CN103149156A - Double-channel light cavity ring-down atmospheric aerosol extinction instrument and extinction factor measuring method - Google Patents
Double-channel light cavity ring-down atmospheric aerosol extinction instrument and extinction factor measuring method Download PDFInfo
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- CN103149156A CN103149156A CN201310087153XA CN201310087153A CN103149156A CN 103149156 A CN103149156 A CN 103149156A CN 201310087153X A CN201310087153X A CN 201310087153XA CN 201310087153 A CN201310087153 A CN 201310087153A CN 103149156 A CN103149156 A CN 103149156A
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Abstract
The invention provides a double-channel light cavity ring-down atmospheric aerosol extinction instrument and an extinction factor measuring method. According to the extinction instrument, utilizes a double-channel light cavity ring-down spectrum technology is applied to carry out in-situ real-time measurement on an extinction factor of atmospheric aerosol. The instrument comprises a light path system, a circuit system and a gas path system, wherein the light path system is internally provided with a first light cavity and a second light cavity, and the first light cavity and the second light cavity are utilized as double channels; and the gas path system respectively provides atmospheric gas and background atmospheric gas containing the aerosol for the first light cavity and the second light cavity, the circuit system can eliminate the transformation of the extinction factor of the aerosol caused by gas change in real time, and the extinction factor value of the atmospheric aerosol is accurately measured in a real time.
Description
Technical field
The present invention relates to the fields of measurement of Aerosol Extinction Coefficients, relate to more specifically the measuring method of a kind of binary channels optical cavity ring-down atmospheric aerosol delustring instrument and Aerosol Extinction Coefficients.
Background technology
The atmospheric aerosol delustring refers to that Atmospheric Grains or drop produce scattering and absorption loss to light, make light by the time phenomenon decayed occurs.Will accurately obtain the extinction coefficient of atmospheric aerosol, usually aerocolloidal astigmatic coefficient and absorption coefficient are measured respectively in employing, the adding and be exactly Aerosol Extinction Coefficients of astigmatic coefficient and absorption coefficient.At present, the measurement of astigmatic coefficient is comparative maturity, can realize measuring quickly and accurately, and experimental error can reach 10
-1mm
-1but the measurement of absorption coefficient does not also reach such precision.The measurement of aerocolloidal absorption adopts filter membrane sampling absorption techniques and optoacoustic photoelectric spectrum technology usually, these two kinds of technology are because device sensitivity limits, or may change the gasoloid nature in measuring process, have error large, detect limit for height, the shortcoming such as temporal resolution is low.
The filter membrane sampling absorption apparatus is by being trapped in atmospheric aerosol on the filter membrane surface, measure certain flow and be trapped in the absorption of the gasoloid on filter membrane surface to special wavelength light in the lower unit interval of situation, deduct the astigmatic effect of filter membrane itself, obtain the absorption coefficient of atmospheric aerosol.The optical property of atmospheric aerosol and its form are closely connected, and it is to increase or reduce compared to being suspended in the impact of airborne form on absorption coefficient that the very difficult assessment of filter film technology is deposited in the filter membrane surface.In addition, introduced filter membrane in measuring process, due to the cross section sensitive question that its special fibre structure causes, the blank value consistance of different filter membranes is poor, causes larger experiment uncertainty.Simultaneously, the light source of filter membrane sampling absorption apparatus not adopts monochromatic source, process medium wavelength (or frequency) wider distribution at each special wavelength light of screening, also can cause measuring error, the inaccuracy of measuring reaches 30%, can't meet accurate, the fast-changing measurement of real atmosphere Aerosol Extinction.
For fear of introducing the impact of filter membrane on the Aerosol Extinction measurement, the eighties in last century, the optoacoustic Photoelectric Spectrometer was invented to realize the in site measurement of optical properties of aerosol.Gasoloid can be to discharge the mode de excitation of heat energy after absorbing special wavelength light, the heat energy discharged makes aerocolloidal surrounding gas medium produce the periodic pressure fluctuation by light frequency, obtain photoacoustic signal after detecting amplification by highly sensitive microphone, the intensity of photoacoustic signal is the absorption of gasoloid to special wavelength light.Because the optoacoustic Photoelectric Spectrometer heat energy that light absorption causes to specific wavelength discharges, may make the contained volatile substances such as ammonium nitrate of gasoloid evaporate in gas medium, perhaps change damp condition and then gasoloid water cut and particle diameter are changed, the measurement of final impact to extinction coefficient, increase measuring error.
