Topping this list was the opening of Gamma- sphere-the world's most powerful instrument for detecting gamma rays. Built and installed at the Laboratory's 88-Inch Cyclotron with the active participation of scientists at other institutions, including Argonne, Lawrence Livermore, and Oak Ridge national laboratories, Gammasphere is the country's newest national user facility. When construction is complete, Gammasphere will feature a honeycomb of high-resolution germanium crystal detectors and bismuth-germanate scintillation counters that will make it a hundred times more sensitive to gamma rays than previous detectors. This capability will enable users to study the short-lived (50 trillionths of a second) nuclear states collectively known as "superdeformation." This phenomenon occurs when a fast-moving beam of ions strikes a target and fuses the nuclei of the projectile and target ions into a hot, rapidly spinning compound nuclei. The spinning rotation causes the compound nuclei to assume unusual shapes (like footballs or pancakes), that emit gamma rays when they cool off and slow down. Detecting and analyzing these gamma rays yields vital information on what happens to atomic nuclei under the extreme physical conditions that can exist on earth in accelerators, or in white dwarfs, neutron stars, and other exotic objects in the cosmos. With 85 of its 110 germanium crystal detectors now in place, experiments at Gammasphere are already under way, and potential users are lining up.
Progress also continued this past year on a high-energy physics detector called STAR, which stands for Solenoidal Tracker at RHIC-the Relativistic Heavy Ion Collider now being built at Brookhaven National Laboratory. From the heydays of the now retired Bevatron accelerator, Berkeley Lab scientists have led the United States in the study of relativistic heavy ions (electrically charged atoms traveling at nearly the speed of light). Now, our scientists are spearheading a collaboration in which nearly 200 scientists and engineers from 26 other institutions will construct what will be the first of two large-scale detectors intended for RHIC. STAR is designed to identify and measure had- rons, particles that interact through the strong force. It will also be used to analyze the highly energetic particle "jets" produced when quarks or gluons collide head on. The goal is to understand the mysterious state of matter known as quark-gluon plasma, which is at the core of neutron stars. Scientists think quark-gluon plasmas were the dominant state of matter in the universe about one microsecond after the Big Bang.
