Stephen Streiffer is the director of the Advanced Photon Source at Argonne National Laboratory.
Stephen Streiffer is the director of the Advanced Photon Source at Argonne National Laboratory.
Photo courtesy of Argonne National Laboratory

This is a continuing profile series on the directors of the Department of Energy (DOE) Office of Science User Facilities. These scientists lead a variety of research institutions that provide researchers with the most advanced tools of modern science including accelerators, colliders, supercomputers, light sources and neutron sources, as well as facilities for studying the nano world, the environment, and the atmosphere.

Contributing Author Credit: Jo Napolitano is an Argonne Associate at Argonne National Laboratory, email at


Meet the director:

Stephen K. Streiffer served as the interim director of the Advanced Photon Source (APS) at Argonne National Laboratory, a Department of Energy Office of Science user facility, for a year before becoming its permanent leader in 2015. He loves the diversity of the science conducted at the facility, saying the breadth of the research is remarkable. “I’m still in awe of all we’re able to do,” he said. “The APS has facilitated a number of critical discoveries in myriad areas of science, impacting everything from materials for batteries to the environment to the development of lifesaving pharmaceuticals. This research has transformed the way we live. I’m thrilled to be a part of it.”

The director’s background:

Streiffer first became interested in science as a small child: It was NASA that drew him in.

“One of my earliest memories was of the Apollo moon landing,” he said. “It really set the imagination free in terms of what science, engineering and technology can do. I was about three years old, so this has been a lifelong passion.”

Streiffer went on to study physics, chemistry, and electrical engineering as an undergraduate at Rice University. But it was materials science and engineering that truly grabbed him. He continued his studies in this field at Stanford University, where he earned his doctoral degree.

“One of the things you learn about in materials science is the atomic crystal structure of various materials,” he said. “I knew I was on the right track because I fixated on the topic even outside of class. I remember, as an undergrad at Rice, sitting on a granite bench, staring down at all the individual rock crystals, wondering about their structure. I knew at that point I was hooked.”

Streiffer, who first came to Argonne in 1998 as an assistant scientist, started using the APS for his own research projects two years later. Back then, he was studying the way lead titanate films grew when deposited from a chemical vapor, as well as the transformations in crystal structure in the films as a function of temperature.

Lead titanate is a prototype of a class of materials known as ferroelectrics. Ferroelectrics are those substances capable of retaining the electric polarization of an applied electric field. They drive the microphones and speakers in our phones and control ink flow in inkjet printers.

“I was intrigued by this, because with the APS we had the ability to literally see individual atomic layers depositing on the surface of our growing films,” he said. “We could then use the APS to watch the transition from the nonferroelectric to the ferroelectric state in the samples – and answer questions about that transition that had been the subject of debate for decades.”

The facility:

The APS provides ultra-bright, high-energy, storage-ring-generated X-ray beams for research in almost all scientific disciplines.

It provides unique tools for understanding the structure, chemical composition, topology, electronic configuration, and dynamics of materials and chemicals.

The facility helps researchers create more energy efficient batteries, improve our understanding of the materials buried well beneath the Earth’s surface, and facilitate the development of new and better drug treatments.

It’s Streiffer’s job to oversee operations at the APS. He guides the long-term vision for the facility and ensures that researchers – who come from around the world – have successful experimental runs.

The APS employs approximately 500 people and serves more than 5,000 unique users each year, helping them complete more than 6,000 experiments annually.

The facility is anticipating an $815 million upgrade that will greatly increase the brightness and coherence of its X-rays, vastly expanding its scientific reach.

DOE is replacing the electron storage ring and building new beamlines to make use of the new X-rays. The electron accelerator will shut down for a year during this transformation, currently planned for 2022. Such massive improvement projects are rare, happening only once every two or three decades.

“The upgrade will make the X-rays we produce 200 to 1,000 times brighter and more coherent (depending on wavelength) than today,” Streiffer said. “This will allow us to examine samples hundreds of times more rapidly than we can right now.”

Streiffer used the study of jet engine materials to explain the difference between what the APS can do now versus after the upgrade.

