CN105067571B - A kind of Laser induced plasma spectroscopy intensifier - Google Patents

Abstract

The invention provides a laser-induced plasma spectrum enhancement device, which belongs to the field of laser plasma spectrum detection. The device includes a diverging cavity, focusing lens, converging cavity, fiber optic probe, base, adjustable sample stage, plasma, inert gas interface and laser filter. The diverging cavity, focusing lens, base and laser filter form a closed space, and the inert gas The interface is connected to the divergent cavity, the sample is placed on the adjustable sample stage, and the adjustable sample stage is installed on the base. The device, together with a pulsed laser, an optical system, a spectrometer, and an inert gas protection system, realizes the spectral enhancement of laser-induced breakdown spectroscopy. The device enhances the plasma spectrum, weakens background light interference, has simple structure, low cost, does not need to consume other forms of energy, and is easy to operate.

Description

A laser-induced plasma spectral enhancement device

technical field

The invention relates to the field of laser plasma spectrum detection, in particular to a laser-induced plasma spectrum enhancement device.

Background technique

Laser-induced breakdown spectroscopy (LIBS for short) uses a focused high-energy pulsed laser incident on the surface of the sample to generate plasma. By analyzing the radiation spectrum of the plasma, the elemental composition of the sample can be deduced. and content. LIBS technology has many significant advantages: it can detect all elements, multiple elements can be detected at the same time, no vacuum is needed, sample preparation is simple or no preparation is required, the analyzed sample is almost non-destructive, real-time analysis, in situ detection and remote detection, etc. However, the poor detection limit and low analysis precision lead to the low detection sensitivity of LIBS, which has become the bottleneck of the development of this technology. For the above shortcomings of LIBS, the detection sensitivity of LIBS can be improved by enhancing the spectral intensity of LIBS and improving the sensitivity and precision of LIBS detection. A large number of research results have shown that magnetic confinement devices, spatial confinement devices, and double-pulse excitation can significantly increase the intensity of laser-induced plasma spectral lines.

However, the structure of the magnetic confinement device is complicated, it is inconvenient to install, and the efficiency is low. Generally, it can only be enlarged by 2-3 times, and it needs to consume electric energy. The amplification effect of the double-pulse excitation method is better, but the cost is high and the optical path is complicated. Commonly used spatial confinement devices have a single function, cannot directly collect spectra, and the device is complex to build. The hemispherical shape with the best amplification effect can be enhanced by 12 times.

Contents of the invention

The technical problem to be solved by the present invention is to provide a laser-induced plasma spectrum enhancement device.

The device includes a diverging cavity, a focusing lens, a converging cavity, an optical fiber probe, a base, an adjustable sample stage, an inert gas interface, and a laser filter. Connected to the diverging cavity, the other side of the focusing lens is connected to the converging cavity, the converging cavity and the diverging cavity are connected and fixed by nuts, the fiber optic probe is on the converging cavity, the adjustable sample stage is installed on the base, and the sample is placed on the adjustable sample stage. Excite the sample to generate plasma.

The diverging cavity can reflect the spectrum emitted by the plasma sphere into parallel light. After passing through the focusing lens, the light is focused on the fiber optic probe of the converging cavity. Compared with the traditional light receiving method to receive a small amount of spectrum, this device receives the left hemisphere reflection Most of the spectrum directly irradiated by the right hemisphere realizes the effect of increasing the light-receiving area, thereby greatly enhancing the spectral intensity.

The excited plasma is confined to the closed space surrounded by the diverging cavity, the focusing lens, the base, and the laser filter. The shock wave generated with the plasma will propagate outward at supersonic speed. When it propagates to the inner wall of the closed cavity Reflection occurs on the inner wall, and the reflected shock wave will compress the plasma. The volume of the compressed plasma becomes smaller, and the internal temperature of the plasma increases and becomes brighter, thereby releasing a stronger spectrum of atoms and ions.

