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RSS2015 Vol. 27, No. 08
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2015,
27: 081001.
doi: 10.11884/HPLPB201527.081001
Abstract:
The Fresnel reflection light model of fiber splicing point was analyzed, and it was concluded that there is a linear relationship between the scattered light power of splicing point and output optical power. The oscillator and pump source power detecting device of a kW-class fiber laser were designed with this conclusion, and mounted on a kW-class fiber laser in experiments. Through the establishment of linear estimation function using the least squares method for the fiber splice scattered light power of fiber laser oscillator and pump source, the relationship between the output power and the fiber splice scattered light power of fiber was fitted. The linear relationship was verified by experiments. Experiments show that the linearity of the method using splice scattered light power indirect measurement of fiber laser output power wasless than 4%.
The Fresnel reflection light model of fiber splicing point was analyzed, and it was concluded that there is a linear relationship between the scattered light power of splicing point and output optical power. The oscillator and pump source power detecting device of a kW-class fiber laser were designed with this conclusion, and mounted on a kW-class fiber laser in experiments. Through the establishment of linear estimation function using the least squares method for the fiber splice scattered light power of fiber laser oscillator and pump source, the relationship between the output power and the fiber splice scattered light power of fiber was fitted. The linear relationship was verified by experiments. Experiments show that the linearity of the method using splice scattered light power indirect measurement of fiber laser output power wasless than 4%.
2015,
27: 081002.
doi: 10.11884/HPLPB201527.081002
Abstract:
In order to investigate the melt removal effects of the metal plate under laser irradiation, a three-dimensional thermal model based on finite volume method(FVM) was constructed. The model employs a database of material properties, such as the heat capacity, the thermal conductivity, and the absorptivity. An important feature of these properties is their temperature dependence. As molten metal would be carried out of the surface by the airflow, the boundary condition control volumes and iterative algorithm were modified and the finite volume equation could be solved in irregular domain. Also a three dimensional program code was developed with Fortran language. It was found that the program can perform a high-accuracy simulation of airflow-induced melt removal effects of metal plate under laser irradiation.
In order to investigate the melt removal effects of the metal plate under laser irradiation, a three-dimensional thermal model based on finite volume method(FVM) was constructed. The model employs a database of material properties, such as the heat capacity, the thermal conductivity, and the absorptivity. An important feature of these properties is their temperature dependence. As molten metal would be carried out of the surface by the airflow, the boundary condition control volumes and iterative algorithm were modified and the finite volume equation could be solved in irregular domain. Also a three dimensional program code was developed with Fortran language. It was found that the program can perform a high-accuracy simulation of airflow-induced melt removal effects of metal plate under laser irradiation.
2015,
27: 081003.
doi: 10.11884/HPLPB201527.081003
Abstract:
In order to analyze the spectral characteristics of the reflected sun light by different targets, research the ways to reduce disturbance in passive ranging, using spectrometer as measuring equipment, 200 W tungsten halogen lamp as simulated target, glass plate, aluminum plate and plastic plate as interference target, the spectrum of simulated target and the spectra reflected by interference target are acquired and analyzed. In the experiment, the reflected spectrum of interference target and the radiation spectrum of tungsten halogen lamp are acquired, and oxygen absorption is calculated. The difference of oxygen absorption between mirror reflection interference target, diffuse reflection target, the reflection of background and tungsten halogen lamp is analyzed. The result shows that: at 455 m, the oxygen absorption of reflection of mirror target and diffuse reflection target is twice to triple of tungsten halogen lamp. Hence, at a certain distance, the difference of oxygen absorption can be used as a threshold to distinguish targets, and improve detection probability.
In order to analyze the spectral characteristics of the reflected sun light by different targets, research the ways to reduce disturbance in passive ranging, using spectrometer as measuring equipment, 200 W tungsten halogen lamp as simulated target, glass plate, aluminum plate and plastic plate as interference target, the spectrum of simulated target and the spectra reflected by interference target are acquired and analyzed. In the experiment, the reflected spectrum of interference target and the radiation spectrum of tungsten halogen lamp are acquired, and oxygen absorption is calculated. The difference of oxygen absorption between mirror reflection interference target, diffuse reflection target, the reflection of background and tungsten halogen lamp is analyzed. The result shows that: at 455 m, the oxygen absorption of reflection of mirror target and diffuse reflection target is twice to triple of tungsten halogen lamp. Hence, at a certain distance, the difference of oxygen absorption can be used as a threshold to distinguish targets, and improve detection probability.
2015,
27: 081004.
doi: 10.11884/HPLPB201527.081004
Abstract:
According to angular multiplexing technique, a multiplexing decoding method is presented. In this method, multiplexing decoding is achieved by two steps: in the first step the beams between the layers are decoded, and in the second step the beams in each layer are decoded. The optical elements are arranged in rectangular arrays and piled layer by layer. A specific optical design was made for the 18 beams XeCl high power excimer laser system in our laboratory. For this multiplexing decoding method, decoding accuracy is adjustable, compatibility with alignment and measurement is good, and optical structures are easy to fabricate and assemble.
According to angular multiplexing technique, a multiplexing decoding method is presented. In this method, multiplexing decoding is achieved by two steps: in the first step the beams between the layers are decoded, and in the second step the beams in each layer are decoded. The optical elements are arranged in rectangular arrays and piled layer by layer. A specific optical design was made for the 18 beams XeCl high power excimer laser system in our laboratory. For this multiplexing decoding method, decoding accuracy is adjustable, compatibility with alignment and measurement is good, and optical structures are easy to fabricate and assemble.
2015,
27: 081005.
doi: 10.11884/HPLPB201527.081005
Abstract:
Achieving pulse compression and high energy is significant in the construction of an excimer laser angular multiplexing system. The laser pulse profile and energy extraction efficiency were studied changing the input seed intensity. An excimer laser amplification model was built based on four-level rate equations and excimer reaction kinetics. The amplification process was calculated and important parameters were numerically described, which were consistent with the experiment results. Moreover, the energy extraction efficiency of the amplifier was given under different input intensity by this model. The results show that about 95% of the amplified laser energy can be extracted when the laser pulse interval is 9.3 ns. Obviously, 9.3 ns laser pulse interval is a suitable choice for this excimer laser system.
Achieving pulse compression and high energy is significant in the construction of an excimer laser angular multiplexing system. The laser pulse profile and energy extraction efficiency were studied changing the input seed intensity. An excimer laser amplification model was built based on four-level rate equations and excimer reaction kinetics. The amplification process was calculated and important parameters were numerically described, which were consistent with the experiment results. Moreover, the energy extraction efficiency of the amplifier was given under different input intensity by this model. The results show that about 95% of the amplified laser energy can be extracted when the laser pulse interval is 9.3 ns. Obviously, 9.3 ns laser pulse interval is a suitable choice for this excimer laser system.
2015,
27: 081006.
doi: 10.11884/HPLPB201527.081006
Abstract:
A one-dimensional fluid model is used to investigate the kinetics of discharge excited ArF excimer laser. Voltage-current waveforms of the gas discharge process coupling with the discharge circuit are obtained. Temporal-spatial evolution of electron number density, photon number density and electric field are obtained and influence of discharge parameters on the laser output are analyzed. The results show that circuit parameters, pressure and fluorine gas ratio all have significant influence on laser output. The inductance has a little influence on the output which result in a large parameter set. Low peaking capacitance is beneficial to long pulse and too high or too low pressure and fluorine gas ratio result in small output.
A one-dimensional fluid model is used to investigate the kinetics of discharge excited ArF excimer laser. Voltage-current waveforms of the gas discharge process coupling with the discharge circuit are obtained. Temporal-spatial evolution of electron number density, photon number density and electric field are obtained and influence of discharge parameters on the laser output are analyzed. The results show that circuit parameters, pressure and fluorine gas ratio all have significant influence on laser output. The inductance has a little influence on the output which result in a large parameter set. Low peaking capacitance is beneficial to long pulse and too high or too low pressure and fluorine gas ratio result in small output.
2015,
27: 081007.
doi: 10.11884/HPLPB201527.081007
Abstract:
Cadmium selenide can be used in the all optical framing camera and streak camera for ultrafast X-ray detection. Based on time-resolved pumping system with phase object, we studied the nonlinear properties of bulk cadmium selenide at 1030 nm under femtosecond pulse by two-photon absorption and got the nonlinear properties of two-photon absorbing coefficient, free-carrier absorption cross section, and free-carrier life time. According to the experiment, the nonliear response of cadmium selenide is a combination of bound-electron effects and two-photon-induced free-carrier effects. The Kerr effect and the two-photon excitation are transient, and the free-carrier recombination lasts for a long time. The experiment has provided useful data of carrier parameters and images foe design.
Cadmium selenide can be used in the all optical framing camera and streak camera for ultrafast X-ray detection. Based on time-resolved pumping system with phase object, we studied the nonlinear properties of bulk cadmium selenide at 1030 nm under femtosecond pulse by two-photon absorption and got the nonlinear properties of two-photon absorbing coefficient, free-carrier absorption cross section, and free-carrier life time. According to the experiment, the nonliear response of cadmium selenide is a combination of bound-electron effects and two-photon-induced free-carrier effects. The Kerr effect and the two-photon excitation are transient, and the free-carrier recombination lasts for a long time. The experiment has provided useful data of carrier parameters and images foe design.
2015,
27: 081008.
doi: 10.11884/HPLPB201527.081008
Abstract:
A novel monolithically integrated double microring resonator coupled dual-wavelength semiconductor laser is proposed. Two microring resonators incorporated in the laser cavity are used as the strong mode-selection filters to select the resonance modes by vernier effect and the equivalent reflective mirrors to form the traveling-wave cavity. A cleavage-free traveling-wave laser cavity replaces the standing-wave FP cavity formed by cleaved reflective facets. Theoretical simulations show that, compared to standing-wave supported structures, traveling-wave structure double microring coupled laser offers many promising advantages, including simple fabrication, reasonably low threshold current of about 34 mA and good side-mode suppression ratio (SMSR) of over 31 dB. The new design can provide dual wavelength lasing with excellent uniformity and stability as the gain peak of the active region and the resonance modes distribution are controlled properly.
