Detect the laser optical cavity ring-down spectrometer of aerosol extinction and scattering coefficient simultaneously
Technical field
The utility model relates to the online detection field of atmospheric aerosol optical property, particularly relates to a kind of laser optical cavity ring-down spectrometer that simultaneously detects aerosol extinction and scattering coefficient.
Background technology
Atmospheric aerosol is that the whole world and regional climate change the important driving factor, but gasoloid is also one of uncertainty source maximum in current climatic study simultaneously, diversity, the spatial and temporal distributions in its reason atmospheric aerosol source on Global Scale differs greatly, the very big uncertainty that the restriction of measuring technique is measured gasoloid absorption characteristic is also a major reason.Research can be measured extinction coefficient and scattering coefficient simultaneously or be measured the new technology of scattering coefficient and absorption coefficient simultaneously, and atmospheric science research and meteorological field are had to important practical value and meaning.
The multiple reflections characteristic of cavity ring down spectroscopy technology based on high reflective mirror, in shorter distance, realize long equivalent light path (can reach the even tens of kms of thousands of rice), there is hypersensitivity and low detectability, be very suitable for the OPTICAL PROPERTIES of atmospheric aerosol and the detection analysis of various trace gas.
At present, extinction coefficient can pass through cavity ring down spectroscopy technology Measurement accuracy, and uncertainty is less than 3%, and comparative maturity of the measurement of scattering coefficient, uses integration turbidimeter, and it is uncertain minimum reaches 5%; Both are in conjunction with accurately measuring extinction coefficient and scattering coefficient, then calculate absorption coefficient and single scattering albedo will be a kind of desirable measuring method.But the method, adopts two different instruments to measure respectively extinction coefficient and scattering coefficient, can be subject to the uncertain impact of synchronism of sample analysis time; The more important thing is, the operation wavelength operation wavelength common and that scattering coefficient is measured of measurement of extinction coefficient is inconsistent, needs additional calculating, by both unified Same Wavelengths that arrives, can introduce calculation error, the uncertainty that increase single scattering albedo is measured.Therefore, exploitation can be measured the method for Aerosol Extinction and scattering coefficient on same instrument simultaneously, obtain gasoloid absorption coefficient and single scattering albedo simultaneously, to improving accuracy and the reliability that coefficient absorbs and single scattering albedo is measured, be extremely important.
Utility model content
In order to overcome above-mentioned technical matters, the purpose of this utility model is to provide a kind of laser optical cavity ring-down spectrometer that can simultaneously detect aerosol extinction and scattering coefficient.
The technical scheme that the utility model adopts is:
A kind of laser optical cavity ring-down spectrometer that simultaneously detects aerosol extinction and scattering coefficient, comprise light path system, detection system and air-channel system, described light path system comprises light source and receives the optical cavity of light source output light, described detection system comprises data processing equipment and the first photomultiplier being connected with data processing equipment signal respectively, the second photomultiplier, described the first photomultiplier is used for the detection of optical cavity transmitted light and is positioned at optical cavity output terminal, described the second photomultiplier is for scattered light integral measurement and stretch into optical cavity from optical cavity side, described air-channel system is periodically optical cavity sampling gas or background gas.
As the further improvement of technique scheme, described the second photomultiplier is perpendicular to the optical path direction in optical cavity and be positioned at the middle part of optical cavity light path side.
As the further improvement of technique scheme, described light path system comprises gatherer, and described gatherer, between light source and optical cavity, is exported light by light source and imported in optical cavity.
As the further improvement of technique scheme, described gatherer comprises primary event mirror, secondary reflection mirror, the first diaphragm and the second diaphragm, light is first adjusted beam direction after the reflection of primary event mirror and secondary reflection mirror, pass through successively again the first diaphragm and the second diaphragm to adjust beam diameter, finally enter optical cavity.
As the further improvement of technique scheme, described optical cavity comprises perpendicular to the incident high reflective mirror of optical path direction and transmission high reflective mirror, described incident high reflective mirror and transmission high reflective mirror are plano-concave mirror, wherein each concave surface plating high-reflecting film, each concave surface is installed relatively, and light passes from incident high reflective mirror and transmission high reflective mirror center.
As the further improvement of technique scheme, described air-channel system comprises the feeder and the air extractor that connect respectively optical cavity, described feeder comprises the sample gas circuit and the background gas circuit that are connected in parallel, and the input end of described sample gas circuit and background gas circuit is connected to gas circuit selected cell.
