It can release several times as much powerful energy as the global power grid in a billionth of a second. Similar physical conditions can only be found in the center of a nuclear explosion, inside a star or at the edge of a natural black hole, but now they can be realized in a laser the size of a football field in Shanghai. This is the power demonstrated by the giant laser device "Shenguang II" successfully developed in China a few days ago.
"Shenguang II" was built in Shanghai Institute of Optics and Mechanics, China Academy of Sciences, and hundreds of optical devices were integrated in a space the size of a football field. When eight intense lasers are concentrated on a small fuel target ball through a three-dimensional amplification chain in space, they can emit several times the total power of the global power grid in a billionth of a second, thus releasing extremely high pressure and high temperature and triggering a fusion reaction.
"Shenguang II" can be used as a scientific experiment, and the extreme physical conditions produced by the huge energy released in the experiment are of great significance to basic scientific research, the introduction of high-tech applications and new technologies, and the protection of national security.
The future prospect of "Shen Guang" is attractive. According to experts, nuclear fusion is the hope of clean energy in the future. It is predicted that by the middle of this century, scientists can use laser fusion technology to transform abundant isotopes deuterium and tritium in seawater into huge and inexhaustible energy.
The completion of "Shenguang II" has taken a gratifying step for China scientists to obtain energy from seawater. The appearance of "Shen Guang II" indicates that China's high-power laser research and laser nuclear fusion research have entered the advanced ranks in the world. At present, only a few countries such as the United States and Japan can build such a sophisticated giant laser. The overall technical performance of "Shenguang II" has entered the top 5 in the world. Instantly distinguish between giant lasers and global dynamics.
It can release several times as much powerful energy as the global power grid in a billionth of a second. Similar physical conditions can only be found in the center of a nuclear explosion, inside a star or at the edge of a natural black hole, but now they can be realized in a laser the size of a football field in Shanghai. This is the power demonstrated by the giant laser device "Shenguang II" successfully developed in China a few days ago.
"Shenguang II" was built in Shanghai Institute of Optics and Mechanics, China Academy of Sciences, and hundreds of optical devices were integrated in a space the size of a football field. When eight intense lasers are concentrated on a small fuel target ball through a three-dimensional amplification chain in space, they can emit several times the total power of the global power grid in a billionth of a second, thus releasing extremely high pressure and high temperature and triggering a fusion reaction.
"Shenguang II" can be used as a scientific experiment, and the extreme physical conditions produced by the huge energy released in the experiment are of great significance to basic scientific research, the introduction of high-tech applications and new technologies, and the protection of national security.
The future prospect of "Shen Guang" is attractive. According to experts, nuclear fusion is the hope of clean energy in the future. It is predicted that by the middle of this century, scientists can use laser fusion technology to transform abundant isotopes deuterium and tritium in seawater into huge and inexhaustible energy.
The completion of "Shenguang II" has taken a gratifying step for China scientists to obtain energy from seawater. The appearance of "Shen Guang II" indicates that China's high-power laser research and laser nuclear fusion research have entered the advanced ranks in the world. At present, only a few countries such as the United States and Japan can build such a sophisticated giant laser. The overall technical performance of "Shenguang II" has entered the top 5 in the world. Laser technology is used for all kinds of detection and measurement.
Laser technology is used for all kinds of detection and measurement.
The application of laser technology in detection is mainly realized by using the excellent characteristics of laser as light source and cooperating with corresponding photoelectric elements. It has the advantages of high precision, wide measurement range, short detection time and non-contact, and is often used to measure parameters such as length, displacement, speed and vibration. When the measured object is irradiated by laser, some characteristics of laser will change. By measuring its response, such as intensity, speed or type, we can know the shape, physical and chemical characteristics of the measured object, as well as their variation. The types of response include: the release of products such as light, sound, heat, ions and neutral particles, and the changes of amplitude, phase, frequency, polarized light direction and propagation direction of reflected light, transmitted light and scattered light.
◆ Laser Ranging The basic principle of laser ranging is: emit a laser with a speed of C to the measured target, and measure its return time, so as to get the distance d between the laser and the measured target. Namely: d = CT/2
Where the time interval between the t- laser emission and the reception of the return signal. It can be seen that the accuracy of this laser ranging depends on the accuracy of time measurement. Because it uses a pulsed laser beam, in order to improve the accuracy, it is required that the laser pulse width is narrow and the optical receiver responds quickly. Therefore, high-output solid-state lasers and carbon dioxide lasers are often used as laser sources for long-distance measurement. In short-range measurement, gallium arsenide semiconductor laser is used as laser source.
