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RSS2004 Vol. 16, No. 01
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2004,
16.
Abstract:
With the help of wave theory of light, the effect of hole grating gradient on farfield is analyzed by numerical calculation in this paper. The results show that the systemic error of measurement of intensity(power, beam quality, etc. ) of farfield is definite, and the more the gradient is ,the more the diffractive grade is, the bigger the effect. The smaller gradient and diffractive grade should be chosen while using hole grating to diagnose the beam power and quality.
With the help of wave theory of light, the effect of hole grating gradient on farfield is analyzed by numerical calculation in this paper. The results show that the systemic error of measurement of intensity(power, beam quality, etc. ) of farfield is definite, and the more the gradient is ,the more the diffractive grade is, the bigger the effect. The smaller gradient and diffractive grade should be chosen while using hole grating to diagnose the beam power and quality.
2004,
16.
Abstract:
For some optical films, laser conditioning is an effective way to improve their damage threshold. The one of popular theoretical model for laser conditioning mechanism is the defectseliminated model. In this paper, the influence of laser conditioning on optical films are analyzed by optical parameters testing of the films before and after laser conditioning. It shows that the process of laser conditioning for optical films is the films defectseliminated, solidified and cleaned process.
For some optical films, laser conditioning is an effective way to improve their damage threshold. The one of popular theoretical model for laser conditioning mechanism is the defectseliminated model. In this paper, the influence of laser conditioning on optical films are analyzed by optical parameters testing of the films before and after laser conditioning. It shows that the process of laser conditioning for optical films is the films defectseliminated, solidified and cleaned process.
2004,
16.
Abstract:
The coupled wave theory of nonlinear optics is adopted to establish twodimensional theoretical model of seeded、narrowband pumped transverse SBS. The numerical investigation of steadystate situation is offered and the planar distribution of scattering light intensity is obtained. The calculation shows that scattering light has the character of local concentration, and the maximum of scattering light intensity is much greater than the pump light intensity as a result of “space compression” effect. This paper also analyzes the variation of scattering light intensity with different pump conditions and different material parameters and puts some qualitative conclusions.
The coupled wave theory of nonlinear optics is adopted to establish twodimensional theoretical model of seeded、narrowband pumped transverse SBS. The numerical investigation of steadystate situation is offered and the planar distribution of scattering light intensity is obtained. The calculation shows that scattering light has the character of local concentration, and the maximum of scattering light intensity is much greater than the pump light intensity as a result of “space compression” effect. This paper also analyzes the variation of scattering light intensity with different pump conditions and different material parameters and puts some qualitative conclusions.
2004,
16.
Abstract:
The broadband USED CARS measurements of temperature and N2 concentration in the combustion of solid propellant at atmospheric pressure are reported. The singlepulse N2 CARS spectra have been obtained from solid propellant combustion. The CARS data are analyzed by comparison with theoretical spectra generated at various temperatures and N2 concentrations. The temperatures and N2 concentrations of the solid propellant flame at different height have been measured and the results indicate temperature up to 2 250K with N2 concentration of 16%～20%.
The broadband USED CARS measurements of temperature and N2 concentration in the combustion of solid propellant at atmospheric pressure are reported. The singlepulse N2 CARS spectra have been obtained from solid propellant combustion. The CARS data are analyzed by comparison with theoretical spectra generated at various temperatures and N2 concentrations. The temperatures and N2 concentrations of the solid propellant flame at different height have been measured and the results indicate temperature up to 2 250K with N2 concentration of 16%～20%.
2004,
16.
Abstract:
In this paper, taking into account both the selfphasemodulation (SPM) and the lowest and second order group velocity dispersion (GVD), the propagation equations of ultrashort pulses is given through numerical analysis. The influence of input intensity on ultrashort pulses in Fibonacci superlattice is analyzed. The calculations show that the input intensity cause broadening in the spectrum and set a limit to effective length of superlattice, which is an important factor for frequency conversion.
