March 8, 2013
Siegfried Glenzer vividly remembers his excitement when he first used a powerful research laser. A physics major at Ruhr University Bochum in Germany, he took the temperature of plasma created during a fusion energy experiment by aiming a ruby laser at it.
"I thought it was really cool that lasers could directly measure such extreme heat – thousands of degrees," Glenzer said.
Twenty-five years later, Glenzer has joined SLAC as a distinguished staff scientist in the Stanford Institute for Materials and Energy Sciences (SIMES). He spent the last 18 years at Lawrence Livermore National Laboratory, where he was lead experimentalist and plasma physics group leader for the National Ignition Facility (NIF), the world's largest and most energetic laser. He was named a Fellow of the American Physical Society in 2001, and two years later was awarded the society's John Dawson Award for Excellence in Plasma Physics.
Glenzer said the intense X-ray laser pulses created by SLAC's Linac Coherent Light Source (LCLS) provide great opportunities to explore high-energy-density science, a field the National Research Council once called "The X-Games of Contemporary Science."
"Siegfried brings international leadership to SLAC in the science of materials under extreme conditions," said Tom Devereaux, SIMES director and associate lab director for photon science. "He will also help strengthen the synergy between the Photon Science Directorate and LCLS."
Glenzer is a world-renowned expert in a laser technique known as X-ray Thomson scattering, which is based on the interaction of electromagnetic waves, such as light, with free electrons. It is used to determine the properties of matter that has been heated and compressed to high temperatures and/or pressures, and is especially powerful in sensing the temperature of plasma – the high-temperature state of matter in which electrons and nuclei move independently of each other. (Familiar examples of plasma include fluorescent lights, plasma televisions, lightning bolts and stars.)
Glenzer said he's looking forward to using the 4-trillion-watt (terawatt) ultrashort pulse laser at LCLS's Matter in Extreme Conditions (MEC) instrument to heat and shock-compress matter to extremely high temperatures and pressures. During the instant of maximum compression, an ultrshort LCLS X-ray pulse hits the sample, producing Thomson scattering that reveals the properties of the compressed material.
The lasers at MEC can produce exotic states of matter ranging from warm dense matter, in which only some of the material's electrons have been liberated, to high-density plasmas that have been crushed and heated until their atoms' electron shells are smashed together, dramatically changing their properties.
Short animation of the Matter in Extreme Conditions (MEC) instrument. (Credit: Gregory Stewart/SLAC)
"The more powerful the laser, the denser and hotter the plasma you can create," Glenzer said. This summer, the power of MEC's short-pulse laser will be increased to 30 terawatts. Glenzer has proposed a multi-year plan to ultimately increase the laser's power to 10 quadrillion watts (petawatts), delivered in pulses only 35 femtoseconds, or millionths of a billionth of a second, long.
Experiments with these increasingly powerful lasers should be able to simulate how cosmic rays are produced, enable a tabletop source of betatron X-rays and create an antimatter plasma.
“These plasmas are very hard to create,” Glenzer said. “And once you make them, it’s difficult to know what’s actually going on within them. That’s a big challenge, which I find a lot of fun.”