Near-infrared continuous wave cavity ring-down spectroscopy was applied to mea- sure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry a...Near-infrared continuous wave cavity ring-down spectroscopy was applied to mea- sure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry and the removal of air pollutants by non-thermal plasmas. The P-branches of OH X2YIi （vI ： 2 ＋-- it 0） bands were used for number density measurements. The OH number density and plasma temperature were determined for different applied voltages, gas pressures and concentrations of both oxygen and water. The temporal evolu- tion of the OH number density was obtained by using the ＂time window＂ method, which was used to extract individual ring-down times at different times in a half period of the sine wave applied voltage in dielectric barrier discharge plasmas.展开更多
NO3 and N2O5 are important participants in nocturnal atmospheric chemical processes,and their concentrations are of great significance in the study of the mechanism of nocturnal atmospheric chemical reactions.A two-ch...NO3 and N2O5 are important participants in nocturnal atmospheric chemical processes,and their concentrations are of great significance in the study of the mechanism of nocturnal atmospheric chemical reactions.A two-channel diode laser based cavity ring-down spectroscopy(CRDS)instrument was developed to monitor the concentrations of NO3 and N2O5 in the atmosphere.The effective absorption length ratio and the total loss coefficient of the instrument were calibrated using laboratory standard samples.The effective absorption cross section of NO3 at 662 nm was derived.A detection sensitivity of 1.1 pptv NO3 in air was obtained at a time resolution of 1 s.N2O5 was converted to NO3 and detected online in the second CRDS channel.The instrument was used to monitor the concentrations of NO3 and N2O5 in the atmosphere of winter in Hefei in real time.By comparing the concentration changes of pollutants such as nitrogen oxides,ozone,PM2:5 in a rapid air cleaning process,the factors affecting the concentrations of NO3 and N2O5 in the atmosphere were discussed.展开更多
Continuous-wave cavity ring-down spectroscopy(CW-CRDS)is an important technical means to monitor greenhouse gases in atmospheric environment.In this paper,a CW-CRDS system is built to meet the needs of atmospheric met...Continuous-wave cavity ring-down spectroscopy(CW-CRDS)is an important technical means to monitor greenhouse gases in atmospheric environment.In this paper,a CW-CRDS system is built to meet the needs of atmospheric methane monitoring.The problem of mode matching is explained from the perspective of transverse mode and longitudinal mode,and the influence of laser injection efficiency on measurement precision is further analyzed.The results of cavity ring-down time measurement show that the measurement precision is higher when the laser is coupled with the fundamental mode.In the experiment,DFB laser is used to calibrate the system with standard methane concentration,and the measurement residual is less than±4×10^(-4)μs^(-1).The methane concentration in the air is monitored in real time for two days.The results show the consistency of the concentration changes over the two days,which further demonstrates the reliability of the system for the measurement of trace methane.By analyzing the influence of mode matching,it not only assists the adjustment of the optical path,but also further improves the sensitivity of the system measurement.展开更多
H_(2)S is one of the most important characteristic decomposition components of SF_(6)insulated gas,and the detection of trace H_(2)S is significant for early fault diagnosis of gas insulated electrical equipment.A 157...H_(2)S is one of the most important characteristic decomposition components of SF_(6)insulated gas,and the detection of trace H_(2)S is significant for early fault diagnosis of gas insulated electrical equipment.A 1578 nm wavelength distributed feedback diode laser(DFB-DL)based cavity ring-down spectroscopy(CRDS)experimental platform is developed to monitor the concentrations of H_(2)S in SF_(6)and SF_(6)/N_(2)mixture carrier gas.The detection sensitivity is higher than 1×10^(-6).The absorption cross section parameterσis vital for calculating the concentration.With repeated experiments using standard gas samples,parameterσof H_(2)S in pure SF_(6)and SF_(6)/N_(2)mixture carrier with different mixing ratios is calibrated.Compared with the simulatedσvalues,the influence of carrier gas on the broadening of spectral profile is discussed.The variation of absorption cross sectionσwith different carrier gas mixing ratios is studied as well,so that the calculation of the concentration in the carrier gas of any mixing ratio is possible.Thus,the application of CRDS in trace component detection of gas insulated electrical equipment is promising.展开更多
A cavity ring-down spectrometer （CRDS） is constructed with a single-mode continuous-wave Ti：Sapphire laser. It allows attaining a minimum detectable absorption of 1.8× 10^-10cm^-1. The spectrometer is applied ...A cavity ring-down spectrometer （CRDS） is constructed with a single-mode continuous-wave Ti：Sapphire laser. It allows attaining a minimum detectable absorption of 1.8× 10^-10cm^-1. The spectrometer is applied to record the overtone spectrum of ^12C2H2 in the 12240- 12350 cm-1. Compared with the previous CRDS and intra-cavity laser absorption spectroscopy studies in the same region, the present measurement achieved better sensitivity and better precision as well. As a result, the ro-vibrational parameters of the high overtone bands of acetylene at 12290.12, 12311.82, and 12350.61 cm^-1 have been refined. The advantages of the present CRD spectrometer is also demonstrated by the newly observed and well characterized perturbation on the f component of the very weak band near 12289 cm^-1. The quantitative measurement capability of the spectrometer is verified with the measurement of the water lines and employed to give the absolute band intensities of those three acetylene bands.展开更多
Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the a...Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range(FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down(CRD) method, the rapidly swept-frequency(SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.展开更多
基金supported by National Natural Science Foundation of China (Nos.10475015, 10975029)
文摘Near-infrared continuous wave cavity ring-down spectroscopy was applied to mea- sure the OH radicals in dielectric barrier discharge plasmas, which play an important role in combustion systems, atmospheric chemistry and the removal of air pollutants by non-thermal plasmas. The P-branches of OH X2YIi （vI ： 2 ＋-- it 0） bands were used for number density measurements. The OH number density and plasma temperature were determined for different applied voltages, gas pressures and concentrations of both oxygen and water. The temporal evolu- tion of the OH number density was obtained by using the ＂time window＂ method, which was used to extract individual ring-down times at different times in a half period of the sine wave applied voltage in dielectric barrier discharge plasmas.