Cavity ring down spectroscopy technology is created in 1988 by O ' Keefe, there is detectability low, the temporal resolution advantages of higher, be widely used in the research of gas extinction coefficient, its principle is that a branch of short-pulse laser is entered into to an optical resonator by the coupling platform, resonator cavity is relative by pair of parallel, radius-of-curvature is r, and the catoptron that reflectivity is R forms.When vacuum, the light intensity in optical resonator can temporal evolution
, L is cavity length, and c is the light velocity, and t is the time of laser pulse in cavity.While in optical cavity, gas being arranged, the light intensity temporal evolution
.
α g, ext the extinction coefficient of gas,
lit is the absorption optical path length of sample.While passing into gasoloid (being to be mixed with gasoloid in gas) in optical cavity, above formula becomes
,
α s, ext it is aerocolloidal extinction coefficient.Therefore by measuring respectively background gas and gas and aerocolloidal ring-down time, just can obtain aerocolloidal extinction coefficient,
.Optical cavity ring-down aerosol extinction instrument just is based on the extinction coefficient that this principle of work records atmospheric aerosol, but existing optical cavity ring-down aerosol extinction instrument all is based on single pass optical cavity ring-down aerosol extinction instrument, it is when measuring atmospheric aerosol, usually the hypothesis background gas is stable mutually in following period of time, the variation of gas delustring can be ignored in the certain hour section, therefore measure the ring-down time of a background gas within the regular hour, then this value is input in program, apply the Aerosol Extinction that this background gas ring-down time calculates a period of time.Because the concentration changes with time of some gas in real atmosphere is very fast, if replace gas extinction coefficient in a period of time with the gas extinction coefficient of a time point, can bring error to the measurement of Aerosol Extinction, therefore this existing optical cavity ring-down aerosol extinction instrument still exists error in the measurement to the real atmosphere Aerosol Extinction, especially when the concentration change of background gas is very fast, this error even affects the exact value of Aerosol Extinction value, therefore if obtain in real time Aerosol Extinction accurately, be necessary that Real-Time Monitoring gas comprises the variation of the extinction coefficient of background gas, and existing single channel optical cavity ring-down aerosol extinction instrument can't be accomplished this Real-Time Monitoring.
Summary of the invention
The present invention changes the gasoloid nature in order to overcome conventional measurement techniques in measuring the atmospheric extinction coefficient process, detect limit for height, and error is large, the shortcomings such as temporal resolution is low, a kind of binary channels optical cavity ring-down atmospheric aerosol delustring instrument is proposed, using the binary channels cavity ring down spectroscopy technology to carry out original position to the extinction coefficient of atmospheric aerosol measures in real time, adopt two optical cavity passages to measure respectively background gas and background gas and aerocolloidal extinction coefficient, pass through conduct compute order, can deduct in real time the variation that changes the aerocolloidal extinction coefficient caused due to background gas, reach real-time, measure exactly Aerosol Extinction Coefficients, finally obtain point-device Aerosol Extinction Coefficients value.
It is as follows that the present invention solves the problems of the technologies described above the technical scheme of specifically taking:
A kind of binary channels optical cavity ring-down atmospheric aerosol delustring instrument, comprise light path system, Circuits System and air-channel system, described light path system comprises the first optical cavity 1, the second optical cavity 2 and light source, the light of described light source output imports respectively described the first optical cavity 1 and the second optical cavity 2, and forms therein vibration respectively; Described air-channel system comprises protection gas circuit and sample gas gas circuit, and described protection gas circuit provides protection gas to each optical cavity, and described sample gas gas circuit provides and contains aerocolloidal atmospheric gas to described the first optical cavity 1, to described the second optical cavity 2, provides the background atmospheric gas; Described Circuits System comprises the first photomultiplier 8, the second photomultiplier 9 and calculation processing unit, described the first photomultiplier 8 exports calculation processing unit to for receiving after declining of the first optical cavity 1 output swung light signal and be converted into electric signal, described the second photomultiplier 9 exports calculation processing unit to for the attenuate light signal that receives the second optical cavity 2 output and after being converted into electric signal, described calculation processing unit is processed by analysis and is obtained respectively declining of two optical cavities and swing curve and ring-down time, and calculates the extinction coefficient of atmospheric aerosol based on this.
