If you need to construct and run a $70 million darkish matter detector, you are going to have a hefty procuring listing. You may want to purchase a whole lot of photomultiplier tubes, arrange elaborate electronics, and pay graduate college students, for starters. And 20 p.c of your money goes to go to only one factor: xenon fuel. You may want 200 metal bottles of the stuff, purified from the Earth’s ambiance, at a worth that may fluctuate wildly round $100,000 a bottle.
The physicists engaged on a venture known as LUX-ZEPLIN found this in 2015, after they have been have been growing their funds. The group is at the moment putting in an enormous darkish matter detector underground in a former mine in South Dakota, the place they hope to catch a glimpse of a hypothesized dark matter particle known as a WIMP. And the xenon payments. Ouch. “No, we don’t get a break as a result of we’re poor, ravenous scientists,” says physicist Murdock Gilchriese of the 250-member experiment.
Solely a handful of firms produce xenon fuel globally, by extracting it from the air at so-called air separation crops. Xenon makes up about zero.00001 p.c of Earth’s ambiance, a focus akin to a pot of soup seasoned with a single grain of salt. For these firms, xenon manufacturing is only a facet gig, amounting to pocket change: Their extra profitable product is pure oxygen, which the metal trade buys to energy their furnaces. “No one builds a plant only for xenon,” says Richard Betzendahl, a fuel trade guide and distributor. “There’s no economics in that.”
However it’s the lifeblood of darkish matter experiments. Over the past decade, physicists have constructed more and more gargantuan detectors full of cooled, liquefied xenon to seek for darkish matter, a hypothesized substance that physicists suppose makes up 85 p.c of the universe’s mass, in accordance with a long time of telescope observations. The detectors sense flashes of sunshine that ought to seem when a darkish matter particle bumps right into a xenon nucleus. They’ve chosen to make use of xenon as a result of it’s not reactive, which suggests much less noise of their detector, and since it has a big nucleus, which makes it simpler for darkish matter to hit.
When LUX-ZEPLIN begins taking information in 2020, it would want 10 tons of xenon. They’ll buy xenon fuel, purify it even additional, and liquefy it for his or her detector. Different teams, just like the XENON collaboration based mostly in Italy, are planning even larger detectors; the extra xenon you employ, the extra seemingly you’ll catch a darkish matter particle.
A number of years in the past, Gilchriese’s group did the maths. The world produces about 40 tons of xenon a 12 months. LUX-ZEPLIN wanted a couple of quarter of the world’s yearly manufacturing.
Then, they went procuring.
They began by hiring Betzendahl as a guide. “I didn’t know a lot concerning the xenon market,” says Gilchriese. Xenon, it seems, has a wide range of makes use of starting from the mundane to the cosmic. Mild bulb producers put xenon fuel inside incandescent bulbs to make the tungsten filament last more. House missions additionally use xenon as rocket gas to launch satellites.
Additionally they realized that they wanted to time their bid excellent. The value of xenon peaks and falls like a seismograph. “It may be 10 instances what it was the earlier 12 months,” says Betzendahl.
That’s as a result of lately, firms have developed, adopted, and deserted new applied sciences that require massive quantities of xenon. In 2008, Toshiba ordered 1 / 4 of the world’s xenon provide for a brand new semiconductor know-how, which triggered the value of xenon to extend tenfold. “Then, they discovered how do it with lots much less xenon, and the value collapsed once more,” says Betzendahl. Immediately, costs are rising, maybe as a result of Samsung has began shopping for xenon for a brand new etching know-how.
So Gilchriese’s group, on Betzendahl’s advice, requested firms to ship the xenon over a number of years. LUX-ZEPLIN will get its cash from the federal government in an batches: just a few million the final three years “Even when we had the cash to purchase it suddenly, it was very clear that it could disrupt the market,” says Gilchriese. Additionally they had to purchase the xenon from a number of firms, largely based mostly within the US and China. And due to Betzendahl’s recommendation, and possibly simply luck, they managed to purchase most of their xenon when costs dropped.
Gilchriese is completed shopping for xenon, a minimum of for just a few years. However physicists are pondering the development of extra xenon-based darkish matter experiments. The PandaX experiment in China is planning to construct a detector containing 4 tons of liquid xenon. The XMASS collaboration in Japan aspires to a construct a 20-ton detector. XENON has broached the opportunity of a 50-ton detector. Gilchriese has requested certainly one of his xenon sellers how that buy may work. The decision? “It’ll be actually laborious to get 50 tons of xenon,” he says.
They’d have to purchase it in batches once more, over an extended time period, and hope they’ll purchase all of it at a hard and fast worth. Although physicists need extra of it, it’s unlikely that firms are going to churn out considerably extra xenon, says Betzendahl. Within the three years or so it takes to plan and construct a plant with xenon extraction functionality, xenon costs might plummet. A number of air separation crops don’t even trouble extracting xenon and simply let the fuel escape again into the ambiance.
And xenon prospects don’t have a variety of choices. Some folks within the xenon trade have toyed with the thought of extracting it from pure fuel, the place it happens in increased focus than common air. However proper now, air separation crops are actually the one method to harvest xenon, says Betzendahl.
Within the early days of the LUX-ZEPLIN experiment, Gilchriese’s group truly thought-about constructing their very own xenon manufacturing plant. Nervous concerning the fluctuations within the xenon market, they puzzled if they might simply do it themselves. “Admittedly, it was a stab at the hours of darkness,” says Gilchriese.
They requested some engineers to estimate how a lot it could price. “It simply was not possible,” says Gilchriese. “It was many tens of thousands and thousands of simply to arrange the plant. And you need to design it. The place wouldn’t it go? And then you definately truly must run it. what I imply? You’re actually not going to compete with individuals who do that as an add-on to a a lot bigger market.”
On the intense facet, darkish matter experiments don’t eat xenon—the 10 tons simply keep within the detector, inert, in LUX-ZEPLIN’s detector for its 5 years of operation. “Sometime they’ll have a variety of product to promote in the marketplace,” says Betzendahl. They might recycle the xenon in one other experiment. Or they might hoard it and watch for the value to spike once more.