Direct and Indirect Studies of Astrophysical Reactions

天体物理反应的直接和间接研究

• 批准号: SAPIN-2020-00052
• 负责人: Christian, Gregory
• 金额: $ 5.54万
• 依托单位: Saint Mary's University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=743978
• 关键词: Direct; Indirect; Studies; Astrophysical; Reactions

The vast majority of the elements making up the world around us were formed through sequences of nuclear reactions and decays occurring in stars. These nuclear processes are responsible for energy generation in quiescent stellar burning, as well as stellar explosions such as novae, supernovae, and X-ray bursts. At the same time, these reaction/decay chains transmutate the initial "seed" elements (hydrogen and helium, formed in the Big Bang) into heavier species - eventually filling nearly the entire periodic table. The overarching goal of this research project is to better understand the rates of key reactions which have a significant impact on nucleosynthesis and/or energy generation in stellar burning and stellar explosions. The rates of key reactions - which have been identified in sensitivity studies involving computer simulations of stellar processes - will be studied through direct and indirect measurements using stable and rare-isotope beams from the TRIUMF/ISAC accelerator facility. Direct measurements will employ the world-leading DRAGON recoil separator, including an upgraded LaBr ?-ray detector array, to measure the strengths and energies of key resonances that dominate stellar proton and alpha capture rates. In these direct-measurement experiments, resonance strengths will be determined by impinging a heavy-ion beam onto an extended, windowless hydrogen or helium gas target, with the beam energy tuned to be on resonance. The resulting reaction products (heavy recoils and ? rays) will be counted and used to determine the reaction yield, which is proportional to the resonance strength. At the same time, the position of the reaction within the extended target will be used to precisely determine the resonance energy. In many cases, the resonance energy measurement will make use of a novel "resonance timing" technique, which capitalizes on the superior timing resolution of LaBr scintillators. For reactions that are too weak to measure in the laboratory, or for which sufficient rare-isotope beam intensities are not available, indirect techniques will be used to determine the resonance strengths of interest. In particular, transfer reactions will be used to measure spectroscopic factors for important resonances - quantities which are directly proportional to the resonance strength. The indirect-measurement component of the proposal will include development of a new program of inverse-kinematics (d,n) experiments at TRIUMF, using the IRIS solid H2 target and the TexNEUT neutron detector array currently under construction. This promising technique offers an opportunity to indirectly determine key resonance strengths for a wide array of reactions for which direct measurements are not presently feasible.

构成我们周围世界的绝大多数元素都是通过恒星中发生的一系列核反应和衰变形成的。这些核过程负责在静止恒星燃烧中产生能量，以及恒星爆炸，如新星，超新星和X射线爆发。与此同时，这些反应/衰变链将最初的“种子”元素（氢和氦，在大爆炸中形成）转化为更重的物质-最终几乎填满了整个周期表。该研究项目的总体目标是更好地了解对恒星燃烧和恒星爆炸中的核合成和/或能量产生有重大影响的关键反应的速率。将利用TRIUMF/ISAC加速器设施的稳定和稀有同位素束，通过直接和间接测量，研究关键反应的速率-这些反应是在涉及计算机模拟恒星过程的敏感性研究中确定的。直接测量将采用世界领先的DRAGON反冲分离器，包括升级的LaBr？射线探测器阵列，以测量主导恒星质子和阿尔法捕获率的关键共振的强度和能量。在这些直接测量实验中，共振强度将通过将重离子束撞击到扩展的无窗氢气或氦气靶上来确定，其中束能量被调谐为共振。所产生的反应产物（重反冲和？射线）将被计数并用于确定与共振强度成比例的反应产率。同时，反应在扩展靶内的位置将用于精确地确定共振能量。在许多情况下，共振能量测量将利用一种新的“共振定时”技术，该技术利用了LaBr晶体管的上级定时分辨率。对于太弱而无法在实验室中测量的反应，或者没有足够的稀有同位素束强度的反应，将使用间接技术来确定感兴趣的共振强度。特别是，转移反应将用于测量重要共振的光谱因子-与共振强度成正比的量。该提案的间接测量部分将包括在TRIUMF开发一个新的逆运动学（d，n）实验计划，使用IRIS固体H2靶和目前正在建设的TexNEUT中子探测器阵列。这种有前途的技术提供了一个机会，间接确定关键的共振强度为广泛的反应，直接测量目前是不可行的。