Delphine Domange

Detailed beam aperture model for the CERN Proton Synchrotron

Abstract

The CERN Proton Synchrotron (PS) accelerates beams up to 26 GeV/c for a wide variety of experiments and to feed the Large Hardon Collider. Controlling and reducing beam losses during operation cycles is fundamental to the overall performance of the machine. To study these beam losses, numerical simulations are computed via MAD-X, a software package developed by CERN. The simulation relies on the aperture models of the different machine elements (magnets, radiofrequency cavities, vacuum tanks and pipes). This project aims to study the aperture of the PS to improve the simulations. Using 3D CAD models and drawings of the PS pipe, a Python code is developed with the pythonOCC library to extract the aperture of these machine elements from the 3D pipemodel. The code studies the aperture at different points along the pipe by making cutting planes to extract the aperture as a list of points. The points corresponding to the inner layer of the pipe are discriminated to be used in the MAD-X program to study particle losses. As the simulations made with the aperture are very time-consuming, a geometric fit of the aperture can be used in theMAD-X program to speed up the calculation. The pipe of the PS is mainly elliptical, so a code to calculate the largest ellipse inscribed in the aperture is developed. Using the elliptic fit to replace the aperture in the simulation is accurate because it covers a large part of the beam. The study of the aperture is made for the parts of the PS pipe where the beam is bent. The data obtained for the aperture and the fit are saved in a database shared with the team in charge of the simulation.