2022-04-27 ｱﾒﾘｶ・ﾛｰﾚﾝｽﾘﾊﾞﾓｱ国立研究所(LLNL)
この反応は、500keV以下の質量中心エネルギーで最大の断面積を持つことが知られており、核融合エネルギーの有力候補である。この反応には、さまざまな分岐がある。この反応には、強い中性子を生成する枝と、それよりかなり弱いγを生成する枝があり、後者は前者より5桁も弱い。
D-T γ-中性子分岐比は原子核物理やプラズマ物理の観点から基本的な興味であり、より正確な測定はこれらの分野の理論的な努力を補強することができる。また、この分岐比は、核融合や関連する国家安全保障への応用を目指した実験的な取り組みにおいても興味深いものである。
＜関連情報＞
- https://www.llnl.gov/news/researchers-update-measurement-ratios-key-inertial-confinement-fusion-experiments
- https://journals.aps.org/prc/abstract/10.1103/PhysRevC.104.054611
慣性核融合プラズマを用いた重水素-三重水素γ-中性子分岐比のクロスキャリブレーション Inertial-confinement fusion-plasma-based cross-calibration of the deuterium-tritium γ-to-neutron branching ratio
J. Jeet, A. B. Zylstra, M. Rubery, Y. Kim, K. D. Meaney, C. Forrest, V. Glebov, C. J. Horsfield, A. M. McEvoy, and H. W. Herrmann
Physical Review Published 29 November 2021
ABSTRACT
The deuterium-tritium (D-T) γ-to-neutron branching ratio [3H(d,γ)5He/3H(d,n)4He] has been determined previously under inertial-confinement fusion (ICF) conditions and in beam-target based experiments. In the former case, neutron-induced backgrounds are mitigated compared to the latter due to the short pulse nature of ICF implosions and the use of gas Cherenkov γ-ray detectors. An added benefit of ICF based measurements is the ability to achieve lower center-of-mass energies as compared to accelerators. Previous ICF based experiments however report a large uncertainty in the D-T γ-to-neutron branching ratio of ≈48%, which arises from the necessity of an absolute detector calibration and/or a cross-calibration against the D-3He γ-to-proton branching ratio. A more precise value for the branching ratio based on data taken at the OMEGA laser facility is reported here, which relies on a cross-calibration against the better known 12C neutron inelastic scattering cross section. A D-T branching ratio value of (4.6±0.6)×10−5 is determined by this method.
