The trigger characteristics of a multi-gap gas switch with double insulating layers,a square-groove electrode supporter and a UV pre-ionizing structure are investigated aided by a high sensitivity fiber-bundle array d...The trigger characteristics of a multi-gap gas switch with double insulating layers,a square-groove electrode supporter and a UV pre-ionizing structure are investigated aided by a high sensitivity fiber-bundle array detector, a UV fiber detector, and a framing camera, in addition to standard electrical diagnostics. The fiber-bundle-array detector is used to track the turn-on sequence of each electrode gap at a timing precision of 0.6 ns. Each fiber bundle, including five fibers with different azimuth angles, aims at the whole emitting area of each electrode gap and is fed to a photomultiplier tube. The UV fiber detector with a spectrum response of 260-320 nm,including a fused-quartz fiber of 200 μm in diameter and a solar-blinded photomultiplier tube, is adopted to study the effect of UV pre-ionizing on trigger characteristics. The framing camera,with a capacity of 4 frames per shot and an exposure time of 5 ns, is employed to capture the evolution of channel arcs. Based on the turn-on light signal of each electrode gap, the breakdown delay is divided into statistical delay and formative delay. A decrease in both of them, a smaller switch jitter and more channel arcs are observed with lower gas pressure. An increase in trigger voltage can reduce the statistical delay and its jitter, while higher trigger voltage has a relatively small influence on the formative delay and the number of channel arcs. With the UV pre-ionizing structure at 0.24 MPa gas pressure and 60 kV trigger voltage, the statistical delay and its jitter can be reduced by 1.8 ns and 0.67 ns, while the formative delay and its jitter can only be reduced by 0.5 ns and 0.25 ns.展开更多
Optical diagnostics are essential in monitoring the progression of plasma in high-energy-density physics research.The abrupt transitions in plasma evolution,whether caused by laser irradiation or hydrodynamic instabil...Optical diagnostics are essential in monitoring the progression of plasma in high-energy-density physics research.The abrupt transitions in plasma evolution,whether caused by laser irradiation or hydrodynamic instabilities,cannot be accurately distinguished using only two-dimensional[2D]gated detectors or a streak camera individually.In this paper,we introduce a hybrid diagnostic system that combines a streak camera and gated detectors.This innovative approach enables us to measure both the plasma density evolution and 2D morphology simultaneously.These advanced diagnostics have been utilized in recent laboratory astrophysics experiments,effectively capturing the plasma flow density distribution and flow velocity.展开更多
Based on machine learning models,an approach for the type recognition of oxygenated additives(ester isomers,i.e.,methyl butyrate,methyl crotonate,ethyl acrylate,and ethyl acrylate)via optical diagnostics was proposed....Based on machine learning models,an approach for the type recognition of oxygenated additives(ester isomers,i.e.,methyl butyrate,methyl crotonate,ethyl acrylate,and ethyl acrylate)via optical diagnostics was proposed.By utilizing optical diagnostic methods flame features were extracted,and three models including random forest(RF),artificial neural network(ANN),and support vector machine(SVM),were employed to establish the relationship between flame images and oxygenated additives.Moreover,the impact of multiple factors on model performance,including image compression,dataset size,and feature number was also investigated.The images of flame obtained from inverse diffusion flame under four different oxygenated additives and various combustion conditions were used as examples to examine the effectiveness of the proposed approach.Results indicated that the accuracy of the recognition of ester isomers by the proposed approach exceeded 90%.Furthermore,it is observed that image compression had minimal impact on prediction accuracy but significantly reduced processing time.Different types of features contributed to predicting the type of ester isomers variously,and all models exhibited improved accuracy with an increased number of features.The number of samples significantly affected model accuracy.The investigation of feature missing and insufficient training samples suggested that ANN and RF models were more suitable for cases with many missing features,while SVM was more suitable for dealing with small samples.展开更多
Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentati...Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentation instability in high-density region induces the local density modification. Large-scale toroidal magnetic fields confine plasma expansion in the transverse direction, resulting in the formation of a plasma jet. The plasma expansion along the target normal direction is found to scale as t1/2.展开更多
