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Lab Breakthrough: X-ray Laser Captures Atoms and Molecules in Action

July 18, 2012 - 12:51pm


The Linac Coherent Light Source at SLAC is the world's most powerful X-ray laser, which helps researchers understand the extreme conditions found in the hearts of stars and giant planets guiding research into nuclear fusion, the mechanism that powers the sun. View the entire Lab Breakthrough playlist.

SLAC National Accelerator Lab physicist Uwe Bergmann works with the world’s first free electron X-ray laser to figure out such mysteries as how sunlight splits water into oxygen to uncovering some of Archimede’s original writings. 

This Q&A and video are part of the Lab Breakthrough series, which highlights innovations developed at the National Labs. 

Question: Why is investigating the fundamental processes of the universe so important?

Uwe Bergmann: The natural laws and mechanisms that control everything we experience have evolved and created our current world over immense scales of time. Even the most grand and complex experiments we can create as humans will never hold a candle to what nature itself has learned by trial and error in the history of the universe. So by studying those fundamental processes and trying to understand why and how they work, often in surprising and non-intuitive ways, we are essentially picking apart nature’s lessons for our own education and benefit. On another level, it’s also simply about curiosity.

Q: You mentioned that the accelerator that drives the Linac Coherent Light Source (LCLS) was the originally designed for a different purpose. What was that original purpose?

UB: People today may be aware of the Large Hadron Collider, or LHC, in Geneva, but 50 years ago SLAC built one of the most powerful particle colliders. Unlike LHC, which is a ring, our collider was built to accelerate particles in a straight line. This linear collider gave science its first evidence of subatomic particles called quarks and won scientists here three Nobel Prizes, but like all cutting edge technology it was eventually replaced with newer and better models.

The laboratory was fortunate because a smart and forward-looking group of people realized the linear accelerator itself could still be very valuable for a new purpose. It was suggested that a portion of the accelerator could be converted to become a powerful source of X-rays. Hence, the Linac Coherent Light Source, or LCLS, was built and became the world’s first hard X-ray free-electron laser. Rather than accelerate particles to collide them, it accelerates particles in a special way to create extremely bright bunches of photons, which researchers can harness for a variety of important experiments.

Q: Who can use the LCLS for their research, and how are they selected? 

UB: LCLS’s pulses are about 10 billion times brighter and one thousand times shorter than those from other X-ray sources and this opens a lot of unique possibilities for research, so to get approval for an experiment on it is very competitive. In fact, we’re currently only able to accept less than one in four proposals.

To balance many different types of research, from atomic physics to materials science to biology, and so on, we select only the top proposals from each field.  We also need to assure that the proposals are feasible and have a good chance of success. Many of the teams have done preliminary experiments at other facilities and months of preparation before they come to us to make the most of the extremely valuable time on LCLS.

Q: I know that work often builds from other work in a ‘standing on the shoulders of giants’ type of way. Are there any particular technologies or discoveries that act as a basis for your work?

UB: Of course that’s correct. Though often the “giants” seem to get a lot of credit when in reality science proceeds over numerous smaller individual contributions building on the many contributions before that. 

My own area of work is particularly in developing and using X-ray techniques, most of which have been conceived over the past 100 years since X-rays were first discovered in 1895. Most people think of X-rays as images that show the inner parts of your body when going to the doctor or the dentist, but they have a tremendous number of uses in any parts of science. Techniques including various ways of X-ray imaging, spectroscopy, scattering and diffraction have all been continuously developed and refined over the past century, and we are still coming up with new ones.

Q: Would I see, perhaps unknowingly, the affect of LCLS research in everyday life? If not today, only being turned on in 2009, will we ever?

UB: Because LCLS is such a revolutionary new machine, it will take some more time before the potential is fully understood and embraced by the larger science community in physics, chemistry, biology and technology.

To give more direct examples though, research done on other types of light sources resulted in materials you might have in your flat panel TV or modern gaming consoles, drugs that treat cancer and HIV, and components of solar panels, electric motors and LED lighting.

If you ask me again in five years, I have no doubt we’ll be able to point to some big advances that never would have been possible without this incredible facility. It will be fascinating to see which ones they will be.

Visit the Lab Breakthroughs topic page for the most recent breakthroughs highlighted in the video series.