A novel monolithically integrated double microring resonator coupled dual-wavelength semiconductor laser is proposed. Two microring resonators incorporated in the laser cavity are used as the strong mode-selection filters to select the resonance modes by vernier effect and the equivalent reflective mirrors to form the traveling-wave cavity. A cleavage-free traveling-wave laser cavity replaces the standing-wave FP cavity formed by cleaved reflective facets. Theoretical simulations show that, compared to standing-wave supported structures, traveling-wave structure double microring coupled laser offers many promising advantages, including simple fabrication, reasonably low threshold current of about 34 mA and good side-mode suppression ratio (SMSR) of over 31 dB. The new design can provide dual wavelength lasing with excellent uniformity and stability as the gain peak of the active region and the resonance modes distribution are controlled properly.
2015,
27: 081009.
doi: 10.11884/HPLPB201527.081009
Abstract:
The mono-bi-and trilayer graphene samples were prepared by chemical vapor deposition method and transferred to substrate. Damage effect of the graphene under 1064 nm nanosecond laser irradiation was quantified by taking Hall Effect and Raman spectra measurements. The results show that, the laser induced damage threshold values of the mono-bi-and trilayer graphene samples decrease accordingly: mono layer, 0.45 J/cm2; bilayer, 0.34 J/cm2; 3 layer, 0.23 J/cm2. When the laser energy is higher than the threshold, the sheet resistance of graphene increases, and the carrier mobility decreases. Damaged area was observed by optical microscope after high energy laser irradiation. In the damaged area, the Raman intensity ratios of the G peak (1580 cm-1) to the 2D peak (2700 cm-1) decrease. The results demonstrate that the 1064 nm nanosecond laser irradiation can exfoliate the multilayer graphene without inducing structure defects.
The mono-bi-and trilayer graphene samples were prepared by chemical vapor deposition method and transferred to substrate. Damage effect of the graphene under 1064 nm nanosecond laser irradiation was quantified by taking Hall Effect and Raman spectra measurements. The results show that, the laser induced damage threshold values of the mono-bi-and trilayer graphene samples decrease accordingly: mono layer, 0.45 J/cm2; bilayer, 0.34 J/cm2; 3 layer, 0.23 J/cm2. When the laser energy is higher than the threshold, the sheet resistance of graphene increases, and the carrier mobility decreases. Damaged area was observed by optical microscope after high energy laser irradiation. In the damaged area, the Raman intensity ratios of the G peak (1580 cm-1) to the 2D peak (2700 cm-1) decrease. The results demonstrate that the 1064 nm nanosecond laser irradiation can exfoliate the multilayer graphene without inducing structure defects.
2015,
27: 081010.
doi: 10.11884/HPLPB201527.081010
Abstract:
The surface discharge optical pumping source is a key unit of high power XeF blue-green laser with pulse repetition mode. To increase the lifetime of the high power XeF blue-green laser, it is very important to develop a kind of surface discharge optical pumping source which emit strong UV radiation with a long lifespan. In this paper, three kinds of sectioned surface discharge optical pumping sources, which are made from Al2O3 ceramic substrate, BN ceramic substrate and Teflon substrate, are developed respectively, and the electrical, radiation and ablation characteristics of them are examined. Based on discharge current waveform, the equivalent inductance, resistance and energy deposition efficiency of these sources are calculated. UV radiation intensities of the sources are compared by their discharge emission spectrum. Anti-ablative performances of the material are estimated by average line ablation rate which is calculated after 1000 shots. By comparing experimental results from three kinds of surface discharge optical pumping sources, it is found that the best energy deposition efficiency, which is above 82%, is obtained from surface discharge optical pumping source with Al2O3 ceramic substrate, and the UV radiation enhancement is observed in its radiation spectra, with an average line ablation rate less than 0.15 m/shot. The normal working condition is as follows: the charge voltage ranges from 13.5 kV to 26.8 kV, the discharge gap length is 8 cm, and 60%Ar-40% N2 mix gas pressure is 100 kPa. It is believed that Al2O3 ceramic substrate may be utilized to obtain long lifetime XeF blue-green laser.
The surface discharge optical pumping source is a key unit of high power XeF blue-green laser with pulse repetition mode. To increase the lifetime of the high power XeF blue-green laser, it is very important to develop a kind of surface discharge optical pumping source which emit strong UV radiation with a long lifespan. In this paper, three kinds of sectioned surface discharge optical pumping sources, which are made from Al2O3 ceramic substrate, BN ceramic substrate and Teflon substrate, are developed respectively, and the electrical, radiation and ablation characteristics of them are examined. Based on discharge current waveform, the equivalent inductance, resistance and energy deposition efficiency of these sources are calculated. UV radiation intensities of the sources are compared by their discharge emission spectrum. Anti-ablative performances of the material are estimated by average line ablation rate which is calculated after 1000 shots. By comparing experimental results from three kinds of surface discharge optical pumping sources, it is found that the best energy deposition efficiency, which is above 82%, is obtained from surface discharge optical pumping source with Al2O3 ceramic substrate, and the UV radiation enhancement is observed in its radiation spectra, with an average line ablation rate less than 0.15 m/shot. The normal working condition is as follows: the charge voltage ranges from 13.5 kV to 26.8 kV, the discharge gap length is 8 cm, and 60%Ar-40% N2 mix gas pressure is 100 kPa. It is believed that Al2O3 ceramic substrate may be utilized to obtain long lifetime XeF blue-green laser.
2015,
27: 081011.
doi: 10.11884/HPLPB201527.081011
Abstract:
The third order nonlinearities in optical materials could induce chaos of the optical field when the material characteristic and laser parameters satisfy some special requirements. In this paper, we start from the Maxwell equations, derive the Maxwell-Bloch equations based on third order nonlinear material, and then transform them into the Lorentz form. Based on these equations, the stable optical field evolution and the chaos are numerically simulated. According to the simulating results, chaos will happen in third order nonlinear material, which leads to unpredictable nonlinear phase shift of the optical field. Such chaos is disadvantageous in suppressing the nonlinear self-focusing in such materials.
The third order nonlinearities in optical materials could induce chaos of the optical field when the material characteristic and laser parameters satisfy some special requirements. In this paper, we start from the Maxwell equations, derive the Maxwell-Bloch equations based on third order nonlinear material, and then transform them into the Lorentz form. Based on these equations, the stable optical field evolution and the chaos are numerically simulated. According to the simulating results, chaos will happen in third order nonlinear material, which leads to unpredictable nonlinear phase shift of the optical field. Such chaos is disadvantageous in suppressing the nonlinear self-focusing in such materials.
2015,
27: 082001.
doi: 10.11884/HPLPB201527.082001
Abstract:
This paper presents an ion-electron non-equilibrium model for relaxing the central hot-spot ignition conditions in inertial confinement fusion. The model emphasizes that the hot-spot ion temperature is higher than its electron temperature, so that the hot-spot nuclear reactions are enhanced and its energy leaks from radiation bremsstrahlung and electron conduction are relatively reduced. Both the hot-spot self-heating analysis and a more comprehensive hot-spot ignition-and-burn dynamics analysis show that as compared with the commonly used equilibrium model, the ignition region would be significantly enlarged in the hot-spot R-T space. Simulations are also done using the LARED-S code to show that a tuned radiation-drive wedged-peak pulse, which creates a secondary shock, could be utilized to enhance hot-spot non-equilibrium.
This paper presents an ion-electron non-equilibrium model for relaxing the central hot-spot ignition conditions in inertial confinement fusion. The model emphasizes that the hot-spot ion temperature is higher than its electron temperature, so that the hot-spot nuclear reactions are enhanced and its energy leaks from radiation bremsstrahlung and electron conduction are relatively reduced. Both the hot-spot self-heating analysis and a more comprehensive hot-spot ignition-and-burn dynamics analysis show that as compared with the commonly used equilibrium model, the ignition region would be significantly enlarged in the hot-spot R-T space. Simulations are also done using the LARED-S code to show that a tuned radiation-drive wedged-peak pulse, which creates a secondary shock, could be utilized to enhance hot-spot non-equilibrium.
2015,
27: 082002.
doi: 10.11884/HPLPB201527.082002
Abstract:
In atomic oxygen ground simulation equipment, a current source is used to constrain the emittance of atomic oxygen by utilizing magnetic mirror effect. The current source is also used to calibrate the atomic oxygen parameter measuring instruments. A precision voltage-controlled current source based on the op amp is developed. In order to mitigate the influence of the power supply ripple, a switching power supply filter is developed. The testing results show that the switching power supply filter can reduce the switching power supply noise effectively. The ripple coefficient of +15 V power supply drops to millionth. The constant current source can output a current from 10 pA to 1 A, whose accuracy is 500 fA. Its load stability is excellent.
In atomic oxygen ground simulation equipment, a current source is used to constrain the emittance of atomic oxygen by utilizing magnetic mirror effect. The current source is also used to calibrate the atomic oxygen parameter measuring instruments. A precision voltage-controlled current source based on the op amp is developed. In order to mitigate the influence of the power supply ripple, a switching power supply filter is developed. The testing results show that the switching power supply filter can reduce the switching power supply noise effectively. The ripple coefficient of +15 V power supply drops to millionth. The constant current source can output a current from 10 pA to 1 A, whose accuracy is 500 fA. Its load stability is excellent.
2015,
27: 082003.
doi: 10.11884/HPLPB201527.082003
Abstract:
In order to improve performance of the X-ray streak camera cathode, we propose a new fabrication method of X-ray streak camera cathode, the benefit of this method is that the thickness of the substrate film using polycarbonate as raw material can be reduced to 300 nm. Thus the spectral response sensitivity of the cathode can be improved as the absorption to incident X-ray of the substrate film can be reduced. Absolute calibration of Au and CsI cathodes made by this method was carried out in Beijing Synchrotron Radiation Source (BSRF). Spectral response sensitivities of the two kinds of cathodes were obtained in the energy range of 60-5500 eV. Calibration results show that CsI cathode has a high spectral response sensitivity in the whole energy range of 60-5500 eV, and the spectral response sensitivity in carbon absorption edge is only about 9/10 lower.
