Email alert
RSS2015 Vol. 27, No. 07
Recommend Articles
Display Method:
2015,
27: 070101.
doi: 10.11884/HPLPB201527.070101
Abstract:
More than 10 kW power was generated by a W-band, third harmonic gyrotron. A cylindrical open cavity with an iris structure was used. The operation mode of the third harmonic gyrotron was TE02. In the test, the pulse duration was 20 s. The beam voltage and current were 45 kV and 3 A, respectively. When the magnetic field was 1.2 T, the frequency observed was 95.22 GHz. The output power was 13.4 kW, corresponding to the efficiency of 9.9 %.
More than 10 kW power was generated by a W-band, third harmonic gyrotron. A cylindrical open cavity with an iris structure was used. The operation mode of the third harmonic gyrotron was TE02. In the test, the pulse duration was 20 s. The beam voltage and current were 45 kV and 3 A, respectively. When the magnetic field was 1.2 T, the frequency observed was 95.22 GHz. The output power was 13.4 kW, corresponding to the efficiency of 9.9 %.
2015,
27: 070102.
doi: 10.11884/HPLPB201527.070102
Abstract:
A diode-cladding-pumped mid-infrared passively Q-switched Er3+-doped ZBLAN fiber laser with an average output power of watt-level based on a semiconductor saturable absorber mirror (SESAM) is demonstrated. Stable pulse train was produced at a slope efficient of 17.8% with respect to the launched pump power. The maximum average power of 1.0 W at a repetition rate of 146.3 kHz was achieved with a corresponding pulse energy of 6.9 J. The maximum peak power was calculated to be 21.7 W.
A diode-cladding-pumped mid-infrared passively Q-switched Er3+-doped ZBLAN fiber laser with an average output power of watt-level based on a semiconductor saturable absorber mirror (SESAM) is demonstrated. Stable pulse train was produced at a slope efficient of 17.8% with respect to the launched pump power. The maximum average power of 1.0 W at a repetition rate of 146.3 kHz was achieved with a corresponding pulse energy of 6.9 J. The maximum peak power was calculated to be 21.7 W.
2015,
27: 071001.
doi: 10.11884/HPLPB201527.071001
Abstract:
A closed pressure atomization spray cooling system with R600a was used to study the heat transfer process of spray cooling. The modeling of droplets impinging on hot surface was built and the moving state was analyzed. The convective heat transfer of liquid film was ignored and Weber number was used to amend the heat transfer convection coefficient between the droplets and the heater surface. Furthermore, the theory of secondary nucleate boiling was referenced to amend empirical correlation of nucleate boiling. Based on the above analysis, empirical correlations of heat transfer coefficient were built by considering the convection and nucleate boiling. By comparing to the correlations and experimental measurements of other researchers, and comparing to different coolants and experimental systems, we found that the errors of the predicted values and the experimental measurements were within 20%. So the empirical correlation can well predict the heat transfer coefficient of closed pressure spray cooling system.
A closed pressure atomization spray cooling system with R600a was used to study the heat transfer process of spray cooling. The modeling of droplets impinging on hot surface was built and the moving state was analyzed. The convective heat transfer of liquid film was ignored and Weber number was used to amend the heat transfer convection coefficient between the droplets and the heater surface. Furthermore, the theory of secondary nucleate boiling was referenced to amend empirical correlation of nucleate boiling. Based on the above analysis, empirical correlations of heat transfer coefficient were built by considering the convection and nucleate boiling. By comparing to the correlations and experimental measurements of other researchers, and comparing to different coolants and experimental systems, we found that the errors of the predicted values and the experimental measurements were within 20%. So the empirical correlation can well predict the heat transfer coefficient of closed pressure spray cooling system.
2015,
27: 071002.
doi: 10.11884/HPLPB201527.071002
Abstract:
Model establishment and simulation researches on the cementation structures are introduced in this paper. Using a 3D glass with a small cylinder itched on one side for the bonding instead of the plate glass, the parameters and the structure of the wave-front corrector have been optimized. Simulation and experiment analysis show that the stress left in the phase corrector declined obviously and the higher-order spatial surface aberration is limited to a lower level.
Model establishment and simulation researches on the cementation structures are introduced in this paper. Using a 3D glass with a small cylinder itched on one side for the bonding instead of the plate glass, the parameters and the structure of the wave-front corrector have been optimized. Simulation and experiment analysis show that the stress left in the phase corrector declined obviously and the higher-order spatial surface aberration is limited to a lower level.
2015,
27: 071003.
doi: 10.11884/HPLPB201527.071003
Abstract:
Fourier heat transfer model and solid-liquid couple method were used to analyze the thermal characteristics of thin-wall metal under nanosecond laser pulse. The high-power heat source operated with a fixed pulse width of 30 ns. It is found that the changes of fluid and solid wall temperature depend on operating time. During an individual pulse, the inside temperature in solid wall increases rapidly within 30 ns pulse heating period, then begins to decrease after 1ms. After 50 ms, the radial distribution of solid temperature becomes uniform gradually. Under the repetitively operated pulse with 40 Hz frequency, the wall temperature oscillates with the same frequency. After a certain time, the temperature oscillation becomes equilibrium and changes within a certain range. If the pulse heating is stopped, both the fluid and wall temperature will sharply decrease to the initial values within 2 s. The effects of fluid flow rate and physical properties of solid wall are also discussed. Both the increase of flow rate and solid thermal diffusivity can decrease the wall temperature and accelerate thermal balance.
Fourier heat transfer model and solid-liquid couple method were used to analyze the thermal characteristics of thin-wall metal under nanosecond laser pulse. The high-power heat source operated with a fixed pulse width of 30 ns. It is found that the changes of fluid and solid wall temperature depend on operating time. During an individual pulse, the inside temperature in solid wall increases rapidly within 30 ns pulse heating period, then begins to decrease after 1ms. After 50 ms, the radial distribution of solid temperature becomes uniform gradually. Under the repetitively operated pulse with 40 Hz frequency, the wall temperature oscillates with the same frequency. After a certain time, the temperature oscillation becomes equilibrium and changes within a certain range. If the pulse heating is stopped, both the fluid and wall temperature will sharply decrease to the initial values within 2 s. The effects of fluid flow rate and physical properties of solid wall are also discussed. Both the increase of flow rate and solid thermal diffusivity can decrease the wall temperature and accelerate thermal balance.
2015,
27: 071004.
doi: 10.11884/HPLPB201527.071004
Abstract:
This paper compared the results of laboratory measurements of the Stokes scattering matrix of non-spherical fly ash aerosols at a visible wavelength with the results of Lorenz-Mie computations for projected area equivalent spheres. Bidirectional reflectance functions (BRDFs) were calculated and analyzed by DISORT with scattering phase function calculated using Lorenz-Mie theory and measured in an experiment. The results show poor agreement between experimental scattering matrix of non-spherical fly ash aerosol particles and that of Lorenz-Mie calculation for most scattering angles. However, their asymmetry factors are similar. The variation trend of BRDF of spherical particles is basically consistent with that of non-spherical particles, but the BRDF curve of spherical particles is more variable. With the increasing of aerosol optical depth, the curves of BRDF of spherical particles and non-spherical particles go to a steady and similar value. Assumption of spherical particles will result in a certain error under thin optical depth, the relative error of BRDF will grow up to 60%, therefore the influence of non-spherical characteristics must be taken into consideration. However, when the optical depth is larger, the relative error of BRDF is usually lower than 10%, spherical particle assumption has certain applicability.
This paper compared the results of laboratory measurements of the Stokes scattering matrix of non-spherical fly ash aerosols at a visible wavelength with the results of Lorenz-Mie computations for projected area equivalent spheres. Bidirectional reflectance functions (BRDFs) were calculated and analyzed by DISORT with scattering phase function calculated using Lorenz-Mie theory and measured in an experiment. The results show poor agreement between experimental scattering matrix of non-spherical fly ash aerosol particles and that of Lorenz-Mie calculation for most scattering angles. However, their asymmetry factors are similar. The variation trend of BRDF of spherical particles is basically consistent with that of non-spherical particles, but the BRDF curve of spherical particles is more variable. With the increasing of aerosol optical depth, the curves of BRDF of spherical particles and non-spherical particles go to a steady and similar value. Assumption of spherical particles will result in a certain error under thin optical depth, the relative error of BRDF will grow up to 60%, therefore the influence of non-spherical characteristics must be taken into consideration. However, when the optical depth is larger, the relative error of BRDF is usually lower than 10%, spherical particle assumption has certain applicability.
2015,
27: 071005.
doi: 10.11884/HPLPB201527.071005
Abstract:
In this paper, we present an algorithm, which is incorporated into geometrical calibration, to accurately and efficiently calibrate and correct the nonlinearity. The proposed method utilizes phase to obtain the intensity correspondences between projected patterns and recorded images. Based on the intensity correspondences, the nonlinear response of the system is further retrieved. Along with geometrical calibration, without adjusting setup or using any additional specially-designed structured light patterns, a look-up table for correcting the nonlinear response is directly and accurately derived, and is applied to the intensities of the patterns before projection. Experiments show that the root mean square of the phase error is significantly reduced by a factor of 21.8 times.
In this paper, we present an algorithm, which is incorporated into geometrical calibration, to accurately and efficiently calibrate and correct the nonlinearity. The proposed method utilizes phase to obtain the intensity correspondences between projected patterns and recorded images. Based on the intensity correspondences, the nonlinear response of the system is further retrieved. Along with geometrical calibration, without adjusting setup or using any additional specially-designed structured light patterns, a look-up table for correcting the nonlinear response is directly and accurately derived, and is applied to the intensities of the patterns before projection. Experiments show that the root mean square of the phase error is significantly reduced by a factor of 21.8 times.
2015,
27: 071006.
doi: 10.11884/HPLPB201527.071006
Abstract:
High-power laser induced shocks were used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s at Shenguang-Ⅱ laser facility. The free surface velocity histories of shock-loaded samples, 150 m thick and with initial temperature from 293 K to 873 K, were recorded using velocity interferometer system for any reflector (VISAR). From the free surface velocity profile ,spall strength and yield stress are calculated, which shows that spall strength declines while yield strength increases with initial temperature increasing. The loaded samples were recovered for metallographic analysis through Laser Scanning Confocal Microscopy. It is found that there are more micro-voids and more bigger voids near the spall plane. Meanwhile, the grain size increases with temperature slowly except the sharp change at 893K(near melting point). Besides, the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with initial temperature increasing.
High-power laser induced shocks were used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s at Shenguang-Ⅱ laser facility. The free surface velocity histories of shock-loaded samples, 150 m thick and with initial temperature from 293 K to 873 K, were recorded using velocity interferometer system for any reflector (VISAR). From the free surface velocity profile ,spall strength and yield stress are calculated, which shows that spall strength declines while yield strength increases with initial temperature increasing. The loaded samples were recovered for metallographic analysis through Laser Scanning Confocal Microscopy. It is found that there are more micro-voids and more bigger voids near the spall plane. Meanwhile, the grain size increases with temperature slowly except the sharp change at 893K(near melting point). Besides, the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with initial temperature increasing.
