Preparation of Isotopic ¹⁰B Target

In order to measure accurately the reaction cross sections of ¹⁰B(n, α)⁷Li and ¹⁰B(n, t2α), 10B targets with the thickness of 50-350 μg/cm² should be prepared. The preparation technology of isotopic ¹⁰B target was studied. The three-step method of “pressing-sintering-evaporation” was determined. The effects of substrate temperature on the growth process, structure and adhesion of ¹⁰B film were studied. The inhomogeneity of ¹⁰B target was also measured and analyzed. The results show that the evaporation rate of isotopic ¹⁰B target prepared by intermittent electrostatic focusing fine-tuning electron bombardment method should be less than 0.02 μg/(cm²·s). The optimum distance between filament plane and ¹⁰B column is 10.5-11 mm. The growth of ¹⁰B film is compact and crystallizes gradually with the increase of substrate temperature, and the adhesion between film and substrate is better. The optimum substrate temperature is about 300 ℃. For the preparation of isotopic ¹⁰B target with the size of Ø80 mm, the inhomogeneity can be controlled within 10%. The ¹⁰B targets with the thickness less than 350 μg/cm² were successfully fabricated on Ta and Al substrates, and used in the measurements of nuclear physics experiments.