surface turns due to antenna mirror thermal distortion. The turn magnitude order is 100 μrad when the thermal tension is not released，so the beam transferred has a large deflect and the performance of the space-to-ground laser communication links will suffer seriously. Applying limited element analysis to analyze reasonable application of pressing-plate method shows that normal angle deviation of mirror body after the thermal tension being released can be 3 order magnitude smaller, and the beam direction deviation caused by thermal distortion can be well retarded.
When a low-orbit satellite moves under thermal condition, the normal line of the antenna mirror surface turns due to antenna mirror thermal distortion. The turn magnitude order is 100 μrad when the thermal tension is not released，so the beam transferred has a large deflect and the performance of the space-to-ground laser communication links will suffer seriously. Applying limited element analysis to analyze reasonable application of pressing-plate method shows that normal angle deviation of mirror body after the thermal tension being released can be 3 order magnitude smaller, and the beam direction deviation caused by thermal distortion can be well retarded.
2005,
17.
Abstract:
Fe/Al compound thin films were fabricated by pulse laser deposition(PLD) and its X-ray photon electron spectroscopy(XPS) examinations were conducted. The surface morphology and oxidation were analyzed with atomic force microscope(AFM) and scanning electron microscope(SEM). The results show that the surface roughness of Fe/Al compound thin films depends on the substrate temperature, the higher the temperature is, the smoother the surface of the film becomes. The rms roughness of the film which was fabricated at a subseracte temperature of 200 ℃ is 0.154 nm. The distribution of Fe and Al in the film is uniform ,and the ratio between Fe and Al in the compound films is 1∶3. An oxidation layer of Al2O3 and FeO is formed at the surface of the Fe/Al compound thin films after exposure to air.
Fe/Al compound thin films were fabricated by pulse laser deposition(PLD) and its X-ray photon electron spectroscopy(XPS) examinations were conducted. The surface morphology and oxidation were analyzed with atomic force microscope(AFM) and scanning electron microscope(SEM). The results show that the surface roughness of Fe/Al compound thin films depends on the substrate temperature, the higher the temperature is, the smoother the surface of the film becomes. The rms roughness of the film which was fabricated at a subseracte temperature of 200 ℃ is 0.154 nm. The distribution of Fe and Al in the film is uniform ,and the ratio between Fe and Al in the compound films is 1∶3. An oxidation layer of Al2O3 and FeO is formed at the surface of the Fe/Al compound thin films after exposure to air.
2005,
17.
Abstract:
A distorted wavefront model is set up, according to the practical distorted wavefront of the optical components. In the calculation of phase RMS gradient, three different ways to handle the distorted wavefront are introduced.They are handling directly, Hanning window handling and the best one is the Hanning window handling, Fourier transformation, low-filter, inverse Fourier transformation, inverse Hanning window are accomplished in order after adding the zero-sampling points to the original distorted wavefront edges, finally a modelled distorted wavefront is cut off with the same size as the original one on the distorted wavefront gotten. RMS error of phase gradient of the wavefront can be the least. The correlations between the number of adding zero-sampling points,the size of wavefront
A distorted wavefront model is set up, according to the practical distorted wavefront of the optical components. In the calculation of phase RMS gradient, three different ways to handle the distorted wavefront are introduced.They are handling directly, Hanning window handling and the best one is the Hanning window handling, Fourier transformation, low-filter, inverse Fourier transformation, inverse Hanning window are accomplished in order after adding the zero-sampling points to the original distorted wavefront edges, finally a modelled distorted wavefront is cut off with the same size as the original one on the distorted wavefront gotten. RMS error of phase gradient of the wavefront can be the least. The correlations between the number of adding zero-sampling points,the size of wavefront
2005,
17.
Abstract:
Based on the optics manufacture actualitys in our country, different parameters used to value the optics profile for high power laser drivers are expatiated with the concept of spatial wavelength region. At the same time, the importance of each parameter is illustrated through its influence on farfield focus distribution. This article put forward the integrative evaluate mode for profile and prescribed all these parameters roundly. It gives a reference to value the optics profile.