2015,
27: 071007.
doi: 10.11884/HPLPB201527.071007
Abstract:
Because plasma generated through laser ablation takes on a Gaussian form, dimensional distribution of quantity and kinetic energy of particles are terribly uneven, its difficult to prepare large area films with uniform thickness and performance by pulse laser deposition. In our study, a translation device was designed, the shifting velocity of the rotational substrate increased gradually while approaching the center of plasma, whereas decreased gradually while departing in order to obtain a uniform film. The math model of influence of motion parameters on thickness of the film was founded. Finally, through simulation and optimization, the uniform diamond-like carbon film with diameter of 200 mm and thickness variation below 4% was prepared by pulse laser deposition.
Because plasma generated through laser ablation takes on a Gaussian form, dimensional distribution of quantity and kinetic energy of particles are terribly uneven, its difficult to prepare large area films with uniform thickness and performance by pulse laser deposition. In our study, a translation device was designed, the shifting velocity of the rotational substrate increased gradually while approaching the center of plasma, whereas decreased gradually while departing in order to obtain a uniform film. The math model of influence of motion parameters on thickness of the film was founded. Finally, through simulation and optimization, the uniform diamond-like carbon film with diameter of 200 mm and thickness variation below 4% was prepared by pulse laser deposition.
2015,
27: 071008.
doi: 10.11884/HPLPB201527.071008
Abstract:
To study the mechanism of ripple effect existing in optical-feedback cavity ring-down spectroscopy, data processing method is applied to analyze the typical characteristics of ripple effect, including the period and amplitude, based on the measured data with a 49.1 cm long V-shaped glass ceramics cavity in the different circumstances and spectral ranges. It is believed that the ripple effect presents the obvious incomplete interference, and its period and amplitude are mainly determined by the structure of V-shaped cavity and its surface pollution status of folded-mirror, respectively, have little relation with the spectral scanning region. All these show that the spectral ripple is mainly from the part interference effect of light on folded-mirror.
To study the mechanism of ripple effect existing in optical-feedback cavity ring-down spectroscopy, data processing method is applied to analyze the typical characteristics of ripple effect, including the period and amplitude, based on the measured data with a 49.1 cm long V-shaped glass ceramics cavity in the different circumstances and spectral ranges. It is believed that the ripple effect presents the obvious incomplete interference, and its period and amplitude are mainly determined by the structure of V-shaped cavity and its surface pollution status of folded-mirror, respectively, have little relation with the spectral scanning region. All these show that the spectral ripple is mainly from the part interference effect of light on folded-mirror.
2015,
27: 071009.
doi: 10.11884/HPLPB201527.071009
Abstract:
A novel phase aberration correcting method based on combined deformable mirrors (DMs) in a slab master oscillator and power amplifier solid state laser system is proposed and validated experimentally. The adaptive optics(AO) system with combined deformable mirrors composed of a one-dimension (1D) DM with 11 actuators and a two-dimensional (2D) DM with 67 valid actuators, has been designed to correct the phase aberrations, which doesnt need the high voltage drivers and has an excellent correcting efficiency of the high order phase aberrations. The experimental results show that the wave front of the slab laser beam is compensated well and the root mean square (RMS) of the residual wave front is less than 0.08 m. The beam quality of the slab laser in the far field is improved to 1.67.
A novel phase aberration correcting method based on combined deformable mirrors (DMs) in a slab master oscillator and power amplifier solid state laser system is proposed and validated experimentally. The adaptive optics(AO) system with combined deformable mirrors composed of a one-dimension (1D) DM with 11 actuators and a two-dimensional (2D) DM with 67 valid actuators, has been designed to correct the phase aberrations, which doesnt need the high voltage drivers and has an excellent correcting efficiency of the high order phase aberrations. The experimental results show that the wave front of the slab laser beam is compensated well and the root mean square (RMS) of the residual wave front is less than 0.08 m. The beam quality of the slab laser in the far field is improved to 1.67.
2015,
27: 071010.
doi: 10.11884/HPLPB201527.071010
Abstract:
Using standard phase structures with high quality is the precondition for accurate calibration of system transfer function(STF) of the interferometric measurement system, which guarantees the accurate measurement of the optical wavefront or surface informations in the mid and high spatial frequency bands. Two types of typical standard phase structures are simulated and analyzed, one is the binary pseudo-random(BPR) grating, and the other is the step. According to the comparison of the effect of the fabrication imperfections on the measurement of system transfer function between the BPR grating and the step, more reliable calibration of the STF in mid and high spatial frequency bands can be obtained using BPR grating as the standard, when the error parameters are the same. The changes of the corresponding PSD are also analyzed, when the BPR grating is oversampled or undersampled by CCD, the PSD will decline with the frequency, and the effect of sampling on the STF calibration can be removed by modifying the height distribution of the theoretical BPR grating.
Using standard phase structures with high quality is the precondition for accurate calibration of system transfer function(STF) of the interferometric measurement system, which guarantees the accurate measurement of the optical wavefront or surface informations in the mid and high spatial frequency bands. Two types of typical standard phase structures are simulated and analyzed, one is the binary pseudo-random(BPR) grating, and the other is the step. According to the comparison of the effect of the fabrication imperfections on the measurement of system transfer function between the BPR grating and the step, more reliable calibration of the STF in mid and high spatial frequency bands can be obtained using BPR grating as the standard, when the error parameters are the same. The changes of the corresponding PSD are also analyzed, when the BPR grating is oversampled or undersampled by CCD, the PSD will decline with the frequency, and the effect of sampling on the STF calibration can be removed by modifying the height distribution of the theoretical BPR grating.
2015,
27: 071011.
doi: 10.11884/HPLPB201527.071011
Abstract:
The extinction characteristics of aerosol have great influence on the effective transmission of laser propagating in atmosphere. In recent years, with the declining of air quality, the aerosol pollution is becoming serious. In order to analyze the dependence of extinction coefficient on ambient relative humidity(RH) under two cases of weather in coastal area, visibility, as well as relative humidity in the southeast coastal area of China is measured by experiments. The results show that the deliquescence points of aerosol particles under the two kinds of weather are both about 80%, and that after deliquescence, the extinction coefficient increases with the increasing of relative humidity. For the laser with a wavelength of 1.06 m, an order of difference of magnitude for extinction coefficient of haze and fine weather is obtained. However, when 80%＜RH＜90%, relative increasing of the aerosol extinction coefficient under two conditions is similar, the f(RH) ranging from 1 to 2 mostly; for RH＞90%, the difference is very large. The f(RH) increases by two orders of magnitude in good weather, which is of significance on laser propagation in the atmosphere.
The extinction characteristics of aerosol have great influence on the effective transmission of laser propagating in atmosphere. In recent years, with the declining of air quality, the aerosol pollution is becoming serious. In order to analyze the dependence of extinction coefficient on ambient relative humidity(RH) under two cases of weather in coastal area, visibility, as well as relative humidity in the southeast coastal area of China is measured by experiments. The results show that the deliquescence points of aerosol particles under the two kinds of weather are both about 80%, and that after deliquescence, the extinction coefficient increases with the increasing of relative humidity. For the laser with a wavelength of 1.06 m, an order of difference of magnitude for extinction coefficient of haze and fine weather is obtained. However, when 80%＜RH＜90%, relative increasing of the aerosol extinction coefficient under two conditions is similar, the f(RH) ranging from 1 to 2 mostly; for RH＞90%, the difference is very large. The f(RH) increases by two orders of magnitude in good weather, which is of significance on laser propagation in the atmosphere.
2015,
27: 071012.
doi: 10.11884/HPLPB201527.071012
Abstract:
We have achieved 856 W spectral beam combining output of two fiber lasers employing a transmitting volume Bragg grating (TVBG), which is the highest combining power of spectral beam combination by VBGs. The total spectral combining efficiency is 73.7% and the beam quality of combining beam is 7.9 and 2.7 in x and y direction, respectively. Though the diffraction beam is seriously stretched by angular dispersion of TVBG, the transmission beam preserves its beam properties in the high average power spectral beam combining. This indicates that the broadband fiber lasers (the spectral bandwidth is over 4 nm) can be used as transmission beam in high efficiency spectral beam combination of VBGs for higher combining power output.
We have achieved 856 W spectral beam combining output of two fiber lasers employing a transmitting volume Bragg grating (TVBG), which is the highest combining power of spectral beam combination by VBGs. The total spectral combining efficiency is 73.7% and the beam quality of combining beam is 7.9 and 2.7 in x and y direction, respectively. Though the diffraction beam is seriously stretched by angular dispersion of TVBG, the transmission beam preserves its beam properties in the high average power spectral beam combining. This indicates that the broadband fiber lasers (the spectral bandwidth is over 4 nm) can be used as transmission beam in high efficiency spectral beam combination of VBGs for higher combining power output.
2015,
27: 071013.
doi: 10.11884/HPLPB201527.071013
Abstract:
The suppression methods of stimulated Brillouin scattering (SBS) in high power fiber laser are analyzed. The results indicate broadening the spectrum with high speed phase modulation is one of the most effective ways to suppress SBS. With a broadband noise generator, kW level several 10 GHz linewidth fiber lasers, which are suitable for spectral beam combining, can be easily developed. On purpose of optimizing the parameters of the fiber laser, we calculate the relationship between the laser linewidth and the SBS threshold. At the same time, the effect of noise modulation parameters on spectral broadening is analyzed by numerical calculation. By broadband noise high speed phase modulation, the linewidth of the seed is broadened to 13 GHz. With a two-stage amplifying, the power is enhanced to 10 W. A 20/400 m commercial Yb-doped fiber is used in the final stage amplifier, which convinces central wavelength 1064 nm, linewidth 13 GHz, maximum power 1.06 kW fiber laser. The M2 is better than 1.2 and the O-O efficiency is 86%. During the whole experimental process, the mode instability is not observed. By broadening the bandwidth of the noise generator or enhancing the modulation depth, a higher power narrow linewidth fiber laser can be expected.
The suppression methods of stimulated Brillouin scattering (SBS) in high power fiber laser are analyzed. The results indicate broadening the spectrum with high speed phase modulation is one of the most effective ways to suppress SBS. With a broadband noise generator, kW level several 10 GHz linewidth fiber lasers, which are suitable for spectral beam combining, can be easily developed. On purpose of optimizing the parameters of the fiber laser, we calculate the relationship between the laser linewidth and the SBS threshold. At the same time, the effect of noise modulation parameters on spectral broadening is analyzed by numerical calculation. By broadband noise high speed phase modulation, the linewidth of the seed is broadened to 13 GHz. With a two-stage amplifying, the power is enhanced to 10 W. A 20/400 m commercial Yb-doped fiber is used in the final stage amplifier, which convinces central wavelength 1064 nm, linewidth 13 GHz, maximum power 1.06 kW fiber laser. The M2 is better than 1.2 and the O-O efficiency is 86%. During the whole experimental process, the mode instability is not observed. By broadening the bandwidth of the noise generator or enhancing the modulation depth, a higher power narrow linewidth fiber laser can be expected.