In this paper, taking into account both the selfphasemodulation (SPM) and the lowest and second order group velocity dispersion (GVD), the propagation equations of ultrashort pulses is given through numerical analysis. The influence of input intensity on ultrashort pulses in Fibonacci superlattice is analyzed. The calculations show that the input intensity cause broadening in the spectrum and set a limit to effective length of superlattice, which is an important factor for frequency conversion.
2004,
16.
Abstract:
In this paper, the experimental results that detector system of three PC HgCdTe units is destroyed by 3.8μm laser are reported and analyzed qualitatively. Researches indicate that components of detector system which are Ge window, filter and detectors are destroyed when laser power density reaches 411W/cm2. Analyses show ablation heat is the most important reason of detector system damage in this experiment.
In this paper, the experimental results that detector system of three PC HgCdTe units is destroyed by 3.8μm laser are reported and analyzed qualitatively. Researches indicate that components of detector system which are Ge window, filter and detectors are destroyed when laser power density reaches 411W/cm2. Analyses show ablation heat is the most important reason of detector system damage in this experiment.
2004,
16.
Abstract:
The principle of atmospheric coherence length measurement via differential image motion measure of the optical wave's angleofarrival fluctuation is introduced. An instrument for the measurement of atmospheric coherence length both in the daytime and at night were described. The statistical characteristics of the atmospheric coherence length in the daytime and at night were analyzed from some primary observation results. It shows that the refractive index structure constant varies with the time in total layer, and the timevarying behavior is basically in accordance with that of the boundary layer, that is, the atmospheric coherence length during the period of sunrise and sundown is much larger than that in the other periods.
The principle of atmospheric coherence length measurement via differential image motion measure of the optical wave's angleofarrival fluctuation is introduced. An instrument for the measurement of atmospheric coherence length both in the daytime and at night were described. The statistical characteristics of the atmospheric coherence length in the daytime and at night were analyzed from some primary observation results. It shows that the refractive index structure constant varies with the time in total layer, and the timevarying behavior is basically in accordance with that of the boundary layer, that is, the atmospheric coherence length during the period of sunrise and sundown is much larger than that in the other periods.
2004,
16.
Abstract:
In order to test Xray laser (XRL) series programs, simulations of some experiments of Nelike Ge XRL were completed, including domestic experiments driven with longpulse (1ns) and international experiments driven with multiple-pulse. In the case of longpulse, for three lines of 19.6, 23.2, 23.6nm, theoretical results are mainly consistent with experimental data. And in the case of multiplepulse, theoretical simulations are also consistent with experiments except the experiments with seriously overionized recombination plasmas. This work has laid the foundation of later effort to design Nelike Ge XRL resource which is used to diagnose plasma of ICF.
In order to test Xray laser (XRL) series programs, simulations of some experiments of Nelike Ge XRL were completed, including domestic experiments driven with longpulse (1ns) and international experiments driven with multiple-pulse. In the case of longpulse, for three lines of 19.6, 23.2, 23.6nm, theoretical results are mainly consistent with experimental data. And in the case of multiplepulse, theoretical simulations are also consistent with experiments except the experiments with seriously overionized recombination plasmas. This work has laid the foundation of later effort to design Nelike Ge XRL resource which is used to diagnose plasma of ICF.
2004,
16.
Abstract:
A sol containing SiO2 particles was prepared by the base catalyzed hydrolysis and polycondensation of tetraethoxysilane (TEOS) through sol-gel process. A solution containing double-chain polymer of methyltriethoxysilane (MTES) was also prepared under acid condition, as the introducer of water repellence. After mixing these two kinds of sols, spinning coating was used to deposit films on glass. Several techniques-photon correlation spectrum，TEM and small angle X-ray scattering, were used to characterize the microstructure. The transmission and wet-angle for water of films were measured by UV-Vis and contact angle analyzer. The reflection -can be reduced to 0.01% and the wet-angle for water was 118°at most. A Nd:YAG laser was used to determine the laser damage threshold of film at 1 064nm.
