Understanding Nature, Accelerating Electrons, and Advancing Science

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Photo courtesy of Matt Beardsley/SLAC

Claudio Pellegrini (right) and SLAC scientist Herman Winick in the klystron gallery of SLAC's linear accelerator. Pellegrini and Winick were instrumental in making the idea for LCLS a reality.

Coherence

"On the Nature of Things" is a 1^st century B.C. epic poem that "explains in beautiful verses that matter is built with atoms," says physicist Claudio Pellegrini about his favorite poem, written by the Roman Lucretius. "Understanding nature is important to escape superstition and live 'pursuing happiness,' with reason and without fear."

Lucretius' guidance informed not only the physicist's youth but a full career of better understanding nature, which this month will earn him the 2014 U.S. Department of Energy (DOE) Fermi Award, one of the nation's oldest and most prestigious awards for scientific achievements. On October 20, Pellegrini is being honored for his pioneering research to develop the X-ray free-electron laser.

In the grand tradition of the renowned Italian physicists who have come before him, Claudio Pellegrini has created a lifetime of scientific advances with new theories and achievements.

His childhood in a small village in the mountains east of Rome taught him endurance and ingenuity. Enemy soldiers occupied his village and food and safety were precious and scarce during the war. "I remember those years very well," said Pellegrini. "Our main interest was to find enough food for the family and survive to the end of the war."

He did survive. At school, his humanities and philosophy professors introduced him to Greek philosophers and their search for understanding nature with reason and observation. He attended the University of Rome, earning his masters, then completing a thesis for his "Libera Docenza" [Ph.D] at the first high energy physics laboratory in Italy, the Frascati National Laboratory.

Defining Moments

Pellegrini's earliest work at Frascati National Laboratory was the design and development of electron-positron colliders. Colliders are particle accelerators, designed to send electrons against a target or against another stream of accelerated electrons. The collision results are used by researchers studying interactions in the subatomic world.

There, he looked for effects that limited a collider's luminosity and discovered the effect he named the "Head-Tail Effect," a collective instability in electron beams which can strongly limit the beam intensity. Pellegrini's theory indicated a way to control this effect and improve the performance of the colliders.

In 1978 Pellegrini joined DOE's Brookhaven National Lab, where he was part of the team to organize the Center for Accelerator Physics. He served as both Co-Director of the CAP and Associate Chairman of Brookhaven's National Synchrotron Light Source from 1986-1989. During his 11 years at BNL, his interest focused on free-electron lasers, becoming his main field of research.

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Photo courtesy of C. Pellegrini

Claudio Pellegrini is awarded the 2014 Fermi Award.

Pellegrini moved to UCLA in 1989, accepting a position as professor and later Chair of the Department of Physics and Astronomy.

In 1992, researchers met at the "Workshop on Fourth Generation Light Sources" to discuss the next development for the SLAC Stanford Synchrotron Radiation Light Source (SSRL) facility. Many of the 146 attendees supported continuing the current direction of the research facility. Pellegrini also attended, ready to present his ideas.

Pellegrini trusted his conviction that the next step for the SSRL was not the larger storage ring most SLAC researchers wanted and planned for. He saw a different road.

By making use of part of SLAC's 2-mile-long linear accelerator, Pellegrini believed that an even brighter electron beam was possible, built at relatively low cost. This new kind of laser would operate in the previously unreachable short X-ray wavelength range of 4 nanometers to 0.1 nanometers and produce an astonishing 10 gigawatts of peak power – the world's first x-ray laser of this magnitude.

"When I presented my paper at this workshop, of course there was interest and there were two kinds of reactions. A number of people believed it was a crazy idea, it would never work," said Pellegrini. "But some other people took up the challenge and could see there was real possibility." At that time it was a risky proposal, based on a yet-unproven theory.

"But I was convinced that a free-electron laser (FEL) was the real way to go to have a break-through, a real revolution of performance of SLAC's lightsource.

"In 1998 we succeeded in showing the validity of the FEL SASE [self-amplified spontaneous emission] theory in two experiments. That was another moment of great joy." These were a joint effort between UCLA-Los Alamos National Laboratory (LANL) and a second among SLAC-UCLA-BNL-LANL that set the stage for the main effort.

The project received initial funding from DOE in 2001. In the spring of 2009 this new tool – the Linac Coherent Light Source (LCLS) – began operations as the first hard X-ray free-electron laser (XFEL) in the world, able to produce hard X-rays which researchers use to see down to the level of atoms and molecules. This XFEL was powerful enough to show the atomic structure of single molecules and has enabled new areas of ultrafast X-ray physics, atomic physics, chemistry, biology, and materials science. The technology is now widely spread and used.

Pellegrini recently retired from UCLA with the title Distinguished Professor Emeritus in the Department of Physics and Astronomy; he lectures at seminars on electron and photon beam physics; and he continues to work with SLAC researchers to increase the capabilities of LCLS.

"I have been lucky enough to have several Aha! moments," said Pellegrini. "I can mention the discovery and experimental test of the Head-Tail Effect, the development and experimental verification of the SASE FEL theory.

"The special moments are when the theories that one has developed are verified by the experimental data. Without that test, a theory can be nice and elegant, but it can only be considered a working hypothesis. But when you see that what you have developed mathematically is what really happens in nature, wow, that is something different, and everything comes together.

"During my life I worked with people from all countries and we all share the language of science and understand each other. Science is really an international enterprise and helps to bring people together. Science gives us the only verifiable knowledge, limited but certain and valid for everybody, female or male, whatever the ethnic origin and culture," said Pellegrini. "How far will science go? How much can we explain with science? We do not know, but every additional bit of knowledge is worth working for."

The Fermi Award is a Presidential award and is one of the oldest and most prestigious science and technology honors bestowed by the U.S. Government. The Enrico Fermi Award is given to encourage excellence in research in energy science and technology benefiting humankind; to recognize scientists, engineers, and science policymakers who have given unstintingly over their careers to advance energy science and technology; and to inspire people of all ages through the examples of Enrico Fermi, and the Fermi Award laureates who followed in his footsteps, to explore new scientific and technological horizons.

A Fermi Award winner receives a citation signed by the President of the United States and the Secretary of Energy, a gold-plated medal bearing the likeness of Enrico Fermi, and an honorarium of $50,000. In the event the Award is given to more than one individual in the same year, the recipients share the honorarium equally. The Fermi Award is administered on behalf of the White House by the U.S. Department of Energy's Office of Science.

The Office of Science is the single largest supporter of basic energy 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 http://science.energy.gov.

Sandra Allen McLean is a Communications Specialist in the Office of Science, [email protected].