Name: Inside the Superconducting X-ray Laser Engineered to Image the Atomic World
Uploaded: 2020-12-15T18:30:45.000Z
Duration: 8 min 28 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

This is the world's brightest x-ray laser. At the time of its first light in 2009, the

Linac Coherent Light Source generated x-ray pulses a billion times brighter than anything

around. The LCLS is a tool unlike anything before it. We're able to deliver these pulses

of x-rays in one millionth of one billionth of a second. This MASSIVE MACHINE allows scientists

to take ultrafast snapshots of the INVISIBLE WORLD, imaging MOLECULES AND ATOMS, documenting

how they change and evolve over time. But the LCLS maxes out at 120 pulses per second.

So to see the ultra small world like never before, scientists and engineers are building

something new. The LCLS-II is going to take the free electron laser field up another quantum

leap. This will be unprecedented and will allow for a beam that's 8,000 times

brighter than the LCLS beam at this million pulses per second.

At this national lab, hidden deep underground, scientists have been conducting groundbreaking research for

decades. The whole tunnel and the whole building that we see here, is about three kilometers

long and the original project used that full three kilometers. Currently, the LCLS accelerator

is in the final kilometer. The LCLS is short for the Linac Coherent Light

Source. It's the world's first hard x-ray free electron laser. The LCLS uses a particle

accelerator to fire extremely bright electrons to create fast pulses of hard x-rays, which

is why the machine is called an x-ray laser. Back in the '90s at SLAC they figured out

a way to turn those super bright electron beams into very intense and bright and powerful

x-ray laser pulses. We have ultraviolet lasers trained and aimed at this piece of copper,

and we pulse that optical laser about 100 times a second creating an electron pulse.

We channel those electron pulses into the accelerator. The accelerator then uses big,

longstanding technology called klystrons. And we can think of them as microwave ovens,

and the microwave ovens basically accelerate these electrons. And as we accelerate those

electrons what makes the LCLS really go, are what are called undulators. If you take an

electron through magnets, the electron bends and when it bends it gives off x-rays. We

then are able to focus the x-rays into different sample materials. Whether that sample is an

amino acid, or graphene, or supercooled water, it gets frozen in time by strobe-like pulses,

which last for just a few femtoseconds. A femtosecond is a quadrillionth of a second.

It's one millionth of one billionth of a second. We would picture that

as a one with fifteen zeros in front of it. This time scale allows scientists to track

the motion of atoms! Allowing researchers across disciplines to probe the far reaches

of our scientific knowledge. Empowering them to make “molecular movies” that show chemistry

in action, study the structure and motion of proteins for next generation drugs and

image quantum materials with unprecedented resolution. It's a tool for exploration.

transformational science in chemistry, biology, and physics. The LCLS-I, if you would like to say, the original build,

was great to look at how molecular structure is evolving through time using bright x-rays

and taking snapshots. But researchers wanted to go BEYOND looking at molecular structures.

And they wanted a machine that fired EVEN FASTER! The LCLS-II accelerator is a superconducting

accelerator designed to produce a very intense burst of x-rays at a very high repetition

rate. We're talking about magnitudes far greater than its predecessor. This new accelerator

will go from 120 pulses per second up to 1 MILLION pulses per second! Which means

more shots per second allows you to collect more information in a shorter period of time,

which helps boost science output. But it's not just about quantity. It's about what

we can see with the LCLS-II. With LCLS-I, we will look at the structure. On LCLS-II,

we might want to look at how the energy flows through those degrees of freedom in that system.

The LCLS-II will be able to image atoms, molecules, and subatomic interactions at greater

resolutions thanks to its superconducting accelerator. For LCLS-II, we will be installing

37 cryo modules. Each of our cryo modules in the tunnel is roughly 12 meters long and

each has eight accelerating cavities inside of it. We're using these new niobium cavities.

They're superconducting and the way we get them superconducting is we bathe them in liquid

helium. So it's two degrees above absolute zero, where in principle, all motion stops.

This ultra cool upgrade is a big change from the LCLS, which uses a copper accelerator

and operates at room temperature. Superconductors, when you cool them down cold enough, they

have no electrical resistance. So they don't heat up at all. Since you're not heating your

structure up, you can run it continuously.  In our case, this allows us to make the jump

from 120 pulses per second up to a million pulses per second. But installing 37 twelve-meter-long

cryomodules inside a narrow, underground tunnel nine meters below is no easy feat.

This is a cryomodule here. It's 40 feet long, so we do string all them together,

so they're in three different strings. The one that we're standing in front of right now is by far the largest.

As engineers, we have to come up with some clever ways of just how to fit all of these big pieces of

equipment through the tunnel and maneuver around them to make sure that they're installed

properly. The installation itself, right now, is about 95 percent complete in the tunnel.

In addition to having a new, superconductive accelerator, LCLS-II is also getting new undulators,

which will create magnetic fields TENS OF THOUSANDS times stronger than the Earth's

magnetic field. So we are inside the hutch called

the TMO instrument. This is one of the very first stops for the LCLS-II superconducting

beam when it comes online. And what this is really tuned to do is to look at the dynamic

properties of how energy is transferred from one state to another. Once operational, the

new accelerator is capable of producing more x-ray pulses in a few hours than the LCLS

has produced over its entire lifetime! — generating terabytes of data each second. All this new

power will undoubtedly lead to an influx of breakthroughs and discoveries. As we scan

through time, we're able then to map out how these molecules break apart, and that tells

us something about fundamental AMO physics. Another aspect of it is looking at how the

energy flows through quantum materials. But even with this new accelerator's exciting

potential, that doesn't mean the LCLS is going anywhere. The LCLS is here to stay.

What LCLS-II will provide is really a compliment. So the two machines will continue to work

together. With LCLS operating in a harder x-ray regime and LCLS-II providing what they

call soft or tender x-rays, which really allow you to probe different states of matter at

this much higher repetition rate. The new accelerator will take over the first kilometer

in the tunnel, while the original will remain in its current position at the end. The LCLS-II

is currently on target to get “first light” in summer 2022. It's really cool to be able

to come here and work on a machine that's really going to help people, really going

to help scientists make all these great discoveries. One of the most important things for big science

experiments is planning for the future. LCLS-II is being built at a key time in x-ray science.

What LCLS-II can provide really is groundbreaking and addresses an area that can't be identified

or worked on at any other facility. Now that we know that we have this source that's going

to enable much more science, we're going to tackle new, harder scientific fields, and

so we're just not going to be stagnant and just say, "Oh, we can do that experiment that

much better and that much shorter in time." No, we want to go for the hard stuff, and

so we're going to have to really look at and utilize that new superconducting source to its fullest.