2015,
27: 071014.
doi: 10.11884/HPLPB201527.071014
Abstract:
The damage effects of CW laser on carbon fiber/epoxy composite were studied experimentally at 0.5, 0.85 Mach airflow and no airflow on material surface. Through the thermal weight loss curves of epoxy, carbon fiber and carbon fiber/epoxy composite analysis, the rear surface temperatures and the ablation patterns were compared. The results show that because of material combustion prevented and cooling effect, the damage zone is bigger, the last temperature is higher and the time of the temperature rise is longer under no airflow condition. When the flow speed ranges from 0.5 Mach to 0.85 Mach, the damage difference of carbon fiber/epoxy composite irradiated by CW laser is not obvious.
The damage effects of CW laser on carbon fiber/epoxy composite were studied experimentally at 0.5, 0.85 Mach airflow and no airflow on material surface. Through the thermal weight loss curves of epoxy, carbon fiber and carbon fiber/epoxy composite analysis, the rear surface temperatures and the ablation patterns were compared. The results show that because of material combustion prevented and cooling effect, the damage zone is bigger, the last temperature is higher and the time of the temperature rise is longer under no airflow condition. When the flow speed ranges from 0.5 Mach to 0.85 Mach, the damage difference of carbon fiber/epoxy composite irradiated by CW laser is not obvious.
2015,
27: 072001.
doi: 10.11884/HPLPB201527.072001
Abstract:
Ultra-low density cellulose triacetate (TAC) spheres and ellipsoid aerogels used for quasi-spherical Z-pinch were fabricated in special moulds by using TAC granules as raw material and controlling the processing of dissolution, gelation and supercritical carbon dioxide drying. The solution-gelation processing of TAC solution when cooled to room temperature, the rheological behavior of TAC gel, and the inside microstructure and the thermogravimetry (TG) analysis of TAC aerogel were investigated. TAC solution turns to gel with high transparence when cooled to room temperature. The SEM photos showed that the aerogels had a three-dimensional nanostructured solid network and a nanoporous network together with fiber sizes about 20-40 nm. The TAC granules and the TAC aerogels were thermally stable up to 320 ℃ as indicated by TG analysis. These TAC sphere and ellipsoid aerogels were successfully used in quasi-spherical Z-pinch experiment.
Ultra-low density cellulose triacetate (TAC) spheres and ellipsoid aerogels used for quasi-spherical Z-pinch were fabricated in special moulds by using TAC granules as raw material and controlling the processing of dissolution, gelation and supercritical carbon dioxide drying. The solution-gelation processing of TAC solution when cooled to room temperature, the rheological behavior of TAC gel, and the inside microstructure and the thermogravimetry (TG) analysis of TAC aerogel were investigated. TAC solution turns to gel with high transparence when cooled to room temperature. The SEM photos showed that the aerogels had a three-dimensional nanostructured solid network and a nanoporous network together with fiber sizes about 20-40 nm. The TAC granules and the TAC aerogels were thermally stable up to 320 ℃ as indicated by TG analysis. These TAC sphere and ellipsoid aerogels were successfully used in quasi-spherical Z-pinch experiment.
2015,
27: 072002.
doi: 10.11884/HPLPB201527.072002
Abstract:
The whole sphere lapping is important to fabrication of a metal capsule (hollow microsphere) which is a vital part of the ignition target. In this paper, the metal titanium sphere was machined by using the four-axis sphere lapping technique. The surface roughness was characterized by means of talysurf series 2 and the roundness by means of surface profile-meter. The results indicated that the surface roughness of the part was less than 10 nm and the roundness was less than 1.0 m.
The whole sphere lapping is important to fabrication of a metal capsule (hollow microsphere) which is a vital part of the ignition target. In this paper, the metal titanium sphere was machined by using the four-axis sphere lapping technique. The surface roughness was characterized by means of talysurf series 2 and the roundness by means of surface profile-meter. The results indicated that the surface roughness of the part was less than 10 nm and the roundness was less than 1.0 m.
2015,
27: 072003.
doi: 10.11884/HPLPB201527.072003
Abstract:
Two-dimensional PIC (particle-in-cell) simulation is used to investigate the interaction between ultra-intense short-pulse lasers with tube targets. When an ultra-intense super-Gaussian laser pulse propagates at a grazing incidence angle into the tube target, GeV-class electron acceleration is observed on the inner surface. Fast electrons are confined along the surface by quasistatic electric and magnetic fields, resulting in a small divergence angle of the generated electron beam. These surface fast electrons can be accelerated for a long distance along the tube; as a result, the energy conversion efficiency is very high. The influence of the laser intensity and the transverse profile on the surface electron acceleration process is also discussed in the article.
Two-dimensional PIC (particle-in-cell) simulation is used to investigate the interaction between ultra-intense short-pulse lasers with tube targets. When an ultra-intense super-Gaussian laser pulse propagates at a grazing incidence angle into the tube target, GeV-class electron acceleration is observed on the inner surface. Fast electrons are confined along the surface by quasistatic electric and magnetic fields, resulting in a small divergence angle of the generated electron beam. These surface fast electrons can be accelerated for a long distance along the tube; as a result, the energy conversion efficiency is very high. The influence of the laser intensity and the transverse profile on the surface electron acceleration process is also discussed in the article.
2015,
27: 072004.
doi: 10.11884/HPLPB201527.072004
Abstract:
There are some scratches of shallow depth (about 25 nm) or narrow width (collectively referred to as weak scratches) during defects detection on the super-smooth optical components. In the dark field imaging detection, the scattered light of the weak scratches produces such a low gray value, even masked in the background light, as a result, they are very difficult to identify by visual or conventional machine vision, and could be undetected. To solve this problem, based on the existing surface defects evaluation system (SDES), according to the scratches gray features, the dual-threshold classification method to extract scratches defects is proposed. In low threshold scratches processing, according to the frequency characteristics of the weak scratches, background contrast and spatial characteristics, the algorithm of frequency domain filtering with background difference is adopted. By spatial domain and frequency domain filtering algorithms, interference points and high luminance noise points are eliminated. In addition, background can be extracted since its geometric characteristics are different from weak scratches. Further, weak scratches with enhanced contrast are extracted, and finally, these scratches are used in high threshold information extraction of subsequent scratches feature together with the normal gray level scratches. Thus all the scratches information is obtained for calculating the total length of scratches and grading of defects maximum length. Experimental results show that the algorithm proposed avoids introducing irregular background noise by a low binarization threshold, and also improves the contrast of scratches and background. At present, the algorithm has been applied to inertial confinement fusion systems in large aperture optical surface scratches quantitative detection, and the length detection accuracy has been raised to about 80%.
There are some scratches of shallow depth (about 25 nm) or narrow width (collectively referred to as weak scratches) during defects detection on the super-smooth optical components. In the dark field imaging detection, the scattered light of the weak scratches produces such a low gray value, even masked in the background light, as a result, they are very difficult to identify by visual or conventional machine vision, and could be undetected. To solve this problem, based on the existing surface defects evaluation system (SDES), according to the scratches gray features, the dual-threshold classification method to extract scratches defects is proposed. In low threshold scratches processing, according to the frequency characteristics of the weak scratches, background contrast and spatial characteristics, the algorithm of frequency domain filtering with background difference is adopted. By spatial domain and frequency domain filtering algorithms, interference points and high luminance noise points are eliminated. In addition, background can be extracted since its geometric characteristics are different from weak scratches. Further, weak scratches with enhanced contrast are extracted, and finally, these scratches are used in high threshold information extraction of subsequent scratches feature together with the normal gray level scratches. Thus all the scratches information is obtained for calculating the total length of scratches and grading of defects maximum length. Experimental results show that the algorithm proposed avoids introducing irregular background noise by a low binarization threshold, and also improves the contrast of scratches and background. At present, the algorithm has been applied to inertial confinement fusion systems in large aperture optical surface scratches quantitative detection, and the length detection accuracy has been raised to about 80%.
2015,
27: 072005.
doi: 10.11884/HPLPB201527.072005
Abstract:
The principle of penumbral imaging is experimentally validated based on the microfocus X-ray source. Using pinhole imaging, the microfocus source is directly measured; then the basic principles of penumbral hole imaging, penumbral cone imaging and penumbral ring imaging are introduced, as well as the penumbral imaging results on the microfocus sources and Wiener filtering reconstruction results. According to the results, the diagnostic capability of penumbral cone is the same with penumbral hole imaging, the size of the reconstruction image agrees with that of the source image, and the diagnostic capability of penumbral ring imaging is better, the size and shape of the reconstruction image are closer to that of the source image.
The principle of penumbral imaging is experimentally validated based on the microfocus X-ray source. Using pinhole imaging, the microfocus source is directly measured; then the basic principles of penumbral hole imaging, penumbral cone imaging and penumbral ring imaging are introduced, as well as the penumbral imaging results on the microfocus sources and Wiener filtering reconstruction results. According to the results, the diagnostic capability of penumbral cone is the same with penumbral hole imaging, the size of the reconstruction image agrees with that of the source image, and the diagnostic capability of penumbral ring imaging is better, the size and shape of the reconstruction image are closer to that of the source image.
2015,
27: 073001.
doi: 10.11884/HPLPB201527.073001
Abstract:
A power divider based on transmission-line transformer in ultra-shortwave band is designed. The model of the power divider is given using the telegraph equation. Its characteristics including input SWR, transmission coefficient, isolation and the changes of these characteristics caused by different compensated capacitances are analyzed. The results of calculation indicate that the proper compensation capacitance could decrease the input SWR, increase the transmission coefficient and the isolation. The results of the experiment indicate that the changes of the characteristics of the power divider are consistent with the analysis and calculation when compensated with capacitance.
A power divider based on transmission-line transformer in ultra-shortwave band is designed. The model of the power divider is given using the telegraph equation. Its characteristics including input SWR, transmission coefficient, isolation and the changes of these characteristics caused by different compensated capacitances are analyzed. The results of calculation indicate that the proper compensation capacitance could decrease the input SWR, increase the transmission coefficient and the isolation. The results of the experiment indicate that the changes of the characteristics of the power divider are consistent with the analysis and calculation when compensated with capacitance.
2015,
27: 073002.
doi: 10.11884/HPLPB201527.073002
Abstract:
A quasi-optical mode converter for high power gyrotron, consisting of a Denisov launcher and four mirror reflectors is designed and studied. Applying the geometrical optics, the operation mechanism of the Denisov launcher is analyzed in detail and the Gauss-like field distribution achieved on the inner wall is derived. The method for designing a dimpled wall launcher is proposed based on coupled mode theory. As an example, the launcher and mirror parameters are selected and optimized for a 110 GHz, TE22,6 mode gyrotron. Finally, a simulation code is developed to calculate the field distribution at aperture or on the mirrors. Numerical result indicates that a Gaussian-like beam is obtained through the output window, which scalar content is 95.8% and the conversion efficiency of the system is 94.7%.
