Nygren, Poskanzer and Stephens Named Distinguished Scientists by Berkeley Lab

December 15, 1995

By Ron Kolb, RRKolb@LBL.gov

Three researchers who have achieved international acclaim for their accomplishments in designing unusual detector systems have been promoted to the rare Distinguished Scientist classification at Berkeley Lab.

David Nygren in the Physics Division and Arthur Poskanzer and Frank Stephens in the Nuclear Science Division were named by Laboratory Director Charles Shank to receive the prestigious "Distinguished" title, which is currently shared by just three others at the Lab.

In his appointment letters, Shank noted that the Distinguished Scientist rank is "reserved for the most exceptional senior scientists. It is expected that the Laboratory will have only a few such stars at any given time."

The Distinguished Staff Scientist/Engineer level is reserved for those who "have a sustained history of distinguished scientific and technical achievements and/or have directly contributed to the Laboratory's preeminence," according to the Lab Regulations and Procedures Manual. The incumbents are "seen as nationally or internationally recognized authorities and leaders in their field; their expertise is sought after by professional colleagues."

Nygren, 57, was nominated by Physics Division Director Robert Cahn, who cited his invention of the Time Projection Chamber (TPC), which has had a profound effect on both particle and nuclear physics, and his pioneering work on pixel detectors. Cahn also cited his innovative design for an x-ray imaging device based on silicon detectors and high-speed data acquisition, and his current work in very-large-scale neutrino detectors.

"The TPC opened new opportunities for experimentation across a broad range of particle and nuclear physics," Cahn said. "The purity and power of his proposal are why, more than 20 years later, new TPCs are still being built."

Nygren, who has been called the most distinguished developer of particle detection instruments in the country, has been with Berkeley Lab since 1973 and is a previous winner of the prestigious E. O. Lawrence Award.

Poskanzer, 64, nominated by former Nuclear Science Division Director James Symons, has been influential as the head of the Relativistic Heavy Ion Program. Symons credited Poskanzer's leadership in uniting the diverse elements of the Relativistic Nuclear Collisions program into a dominant group, within which the STAR detector has been developed as "one of the principal reasons that DOE has maintained a significant nuclear physics presence" at the Laboratory.

A scientist at Berkeley Lab since 1966, Poskanzer is considered a pioneer in the use of high energy reactions to produce nuclei far from stability, especially in the low-Z region. He is the co-discoverer of 28 isotopes. In the field of relativistic heavy ion reactions, he has led a group effort pioneering in the experimental study of central collisions. Poskanzer was co-leader of the Plastic Ball project, which discovered the collective flow of nuclear matter. He is spending this year at CERN in Switzerland, studying nuclear collisions in a new energy domain in search of the predicted Quark-Gluon Plasma.

Now in his 41st year at Berkeley Lab, Stephens, 64, is the originator and spiritual leader of the Gammasphere project, the gamma-ray detector that was officially dedicated on Dec. 1. "His vision has moved the nuclear structure community into the technical big-time, and his detector provides the principal justification for continued operation of the 88-Inch Cyclotron," Symons said in his nomination.

Stephens is one of the foremost authorities on the structure of nuclei and the relationship of that structure to phenomena in other branches of physics. Utilizing heavy-ion beams from the 88-Inch Cyclotron, he has explored the collective properties in nuclei, high angular momentum phenomena, giant resonances, and nuclear reaction mechanisms for which he was awarded the Bonner Prize by the American Physical Society in 1980.

Division nominations were reviewed by the 12-member Laboratory Staff Committee, which forwarded recommendations to Shank for appointment. Physicist George Gidal, chair of the committee, said the honorees share the qualities of "long and sustained work in a particular discipline, national and international recognition, and a single-minded dedication to pushing their field to new heights. And they are innovative, constantly seeking new techniques that often lead to whole new fields of science."

Gidal said the "Distinguished" class is intentionally limited to a small percentage of the approximately 130 senior scientists at the Lab. Other Berkeley Lab staff members who have achieved "Distinguished" career status include former Laboratory directors Andrew Sessler and David Shirley, and retired engineer Frederick Goulding.