Further according to delustring instrument of the present invention, wherein said light path system also comprises the light modulation unit, be arranged between described light source and optical cavity, for the light beam splitting that light source is sent, import described the first optical cavity 1 and the second optical cavity 2 be arranged in parallel, and the adjustment light beam forms damped oscillation therein.
Further according to delustring instrument of the present invention, wherein said light modulation unit comprises a spectroscope 4, three catoptrons 5 and two groups of adjustable light barriers 6, be divided into two-beam after the reflection of the light that described light source 3 sends by described spectroscope 4 and transmission, wherein light beam enters the first optical cavity 1 after first mirror reflects and first group of grating adjusting, and another light beam enters the second optical cavity 2 after vertically disposed another two catoptrons, 5 reflections and second group of grating adjusting.
Further, according to delustring instrument of the present invention, centered by wherein said light source 3, wavelength is at the semiconductor pumped high-frequency impulse laser instrument of green light band, and laser is triggered by external trigger, and has the heat dissipation metal support.
Further according to delustring instrument of the present invention, wherein said optical cavity is comprised of cavity and high reflection mirror, high reflection mirror is parallel relatively to be fixed on the cavity two ends and to keep airtight, and described high reflection mirror is contained in adjustable mirror holder, in order to regulate the angle of its minute surface and incident light.
Further according to delustring instrument of the present invention, the semiconductor pumped Q-switched laser that centered by wherein said light source 3, wavelength is 10 μ J at 532nm, single beam pulse energy; Described high reflection mirror adopts that the foveal reflex wave band is 99.9985% at 540nm, reflectivity, the high reflection mirror of 0.8 foot of radius-of-curvature 1m, diameter; Described cavity is cylindrical stainless-steel tube cavity, and cavity diameter is 42mm.
Further according to delustring instrument of the present invention, wherein said calculation processing unit comprises digital delay generator 11, computing machine 10 and data collecting card 12, the output terminal of wherein said digital delay generator 11 connects light source 3 and data collecting card 12 simultaneously, form the light path control part, for triggering light source pulse and computer runs programs, the output terminal of described photomultiplier is connected in described data collecting card 12, and described data collecting card 12 is connected with computing machine 10.
Further according to delustring instrument of the present invention, the high-tension electricity that wherein said photomultiplier adopts stabilized voltage supply to provide, and with described data collecting card composition data collecting part; Described data collecting card is several 24 for gathering, the Dual-Channel High-Speed Data Acquisition card of acquisition rate 100MHz; The degree of accuracy of described digital delay generator 11 reaches nanosecond.
Further according to delustring instrument of the present invention; wherein said protection gas circuit is communicated in described optical cavity in the position of closing on its high reflection mirror of each optical cavity; will protect gas to be passed into the minute surface front end of each high reflection mirror of optical cavity; described sample gas gas circuit comprises background gas supply gas circuit and gasoloid gas supply gas circuit, and two supply gas circuits share same equally gas air inlet pipeline and aspiration pump.
Further according to delustring instrument of the present invention, wherein said protection gas circuit comprises four branch roads, position at the close two ends of the first optical cavity 1 high reflection mirror connects two branch roads, in the position of the close two ends of the second optical cavity 2 high reflection mirror, connects another two branch roads; Protection gas wherein adopts high pure nitrogen and does not contain the aerosol particle thing.
Further according to delustring instrument of the present invention, specifically being configured to of wherein said sample gas gas circuit: sample gas air inlet pipeline is divided into two air inlet paths after a threeway; The first air inlet path is divided into again two branch roads and is communicated with cavity from the front and rear part of the first optical cavity 1 respectively, forms gasoloid gas supply gas circuit; The second air inlet path also is divided into two branch roads and is communicated with cavity from the front and rear part of the second optical cavity 2 respectively, forms background gas supply gas circuit, and be added with filtrator on described the second air inlet path; The gas exhaust piping arranged on the gas exhaust piping arranged on described the first optical cavity 1 and described the second optical cavity 2 is connected in same aspiration pump.
Further, according to delustring instrument of the present invention, wherein said filtrator is the aerosol particle filtrator, the membrane pump that described aspiration pump is adjustable flow, and flow range is at 1-10L/min.
