Doctoral researcher improves performance, detection efficiency of neutron detectors

Sara Harrison

As a stranger to the realm of internships, Sara Harrison was surprised by the knowledge, experience and direction she gained by participating in the U.S. Department of Homeland Security (DHS) HS-STEM (homeland security related science, technology, engineering and mathematics) Summer Internship Program.

The program provides the opportunity for students majoring in DHS-related science, technology, engineering, and mathematics disciplines to conduct research in DHS mission-relevant areas at federal research facilities located across the country.

As a doctorate student in electrical engineering at Leland Stanford Junior University, the internship provided her the chance to expand her interests and explore semiconductor fabrication, a research interest outside her current focus area. Harrison joined her mentor, Rebecca Nikolic, and a team of researchers in Lawrence Livermore National Laboratory’s (LLNL) Materials Engineering Division focused on improving the performance and detection efficiency of solid state thermal neutron detectors.

“My research involves using conformal surface doping techniques to modify the depletion depth profile of a silicon-based, high efficiency solid state thermal neutron detector,” Harrison explained. “Neutron detectors are one of the essential tools to spot nuclear threats and there has been a recent increase in demand for border security devices capable of detecting the transport of fissile materials in cargo. The dwindling U.S. stockpile of Helium-3 gas used in conventional detectors has highlighted the crucial need for alternative neutron detector technologies.”

Solid state thermal neutron detectors, when compared with conventional gas-filled detectors, have the potential to be more compact, operate at lower voltages, and be more robust against vibration induced noise. Much of her research time took place in a cleanroom, an environmentally controlled room that protects the highly-sensitive technologies her team tests.

Harrison, who is in the last year of her doctoral studies, enjoyed the opportunity to change gears from the research in which she is typically involved. She even admits to feeling regretful for not getting involved in an internship program sooner.

“The experience and insight I have gained in detector device design and operation through interacting with an excellent group of research scientists and engineers could easily be applied to my current Ph.D. research,” she said. “Participating in this internship program has allowed me to become better acquainted with working in a national laboratory and to develop a greater understanding for the scientific and engineering challenges facing the nation.”

In addition to learning about these newly-found areas of interest, Harrison learned much about what it means to work in a national laboratory.

“My brother is a computer scientist at LLNL,” she said. “Prior to the internship, I attended a couple of ‘Family and Friends’ open house events, which helped me gain an appreciation and understanding of the scope of scientific research and careers opportunities available at a national laboratory. Since I have been at LLNL, I have learned that the scope of the research and opportunities are so much larger than I had realized. This opportunity has helped me realize I would like to continue to contribute to projects that address national security by working at a national laboratory after graduation.”

The HS-STEM Summer Internship Program is funded by DHS and administered through the U.S. Department of Energy’s Oak Ridge Institute for Science and Education (ORISE). ORISE is managed for DOE by ORAU.