In order to improve performance of the X-ray streak camera cathode, we propose a new fabrication method of X-ray streak camera cathode, the benefit of this method is that the thickness of the substrate film using polycarbonate as raw material can be reduced to 300 nm. Thus the spectral response sensitivity of the cathode can be improved as the absorption to incident X-ray of the substrate film can be reduced. Absolute calibration of Au and CsI cathodes made by this method was carried out in Beijing Synchrotron Radiation Source (BSRF). Spectral response sensitivities of the two kinds of cathodes were obtained in the energy range of 60-5500 eV. Calibration results show that CsI cathode has a high spectral response sensitivity in the whole energy range of 60-5500 eV, and the spectral response sensitivity in carbon absorption edge is only about 9/10 lower.
2015,
27: 082004.
doi: 10.11884/HPLPB201527.082004
Abstract:
The ultrafine Ni80Cr20 alloy wire was prepared by cold drawing technology. To improve the through-die efficiency in ultrafine Ni80Cr20 alloy wire preparation, we explored a new ultrafine wire corrosion-head and through-die method, by which an electrochemical workstation provided precise corrosion time and a super depth of field microscope magnified apertures of diamond dies. Afterwards, we did experiments on the corrosion-head and through-die process of the 25.60 m ultrafine Ni80Cr20 alloy wire. The research process was also carried out for the 25.60 m diameter ultrafine wire cold drawn to 21.14 m. The experiment results show that the electrolysis with voltage of 5 V, 0.2 mol/L HCl solution as electrolyte, a second corrosion time and aperture of die magnified 200 times, successfully prepared the 21.14 m ultra-fine wire. This method resolves the issue of corrosion-head time inaccuracy and manual through-die difficulty, greatly improves the efficiency and success rate of through-die.
The ultrafine Ni80Cr20 alloy wire was prepared by cold drawing technology. To improve the through-die efficiency in ultrafine Ni80Cr20 alloy wire preparation, we explored a new ultrafine wire corrosion-head and through-die method, by which an electrochemical workstation provided precise corrosion time and a super depth of field microscope magnified apertures of diamond dies. Afterwards, we did experiments on the corrosion-head and through-die process of the 25.60 m ultrafine Ni80Cr20 alloy wire. The research process was also carried out for the 25.60 m diameter ultrafine wire cold drawn to 21.14 m. The experiment results show that the electrolysis with voltage of 5 V, 0.2 mol/L HCl solution as electrolyte, a second corrosion time and aperture of die magnified 200 times, successfully prepared the 21.14 m ultra-fine wire. This method resolves the issue of corrosion-head time inaccuracy and manual through-die difficulty, greatly improves the efficiency and success rate of through-die.
2015,
27: 082006.
doi: 10.11884/HPLPB201527.082006
Abstract:
A self-supported PC membrane was prepared through chemical vapor deposition process, and CsI was evaporated onto PC surface. Then a large-area self-supported CsI/PC membrane was prepared. The thickness of PC membrane was 300 nm, and that of CsI membrane was controlled between 100 nm to 1 m. The effects of deposition speed and deliquescence on morphology and structure were analyzed by SEM and XRD. The photoelectric conversion property was analyzed by Manson X-ray source. The energy spectral response peak value of CsI/PC membrane was above 3000 A/W which was calibrated at Beijing synchrotron radiation facility. The membrane was applied to X-ray streak camera on SG Ⅲ facility and distinct X-ray images were captured.
A self-supported PC membrane was prepared through chemical vapor deposition process, and CsI was evaporated onto PC surface. Then a large-area self-supported CsI/PC membrane was prepared. The thickness of PC membrane was 300 nm, and that of CsI membrane was controlled between 100 nm to 1 m. The effects of deposition speed and deliquescence on morphology and structure were analyzed by SEM and XRD. The photoelectric conversion property was analyzed by Manson X-ray source. The energy spectral response peak value of CsI/PC membrane was above 3000 A/W which was calibrated at Beijing synchrotron radiation facility. The membrane was applied to X-ray streak camera on SG Ⅲ facility and distinct X-ray images were captured.
2015,
27: 082007.
doi: 10.11884/HPLPB201527.082007
Abstract:
The D-D filled capsule implosion experiment is performed on Shenguang Ⅲ prototype laser facility. One-dimensional hydrodynamic numerical simulations show that neutron yield mechanism can be controlled by different D-D gas pressure and CH shell thickness. In experiments, the high gas filling pressure and thin shell thickness capsule is proposed for shock yield only implosion design. Meantime, many important implosion parameters such as neutron yield, bang-time are collected. The optimized experimental neutron yield is 9.9107 (9.7%) and the ratio between the experimental value and the 1D simulated value reached 90%. On the other hand, two types of unregular targets (extra high asymmetry and RT instability) are designed and experiments are proposed. The experimental results show that the multi-dimensional factors have little influence on implosion performance. Finally, the quasi-one-dimensional implosion is achieved based on high pressure and thin shell target.
The D-D filled capsule implosion experiment is performed on Shenguang Ⅲ prototype laser facility. One-dimensional hydrodynamic numerical simulations show that neutron yield mechanism can be controlled by different D-D gas pressure and CH shell thickness. In experiments, the high gas filling pressure and thin shell thickness capsule is proposed for shock yield only implosion design. Meantime, many important implosion parameters such as neutron yield, bang-time are collected. The optimized experimental neutron yield is 9.9107 (9.7%) and the ratio between the experimental value and the 1D simulated value reached 90%. On the other hand, two types of unregular targets (extra high asymmetry and RT instability) are designed and experiments are proposed. The experimental results show that the multi-dimensional factors have little influence on implosion performance. Finally, the quasi-one-dimensional implosion is achieved based on high pressure and thin shell target.
2015,
27: 083001.
doi: 10.11884/HPLPB201527.083001
Abstract:
This paper deals with the numerical simulation of magnetic nonlinear transmission line(NLTL) with cross-linking element. The simulation is based on the iteration of voltage and current in NLTL element which is described in the time-domain differential equation. The hysteretic properties is studied by the J-A model. The dispersion formula is derived from circuit equation, and a magnetic NLTL is designed with an operation frequency of 300 MHz. By this numerical simulation, the peak-peak voltage of output pulses is on load no less than 40 kV, center frequency 303 MHz with voltage of feeding pulse of 30 kV.
This paper deals with the numerical simulation of magnetic nonlinear transmission line(NLTL) with cross-linking element. The simulation is based on the iteration of voltage and current in NLTL element which is described in the time-domain differential equation. The hysteretic properties is studied by the J-A model. The dispersion formula is derived from circuit equation, and a magnetic NLTL is designed with an operation frequency of 300 MHz. By this numerical simulation, the peak-peak voltage of output pulses is on load no less than 40 kV, center frequency 303 MHz with voltage of feeding pulse of 30 kV.
2015,
27: 083002.
doi: 10.11884/HPLPB201527.083002
Abstract:
With the background of research on high power microwave source power combined efficiency with random phase, the impact of random phase errors with normal probability distribution on power combined efficiency of antenna array was calculated. A modified normal probability density function with bounded phase error was used to analyze the microwave power combined efficiency. As an example, a 1010 elements antenna array with normal probability phase error distribution was used to simulate the relationship between the standard error and the combined efficiency. It shows that the calculation precision was improved obviously with the corrected power combined efficiency, providing reference to the research of high power microwave power combination.
With the background of research on high power microwave source power combined efficiency with random phase, the impact of random phase errors with normal probability distribution on power combined efficiency of antenna array was calculated. A modified normal probability density function with bounded phase error was used to analyze the microwave power combined efficiency. As an example, a 1010 elements antenna array with normal probability phase error distribution was used to simulate the relationship between the standard error and the combined efficiency. It shows that the calculation precision was improved obviously with the corrected power combined efficiency, providing reference to the research of high power microwave power combination.
2015,
27: 083003.
doi: 10.11884/HPLPB201527.083003
Abstract:
By using the mode-matching method, a theoretical model is presented to analyze the reflection characteristics of the coaxial Bragg structures corrugated with rectangular ripples, where the inner-rod and outer-wall ripples have random parameters due to fabrication error. Numerical simulations are carried out to investigate the effect of the errors of the corrugated depth, corrugated width, length of period and ripple position on the reflectivity frequency response for a coaxial Bragg structure which operates with TEM mode in the vicinity of 220 GHz. Numerical results reveal that, with a given range of error values, the random errors of corrugated width and ripple position have less influence on the reflection spectrum, while the random errors of corrugated depth and length of period critically affect the reflection properties of the example structure. Therefore, the manufacturing tolerances of these two parameters should be strictly controlled in accordance with the performance of the devices employed with coaxial Bragg structures. The theoretical model as well as the corresponding numerical code may provide engineering references for further applications of the coaxial Bragg structure with rectangular ripples.
By using the mode-matching method, a theoretical model is presented to analyze the reflection characteristics of the coaxial Bragg structures corrugated with rectangular ripples, where the inner-rod and outer-wall ripples have random parameters due to fabrication error. Numerical simulations are carried out to investigate the effect of the errors of the corrugated depth, corrugated width, length of period and ripple position on the reflectivity frequency response for a coaxial Bragg structure which operates with TEM mode in the vicinity of 220 GHz. Numerical results reveal that, with a given range of error values, the random errors of corrugated width and ripple position have less influence on the reflection spectrum, while the random errors of corrugated depth and length of period critically affect the reflection properties of the example structure. Therefore, the manufacturing tolerances of these two parameters should be strictly controlled in accordance with the performance of the devices employed with coaxial Bragg structures. The theoretical model as well as the corresponding numerical code may provide engineering references for further applications of the coaxial Bragg structure with rectangular ripples.
2015,
27: 083004.
doi: 10.11884/HPLPB201527.083004
Abstract:
Based on the results of the theoretical analyses and simulations, the relationship between the Gaussian pulse parameters (pulse width, pulse amplitude, pulse repetition frequency) and the interference effects on a low noise amplifier (LNA) is discussed. The experiments are carried out on the LNA operating at the 40-80 MHz band to confirm the interference effects. The results show that: the interference characteristics are much depended on the operating band of a LNA and the pulse parameters; the pulse amplitude is the most significant factor among all the pulse parameters; the increase of the values of the above three pulse parameters will enhance the interference effects.