◆ Laser length measurement
According to the optical principle, the relationship between the maximum measurable length L of monochromatic light and the wavelength λ of light source and the width δ λ of spectral line is measured with a common monochromatic light source, and the maximum measurable length is 78cm. If the measured object exceeds 78cm, it must be measured in sections, which will reduce the measurement accuracy. If he-ne laser is used as the light source, the maximum measurable length can reach tens of kilometers. The general measuring range is less than 10m, and the measuring accuracy can be guaranteed within 0.1μ m. ..
◆ Laser interferometry
The principle of laser interferometry is to use the coherent characteristics of laser to process the information of phase change. Because light is a kind of high-frequency electromagnetic wave, it is difficult to observe its phase change directly, so it is much easier to observe by using interference technology to convert the phase difference into the change of light intensity. Generally, the distance, size and shape of the object to be measured can be measured in a non-contact way by using the interference between the reference light on the reference reflection surface and the observation light reflected by the object to be observed, or the interference between the reference light and the light whose phase changes after passing through the object to be observed, and the measurement accuracy can reach the wavelength order of light. Because the wavelength of light is very short, the measurement accuracy is quite high.
◆ Lidar
Lidar is used to emit laser beams into the air and analyze the scattered signal light, so as to know the types, quantities and distances of suspended molecules in the air. By using short pulse laser, the information contained in each pulse can be observed in time series, and the three-dimensional spatial distribution of the object and its moving speed and direction can be obtained. If picosecond pulsed laser is used, its spatial resolution can reach below 10cm. After the laser irradiates an object, it will scatter. According to the change of photon energy, scattering can be divided into elastic scattering and inelastic scattering. Elastic scattering can be divided into Rayleigh scattering and mie scattering. Compared with the laser wavelength, the size of the scatterer is very small, which is called Rayleigh scattering. The scattering corresponding to the laser wavelength is called Michaelis scattering. Rayleigh scattering intensity is inversely proportional to the fourth power of the wavelength of the irradiated laser, so it can be distinguished from Michaelis scattering by changing the wavelength measurement method. Therefore, inelastic scattering also includes Raman scattering and Brillouin scattering. Raman scattering refers to the phenomenon that when light meets atoms or molecules, the frequency of scattered light changes due to the natural vibration of the scatterer and the exchange of rotational energy and energy. Due to the different molecular structures of constituent substances, the characteristics of Raman scattering are also different. Therefore, by splitting the received scattering spectrum, it is easy to identify the molecular species by spectral analysis. Therefore, by measuring the scattered light, we can determine whether there is turbulence in the air (Michaelis scattering) and the types and quantities of various air pollutants such as CO and NO (Raman scattering). It can be seen that lidar technology plays an important role in solving environmental problems.
Measurement is indispensable in industry, such as length measurement, displacement measurement, speed measurement and so on. Different applications require different measurement accuracy, so different means are needed to achieve it. Taking the measurement of length or displacement as an example, when the measurement accuracy is required to be in the order of millimeters, it is enough to use an ordinary meter ruler, while the measurement accuracy of calipers can reach one hundredth of a millimeter and the maximum range is several tens of centimeters. For more accurate measurement in a wider range, especially for real-time measurement of the position or displacement of fast moving objects, the traditional methods have some shortcomings. Laser provides the most powerful tool for precision measurement.
A joint research group composed of Japan Metrology Institute and Tokyo Precision Instrument Company introduced a method to measure the position of three-dimensional moving objects. The system includes four interferometers. The light source used is a He-Ne laser with the wavelength of 632.8 nm, and the measured object is equipped with a light reflector. In an experiment conducted by the research group, a 2-meter-high manipulator moves at a speed of 50 cm per second, and the position of the end mirror of the manipulator is measured systematically, with the measurement accuracy reaching 65438 0 μ m.
Up to now, most interferometers used for accurate displacement measurement are based on stable laser sources to ensure their sufficient coherence length, and the whole system is quite expensive. It is reported that an Israeli company in Jerusalem recently invented a patent to develop a cheap and accurate displacement measurement system based on the inherent stability of He-Ne laser without special stabilization measures. It is said that its performance is similar to that of a relatively expensive and complicated stable laser interferometer displacement meter, and its measurement accuracy reaches 0.3 micron at the distance of 1 meter.
Perhaps one of the most interesting applications of laser interferometer is to measure gravitational waves. Einstein once speculated that strong astronomical events such as star explosion, black hole collision and "initial" collision of the universe may form gravitational waves. However, because this wave is very weak if it exists, it has never been detected for decades, and it is impossible to determine whether it exists.
