- 3025 - LASERS - a path to fusion power of stars? The hope is that such research could lead to fusion power plants, which could provide energy without emitting greenhouse gases or hazardous nuclear waste. These laser installations dedicate many of their experiments to pursuing fusion power. Mimicking the stars.
------------ 3025 - LASERS - a path to fusion power of stars?
- Earth's gassy atmosphere always gets in the way, blurring and distorting the view of celestial objects. Earthbound astronomers would like a way to cancel out this atmospheric distortion. That's where the lasers come in. According to the European Space Organization, ESO, scientists can fire these lasers from one of the Very Large Telescope's component pieces to simulate distant stars.
-
- Then sodium particles in the atmosphere cause the beams to glow orange. Astronomers focus on these artificial stars to measure how much the beams are being blurred by Earth's atmosphere. By practicing with these fake stars, astronomers can effectively calibrate the telescope to correct for atmospheric blurring when looking at real stars, galaxies and explosive objects like Eta Carinae.
-
- Giant lasers can also recreate the mysterious and explosive physics of supernovae. Instead of studying these astronomical explosions remotely through telescopes physicist create something similar to these explosions using the world’s highest-energy lasers.
-
- Astronomers hope to understand the much misunderstood feature of supernovae, the shock waves that form as a result of explosions can increase particles, such as protons and electrons, to extreme energies.
-
- Supernova collisions are considered some of the most powerful particle accelerators in the universe. Some of those particles eventually fall against Earth, after traveling through cosmic distances. Scientists have long been baffled about how these shockwaves give these energy particles their huge increase in speed.
-
- Astronomers have created a supernova-style shockwave in the lab and watched as they sent particles revealing new hints about how this happens in the universe.
-
- Bringing supernova physics to Earth could help solve other mysteries in the universe, such as the origins of cosmic magnetic fields. These explosions also provide some of the basic elements necessary for our existence.
-
- The iron in our blood comes from supernovae. We are literally created from these exploding stars.
-
- A star exploded in a Milky Way satellite galaxy and the light subatomic particles called neutrinos, revealed a wealth of new information about supernovae.
-
- Supernovae are rare events so instead of waiting astronomers are using extremely powerful lasers to recreate the physics observed after supernova explosions. Lasers vaporize a small lens, which can be made of various materials, such as plastic.
-
- The blow produces a rapidly moving plasma explosion, a mixture of charged particles, that mimics the behavior of the erupting plasma from supernovae.
-
- Stellar explosions are triggered when a massive star runs out of fuel and its core falls and bounces. The outer layers of the star explode outward in an explosion that can unleash more energy than the sun will release throughout its 10 billion-year life. The output stream has an unfathomable 100 “quintillions” (10^20) of kinetic energy “yottajoules“ (10^24 joules).
-
- Supernovae can also occur when a dead star called a white dwarf is revived again, for example after ripping off the gas from a companion star, causing an explosion of nuclear reactions that spiral out of control.
-
- In both cases these explosion send a plasma explosion coming out of the star and its surroundings, the interstellar medium, essentially another ocean of plasma particles. Over time, a turbulent, expanding structure called a “supernova remnant” is formed, which generates a beautiful spectacle of light, tens of light-years in diameter, that can persist in the sky for thousands of years after the initial explosion.
-
- Instead of reproducing the entirety of one supernova at a time, physicists try in each experiment to isolate interesting components of the physics that are taking place.
-
- For explosions in space, scientists are at the mercy of nature. But in the lab, they can change parameters and see how the shocks react. Laboratory explosions occur in an instant and are small, only a few inches in diameter.
-
- These experiments, the equivalent of 15 minutes in the life of a real supernova can take only 10 trillionths of a second. And a section of a stellar explosion larger than the diameter of the Earth can be reduced to 100 micrometers. The processes that occur in both are very similar.
-
- To reproduce the physics of a supernova, laboratory explosions must create an extreme environment. To do this, you need a really large laser, which can only be found in some parts of the world, such as NIF, Lawrence Livermore’s National Ignition Facility, and the OMEGA Laser Facility at the University of Rochester in New York.
-
- In both places, a laser is divided into many beams. The largest laser in the world, in NIF, has 192 beams. Each of these beams is amplified to increase its energy exponentially. Afterwards, some or all of these beams are trained on a small carefully designed target.
-
- The laser can deliver more than 500 trillion watts of power for a brief instant, momentarily surpassing total power consumption in the United States by a factor of a thousand.
-
- A single experiment and every laser blast is a great production. Opportunities to use such advanced facilities are scarce and researchers want every detail to be worked out to be sure the experiment will be a success.
-
- Lasers are not the only way to investigate the physics of supernovae in the laboratory. Some researchers use intense bursts of electricity, called “pulsed energy“. Others use small amounts of explosives to fire. The various techniques can be used to understand different stages in the life of supernovae.
