Development of an RF Fragment Separator at the NSCL

极其不稳定的缺中子稀有同位素在诸如x射线暴和新星等爆炸性天体物理事件中起着关键作用。对这些奇异核的物理性质的理解，需要以定量的方式解释从空间x射线天文台获得的一系列新的x射线双星观测结果。这将为解决许多悬而未决的问题铺平道路，比如爆发振荡背后的机制，超级爆发的起源，以及潜在中子星的性质。极缺中子核也可作为核结构的独特探针。它们为核存在的极限提供了测试，它们显示出独特的衰变模式，如单质子和双质子发射。此外，缺中子核还包括一类特殊的核——质子和中子数量相等的同位素。由于质子和中子占据相同的壳层模型轨道，许多核结构效应在这样的原子核中表现得增强。对于自然界中最缺乏中子的经典双魔法核之一100Sn来说尤其如此。双幻核，即质子和中子完全填满核壳，在核物理学中具有特别重要的意义，是核理论的基准和滩头阵地。对100Sn衰变特性的测量被许多人认为是核物理学的“圣杯”之一，并将为重核的β衰变提供独特的见解。位于密歇根州立大学的国家超导回旋加速器实验室（NSCL）在制造极缺中子核方面具有全球独特的能力。这包括足够量的100Sn来测量其衰变的特性，以及所有参与x射线爆发中天体物理快速质子捕获过程的原子核。然而，由于用于产生这些核的弹丸破碎机制的性质，目前的实验装置无法达到必要的光束纯度。因此，许多关键实验无法进行。我们将建立一个射频碎片分离器实验，该实验将用射频场偏转不需要的稀有同位素束污染物，同时传输所需的物种。该装置可以与现有的衰变和反应研究实验装置相结合，并将允许一大批研究生和科学家充分利用国家科学实验室中子亏缺束的生产能力来解决核物理和天体物理中的基本问题。

Extremely unstable neutron deficient rare isotopes play a key role in explosive astrophysical events such as X-ray bursts and Novae. An understanding of the physics of these exotic nuclei is required to interpret in a quantitative way a range of new X-ray binary observations from space based X-ray observatories. This will pave the way to address the many open questions such as the mechanism behind burst oscillations, the origin of superbursts, and the nature of the underlying neutron star. Very neutron deficient nuclei serve also as unique probes of nuclear structure. They provide tests for the limits of nuclear existence, and they show unique decay modes such as one- and two-proton emission. In addition, neutron deficient nuclei include a special class of nuclei - isotopes with equal numbers of protons and neutrons. As protons and neutrons occupy the same shell model orbitals, many nuclear structure effects appear enhanced in such nuclei. This is particularly true for one of the most neutron deficient, classically doubly magic nuclei in nature, 100Sn. Doubly-magic nuclei, where both, protons and neutrons completely fill a nuclear shell, are of particular importance in nuclear physics and serve as benchmarks and beachheads for nuclear theories. The measurement of the decay properties of 100Sn is by many considered one of the "holy grails" of nuclear physics and would provide unique insights into the beta-decay of heavy nuclei. The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University has worldwide unique capabilities in producing extremely neutron deficient nuclei. This includes sufficient amounts of 100Sn to measure the properties of its decays,as well as all nuclei participating in the astrophysical rapid proton capture process in X-ray bursts. However, due to the nature of the projectile fragmentation mechanism used to create these nuclei, current experimental setups do not achieve the necessary beam purity.Many of the key experiments can therefore not be performed. We will build an RF Fragment Separator experiment, which will deflect unwanted rare isotope beam contaminants with an RF field, while transmitting the desired species. This device can be combined with existing experimental setups for decay and reaction studies and will allow a large group of graduate students and scientists to take full advantage of the production capabilities for neutron deficient beams at the NSCL to address fundamental questions in nuclear physics and astrophysics.