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RSS1999 Vol. 11, No. 06
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1999,
11.
Abstract:
The fracture threshold of the woven carbonfiber/epoxy plates with singleside notch under combined mechanical loading and heating by incident beam is studied experimentally and theoretically. The threshold curve was measured and the fracture modes were identified through the observation of microscopy, they are thermal stressing, thermal thinning and thermal puncture. For the mode of thermal stressing corresponding to lower power laser beams, a theoretical criterion of the fracture is developed based on the analysis with fracture mechanics, in agreement with the experimental result.
The fracture threshold of the woven carbonfiber/epoxy plates with singleside notch under combined mechanical loading and heating by incident beam is studied experimentally and theoretically. The threshold curve was measured and the fracture modes were identified through the observation of microscopy, they are thermal stressing, thermal thinning and thermal puncture. For the mode of thermal stressing corresponding to lower power laser beams, a theoretical criterion of the fracture is developed based on the analysis with fracture mechanics, in agreement with the experimental result.
1999,
11.
Abstract:
The action mechanism of both laser-induced temperature rise and lateral force on the large deflections of a clamped circular plate subjected to combined CW laser and lateral force is analyzed and the results indicate that the gradient effects of thermo-softening and temperature moment are of quite importance. The theoretical and FEM results are in quantitatively accordance with each other and also in qualitatively agreement with pertinent theoretical and experimental ones in references.
The action mechanism of both laser-induced temperature rise and lateral force on the large deflections of a clamped circular plate subjected to combined CW laser and lateral force is analyzed and the results indicate that the gradient effects of thermo-softening and temperature moment are of quite importance. The theoretical and FEM results are in quantitatively accordance with each other and also in qualitatively agreement with pertinent theoretical and experimental ones in references.
1999,
11.
Abstract:
Although regenerative amplifier is one of the most used preamplifiers, a number of electrooptical elements are necessary for trapping and dumping the weak signal pulse, which limits the output energy. Based on the basic theory, the gain characteristics of the multipass amplifier is analyzed. A fourpass scheme is employed to carry out the multipass experiments which successfully yield 20mJ output energy.
Although regenerative amplifier is one of the most used preamplifiers, a number of electrooptical elements are necessary for trapping and dumping the weak signal pulse, which limits the output energy. Based on the basic theory, the gain characteristics of the multipass amplifier is analyzed. A fourpass scheme is employed to carry out the multipass experiments which successfully yield 20mJ output energy.
1999,
11.
Abstract:
To give out the stability requirements of every components in the multi-pass amplification system of a large laser facility, a ray- tracing software was developed by using the method of 3×3 matrix and algebra. Using the developed software and by establishing a mathematical model of the layout of TIL, which is a multi-pass high power laser facility, the task of analyzing the relations between the stability of any individual optical component and the position of the beam focus on the target has been fulfilled.
To give out the stability requirements of every components in the multi-pass amplification system of a large laser facility, a ray- tracing software was developed by using the method of 3×3 matrix and algebra. Using the developed software and by establishing a mathematical model of the layout of TIL, which is a multi-pass high power laser facility, the task of analyzing the relations between the stability of any individual optical component and the position of the beam focus on the target has been fulfilled.
1999,
11.
Abstract:
Improvement of beam propagation code for highpower multipass laser amplifier systems has been proposed, where some important effects on the laser beam propagation and amplification have been considered. Numerical illustrative results have been given, and furthermore confirmed in the use of the experimental and modeled data presented by the LawrenceLivermore National Laboratory, showing the validity and advantages of our improved code.
Improvement of beam propagation code for highpower multipass laser amplifier systems has been proposed, where some important effects on the laser beam propagation and amplification have been considered. Numerical illustrative results have been given, and furthermore confirmed in the use of the experimental and modeled data presented by the LawrenceLivermore National Laboratory, showing the validity and advantages of our improved code.
1999,
11.
