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RSS2007 Vol. 19, No. 10
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2007,
19.
Abstract:
The design of a 15 kW, 220 GHz gyrotron operating in TE03 mode is presented according to the linear theory and the nonlinear self-consistent theory of gyrotrons. The gyrotron’s electron beam current is 2 A and its electron beam voltage is 20 kV. The results of the simulation using PIC code show that the efficiency of beam-wave interaction is as high as 37%.
The design of a 15 kW, 220 GHz gyrotron operating in TE03 mode is presented according to the linear theory and the nonlinear self-consistent theory of gyrotrons. The gyrotron’s electron beam current is 2 A and its electron beam voltage is 20 kV. The results of the simulation using PIC code show that the efficiency of beam-wave interaction is as high as 37%.
2007,
19.
Abstract:
In the amplifying process of traditional traveling wave tube(TWT) with longitudinal congregation of electrons, space-charge effect will lead to nonlinear effect affecting output properties of TWT. In this paper a new kind of TWT is introduced and its working principles are analyzed. Structure of the TWT with slow wave system and its dispersion characteristics are analyzed. The affect of apparatus sizes on its working principles is discussed．Electronbeam turns in space whder modulation by the highfrequency transverse electrical field with circularly polarized traveling wave. In the process of amplifying electron beam is locating in the decelerating field without longitudinal congregation so that the nonlinear effect is eliminated. Output properties of TWT are increased.
In the amplifying process of traditional traveling wave tube(TWT) with longitudinal congregation of electrons, space-charge effect will lead to nonlinear effect affecting output properties of TWT. In this paper a new kind of TWT is introduced and its working principles are analyzed. Structure of the TWT with slow wave system and its dispersion characteristics are analyzed. The affect of apparatus sizes on its working principles is discussed．Electronbeam turns in space whder modulation by the highfrequency transverse electrical field with circularly polarized traveling wave. In the process of amplifying electron beam is locating in the decelerating field without longitudinal congregation so that the nonlinear effect is eliminated. Output properties of TWT are increased.
2007,
19.
Abstract:
Dispersion characteristics of the rectangular waveguide grating slow wave system and standing wave factor of the coupling device are studied experimentally. Three kinds of rectangular waveguide gating slow wave structure(SWS) models with rectangular groove, swallow-tailed groove, ladder groove respectively and the SWS with input and output structures are manufactured by the distributed process method. The dispersion and standing wave factor are measured by resonance method. Compared with the theoretical results and simulating results, they match very well.
Dispersion characteristics of the rectangular waveguide grating slow wave system and standing wave factor of the coupling device are studied experimentally. Three kinds of rectangular waveguide gating slow wave structure(SWS) models with rectangular groove, swallow-tailed groove, ladder groove respectively and the SWS with input and output structures are manufactured by the distributed process method. The dispersion and standing wave factor are measured by resonance method. Compared with the theoretical results and simulating results, they match very well.
2007,
19.
Abstract:
The action distance and detection precision of ground penetrating radar(GPR) is directly restricted by the power and stability of its pulser. The stability of the pulser based on avalanche dynatron is good, and it is propitious to improve the detection precision of GPR, but its peak-voltage is lower. In order to increase the output peak voltage of pulser, Marx circuit is used, and its structure is designed for strict comb PCB(printed circuit board) layout. Finally, for a practical GPR, a pulser is designed with 12-stage Marx circuit. The test results are that its peak voltage is higher than 400 V, the pulse width is 600 ps, the repetition frequency is higher than 25 kHz, both the pulse width jitter and the peak voltage jitter are less than 1%.
The action distance and detection precision of ground penetrating radar(GPR) is directly restricted by the power and stability of its pulser. The stability of the pulser based on avalanche dynatron is good, and it is propitious to improve the detection precision of GPR, but its peak-voltage is lower. In order to increase the output peak voltage of pulser, Marx circuit is used, and its structure is designed for strict comb PCB(printed circuit board) layout. Finally, for a practical GPR, a pulser is designed with 12-stage Marx circuit. The test results are that its peak voltage is higher than 400 V, the pulse width is 600 ps, the repetition frequency is higher than 25 kHz, both the pulse width jitter and the peak voltage jitter are less than 1%.
2007,
19.
Abstract:
Based on the bifrequency magnetically insulated transmission line oscillator (BFMILO), a multi-frequency magnetically insulated transmission line oscillator (MFMILO) was put forward. An MFMILO was designed based on the single-frequency MILO, and its high frequencystructure was optimized through electromagnetic simulation. According to different structure parameters, an MFMILO can generate high power microwaves with one-frequency, two-frequency, three-frequency, four-frequency and five-frequency. Simulation results show that an MFMILO can generate microwaves with multi-frequency, and their power efficiencies are less than that of single-frequency MILO. The reasons of less power efficiency are analyzed. The possibility to enhance the power efficiency and frequency quantity of output microw
Based on the bifrequency magnetically insulated transmission line oscillator (BFMILO), a multi-frequency magnetically insulated transmission line oscillator (MFMILO) was put forward. An MFMILO was designed based on the single-frequency MILO, and its high frequencystructure was optimized through electromagnetic simulation. According to different structure parameters, an MFMILO can generate high power microwaves with one-frequency, two-frequency, three-frequency, four-frequency and five-frequency. Simulation results show that an MFMILO can generate microwaves with multi-frequency, and their power efficiencies are less than that of single-frequency MILO. The reasons of less power efficiency are analyzed. The possibility to enhance the power efficiency and frequency quantity of output microw
2007,
19.
Abstract:
The nonlinear left-handed material(LHM) model was analyzed. The expressions of finite-difference time-domain(FDTD) method and perfectly-matched layer in such material were derived. Electromagnetic wave in Kerr nonlinear left-handed material model was simulated. Electromagnetic focus of Kerr nonlinear LHM was observed. Compared to linear LHM, it is observed that the location and the amplitude of the electromagnetic focus in such nonlinear LHM had changed. Various distances from source to LHM slab were concerned. Electric intensity was concentrated at LHM slab edge while the source was far enough.
