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RSS2003 Vol. 15, No. 12
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2003,
15.
Abstract:
The transmissionline theory is used to calculate the latetime HEMP induced sheath current of long lines with different length and termination, which is located near or above the ground. The results show that the induced sheath current on the line with two grounded ends can reach to tens of As. As the line's length grows, the peak value of the sheath current increases, and the increase with the length slows down. When one end of a line have high serial resistance in the grounded wire(the other end is grounded), the peak value of the sheath current decreases obviously.
The transmissionline theory is used to calculate the latetime HEMP induced sheath current of long lines with different length and termination, which is located near or above the ground. The results show that the induced sheath current on the line with two grounded ends can reach to tens of As. As the line's length grows, the peak value of the sheath current increases, and the increase with the length slows down. When one end of a line have high serial resistance in the grounded wire(the other end is grounded), the peak value of the sheath current decreases obviously.
2003,
15.
Abstract:
With particle simulation and experiment, an axial feedback vircator is studied in detail. It shows that the axial feedbacked vircator can lock the microwave operation frequency and increase the microwave power effectively. In our model, It is found that the dominant microwave frequency is approximately unchanged at about 3.5GHz or at about 4.8GHz with the cathodeanode gap greater or less than 1.3cm, respectively, with a diode voltage of about 450kV and the beam current of about 22kA. In addition, it is also found that the coupling of the microwave of 3.5GHz with the cavity mode is good. The experimental results confirm the conclusions obtained in simulation.
With particle simulation and experiment, an axial feedback vircator is studied in detail. It shows that the axial feedbacked vircator can lock the microwave operation frequency and increase the microwave power effectively. In our model, It is found that the dominant microwave frequency is approximately unchanged at about 3.5GHz or at about 4.8GHz with the cathodeanode gap greater or less than 1.3cm, respectively, with a diode voltage of about 450kV and the beam current of about 22kA. In addition, it is also found that the coupling of the microwave of 3.5GHz with the cavity mode is good. The experimental results confirm the conclusions obtained in simulation.
2003,
15.
Abstract:
This paper experimentally studies the coupling coefficient of microwaves into rectangular slots. The frequency range is from 2 to 18GHz. The experimental method is presented, and the experimental setup is established. The experimental results show that the resonant effect will take place if the microwave wavelength is twice about the side length of the rectangular slot, and if the direction of the incident electric field is perpendicular to the long side of the slot. There is a strong coupling band near the resonant frequency, around which the enhancement effect can take place.
This paper experimentally studies the coupling coefficient of microwaves into rectangular slots. The frequency range is from 2 to 18GHz. The experimental method is presented, and the experimental setup is established. The experimental results show that the resonant effect will take place if the microwave wavelength is twice about the side length of the rectangular slot, and if the direction of the incident electric field is perpendicular to the long side of the slot. There is a strong coupling band near the resonant frequency, around which the enhancement effect can take place.
2003,
15.
Abstract:
This paper analyzes transient radiation of transverse electronmagnetic(TEM) horn antenna arrays with FETD method. Influence of the mutual coupling between the elements on far-field radiation is analyzed. The radiation performance at lower frequencies can be improved using the stacked TEM-horn configuration and decreased using rain gutter and square plane TEM-horn configuration. Rain gutter and stacked two-element of half TEM-horn arrays and four-element of half TEM-horn arrays were investigated by simulation and experiments. Experiments of TEM-horn array verified the result of the FDTD simulations．
This paper analyzes transient radiation of transverse electronmagnetic(TEM) horn antenna arrays with FETD method. Influence of the mutual coupling between the elements on far-field radiation is analyzed. The radiation performance at lower frequencies can be improved using the stacked TEM-horn configuration and decreased using rain gutter and square plane TEM-horn configuration. Rain gutter and stacked two-element of half TEM-horn arrays and four-element of half TEM-horn arrays were investigated by simulation and experiments. Experiments of TEM-horn array verified the result of the FDTD simulations．
2003,
15.