Based on the results of the theoretical analyses and simulations, the relationship between the Gaussian pulse parameters (pulse width, pulse amplitude, pulse repetition frequency) and the interference effects on a low noise amplifier (LNA) is discussed. The experiments are carried out on the LNA operating at the 40-80 MHz band to confirm the interference effects. The results show that: the interference characteristics are much depended on the operating band of a LNA and the pulse parameters; the pulse amplitude is the most significant factor among all the pulse parameters; the increase of the values of the above three pulse parameters will enhance the interference effects.
2015,
27: 083005.
doi: 10.11884/HPLPB201527.083005
Abstract:
The vacuum electronic device with sheet beam driven rectangular waveguide gratings is a small size, high gain, easy to fabricated device. It has potential to produce high power terahertz radiation. This paper proposes a novel sheet beam high power device. The dispersion characteristics of the rectangular waveguide grating slow wave structure are analyzed. The coupling impedance is studied in detail. And a W-band sheet beam rectangular waveguide grating backward-wave oscillator(BWO) is simulated. The optimized BWO can produce 42 MW at frequency 86 GHz, driven by a 200 kV, 2kA, 24 mm0.5 mm sheet electron beam. The efficiency is 10.5%.
The vacuum electronic device with sheet beam driven rectangular waveguide gratings is a small size, high gain, easy to fabricated device. It has potential to produce high power terahertz radiation. This paper proposes a novel sheet beam high power device. The dispersion characteristics of the rectangular waveguide grating slow wave structure are analyzed. The coupling impedance is studied in detail. And a W-band sheet beam rectangular waveguide grating backward-wave oscillator(BWO) is simulated. The optimized BWO can produce 42 MW at frequency 86 GHz, driven by a 200 kV, 2kA, 24 mm0.5 mm sheet electron beam. The efficiency is 10.5%.
2015,
27: 083006.
doi: 10.11884/HPLPB201527.083006
Abstract:
In this paper, the reflected wave of a lossy half space is computed by using the combination of Fourier transform and Fresnel formula, and it is introduced to finite difference time domain method (FDTD) calculation region by Equivalence Principle. The results by different incident planes and polarization modes are discussed. The numerical results show that the reflected wave would lead a second time energy burst when the target is located near ground. This method can be applied to computation of near field and coupling energy inside of the target. The effect of half space is not considered in existing study, this method has a basic significance of half space effect analysis for the electronic systems under HPM environment.
In this paper, the reflected wave of a lossy half space is computed by using the combination of Fourier transform and Fresnel formula, and it is introduced to finite difference time domain method (FDTD) calculation region by Equivalence Principle. The results by different incident planes and polarization modes are discussed. The numerical results show that the reflected wave would lead a second time energy burst when the target is located near ground. This method can be applied to computation of near field and coupling energy inside of the target. The effect of half space is not considered in existing study, this method has a basic significance of half space effect analysis for the electronic systems under HPM environment.
2015,
27: 083007.
doi: 10.11884/HPLPB201527.083007
Abstract:
The sheet beam relativistic extended interaction oscillator is a very important high power microwave source with many actual and potential applications. Based on the electromagnetic simulation software and 3D PIC code, a Ka-band sheet beam relativistic extended interaction oscillator is designed. A sheet electron beam with a width-to-height of 30 is adopted to reduce the space charge effect. In order to increase the power capacity of the device, the extended interaction cavity is selected as the high frequency structure. In the PIC simulation, when the beam voltage is 400 kV and current is 2 kA, the device can generate a 240MW output power at 30GHz with an efficiency of 30%.
The sheet beam relativistic extended interaction oscillator is a very important high power microwave source with many actual and potential applications. Based on the electromagnetic simulation software and 3D PIC code, a Ka-band sheet beam relativistic extended interaction oscillator is designed. A sheet electron beam with a width-to-height of 30 is adopted to reduce the space charge effect. In order to increase the power capacity of the device, the extended interaction cavity is selected as the high frequency structure. In the PIC simulation, when the beam voltage is 400 kV and current is 2 kA, the device can generate a 240MW output power at 30GHz with an efficiency of 30%.
2015,
27: 083101.
doi: 10.11884/HPLPB201527.083101
Abstract:
The dispersion property and interaction impedance of a novel sheet-beam 140 GHz folded waveguide was simulated. By CST Microwave Studio, the phase velocity was 0.227c and the dispersion remained flat when the frequency was 140 GHz. The interaction impedance was about 5 at 140 GHz. The beam-wave interaction simulation by CST Particle Studio showed the output power gain reached 24.6 dB. Sheet-beam design was compatible with MEMS micromachining process. Then the folded waveguide was fabricated by multi-step SU-8 UV-LIGA process. The tested return loss S11 and insertion loss S21 were close to -28 dB and -1.2 dB respectively and the output power gain reached 23 dB. Good accordance between test and simulation results indicates the reasonable design and high machining precision by multi-step SU-8 UV-LIGA.
The dispersion property and interaction impedance of a novel sheet-beam 140 GHz folded waveguide was simulated. By CST Microwave Studio, the phase velocity was 0.227c and the dispersion remained flat when the frequency was 140 GHz. The interaction impedance was about 5 at 140 GHz. The beam-wave interaction simulation by CST Particle Studio showed the output power gain reached 24.6 dB. Sheet-beam design was compatible with MEMS micromachining process. Then the folded waveguide was fabricated by multi-step SU-8 UV-LIGA process. The tested return loss S11 and insertion loss S21 were close to -28 dB and -1.2 dB respectively and the output power gain reached 23 dB. Good accordance between test and simulation results indicates the reasonable design and high machining precision by multi-step SU-8 UV-LIGA.
2015,
27: 083102.
doi: 10.11884/HPLPB201527.083102
Abstract:
Efficient transmission of terahertz (THz) wave is an important research direction in development of THz technology. Polymeric photonic crystal fiber (PCF) is ideal in THz waveguide transmission because of the advantages of low loss, low dispersion and fine flexibility to bend. Based on the full vector finite element method (FEM), a hollow-core PCF with operating frequency of 2.5 THz is designed. Some samples made of cyclic olefin copolymer (COC) are fabricated. The fiber transmission performance of THz wave is measured by using the CO2 pump laser THz source. The measured minimum loss is 0.17 dB/cm and the average loss is about 0.5 dB/cm. The fluctuation of transmission loss is less than 5% after the fiber is bent 90, showing good flexibility to bend. The measured mode field distribution results of the output port show that the optical fiber transmits signals through the main mode, so the THz energy is well bound in the core of optical fiber.
Efficient transmission of terahertz (THz) wave is an important research direction in development of THz technology. Polymeric photonic crystal fiber (PCF) is ideal in THz waveguide transmission because of the advantages of low loss, low dispersion and fine flexibility to bend. Based on the full vector finite element method (FEM), a hollow-core PCF with operating frequency of 2.5 THz is designed. Some samples made of cyclic olefin copolymer (COC) are fabricated. The fiber transmission performance of THz wave is measured by using the CO2 pump laser THz source. The measured minimum loss is 0.17 dB/cm and the average loss is about 0.5 dB/cm. The fluctuation of transmission loss is less than 5% after the fiber is bent 90, showing good flexibility to bend. The measured mode field distribution results of the output port show that the optical fiber transmits signals through the main mode, so the THz energy is well bound in the core of optical fiber.
2015,
27: 083201.
doi: 10.11884/HPLPB201527.083201
Abstract:
Based on time domain reflection theory, a novel way to calculate the characteristic impedance of a parallel-plate transmission line is proposed. With CST microwave studio, a simulation model is established to calculate the accurate value of the characteristic impedance of the parallel-plate transmission line. Based on the results, the analytic formula for the characteristic impedance of the parallel-plate transmission line is modified. Furthermore, the effect of broadening of the bottom plate of parallel-plate transmission line on its characteristic impedance is researched. Considering the effect of broadening of bottom plate, a new formula for the characteristic impedance of the parallel-plate transmission line is proposed. The final formula could be applied to the calculation of the characteristic impedance of bounded-wave simulators and other electromagnetic pulse simulators with similar structure.
Based on time domain reflection theory, a novel way to calculate the characteristic impedance of a parallel-plate transmission line is proposed. With CST microwave studio, a simulation model is established to calculate the accurate value of the characteristic impedance of the parallel-plate transmission line. Based on the results, the analytic formula for the characteristic impedance of the parallel-plate transmission line is modified. Furthermore, the effect of broadening of the bottom plate of parallel-plate transmission line on its characteristic impedance is researched. Considering the effect of broadening of bottom plate, a new formula for the characteristic impedance of the parallel-plate transmission line is proposed. The final formula could be applied to the calculation of the characteristic impedance of bounded-wave simulators and other electromagnetic pulse simulators with similar structure.
2015,
27: 083202.
doi: 10.11884/HPLPB201527.083202
Abstract:
In order to achieve an effective simulation for Weibull distribution clutter and create a realistic radar environment, a simulation method for ground clutter in a reverberation chamber based on time-domain waveform design is proposed. This method is based on the fading characteristics of a reverberation chamber channel under generalized stationary uncorrelated scattering and controls the amplitude modulated signal to compensate for the attenuation coefficients. By adjusting the ratio of large and small pulse amplitudes in the input signal sequence, the zero mean amplitude characteristics of the conventional input signal of the reverberation chamber can be changed. Then, by using the measured statistical characteristics of ground clutter as a reference, the obtained electromagnetic environment of the ground clutter in the reverberation chamber is consistent with the statistical parameters of the experimental data. Maximum likelihood estimation and KS-test methods are adopted for the parameter estimation and hypothesis verification. Moreover, the measured data of ground clutter fits the standard Weibull model and the experimental data from the reverberation chamber fit the statistical model of measured ground clutter amplitude. It is proven to be possible to achieve an effective simulation of the actual measurements of ground clutter fluctuation characteristics using a reverberation chamber.
