JPS5876744A - Laser emission spectrochemical analysis - Google Patents

Abstract

PURPOSE:To facilitate the setting of a sample with limited variation in the intensity of emission spectrum due to variation in the sample position by irradiating the sample with an infrared pulse laser beam whose energy density on the surface of a sample is above 2.0X10<9>W/mm.<2>. CONSTITUTION:This laser emission spectrochemical analyzer is equipped with an Nd glass laser beam 22 for irradiating an infrared ray pulse laser beam whose energy density is above 2.0X10<9>W/mm.<2> on the surface of a sample 14 regardless of variation in the sample position, a laser oscillator power source 24 connected thereto 22 and the like. Electric energy stored in the laser oscillator power source 24 is inputted into the laser light source 22 and converted into light energy with the energy density exceeding 2.0X10<9>W/mm.<2> on the surface of the sample. According to this invention, the setting of the sample can be done easily with a limited change in the intensity of the emission spectrum due to variation in the sample position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser emission spectroscopic analysis method, and in particular, spectroscopic analysis of light emitted when a sample is irradiated with laser light, which is suitable for quantitative analysis of impurity elements in steel. Regarding [jt+' Iu of t/-The Emission Spectroscopy Method Y-3.

With the development of l/-the technology, this fl, (i-minute light)
Efforts are underway to use it as an excitation source for go. This laser emission spectrometry basically converts light energy into thermal energy to evaporate and turn a solid sample into plasma, and the light emitted from the plasma is transmitted to the spectrometer using an appropriate light introduction system. However, after separating the spectrum using a diffraction grating or the like, it is attempted to determine the content of the target element by detecting it with a photographic film, a photomultiplier tube, a photodiode, etc.

For this laser emission spectroscopic analysis, an optical system is required, for example, as shown in FIG.
A laser emitting section 10 consisting of a ruby laser or the like that oscillates a laser beam with a wavelength of 0.697u+i, and the laser emitting section 1
A condensing lens 12 for condensing the laser beam emitted from zero and irradiating it onto the surface of the sample 14 placed at the focal position.
and a converging lens 16 for converging the light emitted from the surface of the sample 14, and a spectrometer 518 for performing spectroscopic analysis of the light converged by the converging lens 16, or, Generally, laser irradiation alone has a low signal to background ratio (referred to as SB ratio);
Since highly accurate analysis is difficult, as shown in Figure 2,
In history, an auxiliary electrode 20 is placed between the condensing lens 12 and the sample 14, and the atoms emitted by laser irradiation are captured and guided between the electrodes 20 to be discharged and excited to a higher energy state. 7, devices that provide a strong emission spectrum have been put into practical use.

However, in the conventional method, the sample 14 is accurately placed at the focal position of the condenser lens 12 [2,
It is necessary to align the optical axis of the spectroscope 18 with the laser irradiation position on the sample 14 or with the center portion 20a between the auxiliary electrodes 20. However, in actual analysis, it is difficult to place the sample 14 at a certain distance from the normal pressure condensing lens 12 due to the shape of the sample. However, it was difficult to set the sample at one point where the optical axes of the laser system and the spectrometer thread coincided with each other.The present invention has been made to solve the above-mentioned drawbacks of the conventional method. It is an object of the present invention to provide a highly practical laser emission spectroscopic analysis power method in which there is little change in emission spectrum intensity, and therefore, discrimination settings are easy.

The present invention provides a laser emission spectroscopic analysis method for spectroscopically analyzing the light emitted when a sample is irradiated with a laser beam, and the energy density m' at the sample surface is 2. The sample is irradiated with infrared pulsed laser light so that OX l O' W / Introduction 2 -
The above object is achieved by separating the light emitted from the sample using a spectroscopic means arranged such that the direction perpendicular to the spectroscopic direction is parallel to the laser beam.

Further, the spectroscopic means and the photodetector for detecting the separated emission spectrum are arranged such that the centers of the spectroscopic means and the light receiving window of the photodetector in a direction perpendicular to the spectroscopic direction are the same as the focal point of the laser condensing lens. It is arranged so that it is in-plane.

The present invention will be explained in detail below.

Generally, ruby laser light with a wavelength of 0.69 am is often used as the laser light for laser emission spectroscopy, and in this case, a high-speed switching (Q-switching) element such as a Kerr cell or a Poeke 1S cell is used. In this method, the laser beam is pulsed with a width of +18130, and the irradiation part is brought into a high energy state before the thermal energy is diffused around the laser irradiation part.

