The Star Builders

by Arthur Turrell

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  For Alice

  PROLOGUE A CRAZY IDEA

  “We need a massive amount of research into thousands of new ideas—even ones that might sound a little crazy.”

  —Bill Gates, talking about ways to solve the energy crisis1

  My star-building adventure starts at a restricted-access nuclear facility fifty miles east of San Francisco’s Financial District. The building I’m in is the size of three football fields—American football fields, naturally. It’s called the National Ignition Facility, or NIF. Within, scientists are pushing matter to its limits, re-creating the conditions and reactions that happen inside stars.

  My guide is Dr. Bruno Van Wonterghem, the operations manager for NIF. Back in 1998, he helped design the enormous facility in which we now stand. (It would be over a decade before the machine created at this site was turned on.) What he and the other NIF scientists have built here under the Californian sunshine is the world’s biggest and highest energy laser.

  I’m here to see what happens when this huge laser fires. It’s so powerful that it can only be used in brief spurts, momentary pulses each of which the scientists call a “shot.” As I wait nervously with Bruno, the director of this particular shot enters, his radiation leak detection badge swinging from his shirt, and calls us to the control room.

  As we enter the darkened space, I see that it’s laid out like NASA’s ground control: computer terminals encased in plastic arranged in curved rows; operators peering at graphics, lines of computer code, and scrolling text. Perhaps Bruno knows what I’m thinking because he tells me that the laser system I’m viewing is at least as complex as the space shuttle, with 5 million lines of computer code running the show. In front of us, screens cover the wall. Bruno sees me look at the color-filled panels. “That’s the list of checks that have to be completed.”

  An hour earlier, screens dotted around the facility began to show a colored map of the laser system. Messages sent out over the public address system instructed people to “leave laser bay 1 now, I repeat…” and, later, to “leave laser bay 2.” In an abundance of caution, each bay was then carefully swept to ensure it was empty of human life. As each inspection was completed, the map of the facility began to show red segments indicating that this or that area was ready. The most complex shots take thirty hours of preparation.

  In the control room, I glance behind me and see a couple of people looking nervously through the Plexiglas. One, a man in his mid-thirties with stubble, paces up and down. It’s his experiment, and given that the typical target costs $100,000 to $150,000, you can understand why he’s anxious. The National Ignition Facility, which is hosted at America’s Lawrence Livermore National Laboratory, conducts a range of experiments relating to science and national security. Today’s shot is classified, so I don’t find out too much about what the experiment is—apart from that it concerns the survivability of materials that are subject to extreme radiation. What I’m really here to learn about are the shots aimed at creating a tiny star in the reactor chamber.

  As I wait, it’s almost silent apart from the crackle of a walkie-talkie as one of the twenty or so scientists communicates with colleagues across the building. Bruno says that they’re charging the power supply, the world’s largest capacitor bank, essentially a ginormous fast-release battery. When set off, it will loose four hundred megajoules of energy, equivalent to lighting four hundred sticks of dynamite.

  The shot director begins the countdown, “Ten… nine…,” and the smaller rectangles on the big screens begin to flip from grays and reds to greens. “Eight… seven… six…,” intones the shot director through the public address system, and I see the biggest red bar, for the capacitor bank, begin to fill with green. “Sometimes there’s a last-minute failure or a power supply fails and everything shuts down,” Bruno says, and I anticipate a sudden failure, with all of the greens going to gray. But the countdown continues: “… five… four… three… two… one… SHOT!”

  In the cable-choked master oscillator room behind me, a short beam of infrared light is created. It’s just six meters (approximately twenty feet) long, equivalent to flipping a light switch on for twenty nanoseconds. It contains only a single nanojoule of light energy, nothing when you consider that it takes a whole joule—a billion times more—to lift an apple one meter (approximately three feet).

  The fledgling beam is split into two sets of twenty-four smaller beams by precisely engineered optics. Each set travels down optic fibers to two bays of amplifiers that run almost the length of the building. There, the beams get a 10 billion times boost in energy from another laser. This is merely the start. Again, the light is split, now into a total of 192 different beams traveling in parallel. Lenses are used to expand the width of each beam to the size of an adult’s chest. Any smaller, and the sheer intensity of the light would irrevocably damage the glass as the beams passed through it.

  The capacitors, brimming with electrical energy and each weighing eleven tons, reach a peak power of a terawatt—greater than the entire US national grid—as they fire more than seven thousand xenon flashlamps. The lamps are similar to those used by photographers, except here, where extremes are common, they’re stacked two meters (six and a half feet) high and cooled by nitrogen. The laser beams arrive and the flashlamps fire, streaking bright white light into huge slabs of neodymium-doped phosphate glass (it looks just like ordinary glass except for its pinkish tinge). As the glass absorbs the energy, the neodymium atoms within it enter an unstable, excited state. As the infrared laser beams sweep through the glass, the excited atoms relax, firing out their own infrared light. The effect is to amplify the surging laser beam many, many times over.2

  Mirrors, each minutely deformed by little motors, reflect the incoming beams perfectly evenly so that they go back and forth through the flashlamps for yet more amplification. Start to finish, the initial beam energy is boosted 4 million billion times over. Of the four hundred megajoules in the capacitors, less than 1 percent make it into the laser beam; nevertheless these 192 infrared beams comprise, by a wide margin, the most energetic laser pulse ever created.

