The ultimate goal of physics is really quite
ambitious.
We hope to do nothing less than understand
all of the laws of nature- every one of them-
so we can explain everything we observe- from
quarks to the cosmos, so to speak.
And that is a very big goal.
To make progress requires very big teams of
scientists and the largest and most sophisticated
equipment.
At Fermilab, we have a long history exploring
this frontier of knowledge, including a full
quarter century when we hosted the Tevatron,
which was at the time the highest energy particle
accelerator in the world.
That changed in 2011, when a newer and larger
particle accelerator came online.
That accelerator is called the Large Hadron
Collider, or LHC, and it is located at the
CERN laboratory just outside of Geneva, Switzerland.
Now you might think that might make a Fermilab
scientist like me sad, and I guess it does,
kind of.
After all, I spent decades doing research
using the Tevatron.
It was like losing an old friend.
But luckily, particle physics has always been
highly collaborative, with individuals, universities,
laboratories, and even countries collaborating
with one another.
For decades now, Fermilab scientists have
contributed knowledge, equipment, and effort
to make the LHC research program a success.
And it goes both ways, with CERN researchers
working to help build the Fermilab-hosted
Deep Underground Neutrino Experiment, or DUNE,
which will dominate neutrino research for
the next few decades.
DUNE is definitely cool, but I’m an LHC
guy, so I thought I’d tell you about what
Fermilab is doing to help upgrade the LHC
accelerator and detector complex so it can
explore the energy frontier well into the
2030s.
CERN has embarked on what is called the High
Luminosity Large Hadron Collider Upgrade,
or HL-LHC.
In particle physics lingo, luminosity simply
means the brightness of the beams, which can
be accomplished by injecting more particles
into the beams and by focusing the beams more
tightly.
Using techniques like these, the high luminosity
LHC upgrade will increase the beam luminosity
ten-fold.
This will result in more particle collisions,
with a corresponding increase in the opportunity
to discover rare subatomic particles and their
interactions.
Fermilab’s superb staff of scientists, engineers,
and technical professionals have always worked
at the frontier of high energy research, and
we followed that tradition by identifying
a number of key high luminosity LHC projects
on which to work.
For instance, in order to focus the particle
beams to achieve the desired higher luminosity
will require a series of focusing magnets
that are half again more powerful than the
existing LHC bending magnets.
In collaboration with researchers from other
U.S. Department of Energy laboratories and
CERN, Fermilab scientists designed a new type
of magnet using a superconducting material
called niobium 3 tin.
These magnets can make a magnetic field in
the range of 11 or 12 Tesla, which is crazy
strong.
They’re going to make a big difference in
improving LHC luminosity.
Fermilab is also working on what are called
CRAB cavities, which are accelerator components
that briefly alter the direction of the two
beams of protons that are circulating in opposite
directions to ensure that that the beams are
hitting head-on.
This technology will also increase the luminosity
of the LHC beams.
The actual components for the upgrade will
be built at a number of different places around
the world.
While some components are made here, perhaps
Fermilab’s key contribution is the knowledge
and experience to make these accelerator upgrades
a reality.
Although increasing the collision rate of
the beams is a crucial goal of the LHC research
program, improving the accelerator is not
enough.
After all, there are also particle detectors
arrayed around the accelerator ring and they
were designed for the original LHC.
The original detectors can’t handle the
increase in luminosity.
Fermilab is a leader on the Compact Muon Solenoid,
or CMS.
CMS is one of the two huge particle detectors
on the LHC and we used it to discover the
Higgs boson back in 2012.
Now CMS is big- really big.
It’s five stories tall and it weighs fourteen
thousand tons.
After the upgrades are complete, it will be
like a two billion pixel camera capable of
taking 40 million pictures per second.
The parts of the detector near the point where
the beams collide in the center of the detector
experience a lot of radiation damage due to
the huge rate of particles hitting the detector.
The radiation environment will be even more
daunting in the high luminosity LHC era, so
we have to give much of the detector an overhaul,
especially the parts near where the beam passes
through the center of the detector.
After considerable thought, Fermilab researchers
decided which projects were the ones on which
we could make the biggest impact.
We picked a few.