The present inventors decided to conduct such laser emission spectroscopic analysis using an infrared pulsed laser with even better heat transfer efficiency, and the wavelength 1 emitted by the KNd glass laser on the steel surface.
．． 06 μm infrared pulsed laser light was irradiated and the emission spectrum was observed. As a result, (1) an emission spectrum with a sufficiently excellent SB ratio can be obtained without using an auxiliary electrode;
(2) The intensity of the emission spectrum increases with the laser output, but as shown in the NR3 diagram, it tends to saturate eventually; (3) The minimum area at which the emission spectrum intensity reaches the saturation value is the laser irradiation area on the sample surface. Laser output Jm1n
I have given an example of the fact that a linear relationship exists between the In addition, during the experiment, the pulse width of the laser light? 15 nsec, and the position of the laser 116 is changed by moving the position of the condensing lens. From Figure 4, 2.0 X ] 0' W1m vote 2
It can be seen that if the above output power is obtained, a sufficiently good emission spectrum can be obtained.

By the way, in actual spectroscopic analysis 6, the laser output is constant and 1
7. The setting position of the condenser lens is also fixed. In addition, when the auxiliary electrode is not used, the relationship between the sample and the spectrometer system is an L arrangement as shown in FIG.

Therefore, in the conventional method, the relationship between the laser output and its irradiation area is at one point in the upper left region of the straight line in FIG. However, as is clear from Figure 3,
Even if the laser output is constant, the relationship with the irradiation area is the fourth
It can be seen that as long as it is located above and to the left of the straight line in the figure, it is possible to obtain a sufficiently strong emission spectrum, that is, it is not necessary to set the position of the sample very precisely, if the spectrometer system allows it.

The present invention has been made based on such knowledge.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a laser emission spectrometer employing a laser emission spectrometry method according to the present invention will be described in detail with reference to the drawings.

In this embodiment, as shown in FIG. 5, a Nd glass laser light source 22 and a l/l/
- a laser emitting unit 10 comprising a laser oscillator power supply 24 connected to the laser light source 22, a high-speed switching element power supply 26 for operating a high-speed switching element (not shown) incorporated in the laser beam 22; A rectangular prism 28 for making the infrared pulsed laser beam oscillated from the laser light source 22 of the section 10 incident on the sample 14 at a predetermined angle, a condensing lens 12 similar to the conventional one, and a pair of laser beams. The longitudinal direction of the grating perpendicular to the diffraction direction (direction of arrow A) for spectroscopically analyzing the light emitted from the surface of the sample 14 arranged to face a predetermined direction is parallel to the laser beam. A planar diffraction grating 32 is provided, and an emission spectrum I.
The L-plane diffraction grating 32 and the photodetector include a photodetector 34 such as a photomultiplier tube or a photodiode, which receives the laser beam and has a long light-receiving window in a direction parallel to the laser beam. 34 is a spectroscope 3 arranged so that the longitudinal center of the planar diffraction grating 32 and the longitudinal center of the light receiving window of the photodetector 34 are in the same plane as the focal point of the condenser lens 12.
0, a photodetector control device 36 for moving the photodetector 34 of the spectrometer 30, and a display Ff1138 for displaying the measurement results of the output of the photodetector control device 36. There is.

The action will be explained below. First, 11 laser products and 24 laser products.
The electrical energy stored in the sample is input to the laser light source 22, and is converted into a light energy IL such that the energy density on the sample surface is 2.0×10'W/12 or more regardless of changes in the sample position. At this time, when the electrical energy of the light source is stored in the laser light source 22, the first oscillator 24
A pulse signal is sent to the high-speed switching element power supply 26, the high-speed switching element within the laser light source 22 is activated, and the electrical energy stored in the laser light source 22 is emitted at once.

The infrared pulsed laser beam thus obtained is transmitted through the right-angle prism 28 and the condensing lens 12 so that the energy concentration at the sample surface is 2. It is focused on the surface of the sample 14 so that it is OX 10' W/Im2 or more.

Then, the surface of the sample 14 is locally heated within a certain period of time, turned into plasma, and further generated by HJ.

At this time, the light emitted from the plasma undergoes plane diffraction inside the spectrometer 30! , distributed among children 32. This dispersed light is detected by a photodetector 34 and converted into an electrical signal proportional to the spectral tension @'. This electrical signal is passed through an amplifier or
is input to the display section 38 via the photodetector control device 36,
The measurement result is displayed on display R+138.

In this implementation ((11), once the sample 14 is placed at the focal point of the condensing lens 12, the light is emitted from there, is the diffraction condition? MI '/rubbing': If you set the sample 14 to move jli (1
1,-(also, as shown in FIG. 6(, diffraction condition t1 normal U'-
'7iRnl will be rubbed, and the plane diffraction grating 32
Alternatively, as long as the emission spectrum does not appear outside the light receiving window of the photodetector l'l+' 34, a sufficiently good emission spectrum can be obtained and safe spectroscopic analysis can be performed.