Abstract:
Experimental study on coaxial vircatoris carried out on SINUS accelerator is introduced in this paper. Narrow band high power microwave is obtained and measured in several methods which ensures the accuracy. The result shows that the dominant mode of the output microwave is TE11 in a coaxial vircator without anode reflector. With 300kV diode voltage and 18kA diode current, the generted microwave power is about 200MW at 2.7GHz operating frequency, the conversion efficiency is about 3.6%．
Experimental study on coaxial vircatoris carried out on SINUS accelerator is introduced in this paper. Narrow band high power microwave is obtained and measured in several methods which ensures the accuracy. The result shows that the dominant mode of the output microwave is TE11 in a coaxial vircator without anode reflector. With 300kV diode voltage and 18kA diode current, the generted microwave power is about 200MW at 2.7GHz operating frequency, the conversion efficiency is about 3.6%．
2003,
15.
Abstract:
With the combination of three gain mechanism of double tapered structure, choke and impedance transition based on the two present magnetically insulated transmission line oscillater (MILO) models, a new improved type MILO has been designed through numerical simulation using two and a half dimensional particle in cell (PIC) code. Its peak output power is 6GW in L band when input voltage is 550kV and input current is about 35kA.
With the combination of three gain mechanism of double tapered structure, choke and impedance transition based on the two present magnetically insulated transmission line oscillater (MILO) models, a new improved type MILO has been designed through numerical simulation using two and a half dimensional particle in cell (PIC) code. Its peak output power is 6GW in L band when input voltage is 550kV and input current is about 35kA.
2003,
15.
Abstract:
A compact Lband magnetically insulated transmission line oscillator (MILO) is configured with the reduction of the radius and the length of the cathode, the anodecathode gap, the length and the thickness of the vanes and the period of the slowwave structure. With the use of a 2.5 dimensional fully electromagnetic particleincell code, high power microwave is generated from the device with the average output power of 5.５GW, the frequency of 1.9GHz and the efficiency of 12%. Breakdown can be avoided in the compact MILO and the symmetry of beam emission can be controlled easily.
A compact Lband magnetically insulated transmission line oscillator (MILO) is configured with the reduction of the radius and the length of the cathode, the anodecathode gap, the length and the thickness of the vanes and the period of the slowwave structure. With the use of a 2.5 dimensional fully electromagnetic particleincell code, high power microwave is generated from the device with the average output power of 5.５GW, the frequency of 1.9GHz and the efficiency of 12%. Breakdown can be avoided in the compact MILO and the symmetry of beam emission can be controlled easily.
2003,
15.
Abstract:
In order to improve the performance of the magnetic injection gun(MIG),the beam has the mezzo velocity ratio between 1.5 and 2.0 and transvelocity spread lower than 5%.Three kinds of the magnetic field:the sin function magnetic field,the conic function one and the tanh function one, are discussed. Each kind of field distribution was changed and the simulation shows that:if sin or conic function field is used ,the beam performance can be improved by changing the flat region length,i.e.,moving the turning point near the end of the control anode ,then the velocity ratio will be maximum;if the tanh one is adopted ,and the field angle is in the range 9°to 70°,when the field angle increases,the velocity ratio increases as well as the trans velocity spread remains stable.
In order to improve the performance of the magnetic injection gun(MIG),the beam has the mezzo velocity ratio between 1.5 and 2.0 and transvelocity spread lower than 5%.Three kinds of the magnetic field:the sin function magnetic field,the conic function one and the tanh function one, are discussed. Each kind of field distribution was changed and the simulation shows that:if sin or conic function field is used ,the beam performance can be improved by changing the flat region length,i.e.,moving the turning point near the end of the control anode ,then the velocity ratio will be maximum;if the tanh one is adopted ,and the field angle is in the range 9°to 70°,when the field angle increases,the velocity ratio increases as well as the trans velocity spread remains stable.
2003,
15.