With the development of laser technology, the sensitivity of laser interference precision measurement has been improved unprecedentedly, and people are interested in it again. It has been reported recently that Germany and Britain are building a system called GEO600 near Hanover, Germany, in an attempt to detect gravitational waves. Many research groups from Germany and the United States participated in the research of the system, such as the University of Hanover in Germany, Max Planck Institute of Quantum Optics in Schwab and Einstein Institute in Potsdam, as well as research groups from the University of Glasgow and the University of Wales. The total investment is $6.5438+0.05 million, which is provided by Max Planck Institute in Germany, Volkswagen Foundation and British Particle Physics and Astronomy Research Council.
According to reports, GEO600 is expected to detect changes in the measured length as small as a fraction of the diameter of a single nucleus. This sensitivity is equivalent to a 20 cm change in the distance from the Earth to the center of the Milky Way. In other words, at the distance of 10 circle around the earth, as long as the diameter and length of the atom change, it can be detected! What an incredible and veritable "astronomical figure"!
It is reported that there have been some similar devices in the world before, such as two systems in hanford and Livingston, an Italian pizza system and a Japanese system. GEO600 is a complement to these systems. If the detection is successful in at least four places, the location of the gravitational wave source can also be determined.
The first measurement of gravitational waves will be a major event in physics, and its practical significance lies in enabling astronomers to have an insight into the processes taking place in the universe. Interestingly, the basis of laser generation is Einstein's genius prediction 80 years ago-stimulated radiation transition. Today, people are trying to verify another prediction of this talented scholar with the help of laser (we won't call this prediction a genius for the time being, but once it is confirmed, it will be a great breakthrough in China's laser interferometry technology. April 25, 2007 19:06 Guangming. Com- Guangming Daily.
Beijing, 24 apr (correspondent Zhou Yong, reporter Lian Yuchun): After more than 30 years of application and development, the development of laser interferometric velocimeter (VISAR) in China has made a major breakthrough. The laser interferometric velocimetry system developed by the Institute of Fluid Physics of China Academy of Engineering Physics (China First Institute of Physics) has reached the international advanced level, and its performance indicators have made great contributions to China's weapon development, new material science, astrophysics and earth science.
Experimental research in physics and other fields provides advanced testing methods.
Laser interferometric velocimetry is a testing technology based on optical Doppler effect. It uses laser as the detection light source, and calculates the change of the moving speed of the object by irradiating the surface of the high-speed moving object and depending on the frequency of the reflected laser. This technology can be used to measure the velocity change of high-speed moving objects in a very short time, as well as the free surface velocity and internal particle velocity of various materials under the action of shock wave, which is of great value to study the physical and mechanical response characteristics of materials under extreme conditions such as high temperature and high pressure. Since it was put forward in 1970s, this technology has been mainly used in detonation experiments and damage effect tests of various weapon warheads, and has a strong military application background.
Since 1970s, the First Research Institute of China Academy of Sciences has been paying close attention to the development trend of international laser interferometric velocimetry, and has made efforts to develop laser interferometric velocimetry devices suitable for various detonation experiments. 1985, JSG- 1, the first prototype of three-probe laser interferometer velocimeter in China, was developed, and the free surface velocities of iron, copper, tungsten, aluminum and other targets under detonation were measured. 1989, they developed a four-probe JSG-2 laser interferometer velocimeter, and its performance is equivalent to that of the American velocimeter at the same time. 1994, in order to meet the needs of detonation experiment, Li Zeren et al. put forward the idea of the world's first * * * cavity multi-point laser interferometry, and realized multi-point continuous measurement, expanding one-dimensional physical problems to two-dimensional and three-dimensional research; From 65438 to 0996, they began to develop the prototype of multi-point laser interferometer velocimeter. Up to now, various types of multipoint VISAR have been developed and applied in a large number of detonation experiments, providing systematic and technical support for many domestic units. After 1997, in order to solve the problems that VISAR is easy to lose interference fringes and the system structure is complex when the speed changes rapidly, and to make the laser interferometric velocimetry technology more simple and easy to use in special environment, the laboratory of shock wave physics and detonation physics of a key laboratory of national defense science and technology of Chinese Academy of Sciences began to study the all-fiber laser interferometric velocimetry technology. The research team led by Tan Hua explored single-mode all-fiber velocity interferometry, wide-spectrum multi-mode all-fiber velocity interferometry and all-fiber velocity and displacement interferometry combining single-mode and multi-mode. After nearly ten years' efforts, they have successfully developed a new all-fiber laser displacement interferometric velocimetry device combining multimode with single mode, which overcomes the defects of traditional VISAR and can conveniently and reliably measure the transient velocity of high-speed moving objects under strong load, which is a major breakthrough in the field of laser interferometric velocimetry in China. In 2006, this achievement was published in the internationally renowned journal Applied Physics Communication.