In order to achieve an effective simulation for Weibull distribution clutter and create a realistic radar environment, a simulation method for ground clutter in a reverberation chamber based on time-domain waveform design is proposed. This method is based on the fading characteristics of a reverberation chamber channel under generalized stationary uncorrelated scattering and controls the amplitude modulated signal to compensate for the attenuation coefficients. By adjusting the ratio of large and small pulse amplitudes in the input signal sequence, the zero mean amplitude characteristics of the conventional input signal of the reverberation chamber can be changed. Then, by using the measured statistical characteristics of ground clutter as a reference, the obtained electromagnetic environment of the ground clutter in the reverberation chamber is consistent with the statistical parameters of the experimental data. Maximum likelihood estimation and KS-test methods are adopted for the parameter estimation and hypothesis verification. Moreover, the measured data of ground clutter fits the standard Weibull model and the experimental data from the reverberation chamber fit the statistical model of measured ground clutter amplitude. It is proven to be possible to achieve an effective simulation of the actual measurements of ground clutter fluctuation characteristics using a reverberation chamber.
2015,
27: 083203.
doi: 10.11884/HPLPB201527.083203
Abstract:
To investigate the coupling mechanism between an electromagnetic pulse and a transmission line above the lossy ground, we built an equivalent circuit for the transmission lines above the lossy ground based on the delay extraction-based passive compact transmission-line (DEPACT) macromodeling algorithm. The transmission line above the lossy ground was viewed as a cascade of some transmission line subnetworks. Each transmission line subnetwork was represented by a cascade of lossy and lossless transmission lines. The equivalent circuit for the lossless section existed. The ground impedance was approximated as a rational function by the vector fitting (VF) method, and the equivalent circuit for the lossy section was built by the Laplace Element in HSPICE. The simulation results were compared with the results with the finite difference time domain (FDTD) method and good agreement was obtained. Using this approach, the transient response for the transmission lines above the lossy ground with nonlinear terminations could be obtained easily and accurately.
To investigate the coupling mechanism between an electromagnetic pulse and a transmission line above the lossy ground, we built an equivalent circuit for the transmission lines above the lossy ground based on the delay extraction-based passive compact transmission-line (DEPACT) macromodeling algorithm. The transmission line above the lossy ground was viewed as a cascade of some transmission line subnetworks. Each transmission line subnetwork was represented by a cascade of lossy and lossless transmission lines. The equivalent circuit for the lossless section existed. The ground impedance was approximated as a rational function by the vector fitting (VF) method, and the equivalent circuit for the lossy section was built by the Laplace Element in HSPICE. The simulation results were compared with the results with the finite difference time domain (FDTD) method and good agreement was obtained. Using this approach, the transient response for the transmission lines above the lossy ground with nonlinear terminations could be obtained easily and accurately.
2015,
27: 083204.
doi: 10.11884/HPLPB201527.083204
Abstract:
The computation speed will decrease dramatically in solving the radio wave propagation problems in urban cells for the reason that the grid step of finite difference algorithm for parabolic equation is strictly restricted by wavelength. To solve this problem, the parallel method of finite difference parabolic equation is studied based on JASMIN framework, which is realized by dividing the step surface into multiple patches and being assigned to different processors, and the correctness is verified by comparing with analytic solution. Meanwhile, the efficiency of parallel program is further analyzed. The example shows that the solution efficiency of the finite difference parabolic equation is improved effectively. Finally, the electromagnetic characteristics of a telecom base station in urban cell with nine regular buildings are simulated and analyzed. It shows that the covering characteristics of the base station can be obtained, which will provide reference for the base station location.
The computation speed will decrease dramatically in solving the radio wave propagation problems in urban cells for the reason that the grid step of finite difference algorithm for parabolic equation is strictly restricted by wavelength. To solve this problem, the parallel method of finite difference parabolic equation is studied based on JASMIN framework, which is realized by dividing the step surface into multiple patches and being assigned to different processors, and the correctness is verified by comparing with analytic solution. Meanwhile, the efficiency of parallel program is further analyzed. The example shows that the solution efficiency of the finite difference parabolic equation is improved effectively. Finally, the electromagnetic characteristics of a telecom base station in urban cell with nine regular buildings are simulated and analyzed. It shows that the covering characteristics of the base station can be obtained, which will provide reference for the base station location.
2015,
27: 083205.
doi: 10.11884/HPLPB201527.083205
Abstract:
To improve the protection performance of the helicopter against lightning, this paper builds a simulation environment in the CST Microwave Studio based on the transmission-line matrix method to simulate the UH-60 helicopter struck by high current pulse to study its lightning indirect effects according to SAE-ARP5416A. The distribution of the internal key cabin and the external electromagnetic field of the helicopter, the induced current in the onboard cable produced by the lightning in different paths are discussed. The simulation results indicate that using this simulation method, the helicopter indirect effects struck by lightning can be effectively analyzed and the results can guide the lightning protection design of the helicopter without developing the full-scale helicopter experiment.
To improve the protection performance of the helicopter against lightning, this paper builds a simulation environment in the CST Microwave Studio based on the transmission-line matrix method to simulate the UH-60 helicopter struck by high current pulse to study its lightning indirect effects according to SAE-ARP5416A. The distribution of the internal key cabin and the external electromagnetic field of the helicopter, the induced current in the onboard cable produced by the lightning in different paths are discussed. The simulation results indicate that using this simulation method, the helicopter indirect effects struck by lightning can be effectively analyzed and the results can guide the lightning protection design of the helicopter without developing the full-scale helicopter experiment.
2015,
27: 083206.
doi: 10.11884/HPLPB201527.083206
Abstract:
In order to make it work well under complex electromagnetic environments, the electronic system is usually required to be installed in the shutter. However, for the ventilation and heat dissipation, it is inevitable to make some tiny apertures on the shielding wall. In order to solve the computational problem of terminal responses of the transmission lines in the double-layer shielding cavity with apertures excited by the exterior field, this paper presents a hybrid method. First, the response voltages are computed in the exterior layer shielding cavity by the transmission line model. After the response voltages transmitted into the equivalent magnetic currents, the BLT equation based on the electromagnetic topology theory can be used to compute the induced voltage of the transmission line in the double-layer shielding cavity. Finally, the numerical results show that the terminal response of the transmission line in the double-layer cavity is weaker than that in the single-layer cavity. And the response of the transmission line reaches its maximum value near the cavity and slot resonance. The analytic results give reference to electromagnetic compatibility and the design of the protection of electronic equipment against the external source.
In order to make it work well under complex electromagnetic environments, the electronic system is usually required to be installed in the shutter. However, for the ventilation and heat dissipation, it is inevitable to make some tiny apertures on the shielding wall. In order to solve the computational problem of terminal responses of the transmission lines in the double-layer shielding cavity with apertures excited by the exterior field, this paper presents a hybrid method. First, the response voltages are computed in the exterior layer shielding cavity by the transmission line model. After the response voltages transmitted into the equivalent magnetic currents, the BLT equation based on the electromagnetic topology theory can be used to compute the induced voltage of the transmission line in the double-layer shielding cavity. Finally, the numerical results show that the terminal response of the transmission line in the double-layer cavity is weaker than that in the single-layer cavity. And the response of the transmission line reaches its maximum value near the cavity and slot resonance. The analytic results give reference to electromagnetic compatibility and the design of the protection of electronic equipment against the external source.
2015,
27: 084001.
doi: 10.11884/HPLPB201527.084001
Abstract:
In order to study the vacuum arc ion source, using a streak camera which could transform the temporal signal to spatial signal, and a spectrograph which could separate an incoming wave into a frequency spectrum, we built a time resolution of plasma optical emission spectra diagnosis experiment platform, and measured the time- and spectral-resolution of this diagnosis system, with a time-resolution of 26 ps, and a spectral-resolution of 0.1 nm. Based on this diagnosis system, the temporal evolution of the plasma and the optical emission spectra were acquired in an only one pulse. At the same time, based on the emission spectra theory of the local thermodynamic equilibrium plasma, we established an emission spectra model, and performed the fitting of the emission spectra of experimental plasma spectra to obtain the temporal evolution of the electron temperature and electron density in plasma. Different from conventional Blotzmann plot and Stark broadening methods needed the isolated line, the fitting model established in this work could deal with the overlapped lines due to broadening. The calculated electron temperature and density were about 1 eV and 3.51024 m-3 respectively.
In order to study the vacuum arc ion source, using a streak camera which could transform the temporal signal to spatial signal, and a spectrograph which could separate an incoming wave into a frequency spectrum, we built a time resolution of plasma optical emission spectra diagnosis experiment platform, and measured the time- and spectral-resolution of this diagnosis system, with a time-resolution of 26 ps, and a spectral-resolution of 0.1 nm. Based on this diagnosis system, the temporal evolution of the plasma and the optical emission spectra were acquired in an only one pulse. At the same time, based on the emission spectra theory of the local thermodynamic equilibrium plasma, we established an emission spectra model, and performed the fitting of the emission spectra of experimental plasma spectra to obtain the temporal evolution of the electron temperature and electron density in plasma. Different from conventional Blotzmann plot and Stark broadening methods needed the isolated line, the fitting model established in this work could deal with the overlapped lines due to broadening. The calculated electron temperature and density were about 1 eV and 3.51024 m-3 respectively.
2015,
27: 084002.
doi: 10.11884/HPLPB201527.084002
Abstract:
In the case of nuclear fission and fusion, typical energy neutrons acting on semiconductor devices are analyzed, and the distribution of the secondary particles and their energy spectra are generated. As for the worst case of the neutron, the single event effect (SEE) of Static Random Access Memory (SRAM) on 65 nm process is discussed, and the results of TCAD simulation are given. The results show that the 6 transistor SRAM cell commercial structure is difficult to avoid the SEE. Even Double Interlocked Storage Cell (DICE) structure, in the high density design, also due to the charge sharing effect, the occurrence of Single Event Upset (SEU). Because the charge sharing effect is difficult to obtain by SPICE simulation, the TCAD simulation is more suitable for the SRAM design and verification of the neutron single particle immune. At the end, the SRAM design of the neutron single particle immune on the 65nm process is discussed. It is possible to be more competitive in the way that the 6 transistor SRAM cell is added to the capacitor.