The optical system of the electron cyclotron emission imaging diagnostics on the HL-2A tokamak has been optimized in both the narrow zoom pattern and the wide zoom pattern. The two main features of the improved optica...The optical system of the electron cyclotron emission imaging diagnostics on the HL-2A tokamak has been optimized in both the narrow zoom pattern and the wide zoom pattern. The two main features of the improved optical system are（1） larger coverage of the measurement region in the plasma and（2） a flatter imaging surface. The new optics has good focal characteristics over the whole plasma cross section. The curvature of the field of the image surface（ΔR between the core channel and the edge channel） is within 5.3 cm in the narrow zoom pattern and 6.7 cm in the wide zoom pattern after optimization, whereas the values with the present optics were 23 cm in the narrow zoom pattern and 15 cm in the wide zoom pattern. The optics will be fabricated, tested and installed on the HL-2A tokamak before the next experimental campaign.展开更多
To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future tokamak, a D_α band symmetric visible light diagnostic system w...To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future tokamak, a D_α band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak(EAST). This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%.The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT(Equilibrium Fitting) results. This underscores the system's superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.展开更多
Weibel instability is a promising candidate mechanism for collisionless shock formation in astrophysical systems.Capturing the underlying physics of Weibel instability will help us to understand the astrophysical shoc...Weibel instability is a promising candidate mechanism for collisionless shock formation in astrophysical systems.Capturing the underlying physics of Weibel instability will help us to understand the astrophysical shock formation,magnetic field generation and amplification,particle acceleration,and so on.Laboratory astrophysics,provides a new way to study these microphysics in controlled conditions.At Shenguang-Ⅱlaser facility,the interpenetrating plasma flows are generated by eight laser beams irradiating a pair of opposing foils to mimic the supernova explosion and the ejecta sweeping up the surrounding medium.Evolution of collisionless interpenetrating plasma flows is observed using optical diagnostics.Filamentary structures appear in the interaction region and the associated magnetic strength is measured about 40 T.Theoretical analysis and simulations indicate that these characteristics are induced by nonlinear Weibel instability.展开更多
An introduction to the basics of spectral imaging as applied to biological tissues is presented.An example of a spectral image of a face is used to demonstrate the data and spectral analysis that specify the melanin c...An introduction to the basics of spectral imaging as applied to biological tissues is presented.An example of a spectral image of a face is used to demonstrate the data and spectral analysis that specify the melanin content(M),blood content(B),tissue oxygen saturation(S),water content(W),fraction of scattering due to Rayleigh scattering(f)and due to Mie scattering(1−f),and the reduced scattering coefficient at 500-nm wavelength(µs 500 nm).The sensitivity of reflectance spectra to variation in the various parameters is illustrated.展开更多
The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fibe...The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fiber laser is an effective method that can recover optical properties of the mirror surface. The possibility of cleaning metallic mirrors from films with complex composition by pulsed radiation from a fiber laser has been experimentally researched. It has been shown that the high initial reflection characteristics of optical elements can be recovered by choosing regimes of radiation effect on the deposited surface. Efficient cleaning is ensured by radiation with the power density of less than 107 W/cm2. At this relatively low power density, pollutions are removed in a solid phase and the thermal effect on the mirror is insignificant. Preliminary experiments of the metal mirrors cleaning by fiber laser radiation have demonstrated the possibility of hardware implementation techniques.展开更多
The magnetoplasmadynamic thruster(MPDT) is characterized by its high specific impulse and substantial thrust density, making it a promising propulsion system for deep space exploration missions. In both laboratory exp...The magnetoplasmadynamic thruster(MPDT) is characterized by its high specific impulse and substantial thrust density, making it a promising propulsion system for deep space exploration missions. In both laboratory experiments and practical applications, cathode ablation has emerged as a critical concern. An optical diagnostic approach based on monochromatic radiation temperature measurement, utilizing plume emission spectra and the selection of an appropriate test band, has been successfully employed. This method provides an accurate temperature distribution across the cathode surface, offering a novel testing technique for the optimization and evaluation of magnetic plasma thruster designs.展开更多