In addition, in the above embodiment, the laser light source 22 of Fi, laser emitting unit] 0, the condensing lens 120, and the angle grism 28
was placed. ka, ray---;”N of light emitting part lO
d Glass laser light source 22 (+-1 sample 1
If the right angle prism 28 is installed in a predetermined irradiation direction with respect to 4, it is also possible to omit the right angle prism 28.

Also, in Mi+Ki Jitsuori 1 and Ij, Hikari Judan and 1
．． A planar diffraction grating 32 is used, and the planar diffraction grating 32
Although the longitudinal direction of the grating is parallel to the laser beam, the type of spectroscopic means is not limited to this, for example, a prism is used and the prism is moved in a direction perpendicular to the direction of spectroscopy. It is also possible to arrange the laser beam so that it is parallel to the laser beam.
() - was used, and the longitudinal direction of the light receiving window was arranged so as to be parallel to the light, but the type of photodetector is not limited to this, and for example, a circular light receiving window may be used. It is also possible to arrange the circular light-receiving window so that the diameter direction thereof is parallel to the laser beam.

Further, in the embodiment Ia, the light emitted from the sample 14 was made to directly enter the plane diffraction grating 32 of the spectroscope 30, but the arrangement of the light introduction system is not limited to this. It is also possible to arrange lenses, reflecting mirrors, etc. around the sample 14 to efficiently guide the emission spectrum to the plane diffraction grating 32, etc.

Furthermore, in the above embodiment, one each of the plane diffraction grating 32 and the photodetector 34 were disposed, but a plurality of photodetectors 34 may be installed together, or the plane diffraction grating 32 and the photodetector 34 may be arranged together. It is also possible to provide the detector 34 with a slope set. figure,
It is clear that the method can be similarly applied to the analysis of image tone.

As explained above and in Section 2, according to the present invention, there is little change in the emission spectrum intensity m due to fluctuations in a pair of sample positions, making it easy to set the sample. have an effect.

Using the laser emission spectrometer described in the previous example, the output of the infrared laser is determined as I (l J, pulse r
Gk l 5 n5ec (approx. (i, 7X1 (1”W)
The density of the lattice @1200 pieces/am, the deliciousness of the lattice I Oi
l IIl #l Using a f-curved diffraction grating, a silicon photodiode with a light receiving window height of i 0 mm,
2714.4''A and) 6/1. When we investigated the change in the line spectrum forcing from the top and bottom of the sample, 1tII+VC,l:, we found that the focal point of the quaternary lens was It was confirmed that even if the center VC2t'a was raised or lowered, a nearly constant emission spectrum intensity could be obtained.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of the arrangement of an optical system used in conventional laser emission spectroscopy, and FIG.
FIG. 3 is a perspective view showing another example of the orientation of the optical system used in conventional laser emission spectrometry analysis. Similarly, FIG. 4 is a diagram showing the relationship between the laser irradiation area on the sample surface and the minimum laser output at which the spectral intensity reaches the saturation value, and FIG. A front view including a partial block diagram showing the configuration of an embodiment of a laser emission spectrometer in which the spectroscopic analysis method is adopted, and FIG. FIG. 7 is a perspective view showing changes in the incident position of 1 blue on the grating and the photodetector, and is also a diagram showing an example of the relationship between the moving distance of the sample from the focal point of the condenser lens and the emission spectrum enhancement. . 10... Laser emission section, 12... Condensing lens, 14
. . . Sample, 22 .
...Photodetector. Agent Umoya Ron (and 1 other person)

Claims (2)

[Claims] (1) In a laser emission spectrometry method that spectrally analyzes the light emitted when a sample is irradiated with laser light, the energy density at the sample surface is 2 regardless of changes in the sample position.
．． The sample is irradiated with an infrared pulsed laser beam so that OX is 10°W/llI2 or more, and the light emitted from the sample is irradiated with a spectrometer arranged so that the direction perpendicular to the spectroscopic direction is parallel to the laser beam. A laser emission spectroscopic analysis method characterized by suppressing changes in the emission spectrum due to changes in the sample position by performing spectroscopy using a method. (2) The spectroscopic means and the photodetector for detecting the separated emission spectrum are arranged such that the centers of the spectroscopic means and the light-receiving window of the photodetector in a direction perpendicular to the spectroscopic direction coincide with the focal point of the laser condenser lens. The laser emission spectroscopic analysis method according to claim 1, wherein the laser beams are arranged in the same plane.