Abstract:
This paper investigates, theoretically and experimentally, the elements which influence the gain distribution of laser medium. A high gain laser module and a high energy storage laser module have been manufactured. The experiment results approved that the high gain laser module was pumped uniformly and a TEM00 output energy of 11.8mJ was achieved at a light-light efficiency of 15％. In the high energy storage laser module, a 6mm diameter Nd:YAG rod which is 100mm long was pumped by nine-diode arrays (the peak pump-power is 6 500kW) . Numerical calculation was done to optimize the distance between diode and Nd:YAG. The experiment result approved that the gain coefficient of this module is 0.3/cm, and the storage power is 400mJ per pulse．
This paper investigates, theoretically and experimentally, the elements which influence the gain distribution of laser medium. A high gain laser module and a high energy storage laser module have been manufactured. The experiment results approved that the high gain laser module was pumped uniformly and a TEM00 output energy of 11.8mJ was achieved at a light-light efficiency of 15％. In the high energy storage laser module, a 6mm diameter Nd:YAG rod which is 100mm long was pumped by nine-diode arrays (the peak pump-power is 6 500kW) . Numerical calculation was done to optimize the distance between diode and Nd:YAG. The experiment result approved that the gain coefficient of this module is 0.3/cm, and the storage power is 400mJ per pulse．
2003,
15.
Abstract:
Detection for a faint astronomical object in daytime is an extremely complex issue because of low targetbackgroundcontrast and low signaltonoise ratio. Some ways to improve the detection probability is studied in this paper. The results show, spectral filtering technology is an effective way to improve signaltonoise ratio. The reasonable choice of field of view is helpful to get higher signaltonoise ratio and contrast. With the reasonable choice of field of view and the effective application of morphologybased detection algorithm, the detection efficiency could be greatly improved.
Detection for a faint astronomical object in daytime is an extremely complex issue because of low targetbackgroundcontrast and low signaltonoise ratio. Some ways to improve the detection probability is studied in this paper. The results show, spectral filtering technology is an effective way to improve signaltonoise ratio. The reasonable choice of field of view is helpful to get higher signaltonoise ratio and contrast. With the reasonable choice of field of view and the effective application of morphologybased detection algorithm, the detection efficiency could be greatly improved.
2003,
15.
Abstract:
For farinfrared FEL, it was found that the diffractive loss is so large that it is half of total loss due to the longer wavelength using holecoupled resonator. By changing the size of the hole, the diffractive loss can't be reduced efficiently. To improve the quality of resonator, the simulation and design of the CAEP FIR FEL with inserted scraper output coupler had been made with the help of our 3D FEL oscillator code. It is proved that the inserted scraper is effective and applicable for the FIR FEL. Using inserted scraper output coupler, the optical cavity Q can be tuned freely. The saturated power, the net gain and the coupling efficiency are evaluated as a function of the scraper radius and the distance between scraper and the center of mirror.
For farinfrared FEL, it was found that the diffractive loss is so large that it is half of total loss due to the longer wavelength using holecoupled resonator. By changing the size of the hole, the diffractive loss can't be reduced efficiently. To improve the quality of resonator, the simulation and design of the CAEP FIR FEL with inserted scraper output coupler had been made with the help of our 3D FEL oscillator code. It is proved that the inserted scraper is effective and applicable for the FIR FEL. Using inserted scraper output coupler, the optical cavity Q can be tuned freely. The saturated power, the net gain and the coupling efficiency are evaluated as a function of the scraper radius and the distance between scraper and the center of mirror.
2003,
15.
Abstract:
The temperature distribution in two kinds of solid fuel combustion have been measured instantly by BOXCARS with single laser pulse. The combustions were optimized to solve flutter and bifurcate of flame. The data are acquired at high temporal and spatial resolution, the spatial resolution is about 1.2mm and the time resolution is about 8ns. The temperature is as high as 2 260K in SZFDB1 solid fuel combustion and 2 090K in SZFDB4 solid fuel combustion, The result indicates that temperature at the transient combustion field can be measured preferably by BOXCARS.
The temperature distribution in two kinds of solid fuel combustion have been measured instantly by BOXCARS with single laser pulse. The combustions were optimized to solve flutter and bifurcate of flame. The data are acquired at high temporal and spatial resolution, the spatial resolution is about 1.2mm and the time resolution is about 8ns. The temperature is as high as 2 260K in SZFDB1 solid fuel combustion and 2 090K in SZFDB4 solid fuel combustion, The result indicates that temperature at the transient combustion field can be measured preferably by BOXCARS.
2003,
15.
