- [Narrator] This is
the Sanford Underground Research Facility,
the deepest underground lab in the United States.
[gate clattering open]
It's a converted mine
where more than 10 experiments are being conducted,
experiments that can only take place
far beneath the surface of the earth.
We will tour three different labs
where scientists are studying dark matter,
the nature of neutrinos,
and geothermal energy.
Finally, we'll look at the construction
of one of the largest particle physics experiments
in the world.
This is Wired Field Trip.
[uptempo music]
[fan whirring]
4,850 feet below the surface
researchers make their way to their experiments
every morning.
[elevator shaft clacking]
On the deepest level,
you might think that scientists
are studying the Earth's core,
but instead, these physicists need nearly a mile of rock
to shield their experiments from the sun and space.
[dark beats]
First up, the LUX-Zeplin experiment,
a dark matter detector known as LZ.
- LZ is a dark matter experiment
trying to directly detect the dark matter particles
that we think are flying through the earth all the time.
- [Narrator] So, what exactly is dark matter?
- We think we know as a species
how much stuff there is in our universe
but it turns out that the stuff that we understand,
the stuff that makes us up, me up,
the things that you see around me,
is only about 5% of that total.
So, 95% of the universe's content is a mystery to humanity.
- [Narrator] Dark matter is often referred to
as the invisible glue that holds everything together.
Physicists and astronomers
have been hunting it for decades, all the way up to Hugh.
Here's how the dark matter detector works.
- So there are many, many layers to LZ.
You start at the center with a large bucket of liquid xenon.
Xenon is the heart of our experiment,
it's the target material.
It's what we hope the dark matter is gonna interact with.
- [Narrator] This is a cross section of the experiment.
In the center is the element xenon in liquid form.
The xenon is housed in a chamber that includes many layers,
not only various elements like titanium and gadolinium
but a huge water tank.
And of course, 4,850 feet of rock.
- So there are charge particles
constantly hitting our atmosphere.
Some come from our galaxy,
some come from outside of our galaxy.
Some we don't know where they come from.
But they're hitting our atmosphere
and they make showers and showers of particles.
Those things will light up our detector constantly.
If you try to turn LZ on on the surface,
it would light up like a Christmas tree
and you wouldn't be able to see anything at all.
In our depth,
the rate of those rays is way knocked down
so that we can actually run our experiment.
- [Narrator] The detector also includes
photo multiplier tubes to detect light signals
that could show the presence of dark matter.
- Effectively, what we hope is will happen
is that dark matter will hit a xenon nucleus,
it'll create a little flash of light,
a little flash of charge
and we'll collect those things to see the signal.
- [Narrator] And all of that
is housed in this whole facility.
Hugh is going to walk us through
what goes into maintaining the detector.
- So behind me at the moment
is part of our cryogenic system.
To be liquid,
xenon has to be held at a hundred degrees below zero Celsius
or 165 Kelvin.
So this steel dewar behind us
is filled with liquid nitrogen.
And it is connected to a couple of tubes
that run down into the detector.
[poppy beats]
So here we have the wall of the LZ water tank.
It was built underground,
as you can see, welded from these sections.
So this is filled with something like 70 gallons of water.
So if I open this,
70,000 gallons of water would rush out and drown us all.
[poppy beats]
So in front of us here,
we have what we call the xenon tower,
which is another part of the cryogenics.
If you see these sort of big boa, flexible lines,
there's nitrogen running through those lines
to come down to the xenon tower
where we have a few heat exchangers that cools liquid xenon.
The detector itself has 10 tons of xenon.
- [Narrator] That's about a quarter
of the world's yearly xenon production.
- And one of the reasons we really like xenon
for this experiment is that it is very dense as a liquid.
It's something like three kilograms per liter.
So, that is denser than aluminum.
So, if you put an aluminum block
in our detector, it would float.
- [Narrator] Inside the detector
is one of the most radio quiet places on earth.
They've reduced the amount of radiation
down to almost nothing.