A quasi-optical mode converter for high power gyrotron, consisting of a Denisov launcher and four mirror reflectors is designed and studied. Applying the geometrical optics, the operation mechanism of the Denisov launcher is analyzed in detail and the Gauss-like field distribution achieved on the inner wall is derived. The method for designing a dimpled wall launcher is proposed based on coupled mode theory. As an example, the launcher and mirror parameters are selected and optimized for a 110 GHz, TE22,6 mode gyrotron. Finally, a simulation code is developed to calculate the field distribution at aperture or on the mirrors. Numerical result indicates that a Gaussian-like beam is obtained through the output window, which scalar content is 95.8% and the conversion efficiency of the system is 94.7%.
2015,
27: 073101.
doi: 10.11884/HPLPB201527.073101
Abstract:
A three-stage 220 GHz staggered double vane TWT was proposed in this paper. The coupler structure, as a key part affecting the whole transmission characteristics, was analyzed. By numerical simulation, a novel coupler formed by height gradually changed grating structure and concentric cylindrical connector was proposed for this structure. The particle-in-cell simulation results revealed that the self-excited oscillation was effectively suppressed, and the maximum gain was 30 dB at 220 GHz with a 3 dB bandwidth of 23 GHz. The transmission deficiency caused by the multi electron beam channel was successfully resolved by this novel structure.
A three-stage 220 GHz staggered double vane TWT was proposed in this paper. The coupler structure, as a key part affecting the whole transmission characteristics, was analyzed. By numerical simulation, a novel coupler formed by height gradually changed grating structure and concentric cylindrical connector was proposed for this structure. The particle-in-cell simulation results revealed that the self-excited oscillation was effectively suppressed, and the maximum gain was 30 dB at 220 GHz with a 3 dB bandwidth of 23 GHz. The transmission deficiency caused by the multi electron beam channel was successfully resolved by this novel structure.
2015,
27: 073102.
doi: 10.11884/HPLPB201527.073102
Abstract:
The inject beam of the beam transfer line of THz-FEL device has a long tail since there is no beam cutting device, due to the space limitation. A slit was set in the transfer line to cut the tail. Only the electron at the head of the beam which satisfy the requirement of FEL was left. The calculation using Elegant indicated that the transfer line could transmit the effective part of the beam to the exit. The orbit distortion caused by tolerance of magnets should get reduced to a reasonable level. The calculation using AT for MATLAB indicated that the orbit distortion was minimized ultimately after corrections.
The inject beam of the beam transfer line of THz-FEL device has a long tail since there is no beam cutting device, due to the space limitation. A slit was set in the transfer line to cut the tail. Only the electron at the head of the beam which satisfy the requirement of FEL was left. The calculation using Elegant indicated that the transfer line could transmit the effective part of the beam to the exit. The orbit distortion caused by tolerance of magnets should get reduced to a reasonable level. The calculation using AT for MATLAB indicated that the orbit distortion was minimized ultimately after corrections.
2015,
27: 073201.
doi: 10.11884/HPLPB201527.073201
Abstract:
This paper presents experimental methods to simulate the turbulent plasma around shrinkage aircraft models launched by a two-stage light gas gun and measure its electromagnetic scattering characteristics. Experiments of simulating the turbulent plasma around the hypersonic models are carried out in the ballistic range. The Radar Cross-Section（RCS）measuring methods of the turbulent plasma engendered by the models are introduced. Typical electromagnetic scattering properties obtained in the tests are demonstrated. The experimental results are compared with the calculated results acquired by the first-order distorted wave Born methods. It is found that the turbulent plasma is properly simulated when the models are launched under the conditions of appropriate velocity and pressure. The transition and turbulent wakes are designated in the flow field images of the models acquired by the laser shadowgraph technique. The electron density of the turbulent plasma wake is lower than the critical electron density corresponding to the incident radar wave. The measured RCS signals of the models and the around flow field are three orders of magnitude larger than that of the wakes. The measured echo signals are not periodic. The amplitudes of fluctuations range from 1 dB to 15 dB. The frequencies of the fluctuations range from 0.4 kHz to 40 kHz. The RCS fluctuations of the shrinkage aircraft models are possibly caused by the presence of electrons in the turbulent plasma wakes. The scattering signals intensity of the undercritical turbulent plasma wakes is much larger than those of the backgrounds. The RCS measurements show a good agreement with the calculated results. The RCS measurement technology adopted in the ballistic range tests can be used to investigate the electromagnetic scattering characteristics of the turbulent plasma engendered by hypersonic shrinkage aircraft models.
This paper presents experimental methods to simulate the turbulent plasma around shrinkage aircraft models launched by a two-stage light gas gun and measure its electromagnetic scattering characteristics. Experiments of simulating the turbulent plasma around the hypersonic models are carried out in the ballistic range. The Radar Cross-Section（RCS）measuring methods of the turbulent plasma engendered by the models are introduced. Typical electromagnetic scattering properties obtained in the tests are demonstrated. The experimental results are compared with the calculated results acquired by the first-order distorted wave Born methods. It is found that the turbulent plasma is properly simulated when the models are launched under the conditions of appropriate velocity and pressure. The transition and turbulent wakes are designated in the flow field images of the models acquired by the laser shadowgraph technique. The electron density of the turbulent plasma wake is lower than the critical electron density corresponding to the incident radar wave. The measured RCS signals of the models and the around flow field are three orders of magnitude larger than that of the wakes. The measured echo signals are not periodic. The amplitudes of fluctuations range from 1 dB to 15 dB. The frequencies of the fluctuations range from 0.4 kHz to 40 kHz. The RCS fluctuations of the shrinkage aircraft models are possibly caused by the presence of electrons in the turbulent plasma wakes. The scattering signals intensity of the undercritical turbulent plasma wakes is much larger than those of the backgrounds. The RCS measurements show a good agreement with the calculated results. The RCS measurement technology adopted in the ballistic range tests can be used to investigate the electromagnetic scattering characteristics of the turbulent plasma engendered by hypersonic shrinkage aircraft models.
2015,
27: 073202.
doi: 10.11884/HPLPB201527.073202
Abstract:
This paper discusses system error of integrated optical E-field sensors when measuring high altitude electromagnetic pulse (HEMP). Based on the transfer function of detector and the expression of HEMP, the equations of system error are given. Through analysis of HEMP, the error equations get simplified. And the measurement results influenced by the parameters of the detector and the waveform are analyzed. The results show that the system error increases with the amplitude, full width at half maximum amplitude/rise time and the bias drift and the maximum measurement amplitude is 0.165 times of the half wave electric field and 0.23 times of the half wave electric field when the system error is 5% and 10%. The conclusion can provide a reference for this kind of detectors.
This paper discusses system error of integrated optical E-field sensors when measuring high altitude electromagnetic pulse (HEMP). Based on the transfer function of detector and the expression of HEMP, the equations of system error are given. Through analysis of HEMP, the error equations get simplified. And the measurement results influenced by the parameters of the detector and the waveform are analyzed. The results show that the system error increases with the amplitude, full width at half maximum amplitude/rise time and the bias drift and the maximum measurement amplitude is 0.165 times of the half wave electric field and 0.23 times of the half wave electric field when the system error is 5% and 10%. The conclusion can provide a reference for this kind of detectors.
2015,
27: 073203.
doi: 10.11884/HPLPB201527.073203
Abstract:
The induced current excited by electromagnetic pulse (EMP) would threat electronic equipments connected by the line. The transmission line and electromagnetic scattering models for assessing the electromagnetic stress generated by EMP in system port are discussed, and the detailed study about the impact by the EMP environment, the construction of overhead line and the earth parameters is presented, and a statistical regularity of the line terminal response is given.
The induced current excited by electromagnetic pulse (EMP) would threat electronic equipments connected by the line. The transmission line and electromagnetic scattering models for assessing the electromagnetic stress generated by EMP in system port are discussed, and the detailed study about the impact by the EMP environment, the construction of overhead line and the earth parameters is presented, and a statistical regularity of the line terminal response is given.
2015,
27: 074001.
doi: 10.11884/HPLPB201527.074001
Abstract:
A current-mode detection system and an imaging detection system are designed according to the radiation level at 5.5 m from the target with shielding collimator. The two systems are simulated by Geant4. When the areal density is 10 mg/cm2 and the primary neutron yield is 1012, the current-mode detection system can be used for fuel areal density diagnosis with a signal to noise ratio(SNR) of 40∶1. When the areal density is 10 mg/cm2 and the primary neutron yield is 1011, the imaging detection system can be used for fuel areal density diagnosis with an SNR of 10∶1. If the areal density increases, the SNR is better. However, when the primary neutron yield is 1012, the neutron overlapping occurs. The overlapping probability can be reduced by shortening the exposure time or decreasing the thickness of the plastic scintillator.
A current-mode detection system and an imaging detection system are designed according to the radiation level at 5.5 m from the target with shielding collimator. The two systems are simulated by Geant4. When the areal density is 10 mg/cm2 and the primary neutron yield is 1012, the current-mode detection system can be used for fuel areal density diagnosis with a signal to noise ratio(SNR) of 40∶1. When the areal density is 10 mg/cm2 and the primary neutron yield is 1011, the imaging detection system can be used for fuel areal density diagnosis with an SNR of 10∶1. If the areal density increases, the SNR is better. However, when the primary neutron yield is 1012, the neutron overlapping occurs. The overlapping probability can be reduced by shortening the exposure time or decreasing the thickness of the plastic scintillator.
2015,
27: 074002.
doi: 10.11884/HPLPB201527.074002
Abstract:
To get the mechanism of energy loss in discharge chamber of ion thruster, the energy balance in discharge chamber was studied. Based on 0-D model of discharge performance, the relation of currents balance in discharge chamber was analyzed, combined with the potential distribution, the model of energy loss in discharge chamber was established. Using the LIPS200 thruster as the object of calculation, the respective distribution ratio of various energy loss in the discharge chamber was obtained, and the results between the model calculated and literature were contrasted; Further validation was carried out by test in more conditions (corresponding anode current is 4.0-4.4 A, anode voltage is 34-38 V), and the results indicate that the maximum error is no more than 3%.
To get the mechanism of energy loss in discharge chamber of ion thruster, the energy balance in discharge chamber was studied. Based on 0-D model of discharge performance, the relation of currents balance in discharge chamber was analyzed, combined with the potential distribution, the model of energy loss in discharge chamber was established. Using the LIPS200 thruster as the object of calculation, the respective distribution ratio of various energy loss in the discharge chamber was obtained, and the results between the model calculated and literature were contrasted; Further validation was carried out by test in more conditions (corresponding anode current is 4.0-4.4 A, anode voltage is 34-38 V), and the results indicate that the maximum error is no more than 3%.
