Claudio Pellegrini, 2014


For pioneering research advancing understanding of relativistic electron beams and free-electron lasers, and for transformative discoveries profoundly impacting the successful development of the first hard x-ray free-electron laser, heralding a new era for science.


Distinguished Professor of Physics, emeritus, Department of Physics and Astronomy, University of California, Los Angeles, and SLAC National Accelerator Laboratory.

Undergraduate Institution: University of Rome, Laurea in Fisica cum laude, 1958

Graduate Institution: University of Rome, Libera Docenza, 1965

Professor Claudio Pellegrini is honored for impactful contributions to relativistic beams, and specifically, his critical role in establishing the transformative concept of self-amplified spontaneous emission (SASE), and through his insight and persistence, its realization as the Linac Coherent Light Source at SLAC National Accelerator Laboratory (LCLS), the world’s first hard X-ray free electron laser (XFEL). This instrument, with femtosecond pulses that are a billion times brighter than storage ring based synchrotron light sources, has enabled new areas of ultrafast x-ray physics, atomic physics, plasma physics, chemistry, biology, and materials science, adding the dimension of x-ray atomic-scale imaging to attosecond time-resolved measurements. XFELs are now being realized in Asia and Europe, transforming the nature of X-ray facilities available world-wide.

Dr. Pellegrini’s early work led to the discovery of the “Head-Tail” instability and other collective effects that limit particle beam intensity and collider luminosity, providing both an understating and a solution to allow high currents to be stored in rings. His later studies of free electron lasers (FELs) in the high gain regime as a collective instability promoted new insight into FELs including the self-amplified spontaneous emission (SASE) regime. By extending the FEL into the non-linear regime, he recognized that for electron bunches of sufficiently high density and low emittance, the back-action of the radiation on the bunch itself would drive a collective instability that would organize the bunch into parallel planes of charge, thus greatly enhancing the gain. For a sufficiently long undulator, the gain exponentiation could reach saturation, yielding the theoretical maximum output. This phenomenon was termed Self-Amplified Spontaneous Emission (SASE), and its realization was the key step for enabling a fully coherent and tunable x-ray laser of unprecedented brilliance. He led the group that also provided the first experimental validation of the theoretical models of high gain FELs.

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