And there's so much more that goes into it.
- So these are our electronics racks.
Here's our spare parts.
The SRV.
A neutron generators.
Heaters.
Cryo cooler.
So in this room we have our xenon compressors.
So there's xenon flowing through these gas lines,
constantly being pumped to purify the detector.
- [Narrator] The majority of this experiment
is the researchers collecting data
and waiting and waiting and waiting for something to happen.
So, what happens if they discover dark matter?
- So, dark matter right now is probably one of the biggest
if not the biggest mysteries in particle physics.
So, it would be a huge, huge deal if we discovered it
and it would explain this huge chunk
of our universe that is missing
and would open up a whole new avenue of research.
But there is a chance
that the dark matter properties are so weak
or so different from what we're looking for,
that we will never see it.
And it's quite possible
that when we end our dark matter detection program
we will never have found the actual particle.
So that's a scary proposition, but it's true.
- [Narrator] Before LZ,
there was a smaller detector.
After LZ, there could be a bigger detector.
The more they continue hunting,
the more they can rule out what dark matter is, or isn't.
Nearly a mile underground,
possibly the most concentration of xenon in the universe,
they continue to wait until a small signal
changes our understanding of where we came from.
This is only the first experiment we're looking at today.
Let's go check out another called the Majorana Demonstrator.
[uptempo music]
This is particle physicist, Ralph Massarczyk.
- So here we are a mile underground
studying the nature of neutrinos.
The Majorana demonstrator is looking for a concept known as
neutrinoless double beta decay.
Neutrinoless double beta decay
is a very, very rare decay
that can happen only in a handful of isotopes.
So, if some of these particles vanished during the decay,
it would give us a hint
of how the universe could be created.
- [Narrator] The theory that Ralph's team is working on
is that neutrinos, the subatomic particle
smaller than electrons, are their own antiparticle.
In order to study this theory,
the demonstrator is even more sensitive
than the LZ dark matter detector.
We have to enter a clean room.
The principle is the same as the LZ shield layers;
reduce background radiation.
Even human bodies give off radiation.
That's why the researchers are decked out
in personal protective equipment, including our crew.
- Here we are at the Majorana clean room,
and we are gonna look at the detector today
and see how it's made.
- [Narrator] In the LZ experiment,
the element the physicists
were hoping to see reactions in was xenon.
In Majorana, it's the isotope germanium.
- There's only a handful of isotopes
which can do double beta decay.
Germanium was one of them.
We often compare finding double beta decay
to listen to like a single conversation in a full stadium.
Maybe you go to a Beyonce concert and it's loud
and you wanna talk to your neighbor and he whispers.
That's what you're trying to achieve.
So every kind of radiation is a background, is a noise,
which you constantly try to overcome.
The Majorana experiment is shielded
against natural radiation with several layers of material.
Starts on the outside with roughly 12 inches of poly,
then a very heavy lead shield.
So you see the size of a lead break is roughly
this times four times eight inches.
And there's a few thousands of them installed in the shield.
And then, to the core of the experiment
where we have our electroform copper
which is the cleanest copper in the world,
on which is grown underground here.
And inside this shield we have this,
what we call detector modules.
So, you see this copper vessel
and inside the vessel are our germanium detectors
where we try to look for double beta decay.
A germanium detector is roughly the size of a hockey puck.
And they're arranged here in an area of detectors.
The signals go along this cross arm
through all the shield to this readout electronics,
which are located here behind the shield.
This whole assembly weighs several tons.
So what we do is we place everything on this,
on ball bearings down here, and very slowly push it inside.
It has to be done very slowly
because there's a lot of fragile electronics
and you don't want it to vibrate or to shake or to break.
- [Narrator] In order to assemble the detector,
the researchers have to work in these sealed boxes
that also reduce background radiation.
- So this is our glove box where we actually
assemble the individual detector units,
build bigger assembly of strings of detectors.
And then also assemble the whole module.
Inside the glove box,
you see all the individual copper pieces.
