JPH03150448A - Method for measuring component concentration - Google Patents

Abstract

PURPOSE:To efficiently generate ASE light and to allow the simultaneous execution of laser oscillation by using the ASE light as 2nd Stokes light and simultaneously measuring two kinds of gaseous molecules. CONSTITUTION:The fresh Coherent Anti-Stokes Raman Scattering light (CARS light) generated from the gaseous molecules existing in the part where two dye laser beams are condensed is spectrally analyzed and the concn. of gas is measured from a difference in the spectral intensity of the CARS of the gas. The Amplified Spontaneous Emission (ASE) of the one dye laser is positively generated and is applied as the 2nd Stokes light to the other gaseous molecules. The concns. of two kinds of the gaseous components are thus measured simultaneously. An example of the constitution of this Stokes dye laser is shown in fig. Even if there is the contamination of a measuring window in the course of the measurement, the relative intensity ratio of these two components is not affected.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a CA that is applied to measurement of component concentration of various combustion gases and heat exchangers using multi-component gases such as Kalina cycle.
This article relates to a component concentration measurement method using the R3 method.

[Prior Art] Fig. 3 is a diagram for explaining a conventional component concentration measurement method, in which a laser beam 02 oscillated from an excimer laser 01 is split into two beams by a half mirror 03, and each laser beam is divided into two beams. excites the dye laser 04°05 and oscillates laser light at two different wave numbers, .

Here, the laser light with a wave number KP is called pumping light 06, and the laser light with a wave number 5 is called Stokes light 07.

The wave number Ks of the Stokes light is adjusted so that K, -5 is equal to the energy difference between the ground level and the first excited level of the vibrational energy level of nitrogen. The pumping light and the Stokes light are combined into a -tree beam by a dichroic mirror 08, and the light is focused at =1 measurement point 10 through a lens 09. Here 11 is the last section. Then,
From the part where the laser light is focused (measurement point), a new third light, namely N2, is generated by the nitrogen molecules present there.
CAR9 light is generated. This newly generated N2CA
The R9 light is converted into a parallel beam by the lens 12 together with the other two transmitted laser beams KP and KS, and by the dichroic mirror 13, the transmitted laser beams KP and KS
and N2CARS (WA).

The separated N2CAR9 light 14 is guided to a spectrometer 17 through a mirror 15 and a lens]6.

The N, CARS light separated by the spectrometer is transferred to the photoelectric exchanger 1
8 is converted into a voltage and guided to a signal processor 19, N, C
A spectrum of ARS light is obtained.

The concentration of N2 is determined from this spectral intensity. K.P.
- When the wave number is changed by 5 to match the vibrational energy level difference (first excitation reference base level) of other molecules, such as N20 or NH3, N20 or NH3
The CARS spectra of the above are obtained in the same manner, and the component concentrations can be determined from their spectral intensities.

[Problems to be Solved by the Invention] In the conventional method, only one type of molecule concentration can be measured four times at the same time.

Therefore, conventionally, in order to measure the concentration of two types of molecules at the same time = 1, it was necessary to add another laser and oscillate Stokes light (wave number 2) corresponding to the second molecule. Therefore, there are problems in that the device becomes larger and the cost becomes significantly higher.

An object of the present invention is to provide a component concentration measurement method that can solve the above-mentioned conventional problems.

[Means for Solving the Problems] The component concentration measurement method according to the present invention focuses a dye laser beam with a wave number KP and a dye laser beam with a wave number of 10 on measurement points, and converts Kl' KSI into one gas. By matching the vibrational energy level difference of the molecules, the spectrum of the new CARS light generated from the gas molecules existing in the focused part of the two dye laser beams is analyzed, and the CARS light of the gas CA
In the concentration measurement method, which measures gas concentration from the difference in the spectral intensity of RS, ASE of a dye laser with a wave number Ks+ is actively generated, and the second Stokes light (wave number K S2
) to other gas molecules, 2g! It is characterized by simultaneously measuring the concentration of gaseous components of the following types. That is, in the present invention, in order to simultaneously measure two types of molecules, the ASE light possessed by the dye laser that emits Stokes light (wave number: 1) is actively utilized, and this ASE light is By using it as a Stokes light of 2 (wave number is 2),
It is designed to be able to perform Li1FI on two types of gas molecules at the same time.

[In order to generate ASE light more efficiently than usual, the dye laser for Stokes light is optimally adjusted for laser oscillation as usual, and then the excitation light in the oscillator section of the dye laser is reduced to about half. By weakening it, ASE can be generated efficiently and laser oscillation can be performed at the same time. The intensity ratio of single laser beam and ASE can be changed by changing the degree of attenuation of the excitation light. The reason why ASE occurs efficiently in the above method is considered to be as follows.

