Production of Radioactive Molecules in Radiofrequency Quadrupole Gas-Cells

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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.