Laser Spectroscopy Technology
Theme Keywords： laser spectroscopyspectroscopy technologyoptical measurement
- The Paper
Development of highly sensitive balloon-borne methane measurement system based on cavity ringdown spectroscopy
Abstract：This paper presents the design for a highly sensitive balloon-borne measurement system based on cavity ringdown spectroscopy (CRDS) in order to analyze the vertical distribution of methane above the Tibetan Plateau. The proposed measurement system uses a digital signal processing (DSP) board to lock the cavity mode, acquire the cavity ringdown signal, scan the laser wavelength, and store data. Calculation of the decay rate, spectral curve fitting, and concentration calculations are all performed via DSP. First, the principle of CRDS and the spectrum calculation algorithm are introduced, including details on the improvement of calculation results by using a fixed Gaussian linewidth for fitting the spectral curve. Second, the cavity ringdown signal and spectral curve of the measurement system were analyzed, yielding a signal-to-noise ratio of approximately 62 dB for the cavity ringdown signal. The measurement system was calibrated in the laboratory by measuring standard gases; the maximum standard deviation of the measured values was 2.2×10-9, and the adjusted R-square between nominal values and the RMS of the measured values was 0.998 7. Finally, a field test was conducted in Lulang, Tibet. The instrument was carried by a tethered balloon, and methane concentrations at altitudes between 3 340 m and 6 000 m above sea level were successfully measured. Different trace gases can be measured by replacing the super mirrors in the optical cavity and using lasers with appropriate wavelengths, while the measurement system can be refined further to measure the abundances of certain isotopes.Keywords：spectroscopy;cavity ringdown spectroscopy;isotopes aburdance;highly sensitivity723|951|10
<HTML><L-PDF><Meta-XML>Updated：2020-09-28On-line detection of carbon dioxide in large scale offshore by laser technology
Abstract：Quantitative research on energy and material exchange between the land or ocean and the atmosphere, especially the monitoring of carbon dioxide (CO2) exchange flux, play an important role in the study of global carbon cycle and climate change.We developed an open-path CO2 detection system based on direct absorption spectroscopy technology and derivative spectroscopy technology for on-line measurement across an order of km air path. A movable platform was developed capable of detecting atmospheric variations of CO2 in real time with the integrated optical system of transceiver.Allan variance analysis shows the detection limit of the system is 0.08×10-6 at the integration time of 100 s.The feasibility of the method with the second derivative spectrum is verified by using standard gases with different concentrations for the concentration calibration, and the correlation is 0.998. The continuous operation was carried out at Shenzhen Eco-environment Monitoring Station for 1 month, and the detection results have obvious daily variation periodicity.Comparing the data with the Licor7550-CO2 monitor installed at different points nearby, the data change trend is consistent, and the stabilityof the prototype is better.Keywords：laser spectroscopy;tunable laser diode;openpath;derivative absorption spectrum;direct absorption spectrum938|880|11<HTML><L-PDF><Meta-XML>Updated：2020-08-13Application of standard gas validation and supporting vector machine in spectral fidelity improvement
Abstract：The output of spectroscopy analyzer undergoes slow and subtle distortion when operational for a long period. This results in degradation of the spectral fidelity and it adversely affects the analyzing accuracy. A design based on combination of periodic validation with standard gas and Least Square Supporting Vector Machine (LS-SVM) algorithm was proposed to overcome this issue. For validation, the current spectra and factory calibration spectra of the same standard validation gas were compared. The LS-SVM m Keywords：laser spectroscopy;spectra fidelity;Least Square Supporting Vector Machine(LS-SVM);standard gas validation;spectra restoration458|296|0<HTML><L-PDF>Updated：2020-08-13CO2 concentration detection system for seed respiration
Abstract：To address the problem of low detection accuracy in the traditional method of seedbreathing CO2 concentration measurement, a seedbreathing measurement system based on tunable diode laser absorption spectroscopic technology was proposed to meet the needs of seedbreathing CO2 concentration measurements. First, the system was designed to consist of a seedbreathing container, a distributed feedback laser and control circuit, photoelectric conversion and an amplification circuit, a data acquisition circuit, and upper computer software. The space volume of the seed breathing container was 1.5 L, the laser source was in the 2 004nm band, and the light path of the multiple reflection cell was 16 m. Then, based on Lamberts law and wavelength modulated absorption spectroscopy, the concentration of CO2 produced during seed respiration could be retrieved in real time using second harmonics. The stable repeatability of the CO2 concentration measurement in seed respiration is 0.033%, the linear fitting degree of CO2 concentration is 0.999 38, and the detection limit of CO2 concentration is 1.7×10-6. The change curve of 20g maize seed respiration is obtained by testing waxy maize seeds. The amount of change in waxy maize seed respiration after 12 h is 2 750.5×10-6, and the respiration rate is 229.2×10-6/h. Experimental results show that the system can solve the inability for continuous measurement of CO2 concentration in seed respiration and the low precision of concentration detection.Keywords：CO2;Tunable Diode Laser Absorption Spectroscopy(TDLAS);Multiple reflex pool;seed respiration112|223|6<HTML><L-PDF><Meta-XML>Updated：2020-08-13CO2 concentration detection system for seed respiration
