A coaxial double-pulse laser remote online micro-area in-situ water molecule analyzer

Abstract

The application discloses a coaxial double-pulse laser remote online micro-area in-situ water molecule analyzer, a pulse control generator controls synchronous or delayed work of two lasers; two paths of expanded lasers are coaxially transmitted after being reflected by a mirror and a right-angle prism, a climbing optical system lifts the optical path, and then the laser is focused on the sample surface by a focusing mirror; the sample is placed in an ablation cell, and the ablation cell is placed on a three-dimensional moving platform; a camera shoots the sample surface in real time, and a control signal is fed back to a three-dimensional platform controller to control the three-dimensional moving platform to move, so that the laser is automatically focused on the sample surface; the spectral signal of the sample surface is reversely transmitted to a light collecting device, and then transmitted to a spectrometer, the spectral signal is detected by the spectrometer, and the water molecule and isotope composition information in the sample are obtained. The application can be used as a lunar probe flight load, and can remotely, non-contact, real-time online and micro-area in-situ detect lunar soil water ice, water molecule of water-containing mineral, H and O isotope composition and ratio.

Description

Technical Field

[0001] This invention belongs to the field of Earth and planetary chemical analysis, specifically relating to a coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer. Background Technology

[0002] The potential presence of abundant water ice in the permanently shadowed regions of the Moon has become a hot topic in current lunar exploration due to its significant scientific importance and potential applications. Since the 1990s, with technological advancements, methods for detecting lunar water ice have become increasingly sophisticated. Researchers have utilized radar, neutron spectroscopy, spectrometers, impact experiments, and other detection technologies to explore the Moon and conduct laboratory testing and analysis on lunar return samples. Among these, spectroscopic methods can infer water ice content by detecting the OH / H2O composition. Spectroscopic techniques are widely used, including the Lunar Mineralogical Mapper (M3) instrument on the Chandrayaan-1 mission, the High Resolution Infrared Spectrometer (HRIR) on the Deep Impact EPOXI mission, the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft, and the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) on the OSIRIS-REx mission. All of these experiments have demonstrated the presence of water in the permanently shadowed regions of the Moon.

[0003] However, existing methods for remote sensing lunar water ice detection each have their limitations: radar is only sensitive to large blocks of pure water ice and cannot eliminate the influence of terrain roughness; neutron detectors can only confirm the presence of hydrogen in the target area; due to the shallow extinction length of the emitted light in the lunar regolith, spectroscopic methods can only detect water ice exposed on the lunar surface; while sampling and returning to the laboratory for measurement can obtain high-precision test results, the sampling location is singular and the sample return and testing process are prone to contamination. In the permanently shadowed areas of the lunar polar regions, there is no light, extremely low temperature, high vacuum, and no direct communication with the Earth. When conducting in-situ contact mechanical sampling, the high-intensity lunar regolith water ice structure is usually detected in situ using high-frequency impact drilling and high-speed kinetic energy erosion, resulting in a complex dynamic relationship between the detection equipment and the lunar regolith water ice structure. Based on the current situation, in future lunar exploration missions, the spacecraft payload will be suspended in the permanently shadowed areas of the lunar polar regions to complete short-term, remote, non-contact (a few meters to tens of meters), micro-area in-situ (micrometer level), and real-time online (second level) exploration, and then fly back to the sunlit area outside the shadow. This is theoretically the most effective way to directly verify the existence, distribution characteristics, occurrence state, and origin of lunar water ice. Summary of the Invention

[0004] The purpose of this invention is to provide a coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer, which enables remote, non-contact, real-time online, micro-area in-situ detection of water molecules and H and O isotope composition and ratios on Earth or planets via coaxial transmission of multiple wavelengths or the same wavelength but different pulse widths of dual lasers.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0006] A coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer includes two lasers of different wavelengths or the same wavelength but different pulse widths, a pulse control generator, a beam expander, a reflector, a right-angle prism, a climbing optical system, a focusing lens, an ablation cell, a three-dimensional moving platform, a camera, a three-dimensional platform controller, a focusing device, and a spectrometer.