The nonlinear left-handed material(LHM) model was analyzed. The expressions of finite-difference time-domain(FDTD) method and perfectly-matched layer in such material were derived. Electromagnetic wave in Kerr nonlinear left-handed material model was simulated. Electromagnetic focus of Kerr nonlinear LHM was observed. Compared to linear LHM, it is observed that the location and the amplitude of the electromagnetic focus in such nonlinear LHM had changed. Various distances from source to LHM slab were concerned. Electric intensity was concentrated at LHM slab edge while the source was far enough.
2007,
19.
Abstract:
PIC simulation of beam-wave interaction of 8 mm 2-harmonic gyroklystron was carried out. The influences of the high frequency structure, beam parameters and magnetic field on the output power, efficiency and gain were studied. When the coefficient of the magnetic field was 0.511 8, the beam voltage was 70 kV, the beam current was 16 A and the input power was 80 W, the output power was about 430 kW, the transfer efficiency was 38%, the gain was over 37 dB and the 3 dB bandwidth was over 210 MHz.
PIC simulation of beam-wave interaction of 8 mm 2-harmonic gyroklystron was carried out. The influences of the high frequency structure, beam parameters and magnetic field on the output power, efficiency and gain were studied. When the coefficient of the magnetic field was 0.511 8, the beam voltage was 70 kV, the beam current was 16 A and the input power was 80 W, the output power was about 430 kW, the transfer efficiency was 38%, the gain was over 37 dB and the 3 dB bandwidth was over 210 MHz.
2007,
19.
Abstract:
This paper presents a 3-D model for double-gap open cavity of S-band relativistic klystron amplifier. By observing the response of the current driver, the high frequency characteristics including resonant frequency, loaded quality factor (Q), field distribution and character impedance of the open cavity are calculated. The effect of the open cavity size on the resonant frequency, loaded Q value and the character impedance are discussed. The results show that the frequency mainly depends on the radius of the cavity and the loaded Q value diminishs owing to the increase of the angle of the coupling hole, and the character impedance declines due to the increase of the radius and the decrease of the gap length of the cavity. The analysis provides a theoretical basis for the design of the doubl
This paper presents a 3-D model for double-gap open cavity of S-band relativistic klystron amplifier. By observing the response of the current driver, the high frequency characteristics including resonant frequency, loaded quality factor (Q), field distribution and character impedance of the open cavity are calculated. The effect of the open cavity size on the resonant frequency, loaded Q value and the character impedance are discussed. The results show that the frequency mainly depends on the radius of the cavity and the loaded Q value diminishs owing to the increase of the angle of the coupling hole, and the character impedance declines due to the increase of the radius and the decrease of the gap length of the cavity. The analysis provides a theoretical basis for the design of the doubl
2007,
19.
Abstract:
In an anechoic chamber and an open area test site, using several narrow-band and ultra-wide spectrum high power microwave sources and measurement systems of radiating field, the shielding effectiveness of a special electromagnetic material to non-nuclear electromagnetic pulse was studied experimently. For the technically designed samples of testing window and shielding-enclosure models, when the thickness of the window samples (or the wall of the model) is greater than 30 mm, the shielding effectiveness to narrowband high power microwave can exceed 80 dB and to ultra-wide spectrum high power microwave, 50 dB. The material can be widely applied to class Ⅲ fortified structures. It can be cautiously applied to class Ⅱ or Ⅰ fortified structures when the electromagnetic.
In an anechoic chamber and an open area test site, using several narrow-band and ultra-wide spectrum high power microwave sources and measurement systems of radiating field, the shielding effectiveness of a special electromagnetic material to non-nuclear electromagnetic pulse was studied experimently. For the technically designed samples of testing window and shielding-enclosure models, when the thickness of the window samples (or the wall of the model) is greater than 30 mm, the shielding effectiveness to narrowband high power microwave can exceed 80 dB and to ultra-wide spectrum high power microwave, 50 dB. The material can be widely applied to class Ⅲ fortified structures. It can be cautiously applied to class Ⅱ or Ⅰ fortified structures when the electromagnetic.
2007,
19.
Abstract:
The experimental study of a passive mode locked Yb3+ doped fiber laser was reported, which utilized a 8 shaped ring cavity with semiconductor saturable absorber mirror(SESAM) as well as the polarizer and polarization controllers. Combining the effect of non-linear polarization rotation with the self starting of SESAM, stable operations of Q switched and CW mode locked regime at the low pump power were achieved. When the pump power was 18 mW, the Q switched pulse with a repetition of 16 kHz, a pulse width of 4 μs ,and an output spectrum width of 2.34 nm was obtained. When the pump power was 60 mW, the output power of mode locked pulses was 8 mW, the repetition was 20 MHz, the output spectrum width was 3.54 nm, and the pulse width was ps or sub ps orders. The tunable phenomenon with proper
The experimental study of a passive mode locked Yb3+ doped fiber laser was reported, which utilized a 8 shaped ring cavity with semiconductor saturable absorber mirror(SESAM) as well as the polarizer and polarization controllers. Combining the effect of non-linear polarization rotation with the self starting of SESAM, stable operations of Q switched and CW mode locked regime at the low pump power were achieved. When the pump power was 18 mW, the Q switched pulse with a repetition of 16 kHz, a pulse width of 4 μs ,and an output spectrum width of 2.34 nm was obtained. When the pump power was 60 mW, the output power of mode locked pulses was 8 mW, the repetition was 20 MHz, the output spectrum width was 3.54 nm, and the pulse width was ps or sub ps orders. The tunable phenomenon with proper
2007,
19.