In the case of nuclear fission and fusion, typical energy neutrons acting on semiconductor devices are analyzed, and the distribution of the secondary particles and their energy spectra are generated. As for the worst case of the neutron, the single event effect (SEE) of Static Random Access Memory (SRAM) on 65 nm process is discussed, and the results of TCAD simulation are given. The results show that the 6 transistor SRAM cell commercial structure is difficult to avoid the SEE. Even Double Interlocked Storage Cell (DICE) structure, in the high density design, also due to the charge sharing effect, the occurrence of Single Event Upset (SEU). Because the charge sharing effect is difficult to obtain by SPICE simulation, the TCAD simulation is more suitable for the SRAM design and verification of the neutron single particle immune. At the end, the SRAM design of the neutron single particle immune on the 65nm process is discussed. It is possible to be more competitive in the way that the 6 transistor SRAM cell is added to the capacitor.
2015,
27: 084003.
doi: 10.11884/HPLPB201527.084003
Abstract:
The arc discharge of ion source in neutral beam injection has the nonlinear characteristic of gas discharge plasma, and this high-power electric arc is influenced by the gas pressure, outside magnetic field and state of cathode in the process of discharging. It is difficult to be closed-loop controlled stably with a power supply of phase control thyristor voltage scaling technology. Therefore, this paper puts forward a multiphase and multiple high-current DC/DC converter with fast response speed, high rate of current rise, lower output ripple current, et al. The converter greatly improved the closed-loop control stability of the arc discharge of ion source. An inductance energy recovery circuit was designed, thus the arc power supply is able to rapidly reduce the output current by 0%-100% (adjustable) according to the system requirements, then return to normal output in accordance with the control signal, forming a notch in the arc current waveform. Using the super capacitor energy storage technology, the volume of the power supply is decreased to one third, with the power output not affected by the power network fluctuation. The experimental waveforms prove that: the maximum output specification of the arc power supply is 220 kW/1500 A, output ripple current is less than 1%, current rise-time is in the order of 100 s, the maximum overshoot is less than 3%, and the power supply meets the requirements of the 5 MW neutral beam injection system and the ion source device.
The arc discharge of ion source in neutral beam injection has the nonlinear characteristic of gas discharge plasma, and this high-power electric arc is influenced by the gas pressure, outside magnetic field and state of cathode in the process of discharging. It is difficult to be closed-loop controlled stably with a power supply of phase control thyristor voltage scaling technology. Therefore, this paper puts forward a multiphase and multiple high-current DC/DC converter with fast response speed, high rate of current rise, lower output ripple current, et al. The converter greatly improved the closed-loop control stability of the arc discharge of ion source. An inductance energy recovery circuit was designed, thus the arc power supply is able to rapidly reduce the output current by 0%-100% (adjustable) according to the system requirements, then return to normal output in accordance with the control signal, forming a notch in the arc current waveform. Using the super capacitor energy storage technology, the volume of the power supply is decreased to one third, with the power output not affected by the power network fluctuation. The experimental waveforms prove that: the maximum output specification of the arc power supply is 220 kW/1500 A, output ripple current is less than 1%, current rise-time is in the order of 100 s, the maximum overshoot is less than 3%, and the power supply meets the requirements of the 5 MW neutral beam injection system and the ion source device.
2015,
27: 084004.
doi: 10.11884/HPLPB201527.084004
Abstract:
Microstructured neutron detectors (MSNDs) can achieve a tenfold increase in neutron detection efficiency over the traditional planar detectors. However, the overall detection efficiency is determined by their microstructured features. In this work, we report the influences of microstructured feature and backfilling density on the intrinsic thermal neutron detection efficiency. The design of MSND with trench patterns is optimized. The detection efficiency decreases when the trench gap is increased. The trench width can be optimized when the trench gap is fixed. The detection efficiency increases by increasing the trench depth. MSNDs having trenches with 15 m width and 5 m gap can achieve high detection efficiency and efficiency stability. With the lower level discriminator (LLD) setting at 300 keV, the detection efficiency of MSND with 15 m width, 5m gap and 200 m depth can achieve 37.77% intrinsic efficiency, which is 9.2 times higher than that of the planar semiconductor neutron detectors; The neutron to gamma-ray rejection ratio is 4.1103 for gamma rays of a 137Cs source, which is 23.7 times higher than planar ones. This work demonstrates the outstanding neutron detection efficiency and neutron to gamma-ray rejection ratio of MSNDs with trench patterns.
Microstructured neutron detectors (MSNDs) can achieve a tenfold increase in neutron detection efficiency over the traditional planar detectors. However, the overall detection efficiency is determined by their microstructured features. In this work, we report the influences of microstructured feature and backfilling density on the intrinsic thermal neutron detection efficiency. The design of MSND with trench patterns is optimized. The detection efficiency decreases when the trench gap is increased. The trench width can be optimized when the trench gap is fixed. The detection efficiency increases by increasing the trench depth. MSNDs having trenches with 15 m width and 5 m gap can achieve high detection efficiency and efficiency stability. With the lower level discriminator (LLD) setting at 300 keV, the detection efficiency of MSND with 15 m width, 5m gap and 200 m depth can achieve 37.77% intrinsic efficiency, which is 9.2 times higher than that of the planar semiconductor neutron detectors; The neutron to gamma-ray rejection ratio is 4.1103 for gamma rays of a 137Cs source, which is 23.7 times higher than planar ones. This work demonstrates the outstanding neutron detection efficiency and neutron to gamma-ray rejection ratio of MSNDs with trench patterns.
2015,
27: 084005.
doi: 10.11884/HPLPB201527.084005
Abstract:
Large planar plasma sheets with size of 60 cm60 cm, maximum current of 3 A and duration of 200 s, were obtained in a pulsed linear hollow cathode discharge device under 15 mT magnetic field confinement. The electron density 2-D distribution in the thickness direction and its evolution of plasma sheets with pressures between 90 Pa to 210 Pa were obtained by Langmuir probe using the fast frame function of oscilloscope and the rotating hollow cathode method. The effects of pressure on the time needed to reach the maximum peak density in the thickness direction, the maximum peak density and the full width at half maximum (FWHM) peak density, were investigated. The results show that, as the pressure decreased, the time reaching the maximum peak density in the thickness direction and the FWHM peak density diminished, while the maximum peak density in the thickness direction increased. These results could be utilized to manipulate the parameters of large planar plasma sheets.
Large planar plasma sheets with size of 60 cm60 cm, maximum current of 3 A and duration of 200 s, were obtained in a pulsed linear hollow cathode discharge device under 15 mT magnetic field confinement. The electron density 2-D distribution in the thickness direction and its evolution of plasma sheets with pressures between 90 Pa to 210 Pa were obtained by Langmuir probe using the fast frame function of oscilloscope and the rotating hollow cathode method. The effects of pressure on the time needed to reach the maximum peak density in the thickness direction, the maximum peak density and the full width at half maximum (FWHM) peak density, were investigated. The results show that, as the pressure decreased, the time reaching the maximum peak density in the thickness direction and the FWHM peak density diminished, while the maximum peak density in the thickness direction increased. These results could be utilized to manipulate the parameters of large planar plasma sheets.
2015,
27: 084006.
doi: 10.11884/HPLPB201527.084006
Abstract:
For the images obtained by the flash radiography with an anti-scatter grid, impulse noises exist and need to be removed before further image processing. An improved switching median filter method is proposed in this paper for the task. In the method, the grayscales of a pixel and the median of its neiborhoods are utilized together to construct an impulse-noise-judger. If the value of the impulse-noise-judger is larger than a predefined threshold, the pixel is regarded as noise, and is replaced by the median. By implementing this operation on an initial image repeatedly, each with the same threshold, one can get satisfying result of impulse noise suppression. This is testified for simulated and real experiment images. The proposed method is superior to the standard median filter method in that it retains the original details of the images better.
For the images obtained by the flash radiography with an anti-scatter grid, impulse noises exist and need to be removed before further image processing. An improved switching median filter method is proposed in this paper for the task. In the method, the grayscales of a pixel and the median of its neiborhoods are utilized together to construct an impulse-noise-judger. If the value of the impulse-noise-judger is larger than a predefined threshold, the pixel is regarded as noise, and is replaced by the median. By implementing this operation on an initial image repeatedly, each with the same threshold, one can get satisfying result of impulse noise suppression. This is testified for simulated and real experiment images. The proposed method is superior to the standard median filter method in that it retains the original details of the images better.
2015,
27: 085001.
doi: 10.11884/HPLPB201527.085001
Abstract:
According to the DPS-QKD (differential phase shift quantum key distribution) experiment demand for high-speed electro-optic modulator, the solid state switching technology and transformer isolation technology were applied to the design of a high speed electro optic modulator with a repetition rate of 45 kHz and a pulse of 2 kV. The modulation circuit includes two parts which can generate negative and positive 1000 V high voltage pulses respectively. The rise time and fall time of the positive high voltage pulse are 50.44 ns and 44.6 ns, and those of the negative high voltage pulses are 52.29 ns and 50.44 ns. The extinction ration is up to 23 dB when the modulator modulates the Pockels cell, which completely satisfies the need of DPS-QKD experiment.
According to the DPS-QKD (differential phase shift quantum key distribution) experiment demand for high-speed electro-optic modulator, the solid state switching technology and transformer isolation technology were applied to the design of a high speed electro optic modulator with a repetition rate of 45 kHz and a pulse of 2 kV. The modulation circuit includes two parts which can generate negative and positive 1000 V high voltage pulses respectively. The rise time and fall time of the positive high voltage pulse are 50.44 ns and 44.6 ns, and those of the negative high voltage pulses are 52.29 ns and 50.44 ns. The extinction ration is up to 23 dB when the modulator modulates the Pockels cell, which completely satisfies the need of DPS-QKD experiment.
2015,
27: 085002.
doi: 10.11884/HPLPB201527.085002
Abstract:
To improve the capability of passive electromagnetic armor against shaped charge jet (SCJ), the linear perturbation control equation of SCJ under the axial pulse current is constructed by magneto hydrodynamic instability theory and superposition theorem, and the variation law of SCJ pinching and kinking instability growth rates related to viscosity and time are analyzed. The deformation trend of SCJ is obtained and the formula used to calculate the SCJ deformation can be get by numerical means. Finally, the static penetration experiment with 39.2 mm diameter armor-piercing projectile and the kinking experiment with 1.75 mm diameter copper wire are carried out. The experimental results demonstrate that the axial pulse current can destroy the SCJ because of necking or kinking perturbation and confirm the validity of the theoretical analysis.
