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12 min read<\/p>\n12 min read<\/p>\n
FUSION IS THE ENGINE OF THE UNIVERSE. The smallest microbe to the most complex life found on alien worlds exist because of the cataclysmic physics happening at the heart of every star. Every pinprick of light in the night sky is a mixture of immense gravity and heat creating a self-sustaining thermonuclear explosion that makes life possible.<\/p>\n
For nearly a century, scientists have known that this explosive dance of ionized plasma at the heart of our sun is what bathes our planet in light and heat. And since that discovery, universities, laboratories, government agencies, and international coalitions have invested billions into finding some way to bottle the sun and generate clean, limitless energy<\/a>.<\/p>\n Dozens of private companies funded by some of the richest people in the world are forging ahead with varying ways to create commercial fusion<\/a>. One of the newest firms in the race for limitless energy wants to harness the laser-blasting tech behind America\u2019s greatest fusion breakthrough to date, while other firms are taking a different route that involves magnets, superconductors, and super-hot plasma.<\/p>\n No matter which approach wins out, if we hope to make commercial fusion a reality within the coming decades, it\u2019ll take a level of scientific dedication (and funding) that would make the Apollo program look like a high school science project.<\/p>\n This is the story of nuclear fusion\u2014how it works, where it\u2019s headed, and what kind of human society it\u2019ll leave in its wake.<\/p>\n FOR ALL THE GRANDIOSE PROMISES OF NUCLEAR FUSION, the science at its heart happens on an extremely small atomic scale. At its most basic level, nuclear fusion occurs when two light nuclei (i.e. hydrogen) combine or fuse together to form a heavier isotope called helium-4. Meanwhile, fission<\/a>, which is the science that powers all nuclear reactors today, is sort of the opposite: a neutron particle slams into a larger atom, such as Uranium-235, and splits it into two smaller ones, like barium and krypton.<\/p>\n \u201cChemistry is basically the story of atoms trying to be more stable, and they\u2019re going to find partners to react with to be more stable,\u201d says Vincent Tang, Ph.D., principal deputy director at the National Ignition Facility and Lawrence Livermore National Laboratory. \u201cWhen they find a partner that makes them more stable, they release energy as heat or light\u2014the same analogy holds for nuclear reactions. If they partner up and they fuse, or fiss, they want to become more stable\u2014they want to become Iron-56.\u201d<\/p>\n Easier said than done, because these two hydrogen protons desperately don\u2019t want to fuse. Under normal conditions, two positively charged protons would simply repel due to electrostatic repulsion, basically the atomic version of trying to force two negative poles of a bar magnet together; it\u2019s possible, but it\u2019s not easy.<\/p>\n To force two nuclei together (a single proton is the nucleus of a hydrogen atom), they must overcome this repulsion so that the strong nuclear force\u2014one of the four fundamental forces in the universe that holds together an atom\u2019s nucleus\u2014takes over and fuses the two hydrogen atoms together.<\/p>\n To do that, things need to get hot, like plasma hot, because heat excites atoms, breaks them apart, and speeds them up so that they overcome this mutual electrostatic resistance. Even the heat at the center of the sun isn\u2019t hot enough to normally fuse these elements, but a concept known as quantum tunneling allows a fraction of hydrogen protons to fuse.<\/p>\n Here\u2019s where these unseen atomic and quantum processes can create something as incredible as our sun. When two hydrogen atoms fuse in the core of the sun, the resulting helium atom weighs less than the two original hydrogen atoms. As Albert Einstein and his famous equation E = MC\u00b2 tells us, mass doesn\u2019t simply disappear, but is instead converted into energy.<\/p>\n To achieve a more efficient reaction at lower temperatures, scientists instead use two hydrogen isotopes called deuterium and tritium to fuse into helium (while also producing one spare neutron).<\/p>\n Why Deuterium and Tritium?