Gain Matching the Medusa Array
Student Researchers: Sarah Thompson, Heather Olliver (SUNY Geneseo)
Faculty Advisor: Dr. Stephen Padalino (SUNY Geneseo)
Collaborators: Dr. Vladamir Glebov (Laboratory for Laser Energetics, University of Rochester)
Dr. Craig Sangster (LLNL)
The Laboratory for Laser Energetics at the University of Rochester is currently investigating laser driven inertial confinement fusion with hopes of producing, capturing, and eventually utilizing the copious amounts of energy released in nuclear fusion reactions. Medusa, an array of over 800 proton recoil detectors, is one constituent of the melange of diagnostics used to collect vital information about each fusion experiment. In particular, Medusa is utilized to detect neutrons that are produced in the T(d,n) and D(d,n) reactions. Recently, while conducting investigations at LLNL regarding the efficiency of the Medusa array, it was discovered that the detectors were not satisfactorily gain matched. This issue was examined in more detail at the State University of New York at Geneseo using neutrons from an 80 gram PuBe source. Using a representative set of detectors from the Medusa array and a small PuBe source that emits a range of neutrons up to 11 MeV, it was observed that the net difference in the endpoints of the detectors’ energy spectra was 3.2 MeV. The Medusa array was originally gain matched using a low energy gamma ray source. One hypothesis was that the detectors could not be gain matched using gamma rays and then used successfully to detect neutrons. Another conjecture was that the detectors could not be gain matched using a low energy source and then accurately used to detect high energy neutrons. Both proposals were investigated by gain matching the set of detectors with a 1274 keV gamma ray source and also with the large PuBe source. It was concluded that both speculations were incorrect.