CN105762055A - Mass spectrum device for research of plasma-micromolecule system reaction - Google Patents

Abstract

The invention relates to a mass spectrometry device for studying plasma-small molecule system reaction. The mass spectrometry device for studying the plasma-small molecule system reaction comprises a plasma-small molecule reaction unit (1), a femtosecond laser ionization system (2), an ion extraction system (3), a mass analyzer (4), Vacuum chamber (5). Among them, the nanosecond laser sputtering solid target is used to generate plasma, and the gas phase small molecules enter the plasma generation area through the capillary, and react with the plasma near the surface of the target. Femtosecond laser ionization technology was used to ionize the reaction products, and finally, combined with time-of-flight mass spectrometry, the reaction products were analyzed and confirmed. The device can accurately, efficiently and real-time characterize the product composition of the reaction between plasma and gas phase molecules, and provide model support for the accurate cognition of the actual plasma and gas reaction in the production process.

Description

A Mass Spectrometry Device for Studying Plasma-Small Molecule System Reaction

technical field

The invention relates to the field of microscopic chemical reaction kinetics, in particular to a mass spectrometry device for studying the reaction of plasma and gas-phase small molecule systems, which can accurately analyze the products of the reaction process between plasma and gas-phase small molecules.

Background technique

Microscopic chemical reaction kinetics aims to explore the chemical reaction process at the atomic and molecular level, and hopes to realize the regulation of the reaction and make the reaction proceed in a more favorable direction. Plasma is an unavoidable companion in the laser processing process. A relatively simple example, such as in the process of high-power laser cutting metal, will generate plasma when the laser power reaches a certain threshold. The generation of the above-mentioned plasma will defocus the laser and absorb the energy of the laser so that the cutting ability of the laser is greatly weakened. However, it should be noted that if different auxiliary cutting gases are used during the cutting process, the generation of the plasma will change accordingly. For example, when nitrogen is used as auxiliary gas for laser cutting, plasma will be easily generated with the increase of laser power. The big difference is that if oxygen is used as auxiliary gas, the above plasma will be suppressed to a certain extent. Combined with some previous research methods, such as spectroscopy and other analysis methods, it is recognized that the participation of oxygen in the above-mentioned cutting process is not only used as an auxiliary gas to provide some physical functions, such as driving metal slag from the cutting area, but also The reaction with metal suppresses the generation of plasma, and the function of nitrogen is only as an auxiliary gas to drive away the slag, and there is no other reaction, such as the reaction with plasma. For a clear understanding of the above process, there is still a lack of clear images. To a large extent, the understanding of the above-mentioned reactions involving plasma and oxygen is limited due to the limitations of the above-mentioned model establishment and analysis methods.

In recent years, with the rapid development of analytical methods, mass spectrometry, spectroscopy, and energy spectroscopy can all study the reaction process at the molecular level. Among them, mass spectrometry, as a universal analytical technique, has received more and more attention and application in recent years. At the same time, time-of-flight mass spectrometry has gradually become one of the most promising analytical methods in the field of mass spectrometry because of its high resolution, high sensitivity, simple structure, and high cost performance. In addition, with the maturity of ultrashort pulse laser technology, the application of high power density laser has become more and more popular. Femtosecond laser technology has gradually become a new development direction of time-of-flight mass spectrometry ionization means because of its ultrashort laser pulse (pulse width is on the order of 10 ^-15 seconds). After the femtosecond laser is focused, it is very easy to obtain a power density of terawatt level, which can greatly improve the ionization efficiency of the analyzed product. The combination of efficient ionization means and high-resolution analysis technology makes it possible to understand the progress of plasma reaction process.

Contents of the invention

The present invention is made in view of the above facts, and its purpose is to provide a mass spectrometer for researching plasma-small molecule system reactions;

In order to achieve the above object, the technical solution adopted in the present invention is as shown in Figure 1:

A mass spectrometry device for studying plasma-small molecule system reactions, comprising a plasma-small molecule reaction unit (1), an ion extraction system (3) and a mass analyzer (4) placed in a closed container; the plasma - The small molecule reaction unit (1) includes a hollow and airtight reaction chamber, which is provided with a vacuum port connected to a vacuum pump; a metal target is arranged in the reaction chamber, and the nanosecond laser emitted by the nanosecond laser is irradiated on the metal target On the right side of the surface, one end of a gas pipeline is connected to the gas source, and the other side is on the right side of the metal target in the gas pipeline. On the right side surface, a reaction area is formed on the right side of the metal target, and the femtosecond laser emitted by the femtosecond laser is irradiated into the reaction area; the opening on the right side of the reaction chamber, the opening on the left side of the airtight container, the opening on the right side of the reaction chamber, airtight container Through the airtight connection of the opening; the ion extraction system (3) includes two extraction electrodes, ion beam focusing lens group and two pairs of deflection electrodes in sequence from left to right; the extraction electrodes are two flat plates arranged in parallel, respectively There is a truncated conical protrusion, and a through hole through the flat plate is arranged on the truncated conical protrusion along the axial direction. The through holes on the two flat plates are coaxial; the ion beam focusing lens group includes three coaxial and spaced from left to right, The hollow cylindrical metal electrode, the deflection electrode is composed of two sets of metal parallel plates, the plates of the first set of electrodes are placed perpendicular to the plates of the second set; the two extraction electrodes are coaxial with the ion beam focusing lens group, and they The axis of the electrode is located between the two plates of the first group of electrodes and the two plates of the second group; the through hole of the extraction electrode faces the right surface of the metal target irradiated by the nanosecond laser; the mass analyzer is located in the extraction electrode On the right side, a vacuum port connected to a vacuum pump is provided on the airtight container near the mass analyzer; the ions generated by the plasma-small molecule reaction unit enter the mass analyzer for mass analysis after passing through the ion extraction system.

Further, the two plates of the extraction electrode are separated by an insulating gasket with a hole in the middle; the vacuum pump is a mechanical pump and a molecular pump for gas vacuuming.

Further, a potential is applied to the left extraction electrode and the metal target, and the right extraction electrode is grounded; DC voltage is applied to the ion beam focusing lens group and the two pairs of deflection electrodes.

Further, the functions of each part are as follows:

(a) The plasma-small molecule reaction unit (1) can generate plasma and react with the small molecule system;

(b) Femtosecond laser ionization system (2) ionizes the above reaction product;

(c) ion extraction system (3) extracting and accelerating shaping the ionized ions in the reaction product, and making the ion beam enter the time-of-flight mass spectrometer;

(d) The mass analyzer (4) separates the ions entering the region in time according to the difference in kinetic energy, and is converted into an analyzable voltage signal by the mass spectrometer detector;

(f) Vacuum chamber (5) provides high vacuum environment for plasma-small molecule reaction and mass analyzer.

Further, laser sputtering is used to generate plasma in the plasma-small molecule reaction unit (1). The sputtering laser is a pulsed laser, the pulse width is on the order of nanoseconds (1-1000 nanoseconds), and the wavelength can be 300 nanometers to 1200 nanometers. The nanosecond laser is focused on a solid target through a focusing lens, and the power at the focusing position is greater than or equal to 10 ⁵ W/cm ² .

Furthermore, the solid target in the plasma-small molecule reaction unit (1) is fixed on a four-dimensional adjustment frame, and the four-dimensional adjustment frame can realize three-dimensional translation adjustment and one-dimensional rotation adjustment. The above-mentioned reaction gas enters the plasma generation region in a jet flow through a capillary tube and reacts with the plasma. The inner diameter of the above-mentioned capillary is 0.01 mm to 1 mm. The reaction concentration of gas molecules is adjusted by adjusting the pressure before the gas enters the capillary.

Further, a femtosecond laser ionization system (2) is used to ionize neutral products in the plasma-small molecule reaction process. The femtosecond laser can generate laser pulses with a width of 10-1000 femtoseconds, a frequency of 1-1000 Hz, and a focused power density of more than 10 ¹² W/cm ² . The femtosecond laser ionization area is located at a distance of 5-15 cm from the surface of the nanosecond laser sputtering target.

Further, the ion extraction system (3) can accelerate and shape the above-mentioned ionized products. The ion extraction system (3) includes two extraction cones, an ion beam focusing lens group and two pairs of deflection electrodes. The extraction cone has a cone solid angle of 20 to 50 degrees, a cone opening of 0.5 to 5 mm, a cone bottom diameter of 7 to 50 mm, and a cone length of 5 to 50 mm. The ion extraction cones are separated by insulating spacers with a spacing of 3 to 20 mm. The ion beam focusing lens group includes three cylindrical metal electrodes, the outer diameter of the group of electrodes is 7 to 50 mm, the inner diameter is 5 to 45 mm, the length is 3 to 50 mm, and the electrode distance is 2 to 25 mm. The deflection electrodes consist of two sets of metal parallel plates placed vertically. The distance between each group of electrode sheets is 5 to 35 mm. The electrode sheet is rectangular with a side length dimension of 10 to 50 mm. The extraction cone and the ion beam focusing lens group are stacked coaxially, and the distance between the top of the first extraction cone and the region of the nanosecond laser sputtering solid target is 6 to 25 mm.