Further according to delustring instrument of the present invention, computing machine in wherein said calculation processing unit (10) swings curve by declining in matching the first optical cavity and obtains the wherein ring-down time of gasoloid atmospheric gas, swing curve by declining in matching the second optical cavity and obtain the wherein ring-down time of background atmospheric gas, substitution formula
calculate the extinction coefficient of atmospheric aerosol, in formula, L is cavity length, and c is the light velocity,
lthe absorption optical path length of sample,
for the ring-down time of gasoloid atmospheric gas,
for the ring-down time of background atmospheric gas,
for extinction coefficient school null value.
A kind ofly use delustring instrument of the present invention to carry out the method for Aerosol Extinction Coefficients monitoring, comprise the following steps:
1), open light source, adjust the light modulation unit, the light that light source is sent is inducted into the first optical cavity (1) and the second optical cavity (2), open the digital delay generator in calculation processing unit, trigger light source and computer runs programs, heighten its photomultiplier transit tube voltage, form vibration in two optical cavities;
2), the protection gas circuit of connection air-channel system provides protection gas to each optical cavity; the sample gas gas circuit of air-channel system is connected to atmosphere; open aspiration pump; at the first optical cavity (1), front or sample gas route mouth adds filtrator temporarily; to two optical cavities, school is zero simultaneously, the ring-down time of the first optical cavity (1) and the second optical cavity (2) when the school obtained is zero
,
be input in computing machine, utilize formula
calculate the extinction coefficient school null value of cavity, then remove the interim filtrator arranged on the front or route mouth of the first optical cavity (1);
3), to described the first optical cavity (1), provide and contain aerocolloidal atmospheric gas, provide the background atmospheric gas to described the second optical cavity (2), computing machine in described calculation processing unit obtains declining in each optical cavity and swings curve, by matching, obtains gas and aerocolloidal ring-down time in the first optical cavity (1)
and the ring-down time of the middle background gas of the second optical cavity (2)
, the substitution formula
computing obtains the extinction coefficient of atmospheric aerosol, wherein
the extinction coefficient school null value obtained during for above-mentioned cavity school zero.
Utilize binary channels optical cavity ring-down atmospheric aerosol delustring instrument of the present invention can reach following technique effect:
(1) can realize the accurate monitoring to Aerosol Extinction Coefficients, the extinction coefficient degree of accuracy recorded can reach 10
-1mm
-1, effectively reduce error effect;
(2) realized the Real-Time Monitoring to Aerosol Extinction Coefficients, temporal resolution can reach 1s, has improved greatly temporal resolution;
(3) realize the in site measurement to sample, avoided the change to the gasoloid nature, reduced detectability simultaneously, guaranteed monitoring accuracy;
(4) the described binary channels optical cavity ring-down atmospheric aerosol light path of delustring instrument based on integrated and the circuit of robotization, control simply, and automaticity is high.
The accompanying drawing explanation
Accompanying drawing 1 is binary channels optical cavity ring-down atmospheric aerosol delustring instrument one-piece construction schematic diagram of the present invention;
Accompanying drawing 2 is light path system structural representation in binary channels optical cavity ring-down atmospheric aerosol delustring instrument of the present invention;
Accompanying drawing 3 is circuit system structure schematic diagram in binary channels optical cavity ring-down atmospheric aerosol delustring instrument of the present invention;
Accompanying drawing 4 is air-channel system structural representation in binary channels optical cavity ring-down atmospheric aerosol delustring instrument of the present invention;
In accompanying drawing, the implication of each Reference numeral is as follows:
1, the first optical cavity; 2, the second optical cavity; 3, laser instrument; 4, spectroscope; 5, catoptron; 6, grating; 7, filtrator; 8, the first photomultiplier; 9, the second photomultiplier; 10, computing machine; 11, digital delay generator; 12, data collecting card.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is described in detail, but protection domain not thereby limiting the invention.