If you look at these pieces,
it can be as small as very tiny nuts,
but these copper pieces also all go all the way up
to the several hundred pounds heavy shield plates
which you saw before in the outer shield.
So, at the end,
you are actually gonna wear four layers of gloves.
The two gloves we are already wearing,
the rubber gloves and an innermost layer for cleanliness.
And now, you can imagine
you have to pick up very tiny pieces like these ones.
This is roughly the size of a germanium detector
and you have to assemble it.
A simple test, like just putting a nut
on a bolt, becomes complicated
as soon as you have several layers of glove on.
- [Narrator] What else is a part of this experiment?
- Here, you see the readout electronics
of the germanium detectors.
This is a hovercraft.
This is the copper baths.
- [Narrator] One of the more unique elements
of the Majorana demonstrator
is that researchers are growing copper.
- It starts with this very pure copper nuggets.
And they're put into a bath with acid
where, through an electric field, they're very slowly
only the copper drifts to this bigger mandrels.
- [Narrator] When the copper is ready,
the scientists move it into the machine room
to make parts out of it.
- Once they come off, they look like this.
So you have this massive copper pieces
which are then get flattened out.
And the copper pieces end up like this.
- [Narrator] All of this chemistry, engineering and physics
goes into discovering the nature of neutrinos.
So what happens if they find what they're looking for?
- If we're able to show
that neutrinos are their own antiparticles,
it would show that the standard model as it exists
is not complete.
In each process, the same amount of,
if matter goes in, matter should come out.
If this is not suddenly not the case anymore,
you open up a whole can of worms. [laughing]
- [Narrator] These physicists are searching
for invisible particles
that our entire understanding of science can't account for.
Do you believe in magic at all?
- No. [laughing]
I don't believe in magic in the sense of
there's a magician who can make things disappear,
but the way everything fits together,
the way that particles drift in an electric field,
the way a germanium detector works
is its own little magic.
Physics itself has its own magic.
I'm lucky enough that I'm allowed to work in what I love.
So, I love it.
Gonna be a lifelong pursuit for me.
I hope. [laughing]
- [Narrator] The researchers are entering
the next phase of the Majorana Demonstrator Project
which will go on for another couple of years.
Let's get out of the 4850 and go to another level.
[gate clattering open]
[indistinct talking]
[uptempo music]
- Welcome to the 4,100
where we're studying geothermal energy.
- [Narrator] Hunter and Paul
are part of one of the biggest geothermal research projects
in the country.
- Geothermal's been around for a long time.
And people have learned over the last few hundred years
that they could use the earth
to both heat and cool their house.
And they did this through technology
called geothermal heat pumps.
This research focuses on
a different kind of geothermal energy,
and that is called EGS,
or enhanced geothermal systems.
- [Narrator] Basically,
not every country can be like Iceland
where there's a high concentration of volcanoes.
The next generation of geothermal research
is exploring the technology of hydraulic fracturing.
- So the idea for EGS is quite simple, actually.
You drill two wells side by side.
You create a fracture that connects these two wells
and then you can circulate water
from the surface down the borehole, through the fracture
and produce steam or hot fluid out of the other borehole.
And that is where the energy comes from.
Now, just imagine you set those boreholes up like a radiator
and you put fractures one right after the other.
Now you have something that could produce power
for tens of millions of people.
- [Narrator] EGS CoLab is studying how the earth interacts
with fluids underground.
- We drilled nine boreholes with five of them
targeted for stimulation and production, basically.
- [Narrator] The goal of stimulation holes
is to stress test rocks to gather as much data as possible.
- These are the five boreholes
in which the straddle packers will be deployed in.
Packers are used in hydraulic fracturing,
both in experiments and also in industry.
This is a packer element and this is a packer element.
You can think of these as Kevlar balloons.
And so, what we do is we inflate these with water.
They seal the borehole, and then if we're pumping water in,
it comes out of this little hole
and it fills up the volume in the borehole
between these two balloons.
That will generate a fracture, or it will open a fracture
if the fracture already exists.
