Abstract - Stephan Russenschuck

High-quality magnetic measurements are crucial at different phases of an accelerator project; to validate numerical models and the design of the normal and superconducting magnets, magnet-to-magnet reproducibility during series production, and feedback to the machine operation. Unfortunately, no universal method exists for these measurements and the numbers of magnets are usually small; not only prototypes but not an industrial series either. Moreover, the uncertainty must remain below 10-4 for the absolute and 10-6 for the relative measured quantities. Often it is therefore required to develop specialized transducers for the project. The learnt project management structure applicable to such development and measurement campaigns is the value-shop model, keeping the administrative overheads at a bare minimum.

While the GUM (Guide to the Expression of Uncertainty in Measurement) covers extensively random and systematic errors, the more complex magnetic measurements suffer from intrinsic errors (due to the necessary model-order reduction in the physical modelling), ignorance (due to the non-availability of predictive models of 3D effects, hysteresis, and multi-physics effects such as magnetostriction) and gross-errors (due to operational errors such as mix-up of calibration data). While gross-errors can be avoided by a proper quality assurance structure and database management system, ignorance can be identified by imposing the regularity conditions of magnetic field (field avatars) or supplementing numerical models by digital twins derived from measured quantities.

Stephan Russenschuck studied Electrical Engineering at the Technical University Darmstadt (TUD), Germany. He received the Dipl.-Ing degree in 1986 and the Dr.-Ing. degree in 1990 both from the Technical University Darmstadt. In 2000 he was recognized as a University Lecturer (Habilitation) for Theory of Electromagnetic Fields at the University of Vienna, Austria.
S. Russenschuck is a senior staff member in the Accelerator Technology (TE) Department of the European Organization for Nuclear Research, CERN, Geneva, Switzerland. He is the leader of the magnetic measurement section in the TE department and the chairman of the technical and doctoral student committee (TSC).
During the construction period of the LHC he was responsible for the electromagnetic design of the LHC main dipole magnets and later for the magnet polarities and the electrical quality assurance of the LHC machine.
His research interests are mathematical optimization and numerical field computation techniques in support of magnet design, magnetic measurements, and machine operation. S. Russenschuck is the author of the numerical field computation program ROXIE and the author of the book “Field computation for accelerator magnets” published at Wiley-VCH.