A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installe...A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installed along the pipeline acting as a sensor, The experiments show that the cable swells when exposed to oil and induced additional bending losses inside the fiber, and the optical attenuation of the fiber coated by a thin skin with periodical hardness is sensitive to deformation and vibration caused by oil leakage, tampering, or mechanical impact. The region where the additional attenuation occurred is detected and located by DOFS based on OTDR, the types of pipeline accidents are identified according to the characteristics of transmitted optical power received by an optical power meter, Another prototype of DOFS based on a forward traveling frequency-modulated continuous-wave （FMCW） is also proposed to monitor pipeline. The advantages and disadvantages of DOFSs based on OTDR and FMCW are discussed. The experiments show that DOFSs are capable of detecting and locating distant oil pipeline leakages and damages in real time with an estimated precision of ten meters over tens of kilometers.展开更多
The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the ...The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the behavior in plasma.In this paper,a glass vacuum chamber and a pair of plate electrodes were designed and fabricated,using 13.56 MHz radio frequency（RF）discharge technology to ionize the working gas of Ar.This discharge was mathematically described with equivalent circuit model.The discharge voltage and current of the plasma were measured atdifferent pressures and different powers.Based on the capacitively coupled homogeneous discharge model,the equivalent circuit and the analytical formula were established.The plasma density and temperature were calculated by using the equivalent impedance principle and energy balance equation.The experimental results show that when RF discharge power is 50–300 W and pressure is 25–250 Pa,the average electron temperature is about 1.7–2.1 e V and the average electron density is about 0.5？×10^17–3.6？×10^17m^-3.Agreement was found when the results were compared to those given by optical emission spectroscopy and COMSOL simulation.展开更多
AIM： To evaluate and compare the diagnostic capabilities of peripapillary retinal nerve fiber layer（p-RNFL） parameters of Spectralis optical coherence tomography（OCT） versus Stratus OCT to detect glaucoma in pati...AIM： To evaluate and compare the diagnostic capabilities of peripapillary retinal nerve fiber layer（p-RNFL） parameters of Spectralis optical coherence tomography（OCT） versus Stratus OCT to detect glaucoma in patients with high myopia. METHODS： This is a retrospective, cross-sectional study. Sixty highly myopic eyes of 60 patients were enrolled, with 30 eyes in the glaucoma group and 30 eyes in the control group. All eyes received peripapillary imaging of the optic disc using Stratus and Spectralis OCT. Areas under the receiver operating characteristic curve（AUROC） and the sensitivity at specificity of 〉80% and 〉95% for p-RNFL parameters obtained using the two devices to diagnose glaucoma were analysed and compared. RESULTS： In Spectralis OCT, p-RNFL thickness parameters with the largest AUROC were the temporal-inferior sector（0.974） and the inferior quadrant（0.951）, whereas in Stratus OCT, the best parameters were the 7-o＇clock sector（0.918） and the inferior quadrant（0.918）. Compared to the Stratus OCT parameters, the Spectralis OCT parameters demonstrated generally higher AUROC; however, the difference was not statistically significant. CONCLUSION： The best p-RNFL parameters for diagnosing glaucoma in patients with high myopia were the temporal-inferior sector on Spectralis OCT and the 7-o＇clock sector on Stratus OCT. There were no significant differences between the AUROCs for Spectralis OCT and Stratus OCT, which suggest that the glaucoma diagnostic capabilities of these two devices in patients with high myopia are similar.展开更多
The optical noninvasive diagnostic of characteristic of silicon semiconductor devices by using a InGaAsP/InP semiconductor laser as an optical probe is reported. The principle of experimental method is based on the de...The optical noninvasive diagnostic of characteristic of silicon semiconductor devices by using a InGaAsP/InP semiconductor laser as an optical probe is reported. The principle of experimental method is based on the dependence of the optical refractive index on the carrier charge density in the active region of devices and detection of variation of refractive index by two laser beam interferometric techniques.展开更多
The increasingly stringent emission regulations and fuel consumption requirements have elevated the demands of internal combustion engines with higher fuel efficiency and lower emissions.It has been widely demonstrate...The increasingly stringent emission regulations and fuel consumption requirements have elevated the demands of internal combustion engines with higher fuel efficiency and lower emissions.It has been widely demonstrated that fash boiling spray can generate shorter and wider spray with improved atomization and evaporation to promote a better air-fuel mixing process.In this study,macroscopic(far-field)spray morphologies and primary breakup(near-field)characteristics of a two-hole gasoline direct injection injector are investigated under non-flash boiling and flash boiling conditions.High speed macroscopic and microscopic imaging was used to capture the overall spray structure and near-field characteristics,respectively.N-Hexane is used as the test fuel with the injection pressure ranging from 10 MPa up to 40 MPa.For sub-cooled liquid fuel sprays,increasing fuel pressure contributes to enhanced fuel atomization and evaporation.Evident collapses occurred under fare flash boiling conditions,and higher injection pressure weakened this phenomenon since the spray cone angle decreased due to a higher injection velocity.展开更多