As the further improvement of technique scheme, in described background gas circuit, be connected to filtrator.
As the further improvement of technique scheme, described gas circuit selected cell is electric T-shaped valve, and two outlets of described electric T-shaped valve connect respectively sample gas circuit and background gas circuit, and entrance connects gas to be measured.
As the further improvement of technique scheme, described air extractor is aspiration pump, and described aspiration pump provides power for optical cavity air inlet.
As the further improvement of technique scheme, described data processing equipment comprises that point level signal connects the data collecting card of the first photomultiplier and the second photomultiplier, and described data collecting card connects host computer.
The beneficial effects of the utility model are: the utility model periodically passes into optical cavity by background gas with aerocolloidal sample gas by air-channel system, detect respectively transmitted light and the scattered light of optical cavity with the first photomultiplier and the second photomultiplier, obtain respectively the ring-down time of background gas and the ring-down time of sample gas by matching, calculate aerocolloidal extinction coefficient; Calculate the ratio of transmitted light and scattered light intensity simultaneously, obtain aerocolloidal scattering coefficient, on this basis, can further obtain the important parameter of the optical property of the atmospheric aerosols such as aerocolloidal absorption coefficient, single scattering albedo, it detects, and error is little, precision is high.
Brief description of the drawings
Below in conjunction with drawings and embodiments, the utility model is further illustrated.
Fig. 1 is schematic diagram of structure of the present utility model.
Embodiment
As shown in Figure 1, a kind of laser optical cavity ring-down spectrometer that simultaneously detects aerosol extinction and scattering coefficient, comprise light path system, detection system and air-channel system, light path system comprises light source and receives the optical cavity 1 of light source output light, detection system comprises data processing equipment and the first photomultiplier 2 being connected with data processing equipment signal respectively, the second photomultiplier 3, the first photomultiplier 2 is for the detection of optical cavity 1 transmitted light and be positioned at optical cavity 1 output terminal, the second photomultiplier 3 stretches into optical cavity 1 for scattered light integral measurement and from optical cavity 1 side, air-channel system is periodically optical cavity 1 sampling gas or background gas.The present embodiment utilizes optical cavity ring-down spectroscopic methodology to obtain aerocolloidal extinction coefficient by the transmitted light of measuring optical cavity, simultaneously, utilize and the similar but distinguishing principle of integrating nephelometer, measure the integration of the scattered light of gasoloid in certain angle in optical cavity, contrast with transmitted light again, calculate aerocolloidal scattering coefficient.
In the present embodiment, detection zone of the interior formation of optical cavity 1, the range of exposures of detection zone in light path, in the occupied region of gasoloid.Preferably, the second photomultiplier 3 is perpendicular to the optical path direction in optical cavity 1 and be positioned at the middle part of side, detection zone, and for the measurement of the interior aerocolloidal scattered light integration of optical cavity 1, this photomultiplier can detect that angle is the scattered light of 5 ° ~ 175 °.
Preferably, light source is pulsed laser 14, and light path system also comprises gatherer, and gatherer, between laser instrument 14 and optical cavity 1, imports laser beam in optical cavity 1.Gatherer is made up of primary event mirror 4, secondary reflection mirror 5, the first diaphragm 6 and the second diaphragm 7, and primary event mirror 4 and secondary reflection mirror 5 are plane mirror, can make laser beam regulate arbitrarily in the certain angle of optical cavity 1 region; The first diaphragm 6 and the second diaphragm 7, for limiting the diameter of laser beam, are convenient to optical path adjusting; Light is first parallel to optical cavity 1 and passes through successively the first diaphragm 6 and the second diaphragm 7 to adjust beam diameter after the reflection of primary event mirror 4 and secondary reflection mirror 5, finally enters optical cavity 1.
Preferably, optical cavity 1 comprises perpendicular to the incident high reflective mirror 8 of laser beam and transmission high reflective mirror 9, incident high reflective mirror 8 and transmission high reflective mirror 9 are plano-concave mirror, the emission wavelength of two plano-concave mirrors and laser instrument 14 matches, wherein each concave surface plating high-reflecting film, radius-of-curvature is 1mm, reflectivity is higher than 99.99%, each concave surface is installed relatively, and light passes from incident high reflective mirror 8 and transmission high reflective mirror 9 centers.The first photomultiplier 2 is positioned at the rear end of transmission high reflective mirror 9, for receiving the light signal transmiting from optical cavity 1, and light signal is converted into electric signal to carry out the observation of change in optical signal, and this photomultiplier is mainly used in the detection of Aerosol Extinction.