A Stokes dye laser for CARS usually undergoes two-stage amplification and consists of an oscillator, a preamplifier, and a main amplifier. Each of these incorporates a dye cell, which is excited with excitation light from the outside. At this time, the concentration of each dye cell and the ratio of excitation light intensity to each cell are adjusted to be optimal for laser oscillation.
SE hardly occurs. However, at this time, if only the excitation light from the oscillator section is weakened by about half, the laser light from the oscillator is also weakened by about half.

With weak laser light, it is not possible to draw out all the energy stored in the preamplifier and main amplifier (the gain at each amplifier depends on the intensity of the incident laser light), so excess energy is stored in each amplifier. There will be.

This extra energy is first generated as ASE light in a preamplifier, amplified in a main amplifier, and output as ASE light with an intensity that is high enough to be used in CARS.

[Example] The basic configuration of the apparatus for carrying out the method of the present invention is the same as that shown in FIG. 3, so the description thereof will be omitted. This is the inside of laser 05. FIG. 1 shows an example of the configuration of this Stokes dye laser.

In FIG. 1, 50 is an oscillator section, 51 is a preamplifier section, and 52 is a main amplifier.
The prism 53 constitutes a resonator, and the wavelength of the laser beam 56 as an output is selected by rotating the prism 53. 57 is a stop that defines the spatial mode of the laser; 58, 59 .
60 are dye cells for the oscillator, preamplifier, and main amplifier, respectively; 61, 62, and 63 are excitation lights for exciting each dye cell, and excimer laser light is usually used. 64 is a shielding plate for blocking a part of the oscillator excitation light 61.

Wavelength selection for simultaneous two-component Al 11 fixing is performed as follows. Taking the concentration measurement of H, O and NH as an example,
First, rhodamine 6G, a dye that efficiently generates ASE, is selected. The wavelength λASE of ASE of Rhodamine 6G is a unique value and has the following value.

Here, KAsE is the wave number of ASE.

Since this value is used as the second Stokes beam, λ52−
1/K 52-571 nm...-
(2) becomes. However, KS2 is the wave number of the second Stokes light. Due to the characteristics of ASE, the second Stokes beam must be selected from the one with the smaller Raman shift of the two molecular species. Since the Raman shifts of N20 and NH3 are 3654 cm-' and 3334 cm, respectively, the molecule corresponding to the second Stokes light is NH3. Therefore, the wavelength λP of the pumping laser is 3334 cm-', where KP is the wave number of the pumping laser, K, 2 is the wave number of the second Stokes beam, Δ and □3 are the Raman shifts of NH, and 3334 cm-'. Ks2 is KS2 from equation (2)
-17513cm-', so λp -479nm
becomes.

The wavelength λ of the first Stokes light, I is λs+-1/Ks+-1/ (KP-△KH20)...
・(4) Here, ΔK +1□0 is 36 with the Raman shift of N20.
It is 54 cm-'.

Therefore, λs+-582 nm.

FIG. 2 shows an example of the light intensity of NH and N20, which allows the concentration of each to be determined.

The contrast between light intensity and concentration is calibrated in advance.

Other gases such as CO can also be used.

[Effects of the Invention] (1) Since two components can be measured simultaneously, even if the measurement window becomes dirty during measurement, the relative intensity ratio of those two components is not affected.

(2) If a molecule whose concentration is known in the measured system, such as N2 in the air, is selected as one of the molecules to be measured, even if the measured 1fl + byssus is subjected to various disturbances, other components will not be affected by the disturbance. can be measured.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a Stokes dye laser in a component concentration measuring device used to carry out the method of the present invention, and FIG. 2 is a diagram showing an example of a spectrum obtained by the method of the present invention. FIG. 3 is a configuration diagram of a conventional component concentration measuring device. 50... Oscillator section, 51... Preamplifier section, 5
2... Main amplifier section, 58-60... Dye cell,
61-63... Excitation light, 64... Shielding plate.

Claims (1)

[Claims] A dye laser beam with a wave number K_P and a dye laser beam with a wave number K_S_1 are respectively focused on a measurement point, and the dye laser beam with a wave number K_P - K_S_
By matching 1 to the vibrational energy level difference (difference between the ground level and the first vibrational excitation level) of one gas molecule, the above 2 can be obtained.
New CARS light (Coherent
Anti-StokesRamanScatterin
In the concentration measurement method, in which the gas concentration is measured from the difference in the spectral intensity of the gaseous CARS, ASE (Amplified SpontaneousEmiss) of the dye laser with the wave number K_S_1 is analyzed.
ion) is actively generated and applied to other gas molecules as second Stokes light (wave number K_S_2) to simultaneously measure the concentrations of two types of gas components.