Indirect methods in nuclear astrophysics

恒星中发生的核反应和恒星爆炸产生了构成地球和所有生物的化学元素。它们还产生维持地球生命的太阳能。对元素形成的定量理解需要它们产生环境的理论模型和相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，只要有必要的核束和靶。许多重要的原子核都具有放射性，在它们衰变之前只能产生少量。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，我们必须经常对天体物理学上重要的反应所涉及的原子核的性质进行间接测量。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波谱仪来筛选核反应的产物，以便找到通常产生量很小的重要产物。这些电磁滤波器允许确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新的反冲质谱仪，称为EMMA（电磁质量分析仪），它将使这些重要的核天体物理测量在加拿大国家核和粒子物理实验室TRIUMF进行。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。这笔赠款将资助我在EMMA的工作和我在间接核天体物理学方面的其他努力，以及支持我监督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.