Abstract:
A partially coherent cosh-Gaussian (ChG) beam is introduced by means of adding a Gaussian term of the spatial degree of coherence. The analytical expression for partially coherent ChG beams propagating through a paraxial optical ABCD system is derived and used to study their propagation properties and spatial shaping. The intensity profile of partially coherent ChG beams can not remain unchanged upon propagation and depends on the propagation distance and decentered parameter, and on the spatial coherence parameter. By suitable variation of the decentered parameter and the spatial coherence parameter of partially coherent ChG beams at a fixed propagation distance, the spatial beam is shaped. The beam quality factor of partially coherent ChG beams decreases with increasing spatially coheren
A partially coherent cosh-Gaussian (ChG) beam is introduced by means of adding a Gaussian term of the spatial degree of coherence. The analytical expression for partially coherent ChG beams propagating through a paraxial optical ABCD system is derived and used to study their propagation properties and spatial shaping. The intensity profile of partially coherent ChG beams can not remain unchanged upon propagation and depends on the propagation distance and decentered parameter, and on the spatial coherence parameter. By suitable variation of the decentered parameter and the spatial coherence parameter of partially coherent ChG beams at a fixed propagation distance, the spatial beam is shaped. The beam quality factor of partially coherent ChG beams decreases with increasing spatially coheren
2007,
19.
Abstract:
To improve in -phase supermode selection for 7 -core fiber laser, a novel cascade system, which consists of a multicore fiber laser as the seeding signal source and a multicore fiber amplifier, was proposed. The transverse supermode competition was analyzed based on a set of rate equations. The ratio of the power of the lower -order modes to the total output power can be reduced to less than 1%, with the optimum distance between the output end of the fiber laser and the input end of fiber amplifier. The results show that the cascade system can improve in -phase supermode selection effectively, which ensures much better beam quality, compared to the multicore fiber lasers with single Talbot cavity.
To improve in -phase supermode selection for 7 -core fiber laser, a novel cascade system, which consists of a multicore fiber laser as the seeding signal source and a multicore fiber amplifier, was proposed. The transverse supermode competition was analyzed based on a set of rate equations. The ratio of the power of the lower -order modes to the total output power can be reduced to less than 1%, with the optimum distance between the output end of the fiber laser and the input end of fiber amplifier. The results show that the cascade system can improve in -phase supermode selection effectively, which ensures much better beam quality, compared to the multicore fiber lasers with single Talbot cavity.
2007,
19.
Abstract:
The coupling rules of different thickness polyaryl amide-fibers/epoxy and carbon-fibers/epoxy composites radiated by different intensity continuous wave laser beam with wavelength of 1.319 mm were studied by double integrating spheres-photodiode system. The results show that the reflectivity and energy coupling rate of polyaryl amide-fibers/epoxy composite increase while it’s transmissivity decreases when composite thickness increases. The reflectivity and transmissivity increase but energy coupling rate decreases when laser intensity increases. Although the bulk absorption coefficient decreases when composite thickness increases, the change of laser intensity has no effect on it. The carbon-fiber/epoxy composite’s reflectivity increase and it’s energy coupling rate decreases when laser
The coupling rules of different thickness polyaryl amide-fibers/epoxy and carbon-fibers/epoxy composites radiated by different intensity continuous wave laser beam with wavelength of 1.319 mm were studied by double integrating spheres-photodiode system. The results show that the reflectivity and energy coupling rate of polyaryl amide-fibers/epoxy composite increase while it’s transmissivity decreases when composite thickness increases. The reflectivity and transmissivity increase but energy coupling rate decreases when laser intensity increases. Although the bulk absorption coefficient decreases when composite thickness increases, the change of laser intensity has no effect on it. The carbon-fiber/epoxy composite’s reflectivity increase and it’s energy coupling rate decreases when laser
2007,
19.
Abstract:
High powers of the harmonics can be achieved through nonlinear harmonic generation in high gain single pass FEL, which may be used to get shorter wavelengths or to relax some stringent requirements on the electron beam quality for the 4th generation light source. In this paper, the 3rd nonlinear harmonic generation in Shanghai Deep Ultraviolet Free Electron Laser source is investigated by a 3D simulation code, including the sensitivity of nonlinear harmonic generation to several crucial parameters of the FEL system. The results show that the power of the 3rd nonlinear harmonic radiation can be as high as 2% of the fundamental power. In addition, the experiment and measurement of the 3rd harmonic radiation is proposed.
High powers of the harmonics can be achieved through nonlinear harmonic generation in high gain single pass FEL, which may be used to get shorter wavelengths or to relax some stringent requirements on the electron beam quality for the 4th generation light source. In this paper, the 3rd nonlinear harmonic generation in Shanghai Deep Ultraviolet Free Electron Laser source is investigated by a 3D simulation code, including the sensitivity of nonlinear harmonic generation to several crucial parameters of the FEL system. The results show that the power of the 3rd nonlinear harmonic radiation can be as high as 2% of the fundamental power. In addition, the experiment and measurement of the 3rd harmonic radiation is proposed.
2007,
19.
Abstract:
Environmental vibrations may cause the positive-branch confocal unstable cavity length to be maladjusted, moreover, thermal effect directly leads to cavity mirrors distortion. As a result, there will be many kinds of phase aberrations in the output beam. In order to correct the defocus aberration, this paper presents two analytic methods to analyze the defocus aberration generated under two different conditions. One is to analyze the relative position misalignment of cavity mirrors leading to defocus aberrations. The other is to analyze the distortion of cavity mirrors leading to defocus aberrations. The relation of the defocus and cavity length as well as the relation of the defocus and cavity mirrors’ distortion are obtained. The conclusion results show that the change of the cavity len
Environmental vibrations may cause the positive-branch confocal unstable cavity length to be maladjusted, moreover, thermal effect directly leads to cavity mirrors distortion. As a result, there will be many kinds of phase aberrations in the output beam. In order to correct the defocus aberration, this paper presents two analytic methods to analyze the defocus aberration generated under two different conditions. One is to analyze the relative position misalignment of cavity mirrors leading to defocus aberrations. The other is to analyze the distortion of cavity mirrors leading to defocus aberrations. The relation of the defocus and cavity length as well as the relation of the defocus and cavity mirrors’ distortion are obtained. The conclusion results show that the change of the cavity len
2007,
19.
