Research on Neutron Electric Dipole Moment

Experiments searching for a neutron electric dipole moment are being carried out at Oak Ridge and Brookhaven National Laboratories. At Oak Ridge, Norman F. Ramsey, of Harvard, with Philip Miller, William Dress and James Baird, is now engaged in an experiment similar to the neutron magnetic resonance experiment of James H. Smith, Edward M. Purcell and Ramsey, reported in Phys. Rev. 78, 807 (1950) and Phys. Rev. 108, 120(1957). However, much slower neutrons are used even though the moderator is at room temperature or somewhat above. Those few neutrons which have a velocity of approximately 70 m/sec are selected out of the total Maxwellian velocity distribution. The loss in intensity by this severe velocity selection is compensated to some degree by the fact that totally reflecting neutron pipes can be used to overcome partially the loss of intensity that goes inversely with the square of the distance from the source. Such neutron pipes have been used previously by Heinz Maier‐Leibnitz and others, but not at such extremely low velocities.