A.P. Serebrov

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.

A search for the electric dipole moment of the neutron using ultracold neutrons

Abstract The results of measurements of the electric dipole moment (EDM) of the neutron using ultra-cold neutrons (UCN) are presented. A description is given of the source of UCN devised, and of a magnetic resonance spectrometer confining UCN for ≈ 5 s. The use of a double-chamber spectrometer and a system for double analysis of polarization enabled us to eliminate most of the systematic errors possible. The measurements resulted in the EDM d =(4±7.5) × 10 −25 e · cm. From this it is inferred that ¦d¦ −24 e · cm at the confidence level of 90%.

A liquid hydrogen source of ultra-cold neutrons

Abstract A liquid hydrogen source of ultra-cold neutrons (UCN) developed for an experimental search for the electric dipole moment of the neutron is described. The results of an investigation of the yield of UCN from gaseous, liquid, and solid hydrogen as a function of temperature are presented. The UCN counting rate obtained at the output of the 6 × 7 cm 2 neutron guide tube is 5 × 10 4 n/s. This counting rate corresponds to a flux of neutrons whose velocity along the axis of the neutron guide tube is below 7 m/s. Preliminary measurements of the UCN yield from liquid and solid deuterium have been carried out.

Spin filters and supermirrors: a comparison study of two methods of high-precision neutron polarisation analysis

Abstract The precise knowledge of the neutron polarisation is needed in tests of the electroweak Standard Model using angular correlations in polarised neutron beta decay. We performed an experimental comparison study of two different methods of polarisation analysis of a cold neutron beam which are based on spin-dependent reflection, respectively, transmission. The compared devices are a supermirror analyser used in prior neutron decay studies and an opaque transmission spin filter of either polarised 3 He or polarised protons. The results of the neutron polarisation measured with the supermirror analyser and with the spin filter coincided in three different experiments within 0.1–0.2%.

Testing a Prototype of the Neutron Magnetic Resonance Stabilization System

The design of a multichannel system of stabilization of the magnetic resonance of ultracold neutrons in a multichamber spectrometer developed in the search for the electric dipole moment (EDM) of the neutron is briefly described. The results of tests on a prototype of this system are presented, which show the possibility of ensuring the stability of resonance lines that is equivalent to a magnetic field variation not exceeding ∼30 fT over a 100-s period of EDM measurements.

Permanent-magnet trap for ultracold neutron storage

The design of a permanent-magnet trap for ultracold neutron (UCN) storage is described. This trap excludes neutron collisions with the walls and, hence, eliminates anomalous losses. Used in the experiments on the neutron lifetime determination such UCN traps remove the main systematic error related to the anomalous neutron losses on the walls.

Quantum Magnetometer for Stabilization of the Neutron Magnetic Resonance

The design of a quantum magnetometer on cesium vapor is described. The device is intended for stabilization of the neutron resonance in experiments devoted to the search for the electric dipole moment (EDM) of neutron. The choice of this magnetometer type is justified and its potential sensitivity is estimated.

A noise-immune cesium magnetometer

A high-sensitivity (∼1 fT at a 100-s measurement time) self-generating magnetometer based on the optical orientation of cesium atoms and intended for measurements of absolute values of weak (∼2 × 10−6 T) magnetic fields is described. Its distinctive feature is the complete optical isolation of the magnetic sensor from the electronic units, allowing one to perform magnetic measurements under conditions of high electromagnetic noise. It is proposed that the magnetometer be used as part of the multichannel system for stabilizing the neutron magnetic resonance in the search for the electrical dipole moment of a neutron.