Abstract:
A portable Mie lidar has been developed for both daytime and nighttime aerosol measurements. The overall structure and specifications of the portable Mie lidar are described. The primary observational aerosol extinction profiles at 532nm are also presented and discussed in this paper. Signals detected by portable Mie lidar can reach about 25km at nighttime and 15km at daytime. It can also be used to measure the thickness and peak extinction value of cirrus．
A portable Mie lidar has been developed for both daytime and nighttime aerosol measurements. The overall structure and specifications of the portable Mie lidar are described. The primary observational aerosol extinction profiles at 532nm are also presented and discussed in this paper. Signals detected by portable Mie lidar can reach about 25km at nighttime and 15km at daytime. It can also be used to measure the thickness and peak extinction value of cirrus．
2003,
15.
Abstract:
A chemical oxygen-iodine laser (COIL) with nitrogen buffer gases was designed and experimentally investigated. An output power of 2.6kW was obtained for a chlorine flowrate of 140mmol/s, corresponding to a chemical efficiency of 20.4% and a nozzle power flux of 74W/cm2 . The results approach the performance of the similar scale COIL with helium buffer gases in previous research．
A chemical oxygen-iodine laser (COIL) with nitrogen buffer gases was designed and experimentally investigated. An output power of 2.6kW was obtained for a chlorine flowrate of 140mmol/s, corresponding to a chemical efficiency of 20.4% and a nozzle power flux of 74W/cm2 . The results approach the performance of the similar scale COIL with helium buffer gases in previous research．
Evaluating refractive index structure constant and characterizing spectrum of atmospheric turbulence
2003,
15.
Abstract:
Characteristics of temperature's fluctuation measured at the maritime atmospheric surface layer is analyzed. The result is that the power spectrum of virtual temperature varies with time. Then refractive index structure constant evaluated with different average times are compared. In the end, an algorithm according to the inherent state's changing of the atmosphere is built to estimate refrective index structure constant.
Characteristics of temperature's fluctuation measured at the maritime atmospheric surface layer is analyzed. The result is that the power spectrum of virtual temperature varies with time. Then refractive index structure constant evaluated with different average times are compared. In the end, an algorithm according to the inherent state's changing of the atmosphere is built to estimate refrective index structure constant.
2003,
15.
Abstract:
Six types of Nd3+ laser glasses of N31 phosphate laser glasses are experimented and analyzed by JuddOfelt model. the experiment result shows that when the Nd3+ concentrations increases, the stimulatedemission cross section of the Nd3+ laser glasses decreases. therefore, the influence of Nd3+ should be considered in laser system design.
Six types of Nd3+ laser glasses of N31 phosphate laser glasses are experimented and analyzed by JuddOfelt model. the experiment result shows that when the Nd3+ concentrations increases, the stimulatedemission cross section of the Nd3+ laser glasses decreases. therefore, the influence of Nd3+ should be considered in laser system design.
2003,
15.
Abstract:
The oxide laser reflecting multi-layers of Ta2O5 and SiO2 were prepared by double ion-beams sputtering method. The deposition techniques, the uniformity of layer thickness, and the optical charactes were studied. A uniform distribution is achieved by means of changing the tilt degree of substrate and the oscillating degree of the target. In addition, the refractive index, the structure of the layers, center wavelength of 633nm and 1 315nm baffleboard, AR coatings and times control method were presented and discussed.
The oxide laser reflecting multi-layers of Ta2O5 and SiO2 were prepared by double ion-beams sputtering method. The deposition techniques, the uniformity of layer thickness, and the optical charactes were studied. A uniform distribution is achieved by means of changing the tilt degree of substrate and the oscillating degree of the target. In addition, the refractive index, the structure of the layers, center wavelength of 633nm and 1 315nm baffleboard, AR coatings and times control method were presented and discussed.
2003,
15.
Abstract:
In this paper，numerical method was used to quantitatively calculate the limited uniformintensity focused beam spreading induced by atmospheric turbulence. The effect of obscuring ratio on the beam spreading was analyzed. The results show that the obscuring ratio has obvious influence on the beam spreading in weak turbulence. But when turbulence is strong， this influence can be neglected and the beam spreading is mainly determined by the intensity of turbulence effects. Moreover，the scaling relation between the beam spreading and the characteristic parameter described turbulence effects is derived.