Abstract:
An analytical expression of the threshold pump power of the fiber laser with three-energy-level dopants has been obtained from rate equations including loss coefficients of the pump and laser radiations. And the rate equations describing the threshold pumped fiber lasers have been analytically solved, following the derivation of the implicit expression specifying the pump power variation along the fiber and explicit expressions of the position dependent population densities on the three energy levels in terms of the pump power variation. With these expressions, threshold characteristics of the fiber lasers have been studied. The threshold pump power grows monotonously with the increase of the loss coefficient of the pump radiation. The population density of the upper level decreases with t
An analytical expression of the threshold pump power of the fiber laser with three-energy-level dopants has been obtained from rate equations including loss coefficients of the pump and laser radiations. And the rate equations describing the threshold pumped fiber lasers have been analytically solved, following the derivation of the implicit expression specifying the pump power variation along the fiber and explicit expressions of the position dependent population densities on the three energy levels in terms of the pump power variation. With these expressions, threshold characteristics of the fiber lasers have been studied. The threshold pump power grows monotonously with the increase of the loss coefficient of the pump radiation. The population density of the upper level decreases with t
2007,
19.
Abstract:
Based on the coupled differential equations of Brillouin scattering on laser intensity, the mechanism of incoherent beam combining using stimulated Brillouin scattering was analyzed in multimode fibers. The result shows that the Stokes beam generated propagates in the LP01 mode, and the process of incoherent beam combing is an inverse process that the mixed beams are decomposed into the linearly polarized beam. The incoherent beam combining by stimulated Brillouin scattering was modeled, and the combined output power was calculated. The calculated output powers are consistent with Russel’s experimental results. The intensity distribution of the combined beam was also investigated. It shows that the combined intensity depends on the mode field size, the effective approach to increase the c
Based on the coupled differential equations of Brillouin scattering on laser intensity, the mechanism of incoherent beam combining using stimulated Brillouin scattering was analyzed in multimode fibers. The result shows that the Stokes beam generated propagates in the LP01 mode, and the process of incoherent beam combing is an inverse process that the mixed beams are decomposed into the linearly polarized beam. The incoherent beam combining by stimulated Brillouin scattering was modeled, and the combined output power was calculated. The calculated output powers are consistent with Russel’s experimental results. The intensity distribution of the combined beam was also investigated. It shows that the combined intensity depends on the mode field size, the effective approach to increase the c
2007,
19.
Abstract:
Based on the simulated results of normalized Z-scan transmittance by using ABCD formalism and q parameter, analysis on the variational characteristics of Z-scan curves with nonlinear phase shifts proves that the asymmetry of the curve is more greatly affected by nonlinear refractive phase distortion than by nonlinear absorptive one, and that the Z-scan curves of a certain media with strong saturated absorption and weak self-focusing third-order nonlinearity will not hold the dispersive-like characteristics any more. With the absorptive nonlinear phase shift of 0.9 and coupling factor of -10 in the transmittance expression, the fitting with the experimental data for ZnCdSe-ZnSe(MQWs) of 1 μm thickness conducted with 532 nm TEM00 brought in almost the same results of third-order nonlinear
Based on the simulated results of normalized Z-scan transmittance by using ABCD formalism and q parameter, analysis on the variational characteristics of Z-scan curves with nonlinear phase shifts proves that the asymmetry of the curve is more greatly affected by nonlinear refractive phase distortion than by nonlinear absorptive one, and that the Z-scan curves of a certain media with strong saturated absorption and weak self-focusing third-order nonlinearity will not hold the dispersive-like characteristics any more. With the absorptive nonlinear phase shift of 0.9 and coupling factor of -10 in the transmittance expression, the fitting with the experimental data for ZnCdSe-ZnSe(MQWs) of 1 μm thickness conducted with 532 nm TEM00 brought in almost the same results of third-order nonlinear
2007,
19.
Abstract:
In the experiment of laser induced damage to optical fiber, a positioning hole was added in the experimental setup, which was useful to alignment of the laser beam. The beam size was measured in the knife edge way and the CCD way, the results of the two ways were in agreement. The ways of judgment and test were investigated, and the method to calculate zero probability damage thresholds was introduced. Reference on “GJB1487-92 test method for laser optical elements” and “ISO11245 test method for laser radiation induced damage threshold of optical surfaces”, the experimental setup of laser induced damage to fibers, fiber damage judgment criterions and data processing methods were introduced and validated. The damage threshold tests of fused silica, step-index, and multimode fiber were c
In the experiment of laser induced damage to optical fiber, a positioning hole was added in the experimental setup, which was useful to alignment of the laser beam. The beam size was measured in the knife edge way and the CCD way, the results of the two ways were in agreement. The ways of judgment and test were investigated, and the method to calculate zero probability damage thresholds was introduced. Reference on “GJB1487-92 test method for laser optical elements” and “ISO11245 test method for laser radiation induced damage threshold of optical surfaces”, the experimental setup of laser induced damage to fibers, fiber damage judgment criterions and data processing methods were introduced and validated. The damage threshold tests of fused silica, step-index, and multimode fiber were c
2007,
19.