[0007] The pulse control generator controls the two lasers to operate, making them emit light synchronously or with a delay. The beam expander is located at the output port of the two lasers. After the beam is expanded, the two lasers are reflected by a mirror and transmitted coaxially by a right-angle prism. The transmission optical path is raised by a climbing optical system, and then the laser is focused onto the sample surface by a focusing lens.

[0008] The sample is placed in an ablation tank, which is placed on a three-dimensional moving platform. The camera captures images of the sample surface in real time and transmits the images to the three-dimensional platform controller, which controls the movement of the three-dimensional moving platform to achieve automatic focusing of the laser on the sample surface.

[0009] The spectral signal from the sample surface is transmitted in reverse to the focusing device, and then to the spectrometer. The spectrometer detects the spectral signal to obtain information on the water molecule and isotope composition within the sample.

[0010] Furthermore, it also includes two photodetectors and an oscilloscope. The two photodetectors detect the scattered light of the two lasers respectively and transmit it to the oscilloscope to obtain the accurate time delay of the two lasers. Adjusting the time delay of the two lasers enables the dual pulses to etch the sample and heat the etch feather respectively.

[0011] Furthermore, it also includes a half-wave plate and a polarizer, which are located behind the beam expander and are used to control the laser energy.

[0012] Furthermore, it also includes a plano-concave lens, which is located in front of the climbing optical system and is used to adjust the laser focus position.

[0013] Furthermore, the climbing optical system includes two mirrors at a 45-degree angle to the optical path.

[0014] Furthermore, the ablation tank is equipped with an optical glass window, which faces the sample surface to allow the laser to pass through.

[0015] Furthermore, it also includes a first dichroic mirror and a second dichroic mirror. The laser, after climbing, passes through the first dichroic mirror, the second dichroic mirror, the focusing mirror, and the optical glass window in sequence before being focused onto the sample surface. The reflected light then passes through the optical glass window, the focusing mirror, and the second dichroic mirror in sequence before entering the camera. The plasma emission light generated by the ablation of the sample passes through the optical glass window, the focusing mirror, the second dichroic mirror, and the first dichroic mirror in sequence before being transmitted to the focusing device.

[0016] Furthermore, it also includes a molecular pump and a carrier gas device. The ablation cell is connected to the molecular pump and the carrier gas device for conducting experiments under different degrees of vacuum conditions or different gas environments.

[0017] Furthermore, after being transmitted to the spectrometer, machine learning is used to demodulate and process the spectral signal, and to invert the content of major and trace elements, as well as the isotopic composition and ratio of the sample.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] This invention employs a combination of optical components such as beam expanders, polarizers, half-wave plates, beam splitters, dichroic mirrors, reflectors, and focusing mirrors to coaxially couple two laser pulses of different or the same wavelength, enabling remote focusing and ablation of the laser. This achieves dual-pulse laser-induced plasma, enhancing the intensity of atomic and molecular spectral signals, increasing the signal-to-noise ratio, and lowering the detection limit. The delay between the two lasers can be precisely adjusted through the control of the photodetector signal and the signal generator. Combining a three-dimensional moving platform, a CCD camera, and artificial intelligence sensing and control technology, self-focusing of the laser onto the sample surface can be achieved. By incorporating a molecular pump and carrier gas device, different levels of vacuum can be created, and inert gases of different compositions, such as He / Ar, can be introduced to study the enhancement effect of molecular spectral signals under different environmental conditions (e.g., different vacuum levels, inert gas concentrations, and pressures). This powerful and easy-to-operate system enables remote, non-contact, real-time, in-situ micro-area analysis of water molecules in lunar regolith, water ice, or other geological samples, and can invert isotopic components and compositions such as H and O. It has significant and broad application prospects in fields such as Earth and planetary analytical chemistry. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer of the present invention.

