Mass Measurements of Neutron-Deficient Yb Isotopes and Nuclear Structure at the Extreme Proton-Rich Side of the N=82 Shell

International audienceHigh-accuracy mass measurements of neutron-deficient Yb isotopes have been performed at TRIUMF using TITAN’s multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). For the first time, an MR-TOF-MS was used on line simultaneously as an isobar separator and as a mass spectrometer, extending the measurements to two isotopes further away from stability than otherwise possible. The ground state masses of Yb150,153 and the excitation energy of Ybm151 were measured for the first time. As a result, the persistence of the N=82 shell with almost unmodified shell gap energies is established up to the proton drip line. Furthermore, the puzzling systematics of the h11/2-excited isomeric states of the N=81 isotones are unraveled using state-of-the-art mean field calculation

Optimising Ion Transport in a Thermal Ionisation Mass Spectrometer and Plasma Ion Source Using Monte Carlo Simulations

The controlled collimation of ion beams is of paramount importance in particle accelerators, high energy beamlines, and detector systems, as it determines the functionality, sensitivity and resolution of the instruments. In this thesis the ion source of a thermal ionization mass spectrometer (TIMS), comprised of a heated filament followed by a series of ion optical lenses, was modelled and Monte Carlo simulations were performed using SIMION. The potentials of three of the electrostatic lenses were optimized, in order to maximize the illuminated area of the exit slit. The optimization method employed achieved up to a 44 % increase in experimental signal intensity when compared to the existing manufacturer-provided lens tuning algorithm. 3D plots were effective in visualizing whether this new voltage configuration leads to a solution which lies in a local or global optimum, showing that the previous tuning technique was rarely successful in achieving the global optimum. This modelling and optimization approach was then used to aid the commissioning of a plasma ion source at the TITAN experiment at TRIUMF. The Plasma Ion Source (PIS), comprised of a heated filament followed by an anode, Einzel lens and X-Y correction steerers, was modelled and Monte Carlo simulations were performed. Optimising the voltage configurations in these simulations has proved successful in the commissioning of the PIS at the TITAN experiment in thermal mode, where ions from the source have been characterised using the time-of-flight method. The PIS will be able to deliver important calibration beams to TITAN’s experiments and will also enable off-line, high precision isotope composition measurements with the Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF MS)

A Design for a 3 TeV Rapid Cycling Synchrotron for Muon Acceleration in the SPS Tunnel

Current proposals for new high-energy physics machines either focus on building ever-larger circular hadron colliders, such as the proposed FCC- hh, or on electron-positron linac designs, such as CLIC and ILC. However, muon colliders present an alternative approach to probing new physics at the energy frontier while also offering a number of advantages over hadron or electron-positron colliders. A detailed design for the acceleration stage of a future 3 TeV centre of mass energy muon collider is proposed. The acceleration of muons to 1.5 TeV would be achieved in two hybrid Rapid Cycling Synchrotrons (RCSs), which would both be situated in the existing SPS tunnel at CERN. RCS1 would accelerate counter rotating muons and antimuons from 100 GeV to 900 GeV before they would be injected into RCS2 where they would then be accelerated up to 1.5 TeV. The lattice design was optimised to fit into the SPS tunnel and two dispersion suppressor schemes are presented. Longitudinal simulations were performed in order to study beam loss and collective effects over the acceleration cycle. A radiofrequency cavity was designed, where the optimal frequency and cavity geometry were investigated, before being modelled in 3D. Designs for the normal conducting dipoles and quadrupoles are presented, which meet the requirements detailed in the lattice design while also minimising power consumption. Radiation deposition in the accelerator was also investigated, along with a study on the environmental exposure from neutrino radiation