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Precision imaging of 4.4 MeV gamma rays using a 3-D position sensitive Compton camera

By Ayako Koide, Jun Kataoka, Takamitsu Masuda, Saku Mochizuki, Takanori Taya, Koki Sueoka, Leo Tagawa, Kazuya Fujieda, Takuya Maruhashi, Takuya Kurihara and Taku Inaniwa


Imaging of nuclear gamma-ray lines in the 1-10 MeV range is far from being established in both medical and physical applications. In proton therapy, 4.4 MeV gamma rays are emitted from the excited nucleus of either 12^C^* or 11^B^* and are considered good indicators of dose delivery and/or range verification. Further, in gamma-ray astronomy, 4.4 MeV gamma rays are produced by cosmic ray interactions in the interstellar medium, and can thus be used to probe nucleothynthesis in the universe. In this paper, we present a high-precision image of 4.4 MeV gamma rays taken by newly developed 3-D position sensitive Compton camera (3D-PSCC). To mimic the situation in proton therapy, we first irradiated water, PMMA and Ca(OH)_2 with a 70 MeV proton beam, then we identified various nuclear lines with the HPGe detector. The 4.4 MeV gamma rays constitute a broad peak, including single and double escape peaks. Thus, by setting an energy window of 3D-PSCC from 3 to 5 MeV, we show that a gamma ray image sharply concentrates near the Bragg peak, as expected from the minimum energy threshold and sharp peak profile in the cross section of 12^C(p,p)12^C^*.Comment: 11 pages, 7 figures; accepted for publication in Nature Scientific Report

Topics: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Year: 2018
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