Abstract:
A fiber coupled diode laser pumped Tm:YAP laser operating at room temperature(291 K) is reported. Using the focus-coupling system of 1∶1, the maximum output power 2.2 W is achieved at 1 928 nm, the optical-optical efficiency is 31% and the slope efficiency is 41%. The parameters which induce the change of output power, such as output coupler, operation temperature of crystal and the parameter of cavity, are analyzed. The results show that the output decreases linearly with the temperature-rise of the crystal. Because of the severe vapor absorption near 1.9 mm, the loss caused by absorption of vapor in the cavity is an important factor that decreases the laser output.
A fiber coupled diode laser pumped Tm:YAP laser operating at room temperature(291 K) is reported. Using the focus-coupling system of 1∶1, the maximum output power 2.2 W is achieved at 1 928 nm, the optical-optical efficiency is 31% and the slope efficiency is 41%. The parameters which induce the change of output power, such as output coupler, operation temperature of crystal and the parameter of cavity, are analyzed. The results show that the output decreases linearly with the temperature-rise of the crystal. Because of the severe vapor absorption near 1.9 mm, the loss caused by absorption of vapor in the cavity is an important factor that decreases the laser output.
2007,
19.
Abstract:
The development of digital war field brings on the increasing of infrared image transmission, thus image compression is needed to meet the requirement, and motion estimation is the key section of the image compression. In this paper, a new search algorithm, diamond and square search(DSS) is proposed by analyzing the motion vector distribution. The algorithm employs two search patterns——the diamond search(DS) pattern and the square search pattern. In the first search step, the diamond search pattern is centered at the origin of the search window, and 5 checking points are tested. If the point with the minimum sum of absolute difference(SAD) is not located at the center, the diamond search pattern is repeated, until the minimum SAD point is located at the center of the diamond, then the se
The development of digital war field brings on the increasing of infrared image transmission, thus image compression is needed to meet the requirement, and motion estimation is the key section of the image compression. In this paper, a new search algorithm, diamond and square search(DSS) is proposed by analyzing the motion vector distribution. The algorithm employs two search patterns——the diamond search(DS) pattern and the square search pattern. In the first search step, the diamond search pattern is centered at the origin of the search window, and 5 checking points are tested. If the point with the minimum sum of absolute difference(SAD) is not located at the center, the diamond search pattern is repeated, until the minimum SAD point is located at the center of the diamond, then the se
2007,
19.
Abstract:
The mathematical field model of induction heating was developed for the fabrication of glass-coated copper microwire. The skin effect in the long solid cylinder billet and distribution of electromagnetic field were described. Moreover, the figures of the electromagnetic and eddy current density were obtained with the MATLAB software. The effect factors of the distribution of electro-magnetic field were analyzed. The results show that the intensity of magnetic field decreases with diameters and numbers of induction coil increasing. The glass-coated copper microwire with a diameter of 18 mm and 3.3 mm of copper microwire in diameter was characterized by scanning electron microscope and X-ray diffraction.
The mathematical field model of induction heating was developed for the fabrication of glass-coated copper microwire. The skin effect in the long solid cylinder billet and distribution of electromagnetic field were described. Moreover, the figures of the electromagnetic and eddy current density were obtained with the MATLAB software. The effect factors of the distribution of electro-magnetic field were analyzed. The results show that the intensity of magnetic field decreases with diameters and numbers of induction coil increasing. The glass-coated copper microwire with a diameter of 18 mm and 3.3 mm of copper microwire in diameter was characterized by scanning electron microscope and X-ray diffraction.
2007,
19.
Abstract:
A thin aluminum-dot target was presented to avoid gradients in temperature and density and self-absorption of the lines. The target is a film consisting of 20 mm thick CH substrate and 0.1 mm thick aluminum dot with diameter of 200 mm covered by 0.1 mm thick CH on the dot surface. The quasi-quantitative X-ray spectrum has been derived from the film recording signal by correcting the film response, filter absorption and the diagnostic geometry of the spectrometer and neglecting X-ray wavelength dependence of the crystal diffraction efficiency due to relatively small wavelength range. A non-local thermodynamic equilibrium spectral code was applied to simulate the measured aluminum spectrum. Good agreement between the measurement and the simulation was obtained through direct comparison and n
A thin aluminum-dot target was presented to avoid gradients in temperature and density and self-absorption of the lines. The target is a film consisting of 20 mm thick CH substrate and 0.1 mm thick aluminum dot with diameter of 200 mm covered by 0.1 mm thick CH on the dot surface. The quasi-quantitative X-ray spectrum has been derived from the film recording signal by correcting the film response, filter absorption and the diagnostic geometry of the spectrometer and neglecting X-ray wavelength dependence of the crystal diffraction efficiency due to relatively small wavelength range. A non-local thermodynamic equilibrium spectral code was applied to simulate the measured aluminum spectrum. Good agreement between the measurement and the simulation was obtained through direct comparison and n
2007,
19.
Abstract:
Pulsed laser deposition(PLD) was used to prepare superhard amorphous carbon films. The films’ surface appearance, structure, residual stress, hardness and XPS spectra were researched. AFM and SEM images show the film fabricated by PLD is flat, smooth and compact with the root mean square roughness less than 1nm (the maximum is 0.877 nm). Large residual stress of the films was measured by XRD, which would cause corrugation and break in the films prepared under high laser repetition frequency and fluence. However, the stress would relax under 300 ℃ annealing temperature. Nanoindentation test shows that hardness and Young’s modulus of film were over 20 GPa and 200 GPa respectively. XPS tells that the content of sp3 was between 39% and 53%, which was in direct proportion to laser fluence.
Pulsed laser deposition(PLD) was used to prepare superhard amorphous carbon films. The films’ surface appearance, structure, residual stress, hardness and XPS spectra were researched. AFM and SEM images show the film fabricated by PLD is flat, smooth and compact with the root mean square roughness less than 1nm (the maximum is 0.877 nm). Large residual stress of the films was measured by XRD, which would cause corrugation and break in the films prepared under high laser repetition frequency and fluence. However, the stress would relax under 300 ℃ annealing temperature. Nanoindentation test shows that hardness and Young’s modulus of film were over 20 GPa and 200 GPa respectively. XPS tells that the content of sp3 was between 39% and 53%, which was in direct proportion to laser fluence.