As shown in Figure 1, binary channels optical cavity ring-down atmospheric aerosol delustring instrument integral body of the present invention comprises light path system, Circuits System and air-channel system, wherein light path system at least comprises the first optical cavity 1, the second optical cavity 2 and as the laser instrument 3 of light source, the one-wavelength laser guiding of laser instrument 3 outputs enters as twin-channel the first optical cavity 1 and the second optical cavity 2, and forms therein vibration simultaneously; Described air-channel system comprises protection gas circuit and sample gas gas circuit; for to described the first optical cavity 1 and the second optical cavity 2, protection gas being provided and treating test sample gas; wherein sample gas gas circuit provides the background atmospheric gas to the second optical cavity, to the first optical cavity, provides and contains aerocolloidal atmospheric gas.After air-channel system provides sample gas to described light path system, form damped oscillation in light path system two optical cavities, the two-way attenuate light signal of its output is accepted by Circuits System, described Circuits System at least comprises the first photomultiplier 8 and the second photomultiplier 9 that receives two-way attenuate light signal with two corresponding being respectively used to of optical cavity, the counter 10 be connected with photomultiplier, an and digital delay generator 11 that is connected in laser instrument 3 and computing machine 10, described the first photomultiplier 8 and the second photomultiplier 9 are converted into electric signal by the attenuate light signal of the first optical cavity 1 and the second optical cavity 2 outputs, and export in computing machine 10, utilize pre-set programs to form to decline and swing curve, obtain in the first optical cavity 1 ring-down time of background gas in gas and aerocolloidal ring-down time and the second optical cavity 2 by matching, the substitution formula
can obtain the extinction coefficient of atmospheric aerosol, in formula, L is cavity length, and c is the light velocity,
lthe absorption optical path length of sample,
for the ring-down time of gasoloid atmospheric gas,
for the ring-down time of background atmospheric gas,
for extinction coefficient school null value.Synchronously trigger laser pulse and computing machine by described digital delay generator, guaranteed monitoring accuracy.
Further as shown in Figure 2, described light path system comprises lasing light emitter 3, two optical cavities that be arranged in parallel 1,2 and light modulation unit.Wherein said lasing light emitter 3 is the high-frequency impulse laser instrument, preferably adopts the semiconductor pumped Q-switched laser of 532nm wavelength, and laser is triggered by external trigger, single beam pulse energy 10 μ J, and laser instrument is equipped with the metallic aluminium support with good thermal conductance ability.Described optical cavity 1,2 preferably is comprised of stainless steel cavity and high reflection mirror, and high reflection mirror is fixed on the cavity two ends and keeps airtight with flange, and parallel relatively high reflection mirror is contained in adjustable mirror holder, in order to the minute surface of regulating high reflection mirror and the angle of incident light; Preferred described high reflection mirror adopts that the foveal reflex wave band is 99.9985% at 540nm, reflectivity, the high reflection mirror of 0.8 foot of radius-of-curvature 1m, diameter.Described stainless steel cavity preferably adopts two cylindrical stainless-steel tube cavitys, cavity diameter is 42mm, gas sampling mouth diameter 12mm, the sample introduction gas that air-channel system provides is divided into two-way after by a threeway, wherein a road enters the first cavity 1 detected as gasoloid, the high-efficient granule filtrator 7 of leading up in addition enters the second cavity 2 that gas detects as a setting, gas outlet diameter 12mm, flange before the high reflection mirror frame has the aperture of 3mm to pass into high pure nitrogen as protection gas, guarantee that minute surface is not subject to Aerosol Pollution, optical cavity inside and the equal sanding and polishing of all interface tubes are processed, reduce the loss of gasoloid in cavity.Described light modulation unit comprises a spectroscope 4, three catoptrons 5 and two groups of adjustable light barriers 6, between lasing light emitter and optical cavity, its arrangement as shown in Figure 2, be divided into two bundle incident lights after the reflection of the laser that lasing light emitter 3 sends by spectroscope 4 and transmission, wherein light beam is regulated and is entered the first optical cavity 1 through catoptron 5 reflection and grating 6, and another light beam enters the second optical cavity 2 through vertically disposed two catoptrons, 5 reflections and grating 6 adjustings.Described light path system is when assembling, by described laser instrument and support thereof, the light modulation unit, optical cavity and support thereof are arranged on optical sheet successively as shown in Figure 2, and after two optical cavities corresponding two photomultipliers that Circuits System is set, regulate again the high reflection mirror of optical cavity, make its minute surface parallel relatively, forming declines swings optical cavity, two optical cavity passages share a lasing light emitter, as spectroscope 4, light source is divided into to two bundles with 1/2 light splitting piece, by the catoptron shown in Fig. 2, light path is incorporated in the cavity of two optical cavities respectively, make incident light Multi reflection in two optical cavities by regulating light path, form time dependent the declining of light intensity and swing curve.
