Indirect methods in nuclear astrophysics

发生在恒星中的核反应和恒星爆炸产生了化学元素，地球和所有生物都是由这些化学元素组成的。它们还产生太阳能，维持地球上的生命。要定量地了解元素的形成，既需要它们产生的环境的理论模型，也需要有关核反应速率的详细实验知识。其中一些反应速率可以在实验室中直接测量，前提是有必要的核束和靶子。许多重要的原子核都是放射性的，在它们解体之前只能产生少量的核。这意味着许多直接测量不可能在合理的时间内以足够的精度进行。因此，我们必须经常求助于间接测量参与天体物理上重要反应的原子核的性质。这些间接测量可以提供与直接测量相同的信息。核天体物理学中的间接测量需要精密的电磁分光仪来筛选核反应的产物，以便找到通常只有很少量产生的重要产物。这些电磁滤光片可以测定核反应中产生的原子核的质量和电荷。我已经开始设计一种名为EMMA(电磁质量分析器)的新型反冲质谱仪，它将允许在加拿大国家核物理和粒子物理实验室TRIUMF进行核天体物理中的这些重要测量。EMMA将使TRIUMF的科学家能够利用新的ISAC-II加速器提供的强放射性核束来确定天体物理反应速率。这笔资金将用于资助我在Emma方面的工作，以及我在间接核天体物理学方面的其他努力，以及支持我指导的研究生和博士后研究助理。

Nuclear reactions that occur in stars and stellar explosions produced the chemical elements out of which the Earth and all living beings are made. They also generate the solar energy that sustains life on Earth. A quantitative understanding of the formation of the elements requires both theoretical models of the environments in which they are produced and detailed experimental knowledge of relevant nuclear reaction rates. Some of these reaction rates can be measured directly in the lab, provided the requisite nuclear beams and targets are available. Many of the important nuclei are radioactive, and can only be produced in small amounts before they disintegrate. This implies that many direct measurements are impossible to make with sufficient precision in a reasonable amount of time. Accordingly, we must often resort to indirect measurements of the properties of nuclei involved in astrophysically important reactions. These indirect measurements can provide the same information that direct measurements do. Indirect measurements in nuclear astrophysics require elaborate electromagnetic spectrometers to sift through the products of nuclear reactions in order to find the important ones that are usually produced in very small amounts. These electromagnetic filters allow the determination of the masses and electric charges of nuclei produced in nuclear reactions. I have begun design work on a new recoil mass spectrometer called EMMA (Electromagnetic Mass Analyser) that will allow these important measurements in nuclear astrophysics to be carried out at TRIUMF, Canada's national laboratory for nuclear and particle physics. EMMA will enable scientists at TRIUMF to exploit the intense beams of radioactive nuclei provided by the new ISAC-II accelerator to determine astrophysical reaction rates. This grant will fund my work on EMMA and my other efforts in indirect nuclear astrophysics, as well as support the graduate students and postdoctoral research associate I supervise.