DEMAND - Direct Experimental Measurements of Astrophysical reactions using Neutron Detectors

了解化学元素在哪里以及如何形成是人类历史上最重要的问题之一。这些元素是生命存在的原因，也是我们宇宙丰富多样的原因。现在我们知道，几乎所有的化学元素都是在垂死恒星的中心形成的。天文学和陨石学的显著进步已经产生了一系列令人震惊的关于这种灾难性天文事件的新观测数据，使我们对它们的性质有了前所未有的了解。然而，尽管获得了丰富的观测数据，恒星核合成的许多关键阶段仍未完全了解。事实上，似乎我们得到的观察越多，我们的问题就越多。最近，对银河系中一些最古老的恒星中比铁更重的元素的观察导致了锶和银之间元素起源的范式转变。特别是，现在认为这些元素是通过一系列α俘获反应在核心坍缩超新星中产生的。不幸的是，关于这些反应发生速度的实验数据很少，主要是由于在实验室中测量这些过程极其困难。在这个项目中，我们的目标是开发一种新的实验技术来直接测量发生在核心坍缩超新星中的反应，并解决这些高能恒星爆炸是否负责锶和银之间“轻”重元素的合成这一悬而未决的问题。

Understanding where and how the chemical elements were formed represents one of the most important questions in human history. These elements are responsible for the existence of life, as well as the rich variety of our Universe, and it is now known that almost all the chemical elements were forged in the hearts of dying stars. Remarkable advancements in astronomy and meteoritics have produced a slew of astounding new observational data on such cataclysmic astronomical events, giving us unprecedented insight into their properties. However, despite the wealth of observational data obtained, many key stages of stellar nucleosynthesis are still not fully understood. In fact, it seems as though the more observations we obtain, the more questions we have. Recently, observations of elements heavier than iron in some of the oldest stars in our Galaxy has resulted in a paradigm shift in the origin of elements between strontium and silver. In particular, it is now thought that these elements were created in core collapse supernovae via a series of alpha capture reactions. Unfortunately, very little experimental data exists on how fast these reactions occur, mainly due to extreme difficulty in measuring such processes in a laboratory.In this project, we aim to develop a new experimental technique for the direct measurement of reactions that occur in core-collapse supernovae and resolve the outstanding issue of whether or not these energetic stellar explosions are responsible for the synthesis of "light" heavy elements between strontium and silver.