2015,
27: 074003.
doi: 10.11884/HPLPB201527.074003
Abstract:
Compensated neutron logging is often affected by log environmental temperature, thus it is necessary to do temperature correction for neutron log porosity by numerical simulation. In Monte Carlo simulation, the S(,)model of light water can only be used at some given temperature. Based on the principle of thermal neutron scattering，the frequency spectra of interpolation with different temperature and the latest release of version VII of Evaluated Nuclear Data File(ENDF/B-VII.1), a new fine ACE(a compact ENDF) formatted thermal neutron scattering database of light water was developed by NJOY99 code. The validation of data were done by a suite of criticality benchmarks, it is concluded that the results of benchmarks, the existing database and the newly developed database are in good agreement. A good result was achieved in temperature correction of well-logging data with the new database.
Compensated neutron logging is often affected by log environmental temperature, thus it is necessary to do temperature correction for neutron log porosity by numerical simulation. In Monte Carlo simulation, the S(,)model of light water can only be used at some given temperature. Based on the principle of thermal neutron scattering，the frequency spectra of interpolation with different temperature and the latest release of version VII of Evaluated Nuclear Data File(ENDF/B-VII.1), a new fine ACE(a compact ENDF) formatted thermal neutron scattering database of light water was developed by NJOY99 code. The validation of data were done by a suite of criticality benchmarks, it is concluded that the results of benchmarks, the existing database and the newly developed database are in good agreement. A good result was achieved in temperature correction of well-logging data with the new database.
2015,
27: 074004.
doi: 10.11884/HPLPB201527.074004
Abstract:
For solving the identification problem in 252Cf-source-driven noise analysis method, we used the compressive sensing theory and the nearest neighbor recognition algorithm, proposed a new classification method named CSKNN method, and then analysed identification probability. The experimental results show that for the classification and identification purposes, the CSKNN identification method only needs a few observations (the ratio between the number of measured values and the fission neutron signal length is no less than 0.1). When the signal to noise ratio increases, the recognition probability will converge faster to 100% and be less sensitive to K. Hence, the CSKNN method is reasonable and feasible, not only because it improves the real-time performance of nuclear arms control verification, but also effectively reduces the sampling cost. Most importantly, it provides a new theoretical basis and implementation method for the online classification of nuclear material concentration.
For solving the identification problem in 252Cf-source-driven noise analysis method, we used the compressive sensing theory and the nearest neighbor recognition algorithm, proposed a new classification method named CSKNN method, and then analysed identification probability. The experimental results show that for the classification and identification purposes, the CSKNN identification method only needs a few observations (the ratio between the number of measured values and the fission neutron signal length is no less than 0.1). When the signal to noise ratio increases, the recognition probability will converge faster to 100% and be less sensitive to K. Hence, the CSKNN method is reasonable and feasible, not only because it improves the real-time performance of nuclear arms control verification, but also effectively reduces the sampling cost. Most importantly, it provides a new theoretical basis and implementation method for the online classification of nuclear material concentration.
2015,
27: 074005.
doi: 10.11884/HPLPB201527.074005
Abstract:
Kr is one of the preferred propellants for the low cost ion thruster. The Kr plasma transport process was simulated with a 3D PIC method, and results were compared with those using the traditional Xe propellant. The influence of propellant type on optics performance was analyzed, such as the beam distribution, ions through rate and divergence angle loss. The results show that: the screen grid sheath of Kr plasma in discharge cavity is deeper than that of Xe plasma, and ions through rate of screen grid is higher; the axial velocity of Kr ion is bigger than that of Xe ion near the accelerator grid hole, which means the radial displacement distance is relatively small and the accelerator grid current caused by ion impact decreases; the divergence angle loss of Kr propellant is the same as that of Xe propellant, but the operation current is higher; the thrust of Kr decreases about 20% compared with that of Xe propellant for the same beam current and accelerating potential. The results of the study have important significance to optimize the propellant for ion thruster.
Kr is one of the preferred propellants for the low cost ion thruster. The Kr plasma transport process was simulated with a 3D PIC method, and results were compared with those using the traditional Xe propellant. The influence of propellant type on optics performance was analyzed, such as the beam distribution, ions through rate and divergence angle loss. The results show that: the screen grid sheath of Kr plasma in discharge cavity is deeper than that of Xe plasma, and ions through rate of screen grid is higher; the axial velocity of Kr ion is bigger than that of Xe ion near the accelerator grid hole, which means the radial displacement distance is relatively small and the accelerator grid current caused by ion impact decreases; the divergence angle loss of Kr propellant is the same as that of Xe propellant, but the operation current is higher; the thrust of Kr decreases about 20% compared with that of Xe propellant for the same beam current and accelerating potential. The results of the study have important significance to optimize the propellant for ion thruster.
2015,
27: 074101.
doi: 10.11884/HPLPB201527.074101
Abstract:
Counter-Meshing Gears (CMG) mechanism is an elaborate discrimination mechanism which can be used in mechanical combination locks for high-consequence system surety applications. Discrimination function of the CMG mechanism is defined by its two composite gears with several fixed stacked coded gear levels, which are coupled at each gear level. Level minimization of the CMG composite gear assembly is desired for engineering optimization, and the knowledge of which is based on insight into the physics behind the CMG mechanism. A conclusion that the minimum composite gear level of the typeⅠ CMG mechanism is 3 has been reported previously. But for the typeⅡCMG mechanism with a unique finger print feature, its minimum gear level problem is far more complicated. As the arbitrary Unlocking Symbol Sequence in the NA+NB form can be degenerated to the MAB(MN) form whereas maintains the same chromatic number of the Critical Trap Grids(CTGs) in the Coding-oriented 2-D maze map, and those CTGs pairwise hetero-level constraints present periodicity when the MAB continually gets lengthened or shortened with any amount 3AB, the 2-D maze mapping transform and the Cross Criterion which defines CTGs pairwise hetero-level constraints are used firstly to convert the minimum gear levels, proving process into getting the vertex coloring chromatic number of the undirected graph G(V, E) corresponding to the three basic patterns of the type Ⅱ CMG mechanism, i.e. 3AB(or 6AB), 4AB and 5AB, and the resulted chromatic number is 3, 5 and 6 respectively. And we finally conclude that the type Ⅱ CMG mechanism must be subdivided into three patterns corresponding to the degenerated Unlocking Symbol Sequenceas (3n)AB, (3n+1)AB and (3n+2)AB(n is the natural number 1, 2, ), with minimum gear level of 3, 5 and 6 respectively. That also means, as to the type Ⅱ CMG mechanism, the minimum composite gear levels is periodically dominated by the Unlocking Symbol Sequence structure.And the 3-templates coloring method is presented for easy and rapid coding for the type Ⅱ CMG mechanism with the minimum composite gear levels.
Counter-Meshing Gears (CMG) mechanism is an elaborate discrimination mechanism which can be used in mechanical combination locks for high-consequence system surety applications. Discrimination function of the CMG mechanism is defined by its two composite gears with several fixed stacked coded gear levels, which are coupled at each gear level. Level minimization of the CMG composite gear assembly is desired for engineering optimization, and the knowledge of which is based on insight into the physics behind the CMG mechanism. A conclusion that the minimum composite gear level of the typeⅠ CMG mechanism is 3 has been reported previously. But for the typeⅡCMG mechanism with a unique finger print feature, its minimum gear level problem is far more complicated. As the arbitrary Unlocking Symbol Sequence in the NA+NB form can be degenerated to the MAB(MN) form whereas maintains the same chromatic number of the Critical Trap Grids(CTGs) in the Coding-oriented 2-D maze map, and those CTGs pairwise hetero-level constraints present periodicity when the MAB continually gets lengthened or shortened with any amount 3AB, the 2-D maze mapping transform and the Cross Criterion which defines CTGs pairwise hetero-level constraints are used firstly to convert the minimum gear levels, proving process into getting the vertex coloring chromatic number of the undirected graph G(V, E) corresponding to the three basic patterns of the type Ⅱ CMG mechanism, i.e. 3AB(or 6AB), 4AB and 5AB, and the resulted chromatic number is 3, 5 and 6 respectively. And we finally conclude that the type Ⅱ CMG mechanism must be subdivided into three patterns corresponding to the degenerated Unlocking Symbol Sequenceas (3n)AB, (3n+1)AB and (3n+2)AB(n is the natural number 1, 2, ), with minimum gear level of 3, 5 and 6 respectively. That also means, as to the type Ⅱ CMG mechanism, the minimum composite gear levels is periodically dominated by the Unlocking Symbol Sequence structure.And the 3-templates coloring method is presented for easy and rapid coding for the type Ⅱ CMG mechanism with the minimum composite gear levels.
2015,
27: 074102.
doi: 10.11884/HPLPB201527.074102
Abstract:
By two-step method, the carbon-water nanofluids were made from the carbon nanotubes and a certain proportional dispersant in deionized water. The influences of mass fraction, diameter of carbon nanotubes on the solidification and melting properties of nanofluids were studied by differential scanning calorimetry(DSC). The experiment results indicated that the onset temperature of solidification and solidification temperature increased with increasing mass fraction of carbon nanotubes, and compared with the same mass fraction of multi-wall carbon nanofluids, the solidification temperature of single-wall carbon nanofluids increased more. The fusion temperature wasnt affected by mass fraction of carbon nanotubes, the latent heat decreased with increasing mass fraction of carbon nanotubes.
By two-step method, the carbon-water nanofluids were made from the carbon nanotubes and a certain proportional dispersant in deionized water. The influences of mass fraction, diameter of carbon nanotubes on the solidification and melting properties of nanofluids were studied by differential scanning calorimetry(DSC). The experiment results indicated that the onset temperature of solidification and solidification temperature increased with increasing mass fraction of carbon nanotubes, and compared with the same mass fraction of multi-wall carbon nanofluids, the solidification temperature of single-wall carbon nanofluids increased more. The fusion temperature wasnt affected by mass fraction of carbon nanotubes, the latent heat decreased with increasing mass fraction of carbon nanotubes.
2015,
27: 074103.
doi: 10.11884/HPLPB201527.074103
Abstract:
Si－Yb quantum cascade and Si－Yb－Si PIN hybrid light-emitting diode is designed for optical communication, which is easy to be integrated on silicon chip. Photoluminescence (PL) and electroluminescence (EL) dynamics on nanosilicon deposited by Yb is investigated. Sharper PL peaks near 700 nm are observed on silicon quantum dots (Si QDs) coated by Yb. The enhanced EL peaks in the wavelength region from 1250 nm to 1650 nm are measured on silicon film deposited by Yb. It is discovered that the EL intensity enhances and the peaks number increases with increasing number of Si－Yb layers. The emission wavelength could be manipulated into the window of optical communication by Si－Yb bonding on nanosilicon.
Si－Yb quantum cascade and Si－Yb－Si PIN hybrid light-emitting diode is designed for optical communication, which is easy to be integrated on silicon chip. Photoluminescence (PL) and electroluminescence (EL) dynamics on nanosilicon deposited by Yb is investigated. Sharper PL peaks near 700 nm are observed on silicon quantum dots (Si QDs) coated by Yb. The enhanced EL peaks in the wavelength region from 1250 nm to 1650 nm are measured on silicon film deposited by Yb. It is discovered that the EL intensity enhances and the peaks number increases with increasing number of Si－Yb layers. The emission wavelength could be manipulated into the window of optical communication by Si－Yb bonding on nanosilicon.