A new integrated technique for fast and accurate measurement of the quasi-optics, especially for the microwave/millimeter wave diagnostic systems of fusion plasma, has been developed. Using the LabVIEW-based comprehen...A new integrated technique for fast and accurate measurement of the quasi-optics, especially for the microwave/millimeter wave diagnostic systems of fusion plasma, has been developed. Using the LabVIEW-based comprehensive scanning system, we can realize not only automatic but also fast and accurate measurement, which will help to eliminate the effects of temperature drift and standing wave/multi-reflection. With the Matlab-based asymmetric two-dimensional Gaussian fitting method, all the desired parameters of the microwave beam can be obtained. This technique can be used in the design and testing of microwave diagnostic systems such as reflectometers and the electron cyclotron emission imaging diagnostic systems of the Experimental Advanced Superconducting Tokamak.展开更多
A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy（OES）.The s...A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy（OES）.The samples of AISI 304 are nitrided for different treatment times under optimum conditions.The treated samples were analyzed by X-ray diffraction（XRD） to explore the changes induced in the crystallographic structure.The XRD pattern confirmed the formation of iron and chromium nitrides arising from incorporation of nitrogen as an interstitial solid solution in the iron lattice.A Vickers microhardness tester was used to evaluate the surface hardness as a function of treatment time（h）.The results showed clear evidence of improved surface hardness and a substantial amount of decrease in the treatment time compared with the previous work.展开更多
Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goa...Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goal is to provide a systematic assessment on combustion characteristics in diluted regimes for its application to environmentally-friendly approaches such as biogas combustion and exhanst-gas recirculation technology. Two main diluting species, N2 and CO2, are tested at various dilution rates. The results obtained by means of optical diagnostics show that five main flame regimes can be observed for Nz-diluted flames by changing excess air and dilution rate. CO2-diluted flames follow the same pattern evolution except that all the domains are shifted to lower excess air. Both N2 and CO2 dilution affect the lean blow- out （LBO） limits negatively. This behavior can be counter-balanced by reactant preheating which is able to broaden the flammability domain of the diluted flames. Flame reactivity is degraded by increasing dilution rate. Meanwhile, flames are thickened in the presence of both diluting species. NOx emissions are significantly reduced with dilution and proved to be relevant to flame stability diagrams： slight augmentation in NOx emission profiles is related to transitional flame states where instability occurs. Although dilution results in increase in CO emissions at certain levels, optimal dilution rates can still be proposed to achieve an ideal compromise.展开更多
Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples w...Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction （XRD） to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase （TN） owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth （μm）. The results showed clear evidence of surface changes with substantial increase in surface hardness.展开更多
This paper first demonstrates second-harmonic generation （SHG） in the intact cell nucleus, which acts as an optical indicator of DNA malignancy in prostate glandular epithelial cells. Within a scanning region of 2.7...This paper first demonstrates second-harmonic generation （SHG） in the intact cell nucleus, which acts as an optical indicator of DNA malignancy in prostate glandular epithelial cells. Within a scanning region of 2.7 μm×2.7μm in cell nuclei, SHG signals produced from benign prostatic hyperplasia （BPH） and prostate carcinoma （PC） tissues （mouse model C57BL/6） have been investigated. Statistical analyses （t test） of a total of 405 measurements （204 nuclei from BPH and 201 nuclei from PC） show that SHG signals from BPH and PC have a distinct difference （p 〈 0.05）, suggesting a potential optical method of revealing very early malignancy in prostate glandular epithelial cells based upon induced biochemical and/or biophysical modifications in DNA.展开更多
基金supported by National Natural Science Foundation of China(No.11105109)
