京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22249号 / 理博第4563号 / 新制||理||1655(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 前田 啓一, 講師 LEE Shiu Hang, 教授 長田 哲也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

A possible mechanism to explain the origin of around 35 neutron–deficient stable isotopes with mass A≥75 between 74 Se and 196 Hg, known as the p–nuclei is the nucleosynthesis in the proton–rich neutrino–driven winds of core–collapse supernovae via the νp–process. However this production scenario is very sensitive to the underlying supernova dynamics and the nuclear physics input. As far as nuclear uncertainties are concerned, the breakout reaction from the pp-chains, 7Be(α, γ)11C, has been identified as an important link which can influence the nuclear flow and therefore the efficiency of the νp–process. However its reaction rate is not well known over the relevant energy range (T9 = 1.5–3). In this thesis we report on the direct first measurement of two resonances of the 7Be(α, γ)11 C reaction with previously unknown strengths using an intense radioactive 7Be beam from ISAC and the DRAGON recoil separator in inverse kinematics. Since resonance strength measurements with low mass beams using recoil separators depend strongly on the recoil angular distribution, which can exceed the acceptance of the separator, we first performed a proof–of–principle test by measuring a known resonance of the 6Li(α, γ)10B reaction, which also presents a similar challenge. Our results from the 6Li(α, γ)10B reaction are in agreement with literature, showing that DRAGON can measure resonance strengths of reactions for which the maximum momentum cone of the recoils exceeds its acceptance. From the newly measured 7Be(α, γ)11C resonance strengths we calculated the new reaction rate which is lower than the current recommended by 10–50% and constrained to 5–10% in the relevant temperature region. Using this new rate, we performed detailed nucleosynthesis calculations which suggest that there is no effect the production of light p–nuclei, but a production increase for CNO elements of up to an order of magnitude is observed. / Dissertation / Doctor of Philosophy (PhD)