Abstract:
The aim of this research subject is to develop a precise time relationship logic for MOPA system, starting manner for every devices and some hard wires of the control system. Coaxial single turn magnetic switch and pulse high voltage transformer can produce 150kV pulse high voltage with less than 200ns in rise time. The Marx generators in preamplifier and main amplifier of MOPA system are trigged with this type of high voltages, the jitters of voltage developing time are less than 13ns and 23ns respectively, when the gas spark gaps in Marx are charged to 90% of their self breakdown voltage. When the main gas switches in accelerators are trigged by KrF laser the jitter time less than 10ns is achieved for whole pumping power system.
The aim of this research subject is to develop a precise time relationship logic for MOPA system, starting manner for every devices and some hard wires of the control system. Coaxial single turn magnetic switch and pulse high voltage transformer can produce 150kV pulse high voltage with less than 200ns in rise time. The Marx generators in preamplifier and main amplifier of MOPA system are trigged with this type of high voltages, the jitters of voltage developing time are less than 13ns and 23ns respectively, when the gas spark gaps in Marx are charged to 90% of their self breakdown voltage. When the main gas switches in accelerators are trigged by KrF laser the jitter time less than 10ns is achieved for whole pumping power system.
1999,
11.
Abstract:
The experimental data of atmospheric refractive index structure parameter in the surface layer over the complex terrian measured at the top of a peninsula in Hefei were analysed.It is shown that because of a large area of water possessing large thermal capacity existing, the variation of is complicated and variety. experience formulas used for estimation of in the surface layer over water and land were obtained.A method used for estimation of in the surface layer over complex terrain was presented.
The experimental data of atmospheric refractive index structure parameter in the surface layer over the complex terrian measured at the top of a peninsula in Hefei were analysed.It is shown that because of a large area of water possessing large thermal capacity existing, the variation of is complicated and variety. experience formulas used for estimation of in the surface layer over water and land were obtained.A method used for estimation of in the surface layer over complex terrain was presented.
1999,
11.
Abstract:
The profile of structure constant of refractive index Cn2 is gained with balloon borne instrument in Hefei, Kunming and Xianghe. From the experimental profile, the characters of Cn2 changing with the altitude are given. After compares with several models, the fitting formulae are list. In the end, the statistical distribution character of Cn2 is also discussed.
The profile of structure constant of refractive index Cn2 is gained with balloon borne instrument in Hefei, Kunming and Xianghe. From the experimental profile, the characters of Cn2 changing with the altitude are given. After compares with several models, the fitting formulae are list. In the end, the statistical distribution character of Cn2 is also discussed.
1999,
11.
Abstract:
Precision synchronization of high brightness facility is obtained and a delay triggering control signal is produced with wide range(1ns～999μs) high precision(1ns) adjustment and multipass output(20 passes) through the use of high performance fastECL circuit, standard frequency counting method and high precision linear saw tooth wave voltage generator．
Precision synchronization of high brightness facility is obtained and a delay triggering control signal is produced with wide range(1ns～999μs) high precision(1ns) adjustment and multipass output(20 passes) through the use of high performance fastECL circuit, standard frequency counting method and high precision linear saw tooth wave voltage generator．
1999,
11.
Abstract:
A neutron streak image tube has been designed with high detection efficiency. The large-area photocathode (f 10 mm) consists of CsI on an Al foil, which is backed with a piece of polyethylene (CH2). The tube has no slit and the cross-over of the electron beam is focused on the front surface of the MCP. The calculated time resolution is 43 ps for 14.1 MeV neutrons. It is estimated that our tube can record signals from the implosion of DT-filled targets producing yields of 1 108 neutrons with a target to photocathode distance of 5 cm. The neutron streak image tube also can be used to determine the temperature of the plasma of the implosion of DT-filled targets by measuring the Doppler broadening.