2007,
19.
Abstract:
Based on the model of transient stimulated rotational Raman scattering(SRRS) and the phase perturbation theory, the effects of pump intensity and pulse width on the threshold and the conversion efficiency of SRRS during the propagation in long air path were quantitatively analyzed. The effects of the phase perturbation on the beam quality of the pump field and the Stokes field were discussed. The results show that the threshold distance of SRRS decreases with increasing the intensity and the pulse width of the pump laser. The phase perturbation of the initial pump field has effect on the intensity distributions of the Stokes and the pump fields, and the influence of the phase perturbation of the initial pump field on the Stokes field is more obvious than that on the pump field. The SRRS ef
Based on the model of transient stimulated rotational Raman scattering(SRRS) and the phase perturbation theory, the effects of pump intensity and pulse width on the threshold and the conversion efficiency of SRRS during the propagation in long air path were quantitatively analyzed. The effects of the phase perturbation on the beam quality of the pump field and the Stokes field were discussed. The results show that the threshold distance of SRRS decreases with increasing the intensity and the pulse width of the pump laser. The phase perturbation of the initial pump field has effect on the intensity distributions of the Stokes and the pump fields, and the influence of the phase perturbation of the initial pump field on the Stokes field is more obvious than that on the pump field. The SRRS ef
2007,
19.
Abstract:
ICF glass targets were treated by electroless plating technology. Magnetic Ni-P coatings cover the surface of ICF glass targets, so the plated ICF glass targets are magnetic and could be used in research of magnetic suspension experiment. The composition, structure, morphology and the magnetic property of the Ni-P coated ICF targets were analyzed by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The results show that the global degree, the homocentric degree and the mural uniformity of the plated ICF glass targets were nearly the same as those of the ICF glass targets before plating. However, the surface smoothness of plated ICF glass targets is worse.
ICF glass targets were treated by electroless plating technology. Magnetic Ni-P coatings cover the surface of ICF glass targets, so the plated ICF glass targets are magnetic and could be used in research of magnetic suspension experiment. The composition, structure, morphology and the magnetic property of the Ni-P coated ICF targets were analyzed by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The results show that the global degree, the homocentric degree and the mural uniformity of the plated ICF glass targets were nearly the same as those of the ICF glass targets before plating. However, the surface smoothness of plated ICF glass targets is worse.
2007,
19.
Abstract:
This paper focused on the Yang’s module and the tensile strength of hollow glass microspheres which serve as inertial confinement fusion targets. Calculation indicated that for aspect ratio more than 90 the buckling was the failure mode when the gas pressure outside the capsule was high. Apparatuses for measuring the buckle and burst strengthes of microspheres were built. Based on the primary experiments, the calculations show that the Yong’s modular was 55~75 GPa and the tensile strength was 90~140 MPa for hollow glass microspheres.
This paper focused on the Yang’s module and the tensile strength of hollow glass microspheres which serve as inertial confinement fusion targets. Calculation indicated that for aspect ratio more than 90 the buckling was the failure mode when the gas pressure outside the capsule was high. Apparatuses for measuring the buckle and burst strengthes of microspheres were built. Based on the primary experiments, the calculations show that the Yong’s modular was 55~75 GPa and the tensile strength was 90~140 MPa for hollow glass microspheres.
2007,
19.
Abstract:
A key problem in streak camera data processing is how to determine the position of the signal pulse, and the results will be effected by the signal to noise ratio(SNR) of the experimental data and the signal pulse position determination method. In the paper, FWHM(half maximum and half width) method is used to determine the single pulse position. The method could determine the signal pulse position with sub-pixel precision when the SNR more than 100∶1. As for the data with bad signal to noise ratio(SNR less than 10∶1), a Fast Fourier Transform method is used to filter the noise first, then the pulse position is determined by the FWHM method. And the streak camera calibration data of the super-fast sweep rate was processed. The sweep speed is (0.214±0.002 9)ps/pixel. The linear dependent
A key problem in streak camera data processing is how to determine the position of the signal pulse, and the results will be effected by the signal to noise ratio(SNR) of the experimental data and the signal pulse position determination method. In the paper, FWHM(half maximum and half width) method is used to determine the single pulse position. The method could determine the signal pulse position with sub-pixel precision when the SNR more than 100∶1. As for the data with bad signal to noise ratio(SNR less than 10∶1), a Fast Fourier Transform method is used to filter the noise first, then the pulse position is determined by the FWHM method. And the streak camera calibration data of the super-fast sweep rate was processed. The sweep speed is (0.214±0.002 9)ps/pixel. The linear dependent
2007,
19.
Abstract:
Based on the coupled wave theory, the helical waveguide(serpentine-type) TEm1-TE11 mode converter was studied. A 94 GHz six-period TE01-TE11 mode converter was designed and numerically analysed and simulated. A 10.24 GHz four-period TE31-TE11 mode converter was analysed and simulated. The ratio of mode constituents in the mode converter was obtained by solving coupled wave equation, which was employed to modify the structure parameters. The convert efficiency of these two devices reached 98% at center frequency and the bandwith of more than 95% exceeded 2 GHz. The simulation results agree well with the theoretical ones.
Based on the coupled wave theory, the helical waveguide(serpentine-type) TEm1-TE11 mode converter was studied. A 94 GHz six-period TE01-TE11 mode converter was designed and numerically analysed and simulated. A 10.24 GHz four-period TE31-TE11 mode converter was analysed and simulated. The ratio of mode constituents in the mode converter was obtained by solving coupled wave equation, which was employed to modify the structure parameters. The convert efficiency of these two devices reached 98% at center frequency and the bandwith of more than 95% exceeded 2 GHz. The simulation results agree well with the theoretical ones.