<\/p>\n At the atomic heart of the world\u2019s fusion efforts are two isotopes of hydrogen\u2014deuterium and tritium\u2014and the promise of this atomic coupling is enormous, as just one gram of deuterium-tritium fuel releases the equivalent energy of 2,400 gallons of oil. <\/p>\n This fusion combo comes with two major benefits: the two fuels fuse at lower temperatures than other isotope combinations and they\u2019re both easy to procure\u2014at least compared to isotopes like Helium-3 (which accounts for 0.0001 percent of helium on Earth). <\/p>\n Unlike hydrogen, deuterium contains an extra neutron in its nucleus, and because water made with deuterium is 10 percent heavier than normal water, it\u2019s often referred to as \u201cheavy water.\u201d This isotope is commonly found in the world\u2019s oceans, making up one atom out of every 6,500 hydrogen atoms.<\/p>\n On the other hand, tritium, which contains two spare neutrons, is much harder to find. The isotope decays quickly with a 12-year half-life, and is only created naturally through interactions with cosmic rays, which doesn\u2019t produce nearly enough tritium for commercial fusion reactors. Right now, there is only roughly 25 to 30 kilograms of tritium globally, making the price of tritium roughly $35,000 per gram. Luckily, scientists can breed more tritium by exposing an energetic neutron to lithium-6, which creates a low-energy fission reaction that splits the lithium into helium and tritium. <\/p>\n Future fusion reactors will likely need to contain a tritium breeding subsystem to secure a steady supply of the isotope, and in February 2024, the U.K. and Canada announced a joint research effort focused on securing a tritium supply for a future powered by fusion.<\/p>\n Creating this initial fusion reaction\u2014and, most crucially, sustaining it\u2014has been the work of nuclear physicists around the world for nearly a century. Although fusion reactors can come in many shapes and sizes, they essentially fall into three categories, defined by how each machine confines the super-hot plasma needed to create fusion reactions: gravitational, inertial, and magnetic confinement fusion reactors.<\/p>\n A GRAVITATIONAL CONFINEMENT FUSION REACTOR is a fancy way of saying \u201cthe sun.\u201d Because of its immense size, the sun is essentially a burning cocktail of heat and pressure, which provides the perfect environment for fusion. Fusion in the sun follows a multi-step thermonuclear reaction process (or nucleosynthesis<\/a>), known as the proton-proton chain.<\/p>\n In this process, four hydrogen protons and two electrons fuse in a multi-step process and eventually create Helium-4, two electron neutrinos, and six gamma rays<\/a> (which we eventually experience as sunlight on Earth). Helium-4, an isotope of helium, has a remarkably stable nucleus; it\u2019s also an outlier on the nuclear binding energy curve, a graph that shows how tightly atomic nuclei are held together across different elements (see below). So, when atoms fuse to form helium-4, even more energy is produced, and though these reactions don\u2019t have a high probability of fusing, the sun\u2019s \u201ctoo big to fail\u201d philosophy makes up for these energy inefficiencies.<\/p>\n The nuclear binding energy curve peaks at iron and nickel before slowly sloping downward again. But there is a narrow, isolated peak at helium due to its impressive stability at a low mass.<\/p>\n \u201cThe sun works in a very different fusion regime,\u201d Tang explains. \u201cThe confinement time is really large in the sun \u2026 [there\u2019s also] a much lower probability for each fusion event, but that\u2019s ok because it\u2019s so huge and there\u2019s so many nuclei in the sun.\u201d<\/p>\n The sun experiences 100 million quadrillion quadrillion fusion reactions every second, and has been undergoing this form of nucleosynthesis for five billion years. In another five billion years, the sun will exhaust the hydrogen responsible for those initial reactions in the proton-proton chain, and the star will start burning helium, thus transitioning to a Red Giant (and having the unfortunate side effect of destroying Earth).<\/p>\n The sun provides an awe-inspiring blueprint for how to achieve nuclear fusion, but there are few problems that make mimicking the sun an impossibility. For one, Earth is nowhere near massive enough to rely on gravity for confinement, and because of this gravitational deficiency, any terrestrial fusion reactor would also need to be many times hotter than the sun to be effective.<\/p>\n Nuclear physicists and engineers have worked for nearly a century trying to overcome these physical limitations, and they\u2019ve come up with basically two possible solutions. One uses magnets, the other, inertia.<\/p>\n CONTAINING PLASMA IS A TRICKY BUSINESS. This soup of electrons, protons, and neutrons needs to push the mercury to at least 100 million degrees Celsius (for deuterium-tritium reactions), but getting plasma that hot isn\u2019t necessarily the hard part. Making sure that plasma stays confined and doesn\u2019t touch anything else\u2014well, that\u2019s another story.