Further, the mass analyzer (4) can adopt a linear or reflective time-of-flight mass spectrometer, and the detector of the mass spectrometer is an ion detector based on a microchannel plate amplification method.

Further, the system control and data acquisition unit (6) can control the turn-on time of the nanosecond laser, the femtosecond laser and the high-voltage pulse applied by the ion extraction cone. The system control and data acquisition unit (5) controls the femtosecond laser ionization system (2) to turn on within 0.5-20 microseconds after the nanosecond laser is turned on, and the high voltage turn-on time of the ion extraction system (3) is the same as that of the femtosecond laser ionization system (2) Synchronized or turned on within 5 microseconds thereafter.

Further, the vacuum chamber (5) is composed of two stages of vacuum chambers, and each stage of vacuum chambers is composed of a combination of a mechanical pump and a molecular pump. In the early stage of device operation, the vacuum chamber is firstly pumped by the mechanical pump, and then the molecular pump is used to fine-pump the vacuum chamber, so as to achieve a high vacuum or ultra-high vacuum state. During the plasma-small molecule reaction process, the vacuum degree of the reaction chamber (5a) is better than 10 ^-3 Pa, and the vacuum degree of the fieldless flight chamber is better than 10 ^-5 Pa.

The invention utilizes the plasma generated by the nanosecond laser sputtering solid target to model the plasma generation process in the actual process in terms of power density, and uses the femtosecond laser as an ionization means to realize efficient ionization of products. Combined with the time-of-flight mass spectrometry analysis method, the products in the plasma-small molecule system reaction process can be analyzed accurately in real time, so as to achieve a clear understanding of the above reaction process, and provide a model basis for theoretical analysis of corresponding problems in the actual production and processing process .

Description of drawings

Fig. 1 schematic diagram of the principle of an embodiment of the present invention;

Fig. 2 is the mass spectrum of the reaction product of iron plasma and oxygen obtained in the embodiment of the present invention.

1-plasma-molecular reaction unit; 1a-target rack; 1b-nanosecond laser; 1c-gas; 2-femtosecond laser ionization system; 3-ion extraction system; 4-mass analyzer; 5-vacuum cavity body; 5a-reaction cavity; 5b-field-free flight cavity.

The side views in the figures are schematic and not drawn to scale. However, the same or similar components in different figures are given the same symbols in the figures.

detailed description

Some characteristics and advantages of the present invention will be illustrated below through specific embodiments. The present invention is a kind of mass spectrometry device for researching plasma-small molecule system reaction designed in the following way, as shown in Figure 1, this device comprises plasma-small molecule reaction unit (1), femtosecond laser ionization system ( 2), an ion extraction system (3), a mass analyzer (4), and a vacuum chamber (5). Among them, the nanosecond laser sputtering solid target is used to generate plasma, and the gas phase small molecules enter the plasma generation area through the capillary, and react with the plasma near the surface of the target. Femtosecond laser ionization technology was used to ionize the reaction products, and finally, combined with time-of-flight mass spectrometry, the reaction products were analyzed and confirmed. The device can accurately, efficiently and real-time characterize the product composition of the reaction between plasma and gas phase molecules.