Based on the optics manufacture actualitys in our country, different parameters used to value the optics profile for high power laser drivers are expatiated with the concept of spatial wavelength region. At the same time, the importance of each parameter is illustrated through its influence on farfield focus distribution. This article put forward the integrative evaluate mode for profile and prescribed all these parameters roundly. It gives a reference to value the optics profile.
2005,
17.
Abstract:
The physical equations of direct-drive cylindrical hydrodynamic instability in the LARED-S code, the geometry for the direct-drive cylindrical targets, the slide grids and some related techniques in the simulation are given in the paper. In the simulation of direct-drive cylindrical implosion experiments at OMEGA laser facility, the physical model of the target is simplified. The ablator, the marker layer and the interior foam of the target are taken as ideal gases, with different densities and the completely ionized charge state and single-temperature approximation are supposed during the implosion. The effect of classical electron thermal conduction is included while other factors such as radiation transport and nonlocal electron transport are neglected in the calculations. Simulation re
The physical equations of direct-drive cylindrical hydrodynamic instability in the LARED-S code, the geometry for the direct-drive cylindrical targets, the slide grids and some related techniques in the simulation are given in the paper. In the simulation of direct-drive cylindrical implosion experiments at OMEGA laser facility, the physical model of the target is simplified. The ablator, the marker layer and the interior foam of the target are taken as ideal gases, with different densities and the completely ionized charge state and single-temperature approximation are supposed during the implosion. The effect of classical electron thermal conduction is included while other factors such as radiation transport and nonlocal electron transport are neglected in the calculations. Simulation re
2005,
17.
Abstract:
Study of stress in Mo/Si multilayers is carried out for application of extreme ultraviolet multilayer coatings in the diagnosis of high density plasmas and extreme ultraviolet lithography. Stress generating mechanisms is discussed. Precise measurement of stress is taken by ZYGO interferometer. It is observed that the growth of the Mo component in the multilayers is tensile, while that of the Si component is compressive. The residual stress in a 40-bilayer Mo/Si multilayer coating with high reflectivity is -500 MPa (compressive), stress generation may be attributed to the interfacial diffusion. By varying Mo-to Si thickness ratio(Γ), the stress in multilayers can be compensated to a certain extent. However, the reflectance of Mo/Si multilayers is reduced correspondently.
Study of stress in Mo/Si multilayers is carried out for application of extreme ultraviolet multilayer coatings in the diagnosis of high density plasmas and extreme ultraviolet lithography. Stress generating mechanisms is discussed. Precise measurement of stress is taken by ZYGO interferometer. It is observed that the growth of the Mo component in the multilayers is tensile, while that of the Si component is compressive. The residual stress in a 40-bilayer Mo/Si multilayer coating with high reflectivity is -500 MPa (compressive), stress generation may be attributed to the interfacial diffusion. By varying Mo-to Si thickness ratio(Γ), the stress in multilayers can be compensated to a certain extent. However, the reflectance of Mo/Si multilayers is reduced correspondently.
2005,
17.
Abstract:
The process of radiative ablation and neutron yields of DD-capsule with CH shell implosion driven by Plank spectrum and nonequilibrium spectrum radiation fields was numerically studied using 1-D RDMG code of multigroup-nonequilibrium radiation hydrodynamics. The simulation results were compared with the experimental results. The results of the simulation show that the nonequilibrium of energy spectrum distribution of the hohlraum radiation source, especially the M-band of it, will preheat DD in the capsule obviously, decrease the compressing ratio, electron and ion temperatures of DD gas, and therefore decrease the neutron yields markedly. The simulation results also show that the law of decreasing of neutron yields with increasing of the CH-sell thickness is in agreement with the experime
The process of radiative ablation and neutron yields of DD-capsule with CH shell implosion driven by Plank spectrum and nonequilibrium spectrum radiation fields was numerically studied using 1-D RDMG code of multigroup-nonequilibrium radiation hydrodynamics. The simulation results were compared with the experimental results. The results of the simulation show that the nonequilibrium of energy spectrum distribution of the hohlraum radiation source, especially the M-band of it, will preheat DD in the capsule obviously, decrease the compressing ratio, electron and ion temperatures of DD gas, and therefore decrease the neutron yields markedly. The simulation results also show that the law of decreasing of neutron yields with increasing of the CH-sell thickness is in agreement with the experime
2005,
17.