文摘The trigger characteristics of a multi-gap gas switch with double insulating layers,a square-groove electrode supporter and a UV pre-ionizing structure are investigated aided by a high sensitivity fiber-bundle array detector, a UV fiber detector, and a framing camera, in addition to standard electrical diagnostics. The fiber-bundle-array detector is used to track the turn-on sequence of each electrode gap at a timing precision of 0.6 ns. Each fiber bundle, including five fibers with different azimuth angles, aims at the whole emitting area of each electrode gap and is fed to a photomultiplier tube. The UV fiber detector with a spectrum response of 260-320 nm,including a fused-quartz fiber of 200 μm in diameter and a solar-blinded photomultiplier tube, is adopted to study the effect of UV pre-ionizing on trigger characteristics. The framing camera,with a capacity of 4 frames per shot and an exposure time of 5 ns, is employed to capture the evolution of channel arcs. Based on the turn-on light signal of each electrode gap, the breakdown delay is divided into statistical delay and formative delay. A decrease in both of them, a smaller switch jitter and more channel arcs are observed with lower gas pressure. An increase in trigger voltage can reduce the statistical delay and its jitter, while higher trigger voltage has a relatively small influence on the formative delay and the number of channel arcs. With the UV pre-ionizing structure at 0.24 MPa gas pressure and 60 kV trigger voltage, the statistical delay and its jitter can be reduced by 1.8 ns and 0.67 ns, while the formative delay and its jitter can only be reduced by 0.5 ns and 0.25 ns.
基金supported by the Chinese Academy of Sciences Youth Interdisciplinary Teamthe National Natural Science Foundation of China(Nos.12473099 and 11873061)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA25030500,XDA25030100,XDA25030300,XDA25010100,XDA25010300,and XDA25020101)the National Key R&D Program of China(No.2022YFA1603204)。
文摘Optical diagnostics are essential in monitoring the progression of plasma in high-energy-density physics research.The abrupt transitions in plasma evolution,whether caused by laser irradiation or hydrodynamic instabilities,cannot be accurately distinguished using only two-dimensional[2D]gated detectors or a streak camera individually.In this paper,we introduce a hybrid diagnostic system that combines a streak camera and gated detectors.This innovative approach enables us to measure both the plasma density evolution and 2D morphology simultaneously.These advanced diagnostics have been utilized in recent laboratory astrophysics experiments,effectively capturing the plasma flow density distribution and flow velocity.
基金supported by the National Natural Science Foundation of China(Grant Nos.52076110,52376115,and 52106160)。
文摘Based on machine learning models,an approach for the type recognition of oxygenated additives(ester isomers,i.e.,methyl butyrate,methyl crotonate,ethyl acrylate,and ethyl acrylate)via optical diagnostics was proposed.By utilizing optical diagnostic methods flame features were extracted,and three models including random forest(RF),artificial neural network(ANN),and support vector machine(SVM),were employed to establish the relationship between flame images and oxygenated additives.Moreover,the impact of multiple factors on model performance,including image compression,dataset size,and feature number was also investigated.The images of flame obtained from inverse diffusion flame under four different oxygenated additives and various combustion conditions were used as examples to examine the effectiveness of the proposed approach.Results indicated that the accuracy of the recognition of ester isomers by the proposed approach exceeded 90%.Furthermore,it is observed that image compression had minimal impact on prediction accuracy but significantly reduced processing time.Different types of features contributed to predicting the type of ester isomers variously,and all models exhibited improved accuracy with an increased number of features.The number of samples significantly affected model accuracy.The investigation of feature missing and insufficient training samples suggested that ANN and RF models were more suitable for cases with many missing features,while SVM was more suitable for dealing with small samples.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 19854001 &19825110) the National High-Tech IGF Committee, the Laboratory for Laser Fusion of China Academy of Engineering Physics the Pre-research Foundation of
文摘Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentation instability in high-density region induces the local density modification. Large-scale toroidal magnetic fields confine plasma expansion in the transverse direction, resulting in the formation of a plasma jet. The plasma expansion along the target normal direction is found to scale as t1/2.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB104000)
文摘The optical system of the electron cyclotron emission imaging diagnostics on the HL-2A tokamak has been optimized in both the narrow zoom pattern and the wide zoom pattern. The two main features of the improved optical system are（1） larger coverage of the measurement region in the plasma and（2） a flatter imaging surface. The new optics has good focal characteristics over the whole plasma cross section. The curvature of the field of the image surface（ΔR between the core channel and the edge channel） is within 5.3 cm in the narrow zoom pattern and 6.7 cm in the wide zoom pattern after optimization, whereas the values with the present optics were 23 cm in the narrow zoom pattern and 15 cm in the wide zoom pattern. The optics will be fabricated, tested and installed on the HL-2A tokamak before the next experimental campaign.