Inert gas is filled into the closed space surrounded by diverging cavity, focusing lens, base and laser filter through the inert gas interface to isolate the air, avoid the interference of elemental components in the air, and reduce the interference of air on the measurement results.

The laser filter can only allow the light of the same wavelength as the laser to enter, and block the light of other wavelengths from entering the device, so that there is no external background light interference and the signal-to-noise ratio is increased.

The focal point of the diverging cavity coincides with the left focal point of the focusing lens, and the right focus of the focusing lens is on the fiber optic probe of the converging cavity, so that the light reflected from the left diverging cavity can be accurately focused on the converging lens after passing through the focusing lens. cavity fiber optic probe.

The base is equipped with an adjustable sample stage, which can adjust the height of the sample. By adjusting the adjustable sample stage, the distance between the upper surface of the sample and the focal point of the divergent cavity can be controlled, that is, the plasma generated by the sample excited by the laser can always be at the focal point, and the sample can be rotated by a certain amount. Angle, to achieve the measurement of multiple positions of the sample.

The inner wall of the diverging cavity includes but is not limited to a concave mirror embedded in a certain curve, or the plasma spectrum is reflected by coating the inner wall of the diverging cavity.

The device, together with a pulsed laser, an optical system, a spectrometer, and an inert gas protection system, realizes the spectral enhancement of laser-induced breakdown spectroscopy.

The beneficial effects of above-mentioned technical scheme of the present invention are as follows:

1. Combined with spatial constraints and spectral reflection, reconvergence can greatly enhance the spectral intensity;

2. The interior of the device cavity is sealed, there is almost no background light interference, and it is protected by inert gas, and the signal-to-noise ratio is high;

3. The device is easy to use, the height and position of the sample can be adjusted, and the optical fiber probe is installed in the converging cavity to facilitate spectrum collection;

4. The installation cost is low, and no other energy consumption is required.

Description of drawings

Fig. 1 is a schematic structural diagram of a laser-induced plasma spectral enhancement device of the present invention;

Fig. 2 is a schematic diagram of the installation relationship of the laser-induced plasma spectral enhancement device of the present invention;

Fig. 3 is a schematic diagram of the internal optical path of the laser-induced plasma spectrum enhancement device of the present invention.

Among them: 1- diverging cavity; 2- focusing lens; 3- converging cavity; 4- fiber optic probe; 5- base; 6- adjustable sample stage; 7- sample; 8- plasma; 9- inert gas interface; 10- Laser filters.

detailed description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will describe in detail with reference to the drawings and specific embodiments.

The invention provides a laser-induced plasma spectrum enhancement device aiming at the problems of poor sensitivity and complex device of the existing LIBS enhancement device.

As shown in Figure 1, the device includes diverging cavity 1, focusing lens 2, converging cavity 3, fiber optic probe 4, base 5, adjustable sample stage 6, inert gas interface 9 and laser filter 10, diverging cavity 1, focusing lens 2. The base 5 and the laser filter 10 form a closed space. The inert gas interface 9 is connected to the diverging cavity 1. The other side of the focusing lens 2 is connected to the converging cavity 3. The converging cavity 3 and the diverging cavity 1 are connected and fixed by nuts. The optical fiber probe 4 On the converging cavity 3 , an adjustable sample stage 6 is installed on the base 5 , and a sample 7 is placed on the adjustable sample stage 6 , and a laser excites the sample 7 to generate a plasma 8 .

As shown in Figure 2, the device, together with the pulsed laser, optical path system, spectrometer, and inert gas protection system, realizes the spectral enhancement of laser-induced breakdown spectroscopy.

