PLOMB, SD – In an old gold mine a mile underground, inside a titanium tank filled with a rare liquefied gas, scientists have begun the search for what until now has not been found : dark matter.
Scientists are pretty sure the invisible stuff makes up most of the mass in the universe and say we wouldn’t be here without it – but they don’t know what it is. The race to solve this massive mystery has taken a team deep beneath Lead, South Dakota.
The question for scientists is fundamental, says Kevin Lesko, a physicist at Lawrence Berkeley National Laboratory. “What is this wonderful place where I live? Right now, 95% of that is a mystery.
The idea is that a mile of dirt and rock, a giant tank, a second tank, and the purest titanium in the world will block almost all of the cosmic rays and particles that surround and pass through us every day. But dark matter particles, scientists believe, can avoid all of these obstacles. They hope one will fly into the vat of liquid xenon in the inner tank and slam into a xenon core like two balls in a game of pool, revealing its existence in a flash of light seen by a device called “the projection chamber. temporal”.
Scientists announced Thursday that the five-year, $60 million search finally began two months ago after a delay caused by the COVID-19 pandemic. So far, the device has found…nothing. At least no dark matter.
It’s OK, they say. The equipment seems to work to filter out most of the background radiation they hoped to block. “To search for this very rare type of interaction, task number one is to get rid of all ordinary sources of radiation, which would overwhelm the experiment,” said University of Maryland physicist Carter Hall.
And if all their calculations and theories are correct, they think they will only see a few fleeting signs of dark matter per year. The team of 250 scientists estimates they will get 20 times more data over the next two years.
At the end of the experiment, the chances of finding dark matter with this device are “probably less than 50% but greater than 10%”, said Hugh Lippincott, physicist and spokesman for the experiment during a press conference on Thursday.
While it’s far from a sure thing, “you need a little bit of enthusiasm,” Lawrence Berkeley’s Lesko said. “You don’t go into rare research physics with no hope of finding something.”
Two huge Depression-era winches operate an elevator that takes scientists to what is called the LUX-ZEPLIN experiment in the underground Sanford Research Facility. A 10-minute descent ends in a tunnel with cool-to-the-touch walls lined with netting. But the moldy old mine soon leads to a high-tech laboratory where dirt and contamination are the enemy. Helmets are swapped for new, cleaner ones, and a double layer of sky blue booties go over steel-toed safety boots.
The heart of the experiment is the giant tank called the cryostat, lead engineer Jeff Cherwinka said during a December 2019 tour before the device was closed and filled. He described it as “like a thermos” made of “perhaps the purest titanium in the world” designed to keep liquid xenon cold and background radiation to a minimum.