2015,
27: 074104.
doi: 10.11884/HPLPB201527.074104
Abstract:
The thickness increase of photoresist can cause serious distortion of the resist patterns, which greatly affects the performance and application of the device. In this paper, the distortion characteristics of the two-dimensional slices of a high-aspect-ratio microstructure were theoretically investigated in the thickness direction. Meanwhile, an effective correction strategy that includes a doubleside exposure method and a combination of bright serif and gray-scale technique was proposed. The parameters of the mask shape and transmittance were optimized to correct the pattern distortions with the genetic algorithms. The diffracted light field modulation of various layers in the thick resist was employed as a merit function. Simulation results show that the pattern quality of internal layers of resist can be significantly improved by the proposed optimization method. The characteristic parameters such as feature size and sidewall angle match the design goal. Due to its flexibility, the optimization method proposed in this paper can be applied to more complex pattern by using appropriate extrapolation technique.
The thickness increase of photoresist can cause serious distortion of the resist patterns, which greatly affects the performance and application of the device. In this paper, the distortion characteristics of the two-dimensional slices of a high-aspect-ratio microstructure were theoretically investigated in the thickness direction. Meanwhile, an effective correction strategy that includes a doubleside exposure method and a combination of bright serif and gray-scale technique was proposed. The parameters of the mask shape and transmittance were optimized to correct the pattern distortions with the genetic algorithms. The diffracted light field modulation of various layers in the thick resist was employed as a merit function. Simulation results show that the pattern quality of internal layers of resist can be significantly improved by the proposed optimization method. The characteristic parameters such as feature size and sidewall angle match the design goal. Due to its flexibility, the optimization method proposed in this paper can be applied to more complex pattern by using appropriate extrapolation technique.
2015,
27: 075001.
doi: 10.11884/HPLPB201527.075001
Abstract:
Time-domain singular value decomposition(SVD) technique is used for mode analysis of the near-fields of 10 meter-high bounded wave electromagnetic pulse (EMP) simulator with distributed terminator, which are provided by parallelized finite-difference time-domain(FDTD) method. The changes of singular values of 3 dominant modes(TEM, TM1 and TM2 mode) of the fields in the simulator with/without a test object are given. And the changes of the singular values with the test objects place in the simulator and the height of the test object are presented. The results show that the high-frequency component of TEM mode decreases as the electromagnetic waves propagate in the simulator. The singular values of the 3 dominant modes vary more greatly as the test object moves to the source more. The singular values of TEM mode of the fields near the test object have two points with the extreme values and the horizontal distance of the two points is almost equal to the horizontal size of the test object, as the ratio of the objects height to the distance between simulators two plates is less than 60%.
Time-domain singular value decomposition(SVD) technique is used for mode analysis of the near-fields of 10 meter-high bounded wave electromagnetic pulse (EMP) simulator with distributed terminator, which are provided by parallelized finite-difference time-domain(FDTD) method. The changes of singular values of 3 dominant modes(TEM, TM1 and TM2 mode) of the fields in the simulator with/without a test object are given. And the changes of the singular values with the test objects place in the simulator and the height of the test object are presented. The results show that the high-frequency component of TEM mode decreases as the electromagnetic waves propagate in the simulator. The singular values of the 3 dominant modes vary more greatly as the test object moves to the source more. The singular values of TEM mode of the fields near the test object have two points with the extreme values and the horizontal distance of the two points is almost equal to the horizontal size of the test object, as the ratio of the objects height to the distance between simulators two plates is less than 60%.
2015,
27: 075002.
doi: 10.11884/HPLPB201527.075002
Abstract:
One of the most important parameters of the intense pulsed ion beam(IPIB) is the distribution of the energy density at the cross section. Aiming to solve the problem of traditional diagnostic methods for beam energy density, we measured the temperature distribution of the reverse side of target by infrared camera to develop the infrared diagnostic techniques of IPIB energy density distribution. For IPIB of energy density about 1 J/cm2 and pulse width about 100 ns, the error using this method is less than 5% and the spatial resolution achieves 1-2 mm. The method has the advantages of easy operation and low cost, it is an efficient prompt monitoring method for the IPIB energy density distribution.
One of the most important parameters of the intense pulsed ion beam(IPIB) is the distribution of the energy density at the cross section. Aiming to solve the problem of traditional diagnostic methods for beam energy density, we measured the temperature distribution of the reverse side of target by infrared camera to develop the infrared diagnostic techniques of IPIB energy density distribution. For IPIB of energy density about 1 J/cm2 and pulse width about 100 ns, the error using this method is less than 5% and the spatial resolution achieves 1-2 mm. The method has the advantages of easy operation and low cost, it is an efficient prompt monitoring method for the IPIB energy density distribution.
2015,
27: 075003.
doi: 10.11884/HPLPB201527.075003
Abstract:
A compact air-core pulse transformer with an energy conversion efficiency of 50% was theoretically investigated. The transformer was employed to repetitively charge a small-sized solid state Marx modulator. A pulse forming network (PFN) was added to each stage of the Marx to lengthen the pulse width to several ten ns. By an in-depth analysis of the equivalent circuit of pulse transformer, the expressions for calculating the energy conversion efficiency, the peak of the secondary voltage, the peak and steepness of the primary current of the transformer were deduced in this paper. The calculation results were compared with the simulation ones by Pspice software. The analysis results indicate that the theoretical calculation of the primary voltage and current waveform were in accordance with the results of the simulative calculations. Therefore, the correctness of the theory in this paper was verified. Meanwhile, the structural parameters of the transformer with an energy conversion efficiency of 50% were obtained by theoretical calculation. The parameters will provide a theoretical guidance for the design and fabrication of the pulse transformer.
A compact air-core pulse transformer with an energy conversion efficiency of 50% was theoretically investigated. The transformer was employed to repetitively charge a small-sized solid state Marx modulator. A pulse forming network (PFN) was added to each stage of the Marx to lengthen the pulse width to several ten ns. By an in-depth analysis of the equivalent circuit of pulse transformer, the expressions for calculating the energy conversion efficiency, the peak of the secondary voltage, the peak and steepness of the primary current of the transformer were deduced in this paper. The calculation results were compared with the simulation ones by Pspice software. The analysis results indicate that the theoretical calculation of the primary voltage and current waveform were in accordance with the results of the simulative calculations. Therefore, the correctness of the theory in this paper was verified. Meanwhile, the structural parameters of the transformer with an energy conversion efficiency of 50% were obtained by theoretical calculation. The parameters will provide a theoretical guidance for the design and fabrication of the pulse transformer.
2015,
27: 075004.
doi: 10.11884/HPLPB201527.075004
Abstract:
Differential-output current loops (B-dot probes) were designed and calibrated to derive inner-MITL current in the PTS facility. The B-dots upper limiting frequency was 51.7 MHz in frequency response experiments, which was satisfactory for current measurement in our experiments. The B-dots were calibrated using a radial transmission line that was driven by an azimuthally symmetric current pulse. And then the B-dots were calibrated using a radial transmission line with a post-hole convolute feeding structure. The result indicates that the sensitivity of B-dots are consistent in the two calibration systems. The interference test and experiments with variable peak currents were performed to focus on B-dot linearity, and insulation, pressure exerted by magnetic fields, energy absorbing and related temperature rise of B-dot were analyzed in order to assess the validity of B-dot calibration. The results imply that the B-dots are valid for several mega-ampere current measurements. Also, it shows that outer-MITL current and inner-MITL current are self-consistent in PTS experiment.
Differential-output current loops (B-dot probes) were designed and calibrated to derive inner-MITL current in the PTS facility. The B-dots upper limiting frequency was 51.7 MHz in frequency response experiments, which was satisfactory for current measurement in our experiments. The B-dots were calibrated using a radial transmission line that was driven by an azimuthally symmetric current pulse. And then the B-dots were calibrated using a radial transmission line with a post-hole convolute feeding structure. The result indicates that the sensitivity of B-dots are consistent in the two calibration systems. The interference test and experiments with variable peak currents were performed to focus on B-dot linearity, and insulation, pressure exerted by magnetic fields, energy absorbing and related temperature rise of B-dot were analyzed in order to assess the validity of B-dot calibration. The results imply that the B-dots are valid for several mega-ampere current measurements. Also, it shows that outer-MITL current and inner-MITL current are self-consistent in PTS experiment.
2015,
27: 075005.
doi: 10.11884/HPLPB201527.075005
Abstract:
Three charging methods, the DC chopper, the invariable voltage and the step voltage were analyzed in this paper. They were compared from the work principle, facilitys guide line, efficiency and ripple. Then the simulation models were constituted. The theoretical derivation and simulation results show that the efficiency of the step voltage arrives 0.911, which is better than the 0.5 of the invariable voltage. The guideline for the step voltage is n times lower than that for the DC chopper and it can confine the current ripple in 16% or even better with no increasing in switch waste. The experiment was conducted on a multilevel hybrid energy storage swatch for step voltage method. The result matches the simulation result well. So we get conclusion that the step voltage is the best method for the multilevel hybrid energy storage device.
Three charging methods, the DC chopper, the invariable voltage and the step voltage were analyzed in this paper. They were compared from the work principle, facilitys guide line, efficiency and ripple. Then the simulation models were constituted. The theoretical derivation and simulation results show that the efficiency of the step voltage arrives 0.911, which is better than the 0.5 of the invariable voltage. The guideline for the step voltage is n times lower than that for the DC chopper and it can confine the current ripple in 16% or even better with no increasing in switch waste. The experiment was conducted on a multilevel hybrid energy storage swatch for step voltage method. The result matches the simulation result well. So we get conclusion that the step voltage is the best method for the multilevel hybrid energy storage device.
2015,
27: 075006.
doi: 10.11884/HPLPB201527.075006
Abstract:
Based on the fast semiconductor switch with high voltage and high power, PFN and the technology of the concentric and sameness space transfer, a modularity fast pulse trigger with many channels in-phase was designed. The above pulse trigger with a load of 50 can export two fast pulse trigger signals that is one signal with more than 20 V output voltage (four channels), less than 820 ps fall time, more than100 ns pulse width and another signal with more than 100 V output voltage (four channels), less than 1.4 ns fall time, more than100 ns pulse width, and with the exterior trigger, the jitter of the pulse trigger achieves 2 ns and the in-phase decentralization character of the pulse output achieves 36.6 ps. The experiment results of single exterior trigger and exterior trigger with 5 kHz repetitive frequency for the above modularity fast pulse trigger were given, and the experiment result validates the theory and method of the concentric and sameness space transfer.