A neutron streak image tube has been designed with high detection efficiency. The large-area photocathode (f 10 mm) consists of CsI on an Al foil, which is backed with a piece of polyethylene (CH2). The tube has no slit and the cross-over of the electron beam is focused on the front surface of the MCP. The calculated time resolution is 43 ps for 14.1 MeV neutrons. It is estimated that our tube can record signals from the implosion of DT-filled targets producing yields of 1 108 neutrons with a target to photocathode distance of 5 cm. The neutron streak image tube also can be used to determine the temperature of the plasma of the implosion of DT-filled targets by measuring the Doppler broadening.
1999,
11.
Abstract:
The scattering of relativistic electron in the intense laser field and Debye shield Coulomb potential has been studied in terms of the second order relativistic approximation of the Dirac equation including the intense laser field. Specially, the relationship between the scattering cross section and the interaction parameters (laser pulse shape, laser frequency, laser intensity and the parameter of shield Coulomb potential etc.) has been shown and discussed.
The scattering of relativistic electron in the intense laser field and Debye shield Coulomb potential has been studied in terms of the second order relativistic approximation of the Dirac equation including the intense laser field. Specially, the relationship between the scattering cross section and the interaction parameters (laser pulse shape, laser frequency, laser intensity and the parameter of shield Coulomb potential etc.) has been shown and discussed.
1999,
11.
Abstract:
The spectral intensities are measured by using a flat-field grating spectrograph and a equally spaced grooves grating spectrograph with a laser-produced C-plasma as a soft X-ray source. The efficiencies on different diffraction orders are given relative to the first order.
The spectral intensities are measured by using a flat-field grating spectrograph and a equally spaced grooves grating spectrograph with a laser-produced C-plasma as a soft X-ray source. The efficiencies on different diffraction orders are given relative to the first order.
1999,
11.
Abstract:
It is not reliable to estimate the saturation laser intensity and the photon energy for the highest order harmonic using Ammosov-Delone-Kraimov(ADK) tunneling ionization theory in generation of high order harmonic when pulse duration of drive laser is shorter than picosecond. In this paper, new expressions for the saturation laser intensity and the photon energy for the highest order harmonic for an arbitrary laser pulse duration have been derived. Based on the expressions, the optimized parameters have been achieved to generate high order harmonic.
It is not reliable to estimate the saturation laser intensity and the photon energy for the highest order harmonic using Ammosov-Delone-Kraimov(ADK) tunneling ionization theory in generation of high order harmonic when pulse duration of drive laser is shorter than picosecond. In this paper, new expressions for the saturation laser intensity and the photon energy for the highest order harmonic for an arbitrary laser pulse duration have been derived. Based on the expressions, the optimized parameters have been achieved to generate high order harmonic.
1999,
11.
Abstract:
Employing Q-modulating YAG pulse laser as source, using metal Cu as sample, using CCD detector to collect the transient spectrum and using Boltzmann distribution method, the temperature of the laser plasma is measured. From the results we know when the laser pulse energy is 100mJ, Cu spectrum mainly consists of atomic excitation lines and its temperature is 14063.8K. This work has great potential for investigating the interaction processes between laser and matter.
Employing Q-modulating YAG pulse laser as source, using metal Cu as sample, using CCD detector to collect the transient spectrum and using Boltzmann distribution method, the temperature of the laser plasma is measured. From the results we know when the laser pulse energy is 100mJ, Cu spectrum mainly consists of atomic excitation lines and its temperature is 14063.8K. This work has great potential for investigating the interaction processes between laser and matter.
1999,
11.
Abstract:
Laser energy deposition is described by the spatial derivative of laser intensity in the simulation study of the laser-target interaction. But the equation for laser energy deposition used in our present code is divergent on the critical surface. In the present paper, a modified equation for laser energy deposition, which does not contain singularity, is derived. Some discusses and one dimensional laser-target interaction simulation results are presented.
Laser energy deposition is described by the spatial derivative of laser intensity in the simulation study of the laser-target interaction. But the equation for laser energy deposition used in our present code is divergent on the critical surface. In the present paper, a modified equation for laser energy deposition, which does not contain singularity, is derived. Some discusses and one dimensional laser-target interaction simulation results are presented.