[0021] In the diagram: 1-First laser, 2-Second laser, 3-Beam expander, 4-Half-wave plate, 5-Polarizer, 6-Right-angle polarizing prism, 7-Planar-concave lens, 8-Optical path climbing system reflector, 91-First dichroic mirror, 92-Second dichroic mirror, 10-Focusing lens, 11-Etching pool, 12-CCD camera, 13-3D platform controller, 14-3D moving platform, 15-Computer, 16-Focusing device, 17-Spectrometer, 18-Delay control generator, 19-Oscilloscope, 20-Photodetector, 21-Molecular pump, 22-Connecting pipe, 23-Reflector. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for explaining the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0023] This invention belongs to the field of earth and planetary chemical analysis, specifically relating to a coaxial, remote, non-contact, real-time, online, micro-area in-situ analysis system using multiple or identical wavelengths but different pulse widths of lasers. It is primarily used for analyzing water molecules, as well as the composition and isotopic components of H and O elements. This invention's coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer coaxially couples laser pulses of different or identical wavelengths to achieve remote dual-pulse laser detection. Combined with a three-dimensional moving platform, a CCD camera, and artificial intelligence sensing and control technology, it achieves self-focusing of the laser onto the sample surface. Combined with a molecular pump and carrier gas device, it can study the enhancement effect of molecular spectral signals under different environmental conditions. This invention is technologically advanced and powerful, helping to improve the intensity of atomic and molecular spectral signals, increase the signal-to-noise ratio, and lower the detection limit, enabling the detection of water molecules and isotopes.

[0024] Currently, geochemical analysis, especially solid-state micro-area geochemical analysis, relies on the combined use of laser ablation sampling systems and multi-cup plasma mass spectrometry (MCMS) to measure the elemental and isotopic content or ratios of samples. However, MMS is bulky, expensive, and easily affected by external gas environments, making it impossible to perform high-precision quantification of H and O isotopes and water molecules at room temperature and pressure. To address these issues, this invention provides a low-cost, rapid, convenient, in-situ, remote, and non-contact method for detecting water ice in permanently shadowed regions of lunar polar areas and retrieving H or O isotopic composition and ratios. This provides direct evidence for solving Earth and planetary science questions related to water molecules or H or O isotopes.

[0025] The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer of the present invention includes two lasers with different wavelengths or the same wavelength but different pulse widths, a beam expander, a reflector, a dichroic mirror, a focusing mirror, a three-dimensional moving platform, a camera, a machine vision control module, and a vacuum pump, etc.

[0026] The system comprises a pulse control generator that controls two lasers to operate synchronously or with delayed emission. The two laser pulses are expanded, attenuated, coupled, raised, and focused onto the sample surface. One laser beam is focused onto the sample surface and ablates it, while the other laser beam heats the plasma induced by the preceding laser beam. Each laser's exit port is equipped with a beam expander. The expanded laser beams are reflected by mirrors and then transmitted coaxially through right-angle prisms. A raised optical system elevates the transmission path, and a focusing lens then focuses the laser beam onto the sample surface.

[0027] The sample is placed in an ablation tank, and a three-dimensional control platform controls the movement of the ablation tank. The three-dimensional control platform includes a three-dimensional platform controller and a three-dimensional moving platform. A CCD camera captures images of the sample surface in real time, and through artificial intelligence sensing and control technology, signals are fed back to the three-dimensional control platform to achieve self-focusing of the laser on the sample surface.

[0028] The spectral signal from the sample surface is transmitted in reverse and received by a focusing device, then sent to a spectrometer. Finally, the spectrometer detects the spectral signal to obtain information on the water molecule and isotopic composition within the sample. This invention enables remote, non-contact, real-time, online, micro-area in-situ detection of water molecules, H and O isotopic composition, and ratios in lunar regolith water ice and water-bearing minerals on Earth.