2007,
19.
Abstract:
One dimension model of the coaxial explosive magnetic generator (CEMG) has built up. The model consists of 1-D model for explosion driven central tube(armature), 1-D model for magnetic flux diffusion, 1-D model for conductor resistivity and the circuit model. A code (CEMG 2.0) was compiled. With the aid of code CEMG2.0, the 43 cm Ranchero generator designed by LANL has been calculated. The results agrees well with the experiments and the calculation of code RAVEN provided by LANL．
One dimension model of the coaxial explosive magnetic generator (CEMG) has built up. The model consists of 1-D model for explosion driven central tube(armature), 1-D model for magnetic flux diffusion, 1-D model for conductor resistivity and the circuit model. A code (CEMG 2.0) was compiled. With the aid of code CEMG2.0, the 43 cm Ranchero generator designed by LANL has been calculated. The results agrees well with the experiments and the calculation of code RAVEN provided by LANL．
2007,
19.
Abstract:
High power delayed breakdown device(DBD) switches containing fifteen seriesconnected semiconductor structures are introduced. The seriesconnected DBD switches have been applied to fast risetime trigger generator. The experimental results show that the input pulse is sharpened significantly by seriesconnected DBD switches.The seriesconnected DBD switches have a holdoff voltage 60 kV, and the risetime is reduced from 95 ns to 21.5 ns.The pulse width of output pulse is 50 ns．
High power delayed breakdown device(DBD) switches containing fifteen seriesconnected semiconductor structures are introduced. The seriesconnected DBD switches have been applied to fast risetime trigger generator. The experimental results show that the input pulse is sharpened significantly by seriesconnected DBD switches.The seriesconnected DBD switches have a holdoff voltage 60 kV, and the risetime is reduced from 95 ns to 21.5 ns.The pulse width of output pulse is 50 ns．
2007,
19.
Abstract:
With the aid of a semi-analytic treatment, the performance of rod-pinch diode with or without ions was characterized via particle-in-cell simulations. With the increase of diode current, the sequential transitions of the space-charge-limited flow, weakly pinched flow and magnetically insulated flow were clearly shown from electrons position and space current flow patterns. It is concluded that critical magnetically insulated current can be reached at lower voltage when ion emission is allowed, and only with ions, electrons can propagate along the anode surface and pinch can form at the tip of the rod; ions are necessary for rod pinch diode which can provide a small-area, high-yield X-ray source for pulsed radiography.
With the aid of a semi-analytic treatment, the performance of rod-pinch diode with or without ions was characterized via particle-in-cell simulations. With the increase of diode current, the sequential transitions of the space-charge-limited flow, weakly pinched flow and magnetically insulated flow were clearly shown from electrons position and space current flow patterns. It is concluded that critical magnetically insulated current can be reached at lower voltage when ion emission is allowed, and only with ions, electrons can propagate along the anode surface and pinch can form at the tip of the rod; ions are necessary for rod pinch diode which can provide a small-area, high-yield X-ray source for pulsed radiography.
2007,
19.
Abstract:
One compact long pulse generator was presented, whose spiral pulse forming line consisted of an inner conductor and an outer shield composed of magnetic material. The spiral pulse forming line was charged by a built-in high coupling Tesla transformer, whose primary coil was adjacent to the outer shield and the secondary coil was located between the central spiral conductor and the outer shield. Theoretic calculation to characteristic parameters and numerical simulation of wave transmission on spiral forming line were given. The principle verifying experiment to generate a long pulse on a spiral line was proceeded preliminarily. The experimental results show that such structure design is feasible.
One compact long pulse generator was presented, whose spiral pulse forming line consisted of an inner conductor and an outer shield composed of magnetic material. The spiral pulse forming line was charged by a built-in high coupling Tesla transformer, whose primary coil was adjacent to the outer shield and the secondary coil was located between the central spiral conductor and the outer shield. Theoretic calculation to characteristic parameters and numerical simulation of wave transmission on spiral forming line were given. The principle verifying experiment to generate a long pulse on a spiral line was proceeded preliminarily. The experimental results show that such structure design is feasible.
2007,
19.
Abstract:
A new concept for monitoring electron beam position based on two off-axis cavities is proposed, main performances of the beam position monitor are discussed using its main parameters, such as normalized shunt impedence. Two off-axis cavities excited dipole mode TM110 by off-center beam provides microwave signals strong enough for the detection of beam position, which can be measured directly by the ratio of the dipole mode amplitude from two cavities. The change of dipole mode amplitude reflects the beam displacement. RF front-end circuits are simplified by the method without phase detection and the common mode is heavily suppressed. Eigenmode characteristics as well as mode coupling coefficient between two cavities are studied by MAFIA and HFSS simulations, which prove the function of the
A new concept for monitoring electron beam position based on two off-axis cavities is proposed, main performances of the beam position monitor are discussed using its main parameters, such as normalized shunt impedence. Two off-axis cavities excited dipole mode TM110 by off-center beam provides microwave signals strong enough for the detection of beam position, which can be measured directly by the ratio of the dipole mode amplitude from two cavities. The change of dipole mode amplitude reflects the beam displacement. RF front-end circuits are simplified by the method without phase detection and the common mode is heavily suppressed. Eigenmode characteristics as well as mode coupling coefficient between two cavities are studied by MAFIA and HFSS simulations, which prove the function of the
2007,
19.
Abstract:
Theory of the light instantaneously emitted by Cherenkov radiation is applied to diagnosing peak current and electron-beam micro-pulse bunch structure of RF-linac. The relativistic electron-beam hitting fused silica generates visible light, which is measured by ps-streak camera. Therefore, parameters of electron-beam micro-pulse can be obtained. This method can diagnose breadth and bunch structure of electron-beam micro-pulse of L-band RF-linac,which makes it possible to form a suit of on-line measurement system of electron-beam micro-pulse of an accelerator.