Before use, the focusing lens 2 is placed in the installation position between the diverging cavity 1 and the converging cavity 3, and the two cavities are connected and fixed by nuts, and the focusing lens 2 is clamped to make it integrated. Place the sample 7 on the adjustable sample stage 6 of the base 5, adjust the adjustable sample stage 6 so that the distance between the upper surface of the sample 7 and the upper surface of the base 5 is appropriate, so that the plasma 8 can be ensured at the focal point of the concave mirror in the diverging cavity . After building the pulse laser, spectrometer, and external optical path system, adjust the external optical path to focus the laser on the surface of the sample 7 . Finally, the connected diverging cavity 1, focusing lens 2, and converging cavity 3 are placed on the base 5 as a whole, so that they are tightly bonded to form a whole. At this point, the installation of the device is completed, and then the inert gas is connected to the diverging cavity 1 through the inert gas interface 9, and the optical fiber of the spectrometer is connected to the converging cavity 3.

As shown in Figure 3, during the experiment, the pulsed laser is focused by the external optical path system and then passes through the laser filter 10 on the diverging cavity 1 and hits the sample 7, and the spectrum is reflected by the inner wall of the diverging cavity 1 into parallel light and directed to the focusing lens 2. After focusing by the focusing lens 2, a focus is formed on the fiber optic probe 5 at the bottom of the converging cavity 3, and the large-area reflected light from the left hemisphere and the direct light from the right sphere are collected into the fiber optic probe 5 to greatly enhance the spectral intensity. On the other hand, the excited plasma 8 is confined in the closed space enclosed by the diverging cavity 1, the focusing lens 2 and the base 5, and the shock wave produced with the plasma 8 will propagate outward at supersonic speed. When the inner wall of the cavity is closed, reflection occurs on the inner wall, and the reflected shock wave will compress the plasma 8, and the volume of the compressed plasma 8 becomes smaller, and the internal temperature of the plasma increases and becomes brighter, thereby releasing stronger atoms, ion spectrum.

The above description is a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (7)

1. A laser-induced plasma spectral enhancement device, characterized in that: comprising a diverging cavity (1), a focusing lens (2), a converging cavity (3), an optical fiber probe (4), a base (5), an adjustable sample stage (6), the inert gas interface (9) and the laser filter (10), the divergent cavity (1), the focusing lens (2), the base (5) and the laser filter (10) form a closed space, and the inert gas interface (9 ) is connected to the diverging cavity (1), one side of the focusing lens (2) is connected to the converging cavity (3), the converging cavity (3) and the diverging cavity (1) are connected and fixed by nuts, and the optical fiber probe (4) is connected to the converging cavity (3) ), the adjustable sample stage (6) is installed on the base (5), the sample (7) is placed on the adjustable sample stage (6), and the laser excites the sample (7) to generate plasma (8). 2. A kind of laser-induced plasma spectrum enhancement device according to claim 1, characterized in that: said divergence cavity (1) reflects the spectrum emitted by the spherical surface of plasma (8) into parallel light, and passes through the focusing lens ( 2) After that, focus the light on the fiber optic probe (4) of the converging cavity (3). 3. A kind of laser-induced plasma spectrum enhancement device according to claim 1, characterized in that: said diverging cavity (1), focusing lens (2), base (5), and laser filter (10) are surrounded by Fill the closed space with inert gas through the inert gas interface (9) to isolate the air. 4. A laser-induced plasma spectrum enhancement device according to claim 1, characterized in that: the laser filter (10) can only allow light with the same wavelength as the laser to enter, and prevent light with other wavelengths from entering the device. 5. A kind of laser-induced plasma spectrum enhancement device according to claim 1, characterized in that: the focal point of the diverging cavity (1) coincides with the left focus position of the focusing lens (2), and the focusing lens (2) The right focus of is on the fiber optic probe (4) of the converging cavity (3). 6. A kind of laser-induced plasma spectrum enhancement device according to claim 1, characterized in that: by adjusting the height of the adjustable sample stage (6), the distance between the upper surface of the sample (7) and the focal point of the diverging cavity (1) is controlled distance. 7. A laser-induced plasma spectral enhancement device according to claim 1, characterized in that: the inner wall of the diverging cavity (1) uses a concave mirror embedded with a certain curve, or the inner wall of the diverging cavity (1) is coated way to reflect the plasma spectrum.