Abstract:
Gain characteristics of a large-aperture Ti:sapphire disk is studied in detail. To achieve large energy output, the pump energy fluence and beam size were analyzed and optimized. The results is that, for a Ti:sapphire crystal of 80 mm×17 mm, the optimum beam size is about 50 mm with 50 J pump energy, for a Ti:sapphire crystal of 80 mm×30 mm, the optimum beam size is about 60 mm with 90 J pump energy. To suppress the transverse parasitic oscillation and ASE across the large-aperture Ti:sapphire crystal, the periphery fo the disk is cladded with an index-matched thermoplastic polymer material, which increases the oscillation threshold from 13 to 2 100. The multihundred-terawatt amplifier is four-pass configured with a 17 mm long Ti:sapphire disk with 80 mm in diameter and. The pump energ
Gain characteristics of a large-aperture Ti:sapphire disk is studied in detail. To achieve large energy output, the pump energy fluence and beam size were analyzed and optimized. The results is that, for a Ti:sapphire crystal of 80 mm×17 mm, the optimum beam size is about 50 mm with 50 J pump energy, for a Ti:sapphire crystal of 80 mm×30 mm, the optimum beam size is about 60 mm with 90 J pump energy. To suppress the transverse parasitic oscillation and ASE across the large-aperture Ti:sapphire crystal, the periphery fo the disk is cladded with an index-matched thermoplastic polymer material, which increases the oscillation threshold from 13 to 2 100. The multihundred-terawatt amplifier is four-pass configured with a 17 mm long Ti:sapphire disk with 80 mm in diameter and. The pump energ
2005,
17.
Abstract:
The pre-pulse duration and contrast are very important in the ultra-high power CPA laser system. The effects of the self phase modulation (SPM) were simulated on the peak intensity, pre-pulse duration and contrast of the compressed pulse, when the chirped pulse duration was 141 ps, the chirp coefficient was 1 000 and the B-integral value was 0, 1 or 2. The results show that when the B-integral value is 2, the SPM causes the peak intensity of the compressed pulse to decrease to 65%, and the pulse duration and pre-pulse duration to increase to 200 % and 300% respectively. When the B-integral ranges from 0.5 to 2, an approximate linear formulation can be used to describe the relationship between the pre-pulse duration and the B-integral value.
The pre-pulse duration and contrast are very important in the ultra-high power CPA laser system. The effects of the self phase modulation (SPM) were simulated on the peak intensity, pre-pulse duration and contrast of the compressed pulse, when the chirped pulse duration was 141 ps, the chirp coefficient was 1 000 and the B-integral value was 0, 1 or 2. The results show that when the B-integral value is 2, the SPM causes the peak intensity of the compressed pulse to decrease to 65%, and the pulse duration and pre-pulse duration to increase to 200 % and 300% respectively. When the B-integral ranges from 0.5 to 2, an approximate linear formulation can be used to describe the relationship between the pre-pulse duration and the B-integral value.
2005,
17.
Abstract:
With ray tracing analysis method, a theoretical analysis of wavefront aberration is made in pulse compression gratings. A model made up of pulse compression grating pair with wavefront aberration is applied to calculate the effect of the wavefront aberration on pulse compression. The preliminary conclusion shows that the maximum rate of compression ratio changes is about 2% and the change rate is less when the peak-to-valley value of wavefront aberration is less than a quarter of wavelength and incident angle is properly．
With ray tracing analysis method, a theoretical analysis of wavefront aberration is made in pulse compression gratings. A model made up of pulse compression grating pair with wavefront aberration is applied to calculate the effect of the wavefront aberration on pulse compression. The preliminary conclusion shows that the maximum rate of compression ratio changes is about 2% and the change rate is less when the peak-to-valley value of wavefront aberration is less than a quarter of wavelength and incident angle is properly．
2005,
17.
