David
Nygren's inventions and innovations in radiation detection have transformed
research in particle and nuclear physics and cosmology. His ingenious
designs, of striking simplicity and unprecedented resolution, have enabled a
broad range of measurements, from the imaging of complex events at high
luminosity colliders to searches for the rarest low energy phenomena, as well
as the observation of very high energy neutrino interactions in the world’s
oceans and deep within Antarctic ice.
Dave, with
a PhD from the University of Washington, started his scientific career in 1967,
as a Research Associate at Columbia University’s Nevis Laboratory, under the
direction of and in collaboration with Jack Steinberger, and later with Bill
Carithers. At Nevis, Dave observed, and measured, effects of CP violation
in the decay of KL mesons. Early in that work he and
others at Nevis built what was then the world’s largest multi-wire proportional
counter, an important advance in particle-detector instrumentation.
In 1973
Dave left Columbia and joined Lawrence Berkeley Laboratory as a Division Fellow. Soon afterwards, in
1974, he invented the Time Projection Chamber (TPC), an
entirely new, distinctive, and extraordinarily powerful device to detect,
identify, and track multitudes of charged particles in three dimensions.
The first large TPC was the heart of the PEP-4 experiment, operated from 1981-1989 at the SLAC Positron
Electron Collider. Since that time, the TPC has been variously developed to
become the internationally preferred detector in a wide range of
elementary-particle and nuclear physics experiments. Large TPCs were central
to the ALEPH and DELPHI detectors at CERN's Large Electron Positron collider
(LEP). Between 1989 and 2001, these detectors studied the Z and W bosons and established the validity of the Standard
Model of particle physics through a series of precision measurements.
Since 2000, the STAR-TPC, at the Relativistic Heavy Ion Collider (RHIC)
at the Brookhaven National Laboratory, has studied collisions of matter at high
energy density, and probed the fundamental interactions of quarks and gluons. Images
of the gold-on-gold collisions from RHIC have graced the front page of The New York Times, as well as several
book covers. The ALICE detector, which is used to study heavy ion
collisions at the Large Hadron Collider (LHC) at CERN, relies on a TPC to
measure these interactions at even higher energy. The TPC has proved to
be invaluable not only in experiments where there are frequent, and complex,
multiparticle events, but also in rare-event experiments. The TPC in the
ICARUS experiment in the Gran Sasso Laboratory (LNGS), in Italy, uses liquid
argon in place of gas to measure high-energy neutrino interactions with a beam
generated at CERN. Liquid-xenon filled TPCs are now a primary means of
searching for WIMP dark matter particles, where the recoil energies are
measured in tens of keV. From keVs to TeVs, TPCs are still at the
forefront of particle and nuclear physics research, some forty years after
their invention.
Dave was
named Senior Physicist at LBNL in 1975; in 1986, he became a Fellow of the
American Physical Society; in 2000 he was inducted as a member of the National
Academy of Sciences. Dave’s work has been honored with acclaim; he has received:
the DOE’s E. O. Lawrence Award, 1985, “For the development of experimental
techniques in particle physics and especially for the invention of the Time
Projection Chamber." In 1998 he was awarded the American Physical
Society’s W.K.H. Panofsky Prize, "For the concept, development, and
application of the time projection chamber (TPC), enabling unprecedented
studies of complex topologies of charged particles produced in high-energy
collisions of interest to both high energy and nuclear physics.” In 1995 Dave
was promoted to the rare Distinguished
Scientist classification at LBNL for his “sustained history of
distinguished scientific and technical achievements,” and in 2013 he received
the Director's Lifetime Achievement Award, “for Exceptional Achievement.”
In the late 1980s, with the planned
Superconducting Super Collider (SSC) under construction, Dave and collaborators
pursued a variety of electronics-based approaches to particle detection and
measurement. Dave initiated a research path at LBNL aimed at developing smart-pixel arrays.
This work led to the LBNL pixel system based on a column-architecture
concept, and was realized by a team led by Kevin Einsweiler. Today this system
provides precision tracking for the ATLAS experiment at the LHC. Another result
of this was a suggestion by Dave for the development at LBNL of fully depleted
CCDs. The realization by Steve Holland was a great success and these are now
widely used in astronomical imaging and spectroscopy.
In the
1990s Dave pioneered the application of fast waveform sampling and digitization
techniques while he was a Distinguished Visiting Scientist at the Jet
Propulsion Laboratory, Pasadena, California (1995-1997). His work detecting
neutrinos led first to the KAMLAND neutrino detector in Japan and then to his
transformation of the ICECUBE array in Antarctica and its spectacular
discoveries, noted recently as the “2013 Breakthrough of the Year” by Physics
World. A graphic of the array graced the cover of the November 22, 2013
issue of Science.
Dave’s
creative particle detection schemes have transformed other fields as well.
By turning silicon strip detectors, designed for particle physics, on
their ends, he created detectors with superb spatial resolution able to count
individual x-rays for medical applications. This low-dose system produces
data superior to that of previous methods used clinically in mammographic
radiology, thereby sparing women both additional testing and excessive dose.
Dave’s concept was later developed commercially in Sweden, and now is
the most widely used method for digital mammographic screening in Europe,
Japan, Australia, and is currently making headway in the Middle East and North
America.
Most recently,
Dave has been pioneering new high-pressure xenon-gas detection TPC methods for
double-beta decay and dark-matter searches as a member of the NEXT
collaboration.
Dave has
yet to indicate what will be his next act, something that we all
should eagerly await. It is sure to come.