A sol containing SiO2 particles was prepared by the base catalyzed hydrolysis and polycondensation of tetraethoxysilane (TEOS) through sol-gel process. A solution containing double-chain polymer of methyltriethoxysilane (MTES) was also prepared under acid condition, as the introducer of water repellence. After mixing these two kinds of sols, spinning coating was used to deposit films on glass. Several techniques-photon correlation spectrum，TEM and small angle X-ray scattering, were used to characterize the microstructure. The transmission and wet-angle for water of films were measured by UV-Vis and contact angle analyzer. The reflection -can be reduced to 0.01% and the wet-angle for water was 118°at most. A Nd:YAG laser was used to determine the laser damage threshold of film at 1 064nm.
2004,
16.
Abstract:
The characters of sapphire, especially its birefringence, are investigated. The antireflection films(AR) on sapphire are designed and prepared. The film's properties, such as wavefront, morphology, are measured and analyzed. A laser heat distortion experiment is carried out, and the variation of wavefront of coated sapphire and quartz are detected. A damage threshold of at least 10kW/cm2 is determined of the coated sapphire.
The characters of sapphire, especially its birefringence, are investigated. The antireflection films(AR) on sapphire are designed and prepared. The film's properties, such as wavefront, morphology, are measured and analyzed. A laser heat distortion experiment is carried out, and the variation of wavefront of coated sapphire and quartz are detected. A damage threshold of at least 10kW/cm2 is determined of the coated sapphire.
2004,
16.
Abstract:
The relation between the angle of off-axis-light and the depolarization loss has been calculated under different incidence of polarization. The results show when the thickness of crystal was settled, the depolarization loss is directly proportional to the angle of off-axis-light and the angle between the polarization of laser beam and the main axis of crystal in some confine. When the thickness of crystal is 10mm, the depolarization loss under different case was measured. When the angle of off-axis-light is less than 15mrad, the depolarization loss of electro-optical crystal is less than 0.5%, but when the angle is larger than 15mrad, the depolarization increases very quickly. The measurement results are in accord with ones of the calculation.
The relation between the angle of off-axis-light and the depolarization loss has been calculated under different incidence of polarization. The results show when the thickness of crystal was settled, the depolarization loss is directly proportional to the angle of off-axis-light and the angle between the polarization of laser beam and the main axis of crystal in some confine. When the thickness of crystal is 10mm, the depolarization loss under different case was measured. When the angle of off-axis-light is less than 15mrad, the depolarization loss of electro-optical crystal is less than 0.5%, but when the angle is larger than 15mrad, the depolarization increases very quickly. The measurement results are in accord with ones of the calculation.
2004,
16.
Abstract:
Timeresolved and timeintegrated stimulated Raman scattering (SRS) spectra from gold hohlraum irradiated with 351nm laser light are measured. The experimental results are inconsistent with the prediction of the convective SRS theory and enhanced incoherent Thomson scattering model. The analyses show that the prediction of SRS in filaments agrees reasonably with the experimental results. Based on the model of the coupling between filaments and SRS, the method of diagnosing plasma density with SRS spectrum was developed. The calculated result shows that the difference between the model and the convective SRS theory is less than 10%, which agrees with the conclusion made by Afsharrad［Phys. Fluids B 4,1301(1992)］.
Timeresolved and timeintegrated stimulated Raman scattering (SRS) spectra from gold hohlraum irradiated with 351nm laser light are measured. The experimental results are inconsistent with the prediction of the convective SRS theory and enhanced incoherent Thomson scattering model. The analyses show that the prediction of SRS in filaments agrees reasonably with the experimental results. Based on the model of the coupling between filaments and SRS, the method of diagnosing plasma density with SRS spectrum was developed. The calculated result shows that the difference between the model and the convective SRS theory is less than 10%, which agrees with the conclusion made by Afsharrad［Phys. Fluids B 4,1301(1992)］.
2004,
16.
Abstract:
This paper experimentally studies the coupling coefficient of microwaves into apertures with different shapes and sizes. The apertures used in the experiment mainly include elliptic aperture, circle, square loop, crossed rectangular slots, circular aperture, square aperture, equilateral triangular aperture, and parelleloriented rectangular slots. The coupling coefficients for these apertures in the frequency range from 2 to 18GHz are presented and compared with that for the rectangular slot.