Abstract:
The superconducting accelerator has high quality factor, so the decay time of the field emitted by beam is much longer than that in normal conducting cavity. This results in the strong interaction between the SC cavity and the beam through it. The high order mode field excited by short bunches could effect the beam and cause beam break up. In this paper, the total high order mode power of TESLA 9-cell cavity with the beam load of 1 mA was estimated．The result shows that the phase shifts of high ovder mode, referring to major eigen frequencies of the cavity, are more than π/4. There would be no resonant buildup. The total high order module power is in mW level.
The superconducting accelerator has high quality factor, so the decay time of the field emitted by beam is much longer than that in normal conducting cavity. This results in the strong interaction between the SC cavity and the beam through it. The high order mode field excited by short bunches could effect the beam and cause beam break up. In this paper, the total high order mode power of TESLA 9-cell cavity with the beam load of 1 mA was estimated．The result shows that the phase shifts of high ovder mode, referring to major eigen frequencies of the cavity, are more than π/4. There would be no resonant buildup. The total high order module power is in mW level.
2005,
17.
Abstract:
In this paper, fine-structure energy levels of configurations 4s24p3 and 4s4p4 for Arsenic isoelectronic sequence ions from KrIVto CdXVI are analysed by multi-configuration Hartree-Fock plus exchange-statistical-potential with relativistic corrections (HXR) method in Cowan'code. By analyzing variation of differences between the experimental data and the associated theoretical energies with Zc along the sequence, a new formula has been found for fit calculation. With this new formula, the fine-structure levels of the configurations mentioned above are predicted, the uncertainty of most predicted energy level values with the associated experimental results are not more than 100 cm-1. The wavelengths, oscillator strengths and probabilities of transitions 4s24p3_4s4p4 calculated with HXR meth
In this paper, fine-structure energy levels of configurations 4s24p3 and 4s4p4 for Arsenic isoelectronic sequence ions from KrIVto CdXVI are analysed by multi-configuration Hartree-Fock plus exchange-statistical-potential with relativistic corrections (HXR) method in Cowan'code. By analyzing variation of differences between the experimental data and the associated theoretical energies with Zc along the sequence, a new formula has been found for fit calculation. With this new formula, the fine-structure levels of the configurations mentioned above are predicted, the uncertainty of most predicted energy level values with the associated experimental results are not more than 100 cm-1. The wavelengths, oscillator strengths and probabilities of transitions 4s24p3_4s4p4 calculated with HXR meth
2005,
17.
Abstract:
A generalized equation, which governs the dependence of space charge current flow on conducting current in three relativistic configurations, is deduced from Poisson's equation with assumption of space-charge-limited flow and electrons' canonical momentum conservation. A method for solution to the equation is introduced and the characteristic of the solution for the three configurations is discussed. It is concluded that for these configurations the effect of conducting current on magnetic insulation is much significant with increase of anode voltage, and that for the same anode voltage their SCL flows will behave differently when their geometrical factors become small, with the SCL flow of the two non-plane conductors smaller than that of the plane conductor for negative polarity and larg
A generalized equation, which governs the dependence of space charge current flow on conducting current in three relativistic configurations, is deduced from Poisson's equation with assumption of space-charge-limited flow and electrons' canonical momentum conservation. A method for solution to the equation is introduced and the characteristic of the solution for the three configurations is discussed. It is concluded that for these configurations the effect of conducting current on magnetic insulation is much significant with increase of anode voltage, and that for the same anode voltage their SCL flows will behave differently when their geometrical factors become small, with the SCL flow of the two non-plane conductors smaller than that of the plane conductor for negative polarity and larg
2005,
17.