Further as shown in Figure 3, described Circuits System comprises digital delay generator 11, two photomultipliers 8,9 and high-voltage power supply, computing machine 10 and data collecting card 12, the output terminal of wherein said digital delay generator 11 is connecting laser 3 and data collecting card 12 simultaneously, form the light path control part, for triggering laser pulse and computing machine 10, described two photomultipliers 8,9 output terminal connects described data collecting card 12, and described data collecting card 12 is connected with computing machine 10.Described photomultiplier 8,9 has fast, the highly sensitive characteristics of response, adopts stabilized voltage supply that high-voltage power supply is provided, and guarantees the stable of signal, the laser signal spilt for receiving optical cavity, and with described computing machine and data collecting card composition data collecting part.Described data collecting card is several 24 for gathering, the Dual-Channel High-Speed Data Acquisition card of acquisition rate 100MHz, and its ring-down time is 10-60 μ s, 100 MHz, this high-speed data acquisition card can guarantee the input of photomultiplier and the authenticity of laser trigger signal, avoids declining swinging the distortion of curve.Degree of accuracy reaches the digital delay generator 11 of nanosecond for triggering laser instrument 3 and computing machine 10, after laser triggers, at optical cavity 1,2 interior formation decline and swing, and the laser spilt by high reflection mirror is converted into electric signal by photomultiplier 8,9, after gathering, high-speed data acquisition card 11 is recorded in the computer program of computing machine 10, formation declines and swings curve, and after declining and swinging average 1000 times of curve, matching obtains ring-down time
τ, by sequential operation and in conjunction with formula
can obtain Aerosol Extinction Coefficients, temporal resolution can reach 1s.
Further as shown in Figure 4, described air-channel system comprises two parts, protection gas circuit and sample gas gas circuit.Described protection gas circuit by air inlet pipeline be divided into many branch roads and respectively at each optical cavity near the position of high reflection mirror together with in described optical cavity, preferred described air inlet pipeline is divided into four branch roads through four-way, described branch road adopts the tubule of 3mm diameter and is communicated in optical cavity, the first optical cavity connects two branch roads near high reflection mirror position, two ends, the second optical cavity connects another two branch roads near high reflection mirror position, two ends, (in stereographic map, protection gas can have same air inlet pipeline) as shown in Figure 4, described protection gas adopts 99.99% high pure nitrogen, not containing the aerosol particle thing, to 532 nm wavelength light without absorption, be passed into respectively the minute surface front end of two pairs of high reflection mirrors to guarantee that minute surface is not subject to Aerosol Pollution.Described sample gas gas circuit is divided into two air inlet paths after a threeway, each air inlet path is divided into respectively again two branch roads and enters cavity near the front and back end of each optical cavity, the gas circuit of two cavitys adopts parallel join, be added with high-efficiency aerosol filter 7 on air inlet path before one of them cavity, make the gas that enters this cavity for not containing aerocolloidal background gas, thereby the extinction coefficient of measuring background gas by this cavity 2 changes, another cavity is used for the aerocolloidal extinction coefficient of measurement gas, the exhaust outlet of two cavitys connects same aspiration pump simultaneously, to guarantee the consistance of gas physical parameter in two optical cavities.
The method that adopts binary channels optical cavity ring-down atmospheric aerosol delustring instrument of the present invention to carry out the Aerosol Extinction Coefficients measurement, that is the use step of this binary channels optical cavity ring-down atmospheric aerosol delustring instrument is as follows:
At first, open laser instrument 3, adjust the light modulation unit, the laser that laser instrument is sent is divided into two-beam through light modulation unit spectroscope and passes through respectively two optical cavities of central authorities' introducing of high reflection mirror, open digital delay generator, trigger laser and computer runs programs, heighten the photomultiplier transit tube voltage;
Secondly, the sample gas gas circuit of air-channel system is connected to atmosphere, open aspiration pump, flow control is at 6-10L/min, before the first optical cavity 1 or sample gas route mouth first additionally add filtrator, with to two cavitys school zero simultaneously, the ring-down time of cavity 1 and cavity 2 during by the school zero that obtains
,
parameter is input in computing machine, utilizes formula
calculate the extinction coefficient school null value of cavity, the interim filtrator arranged before then removing the first cavity 1 or on the route mouth, start to gather the actual attenuation light signal in each optical cavity;
Finally, the laser in described computing machine in each optical cavity of acquisition declines and swings curve, and matching obtains gas and aerocolloidal ring-down time in the first optical cavity 1
and the ring-down time of the second background gas in optical cavity 2
, the substitution formula
calculating can obtain the extinction coefficient of atmospheric aerosol, wherein
the extinction coefficient school null value obtained during for above-mentioned cavity school zero.