This paper experimentally studies the coupling coefficient of microwaves into apertures with different shapes and sizes. The apertures used in the experiment mainly include elliptic aperture, circle, square loop, crossed rectangular slots, circular aperture, square aperture, equilateral triangular aperture, and parelleloriented rectangular slots. The coupling coefficients for these apertures in the frequency range from 2 to 18GHz are presented and compared with that for the rectangular slot.
2004,
16.
Abstract:
The experiment of mass jet distribution in gas spark gaps was carried out under microsecond hundred-kiloampere current pulse. Four kinds of electrode materials were studied in experiment. The results show that the direction of mass jet is independent of electrode material and normal to the electrode surface at the arc spot. The angle of divergence is about 12°and the mass distribution of jet is approximate to cos nφ(n≈1 400).
The experiment of mass jet distribution in gas spark gaps was carried out under microsecond hundred-kiloampere current pulse. Four kinds of electrode materials were studied in experiment. The results show that the direction of mass jet is independent of electrode material and normal to the electrode surface at the arc spot. The angle of divergence is about 12°and the mass distribution of jet is approximate to cos nφ(n≈1 400).
2004,
16.
Abstract:
To meet the requirements of the Beijing electron positron linear accelerator upgrading, the studies on beam optics and orbit correction calculation are carried out. A program for beam optics and orbit correction calculation is developed. By means of least square method, the satisfying results are obtained. The program can actually refect the energy variation along the LINAC. With the program, beam optics parameters can be calculated and beam orbit can be corrected online. And the program will be used on BEPCⅡ LINAC.
To meet the requirements of the Beijing electron positron linear accelerator upgrading, the studies on beam optics and orbit correction calculation are carried out. A program for beam optics and orbit correction calculation is developed. By means of least square method, the satisfying results are obtained. The program can actually refect the energy variation along the LINAC. With the program, beam optics parameters can be calculated and beam orbit can be corrected online. And the program will be used on BEPCⅡ LINAC.
2004,
16.
Abstract:
The button electrode is one that widely used in high energy accelerators, such as storage ring, and the button electrode has many merit like high accuracy, high resolution, resisting magnetic field, simple machinery, without magnetic core and low cost, etc. It's helpful that the button electrode is used as the beam position monitor in the linear induction accelerator. The experimental facilities have bean designed and set up and it can simulate the beam of linear induction accelerator. The button electrode beam position monitor experiment have been done on the experimental facilities. The result of the experiment prove that the button electrode has an accuracy of 0.5mm，and can reflect the wave of electronbeam accurately.
The button electrode is one that widely used in high energy accelerators, such as storage ring, and the button electrode has many merit like high accuracy, high resolution, resisting magnetic field, simple machinery, without magnetic core and low cost, etc. It's helpful that the button electrode is used as the beam position monitor in the linear induction accelerator. The experimental facilities have bean designed and set up and it can simulate the beam of linear induction accelerator. The button electrode beam position monitor experiment have been done on the experimental facilities. The result of the experiment prove that the button electrode has an accuracy of 0.5mm，and can reflect the wave of electronbeam accurately.
2004,
16.