<\/p>\n \u201cFor fusion, you have to do three things\u2014you have to get enough particles together, you have to get them hot enough, and you need to hold them long enough for the reaction to take place,\u201d says Phil Ferguson, Ph.D., director of the Material Plasma Exposure eXperiment (MPEX) Project at Oak Ridge National Laboratory. \u201cYou need a material solution. Give me the materials that can hold this thing together, at temperature, to be efficient.\u201d<\/p>\n Enter the tokamak<\/a>, a fusion machine of unimaginable sophistication. Designed by scientists in the Soviet Union in the late 1950s, the name \u201ctokamak\u201d is a Russian acronym for \u201ctoroidal chamber with magnetic coils.\u201d Toroidal is just a wonky physics way of saying \u201cdonut-shaped,\u201d but it\u2019s the \u201cmagnetic coils\u201d part that is the most important. At their most basic, tokamaks use a meticulously designed array of electromagnets, as well as an electromagnetic pulse in the plasma itself, to create a contained fusion reaction\u2014emphasis on the word \u201ccontained.\u201d<\/p>\n \u201cYou don\u2019t really want that really hot plasma touching the metal walls because it will damage the walls, but it\u2019ll also damage the plasma,\u201d says Wayne Solomon, Ph.D., vice president of General Atomics\u2019 Vice Magnetic Fusion Energy Division. \u201cYou won\u2019t be able to keep it hot if you\u2019re touching something cold.\u201d (General Atomics operates the largest fusion tokamak in the U.S., known as D-III D.)<\/p>\n Speaking of something cold, these magnets are superconducting, meaning they experience no electrical resistance whatsoever; theoretically, an electric current could exist within a superconductor<\/a> forever. However, many superconducting materials can only operate at temperatures approaching absolute zero, or -459.67 degrees Fahrenheit. So magnetic fusion reactors effectively need to contain some of the most extreme temperatures in the universe at the same time.<\/p>\n \u201cAt the center of the device, you\u2019ve got something that can be ten times hotter than the center of the sun,\u201d Solomon says. \u201cIf you continue toward the wall, you\u2019re around room temperature, and then you get to the actual magnets, which are around absolute zero.\u201d<\/p>\n Tokamaks and another magnetic confinement ideas, known as \u201cstellarators,\u201d mainly differ in how the magnets contain the plasma, but both work on the underlying principle of using superconducting magnets to bottle a star.<\/p>\n So once you have this suspended, contained plasma inside a vacuum chamber, how exactly does it power the lights in your home? Between the plasma and magnets is a layer of complicated technology with a surprisingly low-tech name: a blanket. But these \u201cblankets\u201d are not for snuggling. For example, the International Thermonuclear Experimental Reactor (ITER) in southern France, one of the most advanced tokamaks on the planet, will use 440 blanket modules (weighing in at 4.6 tonnes each) to transfer fusion energy into usable electricity<\/a>.<\/p>\n Covered in beryllium, these blankets collect the kinetic energy of neutrons and convert that energy into heat (and they can also breed tritium, more on that later). That heat is transferred to water coolant, which is then used in turbines powered by electromagnetic induction, which is how every power plant\u2014whether coal or nuclear\u2014works today. This is one of the most technically challenging aspects of magnetic confinement fusion because it directly interacts with plasma.<\/p>\n \u201cThe plasma is 100 million degrees and you want to contain it in this bottle, but if you\u2019ve ever seen pictures of the sun, you get instabilities\u2014little flares come out,\u201d says Ferguson, who is currently designing plasma-rated materials for ORNL\u2019s MPeX project. \u201cAt 100 million degrees, those flares touch this wall. You only have to handle it for an instant, but even for an instant, 100 million degrees is pretty intense.\u201d<\/p>\n More than 60 years after their inception, tokamaks are still considered by many fusion scientists, as well as the U.S. Department of Energy, as the leading magnetic fusion concept, as they\u2019re currently the most adept at confining plasma and keeping it hot\u2014a must-have feature for any future fusion power plant.<\/p>\n But there\u2019s another fusion idea that takes a radically different approach, and this machine has been able to achieve something completely unprecedented in the century-long history of fusion science.