In the present embodiment, data processing equipment comprises that point level signal connects the data collecting card 13 of the first photomultiplier 2 and the second photomultiplier 3, and data collecting card 13 connects host computer.Data collecting card 13 gathers the electric signal of the first photomultiplier 2 and the second photomultiplier 3, and processes being transferred to host computer computer after its digitizing, calculates extinction coefficient and scattering coefficient, and derives absorption coefficient and single scattering albedo.
Preferably, air-channel system comprises the feeder and the air extractor that connect respectively optical cavity 1.Air extractor is aspiration pump 12, for optical cavity 1 air inlet provides power.Feeder comprises the sample gas circuit and the background gas circuit that are connected in parallel, the input end of sample gas circuit and background gas circuit is connected to the electric T-shaped valve 11 as gas circuit selected cell, two outlets of electric T-shaped valve 11 connect respectively sample gas circuit and background gas circuit, entrance connects gas to be measured, is connected to filtrator 10 in background gas circuit.Filtrator 10 can be removed the gasoloid in gas to be measured, as the background of measuring; Electric T-shaped valve 11 is for the switching of background gas and testing sample gas.
Detection system in the present embodiment also comprises a governor circuit 15, and this governor circuit 15 is realized Power supply and control to light source, electric T-shaped valve 11, aspiration pump 12, data collecting card 13 and the power supply of the first photomultiplier 2 and the second photomultiplier 3.
The principle of work of the present embodiment is: the pulse laser that laser instrument 14 sends, after elder generation, regulate through primary event mirror 4 and secondary reflection mirror 5, through the first diaphragm 6 and the second diaphragm 7, then be coupled into optical cavity 1 from one end of incident high reflective mirror 8, because the reflectivity of optical cavity 1 is high, laser is vibration back and forth in optical cavity 1, there is certain transmission in eyeglass simultaneously, laser intensity meeting slow decreasing, swings thereby form to decline in optical cavity 1, and light intensity is along with the variation of time is single index decay.Can detect by the first photomultiplier 2 of transmission high reflective mirror 9 rear ends the variation of transmitted light, reflect the variation tendency of light in optical cavity 1, the speed swinging that declines can be weighed with ring-down time, and ring-down time is larger, and optical attenuation is slower; Otherwise ring-down time is less, optical attenuation is faster; If there is delustring medium in optical cavity 1, as gasoloid, the decay of laser will be accelerated, and is reflected as ring-down time and diminishes, and by the ring-down time measuring, can calculate the extinction coefficient of cavity medium.In real work, provide gas circuit power by aspiration pump 12, order about testing sample gas and constantly enter into instrument, measure.Switch by sample gas and the background gas after filter 10 filters by electric T-shaped valve 11, record respectively the extinction coefficient when comprising gasoloid and not containing gasoloid, both subtract each other, and can obtain aerocolloidal extinction coefficient.Simultaneously, the second photomultiplier 3 that is arranged in optical cavity 1 side can detect the aerocolloidal scattered light situation of change of optical cavity 1, the proportional relation of light intensity in scattered light and optical cavity 1, the ratio of scattered light and incident light is scattering coefficient, and light intensity in transmitted light and optical cavity 1 that the first photomultiplier 2 detects is also proportional, can first calculate like this ratio of the light intensity that the second photomultiplier 3 and the first photomultiplier 2 detect, then test and accurately obtain aerocolloidal scattering coefficient by correction.In process, the Power supply and control of all electronic units completes by governor circuit 15, and the electric signal of the first photomultiplier 2 and the second photomultiplier 3 is gathered, is transferred to host computer after digitizing again by data collecting card 13, carries out data processing.
The method of this spectrometer and detection is owing to not being subject to the impact of the intensity of light source, and equivalent optical path length, has the feature highly sensitive, detectability is low.
The present embodiment can obtain aerocolloidal extinction coefficient and scattering coefficient simultaneously, further can calculate the key parameter of the optical properties of aerosol such as aerocolloidal absorption coefficient and single scattering albedo, can greatly improve the use value of instrument, the range of application of expansion instrument.
The above be the utility model preferred embodiment, it does not form the restriction to the utility model protection domain.