-
- The result of a violent inflow of energy, the shockwaves are marked by a sharp rise in temperature, density and pressure. On Earth, shockwaves cause the sound boom of a supersonic jet, the thunder blow in a storm, and the damaging pressure wave that can break windows after a massive explosion.
-
- On Earth these shockwaves form when air molecules collide with each other, accumulating molecules in a wave of high density, high pressure, and high temperature.
-
- In cosmic environments, shockwaves do not occur in air, but in plasma, a mixture of protons, electrons, and ions, electrically charged atoms. There, the particles can be diffuse enough not to collide directly as in air.
-
- In such a plasma, the accumulation of particles occurs indirectly, the result of electromagnetic forces pushing and pulling the particles. If a particle changes trajectory it’s because it feels a magnetic field or an electric field.
-
- But exactly how those fields form and grow and how such a shockwave results, was hard to decipher. Researchers have no way of seeing the process in real supernovae; the details are too small to observe with telescopes.
-
- These shock waves are known as collision-free shock waves. The particles from these shocks can reach amazing energies. In supernova remnants, particles can gain up to 1,000 trillion volts of electrons, far exceeding the several trillion volts of electrons reached in the largest man-made particle accelerator, the Large Hadron Collider near Geneva.
-
- But the way particles can navigate supernova shocks to reach their amazing energies has been mysterious.
-
- To understand how supernova shock waves increase particles, you need to understand how shockwaves form in supernova remnants. To get there, we have to understand how strong magnetic fields arise. Without them, the shock wave cannot form.
-
- The electric and magnetic fields are closely intertwined. When electrically charged particles move, they form small electric currents, which generate small magnetic fields. And the magnetic fields themselves send charged particles by pulling out the cork stopper, bending their trajectories. Moving magnetic fields also create electric fields.
-
- The result is a complex process of feedback of particles and fields that cause a shock wave. It's a self-modulating, self-controlled, self-reproducing structure.
-
- All this complexity can only develop after a magnetic field is formed. But the random movements of individual particles generate only small, transient magnetic fields. To create a meaningful field, some process within a supernova remnant must reinforce and amplify the magnetic fields. It has long been expected that a theoretical process called “Weibel instability“, first thought of in 1959, would do just that.
-
- In a supernova, the plasma flowing outward in the explosion meets the plasma in the interstellar medium. According to the theory behind Weibel's instability, the two sets of plasma break into filaments as they flow together, like two hands with fingers intertwined.
-
- These filaments act as wires that carry current. And where there is current, there is a magnetic field. The magnetic fields of the filaments strengthen the currents, further improving the magnetic fields. The electromagnetic fields could then be strong enough to redirect and retard the particles, causing them to accumulate in a shockwave.
-
- In 2015 the researchers detected magnetic fields, but did not directly detect current filaments. Finally, in 2020, the team reported that a new experiment would produce the first direct measurements of currents forming as a result of Weibel's instability, confirming scientists' ideas about how fields could form. strong magnetic. in supernova remnants.
-
- For that new experiment researchers launched seven lasers each on two opposing targets. This resulted in two plasma currents flowing at each other up to 1,500 kilometers per second, a speed fast enough to orbit the Earth twice in less than a minute.
-
- When the two fluxes were found, they separated into current filaments producing magnetic fields of 30 tesla, approximately 20 times the strength of the magnetic fields in many MRI machines.
-
- Once the researchers saw magnetic fields, the next step was to create a shockwave and observe it by accelerating the particles. Then researchers hit two disk-shaped targets with 84 laser beams each, or nearly half a million joules of energy, roughly the same as the kinetic energy of a car traveling a road at 60 miles per hour.
-
- The team also found that electrons had been accelerated by shock waves, reaching energies more than 100 times higher than those of ambient plasma particles. For the first time, scientists have seen particles surfing shockwaves like those found in supernova remnants.
-
- In a supernova remnant and in the experiment, a small number of particles are accelerated as they cross the shockwave, going back and forth repeatedly to accumulate energy. But to cross the shockwave, electrons need some energy to get started.
-
- Huge laser facilities like NIF and OMEGA are usually built to study nuclear fusion, the same source of energy that powers the sun. Using lasers to compress and heat a target can cause the nuclei to fuse with each other, releasing energy in the process.
-
- The hope is that such research could lead to fusion power plants, which could provide energy without emitting greenhouse gases or hazardous nuclear waste. But so far, scientists have yet to draw more energy from fusion than they put in, a necessity for practical power generation.
-
- Thus, these laser installations dedicate many of their experiments to pursuing fusion power.
-
- Understanding supernovae could help make fusion power a reality as well, as celestial plasma exhibits some of the same behaviors as plasma from fusion reactors.
-
February 5, 2021 3025
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
--------------------- --- Sunday, February 7, 2021 ---------------------------
No comments:
Post a Comment