This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the conventional diagram of an atom, the center depicts a nucleus—a spherical cluster of protons and neutrons. But that sphere is a simplification: nuclei can deform into exotic shapes that appear more like a pear, football or Frisbee.
Understanding why and when nuclei distort is crucial for predicting and modeling how they will behave. Researchers at Lawrence Livermore National Laboratory (LLNL) have developed a new detector, CHICOX (Compact Heavy Ion Counter version X), that opens up a new era of extremely sensitive studies of nuclear shapes. "Nuclear theorists are working toward a comprehensive, predictive model of nuclei and how they behave.
The data we measure with CHICOX are a good test of these models," said LLNL scientist Daniel Rhodes. Details appear in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. CHICOX was built to work in tandem with another instrument: the Gamma-Ray Energy Tracking Array, or GRETA.
During an experiment, a beam of particles strikes a stationary target material. When one of those particles hits a nucleus, they both scatter. The extra energy imparted by this process excites the projectile nucleus, which vibrates, rotates and emits gamma rays as it returns to a more stable state.
CHICOX measures the trajectory of the scattered particle, while GRETA detects the gamma rays that are released. "When two nuclei collide, we detect the particles with CHICOX and then the gamma rays are captured by GRETA," said LLNL scientist Ching-Yen Wu. "If we don't have CHICOX, then we don't know when the nuclei collide.
And when they collide, they scatter at different angles. Without that angle, the gamma-ray information is lost." Together, the instruments make what is called a coincidence measurement. If they both see a signal at approximately the same time, they mark it as a single event.
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