Based on the fast semiconductor switch with high voltage and high power, PFN and the technology of the concentric and sameness space transfer, a modularity fast pulse trigger with many channels in-phase was designed. The above pulse trigger with a load of 50 can export two fast pulse trigger signals that is one signal with more than 20 V output voltage (four channels), less than 820 ps fall time, more than100 ns pulse width and another signal with more than 100 V output voltage (four channels), less than 1.4 ns fall time, more than100 ns pulse width, and with the exterior trigger, the jitter of the pulse trigger achieves 2 ns and the in-phase decentralization character of the pulse output achieves 36.6 ps. The experiment results of single exterior trigger and exterior trigger with 5 kHz repetitive frequency for the above modularity fast pulse trigger were given, and the experiment result validates the theory and method of the concentric and sameness space transfer.
2015,
27: 075101.
doi: 10.11884/HPLPB201527.075101
Abstract:
With the purpose of measuring small beam size of HLS Ⅱ after upgrade, a beam transverse size and emittance measurement system of HLS Ⅱ has been developed. This paper introduces briefly the principle of measuring beam transverse size using interferometry in visible light. It illustrates in detail the software system, hardware system and the image processing algorithm of the measurement system. In order to eliminate the background noise of CCD, a lookup table between the background noise of CCD and the beam intensity has been established. In conclusion, the experiment results are presented at multi-bunch mode. The measured beam horizontal size is 265 m and the measurement error is 5.78 m, and the beam vertical size is 114 m and the measurement error is 4.89 m.
With the purpose of measuring small beam size of HLS Ⅱ after upgrade, a beam transverse size and emittance measurement system of HLS Ⅱ has been developed. This paper introduces briefly the principle of measuring beam transverse size using interferometry in visible light. It illustrates in detail the software system, hardware system and the image processing algorithm of the measurement system. In order to eliminate the background noise of CCD, a lookup table between the background noise of CCD and the beam intensity has been established. In conclusion, the experiment results are presented at multi-bunch mode. The measured beam horizontal size is 265 m and the measurement error is 5.78 m, and the beam vertical size is 114 m and the measurement error is 4.89 m.
2015,
27: 075102.
doi: 10.11884/HPLPB201527.075102
Abstract:
A new waveguide-coupled prebuncher and a new beam phase cavity working at S-band are designed. For increasing the power capacity, the waveguide coupling mechanism is used instead of the traditional coaxial ring coupling for the prebuncher. An eccentric circle structure of the cavity is adopted to solve the problem of an asymmetric electrical field along the radial direction caused by the introduction of the waveguide coupling window, which improves the beam quality on high beam current. The measurement results of a coupling coefficient of 1.73, an unloaded quality factor of 2195 as well as a variable frequency range from 2 854.55 MHz to 2 856.9 MHz are got in the final prototype of prebuncher. For measuring the timing between beam and RF pulse in order to compensate the input power with the high beam current, a beam phase cavity is chosen to be the on-line equipment for the real-time measurement of beam phase. The beam phase cavity has a rotational symmetrical structure, and two coaxial coupling rings are used to extract the inducted signal from the beam, which will be used as the reference signal of the phase-controlling system. The prototype of beam phase cavity has a measurement result of an unloaded quality factor of 2392, a 3 dB bandwidth of 2.05 MHz as well as a variable frequency range from 2 805.45 MHz to 2 809.45 MHz. The measurement results match well with the simulation results.
A new waveguide-coupled prebuncher and a new beam phase cavity working at S-band are designed. For increasing the power capacity, the waveguide coupling mechanism is used instead of the traditional coaxial ring coupling for the prebuncher. An eccentric circle structure of the cavity is adopted to solve the problem of an asymmetric electrical field along the radial direction caused by the introduction of the waveguide coupling window, which improves the beam quality on high beam current. The measurement results of a coupling coefficient of 1.73, an unloaded quality factor of 2195 as well as a variable frequency range from 2 854.55 MHz to 2 856.9 MHz are got in the final prototype of prebuncher. For measuring the timing between beam and RF pulse in order to compensate the input power with the high beam current, a beam phase cavity is chosen to be the on-line equipment for the real-time measurement of beam phase. The beam phase cavity has a rotational symmetrical structure, and two coaxial coupling rings are used to extract the inducted signal from the beam, which will be used as the reference signal of the phase-controlling system. The prototype of beam phase cavity has a measurement result of an unloaded quality factor of 2392, a 3 dB bandwidth of 2.05 MHz as well as a variable frequency range from 2 805.45 MHz to 2 809.45 MHz. The measurement results match well with the simulation results.
2015,
27: 075103.
doi: 10.11884/HPLPB201527.075103
Abstract:
The temperature rise, caused by high power laser, would destroy the activation layer of the NEA GaAs photocathode. In this paper, the temperature rise is studied theoretically and experimentally. With some theoretical analysis, the thermal transfer between the NEA wafer and the puck is proved as the most important factors that affect the temperature. To the thermal transfer, the GaAs vacuum indium soldering chamber is built and the vacuum soldering technology is explored. Some comparative experiments with and without indium soldering are also presented in this paper. The results, both in the atmosphere and in vacuum, indicate that indium provides effective thermal contact between the GaAs cathode and the puck, enhancing the thermal transfer and slowing down the temperature rise. These studies increase the operational lifetime of NEA GaAs illuminated by several-watt laser more than 20 times eventually.
The temperature rise, caused by high power laser, would destroy the activation layer of the NEA GaAs photocathode. In this paper, the temperature rise is studied theoretically and experimentally. With some theoretical analysis, the thermal transfer between the NEA wafer and the puck is proved as the most important factors that affect the temperature. To the thermal transfer, the GaAs vacuum indium soldering chamber is built and the vacuum soldering technology is explored. Some comparative experiments with and without indium soldering are also presented in this paper. The results, both in the atmosphere and in vacuum, indicate that indium provides effective thermal contact between the GaAs cathode and the puck, enhancing the thermal transfer and slowing down the temperature rise. These studies increase the operational lifetime of NEA GaAs illuminated by several-watt laser more than 20 times eventually.
2015,
27: 075104.
doi: 10.11884/HPLPB201527.075104
Abstract:
A permanent magnet focused IH type drift tube linac (IH-DTL)cavity was designed for accelerating low energy proton. Using adaptive dimension adjustment, the beam phase at the center of every drift tube was adjusted to be equal to the set value. The IH-DTL designed in this paper has a length of 0.96 m and a shunt impedance of about 90 M/m, it can accelerate protons from 0.75 MeV to 2.5 MeV. The beam envelope in the IH-DTL was computed by the program TRACE3D. If the beam halo and errors were neglected, the beam loss can be controlled to be approximately 0.1% when the beam current is 50 mA.
A permanent magnet focused IH type drift tube linac (IH-DTL)cavity was designed for accelerating low energy proton. Using adaptive dimension adjustment, the beam phase at the center of every drift tube was adjusted to be equal to the set value. The IH-DTL designed in this paper has a length of 0.96 m and a shunt impedance of about 90 M/m, it can accelerate protons from 0.75 MeV to 2.5 MeV. The beam envelope in the IH-DTL was computed by the program TRACE3D. If the beam halo and errors were neglected, the beam loss can be controlled to be approximately 0.1% when the beam current is 50 mA.
2015,
27: 075105.
doi: 10.11884/HPLPB201527.075105
Abstract:
Focus spot drift of electron-beam seriously influences the radiation experimental efficiency of electronic devices. A simple method was introduced which could restrain the focus spot drift of electron-beam in the paper. A small stainless cathode was designed and experimented. The experimental results of small cathode were compared with the results of classical annular velvet cathode. It is shown that the probability of the spot stays at the center of anode is about 67%,and the probability of the spot stays at the circle area with diameter of 35 mm is about 100%. Focus spot drift was obviously restrained using the small stainless cathode, while the probability of the spot stays at the center of anode is only about 20%, and the probability of the spot stays at circle area with diameter of 40-60 mm is higher than 60% for the annular velvet cathode.
Focus spot drift of electron-beam seriously influences the radiation experimental efficiency of electronic devices. A simple method was introduced which could restrain the focus spot drift of electron-beam in the paper. A small stainless cathode was designed and experimented. The experimental results of small cathode were compared with the results of classical annular velvet cathode. It is shown that the probability of the spot stays at the center of anode is about 67%,and the probability of the spot stays at the circle area with diameter of 35 mm is about 100%. Focus spot drift was obviously restrained using the small stainless cathode, while the probability of the spot stays at the center of anode is only about 20%, and the probability of the spot stays at circle area with diameter of 40-60 mm is higher than 60% for the annular velvet cathode.
2015,
27: 076001.
doi: 10.11884/HPLPB201527.076001
Abstract:
A 44 common-grid pixelated CdZnTe detector with different pixel sizes is designed and fabricated using the CdZnTe crystal. By the spectra measurement combined with weighting potential and electric field simulation, the small pixel effect and guide effect in common-grid pixelated CdZnTe detector are investigated. Results show that the spectroscopic characteristics of lager pixels are degraded since the small pixel effect is not strong enough to remove the hole trailing. While the spectroscopic characteristics of smaller pixels are also degraded since the serious charge loss in volume and surface layer between pixels and common-grid. An optimal energy resolution of 3.80% FWHM at 662 keV(137Cs radiation source) is obtained from the 0.8 mm wide pixel. Excessive high bias voltage increases the surface leakage current between pixels and common-grid, which in turn degrades the spectroscopic characteristics. The optimal bias voltage is -60 V for 0.8 mm wide pixel.
A 44 common-grid pixelated CdZnTe detector with different pixel sizes is designed and fabricated using the CdZnTe crystal. By the spectra measurement combined with weighting potential and electric field simulation, the small pixel effect and guide effect in common-grid pixelated CdZnTe detector are investigated. Results show that the spectroscopic characteristics of lager pixels are degraded since the small pixel effect is not strong enough to remove the hole trailing. While the spectroscopic characteristics of smaller pixels are also degraded since the serious charge loss in volume and surface layer between pixels and common-grid. An optimal energy resolution of 3.80% FWHM at 662 keV(137Cs radiation source) is obtained from the 0.8 mm wide pixel. Excessive high bias voltage increases the surface leakage current between pixels and common-grid, which in turn degrades the spectroscopic characteristics. The optimal bias voltage is -60 V for 0.8 mm wide pixel.
2015,
27: 076002.
doi: 10.11884/HPLPB201527.076002
Abstract:
A novel radiochromic gel dosimeter was developed through dispersing nanovesicles self-assembled by diacetylene into the gel matrix. The vesicle morphology was observed through electron microscopy; The radiochromic gels were irradiated by CL-1000 UV crosslinker and their dosimetry performance was tested and studied. Results indicate that these radiochromic gels have good linear response to UV irradiation in the energy density range of 5~150 mJ/cm2. In addition, the radiochromic gels overcome the limitations of the existing gel dosimeter such as diffusion effect, post-radiation effect, and poor forming ability. Hence, the radiochromic diacetylene vesicle gel dosimeters developed could be generally applied to 3D dose distribution measurement with optical readout.