Only below that the preferred embodiment of the present invention is described; technical scheme of the present invention is not limited to this; the any known distortion that those skilled in the art do on the basis of major technique of the present invention design all belongs to the claimed technology category of the present invention, and the concrete protection domain of the present invention is as the criterion with the record of claims.
Claims (14)
1. a binary channels optical cavity ring-down atmospheric aerosol delustring instrument, comprise light path system, Circuits System and air-channel system, it is characterized in that: described light path system comprises the first optical cavity (1), the second optical cavity (2) and light source, and the light of described light source output imports respectively described the first optical cavity (1) and the second optical cavity (2), described air-channel system comprises protection gas circuit and sample gas gas circuit, described protection gas circuit provides protection gas to each optical cavity, described sample gas gas circuit provides and contains aerocolloidal atmospheric gas to described the first optical cavity (1), to described the second optical cavity (2), provides the background atmospheric gas, described Circuits System comprises the first photomultiplier (8), the second photomultiplier (9) and calculation processing unit, described the first photomultiplier (8) exports calculation processing unit to for receiving after declining of the first optical cavity (1) output swung light signal and be converted into electric signal, described the second photomultiplier (9) exports calculation processing unit to for the attenuate light signal that receives the second optical cavity (2) output and after being converted into electric signal, described calculation processing unit is processed by analysis and is obtained respectively declining of two optical cavities and swing curve and ring-down time, and calculate the extinction coefficient of atmospheric aerosol based on this.
2. delustring instrument according to claim 1, it is characterized in that, described light path system also comprises the light modulation unit, be arranged between described light source and optical cavity, import for the light beam splitting that light source is sent described the first optical cavity (1) and the second optical cavity (2) be arranged in parallel, and the adjustment light beam forms damped oscillation therein.
3. delustring instrument according to claim 2, it is characterized in that, described light modulation unit comprises a spectroscope (4), three catoptrons (5) and two groups of adjustable light barriers (6), be divided into two-beam after the reflection of the light that described light source sends by described spectroscope (4) and transmission, wherein light beam enters the first optical cavity (1) after first mirror reflects and first group of grating adjusting, and another light beam enters the second optical cavity (2) after vertically disposed another two catoptrons (5) reflection and second group of grating adjusting.
4. according to the described delustring instrument of claim 1-3 any one, it is characterized in that, centered by described light source, wavelength is at the semiconductor pumped high-frequency impulse laser instrument (3) of green light band, and laser is triggered by external trigger, and has the heat dissipation metal support.
5. according to the described delustring instrument of claim 1-4 any one, it is characterized in that, described optical cavity is comprised of cavity and high reflection mirror, high reflection mirror is parallel relatively to be fixed on the cavity two ends and to keep airtight, and described high reflection mirror is contained in adjustable mirror holder, in order to regulate the angle of its minute surface and incident light.
6. delustring instrument according to claim 5, is characterized in that, the semiconductor pumped Q-switched laser that centered by described light source, wavelength is 10 μ J at 532nm, single beam pulse energy; Described high reflection mirror adopts that the foveal reflex wave band is 99.9985% at 540nm, reflectivity, the high reflection mirror of 0.8 foot of radius-of-curvature 1m, diameter; Described cavity is cylindrical stainless-steel tube cavity, and cavity diameter is 42mm.
7. according to the described delustring instrument of claim 1-6 any one, it is characterized in that, described calculation processing unit comprises digital delay generator (11), computing machine (10) and data collecting card (12), the output terminal of wherein said digital delay generator (11) connects light source and data collecting card (12) simultaneously, form the light path control part, for triggering light source pulse and computer runs programs, the output terminal of described photomultiplier is connected in described data collecting card (12), and described data collecting card (12) is connected with computing machine (10).
