Production of Radioactive Molecules in Radiofrequency Quadrupole Gas-Cells

放射性分子（RM）是含有稀有放射性同位素的外来分子物种。下一代亚原子物理实验希望使用RM来寻找标准模型之外的物理学，即，基本对称性，暗物质的含义，以及基本量子化学。像TRIUMF这样的设施可以在其热腔靶离子源中合成有限组的外来RM。然而，这些分子在腔靶和提取系统中通过裂变、分裂和碎裂之后的反应运动学的高度低效和复杂的级联形成。这些知之甚少的分子过程发生在初级质子束撞击含有不同元素的金属箔或复合陶瓷形式的固体靶之后。即将到来的亚原子研究需要以高纯度和产量有效地创造所需的稀有分子。然而，热腔在线靶中的极端非平衡条件（例如，高温、差真空、高辐射场、同量异位素干扰、不利的化学条件和反应能量）对用于实验的目标RM产生提出了主要挑战。本研究将探讨如何利用稀有同位素在射频四极气体室中进行离子-气体反应化学来产生RM。TRIUMF将开发两种新的离子束系统：（1）离子反应池（IRC）和（2）ARIEL离子束冷却聚束器（ARQB）。入射的正稀有同位素束被引入氦气池，在那里电场限制离子。在受控条件下，放射性离子与纯气体或蒸汽反应物之间发生化学反应。产物分子最终从出口被输送到亚原子物理实验中。像IRC和ARQB这样的反应堆是通用的，高效的，可控的，而不是在热靶环境中，热靶环境中充满了来自所有元素和同位素的反应物，这些反应物是由溅射，碎裂和裂变产生的。尽管在其他领域已经建立了气体反应池，但丰富的可能的气体反应化学仍然没有被亚原子物理学所利用。目前，没有其他实验室拥有专门的在线稀有分子束设施。这项研究有可能（1）在TRIUMF建立一个长期的RM设施，（2）显着扩大TRIUMF在加拿大亚原子物理学的光束组合，（3）加强即将到来的低能量精确亚原子分子实验的科学机会，（4）为学生提供许多跨学科的机会，（5）与外部合作伙伴发展新的科学合作，（6）支持加拿大高科技产业发展新的尖端仪器。

Radioactive molecules (RM) are exotic molecular species containing rare radioisotopes. Next-generation subatomic physics experiments wish to use RM in new searches for physics beyond the Standard Model, i.e., fundamental symmetries, implications for dark matter, and fundamental quantum chemistry. Facilities like TRIUMF can synthesize limited sets of exotic RM in their hot-cavity target ion sources. However, these molecules form in cavity targets and extraction systems by a highly inefficient and complex cascade of reaction kinematics following fission, spallation and fragmentation. These poorly understood molecular processes occur after the primary proton beam impinges on solid targets containing different elements in the form of metal foils or composite ceramics. Upcoming subatomic studies require efficient creation of the required rare molecule at high purity and yield. However, extreme non-equilibrium conditions in hot-cavity on-line targets (e.g., high temperatures, poor vacuum, high radiation fields, isobaric interferences, unfavorable chemical conditions and reaction energies) present a major challenge to targeted RM creation for experiments. This research will study how to create RM by ion-gas reaction chemistry with rare isotopes inside radiofrequency quadrupole (RFQ) gas-cells. Two new RFQ systems will be developed at TRIUMF: (1) an ion reaction cell (IRC), and (2) the ARIEL RFQ cooler-buncher (ARQB). Incoming positive rare isotope beams are brought into the RFQ gas-cell, where electric fields confine the ions. Chemical reactions occur between the radioactive ions and pure gaseous or vapor reactants under controlled conditions. Product molecules are finally delivered from the RFQ exit to the subatomic physics experiments. RFQ's like the IRC and ARQB are versatile, efficient, and controlled, rather than inside hot target environments abundant with reactants from all elements and isotopes produced by spallation, fragmentation and fission. The rich array of possible gas-reaction chemistries remains unexploited for subatomic physics, although RFQ reaction-cells are established in other fields. Currently, no other laboratory has a dedicated on-line rare molecule beam facility. This research has the potential to (1) establish a long-term RM facility at TRIUMF, (2) significantly expand the portfolio of beams at TRIUMF for subatomic physics in Canada, (3) strengthen the science opportunities for upcoming low-energy precision subatomic experiments with molecules, (4) offer many interdisciplinary opportunities for students, (5) develop new scientific collaborations with external partners, and (6) support Canadian high-tech industry for new leading-edge instruments.