Abstract:
Transmission electron microscopy (TEM) was utilized to characterize the damage structure and the formation of Xe bubbles in 200 keV Xe+ implanted yttria-stabilized zirconia (YSZ) single crystals with different fluences. TEM analysis results showed that the density of defect clusters increased with increasing ion fluence. The density of defect clusters increased rapidly and formed clear interstitial type dislocation loops within dose range from 1×1015 Xe＋cm－２to 1×1016 Xe+ cm－2, and then the density of defect clusters increased slowly up to a dose of 1×1017 Xe+ cm－2. Small bubbles (2~4 nm in diameter) precipitate in the sample at a dose of 1×1017 Xe+ cm－2. No amorphization was observed in the selected area diffraction (SAD) pattern. These results also made it clear that no amorphiz
Transmission electron microscopy (TEM) was utilized to characterize the damage structure and the formation of Xe bubbles in 200 keV Xe+ implanted yttria-stabilized zirconia (YSZ) single crystals with different fluences. TEM analysis results showed that the density of defect clusters increased with increasing ion fluence. The density of defect clusters increased rapidly and formed clear interstitial type dislocation loops within dose range from 1×1015 Xe＋cm－２to 1×1016 Xe+ cm－2, and then the density of defect clusters increased slowly up to a dose of 1×1017 Xe+ cm－2. Small bubbles (2~4 nm in diameter) precipitate in the sample at a dose of 1×1017 Xe+ cm－2. No amorphization was observed in the selected area diffraction (SAD) pattern. These results also made it clear that no amorphiz
2004,
16.
Abstract:
A detailed discussion is carried out on some basic problems related with the coupling loop of radio frequency quadrupole with intense beams. A preliminary design of the coupling loop is given. By making use of some results got from the simulations on radio frequency quadrupole with two-dimension code Superfish, the size of the coupling loop and power dissipation on the loop are calculated. These results are helpful in determining the size of the coupling loop in experiments.
A detailed discussion is carried out on some basic problems related with the coupling loop of radio frequency quadrupole with intense beams. A preliminary design of the coupling loop is given. By making use of some results got from the simulations on radio frequency quadrupole with two-dimension code Superfish, the size of the coupling loop and power dissipation on the loop are calculated. These results are helpful in determining the size of the coupling loop in experiments.
2004,
16.
Abstract:
In this paper, the beam loading effect of RF system and the conditions of Robinson instability are analyzed in detail. By the study of the injection beam intensity limit dependent on detune angle and visible detune angle, it is found that the storage ring can be injected to more than 300mA current intensity to attain the design target of phase II project in the lower energy injection situation of Hefei Storage Ring if a certain power is feed in the RF cavity and a certain tuning angle of the RF cavity is set.
In this paper, the beam loading effect of RF system and the conditions of Robinson instability are analyzed in detail. By the study of the injection beam intensity limit dependent on detune angle and visible detune angle, it is found that the storage ring can be injected to more than 300mA current intensity to attain the design target of phase II project in the lower energy injection situation of Hefei Storage Ring if a certain power is feed in the RF cavity and a certain tuning angle of the RF cavity is set.
2004,
16.
Abstract:
This paper introduces the turnbyturn system of Hefei Light Source (HLS), and presents the analysis of the experiment results, as well as its application in commission of upgraded injection system of HLS. The signal processor of the system adopts a logratio electronics circuit. Up to 2s data acquisition is available. Injection kickers are used to excite beam for monitoring damping rate and β oscillation.
This paper introduces the turnbyturn system of Hefei Light Source (HLS), and presents the analysis of the experiment results, as well as its application in commission of upgraded injection system of HLS. The signal processor of the system adopts a logratio electronics circuit. Up to 2s data acquisition is available. Injection kickers are used to excite beam for monitoring damping rate and β oscillation.
2004,
16.
Abstract:
The stochastic momentum cooling with a notch filter that will be built on HIRFL-CSRm is described and formulated with Fokker-Planck equation. The square of the standard deviation of energy error and the initial cooling time are obtained. This provides a guide to analysis of experimental data and design of the cooling system, e.g.optimization of the system passband and gain, specification of accuracy of the signal's transmission, etc．
The stochastic momentum cooling with a notch filter that will be built on HIRFL-CSRm is described and formulated with Fokker-Planck equation. The square of the standard deviation of energy error and the initial cooling time are obtained. This provides a guide to analysis of experimental data and design of the cooling system, e.g.optimization of the system passband and gain, specification of accuracy of the signal's transmission, etc．
2004,
16.
Abstract:
A MachZehnder interferometer was developed for studying the plasma implosion in zpinch. The experiment with the interferometer was conducted on a small gaspuff Zpinch device and clear interferograms were obtained. By counting the fringe shift on the interferograms, the average electron densities of plasma well before its final pinch were calculated to be on the order of 1017~1018cm-3. If a beam splitter with time delay is inserted between the YAG laser and the MZ interferometer, a multiframe interferometer could be constructed, which is capable of taking several pictures within a single shot of Zpinch discharge.