基金Hao Wu,Jian Chen,An-wen Liu,and Shui-ming Hu acknowledge the supports from the Ministry of Science and Technology of China(No.2013BAK12B00)the National Natural Science Foundation of China(No.21427804).
文摘NO3 and N2O5 are important participants in nocturnal atmospheric chemical processes,and their concentrations are of great significance in the study of the mechanism of nocturnal atmospheric chemical reactions.A two-channel diode laser based cavity ring-down spectroscopy(CRDS)instrument was developed to monitor the concentrations of NO3 and N2O5 in the atmosphere.The effective absorption length ratio and the total loss coefficient of the instrument were calibrated using laboratory standard samples.The effective absorption cross section of NO3 at 662 nm was derived.A detection sensitivity of 1.1 pptv NO3 in air was obtained at a time resolution of 1 s.N2O5 was converted to NO3 and detected online in the second CRDS channel.The instrument was used to monitor the concentrations of NO3 and N2O5 in the atmosphere of winter in Hefei in real time.By comparing the concentration changes of pollutants such as nitrogen oxides,ozone,PM2:5 in a rapid air cleaning process,the factors affecting the concentrations of NO3 and N2O5 in the atmosphere were discussed.
基金This research is financial supported by the Natural National Science Foundation of China(Grant Nos.11874364,41877311,and 42005107)the National Key Research and Development Program of China(Grant No.2017YFC0805004)the CAS&Bengbu Technology Transfer Project(Grant No.ZKBB202102).
文摘Continuous-wave cavity ring-down spectroscopy(CW-CRDS)is an important technical means to monitor greenhouse gases in atmospheric environment.In this paper,a CW-CRDS system is built to meet the needs of atmospheric methane monitoring.The problem of mode matching is explained from the perspective of transverse mode and longitudinal mode,and the influence of laser injection efficiency on measurement precision is further analyzed.The results of cavity ring-down time measurement show that the measurement precision is higher when the laser is coupled with the fundamental mode.In the experiment,DFB laser is used to calibrate the system with standard methane concentration,and the measurement residual is less than±4×10^(-4)μs^(-1).The methane concentration in the air is monitored in real time for two days.The results show the consistency of the concentration changes over the two days,which further demonstrates the reliability of the system for the measurement of trace methane.By analyzing the influence of mode matching,it not only assists the adjustment of the optical path,but also further improves the sensitivity of the system measurement.
基金supported in part by the National Key R&D Program of China(No.2021YFF0603100)in part by the Leading Innovation and Entrepreneurship Team in Zhejiang Province(No.2019R01014)
文摘H_(2)S is one of the most important characteristic decomposition components of SF_(6)insulated gas,and the detection of trace H_(2)S is significant for early fault diagnosis of gas insulated electrical equipment.A 1578 nm wavelength distributed feedback diode laser(DFB-DL)based cavity ring-down spectroscopy(CRDS)experimental platform is developed to monitor the concentrations of H_(2)S in SF_(6)and SF_(6)/N_(2)mixture carrier gas.The detection sensitivity is higher than 1×10^(-6).The absorption cross section parameterσis vital for calculating the concentration.With repeated experiments using standard gas samples,parameterσof H_(2)S in pure SF_(6)and SF_(6)/N_(2)mixture carrier with different mixing ratios is calibrated.Compared with the simulatedσvalues,the influence of carrier gas on the broadening of spectral profile is discussed.The variation of absorption cross sectionσwith different carrier gas mixing ratios is studied as well,so that the calculation of the concentration in the carrier gas of any mixing ratio is possible.Thus,the application of CRDS in trace component detection of gas insulated electrical equipment is promising.
基金V. ACKNOWLEDGMENTS We are indebted to D. Romanini and S. Kassi for helpful discussion. This work was supported by the National Natural Science Foundation of China （No.20903085 and No.20533060）, Chinese Ministry of Science and Technology （No.2006CB922001 and No.2007CB815203）, and the Fok Ying Tong Education Foundation （No. 101013）.
文摘A cavity ring-down spectrometer （CRDS） is constructed with a single-mode continuous-wave Ti：Sapphire laser. It allows attaining a minimum detectable absorption of 1.8× 10^-10cm^-1. The spectrometer is applied to record the overtone spectrum of ^12C2H2 in the 12240- 12350 cm-1. Compared with the previous CRDS and intra-cavity laser absorption spectroscopy studies in the same region, the present measurement achieved better sensitivity and better precision as well. As a result, the ro-vibrational parameters of the high overtone bands of acetylene at 12290.12, 12311.82, and 12350.61 cm^-1 have been refined. The advantages of the present CRD spectrometer is also demonstrated by the newly observed and well characterized perturbation on the f component of the very weak band near 12289 cm^-1. The quantitative measurement capability of the spectrometer is verified with the measurement of the water lines and employed to give the absolute band intensities of those three acetylene bands.
基金Project supported by National Key Research and Development Program of China (Grant No.2022YFA1603403)。
文摘Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range(FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down(CRD) method, the rapidly swept-frequency(SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.
基金supported by the National Natural Foundation of China(No.21827804,No.22103075,No.22173089)the National Key R&D Program of China(No.2021YFA0716801,No.2017YFA0303502)。
基金jointly supported by the National Natural Science Foundation of China(No.22273093,No.41905018,No.21903080)the Ministry of Science and Technology of China(No.2022YFF0606500)。