Abstract:
A method adopting the charge analog digital conversion technique to calibrate a current scintillation detector is described. Each pulse charge produced by a single particle is collected and recorded. Calculating the mean current, the sensitivity of the detector is measured. The results agree with the measurement presented by the traditional direct current method within ±8%. This new method can get higher accuracy, subtract background easily and it does not depend on the intensity of the radiation source. By applying time-of-flight method, it is capable of particle discrimination. It can separate the pulse charge produced by neutron from that produced by gamma in a neutron-gamma mixed field. The sensitivity of current detector to each type of particle can be measured separately. This metho
A method adopting the charge analog digital conversion technique to calibrate a current scintillation detector is described. Each pulse charge produced by a single particle is collected and recorded. Calculating the mean current, the sensitivity of the detector is measured. The results agree with the measurement presented by the traditional direct current method within ±8%. This new method can get higher accuracy, subtract background easily and it does not depend on the intensity of the radiation source. By applying time-of-flight method, it is capable of particle discrimination. It can separate the pulse charge produced by neutron from that produced by gamma in a neutron-gamma mixed field. The sensitivity of current detector to each type of particle can be measured separately. This metho
2005,
17.
Abstract:
A compact helical explosively-driven magnetic flux compression generator (MFCG) using rechargeable battery as initial energy source has two stages, one acts as an energy amplifier, the other serves as a pulse sharper to match high inductance load. The initial energy source includes a capacitor of 220μF charged with 6kV,a rechargeable battery and a high voltage converter. It takes about 5 minutes to charge the battery with 6 kV before the MFCG running, and the voltage of the battery is still larger than 11 V after five times. The results shows that this compact initial energy source system can stably offer larger initial energy, and the cascaded MFCG which is small and light can offer 120 kA current with a risetime of 15 μs to a large inductance load which is 4 μH.
A compact helical explosively-driven magnetic flux compression generator (MFCG) using rechargeable battery as initial energy source has two stages, one acts as an energy amplifier, the other serves as a pulse sharper to match high inductance load. The initial energy source includes a capacitor of 220μF charged with 6kV,a rechargeable battery and a high voltage converter. It takes about 5 minutes to charge the battery with 6 kV before the MFCG running, and the voltage of the battery is still larger than 11 V after five times. The results shows that this compact initial energy source system can stably offer larger initial energy, and the cascaded MFCG which is small and light can offer 120 kA current with a risetime of 15 μs to a large inductance load which is 4 μH.
2005,
17.
Abstract:
The measurement uncertainty is often evaluated by a probabilistic approach, but such evaluation is not always adapted to imprecise measurement data. This paper focuses on the use of the evidence theory to evaluate the measurement uncertainty of imprecise neutrons data. A formula is presented to measure and calculate the measurement uncertainty of imprecise neutrons data coming from imprecise physical sensors and approximate estimations provided by experts, the validity of the formula is demonstrated by two examples. The formula can be applied to precise neutrons data too.
The measurement uncertainty is often evaluated by a probabilistic approach, but such evaluation is not always adapted to imprecise measurement data. This paper focuses on the use of the evidence theory to evaluate the measurement uncertainty of imprecise neutrons data. A formula is presented to measure and calculate the measurement uncertainty of imprecise neutrons data coming from imprecise physical sensors and approximate estimations provided by experts, the validity of the formula is demonstrated by two examples. The formula can be applied to precise neutrons data too.
2005,
17.
