Development of a quasi-monoenergetic 6 MeV Gamma Facility at NASA Goddard Space Flight Center

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• 作者：Suzanne F. Nowicki^a ; ^b ; ^c ; ^{suzanne.f.nowicki@nasa.gov} ; Stanley D. Hunter^c ; Ann M. Parsons^c
• 关键词：6.129 MeV ; Monoenergetic ; Facility ; Characterization ; Calibration ; Gamma-ray ; Neutron ; Pulsed neutron generator
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2013
• 出版时间：21 March, 2013
• 年：2013
• 卷：705
• 期：Complete
• 页码：111-116
• 全文大小：1433 K

文摘

The 6 MeV Gamma Facility has been developed at NASA Goddard Space Flight Center (GSFC) to allow in-house characterization and testing of a wide range of gamma-ray instruments such as pixelated CdZnTe detectors for planetary science and Compton and pair-production imaging telescopes for astrophysics. The 6 MeV Gamma Facility utilizes a circulating flow of water irradiated by 14 MeV neutrons to produce gamma rays via neutron capture on oxygen (¹⁶O(n,p)¹⁶N¡ú¹⁶O?¡ú¹⁶O+¦Ã). The facility provides a low cost, in-house source of 2.742, 6.129 and 7.117 MeV gamma rays, near the lower energy range of most accelerators and well above the 2.614  MeV line from the ²²⁸Th decay chain, the highest energy gamma ray available from a natural radionuclide. The 7.13 s half-life of the ¹⁶N decay allows the water to be irradiated on one side of a large granite block and pumped to the opposite side to decay. Separating the irradiation and decay regions allows for shielding material, the granite block, to be placed between them, thus reducing the low-energy gamma-ray continuum. Comparison between high purity germanium (HPGe) spectra from the facility and a manufactured source, ²³⁸Pu/¹³C, shows that the low-energy continuum from the facility is reduced by a factor ¡«30 and the gamma-ray rate is ¡«100 times higher at 6.129 MeV.