Experimental investigation of accelerator beam dynamics with a linear Paul trap

This thesis describes a range of experiments performed using a linear Paul trap to investigate the transverse beam dynamics of intense hadron accelerators. Due to the complexity of the dynamics in intense hadron accelerators, it is advantageous to use a scaled experiment to gain insight into these machines. A Paul trap is used to study accelerator dynamics, as the Hamiltonians of the two systems are equivalent. The IBEX Paul trap at the Rutherford Appleton Laboratory, Oxfordshire, has been commissioned. The first trapping of argon ions is observed, and the system is characterised, developing an understanding of the ion creation process, ion lifetime, longitudinal temperature, transverse emittance, and the process of ion extraction from the trap. A Faraday cup and MCP are used as diagnostics for the trap and are calibrated carefully to detect accurately the number of ions confined. Both the IBEX and S-POD (Hiroshima University, Japan) linear Paul traps are used to study space-charge-driven resonances quantitatively for the first time. The particle-in-cell code Warp is used to gain a deeper understanding of the experiment and to assist with the interpretation of results. Values are extracted describing the location of the greatest ion loss in tune space for a given intensity for equal transverse tunes. These values are compared to values predicted both analytically and through simulation. In the second half of this thesis, a design for a novel particle accelerator is considered, using the theory of Nonlinear Integrable Optics (NIO). In NIO, a highly nonlinear magnet is inserted into a linear lattice (known as a T-insert), resulting in regular and bounded particle motion. Detailed studies are undertaken to ascertain whether a simpler version of this theory, Quasi-Integrable nonlinear Optics (QIO), can be tested in a Paul trap. A T-insert lattice is designed to meet the constraints of QIO, as well as the constraints imposed by the IBEX hardware. A number of these lattices are tested on the IBEX trap, confirming that enough ions are confined to study QIO in the presence of space-charge forces and that it is possible to create a T-insert with sufficient precision. To verify that the T-insert lattice created within the Paul trap meets the conditions for QIO, a method to measure the beta function in a Paul trap has been designed and tested. Finally, a series of simulations are presented, showing that with a simple upgrade to the IBEX trap it is possible to create an octupole potential of high-enough quality to test QIO, while also retaining the ability to create a high-quality quadrupole to make the T-insert lattice. The impact of misalignment and scraping within the trap on the dynamic aperture and tune spread is studied using Warp. The resistance of the lattice to resonant excitation is investigated. The experimental and simulation studies described show that QIO can be tested in a Paul trap, and pave the way for a range of studies of this exciting concept.