Abstract:
The selection of medium material and the parameter design has the key influence on the loss of pulse transmission line. According to distributed parameter theory and electromagnetic microwave theory, the computing formulas of loss of epoxy-glass-fiber (FR-4) and Polytetrafluoroethylene (F4B) materials are given. When the characteristic impedance of microstrip is 50 W and the operating frequency is 10 GHz, the attenuation factor of medium of FR-4 and F4B materials are respectively 0.095dB/cm and 0.0023dB/cm. When the thickness of microstrip is 18 mm and the thickness of medium is 0.25 mm, the attenuation factor of conductor of FR-4 and F4B materials are respectively 0.049 9 dB/cm and 0.035 7 dB/cm. The numerical computing and simulation results show that the loss of medium and conductor of
The selection of medium material and the parameter design has the key influence on the loss of pulse transmission line. According to distributed parameter theory and electromagnetic microwave theory, the computing formulas of loss of epoxy-glass-fiber (FR-4) and Polytetrafluoroethylene (F4B) materials are given. When the characteristic impedance of microstrip is 50 W and the operating frequency is 10 GHz, the attenuation factor of medium of FR-4 and F4B materials are respectively 0.095dB/cm and 0.0023dB/cm. When the thickness of microstrip is 18 mm and the thickness of medium is 0.25 mm, the attenuation factor of conductor of FR-4 and F4B materials are respectively 0.049 9 dB/cm and 0.035 7 dB/cm. The numerical computing and simulation results show that the loss of medium and conductor of
2005,
17.
Abstract:
64 keV Ni ion implantation of a dose of 1×1017cm-2 was performed at room temperature in rutile TiO2 single crystals in which metallic Ni nanoparticles formed directly. Transmission electron microscopy and a superconducting quantum interference device (SQUID) magnetometer were used to characterize the microstructure and magnetic properties of Ni nanoparticles in TiO2. Metal Ni nanopartilces with size ranging 3~18 nm was observed in the near surface of TiO2. A high-resolution electron microscopy (HREM) image indicated the Ni-implanted area had been entirely amorphized. Magnetic measurement indicated that the coercive force of Ni nanoparticles was about 16.8 kA·m-1 at 10 K, which was larger than that of bulk materials of Ni. The blocking temperature obtained from ZFC/FC curves was about 85
64 keV Ni ion implantation of a dose of 1×1017cm-2 was performed at room temperature in rutile TiO2 single crystals in which metallic Ni nanoparticles formed directly. Transmission electron microscopy and a superconducting quantum interference device (SQUID) magnetometer were used to characterize the microstructure and magnetic properties of Ni nanoparticles in TiO2. Metal Ni nanopartilces with size ranging 3~18 nm was observed in the near surface of TiO2. A high-resolution electron microscopy (HREM) image indicated the Ni-implanted area had been entirely amorphized. Magnetic measurement indicated that the coercive force of Ni nanoparticles was about 16.8 kA·m-1 at 10 K, which was larger than that of bulk materials of Ni. The blocking temperature obtained from ZFC/FC curves was about 85
2005,
17.
Abstract:
A coaxial electrode experimental apparatus with water dielectric capacitor was set up, high voltage breakdown experiments for polished and unpolished surface of electrodes with microsecond charging were respectively carried out. The experimental results are shown as follows: (1) polished surface of electrodes effectively improves the capacity to maintain the high electrical voltage for water dielectric; (2) breakdown stress for surface polished electrode of roughness (0.4~0.8 μm) is in better agreement with Martin formula than roughly polished one(1.6~3.2 μm); (3) primary mechanism to increase the breakdown stress of water dielectric is that, field emission currents to heat the bubble become weak on the cathode for polished surface of the electrodes and the time lag to breakdown is incre
A coaxial electrode experimental apparatus with water dielectric capacitor was set up, high voltage breakdown experiments for polished and unpolished surface of electrodes with microsecond charging were respectively carried out. The experimental results are shown as follows: (1) polished surface of electrodes effectively improves the capacity to maintain the high electrical voltage for water dielectric; (2) breakdown stress for surface polished electrode of roughness (0.4~0.8 μm) is in better agreement with Martin formula than roughly polished one(1.6~3.2 μm); (3) primary mechanism to increase the breakdown stress of water dielectric is that, field emission currents to heat the bubble become weak on the cathode for polished surface of the electrodes and the time lag to breakdown is incre
2005,
17.