8. delustring instrument according to claim 7, is characterized in that, the high-tension electricity that described photomultiplier adopts stabilized voltage supply to provide, and with described data collecting card composition data collecting part; Described data collecting card is several 24 for gathering, the Dual-Channel High-Speed Data Acquisition card of acquisition rate 100MHz; The degree of accuracy of described digital delay generator (11) reaches nanosecond.
9. according to the described delustring instrument of claim 1-8 any one; it is characterized in that; described protection gas circuit is communicated in described optical cavity in the position of closing on its high reflection mirror of each optical cavity; will protect gas to be passed into the minute surface front end of each high reflection mirror of optical cavity; described sample gas gas circuit comprises background gas supply gas circuit and gasoloid gas supply gas circuit, and two supply gas circuits share same equally gas air inlet pipeline and aspiration pump.
10. delustring instrument according to claim 9, it is characterized in that, described protection gas circuit comprises four branch roads, in the position of the close two ends of the first optical cavity (1) high reflection mirror, connects two branch roads, in the position of the close two ends of the second optical cavity (2) high reflection mirror, connects another two branch roads; Protection gas wherein adopts high pure nitrogen and does not contain the aerosol particle thing.
11. according to the described delustring instrument of claim 9 or 10, it is characterized in that specifically being configured to of described sample gas gas circuit: sample gas air inlet pipeline is divided into two air inlet paths after a threeway; The first air inlet path is divided into again two branch roads and is communicated with cavity from the front and rear part of the first optical cavity (1) respectively, forms gasoloid gas supply gas circuit; The second air inlet path also is divided into two branch roads and is communicated with cavity from the front and rear part of the second optical cavity (2) respectively, forms background gas supply gas circuit, and be added with filtrator on described the second air inlet path; The upper gas exhaust piping arranged of described the first optical cavity (1) and the upper gas exhaust piping arranged of described the second optical cavity (2) are connected in same aspiration pump.
12. delustring instrument according to claim 11, is characterized in that, described filtrator is the aerosol particle filtrator, the membrane pump that described aspiration pump is adjustable flow, and flow range is at 1-10L/min.
13. according to the described delustring instrument of claim 1-12 any one, it is characterized in that, computing machine in described calculation processing unit (10) swings curve by declining in matching the first optical cavity and obtains the wherein ring-down time of gasoloid atmospheric gas, swing curve by declining in matching the second optical cavity and obtain the wherein ring-down time of background atmospheric gas, substitution formula
calculate the extinction coefficient of atmospheric aerosol, in formula, L is cavity length, and c is the light velocity,
lthe absorption optical path length of sample,
for the ring-down time of gasoloid atmospheric gas,
for the ring-down time of background atmospheric gas,
for extinction coefficient school null value.
14. the method that right to use requires the described delustring instrument of 1-13 any one to carry out the Aerosol Extinction Coefficients monitoring, is characterized in that, comprises the following steps:
1), open light source, adjust the light modulation unit, the light that light source is sent is inducted into the first optical cavity (1) and the second optical cavity (2), open the digital delay generator in calculation processing unit, trigger light source and computer runs programs, heighten its photomultiplier transit tube voltage, form vibration in two optical cavities;
2), the protection gas circuit of connection air-channel system provides protection gas to each optical cavity; the sample gas gas circuit of air-channel system is connected to atmosphere; open aspiration pump; at the first optical cavity (1), front or sample gas route mouth adds filtrator temporarily; to two optical cavities, school is zero simultaneously, the ring-down time of the first optical cavity (1) and the second optical cavity (2) when the school obtained is zero
,
be input in computing machine, utilize formula
calculate the extinction coefficient school null value of cavity, then remove the interim filtrator arranged on the front or route mouth of the first optical cavity (1);
3), to described the first optical cavity (1), provide and contain aerocolloidal atmospheric gas, provide the background atmospheric gas to described the second optical cavity (2), computing machine in described calculation processing unit obtains declining in each optical cavity and swings curve, by matching, obtains gas and aerocolloidal ring-down time in the first optical cavity (1)
and the ring-down time of the middle background gas of the second optical cavity (2)
, the substitution formula
computing obtains the extinction coefficient of atmospheric aerosol, wherein
the extinction coefficient school null value obtained during for above-mentioned cavity school zero.
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