<\/p>\n ON DECEMBER 5, 2022, SCIENTISTS AT THE NATIONAL IGNITION FACILITY at Lawrence Livermore National Laboratory in California fired 192 lasers at a small pellet and essentially squeezed the deuterium-tritium fuel inside. Like many times before, the inertial confinement experiment generated only a few nanoseconds of fusion, but this time, something was different. This time, the experiment got more energy out of the reaction than it had put in.<\/p>\n Humanity had finally achieved ignition<\/a>.<\/p>\n \u201cSome of that fusion energy stops in the plasma and then it makes it even hotter. \u2026 Now, it\u2019s even more likely for there to be more fusion,\u201d Tang says. \u201cThat\u2019s when you have ignition, when the fusion reaction is starting to bootstrap itself enough that it\u2019s producing more energy than the plasma uses.\u201d<\/p>\n Unlike magnetic confinement reactors like tokamaks and stellarators, inertial confinement ditches magnets and instead relies on the implosion of the fuel pellet itself to sustain the reaction. After NIFs 192 infrared lasers traveled through a complicated series of laser banks and power amplifiers, increasing the lasers\u2019 combined energy to a petawatt (one quadrillion watts), the beams were converted into ultraviolet rays that converged on a small capsule known as a hohlraum (German for \u201chollow area\u201d).<\/p>\n This superheated capsule created an x-ray bath that finally squeezed the spherical deuterium-tritium pellet inside. Collapsing at roughly 250 miles per second, the fusion reaction took place before the fuel could disassemble, so in a sense, the plasma was effectively contained by its own inertia. The length of this \u201ccontainment\u201d lasted only 100 trillionths of a second, but it was long enough to produce a significant amount of energy.<\/p>\n During NIF\u2019s now-famous ignition shot, the facility delivered 2.05 megajoules (MJ) of energy to the target and produced 3.15 MJ, which means the fusion reaction was, for a short time, fueling itself. Although these numbers seem small, Tang argues that the result is even more impressive than it seems at first glance.<\/p>\n Because energy is lost when transferring ultraviolet lasers into x-rays inside the hohlraum, the actual amount of energy used to start the fusion reaction was actually around 250 to 300 kilojoules, roughly twelve times less than the energy gained from the reaction. While the NIF experiment uses an indirect drive process<\/a>, other inertial confinement reactors are experimenting with direct drives, which deliver the laser\u2019s energy directly to the deuterium-tritium capsule (though these concepts also suffer other kinds of energy loss).<\/p>\n This entire process lasts for much less than a blink of an eye, so any future commercial reactor based on this technology would use this same process but deliver about 10 of these mini-explosions a second\u2014essentially creating microscopic sun for just a few nanoseconds at time.<\/p>\n \u201cThe NIF technology is from the 80s and 90s \u2026 and it wasn\u2019t required to run 10 times a second,\u201d Tang says, emphasizing that one of the laser\u2019s main missions was for actually testing nuclear weapons\u2014not creating the next-generation of clean energy. \u201cNIF is not efficient \u2026 if you want to go 10 times a second, you\u2019d use laser diodes.\u201d<\/p>\n Luckily, there\u2019s already a laser that can deliver those 10 beams per second, and it\u2019s called the High-Repetition-Rate Advanced Petawatt Laser System (HALPS). Because NIF is designed using flash lamp technology, the system requires a significant cooldown period between uses. HALPS, on the other hand, uses advanced laser diodes to deliver the same amount of energy but with hardly any cooling at all.<\/p>\n Denver-based Xcimer Energy is fully committed to the inertial fusion approach, focusing on the power of the lasers themselves. The team hopes to create the world\u2019s largest laser, based on technology originally designed in the \u201cStar Wars\u201d Strategic Defense Initiative of the 1980s. This machine will be a krypton fluoride laser that\u2019s a combination of \u201cgas\u201d optics and eximcer laser amplifiers, which are already used in semiconductor lithography and other industrial applications. The results will (hopefully) pump out high beam energies that produce \u201c10 times higher laser energy at 10 times higher efficiency and over 30 times lower cost per joule than the National Ignition Facility (NIF) laser system,\u201d according to a June 2024 press release<\/a>.