Abstract:
This paper presents a new theory to explain the synchrotron radiation. When charged particle does circular motion in the accelerator, the magnetic field of the accelerator can be taken as periodic, and equivalent to virtual photon. By Compton scattering of virtual photon and charged particle, the virtual photon can be transformed into photon to radiate out. According to this theory，the formula of photon wavelength in synchrotron radiation is found out, and the calculation results of wavelength is consonant with experimental data．
This paper presents a new theory to explain the synchrotron radiation. When charged particle does circular motion in the accelerator, the magnetic field of the accelerator can be taken as periodic, and equivalent to virtual photon. By Compton scattering of virtual photon and charged particle, the virtual photon can be transformed into photon to radiate out. According to this theory，the formula of photon wavelength in synchrotron radiation is found out, and the calculation results of wavelength is consonant with experimental data．
2005,
17.
Abstract:
The voltage response of a printed circuit board (PCB) in a metallic shielding enclosure excited by an external electromagnetic field is an important factor when considering the coupling of an external electromagnetic field to electronic systems. In this paper, the voltage response of PCB excited by an external source is calculated under two conditions: in free space and in the shielding enclosure. The frequency spectrum of voltage is calculated. When the PCB is put into the cavity with a long slot, some cases are considered including different electric field directions of incident source and different slot shapes. The variance of coupling coefficient is also calculated．
The voltage response of a printed circuit board (PCB) in a metallic shielding enclosure excited by an external electromagnetic field is an important factor when considering the coupling of an external electromagnetic field to electronic systems. In this paper, the voltage response of PCB excited by an external source is calculated under two conditions: in free space and in the shielding enclosure. The frequency spectrum of voltage is calculated. When the PCB is put into the cavity with a long slot, some cases are considered including different electric field directions of incident source and different slot shapes. The variance of coupling coefficient is also calculated．
2005,
17.
Abstract:
The initial value of the convergence half angle in the iterative synthesis is discussed and a more logical function is given for assigning it. With the application of the new function, the results of normal and high -convergence Pierce guns are completely the same with the results which are obtained with the application of Vaughan's, and reasonable results are got of the low -convergence ones which can not be settled by Vaughan's method. Therefore, the new function extends the application range of the iterative synthesis from the high -convergence to the low -convergence Pierce guns．
The initial value of the convergence half angle in the iterative synthesis is discussed and a more logical function is given for assigning it. With the application of the new function, the results of normal and high -convergence Pierce guns are completely the same with the results which are obtained with the application of Vaughan's, and reasonable results are got of the low -convergence ones which can not be settled by Vaughan's method. Therefore, the new function extends the application range of the iterative synthesis from the high -convergence to the low -convergence Pierce guns．
2005,
17.
Abstract:
Characteristics of ion noise in a klystron was discussed by using a hybrid model. One-dimensional particle-in-Cell method (PIC) simulation code is developed and the relation between ion noise and phase distortion was obtained. The characteristics of the ion noise in a klystron are treated as an example to be analyzed by this PIC code and the diagnosis of ion current on cathode was made. The numerical simulation results accord with measured values very well. When the beam current increases, the ion noise amplitude will decrease and become stable. There exists on optimal value of magnetic focusing field and beam voltage, which can minimize the ion noise amplitude.
Characteristics of ion noise in a klystron was discussed by using a hybrid model. One-dimensional particle-in-Cell method (PIC) simulation code is developed and the relation between ion noise and phase distortion was obtained. The characteristics of the ion noise in a klystron are treated as an example to be analyzed by this PIC code and the diagnosis of ion current on cathode was made. The numerical simulation results accord with measured values very well. When the beam current increases, the ion noise amplitude will decrease and become stable. There exists on optimal value of magnetic focusing field and beam voltage, which can minimize the ion noise amplitude.
2005,
17.
