Generation of Periodic Magnetic Field Using Bulk MgB2

The generation of strong periodic magnetic fields with short periodic lengths is very attractive for accelerator-based compact high-power future light sources. We have developed a new type of undulator using HTS bulk material to overcome the field strength limitation due to the maximum energy product (
BH
)
_max
of permanent magnets and the engineering current density of superconducting wires. REBCO bulk is the most attractive material for realizing high-field undulators because of its extremely high
J
_c
at low temperatures. However, REBCO bulk requires a melt growth process with seed crystals to produce a single-domain superconducting bulk, and this process tends to introduce batch-to-batch variations in
J
_c
. As a result, it is difficult to precisely control the peak-to-peak magnetic field fluctuations of the periodic magnetic field. Therefore, we focused on MgB
₂
, which does not show weakly linked electromagnetic behavior, and thus does not require a melt growth process with seed crystals. In this study, we demonstrated for the first time in the world the generation of a periodic magnetic field using MgB
₂
bulk arrays and confirmed that the peak-to-peak fluctuations are smaller than those of REBCO bulk.