A MachZehnder interferometer was developed for studying the plasma implosion in zpinch. The experiment with the interferometer was conducted on a small gaspuff Zpinch device and clear interferograms were obtained. By counting the fringe shift on the interferograms, the average electron densities of plasma well before its final pinch were calculated to be on the order of 1017~1018cm-3. If a beam splitter with time delay is inserted between the YAG laser and the MZ interferometer, a multiframe interferometer could be constructed, which is capable of taking several pictures within a single shot of Zpinch discharge.
2004,
16.
Abstract:
The standard pure permanent magnet (PPM) undulator has been analyzed by 3-dimensional electromagnetic computation software, the Modeller in Opera3D. The amplitude and phase angle of fundamental and harmonic induction fields in it are given for different air gaps. They show that all harmonic induction fields in standard PPM undulator are two orders lower than their fundamental induction field. This conclusion is verified by the related magnetic measurements to one standard PPM undulator in optical klystron with 0.5mm×1mm Hall probe. The paper also presents comparisons between theoretic results with analysis equation as well as 3D Finite Element computations and magnetic measurement with hall probe. In furthermore, inserted very small airgaps along beam direction in PPM undulator, leaving s
The standard pure permanent magnet (PPM) undulator has been analyzed by 3-dimensional electromagnetic computation software, the Modeller in Opera3D. The amplitude and phase angle of fundamental and harmonic induction fields in it are given for different air gaps. They show that all harmonic induction fields in standard PPM undulator are two orders lower than their fundamental induction field. This conclusion is verified by the related magnetic measurements to one standard PPM undulator in optical klystron with 0.5mm×1mm Hall probe. The paper also presents comparisons between theoretic results with analysis equation as well as 3D Finite Element computations and magnetic measurement with hall probe. In furthermore, inserted very small airgaps along beam direction in PPM undulator, leaving s
2004,
16.
Abstract:
HLS (Hefei light source) is a dedicated synchrotron radiation light source, where charged beam with low energy is injected and accumulated in the ring, and then the beam is synchronously accelerated to high energy and circulates in storage ring. During ramping process, with the drastic increasing synchrotron radiation energy loss of particle, beam loading is changing and appropriate adjustment of RF parameters is necessary in order to keep beam stability. In this paper, two possible RF adjustment modes for ramping in HLS are discussed and optimum RF status during operation in high energy is calculated.
HLS (Hefei light source) is a dedicated synchrotron radiation light source, where charged beam with low energy is injected and accumulated in the ring, and then the beam is synchronously accelerated to high energy and circulates in storage ring. During ramping process, with the drastic increasing synchrotron radiation energy loss of particle, beam loading is changing and appropriate adjustment of RF parameters is necessary in order to keep beam stability. In this paper, two possible RF adjustment modes for ramping in HLS are discussed and optimum RF status during operation in high energy is calculated.
2004,
16.
Abstract:
The equilibrium and stability properties of foil-focused electron beam in terms of its envelope equation is studied.Results are as follows:(1) The parameters of the electron beam, the radius of the waveguide tube and the distance between foils must obey a relation in terms of foil-focusing; (2) Equilibrium of the electrion beam with the initial emittance is generally stable for foil-focusing; (3) The hole on foil does not affect focusing if its radius is equal or slight larger than the radius of the electron beam．
The equilibrium and stability properties of foil-focused electron beam in terms of its envelope equation is studied.Results are as follows:(1) The parameters of the electron beam, the radius of the waveguide tube and the distance between foils must obey a relation in terms of foil-focusing; (2) Equilibrium of the electrion beam with the initial emittance is generally stable for foil-focusing; (3) The hole on foil does not affect focusing if its radius is equal or slight larger than the radius of the electron beam．
2004,
16.