In this paper，numerical method was used to quantitatively calculate the limited uniformintensity focused beam spreading induced by atmospheric turbulence. The effect of obscuring ratio on the beam spreading was analyzed. The results show that the obscuring ratio has obvious influence on the beam spreading in weak turbulence. But when turbulence is strong， this influence can be neglected and the beam spreading is mainly determined by the intensity of turbulence effects. Moreover，the scaling relation between the beam spreading and the characteristic parameter described turbulence effects is derived.
2003,
15.
Abstract:
Based on the load current of S300 machine, in Russia, optimal combinations of radius and mass per unit length of tungsten wirearrays were obtained by a lot of optimal calculation by means of 0D model, under different drive current with peak value of 2.5MA, 4MA, 5MA, 6MA, 8MA, and 20MA, respectively. The calculation shows that the optimal linear mass increases with the rising time of current, and that the maximal kinetic energy of implosion is in direct proportion to square of current peak value.
Based on the load current of S300 machine, in Russia, optimal combinations of radius and mass per unit length of tungsten wirearrays were obtained by a lot of optimal calculation by means of 0D model, under different drive current with peak value of 2.5MA, 4MA, 5MA, 6MA, 8MA, and 20MA, respectively. The calculation shows that the optimal linear mass increases with the rising time of current, and that the maximal kinetic energy of implosion is in direct proportion to square of current peak value.
2003,
15.
Abstract:
Indirect-drive targets is a capsule encased in a cylindrical Au hohlraum with two laser entrance at opposite ends. The capsule is composed of gas fuel, glass shell and CH ablator. There is no way to measure the amount of gas fuel in the capsule after coating the CH layer. This paper focuses on the difference between the hollow glass microsphere general properties and the individual. Preliminary experiments have been performed to determine the statistical distribution of the hollow glass microsphere diameter, wall thickness and permeability based on the experiment data. The permeability differs although the diameter and wall thickness are the same. In order to measure the inner gas amount the permeability should keep homologenous or similar by taking any sample for measurement. A method is
Indirect-drive targets is a capsule encased in a cylindrical Au hohlraum with two laser entrance at opposite ends. The capsule is composed of gas fuel, glass shell and CH ablator. There is no way to measure the amount of gas fuel in the capsule after coating the CH layer. This paper focuses on the difference between the hollow glass microsphere general properties and the individual. Preliminary experiments have been performed to determine the statistical distribution of the hollow glass microsphere diameter, wall thickness and permeability based on the experiment data. The permeability differs although the diameter and wall thickness are the same. In order to measure the inner gas amount the permeability should keep homologenous or similar by taking any sample for measurement. A method is
2003,
15.
Abstract:
The RayleighTaylor instability caused by a density gradient is very important in the inertial confinement fusion. With the passive scalar transport model, behaviors of the interface with various initial length scales are simulated. It appears that the initial form has a significant influence upon the interfacial motion. Long grooves grow more slowly than square shaped perturbations. And generally the mixing process in the vertical direction may be decreased by the interaction between bubbles with different scales.
The RayleighTaylor instability caused by a density gradient is very important in the inertial confinement fusion. With the passive scalar transport model, behaviors of the interface with various initial length scales are simulated. It appears that the initial form has a significant influence upon the interfacial motion. Long grooves grow more slowly than square shaped perturbations. And generally the mixing process in the vertical direction may be decreased by the interaction between bubbles with different scales.
2003,
15.
Abstract:
The picosecond pulse was obtained by two-stage stimulated Brillouin scattering (SBS) compressor to compress 8ns laser pulse. The experiment used CCl4 as SBS medium. The laser pulse duratiuon was compressed to 1.5ns by the first stage compressor. In the second compress stage, the experiment investigated the compress procession using 532nm and 1 064nm as puming light separately. The shortest pulse of 60ps was obtained. The results show that the pulse duration shorter than the medium acoustic lifetime can be achieved by SBS compressor.
