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A neutral beam injector hands each accelerated ion back an electron just before it leaves, so the tokamak’s magnets ignore the beam.<\/p>\n
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Finished and lidded, the double beam box will weigh around 33,000 pounds, which UKAEA pegs at two and a half African elephants.<\/p>\n
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The vessel is built from 316L stainless steel, the grade used in offshore structures and medical implants, and holds about 700 cubic feet inside.<\/p>\n
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UKAEA expects all major hardware fitted inside the box by the end of fall 2027, with experiments scheduled to start in 2028.<\/p>\n
Unlocks at 80% of the articleKeep reading to reveal itShow me in the article2 MONTHS AGO \u00b7 ENERGYA British fusion machine ran more than 1,100 plasmas at 54 million degrees, held the edge steady four separate ways so it stopped throwing the bursts that chew up the walls, and learned to find the plasma by reading the glow from the exhausts above and below it<\/a>2 MONTHS AGO \u00b7 ENERGYAmerican-built magnetic sensors have just arrived in Prague for a tokamak designed to hit 5 tesla and 2 million amps, after their shielding took microwave beams at a 2.1-millimeter wavelength inside a German fusion machine, and they beat the 200-ton steel skeleton there<\/a>1 MONTH AGO \u00b7 ENERGYAn 80-foot fusion machine in California had its priciest sections pulled off both ends \u2014 the quartz tubes that fired two plasma rings together at 670,000 mph \u2014 and the shortened machine still makes its plasma, with eight particle beams building the magnetic trap instead<\/a>4 WEEKS AGO \u00b7 ENERGYA 5.8-foot lithium wall caved in at nearly 600 mph around a plasma inside a Canadian fusion machine and squeezed its electrons past 22 million degrees in about 3 milliseconds, and the liner gets wrecked on every shot and pulled out for a new one<\/a>TODAY \u00b7 THIS ARTICLEA 13-ton steel box was just craned into place at a British fusion machine, and once two more particle beam injectors go inside, the beam power heating its plasma doubles from 4.4 to 8.8 megawatts and its temperature is expected to climb from 54 million to 108 million degrees<\/p>\n Ask The Box:<\/p>\n Which is bigger, MAST Upgrade or Princeton’s NSTX-U spherical tokamak?Will MAST Upgrade’s 2028 beam results arrive in time to shape STEP’s design?How does a neutral beam injector add the electron back to its fast ions?<\/p>\n Anyone who\u2019s helped a buddy move a fridge knows lifting the thing is easy. Getting it through a doorway without gouging the frame, the floor or your own knuckles is where the swearing starts.<\/p>\n So spare a thought for the engineers at the UK Atomic Energy Authority, who just did a version of that with about 26,500 pounds of stainless steel. On November 3, UKAEA announced<\/a> that its engineers had maneuvered a vessel it calls the double beam box into position at MAST Upgrade, the agency\u2019s flagship fusion machine at its Culham Campus in Oxfordshire. In American terms, that\u2019s a little over 13 tons of steel swinging on a crane inside a fusion lab, which is a pretty nerve-racking thing to do with a crane.<\/p>\n The box won\u2019t make any heat itself. It\u2019s a housing. UKAEA describes it as a double-decker vessel built to hold two neutral beam injectors, and once those are fitted, the beams heating the machine\u2019s plasma go from 4.4 megawatts of power to 8.8.<\/p>\n So what\u2019s a neutral beam, and why does it need a box this heavy?<\/p>\n So how do you heat something that\u2019s already 54 million degrees?<\/p>\n MAST Upgrade is a tokamak. That\u2019s a machine that holds a cloud of superheated hydrogen, called a plasma, inside a cage of magnetic fields so it never touches the walls. UKAEA bills it as the world\u2019s largest operational spherical tokamak, and \u201cspherical\u201d just means the usual donut shape has been squeezed until it\u2019s closer to a ball with a narrow hole through the middle.<\/p>\n The magnets are where it gets tricky. They steer anything with an electric charge, which is great for keeping the plasma in place. It\u2019s less great when you want to push extra energy in from outside, because charged particles fired at the plasma get steered away too.