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XENON1T Collaboration

This New Ultra-Sensitive Instrument Will Hunt Down Dark Matter

And we have a pretty good idea where to look.

13 NOV 2015

There's five times more dark matter in the Universe than normal, everyday matter – that is the standard atoms and molecules making up the world we're familiar with – but despite its volume, dark matter is notoriously difficult to spot. 


To try and understand more about this mysterious hidden matter, scientists are hard at work constructing a new instrument at the Gran Sasso Underground Laboratory in Italy, as reports

And it’s pretty good timing, as physicists are getting more and more convinced that colliding dark matter could be behind a series of powerful gamma rays spotted shooting out from the centre of the Milky Way.

Researchers have now eliminated other explanations for the gamma rays, but they’re going to need some more direct confirmation of dark matter in order to win over skeptics. Which is where a device like this one could come in handy.

The instrument is called the XENON1T and it's designed to be more sensitive than anything that's gone before it: 21 research groups from the United States, Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden and the United Arab Emirates have joined forces to help build the machine, which was inaugurated on 11th November.

Some of the world's best minds have been looking for dark matter for many decades, but up until now scientists have only been able to observe it indirectly, through its effect on the rest of our universe – we know it's out there in space, but we can't look at it directly as it emits neither light nor energy. Experts believe that a new, stable elementary particle is at the heart of dark matter, but we don't yet know what it is.

XENON1T should help in that search. "We expect that several tens of thousands of dark matter particles per second are passing through the area of a thumbnail," said the University of Chicago's Luca Grandi.

"The fact that we did not detect them yet tells us that their probability to interact with the atoms of our detector is very small, and that we need more sensitive instruments to find the rare signature of this particle."

The new instrument takes up a site measuring 110 metres long, 15 metres wide and 15 metres high; it's encased in a 10-metre-diameter water shield and 1,400 metres of solid rock to block out cosmic rays and radioactive background radiation, while the instrument itself has a mass of 3,500 kilograms.

At the heart of the process is the ultra-pure noble gas xenon, cooled down to –95 degrees Celsius to turn it into liquid form. Tiny flashes of light passing through the cooled xenon are observed by 248 sensitive photosensors for any trace of dark matter particles, and the researchers have compared the setup to a giant Thermos flask.

And even if the XENON1T comes up short in its main task, then more help is already on the way. "Of course we want to detect the dark matter particle," added Grandi, "but even if we have only found some hints after two years, we are in an excellent position to move on as we are already now preparing the next step of the project, which will be the far more sensitive XENONnT."

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