Abstract：To address the problem of low detection accuracy in the traditional method of seed-breathing CO2 concentration measurement, a seed-breathing measurement system based on tunable diode laser absorption spectroscopic technology was proposed to meet the needs of seed-breathing CO2 concentration measurements. First, the system was designed to consist of a seed-breathing container, a distributed feedback laser and control circuit, photoelectric conversion and an amplification circuit, a data acquisition circuit, Keywords：CO2;Tunable Diode Laser Absorption Spectroscopy(TDLAS);multiple reflection cell;seed respiration509|13|9Updated：2020-08-13Detection of heavy metal Pb in soil by filament-nanosecond laser induced breakdown spectroscopy
Abstract：In this study, quantitative analysis of heavy metal lead in soil was conducted by femtosecond laser-filament-laser-induced breakdown spectroscopy (Filament-ns DP-LIBS). First, a femtosecond laser plasma wire was used to ablate the lead-containing soil sample, and a low-density soil particle source was sprayed outward. Then, following interpulse delay time Δ t, another nanosecond laser beam was used to re-ablate the low-density soil particle source to enhance spectral intensity, compress spectral line width, Keywords：filament-nanosecond laser induced breakdown spectroscopy;spectral resolution;soil heavy metal pollution;Pb element528|384|0<HTML><L-PDF>Updated：2020-08-13Application of TDLAS technology to multicomponent detection in olefin production process
Abstract：Multicomponent online gas measurement in the production of olefin is an important approach for effective control and improvement of the overall efficiency of the production process. In this study, we took the online measurement of CO and CO2 for an olefin cracking furnace coal cleaning process as the application example. A Tunable Diode Laser Absorption Spectroscopy (TDLAS) based analyzing platform was developed to facilitate multicomponent measurement. To simulate the reaction process, we designed 0-5% ran Keywords：olefin production;cracking furnace coal cleaning;tunable diode laser absorption spectroscopy (TDLAS);multicomponent analysis;multivariate classical least square fitting (CLS);partial least square fitting (PLS)566|465|0<HTML><L-PDF>Updated：2020-08-13Laser heterodyne spectrometer for solar spectrum measurement in the 3.53 μm region
Abstract：Laser heterodyne technology has high spectral resolution characteristics, and it is commonly used for atmospheric measurements, especially in the measurement of total atmospheric transmittance and gas column density inversion. For these reasons, a heterodyne system with a narrow-linewidth 3.53 μm Distributed Feedback Interband Cascade Laser (DFB-ICL) as a local oscillator was designed to measure the absorption spectrum of water vapor and methane in the atmosphere. This system has a spectral resolution of 0. Keywords：laser heterodyne;spectral resolution;signal-to-noise ratio;column density501|542|10<HTML><L-PDF>Updated：2020-08-13Compact mid-infrared trace gas detection system based on TDLAS and ICL
Abstract：Two compact Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensor systems were developed based on different structural optical cores. The two optical cores combine two recent developments; gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPC), with the aim of developing a compact TDLAS-based sensor for mid-IR gas detection with high detection sensitivity and low power consumption. The two-floor structure sensor was used for methane (CH4) measurements and the single-floor structure Keywords：laser sensors;semiconductor lasers;quantum cascade;spectroscopy;Infrared602|431|0<HTML><L-PDF>Updated：2020-08-13Measurement of low water vapor dew-point temperature based on tunable diode laser absorption spectroscopy
Abstract：The dew-point temperature is an important parameter of gas. Moreover, there is an urgent need for developing techniques that can facilitate the accurate, rapid, continuous, and direct measurement of low dew point temperatures. In this regard, an approach based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) was developed. Firstly, our TDLAS hygrometer was compared with a chilled mirror hygrometer at Anhui Provincial Meteorological Bureau. Secondly, a free-path measurement apparatus was designed with Keywords：Tunable Diode Laser Absorption Spectroscopy(TDLAS);dew-point temperature;saturated vapor pressure;water vapor670|594|0<HTML><L-PDF>Updated：2020-08-13