Abstract:
HEMP coupling tests of the cable near ground were conducted. The relations of inducing skin current of shielding layer, core voltage and core current with the environment field were obtained. The change of shield layer current wave with grounding state of external shield and core voltage with loading resistance was analyzed. According to the dependence of shield layer current oscillating frequency on electromagnetic wave propagation velocity, conception of transporting line of shield layer-ground with equivalent relative dielectric constant was presented. fited equation of equivalent relative dielectric constant with change of cable height was given. There a good coincidence in the calculation of shield layer current and measuring results in the aspect of waveform, oscillating circle and a
HEMP coupling tests of the cable near ground were conducted. The relations of inducing skin current of shielding layer, core voltage and core current with the environment field were obtained. The change of shield layer current wave with grounding state of external shield and core voltage with loading resistance was analyzed. According to the dependence of shield layer current oscillating frequency on electromagnetic wave propagation velocity, conception of transporting line of shield layer-ground with equivalent relative dielectric constant was presented. fited equation of equivalent relative dielectric constant with change of cable height was given. There a good coincidence in the calculation of shield layer current and measuring results in the aspect of waveform, oscillating circle and a
2004,
16.
Abstract:
The paper introduces a virtual cathode oscillator (vircator) with quasioptical resonator. The resonator offers selfconsistent feedback and modechoosing mechanisms. It serves the purpose of enhancing the transform efficiency, shortening the saturated time and achieving both stable frequency and narrow bandwidth. The property of the system is analyzed by means of the scalar wave theory. Results of 2.5D numerical simulation of the device are presented. A powerful microwave with quasiGauss mode which is apt to focus and radiate is obtained at 7.0GHz, the time average output power overtakes 1.3GW, and the average efficiency approximates to 10%. The simulation confirms the conclusion of the theoretic analysis.
The paper introduces a virtual cathode oscillator (vircator) with quasioptical resonator. The resonator offers selfconsistent feedback and modechoosing mechanisms. It serves the purpose of enhancing the transform efficiency, shortening the saturated time and achieving both stable frequency and narrow bandwidth. The property of the system is analyzed by means of the scalar wave theory. Results of 2.5D numerical simulation of the device are presented. A powerful microwave with quasiGauss mode which is apt to focus and radiate is obtained at 7.0GHz, the time average output power overtakes 1.3GW, and the average efficiency approximates to 10%. The simulation confirms the conclusion of the theoretic analysis.
2004,
16.
Abstract:
A measurement system on power density of high power microwave radiation is presented. The system is based on peak detecting diode, waveguide system, and power decrease structure. The system is focused on lowerror and the stability of structure. Calibrating Methods are also presented. The system is suitable for many occasions.
A measurement system on power density of high power microwave radiation is presented. The system is based on peak detecting diode, waveguide system, and power decrease structure. The system is focused on lowerror and the stability of structure. Calibrating Methods are also presented. The system is suitable for many occasions.
2004,
16.
Abstract:
A fully three-dimensional (3-D) of an electron beam optical model focused by a periodic permanent magnet (PPM) stack has been developed using 3-D particle-in-cell (PIC) code of MAFIA, the static magnetic field and electron beam transmission characteristics were simulated using static solver and PIC module. The characteristics of the electron beam confined by the PPM stack are analyzed and the effects of the peak magnetic flux density, magnetic tapering, initial transversal velocity distribution are mainly discussed. Some useful data are obtained for the PPM stack engineering design and optimization.
A fully three-dimensional (3-D) of an electron beam optical model focused by a periodic permanent magnet (PPM) stack has been developed using 3-D particle-in-cell (PIC) code of MAFIA, the static magnetic field and electron beam transmission characteristics were simulated using static solver and PIC module. The characteristics of the electron beam confined by the PPM stack are analyzed and the effects of the peak magnetic flux density, magnetic tapering, initial transversal velocity distribution are mainly discussed. Some useful data are obtained for the PPM stack engineering design and optimization.
2004,
16.
