Contribution to the magnetic metrology of accelerators multipoles magnets : synchrotron SOLEIL storage ring quadrupoles

Overview & Synopsis

In particle accelerators, more particularly in synchrotrons like SOLEIL, the particle beam is submitted to very strict constraints in order to improve the synchrotron radiation properties. The behaviour of the electron beam depends on the magnetic field distribution along the machine, mainly produced by the multipolar magnets of the storage ring (SR). Among them, the SOLEIL quadrupoles makes the electron beam very sensitive to their magnetic field errors due to some manufacturing defects. In that context, two main parameters are very important concerning the quadrupoles: the magnetic axis location and the magnetic field orientation in the transverse plane. These quantities are to be quantified and corrected by means of magnetic measurements. The first part of this thesis is mainly devoted to the presentation of the quadrupole constraint origin. In that context, the accelerator history and a brief review of the existing magnetic measurement method are presented. In the second chapter, theoretical tools regarding rotating coils are detailed. A model is proposed to simulate the effects of rotating coil defects on the magnetic measurements. Then, to quantify these defects, a method is detailed in order to take them into account during the measurements. A third chapter is devoted to the magnetic measurement bench set up and to the experimental results of the SR multipolar magnet measurements. Finally, the last chapter deals with the beam-based alignment (BBA) of the SR multipoles. A method is validated for quadrupoles and an innovative BBA method is proposed in the case of sextupoles