<\/p>\n A neutral beam injector gets around that with a pretty clever trick. It speeds up positively charged particles, then hands each one back an electron just before it leaves, so what comes out is a beam of fast atoms with no charge at all. The magnets basically ignore them. Once those atoms are inside the plasma, collisions knock the electron off again, the magnetic field traps them, and they pass their energy on by bumping into everything around them.<\/p>\n If you want the kitchen version, it\u2019s like warming a bath by throwing in pebbles that are moving absurdly fast. UKAEA says that\u2019s how its injectors get the plasma past 54 million degrees Fahrenheit today. We\u2019ve covered a California machine that uses eight of these beams to build its whole magnetic trap<\/a>, so the technology isn\u2019t exotic. It\u2019s just heavy.<\/p>\n Autonoci\u00f3n Newsletter<\/p>\n No spam. Unsubscribe anytime. Privacy policy (opens in new window)<\/a><\/p>\n With two more injectors on top of the ones MAST Upgrade already has, total beam power climbs from 4.4 megawatts to 8.8. UKAEA expects the plasma to get hotter too, going from about 54 million degrees to about 108 million. Keep the word \u201cexpected\u201d in mind there. The new injectors haven\u2019t been installed, so nobody\u2019s run a single plasma with them.<\/p>\n TARGET<\/p>\n Neutral beam heating<\/p>\n 8.8 MW<\/p>\n Up from 4.4 MW once two more injectors are fitted inside the new box.<\/p>\n Plasma temperature<\/p>\n 108M \u00b0F<\/p>\n Expected, up from about 54 million degrees today. No plasma has run with the new beams yet.<\/p>\n Weight<\/p>\n 26,500 lb<\/p>\n The vessel as it went in. About 33,000 lb once it\u2019s finished with its lid.<\/p>\n First experiments<\/p>\n 2028<\/p>\n Major hardware fitted inside the box by the end of fall 2027, per UKAEA.<\/p>\n The box is mostly empty for now<\/p>\n Finished, with its lid on, the vessel will weigh around 33,000 pounds, or roughly 16.5 tons, according to UKAEA. The agency\u2019s own comparison is two and a half African elephants, which is a very British way to describe a steel tank, and I\u2019m not going to argue with it.<\/p>\n Inside, there\u2019s about 700 cubic feet of space, or roughly 130 bathtubs by UKAEA\u2019s count. The whole thing is built from 316L stainless steel, the same grade that goes into offshore structures and medical implants. UKAEA says it picked that steel because it\u2019s strong, it doesn\u2019t corrode and it works well in a vacuum.<\/p>\n The vacuum matters a lot here. Any stray gas floating around in the box can put the charge back on those fast atoms before they reach the plasma, and then the magnets bat them away like everything else. Some materials also slowly leak gas that\u2019s trapped inside them, which you really don\u2019t want in a place that has to stay almost perfectly empty.<\/p>\n That\u2019s why one of the next jobs is fitting a cryopump inside the box. A cryopump is basically a surface kept so cold that stray gas freezes onto it and stays put, and UKAEA says this one will control the pressure inside the vessel.<\/p>\n I couldn\u2019t find the box\u2019s actual dimensions in anything UKAEA has published, just its weight and its volume, so I can\u2019t tell you how tall that double-decker stack stands.<\/p>\n Why would anyone want a hotter plasma?<\/p>\n Because the machines that come after this one will run hotter, and somebody has to find out what gives first. Andrew Thornton, head of MAST Upgrade operations at UKAEA, said the extra heating means \u201cwe will explore plasma conditions we simply couldn\u2019t reach before.\u201d<\/p>\n He pointed to two things in particular. One is whether plasma at higher pressure stays stable. The other is how the machine\u2019s exhaust system copes with hotter, higher-performance plasma. Thornton called both crucial questions for STEP, the UK\u2019s planned prototype fusion power plant, and for the plants that follow it.<\/p>\n I\u2019d argue the exhaust question is the more interesting one. In a tokamak, the exhaust is a set of surfaces where the heat and particles leaking out of the plasma get steered on purpose, so they don\u2019t land on the rest of the wall. MAST Upgrade has spent years on that problem, and in its last round of experiments it learned to track its plasma by the glow coming off those surfaces<\/a>, along with several ways to stop the plasma\u2019s edge from throwing bursts at the walls. All of that happened at the heating power the machine has now. Doubling the beams is a pretty direct way to find out whether those tricks still hold up.<\/p>\n