Homogeneous magnetic field for the neutron electric dipole moment (n-EDM) measurement using ultra-coldneutrons

Automatic compensation system for the environmental magnetic field has been developed for the neutron electric dipole moment (n-EDM) measurement using ultra-cold neutrons (UCN). In the test experiment, a magnetic field of ~ 40 μT including geomagnetism with the field gradient of ~ − 9 μT/m was successfully suppressed. The suppression factors were consistent with the feed-back gains. Our goal is to achieve a suppression by a factor of 10 3 , necessary for the n-EDM measurement of the order of 10 −27 ecm.