He was educated at the
Sapienza University of Rome where he received the Laurea in Fisica
summa cum laude in 1958 and the Libera Docenza, in 1965. From 1958 to 1978, he worked at the
Laboratori Nazionali di Frascati for high energy and nuclear physics. In the early 1960s, he was at the
Nordic Institute for Theoretical Physics (NORDITA) in
Copenhagen, working on an alternative formulation of the theory of
general relativity using tetrad fields to obtain, among other things, a better description of the energy-momentum complex. (See
Teleparallelism for a summary of the theoretical context of this work.) In 1978, he moved to the United States and began work at
Brookhaven National Laboratory, where he was an Associate Chairman of the
National Synchrotron Light Source and co-director at the Center for Accelerator Physics. In 1989, he accepted an appointment at the
University of California at Los Angeles (UCLA) as a professor of physics, and later became a distinguished professor. In 1968 he discovered a novel collective effect, the head-tail instability, which limits the
luminosity of a collider. The theory suggested a way to control the instability that has been applied to all colliders and storage rings, increasing the collider luminosity and extending their reach to explore elementary particle physics. At Brookhaven, he studied
free electron lasers (FELs) and their application to the generation of high intensity coherent X-ray pulses. In 1992, based on these studies, he proposed building an X-ray FEL at
SLAC National Accelerator Laboratory based on
self-amplified spontaneous emission (SASE) in order to create
femtosecond long, one
angstrom,
coherent, X-ray pulses. From 1998 to 2001, Pellegrini and his collaborators demonstrated experimentally the validity of the SASE theory. This work and the 1992 proposal led to the construction of the Linac Coherent Light Source (LCLS), the first 1-angstrom X-ray laser, which has been successfully operating at SLAC since 2009. LCLS has opened a new window for the exploration of atomic and molecular science at the one angstrom-one femtosecond length and time scale characteristic of these phenomena. == Honors and awards ==