Abstract:
Through numerical calculation, the high frequency characteristics of magnetically insulated line oscillator （MILO） coaxial slow wave structure(SWS)，the frequency of the eigen-modes and its distribution of coaxial SWS are presented. The sizes of MILO are:the inner radius of the primary SWS and RF choke 4.6 cm and 4.2 cm,respectively, the cathode radius 3 cm. When the frequency in MILO is from 3.6 to 4.4 GHz, the RF chock cavity stops leakage of microwaves toward the pulse power, unexpectedly increases the output power. The cutoff frequency of the primary SWS is from 4.5 to 4.9 GHz. A wave whose frequency is near cutoff is evanescent in the primary SWS. The eigen-frequency of MILO with open boundary was calculated and the Q-value in the cavity was given by the experimental results. The fr
Through numerical calculation, the high frequency characteristics of magnetically insulated line oscillator （MILO） coaxial slow wave structure(SWS)，the frequency of the eigen-modes and its distribution of coaxial SWS are presented. The sizes of MILO are:the inner radius of the primary SWS and RF choke 4.6 cm and 4.2 cm,respectively, the cathode radius 3 cm. When the frequency in MILO is from 3.6 to 4.4 GHz, the RF chock cavity stops leakage of microwaves toward the pulse power, unexpectedly increases the output power. The cutoff frequency of the primary SWS is from 4.5 to 4.9 GHz. A wave whose frequency is near cutoff is evanescent in the primary SWS. The eigen-frequency of MILO with open boundary was calculated and the Q-value in the cavity was given by the experimental results. The fr
2005,
17.
Abstract:
Theoretical and particle simulation methods are used to investigate the transportation processes of intense relativistic electron beam(IREBs) guided by low magnetic field. It is shown that in the foilless diode, a magnetic field of tapered profile along the A-K gap can restrain the radial movement of electrons, and the undulation of radial movement is decreased in waveguide. Electrons movement guided by the magnetic field decreasing gradually along the tapered waveguide are also studied, it is found that the radial undulation of electrons is not enlarged, though the magnetic field decrease along the waveguide. A proper profile can reduce the requirement of the guiding magnetic field, it is advantageous to realize the high power microwave devices packed by permanent magnet.
Theoretical and particle simulation methods are used to investigate the transportation processes of intense relativistic electron beam(IREBs) guided by low magnetic field. It is shown that in the foilless diode, a magnetic field of tapered profile along the A-K gap can restrain the radial movement of electrons, and the undulation of radial movement is decreased in waveguide. Electrons movement guided by the magnetic field decreasing gradually along the tapered waveguide are also studied, it is found that the radial undulation of electrons is not enlarged, though the magnetic field decrease along the waveguide. A proper profile can reduce the requirement of the guiding magnetic field, it is advantageous to realize the high power microwave devices packed by permanent magnet.
2005,
17.
Abstract:
Starting from general transmission line equation with an electron beam, a self-consistent nonlinear analysis on 3 mm band second-harmonic complex cavity gyrotron with gradual transition is presented, in which the multiple mode interacting with a electron beam and mode coupling are taken into account, through a simulation code of self-consistent nonlinear beam-wave interaction made by ourselves. The influences of the magnetic field coefficient and current and the velocity ratio of the electron beam under the interaction between the electron beam and H02-H03 RF field for second-harmonic gyrotron are analyzed. The results show that an electron efficiency over 27% is predicted for suitable dimensions for the complex cavity and magnetic field coefficient and current and the velocity ratio of th
Starting from general transmission line equation with an electron beam, a self-consistent nonlinear analysis on 3 mm band second-harmonic complex cavity gyrotron with gradual transition is presented, in which the multiple mode interacting with a electron beam and mode coupling are taken into account, through a simulation code of self-consistent nonlinear beam-wave interaction made by ourselves. The influences of the magnetic field coefficient and current and the velocity ratio of the electron beam under the interaction between the electron beam and H02-H03 RF field for second-harmonic gyrotron are analyzed. The results show that an electron efficiency over 27% is predicted for suitable dimensions for the complex cavity and magnetic field coefficient and current and the velocity ratio of th