<\/p>\n But there\u2019s a long road of advancements, efficiency improvements, and groundbreaking material science that needs to happen before NIF\u2019s ignition breakthrough transforms into an inertial confinement power plant. But after finally achieving ignition, the story of inertial fusion is heading into a new era.<\/p>\n \u201cThis is just the end of the beginning,\u201d Tang says. \u201cThere\u2019s still so much to do.\u201d<\/p>\n AS WITH MANY ENGINEERING CHALLENGES, things aren\u2019t as black and white as \u201cteam magnet\u201d and \u201cteam inertia.\u201d Some proposals, like the magneto-inertial fusion borrows a little bit of both while some inertial fusion concepts, like magnetized liner inertial fusion, throw in a teeny bit of magnetism to sustain inertial fusion reactions for longer.<\/p>\n With ignition finally achieved, physics shows that bottling the stars on our planets is possible, but can we develop the exotic materials and incredible technology to make it possible?<\/p>\n \u201cReally sustaining the fusion core, getting the performance as high as possible so you can make the device as efficient, compact, and cost effective as possible is really important,\u201d Solomon says. \u201cNow\u2019s the time to really step up the effort on the technology side of things.\u201d<\/p>\n For one, engineers are still trying to build a working blanket\u2014the technology that essentially turns all this fusion goodness into electricity we can use. Secondly, scientists are developing materials that can withstand the intense temperatures found within these machines, whether tokamaks, stellarators, or inertial confinement reactors. \u201cWe are still lacking a breakthrough in materials,\u201d Ferguson says.<\/p>\n Apart from neutron-capturing technologies and high-tech materials, fusion scientists and engineers still need to figure out how to close the deuterium-tritium fuel cycle. While deuterium is abundant on Earth, tritium is much more rare. Making more tritium could make reactors both economically viable and more efficient\u2014two things any fusion reactor needs if it hopes to escape the lab.<\/p>\n Meanwhile, interest in the potential of fusion energy is heating up. Investment in fusion technology skyrocketed in 2022, and private companies are beginning to investigate ways to bring this technology to market.<\/p>\n \ud83d\udca1 Learn More<\/p>\n General Atomics also announced plans in October 2022 to build a fusion pilot plant. ITER, the largest magnetic confinement fusion reactor, is scheduled to achieve \u201cfirst plasma\u201d by 2025. The successor of ITER, called the Demonstration power plant (DEMO), is already under construction, and is designed to bridge the gap between lab-based experiments and commercialized energy. However, this project isn\u2019t scheduled to go online until the 2050s.<\/p>\n Meanwhile reactors around the world, like the Joint European Torus (JET) in the U.K., the JT-60SA tokamak in Japan, and the D-III D in the U.S. continue investigating the unknown mysteries of fusion.<\/p>\n But that future is coming.<\/p>\n \u201cThis is the energy of the universe,\u201d Tang says. \u201cIf we figure out how to harness this effectively and efficiently, this is it. This is the end. This is the solution. Everything we understand about how the universe works, we\u2019ve now figured out how to leverage its fundamental source of energy.<\/p>\n \u201cWe\u2019ve got to keep pushing forward.\u201d Darren lives in Portland, has a cat, and writes\/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"12 min read FUSION IS THE ENGINE OF THE UNIVERSE. The smallest microbe to the most complex life…\n","protected":false},"author":2,"featured_media":359513,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[7094,5770,111,139,69,393,147],"class_list":{"0":"post-359512","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-7094","9":"tag-core","10":"tag-new-zealand","11":"tag-newzealand","12":"tag-nz","13":"tag-physics","14":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/359512","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=359512"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/359512\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/359513"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=359512"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=359512"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=359512"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/www.popularmechanics.com\/_assets\/design-tokens\/fre\/static\/icons\/arrow-right-regular.e879c19.svg\"){kind=icon}
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