1999,
11.
Abstract:
In the Inertial Confinement Fusion(ICF) system, rigorous requirements of target illumination are requested, such as top flat, steep edge, low sidelobes and high light efficiency. Binary optical element(BOE) is a very important approach to realize the above requirements. A hybrid algorithm, GLUSA(Global/local united search algorithm), was developed for designing phases of the BOE. The simulated results showed that BOE arrays applied can decrease the sensitivity of the input phase and amplitude distortion. A 16phaselevel BOE was manufactured by a pattern generator, photolothography and ionetching sequentially. Based on the optical Computerized Tomography(CT), a measurement system for twodimensional intensity distribution has been set up. Experiment results declare that the focal spo
In the Inertial Confinement Fusion(ICF) system, rigorous requirements of target illumination are requested, such as top flat, steep edge, low sidelobes and high light efficiency. Binary optical element(BOE) is a very important approach to realize the above requirements. A hybrid algorithm, GLUSA(Global/local united search algorithm), was developed for designing phases of the BOE. The simulated results showed that BOE arrays applied can decrease the sensitivity of the input phase and amplitude distortion. A 16phaselevel BOE was manufactured by a pattern generator, photolothography and ionetching sequentially. Based on the optical Computerized Tomography(CT), a measurement system for twodimensional intensity distribution has been set up. Experiment results declare that the focal spo
1999,
11.
Abstract:
This paper describes an electron gun for the 7.6cm YAG projection CRT which was developed for a new 122cm rear and 183cm front projection TVs. On the green YAG CRT phosphor screen, the diameter of beam spot is near 0.065～0.080cm at cathode currents of 0.5～1.0mA, and the resolution is more than 1400 TVL.
This paper describes an electron gun for the 7.6cm YAG projection CRT which was developed for a new 122cm rear and 183cm front projection TVs. On the green YAG CRT phosphor screen, the diameter of beam spot is near 0.065～0.080cm at cathode currents of 0.5～1.0mA, and the resolution is more than 1400 TVL.
1999,
11.
Abstract:
The radiation of Ultra-wide band (UWB) pulse is a new subject in antenna field. This paper describes a new type of the UWB radiating antenna, high repetition-rate and high power impulse generator and half paraboloidal impulse radiating antenna (IRA) including antenna theory, system engineering design and experiment. The output of the compact high power system of half IRA designed and constructed has the peak electric field of 13kV/m at a distance of 30m.
The radiation of Ultra-wide band (UWB) pulse is a new subject in antenna field. This paper describes a new type of the UWB radiating antenna, high repetition-rate and high power impulse generator and half paraboloidal impulse radiating antenna (IRA) including antenna theory, system engineering design and experiment. The output of the compact high power system of half IRA designed and constructed has the peak electric field of 13kV/m at a distance of 30m.
1999,
11.
Abstract:
Based on the theory of the transmission of the electromagnetic waves in elliptic waveguides, the cutoff wavelength and power attenuation constant with any elliptic eccentricity are studied and the precise calculation of Mathieu functions is appropriately resolved. The results are satisfactory and in agreement with those reported abroad .Besides, the suitable regions of changing eccentricity of variant wave modes are greatly expanded (from 1% to 99%).
Based on the theory of the transmission of the electromagnetic waves in elliptic waveguides, the cutoff wavelength and power attenuation constant with any elliptic eccentricity are studied and the precise calculation of Mathieu functions is appropriately resolved. The results are satisfactory and in agreement with those reported abroad .Besides, the suitable regions of changing eccentricity of variant wave modes are greatly expanded (from 1% to 99%).
1999,
11.
Abstract:
The sensor technology for high power microwave vector field by using recording characteristics of magneto-optic crystal is described in this paper. The multipoint array measurements on the microwave field of the cacinotron oscillator indicate that the sensor system has no effect on the measured field and has an anti-interference ability, its spatial resolution is 1mm. The sensor can measure the field’s main modes TM01,TE01 and TE11, and the field intensities and powers of these modes. The estimations of the total power agree well with the results which are measured by horn coupler.
