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: $ 5.25万
• 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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741729
• 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腐烂形成的。这些核过程负责静止恒星燃烧的能量产生，以及恒星爆炸，例如Novae，Supernovae和X射线爆发。同时，这些反应/衰减链会传播初始的“种子”元素（在大爆炸中形成的氢和氦气）变成较重的物种 - 最终填充了几乎整个元素周期表。该研究项目的总体目标是更好地了解关键反应的速率，这些反应对恒星燃烧和恒星爆炸的核合成和/或能量产生产生重大影响。将通过直接和间接测量进行使用稳定和稀有异位素束的直接测量来研究关键反应的敏感性研究速率 - 在涉及恒星过程的计算机模拟的敏感性研究中已鉴定出来。直接测量将采用世界领先的龙后坐力分离器，包括升级的LABR？ - 射线检测器阵列，以衡量主导恒星质子和α捕获率的关键共振的优势和能量。在这些直接测量实验中，将通过将重离子束撞击到扩展的，无窗的氢或氦气靶标上来确定共振强度，并将梁的能量调节为共振。将计数并使用所得的反应产物（重后线和射线）来确定反应产量，该反应产量与共振强度成正比。同时，反应在扩展目标中的位置将用于精确确定共振能。在许多情况下，共振能量测量将利用一种新颖的“共振时间”技术，该技术利用了LABR闪烁体的出色时序解决方案。对于实验室中太弱而无法测量的反应，或者没有足够的稀有异位束强度，间接技术将用于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。该提案的间接测量成分将包括开发triumf的新计划（D，N）实验，使用IRIS Solid H2目标和目前正在构建的Texneut中子探测器阵列。这项有希望的技术提供了一个机会，可以间接确定广泛的反应的关键共振强度，目前直接测量不可行。