Magnetic Field Characterization with Circular Scan and Multipole Moment Analysis

For the optimisation of an accelerator like FLUTE which aims at producing femtosecond bunches by means of a specially designed compressor chicane, it is important to take into account the detailed properties of the real and magnets in the beam dynamics simulations. A typical approach to do so is to use particle tracking through flux density maps, measured e.g. by a 3D Hall probe on a sufficiently dense 3D grid and interpolated by an appropriate integration procedure. This approach yields accurate results but can be very time consuming both, regarding the measurement and the simulation. For the FLUTE quadrupole and chicane dipole magnets, we have in addition to this method investigated the alternative approach of measuring the radial flux density component on a cylinder surface concentric with the beam axis and representing the field in the beam dynamics simulations by a set of magnet slices with the multipole components deduced from the measurement. In this contribution the calibration and measurement procedure is described and the two measurement and representation approaches are compared to each other.