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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

Abstract

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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