Measurement of magnetic fields with hysteresis effects in bending magnet for beam transport

TOSCA is one of the de facto standard software for magnetic analysis and it has been used for accelerator magnet design until now, however, hysteresis effects is one of the biggest challenge which has not be taken into account at the designing stage. In recent years, "play model" was proposed which can be incorporated into finite element magnetic field analysis with ease and the hysteresis effects can be qualitatively evaluated, thus, there is a possibility that design accuracy of the accelerator magnets will be significantly improved. The "play model" is based on the idea of the "direct current hysteresis", therefore, to apply the "play model" to the accelerator magnets, quantitative discussions on the coupling between the hysteresis effects, and time-dependent effects such as magnetic after effects, and eddy current effects are required. The objective of this work is to quantitatively evaluate the influence of current excitation pattern of accelerator electromagnet and to judge applicability of direct current hysteresis model for magnetic field design of electromagnets for accelerator. We are now constructing a measurement system of the magnetic fields of the bending magnet for beam transport. By the development of this technique, it may be possible to design and control the magnetic field of the FFAG accelerators, taking hysteresis effects into account, and tunes of FFAG accelerator would be adjusted to improve the beam intensity. (author)