基金supported by the National MCF Energy R&D Program of China (Nos. 2018YFE0302103 and 2018YFE 0302100)National Natural Science Foundation of China (Nos. 12205195 and 11975277)。
文摘To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future tokamak, a D_α band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak(EAST). This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%.The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT(Equilibrium Fitting) results. This underscores the system's superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1603200 and 2022YFA1603204)the Fund from the Chinese Academy of Sciences Youth Interdisciplinary Team(Grant No.JCTD2022-05)+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciences,the National Natural Science Foundation of China(Grant Nos.11873061 and 12473099)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA25030500,XDA25010100,and XDA25030200)。
文摘Weibel instability is a promising candidate mechanism for collisionless shock formation in astrophysical systems.Capturing the underlying physics of Weibel instability will help us to understand the astrophysical shock formation,magnetic field generation and amplification,particle acceleration,and so on.Laboratory astrophysics,provides a new way to study these microphysics in controlled conditions.At Shenguang-Ⅱlaser facility,the interpenetrating plasma flows are generated by eight laser beams irradiating a pair of opposing foils to mimic the supernova explosion and the ejecta sweeping up the surrounding medium.Evolution of collisionless interpenetrating plasma flows is observed using optical diagnostics.Filamentary structures appear in the interaction region and the associated magnetic strength is measured about 40 T.Theoretical analysis and simulations indicate that these characteristics are induced by nonlinear Weibel instability.
基金the National Institutes of Health(RO1-HL084013).
文摘An introduction to the basics of spectral imaging as applied to biological tissues is presented.An example of a spectral image of a face is used to demonstrate the data and spectral analysis that specify the melanin content(M),blood content(B),tissue oxygen saturation(S),water content(W),fraction of scattering due to Rayleigh scattering(f)and due to Mie scattering(1−f),and the reduced scattering coefficient at 500-nm wavelength(µs 500 nm).The sensitivity of reflectance spectra to variation in the various parameters is illustrated.
文摘The development of cleaning optics and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The cleaning of optical surface by pulsed radiation from a fiber laser is an effective method that can recover optical properties of the mirror surface. The possibility of cleaning metallic mirrors from films with complex composition by pulsed radiation from a fiber laser has been experimentally researched. It has been shown that the high initial reflection characteristics of optical elements can be recovered by choosing regimes of radiation effect on the deposited surface. Efficient cleaning is ensured by radiation with the power density of less than 107 W/cm2. At this relatively low power density, pollutions are removed in a solid phase and the thermal effect on the mirror is insignificant. Preliminary experiments of the metal mirrors cleaning by fiber laser radiation have demonstrated the possibility of hardware implementation techniques.
文摘The magnetoplasmadynamic thruster(MPDT) is characterized by its high specific impulse and substantial thrust density, making it a promising propulsion system for deep space exploration missions. In both laboratory experiments and practical applications, cathode ablation has emerged as a critical concern. An optical diagnostic approach based on monochromatic radiation temperature measurement, utilizing plume emission spectra and the selection of an appropriate test band, has been successfully employed. This method provides an accurate temperature distribution across the cathode surface, offering a novel testing technique for the optimization and evaluation of magnetic plasma thruster designs.
基金This project is supported by R&D Foundation of National Petroleum Corporation (CNPC) of China(No.2001411-4).
