Newswise — It might be difficult to imagine a job that spans understanding the cosmos, bringing fusion energy to Earth, and treating cancer, but that’s exactly what Siegfried Glenzer does.
He works with high-powered lasers, a field of science that has interested him since his first glimpse of a laser laboratory during a college tour in Germany. Because, as he puts it, “There’s so much control, and you can do so many things with lasers.”
Glenzer came to SLAC National Accelerator Laboratory after working 19 years at another national lab, Lawrence Livermore National Laboratory. At SLAC, he started an exploratory science program that looks at matter in extreme conditions. Glenzer’s research team uses lasers to create materials that are under high pressure, similar to the interiors of planets and stars.
In addition to learning about other worlds, he has a long-term goal of creating a fusion energy source. And along the way, there have been added discoveries.
What exactly is “high energy density science”?
It means you have matter or material with a lot of energy in it. The energy is so densely packed that the material is under enormous pressure. So “high energy density science” can also stand for “material at extreme pressure.”
How do you create these extreme environments?
We need a powerful laser to start with. We focus those laser beams to tiny spots—like on the micron scale. A human hair is 50 microns, and these spots are a tenth of the diameter of a human hair.
Putting a lot of energy in a very small area produces “high energy density” science. We want to measure the physical properties of these materials.
What can we learn from these measurements?
It’s important for our knowledge of how the planets came about, the evolution of the cosmos. And it’s also important for our endeavor to create fusion energy.
Energy in the sun is produced by nuclear fusion. If we can reproduce that on the planet in a controlled way, we have the perfect energy source.
There are also practical, near-term applications. For example, in order to create the extreme material states, we are using powerful lasers. And we discovered that when we fire those laser beams at materials, we accelerate particles to high energies. Where those lasers interact with the materials very energetic particles are produced—protons, electrons, hadrons, X-rays and gamma rays.
These particle movements lead to an instability that can create a shockwave. We can form the instabilities that lead to collisions, so we have a control mechanism, and we just discovered that. What we believe we can do is use that process to our advantage to accelerate particles. So we could have a proton source where we could produce a proton beam at very high energies. That’s currently being investigated as a way to treat cancer.
This is one of the advantages of lasers—they’re so versatile. We do laboratory astrophysics, we do fusion energy discovery science, and we do very practical accelerator physics for tumor therapy.
Why is the timescale important? Why do you need an ultrafast laser?
In this realm of science, a series of processes are happening, all on the femtosecond timescale.
The laser interacts with electrons in the materials in femtoseconds, and the light pushes around the electrons. The electrons gain energy and stream through a target. Magnetic fields form around the energized electrons that can coalesce and form a shockwave. That’s called a “collisionless shock.”
That process has been conjectured to be the origin of cosmic rays. Cosmic rays are one of the fundamental processes that mankind still seeks to understand. They are the most energetic particles that we know of. It’s a million times more energetic than what we can produce on Earth at the Large Hadron Collider. And we are looking for the process that explains how these energetic particles came about.
In addition to the high power optical lasers that create these extreme conditions, we also have an intense X-ray beam, the Linac Coherent Light Source (LCLS). This laser also has femtosecond capabilities—we can create ultrafast pulses—but at a higher energy than visible light. The X-ray laser allows us to take snapshots of the incredibly fast processes that occur.
So we’ve done experiments where we fire an optical laser on a small piece of carbon, create this environment where the electrons are being pushed out and create shockwaves, and then use X-rays to visualize the shockwaves.
These processes might happen in femtoseconds, but how long will it take to create a fusion energy source?
One of the big misconceptions is that people think it cannot happen. They don’t like thinking on a 20- or 30-year timescale. But there are now fusion experiments happening all over the world. We’re making progress. People just have to accept that science can take more than a year or two to see results. It may take decades.
Fusion is happening every day in the sun, so all we have to do is look up in the sky and ask “Can we control it in the laboratory? How bright are we? And how willing are we as a community to make it happen?”