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UBC Theses and Dissertations

Towards high precision mass measurements of short-lived exotic isotopes using highly charged ions at the TITAN Penning trap system Brodeur, Maxime

Abstract

The TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) experiment will use Penning trap (PT) for precise mass determinations on short-lived isotopes at ISAC. An Electron Beam Ion Trap (EBIT) is used to charge breed ions to a charge state q. The PT mass resolution is directly proportional to q, resulting in a significant increase in the achieved precision. This PT system will allow very accurate mass determination, via time-of-flight (TOF) measurements, on the order of δm/m ≈ 10⁻⁸ on isotopes with a half-lives of about 50 ms using highly charged ions (HCI). This thesis presents work on TITAN's PT design, as well as studies carried out at other PT experiments. Since after the EBIT a beam of HCIs needs to be efficiently transferred into and out of the PT, additional complications arise, therefore, ion flight simulations of the injection and the extraction of ions from the PT were performed. Simulations have determined the optimal ion optics to minimize the diameter of the ion bunch entering the PT. Simulations of TITAN's Lorentz steerer, the first one for HCIs, have shown it is possible to inject the sample, such that additional preparation in the PT become obsolete. This reduces the required time and presents an important improvement for operation with short-lived species. TOF simulations to optimize the extraction geometry for HCI and singly charged ions were carried out. The resulting geometry for injection, PT structure, and extraction has been designed and is under construction. In addition, two complementary projects were made on existing PT experiments. First, a magnetic field stability study of ISOLTRAP's PT has found a magnetic field-temperature correlation and a day-night temperature variation inside the magnet bore. This presents an important determination of a source of systematic uncertainty similar to what TITAN will have. Finally, a reference laser ablation ion source for the Canadian Penning trap experiment has been designed and is presented.

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