MRI: Development of a Helium-Jet Ion-Guide System for Harvesting Rare Isotopes and Commensal Operation at NSCL

国家超导回旋加速器实验室（NSCL）是美国最重要的加速核的设施，目的是研究核结构。 NSCL开发了世界上独一无二的新的实验能力与再加速稀有同位素束，确保在全球稀有同位素物理学的持续领导作用。随着NSCL最近研究能力的扩大，对用于核物理实验的这些光束的需求从未如此之高。这里提出的仪器，称为氦喷射离子气体系统（HJ-IGS），将允许同时进行两个实验，每个实验使用NSCL的不同检测器系统，这将扩大实验的数量，从而有助于满足增加我们对核的理解的实验需求。氦喷射离子源过去曾用于收集同位素，但使用这种系统在射弹碎裂设施中收集研究人员可用的一些最稀有的同位素的想法是新颖的。在初级稀有同位素束的净化过程中，弯曲出中心束路径的稀有同位素被停止并收集在充满充满气溶胶的氦气的高压室中，停止的同位素将附着在气溶胶上。在高压差下，收集到的同位素通过40米长的毛细管快速输送到离子源，离子源将同位素纯化后注入束线，该束线可以为主要实验中未使用的几个站之一提供能量。这使得两个实验可以同时进行：一个实验是使用射弹碎片直接产生的快速稀有同位素束，另一个实验是使用HJ-IGS中收集、运输、电离和纯化的同位素进行停止或重新加速的束。在核结构和核天体物理学以及基本相互作用和对称性领域需求很高的最先进的实验，包括原子阱中的高精度质量测量、束内激光光谱学和偏振、核衰变光谱学以及使用有源靶时间投影室的低能反应研究等各种技术。

The National Superconducting Cyclotron Laboratory (NSCL) is the nation's premier facility to accelerate nuclei with the purpose of studying nuclear structure. NSCL has developed world-unique new experimental capabilities with reaccelerated rare-isotope beams, ensuring a continued leadership role in rare-isotope physics worldwide. With the recent expansion of research capabilities at NSCL, demand for these beams to be used in nuclear physics experiments has never been higher. The instrument proposed here, called a Helium-Jet Ion Gas System (HJ-IGS) will allow for commensal running of two experiments simultaneously, each using different detector systems at NSCL, which will expand the number of experiments and hence help to meet the demand for experiments that increase our understanding of nuclei.Helium-Jet Ion Sources have been used for harvesting isotopes in the past, but the idea to use such a system to harvest some of the rarest isotopes available to researchers in a projectile fragmentation facility is novel. Rare isotopes that are bent out of the central beam path during the purification process of the primary rare-isotope beam are stopped and collected in a high-pressure cell filled with Helium saturated with aerosols to which the stopped isotopes will attach. With a high-pressure differential, the collected isotopes are quickly transported through a 40 meter-long capillary to an ion source that injects the isotopes, after purification, into a beam line that can feed one of several stations not used in the primary experiment. This allows two experiments to be performed at the same time: an experiment using a fast rare isotope beam directly produced in projectile fragmentation and an experiment with stopped or reaccelerated beams using the harvested, transported, ionized and purified isotopes in the HJ-IGS. State-of-the-art experiments that are in high demand in the fields of nuclear structure and nuclear astrophysics, as well as fundamental interactions and symmetries, and include such diverse techniques as high-precision mass measurements in atom traps, in-beam laser spectroscopy and polarization, nuclear decay spectroscopy, and low-energy reaction studies with an active-target time projection chamber.