Example 1

Product Analysis of Iron Plasma Reacted with Oxygen

This example is intended to illustrate the performance of the device for analyzing and characterizing the product after the iron plasma reacts with oxygen. In this embodiment, iron plasma is generated by nanosecond laser sputtering. The parameters of the nanosecond laser are as follows. The laser wavelength is 532 nanometers, the repetition rate is 20 Hz, the energy is 30 milliwatts, and the pulse width is 20 nanoseconds. It is focused on the surface of iron through a lens with a focal length of 30 cm. The power density of the area laser is about 2.75×10 ⁷ W/cm ² . High-purity oxygen (99.99%) enters the plasma generation area through a metal capillary with an inner diameter of 0.5 mm in the form of a jet. The voltage applied to the extraction electrodes was 1600 volts. The femtosecond laser uses a pulse width of 30-40 femtoseconds, an energy of 3.3 millijoules, and a wavelength of around 800 nanometers. It is focused by a lens with a focal length of 40 centimeters at a distance of 8 millimeters from the iron and sputtering laser reaction area to ionize the reaction product. As shown in Figure 2, the picture in Figure 2a on the top represents only the nanosecond laser sputtering, at this time only the signal of Fe ⁺ can be observed, although the iron plasma has reacted with oxygen, but it is neutral and cannot be carried out. Analyze probes. Figure 2b shows that only the femtosecond laser exists, and the nanosecond laser does not enter at this time, and only oxygen exists in the ionization analysis area, so only the ion signal of oxygen is observed when only the femtosecond laser exists. Shown in Figure 2c is the mass spectrometry signal obtained by femtosecond laser ionization analysis after the nanosecond laser induces plasma and reacts with oxygen. Iron oxide ions can be clearly seen from the mass spectrum. Second laser sputtering produces iron ions, as well as products such as oxygen atomic ions and corresponding divalent ion products generated by plasma-induced oxygen dissociation. The above results fully demonstrate to us the excellent performance of the invention in real-time characterization of the plasma-small molecule reaction process and its products.

Those skilled in the art will understand that the above embodiments are given purely by way of example, and that some changes are possible.

Claims (11)

1. the mass spectrometric apparatus being used for studying plasma-small molecule systems reaction, it is characterised in that: include plasma-little molecular reaction unit (1), ion extraction system (3) and mass analyzer (4) and be placed in a hermetic container；Plasma-little molecular reaction unit (1) includes the reaction chamber that hollow is airtight, and reaction chamber is provided with the vacuum orifice being connected with vacuum pump；Metal targets it is provided with in reaction chamber, the nanosecond laser that nanosecond laser sends is irradiated in the right lateral surface of metal targets, one end of one gas piping is connected with source of the gas, opposite side is in the right side of gas piping metal targets, right lateral surface that the gas purging injected by gas piping irradiates to nanosecond laser, metal targets, forming a reaction zone in the right side of metal targets, the femtosecond laser that femto-second laser sends is irradiated in reaction zone；Reaction chamber right openings, opening on the left of hermetic container, reaction chamber right openings, hermetic container passes through the airtight connection of opening part；Ion extraction system (3) includes two panels from left to right successively and extracts electrode, ion beam focusing battery of lens and two pairs of deflecting electrodes；Extracting electrode is the two pieces of flat boards be arrangeding in parallel, is respectively equipped with truncated cone projection in the left side of flat board, is provided with through the through hole of flat board in truncated cone projection in the axial direction, and the through hole on two pieces of flat boards is coaxial；Ion beam focusing battery of lens include three from left to right coaxial spaced arrange, the cylindrical metallic electrode of hollow, deflecting electrode is made up of two groups of metal parallel plates, the perpendicular placement of pole plate of the pole plate of first group of electrode and second group；It is coaxial with ion beam focusing battery of lens that two panels extracts electrode, and their axis is between two pole plates of first group of electrode and two pole plates of second group；Right lateral surface that the through hole of extraction electrode irradiates towards nanosecond laser, metal targets；Mass analyzer is positioned at the right side extracting electrode, is provided with, in the hermetic container near mass analyzer side, the vacuum orifice being connected with vacuum pump；The ion that plasma-little molecular reaction unit produces enters after ion extraction system in mass analyzer and carries out quality analysis.

2. mass spectrometric apparatus according to claim 1, it is characterised in that: extract insulation spacer isolation with holes by middle part between two pieces of flat boards of electrode；Vacuum pump is mechanical pump and the molecular pump of gas evacuation.

3. mass spectrometric apparatus according to claim 1, it is characterised in that: extracting in left side and apply electromotive force in electrode and metal targets, electrode ground connection is extracted on right side；DC voltage is applied in ion beam focusing battery of lens and two pairs of deflecting electrodes.

4. mass spectrometric apparatus according to claim 1, it is characterised in that:

A () plasma-little molecular reaction unit (1) can produce plasma and react with small molecule systems；

B above-mentioned product is ionized by () femtosecond laser ionization system (2)；

C the ion being ionized in product is carried out extracting acceleration shaping by () ion extraction system (3), and make this ion beam enter flight time mass spectrum；

D () mass analyzer (4) makes the ion in this region of entrance separate in time according to the difference of kinetic energy, and converted to the voltage signal that can analyze by mass spectrometry detector；

E () vacuum chamber (5) provides high vacuum environment for plasma-little molecular reaction and mass analyzer.