文摘A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installed along the pipeline acting as a sensor, The experiments show that the cable swells when exposed to oil and induced additional bending losses inside the fiber, and the optical attenuation of the fiber coated by a thin skin with periodical hardness is sensitive to deformation and vibration caused by oil leakage, tampering, or mechanical impact. The region where the additional attenuation occurred is detected and located by DOFS based on OTDR, the types of pipeline accidents are identified according to the characteristics of transmitted optical power received by an optical power meter, Another prototype of DOFS based on a forward traveling frequency-modulated continuous-wave （FMCW） is also proposed to monitor pipeline. The advantages and disadvantages of DOFSs based on OTDR and FMCW are discussed. The experiments show that DOFSs are capable of detecting and locating distant oil pipeline leakages and damages in real time with an estimated precision of ten meters over tens of kilometers.
基金supported by National Natural Science Foundation of China(Grant No.61378037)the Fundamental Research Funds for the Central Universities(Nos.2013B33614,2017B15214)+1 种基金the Research Funds of Innovation and Entrepreneurship Education Reform for Chinese Universities(No.16CCJG01Z004)the Changzhou Science and Technology Program(No.CJ20160027)
文摘The capacitively coupled radio frequency（CCRF）plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the behavior in plasma.In this paper,a glass vacuum chamber and a pair of plate electrodes were designed and fabricated,using 13.56 MHz radio frequency（RF）discharge technology to ionize the working gas of Ar.This discharge was mathematically described with equivalent circuit model.The discharge voltage and current of the plasma were measured atdifferent pressures and different powers.Based on the capacitively coupled homogeneous discharge model,the equivalent circuit and the analytical formula were established.The plasma density and temperature were calculated by using the equivalent impedance principle and energy balance equation.The experimental results show that when RF discharge power is 50–300 W and pressure is 25–250 Pa,the average electron temperature is about 1.7–2.1 e V and the average electron density is about 0.5？×10^17–3.6？×10^17m^-3.Agreement was found when the results were compared to those given by optical emission spectroscopy and COMSOL simulation.
基金Supported by Kaohsiung Chang Gung Memorial Hospital,Kaohsiung,Taiwan,China(No.CMRPG8C0541)
文摘AIM： To evaluate and compare the diagnostic capabilities of peripapillary retinal nerve fiber layer（p-RNFL） parameters of Spectralis optical coherence tomography（OCT） versus Stratus OCT to detect glaucoma in patients with high myopia. METHODS： This is a retrospective, cross-sectional study. Sixty highly myopic eyes of 60 patients were enrolled, with 30 eyes in the glaucoma group and 30 eyes in the control group. All eyes received peripapillary imaging of the optic disc using Stratus and Spectralis OCT. Areas under the receiver operating characteristic curve（AUROC） and the sensitivity at specificity of 〉80% and 〉95% for p-RNFL parameters obtained using the two devices to diagnose glaucoma were analysed and compared. RESULTS： In Spectralis OCT, p-RNFL thickness parameters with the largest AUROC were the temporal-inferior sector（0.974） and the inferior quadrant（0.951）, whereas in Stratus OCT, the best parameters were the 7-o＇clock sector（0.918） and the inferior quadrant（0.918）. Compared to the Stratus OCT parameters, the Spectralis OCT parameters demonstrated generally higher AUROC; however, the difference was not statistically significant. CONCLUSION： The best p-RNFL parameters for diagnosing glaucoma in patients with high myopia were the temporal-inferior sector on Spectralis OCT and the 7-o＇clock sector on Stratus OCT. There were no significant differences between the AUROCs for Spectralis OCT and Stratus OCT, which suggest that the glaucoma diagnostic capabilities of these two devices in patients with high myopia are similar.
文摘The optical noninvasive diagnostic of characteristic of silicon semiconductor devices by using a InGaAsP/InP semiconductor laser as an optical probe is reported. The principle of experimental method is based on the dependence of the optical refractive index on the carrier charge density in the active region of devices and detection of variation of refractive index by two laser beam interferometric techniques.
基金the National Natural Science Foundation of China(No.52006140)。
文摘The increasingly stringent emission regulations and fuel consumption requirements have elevated the demands of internal combustion engines with higher fuel efficiency and lower emissions.It has been widely demonstrated that fash boiling spray can generate shorter and wider spray with improved atomization and evaporation to promote a better air-fuel mixing process.In this study,macroscopic(far-field)spray morphologies and primary breakup(near-field)characteristics of a two-hole gasoline direct injection injector are investigated under non-flash boiling and flash boiling conditions.High speed macroscopic and microscopic imaging was used to capture the overall spray structure and near-field characteristics,respectively.N-Hexane is used as the test fuel with the injection pressure ranging from 10 MPa up to 40 MPa.For sub-cooled liquid fuel sprays,increasing fuel pressure contributes to enhanced fuel atomization and evaporation.Evident collapses occurred under fare flash boiling conditions,and higher injection pressure weakened this phenomenon since the spray cone angle decreased due to a higher injection velocity.