The sensor technology for high power microwave vector field by using recording characteristics of magneto-optic crystal is described in this paper. The multipoint array measurements on the microwave field of the cacinotron oscillator indicate that the sensor system has no effect on the measured field and has an anti-interference ability, its spatial resolution is 1mm. The sensor can measure the field’s main modes TM01,TE01 and TE11, and the field intensities and powers of these modes. The estimations of the total power agree well with the results which are measured by horn coupler.
1999,
11.
Abstract:
This paper addresses the numerical analysis method for a circular waveguide bevel cut radiator (Vlasov-Nakajima radiator) which is used as the first step in the design of a high power microwave Vlasov-type mode converter. The radiation field launched from the radiator can be considered as the sum of the field radiated by the circular aperture and the field scattered by the bevel cut. The former is predicated by Kirchhoff-Kottler integration. The latter is calculated by physical-optics approach. Numerical far-field radiation patterns are compared to measured results. The theoretical analysis of the frequency characteristic of the radiator shows that it has luminary electrical scan ability.
This paper addresses the numerical analysis method for a circular waveguide bevel cut radiator (Vlasov-Nakajima radiator) which is used as the first step in the design of a high power microwave Vlasov-type mode converter. The radiation field launched from the radiator can be considered as the sum of the field radiated by the circular aperture and the field scattered by the bevel cut. The former is predicated by Kirchhoff-Kottler integration. The latter is calculated by physical-optics approach. Numerical far-field radiation patterns are compared to measured results. The theoretical analysis of the frequency characteristic of the radiator shows that it has luminary electrical scan ability.
1999,
11.
Abstract:
A high-efficient relativistic backward wave oscillator with a single-step change in the couple impedance has been designed and analyzed in the paper. An electromagnetic particle-in-cell code is being used to investigate the nonlinear beam-wave interaction in the device and other design optimization issues. The simulation results show that the device can generate 800MW peak power microwave at (9.16±0.03) GHz in the TM01 mode driven by 500kV , 5.5kA electron beams. The peak power efficiency is about 30%. The device optimum efficiency can be more up to 38% when a section of smooth drift tube lying between cut-off waveguide and slow wave structure is in the optimum condition.
A high-efficient relativistic backward wave oscillator with a single-step change in the couple impedance has been designed and analyzed in the paper. An electromagnetic particle-in-cell code is being used to investigate the nonlinear beam-wave interaction in the device and other design optimization issues. The simulation results show that the device can generate 800MW peak power microwave at (9.16±0.03) GHz in the TM01 mode driven by 500kV , 5.5kA electron beams. The peak power efficiency is about 30%. The device optimum efficiency can be more up to 38% when a section of smooth drift tube lying between cut-off waveguide and slow wave structure is in the optimum condition.
1999,
11.
Abstract:
A detector was developed for measuring ultra-wideband (UWB) transient electromagnetic field in the free-space .It is a small TEM horn antenna with gradually changed impedance. The major part of this paper is to describe the method of calibrating the detector’s sensitivity .Results show that in the range of 50Mhz~ 2.2Ghz, the detector’s sensitivity is with linear phase and a uniform magnitude within 20% . The error of calibrating is less than 12% .
A detector was developed for measuring ultra-wideband (UWB) transient electromagnetic field in the free-space .It is a small TEM horn antenna with gradually changed impedance. The major part of this paper is to describe the method of calibrating the detector’s sensitivity .Results show that in the range of 50Mhz~ 2.2Ghz, the detector’s sensitivity is with linear phase and a uniform magnitude within 20% . The error of calibrating is less than 12% .
1999,
11.