- [Narrator] Today, they are sending a camera
down the borehole to understand it more.
- So what we're pushing in here
is called an optical televiewer.
And what that is is a camera
at the end of the probe
that's basically taking 360 degree pictures of the borehole.
And what we're seeing on this screen right now
is a live image of the televiewer.
You're getting a picture of what the core left behind
the open borehole and the rock formation.
- [Narrator] Let's walk down the cavern
and take a look at the rock.
- These are core
that were extracted during the drilling of these boreholes.
This is the Yates amphibolite,
basically a very dense crystal and metamorphic rock.
You're talking a billion year old plus rock.
So, this is like the foundations of life on earth
and so forth.
This is a neat piece.
So, here we are catching the Yates amphibolite here,
but also a quartz vein on this side.
So, a pretty neat 360 degree view
of an intersection with different types of rock.
- [Narrator] What else is part of the experiment?
- This is a micro seismic
and source seismic acquisition system.
These are fiber enclosures.
- This is our RO unit.
Chiller unit.
Triplex pump.
This is the DAQ box.
There are the brains of the system.
This is an alcove.
It's also where our coffee maker is
because we're super sophisticated
- [Narrator] EGS CoLab's data
aims to be proving ground for geothermal energy
around the country.
Before we leave today, let's quickly go back
to the 4,850 level
and check out what's down this cavern.
[fans whirring]
Down here in the darkness,
engineers are building the single largest physics experiment
in the world.
[uptempo music]
- Deep Underground Neutrino Experiment
is a massive series of detectors
a mile underground here at the Sanford Lab
that's going to detect neutrinos that are generated
at the Firmilab in Batavia, Illinois.
And so, those neutrinos
will pass directly through the earth to here.
And we'll be able to see how neutrinos oscillate
over that distance.
The detectors that we're building
are going to hold 17,000 tons of liquid argon each.
And to give you an idea of the scale of what that is,
that's 63 feet across, 63 feet tall,
and about 220 feet overall length per detector.
And we've planned for four of these detectors.
So, you can picture the caverns
that have to be built to house those large detectors.
So, when the neutrino reacts,
it's going to create a flash of light, if you will.
And by creating this drift inside of the argon,
we can actually move that flash
in a way that we can observe it.
So, overall construction of the LBNF and DUNE Project
will take over 10 years.
Building underground is like building a ship in a bottle.
We have to disassemble everything
into small enough pieces to take it down underground.
And when we get underground, we have to reassemble it
in these large caverns, which are like the bottle.
Everything we do is going a mile down a shaft
and it's gotta fit inside that shaft.
There's no two ways around it.
We're not gonna build a larger shaft.
So everything has to consider that
as we're designing and building this facility
- [Narrator] Even though these mine shafts
are around 90 years old,
they are still state of the art engineering.
- The hoists at this facility are very unique.
In fact, there's four of them in the world
that are like this, and they're incredibly well designed.
They're a cylindrical conical drum.
And so that conical section allows it to
automatically slow down
without changing the motor speed at all.
As you go to the smaller diameter,
you're getting less distance per rotation
and that helps you with the torque
that's necessary to lift the conveyances.
Everything about this project is unprecedented.
The size of the caverns that are be being built
a mile underground; unprecedented.
The size of the detectors; unprecedented.
The size of the collaboration; not quite unprecedented,
but there's only about three that have ever happened
that are of this magnitude.
The type of science we're doing,
and the type of science that this facility
in general is doing is really unprecedented,
and is the type of things
that my grandkids will read about in textbooks
and be able to say, "My granddad worked on that."
This is the experiment
that the particle physics community
is really focused on as their top priority.
- [Narrator] There are so many other experiments going on
at the Stanford Underground Lab
that we don't have time for.
On this level,
biology experiments are looking at extremophiles.
On this level, equipment testing
for various industries in NASA.
Now, we have to go above the surface.
And that's our Wired Field Trip.
See you next time.
[inspiring music]