Yu.V. Borisov

New measurement of the electric dipole moment of the neutron

Abstract A new experiment on the search for the electric dipole moment of the neutron was carried out using a magnetic resonance set-up with electric field and stored ultracold neutrons. The EDM of the neutron was measured to be +(2.6±4.2±1.6)×10−26 e cm, the first error being RMS or statistical and the second one systematical. An upper limit at the 95% CL is |dn|

A new upper limit on the electric dipole moment of the neutron

Abstract New measurements have reduced the upper limit for the electric dipole moment of the neutron to | d | −25 e cm (90% confidence level).

Search for an Electric Dipole Moment of the Neutron

The result of measuring the electric dipole moment (EDM) of the neutron by using ultracold neutrons is presented. The results of the measurements give the value of the EDM: d/sub n/4=(plus-or-minus7.5) x 10/sup -25/ excm. Hence, it can be concluded that vertical-bardvertical-bar<1.6 x 10/sup -24/ excm at the 90% confidence level.

Cubic boron nitride: A New prospective material for ultracold neutron application

Abstract At the ultracold neutron (UCN) source of the TRIGA research reactor in Mainz, we have measured for the first time the material optical wall-potential of cubic boron nitride. The measurements were performed with a time-of-flight (TOF) spectrometer. The samples investigated had a wall-potential of ( 305 ± 15 ) neV . This value is in good agreement with the result extracted from neutron reflectometry data and theoretical expectations. Because of its high critical velocity for UCN and its good dielectric characteristics, cubic boron nitride coatings (isotopically enriched) will be useful for a number of applications in UCN experiments.

Fast multichannel stabilization of the magnetic resonance in a magneto-resonance spectrometer

Abstract A method of fast stabilization of the magnetic resonance in a magnetic resonance spectrometer has been developed and tested. The source of the oscillatory field is the synthesizer which frequency follows variations of the average magnetic field in spectrometer. To search for the neutron electric dipole moment in the experimental setup under unfavorable conditions in the reactor experimental hall a stability of the magnetic resonance has been achieved that is equivalent to a magnetic field stability at the level of ≈ 2.5 × 10 −12 T per 6 min in a volume of about 501 with an electric field of 1.5 MV/m.

Anomalous behavior of the dispersion of a neutron transmitting through a crystal at nearly Bragg energies

The features of the propagation of a neutron through a crystal at nearly Bragg energies has been studied within the framework of the preparation of an experiment on the search for the electric dipole moment of a neutron by the crystal diffraction method. The time of passage of the neutron through the crystal has been studied as a function of the deviation from the Bragg condition. The anomalous behavior of the dispersion of the neutron, i.e., the energy dependence of its average velocity, has been observed. It has been shown that the derivative dv/dE for the diffracting neutron at nearly Bragg energies can be three or four orders of magnitude larger than this derivative for a free neutron. This opens new possibilities in precision neutron spectroscopy.

Observation of small changes in the energy of a neutron in an alternating magnetic field

A method for measuring small changes in the energy of a neutron has been proposed on the basis of the anomalous behavior of the dispersion of the neutron in the crystal near Bragg “resonance.” A high sensitivity of the method allows the observation of the acceleration of the neutron in the alternating magnetic field. It has been found that the small difference between the energies of two spin states of the neutron (parallel and antiparallel to the magnetic field) leads to significant spatial splitting of wave packets and, correspondingly, to the depolarization of the neutron beam.

Two-crystal focusing effect

The effect of two-crystal focusing of neutrons at Laue diffraction from large perfect silicon crystals has been studied. It has been shown that the focusing effect makes it possible to reach an angular resolution better than 0.03″, which is about 0.01 of the width of a Bragg reflection. This circumstance allows a new ultraprecision neutron-spectrometry method based on the method of spin-echo small-angle neutron scattering in combination with Laue diffraction.