“Right now, we can study a material that is representative of a turbine blade in a jet engine and understand its structure under conditions like those under which it typically operates with a spatial resolution of about 0.25 micrometers, or about 10-millionths of an inch,” he said. “After the upgrade, we will be able to study this same turbine blade material under operating conditions all the way down to the atomic scale, allowing us to follow the specific mechanics by which a turbine blade breaks. Ultimately, this will lead to safer, stronger, and lighter engine components that are not only more reliable, but more energy efficient.”

Stephen Streiffer has led the Advanced Photon Source since 2015.
Stephen Streiffer has led the Advanced Photon Source since 2015.
Photo courtesy of Argonne National Laboratory

Typical day:

Streiffer starts each day by looking at how the electron accelerator complex performed overnight. The APS can run up to 68 experiments at once and often reaches its maximum capacity.

“On the operational side, it’s an extraordinarily complicated machine, so a major part of my job is to make sure it runs smoothly,” he said. “Our typical operational schedule is 24 hours a day, six days a week, with the seventh day used for maintenance and studies of accelerator performance. We run like that for about three months, and then have an approximately month-long shutdown for more extended maintenance and repairs. Putting it all together, we run three cycles like this each year.”

Streiffer loves walking around the experiment hall of the APS, talking with researchers about their work.

“Everyone is really excited about the problem they’re trying to solve,” he said. “They’re doing things that are breathtaking and the results they produce are fabulous.”

He also works on a daily basis with users and other stakeholders to make sure they understand the APS’ capabilities. “This includes providing informational materials to elected representatives at their request so they can understand what we do, as well as generally getting the message out to the public about the science and technology we conduct,” Streiffer said.

But only a portion of his day can be devoted to the daily goings on. About half of his time is spent preparing for the upgrade, which positions the APS to be a global leader among the new generation of storage-ring light sources currently emerging.

“The upgrade is a real game changer,” he said. “It represents the science we are going to do in the future.”

Typical experiment:

Streiffer can count several APS experiments as among his most treasured.

“One of my current favorites involves the development of treatments for Ebola,” he said. “The structure of one of two new effective therapeutic agents was determined here at the APS. We are supporting work that saves lives.”

Another is a recent experiment involving SUE the dinosaur, the famed Tyrannosaurus rex that graces the Field Museum of Natural History in Chicago. Researchers brought SUE’s forearm to the APS to find out whether she used her spindly arms.

“It turns out that SUE had osteoporosis,” Streiffer said. “That means she probably didn’t use her arms very much, and they may indeed have been vestigial.”

Surprisingly, it was yet another experiment that impressed Streiffer’s now-12-year-old son, Ben, back in 2014.

“It turns out, we don’t really understand where the water on the Earth comes from,” Streiffer said. “We also don’t know how much water is in the interior of the Earth versus its surface: There may be more water locked in the mantle than all of the oceans combined.”

To help solve this mystery, scientists brought in mineral samples to study at high pressures at one of the APS’ powerful beamlines.

“The researchers took samples of certain hydrated minerals and used the APS to study how they release water and melt at high temperatures and pressures representative of the Earth’s mantle,” Streiffer said. “By combining these results with high-resolution images of the mantle obtained from seismometers, they found clear signs of this ‘dehydration melting’ where mantle material is moving downward. This implies that vast quantities of water are cycled into the interior of the earth through minerals that begin their journey in a hydrated state.”

Streiffer’s son heard about the experiment on the radio and was flabbergasted to learn from his father that it was performed where he worked.

“He had no idea the APS was so important!” Streiffer said. “It was just the place his dad went every day.”

Best advice for a future director at the APS:

“Never limit your horizons,” Streiffer said. “Every day, we find that we can help solve more problems than we ever thought possible. And our capabilities are about to get even better.”


In Fiscal Year 2021, our 28 user facilities welcomed more than 33,000 researchers from academia, industry, and government research enterprises from all 50 states and the District of Columbia to perform scientific research. For details on the individual Office of Science User Facilities, please go to

Please go to Profiles of User Facilities Directors to read more articles on the directors for the Office of Science user facilities.

The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website.