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Gamma Rays, Watch Out: There’s a New Detector in Town

Heather Crawford and her team of researchers are developing a prototype for an ultrahigh-rate high-purity germanium detector that can count 2 to 5 million gamma rays per second while maintaining high resolution. (Credit: Marilyn Chung/Berkeley Lab)

Heather Crawford has always had a natural bent for science. When she was a high school student in her native Canada, she took all the science electives within reach without a second thought. She went into college thinking she would study biochemistry, but that all changed when she took her first class in nuclear science – the study of the subatomic world. Her professors noticed her talent for nuclear chemistry, and soon she found herself working as an undergraduate researcher in nuclear science at TRIUMF, the accelerator facility in Vancouver, Canada.

Today, Crawford is a staff scientist in the Nuclear Science Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). With funding from an Early Career Laboratory Directed Research and Development (LDRD) award announced last year, she and her team of researchers have been developing a prototype for an ultrahigh-rate high-purity germanium (HPGe) detector that can count 2 to 5 million gamma rays per second while maintaining high resolution, allowing them to accurately measure the energy spectrum under extreme conditions. A conventional HPGe detector loses resolution when it goes above 50,000 counts per second.

Gamma rays hail from nuclear decays and reactions within neutron stars, supernova explosions, and regions around black holes. But they also have origins here on Earth: Gamma rays are generated by radioactive decay, or reactions in nuclear power plants, for example. Their ubiquity thus serves as an all-purpose clue for solving wide-ranging mysteries, from tracking down isotope “fingerprints” of elements in stars, to assessing the impact of a nuclear power plant disaster.

Crawford said that the ultrafast, high-resolution detector will allow scientists to do more research in less time, collecting gamma-ray statistics at 10 to 100 times the rate previously possible. This opens up new possibilities for gamma-ray spectroscopy in the rarest nuclear systems, such as superheavy elements. “Whenever you’re doing gamma-ray spectroscopy, it’s about resolution and efficiency – ideally, you want an experiment to run for a couple of weeks, not years,” she added.

With the design for the small yet mighty detector finalized last month – the device measures just 3 inches wide and 3 inches tall – Crawford and her team look forward to testing the prototype, which is being fabricated at Berkeley Lab’s Semiconductor Detector Laboratory, first as an individual detector, and then moving toward an array.

“This LDRD gave us a unique opportunity to gain a deeper understanding of how germanium detectors work. Berkeley Lab has always been at the forefront of physics and nuclear science. If our prototype works, we will continue to move forward and push the science of both HPGe detectors and heavy elements,” she said.