Precision measurements with trapped radioactive ions using the Canadian Penning Trap Mass spectrometer and associated ion traps at the Argonne National Laboratory

使用阿贡国家实验室的加拿大彭宁阱质谱仪和相关离子阱对捕获的放射性离子进行精确测量

• 批准号: SAPPJ-2014-00024
• 负责人: Sharma, Kumar
• 金额: $ 8.01万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=568020
• 关键词: Precision; measurements; trapped; radioactive; ions

This work centres on the precise measurement of the atomic masses and other properties of nuclei far from stability. The results provide information on the energy released in nuclear reactions involving nuclei in these exotic regions. Such information is important in predicting the rates and pathways of nuclear reactions that power explosive astrophysical events that are candidates for the nucleosynthesis of the heavier elements (through the rp-, nu-p- and r-processes). They also allow the study of fundamental symmetries in particle physics theories and the evolution of nuclear structure in regions where the nuclei have extreme neutron-to-proton ratios. The measurements are conducted with the Canadian Penning Trap Mass Spectrometer (CPT) which operates on-line to the ATLAS accelerator system at the Argonne National Laboratory. The energetic products of nuclear reactions are slowed in a gas cell and collected, cooled and purified in a series of ion traps. This ion-cloud of exotic nuclides is then transferred to a precision Penning trap where the mass of the ions can be measured to precisions of a few parts per billion. Alternately, the ions can also be transferred to a radio-frequency quadrupole ion trap (RFQ) where they are suspended in helium gas. Such a cloud of exotic nuclei, nearly at rest, provides a unique opportunity to study the correlations between the beta particles and the neutrinos and other particles emitted in their decay. The following initiatives are either planned or in progress: • The CPT has been moved from its original location and installed on-line to the low-energy beam line of the new CARIBU facility at ATLAS. CARIBU utilizes a large scale version of the same gas stopping technique described above to provide a source of very neutron-rich nuclides, produced in the fission of 252-Cf. With this new source the measurements can push even closer to the neutron drip line and provide data that are very useful for improving our models for r-process nucleosynthesis. This campaign is expected to conclude in 2014. • Subsequently, we plan to move the CPT mass spectrometer to a location in experimental area III at ATLAS to make use of the unique availability of high-intensity energetic beams of heavy nuclei, to produce very neutron-rich nuclei in regions heavier than those available through fission. These very exotic nuclei will once again be stopped in a gas catcher and presented for measurement into a newly constructed multiple-reflection time-of-flight mass spectrometer and the CPT mass spectrometer systems. This new arrangement should provide us with unique opportunities to push the boundaries of our knowledge of exotic nuclei further towards the N=126 neutron-rich region critical for the formation of the final abundance peak in the r-process. • Our original target and gas catcher system are now used to load an open geometry RFQ trap that we call the BPT. The trap is surrounded by various detectors that allow us to study beta-neutrino correlations in the decay of the trapped particles. We are examining the beta decay of the mass 8 system (8-Li and 8-B) which are sensitive individually to tensor currents, and when combined, to second class currents. • A second RFQ trap of is under construction at the CARIBU facility where it will be used to study beta-delayed neutron emission from the trapped ions. The results will delineate the decay modes of neutron-rich nuclei which play a role in nucleosynthesis. They are also relevant to understanding nuclear reactor kinetics and inform safety considerations with nuclear power plants. • Other mass measurements with trapped ions of particular interest will be undertaken as opportunities arise.

这项工作集中在远离稳定性的原子质量和其他核能的精确度量上。结果提供了有关这些外来区域涉及核反应中释放的能量的信息。这样的信息对于预测核反应的速率和途径很重要，这些核反应爆炸性的天体物理事件是候选较重元件的核合成的候选者（通过RP-，NU-P-和R-Processes）。它们还允许研究粒子物理学理论中的基本对称性以及核结构在核具有极端中子与普罗替型比率的区域中的核结构的演变。这些测量是使用加拿大笔陷阱质谱仪（CPT）进行的，该量质谱仪（CPT）在Argonne National Laboratory的Atlas Accelerator系统上运行。核反应的能量产物在气体电池中放缓，并在一系列离子陷阱中收集，冷却和纯化。然后将外来核苷的离子云转移到一个精确的笔陷阱中，在该陷阱中，可以将离子的质量测量到数十亿分之几的精度。或者，也可以将离子转移到射频四极离子陷阱（RFQ）中，在那里它们被悬浮在氦气中。如此的外来核几乎静止地提供了一个独特的机会，可以研究β颗粒与衰减中发出的其他颗粒之间的相关性。以下计划是计划的，要么正在进行中：•CPT已从其原始位置移动，并在线安装到Atlas新加州工厂的低能梁管线。 Caribu利用上述相同的气体停止技术的大型版本提供了在252-CF裂变中产生的非常富含中子的核素的来源。借助此新来源，测量值可以将其推向中子滴水线，并提供对改善我们用于R过程的核合成模型非常有用的数据。预计该运动将在2014年包括。•随后，我们计划将CPT质谱仪移至Atlas实验区III的位置，以利用高强度的重型核能的独特可用性，以在比裂变中可用的地区产生非常富含中子的核能。这些非常奇特的核将再次在气体捕获器中停止，并进行测量，以进行新建的多反射时间质谱仪和CPT质谱仪系统。这种新的安排应该为我们提供独特的机会，以将我们对异国核的知识的界限进一步推向n = 126中子富裕地区，这对于R-Process中最终抽象峰的形成至关重要。 •现在，我们的原始目标和加油系统用于加载我们称为BPT的开放几何RFQ陷阱。陷阱被各种探测器所包围，使我们能够研究捕获颗粒的衰变中的β-中性相关性。我们正在检查质量8系统（8-LI和8-B）的β衰减，它们对张量电流敏感，并且在组合时对二等电流。 •在加勒比工厂的第二个RFQ陷阱正在建设中，该设施将用于研究被困离子的β延迟中子排放。结果将描述中子富含核能的衰减模式，该模式在核共生中发挥作用。它们还与理解核反应堆动力学有关，并用核电站为安全考虑。 •随着机会的出现，将进行其他质量测量。