Gammasphere

Detector Assembly

1. Electronics Box

These triangular boxes are the connection between Gammasphere and researchers. They pass signals from the detectors to electronics and computers for analysis, and provide high-voltage power for the germanium and BGO detectors.

2. BGO Crystal

Seven bismuth germinate detectors surround each germanium crystal, and detect gamma rays that deposit only part of their energy in the germanium. Eliminating these events in analysis allows researchers to measure very rare gamma-ray decays.

3. Germanium Crystal

When a gamma ray stops in these coffee-cup-sized semiconductors, an applied electric field guides the tiny electric signals generated to electrodes on the crystal's surface. The electrical signal produced is proportional to the gamma-ray's energy.

Gallery: Gammasphere

In the 2003 summer blockbuster The Hulk, this nuclear physics device turns mild-mannered scientist Bruce Banner into the movie's fearsome title character. In the movie, Gammasphere zaps Banner with radiation; in reality, it detects gamma rays from rare and exotic atomic nuclei.

Gammasphere is a $20 million detector array that helps answer fundamental questions about the structure and behavior of atomic nuclei. The device's 110 gamma-ray detectors point to the center of the spherical array, where a beam of nuclei from a particle accelerator smashes into a thin target. The collisions create unstable nuclei that decay by emitting gamma rays, an extremely high-energy form of light. Gammasphere catches and measures as many of the gamma rays as possible, so that scientists can study what happens to nuclei under extreme physical conditions.

The 14-ton device, built at the Lawrence Berkeley National Laboratory by a group of scientists from several US national laboratories and universities, splits its time between LBNL in California and Argonne National Laboratory near Chicago. Since Gammasphere's dedication in December 1995, scientists from all over the world have conducted hundreds of experiments with the array.