Theory of the light instantaneously emitted by Cherenkov radiation is applied to diagnosing peak current and electron-beam micro-pulse bunch structure of RF-linac. The relativistic electron-beam hitting fused silica generates visible light, which is measured by ps-streak camera. Therefore, parameters of electron-beam micro-pulse can be obtained. This method can diagnose breadth and bunch structure of electron-beam micro-pulse of L-band RF-linac,which makes it possible to form a suit of on-line measurement system of electron-beam micro-pulse of an accelerator.
2007,
19.
Abstract:
In order to realize the fast extraction of beam from the HIRFL-CSR (the Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring) main ring, we adopt an extraction system based on FPGA technique. The digital multiplication of clock frequency method is employed in the design of FPGA, to accurately control the charging time and discharging time of Kicker magnet during a high-frequency period. Test results show that the time accuracy of the system reaches 5 ns for beam locating and beam adjusting in the storage ring. At the high-frequency of 1.4 MHz, triggering Kicker can be realized with phase accuracy of 2.5 degree in the scale of 0 to 360 degree.
In order to realize the fast extraction of beam from the HIRFL-CSR (the Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring) main ring, we adopt an extraction system based on FPGA technique. The digital multiplication of clock frequency method is employed in the design of FPGA, to accurately control the charging time and discharging time of Kicker magnet during a high-frequency period. Test results show that the time accuracy of the system reaches 5 ns for beam locating and beam adjusting in the storage ring. At the high-frequency of 1.4 MHz, triggering Kicker can be realized with phase accuracy of 2.5 degree in the scale of 0 to 360 degree.
2007,
19.
Abstract:
Boron neutron capture therapy(BNCT) is a promising approach for treatment of some malignant tumors, which can not be cured by conventional therapies, such as glioblastoma multiforme and melanoma. This paper mainly investigated the choice of the neutron source used for BNCT. Based on the analysis of the clinical requirements of BNCT and the characteristics of various neutron generators, the concept of using radiation frequency quadrupole(RFQ) as the preferred neutron source was brought forward. Since the epithermal neutron emits from the 7Li(p,n)7Be near threshold reaction has low energy and small angular, 1.9 MeV was chosen as the final energy of the RFQ suitable for BNCT. In order to get enough neutron flux the induced proton current should be 100 mA. After choosing the basic parameters,
Boron neutron capture therapy(BNCT) is a promising approach for treatment of some malignant tumors, which can not be cured by conventional therapies, such as glioblastoma multiforme and melanoma. This paper mainly investigated the choice of the neutron source used for BNCT. Based on the analysis of the clinical requirements of BNCT and the characteristics of various neutron generators, the concept of using radiation frequency quadrupole(RFQ) as the preferred neutron source was brought forward. Since the epithermal neutron emits from the 7Li(p,n)7Be near threshold reaction has low energy and small angular, 1.9 MeV was chosen as the final energy of the RFQ suitable for BNCT. In order to get enough neutron flux the induced proton current should be 100 mA. After choosing the basic parameters,
2007,
19.
Abstract:
A new approach to radiation source imaging with a rotating edge was proposed. Differentiating the edge response curve can yield the integration of the emission intensity of the source along the direction of the edge, which is similar to the projection of a source in CT technology. Multiple projections from different directions can be obtained by rotating the edge, from which the distribution of source intensity can be reconstructed. A tungsten alloy step edge was used in the imaging experiment on a 60Co gamma source. The image of the active region of the source could be reconstructed from the edge responses of 400 projections, indicating this new approach is feasible. It can be applied to measure the size of small radiation sources, such as the focus of an X-ray generator, using a step edg
A new approach to radiation source imaging with a rotating edge was proposed. Differentiating the edge response curve can yield the integration of the emission intensity of the source along the direction of the edge, which is similar to the projection of a source in CT technology. Multiple projections from different directions can be obtained by rotating the edge, from which the distribution of source intensity can be reconstructed. A tungsten alloy step edge was used in the imaging experiment on a 60Co gamma source. The image of the active region of the source could be reconstructed from the edge responses of 400 projections, indicating this new approach is feasible. It can be applied to measure the size of small radiation sources, such as the focus of an X-ray generator, using a step edg
Effects of CO2 laser and vacuum plasma cleanings on silica-oil-and-grease polluted quartz substrates
2007,
19.
Abstract:
As an important window material for the target chamber, the quartz substrate's cleaning is vital for its laser damage threshold. In this work, the quartz substrates polluted by evaporated silica-oil-and-grease were cleaned by CO2 laser and plasma and the damage thresholds were studied. The samples were characterized via the optical microscopy photo, the water contact angle, the optical transmittance and the laser damage threshold. The experimental results showed that the substrates could be well cleaned by low energy CO2 laser combined with vacuum subsequent plasma. After cleaning, the water contact angle of the quartz substrates decreased from 63 to 4, the transmittance increased from 92.3% to 93.0%, and the damage threshold increased from 3.77 J/cm2 to 5.09 J/cm2 when irradiated by 351 n
As an important window material for the target chamber, the quartz substrate's cleaning is vital for its laser damage threshold. In this work, the quartz substrates polluted by evaporated silica-oil-and-grease were cleaned by CO2 laser and plasma and the damage thresholds were studied. The samples were characterized via the optical microscopy photo, the water contact angle, the optical transmittance and the laser damage threshold. The experimental results showed that the substrates could be well cleaned by low energy CO2 laser combined with vacuum subsequent plasma. After cleaning, the water contact angle of the quartz substrates decreased from 63 to 4, the transmittance increased from 92.3% to 93.0%, and the damage threshold increased from 3.77 J/cm2 to 5.09 J/cm2 when irradiated by 351 n