They are called the silicon tracking detector,
the endcap hadron calorimeter, the trigger,
and a timing detector.
Now, to be clear, Fermilab isn’t working
on these projects alone.
Many groups are involved.
But we’re a big institution with many people
involved, and therefore we have a disproportionate
impact on the tasks we undertake.
Let me give you an idea of what these upgrades
involve.
First the tracker upgrade.
When two protons collide in the LHC, hundreds
of particles come out.
Even worse, perhaps one or two hundred pairs
of protons can collide at the same time, which
means that at any one time, maybe ten thousand
particles are flying through the detector.
In order to see the path followed by each
particle, we need to use tiny, tiny, detector
elements to try to ensure that each element
is hit by only one particle.
This approach was used in the original CMS
detector with a vast array of very small individual
detectors made of silicon, but that detector
is worn out and needs to be completely replaced.
Researchers at the Fermilab Silicon Detector
Facility are working to build a new silicon
detector.
Then there’s the forward hadron calorimeter.
Calorimeters measure the energy that hits
them and the energy environment near the beam
line is especially intense.
That’s what we call the forward direction.
CMS is removing the existing forward calorimeter
and replacing it with one that uses silicon
detector technology in places where the radiation
environment is high and another technology
called plastic scintillator in regions where
the radiation is lower.
Since scintillator is less expensive than
silicon, this approach achieves the required
performance for lower cost.
A third upgrade on which Fermilab is working
is called the trigger.
Basically, CMS faces a real challenge.
Collisions occur about forty million times
per second, but we can only record about a
thousand of them.
So, we need to decide which collisions to
record and which to discard.
And we have to do it blindingly fast.
We do that by teaching electronics and computers
to scan the data and keep the data of one
collision out of every forty thousand.
The equipment that does this is called a trigger.
Improvements in electronics and computer technology
are allowing us to vastly improve our ability
to properly select and record only the most
interesting collisions.
The fourth upgrade of the CMS detector on
which Fermilab researchers are working is
called the timing detector.
Every time the two beams of protons pass through
the CMS detector more than one collision occurs.
In fact, something like one or two hundred
collisions simultaneously occur and all of
those tracks are simultaneously passing through
the CMS detector.
Figuring out which of those tracks came from
which collision is pretty hard.
However, if we can measure the time precisely
enough, that can help us identify which tracks
are the ones we care about.
The goal of the timing detector is to measure
things with a precision of thirty picoseconds,
which is a millionth of a millionth of a second,
which will vastly improve our ability to sort
everything out.
Now, it would be dishonest if we didn’t
acknowledge that these projects are not something
that Fermilab is working on alone.
CMS is an international project, with something
like three thousand scientists working on
it.
But Fermilab has more collaborators working
on CMS than any other institution beside CERN
itself, and we certainly take pride in our
contribution.
However, we must admit that a project this
big does, indeed, take a village.
And the contribution goes beyond the technical.
Fermilab is the institution that houses what
is called the Project Office for work done
on CMS by U.S. institutions.
We have the administrative and organizational
capabilities to make sure that money and resources
are responsibly used to achieve the experiment’s
goals.
If that weren’t enough, Fermilab also houses
the LPC, short for LHC Physics Center, which,
in addition to our own staff, hosts a hundred
or so visiting researchers.
At any moment, hundreds of CMS researchers
are collaborating in our corridors.
The High Luminosity LHC won’t start operations
until the mid- or late-2020s at the earliest,
but when it does, it will operate for at least
a decade – perhaps even into the 2040s.
This project is the flagship of the high energy
frontier for the foreseeable future- certainly,
for the rest of my career.
We expect to collect at least ten times more
data than we’ve collected so far, and it
will likely be more than that.
It always is.
It’s impossible to say what we might discover
with all that data, and I don’t know about
you, but I’m chomping at the bit to start
looking.
I liked this video, because it was a reminder
that discoveries like the Higgs boson only
occur because of a huge effort and years of
preparation to build the equipment that makes
it happen.
No accelerator and no detector means no discoveries.
And we kind of like discoveries.
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It sounds like the LHC will be studying physics
for decades which works for me, because- as
you know- physics is everything.