To improve the capability of passive electromagnetic armor against shaped charge jet (SCJ), the linear perturbation control equation of SCJ under the axial pulse current is constructed by magneto hydrodynamic instability theory and superposition theorem, and the variation law of SCJ pinching and kinking instability growth rates related to viscosity and time are analyzed. The deformation trend of SCJ is obtained and the formula used to calculate the SCJ deformation can be get by numerical means. Finally, the static penetration experiment with 39.2 mm diameter armor-piercing projectile and the kinking experiment with 1.75 mm diameter copper wire are carried out. The experimental results demonstrate that the axial pulse current can destroy the SCJ because of necking or kinking perturbation and confirm the validity of the theoretical analysis.
2015,
27: 085101.
doi: 10.11884/HPLPB201527.085101
Abstract:
Vacuum system is one of the most important subsystems of the injector Ⅱ for accelerator driven sub-critical system (ADS), whose performance determines the quality of the injectors beam. A remote control system based on the Experimental and Physics Industrial Control System (EPICS) is introduced to serve the vacuum system and to validate its performance. Programmable Logic Controller (PLC) and serial port servers are chosen to fulfill the requirements and to implement the control functions. The supervisory control procedure is programmed with LabVIEW , and the communication with EPICS is implemented with the use of the Datalogging Supervisory Control (DSC) module. The vacuum control system has a simple structure and works stably, which will contribute to the 5 MeV beam commission.
Vacuum system is one of the most important subsystems of the injector Ⅱ for accelerator driven sub-critical system (ADS), whose performance determines the quality of the injectors beam. A remote control system based on the Experimental and Physics Industrial Control System (EPICS) is introduced to serve the vacuum system and to validate its performance. Programmable Logic Controller (PLC) and serial port servers are chosen to fulfill the requirements and to implement the control functions. The supervisory control procedure is programmed with LabVIEW , and the communication with EPICS is implemented with the use of the Datalogging Supervisory Control (DSC) module. The vacuum control system has a simple structure and works stably, which will contribute to the 5 MeV beam commission.
2015,
27: 085102.
doi: 10.11884/HPLPB201527.085102
Abstract:
The high energy climbing segment of the Wuwei Heavy Ion Medial Machine has a vertical span of about 18 meters. Due to the suspended installation of oversized and overweighted components, the small installation space and lack of straight sight conditions, the position and angle of the placed magnet is different from the magnet in ground situation, which brings big challenges to the installation alignment. By the aid of a laser tracker and a three-dimensional control network, through multiple coordinate conversion, we explored a new method to eliminate the deviation brought by adjusting the angle of magnet in the climbing segment. This method has effectively improved the efficiency of installation alignment and guaranteed a deviation below 0.10 mm for each finally installed magnet in each dimension. The results are better than the installation precision demands of the Heavy Ion Medical Machine, which provides a strong guarantee for advancing the overall installation process.
The high energy climbing segment of the Wuwei Heavy Ion Medial Machine has a vertical span of about 18 meters. Due to the suspended installation of oversized and overweighted components, the small installation space and lack of straight sight conditions, the position and angle of the placed magnet is different from the magnet in ground situation, which brings big challenges to the installation alignment. By the aid of a laser tracker and a three-dimensional control network, through multiple coordinate conversion, we explored a new method to eliminate the deviation brought by adjusting the angle of magnet in the climbing segment. This method has effectively improved the efficiency of installation alignment and guaranteed a deviation below 0.10 mm for each finally installed magnet in each dimension. The results are better than the installation precision demands of the Heavy Ion Medical Machine, which provides a strong guarantee for advancing the overall installation process.
2015,
27: 085103.
doi: 10.11884/HPLPB201527.085103
Abstract:
This paper introduces the phase reverse system designed for SLAC Energy Doubler (SLED) based on Field Programmable Gate Array (FPGA). The phase reverse system is composed of a microwave IQ vector modulator, a FPGA board with the high speed DAC unit. Modulated by the DAC output pulse signal, the IQ modulator transforms the RF CW input signal into 4 s pulse output signal, whose phase is reversed to 180 at the moment of 3 s. The test results show that the phase reversal accuracy is about 1802, and the stability is better than 0.5. The RF power gains of six SLEDs are more than 7 dB, the maximum 7.54 dB is achieved. The long-term variation of the power gain is 0.1 dB.
This paper introduces the phase reverse system designed for SLAC Energy Doubler (SLED) based on Field Programmable Gate Array (FPGA). The phase reverse system is composed of a microwave IQ vector modulator, a FPGA board with the high speed DAC unit. Modulated by the DAC output pulse signal, the IQ modulator transforms the RF CW input signal into 4 s pulse output signal, whose phase is reversed to 180 at the moment of 3 s. The test results show that the phase reversal accuracy is about 1802, and the stability is better than 0.5. The RF power gains of six SLEDs are more than 7 dB, the maximum 7.54 dB is achieved. The long-term variation of the power gain is 0.1 dB.
2015,
27: 085104.
doi: 10.11884/HPLPB201527.085104
Abstract:
Beam-beam effect is a main factor limiting the performance of colliders. The limitation may be alleviated by compensation techniques. We proposed two types of head-on beam-beam compensation schemes with four beams and analyzed the principle of these schemes in theory. We investigated the effects of head-on beam-beam compensation with an Energy Recovery Linac (ERL) on the proton beam dynamics in SPPC. The beam distribution, tune footprint and beam loss rate are analyzed. From the simulation result, we found that head-on beam-beam compensation can reduce the tune footprint of each bunch and improve the beam lifetime effectively. Therefore bunch current and consequently the luminosity will increase very much with the beam-beam compensation.
Beam-beam effect is a main factor limiting the performance of colliders. The limitation may be alleviated by compensation techniques. We proposed two types of head-on beam-beam compensation schemes with four beams and analyzed the principle of these schemes in theory. We investigated the effects of head-on beam-beam compensation with an Energy Recovery Linac (ERL) on the proton beam dynamics in SPPC. The beam distribution, tune footprint and beam loss rate are analyzed. From the simulation result, we found that head-on beam-beam compensation can reduce the tune footprint of each bunch and improve the beam lifetime effectively. Therefore bunch current and consequently the luminosity will increase very much with the beam-beam compensation.
2015,
27: 085105.
doi: 10.11884/HPLPB201527.085105
Abstract:
A 1D dynamic sheath model of collisionless plasma is used to calculate the change of sheath edge with time. The calculation is performed for short duration pulses and long duration pulses respectively. For short duration pulses, the plasma sheath edge lags behind the plasma density. For long duration pulses, the velocity of the sheath edge movement is correlative to the initial ion velocity. The steady edge location is correlative to the product of the initial ion velocity and the plasma density.
A 1D dynamic sheath model of collisionless plasma is used to calculate the change of sheath edge with time. The calculation is performed for short duration pulses and long duration pulses respectively. For short duration pulses, the plasma sheath edge lags behind the plasma density. For long duration pulses, the velocity of the sheath edge movement is correlative to the initial ion velocity. The steady edge location is correlative to the product of the initial ion velocity and the plasma density.
2015,
27: 085106.
doi: 10.11884/HPLPB201527.085106
Abstract:
The Accelerator Driven Subcritical System (ADS), using proton beam hitting on the target to produce neutron for spending fuel stable increment or accelerating evolution, aims at finding key solutions for nuclear fuel stable provision and for the safe nuclear waste treatment. The injector Ⅰ and the main linac will be designed and fabricated by IHEP. The RF power source system provides 325 MHz continuous wave power for RFQ cavity of ADS injector Ⅰ and beam energy reaches several MeV through RFQ cavity. RF power source system includes 600 kW continuous wave klystron, 80 kV/18 A PSM power supply based on pulsed step modulation techniques, circulator and corresponding waveguide transmission system for ADS injector Ⅰ. According to the overall design for ADS system and RFQ technical parameters, overall layout, technical specifications and design requirements of RF power source system are proposed, equipment installation and commissioning are carried out, and the system has passed the expert acceptance testing.
The Accelerator Driven Subcritical System (ADS), using proton beam hitting on the target to produce neutron for spending fuel stable increment or accelerating evolution, aims at finding key solutions for nuclear fuel stable provision and for the safe nuclear waste treatment. The injector Ⅰ and the main linac will be designed and fabricated by IHEP. The RF power source system provides 325 MHz continuous wave power for RFQ cavity of ADS injector Ⅰ and beam energy reaches several MeV through RFQ cavity. RF power source system includes 600 kW continuous wave klystron, 80 kV/18 A PSM power supply based on pulsed step modulation techniques, circulator and corresponding waveguide transmission system for ADS injector Ⅰ. According to the overall design for ADS system and RFQ technical parameters, overall layout, technical specifications and design requirements of RF power source system are proposed, equipment installation and commissioning are carried out, and the system has passed the expert acceptance testing.
2015,
27: 086001.
doi: 10.11884/HPLPB201527.086001
Abstract:
This paper presents the analytical relation between the electrostatic potential inside the semiconductor and the positive oxide trapped charge at the interface. The expressions for N/P type materials are deduced after the accumulation/depletion approximation to Poisson equation and the truncation approximation to its boundary conditions. The solutions are self-consistent and complete. The exact numerical solutions are also given in this paper. The comparisons between the approximate analytical relations and the numerical solutions show that the analytical relations are good approximations except the case where strong inversion due to net positive oxide charge has occurred on the surface of P type material. Based on the criterion of the occurring of the strong inversion, the requirement for the surface density of positive trapped oxide charge to guarantee the visibility of depletion approximation is given. This work can be helpful in correctly analyzing mechanisms and magnitudes of the damage in the environment involving ionizing radiation in bipolar devices.
This paper presents the analytical relation between the electrostatic potential inside the semiconductor and the positive oxide trapped charge at the interface. The expressions for N/P type materials are deduced after the accumulation/depletion approximation to Poisson equation and the truncation approximation to its boundary conditions. The solutions are self-consistent and complete. The exact numerical solutions are also given in this paper. The comparisons between the approximate analytical relations and the numerical solutions show that the analytical relations are good approximations except the case where strong inversion due to net positive oxide charge has occurred on the surface of P type material. Based on the criterion of the occurring of the strong inversion, the requirement for the surface density of positive trapped oxide charge to guarantee the visibility of depletion approximation is given. This work can be helpful in correctly analyzing mechanisms and magnitudes of the damage in the environment involving ionizing radiation in bipolar devices.