  The beams follow mirrored paths up, around, and along the building. They pass around the control room with Bruno and me inside. They’re heading for the target chamber, their 1.5-kilometer (just under five thousand feet) trip nearing its end. Each beam passes through two giant slabs of crystal. The first changes the color of the incoming laser light, converting much of the infrared to a vibrant green. The two colors pass through a second slab of crystal where they mix like paint to make a third color of light. This new beam is packed with high-energy ultraviolet photons that are beyond our visual range.

  The beams enter the target chamber, a ten-meter-radius (approximately thirty feet) sphere of ten-centimeter-thick (approximately four inches) aluminium panels rounded off with thirty centimeters (approximately one foot) of concrete. Inside, it’s mostly empty space kept under a strong vacuum. The beams enter, and each is focused to a round spot the diameter of a human hair.

  On an unclassified star-creating experiment, a cylinder of gold sits in the center of the chamber. The 192 laser beams are aimed at its ends, 96 on each, to a precision of fifty-millionths of a meter. This level of precision is like trying to hit a dartboard’s bull’s-eye
from a kilometer (approximately 0.6 miles) away. The gold cylinder is nine millimeters (a little over one-third of an inch) long and chilled to an incredible 19 degrees above absolute zero (-254 degrees Celsius)—colder than the surface of Neptune. The beams, entering through the ends, hit the cylinder’s inner gold walls. The timer starts, and improbable though it sounds, what happens in the subsequent twenty nanoseconds could change the world.

  In the first eight nanoseconds, the beams pack so much energy into the cylinder walls that the gold atoms are ripped apart. The ionized gold pumps the energy straight back out as yet another type of light—X-rays. Unlike laser light, which moves in lockstep, the X-rays race off in every direction.

  The bath of X-rays fills the cylinder, and fourteen nanoseconds in, they reach a capsule at its center. The capsule is about the size of the pupil in your eye and so perfectly spherical that if it were as big as the Earth, the largest imperfection would be just 10 percent of the height of Mount Everest. Making a sphere so small and so perfect took hours of dexterous work with futuristic tools. The outer layer of the capsule is, incredibly, made of diamond. There’s a middle layer of cold, solid hydrogen, and an inner layer of gaseous hydrogen. X-rays vaporize the outer layer, pushing hot material away from it. Just as a rocket expels hot material in one direction to move in the opposite direction, the rapid vaporization of the outer layer in one direction forces the capsule to contract. The speed is dramatic; the collapse of the capsule proceeds at a pace in excess of 350 kilometers per second (approximately 800,000 miles per hour).

  The solid layer of hydrogen and its gassy center accelerate inward on themselves. They eventually reach just a thirtieth of the original capsule radius; it’s as if the Earth shrank to a ball 260 miles across—much like trying to squeeze a soccer ball down to the size of a pea. The solid layer of hydrogen becomes so tightly squeezed that a teacup full of it would have a mass of over 200 kilograms (approximately 440 pounds).

  In the capsule’s gas center, the implosion ratchets up the temperature. The atoms in the capsule may be different, but the temperatures, pressures, and densities are similar to those found in the Sun: a tiny star has been lit. The pressure alone is 300 billion times what we experience on Earth. At the temperatures within the capsule, ripped apart hydrogen atoms crash into one another so energetically that their nuclei begin to react. But not in the chemical reactions that you might have seen in school science classes. These are nuclear reactions, nuclear fusion reactions.

  Nuclear fusion reactions are very special. They’re perhaps the most important reactions in the universe: they’re what fills it with light.

  Just as in stars, in each fusion reaction the nuclei of atoms are squeezed together, coalesce, and give birth to new atoms. As they do this, they also unleash vast quantities of energy. At NIF, hydrogen nuclei combine to make helium nuclei. The fusion-released energy manifests in the frenzied speed of the helium, each nucleus rushing out at 13 million meters (a little more than 42 million feet) per second. As the outgoing nuclei crash into surrounding hydrogen nuclei, they heat those nuclei up, increasing the chances that more hydrogen will react, making more fast helium nuclei, and so on.

  Nearly twenty nanoseconds after the lasers have entered the cylinder, in excess of 10 million billion reactions have happened. Each one turns matter, the stuff we’re all made of, directly into energy.3

  Eventually, the ball of hot fusion fuel is unable to remain whole. It’s not natural to have an object 0.1 millimeters (approximately four thousandths of an inch) across, as hot and as high pressure as the Sun’s core, fusing in the center of a ten-meter (a little more than thirty-two feet) vacuum chamber. The fuel quivers and wobbles; it’s only held in place briefly by its own inertia. Sound waves, positively sluggish compared to the particles, travel through it, breaking it up. The reactions are over. The star is dead. At least, until the next shot from the laser, and the next target.

  “Not very spectacular,” Bruno says after the shot is over. I don’t believe him, not even for a nanosecond.