基金supported by National Natural Science Foundation of China(Grant Nos.10990211,11475173)the ITER Domestic Program of China(Grant Nos.2013GB106002,2014GB109002)
文摘A new integrated technique for fast and accurate measurement of the quasi-optics, especially for the microwave/millimeter wave diagnostic systems of fusion plasma, has been developed. Using the LabVIEW-based comprehensive scanning system, we can realize not only automatic but also fast and accurate measurement, which will help to eliminate the effects of temperature drift and standing wave/multi-reflection. With the Matlab-based asymmetric two-dimensional Gaussian fitting method, all the desired parameters of the microwave beam can be obtained. This technique can be used in the design and testing of microwave diagnostic systems such as reflectometers and the electron cyclotron emission imaging diagnostic systems of the Experimental Advanced Superconducting Tokamak.
基金supported by QAU URF,Pakistan Science Foundation(PSF)Project No.PSF/RES/Phys(152),HEC Project 20-2002(R&D)and HEC Project for Plasma Physics Laboratory Gomal University
文摘A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy（OES）.The samples of AISI 304 are nitrided for different treatment times under optimum conditions.The treated samples were analyzed by X-ray diffraction（XRD） to explore the changes induced in the crystallographic structure.The XRD pattern confirmed the formation of iron and chromium nitrides arising from incorporation of nitrogen as an interstitial solid solution in the iron lattice.A Vickers microhardness tester was used to evaluate the surface hardness as a function of treatment time（h）.The results showed clear evidence of improved surface hardness and a substantial amount of decrease in the treatment time compared with the previous work.
基金Project supported by the China Scholarship Council
文摘Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goal is to provide a systematic assessment on combustion characteristics in diluted regimes for its application to environmentally-friendly approaches such as biogas combustion and exhanst-gas recirculation technology. Two main diluting species, N2 and CO2, are tested at various dilution rates. The results obtained by means of optical diagnostics show that five main flame regimes can be observed for Nz-diluted flames by changing excess air and dilution rate. CO2-diluted flames follow the same pattern evolution except that all the domains are shifted to lower excess air. Both N2 and CO2 dilution affect the lean blow- out （LBO） limits negatively. This behavior can be counter-balanced by reactant preheating which is able to broaden the flammability domain of the diluted flames. Flame reactivity is degraded by increasing dilution rate. Meanwhile, flames are thickened in the presence of both diluting species. NOx emissions are significantly reduced with dilution and proved to be relevant to flame stability diagrams： slight augmentation in NOx emission profiles is related to transitional flame states where instability occurs. Although dilution results in increase in CO emissions at certain levels, optimal dilution rates can still be proposed to achieve an ideal compromise.
基金supported partially by the Higher Education Commission Research Project for Plasma Physics of Pakistan
文摘Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction （XRD） to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase （TN） owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth （μm）. The results showed clear evidence of surface changes with substantial increase in surface hardness.
基金Project supported by the National Natural Science Foundation of China (Grant No. 30470495)the Key Laboratory of Optoelectronic Science and Technology for Medicine,Fujian Normal University
文摘This paper first demonstrates second-harmonic generation （SHG） in the intact cell nucleus, which acts as an optical indicator of DNA malignancy in prostate glandular epithelial cells. Within a scanning region of 2.7 μm×2.7μm in cell nuclei, SHG signals produced from benign prostatic hyperplasia （BPH） and prostate carcinoma （PC） tissues （mouse model C57BL/6） have been investigated. Statistical analyses （t test） of a total of 405 measurements （204 nuclei from BPH and 201 nuclei from PC） show that SHG signals from BPH and PC have a distinct difference （p 〈 0.05）, suggesting a potential optical method of revealing very early malignancy in prostate glandular epithelial cells based upon induced biochemical and/or biophysical modifications in DNA.