The picosecond pulse was obtained by two-stage stimulated Brillouin scattering (SBS) compressor to compress 8ns laser pulse. The experiment used CCl4 as SBS medium. The laser pulse duratiuon was compressed to 1.5ns by the first stage compressor. In the second compress stage, the experiment investigated the compress procession using 532nm and 1 064nm as puming light separately. The shortest pulse of 60ps was obtained. The results show that the pulse duration shorter than the medium acoustic lifetime can be achieved by SBS compressor.
2003,
15.
Abstract:
The distance between the electrodes of accelerator will shrink when the target chamber is pumped to vacuum. This may lead to the failure of the loaded wire-arrays since they can not keep the required state. A solution to this problem is the novel method to design and fabricate the wire-arrays which have self-adapting adjustment to meet the changes of the electrodes distances. During the fabrication of the arrays, the springs are pre-compressed short of about 3mm, the wires are fixed and distributed in between two fixtures which are to be loaded to the electrodes. Tests and applications were employed and the results show that the fabricated wire-arrays can be used in chambers with electrodes arranged in any directions. Further more, the novel techniques facilitate the fabrication, storage,
The distance between the electrodes of accelerator will shrink when the target chamber is pumped to vacuum. This may lead to the failure of the loaded wire-arrays since they can not keep the required state. A solution to this problem is the novel method to design and fabricate the wire-arrays which have self-adapting adjustment to meet the changes of the electrodes distances. During the fabrication of the arrays, the springs are pre-compressed short of about 3mm, the wires are fixed and distributed in between two fixtures which are to be loaded to the electrodes. Tests and applications were employed and the results show that the fabricated wire-arrays can be used in chambers with electrodes arranged in any directions. Further more, the novel techniques facilitate the fabrication, storage,
2003,
15.
Abstract:
The design and characterization of a Ti:sapphire highintensity laser system is presented. A spatial fourpass imagedelayed amplifier, which can output good quality beam, is employed in the system. The system is demonstrated in order to reach the intensity in excess of 3×1018W/cm2 for ultraintensity field experiments. In order to decrease the effects of gain narrowing, an acoustooptic programmable dispersive filter is applied after the femtosecond oscillator.
The design and characterization of a Ti:sapphire highintensity laser system is presented. A spatial fourpass imagedelayed amplifier, which can output good quality beam, is employed in the system. The system is demonstrated in order to reach the intensity in excess of 3×1018W/cm2 for ultraintensity field experiments. In order to decrease the effects of gain narrowing, an acoustooptic programmable dispersive filter is applied after the femtosecond oscillator.
2003,
15.
Abstract:
This paper introduces the digitized design of the cooling system of 2kW traveling wave accelerator which is used for killing anthrax. The parameters of cooling system was calculated and optimized by means of finite element analysis. The work was done with the CAD software IDEAS. As a result, a compact jacket style structure of stainless steel is got and employed in the accelerator. The system is very robust again surrounding temperature change. Now the cooling facility is running well.
This paper introduces the digitized design of the cooling system of 2kW traveling wave accelerator which is used for killing anthrax. The parameters of cooling system was calculated and optimized by means of finite element analysis. The work was done with the CAD software IDEAS. As a result, a compact jacket style structure of stainless steel is got and employed in the accelerator. The system is very robust again surrounding temperature change. Now the cooling facility is running well.
2003,
15.
Abstract:
This paper presents a Fokker-Planck equation to describe the distribution of the particles in bunch, which includes synchrotron radiation damping effect. The subject of longitudinal microwave instability of a single bunched beam in a circular accelerator is studied with perturbation approach based on the Fokker-Planck equation, the potential well distortion effect and the synchrotron radiation damping effect being also included. The result shows that the threshold in the case of radiation damping included is a little higher than that in the case of no damping included.
This paper presents a Fokker-Planck equation to describe the distribution of the particles in bunch, which includes synchrotron radiation damping effect. The subject of longitudinal microwave instability of a single bunched beam in a circular accelerator is studied with perturbation approach based on the Fokker-Planck equation, the potential well distortion effect and the synchrotron radiation damping effect being also included. The result shows that the threshold in the case of radiation damping included is a little higher than that in the case of no damping included.