Abstract:
On the way of pursuing the high Q value microwave resonant cavity, people are familiar with the property and producing technology of low temperature superconducting resonance cavity (Nb cavity), but aren't completed with producing high Q superconducting resonator with high temperature superconducting material. This paper analyzes the surface resistant of high temperature superconductor, the make technics and its microstructure, and studies the possibility and relative physical problem of making microwave resonance with YBCO high temperature superconductor. In the experiment, one plate by YBCO balk was replace, the Q of the resonator increases 4 times. It is expected to reach 70 times at 20K if the resonator is all made of YBCO material, and the performance of the resonator is improved obvi
On the way of pursuing the high Q value microwave resonant cavity, people are familiar with the property and producing technology of low temperature superconducting resonance cavity (Nb cavity), but aren't completed with producing high Q superconducting resonator with high temperature superconducting material. This paper analyzes the surface resistant of high temperature superconductor, the make technics and its microstructure, and studies the possibility and relative physical problem of making microwave resonance with YBCO high temperature superconductor. In the experiment, one plate by YBCO balk was replace, the Q of the resonator increases 4 times. It is expected to reach 70 times at 20K if the resonator is all made of YBCO material, and the performance of the resonator is improved obvi
2004,
16.
Abstract:
A high power and alterable frequency axial acceletron is studied in this paper. By adding the middle cavity, the RF at the cathode surface is increased and the current modulation coefficient is enhanced, the first order current modulation coefficient is 140% and the second is 68%. By adjusting the output cavity, in terms of the twodimensional fully electronmagnetic particalincell(PIC) simulation, the output power of 1.25GW at 2.2GHz and 480MW at 4.4GHz have been obtained.
A high power and alterable frequency axial acceletron is studied in this paper. By adding the middle cavity, the RF at the cathode surface is increased and the current modulation coefficient is enhanced, the first order current modulation coefficient is 140% and the second is 68%. By adjusting the output cavity, in terms of the twodimensional fully electronmagnetic particalincell(PIC) simulation, the output power of 1.25GW at 2.2GHz and 480MW at 4.4GHz have been obtained.
2004,
16.
Abstract:
The interaction between an ultrashort ultraintense laser pulse and a solid target with a low density preplasma is examined. Both linear and circular polarizations of the laser are considered. The electrons in the preplasma are accelerated by the ponderomotive force of propagating laser pulse, and the dependences of the maximum electron energy on the laser intensity and the preplasma density are examined. The target electrons are accelerated by ＪＢ mechanism, and the maximum energy achieved is much lower than that of the preplasma electrons. In this sense, the preplasma is advantageous for energetic electrons generation in the ultrashort ultraintense lasersolid interaction.
The interaction between an ultrashort ultraintense laser pulse and a solid target with a low density preplasma is examined. Both linear and circular polarizations of the laser are considered. The electrons in the preplasma are accelerated by the ponderomotive force of propagating laser pulse, and the dependences of the maximum electron energy on the laser intensity and the preplasma density are examined. The target electrons are accelerated by ＪＢ mechanism, and the maximum energy achieved is much lower than that of the preplasma electrons. In this sense, the preplasma is advantageous for energetic electrons generation in the ultrashort ultraintense lasersolid interaction.
2004,
16.
Abstract:
The propagation of ultrashort pulsed Bessel beams in free space within and beyond the paraxial approximation is studied. It is shown that the nonparaxial effect does not affect their spatial pulse profile, which retains the Bessel shape unchanged upon propagation, whereas it affects their temporal pulse form if the spatial parameter becomes relatively large. The condition, under which the paraxial approximation is valid, is found to be ＜ min/2c, where min denotes the minimum frequency of the pulse spectrum and cis the velocity of light.
The propagation of ultrashort pulsed Bessel beams in free space within and beyond the paraxial approximation is studied. It is shown that the nonparaxial effect does not affect their spatial pulse profile, which retains the Bessel shape unchanged upon propagation, whereas it affects their temporal pulse form if the spatial parameter becomes relatively large. The condition, under which the paraxial approximation is valid, is found to be ＜ min/2c, where min denotes the minimum frequency of the pulse spectrum and cis the velocity of light.
