2023-06-24 05:30:37
X-ray lasers have long been the stuff of science fiction. The first of these did not become operational for a scientific purpose until twelve years ago, at Stanford University as a facility of the Office of Science of the US Department of Energy. The instrument, known as the Linear Accelerator Coherent Light Source (LCLS), draws its power from the world’s tallest linear particle accelerator, at SLAC National Accelerator Laboratory. Through it, strange states of matter were formed that did not occur anywhere else in the universe, by exposing atoms, molecules, and solids to high-intensity X-ray pulses. So what is this device? And what are its characteristics? Contents of the article: The mechanism of X-ray work If we put an atom, a molecule, or a grain of dust in the face of the most powerful X-ray laser in the world, it will not have any chance of survival. The temperature of the laser-illuminated substance reaches more than a million “kelvins”, as in the case of the sun. And that in less than one trillionth of a second. For example, neon atoms subject to such exceptional circumstances lose all of their ten electrons quickly, and once they lose their protective electronic shell, they explode away from neighboring atoms. The path of its debris is a very fascinating sight for physicists. What makes this process so amazing is that the laser light knocks the electrons out of the atom from the inside out. But the electrons, which surround the nucleus of the atom in orbital layers similar to layers of onions, do not all interact homogeneously with the X-ray beam. Because the outer layers are almost transparent to these rays. Therefore, the inner layer is the one that falls under the brunt of the radiation, just as the coffee is heated in the cup placed in a microwave oven long before the cup – as shown in the corresponding figure. The x-rays expel the electrons of the inner K_ orbital. The two electrons in that layer go out, leaving behind an empty space, so the atom becomes hollow. Within a few femtoseconds, more electrons are sucked in to replace the lost electrons. The cycle of forming the inner cavity and filling the void is repeated until there are no electrons left around the atom. This process occurs in molecules and in solid matter as well.[1] But this strange condition lasts only a few femtoseconds. In solids, matter disintegrates into an ionized state, that is, into a dense and hot plasma that is usually found only in exceptional circumstances such as nuclear fusion reactions or in the centers of huge planets. On planet Earth, there is no equal to the fleeting extremes that arise when an atom interacts with an X-ray laser beam. LCLS revived and opened new horizons In fact, the first X-ray laser derived its energy from an underground nuclear bomb test. He built that laser for a secret project called Excalibur. Laboratory implemented <لورنس ليفرمور> national. And that device was one of the components of the Strategic Defense Initiative launched by the former US President <رونالد ريكان> And called Star Wars in the eighties of the last century. Its purpose was to shoot down missiles and satellites.[2] The laser is known as the Linear Coherent Light Source Accelerator (LCLS) at the Stanford Linear Accelerator Center (SLAC). It awakens memories of those “Star Wars” anti-missile systems.[3] Stanford University built it as the world’s tallest electron accelerator. The accelerator is three kilometers long and appears from space as a needle pointed at the heart of the university campus. The linac owes its origins to the many discoveries and Nobel prizes that have kept the United States at the forefront of elementary particle physics for decades. Since the reassignment of new tasks in the month 2009/10. For atomic and plasma physics, chemistry, dense matter physics and biology, it is what the Large Hadron Collider (LHC) is. The X-ray pulses of the LCLS can be so short (a few femtoseconds) that they make the atoms appear rigid. This enables physicists to see chemical reactions as they occur. These pulses are also very bright, allowing the imaging of proteins and other biological molecules that have been particularly difficult to study. Shadows of Atoms and Imaging of Tiny Distances The X-ray laser combines two of the main tools used by today’s experimental physicists. They are synchrotrons and ultrafast lasers. As for the synchrotrons, they are accelerators with a ring shape in which the electrons rotate, and they emit x-rays that enter measuring devices placed around the perimeter of the machine in the form of a wheel with rods emanating from its center. Synchrotron X-rays are used to study the depths of atoms, molecules and nanoscale systems. X-ray light is ideal for this purpose, because its wavelengths are the size of an atom. [4] Therefore, atoms generate shadows within the X-ray beam. In addition, the X-rays can be modified to see certain types of atoms. Like iron atoms only, for example, and shows where they are located within the solid body or within a large molecule such as hemoglobin particles (iron is responsible for the red color of blood). But what X-rays can’t do is track atomic motion