5. mass spectrometric apparatus according to claim 1, it is characterised in that:

The method adopting laser splash in plasma-little molecular reaction unit (1) produces plasma；This sputtering laser is pulse laser, and pulse width is nanosecond order (1-1000 nanosecond), and wavelength can be 300 nanometers-1200 nanometers；This nanosecond laser focuses on solid target through condenser lens, at the power of focal position be more than or equal to 10⁵W/cm²。

6. mass spectrometric apparatus according to claim 1, it is characterised in that:

Solid target in plasma-little molecular reaction unit (1) is fixed on a four-dimensional adjusting bracket, and this four-dimension adjusting bracket can realize the three-dimensional translating to solid target and regulate and one-dimensional rotation adjustment；Above-mentioned reacting gas enters plasma generation area in the way of jet by a capillary tube and reacts with plasma；Above-mentioned capillary inner diameter 0.01 millimeter to 1 millimeter；The reaction density of gas molecule is regulated by the pressure before regulating gas entrance capillary tube.

7. mass spectrometric apparatus according to claim 1, it is characterised in that:

Femtosecond laser ionization system (2) is used to the neutral products in ionic plasma-little processes of molecular reactions；This femtosecond laser can be produce laser pulse width at 10-1000 femtosecond, frequency 1-1000 hertz, the power density after focusing is 10¹²W/cm²Above；Femtosecond laser ionized space is positioned at nanosecond laser sputtering target material surface location distance 5-15 centimetre.

8. the mass spectrometric apparatus for studying plasma-small molecule systems reaction according to claim 1, it is characterised in that:

The above-mentioned product being ionized can be accelerated and shaping by ion extraction system (3)；This ion extraction system (3) includes two panels and extracts cone, ion beam focusing battery of lens and two pairs of deflecting electrodes；Extracting cone conical solid angle is 20 to 50 degree, cone perforate 0.5 to 5 millimeter, conical lower portion diameter 7 to 50 millimeters, cone length 5 to 50 millimeters；Isolated by insulation spacer between the ion extraction cone, spacing 3 to 20 millimeters；Ion beam focusing battery of lens includes three cylindrical metal electrodes, this group electrode external diameter 7 to 50 millimeters, internal diameter 5 to 45 millimeters, length 3 to 50 millimeters, electrode spacing 2 to 25 millimeters；Deflecting electrode is made up of two groups of metal parallel plates, and this two arrays of electrodes is vertically placed；Often group electrode slice spacing 5 to 35 millimeters；Electrode slice is rectangle, and size dimension is 10 to 50 millimeters；Said extracted cone and ion beam focusing battery of lens coaxially pile up placement, and put forward the zone length 6 to 25 millimeters that first extracts the vertex of a cone distance nanosecond laser sputtering solid target of cone.

9. mass spectrometric apparatus according to claim 1, it is characterised in that:

Mass analyzer (4) can adopt orthoscopic or reflective flight time mass spectrum, and this mass spectrographic detector is the ion detector amplifying mode based on microchannel plate.

10. mass spectrometric apparatus according to claim 1, it is characterised in that:

System Control & data acquisition unit (6) can control the opening time of the high-voltage pulse that nanosecond laser, femtosecond laser and the ion extraction cone apply；System Control & data acquisition unit (5) controls femtosecond laser ionization system (2) and opens in the time of 0.5-20 microsecond after nanosecond laser is opened, and the high-pressure opening time of ion extraction system (3) is Tong Bu with femtosecond laser ionization system (2) or unlatching within 5 microseconds behind.

11. mass spectrometric apparatus according to claim 1, it is characterised in that:

Vacuum chamber (5) is made up of left and right two-stage vacuum cavity, and every grade of vacuum cavity has one group of mechanical pump and adds the vacuum pump combination composition of molecular pump；First vacuum chamber is slightly taken out by the early stage at plant running by mechanical pump, has molecular pump that vacuum chamber is carried out essence afterwards again and takes out, thus reaching fine vacuum or ultra-high vacuum state；In plasma-little molecular reaction generating process, the vacuum of reaction chamber (5a) is better than 10^-3Pa, the vacuum in field-free flight chamber is better than 10^-5Pa。