  Star Power

  The idea of building a small slice of star matter on Earth has, since the 1940s, captivated scientists, governments, billionaires, entrepreneurs, celebrities, a pornography magnate, and even a few dictators. The scientists of the National Ignition Facility aren’t alone; for years, groups all around the world have been devising elaborate star machines that stretch human ingenuity to the breaking point. Now those star machines are being built and operated. The machines range from contraptions cobbled together on a shoestring to a seven-storey mechanical doughnut rising out of the French countryside. The star-trapping tricks they use are straight out of science fiction: force fields, lasers, and pneumatic pistons. The teams that build them are comprised of physicists, engineers, mathematicians, and computer scientists who’ve dedicated their entire careers to containing and controlling the nuclear forge that is a fusion reaction. They are the star builders.

  At best, creating a mini-star on our home planet sounds highly inadvisable. At worst, it sounds like the diabolical plan of a villain from a James Bond or Star Wars film. In this book, I’m going to show why the star builders’ ideas, crazy as they might seem, could actually save the planet, and who’s ahead in the race to control and exploit star power.

  The real goal of the star builders isn’t to re-create a star exactly, but to re-create and control the power source of stars—nuclear fusion—here on Earth. Nuclear fusion is different from nuclear fission, the reaction that occurs in today’s nuclear power plants. In nuclear fission reactions, large nuclei—the cores of atoms—are ripped apart into smaller nuclei. In contrast, nuclear fusion creates larger nuclei out of two smaller nuclei. Both types of reaction get their name because they happen to the core of an atom, the nucleus. But their risks, the amount of energy they release, the nuclei that will undergo them, and the technologies needed to make them happen are very different.

  Controlled nuclear fusion is just the last, unconquered part of a quartet of nuclear technologies. The other three are controlled fission as used in today’s nuclear reactors, uncontrolled fission as used in atomic bombs, and uncontrolled fusion as unleashed in thermonuclear, or hydrogen, bombs. All of the other three were demonstrated in the 1940s and 1950s. We still don’t know how to do the fourth, but the star builders are trying hard: and they say that they’re getting close.

  What does it mean to control, or achieve, nuclear fusion? For star builders, it’s not just about making a few atoms fuse together to form bigger atoms. Actually, as nuclear physics goes, that’s easy enough. Plenty of people have done it already, whether in laboratories with thousands of staff or in the school classroom, like the boy who trawled eBay for parts to build a fusion machine. But the amount of energy generated by these rigs is piffling compared to the energy used to make them work.4

  Star builders are trying to show that fusion can produce more energy than it uses, that fusion is a viable power source. Producing more energy from reactions than it takes to get those reactions going in the first place is the first step. “Breakeven,” “net energy gain,” or the self-perpetuating “ignition”—star builders use lots of terminology, but it all means “more energy out than in.” And teams of star builders around the world are racing to be the first to do it.

  Net energy gain is exactly what you get when you light a log with a match; it doesn’t take much energy to light a match, but the roaring fire it ignites releases that energy many times over as heat and light. Star builders often talk about this in percentage terms, with 100 percent being breakeven and greater than 100 percent being net energy gain.

  But getting to 100 percent, as much energy out as in, is an enormous scientific and technical challenge. No one has yet done it. And that feat is the key to unlocking fusion as a power source. Once star builders have shown that fusion can deliver just as much energy out as was put in, it’s just a matter of optimization to get even more energy out. Only then will fusion be able to change the world. It’s the
difference between the Wright brothers’ plane not flying at all, and its flying 250 meters (approximately 820 feet). Making the leap from flying 250 meters to flying for miles is easier than being rooted to the ground and figuring out how to fly. Psychologically, getting to the first level of accomplishment is everything.

  Eventually, star builders want to achieve a gain of 3,000 percent (thirty times energy out for energy in), or even 10,000 percent (one hundred times). To the star builders, really achieving fusion means creating a genuine power source based on the nuclear reaction that keeps the Sun shining.

  This is phenomenally difficult. If I say that controlling fusion to produce energy is the biggest technological challenge that we’ve ever taken on as a species, it will sound like hyperbole. But it’s true. Fusion at NIF needs, first, temperatures in the hundreds of millions of degrees, and second, matter as densely squished as the material in the Sun’s core. The complexity of the machines is beyond anything we’ve ever designed. There are tens of millions of individual parts to a star machine. NASA’s space shuttle had just 2.5 million. I’ll keep returning to the space analogy because, honestly, there are few other close comparisons when it comes to the scale of the challenge—and there are few environments anywhere near as extreme as those in star machines.5

  There are two practical ways to create the magic conditions that make fusion happen. One is called magnetic confinement fusion and the other is inertial confinement fusion. There’s gravity too, of course, but for that you need scales bigger than can be created on Earth: you need, quite literally, a star. The magnetic approach is to bind the hot matter in a reactor with an invisible web of magnetic fields. The inertial approach sets matter crashing into itself, thereby both heating and compressing it, and aims to get all the fusion done before the assembled star matter falls apart again. NIF uses lasers to do this.