Nuclear Astrophysics at TRIUMF-ISAC: Stellar Burning Reaction Studies with DRAGON and TUDA

目前公认的是，大多数比硼重的化学元素是在恒星中通过核反应产生的，核反应涉及稳定的放射性原子核和放射性衰变。有助于这种核合成的恒星演化的各个阶段的天体物理模型（例如在新星和超新星中看到的静止燃烧或爆炸过程）最近变得更加先进，能够很好地预测天文观测结果。这方面的例子包括组成我们太阳系的尘埃颗粒中冻结的同位素丰度、合成的长寿命放射性核素产生的伽马射线通量、光学或x射线光度等。这些量可以与天文观测进行比较，包括轨道伽马射线天文台或实验室对流星颗粒的测量。这种比较是天体物理学和宇宙学领域的有力工具，为我们提供了恒星内部核过程及其爆炸的最直接成像技术。为了改进模型，从而提高我们对这些强大而神秘的恒星事件的理解，需要对能量产生和核合成中涉及的核反应有精确的了解。******在TRIUMF-ISAC的核天体物理项目解决这些问题，通过直接和间接测量天体物理重要的核反应与放射性和稳定的加速离子束。这主要是在著名的DRAGON反冲分离器设施和TUDA带电粒子阵列设施完成的。此外，该计划参与者还参与了最先进的恒星模型研究（使用MESA-NuGrid）和从头算核理论计算。******我们的提案将要求为DRAGON项目的持续运营和发展提供资金，包括雇用3名博士后研究助理，他们的存在是DRAGON过去成功的基础。我们还要求继续培养研究生等高素质人才，为上述天体物理学案例进行尖端测量。我们还将为TUDA项目申请一名博士后研究助理。博士后也将使用DSL和SHARC设施，在一个综合的核天体物理项目中进行免费的研究。* * * * * * * *

It is presently accepted that most of the chemical elements heavier than boron were produced in stars through nuclear reactions involving stable and radioactive nuclei and radioactive decays. Astrophysical models of the various stages of stellar evolution (e.g. quiescent burning, or explosive processes as seen in novae and supernovae) that contribute to this nucleosynthesis have recently become more advanced, enabling good predictions of astronomical observables. Examples of these are isotopic abundances frozen into dust grains that make up our solar system, gamma-ray fluxes from synthesized long-lived radionuclides, optical or x-ray luminosity etc. These quantities can be compared with astronomical observations, including those from orbiting gamma ray observatories or laboratory measurements on meteoric grains. This comparison is a powerful tool in the field of astrophysics and cosmology, giving us the most direct imaging technique of the nuclear processes inside stars and their explosions. In order to improve the models, and therefore advance our understanding of these powerful and mysterious stellar events, a precise knowledge of the nuclear reactions involved in energy generation and nucleosynthesis is required. ******The Nuclear Astrophysics program at TRIUMF-ISAC addresses these issues by making direct and indirect measurements of astrophysically important nuclear reactions with radioactive and stable accelerated ion beams. This is primarily done at the well-known DRAGON recoil separator facility, and at the TUDA charged particle array facility. In addition, the program participants engage in state-of-the art stellar model studies (using MESA-NuGrid) and ab-initio nuclear theory calculations.******Our proposal will request funding for the continued operation and development of the DRAGON program, including the hiring of 3 Post-Doctoral Research Associates, the existence of which has been the foundation of DRAGON's past success. We also request continuation of training of highly-qualified personnel such as Graduate Students, to make the cutting-edge measurements for the astrophysics cases mentioned above. We will also request one Post-Doctoral Research Associate for the TUDA program. Postdocs will also work using the DSL and SHARC facilities, performing complimentary research in a comprehensive nuclear astrophysics program. ********