Abstract:
According to the longitudinal matching requirement of the HIRFL two cyclotrons, a scheme of the new B1 buncher has been introduced. Both the moving short-circuit plate and the two movable capacity plates are employed to meet the large frequency range (22~54MHz) requirement. With the help of three-dimensional electromagnetic field computation code MAFIA, the frequency range, Q factor, power losses and surface current distribution of the B1 cavity have been computed. The errors in computation and the feasibility of the scheme have been discussed also in this paper.
According to the longitudinal matching requirement of the HIRFL two cyclotrons, a scheme of the new B1 buncher has been introduced. Both the moving short-circuit plate and the two movable capacity plates are employed to meet the large frequency range (22~54MHz) requirement. With the help of three-dimensional electromagnetic field computation code MAFIA, the frequency range, Q factor, power losses and surface current distribution of the B1 cavity have been computed. The errors in computation and the feasibility of the scheme have been discussed also in this paper.
1999,
11.
Abstract:
Maximum current density of 123A/cm2 has been obtained from PZT ferroelectric cath-odes in this study. The electron emission was driven by a high voltage pulsed generator, which supplied 150ns pulses. The ferroelectric samples were put in the vacuum cell and the exerting voltage was perpendicular to the polar dirrection. The effects of the material parameters on the electron emission from ferroelectric cathode. Such as the dielectric, piezoelectric and ferroelectric characteristics, were investi, The dielectric constant and the remnant polarizatin as well as the piezoelectric constant are all decreased, after the samples were tested by electron emission, this phenomenon is in conformity with the fast polarization theory. It has been proved that the emitted curent densities can by increased
Maximum current density of 123A/cm2 has been obtained from PZT ferroelectric cath-odes in this study. The electron emission was driven by a high voltage pulsed generator, which supplied 150ns pulses. The ferroelectric samples were put in the vacuum cell and the exerting voltage was perpendicular to the polar dirrection. The effects of the material parameters on the electron emission from ferroelectric cathode. Such as the dielectric, piezoelectric and ferroelectric characteristics, were investi, The dielectric constant and the remnant polarizatin as well as the piezoelectric constant are all decreased, after the samples were tested by electron emission, this phenomenon is in conformity with the fast polarization theory. It has been proved that the emitted curent densities can by increased
1999,
11.
Abstract:
The article presents the study of beam longitudinal motion and the physical design of the longitudinal matching devices at HIRFL. Two linear bunchers are used on the verylow energy SFC axial injection beam line and the new idea of halffrequency bunching mode is introduced to compensate the longitudinal mismatching between the cyclotrons. The two bunchers on the low energy beam line are designed to work at multimode for reason of the large acceleration range at HIRFL.
The article presents the study of beam longitudinal motion and the physical design of the longitudinal matching devices at HIRFL. Two linear bunchers are used on the verylow energy SFC axial injection beam line and the new idea of halffrequency bunching mode is introduced to compensate the longitudinal mismatching between the cyclotrons. The two bunchers on the low energy beam line are designed to work at multimode for reason of the large acceleration range at HIRFL.
1999,
11.
Abstract:
The article analyzed the bipolar flow in high-power diode and operating principle of reflex diode, magnetic insulating diode and pinch diode for improving ion beam generation efficiency, summarized and pointed out research development and developing direction of high-power ion beams.
The article analyzed the bipolar flow in high-power diode and operating principle of reflex diode, magnetic insulating diode and pinch diode for improving ion beam generation efficiency, summarized and pointed out research development and developing direction of high-power ion beams.
1999,
11.
Abstract:
A convenient method of measuring the ground electric field of EMP simulator has been proposed and developed. The device for the method has simple structure. It is passive, even not limited by voltage and has wide bandwidth. The method can be applied in measuring electric field of complicated electromagnitic environment. It can transmit high amplitude signal, so signal to noise ratio of the device is improved.
A convenient method of measuring the ground electric field of EMP simulator has been proposed and developed. The device for the method has simple structure. It is passive, even not limited by voltage and has wide bandwidth. The method can be applied in measuring electric field of complicated electromagnitic environment. It can transmit high amplitude signal, so signal to noise ratio of the device is improved.