2015,
27: 086002.
doi: 10.11884/HPLPB201527.086002
Abstract:
MCNP calculations are frequently used to analyze a variety of radiological science applications. This study tries to develop a rapid calculation method evaluating the value nearby where values of 3 points have been calculated with MCNP code. Firstly the physical rules of particle transportation is analyzed. Inverse distance weighting way and the physical law are considered. Meanwhile the range in three-dimensional space that could be calculated using the method is discussed and given. Then a formula for fast calculation of interpolating position with known values calculated with MCNP code is deduced. And the calculating code is composed in order to verify the method. In the end values calculated with the interpolation method and with MCNP code are directly compared. It is proved that the rapid calculation method is very reliable, and the error of this method is below 10%.
MCNP calculations are frequently used to analyze a variety of radiological science applications. This study tries to develop a rapid calculation method evaluating the value nearby where values of 3 points have been calculated with MCNP code. Firstly the physical rules of particle transportation is analyzed. Inverse distance weighting way and the physical law are considered. Meanwhile the range in three-dimensional space that could be calculated using the method is discussed and given. Then a formula for fast calculation of interpolating position with known values calculated with MCNP code is deduced. And the calculating code is composed in order to verify the method. In the end values calculated with the interpolation method and with MCNP code are directly compared. It is proved that the rapid calculation method is very reliable, and the error of this method is below 10%.
2015,
27: 086003.
doi: 10.11884/HPLPB201527.086003
Abstract:
The performance of boiling devices is limited by boiling crisis (burnout and dryout) characterized by the critical heat flux (CHF). The implementation of some related study is a key step for deeply understanding the mechanism of CHF and its enhancement. This experimental study is concerned with the dynamics and stability of liquid film flow under adiabatic condition, which plays an important role in understanding film rupture and dryout in boiling heat transfer. The rectangular test channel is made of optical glass. A stratified flow is formed in channel by supplying de-ionized water and air to the inlet of test section separately, with water flowing along the bottom surface while air flowing above the liquid film. A confocal microscopy is applied to acquire the evolution of the liquid film thickness, and a high-speed camera is employed to record the film dynamics. Based on the experimental data, a profile of liquid film thickness is obtained along the test channel. It is found that given a constant water flow rate, the mean thickness of the liquid film decreases with increasing the air flow rate. As the air flow rate reaches a critical value, a localized rupture of the liquid film occurs.
The performance of boiling devices is limited by boiling crisis (burnout and dryout) characterized by the critical heat flux (CHF). The implementation of some related study is a key step for deeply understanding the mechanism of CHF and its enhancement. This experimental study is concerned with the dynamics and stability of liquid film flow under adiabatic condition, which plays an important role in understanding film rupture and dryout in boiling heat transfer. The rectangular test channel is made of optical glass. A stratified flow is formed in channel by supplying de-ionized water and air to the inlet of test section separately, with water flowing along the bottom surface while air flowing above the liquid film. A confocal microscopy is applied to acquire the evolution of the liquid film thickness, and a high-speed camera is employed to record the film dynamics. Based on the experimental data, a profile of liquid film thickness is obtained along the test channel. It is found that given a constant water flow rate, the mean thickness of the liquid film decreases with increasing the air flow rate. As the air flow rate reaches a critical value, a localized rupture of the liquid film occurs.
2015,
27: 089001.
doi: 10.11884/HPLPB201527.089001
Abstract:
There exists residual tensile stress in the stainless steel welded joints, which makes the stainless steel welded joints sensitive to stress corrosion cracking. Laser shock processing is used to treat stainless steel welded joints. The effect of laser shock processing on optimization of surface residual stress is researched, and the test of stress corrosion is carried out to examine optimization result. With increasing of laser power density, the surface residual tensile stress decreases, but the increment of the decrease is gradually reduced. For example, when impacted with 4.24 GW/cm2 and 2.83 GW/cm2, the residual stress has not obviously changed; moreover, there still exists residual tensile stress in the fluxional zone. It indicates that residual tensile stress cant be eliminated entirely when impacted individually with high power density. With increasing of the impact times, the residual tensile stress will be eliminated absolutely, and the stress gradient decreases from 54.7 MPa/mm to 11.7 MPa/mm. When treated by laser shock processing, the stress corrosion rupture time of the welded specimen increases by 33.48%, which is attributed to residual compressive stress generated by laser shock processing.
There exists residual tensile stress in the stainless steel welded joints, which makes the stainless steel welded joints sensitive to stress corrosion cracking. Laser shock processing is used to treat stainless steel welded joints. The effect of laser shock processing on optimization of surface residual stress is researched, and the test of stress corrosion is carried out to examine optimization result. With increasing of laser power density, the surface residual tensile stress decreases, but the increment of the decrease is gradually reduced. For example, when impacted with 4.24 GW/cm2 and 2.83 GW/cm2, the residual stress has not obviously changed; moreover, there still exists residual tensile stress in the fluxional zone. It indicates that residual tensile stress cant be eliminated entirely when impacted individually with high power density. With increasing of the impact times, the residual tensile stress will be eliminated absolutely, and the stress gradient decreases from 54.7 MPa/mm to 11.7 MPa/mm. When treated by laser shock processing, the stress corrosion rupture time of the welded specimen increases by 33.48%, which is attributed to residual compressive stress generated by laser shock processing.
2015,
27: 089002.
doi: 10.11884/HPLPB201527.089002
Abstract:
Aiming at the problem that the inflow mass capture ratio decreases when the hypersonic inlet is under the undesigned state, a physical model is established and numerical simulation is performed on inflow mass capture control by laser energy deposition. The inflow performance parameters are obtained under continuous and pulsed laser energy depositions. When the laser power is 15 kW, a higher pulsed repetitive rate can result in closer inflow performance as that of continuous energy deposition. When the pulsed repetitive rate is 100 kHz, the inlet flow field is simulated in the state that the pulsed square wave duty factor is 0.1, 0.2, 0.3 and 0.4 respectively. The results indicate that the duty factor has little influence on the inlet performance. When the laser pulse duration is 500 ns and the average laser power is fixed, the flow configuration is much close to that of the continuous energy injection under 200 kHz and 100 kHz pulsed repetitive rate. However, the inflow mass capture ratio decreases when pulsed repetitive rate is 500 kHz and 25 kHz. Therefore, with the increasing of the laser pulsed repetitive rate and decreasing of the average laser power, the inflow mass capture ratio increases effectively, and the energy consumption decreases.
Aiming at the problem that the inflow mass capture ratio decreases when the hypersonic inlet is under the undesigned state, a physical model is established and numerical simulation is performed on inflow mass capture control by laser energy deposition. The inflow performance parameters are obtained under continuous and pulsed laser energy depositions. When the laser power is 15 kW, a higher pulsed repetitive rate can result in closer inflow performance as that of continuous energy deposition. When the pulsed repetitive rate is 100 kHz, the inlet flow field is simulated in the state that the pulsed square wave duty factor is 0.1, 0.2, 0.3 and 0.4 respectively. The results indicate that the duty factor has little influence on the inlet performance. When the laser pulse duration is 500 ns and the average laser power is fixed, the flow configuration is much close to that of the continuous energy injection under 200 kHz and 100 kHz pulsed repetitive rate. However, the inflow mass capture ratio decreases when pulsed repetitive rate is 500 kHz and 25 kHz. Therefore, with the increasing of the laser pulsed repetitive rate and decreasing of the average laser power, the inflow mass capture ratio increases effectively, and the energy consumption decreases.
2015,
27: 089003.
doi: 10.11884/HPLPB201527.089003
Abstract:
The microstructures of acetylene carbon black, byproduct carbon black and furnace conductive carbon black were systematically investigated and the internal relationship between microstructure and application performance was explored to provide a guidance to the production and application of conductive carbon black. X-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscope and laser particle size analyzer were used to conduct systematic research on the microstructure of conductive carbon black. The results show that the key factor for determining the application performance of conductive carbon black is its compatibility with matrix. The byproduct carbon black is hollow-structured and the aggregate branch is advanced. It presents remarkable conductivity in rubber and plastics. The excellent conductivity performance of acetylene carbon black in lithium ion electrodes attributes to its high degree of graphitization, large grain size and high purity.
The microstructures of acetylene carbon black, byproduct carbon black and furnace conductive carbon black were systematically investigated and the internal relationship between microstructure and application performance was explored to provide a guidance to the production and application of conductive carbon black. X-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscope and laser particle size analyzer were used to conduct systematic research on the microstructure of conductive carbon black. The results show that the key factor for determining the application performance of conductive carbon black is its compatibility with matrix. The byproduct carbon black is hollow-structured and the aggregate branch is advanced. It presents remarkable conductivity in rubber and plastics. The excellent conductivity performance of acetylene carbon black in lithium ion electrodes attributes to its high degree of graphitization, large grain size and high purity.
2015,
27: 089004.
doi: 10.11884/HPLPB201527.089004
Abstract:
The light intensity distribution of two nanoparticles irradiated by ultrashort laser is studied. A procedure based on Mie scattering theory and Monte Carlo method is built to simulate and trace the trajectories of photons. Mie scattering theory is mainly used to determine the scattering directions of photons. Through comparing the distribution function of gold particle and blackbody, the scattering between two particles and increasing of laser irradiating width will enhance the light intensity of particles where they are adjacent to each other. The intensity at the bottom of the particle is mainly decided by the albedo and distribution of scattering light.
The light intensity distribution of two nanoparticles irradiated by ultrashort laser is studied. A procedure based on Mie scattering theory and Monte Carlo method is built to simulate and trace the trajectories of photons. Mie scattering theory is mainly used to determine the scattering directions of photons. Through comparing the distribution function of gold particle and blackbody, the scattering between two particles and increasing of laser irradiating width will enhance the light intensity of particles where they are adjacent to each other. The intensity at the bottom of the particle is mainly decided by the albedo and distribution of scattering light.
