Professor Adrian Oeftiger

Abstract:

Longitudinally hollow bunches provide one means to mitigate the impact of transverse space charge. The hollow distributions are created via dipolar parametric excitation during acceleration in CERN's Proton Synchrotron Booster. We present simulation work and beam measurements. Particular emphasis is given to the alleviation of space charge effects on the long injection plateau of the downstream Proton Synchrotron machine, which is the main goal of this study.

Abstract:

Good knowledge of the non-linear properties of the SPS lattice is crucial for modeling and optimizing the machine performance in the presence of collective effects leading to incoherent tune spreads such as space charge, e-cloud and beam coupling impedance. In view of the LHC injectors upgrade (LIU) project and the future SPS operation in a regime dominated by such collective effects, detailed measurements of the SPS non-linear chromaticity and detuning with amplitude have been performed for the two optics configurations presently available for LHC type beams. The measurement results are used to fit systematic multipole components to the main magnets of the SPS MADX model as a basis for the non-linear machine model that can be used for beam dynamics simulations. The implications for the operation of the SPS with the LIU beam parameters are discussed.

Abstract:

The Faddeeva error function is frequently used when computing electric fields generated by two-dimensional Gaussian charge distributions. Numeric evaluation of the Faddeeva function is particularly challenging since there is no single expansion that converges rapidly over the whole complex domain. Various algorithms exist, even in the recent literature there have been new proposals. The many different implementations in computer codes offer different tradeoffs between speed and accuracy. We present an extensive benchmark of selected algorithms and implementations for accuracy, speed and memory footprint, both for CPU and GPU architectures.