[0029] Furthermore, half-wave plates and polarizers can attenuate the energy of two laser pulses, achieving energy control. The laser energy can be adjusted according to experimental requirements, enabling the testing of different pulse energies.

[0030] Furthermore, the photodetector detects the scattered light from the two laser pulses, allowing for the measurement of the time delay between them. The delay between the two lasers can be measured and adjusted to achieve dual-pulse ablation and heating of the ablation plume.

[0031] Furthermore, a plano-concave lens is placed in front of the climbing optical system to adjust the laser focus position.

[0032] Furthermore, the ablation pool is equipped with an optical glass window that faces the sample surface.

[0033] Furthermore, the ablation cell is connected to a molecular pump and a carrier gas device, enabling experiments under different levels of vacuum conditions or different gas environments.

[0034] Furthermore, the laser beam, after climbing, is reflected by a dichroic mirror and then focused onto the sample surface after passing through a focusing mirror and an optical glass window in sequence. The reflected light then passes through the optical glass window, focusing mirror, and dichroic mirror in sequence before entering the focusing device. The spectral signal transmitted by coaxial reflection is then transmitted to the spectrometer after passing through the focusing device. Machine learning is used to demodulate and process the spectral signal, and the content of major and trace elements, as well as the isotopic composition and ratios of the sample, are determined.

[0035] Example:

[0036] The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer of this invention is as follows: Figure 1 As shown, the first laser 1 and the second laser 2 can output laser pulses of the same wavelength but different pulse widths, achieving short-pulse laser ablation of the sample and long-pulse laser heating of the plasma induced by the short-pulse laser; or output laser pulses of different wavelengths and different pulse widths, achieving long-wavelength laser ablation of the sample and short-wavelength laser heating of the plasma induced by the long-wavelength laser. Taking nanosecond lasers and femtosecond lasers of the same wavelength as examples, the first laser 1 outputs femtosecond laser pulses, and the second laser 2 outputs nanosecond laser pulses. During the transmission of the two laser beams, two photodetectors 20 detect the two laser signals respectively and display them on the oscilloscope 19, giving the actual delay between laser pulses, and the delay between the two lasers is controlled by the delay control generator 18. The two laser beams are expanded by the beam expander 3, then attenuated by the half-wave plate 4 and the polarizer 5, and finally coupled to the same optical axis for transmission after passing through the reflector 23 and the right-angle polarizing prism 6. The plano-concave lens 7 is placed in front of the climbing optical system, and the laser focus position is adjusted. Then, the laser light path climbs after passing through the climbing system reflector 8, and after passing through the first dichroic mirror 91 and the second dichroic mirror 92, it is focused on the sample surface by the focusing lens 10 to complete laser ablation and laser heating.

[0037] The sample is placed in a sealed ablation tank 11, which has an optical window at the top to allow laser light to pass through, and is fixed at the bottom to a three-dimensional moving platform 14. The ablation tank 11 is connected to a molecular pump 21 and a carrier gas device 22, which can control the gas environment conditions within the ablation tank. The reflected light from the sample surface propagates upwards, passes through the optical window and focusing lens 10 of the ablation tank 11, and is reflected by a second dichroic mirror 92 to a CCD camera 12. The CCD camera 12 transmits the acquired image data to a computer 15, which, through artificial sensing and control technology, can be controlled by a three-dimensional platform controller 14. 3. The automatic control three-dimensional moving platform 14 moves to complete the positioning and self-focusing of the laser on the sample ablation point; the plasma emitted by the sample ablation also propagates upward, passes through the optical window of the ablation pool 11, the focusing lens, the second dichroic mirror 92 and the first dichroic mirror 91, and is collected by the focusing device 16. The light signal is transmitted to the spectrometer 17 for analysis and detection. After the spectral data is processed by machine learning, the presence of water molecules is confirmed and the H and O isotope composition and ratio are inverted, thereby inverting the composition and content information of atoms, molecules and isotopes in the sample.

