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Reactions induced by fast neutrons in boron trifluoride and the angular distribution of the non-resonant gamma radiation from the bombardment of carbon with protons Heiberg, Severin Andreas


Two boron trifluoride proportional counters, one containing normal isotopic boron and the other boron enriched to 96% B¹⁰, have been irradiated with 4.87-Mev neutrons from the D +.D reaction. In addition to the reactions B¹⁰(n,α)Li⁷and B¹⁰(n,α)Li⁷* with Q-values of 2.79 Mev and 2.31 Mev respectively, two other reactions have been observed, (i) F¹⁹(n,α)N¹⁶and F¹⁹ (n, α)N¹⁶* with Q-values of -1.43±0.15 Mev and -1.77±0.15 Mev and (ii) either B¹⁰ (n,p)Be¹⁰ or B¹⁰ (n,t)Be⁸ with a Q-value of +0.35±0.20 Mev. Due to the presence of these two reactions, the analysis of complex fast neutron spectra by the use of such counters is not feasible. The Q-values for reaction (i) yield a value of the N¹⁶ mass of 16.01110±.00020 MU. Neutrons from a pulsed deuterium beam impinging on a tritium target were used to bombard a boron trifluoride proportional counter containing the normal ratio of B¹¹ to B¹⁰. The half-life of the activity and the energy of the particles emitted indicated that they were due to the immediate breakup of Be⁸ into two alphas after the 0.89 sec. beta decay of the Li⁸ formed by the B¹¹ (n,α)Li⁸ reaction. The process was found to have a cross section of the order of 10 millibarns for 14-Mev neutrons. The angular distribution of the non-resonant gamma radiation from the proton bombardment of C¹² has been measured and found to obey the relation:- I(ɵ)α0.02±.02 + sin²ɵ, for a proton energy of 1,580 kev.

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