  The J-PARC muon $g - 2$/EDM experiment aims to measure the muon magnetic
moment anomaly $a_{\mu} = (g -2) / 2 ~ $ and the muon electric dipole moment
(EDM) $d_{\mu}$. The target sensitivity for $a_{\mu}$ is a statistical
uncertainty of $450 \times 10^{-9}$, and for $d_{\mu}$ it is $1.5 \times
10^{-21}$ $e \cdot \rm{cm}$. The readout electronics require a DC to DC
converter to provide 1.5 V and 3.3 V electric voltage within a specific
environment. To capture the positron decay from the muon, the detector
components are placed in the muon storage area where a 3 T magnetic field is
applied in a vacuum. The extra magnetic field from the converter should be less
than 30 $\mu$T to reach the aforementioned sensitivity on $a_{\mu}$. In
addition, the electric field produced by the converter has to be as small as 1
V/m to also reach the target sensitivity on $d_{\mu}$. For this purpose, we
develop a step-down converter. We discuss the development process and the
performance of our DC to DC converter for the J-PARC muon $g - 2$/EDM
experiment.
