Design of Injection and Extraction Systems with Optimisation of Lattice and Layout for the CERN PS2 Synchrotron

The CERN Proton Synchrotron PS2 is one of the foreseen accelerators for the LHC injector upgrade. This upgrade aims first at increasing the instantaneous luminosity of LHC and second at providing a reliable beam for the CERN accelerator complex. From this aspect, the main characteristics of the PS2 are high reliability for high intensity beams. The goal of this thesis was the design of the machine’s lattice and injection/extraction systems meeting the constraints coming mainly from the LHC beam type but also from beam requirements of experiments at PS2 and the SPS. In the design, the given energy range together with filling schemes for different beam types and RF cogging were first used to define the circumference of the machine. Estimates on the space requirements of injection/extraction systems were made in order to divide the total machine length between arc and long straight section. Existing tunnels for transfer lines together with the minimisation of the total transfer line length favoured a race track shape machine. The energy range of PS2 does not allow to omit transition crossing by injecting above or extracting below transition. Two significantly different lattice types were therefore designed, one with a real value of gamma transition and another with negative momentum compaction (NMC) with imaginary value of gamma transition and thereby no transition crossing. In case of the real gamma transition lattice, diff erent cell structures were studied according to their bending power and optics behaviour. A FODO cell with 90˚ horizontal phase advance met the constraints best and was chosen to build a closed lattice. This lattice was optimised to use as few quadrupole families as possible with a missing magnet scheme chosen to suppress the dispersion in the long straight section. Concerning transition crossing, longitudinal space charge and impedance from the existing PS were scaled to the PS2 to estimate the necessary parameters of a gamma transition jump. A first- and second-order jump scheme were designed and their influence on the bare optics analysed. The second lattice design approach was the NMC. Here, the dispersion function is forced to oscillate between negative and positive values and by placing dipoles mainly in areas of negative dispersion the value of gamma transition can be made imaginary. This lattice suffers from complexity in hardware and operation but it has the big advantage of avoiding transition. The decision for a 40 MHz RF system which does not impinge on the choice of gamma transition simplified designing an NMC lattice that meets the aperture constraints. Concluding the lattice choice, the NMC is presently the PS2 baseline because it avoids the complexities of transition crossing and the inevitable beam loss, which for a high intensity machine is a prime concern. The second part of this thesis concerns the desig n of beam transfer systems. Different beam types necessitate two injection and three extraction systems. On the basis of the constraints from these systems a concept for the whole long straight section was chosen. The structure was decided to be a central split triplet with two FODO cells attached on each side. This allows to place the challenging H- injection in one drift and accomodate the other systems in the FODO cells. Constraints of the different systems were determined and accordingly the optics was optimised. A resulting concept is given for the injection/extraction straight which is interchangeable between the two lattice options.