within a molecule or solid. All we see then is a faint mist. Because the pulses are neither short nor bright enough. The synchrotron can only image particles if they are arranged in crystals, where local forces keep millions of them in neat rows. With regard to lasers, their light is much brighter than normal light because it is coherent light. The electromagnetic field in the laser is not wavy like the surface of a raging sea, but vibrates with smoothness and controlled regularity. Coherence means that the lasers can focus enormous energy into a small spot. And that it can be ignited and extinguished in a short moment of the femtosecond order. Contrast between x-rays and normal lasers Regular lasers operate at wavelengths of visible and near-light. And those lengths are a thousand times greater than the wavelengths necessary to distinguish individual atoms. Just as weather radar can see a rainstorm without distinguishing the raindrops, ordinary lasers can see a moving group of atoms without distinguishing them individually. In order to create a sharp shadow for the observed object, the wavelength of the light must be small and at least of the order of the size of that object. And so we need an x-ray laser. In short, the X-ray laser overcomes the difficulties and drawbacks presented by common tools for imaging matter at very small sizes. But making a device of this type is not an easy task. The idea of building an X-ray laser seemed strange at one time. Considering that making any laser is extremely difficult in and of itself. Ordinary lasers work because the atoms are like little batteries. They absorb small amounts of energy, store them, and then emit them in the form of photons, that is, particles of light. It automatically releases its energy normally, however <أينشتاين> At the beginning of the twentieth century, he had discovered a way to trigger its liberation through a process called simulated emission. If you make the atom absorb a certain amount of energy, and then bombard it with a photon that has a similar amount of energy, the atom releases the absorbed energy, generating a copy of the photon. The two photons (the original and the cloned) are released to stimulate the release of energy from a pair of other atoms, and this is repeated accumulating an army of clones in an exponential chain reaction. The result is laser beams. But even when conditions are right, atoms do not always reproduce photons. The probability of a particular atom emitting a photon when it is bombarded by another photon is small. There is a greater chance for her to release her energy before this happens. Ordinary lasers overcome this limitation by pumping energy into the atoms, while using mirrors that send the reproduced light back and forth to capture new photons. In an X-ray laser, each step of this process is much more difficult to achieve. An X-ray photon can have 1,000 times more energy than a visible photon. So each atom has to absorb a thousand times more energy. Atoms do not retain their energy for a long time. In addition, it is difficult to obtain reflective mirrors for x-rays. Although these drawbacks are not intrinsic, enormous energy is required to create the lasing conditions. Linear Accelerator Parts and How It Works The LCLS is the closest thing humanity has made to a spaceship’s laser cannon. This device derives its power from a linear particle accelerator. It is an amplified version of the electronic cannon used in the old television set, which fires electrons at speeds close to the speed of light. The wavy is the basis of this invention. It makes electrons take a zigzag path. Whenever the electrons change direction, they emit radiation consisting in this case of x-rays. Because the electrons move at a speed close to the speed of the X-rays they emit, this process feeds itself and produces a beam of exceptional intensity and purity.[5] Components of the device: Operating laser: The operating laser generates ultraviolet light pulses that remove pulses of electrons from the cathode. Accelerator: Electric fields accelerate electrons to energies of 12 billion electron volts. This LCLS coherent light source uses one kilometer of the total length of the SLAC accelerator. That is, only a third of it. Band 1 Compressor: Electron pulses enter an attenuated “S” curved path that straightens the arrangement of electrons of varying energies. Package Compressor 2: After a round of acceleration. The pulses enter another compressor, which is longer than the first compressor. Because the energy of the electrons is now greater. Transmission Hall: The magnets here make the pulses bigger or smaller. Corrugated lounge: A group of magnets with alternating polarity causes a zigzag motion of electrons, inducing them to generate an X-ray laser beam. Boot extraction: A strong magnet pulls in the electrons and lets the x-rays continue on their way. Experimental light source station: X-rays do their job. It hits the material and does the job of imaging. Sources: 1- Interaction of X-ray with Atoms 2- Excalibur Project 3- LCLS Overview II SLAC 4- Synchrotron 5- The Ultimate X-ray Machine
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