Speaker
Description
Among nuclear isomers spanning keV to MeV energies, ^{229m}Th is exceptional: its excitation energy of 8.4 eV and radiative lifetime of ~10^3 s make it the lowest-known nuclear excited state. This unique system offers an intrinsic narrow transition with high insensitivity to external electromagnetic fields, establishing ^{229m}Th as the premier candidate for a nuclear optical clock. Such a nuclear clock promises enhanced sensitivity for investigating fundamental physics, including searches for dark matter, a fifth force, and temporal variations in the fine-structure constant, while enabling studies of electron-nucleus coupling via electron bridge processes. Beyond the popular solidstate approaches, trapped triply charged ^{229}Th ions ( ^{229}Th^{3+} ) provide a viable pathway for developing an ionic nuclear clock. This platform offers unprecedented suppression of systematic shifts, potentially reaching accuracies approaching 1×10^{-19} . We present a modified LIT TOF-MS optimized for enhanced Th^{3+} ion loading and detection. A phase-locked RF/HV switch incorporating zero-crossing triggering and a programmable time delay is a key upgrade to minimize RF phase-dependent jitter and enable unambiguous identification of Th ^{3+} ions. To enhance the purity, yield, and lifetime of trapped Th^{3+} ions, the ion loading parameters including ion trap settings (RF amplitude, endcap voltages, loading time), laser ablation pulse energy, helium partial pressure, and ion storage time are optimized. These advances extend trapping lifetimes of Th^{3+} ions to several hundred seconds, an order-of-magnitude improvement over our previous work. Additionally, the reaction rate coefficient of Th^{3+} ions with helium-borne contaminants is measured. Finally, single-pulse ablation of mixed Sr-Th nitrate targets enables direct co-loading of Th^{3+} and ^{88}Sr^{+} ions, with subsequent laser cooling forming multi-component Coulomb crystals for fluorescence detection and laser spectroscopy of Th^{3+} ions.