[0038] In summary, this invention utilizes optical elements such as beam expanders, polarizers, half-wave plates, and focusing lenses, along with two lasers and a delay control generator, to achieve coaxial delayed dual-pulse laser ablation and plasma heating of samples, thereby enhancing atomic and molecular spectral signals. Automatic laser focusing on the sample surface is achieved through dichroic mirrors, a CCD camera, and artificial intelligence sensing and control technology. Furthermore, the sealed ablation pool, molecular pump, and carrier gas device enable control of different gaseous environmental conditions during sample ablation. Finally, a focusing device collects the atomic and molecular emission spectra generated during ablation, which are then detected by a spectrometer to invert the atomic, molecular, and isotopic types and contents of the sample. This invention can serve as a payload for lunar probes, enabling remote, non-contact, real-time, in-situ micro-area analysis of lunar soil water molecules and H and O isotopes. It is easy to operate, has a high signal-to-noise ratio, and has broad application prospects.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer, characterized in that, It includes two lasers with different wavelengths or the same wavelength but different pulse widths, a pulse control generator, a beam expander, a reflector, a right-angle prism, a climbing optical system, a focusing lens, an ablation cell, a three-dimensional moving platform, a camera, a three-dimensional platform controller, a focusing device, and a spectrometer; The pulse control generator controls the two lasers to operate, making them emit light synchronously or with a delay. The beam expander is located at the output port of the two lasers. After the beam is expanded, the two lasers are reflected by a mirror and transmitted coaxially by a right-angle prism. The transmission optical path is raised by a climbing optical system, and then the laser is focused onto the sample surface by a focusing lens. The sample is placed in an ablation tank, which is placed on a three-dimensional moving platform. The camera captures images of the sample surface in real time and transmits the feedback signal to the three-dimensional platform controller, which controls the movement of the three-dimensional moving platform to achieve automatic focusing of the laser on the sample surface. The spectral signal from the sample surface is transmitted in reverse to the focusing device, and then to the spectrometer. The spectrometer detects the spectral signal to obtain information on the water molecule and isotope composition within the sample. After transmission to the spectrometer, machine learning is used to demodulate and process the spectral signal, and to determine the content of major and trace elements, as well as the isotope composition and ratio within the sample.

2. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 1, characterized in that, It also includes two photodetectors and an oscilloscope. The two photodetectors detect the scattered light of the two lasers respectively and transmit it to the oscilloscope to obtain the time delay of the two lasers. Adjust the time delay of the two lasers to achieve the laser pulses to ablate the sample and heat the ablation feather respectively.

3. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 1, characterized in that, It also includes a half-wave plate and a polarizer, which are located behind the beam expander and used to control the laser energy.

4. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 1, characterized in that, It also includes a plano-concave lens, which is located in front of the climbing optical system and is used to adjust the laser focus position.

5. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 1 or 4, characterized in that, The climbing optical system includes two mirrors at a 45-degree angle to the optical path, used to elevate the laser beam transmission and facilitate laser focusing.

6. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 1, characterized in that, An optical glass window is provided on the ablation tank, facing the sample surface to allow laser transmission.

7. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 6, characterized in that, It also includes a first dichroic mirror and a second dichroic mirror. The laser, after climbing, passes through the first dichroic mirror, the second dichroic mirror, the focusing mirror, and the optical glass window in sequence before being focused onto the sample surface. The reflected light passes through the optical glass window, the focusing mirror, and the second dichroic mirror in sequence before entering the camera. The plasma emission light generated by the ablation of the sample passes through the optical glass window, the focusing mirror, the second and first dichroic mirrors in sequence before being transmitted to the focusing device and finally entering the spectrometer.

8. The coaxial dual-pulse laser remote online micro-area in-situ water molecule analyzer according to claim 1, characterized in that, It also includes a molecular pump and a carrier gas device. The ablation cell connects the molecular pump and the carrier gas device and is used to conduct experiments under different degrees of vacuum conditions or different gas environments.

Images