A novel radiochromic gel dosimeter was developed through dispersing nanovesicles self-assembled by diacetylene into the gel matrix. The vesicle morphology was observed through electron microscopy; The radiochromic gels were irradiated by CL-1000 UV crosslinker and their dosimetry performance was tested and studied. Results indicate that these radiochromic gels have good linear response to UV irradiation in the energy density range of 5~150 mJ/cm2. In addition, the radiochromic gels overcome the limitations of the existing gel dosimeter such as diffusion effect, post-radiation effect, and poor forming ability. Hence, the radiochromic diacetylene vesicle gel dosimeters developed could be generally applied to 3D dose distribution measurement with optical readout.
2015,
27: 076003.
doi: 10.11884/HPLPB201527.076003
Abstract:
The lifting device prototype is developed to realize the transportation of tungsten alloy balls. The tungsten alloy balls are new targets used in the accelerator driven subcritical system(ADS). The basic principle is the electromagnetic force of the solenoid. Controlling the power-on and power-off time of a group of solenoids can achieve the movement of magnetic field. The magnetic field acts on the targets to complete the transportation of alloy balls. The solenoid is the main component of the device and its structure should be beneficial to lifting the targets. Ansys Maxwell is used to analyze the distribution of magnetic field for solenoid to determine the structure of the solenoid. It is also used to accomplish simulation at different pulse width for each solenoid. Power-on time and power-off time of each solenoid and the number of solenoids working simultaneously are regulated to simulate the force of alloy ball. Based on the numerical analysis, the processing and experiments of the device prototype have been finished. The results show the device prototype has achieved the desired effect of tungsten slloy ball transportation.
The lifting device prototype is developed to realize the transportation of tungsten alloy balls. The tungsten alloy balls are new targets used in the accelerator driven subcritical system(ADS). The basic principle is the electromagnetic force of the solenoid. Controlling the power-on and power-off time of a group of solenoids can achieve the movement of magnetic field. The magnetic field acts on the targets to complete the transportation of alloy balls. The solenoid is the main component of the device and its structure should be beneficial to lifting the targets. Ansys Maxwell is used to analyze the distribution of magnetic field for solenoid to determine the structure of the solenoid. It is also used to accomplish simulation at different pulse width for each solenoid. Power-on time and power-off time of each solenoid and the number of solenoids working simultaneously are regulated to simulate the force of alloy ball. Based on the numerical analysis, the processing and experiments of the device prototype have been finished. The results show the device prototype has achieved the desired effect of tungsten slloy ball transportation.
2015,
27: 076004.
doi: 10.11884/HPLPB201527.076004
Abstract:
In the last decade a great effort has been made to develop the position-sensitive device for -ray imaging and pixel detectors, scintillation or semiconductor, have been widely used. Currently the the MeV -ray spectroscopy has been desired in many fields. Unfortunately, there is no existing -ray spectroscopy that performs perfectly in such energy range and some detector systems have been proposed for the purpose. As commonly used for pixel detectors, scintillating fibers have the advantage of that they may achieve both the spatial and energy resolution in detecting -rays. We simulate the electron spectrum produced in the fiber via Compton scattering mechanism only and energy deposition spectrum including the photoelectron and electron-positron pair creation mechanisms to the interactions with -ray photons. We can see that the spectrum might allow determining the energy of the incoming -rays, if the Compton edge of the spectrum can be determined. The results of the simulation also show that the energy resolution can be achieved about 10%, and the cross-talks affect little on energy resolution in the bundle configuration. For detecting -rays with energies in the range of several MeV, a fiber of radius of about a few centimeters needs to be used to achieve this resolution. These results suggest that the detector configuration might be used in achieving certain degree energy resolution in detecting -rays under certain circumstances. Since we choose the low mass material to achieve high probability of Compton scattering, another problem is that the detection efficiency for PSF in this energy range is quite low. It is about 15% or less. There exists a contradiction to obtain both well.
In the last decade a great effort has been made to develop the position-sensitive device for -ray imaging and pixel detectors, scintillation or semiconductor, have been widely used. Currently the the MeV -ray spectroscopy has been desired in many fields. Unfortunately, there is no existing -ray spectroscopy that performs perfectly in such energy range and some detector systems have been proposed for the purpose. As commonly used for pixel detectors, scintillating fibers have the advantage of that they may achieve both the spatial and energy resolution in detecting -rays. We simulate the electron spectrum produced in the fiber via Compton scattering mechanism only and energy deposition spectrum including the photoelectron and electron-positron pair creation mechanisms to the interactions with -ray photons. We can see that the spectrum might allow determining the energy of the incoming -rays, if the Compton edge of the spectrum can be determined. The results of the simulation also show that the energy resolution can be achieved about 10%, and the cross-talks affect little on energy resolution in the bundle configuration. For detecting -rays with energies in the range of several MeV, a fiber of radius of about a few centimeters needs to be used to achieve this resolution. These results suggest that the detector configuration might be used in achieving certain degree energy resolution in detecting -rays under certain circumstances. Since we choose the low mass material to achieve high probability of Compton scattering, another problem is that the detection efficiency for PSF in this energy range is quite low. It is about 15% or less. There exists a contradiction to obtain both well.
2015,
27: 076005.
doi: 10.11884/HPLPB201527.076005
Abstract:
Compton current is the main source that generates electromagnetic pulse. To improve the efficiency of calculation of Compton current induced by gamma rays in the atmosphere when the Monte Carlo method is adopted, based on the basic principle of Compton current induced by gamma rays，firstly, this paper calculates the attenuation of the Compton electron in the emitting direction, then a fitting function is figured out between the net electron current and the travel distance of the electron in a given range, finally the analytical and numerical method of calculation of the current density induced by mono-energy gamma rays in the atmosphere is given according to the formula of the differential Compton scattering cross section. The analytical and numerical results are compared with the results of the Monte Carlo calculation, the relative difference of the current densities is less than 10%, and the efficiency is increased by two orders of magnitude. The method provided in this paper can be applied in the fast computing of Compton current in the atmosphere.
Compton current is the main source that generates electromagnetic pulse. To improve the efficiency of calculation of Compton current induced by gamma rays in the atmosphere when the Monte Carlo method is adopted, based on the basic principle of Compton current induced by gamma rays，firstly, this paper calculates the attenuation of the Compton electron in the emitting direction, then a fitting function is figured out between the net electron current and the travel distance of the electron in a given range, finally the analytical and numerical method of calculation of the current density induced by mono-energy gamma rays in the atmosphere is given according to the formula of the differential Compton scattering cross section. The analytical and numerical results are compared with the results of the Monte Carlo calculation, the relative difference of the current densities is less than 10%, and the efficiency is increased by two orders of magnitude. The method provided in this paper can be applied in the fast computing of Compton current in the atmosphere.
2015,
27: 076006.
doi: 10.11884/HPLPB201527.076006
Abstract:
Researching the material performance under neutron irradiation requires accumulative neutron fluence rate which is an important parameter. Al alloy on the upper link chest as a key structural material of Swimming Pool Research Reactor-300(SPRR-300), goes through the whole life of reactor under high neutron irradiation. Hence, the alloy is full of research value. To get the accumulative fluence rate of reactor upper link chest during the whole life span of reactor operation, this paper proposes a solution, namely core merging equivalent calculation method, aiming to deal with the frequent core configuration changing and expanding rationally. Applying this method, we have acquired the accumulative neutron fluence rate and conducted the pertinent error analysis.
Researching the material performance under neutron irradiation requires accumulative neutron fluence rate which is an important parameter. Al alloy on the upper link chest as a key structural material of Swimming Pool Research Reactor-300(SPRR-300), goes through the whole life of reactor under high neutron irradiation. Hence, the alloy is full of research value. To get the accumulative fluence rate of reactor upper link chest during the whole life span of reactor operation, this paper proposes a solution, namely core merging equivalent calculation method, aiming to deal with the frequent core configuration changing and expanding rationally. Applying this method, we have acquired the accumulative neutron fluence rate and conducted the pertinent error analysis.
2015,
27: 079001.
doi: 10.11884/HPLPB201527.079001
Abstract:
The effect of pulse microwave irradiation on the reproductive system of animal and human as well as their offspring is a critical issue that causes interests. In present work, the parental rats were exposed to 2.71 GHz pulses microwave (field strength 48 kV/m, pulse width 750 ns, pulse number 2001, 20010, 20020, respectively), and the DNA damage during the spermatogenesis process, the sperm motility, the growth of the baby offspring, and the learning and memory ability of the adult offspring were studied by means of DNA staining, TUNEL staining, Elisa assay, sperm motility CASA detection, and water maze experiment. The experimental results show that the single irradiation on male rats affects their early spermatogenesis process rather than the sperm motility, while multi-times of irradiation decrease the sperm motility due to the accumulative effect. The growth of baby offspring is temporarily blocked, and the learning and memory ability also trends to be blocked when the parent rats receive the irradiation.
The effect of pulse microwave irradiation on the reproductive system of animal and human as well as their offspring is a critical issue that causes interests. In present work, the parental rats were exposed to 2.71 GHz pulses microwave (field strength 48 kV/m, pulse width 750 ns, pulse number 2001, 20010, 20020, respectively), and the DNA damage during the spermatogenesis process, the sperm motility, the growth of the baby offspring, and the learning and memory ability of the adult offspring were studied by means of DNA staining, TUNEL staining, Elisa assay, sperm motility CASA detection, and water maze experiment. The experimental results show that the single irradiation on male rats affects their early spermatogenesis process rather than the sperm motility, while multi-times of irradiation decrease the sperm motility due to the accumulative effect. The growth of baby offspring is temporarily blocked, and the learning and memory ability also trends to be blocked when the parent rats receive the irradiation.
2015,
27: 073003.
doi: 10.11884/HPLPB201527.073003
Abstract:
The mode controlling is a key process for designing an overmoded relativistic backward wave oscillator. Based on the numerical analysis and particle-in-cell simulation, the common-frequency high-order mode competition and output mode controlling of an overmoded RBWO with a wide-gap reflector are studied. It indicates that the high-order mode is mainly originated from the reciprocal mode conversion and excitation in the RF structures, which can be restrained and controlled by optimizing the sensitive parameters, reducing the conversion factor from fundamental mode to high-order one and adjusting the RF phases of different modes that are reflected back to the beam-wave interaction region from the cathode plate. Finally, a beam-wave conversion efficiency of 40% and an output TM01 mode purity of 98% are obtained at frequency of 9.87 GHz from the concerned overmoded RBWO.
The mode controlling is a key process for designing an overmoded relativistic backward wave oscillator. Based on the numerical analysis and particle-in-cell simulation, the common-frequency high-order mode competition and output mode controlling of an overmoded RBWO with a wide-gap reflector are studied. It indicates that the high-order mode is mainly originated from the reciprocal mode conversion and excitation in the RF structures, which can be restrained and controlled by optimizing the sensitive parameters, reducing the conversion factor from fundamental mode to high-order one and adjusting the RF phases of different modes that are reflected back to the beam-wave interaction region from the cathode plate. Finally, a beam-wave conversion efficiency of 40% and an output TM01 mode purity of 98% are obtained at frequency of 9.87 GHz from the concerned overmoded RBWO.
