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  • 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 timeBut 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 kilometersCurrently, 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 makemolecular moviesthat 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.

  • It really allows for

  • transformational science in chemistry, biology, and physicsThe 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 temperatureSuperconductors, 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 continuouslyIn 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 anywhereThe 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 getfirst lightin 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.

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

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B1 accelerator electron laser tunnel molecular quantum

Inside the Superconducting X-ray Laser Engineered to Image the Atomic World

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    林宜悉 posted on 2020/12/15
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