Polarized Cold Neutrons Research Articles

Circular polarization of γ-quanta in np→d γ reactions with polarized neutrons

The circular polarization of the 2.23 MeV γ-quanta in the reaction np→d γ with polarized cold neutrons has been measured to be P γ =(−1.5±0.3)×10 −3. A high-purity solid parahydrogen target was used. The circular polarization was measured with two magnetic transmission polarimeters, NaI(Tl) crystals with photomultipliers were used as detectors. The result is examined from the point of view of recent theoretical calculations.

Long distance propagation of a polarized neutron beam in zero magnetic field

A beam of fully polarized cold neutrons was transported through a zero magnetic field region of 70 m length without loss of polarization. The purpose of this exercise was twofold: firstly, to demonstrate that the new zero-field neutron spin-echo method will work also for very long neutron flight paths; secondly, to prove in the most direct way that the neutron free-flight region of the ILL neutron-antineutron oscillation experiment was indeed sufficiently field-free (“quasifree condition”) by using the neutrons themselves as a magnetometer. To this purpose the residual magnetic field integrals in the long “zero-field” region were measured with a conventional neutron spin-echo method. The overall spin precession angle of the neutrons during their flight through the long zero-field region was found to be less than 2°.

Computer studies of trajectory focusing effects on total reflection coefficient and energy spectrum of reflected ions: Y Yamamura and W Takeuchi, Rad Effects, 61, 1982, 247–254

We have developed a radio-frequency gradient spin flipper for the effective utilization of the focused and polarized neutron beam obtained using a superconducting sextupole magnet developed for the practical application in the neutron-scattering experiment. The flipper was designed to be effective for the neutron beam with wavelengths longer than 4 Å and the cross section of 50 mm in diameter. The flipper was tested using polarized cold neutrons, and good performance was obtained.

Parity non-conservation in the radiative capture of polarized neutrons by 35Cl

We report a measurement of the forward-backward asymmetry in the radiative capture of polarized cold neutrons in the reaction 35Cl(n, γ) 36Cl where 36Cl is in the ground state. The measured value of the asymmetry is a = (1.57 ± 0.531) × 10 −4. We deduce the mixing between the 2 + capture level and the neighboring 2 − levelto be 〈2 −¦H p.v. ¦2 +〉 = −0.25 ± 0.08 eV before corrections. A measurement of the integral asymmetry of all γ-rays in the neutron capture by 35Cl leads to agreement with measurements at Leningrad.

Evidence of parity violation in neutron capture by 117Sn

An asymmetry measurement in the radiative capture of polarized cold neutrons in the raction 117Sn(n, γ) 118Sn is reported. The result a = (4.4 ± 0.6) × 10 −4 gives a clear evidence of a parity non-conserving effect.

Search for parity violation in neutron-proton capture

A measurement of the asymmetry in radiative neutron-proton capture has been performed using polarized cold neutrons on a parahydrogen target. The result, A γ = (0.6±2.1) × 10 −7, is in agreement with values predicted by various theories of the weak interaction.

Asymmetric Spin-Orbit Effects Calculated for the Total Reflection of Polarized Cold Neutrons

Strange asymmetries observed in magnetic neutron guides are explained in terms of an additional surface current due to the spin-orbit interaction of the neutrons in the Coulomb field of the atoms. This result enhances the approach of the index of refraction for the total reflection of neutrons using the propagator of the Schr\"odinger equation.

Laser strain measurement

Requirements on the field uniformity in neutron polarizers are analyzed in view of the fact that neutron polarizing coatings have been improved during the past decade. The design of magnetic systems that meet new requirements is optimized by numerical simulations. Magnetic systems for wide-aperture multichannel polarizers and analyzers are represented, including (a) the polarizer to be built at channel 4-4′ of the reactor PIK (Gatchina, Russia) for high-flux experiments with a 100×150 mm2 beam of polarized cold neutrons; (b) the fan analyzer covering a 150×100 mm2 window of the detector at the Magnetism Reflectometer (SNS, ORNL, USA); (c) the polarizer and (d) the fan analyzer covering a 220×110 mm2 window of the detector at the reflectometer NERO, which is transferred to PNPI (Russia) from HZG (Germany). Deviations of the field from the vertical did not exceed 2°. The polarizing efficiency of the analyzer at the Magnetism Reflectometer reached 99%, a record level for wide-aperture supermirror analyzers.